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Sample records for zodiacal cloud dust

  1. Sources of zodiacal dust particles

    NASA Astrophysics Data System (ADS)

    Ipatov, S. I.; Mather, J. C.

    2007-08-01

    dust inside Jupiter's orbit, they can not be dominant in the zodiacal cloud because they can not be dominant between orbits of Jupiter and Saturn. The conclusion on a considerable fraction of cometary dust is also in an agreement with our studies [6] of the dynamics of Jupiter-family comets, which showed that some former cometary objects could get high eccentric orbits located entirely inside of Jupiter's orbit and stay in these orbits for a long time. Some of these objects could disintegrate producing a substantial amount of dust. [1] Ipatov S.I., Mather J.C., and Taylor P. (2004) Annals of the New York Acad. of Sciences, 1017, 66-80. [2] Ipatov S.I. and Mather J.C. (2006) Advances in Space Research, 37, 126-137. [3] Ipatov S.I. and Mather J.C., (2007) Dust in Planetary Systems, ed. by H. Krüger and A. Graps, ESA Publications, SP-643, p. 91-94. [4] Ipatov S.I. et al. (2006) 37th LPSC, #1471. [5] Ipatov S.I. et al., astro-ph/0608141. [6] Ipatov S.I. and Mather J.C. (2004) Annals of the New York Acad. of Sciences, 1017, 66-80.

  2. Dynamical Zodiacal Cloud Models Constrained by High Resolution Spectroscopy of the Zodiacal Light

    NASA Technical Reports Server (NTRS)

    Ipatov, S. I.; Kutyrev, A. S.; Madsen, G. J.; Mather, J. C.; Moseley, S. H.; Reynolds, R. J.

    2005-01-01

    We have developed a set of self-consistent dynamical models of the Zodiacal cloud, following the orbital evolution of dust particles. Three populations were considered, originating from the Kuiper belt, asteroids and comets. Using the models developed, we investigated how the solar spectrum is changed by scattering by the zodiacal cloud grains and compared the obtained spectra with the observations.

  3. Studying the Fine Structure and Temporal Variations of the Zodiacal Cloud and Asteroidal Dust Bands Using the 3-Year Near-IR COBE-DIRBE Data

    NASA Technical Reports Server (NTRS)

    Jayaraman, Sumita

    1999-01-01

    The report presents the results of the data analyses of the DIRBE-COBE data set to study the structure of the zodiacal cloud in the near-infrared wavebands at 1.2, 2.2, and 3.4 microns. The cloud has been divided into two components which have been analyzed and studied separately. The annual variation of the flux in the smooth or low frequency component has been measured in all three bands and the presence of any asymmetries due to the Earth's resonant ring have been studied. The high frequency component which primarily consisted of the asteroidal dust bands. Extensive and careful co-addition was done to extract the central bands in all three wavebands. The ten-degree bands are present in the 1.2 and 2.2 microns but not in the 3.4 micron waveband.

  4. Inferring Sources in the Interplanetary Dust Cloud, from Observations and Simulations of Zodiacal Light and Thermal Emission

    NASA Technical Reports Server (NTRS)

    Levasseur-Regourd, A. C.; Lasue, J.

    2011-01-01

    Interplanetary dust particles physical properties may be approached through observations of the solar light they scatter, specially its polarization, and of their thermal emission. Results, at least near the ecliptic plane, on polarization phase curves and on the heliocentric dependence of the local spatial density, albedo, polarization and temperature are summarized. As far as interpretations through simulations are concerned, a very good fit of the polarization phase curve near 1.5 AU is obtained for a mixture of silicates and more absorbing organics material, with a significant amount of fluffy aggregates. In the 1.5-0.5 AU solar distance range, the temperature variation suggests the presence of a large amount of absorbing organic compounds, while the decrease of the polarization with decreasing solar distance is indeed compatible with a decrease of the organics towards the Sun. Such results are in favor of the predominance of dust of cometary origin in the interplanetary dust cloud, at least below 1.5 AU. The implication of these results on the delivery of complex organic molecules on Earth during the LHB epoch, when the spatial density of the interplanetary dust cloud was orders of magnitude greater than today, is discussed.

  5. A Global, Multi-Waveband Model for the Zodiacal Cloud

    NASA Technical Reports Server (NTRS)

    Grogan, Keith; Dermott, Stanley F.; Kehoe, Thomas J. J.

    2003-01-01

    This recently completed three-year project was undertaken by the PI at the University of Florida, NASA Goddard and JPL, and by the Co-I and Collaborator at the University of Florida. The funding was used to support a continuation of research conducted at the University of Florida over the last decade which focuses on the dynamics of dust particles in the interplanetary environment. The main objectives of this proposal were: To produce improved dynamical models of the zodiacal cloud by performing numerical simulations of the orbital evolution of asteroidal and cometary dust particles. To provide visualizations of the results using our visualization software package, SIMUL, simulating the viewing geometries of IRAS and COBE and comparing the model results with archived data. To use the results to provide a more accurate model of the brightness distribution of the zodiacal cloud than existing empirical models. In addition, our dynamical approach can provide insight into fundamental properties of the cloud, including but not limited to the total mass and surface area of dust, the size-frequency distribution of dust, and the relative contributions of asteroidal and cometary material. The model can also be used to provide constraints on trace signals from other sources, such as dust associated with the "Plutinos" , objects captured in the 2:3 resonance with Neptune.

  6. Radar Detectability Studies of Slow and Small Zodiacal Dust Cloud Particles. III. The Role of Sodium and the Head Echo Size on the Probability of Detection

    NASA Astrophysics Data System (ADS)

    Janches, D.; Swarnalingam, N.; Carrillo-Sanchez, J. D.; Gomez-Martin, J. C.; Marshall, R.; Nesvorný, D.; Plane, J. M. C.; Feng, W.; Pokorný, P.

    2017-07-01

    We present a path forward on a long-standing issue concerning the flux of small and slow meteoroids, which are believed to be the dominant portion of the incoming meteoric mass flux into the Earth’s atmosphere. Such a flux, which is predicted by dynamical dust models of the Zodiacal Cloud, is not evident in ground-based radar observations. For decades this was attributed to the fact that the radars used for meteor observations lack the sensitivity to detect this population, due to the small amount of ionization produced by slow-velocity meteors. Such a hypothesis has been challenged by the introduction of meteor head echo (HE) observations with High Power and Large Aperture radars, in particular the Arecibo 430 MHz radar. Janches et al. developed a probabilistic approach to estimate the detectability of meteors by these radars and initially showed that, with the current knowledge of ablation and ionization, such particles should dominate the detected rates by one to two orders of magnitude compared to the actual observations. In this paper, we include results in our model from recently published laboratory measurements, which showed that (1) the ablation of Na is less intense covering a wider altitude range; and (2) the ionization probability, {β }{ip}, for Na atoms in the air is up to two orders of magnitude smaller for low speeds than originally believed. By applying these results and using a somewhat smaller size of the HE radar target we offer a solution that reconciles these observations with model predictions.

  7. Radar Detectability Studies of Slow and Small Zodiacal Dust Cloud Particles. III. The Role of Sodium and the Head Echo Size on the Probability of Detection

    NASA Technical Reports Server (NTRS)

    Janches, D.; Swarnalingam, N.; Carrillo-Sanchez, J. D.; Gomez-Martin, J. C.; Marshall, R.; Nesvorny, D.; Plane, J. M. C.; Feng, W.; Pokorny, P.

    2017-01-01

    We present a path forward on a long-standing issue concerning the flux of small and slow meteoroids, which are believed to be the dominant portion of the incoming meteoric mass flux into the Earth's atmosphere. Such a flux, which is predicted by dynamical dust models of the Zodiacal Cloud, is not evident in ground-based radar observations. For decades this was attributed to the fact that the radars used for meteor observations lack the sensitivity to detect this population, due to the small amount of ionization produced by slow-velocity meteors. Such a hypothesis has been challenged by the introduction of meteor head echo (HE) observations with High Power and Large Aperture radars, in particular the Arecibo 430 MHz radar. Janches et al. developed a probabilistic approach to estimate the detectability of meteors by these radars and initially showed that, with the current knowledge of ablation and ionization, such particles should dominate the detected rates by one to two orders of magnitude compared to the actual observations. In this paper, we include results in our model from recently published laboratory measurements, which showed that (1) the ablation of Na is less intense covering a wider altitude range; and (2) the ionization probability, Beta ip, for Na atoms in the air is up to two orders of magnitude smaller for low speeds than originally believed. By applying these results and using a somewhat smaller size of the HE radar target we offer a solution that reconciles these observations with model predictions.

  8. Radar detectability studies of slow and small Zodiacal Dust Cloud Particles: I. The case of Arecibo 430 MHz meteor head echo observations

    PubMed Central

    Janches, D.; Plane, J.M.C.; Nesvorný, D.; Feng, W.; Vokrouhlický, D.; Nicolls, M.J.

    2016-01-01

    Recent model development of the Zodiacal Dust Cloud (ZDC) model (Nesvorný et al. 2010, 2011b) argue that the incoming flux of meteoric material into the Earth’s upper atmosphere is mostly undetected by radars because they cannot detect small extraterrestrial particles entering the atmosphere at low velocities due to the relatively small production of electrons. In this paper we present a new methodology utilizing meteor head echo radar observations that aims to constrain the ZDC physical model by ground-based measurements. In particular, for this work, we focus on Arecibo 430 MHz observations since this is the most sensitive radar utilized for this type of observations to date. For this, we integrate and employ existing comprehensive models of meteoroid ablation, ionization and radar detection to enable accurate interpretation of radar observations and show that reasonable agreement in the hourly rates is found between model predictions and Arecibo observations when: 1) we invoke the lower limit of the model predicted flux (~16 t/d) and 2) we estimate the ionization probability of ablating metal atoms using laboratory measurements of the ionization cross sections of high speed metal atom beams, resulting in values up to two orders of magnitude lower than the extensively utilized figure reported by Jones (1997) for low speeds meteors. However, even at this lower limit the model over predicts the slow portion of the Arecibo radial velocity distributions by a factor of 3, suggesting the model requires some revision. PMID:27642186

  9. Radar Detectability Studies of Slow and Small Zodiacal Dust Cloud Particles: I. The Case of Arecibo 430 MHz Meteor Head Echo Observations

    NASA Technical Reports Server (NTRS)

    Janches, D.; Plane, J. M. C.; Nesvorny, D.; Feng, W.; Vokrouhlicky, D.; Nicolls, M. J.

    2014-01-01

    Recent model development of the Zodiacal Dust Cloud (ZDC) model (Nesvorny et al. 2010, 2011b) argue that the incoming flux of meteoric material into the Earth's upper atmosphere is mostly undetected by radars because they cannot detect small extraterrestrial particles entering the atmosphere at low velocities due to the relatively small production of electrons. In this paper we present a new methodology utilizing meteor head echo radar observations that aims to constrain the ZDC physical model by ground-based measurements. In particular, for this work, we focus on Arecibo 430 MHz observations since this is the most sensitive radar utilized for this type of observations to date. For this, we integrate and employ existing comprehensive models of meteoroid ablation, ionization and radar detection to enable accurate interpretation of radar observations and show that reasonable agreement in the hourly rates is found between model predictions and Arecibo observations when: 1) we invoke the lower limit of the model predicted flux (approximately 16 t/d) and 2) we estimate the ionization probability of ablating metal atoms using laboratory measurements of the ionization cross sections of high speed metal atom beams, resulting in values up to two orders of magnitude lower than the extensively utilized figure reported by Jones (1997) for low speeds meteors. However, even at this lower limit the model over predicts the slow portion of the Arecibo radial velocity distributions by a factor of 3, suggesting the model requires some revision.

  10. Radar detectability studies of slow and small zodiacal dust cloud particles. I. The case of Arecibo 430 MHz meteor head echo observations

    SciT

    Janches, D.; Plane, J. M. C.; Feng, W.

    2014-11-20

    Recent model development of the Zodiacal Dust Cloud (ZDC) argues that the incoming flux of meteoric material into the Earth's upper atmosphere is mostly undetected by radars because they cannot detect small extraterrestrial particles entering the atmosphere at low velocities due to the relatively small production of electrons. In this paper, we present a new methodology utilizing meteor head echo radar observations that aims to constrain the ZDC physical model by ground-based measurements. In particular, for this work, we focus on Arecibo 430 MHz observations since this is the most sensitive radar utilized for this type of observations to date.more » For this, we integrate and employ existing comprehensive models of meteoroid ablation, ionization, and radar detection to enable accurate interpretation of radar observations and show that reasonable agreement in the hourly rates is found between model predictions and Arecibo observations when (1) we invoke the lower limit of the model predicted flux (∼16 t d{sup –1}) and (2) we estimate the ionization probability of ablating metal atoms using laboratory measurements of the ionization cross sections of high-speed metal atom beams, resulting in values up to two orders of magnitude lower than the extensively utilized figure reported by Jones for low-speed meteors. However, even at this lower limit, the model overpredicts the slow portion of the Arecibo radial velocity distributions by a factor of three, suggesting that the model requires some revision.« less

  11. Zodiacal light as an indicator of interplanetary dust

    NASA Technical Reports Server (NTRS)

    Weinberg, J. L.; Sparrow, J. G.

    1978-01-01

    The most striking feature of the night sky in the tropics is the zodiacal light, which appears as a cone in the west after sunset and in the east before sunrise. It is caused by sunlight scattered or absorbed by particles in the interplanetary medium. The zodiacal light is the only source of information about the integrated properties of the whole ensemble of interplanetary dust. The brightness and polarization in different directions and at different colors can provide information on the optical properties and spatial distribution of the scattering particles. The zodiacal light arises from two independent physical processes related to the scattering of solar continuum radiation by interplanetary dust and to thermal emission which arises from solar radiation that is absorbed by interplanetary dust and reemitted mainly at infrared wavelengths. Attention is given to observational parameters of zodiacal light, the methods of observation, errors and absolute calibration, and the observed characteristics of zodiacal light.

  12. Zodiacal emission. III - Dust near the asteroid belt

    NASA Technical Reports Server (NTRS)

    Reach, William T.

    1992-01-01

    Properties of the zodiacal dust bands are derived from fits to Infrared Astronomical Satellite profiles of the ecliptic. Three observations lead to the conclusion that the dust-band material is spread over a range of heliocentric distances between the asteroid belt and the sun: parallax, color temperature, and wavelength dependence of the band latitudes. The orientations of the midplanes of the bands are found to be typical of asteroids. A model of 'migrating bands', wherein dust is produced near the asteroid belt and spirals into the sun under the influence of Poynting-Robertson drag, is used to explain the range of heliocentric distances of dust-band material.

  13. Signatures of planets: Observations and modeling of structure in the zodiacal cloud and Kuiper disk

    NASA Astrophysics Data System (ADS)

    Holmes, Elizabeth Katherine

    2002-12-01

    There is a possible connection between structure in evolved circumstellar disks and the presence of planets, our own zodiacal cloud being a proven example. Asymmetries in such a disk could be diagnostic of planets which would be otherwise undetectable. Using COBE DIRBE observations, we link structure in the zodiacal cloud, namely the warp and offset of the cloud, to the presence of planets using secular perturbation theory. In addition, we obtain supplementary ISO observations and determine a scale factor for the data which we apply to calibrate the data to the observed COBE brightness. A Kuiper dust disk will have a resonant structure, with two concentrations in brightness along the ecliptic longitude arising because 10 15% of the Kuiper belt objects are in the 3:2 mean motion resonance with Neptune. We run numerical integrations of particles originating from source bodies trapped in the 3:2 resonance and we determine what percentage of particles remain in the resonance for a variety of particle and source body sizes. The dynamical evolution of the particles is followed from source to sink with Poynting- Robertson light drag, solar wind drag, radiation pressure, the Lorentz force, neutral interstellar gas drag, and the effects of planetary gravitational perturbations included. We then conduct an observational search in the 60 μm COBE data for the Kuiper disk, which is predicted to be, at most, a few percent of the brightness of the zodiacal cloud. By removing emission due to the background zodiacal cloud and the dust bands, we expect to see the trailing/leading signature of Earth's resonant ring. However, when subtracted from the data, we find that none of the empirical background zodiacal cloud models give the residuals predicted by theory. We conclude that a dynamical two-component (both inner and outer) zodiacal cloud model must be created to complete the search. Lastly, we extend our work outside the solar system and obtain upper limits on the flux around ten

  14. Clementine Observations of the Zodiacal Light and the Dust Content of the Inner Solar System

    NASA Technical Reports Server (NTRS)

    Hahn, Joseph M.; Zook, Herbert A.; Cooper, Bonnie; Sunkara, Bhaskar

    2002-01-01

    Using the Moon to occult the Sun, the Clementine spacecraft used its navigation cameras to map the inner zodiacal light at optical wavelengths over elongations of 3 approx. less than epsilon approx. less than 30 deg from the Sun. This surface brightness map is then used to infer the spatial distribution of interplanetary dust over heliocentric distances of about 10 solar radii to the orbit of Venus. The averaged ecliptic surface brightness of the zodiacal light falls off as Z(epsilon) is a member of epsilon(sup -2.45 +/- 0.05), which suggests that the dust cross-sectional density nominally falls off as sigma(r) is a member of r(sup - 1.45 +/- 0.05). The interplanetary dust also has an albedo of alpha approx. = 0.1 that is uncertain by a factor of approx. 2. Asymmetries of approx. 10% are seen in directions east-west and north-south of the Sun, and these may be due the giant planets' secular gravitational perturbations. We apply a simple model that attributes the zodiacal light as due to three dust populations having distinct inclination distributions, namely, dust from asteroids and Jupiter-family comets (JFCs) having characteristic inclinations of i approx. 7 deg, dust from Halley-type comets having i approx. 33 deg, and an isotropic cloud of dust from Oort Cloud comets. The best-fitting scenario indicates that asteroids + JFCs are the source of about 45% of the optical dust cross section seen in the ecliptic at 1 AU but that at least 89% of the dust cross section enclosed by a 1-AU-radius sphere is of a cometary origin. Each population's radial density variations can also deviate somewhat from the nominal sigma(r) is a member of r(sup -1.45). When these results are extrapolated out to the asteroid belt, we find an upper limit on the mass of the light-reflecting asteroidal dust that is equivalent to a 12-km asteroid, and a similar extrapolation of the isotropic dust cloud out to Oort Cloud distances yields a mass equivalent to a 30-km comet, although the latter

  15. Extra-Zodiacal-Cloud Astronomy via Solar Electric Propulsion

    NASA Technical Reports Server (NTRS)

    Benson, Scott W.; Falck, Robert D.; Oleson, Steven R.; Greenhouse, Matthew A.; Kruk, Jeffrey W.; Gardner, Jonathan P.; Thronson, Harley A.; Vaughn, Frank J.; Fixsen, Dale J.

    2011-01-01

    Solar electric propulsion (SEP) is often considered as primary propulsion for robotic planetary missions, providing the opportunity to deliver more payload mass to difficult, high-delta-velocity destinations. However, SEP application to astrophysics has not been well studied. This research identifies and assesses a new application of SEP as primary propulsion for low-cost high-performance robotic astrophysics missions. The performance of an optical/infrared space observatory in Earth orbit or at the Sun-Earth L2 point (SEL2) is limited by background emission from the Zodiacal dust cloud that has a disk morphology along the ecliptic plane. By delivering an observatory to a inclined heliocentric orbit, most of this background emission can be avoided, resulting in a very substantial increase in science performance. This advantage enabled by SEP allows a small-aperture telescope to rival the performance of much larger telescopes located at SEL2. In this paper, we describe a novel mission architecture in which SEP technology is used to enable unprecedented telescope sensitivity performance per unit collecting area. This extra-zodiacal mission architecture will enable a new class of high-performance, short-development time, Explorer missions whose sensitivity and survey speed can rival flagship-class SEL2 facilities, thus providing new programmatic flexibility for NASA's astronomy mission portfolio. A mission concept study was conducted to evaluate this application of SEP. Trajectory analyses determined that a 700 kg-class science payload could be delivered in just over 2 years to a 2 AU mission orbit inclined 15 to the ecliptic using a 13 kW-class NASA's Evolutionary Xenon Thruster (NEXT) SEP system. A mission architecture trade resulted in a SEP stage architecture, in which the science spacecraft separates from the stage after delivery to the mission orbit. The SEP stage and science spacecraft concepts were defined in collaborative engineering environment studies. The

  16. Is the zodiacal light intensity steady. [cloud surface brightness and polarization from OSO-5 data

    NASA Technical Reports Server (NTRS)

    Burnett, G. B.; Sparrow, J. G.; Ney, E. P.

    1974-01-01

    It is pointed out that conclusions reported by Sparrow and Ney (1972, 1973) could be confirmed in an investigation involving the refinement of OSO-5 data on zodiacal light. It had been found by Sparrow and Ney that the absolute value of both the surface brightness and polarization of the zodiacal cloud varied by less than 10% over the 4-yr period from January 1969 to January 1973.

  17. Mid-Infrared Spectrum of the Zodiacal Emission: Detection of Crystalline Silicates in Interplanetary Dust

    NASA Technical Reports Server (NTRS)

    Ootsubo, T.; Onaka, T.; Yamamura, I.; Ishihara, D.; Tanabe, T.; Roellig, T. L.

    2003-01-01

    Within a few astronomical units of the Sun the solar system is filled with interplanetary dust, which is believed to be dust of cometary and asteroidal origin. Spectroscopic observations of the zodiacal emission with moderate resolution provide key information on the composition and size distribution of the dust in the interplanetary space. They can be compared directly to laboratory measurements of candidate materials, meteorites, and dust particles collected in the stratosphere. Recently mid-infrared spectroscopic observations of the zodiacal emission have been made by two instruments on board the Infrared Space Observatory; the camera (ISOCAM) and the spectrophotometer (ISOPHOT-S). A broad excess emission feature in the 9-11 micron range is reported in the ISOCAM spectrum, whereas the ISOPHOT-S spectra in 6-12 microns can be well fitted by a blackbody radiation without spectral features.

  18. The NGST and the Zodiacal Light in the Solar System

    NASA Technical Reports Server (NTRS)

    Gorkavyi, Nick; Ozernoy, Leonid; Mather, John; Taidakova, Tanya

    1999-01-01

    We develop a physical model of the zodiacal cloud incorporating the real dust sources of asteroidal, cometary, and kuiperoidal origin. Using the inferred distribution of the zodiacal dust, we compute its thermal emission and scattering at several wavelengths (1.25, 5, and 20 micron) as a function of NGST location assumed to be at 1 AU or 3 AU. Areas on the sky with a minimum of zodiacal light are determined.

  19. Modeling the effects of an offset of the center of symmetry in the zodiacal cloud

    NASA Astrophysics Data System (ADS)

    Holmes, E. K.; Dermott, S. F.; Xu, Y. L.; Wyatt, M.; Jayaraman, S.

    1998-04-01

    There is a possible connection between structure in circumstellar dust clouds and the presence of planets, our own zodiacal cloud being the prime example. Asymmetries in such clouds could be diagnostic of planets which would be otherwise undetectable. One such feature is an offset of the center of symmetry of the disk with respect to the central star. The offset is caused by the forced eccentricities (ef) of particles in the cloud. The orbit of a particle can be described by a set of five orbital elements: the semi-major axis (a), eccentricity (e), inclination (I), longitude of ascending node (Omega) and the argument of pericenter (omega). In low order secular perturbation theory, osculating elements of small bodies are decomposed into proper and forced elements. The proper elements are dependent on initial conditions while the forced elements are imposed on the particle's orbit by the gravitational perturbations of the planets. This decomposition is still applicable in the presence of drag forces. We compare COBE observations of the variation in average polar brightness of the background cloud, (N + S)/2, with ecliptic longitude of Earth with those of a model cloud made of asteroidal particles which populate the inner solar system according to a 1/rgamma where (gamma) = 1 (Poynting Robertson light drag) distribution. The variation with ecliptic longitude of Earth in mean polar brightness is shown in for the 25 micron waveband. Sine curves are fit to both the COBE observations and the model. The variation in (N+S)/2 with ecliptic longitude of Earth can be represented as a superposition of two sine curves: one for the variation in (N + S)/2 due to the Earth's eccentric orbit and the other for the variation in (N + S)/2 due to the forced eccentricities of particles in the cloud. If the cloud were symmetric about the Sun (i.e., if there were no offset), the maximum and minimum brightnesses of the cloud would occur at perihelion and aphelion, respectively. Looking at

  20. Dynamical Model for the Zodiacal Cloud and Sporadic Meteors

    NASA Technical Reports Server (NTRS)

    Nesvorny, David; Janches, Diego; Vokrouhlicky, David; Pokorny, Petr; Bottke, William F.; Jenniskens, Peter

    2011-01-01

    The solar system is dusty, and would become dustier over time as asteroids collide and comets disintegrate, except that small debris particles in interplanetary space do not last long. They can be ejected from the solar system by Jupiter, thermally destroyed near the Sun, or physically disrupted by collisions. Also, some are swept by the Earth (and other planets), producing meteors. Here we develop a dynamical model for the solar system meteoroids and use it to explain meteor radar observations. We find that the Jupiter Family Comets (JFCs) are the main source of the prominent concentrations of meteors arriving to the Earth from the helion and antihelion directions. To match the radiant and orbit distributions, as measured by the Canadian Meteor Orbit Radar (CMOR) and Advanced Meteor Orbit Radar (AMOR), our model implies that comets, and JFCs in particular, must frequently disintegrate when reaching orbits with low perihelion distance. Also, the collisional lifetimes of millimeter particles may be longer (approx. > 10(exp 5) yr at 1 AU) than postulated in the standard collisional models (approx 10(exp 4) yr at 1 AU), perhaps because these chondrule-sized meteoroids are stronger than thought before. Using observations of the Infrared Astronomical Satellite (IRAS) to calibrate the model, we find that the total cross section and mass of small meteoroids in the inner solar system are (1.7-3.5) 10(exp 11) sq km and approx. 4 10(exp 19) g, respectively, in a good agreement with previous studies. The mass input required to keep the Zodiacal Cloud (ZC) in a steady state is estimated to be approx. 10(exp 4)-10(exp 5) kg/s. The input is up to approx 10 times larger than found previously, mainly because particles released closer to the Sun have shorter collisional lifetimes, and need to be supplied at a faster rate. The total mass accreted by the Earth in particles between diameters D = 5 micron and 1 cm is found to be approx 15,000 tons/yr (factor of 2 uncertainty), which is

  1. Dynamical Model for the Zodiacal Cloud and Sporadic Meteors

    NASA Astrophysics Data System (ADS)

    Nesvorný, David; Janches, Diego; Vokrouhlický, David; Pokorný, Petr; Bottke, William F.; Jenniskens, Peter

    2011-12-01

    The solar system is dusty, and would become dustier over time as asteroids collide and comets disintegrate, except that small debris particles in interplanetary space do not last long. They can be ejected from the solar system by Jupiter, thermally destroyed near the Sun, or physically disrupted by collisions. Also, some are swept by the Earth (and other planets), producing meteors. Here we develop a dynamical model for the solar system meteoroids and use it to explain meteor radar observations. We find that the Jupiter Family Comets (JFCs) are the main source of the prominent concentrations of meteors arriving at the Earth from the helion and antihelion directions. To match the radiant and orbit distributions, as measured by the Canadian Meteor Orbit Radar (CMOR) and Advanced Meteor Orbit Radar (AMOR), our model implies that comets, and JFCs in particular, must frequently disintegrate when reaching orbits with low perihelion distance. Also, the collisional lifetimes of millimeter particles may be longer (gsim 105 yr at 1 AU) than postulated in the standard collisional models (~104 yr at 1 AU), perhaps because these chondrule-sized meteoroids are stronger than thought before. Using observations of the Infrared Astronomical Satellite to calibrate the model, we find that the total cross section and mass of small meteoroids in the inner solar system are (1.7-3.5) × 1011 km2 and ~4 × 1019 g, respectively, in a good agreement with previous studies. The mass input required to keep the zodiacal cloud in a steady state is estimated to be ~104-105 kg s-1. The input is up to ~10 times larger than found previously, mainly because particles released closer to the Sun have shorter collisional lifetimes and need to be supplied at a faster rate. The total mass accreted by the Earth in particles between diameters D = 5 μm and 1 cm is found to be ~15,000 tons yr-1 (factor of two uncertainty), which is a large share of the accretion flux measured by the Long Term Duration

  2. DYNAMICAL MODEL FOR THE ZODIACAL CLOUD AND SPORADIC METEORS

    SciT

    Nesvorny, David; Vokrouhlicky, David; Pokorny, Petr

    2011-12-20

    The solar system is dusty, and would become dustier over time as asteroids collide and comets disintegrate, except that small debris particles in interplanetary space do not last long. They can be ejected from the solar system by Jupiter, thermally destroyed near the Sun, or physically disrupted by collisions. Also, some are swept by the Earth (and other planets), producing meteors. Here we develop a dynamical model for the solar system meteoroids and use it to explain meteor radar observations. We find that the Jupiter Family Comets (JFCs) are the main source of the prominent concentrations of meteors arriving atmore » the Earth from the helion and antihelion directions. To match the radiant and orbit distributions, as measured by the Canadian Meteor Orbit Radar (CMOR) and Advanced Meteor Orbit Radar (AMOR), our model implies that comets, and JFCs in particular, must frequently disintegrate when reaching orbits with low perihelion distance. Also, the collisional lifetimes of millimeter particles may be longer ({approx}> 10{sup 5} yr at 1 AU) than postulated in the standard collisional models ({approx}10{sup 4} yr at 1 AU), perhaps because these chondrule-sized meteoroids are stronger than thought before. Using observations of the Infrared Astronomical Satellite to calibrate the model, we find that the total cross section and mass of small meteoroids in the inner solar system are (1.7-3.5) Multiplication-Sign 10{sup 11} km{sup 2} and {approx}4 Multiplication-Sign 10{sup 19} g, respectively, in a good agreement with previous studies. The mass input required to keep the zodiacal cloud in a steady state is estimated to be {approx}10{sup 4}-10{sup 5} kg s{sup -1}. The input is up to {approx}10 times larger than found previously, mainly because particles released closer to the Sun have shorter collisional lifetimes and need to be supplied at a faster rate. The total mass accreted by the Earth in particles between diameters D = 5 {mu}m and 1 cm is found to be {approx

  3. The Zodiacal Cloud Model applied to the Martian atmosphere. Diurnal variations in meteoric ion layers

    NASA Astrophysics Data System (ADS)

    Carrillo-Sánchez, J. D.; Plane, J. M. C.; Withers, P.; Fallows, K.; Nesvorny, D.; Pokorný, P.

    2016-12-01

    Sporadic metal layers have been detected in the Martian atmosphere by radio occultation measurements using the Mars Express Orbiter and Mars Global Surveyor spacecraft. More recently, metallic ion layers produced by the meteor storm event following the close encounter between Comet Siding Spring (C/2013 A1) and Mars were identified by the Imaging UltraViolet Spectrograph (IUVS) and the Neutral Gas and Ion Mass Spectrometer (NGIMS) on the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Work is now in progress to detect the background metal layers produced by the influx of sporadic meteors. In this study we predict the likely appearance of these layers. The Zodiacal Dust Cloud (ZDC) model for particle populations released by asteroids (AST), and dust grains from Jupiter Family Comets (JFCs) and Halley-Type Comets (HTCs) has been combined with a Monte Carlo sampling method and the Chemical ABlation MODel (CABMOD) to predict the ablation rates of Na, K, Fe, Si, Mg, Ca and Al above 40 km altitude in the Martian atmosphere. CABMOD considers the standard treatment of meteor physics, including the balance of frictional heating by radiative losses and the absorption of heat energy through temperature increases, melting phase transitions and vaporization, as well as sputtering by inelastic collisions with the air molecules. The vertical injection profiles are input into the Leeds 1-D Mars atmospheric model which includes photo-ionization, and gas-phase ion-molecule and neutral chemistry, in order to explore the evolution of the resulting metallic ions and atoms. We conclude that the dominant contributor in the Martian's atmosphere is the JFCs over other sources. Finally, we explore the changes of the neutral and ionized Na, Mg and Fe layers over a diurnal cycle.

  4. A Characterization of the Hot Infrared Background: The Infrared Cirrus, Zodiacal Dust Bands, and Solar System Dust Trails

    DTIC Science & Technology

    1991-04-01

    AD-A239 132 PL -TR-91-2065 A CHARACTERIZATION OF THE HOT INFRARED BACKGROUND: THE INFRARED CIRRUS, ZODIACAL DUST BANDS, AND SOLAR SYSTEM DUST TRAILS F...addressee is no longer employed by your organization, please notify OL-AA PL /IMA, Hanscom AFB, MA 01731. This will assist us in maintaining a current...DECLASSIFICATION /DOWNGRADING SCHEDULE Distribution unlimited 4 PERFORMING ORGANIZATION REPORT NUMBER(S) S MONITORING ORGANIZATION REPORT NUMBER(S) PL -TR-91-2065 6a

  5. Sahara Dust Cloud

    2005-07-15

    In July of 2005, a continent-sized cloud of hot air and dust originating from the Sahara Desert crossed the Atlantic Ocean and headed towards Florida and the Caribbean, captured by the Atmospheric Infrared Sounder onboard NASA Aqua satellite. A Saharan Air Layer, or SAL, forms when dry air and dust rise from Africa's west coast and ride the trade winds above the Atlantic Ocean. These dust clouds are not uncommon, especially during the months of July and August. They start when weather patterns called tropical waves pick up dust from the desert in North Africa, carry it a couple of miles into the atmosphere and drift westward. http://photojournal.jpl.nasa.gov/catalog/PIA00448

  6. Sahara Dust Cloud

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Dust Particles Click on the image for Quicktime movie from 7/15-7/24

    A continent-sized cloud of hot air and dust originating from the Sahara Desert crossed the Atlantic Ocean and headed towards Florida and the Caribbean. A Saharan Air Layer, or SAL, forms when dry air and dust rise from Africa's west coast and ride the trade winds above the Atlantic Ocean.

    These dust clouds are not uncommon, especially during the months of July and August. They start when weather patterns called tropical waves pick up dust from the desert in North Africa, carry it a couple of miles into the atmosphere and drift westward.

    In a sequence of images created by data acquired by the Earth-orbiting Atmospheric Infrared Sounder ranging from July 15 through July 24, we see the distribution of the cloud in the atmosphere as it swirls off of Africa and heads across the ocean to the west. Using the unique silicate spectral signatures of dust in the thermal infrared, AIRS can detect the presence of dust in the atmosphere day or night. This detection works best if there are no clouds present on top of the dust; when clouds are present, they can interfere with the signal, making it much harder to detect dust as in the case of July 24, 2005.

    In the Quicktime movie, the scale at the bottom of the images shows +1 for dust definitely detected, and ranges down to -1 for no dust detected. The plots are averaged over a number of AIRS observations falling within grid boxes, and so it is possible to obtain fractional numbers. [figure removed for brevity, see original site] Total Water Vapor in the Atmosphere Around the Dust Cloud Click on the image for Quicktime movie

    The dust cloud is contained within a dry adiabatic layer which originates over the Sahara Desert. This Saharan Air Layer (SAL) advances Westward over the Atlantic Ocean, overriding the cool, moist air nearer the surface. This burst of very dry air is visible in the

  7. Clouds and Dust Storms

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 2 July 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth.

    Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms.

    This image was acquired during mid-spring near the North Pole. The linear water-ice clouds are now regional in extent and often interact with neighboring cloud system, as seen in this image. The bottom of the image shows how the interaction can destroy the linear nature. While the surface is still visible through most of the clouds, there is evidence that dust is also starting to enter the atmosphere.

    Image information: VIS instrument. Latitude 68.4, Longitude 180 East (180 West). 38 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with

  8. Dust Cloud, Mid Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    1991-01-01

    This view of a dust cloud from a Sahara Desert, North Africa dust storm was taken over the Mid Atlantic Ocean, some 1700 miles from the African coast (24.5N, 45.0W). Dust, sand and other particulate matter from arid regions is frequently stirred up by fast blowing desert winds and carried aloft to high altitudes where it may be transported great distances, sometimes as much as half way around the world.

  9. Cloud Ozone Dust Imager (CODI)

    NASA Astrophysics Data System (ADS)

    Clancy, R. Todd; Dusenbery, Paul; Wolff, Michael; James, Phil; Allen, Mark; Goguen, Jay; Kahn, Ralph; Gladstone, Rany; Murphy, Jim

    1995-01-01

    The Cloud Ozone Dust Imager (CODI) is proposed to investigate the current climatic balance of the Mars atmosphere, with particular emphasis on the important but poorly understood roles which dust and water ice aerosols play in this balance. The large atmospheric heating (20-50 K) resulting from global dust storms around Mars perihelion is well recognized. However, groundbased observations of Mars atmospheric temperatures, water vapor, and clouds since the Viking missions have identified a much colder, cloudier atmosphere around Mars aphelion that may prove as important as global dust storms in determining the interannual and long-term behavior of the Mars climate. The key climate issues CODI is designed to investigate are: 1) the degree to which non-linear interactions between atmospheric dust heating, water vapor saturation, and cloud nucleation influence the seasonal and interannual variability of the Mars atmosphere, and 2) whether the strong orbital forcing of atmospheric dust loading, temperatures and water vapor saturation determines the long-term balance of Mars water, as reflected in the north-south hemispheric asymmetries of atmospheric water vapor and polar water ice abundances. The CODI experiment will measure the daily, seasonal and (potentially) interannual variability of atmospheric dust and cloud opacities, and the key physical properties of these aerosols which determine their role in the climate cycles of Mars. CODI is a small (1.2 kg), fixed pointing camera, in which four wide-angle (+/- 70 deg) lenses illuminate fixed filters and CCD arrays. Simultaneous sky/surface imaging of Mars is obtained at an angular resolution of 0.28 deg/pixel for wavelengths of 255, 336, 502, and 673 nm (similar to Hubble Space Telescope filters). These wavelengths serve to measure atmospheric ozone (255 and 336 nm), discriminate ice and dust aerosols (336 and 673 nm), and construct color images (336, 502, and 673 nm). The CODI images are detected on four 512 x 512

  10. Exozodiacal clouds: hot and warm dust around main sequence stars

    NASA Astrophysics Data System (ADS)

    Kral, Quentin; Krivov, Alexander V.; Defrère, Denis; van Lieshout, Rik; Bonsor, Amy; Augereau, Jean-Charles; Thébault, Philippe; Ertel, Steve; Lebreton, Jérémy; Absil, Olivier

    2017-04-01

    A warm/hot dust component (at temperature $>$ 300K) has been detected around $\\sim$ 20% of stars. This component is called "exozodiacal dust" as it presents similarities with the zodiacal dust detected in our Solar System, even though its physical properties and spatial distribution can be significantly different. Understanding the origin and evolution of this dust is of crucial importance, not only because its presence could hamper future detections of Earth-like planets in their habitable zones, but also because it can provide invaluable information about the inner regions of planetary systems. In this review, we present a detailed overview of the observational techniques used in the detection and characterisation of exozodiacal dust clouds ("exozodis") and the results they have yielded so far, in particular regarding the incidence rate of exozodis as a function of crucial parameters such as stellar type and age, or the presence of an outer cold debris disc. We also present the important constraints that have been obtained, on dust size distribution and spatial location, by using state-of-the-art radiation transfer models on some of these systems. Finally, we investigate the crucial issue of how to explain the presence of exozodiacal dust around so many stars (regardless of their ages) despite the fact that such dust so close to its host star should disappear rapidly due to the coupled effect of collisions and stellar radiation pressure. Several potential mechanisms have been proposed to solve this paradox and are reviewed in detail in this paper. The review finishes by presenting the future of this growing field.

  11. History of the dust released by comets

    NASA Technical Reports Server (NTRS)

    Jambor, B. J.

    1976-01-01

    The Finson-Brobstein theory is used to examine production and history of dust released from periodic comets and to compare dust size distribution in relation to the Zodiacal cloud. Results eliminate all of the bright new comets from contributors to the Zodiacal cloud. Among the periodic comets, all particles of size much smaller than 10 micrometer are also lost. Only the large particles remain as possible contributors.

  12. The exo-zodiacal disk mapper

    NASA Technical Reports Server (NTRS)

    Petro, Larry; Bely, P.; Burg, R.; Wade, L.; Beichman, C.; Gay, J.; Baudoz, P.; Rabbia, Y.; Perrin, J. M.

    1998-01-01

    Zodiacal dust around neighboring stars could obscure the signal of terrestrial planets observed with the Terrestrial Planet Finder (TPF) if that dust is similar to that in the Solar System. Unfortunately, little is known about the presence, or frequency of occurrence of zodiacal dust around stars and so the relevance of zodiacal dust to the design of the TPF, or to the TPF mission, is unknown. It is likely that direct observation of zodiacal dust disks will be necessary to confidently determine the characteristics of individual systems. A survey of a large number of stars in the solar neighborhood that could be candidates for observation with TPF should be undertaken. We present a concept for a space mission to undertake a sensitive, large-scale survey capable of characterizing solar-system-like zodiacal dust around 400 stars within 20 pc of the Sun.

  13. Parameterization of cloud glaciation by atmospheric dust

    NASA Astrophysics Data System (ADS)

    Nickovic, Slobodan; Cvetkovic, Bojan; Madonna, Fabio; Pejanovic, Goran; Petkovic, Slavko

    2016-04-01

    The exponential growth of research interest on ice nucleation (IN) is motivated, inter alias, by needs to improve generally unsatisfactory representation of cold cloud formation in atmospheric models, and therefore to increase the accuracy of weather and climate predictions, including better forecasting of precipitation. Research shows that mineral dust significantly contributes to cloud ice nucleation. Samples of residual particles in cloud ice crystals collected by aircraft measurements performed in the upper tropopause of regions distant from desert sources indicate that dust particles dominate over other known ice nuclei such as soot and biological particles. In the nucleation process, dust chemical aging had minor effects. The observational evidence on IN processes has substantially improved over the last decade and clearly shows that there is a significant correlation between IN concentrations and the concentrations of coarser aerosol at a given temperature and moisture. Most recently, due to recognition of the dominant role of dust as ice nuclei, parameterizations for immersion and deposition icing specifically due to dust have been developed. Based on these achievements, we have developed a real-time forecasting coupled atmosphere-dust modelling system capable to operationally predict occurrence of cold clouds generated by dust. We have been thoroughly validated model simulations against available remote sensing observations. We have used the CNR-IMAA Potenza lidar and cloud radar observations to explore the model capability to represent vertical features of the cloud and aerosol vertical profiles. We also utilized the MSG-SEVIRI and MODIS satellite data to examine the accuracy of the simulated horizontal distribution of cold clouds. Based on the obtained encouraging verification scores, operational experimental prediction of ice clouds nucleated by dust has been introduced in the Serbian Hydrometeorological Service as a public available product.

  14. Dust scattering from the Taurus Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Narayan, Sathya; Murthy, Jayant; Karuppath, Narayanankutty

    2017-04-01

    We present an analysis of the diffuse ultraviolet emission near the Taurus Molecular Cloud based on observations made by the Galaxy Evolution Explorer. We used a Monte Carlo dust scattering model to show that about half of the scattered flux originates in the molecular cloud with 25 per cent arising in the foreground and 25 per cent behind the cloud. The best-fitting albedo of the dust grains is 0.3, but the geometry is such that we could not constrain the phase function asymmetry factor (g).

  15. The dust cloud of the century

    NASA Astrophysics Data System (ADS)

    Robock, A.

    1983-02-01

    The structure and composition of the dust cloud from the 4 April 1982 eruption of the El Chichon volcano in Chiapas state, Mexico, is examined and the possible effects of the dust cloud on the world's weather patterns are discussed. Observations of the cloud using a variety of methods are evaluated, including data from the GOES and NOAA-7 weather satellites, vertically pointing lidar measurements, the SME satellite, and the Nimbus-7 satellite. Studies of the gaseous and particulate composition of the cloud reveal the presence of large amounts of sulfuric acid particles, which have a long mean residence time in the atmosphere and have a large effect on the amount of solar radiation received at the earth's surface by scattering several percent of the radiation back to space. Estimates of the effect of this cloud on surface air temperature changes are presented based on findings from climate models.

  16. Dust in the Small Magellanic Cloud

    NASA Technical Reports Server (NTRS)

    Rodrigues, C. V.; Coyne, G. V.; Magalhaes, A. M.

    1995-01-01

    We discuss simultaneous dust model fits to our extinction and polarization data for the Small Magellanic Cloud (SMC) using existing dust models. Dust model fits to the wavelength dependent polarization are possible for stars with small lambda(sub max). They generally imply size distributions which are narrower and have smaller average sizes compared to those in the Galaxy. The best fits for the extinction curves are obtained with a power law size distribution. The typical, monotonic SMC extinction curve can be well fit with graphite and silicate grains if a small fraction of the SMC carbon is locked up in the grains. Amorphous carbon and silicate grains also fit the data well.

  17. Volcanic Plume from Mt. Unzen, Dust Cloud, cloud Vortices

    1991-12-01

    Stable, south flowing air over the western Pacific Ocean (26.0N, 131.0E) is disturbed by islands south of Korea, resulting in sinuous clouds known as von Karman vortices. The smoke plume from Japan's Mount Unzen Volcano on Kyushu, is visible just west of the large cloud mass and extending southward. A very large, purple tinged dust pall, originating in Mongolia, can be seen on the Earth's Limb, covering eastern China and extending into the East China Sea.

  18. The Zodiacal Emission Spectrum as Determined by COBE and its Implications

    NASA Technical Reports Server (NTRS)

    Fixsen, D. J.; Dwek, Eli; Oliversen, R. (Technical Monitor)

    2002-01-01

    We combine observations from the DIRBE and FIRAS instruments on the COBE satellite to derive an annually-averaged spectrum of the zodiacal cloud in the 10 to 1000 micron wavelength region. The spectrum exhibits a break at approx. 150 microns which indicates a sharp break in the dust size distribution at a radius of about 30 microns The spectrum can be fit with a single blackbody with a lambda(exp -2) emissivity law beyond 150 microns and a temperature of 240 K. We also used a more realistic characterization of the cloud to fit the spectrum, including a distribution of dust temperatures, representing different dust compositions and distances from the sun, as well as a realistic representation of the spatial distribution of the dust. We show that amorphous carbon and silicate dust with respective temperatures of 280 and 274 K at 1 AU, and size distributions with a break at grain radii of 14 and 32 microns, can provide a good fit to the average zodiacal dust spectrum. The total mass of the zodiacal cloud is 2 to 11 Eg (Eg=10(exp 18) g), depending on the grain composition. The lifetime of the cloud, against particle loss by Poynting- Robertson drag and the effects of solar wind, is about 10(exp 5) yr. The required replenishment rate is approx. 10(exp 14) g/yr. If this is provided by asteroid belt alone, the asteroids lifetime would be approx. 3 x 10(exp 10) yr. But comets and Kuiper belt objects may also contribute to the zodiacal cloud.

  19. Evidence of Mineral Dust Altering Cloud Microphysics and Precipitation

    NASA Technical Reports Server (NTRS)

    Min, Qilong; Li, Rui; Lin, Bing; Joseph, Everette; Wang, Shuyu; Hu, Yongxiang; Morris, Vernon; Chang, F.

    2008-01-01

    Multi-platform and multi-sensor observations are employed to investigate the impact of mineral dust on cloud microphysical and precipitation processes in mesoscale convective systems. It is clearly evident that for a given convection strength,small hydrometeors were more prevalent in the stratiform rain regions with dust than in those regions that were dust free. Evidence of abundant cloud ice particles in the dust sector, particularly at altitudes where heterogeneous nucleation process of mineral dust prevails, further supports the observed changes of precipitation. The consequences of the microphysical effects of the dust aerosols were to shift the precipitation size spectrum from heavy precipitation to light precipitation and ultimately suppressing precipitation.

  20. Lidars for smoke and dust cloud diagnostics

    NASA Astrophysics Data System (ADS)

    Fujimura, S. F.; Warren, R. E.; Lutomirski, R. F.

    1980-11-01

    An algorithm that integrates a time-resolved lidar signature for use in estimating transmittance, extinction coefficient, mass concentration, and CL values generated under battlefield conditions is applied to lidar signatures measured during the DIRT-I tests. Estimates are given for the dependence of the inferred transmittance and extinction coefficient on uncertainties in parameters such as the obscurant backscatter-to-extinction ratio. The enhanced reliability in estimating transmittance through use of a target behind the obscurant cloud is discussed. It is found that the inversion algorithm can produce reliable estimates of smoke or dust transmittance and extinction from all points within the cloud for which a resolvable signal can be detected, and that a single point calibration measurement can convert the extinction values to mass concentration for each resolvable signal point.

  1. Modeling Dust in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Zonca, Alberto; Casu, Silvia; Mulas, Giacomo; Aresu, Giambattista; Cecchi-Pestellini, Cesare

    2015-09-01

    We model the extinction profiles observed in the Small and Large Magellanic clouds with a synthetic population of dust grains consisting of core-mantle particles and a collection of free-flying polycyclic aromatic hydrocarbons (PAHs). All different flavors of the extinction curves observed in the Magellanic Clouds (MCs) can be described by the present model, which has been previously (successfully) applied to a large sample of diffuse and translucent lines of sight in the Milky Way. We find that in the MCs the extinction produced by classical grains is generally larger than absorption by PAHs. Within this model, the nonlinear far-UV rise is accounted for by PAHs, whose presence in turn is always associated with a gap in the size distribution of classical particles. This hints either at a physical connection between (e.g., a common cause for) PAHs and the absence of middle-sized dust particles or the need for an additional component in the model that can account for the nonlinear far-UV rise without contributing to the UV bump at ∼217 nm such as, e.g., nanodiamonds.

  2. The temperature of large dust grains in molecular clouds

    NASA Technical Reports Server (NTRS)

    Clark, F. O.; Laureijs, R. J.; Prusti, T.

    1991-01-01

    The temperature of the large dust grains is calculated from three molecular clouds ranging in visual extinction from 2.5 to 8 mag, by comparing maps of either extinction derived from star counts or gas column density derived from molecular observations to I(100). Both techniques show the dust temperature declining into clouds. The two techniques do not agree in absolute scale.

  3. Atmospheric transport of mold spores in clouds of desert dust

    Shinn, E.A.; Griffin, Dale W.; Seba, D.B.

    2003-01-01

    Fungal spores can be transported globally in clouds of desert dust. Many species of fungi (commonly known as molds) and bacteria--including some that are human pathogens--have characteristics suited to long-range atmospheric transport. Dust from the African desert can affect air quality in Africa, Europe, the Middle East, and the Americas. Asian desert dust can affect air quality in Asia, the Arctic, North America, and Europe. Atmospheric exposure to mold-carrying desert dust may affect human health directly through allergic induction of respiratory stress. In addition, mold spores within these dust clouds may seed downwind ecosystems in both outdoor and indoor environments.

  4. On the Effect of Dust Particles on Global Cloud Condensation Nuclei and Cloud Droplet Number

    NASA Technical Reports Server (NTRS)

    Karydis, V. A.; Kumar, P.; Barahona, D.; Sokolik, I. N.; Nenes, A.

    2011-01-01

    Aerosol-cloud interaction studies to date consider aerosol with a substantial fraction of soluble material as the sole source of cloud condensation nuclei (CCN). Emerging evidence suggests that mineral dust can act as good CCN through water adsorption onto the surface of particles. This study provides a first assessment of the contribution of insoluble dust to global CCN and cloud droplet number concentration (CDNC). Simulations are carried out with the NASA Global Modeling Initiative chemical transport model with an online aerosol simulation, considering emissions from fossil fuel, biomass burning, marine, and dust sources. CDNC is calculated online and explicitly considers the competition of soluble and insoluble CCN for water vapor. The predicted annual average contribution of insoluble mineral dust to CCN and CDNC in cloud-forming areas is up to 40 and 23.8%, respectively. Sensitivity tests suggest that uncertainties in dust size distribution and water adsorption parameters modulate the contribution of mineral dust to CDNC by 23 and 56%, respectively. Coating of dust by hygroscopic salts during the atmospheric aging causes a twofold enhancement of the dust contribution to CCN; the aged dust, however, can substantially deplete in-cloud supersaturation during the initial stages of cloud formation and can eventually reduce CDNC. Considering the hydrophilicity from adsorption and hygroscopicity from solute is required to comprehensively capture the dust-warm cloud interactions. The framework presented here addresses this need and can be easily integrated in atmospheric models.

  5. A likely detection of a local interplanetary dust cloud passing near the Earth in the AKARI mid-infrared all-sky map

    NASA Astrophysics Data System (ADS)

    Ishihara, D.; Kondo, T.; Kaneda, H.; Suzuki, T.; Nakamichi, K.; Takaba, S.; Kobayashi, H.; Masuda, S.; Ootsubo, T.; Pyo, J.; Onaka, T.

    2017-07-01

    Context. We are creating the AKARI mid-infrared all-sky diffuse maps. Through a foreground removal of the zodiacal emission, we serendipitously detected a bright residual component whose angular size is about 50° × 20° at a wavelength of 9 μm. Aims: We investigate the origin and the physical properties of the residual component. Methods: We measured the surface brightness of the residual component in the AKARI mid-infrared all-sky maps. Results: The residual component was significantly detected only in 2007 January, even though the same region was observed in 2006 July and 2007 July, which shows that it is not due to the Galactic emission. We suggest that this may be a small cloud passing near the Earth. By comparing the observed intensity ratio of I9 μm/I18 μm with the expected intensity ratio assuming thermal equilibrium of dust grains at 1 AU for various dust compositions and sizes, we find that dust grains in the moving cloud are likely to be much smaller than typical grains that produce the bulk of the zodiacal light. Conclusions: Considering the observed date and position, it is likely that it originates in the solar coronal mass ejection (CME) which took place on 2007 January 25.

  6. Dynamics of Solar System Dust

    NASA Technical Reports Server (NTRS)

    Dermott, Stanley F.

    2002-01-01

    The ongoing aim of the research is to investigate the dynamical and physical evolution of interplanetary dust particles in order to produce a detailed global model of the zodiacal cloud and its constituent components that is capable of predicting thermal fluxes in mid-infrared wave bands to an accuracy of 1% or better; with the additional aim of exploiting this research as a basis for predicting structure in exozodiacal clouds that may be signatures of unseen planets.

  7. Agglomeration of dust in convective clouds initialized by nuclear bursts

    NASA Astrophysics Data System (ADS)

    Bacon, D. P.; Sarma, R. A.

    Convective clouds initialized by nuclear bursts are modeled using a two-dimensional axisymmetric cloud model. Dust transport through the atmosphere is studied using five different sizes ranging from 1 to 10,000 μm in diameter. Dust is transported in the model domain by advection and sedimentation. Water is allowed to condense onto dust particles in regions of supersaturation in the cloud. The agglomeration of dust particles resulting from the collision of different size dust particles is modeled. The evolution of the dust mass spectrum due to agglomeration is modeled using a numerical scheme which is mass conserving and has low implicit diffusion. Agglomeration moves mass from the small particles with very small fall velocity to the larger sizes which fall to the ground more readily. Results indicate that the dust fallout can be increased significantly due to this process. In preliminary runs using stable and unstable environmental soundings, at 30 min after detonation the total dust in the domain was 11 and 30%, respectively, less than a control case without agglomeration.

  8. Inner mean-motion resonances with eccentric planets: a possible origin for exozodiacal dust clouds

    NASA Astrophysics Data System (ADS)

    Faramaz, V.; Ertel, S.; Booth, M.; Cuadra, J.; Simmonds, C.

    2017-02-01

    High levels of dust have been detected in the immediate vicinity of many stars, both young and old. A promising scenario to explain the presence of this short-lived dust is that these analogues to the zodiacal cloud (or exozodis) are refilled in situ through cometary activity and sublimation. As the reservoir of comets is not expected to be replenished, the presence of these exozodis in old systems has yet to be adequately explained. It was recently suggested that mean-motion resonances with exterior planets on moderately eccentric (ep ≳ 0.1) orbits could scatter planetesimals on to cometary orbits with delays of the order of several 100 Myr. Theoretically, this mechanism is also expected to sustain continuous production of active comets once it has started, potentially over Gyr time-scales. We aim here to investigate the ability of this mechanism to generate scattering on to cometary orbits compatible with the production of an exozodi on long time-scales. We combine analytical predictions and complementary numerical N-body simulations to study its characteristics. We show, using order of magnitude estimates, that via this mechanism, low-mass discs comparable to the Kuiper belt could sustain comet scattering at rates compatible with the presence of the exozodis which are detected around Solar-type stars, and on Gyr time-scales. We also find that the levels of dust detected around Vega could be sustained via our proposed mechanism if an eccentric Jupiter-like planet were present exterior to the system's cold debris disc.

  9. Dust in the Small Magellanic Cloud

    NASA Technical Reports Server (NTRS)

    Magalhaes, A. M.

    1993-01-01

    Observations of reddened stars in the Small Magellanic Cloud (SMC) indicate that the interstellar grains in that galaxy may show distinct optical properties from those in the Galaxy. In a careful study of three SMC objects, Prevot showed that the UV extinction law in the SMC is almost linear with inverse wavelength and the 2200A feature is generally absent. The first results of a program to determine the wavelength dependence of the interstellar optical polarization in the SMC indicate that highly polarized objects are scarce. Our study has uncovered, however, several objects with optical polarization greater than around 1 percent: AZV 126, AZV 211, AZV 221, AZV 398, and AZV 456. The latter two have already had their UV extinction law determined. Our aim was to obtain International Ultraviolet Explorer (IUE) data and determine the UV extinction law also for AZV 126, AZV 211, and AZV 221. AZV 456, which presents a 'galactic' extinction law, has a 'normal' value for its wavelength of maximum polarization, lmax, while AZV 398, which shows a 'typical' SMC extinction curve, shows a somewhat smaller value for such wavelength. AZV 126, AZV 211, and AZV 221 all present extreme small values of lmax but had not had its extinction curve in the W determined yet. We therefore aimed at ultimately determining the extinction law in the direction of these three objects. Such results, in combination with the optical polarization data, have an important bearing on constraining the composition and size distribution of the interstellar dust in the SMC. In the last report, the images gathered with IUE, their processing, and the extinction curves derived from them were described. Such extinction curves and the theoretical models developed to interpret the SMC extinction and polarization data are discussed. Details are presented in an enclosed preprint. The activities in our ongoing polarimetric program of determining the magnetic field structure of the SMC and the images collected at

  10. Dust Destruction Rates and Lifetimes in the Magellanic Clouds

    NASA Technical Reports Server (NTRS)

    Temim, Tea; Dwek, Eli; Tchernyshyov, Kirill; Boyer, Martha L.; Meixner, Margaret; Gall, Christa; Roman-Duval, Julia

    2015-01-01

    The nature, composition, abundance, and size distribution of dust in galaxies is determined by the rate at which it is created in the different stellar sources and destroyed by interstellar shocks. Because of their extensive wavelength coverage, proximity, and nearly face-on geometry, the Magellanic Clouds (MCs) provide a unique opportunity to study these processes in great detail. In this paper we use the complete sample of supernova remnants (SNRs) in the MCs to calculate the lifetime and destruction efficiencies of silicate and carbon dust in these galaxies. We find dust lifetimes of 22+/-13 Myr (30+/-17 Myr) for silicate (carbon) grains in the LMC, and 54 +/- 32 Myr (72 +/- 43 Myr) for silicate (carbon) grains in the SMC. The significantly shorter lifetimes in the MCs, as compared to the Milky Way, are explained as the combined effect of their lower total dust mass, and the fact that the dust-destroying isolated SNe in the MCs seem to be preferentially occurring in regions with higher than average dust-to-gas (D2G) mass ratios. We also calculate the supernova rate and the current star formation rate in the MCs, and use them to derive maximum dust injection rates by asymptotic giant branch (AGB) stars and core collapse supernovae (CCSNe). We find that the injection rates are an order of magnitude lower than the dust destruction rates by the SNRs. This supports the conclusion that, unless the dust destruction rates have been considerably overestimated, most of the dust must be reconstituted from surviving grains in dense molecular clouds. More generally, we also discuss the dependence of the dust destruction rate on the local D2G mass ratio and the ambient gas density and metallicity, as well as the application of our results to other galaxies and dust evolution models.

  11. Influence of Saharan dust on cloud glaciation in southern Morocco during the Saharan Mineral Dust Experiment

    NASA Astrophysics Data System (ADS)

    Ansmann, A.; Tesche, M.; Althausen, D.; Müller, D.; Seifert, P.; Freudenthaler, V.; Heese, B.; Wiegner, M.; Pisani, G.; Knippertz, P.; Dubovik, O.

    2008-02-01

    Multiwavelength lidar, Sun photometer, and radiosonde observations were conducted at Ouarzazate (30.9°N, 6.9°W, 1133 m above sea level, asl), Morocco, in the framework of the Saharan Mineral Dust Experiment (SAMUM) in May-June 2006. The field site is close to the Saharan desert. Information on the depolarization ratio, backscatter and extinction coefficients, and lidar ratio of the dust particles, estimates of the available concentration of atmospheric ice nuclei at cloud level, profiles of temperature, humidity, and the horizontal wind vector as well as backward trajectory analysis are used to study cases of cloud formation in the dust with focus on heterogeneous ice formation. Surprisingly, most of the altocumulus clouds that form at the top of the Saharan dust layer, which reaches into heights of 4-7 km asl and has layer top temperatures of -8°C to -18°C, do not show any ice formation. According to the lidar observations the presence of a high number of ice nuclei (1-20 cm-3) does not automatically result in the obvious generation of ice particles, but the observations indicate that cloud top temperatures must typically reach values as low as -20°C before significant ice production starts. Another main finding is that liquid clouds are obviously required before ice crystals form via heterogeneous freezing mechanisms, and, as a consequence, that deposition freezing is not an important ice nucleation process. An interesting case with cloud seeding in the free troposphere above the dust layer is presented in addition. Small water clouds formed at about -30°C and produced ice virga. These virga reached water cloud layers several kilometers below the initiating cloud cells and caused strong ice production in these clouds at temperatures as high as -12°C to -15°C.

  12. Global impact of mineral dust on cloud droplet number concentration

    NASA Astrophysics Data System (ADS)

    Karydis, Vlassis A.; Tsimpidi, Alexandra P.; Bacer, Sara; Pozzer, Andrea; Nenes, Athanasios; Lelieveld, Jos

    2017-05-01

    The importance of wind-blown mineral dust for cloud droplet formation is studied by considering (i) the adsorption of water on the surface of insoluble particles, (ii) particle coating by soluble material (atmospheric aging) which augments cloud condensation nuclei (CCN) activity, and (iii) the effect of dust on inorganic aerosol concentrations through thermodynamic interactions with mineral cations. The ECHAM5/MESSy Atmospheric Chemistry (EMAC) model is used to simulate the composition of global atmospheric aerosol, while the ISORROPIA-II thermodynamic equilibrium model treats the interactions of K+-Ca2+-Mg2+-NH4+-Na+-SO42--NO3--Cl--H2O aerosol with gas-phase inorganic constituents. Dust is considered a mixture of inert material with reactive minerals and its emissions are calculated online by taking into account the soil particle size distribution and chemical composition of different deserts worldwide. The impact of dust on droplet formation is treated through the unified dust activation parameterization that considers the inherent hydrophilicity from adsorption and acquired hygroscopicity from soluble salts during aging. Our simulations suggest that the presence of dust increases cloud droplet number concentration (CDNC) over major deserts (e.g., up to 20 % over the Sahara and the Taklimakan desert) and decreases CDNC over polluted areas (e.g., up to 10 % over southern Europe and 20 % over northeastern Asia). This leads to a global net decrease in CDNC by 11 %. The adsorption activation of insoluble aerosols and the mineral dust chemistry are shown to be equally important for the cloud droplet formation over the main deserts; for example, these effects increase CDNC by 20 % over the Sahara. Remote from deserts the application of adsorption theory is critically important since the increased water uptake by the large aged dust particles (i.e., due to the added hydrophilicity by the soluble coating) reduce the maximum supersaturation and thus cloud droplet

  13. Microgravity combustion of dust clouds: Quenching distance measurements

    NASA Technical Reports Server (NTRS)

    Goroshin, S.; Kleine, H.; Lee, J. H. S.; Frost, D.

    1995-01-01

    The current level of physical understanding of dust combustion phenomena is still in a rudimentary state compared with the understanding of gas combustion processes. The reason for such a lack of fundamental understanding is partially based on the complexity of multiphase combustion and the enormous diversity of chemical-physical properties of heterogeneous combustible mixtures but is largely due to difficulties in the experimental investigation of dust combustion. The influence of gravity on a dust suspension is the main reason. First of all, when particulates (either solid particles or liquid droplets) with a characteristic size of the order of tens of microns are suspended, they rapidly settle in the gravitational field. To maintain a particulate suspension for a time duration adequate to carry out combustion experiments invariably requires continuous convection of particulates at or in excess of the gravitational settling velocity. Of necessity, this makes the experiments turbulent in character and makes it impossible to study laminar dust flames. For particle sizes of the order of microns a stable laminar dust flow can be maintained only for relatively small dust concentrations (e.g., for low fuel equivalence ratios) at normal gravity conditions. High dust loading leads to gravitational instability of the dust cloud and to the formation of recirculation cells in a dust suspension in a confined volume, or to the rapid sedimentation of the dense dust cloud as a whole in an unconfined volume. In addition, many important solid fuels such as low volatile coal, carbon, and boron have low laminar flame speeds (of the order of several centimeters per second). Gravitational convection that occurs in combustion products due to the buoyancy forces disrupts low speed dust flames and, therefore, makes observation of such flames at normal gravity impossible. The only way to carry out 'clean' fundamental experiments in dust combustion over a wide range of dust cloud

  14. Assessment of dust aerosol effect on cloud properties over Northwest China using CERES SSF data

    NASA Astrophysics Data System (ADS)

    Huang, J.; Wang, X.; Wang, T.; Su, J.; Minnis, P.; Lin, B.; Hu, Y.; Yi, Y.

    Dust aerosols not only have direct effects on the climate through reflection and absorption of the short and long wave radiation but also modify cloud properties such as the number concentration and size of cloud droplets indirect effect and contribute to diabatic heating in the atmosphere that often enhances cloud evaporation and reduces the cloud water path In this study indirect and semi-direct effects of dust aerosols are analyzed over eastern Asia using two years June 2002 to June 2004 of CERES Clouds and the Earth s Radiant Energy Budget Scanner and MODIS MODerate Resolution Imaging Spectroradiometer Aqua Edition 1B SSF Single Scanner Footprint data sets The statistical analysis shows evidence for both indirect and semi-direct effect of Asia dust aerosols The dust appears to reduce the ice cloud effective particle diameter and increase high cloud amount On average ice cloud effective particle diameters of cirrus clouds under dust polluted conditions dusty cloud are 11 smaller than those derived from ice clouds in dust-free atmospheric environments The water paths of dusty clouds are also considerably smaller than those of dust-free clouds Dust aerosols could warm clouds thereby increasing the evaporation of cloud droplets resulting in reduced cloud water path semi-direct effect The semi-direct effect may be dominated the interaction between dust aerosols and clouds over arid and semi-arid areas and partly contribute to reduced precipitation

  15. Impact-generated dust clouds around planetary satellites: asymmetry effects

    NASA Astrophysics Data System (ADS)

    Sremčević, Miodrag; Krivov, Alexander V.; Spahn, Frank

    2003-06-01

    In a companion paper (Krivov et al., Impact-generated dust clouds around planetary satellites: spherically symmetric case, Planet. Space. Sci. 2003, 51, 251-269) an analytic model of an impact-generated, steady-state, spherically symmetric dust cloud around an atmosphereless planetary satellite (or planet - Mercury, Pluto) has been developed. This paper lifts the assumption of spherical symmetry and focuses on the asymmetry effects that result from the motion of the parent body through an isotropic field of impactors. As in the spherically symmetric case, we first consider the dust production from the surface and then derive a general phase-space distribution function of the ensemble of ejected dust motes. All quantities of interest, such as particle number densities and fluxes, can be obtained by integrating this phase-space distribution function. As an example, we calculate an asymmetric distribution of dust number density in a cloud. It is found that the deviation from the symmetric case can be accurately described by a cosine function of the colatitude measured from the apex of the satellite motion. This property of the asymmetry is rather robust. It is shown that even an extremely asymmetric dust production at the surface, when nearly all dust is ejected from the leading hemisphere, turns rapidly into the cosine modulation of the number density at distances larger than a few satellite radii. The amplitude of the modulation depends on the ratio of the moon orbital velocity to the speed of impactors and on the initial angular distribution of the ejecta. Furthermore, regardless of the functional form of the initial angular distribution, the number density distribution of the dust cloud is only sensitive to the mean ejecta angle. When the mean angle is small - ejection close to the normal of the surface - the initial dust production asymmetry remains persistent even far from the satellite, but when this angle is larger than about 45°, the asymmetry coefficient

  16. A study of extended zodiacal structures

    NASA Technical Reports Server (NTRS)

    Sykes, Mark V.

    1990-01-01

    Observations of cometary dust trails and zodiacal dust bands, discovered by the Infrared Astronomical Satellite (IRAS) were analyzed in a continuing effort to understand their nature and relationship to comets, asteroids, and processes effecting those bodies. A survey of all trails observed by IRAS has been completed, and analysis of this phenomenon continues. A total of 8 trails have been associated with known short-period comets (Churyumov-Gerasimenko, Encke, Gunn, Kopff, Pons-Winnecke, Schwassmann-Wachmann 1, Tempel 1, and Tempel 2), and a few faint trails have been detected which are not associated with any known comet. It is inferred that all short-period comets may have trails, and that the trails detected were seen as a consequence of observational selection effects. Were IRAS launched today, it would likely observe a largely different set of trails. The Tempel 2 trail exhibits a small but significant excess in color temperature relative to a blackbody at the same heliocentric distance. This excess may be due to the presence of a population of small, low-beta particles deriving from large particles within the trail, or a temperature gradient over the surface of large trail particles. Trails represent the very first stage in the formation and evolution of a meteor stream, and may also be the primary mechanism by which comets contribute to the interplanetary dust complex. A mathematical model of the spatial distribution of orbitally evolved collisional debris was developed which reproduces the zodiacal dust band phenomena and was used in the analysis of dust band observations made by IRAS. This has resulted in the principal zodiacal dust bands being firmly related to the principal Hirayama asteroid families. In addition, evidence for the collisional diffusion of the orbital elements of the dust particles has been found in the case of dust generated in the Eos asteroid family.

  17. The origin and evolution of dust clouds in Central Asia

    Smirnov, V.V.; Gillette, Dale A.; Golitsyn, G.S.; MacKinnon, D.J.

    1994-01-01

    Data from a high resolution radiometer AVHRR (580-680 nm optical lengthwaves) installed on the "NOAA-11" satellite as well as TV (500-700 nm) and IR (8000-12000 nm) equipment of the Russia satellite "Meteor-2/16" were used to study the evolution of dust storms for 1-30 September 1989 in Tajikistan, Uzbekistan, Turkmenistan and Afghanistan. These data help to validate the hypothesis, that long-term dusted boundary layer (duration of the order of a day or more), but of comparatively not high optical density (4-10 km meteorological visibility range at the 20-50 km background), is formed after the northwest intrusions into a region of intensive cold fronts at the surface wind velocities of 7-15 m/s. Stability of dust clouds of vertical power to 3-3.5 km (up to an inversion level) is explained by an action of collective buoyancy factors at heating the dust particles of 2-4 ??m in mean diameter by solar radiation. The more intensive intrusions stimulate a formation of simultaneously dust and water clouds. The last partially reduce the solar radiation (by the calculations of the order of 30-50%) and decrease the role of buoyancy factors. Thus, initiated is the intensive but short-term dusted boundary layer at horizontal visibility of 50-200 m. ?? 1994.

  18. Infrared emission from isolated dust clouds in the presence of very small dust grains

    NASA Technical Reports Server (NTRS)

    Lis, Dariusz C.; Leung, Chun M.

    1991-01-01

    Models of the effects of small grain-generated temperature fluctuations on the IR spectrum and surface brightness of externally heated interstellar dust clouds are presently constructed on the basis of a continuum radiation transport computer code which encompasses the transient heating of small dust grains. The models assume a constant fractional abundance of large and small grains throughout the given cloud. A comparison of model results with IRAS observations indicates that the observed 12-25 micron band emissions are associated with about 10-A radius grains, while the 60-100 micron emission is primarily due to large grains which are heated under the equilibrium conditions.

  19. COLLISIONAL GROOMING MODELS OF THE KUIPER BELT DUST CLOUD

    SciT

    Kuchner, Marc J.; Stark, Christopher C., E-mail: Marc.Kuchner@nasa.go, E-mail: starkc@umd.ed

    2010-10-15

    We modeled the three-dimensional structure of the Kuiper Belt (KB) dust cloud at four different dust production rates, incorporating both planet-dust interactions and grain-grain collisions using the collisional grooming algorithm. Simulated images of a model with a face-on optical depth of {approx}10{sup -4} primarily show an azimuthally symmetric ring at 40-47 AU in submillimeter and infrared wavelengths; this ring is associated with the cold classical KB. For models with lower optical depths (10{sup -6} and 10{sup -7}), synthetic infrared images show that the ring widens and a gap opens in the ring at the location of Neptune; this feature ismore » caused by trapping of dust grains in Neptune's mean motion resonances. At low optical depths, a secondary ring also appears associated with the hole cleared in the center of the disk by Saturn. Our simulations, which incorporate 25 different grain sizes, illustrate that grain-grain collisions are important in sculpting today's KB dust, and probably other aspects of the solar system dust complex; collisions erase all signs of azimuthal asymmetry from the submillimeter image of the disk at every dust level we considered. The model images switch from being dominated by resonantly trapped small grains ('transport dominated') to being dominated by the birth ring ('collision dominated') when the optical depth reaches a critical value of {tau} {approx} v/c, where v is the local Keplerian speed.« less

  20. Astrophysical dust grains in stars, the interstellar medium, and the solar system

    NASA Technical Reports Server (NTRS)

    Gehrz, Robert D.

    1991-01-01

    Studies of astrophysical dust grains in circumstellar shells, the interstellar medium, and the solar system may provide information about stellar evolution and about physical conditions in the primitive solar nebula. The following subject areas are covered: (1) the cycling of dust in stellar evolution and the formation of planetary systems; (2) astrophysical dust grains in circumstellar environments; (3) circumstellar grain formation and mass loss; (4) interstellar dust grains; (5) comet dust and the zodiacal cloud; (6) the survival of dust grains during stellar evolution; and (7) establishing connections between stardust and dust in the solar system.

  1. Simulation of Asia Dust and Cloud Interaction Over Pacific Ocean During Pacdex

    NASA Astrophysics Data System (ADS)

    Long, X.; Huang, J.; Cheng, C.; Wang, W.

    2007-12-01

    The effect of dust plume on the Pacific cloud systems and the associated radiative forcing is an outstanding problem for understanding climate change. Many studies showing that dust aerosol might be a good absorber for solar radiation, at the same time dust aerosols could affect the cloud's formation and precipitation by its capability as cloud condensation nuclei (CCN) and ice forming nuclei (IFN). But the role of aerosols in clouds and precipitation is very complex. Simulation of interaction between cloud and dust aerosols requires recognition that the aerosol cloud system comprises coupled components of dynamics, aerosol and cloud microphysics, radiation processes. In this study, we investigated the interaction between dust aerosols and cloud with WRF which coupled with detailed cloud microphysics processes and dust process. The observed data of SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) and PACDEX (Pacific Dust Experiment) is used as the initialization which include the vertical distributions and concentration of dust particles. Our results show that dust aerosol not only impacts cloud microphysical processes but also cloud microstructure; Dust aerosols can act as effective ice nuclei and intensify the ice-forming processes.

  2. PROGRA2 experiment: new results for dust clouds and regoliths

    NASA Astrophysics Data System (ADS)

    Renard, J.-B.; Hadamcik, E.; Worms, J.-C.; Levasseur-Regourd, A.-C.; Daugeron, D.

    With the CNES-sponsored PROGRA2 facility, linear polarization of scattered light is performed on various types of dust clouds in microgravity during parabolic flights onboard the CNES- and ESA-sponsored A300 Zéro-G aircraft. Clouds of fluffy aggregates are also studied on the ground when lifted by an air-draught. The effect of the physical properties of the particles, such as the grains size and size distribution, the real part of the refractive index, and the structure is currently being studied. The size distribution of the agglomerates is measured in the field of view from the polarized component images. The large number of phase curves already obtained in the various conditions of measurements, in order to build a database (about 160 curves) allows us to better connect the physical properties with the observed polarization of the dust in the clouds. The aim is to compare these curves with those obtained in the solar system by remote-sensing and in-situ techniques for interplanetary dust, cometary coma, and solid particles in planetary atmospheres (Renard et al., 2003). Measurements on layers of particles (i.e. on the ground) are then compared with remote measurements on asteroidal regoliths and planetary surfaces. New phase curves will be presented and discussed i.e. for quartz samples, crystals, fluffy mixtures of alumina and silica, and a high porosity ``regolith'' analogue made of micron-sized silica spheres. This work will contribute to the choice of the samples to be studied with the IMPACT/ICAPS instrument onboard the ISS. J.-B. Renard, E. Hadamcik, T. Lemaire, J.-C. Worms and A.-C. Levasseur-Regourd (2003). Polarization imaging of dust cloud particles: improvement and applications of the PROGRA2 instrument, ASR 31, 12, 2511-2518.

  3. Pioneer 10 observations of zodiacal light brightness near the ecliptic - Changes with heliocentric distance

    NASA Technical Reports Server (NTRS)

    Hanner, M. S.; Weinberg, J. L.; Beeson, D. E.; Sparrow, J. G.

    1976-01-01

    Sky maps made by the Pioneer 10 Imaging Photopolarimeter (IPP) at sun-spacecraft distances from 1 to 3 AU have been analyzed to derive the brightness of the zodiacal light near the ecliptic at elongations greater than 90 degrees. The change in zodiacal light brightness with heliocentric distance is compared with models of the spatial distribution of the dust. Use of background starlight brightnesses derived from IPP measurements beyond the asteroid belt, where the zodiacal light is not detected, and, especially, use of a corrected calibration lead to considerably lower values for zodiacal light than those reported by us previously.

  4. H2, CO, and dust absorption through cold molecular clouds

    NASA Astrophysics Data System (ADS)

    Lacy, John H.; Sneden, Chris; Kim, Hwihyun; Jaffe, Daniel Thomas

    2017-06-01

    We have made observations with IGRINS on the Harlan J. Smith telescope at McDonald Observatory of near-infrared absorption by H2, CO, and dust toward stars behind molecular clouds, primarily the TMC. Prior to these observations, the abundance of H2 in molecular clouds, relative to the commonly used tracer CO, had only been measured toward a few embedded stars, which may be surrounded by atypical gas. The new observations provide a representative sample of these molecules in cold molecular gas. We find N(H2)/Av ~ 0.9e+21, N(CO)/Av ~ 1.6e+17, and H2/CO ~ 6000. The measured H2/CO ratio is consistent with that measured toward embedded stars in various molecular clouds, but half that derived from mm-wave observations of CO emission and star counts or other determinations of Av.

  5. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1977-01-01

    The studies of the evolution of cometary debris are reviewed. The subject is divided into three major sections: (1) the developments in the immediate vicinity of the cometary nucleus, which is the source of the dust; (2) the formation of the dust tail; and (3) the blending of the debris with the dust component of interplanetary matter. The importance of the physical theory of comets is emphasized for the understanding of the early phase of the evolution of cometary dust. A physico-dynamical model designed to analyze the particle-emission mechanism from the distribution of light in the dust tails is described and the results are presented. Increased attention is paid to large particles because of their importance for the evolution of the zodiacal cloud. Finally, implications are discussed for the future in situ investigations of comets.

  6. Evaluating the effect of soil dust particles from semi-arid areas on clouds and climate

    NASA Astrophysics Data System (ADS)

    Kristjansson, J. E.; Hummel, M.; Lewinschal, A.; Grini, A.

    2016-12-01

    Primary ice production in mixed-phase clouds predominantly takes place by heterogeneous freezing of mineral dust particles. Therefore, mineral dust has a large impact on cloud properties. Organic matter attached to mineral dust particles can expand their already good freezing ability further to warmer subzero temperatures. These dust particles are called "soil dust". Dusts emitted from deserts contribute most to the total dust concentration in the atmosphere and they can be transported over long distances. Soil dust is emitted from semi-arid regions, e.g. agricultural areas. Besides wind erosion, human activities like tillage or harvest might be a large source for soil dust release into the atmosphere. In this study, we analyze the influence of soil dust particles on clouds with the Norwegian Earth System Model (NorESM; Bentsen et al., 2013: GMD). The parameterization of immersion freezing on soil dust is based on findings from the AIDA cloud chamber (Steinke et al., in prep.). Contact angle and activation energy for soil dust are estimated in order to be used in the dust immersion freezing scheme of the model, which is based on classical nucleation theory. Our first results highlight the importance of soil dust for ice nucleation on a global scale. Its influence is expected to be highest in the northern hemisphere due to its higher area for soil dust emission. The immersion freezing rates due to additional soil dust can on average increase by a factor of 1.2 compared to a mineral dust-only simulation. Using a budget tool for NorESM, influences of soil dust ice nuclei on single tendencies of the cloud microphysics can be identified. For example, accretion to snow is sensitive to adding soil dust ice nuclei. This can result in changes e.g. in the ice water path and cloud radiative properties.

  7. Mars dust and cloud opacities and scattering properties

    NASA Technical Reports Server (NTRS)

    Clancy, R. T.; Lee, S. W.

    1992-01-01

    We have recently completed an analysis of the visible emission-phase function (EPF) sequences obtained with the solar-band channel of the Infrared Thermal Mapping (IRTM) instrument onboard the two Viking Orbiters. Roughly 100 of these EPF sequences were gathered during the 1977-1980 period, in which the total broadband (.3-3.0 microns) reflectances of the atmosphere/surface above specific locations on Mars were measured versus emission angle as the spacecraft passed overhead. A multiple scattering radiative transfer program was employed to model the EPF observations in terms of the optical depths of dust/clouds, their single scattering albedos and phase functions, and the Lambert albedos and phase coefficient of the underlying surfaces. Due to the predominance of atmospheric scattering at large atmospheric pathlengths and/or large dust opacities, we were able to obtain strong constraints on the scattering properties of dust/clouds and their opacities for a wide range of latitudes, longitudes, and seasons on Mars.

  8. Zodiac II: Debris Disk Science from a Balloon

    NASA Technical Reports Server (NTRS)

    Bryden, Geoffrey; Traub, Wesley; Roberts, Lewis C., Jr.; Bruno, Robin; Unwin, Stephen; Backovsky, Stan; Brugarolas, Paul; Chakrabarti, Supriya; Chen, Pin; Hillenbrand, Lynne; hide

    2011-01-01

    Zodiac II is a proposed balloon-borne science investigation of debris disks around nearby stars. Debris disks are analogs of the Asteroid Belt (mainly rocky) and Kuiper Belt (mainly icy) in our Solar System. Zodiac II will measure the size, shape, brightness, and color of a statistically significant sample of disks. These measurements will enable us to probe these fundamental questions: what do debris disks tell us about the evolution of planetary systems; how are debris disks produced; how are debris disks shaped by planets; what materials are debris disks made of; how much dust do debris disks make sa they grind down; and how long do debris disks live? In addition, Zodiac II will observe hot, young exoplanets as targets of opportunity. The Zodiac II instrument is a 1.1-m diameter SiC telescope and an imaging coronagraph on a gondola carried by a stratospheric balloon. Its data product is a set of images of each targeted debris disk in four broad visible wavelength bands. Zodiac II will address its science questions by taking high-resolution, multi-wavelength images of the debris disks around tens of nearby stars. Mid-latitude flights are considered: overnight test flights within the United States followed by half-global flights in the Southern Hemisphere. These longer flights are required to fully explore the set of known debris disks accessible only to Zodiac II. On these targets, it will be 100 times more sensitive than the Hubble Space Telescope's Advanced Camera for Surveys (HST/ACS); no existing telescope can match the Zodiac II contrast and resolution performance. A second objective of Zodiac II is to use the near-space environment to raise the Technology Readiness Level (TRL) of SiC mirrors, internal coronagraphs, deformable mirrors, and wavefront sensing and control, all potentially needed for a future space-based telescope for high-contrast exoplanet imaging.

  9. Zodiac II: Debris Disk Science from a Balloon

    NASA Technical Reports Server (NTRS)

    Bryden, Geoffrey; Traub, Wesley; Roberts, Lewis C., Jr.; Bruno, Robin; Unwin, Stephen; Backovsky, Stan; Brugarolas, Paul; Chakrabarti, Supriya; Chen, Pin; Hillenbrand, Lynne; hide

    2011-01-01

    Zodiac II is a proposed balloon-borne science investigation of debris disks around nearby stars. Debris disks are analogs of the Asteroid Belt (mainly rocky) and Kuiper Belt (mainly icy) in our Solar System. Zodiac II will measure the size, shape, brightness, and color of a statistically significant sample of disks. These measurements will enable us to probe these fundamental questions: what do debris disks tell us about the evolution of planetary systems; how are debris disks produced; how are debris disks shaped by planets; what materials are debris disks made of; how much dust do debris disks make as they grind down; and how long do debris disks live? In addition, Zodiac II will observe hot, young exoplanets as targets of opportunity. The Zodiac II instrument is a 1.1-m diameter SiC (Silicone carbide) telescope and an imaging coronagraph on a gondola carried by a stratospheric balloon. Its data product is a set of images of each targeted debris disk in four broad visible-wavelength bands. Zodiac II will address its science questions by taking high-resolution, multi-wavelength images of the debris disks around tens of nearby stars. Mid-latitude flights are considered: overnight test flights in the US followed by half-global flights in the Southern Hemisphere. These longer flights are required to fully explore the set of known debris disks accessible only to Zodiac II. On these targets, it will be 100 times more sensitive than the Hubble Space Telescope's Advanced Camera for Surveys (HST/ACS); no existing telescope can match the Zodiac II contrast and resolution performance. A second objective of Zodiac II is to use the near-space environment to raise the Technology Readiness Level (TRL) of SiC mirrors, internal coronagraphs, deformable mirrors, and wavefront sensing and control, all potentially needed for a future space-based telescope for high-contrast exoplanet imaging.

  10. Gathering dust: A galaxy-wide study of dust emission from cloud complexes in NGC 300

    NASA Astrophysics Data System (ADS)

    Riener, M.; Faesi, C. M.; Forbrich, J.; Lada, C. J.

    2018-05-01

    Aims: We use multi-band observations by the Herschel Space Observatory to study the dust emission properties of the nearby spiral galaxy NGC 300. We compile a first catalogue of the population of giant dust clouds (GDCs) in NGC 300, including temperature and mass estimates, and give an estimate of the total dust mass of the galaxy. Methods: We carried out source detection with the multiwavelength source extraction algorithm getsources. We calculated physical properties, including mass and temperature, of the GDCs from five-band Herschel PACS and SPIRE observations from 100 to 500 μm; the final size and mass estimates are based on the observations at 250 μm that have an effective spatial resolution of 170 pc. We correlated our final catalogue of GDCs to pre-existing catalogues of HII regions to infer the number of GDCs associated with high-mass star formation and determined the Hα emission of the GDCs. Results: Our final catalogue of GDCs includes 146 sources, 90 of which are associated with known HII regions. We find that the dust masses of the GDCs are completely dominated by the cold dust component and range from 1.1 × 103 to 1.4 × 104 M⊙. The GDCs have effective temperatures of 13-23 K and show a distinct cold dust effective temperature gradient from the centre towards the outer parts of the stellar disk. We find that the population of GDCs in our catalogue constitutes 16% of the total dust mass of NGC 300, which we estimate to be about 5.4 × 106 M⊙. At least about 87% of our GDCs have a high enough average dust mass surface density to provide sufficient shielding to harbour molecular clouds. We compare our results to previous pointed molecular gas observations in NGC 300 and results from other nearby galaxies and also conclude that it is very likely that most of our GDCs are associated with complexes of giant molecular clouds. The catalogue is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc

  11. The Effect of Asian Dust Aerosols on Cloud Properties and Radiative Forcing from MODIS and CERES

    NASA Technical Reports Server (NTRS)

    Huang, Jianping; Minnis, Patrick; Lin, Bing; Wang, Tianhe; Yi, Yuhong; Hu, Yongxiang; Sun-Mack, Sunny; Ayers, Kirk

    2005-01-01

    The effects of dust storms on cloud properties and radiative forcing are analyzed over northwestern China from April 2001 to June 2004 using data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Aqua and Terra satellites. On average, ice cloud effective particle diameter, optical depth and ice water path of the cirrus clouds under dust polluted conditions are 11%, 32.8%, and 42% less, respectively, than those derived from ice clouds in dust-free atmospheric environments. The humidity differences are larger in the dusty region than in the dust-free region, and may be caused by removal of moisture by wet dust precipitation. Due to changes in cloud microphysics, the instantaneous net radiative forcing is reduced from -71.2 W/m2 for dust contaminated clouds to -182.7 W/m2 for dust-free clouds. The reduced cooling effects of dusts may lead to a net warming of 1 W/m2, which, if confirmed, would be the strongest aerosol forcing during later winter and early spring dust storm seasons over the studied region.

  12. The Origin of the Excess Near-Infrared Diffuse Sky Brightness: Population III Stars or Zodiacal Light?

    NASA Technical Reports Server (NTRS)

    Dwek, Eli

    2006-01-01

    The intensity of the diffuse 1 to 5 micron sky emission from which solar system and Galactic foregrounds have been subtracted is in excess of that expected from energy released by galaxies and stars that formed during the z < 5 redshift interval. The spectral signature of this excess near-infrared background light (NIRBL) component is almost identical to that of reflected sunlight from the interplanetary dust cloud, and could therefore be the result of the incomplete subtraction of this foreground emission component from the diffuse sky maps. Alternatively, this emission component could be extragalactic. Its spectral signature is consistent with that of redshifted continuum and recombination line emission from H-II regions formed by the first generation of very massive stars. In this talk I will present the implications of this excess emission for our understanding of the zodiacal dust cloud, the formation rate of Pop III stars, and the TeV gamma-ray opacity to nearby blazars.

  13. A Chinese Zodiac Mathematical Structure.

    ERIC Educational Resources Information Center

    Lamb, John F., Jr.

    2000-01-01

    Helps students identify the animal that corresponds to the year of their birth according to the Chinese zodiac. Defines the structure of the Chinese zodiac so that the subsets of compatibles and opposites form closed substructures with interesting mathematical properties. (ASK)

  14. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1976-01-01

    The studies of the evolution of cometary debris are reviewed. The subject is divided into three major sections: (1) the developments in the immediate vicinity of the cometary nucleus, which is the source of the dust; (2) the formation of the dust tail; and (3) the blending of the debris with the dust component of interplanetary matter. The importance of the physical theory of comets is emphasized for the understanding of the early phase of evolution. A physico-dynamical model designed to analyze the particle-emission mechanism from the distribution of light in the dust tail is described and the results are presented. Increased attention is paid to large particles because of their importance for the evolution of the zodiacal cloud. Finally, implications are discussed for the future in situ investigations of comets.

  15. Planck early results. XXV. Thermal dust in nearby molecular clouds

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Abergel, A.; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Bernard, J.-P.; Bersanelli, M.; Bhatia, R.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Cabella, P.; Cardoso, J.-F.; Catalano, A.; Cayón, L.; Challinor, A.; Chamballu, A.; Chiang, L.-Y.; Chiang, C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Coulais, A.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Gasperis, G.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Dobashi, K.; Donzelli, S.; Doré, O.; Dörl, U.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Guillet, V.; Hansen, F. K.; Harrison, D.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Hoyland, R. J.; Huffenberger, K. M.; Jaffe, A. H.; Jones, A.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knox, L.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leach, S.; Leonardi, R.; Leroy, C.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacTavish, C. J.; Maffei, B.; Mandolesi, N.; Mann, R.; Maris, M.; Marshall, D. J.; Martin, P.; Martínez-González, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, A.; Naselsky, P.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Pajot, F.; Paladini, R.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Poutanen, T.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, P.; Smoot, G. F.; Starck, J.-L.; Stivoli, F.; Stolyarov, V.; Sudiwala, R.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Torre, J.-P.; Tristram, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Verstraete, L.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Yvon, D.; Zacchei, A.; Zonca, A.

    2011-12-01

    Planck allows unbiased mapping of Galactic sub-millimetre and millimetre emission from the most diffuse regions to the densest parts of molecular clouds. We present an early analysis of the Taurus molecular complex, on line-of-sight-averaged data and without component separation. The emission spectrum measured by Planck and IRAS can be fitted pixel by pixel using a single modified blackbody. Some systematic residuals are detected at 353 GHz and 143 GHz, with amplitudes around -7% and +13%, respectively, indicating that the measured spectra are likely more complex than a simple modified blackbody. Significant positive residuals are also detected in the molecular regions and in the 217 GHz and 100 GHz bands, mainly caused by the contribution of the J = 2 → 1 and J = 1 → 0 12CO and 13CO emission lines. We derive maps of the dust temperature T, the dust spectral emissivity index β, and the dust optical depth at 250 μm τ250. The temperature map illustrates the cooling of the dust particles in thermal equilibrium with the incident radiation field, from 16 - 17 K in the diffuse regions to 13 - 14 K in the dense parts. The distribution of spectral indices is centred at 1.78, with a standard deviation of 0.08 and a systematic error of 0.07. We detect a significant T - β anti-correlation. The dust optical depth map reveals the spatial distribution of the column density of the molecular complex from the densest molecular regions to the faint diffuse regions. We use near-infrared extinction and Hi data at 21-cm to perform a quantitative analysis of the spatial variations of the measured dust optical depth at 250 μm per hydrogen atom τ250/NH. We report an increase of τ250/NH by a factor of about 2 between the atomic phase and the molecular phase, which has a strong impact on the equilibrium temperature of the dust particles. Corresponding author: A. Abergel, e-mail: alain.abergel@ias.u-psud.fr

  16. Attenuation of Ultraviolet Radiation by Dust in Interstellar Clouds

    NASA Astrophysics Data System (ADS)

    Escalante, V.

    1994-07-01

    Se han obtenido soluciones de la ecuación de transporte para la dispersión coherente, no conservativa y anisotrópica para estimar la precisión de métodos aproximados, usados en modelos de nubes en que la luz es atenuada principalmente por el polvo. En los cálculos se ha aplicado el metodo de armónicos esféricos para distintos parámetros del polvo. Se ha explorado la posibilidad de descubrir cambios en las caracterísiticas del polvo mediante observaciones de regiones fotodisociadas. Se muestra que para altos valores del albedo de dispersión simple y del parametro de asimetria de Ia función de fase que son adecuados para el polvo galáctico, no es posible determinar variaciones de más de un factor de 2 en el cociente de gas a polvo. Solutions to the transfer equation for coherent, non-conservative, anisotropic scattering have been obtained in order to estimate the accuracy of approximate methods used in models of clouds where light is attenuated mostly by dust. In the calculations the spherical harmonic method has been applied for different grain parameters. The possibility of discovering changes of dust characteristics through observations of photodissociation regions has been considered. It is shown that for the high values of the single scattering albedo and the asymmetry parameter of the phase function for redistribution that appear to be appropriate for galactic dust, it is not possible to determine variations of more than a factor of 2 in the gas to dust ratio.

  17. Analysis of IRAS solar system dust data

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.; Nicholson, P. D.

    1991-01-01

    Data in the Infrared Astronomical Satellite (IRAS) Zodiacal History File were analyzed to extract dust band locations and peak brightness measurements from approximately 1,000 individual IRAS scans. The study had three goals. One was to show that the prominent solar system dust bands are associated with Hirayama asteroid families and thus that collisions between asteroids account for a significant fraction of the particles in the zodiacal cloud. Recent work suggests that while the Hirayama families are a major source of the dust in the bands, there may also be contributions from two or three smaller, more recently recognized asteroid families. A second goal was to show that there is evidence in the IRAS dust data for the transport of particles from asteroid belt to the Earth by Poynting-Robertson light drag and thus account for the fact that asteroid particles are collected in the Earth's stratosphere. Results of the study will confirm the location of the dust bands within the inner asteroid belt, and show conclusively that the material seen by IRAS is now spread over a wide range of distances from the sun. The third goal was to construct a model of the background zodiacal cloud that satisfies the proper dynamical constraints. Figures are provided to show the scans processed to remove zodiacal background and Galactic signals, and the resulting polynomial fits to the 25 micron scan. The latter provided objective estimates of band widths, peak locations, and peak fluxes. Modelling and analysis of the resulting band data has been presented at several conferences and is the subject of a number of forthcoming papers.

  18. Changes in Stratiform Clouds of Mesoscale Convective Complex Introduced by Dust Aerosols

    NASA Technical Reports Server (NTRS)

    Lin, B.; Min, Q.-L.; Li, R.

    2010-01-01

    Aerosols influence the earth s climate through direct, indirect, and semi-direct effects. There are large uncertainties in quantifying these effects due to limited measurements and observations of aerosol-cloud-precipitation interactions. As a major terrestrial source of atmospheric aerosols, dusts may serve as a significant climate forcing for the changing climate because of its effect on solar and thermal radiation as well as on clouds and precipitation processes. Latest satellites measurements enable us to determine dust aerosol loadings and cloud distributions and can potentially be used to reduce the uncertainties in the estimations of aerosol effects on climate. This study uses sensors on various satellites to investigate the impact of mineral dust on cloud microphysical and precipitation processes in mesoscale convective complex (MCC). A trans-Atlantic dust outbreak of Saharan origin occurring in early March 2004 is considered. For the observed MCCs under a given convective strength, small hydrometeors were found more prevalent in the dusty stratiform regions than in those regions that were dust free. Evidence of abundant cloud ice particles in the dust regions, particularly at altitudes where heterogeneous nucleation of mineral dust prevails, further supports the observed changes of clouds and precipitation. The consequences of the microphysical effects of the dust aerosols were to shift the size spectrum of precipitation-sized hydrometeors from heavy precipitation to light precipitation and ultimately to suppress precipitation and increase the lifecycle of cloud systems, especially over stratiform areas.

  19. CALIPSO Observations of Transatlantic Dust: Vertical Stratification and Effect of Clouds

    NASA Technical Reports Server (NTRS)

    Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Kalashnikova, Olga V.; Kostinski, Alexander B.

    2014-01-01

    We use CALIOP nighttime measurements of lidar backscatter, color and depolarization ratios, as well as particulate retrievals during the summer of 2007 to study transatlantic dust properties downwind of Saharan sources, and to examine the influence of nearby clouds on dust. Our analysis suggests that (1) under clear skies, while lidar backscatter and color ratio do not change much with altitude and longitude in the Saharan Air Layer (SAL), depolarization ratio increases with altitude and decreases westward in the SAL (2) the vertical lapse rate of dust depolarization ratio, introduced here, increases within SAL as plumes move westward (3) nearby clouds barely affect the backscatter and color ratio of dust volumes within SAL but not so below SAL. Moreover, the presence of nearby clouds tends to decrease the depolarization of dust volumes within SAL. Finally, (4) the odds of CALIOP finding dust below SAL next to clouds are about of those far away from clouds. This feature, together with an apparent increase in depolarization ratio near clouds, indicates that particles in some dust volumes loose asphericity in the humid air near clouds, and cannot be identified by CALIPSO as dust.

  20. Rain chemistry and cloud composition and microphysics in a Caribbean tropical montane cloud forest under the influence of African dust

    NASA Astrophysics Data System (ADS)

    Torres-Delgado, Elvis; Valle-Diaz, Carlos J.; Baumgardner, Darrel; McDowell, William H.; González, Grizelle; Mayol-Bracero, Olga L.

    2015-04-01

    It is known that huge amounts of mineral dust travels thousands of kilometers from the Sahara and Sahel regions in Africa over the Atlantic Ocean reaching the Caribbean, northern South America and southern North America; however, not much is understood about how the aging process that takes place during transport changes dust properties, and how the presence of this dust affects cloud's composition and microphysics. This African dust reaches the Caribbean region mostly in the summer time. In order to improve our understanding of the role of long-range transported African dust (LRTAD) in cloud formation processes in a tropical montane cloud forest (TMCF) in the Caribbean region we had field campaigns measuring dust physical and chemical properties in summer 2013, as part of the Puerto Rico African Dust and Cloud Study (PRADACS), and in summer 2014, as a part of the Luquillo Critical Zone Observatory (LCZO) and in collaboration with the Saharan Aerosol Long-Range Transport and Aerosol-Cloud-Interaction Experiment (SALTRACE). Measurements were performed at the TMCF of Pico del Este (PE, 1051 masl) and at the nature reserve of Cabezas de San Juan (CSJ, 60 masl). In both stations we monitored meteorological parameters (e.g., temperature, wind speed, wind direction). At CSJ, we measured light absorption and scattering at three wavelengths (467, 528 and 652 nm). At PE we collected cloud and rainwater and monitored cloud microphysical properties (e.g., liquid water content, droplet size distribution, droplet number concentration, effective diameter and median volume diameter). Data from aerosol models, satellites, and back-trajectories were used together with CSJ measurements to classify air masses and samples collected at PE in the presence or absence of dust. Soluble ions, insoluble trace metals, pH and conductivity were measured for cloud and rainwater. Preliminary results for summer 2013 showed that in the presence of LRTAD (1) the average conductivity of cloud water

  1. Dust in the small Magellanic Cloud. 2: Dust models from interstellar polarization and extinction data

    NASA Technical Reports Server (NTRS)

    Rodrigues, C. V.; Magalhaes, A. M.; Coyne, G. V.

    1995-01-01

    We study the dust in the Small Magellanic Cloud using our polarization and extinction data (Paper 1) and existing dust models. The data suggest that the monotonic SMC extinction curve is related to values of lambda(sub max), the wavelength of maximum polarization, which are on the average smaller than the mean for the Galaxy. On the other hand, AZV 456, a star with an extinction similar to that for the Galaxy, shows a value of lambda(sub max) similar to the mean for the Galaxy. We discuss simultaneous dust model fits to extinction and polarization. Fits to the wavelength dependent polarization data are possible for stars with small lambda(sub max). In general, they imply dust size distributions which are narrower and have smaller mean sizes compared to typical size distributions for the Galaxy. However, stars with lambda(sub max) close to the Galactic norm, which also have a narrower polarization curve, cannot be fit adequately. This holds true for all of the dust models considered. The best fits to the extinction curves are obtained with a power law size distribution by assuming that the cylindrical and spherical silicate grains have a volume distribution which is continuous from the smaller spheres to the larger cylinders. The size distribution for the cylinders is taken from the fit to the polarization. The 'typical', monotonic SMC extinction curve can be fit well with graphite and silicate grains if a small fraction of the SMC carbon is locked up in the grain. However, amorphous carbon and silicate grains also fit the data well. AZV456, which has an extinction curve similar to that for the Galaxy, has a UV bump which is too blue to be fit by spherical graphite grains.

  2. Two-dimensional positive column structure with dust cloud: Experiment and nonlocal kinetic simulation

    NASA Astrophysics Data System (ADS)

    Zobnin, A. V.; Usachev, A. D.; Petrov, O. F.; Fortov, V. E.; Thoma, M. H.; Fink, M. A.

    2018-03-01

    The influence of a dust cloud on the structure of the positive column of a direct current gas discharge in a cylindrical glass tube under milligravity conditions has been studied both experimentally and numerically. The discharge was produced in neon at 60 Pa in a glass tube with a diameter of 30 mm at a discharge current 1 mA. Spherical monodisperse melamine formaldehyde dust particles with a diameter of 6.86 μm were injected into the positive column and formed there a uniform dust cloud with a maximum diameter of 14.4 mm. The shape of the cloud and the dust particle number density were measured. The cloud was stationary in the radial direction and slowly drifted in the axial direction. It was found that in the presence of the dust cloud, the intensity of the neon spectral line with a wavelength by 585.25 nm emitted by the discharge plasma increased by 2.3 times and 2 striations appeared on the anode side of the cloud. A numerical simulation of the discharge was performed using the 2D (quasi-3D) nonlocal self-consistent kinetic model of a longitudinally inhomogeneous axially symmetric positive column [Zobnin et al., Phys. Plasmas 21, 113503 (2014)], which was supplemented by a program module performing a self-consistent calculation of dust particle charges, the plasma recombination rate on dust particles, and ion scattering on dust particles. A new approach to the calculation of particle charges and the screening radius in dense dust clouds is proposed. The results of the simulation are presented, compared with experimental data and discussed. It is demonstrated that for the best agreement between simulated and experimental data, it is necessary to take into account the reflection of electrons from the dust particle surface in order to correctly describe the recombination rate in the cloud, its radial stability, and the dust particle charges.

  3. IRAS observations of dust heating and energy balance in the Rho Ophiuchi dark cloud

    NASA Technical Reports Server (NTRS)

    Greene, Thomas P.; Young, Erick T.

    1989-01-01

    The equilibrium process dust emission in the Rho Ophiuchi dark cloud is studied. The luminosity of the cloud is found to closely match the luminosity of the clouds's known embedded and external radiation sources. There is no evidence for a large population of undetected low-luminosity sources within the cloud and unknown external heating is also only a minor source of energy. Most of the cloud's luminosity is emitted in the mid-to-far-IR. Dust temperature maps indicate that the dust is not hot enough to heat the gas to observed temperatures. A simple cloud model with a radiation field composed of flux HD 147889, S1, and Sco OB2 associations predicts the observed IRAS 60 to 100 micron in-band flux ratios for a mean cloud density n(H2) = 1400. Flattened 12 and 25 micron observations show much extended emission in these bands, suggesting stochastic heating of very small grains or large molecules.

  4. Satellite remote sensing of dust aerosol indirect effects on ice cloud formation.

    PubMed

    Ou, Steve Szu-Cheng; Liou, Kuo-Nan; Wang, Xingjuan; Hansell, Richard; Lefevre, Randy; Cocks, Stephen

    2009-01-20

    We undertook a new approach to investigate the aerosol indirect effect of the first kind on ice cloud formation by using available data products from the Moderate-Resolution Imaging Spectrometer (MODIS) and obtained physical understanding about the interaction between aerosols and ice clouds. Our analysis focused on the examination of the variability in the correlation between ice cloud parameters (optical depth, effective particle size, cloud water path, and cloud particle number concentration) and aerosol optical depth and number concentration that were inferred from available satellite cloud and aerosol data products. Correlation results for a number of selected scenes containing dust and ice clouds are presented, and dust aerosol indirect effects on ice clouds are directly demonstrated from satellite observations.

  5. Galactic and zodiacal light surface brightness measurements with the Atmosphere Explorer satellites

    NASA Technical Reports Server (NTRS)

    Abreu, V. J.; Hays, P. B.; Yee, J. H.

    1982-01-01

    Galactic and zodiacal light surface maps based on the Atmosphere Explorer-C, -D, and -E satellite data are presented at 7320, 6300, 5577, 5200, and 4278 A. A procedure used to generate these maps, which involves separation of the individual stars and diffuse starlight from the zodiacal light, is described in detail. The maps can be used in atmospheric emission studies to correct for galactic emissions which contaminate satellite as well as ground-based photometric observations. The zodiacal light maps show enhanced features which are important for understanding the nature of interplanetary dust.

  6. Exozodiacal Dust Workshop

    NASA Technical Reports Server (NTRS)

    Backman, D. E. (Editor); Caroff, L. J. (Editor); Sandford, S. A. (Editor); Wooden, D. H. (Editor)

    1998-01-01

    The purpose of the workshop was to understand what effect circumstellar dust clouds will have on NASA's proposed Terrestrial Planet Finder (TPF) mission's ability to search for terrestrial-sized planets orbiting stars in the solar neighborhood. The workshop participants reviewed the properties of TPF, summarized what is known about the local zodiacal cloud and about exozodiacal clouds, and determined what additional knowledge must be obtained to help design TPF for maximum effectiveness within its cost constraint. Recommendations were made for ways to obtain that additional knowledge, at minimum cost. The workshop brought together approximately 70 scientists, from four different countries. The active participants included astronomers involved in the study of the local zodiacal cloud, in the formation of stars and planetary systems, and in the technologies and techniques of ground- and space-based infrared interferometry. During the course of the meeting, 15 invited talks and 20 contributed poster papers were presented, and there were four working sessions. This is a collection of the invited talks, contributed poster papers, and summaries of the working sessions.

  7. CALIPSO Observations of Transatlantic Dust: Vertical Stratification and Effect of Clouds

    NASA Technical Reports Server (NTRS)

    Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Kalashnikova, Olga V.; Kostinski, Alexander B.

    2012-01-01

    CALIOP nighttime measurements of lidar backscatter, color and depolarization ratios during the summer of 2007 are used to study transatlantic dust properties downwind of Saharan sources, and to examine the interaction of clouds and dust. We discuss the following findings: (1) while lidar backscatter doesn't change much with altitude in the Saharan Air Layer (SAL), depolarization and color ratios both increase with altitude in the SAL; (2) lidar backscatter and color ratio increase as dust is transported westward in the SAL; (3) the vertical lapse rate of dust depolarization ratio increases within SAL as plumes move westward; (4) nearby clouds barely affect the backscatter and color ratio of dust volumes within SAL but not so below SAL. Finally, (5) the odds of CALIOP finding dust below SAL next to clouds are about 2/3 of those far away from clouds. This feature, together with an apparent increase in depolarization ratio near clouds, indicates that particles in some dusty volumes lose asphericity in the humid air near clouds, and cannot be identified by CALIPSO as dust.

  8. Laboratory Studies of the Cloud Droplet Activation Properties and Corresponding Chemistry of Saline Playa Dust.

    PubMed

    Gaston, Cassandra J; Pratt, Kerri A; Suski, Kaitlyn J; May, Nathaniel W; Gill, Thomas E; Prather, Kimberly A

    2017-02-07

    Playas emit large quantities of dust that can facilitate the activation of cloud droplets. Despite the potential importance of playa dusts for cloud formation, most climate models assume that all dust is nonhygroscopic; however, measurements are needed to clarify the role of dusts in aerosol-cloud interactions. Here, we report measurements of CCN activation from playa dusts and parameterize these results in terms of both κ-Köhler theory and adsorption activation theory for inclusion in atmospheric models. κ ranged from 0.002 ± 0.001 to 0.818 ± 0.094, whereas Frankel-Halsey-Hill (FHH) adsorption parameters of A FHH = 2.20 ± 0.60 and B FHH = 1.24 ± 0.14 described the water uptake properties of the dusts. Measurements made using aerosol time-of-flight mass spectrometry (ATOFMS) revealed the presence of halite, sodium sulfates, and sodium carbonates that were strongly correlated with κ underscoring the role that mineralogy, including salts, plays in water uptake by dust. Predictions of κ made using bulk chemical techniques generally showed good agreement with measured values. However, several samples were poorly predicted suggesting that chemical heterogeneities as a function of size or chemically distinct particle surfaces can determine the hygroscopicity of playa dusts. Our results further demonstrate the importance of dust in aerosol-cloud interactions.

  9. Integrated approach towards understanding interactions of mineral dust aerosol with warm clouds

    NASA Astrophysics Data System (ADS)

    Kumar, Prashant

    2011-12-01

    Mineral dust is ubiquitous in the atmosphere and represents a dominant type of particulate matter by mass. Dust particles can serve as cloud condensation nuclei (CCN), giant CCN (GCCN), or ice nuclei (IN), thereby, affecting cloud microphysics, albedo, and lifetime. Despite its well-recognized importance, assessments of dust impacts on clouds and climate remain highly uncertain. This thesis addresses the role of dust as CCN and GCCN with the goal of improving our understanding of dust-warm cloud interactions and their representation in climate models. Most studies to date focus on the soluble fraction of aerosol particles when describing cloud droplet nucleation, and overlook the interactions of the hydrophilic insoluble fraction with water vapor. A new approach to include such interactions (expressed by the process of water vapor adsorption) is explored, by combining multilayer Frenkel-Halsey-Hill (FHH) physical adsorption isotherm and curvature (Kelvin) effects. The importance of adsorption activation theory (FHH-AT) is corroborated by measurements of CCN activity of mineral aerosols generated from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. A new aerosol generation setup for CCN measurements was developed based on a dry generation technique capable of reproducing natural dust aerosol emission. Based on the dependence of critical supersaturation with particle dry diameter, it is found that the FHH-AT is a better framework for describing fresh (and unprocessed) dust CCN activity than the classical Kohler theory (KT). Ion Chromatography (IC) measurements performed on fresh regional dust samples indicate negligible soluble fraction, and support that water vapor adsorption is the prime source of CCN activity in the dust. CCN measurements with the commonly used wet generated mineral aerosol (from atomization of a dust aqueous suspension) are also carried out. Results indicate that the method is subject

  10. Ignition of Combustible Dust Clouds by Strong Capacitive Electric Sparks of Short Discharge Times

    NASA Astrophysics Data System (ADS)

    Eckhoff, Rolf K.

    2017-10-01

    It has been known for more than half a century that the discharge times of capacitive electric sparks can influence the minimum ignition energies of dust clouds substantially. Experiments by various workers have shown that net electric-spark energies for igniting explosive dust clouds in air were reduced by a factor of the order of 100 when spark discharge times were increased from a few μs to 0.1-1 ms. Experiments have also shown that the disturbance of the dust cloud by the shock/blast wave emitted by "short" spark discharges is a likely reason for this. The disturbance increases with increasing spark energy. In this paper a hitherto unpublished comprehensive study of this problem is presented. The work was performed about 50 years ago, using sparks of comparatively high energies (strong sparks). Lycopodium was used as test dust. The experiments were conducted in a brass vessel of 1 L volume. A transient dust cloud was generated in the vessel by a blast of compressed air. Synchronization of appearance of dust cloud and spark discharge was obtained by breaking the spark gap down by the dust cloud itself. This may in fact also be one possible synchronization mechanism in accidental industrial dust explosions initiated by electrostatic sparks. The experimental results for various spark energies were expressed as the probability of ignition, based on 100 replicate experiments, as a function of the nominal dust concentration. All probabilities obtained were 0%dust cloud for ignition to occur was a function of spark energy and nominal dust concentration, and that the stochastic element was the statistical distribution of the time interval between spark appearance and re-establishment of contact between spark channel and dust

  11. Experiment S001: Zodiacal Light Photography

    NASA Technical Reports Server (NTRS)

    Ney, E. P.; Huch, W. F.

    1971-01-01

    Observations made during the Gemini 5, 9, and 10 missions in the context of their relation to ground-based and balloon-based experiments on dim-light phenomena are reported. Zodiacal light is the visible manifestation of dust grains in orbit around the sun. The negatives that were exposed on the Gemini 9 mission were studied by the use of an isodensitracer to produce intensity isophotes. Data on the following factors were obtained: (1) intensity distribution of the zodiacal light, both morning and evening; (2) the height and intensity of the airglow at various geographic positions; and (3) intensity distribution of the Milky Way in the region of the sky near Cygnus. Also, a previously unreported phenomenon was discovered. This phenomenon appeared as an upward extension of the normal 90-kilometer airglow layer. The extension was in the form of wisps or plumes approximately 5 deg wide and extending upward approximately 5 deg. The results obtained from pictures exposed on the Gemini 10 mission were of qualitative or geometrical value only.

  12. Saharan Dust Event Impacts on Cloud Formation and Radiation over Western Europe

    NASA Technical Reports Server (NTRS)

    Bangert, M.; Nenes, A.; Vogel, B.; Vogel, H.; Barahona, D.; Karydis, V. A.; Kumar, P.; Kottmeier, C.; Blahak, U.

    2013-01-01

    We investigated the impact of mineral dust particles on clouds, radiation and atmospheric state during a strong Saharan dust event over Europe in May 2008, applying a comprehensive online-coupled regional model framework that explicitly treats particle-microphysics and chemical composition. Sophisticated parameterizations for aerosol activation and ice nucleation, together with two-moment cloud microphysics are used to calculate the interaction of the different particles with clouds depending on their physical and chemical properties. The impact of dust on cloud droplet number concentration was found to be low, with just a slight increase in cloud droplet number concentration for both uncoated and coated dust. For temperatures lower than the level of homogeneous freezing, no significant impact of dust on the number and mass concentration of ice crystals was found, though the concentration of frozen dust particles reached up to 100 l-1 during the ice nucleation events. Mineral dust particles were found to have the largest impact on clouds in a temperature range between freezing level and the level of homogeneous freezing, where they determined the number concentration of ice crystals due to efficient heterogeneous freezing of the dust particles and modified the glaciation of mixed phase clouds. Our simulations show that during the dust events, ice crystals concentrations were increased twofold in this temperature range (compared to if dust interactions are neglected). This had a significant impact on the cloud optical properties, causing a reduction in the incoming short-wave radiation at the surface up to -75Wm-2. Including the direct interaction of dust with radiation caused an additional reduction in the incoming short-wave radiation by 40 to 80Wm-2, and the incoming long-wave radiation at the surface was increased significantly in the order of +10Wm-2. The strong radiative forcings associated with dust caused a reduction in surface temperature in the order of -0

  13. The Mars Dust Cycle: Investigating the Effects of Radiatively Active Water Ice Clouds on Surface Stresses and Dust Lifting Potential with the NASA Ames Mars General Circulation Model

    NASA Technical Reports Server (NTRS)

    Kahre, Melinda A.; Hollingsworth, Jeffery

    2012-01-01

    The dust cycle is a critically important component of Mars' current climate system. Dust is present in the atmosphere of Mars year-round but the dust loading varies with season in a generally repeatable manner. Dust has a significant influence on the thermal structure of the atmosphere and thus greatly affects atmospheric circulation. The dust cycle is the most difficult of the three climate cycles (CO2, water, and dust) to model realistically with general circulation models. Until recently, numerical modeling investigations of the dust cycle have typically not included the effects of couplings to the water cycle through cloud formation. In the Martian atmosphere, dust particles likely provide the seed nuclei for heterogeneous nucleation of water ice clouds. As ice coats atmospheric dust grains, the newly formed cloud particles exhibit different physical and radiative characteristics. Thus, the coupling between the dust and water cycles likely affects the distributions of dust, water vapor and water ice, and thus atmospheric heating and cooling and the resulting circulations. We use the NASA Ames Mars GCM to investigate the effects of radiatively active water ice clouds on surface stress and the potential for dust lifting. The model includes a state-of-the-art water ice cloud microphysics package and a radiative transfer scheme that accounts for the radiative effects of CO2 gas, dust, and water ice clouds. We focus on simulations that are radiatively forced by a prescribed dust map, and we compare simulations that do and do not include radiatively active clouds. Preliminary results suggest that the magnitude and spatial patterns of surface stress (and thus dust lifting potential) are substantial influenced by the radiative effects of water ice clouds.

  14. Pyrophoric sulfides influence over the minimum ignition temperature of dust cloud

    NASA Astrophysics Data System (ADS)

    Prodan, Maria; Lupu, Leonard Andrei; Ghicioi, Emilian; Nalboc, Irina; Szollosi-Mota, Andrei

    2017-12-01

    The dust cloud is the main form of existence of combustible dust in the production area and together with the existence of effective ignition sources are the main causes of dust explosions in production processes. The minimum ignition temperature has an important role in the process of selecting the explosion-protected electrical equipment when performing the explosion risk assessment of combustible dusts. The heated surfaces are able to ignite the dust clouds that can form in process industry. The oil products usually contain hydrogen sulfide and thus on the pipe walls iron sulfides can form, which can be very dangerous from health and safety point of view. In order to study the influence of the pyrophoric sulfide over the minimum ignition temperature of combustible dusts for this work were performed several experiments on a residue collected from the oil pipes contaminated with commercially iron sulfide.

  15. Effect of Thin Cirrus Clouds on Dust Optical Depth Retrievals From MODIS Observations

    NASA Technical Reports Server (NTRS)

    Feng, Qian; Hsu, N. Christina; Yang, Ping; Tsay, Si-Chee

    2011-01-01

    The effect of thin cirrus clouds in retrieving the dust optical depth from MODIS observations is investigated by using a simplified aerosol retrieval algorithm based on the principles of the Deep Blue aerosol property retrieval method. Specifically, the errors of the retrieved dust optical depth due to thin cirrus contamination are quantified through the comparison of two retrievals by assuming dust-only atmospheres and the counterparts with overlapping mineral dust and thin cirrus clouds. To account for the effect of the polarization state of radiation field on radiance simulation, a vector radiative transfer model is used to generate the lookup tables. In the forward radiative transfer simulations involved in generating the lookup tables, the Rayleigh scattering by atmospheric gaseous molecules and the reflection of the surface assumed to be Lambertian are fully taken into account. Additionally, the spheroid model is utilized to account for the nonsphericity of dust particles In computing their optical properties. For simplicity, the single-scattering albedo, scattering phase matrix, and optical depth are specified a priori for thin cirrus clouds assumed to consist of droxtal ice crystals. The present results indicate that the errors in the retrieved dust optical depths due to the contamination of thin cirrus clouds depend on the scattering angle, underlying surface reflectance, and dust optical depth. Under heavy dusty conditions, the absolute errors are comparable to the predescribed optical depths of thin cirrus clouds.

  16. Formation of iron nanoparticles and increase in iron reactivity in mineral dust during simulated cloud processing.

    PubMed

    Shi, Zongbo; Krom, Michael D; Bonneville, Steeve; Baker, Alex R; Jickells, Timothy D; Benning, Liane G

    2009-09-01

    The formation of iron (Fe) nanoperticles and increase in Fe reactivity in mineral dust during simulated cloud processing was investigated using high-resolution microscopy and chemical extraction methods. Cloud processing of dust was experimentally simulated via an alternation of acidic (pH 2) and circumneutral conditions (pH 5-6) over periods of 24 h each on presieved (<20 microm) Saharan soil and goethite suspensions. Microscopic analyses of the processed soil and goethite samples reveal the neo-formation of Fe-rich nanoparticle aggregates, which were not found initially. Similar Fe-rich nanoparticles were also observed in wet-deposited Saharen dusts from the western Mediterranean but not in dry-deposited dust from the eastern Mediterranean. Sequential Fe extraction of the soil samples indicated an increase in the proportion of chemically reactive Fe extractable by an ascorbate solution after simulated cloud processing. In addition, the sequential extractions on the Mediterranean dust samples revealed a higher content of reactive Fe in the wet-deposited dust compared to that of the dry-deposited dust These results suggestthat large variations of pH commonly reported in aerosol and cloud waters can trigger neo-formation of nanosize Fe particles and an increase in Fe reactivity in the dust

  17. The determination of cloud masses and dust characteristics from submillimetre thermal emission

    NASA Technical Reports Server (NTRS)

    Hildebrand, R. H.

    1983-01-01

    The principles by which the dust and masses and total masses of interstellar clouds and certain characteristics of interstellar dust grains can be derived from observations of far infrared and submillimeter thermal emission are reviewed. To the extent possible, the discussion will be independent of particular grain models.

  18. Laboratory Studies of the Cloud Droplet Activation Properties and Corresponding Chemistry of Saline Playa Dust

    NASA Astrophysics Data System (ADS)

    Gaston, C.; Pratt, K.; Suski, K. J.; May, N.; Gill, T. E.; Prather, K. A.

    2016-12-01

    Saline playas (dried lake beds) emit large quantities of dust that can facilitate the activation of cloud droplets. Despite the potential importance of playa dust for cloud formation, several models assume that dust is non-hygroscopic highlighting the need for measurements to clarify the role of dust from multiple sources in aerosol-cloud-climate interactions. Here we present water uptake measurements onto playa dust represented by the hygroscopicity parameter κ, which ranged from 0.002 ± 0.001 to 0.818 ± 0.094. Single-particle measurements made using an aircraft-aerosol time-of-flight mass spectrometer (A-ATOFMS) revealed the presence of halite, sodium sulfates, and sodium carbonates that were strongly correlated with κ underscoring the role that dust composition plays in water uptake. Predictions of κ made using bulk chemical techniques generally showed good agreement with measured values; however, several samples were poorly predicted using bulk particle composition. The lack of measurements/model agreement using this method and the strong correlations between κ and single-particle data are suggestive of chemical heterogeneities as a function of particle size and/or chemically distinct particle surfaces that dictate the water uptake properties of playa dust particles. Overall, our results highlight the ability of playa dust particles to act as cloud condensation nuclei that should be accounted for in models.

  19. Possible influences of Asian dust aerosols on cloud properties and radiative forcing observed from MODIS and CERES

    NASA Astrophysics Data System (ADS)

    Huang, Jianping; Minnis, Patrick; Lin, Bing; Wang, Tianhe; Yi, Yuhong; Hu, Yongxiang; Sun-Mack, Sunny; Ayers, Kirk

    2006-03-01

    The effects of dust storms on cloud properties and Radiative Forcing (RF) are analyzed over Northwestern China from April 2001 to June 2004 using data collected by the MODerate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Aqua and Terra satellites. On average, ice cloud effective particle diameter, optical depth and ice water path of cirrus clouds under dust polluted conditions are 11%, 32.8%, and 42% less, respectively, than those derived from ice clouds in dust-free atmospheric environments. Due to changes in cloud microphysics, the instantaneous net RF is increased from -161.6 W/m2 for dust-free clouds to -118.6 W/m2 for dust-contaminated clouds.

  20. The global impact of mineral dust on cloud droplet number concentration

    NASA Astrophysics Data System (ADS)

    Karydis, V.; Tsimpidi, A.; Bacer, S.; Pozzer, A.; Nenes, A.; Lelieveld, J.

    2016-12-01

    This study assesses the importance of mineral dust for cloud droplet formation by taking into account i) the adsorption of water on the surface of insoluble dust particles, ii) the coating of soluble material on the surface of mineral particles which augments their cloud condensation nuclei activity, and iii) the effect of dust on the inorganic aerosol concentrations through thermodynamic interactions with mineral cations. Simulations are carried out with the EMAC chemistry climate model that calculates the global atmospheric aerosol composition using the ISORROPIA-II thermodynamic equilibrium model and considers the gas phase interactions with K+-Ca2+-Mg2+-NH4+-Na+-SO42-NO3-Cl-H2O particle components. Emissions of the inert mineral dust and the reactive dust aerosol components are calculated online by taking into account the soil particle size distribution and chemical composition of different deserts worldwide (Karydis et al., 2016). We have implemented the "unified dust activation parameterization" (Kumar et al., 2011; Karydis et al., 2011) to calculate the droplet number concentration by taking into account the inherent hydrophilicity from adsorption and the acquired hygroscopicity from soluble salts by dust particles. Our simulations suggest that mineral dust significantly increases the cloud droplet number concentration (CDNC) over the main deserts and the adjacent oceans. However, over polluted areas the CDNC decreases significantly in the presence of dust. Furthermore, we investigate the role of adsorption activation of insoluble aerosols and the mineral dust thermodynamic interactions with inorganic anions on the cloud droplet formation. The CDNC sensitivity to the emission load, chemical composition, and inherent hydrophilicity of mineral dust is also tested. ReferencesKarydis, et al. (2011). "On the effect of dust particles on global cloud condensation nuclei and cloud droplet number." J. Geophys. Res. Atmos. 116. Karydis, et al. (2016). "Effects of

  1. Hydrodynamic model of a self-gravitating optically thick gas and dust cloud

    NASA Astrophysics Data System (ADS)

    Zhukova, E. V.; Zankovich, A. M.; Kovalenko, I. G.; Firsov, K. M.

    2015-10-01

    We propose an original mechanism of sustained turbulence generation in gas and dust clouds, the essence of which is the consistent provision of conditions for the emergence and maintenance of convective instability in the cloud. We considered a quasi-stationary one-dimensional model of a selfgravitating flat cloud with stellar radiation sources in its center. The material of the cloud is considered a two-component two-speed continuous medium, the first component of which, gas, is transparent for stellar radiation and is supposed to rest being in hydrostatic equilibrium, and the second one, dust, is optically dense and is swept out by the pressure of stellar radiation to the periphery of the cloud. The dust is specified as a set of spherical grains of a similar size (we made calculations for dust particles with radii of 0.05, 0.1, and 0.15 μm). The processes of scattering and absorption of UV radiation by dust particles followed by IR reradiation, with respect to which the medium is considered to be transparent, are taken into account. Dust-driven stellar wind sweeps gas outwards from the center of the cloud, forming a cocoon-like structure in the gas and dust. For the radiation flux corresponding to a concentration of one star with a luminosity of about 5 ×104 L ⊙ per square parsec on the plane of sources, sizes of the gas cocoon are equal to 0.2-0.4 pc, and for the dust one they vary from tenths of a parsec to six parsecs. Gas and dust in the center of the cavity are heated to temperatures of about 50-60 K in the model with graphite particles and up to 40 K in the model with silicate dust, while the background equilibrium temperature outside the cavity is set equal to 10 K. The characteristic dust expansion velocity is about 1-7 kms-1. Three structural elements define the hierarchy of scales in the dust cocoon. The sizes of the central rarefied cavity, the dense shell surrounding the cavity, and the thin layer inside the shell in which dust is settling provide

  2. Large Interstellar Polarisation Survey. II. UV/optical study of cloud-to-cloud variations of dust in the diffuse ISM

    NASA Astrophysics Data System (ADS)

    Siebenmorgen, R.; Voshchinnikov, N. V.; Bagnulo, S.; Cox, N. L. J.; Cami, J.; Peest, C.

    2018-03-01

    It is well known that the dust properties of the diffuse interstellar medium exhibit variations towards different sight-lines on a large scale. We have investigated the variability of the dust characteristics on a small scale, and from cloud-to-cloud. We use low-resolution spectro-polarimetric data obtained in the context of the Large Interstellar Polarisation Survey (LIPS) towards 59 sight-lines in the Southern Hemisphere, and we fit these data using a dust model composed of silicate and carbon particles with sizes from the molecular to the sub-micrometre domain. Large (≥6 nm) silicates of prolate shape account for the observed polarisation. For 32 sight-lines we complement our data set with UVES archive high-resolution spectra, which enable us to establish the presence of single-cloud or multiple-clouds towards individual sight-lines. We find that the majority of these 35 sight-lines intersect two or more clouds, while eight of them are dominated by a single absorbing cloud. We confirm several correlations between extinction and parameters of the Serkowski law with dust parameters, but we also find previously undetected correlations between these parameters that are valid only in single-cloud sight-lines. We find that interstellar polarisation from multiple-clouds is smaller than from single-cloud sight-lines, showing that the presence of a second or more clouds depolarises the incoming radiation. We find large variations of the dust characteristics from cloud-to-cloud. However, when we average a sufficiently large number of clouds in single-cloud or multiple-cloud sight-lines, we always retrieve similar mean dust parameters. The typical dust abundances of the single-cloud cases are [C]/[H] = 92 ppm and [Si]/[H] = 20 ppm.

  3. Dust in brown dwarfs. III. Formation and structure of quasi-static cloud layers

    NASA Astrophysics Data System (ADS)

    Woitke, P.; Helling, Ch.

    2004-01-01

    In this paper, first solutions of the dust moment equations developed in (Woitke & Helling \\cite{wh2003a}) for the description of dust formation and precipitation in brown dwarf and giant gas planet atmospheres are presented. We consider the special case of a static brown dwarf atmosphere, where dust particles continuously nucleate from the gas phase, grow by the accretion of molecules, settle gravitationally and re-evaporate thermally. Mixing by convective overshoot is assumed to replenish the atmosphere with condensable elements, which is necessary to counterbalance the loss of condensable elements by dust formation and gravitational settling (no dust without mixing). Applying a kinetic description of the relevant microphysical and chemical processes for TiO2-grains, the model makes predictions about the large-scale stratification of dust in the atmosphere, the depletion of molecules from the gas phase, the supersaturation of the gas in the atmosphere as well as the mean size and the mass fraction of dust grains as function of depth. Our results suggest that the presence of relevant amounts of dust is restricted to a layer, where the upper boundary (cloud deck) is related to the requirement of a minimum mixing activity (mixing time-scale τmix ≈ 10 6 s) and the lower boundary (cloud base) is determined by the thermodynamical stability of the grains. The nucleation occurs around the cloud deck where the gas is cool, strongly depleted, but nevertheless highly supersaturated (S ≫ 1). These particles settle gravitationally and populate the warmer layers below, where the in situ formation (nucleation) is ineffective or even not possible. During their descent, the particles grow and reach mean radii of ≈30 \\mum ... 400 \\mum at the cloud base, but the majority of the particles in the cloud layer remains much smaller. Finally, the dust grains sink into layers which are sufficiently hot to cause their thermal evaporation. Hence, an effective transport mechanism

  4. The Coupled Mars Dust and Water Cycles: Understanding How Clouds Affect the Vertical Distribution and Meridional Transport of Dust and Water.

    NASA Technical Reports Server (NTRS)

    Kahre, M. A.

    2015-01-01

    The dust and water cycles are crucial to the current Martian climate, and they are coupled through cloud formation. Dust strongly impacts the thermal structure of the atmosphere and thus greatly affects atmospheric circulation, while clouds provide radiative forcing and control the hemispheric exchange of water through the modification of the vertical distributions of water and dust. Recent improvements in the quality and sophistication of both observations and climate models allow for a more comprehensive understanding of how the interaction between the dust and water cycles (through cloud formation) affects the dust and water cycles individually. We focus here on the effects of clouds on the vertical distribution of dust and water, and how those vertical distributions control the net meridional transport of water. For this study, we utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) combined with the NASA ARC Mars Global Climate Model (MGCM). We demonstrate that the magnitude and nature of the net meridional transport of water between the northern and southern hemispheres during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. We further examine how clouds influence the atmospheric thermal structure and thus the vertical structure of the cloud belt. Our goal is to identify and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

  5. The Mars Dust and Water Cycles: Investigating the Influence of Clouds on the Vertical Distribution and Meridional Transport of Dust and Water.

    NASA Technical Reports Server (NTRS)

    Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.; Brecht, A. S.; Urata, R.

    2015-01-01

    The dust and water cycles are critical to the current Martian climate, and they interact with each other through cloud formation. Dust modulates the thermal structure of the atmosphere and thus greatly influences atmospheric circulation. Clouds provide radiative forcing and control the net hemispheric transport of water through the alteration of the vertical distributions of water and dust. Recent advancements in the quality and sophistication of both climate models and observations enable an increased understanding of how the coupling between the dust and water cycles (through cloud formation) impacts the dust and water cycles. We focus here on the effects of clouds on the vertical distributions of dust and water and how those vertical distributions control the net meridional transport of water. We utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) and the NASA ARC Mars Global Climate Model (MGCM) to show that the magnitude and nature of the hemispheric exchange of water during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. Further, we investigate how clouds influence atmospheric temperatures and thus the vertical structure of the cloud belt. Our goal is to isolate and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

  6. The Mars Dust and Water Cycles: Investigating the Influence of Clouds on the Vertical Distribution and Meridional Transport of Dust and Water

    NASA Astrophysics Data System (ADS)

    Kahre, Melinda A.; Haberle, Robert M.; Hollingsworth, Jeffery L.; Brecht, Amanda S.; Urata, Richard A.

    2015-11-01

    The dust and water cycles are critical to the current Martian climate, and they interact with each other through cloud formation. Dust modulates the thermal structure of the atmosphere and thus greatly influences atmospheric circulation. Clouds provide radiative forcing and control the net hemispheric transport of water through the alteration of the vertical distributions of water and dust. Recent advancements in the quality and sophistication of both climate models and observations enable an increased understanding of how the coupling between the dust and water cycles (through cloud formation) impacts the dust and water cycles. We focus here on the effects of clouds on the vertical distributions of dust and water and how those vertical distributions control the net meridional transport of water. We utilize observations of temperature, dust and water ice from the Mars Climate Sounder (MCS) on the Mars Reconnaissance Orbiter (MRO) and the NASA ARC Mars Global Climate Model (MGCM) to show that the magnitude and nature of the hemispheric exchange of water during NH summer is sensitive to the vertical structure of the simulated aphelion cloud belt. Further, we investigate how clouds influence atmospheric temperatures and thus the vertical structure of the cloud belt. Our goal is to isolate and understand the importance of radiative/dynamic feedbacks due to the physical processes involved with cloud formation and evolution on the current climate of Mars.

  7. Cosmic rays, gas and dust in nearby anticentre clouds. I. CO-to-H2 conversion factors and dust opacities

    NASA Astrophysics Data System (ADS)

    Remy, Q.; Grenier, I. A.; Marshall, D. J.; Casandjian, J. M.

    2017-05-01

    Aims: We aim to explore the capabilities of dust emission and γ rays for probing the properties of the interstellar medium in the nearby anti-centre region, using γ-ray observations with the Fermi Large Area Telescope (LAT), and the thermal dust optical depth inferred from Planck and IRAS observations. We also aim to study massive star-forming clouds including the well known Taurus, Auriga, Perseus, and California molecular clouds, as well as a more diffuse structure which we refer to as Cetus. In particular, we aim at quantifying potential variations in cosmic-ray density and dust properties per gas nucleon across the different gas phases and different clouds, and at measuring the CO-to-H2 conversion factor, XCO, in different environments. Methods: We have separated six nearby anti-centre clouds that are coherent in velocities and distances, from the Galactic-disc background in H I 21-cm and 12CO 2.6-mm line emission. We have jointly modelled the γ-ray intensity recorded between 0.4 and 100 GeV, and the dust optical depth τ353 at 353 GHz as a combination of H I-bright, CO-bright, and ionised gas components. The complementary information from dust emission and γ rays was used to reveal the gas not seen, or poorly traced, by H I, free-free, and 12CO emissions, namely (I) the opaque H iand diffuse H2 present in the Dark Neutral Medium at the atomic-molecular transition, and (II) the dense H2 to be added where 12CO lines saturate. Results: The measured interstellar γ-ray spectra support a uniform penetration of the cosmic rays with energies above a few GeV through the clouds, from the atomic envelopes to the 12CO-bright cores, and with a small ± 9% cloud-to-cloud dispersion in particle flux. We detect the ionised gas from the H iiregion NGC 1499 in the dust and γ-ray emissions and measure its mean electron density and temperature. We find a gradual increase in grain opacity as the gas (atomic or molecular) becomes more dense. The increase reaches a factor of

  8. Dust clouds and plasmoids in Saturn's magnetosphere as seen with four Cassini instruments

    NASA Astrophysics Data System (ADS)

    Khalisi, Emil

    2017-03-01

    We revisit the evidence for a ;dust cloud; observed by the Cassini spacecraft at Saturn in 2006. The data of four instruments are simultaneously compared to interpret the signatures of a coherent swarm of dust that would have remained near the equatorial plane for as long as six weeks. The conspicuous pattern, as seen in the dust counters of the Cosmic Dust Analyser (CDA), clearly repeats on three consecutive revolutions of the spacecraft. That particular cloud is estimated to about 1.36 Saturnian radii in size, and probably broadening. We also present a reconnection event from the magnetic field data (MAG) that leave behind several plasmoids like those reported from the Voyager flybys in the early 1980s. That magnetic bubbles happened at the dawn side of Saturn's magnetosphere. At their nascency, the magnetic field showed a switchover of its alignment, disruption of flux tubes and a recovery on a time scale of about 30 days. However, we cannot rule out that different events might have taken place. Empirical evidence is shown at another occasion when a plasmoid was carrying a cloud of tiny dust particles such that a connection between plasmoids and coherent dust clouds is probable.

  9. Estimating dust production rate of carbon-rich stars in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Nanni, A.; Marigo, P.; Groenewegen, M. A. T.; Aringer, B.; Pastorelli, G.; Rubele, S.; Girardi, L.; Bressan, A.; Bladh, S.

    We compute a grid of spectra describing dusty Circumstellar Envelopes of Thermally Pulsing Asymptotic Giant Branch carbon-rich stars by employing a physically grounded description for dust growth. The optical constants for carbon dust have been selected in order to reproduce simultaneously the most important color-color diagrams in the Near and Mid Infrared bands. We fit the Spectral Energy Distribution of ≈2000 carbon-rich in the Small Magellanic Cloud and we compute their total dust production rate. We compare our results with the ones in the literature. Different choices of the dust-to-gas ratio and outflow expansion velocity adopted in different works, yield, in some cases, a total dust budget about three times lower than the one derived from our scheme, with the same optical data set for carbon dust.

  10. The implications of dust ice nuclei effect on cloud top temperature in a complex mesoscale convective system.

    PubMed

    Li, Rui; Dong, Xue; Guo, Jingchao; Fu, Yunfei; Zhao, Chun; Wang, Yu; Min, Qilong

    2017-10-23

    Mineral dust is the most important natural source of atmospheric ice nuclei (IN) which may significantly mediate the properties of ice cloud through heterogeneous nucleation and lead to crucial impacts on hydrological and energy cycle. The potential dust IN effect on cloud top temperature (CTT) in a well-developed mesoscale convective system (MCS) was studied using both satellite observations and cloud resolving model (CRM) simulations. We combined satellite observations from passive spectrometer, active cloud radar, lidar, and wind field simulations from CRM to identify the place where ice cloud mixed with dust particles. For given ice water path, the CTT of dust-mixed cloud is warmer than that in relatively pristine cloud. The probability distribution function (PDF) of CTT for dust-mixed clouds shifted to the warmer end and showed two peaks at about -45 °C and -25 °C. The PDF for relatively pristine cloud only show one peak at -55 °C. Cloud simulations with different microphysical schemes agreed well with each other and showed better agreement with satellite observations in pristine clouds, but they showed large discrepancies in dust-mixed clouds. Some microphysical schemes failed to predict the warm peak of CTT related to heterogeneous ice formation.

  11. Origins and Dynamics of Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Dermott, Stanley F.

    2005-01-01

    This is a final report for research supported by the National Aeronautics and Space Administration issued through the Office of Space Science Planetary Geology and Geophysics Program, covering all relevant activities during its 3-year period of funding from 02/01/2002 through to 01/31/2005. The ongoing aim of the research supported through this grant, and now through a successor award, is to investigate the origin of interplanetary dust particles (IDPs) and their dynamical and collisional evolution, in order to: (1) understand the provenance of zodiacal cloud particles and their transport from their source regions to the inner solar system; (2) produce detailed models of the zodiacal cloud and its constituent components; (3) determine the origin of the dust particles accreted by the Earth; (4) ascertain the level of temporal variations in the dust environment of the inner solar system and the accretion rate of IDPs by the Earth, and evaluate potential effects on global climate; and to (5) exploit this research as a basis for interpreting the structure observed in exozodiacal clouds that may result from the collisional evolution of planetesimals and the presence of unseen planets.

  12. Results from Automated Cloud and Dust Devil Detection Onboard the MER

    NASA Technical Reports Server (NTRS)

    Chien, Steve; Castano, Rebecca; Bornstein, Benjamin; Fukunaga, Alex; Castano, Andres; Biesiadecki, Jeffrey; Greeley, Ron; Whelley, Patrick; Lemmon, Mark

    2008-01-01

    We describe a new capability to automatically detect dust devils and clouds in imagery onboard rovers, enabling downlink of just the images with the targets or only portions of the images containing the targets. Previously, the MER rovers conducted campaigns to image dust devils and clouds by commanding a set of images be collected at fixed times and downloading the entire image set. By increasing the efficiency of the campaigns, more campaigns can be executed. Software for these new capabilities was developed, tested, integrated, uploaded, and operationally checked out on both rovers as part of the R9.2 software upgrade. In April 2007 on Sol 1147 a dust devil was automatically detected onboard the Spirit rover for the first time. We discuss the operational usage of the capability and present initial dust devil results showing how this preliminary application has demonstrated the feasibility and potential benefits of the approach.

  13. The fundamentally different dynamics of dust and gas in molecular clouds

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Lee, Hyunseok

    2016-03-01

    We study the behaviour of large dust grains in turbulent molecular clouds (MCs). In primarily neutral regions, dust grains move as aerodynamic particles, not necessarily with the gas. We therefore directly simulate, for the first time, the behaviour of aerodynamic grains in highly supersonic, magnetohydrodynamic turbulence typical of MCs. We show that, under these conditions, grains with sizes a ≳ 0.01 micron exhibit dramatic (exceeding factor ˜1000) fluctuations in the local dust-to-gas ratio (implying large small-scale variations in abundances, dust cooling rates, and dynamics). The dust can form highly filamentary structures (which would be observed in both dust emission and extinction), which can be much thinner than the characteristic width of gas filaments. Sometimes, the dust and gas filaments are not even in the same location. The `clumping factor' < n_dust2 > / < n_dust > 2 of the dust (critical for dust growth/coagulation/shattering) can reach ˜100, for grains in the ideal size range. The dust clustering is maximized around scales ˜ 0.2 pc (a/μm) (ngas/100 cm- 3)- 1, and is `averaged out' on larger scales. However, because the density varies widely in supersonic turbulence, the dynamic range of scales (and interesting grain sizes) for these fluctuations is much broader than in the subsonic case. Our results are applicable to MCs of essentially all sizes and densities, but we note how Lorentz forces and other physics (neglected here) may change them in some regimes. We discuss the potentially dramatic consequences for star formation, dust growth and destruction, and dust-based observations of MCs.

  14. Forecast errors in dust vertical distributions over Rome (Italy): Multiple particle size representation and cloud contributions

    NASA Astrophysics Data System (ADS)

    Kishcha, P.; Alpert, P.; Shtivelman, A.; Krichak, S. O.; Joseph, J. H.; Kallos, G.; Katsafados, P.; Spyrou, C.; Gobbi, G. P.; Barnaba, F.; Nickovic, S.; PéRez, C.; Baldasano, J. M.

    2007-08-01

    In this study, forecast errors in dust vertical distributions were analyzed. This was carried out by using quantitative comparisons between dust vertical profiles retrieved from lidar measurements over Rome, Italy, performed from 2001 to 2003, and those predicted by models. Three models were used: the four-particle-size Dust Regional Atmospheric Model (DREAM), the older one-particle-size version of the SKIRON model from the University of Athens (UOA), and the pre-2006 one-particle-size Tel Aviv University (TAU) model. SKIRON and DREAM are initialized on a daily basis using the dust concentration from the previous forecast cycle, while the TAU model initialization is based on the Total Ozone Mapping Spectrometer aerosol index (TOMS AI). The quantitative comparison shows that (1) the use of four-particle-size bins in the dust modeling instead of only one-particle-size bins improves dust forecasts; (2) cloud presence could contribute to noticeable dust forecast errors in SKIRON and DREAM; and (3) as far as the TAU model is concerned, its forecast errors were mainly caused by technical problems with TOMS measurements from the Earth Probe satellite. As a result, dust forecast errors in the TAU model could be significant even under cloudless conditions. The DREAM versus lidar quantitative comparisons at different altitudes show that the model predictions are more accurate in the middle part of dust layers than in the top and bottom parts of dust layers.

  15. Estimating the dust production rate of carbon stars in the Small Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Nanni, Ambra; Marigo, Paola; Girardi, Léo; Rubele, Stefano; Bressan, Alessandro; Groenewegen, Martin A. T.; Pastorelli, Giada; Aringer, Bernhard

    2018-02-01

    We employ newly computed grids of spectra reprocessed by dust for estimating the total dust production rate (DPR) of carbon stars in the Small Magellanic Cloud (SMC). For the first time, the grids of spectra are computed as a function of the main stellar parameters, i.e. mass-loss rate, luminosity, effective temperature, current stellar mass and element abundances at the photosphere, following a consistent, physically grounded scheme of dust growth coupled with stationary wind outflow. The model accounts for the dust growth of various dust species formed in the circumstellar envelopes of carbon stars, such as carbon dust, silicon carbide and metallic iron. In particular, we employ some selected combinations of optical constants and grain sizes for carbon dust that have been shown to reproduce simultaneously the most relevant colour-colour diagrams in the SMC. By employing our grids of models, we fit the spectral energy distributions of ≈3100 carbon stars in the SMC, consistently deriving some important dust and stellar properties, i.e. luminosities, mass-loss rates, gas-to-dust ratios, expansion velocities and dust chemistry. We discuss these properties and we compare some of them with observations in the Galaxy and Large Magellanic Cloud. We compute the DPR of carbon stars in the SMC, finding that the estimates provided by our method can be significantly different, between a factor of ≈2-5, than the ones available in the literature. Our grids of models, including the spectra and other relevant dust and stellar quantities, are publicly available at http://starkey.astro.unipd.it/web/guest/dustymodels.

  16. Mapping the three-dimensional dust extinction towards the supernova remnant S147 - the S147 dust cloud

    NASA Astrophysics Data System (ADS)

    Chen, B.-Q.; Liu, X.-W.; Ren, J.-J.; Yuan, H.-B.; Huang, Y.; Yu, B.; Xiang, M.-S.; Wang, C.; Tian, Z.-J.; Zhang, H.-W.

    2017-12-01

    We present a three-dimensional (3D) extinction analysis in the region towards the supernova remnant (SNR) S147 (G180.0-1.7) using multiband photometric data from the Xuyi Schmidt Telescope Photometric Survey of the Galactic Anticentre (XSTPS-GAC), 2MASS and WISE. We isolate a previously unrecognized dust structure likely to be associated with SNR S147. The structure, which we term as 'S147 dust cloud', is estimated to have a distance d = 1.22 ± 0.21 kpc, consistent with the conjecture that S147 is associated with pulsar PSR J0538 + 2817. The cloud includes several dense clumps of relatively high extinction that locate on the radio shell of S147 and coincide spatially with the CO and gamma-ray emission features. We conclude that the usage of CO measurements to trace the SNR associated MCs is unavoidably limited by the detection threshold, dust depletion and the difficulty of distance estimates in the outer Galaxy. 3D dust extinction mapping may provide a better way to identify and study SNR-MC interactions.

  17. Unraveling the Mystery of Exozodiacal Dust

    NASA Astrophysics Data System (ADS)

    Ertel, S.; Augereau, J.-C.; Thébault, P.; Absil, O.; Bonsor, A.; Defrère, D.; Kral, Q.; Le Bouquin, J.-B.; Lebreton, J.; Coudé du Foresto, V.

    2014-01-01

    Exozodiacal dust clouds are thought to be the extrasolar analogs of the Solar System's zodiacal dust. Studying these systems provides insights in the architecture of the innermost regions of planetary systems, including the Habitable Zone. Furthermore, the mere presence of the dust may result in major obstacles for direct imaging of earth-like planets. Our EXOZODI project aims to detect and study exozodiacal dust and to explain its origin. We are carrying out the first large, near-infrared interferometric survey in the northern (CHARA/FLUOR) and southern (VLTI/PIONIER) hemispheres. Preliminary results suggest a detection rate of up to 30% around A to K type stars and interesting trends with spectral type and age. We focus here on presenting the observational work carried out by our team.

  18. Spectral shifting strongly constrains molecular cloud disruption by radiation pressure on dust

    NASA Astrophysics Data System (ADS)

    Reissl, Stefan; Klessen, Ralf S.; Mac Low, Mordecai-Mark; Pellegrini, Eric W.

    2018-03-01

    Aim. We aim to test the hypothesis that radiation pressure from young star clusters acting on dust is the dominant feedback agent disrupting the largest star-forming molecular clouds and thus regulating the star-formation process. Methods: We performed multi-frequency, 3D, radiative transfer calculations including both scattering and absorption and re-emission to longer wavelengths for model clouds with masses of 104-107 M⊙, containing embedded clusters with star formation efficiencies of 0.009-91%, and varying maximum grain sizes up to 200 μm. We calculated the ratio between radiative and gravitational forces to determine whether radiation pressure can disrupt clouds. Results: We find that radiation pressure acting on dust almost never disrupts star-forming clouds. Ultraviolet and optical photons from young stars to which the cloud is optically thick do not scatter much. Instead, they quickly get absorbed and re-emitted by the dust at thermal wavelengths. As the cloud is typically optically thin to far-infrared radiation, it promptly escapes, depositing little momentum in the cloud. The resulting spectrum is more narrowly peaked than the corresponding Planck function, and exhibits an extended tail at longer wavelengths. As the opacity drops significantly across the sub-mm and mm wavelength regime, the resulting radiative force is even smaller than for the corresponding single-temperature blackbody. We find that the force from radiation pressure falls below the strength of gravitational attraction by an order of magnitude or more for either Milky Way or moderate starbust conditions. Only for unrealistically large maximum grain sizes, and star formation efficiencies far exceeding 50% do we find that the strength of radiation pressure can exceed gravity. Conclusions: We conclude that radiation pressure acting on dust does not disrupt star-forming molecular clouds in any Local Group galaxies. Radiation pressure thus appears unlikely to regulate the star

  19. COSMIC INFRARED BACKGROUND FLUCTUATIONS AND ZODIACAL LIGHT

    SciT

    Arendt, Richard G.; Kashlinsky, A.; Moseley, S. H.

    We performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution or from IRAC observations of high-latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS field at low ecliptic latitude where the zodiacal light intensity varies by factors of ∼2 over the range of solar elongations atmore » which the field can be observed. We find that the white-noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that are evident in the zodiacal light model. At large angular scales (≳100″) where excess power above the white noise is observed, we find no correlation of the power with the modeled intensity of the zodiacal light. This test clearly indicates that the large-scale power in the infrared background is not being caused by the zodiacal light.« less

  20. Cosmic Infrared Background Fluctuations and Zodiacal Light

    NASA Technical Reports Server (NTRS)

    Arendt, Richard G.; Kashlinsky, A.; Moseley, S. H.; Mather, J.

    2017-01-01

    We performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR (near-infrared)background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution or from IRAC (Infrared Array Camera) observations of high-latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS (Cosmic Evolution Survey) field at low ecliptic latitude where the zodiacal light intensity varies by factors of approximately 2 over the range of solar elongations at which the field can be observed. We find that the white-noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that are evident in the zodiacal light model. At large angular scales (greater than or approximately equal to 100 arcseconds) where excess power above the white noise is observed, we find no correlation of the power with the modeled intensity of the zodiacal light. This test clearly indicates that the large-scale power in the infrared background is not being caused by the zodiacal light.

  1. Cosmic Infrared Background Fluctuations and Zodiacal Light

    NASA Astrophysics Data System (ADS)

    Arendt, Richard G.; Kashlinsky, A.; Moseley, S. H.; Mather, J.

    2016-06-01

    We performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution or from IRAC observations of high-latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS field at low ecliptic latitude where the zodiacal light intensity varies by factors of ˜2 over the range of solar elongations at which the field can be observed. We find that the white-noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that are evident in the zodiacal light model. At large angular scales (≳100″) where excess power above the white noise is observed, we find no correlation of the power with the modeled intensity of the zodiacal light. This test clearly indicates that the large-scale power in the infrared background is not being caused by the zodiacal light.

  2. Impact of Long-Range Transported African Dust Events on Cloud Composition and Physical Properties at a Caribbean Tropical Montane Cloud Forest

    NASA Astrophysics Data System (ADS)

    Valle-Diaz, C. J.; Torres-Delgado, E.; Lee, T.; Collett, J. L.; Cuadra-Rodriguez, L. A.; Prather, K. A.; Spiegel, J.; Eugster, W.

    2012-12-01

    We studied the impact of long-range transported African Dust (LRTAD) on cloud composition and properties at the Caribbean tropical montane cloud forest (TMCF) of Pico del Este (PE), as part of the Puerto Rico African Dust and Clouds Study (PRADACS). Here we present results from measurements performed in July 2011. Bulk chemical analysis of cloud water and rainwater showed pH and conductivity higher in the presence of dust. pH and conductivity were also higher for larger cloud droplets (size cut of 17 μm at 50% efficiency) suggesting a higher content of dust in this fraction. The concentration of the water-soluble ions in rainwater was found to be lower than for cloud water. This in turn translates to higher pH and lower conductivity. African dust influence at PE was confirmed by the presence of nss-Ca, Fe, Mg, Na, and Al in cloud/rain water, and inferred by HYSPLIT trajectories and the satellite images from the Saharan Air Layer (SAL). Interstitial single-particle size and chemistry measured using aerosol time-of-flight mass spectrometry revealed mostly sea-salt particles (Na, Cl, Ca) and dust particles (Fe, Ti, Mg, nss-Ca). Anthropogenic influence detected as the presence of EC, a tracer for combustion processes, was found to be fairly small according to ATOFMS measurements. An increase of total organic carbon, total nitrogen, and dissolved organic carbon was observed during LRTAD events. Cloud droplet distributions revealed that LRTAD can lead to more numerous, but smaller cloud droplets (around 8 μm in average) at PE. However, total liquid water content appeared to be unaffected by this shift of droplet sizes. Overall, differences in the studied physicochemical properties of aerosols and clouds during dust and non-dust events were observed. Our results show that during LRTAD events, aerosol-cloud-precipitation interactions are altered at PE. Detailed results will be presented at the meeting.

  3. Atmospheric Movement of Microorganisms in Clouds of Desert Dust and Implications for Human Health

    PubMed Central

    Griffin, Dale W.

    2007-01-01

    Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources. PMID:17630335

  4. Atmospheric movement of microorganisms in clouds of desert dust and implications for human health.

    PubMed

    Griffin, Dale W

    2007-07-01

    Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.

  5. Atmospheric movement of microorganisms in clouds of desert dust and implications for human health

    Griffin, Dale W.

    2007-01-01

    Billions of tons of desert dust move through the atmosphere each year. The primary source regions, which include the Sahara and Sahel regions of North Africa and the Gobi and Takla Makan regions of Asia, are capable of dispersing significant quantities of desert dust across the traditionally viewed oceanic barriers. While a considerable amount of research by scientists has addressed atmospheric pathways and aerosol chemistry, very few studies to determine the numbers and types of microorganisms transported within these desert dust clouds and the roles that they may play in human health have been conducted. This review is a summary of the current state of knowledge of desert dust microbiology and the health impact that desert dust and its microbial constituents may have in downwind environments both close to and far from their sources.

  6. Dust in a compact, cold, high-velocity cloud: A new approach to removing foreground emission

    NASA Astrophysics Data System (ADS)

    Lenz, D.; Flöer, L.; Kerp, J.

    2016-02-01

    Context. Because isolated high-velocity clouds (HVCs) are found at great distances from the Galactic radiation field and because they have subsolar metallicities, there have been no detections of dust in these structures. A key problem in this search is the removal of foreground dust emission. Aims: Using the Effelsberg-Bonn H I Survey and the Planck far-infrared data, we investigate a bright, cold, and clumpy HVC. This cloud apparently undergoes an interaction with the ambient medium and thus has great potential to form dust. Methods: To remove the local foreground dust emission we used a regularised, generalised linear model and we show the advantages of this approach with respect to other methods. To estimate the dust emissivity of the HVC, we set up a simple Bayesian model with mildly informative priors to perform the line fit instead of an ordinary linear least-squares approach. Results: We find that the foreground can be modelled accurately and robustly with our approach and is limited mostly by the cosmic infrared background. Despite this improvement, we did not detect any significant dust emission from this promising HVC. The 3σ-equivalent upper limit to the dust emissivity is an order of magnitude below the typical values for the Galactic interstellar medium.

  7. Satellite-Based Assessment of Possible Dust Aerosols Semi-Direct Effect on Cloud Water Path over East Asia

    NASA Technical Reports Server (NTRS)

    Huang, Jianping; Lin, Bing; Minnis, Patrick; Wang, Tainhe; Wang, Xin; Hu, Yongxiang; Yi, Yuhong; Ayers, J. Kirk

    2006-01-01

    The semi-direct effects of dust aerosols are analyzed over eastern Asia using 2 years (June 2002 to June 2004) of data from the Clouds and the Earth s Radiant Energy System (CERES) scanning radiometer and MODerate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite, and 18 years (1984 to 2001) of International Satellite Cloud Climatology Project (ISCCP) data. The results show that the water path of dust-contaminated clouds is considerably smaller than that of dust-free clouds. The mean ice water path (IWP) and liquid water path (LWP) of dusty clouds are less than their dust-free counterparts by 23.7% and 49.8%, respectively. The long-term statistical relationship derived from ISCCP also confirms that there is significant negative correlation between dust storm index and ISCCP cloud water path. These results suggest that dust aerosols warm clouds, increase the evaporation of cloud droplets and further reduce cloud water path, the so-called semi-direct effect. The semi-direct effect may play a role in cloud development over arid and semi-arid areas of East Asia and contribute to the reduction of precipitation.

  8. A physically-based approach of treating dust-water cloud interactions in climate models

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Karydis, V.; Barahona, D.; Sokolik, I. N.; Nenes, A.

    2011-12-01

    All aerosol-cloud-climate assessment studies to date assume that the ability of dust (and other insoluble species) to act as a Cloud Condensation Nuclei (CCN) is determined solely by their dry size and amount of soluble material. Recent evidence however clearly shows that dust can act as efficient CCN (even if lacking appreciable amounts of soluble material) through adsorption of water vapor onto the surface of the particle. This "inherent" CCN activity is augmented as the dust accumulates soluble material through atmospheric aging. A comprehensive treatment of dust-cloud interactions therefore requires including both of these sources of CCN activity in atmospheric models. This study presents a "unified" theory of CCN activity that considers both effects of adsorption and solute. The theory is corroborated and constrained with experiments of CCN activity of mineral aerosols generated from clays, calcite, quartz, dry lake beds and desert soil samples from Northern Africa, East Asia/China, and Northern America. The unified activation theory then is included within the mechanistic droplet activation parameterization of Kumar et al. (2009) (including the giant CCN correction of Barahona et al., 2010), for a comprehensive treatment of dust impacts on global CCN and cloud droplet number. The parameterization is demonstrated with the NASA Global Modeling Initiative (GMI) Chemical Transport Model using wind fields computed with the Goddard Institute for Space Studies (GISS) general circulation model. References Barahona, D. et al. (2010) Comprehensively Accounting for the Effect of Giant CCN in Cloud Activation Parameterizations, Atmos.Chem.Phys., 10, 2467-2473 Kumar, P., I.N. Sokolik, and A. Nenes (2009), Parameterization of cloud droplet formation for global and regional models: including adsorption activation from insoluble CCN, Atmos.Chem.Phys., 9, 2517- 2532

  9. Water clouds and dust aerosols observations with PFS MEX at Mars

    NASA Astrophysics Data System (ADS)

    Zasova, L.; Formisano, V.; Moroz, V.; Grassi, D.; Ignatiev, N.; Giuranna, M.; Hansen, G.; Blecka, M.; Ekonomov, A.; Lellouch, E.; Fonti, S.; Grigoriev, A.; Hirsch, H.; Khatuntsev, I.; Mattana, A.; Maturilli, A.; Moshkin, B.; Patsaev, D.; Piccioni, G.; Rataj, M.; Saggin, B.

    2005-08-01

    Observations of water ice clouds and dust are among the main scientific goals of the Planetary Fourier Spectrometer (PFS), a payload instrument of the European Mars Express mission. We report some results, obtained in three orbits: 37, 41 and 68. The temperature profile, and dust and water ice cloud opacities are retrieved from the thermal infrared (long-wavelength channel of PFS) in a self-consistent way using the same spectrum. Orographic ice clouds are identified above Olympus (orbit 37) and Ascraeus Mons (orbit 68). Both volcanoes were observed near noon at Ls=337° and 342°, respectively. The effective radius of ice particles is preliminary estimated as 1-3 μm, changing along the flanks. The corresponding visual opacity changes in the interval 0.2-0.4 above Olympus and 0.1-0.6 above Ascraeus Mons. In the case of Ascraeus Mons, the ice clouds were observed mainly above the Southern flank of the volcano with maximum opacity near the summit. In the case of Olympus, the clouds were found above both sides of the top. A different type of ice cloud is observed at latitudes above 50°N (orbit 68) in the polar hood: the effective particle radius is estimated to be 4 μm. Below the 1 mb level an inversion in the temperature profiles is found with maximum temperature at around 0.6 mb. Along orbit 68 it appears above Alba Patera, then it increases to the north and decreases above the CO 2 polar cap. Beginning from latitude 20°S above Tharsis (orbit 68), the ice clouds and dust contribute equally to the spectral shape. Further on, the ice clouds are found everywhere along orbit 68 up to the Northern polar cap, except the areas between the Northern flank of Ascraeus Mons (below 10 km) and the edge of Alba Patera. Orbit 41 is shifted from the orbit 68 by roughly 180° longitude and passes through Hellas. Ice clouds are not visible in this orbit at latitudes below 80°S. The dust opacity is anticorrelated with the surface altitude. From 70°S to 25°N latitude the vertical

  10. Modeling dust emission in the Magellanic Clouds with Spitzer and Herschel

    NASA Astrophysics Data System (ADS)

    Chastenet, Jérémy; Bot, Caroline; Gordon, Karl D.; Bocchio, Marco; Roman-Duval, Julia; Jones, Anthony P.; Ysard, Nathalie

    2017-05-01

    Context. Dust modeling is crucial to infer dust properties and budget for galaxy studies. However, there are systematic disparities between dust grain models that result in corresponding systematic differences in the inferred dust properties of galaxies. Quantifying these systematics requires a consistent fitting analysis. Aims: We compare the output dust parameters and assess the differences between two dust grain models, the DustEM model and THEMIS. In this study, we use a single fitting method applied to all the models to extract a coherent and unique statistical analysis. Methods: We fit the models to the dust emission seen by Spitzer and Herschel in the Small and Large Magellanic Clouds (SMC and LMC). The observations cover the infrared (IR) spectrum from a few microns to the sub-millimeter range. For each fitted pixel, we calculate the full n-D likelihood based on a previously described method. The free parameters are both environmental (U, the interstellar radiation field strength; αISRF, power-law coefficient for a multi-U environment; Ω∗, the starlight strength) and intrinsic to the model (YI: abundances of the grain species I; αsCM20, coefficient in the small carbon grain size distribution). Results: Fractional residuals of five different sets of parameters show that fitting THEMIS brings a more accurate reproduction of the observations than the DustEM model. However, independent variations of the dust species show strong model-dependencies. We find that the abundance of silicates can only be constrained to an upper-limit and that the silicate/carbon ratio is different than that seen in our Galaxy. In the LMC, our fits result in dust masses slightly lower than those found in the literature, by a factor lower than 2. In the SMC, we find dust masses in agreement with previous studies.

  11. Experimental study on the minimum ignition temperature of coal dust clouds in oxy-fuel combustion atmospheres.

    PubMed

    Wu, Dejian; Norman, Frederik; Verplaetsen, Filip; Van den Bulck, Eric

    2016-04-15

    BAM furnace apparatus tests were conducted to investigate the minimum ignition temperature of coal dusts (MITC) in O2/CO2 atmospheres with an O2 mole fraction from 20 to 50%. Three coal dusts: Indonesian Sebuku coal, Pittsburgh No.8 coal and South African coal were tested. Experimental results showed that the dust explosion risk increases significantly with increasing O2 mole fraction by reducing the minimum ignition temperature for the three tested coal dust clouds dramatically (even by 100°C). Compared with conventional combustion, the inhibiting effect of CO2 was found to be comparatively large in dust clouds, particularly for the coal dusts with high volatile content. The retardation effect of the moisture content on the ignition of dust clouds was also found to be pronounced. In addition, a modified steady-state mathematical model based on heterogeneous reaction was proposed to interpret the observed experimental phenomena and to estimate the ignition mechanism of coal dust clouds under minimum ignition temperature conditions. The analysis revealed that heterogeneous ignition dominates the ignition mechanism for sub-/bituminous coal dusts under minimum ignition temperature conditions, but the decrease of coal maturity facilitates homogeneous ignition. These results improve our understanding of the ignition behaviour and the explosion risk of coal dust clouds in oxy-fuel combustion atmospheres. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Dust cloud evolution in sub-stellar atmospheres via plasma deposition and plasma sputtering

    NASA Astrophysics Data System (ADS)

    Stark, C. R.; Diver, D. A.

    2018-04-01

    Context. In contemporary sub-stellar model atmospheres, dust growth occurs through neutral gas-phase surface chemistry. Recently, there has been a growing body of theoretical and observational evidence suggesting that ionisation processes can also occur. As a result, atmospheres are populated by regions composed of plasma, gas and dust, and the consequent influence of plasma processes on dust evolution is enhanced. Aim. This paper aims to introduce a new model of dust growth and destruction in sub-stellar atmospheres via plasma deposition and plasma sputtering. Methods: Using example sub-stellar atmospheres from DRIFT-PHOENIX, we have compared plasma deposition and sputtering timescales to those from neutral gas-phase surface chemistry to ascertain their regimes of influence. We calculated the plasma sputtering yield and discuss the circumstances where plasma sputtering dominates over deposition. Results: Within the highest dust density cloud regions, plasma deposition and sputtering dominates over neutral gas-phase surface chemistry if the degree of ionisation is ≳10-4. Loosely bound grains with surface binding energies of the order of 0.1-1 eV are susceptible to destruction through plasma sputtering for feasible degrees of ionisation and electron temperatures; whereas, strong crystalline grains with binding energies of the order 10 eV are resistant to sputtering. Conclusions: The mathematical framework outlined sets the foundation for the inclusion of plasma deposition and plasma sputtering in global dust cloud formation models of sub-stellar atmospheres.

  13. A study of zodiacal light models

    NASA Technical Reports Server (NTRS)

    Gary, G. A.; Craven, P. D.

    1973-01-01

    A review is presented of the basic equations used in the analysis of photometric observations of zodiacal light. A survey of the methods used to model the zodiacal light in and out of the ecliptic is given. Results and comparison of various models are presented, as well as recent results by the authors.

  14. Impact of Saharan dust on North Atlantic marine stratocumulus clouds: importance of the semidirect effect

    NASA Astrophysics Data System (ADS)

    Amiri-Farahani, Anahita; Allen, Robert J.; Neubauer, David; Lohmann, Ulrike

    2017-05-01

    One component of aerosol-cloud interactions (ACI) involves dust and marine stratocumulus clouds (MSc). Few observational studies have focused on dust-MSc interactions, and thus this effect remains poorly quantified. We use observations from multiple sensors in the NASA A-Train satellite constellation from 2004 to 2012 to obtain estimates of the aerosol-cloud radiative effect, including its uncertainty, of dust aerosol influencing Atlantic MSc off the coast of northern Africa between 45° W and 15° E and between 0 and 35° N. To calculate the aerosol-cloud radiative effect, we use two methods following Quaas et al. (2008) (Method 1) and Chen et al. (2014) (Method 2). These two methods yield similar results of -1.5 ± 1.4 and -1.5 ± 1.6 W m-2, respectively, for the annual mean aerosol-cloud radiative effect. Thus, Saharan dust modifies MSc in a way that acts to cool the planet. There is a strong seasonal variation, with the aerosol-cloud radiative effect switching from significantly negative during the boreal summer to weakly positive during boreal winter. Method 1 (Method 2) yields -3.8 ± 2.5 (-4.3 ± 4.1) during summer and 1 ± 2.9 (0.6 ± 1) W m-2 during winter. In Method 1, the aerosol-cloud radiative effect can be decomposed into two terms, one representing the first aerosol indirect effect and the second representing the combination of the second aerosol indirect effect and the semidirect effect (i.e., changes in liquid water path and cloud fraction in response to changes in absorbing aerosols and local heating). The first aerosol indirect effect is relatively small, varying from -0.7 ± 0.6 in summer to 0.1 ± 0.5 W m-2 in winter. The second term, however, dominates the overall radiative effect, varying from -3.2 ± 2.5 in summer to 0.9 ± 2.9 W m-2 during winter. Studies show that the semidirect effect can result in a negative (i.e., absorbing aerosol lies above low clouds like MSc) or positive (i.e., absorbing aerosol lies within low clouds) aerosol-cloud

  15. Water Ice Clouds and Dust in the Martian Atmosphere Observed by Mars Climate Sounder

    NASA Technical Reports Server (NTRS)

    Benson, Jennifer L.; Kass, David; Heavens, Nicholas; Kleinbohl, Armin

    2011-01-01

    The water ice clouds are primarily controlled by the temperature structure and form at the water condensation level. Clouds in all regions presented show day/night differences. Cloud altitude varies between night and day in the SPH and tropics: (1) NPH water ice opacity is greater at night than day at some seasons (2) The diurnal thermal tide controls the daily variability. (3) Strong day/night changes indicate that the amount of gas in the atmosphere varies significantly. See significant mixtures of dust and ice at the same altitude planet-wide (1) Points to a complex radiative and thermal balance between dust heating (in the visible) and ice heating or cooling in the infrared. Aerosol layering: (1) Early seasons reveal a zonally banded spatial distribution (2) Some localized longitudinal structure of aerosol layers (3) Later seasons show no consistent large scale organization

  16. Size and density distribution of very small dust grains in the Barnard 5 cloud

    NASA Technical Reports Server (NTRS)

    Lis, Dariusz C.; Leung, Chun Ming

    1991-01-01

    The effects of the temperature fluctuations in small graphite grains on the energy spectrum and the IR surface brightness of an isolated dust cloud heated externally by the interstellar radiation field were investigated using a series of models based on a radiation transport computer code. This code treats self-consistently the thermal coupling between the transient heating of very small dust grains and the equilibrium heating of conventional large grains. The model results were compared with the IRAS observations of the Barnard 5 (B5) cloud, showing that the 25-micron emission of the cloud must be produced by small grains with a 6-10 A radius, which also contribute about 50 percent to the observed 12-micron emission. The remaining 12 micron flux may be produced by the polycyclic aromatic hydrocarbons. The 60-and 100-micron radiation is dominated by emission from large grains heated under equilibrium conditions.

  17. Cloud Ozone Dust Imager (CODI). Volume 1; Investigation and Technical Plan

    NASA Technical Reports Server (NTRS)

    Clancy, R. Todd; Dusenbery, Paul; Wolff, Michael; James, Phil; Allen, Mark; Goguen, Jay; Kahn, Ralph; Gladstone, Rany; Murphy, Jim

    1995-01-01

    The Cloud Ozone Dust Imager (CODI) is proposed to investigate the current climatic balance of the Mars atmosphere, with particular emphasis on the important but poorly understood roles which dust and water ice aerosols play in this balance. The large atmospheric heating (20-50 K) resulting from global dust storms around Mars perihelion is well recognized. However, groundbased observations of Mars atmospheric temperatures, water vapor, and clouds since the Viking missions have identified a much colder, cloudier atmosphere around Mars aphelion that may prove as important as global dust storms in determining the interannual and long-term behavior of the Mars climate. The key climate issues CODI is designed to investigate are: 1) the degree to which non-linear interactions between atmospheric dust heating, water vapor saturation, and cloud nucleation influence the seasonal and interannual variability of the Mars atmosphere, and 2) whether the strong orbital forcing of atmospheric dust loading, temperatures and water vapor saturation determines the long-term balance of Mars water, as reflected in the north-south hemispheric asymmetries of atmospheric water vapor and polar water ice abundances. The CODI experiment will measure the daily, seasonal and (potentially) interannual variability of atmospheric dust and cloud opacities, and the key physical properties of these aerosols which determine their role in the climate cycles of Mars. CODI is a small (1.2 kg), fixed pointing camera, in which four wide-angle (+/- 70 deg) lenses illuminate fixed filters and CCD arrays. Simultaneous sky/surface imaging of Mars is obtained at an angular resolution of 0.28 deg/pixel for wavelengths of 255, 336, 502, and 673 nm (similar to Hubble Space Telescope filters). These wavelengths serve to measure atmospheric ozone (255 and 336 nm), discriminate ice and dust aerosols (336 and 673 nm), and construct color images (336, 502, and 673 nm). The CODI images are detected on four 512 x 512

  18. Distribution of Dust from Kuiper Belt Objects

    NASA Technical Reports Server (NTRS)

    Gorkavyi, Nick N.; Ozernoy, Leonid; Taidakova, Tanya; Mather, John C.; Fisher, Richard (Technical Monitor)

    2000-01-01

    Using an efficient computational approach, we have reconstructed the structure of the dust cloud in the Solar system between 0.5 and 100 AU produced by the Kuiper belt objects. Our simulations offer a 3-D physical model of the 'kuiperoidal' dust cloud based on the distribution of 280 dust particle trajectories produced by 100 known Kuiper belt objects; the resulting 3-D grid consists of 1.9 x 10' cells containing 1.2 x 10" particle positions. The following processes that influence the dust particle dynamics are taken into account: 1) gravitational scattering on the eight planets (neglecting Pluto); 2) planetary resonances; 3) radiation pressure; and 4) the Poynting-Robertson (P-R) and solar wind drags. We find the dust distribution highly non-uniform: there is a minimum in the kuiperoidal dust between Mars and Jupiter, after which both the column and number densities of kuiperoidal dust sharply increase with heliocentric distance between 5 and 10 AU, and then form a plateau between 10 and 50 AU. Between 25 and 45 AU, there is an appreciable concentration of kuiperoidal dust in the form of a broad belt of mostly resonant particles associated with Neptune. In fact, each giant planet possesses its own circumsolar dust belt consisting of both resonant and gravitationally scattered particles. As with the cometary belts simulated in our related papers, we reveal a rich and sophisticated resonant structure of the dust belts containing families of resonant peaks and gaps. An important result is that both the column and number dust density are more or less flat between 10 and 50 AU, which might explain the surprising data obtained by Pioneers 10 & 11 and Voyager that the dust number density remains approximately distance-independent in this region. The simulated kuiperoidal dust, in addition to asteroidal and cometary dust, might represent a third possible source of the zodiacal light in the Solar system.

  19. The influence of organic-containing soil dust on ice nucleation and cloud properties

    NASA Astrophysics Data System (ADS)

    Hummel, Matthias; Grini, Alf; Berntsen, Terje K.; Ekman, Annica

    2017-04-01

    Natural mineral dust from desert regions is known to be the most important contributor to atmospheric ice-nucleating particles (INP) which induce heterogeneous ice nucleation in mixed-phase clouds. Its ability to nucleate ice effectively is shown by various laboratory (Hoose and Möhler 2012) and field results (DeMott et al. 2015) and its abundance in ice crystal residuals has also been shown (Cziczo et al. 2013). Thus it is an important player when representing mixed-phase clouds in climate models. MODIS satellite data indicate that 1 /4 of the global dust emission originates from semi-arid areas rather than from arid deserts (Ginoux et al. 2012). Here, organic components can mix with minerals within the soil and get into the atmosphere. These so-called 'soil dust' particles are ice-nucleating active at high sub-zero temperatures, i.e. at higher temperatures than pure desert dust (Steinke et al. 2016). In this study, soil dust is incorporated into the Norwegian Earth System Model (NorESM, Bentsen et al. 2013) and applied to a modified ice nucleation parameterization (Steinke et al. 2016). Its influence on the cloud ice phase is evaluated by comparing a control run, where only pure desert dust is considered, and a sensitivity experiment, where a fraction of the dust emissions are classified as soil dust. Both simulations are nudged to ERA-interim meteorology and they have the same loading of dust emissions. NorESM gives a lower annual soil dust emission flux compared to Ginoux et al. (2012), but the desert dust flux is similar to the MODIS-retrieved data. Although soil dust concentrations are much lower than desert dust, the NorESM simulations indicate that the annual INP concentrations from soil dust are on average lower by a just a factor of 4 than INP concentrations from pure desert dust. The highest soil dust INP concentrations occur at a lower height than for desert dust, i.e at warmer temperatures inside mixed-phase clouds. Furthermore, soil dust INP

  20. The effect of temperature mixing on the observable (T, β)-relation of interstellar dust clouds

    NASA Astrophysics Data System (ADS)

    Juvela, M.; Ysard, N.

    2012-03-01

    Context. Detailed studies of the shape of dust emission spectra are possible thanks to the current instruments capable of simultaneous observations in several sub-millimetre bands (e.g., Herschel and Planck). The relationship between the observed spectra and the intrinsic dust grain properties is known to be affected by the noise and the line-of-sight temperature variations. However, some controversy remains even on the basic effects resulting from the mixing of temperatures along the line-of-sight or within the instrument beam. Aims: Regarding the effect of temperature variations, previous studies have suggested either a positive or a negative correlation between the colour temperature TC and the observed spectral index βObs. Our aim is to show that both cases are possible and to determine the principal factors leading to either behaviour. Methods: We start by studying the behaviour of the sum of two or three modified black bodies at different temperatures. Then, with radiative transfer models of spherical clouds, we examine the probability distributions of the dust mass as a function of the physical dust temperature. With these results as a guideline, we examine the (TC, βobs) relations for different sets of clouds. Results: Even in the simple case of models consisting of two blackbodies at temperatures T0 and T0 + ΔT0, the correlation between TC and βobs can be either positive or negative. If one compares models where the temperature difference ΔT0 between the two blackbodies is varied, the correlation is negative. If the models differ in their mean temperature T0 rather than in ΔT0, the correlation remains positive. Radiative transfer models show that externally heated clouds have different mean temperatures but the widths of their temperature distributions are rather similar. Thus, in observations of samples of such clouds the correlation between TC and βObs is expected to be positive. The same result applies to clouds illuminated by external radiation

  1. The optical depth sensor (ODS) for column dust opacity measurements and cloud detection on martian atmosphere

    NASA Astrophysics Data System (ADS)

    Toledo, D.; Rannou, P.; Pommereau, J.-P.; Foujols, T.

    2016-08-01

    A lightweight and sophisticated optical depth sensor (ODS) able to measure alternatively scattered flux at zenith and the sum of the direct flux and the scattered flux in blue and red has been developed to work in martian environment. The principal goals of ODS are to perform measurements of the daily mean dust opacity and to retrieve the altitude and optical depth of high altitude clouds at twilight, crucial parameters in the understanding of martian meteorology. The retrieval procedure of dust opacity is based on the use of radiative transfer simulations reproducing observed changes in the solar flux during the day as a function of 4 free parameters: dust opacity in blue and red, and effective radius and effective width of dust size distribution. The detection of clouds is undertaken by looking at the time variation of the color index (CI), defined as the ratio between red and blue ODS channels, at twilight. The retrieval of altitude and optical depth of clouds is carried out using a radiative transfer model in spherical geometry to simulate the CI time variation at twilight. Here the different retrieval procedures to analyze ODS signals, as well as the results obtained in different sensitivity analysis are presented and discussed.

  2. Interplanetary dust. [survey of last four years' research

    NASA Technical Reports Server (NTRS)

    Brownlee, D. E.

    1979-01-01

    Progress in the study of interplanetary dust during the past four years is reviewed. Attention is given to determinations of the relative contributions of interstellar dust grains, collisional debris from the asteroid belt and short-period comets to the interplanetary dust cloud. Effects of radiation pressure and collisions on particle dynamics are discussed, noting the discovery of the variation of the orbital parameters of dust particles at 1 AU with size and in situ measurements of dust density between 0.3 and 5 AU by the Helios and Pioneer spacecraft. The interpretation of the zodiacal light as produced by porous absorbing particles 10 to 100 microns in size is noted, and measurements of the Doppler shift, light-producing-particle density, UV spectrum, photometric axis and angular scattering function of the zodiacal light are reported. Results of analyses of lunar rock microcraters as to micrometeoroid density, flux rate, size distribution and composition are indicated and interplanetary dust particles collected from the stratosphere are discussed. Findings concerning the composition of fragile meteoroid types found as cosmic spherules in deep sea sediments are also presented.

  3. Coupling the Mars Dust and Water Cycles: Investigating the Role of Clouds in Controlling the Vertical Distribution of Dust During N. H. Summer

    NASA Technical Reports Server (NTRS)

    Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.; Wilson, R. J.

    2014-01-01

    The dust cycle is critically important for the current climate of Mars. The radiative effects of dust impact the thermal and dynamical state of the atmosphere (Gierasch and Goody, 1968; Haberle et al., 1982; Zurek et al., 1992). Although dust is present in the Martian atmosphere throughout the year, the level of dustiness varies with season. The atmosphere is generally the dustiest during northern fall and winter and the least dusty during northern spring and summer (Smith, 2004). Dust particles are lifted into the atmosphere by dust storms that range in size from meters to thousands of kilometers across (Cantor et al., 2001). During some years, regional storms combine to produce hemispheric or planet encircling dust clouds that obscure the surface and raise atmospheric temperatures by as much as 40 K (Smith et al., 2002). Key recent observations of the vertical distribution of dust indicate that elevated layers of dust exist in the tropics and sub-tropics throughout much of the year (Heavens et al., 2011). These observations have brought particular focus on the processes that control the vertical distribution of dust in the Martian atmosphere. The goal of this work is to further our understanding of how clouds in particular control the vertical distribution of dust, particularly during N. H. spring and summer

  4. Modelling dust polarization observations of molecular clouds through MHD simulations

    NASA Astrophysics Data System (ADS)

    King, Patrick K.; Fissel, Laura M.; Chen, Che-Yu; Li, Zhi-Yun

    2018-03-01

    The BLASTPol observations of Vela C have provided the most detailed characterization of the polarization fraction p and dispersion in polarization angles S for a molecular cloud. We compare the observed distributions of p and S with those obtained in synthetic observations of simulations of molecular clouds, assuming homogeneous grain alignment. We find that the orientation of the mean magnetic field relative to the observer has a significant effect on the p and S distributions. These distributions for Vela C are most consistent with synthetic observations where the mean magnetic field is close to the line of sight. Our results point to apparent magnetic disorder in the Vela C molecular cloud, although it can be due to either an inclination effect (i.e. observing close to the mean field direction) or significant field tangling from strong turbulence/low magnetization. The joint correlations of p with column density and of S with column density for the synthetic observations generally agree poorly with the Vela C joint correlations, suggesting that understanding these correlations requires a more sophisticated treatment of grain alignment physics.

  5. Estimation of Asian Dust Aerosol Effect on Cloud Radiation Forcing Using Fu-Liou Radiative Model and CERES Measurements

    NASA Technical Reports Server (NTRS)

    Su, Jing; Huang, Jianping; Fu, Qiang; Minnis, Patrick; Ge, Jinming; Bi, Jianrong

    2008-01-01

    The impact of Asian dust on cloud radiative forcing during 2003-2006 is studied by using the Earth's Radiant Energy Budget Scanner (CERES) data and the Fu-Liou radiative transfer model. Analysis of satellite data shows that the dust aerosol significantly reduced the cloud cooling effect at TOA. In dust contaminated cloudy regions, the 4-year mean values of the instantaneous shortwave, longwave and net cloud radiative forcing are -138.9, 69.1, and -69.7 Wm(sup -2), which are 57.0, 74.2, and 46.3%, respectively, of the corresponding values in more pristine cloudy regions. The satellite-retrieved cloud properties are significantly different in the dusty regions and can influence the radiative forcing indirectly. The contributions to the cloud radiation forcing by the dust direct, indirect and semi-direct effects are estimated using combined satellite observations and Fu-Liou model simulation. The 4-year mean value of combination of indirect and semi-direct shortwave radiative forcing (SWRF) is 82.2 Wm(sup -2), which is 78.4% of the total dust effect. The direct effect is only 22.7 Wm(sup -2), which is 21.6% of the total effect. Because both first and second indirect effects enhance cloud cooling, the aerosol-induced cloud warming is mainly the result of the semi-direct effect of dust.

  6. Investigating cloud absorption effects: Global absorption properties of black carbon, tar balls, and soil dust in clouds and aerosols

    NASA Astrophysics Data System (ADS)

    Jacobson, Mark Z.

    2012-03-01

    This study examines modeled properties of black carbon (BC), tar ball (TB), and soil dust (SD) absorption within clouds and aerosols to understand better Cloud Absorption Effects I and II, which are defined as the effects on cloud heating of absorbing inclusions in hydrometeor particles and of absorbing aerosol particles interstitially between hydrometeor particles at their actual relative humidity (RH), respectively. The globally and annually averaged modeled 550 nm aerosol mass absorption coefficient (AMAC) of externally mixed BC was 6.72 (6.3-7.3) m2/g, within the laboratory range (6.3-8.7 m2/g). The global AMAC of internally mixed (IM) BC was 16.2 (13.9-18.2) m2/g, less than the measured maximum at 100% RH (23 m2/g). The resulting AMAC amplification factor due to internal mixing was 2.41 (2-2.9), with highest values in high RH regions. The global 650 nm hydrometeor mass absorption coefficient (HMAC) due to BC inclusions was 17.7 (10.6-19) m2/g, ˜9.3% higher than that of the IM-AMAC. The 650 nm HMACs of TBs and SD were half and 1/190th, respectively, that of BC. Modeled aerosol absorption optical depths were consistent with data. In column tests, BC inclusions in low and mid clouds (CAE I) gave column-integrated BC heating rates ˜200% and 235%, respectively, those of interstitial BC at the actual cloud RH (CAE II), which itself gave heating rates ˜120% and ˜130%, respectively, those of interstitial BC at the clear-sky RH. Globally, cloud optical depth increased then decreased with increasing aerosol optical depth, consistent with boomerang curves from satellite studies. Thus, CAEs, which are largely ignored, heat clouds significantly.

  7. Heterogeneous chemistry of atmospheric mineral dust particles and their resulting cloud-nucleation properties

    NASA Astrophysics Data System (ADS)

    Sullivan, Ryan Christopher

    Mineral dust particles are a major component of tropospheric aerosol mass and affect regional and global atmospheric chemistry and climate. Dust particles experience heterogeneous reactions with atmospheric gases that alter the gas and particle-phase chemistry. These in turn influence the warm and cold cloud nucleation ability and optical properties of the dust particles. This dissertation investigates the atmospheric chemistry of mineral dust particles and their role in warm cloud nucleation through a combination of synergistic field measurements, laboratory experiments, and theoretical modeling. In-situ measurements made with a single-particle mass spectrometer during the ACE-Asia field campaign in 2001 provide the motivation for this work. The observed mixing state of the individual ambient particles with secondary organic and inorganic components is described in Chapter 2. A large Asian dust storm occurred during the campaign and produced dramatic changes in the aerosol's composition and mixing state. The effect of particle size and mineralogy on the atmospheric processing of individual dust particles is explored in Chapters 3 & 4. Sulfate was found to accumulate preferentially in submicron iron and aluminosilicate-rich dust particles, while nitrate and chloride were enriched in supermicron calcite-rich dust. The mineral dust (and sea salt particles) were also enriched in oxalic acid, the dominant component of water soluble organic carbon. Chapter 5 explores the roles of gas-phase photochemistry and partitioning of the diacids to the alkaline particles in producing this unique behavior. The effect of the dust's mixing state with secondary organic and inorganic components on the dust particles' solubility, hygroscopicity, and thus warm cloud nucleation properties is explored experimentally and theoretically in Chapter 6. Cloud condensation nucleation (CCN) activation curves revealed that while calcium nitrate and calcium chloride particles were very hygroscopic

  8. The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

    NASA Astrophysics Data System (ADS)

    Wiacek, A.; Peter, T.; Lohmann, U.

    2010-02-01

    This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Without explicitly modelling dust emission and deposition processes, dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Practically none of the simulated air parcels reached regions where homogeneous ice nucleation can take place (T≲-40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through regions supersaturated with respect to ice but subsaturated with respect to water, where "warm" (T≳-40 °C) ice clouds may form prior to supercooled water or mixed-phase clouds. The importance of "warm" ice clouds and the general influence of dust in the mixed-phase cloud region are highly uncertain due to

  9. Hubble space telescope imaging of decoupled dust clouds in the ram pressure stripped Virgo spirals NGC 4402 and NGC 4522

    SciT

    Abramson, Anne; Kenney, Jeffrey D. P., E-mail: anne.abramson@yale.edu, E-mail: jeff.kenney@yale.edu

    We present the highest-resolution study to date of the interstellar medium (ISM) in galaxies undergoing ram pressure stripping, using Hubble Space Telescope BVI imaging of NGC 4522 and NGC 4402, Virgo Cluster spirals that are well known to be experiencing intracluster medium (ICM) ram pressure. We find that throughout most of both galaxies, the main dust lane has a fairly well-defined edge, with a population of giant molecular cloud (GMC) sized (tens- to hundreds-of-pc scale), isolated, highly extincting dust clouds located up to ∼1.5 kpc radially beyond it. Outside of these dense clouds, the area has little or no diffusemore » dust extinction, indicating that the clouds have decoupled from the lower-density ISM material that has already been stripped. Several of the dust clouds have elongated morphologies that indicate active ram pressure, including two large (kpc scale) filaments in NGC 4402 that are elongated in the projected ICM wind direction. We calculate a lower limit on the H I + H{sub 2} masses of these clouds based on their dust extinctions and find that a correction factor of ∼10 gives cloud masses consistent with those measured in CO for clouds of similar diameters, probably due to the complicating factors of foreground light, cloud substructure, and resolution limitations. Assuming that the clouds' actual masses are consistent with those of GMCs of similar diameters (∼10{sup 4}-10{sup 5} M {sub ☉}), we estimate that only a small fraction (∼1%-10%) of the original H I + H{sub 2} remains in the parts of the disks with decoupled clouds. Based on Hα images, a similar fraction of star formation persists in these regions, 2%-3% of the estimated pre-stripping star formation rate. We find that the decoupled cloud lifetimes may be up to 150-200 Myr.« less

  10. Optical Depth Sensor (ODS) for the measurement of dust and clouds properties in the Mars atmosphere

    NASA Astrophysics Data System (ADS)

    Toledo, D.; Rannou, P.; Pommereau, J.-P.; Sarkissian, A.; Foujols, T.

    2014-04-01

    A small and sophisticated optical depth sensor (ODS) has been designed to work in both Martian and Earth environments. The principal goal of ODS is to carry out the opacity due to the Martian dust as well as to characterize the high altitude clouds at twilight, crucial parameters in understanding of Martian meteorology. The instrument was initially designed for the failed MARS96 Russian mission, and also was included in the payload of several other missions [1]. Until recently, it was selected (NASA/ESA AO) in the payload of the atmospheric package DREAMS onboard the MARS 2016 mission. But following a decision of the CNES, it is no more included in the payload. In order to study the performance of ODS under a wide range of conditions as well as its capable to provide daily measurements of both dust optical thickness and high altitude clouds properties, the instrument has participated in different terrestrial campaigns. A good performance of ODS prototype (Figure 1) on cirrus clouds detection and in dust opacity estimation was previously archived in Africa during 2004-2005 and in Brasil from 2012 to nowadays. Moreover, a campaign in the arctic is expected before 2016 where fifteen ODSs will be part of an integrated observing system over the Arctic Ocean, allowing test the ODS performance in extreme conditions. In this presentation we present main principle of the retrieval, the instrumental concept, the result of the tests performed and the principal objectives of ODS in Mars.

  11. Saharan Dust as a Causal Factor of Significant Cloud Cover Along the Saharan Air Layer in the Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Kishcha, Pavel; Da Silva, Arlindo M.; Starobinet, Boris; Alpert, Pinhas

    2016-01-01

    The tropical Atlantic is frequently affected by Saharan dust intrusions. Based on MODIS cloud fraction (CF) data during the ten-year study period, we found that these dust intrusions contribute to significant cloud cover along the Saharan Air Layer (SAL). Below the temperature inversion at the SAL's base, the presence of large amounts of settling dust particles, together with marine aerosols, produces meteorological conditions suitable for the formation of shallow stratocumulus clouds. The significant cloud fraction along the SAL together with clouds over the Atlantic Inter-tropical Convergence Zone contributes to the 20% hemispheric CF asymmetry between the tropical North and South Atlantic. This leads to the imbalance in strong solar radiation, which reaches the sea surface between the tropical North and South Atlantic, and, consequently, affects climate formation in the tropical Atlantic. Therefore, despite the fact that, over the global ocean, there is no noticeable hemispheric asymmetry in cloud fraction, over the significant area such as the tropical Atlantic the hemispheric asymmetry in CF takes place. Saharan dust is also the major contributor to hemispheric aerosol asymmetry over the tropical Atlantic. The NASA GEOS-5 model with aerosol data assimilation was used to extend the MERRA reanalysis with five atmospheric aerosol species (desert dust, sulfates, organic carbon, black carbon, and sea-salt). The obtained ten-year (2002 - 2012) MERRA-driven aerosol reanalysis dataset (aka MERRAero) showed that, over the tropical Atlantic, dust and carbonaceous aerosols were distributed asymmetrically relative to the equator, while other aerosol species were distributed more symmetrically.

  12. Retrieving cloud, dust and ozone abundances in the Martian atmosphere using SPICAM/UV nadir spectra

    NASA Astrophysics Data System (ADS)

    Willame, Y.; Vandaele, A. C.; Depiesse, C.; Lefèvre, F.; Letocart, V.; Gillotay, D.; Montmessin, F.

    2017-08-01

    We present the retrieval algorithm developed to analyse nadir spectra from SPICAM/UV aboard Mars-Express. The purpose is to retrieve simultaneously several parameters of the Martian atmosphere and surface: the dust optical depth, the ozone total column, the cloud opacity and the surface albedo. The retrieval code couples the use of an existing complete radiative transfer code, an inversion method and a cloud detection algorithm. We describe the working principle of our algorithm and the parametrisation used to model the required absorption, scattering and reflection processes of the solar UV radiation that occur in the Martian atmosphere and at its surface. The retrieval method has been applied on 4 Martian years of SPICAM/UV data to obtain climatologies of the different quantities under investigation. An overview of the climatology is given for each species showing their seasonal and spatial distributions. The results show a good qualitative agreement with previous observations. Quantitative comparisons of the retrieved dust optical depths indicate generally larger values than previous studies. Possible shortcomings in the dust modelling (altitude profile) have been identified and may be part of the reason for this difference. The ozone results are found to be influenced by the presence of clouds. Preliminary quantitative comparisons show that our retrieved ozone columns are consistent with other results when no ice clouds are present, and are larger for the cases with clouds at high latitude. Sensitivity tests have also been performed showing that the use of other a priori assumptions such as the altitude distribution or some scattering properties can have an important impact on the retrieval.

  13. The relationship between CO emission and visual extinction traced by dust emission in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Lee, Cheoljong; Leroy, Adam K.; Schnee, Scott; Wong, Tony; Bolatto, Alberto D.; Indebetouw, Remy; Rubio, Monica

    2015-07-01

    To test the theoretical understanding that finding bright CO emission depends primarily on dust shielding, we investigate the relationship between CO emission (ICO) and the amount of dust (estimated from infrared emission and expressed as `AV') across the Large Magellanic Cloud (LMC), the Small Magellanic Cloud, and the Milky Way. We show that at our common resolution of 10 pc scales, ICO given a fixed line of sight AV is similar across all three systems despite the difference in metallicity. We find some evidence for a secondary dependence of ICO on radiation field; in the LMC, ICO at a given AV is smaller in regions of high Tdust, perhaps because of an increased photodissociating radiation field. We suggest a simple but useful picture in which the CO-to-H2 conversion factor (XCO) depends on two separable factors: (1) the distribution of gas column densities, which maps to an extinction distribution via a dust-to-gas ratio; and (2) the dependence of ICO on AV. Assuming that the probability distribution function (PDF) of local Milky Way clouds is universal, this approach predicts a dependence of {X_CO} on Z between Z-1 and Z-2 above about a third solar metallicity. Below this metallicity, CO emerges from only the high column density parts of the cloud and so depends very sensitively on the adopted PDF and the H2/H I prescription. The PDF of low-metallicity clouds is thus of considerable interest and the uncertainty associated with even an ideal prescription for XCO at very low metallicity will be large.

  14. Zodiac II: Debris Disk Imaging Potential

    NASA Technical Reports Server (NTRS)

    Traub Wesley; Bryden, Geoff; Stapelfeldt, Karl; Chen, Pin; Trauger, John

    2011-01-01

    Zodiac II is a proposed coronagraph on a balloon-borne platform, for the purpose of observing debris disks around nearby stars. Zodiac II will have a 1.2-m diameter telescope mounted in a balloon-borne gondola capable of arcsecond quality pointing, and with the capability to make long-duration (several week) flights. Zodiac II will have a coronagraph able to make images of debris disks, meaning that its scattered light speckles will be at or below an average contrast level of about 10(exp -7) in three narrow (7 percent) bands centered on the V band, and one broad (20%) one at I band. We will discuss the potential science to be done with Zodiac II.

  15. Emission from small dust particles in diffuse and molecular cloud medium

    NASA Technical Reports Server (NTRS)

    Bernard, J. P.; Desert, X.

    1990-01-01

    Infrared Astronomy Satellite (IRAS) observations of the whole galaxy has shown that long wavelength emission (100 and 60 micron bands) can be explained by thermal emission from big grains (approx 0.1 micron) radiating at their equilibrium temperature when heated by the InterStellar Radiation Field (ISRF). This conclusion has been confirmed by continuum sub-millimeter observations of the galactic plane made by the EMILIE experiment at 870 microns (Pajot et al. 1986). Nevertheless, shorter wavelength observations like 12 and 25 micron IRAS bands, show an emission from the galactic plane in excess with the long wavelength measurements which can only be explained by a much hotter particles population. Because dust at equilibrium cannot easily reach high temperatures required to explain this excess, this component is thought to be composed of very small dust grains or big molecules encompassing thermal fluctuations. Researchers present here a numerical model that computes emission, from Near Infrared Radiation (NIR) to Sub-mm wavelengths, from a non-homogeneous spherical cloud heated by the ISRF. This model fully takes into account the heating of dust by multi-photon processes and back-heating of dust in the Visual/Infrared Radiation (VIS-IR) so that it is likely to describe correctly emission from molecular clouds up to large A sub v and emission from dust experiencing temperature fluctuations. The dust is a three component mixture of polycyclic aromatic hydrocarbons, very small grains, and classical big grains with independent size distributions (cut-off and power law index) and abundances.

  16. The effect of smoke, dust, and pollution aerosol on shallow cloud development over the Atlantic Ocean

    PubMed Central

    Kaufman, Yoram J.; Koren, Ilan; Remer, Lorraine A.; Rosenfeld, Daniel; Rudich, Yinon

    2005-01-01

    Clouds developing in a polluted environment tend to have more numerous but smaller droplets. This property may lead to suppression of precipitation and longer cloud lifetime. Absorption of incoming solar radiation by aerosols, however, can reduce the cloud cover. The net aerosol effect on clouds is currently the largest uncertainty in evaluating climate forcing. Using large statistics of 1-km resolution MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data, we study the aerosol effect on shallow water clouds, separately in four regions of the Atlantic Ocean, for June through August 2002: marine aerosol (30°S–20°S), smoke (20°S–5°N), mineral dust (5°N–25°N), and pollution aerosols (30°N– 60°N). All four aerosol types affect the cloud droplet size. We also find that the coverage of shallow clouds increases in all of the cases by 0.2–0.4 from clean to polluted, smoky, or dusty conditions. Covariability analysis with meteorological parameters associates most of this change to aerosol, for each of the four regions and 3 months studied. In our opinion, there is low probability that the net aerosol effect can be explained by coincidental, unresolved, changes in meteorological conditions that also accumulate aerosol, or errors in the data, although further in situ measurements and model developments are needed to fully understand the processes. The radiative effect at the top of the atmosphere incurred by the aerosol effect on the shallow clouds and solar radiation is –11 ± 3 W/m2 for the 3 months studied; 2/3 of it is due to the aerosol-induced cloud changes, and 1/3 is due to aerosol direct radiative effect. PMID:16076949

  17. Contact freezing of supercooled cloud droplets on collision with mineral dust particles: effect of particle size

    NASA Astrophysics Data System (ADS)

    Hoffmann, Nadine; Duft, Denis; Kiselev, Alexei; Leisner, Thomas

    2013-04-01

    The contact freezing of supercooled cloud droplets is one of the potentially important and the least investigated heterogeneous mechanism of ice formation in the tropospheric clouds [1]. On the time scales of cloud lifetime the freezing of supercooled water droplets via contact mechanism may occur at higher temperature compared to the same IN immersed in the droplet. However, the laboratory experiments of contact freezing are very challenging due to the number of factors affecting the probability of ice formation. In our experiment we study single water droplets freely levitated in the laminar flow of mineral dust particles acting as the contact freezing nuclei. By repeating the freezing experiment sufficient number of times we are able to reproduce statistical freezing behavior of large ensembles of supercooled droplets and measure the average rate of freezing events. We show that the rate of freezing at given temperature is governed only by the rate of droplet -particle collision and by the properties of the contact ice nuclei. In this contribution we investigate the relationship between the freezing probability and the size of mineral dust particle (represented by illite) and show that their IN efficiency scales with the particle size. Based on this observation, we discuss the similarity between the freezing of supercooled water droplets in immersion and contact modes and possible mechanisms of apparent enhancement of the contact freezing efficiency. [1] - K.C. Young, The role of contact nucleation in ice phase initiation in clouds, Journal of the Atmospheric Sciences 31, 1974

  18. The competition between mineral dust and soot ice nuclei in mixed-phase clouds (Invited)

    NASA Astrophysics Data System (ADS)

    Murray, B. J.; Atkinson, J.; Umo, N.; Browse, J.; Woodhouse, M. T.; Whale, T.; Baustian, K. J.; Carslaw, K. S.; Dobbie, S.; O'Sullivan, D.; Malkin, T. L.

    2013-12-01

    The amount of ice present in mixed-phase clouds, which contain both supercooled liquid water droplets and ice particles, affects cloud extent, lifetime, particle size and radiative properties. The freezing of cloud droplets can be catalysed by the presence of aerosol particles known as ice nuclei. In this talk our recent laboratory and global aerosol modelling work on mineral dust and soot ice nuclei will be presented. We have performed immersion mode experiments to quantify ice nucleation by the individual minerals which make up desert mineral dusts and have shown that the feldspar component, rather than the clay component, is most important for ice nucleation (Atkinson et al. 2013). Experiments with well-characterised soot generated with eugenol, an intermediate in biomass burning, and n-decane show soot has a significant ice nucleation activity in mixed-phase cloud conditions. Our results for soot are in good agreement with previous results for acetylene soot (DeMott, 1990), but extend the efficiency to much higher temperatures. We then use a global aerosol model (GLOMAP) to map the distribution of soot and feldspar particles on a global basis. We show that below about -15oC that dust and soot together can explain most observed ice nuclei in the Earth's atmosphere, while at warmer temperatures other ice nuclei types are needed. We show that in some regions soot is the most important ice nuclei (below -15oC), while in others feldspar dust dominates. Our results suggest that there is a strong anthropogenic contribution to the ice nuclei population, since a large proportion of soot aerosol in the atmosphere results from human activities. Atkinson, J. D., Murray, B. J., Woodhouse, M. T., Carslaw, K. S., Whale, T. F., Baustian, K. J., Dobbie, S., O'Sullivan, D., and Malkin, T. L.: The importance of feldspar for ice nucleation by mineral dust in mixed-phase clouds, Nature, 10.1038/nature12278, (2013). Demott, P. J. 1990. An Exploratory-Study of Ice Nucleation by Soot

  19. High-latitude dust clouds LDN 183 and LDN 169: distances and extinctions

    NASA Astrophysics Data System (ADS)

    Straižys, V.; Boyle, R. P.; Zdanavičius, J.; Janusz, R.; Corbally, C. J.; Munari, U.; Andersson, B.-G.; Zdanavičius, K.; Kazlauskas, A.; Maskoliūnas, M.; Černis, K.; Macijauskas, M.

    2018-03-01

    Interstellar extinction is investigated in a 2°× 2° area containing the dust and molecular clouds LDN 183 (MBM 37) and LDN 169, which are located at RA = 15h 54m, Dec = - 3°. The study is based on a photometric classification in spectral and luminosity classes of 782 stars selected from the catalogs of 1299 stars down to V = 20 mag observed in the Vilnius seven-color system. For control, the MK types for the 18 brightest stars with V between 8.5 and 12.8 mag were determined spectroscopically. For 14 stars, located closer than 200 pc, distances were calculated from trigonometric parallaxes taken from the Gaia Data Release 1. For about 70% of the observed stars, two-dimensional spectral types, interstellar extinctions AV, and distances were determined. Using 57 stars closer than 200 pc, we estimate that the front edge of the clouds begins at 105 ± 8 pc. The extinction layer in the vicinities of the clouds can be about 20 pc thick. In the outer parts of the clouds and between the clouds, the extinction is 0.5-2.0 mag. Behind the Serpens/Libra clouds, the extinction range does not increase; this means that the dust layer at 105 pc is a single extinction source. Full Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A9

  20. Planck early results. XVII. Origin of the submillimetre excess dust emission in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Bernard, J.-P.; Bersanelli, M.; Bhatia, R.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bot, C.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Cabella, P.; Cardoso, J.-F.; Catalano, A.; Cayón, L.; Challinor, A.; Chamballu, A.; Chiang, L.-Y.; Chiang, C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Coulais, A.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Gasperis, G.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Dobashi, K.; Donzelli, S.; Doré, O.; Dörl, U.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Fukui, Y.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Harrison, D.; Helou, G.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Hoyland, R. J.; Huffenberger, K. M.; Jaffe, A. H.; Jones, W. C.; Juvela, M.; Kawamura, A.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knox, L.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leach, S.; Leonardi, R.; Leroy, C.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacTavish, C. J.; Madden, S.; Maffei, B.; Mandolesi, N.; Mann, R.; Maris, M.; Martínez-González, E.; Masi, S.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Onishi, T.; Osborne, S.; Pajot, F.; Paladini, R.; Paradis, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Poutanen, T.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savini, G.; Scott, D.; Seiffert, M. D.; Smoot, G. F.; Starck, J.-L.; Stivoli, F.; Stolyarov, V.; Sudiwala, R.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Torre, J.-P.; Tristram, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Wilkinson, A.; Ysard, N.; Yvon, D.; Zacchei, A.; Zonca, A.

    2011-12-01

    The integrated spectral energy distributions (SED) of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) appear significantly flatter than expected from dust models based on their far-infrared and radio emission. The still unexplained origin of this millimetre excess is investigated here using the Planck data. The integrated SED of the two galaxies before subtraction of the foreground (Milky Way) and background (CMB fluctuations) emission are in good agreement with previous determinations, confirming the presence of the millimetre excess. In the context of this preliminary analysis we do not propose a full multi-component fitting of the data, but instead subtract contributions unrelated to the galaxies and to dust emission. The background CMB contribution is subtracted using an internal linear combination (ILC) method performed locally around the galaxies. The foreground emission from the Milky Way is subtracted as a Galactic Hi template, and the dust emissivity is derived in a region surrounding the two galaxies and dominated by Milky Way emission. After subtraction, the remaining emission of both galaxies correlates closely with the atomic and molecular gas emission of the LMC and SMC. The millimetre excess in the LMC can be explained by CMB fluctuations, but a significant excess is still present in the SMC SED. The Planck and IRAS-IRIS data at 100 μm are combined to produce thermal dust temperature and optical depth maps of the two galaxies. The LMC temperature map shows the presence of a warm inner arm already found with the Spitzer data, but which also shows the existence of a previously unidentified cold outer arm. Several cold regions are found along this arm, some of which are associated with known molecular clouds. The dust optical depth maps are used to constrain the thermal dust emissivity power-law index (β). The average spectral index is found to be consistent with β = 1.5 and β = 1.2 below 500μm for the LMC and SMC respectively

  1. Properties of dust and clouds in the Mars atmosphere: Analysis of Viking IRTM emission phase function sequences

    NASA Technical Reports Server (NTRS)

    Clancy, R. T.; Lee, S. W.

    1991-01-01

    An analysis of emission-phase-function (EPF) observations from the Viking Orbiter Infrared Thermal Mapper (IRTM) yields a wide variety of results regarding dust and cloud scattering in the Mars atmosphere and atmospheric-corrected albedos for the surface of Mars. A multiple scattering radiative transfer model incorporating a bidirectional phase function for the surface and atmospheric scattering by dust and clouds is used to derive surface albedos and dust and ice optical properties and optical depths for these various conditions on Mars.

  2. Gas, dust, stars, star formation, and their evolution in M 33 at giant molecular cloud scales

    NASA Astrophysics Data System (ADS)

    Komugi, Shinya; Miura, Rie E.; Kuno, Nario; Tosaki, Tomoka

    2018-06-01

    We report on a multi-parameter analysis of giant molecular clouds (GMCs) in the nearby spiral galaxy M 33. A catalog of GMCs identifed in 12CO(J = 3-2) was used to compile associated 12CO(J = 1-0), dust, stellar mass, and star formation rate. Each of the 58 GMCs are categorized by their evolutionary stage. Applying the principal component analysis on these parameters, we construct two principal components, PC1 and PC2, which retain 75% of the information from the original data set. PC1 is interpreted as expressing the total interstellar matter content, and PC2 as the total activity of star formation. Young (< 10 Myr) GMCs occupy a distinct region in the PC1-PC2 plane, with lower interstellar medium (ISM) content and star formation activity compared to intermediate-age and older clouds. Comparison of average cloud properties in different evolutionary stages imply that GMCs may be heated or grow denser and more massive via aggregation of diffuse material in their first ˜ 10 Myr. The PCA also objectively identified a set of tight relations between ISM and star formation. The ratio of the two CO lines is nearly constant, but weakly modulated by massive star formation. Dust is more strongly correlated with the star formation rate than the CO lines, supporting recent findings that dust may trace molecular gas better than CO. Stellar mass contributes weakly to the star formation rate, reminiscent of an extended form of the Schmidt-Kennicutt relation with the molecular gas term substituted by dust.

  3. Gas, dust, stars, star formation, and their evolution in M 33 at giant molecular cloud scales

    NASA Astrophysics Data System (ADS)

    Komugi, Shinya; Miura, Rie E.; Kuno, Nario; Tosaki, Tomoka

    2018-04-01

    We report on a multi-parameter analysis of giant molecular clouds (GMCs) in the nearby spiral galaxy M 33. A catalog of GMCs identifed in 12CO(J = 3-2) was used to compile associated 12CO(J = 1-0), dust, stellar mass, and star formation rate. Each of the 58 GMCs are categorized by their evolutionary stage. Applying the principal component analysis on these parameters, we construct two principal components, PC1 and PC2, which retain 75% of the information from the original data set. PC1 is interpreted as expressing the total interstellar matter content, and PC2 as the total activity of star formation. Young (< 10 Myr) GMCs occupy a distinct region in the PC1-PC2 plane, with lower interstellar medium (ISM) content and star formation activity compared to intermediate-age and older clouds. Comparison of average cloud properties in different evolutionary stages imply that GMCs may be heated or grow denser and more massive via aggregation of diffuse material in their first ˜ 10 Myr. The PCA also objectively identified a set of tight relations between ISM and star formation. The ratio of the two CO lines is nearly constant, but weakly modulated by massive star formation. Dust is more strongly correlated with the star formation rate than the CO lines, supporting recent findings that dust may trace molecular gas better than CO. Stellar mass contributes weakly to the star formation rate, reminiscent of an extended form of the Schmidt-Kennicutt relation with the molecular gas term substituted by dust.

  4. Cloud condensation nuclei activity and droplet activation kinetics of wet processed regional dust samples and minerals

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Sokolik, I. N.; Nenes, A.

    2011-08-01

    This study reports laboratory measurements of particle size distributions, cloud condensation nuclei (CCN) activity, and droplet activation kinetics of wet generated aerosols from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. The dependence of critical supersaturation, sc, on particle dry diameter, Ddry, is used to characterize particle-water interactions and assess the ability of Frenkel-Halsey-Hill adsorption activation theory (FHH-AT) and Köhler theory (KT) to describe the CCN activity of the considered samples. Wet generated regional dust samples produce unimodal size distributions with particle sizes as small as 40 nm, CCN activation consistent with KT, and exhibit hygroscopicity similar to inorganic salts. Wet generated clays and minerals produce a bimodal size distribution; the CCN activity of the smaller mode is consistent with KT, while the larger mode is less hydrophilic, follows activation by FHH-AT, and displays almost identical CCN activity to dry generated dust. Ion Chromatography (IC) analysis performed on regional dust samples indicates a soluble fraction that cannot explain the CCN activity of dry or wet generated dust. A mass balance and hygroscopicity closure suggests that the small amount of ions (from low solubility compounds like calcite) present in the dry dust dissolve in the aqueous suspension during the wet generation process and give rise to the observed small hygroscopic mode. Overall these results identify an artifact that may question the atmospheric relevance of dust CCN activity studies using the wet generation method. Based on the method of threshold droplet growth analysis, wet generated mineral aerosols display similar activation kinetics compared to ammonium sulfate calibration aerosol. Finally, a unified CCN activity framework that accounts for concurrent effects of solute and adsorption is developed to describe the CCN activity of aged or hygroscopic dusts.

  5. Do Cloud Properties in a Puerto Rican Tropical Montane Cloud Forest Depend on Occurrence of Long-Range Transported African Dust?

    NASA Astrophysics Data System (ADS)

    Spiegel, Johanna K.; Buchmann, Nina; Mayol-Bracero, Olga L.; Cuadra-Rodriguez, Luis A.; Valle Díaz, Carlos J.; Prather, Kimberly A.; Mertes, Stephan; Eugster, Werner

    2014-09-01

    We investigated cloud properties of warm clouds in a tropical montane cloud forest at Pico del Este (1,051 m a.s.l.) in the northeastern part of Puerto Rico to address the question of whether cloud properties in the Caribbean could potentially be affected by African dust transported across the Atlantic Ocean. We analyzed data collected during 12 days in July 2011. Cloud droplet size spectra were measured using the FM-100 fog droplet spectrometer that measured droplet size distributions in the range from 2 to 49 µm, primarily during fog events. The droplet size spectra revealed a bimodal structure, with the first peak ( D < 6 µm) being more pronounced in terms of droplet number concentrations, whereas the second peak (10 µm < D < 20 µm) was found to be the one relevant for total liquid water content (LWC) of the cloud. We identified three major clusters of characteristic droplet size spectra by means of hierarchical clustering. All clusters differed significantly from each other in droplet number concentration (), effective diameter (ED), and median volume diameter (MVD). For the cluster comprising the largest droplets and the lowest droplet number concentrations, we found evidence of inhomogeneous mixing in the cloud. Contrastingly, the other two clusters revealed microphysical behavior, which could be expected under homogeneous mixing conditions. For those conditions, an increase in cloud condensation nuclei—e.g., from processed African dust transported to the site—is supposed to lead to an increased droplet concentration. In fact, one of these two clusters showed a clear shift of cloud droplet size spectra towards smaller droplet diameters. Since this cluster occurred during periods with strong evidence for the presence of long-range transported African dust, we hypothesize a link between the observed dust episodes and cloud characteristics in the Caribbean at our site, which is similar to the anthropogenic aerosol indirect effect.

  6. Dust Aerosol, Clouds, and the Atmospheric Optical Depth Record over 5 Mars Years of the Mars Exploration Rover Mission

    NASA Technical Reports Server (NTRS)

    Lemmon, Mark T.; Wolff, Michael J.; Bell, James F., III; Smith, Michael D.; Cantor, Bruce A.; Smith, Peter H.

    2014-01-01

    Dust aerosol plays a fundamental role in the behavior and evolution of the Martian atmosphere. The first five Mars years of Mars Exploration Rover data provide an unprecedented record of the dust load at two sites. This record is useful for characterization of the atmosphere at the sites and as ground truth for orbital observations. Atmospheric extinction optical depths have been derived from solar images after calibration and correction for time-varying dust that has accumulated on the camera windows. The record includes local, regional, and globally extensive dust storms. Comparison with contemporaneous thermal infrared data suggests significant variation in the size of the dust aerosols, with a 1 micrometer effective radius during northern summer and a 2 micrometer effective radius at the onset of a dust lifting event. The solar longitude (L (sub s)) 20-136 degrees period is also characterized by the presence of cirriform clouds at the Opportunity site, especially near LS = 50 and 115 degrees. In addition to water ice clouds, a water ice haze may also be present, and carbon dioxide clouds may be present early in the season. Variations in dust opacity are important to the energy balance of each site, and work with seasonal variations in insolation to control dust devil frequency at the Spirit site.

  7. Orbital Evolution of Dust Particles in the Sublimation Zone near the Sun

    NASA Astrophysics Data System (ADS)

    Shestakova, L. I.; Demchenko, B. I.

    2018-03-01

    We have performed the calculations of the orbital evolution of dust particles from volcanic glass ( p-obsidian), basalt, astrosilicate, olivine, and pyroxene in the sublimation zone near the Sun. The sublimation (evaporation) rate is determined by the temperature of dust particles depending on their radius, material, and distance to the Sun. All practically important parameters that characterize the interaction of spherical dust particles with the radiation are calculated using the Mie theory. The influence of radiation and solar wind pressure, as well as the Poynting-Robertson drag force effects on the dust dynamics, are also taken into account. According to the observations (Shestakova and Demchenko, 2016), the boundary of the dust-free zone is 7.0-7.6 solar radii for standard particles of the zodiacal cloud and 9.1-9.2 solar radii for cometary particles. The closest agreement is obtained for basalt particles and certain kinds of olivine, pyroxene, and volcanic glass.

  8. On the size and velocity distribution of cosmic dust particles entering the atmosphere

    PubMed Central

    Carrillo‐Sánchez, J. D.; Feng, W.; Nesvorný, D.; Janches, D.

    2015-01-01

    Abstract The size and velocity distribution of cosmic dust particles entering the Earth's atmosphere is uncertain. Here we show that the relative concentrations of metal atoms in the upper mesosphere, and the surface accretion rate of cosmic spherules, provide sensitive probes of this distribution. Three cosmic dust models are selected as case studies: two are astronomical models, the first constrained by infrared observations of the Zodiacal Dust Cloud and the second by radar observations of meteor head echoes; the third model is based on measurements made with a spaceborne dust detector. For each model, a Monte Carlo sampling method combined with a chemical ablation model is used to predict the ablation rates of Na, K, Fe, Mg, and Ca above 60 km and cosmic spherule production rate. It appears that a significant fraction of the cosmic dust consists of small (<5 µg) and slow (<15 km s−1) particles. PMID:27478282

  9. Positive low cloud and dust feedbacks amplify tropical North Atlantic Multidecadal Oscillation

    DOE PAGES

    Yuan, Tianle; Oreopoulos, Lazaros; Zelinka, Mark; ...

    2016-02-04

    The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the tropical arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropicalmore » trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic, which warms the tropical North Atlantic SST. Together they contribute to the appearance of the tropical arm of AMO. Most current climate models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many climatic studies related to the AMO.« less

  10. Positive Low Cloud and Dust Feedbacks Amplify Tropical North Atlantic Multidecadal Variability

    NASA Technical Reports Server (NTRS)

    Yuan, Tianle; Oraiopoulos, Lazaros; Zelinka, Mark; Yu, Hongbin; Norris, Joel R.; Chin, Mian; Platnick, Steven; Meyer, Kerry

    2016-01-01

    The Atlantic Multidecadal Oscillation (AMO) is characterized by a horseshoe pattern of sea surface temperature (SST) anomalies and has a wide range of climatic impacts. While the tropical arm of AMO is responsible for many of these impacts, it is either too weak or completely absent in many climate model simulations. Here we show, using both observational and model evidence, that the radiative effect of positive low cloud and dust feedbacks is strong enough to generate the tropical arm of AMO, with the low cloud feedback more dominant. The feedbacks can be understood in a consistent dynamical framework: weakened tropical trade wind speed in response to a warm middle latitude SST anomaly reduces dust loading and low cloud fraction over the tropical Atlantic, which warms the tropical North Atlantic SST. Together they contribute to appearance of the tropical arm of AMO. Most current climate models miss both the critical wind speed response and two positive feedbacks though realistic simulations of them may be essential for many climatic studies related to the AMO.

  11. Dust and Gas in the Magellanic Clouds from the Heritage Herschel Key Project. I. Dust Properties and Insights into the Origin of the Submm (Submillimeter) Excess Emission

    NASA Technical Reports Server (NTRS)

    Gordon, Karl D.; Roman-Duval, Julia; Bot, Caroline; Meixner, Margaret; Babler, Brian; Bernard, Jean-Philippe; Bolatto, Alberto; Boyer, Martha L.; Clayton, Geoffrey C.; Engelbracht, Charles; hide

    2014-01-01

    The dust properties in the Large and Small Magellanic Clouds are studied using the HERITAGE Herschel Key Project photometric data in five bands from 100 to 500 micromillimeters. Three simple models of dust emission were fit to the observations: a single temperature blackbody modified by a powerlaw emissivity (SMBB), a single temperature blackbody modified by a broken power-law emissivity (BEMBB), and two blackbodies with different temperatures, both modified by the same power-law emissivity (TTMBB). Using these models we investigate the origin of the submillimeter excess; defined as the submillimeter (submm) emission above that expected from SMBB models fit to observations < 200 micromillimeters. We find that the BEMBB model produces the lowest fit residuals with pixel-averaged 500 micromillimeters submillimeter excesses of 27% and 43% for the Large and Small Magellanic Clouds, respectively. Adopting gas masses from previous works, the gas-to-dust ratios calculated from our fitting results show that the TTMBB fits require significantly more dust than are available even if all the metals present in the interstellar medium (ISM) were condensed into dust. This indicates that the submillimeter excess is more likely to be due to emissivity variations than a second population of colder dust. We derive integrated dust masses of (7.3 plus or minus 1.7) x 10 (sup 5) and (8.3 plus or minus 2.1) x 10 (sup 4) solar masses for the Large and Small Magellanic Clouds, respectively. We find significant correlations between the submillimeter excess and other dust properties; further work is needed to determine the relative contributions of fitting noise and ISM physics to the correlations.

  12. Impact of aerosols, dust, water vapor and clouds on fair weather PG and implications for the Carnegie curve

    NASA Astrophysics Data System (ADS)

    Kourtidis, Konstantinos; Georgoulias, Aristeidis

    2017-04-01

    We studied the impact of anthropogenic aerosols, fine mode natural aerosols, Saharan dust, atmospheric water vapor, cloud fraction, cloud optical depth and cloud top height on the magnitude of fair weather PG at the rural station of Xanthi. Fair weather PG was measured in situ while the other parameters were obtained from the MODIS instrument onboard the Terra and Aqua satellites. All of the above parameteres were found to impact fair weather PG magnitude. Regarding aerosols, the impact was larger for Saharan dust and fine mode natural aerosols whereas regarding clouds the impact was larger for cloud fraction while less than that of aerosols. Water vapour and ice precipitable water were also found to influence fair weather PG. Since aerosols and water are ubiquitous in the atmosphere and exhibit large spatial and temporal variability, we postulate that our understanding of the Carnegie curve might need revision.

  13. PROGRA2 experiment: New results for dust clouds and regoliths analogs

    NASA Astrophysics Data System (ADS)

    Hadamcik, E.; Renard, J.-B.; Levasseur-Regourd, A. C.; Worms, J.-C.

    2006-01-01

    With the PROGRA2 experience, linear polarization of scattered light is measured on various types of dust clouds lifted by microgravity, or by an air-draught. The aim is to compare the phase curves for dust analogs with those obtained in the Solar System (cometary comae, and solid particles in planetary atmospheres) by remote-sensing and in situ techniques. Measurements are also performed on layers of particles (on the ground) and compared with remote measurements on asteroidal regoliths and planetary surfaces. New phase curves have been obtained, e.g., for quartz samples, crystals, fluffy mixtures of silica and carbon blacks and a high porosity regolith analog made of micron-sized silica spheres. This work will contribute to the choice of the samples to be studied with the ICAPS experiment onboard the ISS and on the precursor experiment.

  14. On the Contribution of Asteroid Disruptions to the Interplanetary Dust Flux

    NASA Astrophysics Data System (ADS)

    Kehoe, T. J. J.; Kehoe, A. E.

    2017-12-01

    Recent modeling has shown the significant contribution of micron- to millimeter-sized particles released by the disruption of main-belt asteroids (MBAs) to the interplanetary dust particle (IDP) flux (e.g., Dermott et al., 2002; Nesvorný et al., 2003; Espy Kehoe et al., 2015). In this paper, we present the results of a study that indicates that the dust injected into the zodiacal cloud due to the catastrophic disruption of an asteroid is dominated by the release of its surface regolith particles. Our research suggests that disrupting a single asteroid with diameter O(100 km) will be enough to regenerate the entire zodiacal cloud. The breakup of smaller asteroids with diameters O(10 km) will likely produce more moderate, but still significant, changes in the dust environment of the inner solar system. As collisional disruptions of asteroids in this size range occur more frequently, it is important that we develop a better understanding of the injection of asteroidal material into the zodiacal cloud as a result of these type of events in order to determine the temporal evolution of the interplanetary dust flux. The results presented in this paper will lead to a better understanding of the threat to exploration activities due to the enhanced IDP flux resulting from the disruption of asteroidal regoliths. These findings can be employed to improve engineering models, for example, the NASA Meteoroid Engineering Model (MEM) that is widely utilized to assess the impact hazard to space hardware and activities in the inner solar system due to the natural meteoroid environment (McNamara et al., 2004). This is an important area of concern for current and future mission development purposes.

  15. Sources of cosmic dust in the Earth's atmosphere

    NASA Astrophysics Data System (ADS)

    Carrillo-Sánchez, J. D.; Nesvorný, D.; Pokorný, P.; Janches, D.; Plane, J. M. C.

    2016-12-01

    There are four known sources of dust in the inner solar system: Jupiter Family comets, asteroids, Halley Type comets, and Oort Cloud comets. Here we combine the mass, velocity, and radiant distributions of these cosmic dust populations from an astronomical model with a chemical ablation model to estimate the injection rates of Na and Fe into the Earth's upper atmosphere, as well as the flux of cosmic spherules to the surface. Comparing these parameters to lidar observations of the vertical Na and Fe fluxes above 87.5 km, and the measured cosmic spherule accretion rate at South Pole, shows that Jupiter Family Comets contribute (80 ± 17)% of the total input mass (43 ± 14 t d-1), in good accord with Cosmic Background Explorer and Planck observations of the zodiacal cloud.

  16. Sources of cosmic dust in the Earth's atmosphere.

    PubMed

    Carrillo-Sánchez, J D; Nesvorný, D; Pokorný, P; Janches, D; Plane, J M C

    2016-12-16

    There are four known sources of dust in the inner solar system: Jupiter Family comets, asteroids, Halley Type comets, and Oort Cloud comets. Here we combine the mass, velocity, and radiant distributions of these cosmic dust populations from an astronomical model with a chemical ablation model to estimate the injection rates of Na and Fe into the Earth's upper atmosphere, as well as the flux of cosmic spherules to the surface. Comparing these parameters to lidar observations of the vertical Na and Fe fluxes above 87.5 km, and the measured cosmic spherule accretion rate at South Pole, shows that Jupiter Family Comets contribute (80 ± 17)% of the total input mass (43 ± 14 t d -1 ), in good accord with Cosmic Background Explorer and Planck observations of the zodiacal cloud.

  17. Sources of cosmic dust in the Earth's atmosphere

    PubMed Central

    Carrillo‐Sánchez, J. D.; Nesvorný, D.; Pokorný, P.; Janches, D.

    2016-01-01

    Abstract There are four known sources of dust in the inner solar system: Jupiter Family comets, asteroids, Halley Type comets, and Oort Cloud comets. Here we combine the mass, velocity, and radiant distributions of these cosmic dust populations from an astronomical model with a chemical ablation model to estimate the injection rates of Na and Fe into the Earth's upper atmosphere, as well as the flux of cosmic spherules to the surface. Comparing these parameters to lidar observations of the vertical Na and Fe fluxes above 87.5 km, and the measured cosmic spherule accretion rate at South Pole, shows that Jupiter Family Comets contribute (80 ± 17)% of the total input mass (43 ± 14 t d−1), in good accord with Cosmic Background Explorer and Planck observations of the zodiacal cloud. PMID:28275286

  18. Analysis of Aerosols and Fallout from High-Explosive Dust Clouds. Volume 2

    DTIC Science & Technology

    1977-03-01

    to the situation at hand, where S is an absolute error, AIV- 30 Rio • N(i, - N(i,2) It is to be noted, however, that the Poisson formula specifies the...sphere TNT detonation near Grand Junction, Colorado, on November 13, 1972. Data from the resulting dust cloud was collected by two aircraft and includes...variations. rio Measurements of carbon monoxide were inconclusive due to an unusually high noise level (6 to 8 ppm or considerably higher than the carbon

  19. The Dynamic Community of Interest and Its Realization in ZODIAC

    DTIC Science & Technology

    2009-10-01

    the ZODIAC project. ZODIAC is a network architecture that puts security first and foremost, with security broken down into confidentiality, integrity...hosts, a unified solution for MANETs will work for hosts or routers as well. DYNAMIC COMMUNITIES OF INTEREST The basis of the ZODIAC design is a new dis...narrow scope of each DCoI limits attack propagation, and supports confidentiality ABSTRACT The ZODIAC project has been exploring a security first

  20. Airborne Dust Cloud Measurements at the INL National Security Test Range

    SciT

    Michael L. Abbott; Norm Stanley; Larry Radke

    2007-09-01

    On July 11, 2007, a surface, high-explosive test (<20,000 lb TNT-equivalent) was carried out at the National Security Test Range (NSTR) on the Idaho National Laboratory (INL) Site. Aircraft-mounted rapid response (1-sec) particulate monitors were used to measure airborne PM-10 concentrations directly in the dust cloud and to develop a PM-10 emission factor that could be used for subsequent tests at the NSTR. The blast produced a mushroom-like dust cloud that rose approximately 2,500–3,000 ft above ground level, which quickly dissipated (within 5 miles of the source). In general, the cloud was smaller and less persistence than expected, or thatmore » might occur in other areas, likely due to the coarse sand and subsurface conditions that characterize the immediate NSTR area. Maximum short time-averaged (1-sec) PM-10 concentrations at the center of the cloud immediately after the event reached 421 µg m-3 but were rapidly reduced (by atmospheric dispersion and fallout) to near background levels (~10 µg m-3) after about 15 minutes. This occurred well within the INL Site boundary, about 8 km (5 miles) from the NSTR source. These findings demonstrate that maximum concentrations in ambient air beyond the INL Site boundary (closest is 11.2 km from NSTR) from these types of tests would be well within the 150 µg m-3 24-hour National Ambient Air Quality Standards for PM-10. Aircraft measurements and geostatistical techniques were used to successfully quantify the initial volume (1.64E+9 m3 or 1.64 km3) and mass (250 kg) of the PM-10 dust cloud, and a PM-10 emission factor (20 kg m-3 crater soil volume) was developed for this specific type of event at NSTR. The 250 kg of PM-10 mass estimated from this experiment is almost seven-times higher than the 36 kg estimated for the environmental assessment (DOE-ID 2007) using available Environmental Protection Agency (EPA 1995) emission factors. This experiment demonstrated that advanced aircraft-mounted instruments operated by

  1. Inertia-Centric Stability Analysis of a Planar Uniform Dust Molecular Cloud with Weak Neutral-Charged Dust Frictional Coupling

    NASA Astrophysics Data System (ADS)

    K. Karmakar, P.; Borah, B.

    2014-05-01

    This paper adopts an inertia-centric evolutionary model to study the excitation mechanism of new gravito-electrostatic eigenmode structures in a one-dimensional (1-D) planar self-gravitating dust molecular cloud (DMC) on the Jeans scale. A quasi-neutral multi-fluid consisting of warm electrons, warm ions, neutral gas and identical inertial cold dust grains with partial ionization is considered. The grain-charge is assumed not to vary at the fluctuation evolution time scale. The neutral gas particles form the background, which is weakly coupled with the collapsing grainy plasma mass. The gravitational decoupling of the background neutral particles is justifiable for a higher inertial mass of the grains with higher neutral population density so that the Jeans mode frequency becomes reasonably large. Its physical basis is the Jeans assumption of a self-gravitating uniform medium adopted for fiducially analytical simplification by neglecting the zero-order field. So, the equilibrium is justifiably treated initially as “homogeneous”. The efficacious inertial role of the thermal species amidst weak collisions of the neutral-charged grains is taken into account. A standard multiscale technique over the gravito-electrostatic equilibrium yields a unique pair of Korteweg-de Vries (KdV) equations. It is integrated numerically by the fourth-order Runge-Kutta method with multi-parameter variation for exact shape analyses. Interestingly, the model is conducive for the propagation of new conservative solitary spectral patterns. Their basic physics, parametric features and unique characteristics are discussed. The results go qualitatively in good correspondence with the earlier observations made by others. Tentative applications relevant to space and astrophysical environments are concisely highlighted.

  2. OAO-2 observations of the zodiacal light

    NASA Technical Reports Server (NTRS)

    Lillie, C. F.

    1972-01-01

    Photometric measurements of the night sky brightness have been obtained at twelve wavelengths between 1000 A and 4300 A from above the earth's atmosphere. A preliminary analysis of the data reveals a component of the sky brightness with ecliptic symmetry and an intensity distribution similar to that of the zodiacal light. The ultraviolet spectrum of the zodiacal light can be closely approximated with a two component model in which one component has an albedo proportional to the wavelength lambda and the other component has a scattering efficiency proportional to lambda to lbe minus 19 power.

  3. Raman lidar measurement of water vapor and ice clouds associated with Asian dust layer over Tsukuba, Japan

    NASA Astrophysics Data System (ADS)

    Sakai, Tetsu; Nagai, Tomohiro; Nakazato, Masahisa; Matsumura, Takatsugu

    2004-03-01

    The vertical distributions of particle extinction, backscattering, depolarization, and water vapor mixing ratio were measured using a Raman lidar over Tsukuba (36.1°N, 140.1°E), Japan, on 23-24 April 2001. Ice clouds associated with the Asian dust layer were observed at an altitude of ~6-9 km. The relative humidities in the cloud layer were close to the ice saturation values and the temperature at the top of the cloud layer was ~-35°C, suggesting that the Asian dust acted as ice nuclei at the high temperatures. The meteorological analysis suggested that the ice-saturated region was formed near the top of the dust layer where the moist air ascended in slantwise fashion above the cold-frontal zone associated with extratropical cyclone.

  4. Understanding Asteroid Disruptions Using Very Young Dust Bands

    NASA Astrophysics Data System (ADS)

    Espy Kehoe, Ashley J.; Kehoe, T. J.; Colwell, J. E.; Dermott, S. F.

    2013-10-01

    Zodiacal dust bands are structures that result from the dynamical sculpting of the dust particles released in the catastrophic disruption of an asteroid. Partial dust bands are the recently discovered younger siblings of the dust bands, ones that are still forming and due to very recent disruptions within the last few hundred thousand years. During the early stages of formation, these structures retain information on the original catastrophic disruptions that produced them (since the dust has not yet been lost or significantly altered by orbital or collisional decay). The first partial dust band, at about 17 degrees latitude, was revealed using a very precise method of co-adding the IRAS data set. We have shown that these partial dust bands exhibit structure consistent with a forming band, can be used to constrain the original size distribution of the dust produced in the catastrophic disruption of an asteroid, and these very young structures also allow a much better estimate of the total amount of dust released in the disruption. In order to interpret the observations and constrain the parameters of the dust injected into the cloud following an asteroid disruption, we have developed detailed models of the dynamical evolution of the dust that makes up the band. We model the dust velocity distribution resulting from the initial impact and then track the orbital evolution of the dust under the effects of gravitational perturbations from all the planets as well as radiative forces of Poynting-Robertson drag, solar wind drag and radiation pressure and use these results to produce maps of the thermal emission. Through the comparison of our newly completed dynamical evolution models with the coadded observations, we can put constraints on the parameters of dust producing the band. We confirm the source of the band as the very young Emilkowalski cluster ( <250,000 years; Nesvorny et al., 2003) and present our most recent estimates of the size-distribution and cross

  5. The Dust Cloud TGU H1192 (LDN 1525) in Auriga. II

    NASA Astrophysics Data System (ADS)

    Boyle, Richard P.; Janusz, Robert; Straizys, Vytautas; Zdanavicius, Kazimieras; Maskoliunas, Marius; Kazlauskas, Algirdas

    2016-01-01

    The results of a new investigation of interstellar extinction in the direction of the emission nebulae Sh2-231 and Sh2-235 are presented. The investigation is based on CCD photometry and photometric MK classification in seven areas of 12' by 12' size in the Vilnius seven-color photometric system down to V = 19 mag. Additionally, for the same task we applied 519 red clump giants identified in the surrounding 1.5 deg. by 1.5 deg. area using the results of photometry in the 2MASS and WISE surveys. The dependence of the extinction run with distance allows determining distances to dust clouds and their extinctions. We comparethese new more detailed results with the preliminary results described in our previous paper (V. Straizys et al. 2010, Baltic Astronomy, 19, 169) and the AAS communication at the AAS Meeting No. 219 (Austin), 349.12. The relation of the TGU H1192 dust cloud with the Auriga OB1 association is discussed.

  6. Size-resolved Chemical Composition of Cloud and Rain Water Collected during the Puerto Rico African Dust and Clouds Study (PRADACS) Campaign

    NASA Astrophysics Data System (ADS)

    Torres, E.; Valle Diaz, C. J.; Zurcher, F.; Lee, T.; Collett, J. L.; Fitzgerald, E.; Cuadra, L.; Prather, K. A.; Mayol-Bracero, O. L.

    2011-12-01

    The underlying physico-chemical processes of dust-aerosol interactions are poorly understood; even less understood is how aging impacts cloud properties and climate as the particles travel from Africa to the Caribbean region. Caribbean landmasses have tropical montane cloud forests (TMCFs) that are tightly coupled to the atmospheric hydrologic cycle. Small-scale shifts in temperature and precipitation could have serious ecological consequences. Therefore, this makes TMCFs an interesting ecosystem to see the effects African Dust (AD) might have on cloud formation and precipitation. As part of the Puerto Rico African Dust and Clouds Study (PRADACS) cloud and rain water samples for subsequent chemical analysis were collected at Pico del Este (PE) station in Luquillo, PR (1051 masl) during summer 2011. At PE, two cloud collectors (i.e., single stage (Aluminum version) and 2-stage (Teflon version) Caltech Active Strand Cloudwater Collector (CASCC)), and a rainwater collector were operated. Measurements such as the liquid water content (LWC), pH, conductivity., and composition of single particles using an aerosol time of flight mass spectrometer (ATOFMS) were performed. Preliminary results showed that days with the influence of African dust (AD), had LWC values that ranged from 300 to 500 mg/m3, pH values up to 5.7,, and conductivity up to 180 μS/cm. The ATOFMS showed titanium and iron ions, suggesting the presence of AD as well as, occasionally, sulfate and nitrate ions suggesting the influence of anthropogenic pollution. Results on the chemical composition and the physical properties of cloud, rainwater, and aerosol for the inorganic as well as the organic fraction and how these properties change for the different air masses observed will also be presented.

  7. The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

    NASA Astrophysics Data System (ADS)

    Wiacek, A.; Peter, T.; Lohmann, U.

    2010-09-01

    This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons, without explicitly modelling dust emission and deposition processes. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high ice clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Downstream of the investigated dust sources, practically none of the simulated air parcels reached conditions of homogeneous ice nucleation (T≲-40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through atmospheric regions supersaturated with respect to ice but subsaturated with respect to water, where so-called "warm ice clouds" (T≳-40 °C) theoretically may form prior to supercooled water or mixed-phase clouds. The importance of "warm ice clouds" and the general influence

  8. Metal Evolution and TrAnsport in the Large Magellanic Cloud (METAL): Probing Dust Evolution in Star Forming Galaxies

    NASA Astrophysics Data System (ADS)

    Roman-Duval

    2016-10-01

    METAL is a large spectroscopic and imaging program with HST dedicated to the study of dust evolution in the Large Magellanic Cloud (LMC). The program will obtain FUV and NUV medium-resolution spectra of 33 massive stars in the LMC with STIS and COS complementing existing archival data to measure gas-phase and dust-phase (depletion) elemental abundances. With these spectra, we will subsequently directly measure the dust composition and abundance as a function of environment (surface density, radiation field, dynamical conditions, such as the proximity of supernova remnants or expanding HI shells). The depletion information will be complemented with dust UV extinction curves (i.e., the UV opacity of dust grains as a function of wavelength) derived from either archival IUE, or new COS and low-resolution STIS spectra acquired as part of this program. Together, the depletions and extinction curves will constrain how the dust abundance and properties (composition, size distribution) vary with environment at Z=0.5Zo. In parallel to the spectroscopic observations, we will obtain WFC3 NUV-NIR imaging to map dust extinction parameters (AV, RV) in the vicinity of our targets and calibrate the far-infrared (FIR) emissivity of dust. Our observations we will improve the accuracy of dust mass and extinction estimates in the local and high-redshift universe by up to an order of magnitude.METAL will complement a Cycle 23 HST/STIS program (GO-13778) focused on dust evolution in the Small Magellanic Cloud (SMC) at Z=0.2Zo, and previously published depletion studies in the Milky Way (Jenkins et al. 2009) to provide a comprehensive view of dust evolution as a function of metallicity.

  9. Changes of Dust Opacity with Density in the Orion A Molecular Cloud

    NASA Astrophysics Data System (ADS)

    Roy, Arabindo; Martin, Peter G.; Polychroni, Danae; Bontemps, Sylvain; Abergel, Alain; André, Philippe; Arzoumanian, Doris; Di Francesco, James; Hill, Tracey; Konyves, Vera; Nguyen-Luong, Quang; Pezzuto, Stefano; Schneider, Nicola; Testi, Leonardo; White, Glenn

    2013-01-01

    We have studied the opacity of dust grains at submillimeter wavelengths by estimating the optical depth from imaging at 160, 250, 350, and 500 μm from the Herschel Gould Belt Survey and comparing this to a column density obtained from the Two Micron All Sky Survey derived color excess E(J - K s). Our main goal was to investigate the spatial variations of the opacity due to "big" grains over a variety of environmental conditions and thereby quantify how emission properties of the dust change with column (and volume) density. The central and southern areas of the Orion A molecular cloud examined here, with N H ranging from 1.5 × 1021 cm-2 to 50 × 1021 cm-2, are well suited to this approach. We fit the multi-frequency Herschel spectral energy distributions (SEDs) of each pixel with a modified blackbody to obtain the temperature, T, and optical depth, τ1200, at a fiducial frequency of 1200 GHz (250 μm). Using a calibration of N H/E(J - Ks ) for the interstellar medium (ISM) we obtained the opacity (dust emission cross-section per H nucleon), σe(1200), for every pixel. From a value ~1 × 10-25 cm2 H-1 at the lowest column densities that is typical of the high-latitude diffuse ISM, σe(1200) increases as N 0.28 H over the range studied. This is suggestive of grain evolution. Integrating the SEDs over frequency, we also calculated the specific power P (emission power per H) for the big grains. In low column density regions where dust clouds are optically thin to the interstellar radiation field (ISRF), P is typically 3.7 × 10-31 W H-1, again close to that in the high-latitude diffuse ISM. However, we find evidence for a decrease of P in high column density regions, which would be a natural outcome of attenuation of the ISRF that heats the grains, and for localized increases for dust illuminated by nearby stars or embedded protostars.

  10. DUST AND GAS IN THE MAGELLANIC CLOUDS FROM THE HERITAGE HERSCHEL KEY PROJECT. II. GAS-TO-DUST RATIO VARIATIONS ACROSS INTERSTELLAR MEDIUM PHASES

    SciT

    Roman-Duval, Julia; Gordon, Karl D.; Meixner, Margaret

    2014-12-20

    The spatial variations of the gas-to-dust ratio (GDR) provide constraints on the chemical evolution and lifecycle of dust in galaxies. We examine the relation between dust and gas at 10-50 pc resolution in the Large and Small Magellanic Clouds (LMC and SMC) based on Herschel far-infrared (FIR), H I 21 cm, CO, and Hα observations. In the diffuse atomic interstellar medium (ISM), we derive the GDR as the slope of the dust-gas relation and find GDRs of 380{sub −130}{sup +250} ± 3 in the LMC, and 1200{sub −420}{sup +1600} ± 120 in the SMC, not including helium. The atomic-to-molecular transition is locatedmore » at dust surface densities of 0.05 M {sub ☉} pc{sup –2} in the LMC and 0.03 M {sub ☉} pc{sup –2} in the SMC, corresponding to A {sub V} ∼ 0.4 and 0.2, respectively. We investigate the range of CO-to-H{sub 2} conversion factor to best account for all the molecular gas in the beam of the observations, and find upper limits on X {sub CO} to be 6 × 10{sup 20} cm{sup –2} K{sup –1} km{sup –1} s in the LMC (Z = 0.5 Z {sub ☉}) at 15 pc resolution, and 4 × 10{sup 21} cm{sup –2} K{sup –1} km{sup –1} s in the SMC (Z = 0.2 Z {sub ☉}) at 45 pc resolution. In the LMC, the slope of the dust-gas relation in the dense ISM is lower than in the diffuse ISM by a factor ∼2, even after accounting for the effects of CO-dark H{sub 2} in the translucent envelopes of molecular clouds. Coagulation of dust grains and the subsequent dust emissivity increase in molecular clouds, and/or accretion of gas-phase metals onto dust grains, and the subsequent dust abundance (dust-to-gas ratio) increase in molecular clouds could explain the observations. In the SMC, variations in the dust-gas slope caused by coagulation or accretion are degenerate with the effects of CO-dark H{sub 2}. Within the expected 5-20 times Galactic X {sub CO} range, the dust-gas slope can be either constant or decrease by a factor of several across ISM phases. Further

  11. Cosmic dust and space debris; Proceedings of the Topical Meetings and Workshop 6 of the 26th COSPAR Plenary Meeting, Toulouse, France, June 30-July 11, 1986

    NASA Technical Reports Server (NTRS)

    Mcdonnell, J. A. M. (Editor); Hanner, M. S. (Editor); Kessler, D. J. (Editor)

    1986-01-01

    These proceedings encompass topics in the fields of extraterrestrial material samples, IRAS solar system and dust model results, and earth orbit debris. Attention is given to chemical fractionation during high velocity impact, particle deceleration and survival in multiple thin foil targets, and IRAS studies of asteroids, comets, cometary tails, the zodiacal background, and the three-dimensional modeling of interplanetary dust. Also discussed are the evolution of an earth orbit debris cloud, orbital debris due to future space activities, collision probabilities in geosynchronous orbits, and a bitelescopic survey of low altitude orbital debris.

  12. Foehn-induced effects on local dust pollution, frontal clouds and solar radiation in the Dead Sea valley

    NASA Astrophysics Data System (ADS)

    Kishcha, Pavel; Starobinets, Boris; Savir, Amit; Alpert, Pinhas; Kaplan, Michael

    2018-06-01

    Despite the long history of investigation of foehn phenomena, there are few studies of the influence of foehn winds on air pollution and none in the Dead Sea valley. For the first time the foehn phenomenon and its effects on local dust pollution, frontal cloudiness and surface solar radiation were analyzed in the Dead Sea valley, as it occurred on 22 March 2013. This was carried out using both numerical simulations and observations. The foehn winds intensified local dust emissions, while the foehn-induced temperature inversion trapped dust particles beneath this inversion. These two factors caused extreme surface dust concentration in the western Dead Sea valley. The dust pollution was transported by west winds eastward, to the central Dead Sea valley, where the speed of these winds sharply decreased. The transported dust was captured by the ascending airflow contributing to the maximum aerosol optical depth (AOD) over the central Dead Sea valley. On the day under study, the maximum surface dust concentration did not coincide with the maximum AOD: this being one of the specific effects of the foehn phenomenon on dust pollution in the Dead Sea valley. Radar data showed a passage of frontal cloudiness through the area of the Dead Sea valley leading to a sharp drop in noon solar radiation. The descending airflow over the downwind side of the Judean Mountains led to the formation of a cloud-free band followed by only the partial recovery of solar radiation because of the extreme dust pollution caused by foehn winds.

  13. Ice Nucleation of Bare and Sulfuric Acid-coated Mineral Dust Particles and Implication for Cloud Properties

    SciT

    Kulkarni, Gourihar R.; Sanders, Cassandra N.; Zhang, Kai

    2014-08-27

    Ice nucleation properties of different dust species coated with soluble material are not well understood. We determined the ice nucleation ability of bare and sulfuric acid coated mineral dust particles as a function of temperature (-25 to -35 deg C) and relative humidity with respect to water (RHw). Five different mineral dust species: Arizona test dust (ATD), illite, montmorillonite, quartz and kaolinite were dry dispersed and size-selected at 150 nm and exposed to sulfuric acid vapors in the coating apparatus. The condensed sulfuric acid soluble mass fraction per particle was estimated from the cloud condensation nuclei activated fraction measurements. Themore » fraction of dust particles nucleating ice at various temperatures and RHw was determined using a compact ice chamber. In water-subsaturated conditions, compared to bare dust particles, we found that only coated ATD particles showed suppression of ice nucleation ability while other four dust species did not showed the effect of coating on the fraction of particles nucleating ice. The results suggest that interactions between the dust surface and sulfuric acid vapor are important, such that interactions may or may not modify the surface via chemical reactions with sulfuric acid. At water-supersaturated conditions we did not observed the effect of coating, i.e. the bare and coated dust particles had similar ice nucleation behavior.« less

  14. Metals and dust in the neutral ISM: the Galaxy, Magellanic Clouds, and damped Lyman-α absorbers

    NASA Astrophysics Data System (ADS)

    De Cia, Annalisa

    2018-05-01

    Context. The presence of dust in the neutral interstellar medium (ISM) dramatically changes the metal abundances that we measure. Understanding the metal content in the neutral ISM, and a direct comparison between different environments, has been hampered to date because of the degeneracy to the observed ISM abundances caused by the effects of metallicity, the presence of dust, and nucleosynthesis. Aims: We study the metal and dust content in the neutral ISM consistently in different environments, and assess the universality of recently discovered sequences of relative abundances. We also intend to assess the validity of [Zn/Fe] as a tracer of dust in the ISM. This has recently been cast into doubt based on observations of stellar abundances, and needs to be addressed before we can safely use it to study the ISM. Methods: In this letter we present a simple comparison of relative abundances observed in the neutral ISM in the Galaxy, the Magellanic Clouds, and damped Lyman-α absorbers (DLAs). The main novelty in this comparison is the inclusion of the Magellanic Clouds. Results: The same sequences of relative abundances are valid for the Galaxy, Magellanic Clouds, and DLAs. These sequences are driven by the presence of dust in the ISM and seem "universal". Conclusions: The metal and dust properties in the neutral ISM appear to follow a similar behaviour in different environments. This suggests that a dominant fraction of the dust budget is built up from grain growth in the ISM depending of the physical conditions and regardless of the star formation history of the system. In addition, the DLA gas behaves like the neutral ISM, at least from a chemical point of view. Finally, despite the deviations in [Zn/Fe] observed in stellar abundances, [Zn/Fe] is a robust dust tracer in the ISM of different environments, from the Galaxy to DLAs.

  15. Chemical Speciation of Water Soluble Ions and Metals of Cloud and Rain Water During the Puerto Rico African Dust and Clouds Study (PRADACS) Campaigns

    NASA Astrophysics Data System (ADS)

    Torres, E.; Valle Diaz, C. J.; Lee, T.; Collett, J. L.; Fitzgerald, E.; Cuadra-Rodriguez, L. A.; Prather, K. A.; Sánchez, M.; McDowell, W. H.; Mayol-Bracero, O. L.

    2013-05-01

    The underlying physico-chemical processes of dust particles interactions are poorly understood; even less understood is how aging impacts cloud properties and climate as the particles travel from Africa to the Caribbean region. Caribbean landmasses have tropical montane cloud forests (TMCFs) that are tightly coupled to the atmospheric hydrologic cycle. TMCFs are ecosystems to study the effects African Dust (AD) on cloud formation and precipitation as these are very sensitive ecosystems that respond to small changes in climate. As part of the Puerto Rico African Dust and Clouds Study (PRADACS), chemical analyses were performed on cloud and rain water samples collected at Pico del Este (PE) station in Luquillo, PR (1051 masl) during campaigns held from 2010 to 2012. At PE, two cloud collectors (i.e., single stage (Aluminum version), a 2-stage (Teflon version) Caltech Active Strand Cloudwater Collector (CASCC)), a rainwater collector, and anAerosol Time-Of-Flight Mass Spectrometer (ATOFMS) were operated. Chemical analyses performed on collected samples include pH, conductivity, ion chromatography (IC), and inductive coupled plasma (ICP). Results from these campaigns showed that on days that had air masses with the influence of AD, cloud water samples had higher conductivity and pH values on average (up to 5.7 and 180μS/cm, respectively) than those with air masses without AD influence. An increase in the concentrations of water-soluble ions like non-sea salt calcium and magnesium, and metals like magnesium, calcium and aluminum was observed and the appearance of iron was seen on ICP analyses. The ATOFMS, showed an increase on the amount of particles during AD influence with composition of aluminum, silicates, potassium, iron and titanium aerosols. The increase on the aforementioned species was constant in the three years of sampling, which give us confidence in the identification of the chemical species that are present during the influence of AD.

  16. Spherically Symmetric Gravitational Collapse of a Dust Cloud in Third-Order Lovelock Gravity

    NASA Astrophysics Data System (ADS)

    Zhou, Kang; Yang, Zhan-Ying; Zou, De-Cheng; Yue, Rui-Hong

    We investigate the spherically symmetric gravitational collapse of an incoherent dust cloud by considering a LTB-type spacetime in third-order Lovelock Gravity without cosmological constant, and give three families of LTB-like solutions which separately corresponding to hyperbolic, parabolic and elliptic. Notice that the contribution of high-order curvature corrections have a profound influence on the nature of the singularity, and the global structure of spacetime changes drastically from the analogous general relativistic case. Interestingly, the presence of high order Lovelock terms leads to the formation of massive, naked and timelike singularities in the 7D spacetime, which is disallowed in general relativity. Moveover, we point out that the naked singularities in the 7D case may be gravitational weak therefore may not be a serious threat to the cosmic censorship hypothesis, while the naked singularities in the D ≥ 8 inhomogeneous collapse violate the cosmic censorship hypothesis seriously.

  17. Limb clouds and dust on Mars from VMC-Mars Express images

    NASA Astrophysics Data System (ADS)

    Sanchez-Lavega, Agustin; Chen, Hao Chen; Ordoñez-Etxeberria, Iñaki; Hueso, Ricardo; Cardesin, Alejandro; Titov, Dima; Wood, Simon

    2016-10-01

    We have used the large image database generated by the Visual Monitoring Camera (VMC) onboard Mars Express to first search and then study, the properties of projected features (dust and water clouds) on the planet limb. VMC is a small camera serving since 2007 for public education and outreach (Ormston et al., 2011). The camera consists of a CMOS sensor with a Bayer filter mosaic providing color images in the wavelength range 400-900 nm. Since the observations were performed in an opportunistic mode (nor planned on a science base) the captured events occurred in a random mode. In total 17 limb features were observed in the period spanning from April 2007 to August 2015. Their extent at limb varies from about 100 km for the smaller ones to 2,000 km for the major ones. They showed a rich morphology consisting in series of patchy elements with a uniform top layer located at altitudes ranging from 30 to 85 km. The features are mostly concentrated between latitudes 45 deg North and South covering most longitudes although a greater concentration occurs around -90 to +90 deg. from the reference meridian (i.e. longitude 0 degrees, East or West). Most events in the southern hemisphere occurred for orbital longitudes 0-90 degrees (autumnal season) and in the north for orbital longitudes 330-360 (winter season). We present a detailed study of two of these events, one corresponding to a dust storm observed also with the MARCI instrument onboard Mars Reconnaissance Orbiter, and a second one corresponding to a water cloud.

  18. DUST AND GAS IN THE MAGELLANIC CLOUDS FROM THE HERITAGE HERSCHEL KEY PROJECT. I. DUST PROPERTIES AND INSIGHTS INTO THE ORIGIN OF THE SUBMILLIMETER EXCESS EMISSION

    SciT

    Gordon, Karl D.; Roman-Duval, Julia; Meixner, Margaret

    The dust properties in the Large and Small Magellanic clouds (LMC/SMC) are studied using the HERITAGE Herschel Key Project photometric data in five bands from 100 to 500 μm. Three simple models of dust emission were fit to the observations: a single temperature blackbody modified by a power-law emissivity (SMBB), a single temperature blackbody modified by a broken power-law emissivity (BEMBB), and two blackbodies with different temperatures, both modified by the same power-law emissivity (TTMBB). Using these models, we investigate the origin of the submillimeter excess, defined as the submillimeter emission above that expected from SMBB models fit to observations <200more » μm. We find that the BEMBB model produces the lowest fit residuals with pixel-averaged 500 μm submillimeter excesses of 27% and 43% for the LMC and SMC, respectively. Adopting gas masses from previous works, the gas-to-dust ratios calculated from our fitting results show that the TTMBB fits require significantly more dust than are available even if all the metals present in the interstellar medium (ISM) were condensed into dust. This indicates that the submillimeter excess is more likely to be due to emissivity variations than a second population of colder dust. We derive integrated dust masses of (7.3 ± 1.7) × 10{sup 5} and (8.3 ± 2.1) × 10{sup 4} M {sub ☉} for the LMC and SMC, respectively. We find significant correlations between the submillimeter excess and other dust properties; further work is needed to determine the relative contributions of fitting noise and ISM physics to the correlations.« less

  19. Sensitivity Studies of Dust Ice Nuclei Effect on Cirrus Clouds with the Community Atmosphere Model CAM5

    NASA Technical Reports Server (NTRS)

    Liu, Xiaohong; Zhang, Kai; Jensen, Eric J.; Gettelman, Andrew; Barahona, Donifan; Nenes, Athanasios; Lawson, Paul

    2012-01-01

    In this study the effect of dust aerosol on upper tropospheric cirrus clouds through heterogeneous ice nucleation is investigated in the Community Atmospheric Model version 5 (CAM5) with two ice nucleation parameterizations. Both parameterizations consider homogeneous and heterogeneous nucleation and the competition between the two mechanisms in cirrus clouds, but differ significantly in the number concentration of heterogeneous ice nuclei (IN) from dust. Heterogeneous nucleation on dust aerosol reduces the occurrence frequency of homogeneous nucleation and thus the ice crystal number concentration in the Northern Hemisphere (NH) cirrus clouds compared to simulations with pure homogeneous nucleation. Global and annual mean shortwave and longwave cloud forcing are reduced by up to 2.0+/-0.1Wm (sup-2) (1 uncertainty) and 2.4+/-0.1Wm (sup-2), respectively due to the presence of dust IN, with the net cloud forcing change of -0.40+/-0.20W m(sup-2). Comparison of model simulations with in situ aircraft data obtained in NH mid-latitudes suggests that homogeneous ice nucleation may play an important role in the ice nucleation at these regions with temperatures of 205-230 K. However, simulations overestimate observed ice crystal number concentrations in the tropical tropopause regions with temperatures of 190- 205 K, and overestimate the frequency of occurrence of high ice crystal number concentration (greater than 200 L(sup-1) and underestimate the frequency of low ice crystal number concentration (less than 30 L(sup-1) at NH mid-latitudes. These results highlight the importance of quantifying the number concentrations and properties of heterogeneous IN (including dust aerosol) in the upper troposphere from the global perspective.

  20. The Umov effect in application to an optically thin two-component cloud of cosmic dust

    NASA Astrophysics Data System (ADS)

    Zubko, Evgenij; Videen, Gorden; Zubko, Nataliya; Shkuratov, Yuriy

    2018-04-01

    The Umov effect is an inverse correlation between linear polarization of the sunlight scattered by an object and its geometric albedo. The Umov effect has been observed in particulate surfaces, such as planetary regoliths, and recently it also was found in single-scattering small dust particles. Using numerical modeling, we study the Umov effect in a two-component mixture of small irregularly shaped particles. Such a complex chemical composition is suggested in cometary comae and other types of optically thin clouds of cosmic dust. We find that the two-component mixtures of small particles also reveal the Umov effect regardless of the chemical composition of their end-member components. The interrelation between log(Pmax) and log(A) in a two-component mixture of small irregularly shaped particles appears either in a straight linear form or in a slightly curved form. This curvature tends to decrease while the index n in a power-law size distribution r-n grows; at n > 2.5, the log(Pmax)-log(A) diagrams are almost straight linear in appearance. The curvature also noticeably decreases with the packing density of constituent material in irregularly shaped particles forming the mixture. That such a relation exists suggest the Umov effect may also be observed in more complex mixtures.

  1. The Umov effect in application to an optically thin two-component cloud of cosmic dust

    NASA Astrophysics Data System (ADS)

    Zubko, Evgenij; Videen, Gorden; Zubko, Nataliya; Shkuratov, Yuriy

    2018-07-01

    The Umov effect is an inverse correlation between linear polarization of the sunlight scattered by an object and its geometric albedo. The Umov effect has been observed in particulate surfaces, such as planetary regoliths, and recently it also was found in single-scattering small dust particles. Using numerical modelling, we study the Umov effect in a two-component mixture of small irregularly shaped particles. Such a complex chemical composition is suggested in cometary comae and other types of optically thin clouds of cosmic dust. We find that the two-component mixtures of small particles also reveal the Umov effect regardless of the chemical composition of their end-member components. The interrelation between log(Pmax) and log(A) in a two-component mixture of small irregularly shaped particles appears either in a straight linear form or in a slightly curved form. This curvature tends to decrease while the index n in a power-law size distribution r-n grows; at n > 2.5, the log(Pmax)-log(A) diagrams are almost straight linear in appearance. The curvature also noticeably decreases with the packing density of constituent material in irregularly shaped particles forming the mixture. That such a relation exists suggests the Umov effect may also be observed in more complex mixtures.

  2. Dust in the small Magellanic cloud. 1: Interstellar polarization and extinction data

    NASA Technical Reports Server (NTRS)

    Magalhaes, A. M.; Rodrigues, C. V.; Coyne, C. V.; Piirola, V.

    1996-01-01

    The typical extinction curve for the Small Magellanic Cloud (SMC), in contrast to that for the Galaxy, has no bump at 2175 A and has a steeper rise into the far ultraviolet. For the Galaxy the interpretation of the extinction and, therefore, the dust content of the interstellar medium has been greatly assisted by measurements of the wavelength dependence of the polarization. For the SMC no such measurements existed. Therefore, to further elucidate the dust properties in the SMC we have for the first time measured linear polarization with five colors in the optical region of the spectrum for a sample of reddened stars. For two of these stars, for which there were no existing UV spectrophotometric measurements, but for which we measured a relatively large polarization, we have also obtained data from the International Ultraviolet Explorer (IUE) in order to study the extinction. We also attempt to correlate the SMC extinction and polarization data. The main results are: the wavelength of maximum polarization, lambda(sub max), in the SMC is typically smaller than that in the Galaxy; however, AZC 456, which shows the UV extinction bump, has a lambda(sub max) typical of that in the Galaxy, but its polarization curve is narrower and its bump is shifted to shorter wavelengths as compared to the Galaxy; and from an analysis of both the extinction and polarization data it appears that the SMC has typically smaller grains than those in the Galaxy. The absence of the extinction bump in the SMC has generally been thought to imply a lower carbon abundance in the SMC compared to the Galaxy. We interpret our results to mean that te size distribution of the interstellar grains, and not only the carbon abundance, is different in the SMC as compared to the Galaxy. In Paper 2 we present dust model fits to these observations.

  3. IDE spatio-temporal impact fluxes and high time-resolution studies of multi-impact events and long-lived debris clouds

    NASA Technical Reports Server (NTRS)

    Mulholland, J. Derral; Singer, S. Fred; Oliver, John P.; Weinberg, Jerry L.; Cooke, William J.; Montague, Nancy L.; Wortman, Jim J.; Kassel, Phillip C.; Kinard, William H.

    1992-01-01

    The purpose of the Interplanetary Dust Experiment (IDE) on the Long Duration Exposure Facility (LDEF) was to sample the cosmic dust environment and to use the spatio-temporal aspect of the experiment to distinguish between the various components of the environment: zodiacal cloud, beta meteoroids, meteor streams, interstellar dust, and orbital debris. It was found that the introduction of precise time and even rudimentary directionality as co-lateral observables in sampling the particulate environment in near-Earth space produces an enormous qualitative improvement in the information content of the impact data. The orbital debris population is extremely clumpy, being dominated by persistent clouds in which the fluxes may rise orders of magnitude above the background. The IDE data suggest a strategy to minimize the damage to sensitive spacecraft components, using the observed characteristics of cloud encounters.

  4. TEMPERATURE SPECTRA OF INTERSTELLAR DUST GRAINS HEATED BY COSMIC RAYS. I. TRANSLUCENT CLOUDS

    SciT

    Kalvāns, Juris, E-mail: juris.kalvans@venta.lv

    Heating of whole interstellar dust grains by cosmic-ray (CR) particles affects the gas–grain chemistry in molecular clouds by promoting molecule desorption, diffusion, and chemical reactions on grain surfaces. The frequency of such heating, f{sub T}, s{sup −1}, determines how often a certain temperature T{sub CR}, K, is reached for grains hit by CR particles. This study aims to provide astrochemists with a comprehensive and updated data set on CR-induced whole-grain heating. We present calculations of f{sub T} and T{sub CR} spectra for bare olivine grains with radius a of 0.05, 0.1, and 0.2 μ m and such grains covered withmore » ice mantles of thickness 0.1 a and 0.3 a . Grain shape and structure effects are considered, as well as 30 CR elemental constituents with an updated energy spectrum corresponding to a translucent cloud with A{sub V} = 2 mag. Energy deposition by CRs in grain material was calculated with the srim program. We report full T{sub CR} spectra for all nine grain types and consider initial grain temperatures of 10 K and 20 K. We also provide frequencies for a range of minimum T{sub CR} values. The calculated data set can be simply and flexibly implemented in astrochemical models. The results show that, in the case of translucent clouds, the currently adopted rate for heating of whole grains to temperatures in excess of 70 K is underestimated by approximately two orders of magnitude in astrochemical numerical simulations. Additionally, grains are heated by CRs to modest temperatures (20–30 K) with intervals of a few years, which reduces the possibility of ice chemical explosions.« less

  5. [Signs of the zodiac and personality].

    PubMed

    Angst, J; Scheidegger, P

    1976-01-01

    3074 young men resident in the canton of Zurich, representing 50% of the 19 year old male population, form the fully representative sample of our large scale investigation. We investigated whether personality traits measured by means of the differentiated "Freiburger personality inventory" (FPI) could in any way be correlated to the signs of the zodiac under which the young men were born. The statistical analysis did not reveal any correlation between signs of the zodiac and personality. The claim made by astrologers that people can be characterized according to their sign of the zodiac (sagitarius, taurus, cancer, scorpion) must be refuted. Of course the astrologically founded description of human personality does not base itself on the position of the sun only, however the latter does form a very essential part of the astrological evaluation of people. This, at any rate has been shown to be without any scientific basis. The fact that astrological evaluation of human personality is so popular nowadays can be explained by the fact that even modern people are inclined towards magical thinking.

  6. Foehn-induced effects on dust pollution, frontal clouds and solar radiation in the Dead Sea valley

    NASA Astrophysics Data System (ADS)

    Kishcha, Pavel; Starobinets, Boris; Alpert, Pinhas; Kaplan, Michael

    2017-04-01

    The significant drying up of the Dead Sea over the past 40 years has led to an increase in an exposed area contributing to local dust pollution. Measurements show that, sometimes, in the Dead Sea valley, dust pollution can reach extreme concentrations up to several thousands of micrograms per cubic meters. Our analysis of a meteorological situation shows that a foehn phenomenon can be a causal factor for the aforementioned extreme local dust concentration. This foehn phenomenon creates strong warm and dry winds, which are accompanied by air turbulence and temperature inversion. In our study, foehn-induced effects on dust pollution, frontal clouds and solar radiation were analyzed over the Judean Mountains ( 1000 m) and over the Dead Sea valley (-420 m), using high-resolution numerical simulations and in-situ observations at meteorological stations located across the mountain ridge. An extreme dust episode occurring on March 22, 2013, was analyzed, which was characterized by measured surface dust concentrations of up to 7000 µg m-3 in the Dead Sea valley. We simulated this foehn phenomenon with the 3-km resolution COSMO-ART model. Our analysis has shown that the foehn phenomenon could be observed even over the relatively low Judean Mountains. This analysis was based on various meteorological, pyranometer, radar, and aerosol measurements together with high-resolution model data. In the Dead Sea valley, the maximum aerosol optical depth (AOD) did not coincide with the maximum surface dust concentration. This lack of coincidence indicates difficulties in using satellite-based AOD for initializing dust concentration within numerical forecast systems over this region with complex terrain. In the western Dead Sea valley, strong foehn winds of over 20 m/s were accompanied by maximal air turbulence leading to maximal local dust emissions. Thus, the model showed that, by creating significant turbulence, the foehn phenomenon intensified the saltation (bombardment) mechanism

  7. Planck intermediate results: XXVIII. Interstellar gas and dust in the Chamaeleon clouds as seen by Fermi LAT and Planck $$\\star$$

    DOE PAGES

    Ade, P. A. R.; Aghanim, N.; Aniano, G.; ...

    2015-09-30

    The nearby Chamaeleon clouds have been observed in γ rays by the Fermi Large Area Telescope (LAT) and in thermal dust emission by Planck and IRAS. Cosmic rays and large dust grains, if smoothly mixed with gas, can jointly serve with the H i and 12CO radio data to (i) map the hydrogen column densities, N H, in the different gas phases, in particular at the dark neutral medium (DNM) transition between the H i-bright and CO-bright media; (ii) constrain the CO-to-H 2 conversion factor, X CO; and (iii) probe the dust properties per gas nucleon in each phase andmore » map their spatial variations across the clouds. We have separated clouds at local, intermediate, and Galactic velocities in H i and 12CO line emission to model in parallel the γ-ray intensity recorded between 0.4 and 100 GeV; the dust optical depth at 353 GHz, τ 353; the thermal radiance of the large grains; and an estimate of the dust extinction, A VQ, empirically corrected for the starlight intensity. Furthermore, the dust and γ-ray models have been coupled to account for the DNM gas. The consistent γ-ray emissivity spectra recorded in the different phases confirm that the GeV–TeV cosmic rays probed by the LAT uniformly permeate all gas phases up to the 12CO cores. The dust and cosmic rays both reveal large amounts of DNM gas, with comparable spatial distributions and twice as much mass as in the CO-bright clouds. We give constraints on the H i-DNM-CO transitions for five separate clouds. CO-dark H 2 dominates the molecular columns up to AV ≃ 0.9 and its mass often exceeds the one-third of the molecular mass expected by theory. The corrected A VQ extinction largely provides the best fit to the total gas traced by the γ rays. Nevertheless, we find evidence for a marked rise in A VQ/N H with increasing N H and molecular fraction, and with decreasing dust temperature. The rise in τ 353/NH is even steeper. Here, we observe variations of lesser amplitude and orderliness for the specific power of

  8. How large is the cosmic dust flux into the Earth's atmosphere?

    NASA Astrophysics Data System (ADS)

    Plane, John; Janches, Diego; Gomez-Martin, Juan Carlos; Bones, David; Diego Carrillo-Sanchez, Juan; James, Sandy; Nesvorny, David; Pokorny, Petr

    2016-07-01

    Cosmic dust particles are produced in the solar system from the sublimation of comets as they orbit close to the sun, and also from collisions between asteroids in the belt between Mars and Jupiter. Current estimates of the magnitude of the cosmic dust input rate into the Earth's atmosphere range from 2 to well over 100 tons per day, depending on whether the measurements are made in space, in the middle atmosphere, or at the surface in polar ice cores. This nearly 2 order-of-magnitude discrepancy indicates that there are serious flaws in the interpretation of observations that have been used to make the estimates. Dust particles enter the atmosphere at hyperthermal velocities (11 - 72 km s ^{-1}), and mostly ablate at heights between 80 and 120 km in a region of the atmosphere known as the mesosphere/lower thermosphere (MLT). The resulting metal vapours (Fe, Mg, Si and Na etc.) then oxidize and recondense to form nm-size particles, termed "meteoric smoke". These particles are too small to sediment downwards. Instead, they are transported by the general circulation of the atmosphere, taking roughly 5 years to reach the surface. There is great interest in the role smoke particles play as condensation nuclei of noctilucent ice clouds in the mesosphere, and polar stratospheric clouds in the lower stratosphere. Various new estimates of the dust input will be discussed. The first is from a zodiacal dust cloud model which predicts that more than 90% of the dust entering the atmosphere comes from Jupiter Family Comets; this model is constrained by observations of the zodiacal cloud using the IRAS, COBE and Planck satellites. The cometary dust is predicted to mostly be in a near-prograde orbit, entering the atmosphere with an average velocity around 14 km s ^{-1}. The total dust input should then be about 40 t d ^{-1}. However, relatively few of these particles are observed, even by the powerful Arecibo 430 MHz radar. Coupled models of meteoroid differential ablation

  9. Self-Organization Phenomena in a Cryogenic Gas Discharge Plasma: Formation of a Nanoparticle Cloud and Dust-Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Boltnev, R. E.; Vasiliev, M. M.; Kononov, E. A.; Petrov, O. F.

    2018-04-01

    The dusty plasma structures in a glow discharge of helium in a tube cooled by superfluid helium at a temperature of 1.6 K and higher have been studied experimentally. The bimodal dust plasma formed by clouds of polydisperse cerium dioxide particles and polymer nanoparticles has been analyzed. We have observed wave oscillations in the cloud of polymer nanoparticles (with a size up to 100 nm), which existed in a narrow temperature range from 1.6 to 2.17 K. Vortices have been observed in the dusty plasma structures at helium temperatures.

  10. The 1.1 mm Continuum Survey of the Small Magellanic Cloud: Physical Properties and Evolution of the Dust-selected Clouds

    NASA Astrophysics Data System (ADS)

    Takekoshi, Tatsuya; Minamidani, Tetsuhiro; Komugi, Shinya; Kohno, Kotaro; Tosaki, Tomoka; Sorai, Kazuo; Muller, Erik; Mizuno, Norikazu; Kawamura, Akiko; Onishi, Toshikazu; Fukui, Yasuo; Ezawa, Hajime; Oshima, Tai; Scott, Kimberly S.; Austermann, Jason E.; Matsuo, Hiroshi; Aretxaga, Itziar; Hughes, David H.; Kawabe, Ryohei; Wilson, Grant W.; Yun, Min S.

    2017-01-01

    The first 1.1 mm continuum survey toward the Small Magellanic Cloud (SMC) was performed using the AzTEC instrument installed on the ASTE 10 m telescope. This survey covered 4.5 deg2 of the SMC with 1σ noise levels of 5-12 mJy beam-1, and 44 extended objects were identified. The 1.1 mm extended emission has good spatial correlation with Herschel 160 μm, indicating that the origin of the 1.1 mm extended emission is thermal emission from a cold dust component. We estimated physical properties using the 1.1 mm and filtered Herschel data (100, 160, 250, 350, and 500 μm). The 1.1 mm objects show dust temperatures of 17-45 K and gas masses of 4 × 103-3 × 105 M⊙, assuming single-temperature thermal emission from the cold dust with an emissivity index, β, of 1.2 and a gas-to-dust ratio of 1000. These physical properties are very similar to those of giant molecular clouds (GMCs) in our galaxy and the Large Magellanic Cloud. The 1.1 mm objects also displayed good spatial correlation with the Spitzer 24 μm and CO emission, suggesting that the 1.1 mm objects trace the dense gas regions as sites of massive star formation. The dust temperature of the 1.1 mm objects also demonstrated good correlation with the 24 μm flux connected to massive star formation. This supports the hypothesis that the heating source of the cold dust is mainly local star-formation activity in the 1.1 mm objects. The classification of the 1.1 mm objects based on the existence of star-formation activity reveals the differences in the dust temperature, gas mass, and radius, which reflects the evolution sequence of GMCs. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  11. THE 1.1 mm CONTINUUM SURVEY OF THE SMALL MAGELLANIC CLOUD: PHYSICAL PROPERTIES AND EVOLUTION OF THE DUST-SELECTED CLOUDS

    SciT

    Takekoshi, Tatsuya; Minamidani, Tetsuhiro; Sorai, Kazuo

    The first 1.1 mm continuum survey toward the Small Magellanic Cloud (SMC) was performed using the AzTEC instrument installed on the ASTE 10 m telescope. This survey covered 4.5 deg{sup 2} of the SMC with 1 σ noise levels of 5–12 mJy beam{sup −1}, and 44 extended objects were identified. The 1.1 mm extended emission has good spatial correlation with Herschel 160 μ m, indicating that the origin of the 1.1 mm extended emission is thermal emission from a cold dust component. We estimated physical properties using the 1.1 mm and filtered Herschel data (100, 160, 250, 350, and 500more » μ m). The 1.1 mm objects show dust temperatures of 17–45 K and gas masses of 4 × 10{sup 3}–3 × 10{sup 5} M {sub ⊙}, assuming single-temperature thermal emission from the cold dust with an emissivity index, β , of 1.2 and a gas-to-dust ratio of 1000. These physical properties are very similar to those of giant molecular clouds (GMCs) in our galaxy and the Large Magellanic Cloud. The 1.1 mm objects also displayed good spatial correlation with the Spitzer 24 μ m and CO emission, suggesting that the 1.1 mm objects trace the dense gas regions as sites of massive star formation. The dust temperature of the 1.1 mm objects also demonstrated good correlation with the 24 μ m flux connected to massive star formation. This supports the hypothesis that the heating source of the cold dust is mainly local star-formation activity in the 1.1 mm objects. The classification of the 1.1 mm objects based on the existence of star-formation activity reveals the differences in the dust temperature, gas mass, and radius, which reflects the evolution sequence of GMCs.« less

  12. Constraining dust properties in circumstellar envelopes of C-stars in the Small Magellanic Cloud: optical constants and grain size of carbon dust

    NASA Astrophysics Data System (ADS)

    Nanni, Ambra; Marigo, Paola; Groenewegen, Martin A. T.; Aringer, Bernhard; Girardi, Léo; Pastorelli, Giada; Bressan, Alessandro; Bladh, Sara

    2016-10-01

    We present a new approach aimed at constraining the typical size and optical properties of carbon dust grains in circumstellar envelopes (CSEs) of carbon-rich stars (C-stars) in the Small Magellanic Cloud (SMC). To achieve this goal, we apply our recent dust growth description, coupled with a radiative transfer code to the CSEs of C-stars evolving along the thermally pulsing asymptotic giant branch, for which we compute spectra and colours. Then, we compare our modelled colours in the near- and mid-infrared (NIR and MIR) bands with the observed ones, testing different assumptions in our dust scheme and employing several data sets of optical constants for carbon dust available in the literature. Different assumptions adopted in our dust scheme change the typical size of the carbon grains produced. We constrain carbon dust properties by selecting the combination of grain size and optical constants which best reproduce several colours in the NIR and MIR at the same time. The different choices of optical properties and grain size lead to differences in the NIR and MIR colours greater than 2 mag in some cases. We conclude that the complete set of observed NIR and MIR colours are best reproduced by small grains, with sizes between ˜0.035 and ˜0.12 μm, rather than by large grains between ˜0.2 and 0.7 μm. The inability of large grains to reproduce NIR and MIR colours seems independent of the adopted optical data set. We also find a possible trend of the grain size with mass-loss and/or carbon excess in the CSEs of these stars.

  13. Reanalysis of Mariner 9 UV Spectrometer Data for Ozone, Cloud, and Dust Abundances, and Their Interaction Over Climate Timescales

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1994-01-01

    Mariner 9 UV spectrometer data have been reinverted for the ozone abundance. The spectra were fit by models which covered the full range in observed solar zenith angle, cloud, dust and ozone amount, ice albedo and look angles. Errors in ozone retrieval with this data are tabulated over a range in theses conditions and are shown graphically. This work shows that significant underestimation of ozone occurred in earlier analysis of Mariner 9 data, and that much of the observed variability in Mars ozone is due to masking of ozone by clouds and dust. An in-situ measurement by balloon is recommended as it is the only technique capable of accurately inferring the ozone abundance in all conditions. Recommendations for future research are also presented. 7 manuscripts have been published in refereed journals, and three are in review. A review of these publications and presentations is in the report.

  14. Recent Asteroid Disruptions in the WISE Dataset - Constraining Asteroid Surface Properties Using Solar System Dust Bands

    NASA Astrophysics Data System (ADS)

    Kehoe, A. E.; Shaw, C.; Kehoe, T. J. J.

    2017-12-01

    Zodiacal dust bands are a fine-structure feature of the mid-IR emission profile of the zodiacal cloud. The dust bands have been studied for many years dating back to the InfraRed Astronomical Satellite (IRAS) data of the 1980's. The recent discovery and modeling (Espy et al., 2009; 2010; Espy Kehoe et al., 2015) of a very young, still-forming dust band structure has shown that, in the early stages following an asteroid disruption, much information on the dust parameters of the original disruption is retained in the band. Partial dust bands allow a never-before-seen observational look at the size distribution and cross-sectional area of dust produced in an asteroidal disruption, before it has been lost or significantly altered by orbital and collisional decay. The study of these partial band structures reveals information on the way asteroids disrupt and allow us to reconstruct the surface properties of the parent asteroid, including the depth of the surface regolith and the size distribution of particles composing the regolith. Using the greatly increased sensitivity of the Wide-field Infrared Survey Explorer (WISE), we can now detect much fainter (and thus younger) dust bands. The WISE data also reveals much better longitudinal resolution of the bands, allowing a better constraint on the source and age of the disruption. We will present our newest results from the WISE dataset, including detection of faint partial dust bands, improved models of more prominent bands, and our constraints on the asteroid surface properties from modeling these structures.

  15. Limb clouds and dust on Mars from images obtained by the Visual Monitoring Camera (VMC) onboard Mars Express

    NASA Astrophysics Data System (ADS)

    Sánchez-Lavega, A.; Chen-Chen, H.; Ordoñez-Etxeberria, I.; Hueso, R.; del Río-Gaztelurrutia, T.; Garro, A.; Cardesín-Moinelo, A.; Titov, D.; Wood, S.

    2018-01-01

    The Visual Monitoring Camera (VMC) onboard the Mars Express (MEx) spacecraft is a simple camera aimed to monitor the release of the Beagle-2 lander on Mars Express and later used for public outreach. Here, we employ VMC as a scientific instrument to study and characterize high altitude aerosols events (dust and condensates) observed at the Martian limb. More than 21,000 images taken between 2007 and 2016 have been examined to detect and characterize elevated layers of dust in the limb, dust storms and clouds. We report a total of 18 events for which we give their main properties (areographic location, maximum altitude, limb projected size, Martian solar longitude and local time of occurrence). The top altitudes of these phenomena ranged from 40 to 85 km and their horizontal extent at the limb ranged from 120 to 2000 km. They mostly occurred at Equatorial and Tropical latitudes (between ∼30°N and 30°S) at morning and afternoon local times in the southern fall and northern winter seasons. None of them are related to the orographic clouds that typically form around volcanoes. Three of these events have been studied in detail using simultaneous images taken by the MARCI instrument onboard Mars Reconnaissance Orbiter (MRO) and studying the properties of the atmosphere using the predictions from the Mars Climate Database (MCD) General Circulation Model. This has allowed us to determine the three-dimensional structure and nature of these events, with one of them being a regional dust storm and the two others water ice clouds. Analyses based on MCD and/or MARCI images for the other cases studied indicate that the rest of the events correspond most probably to water ice clouds.

  16. Simulation of the Processes of Formation of a Dust Cloud in a Vacuum and in the Absence of Gravitation

    NASA Astrophysics Data System (ADS)

    Avdeev, A. V.; Boreisho, A. S.; Ivakin, S. V.; Moiseev, A. A.; Savin, A. V.; Sokolov, E. I.; Smirnov, P. G.

    2018-01-01

    This article is devoted to the simulation of the processes of formation of dust clouds in the absence of gravitation, which is necessary for understanding the processes proceeding in dust clusters in outer space, upper planetary atmosphere, and on the surface of space objects, as well as for evaluating the possibilities of creating disperse structures with given properties. The chief aim of the simulation is to determine the general laws of the dynamics of the dust cloud at the initial stage of its formation. With the use of the original approach based on the particle-in-cell method that permits investigating the mechanics of large ensembles of particles on contemporary computational platforms, we consider the mechanics of a dusty medium in the process of its excitation in a closed container due to the vibration of the walls, and then in the process of particle scattering when the container opens in outer space. The main formation mechanisms of a dust formation have been elucidated, and the possibilities of mathematical simulation for predicting spatial and time characteristics of disperse structures have been shown.

  17. Dust Abundance Variations in the Magellanic Clouds: Probing the Life-cycle of Metals with All-sky Surveys

    NASA Astrophysics Data System (ADS)

    Roman-Duval, Julia; Bot, Caroline; Chastenet, Jeremy; Gordon, Karl

    2017-06-01

    Observations and modeling suggest that dust abundance (gas-to-dust ratio, G/D) depends on (surface) density. Variations of the G/D provide timescale constraints for the different processes involved in the life cycle of metals in galaxies. Recent G/D measurements based on Herschel data suggest a factor of 5-10 decrease in dust abundance between the dense and diffuse interstellar media (ISM) in the Magellanic Clouds. However, the relative nature of the Herschel measurements precludes definitive conclusions as to the magnitude of those variations. We investigate variations of the dust abundance in the LMC and SMC using all-sky far-infrared surveys, which do not suffer from the limitations of Herschel on their zero-point calibration. We stack the dust spectral energy distribution (SED) at 100, 350, 550, and 850 microns from IRAS and Planck in intervals of gas surface density, model the stacked SEDs to derive the dust surface density, and constrain the relation between G/D and gas surface density in the range 10-100 M ⊙ pc-2 on ˜80 pc scales. We find that G/D decreases by factors of 3 (from 1500 to 500) in the LMC and 7 (from 1.5× {10}4 to 2000) in the SMC between the diffuse and dense ISM. The surface-density-dependence of G/D is consistent with elemental depletions, and with simple modeling of the accretion of gas-phase metals onto dust grains. This result has important implications for the sub-grid modeling of galaxy evolution, and for the calibration of dust-based gas-mass estimates, both locally and at high redshift.

  18. Rutgers zodiacal light experiment on OSO-6

    NASA Technical Reports Server (NTRS)

    Carroll, B.

    1975-01-01

    A detector was placed in a slowly spinning wheel on OSO-6 whose axis was perpendicular to the line drawn to the sun, to measure the surface brightness and polarization at all elongations from the immediate neighborhood of the sun to the anti-solar point. Different wavelength settings and polarizations were calculated from the known order of magnitude brightness of the zodiacal light. The measuring sequence was arranged to give longer integration times for the regions of lower surface brightness. Three types of analysis to which the data on OSO-6 were subjected are outlined; (1) photometry, (2) colorimetry and (3) polarimetry.

  19. Constraining Dust Properties in Circumstellar Envelopes of C-Stars in the Small Magellanic Cloud: Optical Constants And Grain Size Of Carbon Dust

    NASA Astrophysics Data System (ADS)

    Nanni, Ambra; Marigo, Paola; Groenewegen, Martin A. T.; Aringer, Berhard; Girardi, Léo; Pastorelli, Giada; Bressan, Alessandro; Bladh, Sara

    2016-07-01

    We present our recent investigation aimed at constraining the typical size and optical properties of carbon dust grains in Circumstellar envelopes (CSEs) of carbon-rich stars (C-stars) in the Small Magellanic Cloud (SMC).We applied our recent dust growth model, coupled with a radiative transfer code, to the dusty CSEs of C-stars along the TP-AGB phase, for which we computed spectra and colors. We then compared our modeled colors in the Near and Mid Infrared (NIR and MIR) bands with the observed ones, testing different assumptions in our dust scheme and employing different optical constants data sets for carbon dust. We constrained the optical properties of carbon dust by identifying the combinations of typical grain size and optical constants data set which simultaneously reproduce several colors in the NIR and MIR wavelengths. In particular, the different choices of optical properties and grain size lead to differences in the NIR and MIR colors greater than two magnitudes in some cases. We concluded that the complete set of selected NIR and MIR colors are best reproduced by small grains, with sizes between 0.06 and 0.1 mum, rather than by large grains of 0.2-0.4 mum. The inability of large grains to reproduce NIR and MIR colors is found to be independent of the adopted optical data set and the deviations between models and observations tend to increase for increasing grain sizes. We also find a possible trend of the typical grain size with mss-loss and/or carbon-excess in the CSEs of these stars.The work presented is preparatory to future studies aimed at calibrating the TP-AGB phase through resolved stellar populations in the framework of the STARKEY project.

  20. Measurements of cloud condensation nuclei activity and droplet activation kinetics of wet processed regional dust samples and minerals

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Sokolik, I. N.; Nenes, A.

    2011-04-01

    This study reports laboratory measurements of particle size distributions, cloud condensation nuclei (CCN) activity, and droplet activation kinetics of wet generated aerosols from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. The dependence of critical supersaturation, sc, on particle dry diameter, Ddry, is used to characterize particle-water interactions and assess the ability of Frenkel-Halsey-Hill adsorption activation theory (FHH-AT) and Köhler theory (KT) to describe the CCN activity of the considered samples. Regional dust samples produce unimodal size distributions with particle sizes as small as 40 nm, CCN activation consistent with KT, and exhibit hygroscopicity similar to inorganic salts. Clays and minerals produce a bimodal size distribution; the CCN activity of the smaller mode is consistent with KT, while the larger mode is less hydrophilic, follows activation by FHH-AT, and displays almost identical CCN activity to dry generated dust. Ion Chromatography (IC) analysis performed on regional dust samples indicates a soluble fraction that cannot explain the CCN activity of dry or wet generated dust. A mass balance and hygroscopicity closure suggests that the small amount of ions (of low solubility compounds like calcite) present in the dry dust dissolve in the aqueous suspension during the wet generation process and give rise to the observed small hygroscopic mode. Overall these results identify an artifact that may question the atmospheric relevance of dust CCN activity studies using the wet generation method. Based on a threshold droplet growth analysis, wet generated mineral aerosols display similar activation kinetics compared to ammonium sulfate calibration aerosol. Finally, a unified CCN activity framework that accounts for concurrent effects of solute and adsorption is developed to describe the CCN activity of aged or hygroscopic dusts.

  1. Observations and Modelling of the Zodiacal Light

    NASA Astrophysics Data System (ADS)

    Kelsall, T.

    1994-12-01

    The DIRBE instrument on the COBE satellite performed a full-sky survey in ten bands covering the spectral range from 1.25 to 240 microns, and made measurements of the polarization from 1.25 to 3.5 microns. These observations provide a wealth of data on the radiations from the interplanetary dust cloud (IPD). The presentation covers the observations, the model-independent findings, and the results from the extensive efforts of the DIRBE team to model the IPD. Emphasis is placed on describing the importance of correctly accounting for the IPD contribution to the observed-sky signal for the purpose of detecting the cosmic infrared background. (*) The NASA/Goddard Space Flight Center (GSFC) is responsible for the design, development, and operation of the COBE mission. GSFC is also responsible for the development of the analysis software and for the production of the mission data sets. Scientific guidance is provided by the COBE Science Working Group. The COBE program is supported by the Astrophysics Division of NASA's Office of Space Science.

  2. Accretion of Interplanetary Dust Particles by the Earth

    NASA Astrophysics Data System (ADS)

    Kortenkamp, Stephen J.; Dermott, Stanley F.

    1998-10-01

    Analyses of hypervelocity micrometeoroid impact craters preserved in lunar material and on the panels of the Long Duration Exposure Facility (LDEF) indicate that each year Earth accretes about 3 × 107kg of interplanetary dust particles (IDPs) from the zodiacal cloud (E. Grünet al.1985,Astron. Astrophys.286, 915-924; S. G. Love and D. E. Brownlee, 1993,Science262, 550-553). The size distributions of these lunar and LDEF craters indicate that the mass distribution of IDPs encountering Earth peaks at about 200 μm diameter. This particle-size cutoff may be indicative of collisionally evolved asteroidal dust, where the collisional lifetime of dust particles larger than ∼100 μm is shorter than the time required for their orbits to decay under Poynting-Robertson light drag from the asteroid belt to Earth (B. Å. S. Gustafson, 1994,Annu. Rev. Earth Planet. Sci.22, 553-595). Additionally, analyses of IDPs collected from the stratosphere by high-flying aircraft reveal a diversity in chemical composition which is even narrower than that of the meteorites (G. J. Flynn, 1995,Nature376, 114). Together these findings suggest that IDPs present in the atmosphere and our collections may originate from very limited sources in the asteroid belt. The most abundant sources of dust to be unambiguously linked to the zodiacal cloud are the three asteroid families Eos, Themis, and Koronis-the progenitors of the ten-degree and low-latitude dust bands discovered by the Infrared Astronomical Satellite in 1984. We use direct numerical integration of the full equations of motion to model the orbital evolution of dust particles from these three families as well as from other nonfamily asteroids and from the population of known short period comets. Our simulations include gravitational perturbations from the planets, radiation pressure, and solar wind drag. We find that a large, and perhaps the dominant, fraction of the IDPs accreted by Earth comes from the asteroid families Eos, Themis, and

  3. Aerosol Impacts on California Winter Clouds and Precipitation during CalWater 2011: Local Pollution versus Long-Range Transported Dust

    SciT

    Fan, Jiwen; Leung, Lai-Yung R.; DeMott, Paul J.

    2014-01-03

    Mineral dust aerosols often observed over California in winter and spring, associated with long-range transport from Asia and Sahara, have been linked to enhanced precipitation based on observations. Local anthropogenic pollution, on the other hand, was shown in previous observational and modeling studies to reduce precipitation. Here we incorporate recent developments in ice nucleation parameterizations to link aerosols with ice crystal formation in a spectral-bin cloud microphysical model coupled with the Weather Research and Forecasting (WRF) model, to examine the relative and combined impacts of dust and local pollution particles on cloud properties and precipitation type and intensity. Simulations aremore » carried out for two cloud cases with contrasting meteorology and cloud dynamics that occurred on February 16 (FEB16) and March 02 (MAR02) from the CalWater 2011 field campaign. In both cases, observations show the presence of dust and biological particles in a relative pristine environment. The simulated cloud microphysical properties and precipitation show reasonable agreement with aircraft and surface measurements. Model sensitivity experiments indicate that in the pristine environment, the dust and biological aerosol layers increase the accumulated precipitation by 10-20% from the Central Valley to the Sierra Nevada Mountains for both FEB16 and MAR02 due to a ~40% increase in snow formation, validating the observational hypothesis. Model results show that local pollution increases precipitation over the windward slope of the mountains by few percent due to increased snow formation when dust is present but reduces precipitation by 5-8% if dust is removed on FEB16. The effects of local pollution on cloud microphysics and precipitation strongly depend on meteorology including the strength of the Sierra Barrier Jet, and cloud dynamics. This study further underscores the importance of the interactions between local pollution, dust, and environmental

  4. Cosmic dust in the earth's atmosphere.

    PubMed

    Plane, John M C

    2012-10-07

    This review discusses the magnitude of the cosmic dust input into the earth's atmosphere, and the resulting impacts from around 100 km to the earth's surface. Zodiacal cloud observations and measurements made with a spaceborne dust detector indicate a daily mass input of interplanetary dust particles ranging from 100 to 300 tonnes, which is in agreement with the accumulation rates of cosmic-enriched elements (Ir, Pt, Os and super-paramagnetic Fe) in polar ice cores and deep-sea sediments. In contrast, measurements in the middle atmosphere - by radar, lidar, high-flying aircraft and satellite remote sensing - indicate that the input is between 5 and 50 tonnes per day. There are two reasons why this huge discrepancy matters. First, if the upper range of estimates is correct, then vertical transport in the middle atmosphere must be considerably faster than generally believed; whereas if the lower range is correct, then our understanding of dust evolution in the solar system, and transport from the middle atmosphere to the surface, will need substantial revision. Second, cosmic dust particles enter the atmosphere at high speeds and undergo significant ablation. The resulting metals injected into the atmosphere are involved in a diverse range of phenomena, including: the formation of layers of metal atoms and ions; the nucleation of noctilucent clouds, which are a sensitive marker of climate change; impacts on stratospheric aerosols and O(3) chemistry, which need to be considered against the background of a cooling stratosphere and geo-engineering plans to increase sulphate aerosol; and fertilization of the ocean with bio-available Fe, which has potential climate feedbacks.

  5. Dust in brown dwarfs and extrasolar planets. V. Cloud formation in carbon- and oxygen-rich environments

    NASA Astrophysics Data System (ADS)

    Helling, Ch.; Tootill, D.; Woitke, P.; Lee, G.

    2017-07-01

    Context. Recent observations indicate potentially carbon-rich (C/O > 1) exoplanet atmospheres. Spectral fitting methods for brown dwarfs and exoplanets have invoked the C/O ratio as additional parameter but carbon-rich cloud formation modeling is a challenge for the models applied. The determination of the habitable zone for exoplanets requires the treatment of cloud formation in chemically different regimes. Aims: We aim to model cloud formation processes for carbon-rich exoplanetary atmospheres. Disk models show that carbon-rich or near-carbon-rich niches may emerge and cool carbon planets may trace these particular stages of planetary evolution. Methods: We extended our kinetic cloud formation model by including carbon seed formation and the formation of C[s], TiC[s], SiC[s], KCl[s], and MgS[s] by gas-surface reactions. We solved a system of dust moment equations and element conservation for a prescribed Drift-Phoenixatmosphere structure to study how a cloud structure would change with changing initial C/O0 = 0.43...10.0. Results: The seed formation efficiency is lower in carbon-rich atmospheres than in oxygen-rich gases because carbon is a very effective growth species. The consequence is that fewer particles make up a cloud if C/O0 > 1. The cloud particles are smaller in size than in an oxygen-rich atmosphere. An increasing initial C/O ratio does not revert this trend because a much greater abundance of condensible gas species exists in a carbon-rich environment. Cloud particles are generally made of a mix of materials: carbon dominates if C/O0 > 1 and silicates dominate if C/O0 < 1. A carbon content of 80-90% carbon is reached only in extreme cases where C/O0 = 3.0 or 10.0. Conclusions: Carbon-rich atmospheres form clouds that are made of particles of height-dependent mixed compositions, sizes and numbers. The remaining gas phase is far less depleted than in an oxygen-rich atmosphere. Typical tracer molecules are HCN and C2H2 in combination with a featureless

  6. Sahara Dust

    Atmospheric Science Data Center

    2013-04-15

    article title:  Casting Light and Shadows on a Saharan Dust Storm     ... ocean and dust layer, which are visible in shades of blue and tan, respectively. In the lower panel, heights derived from automated ... cast by the cirrus clouds onto the dust (indicated by blue and cyan pixels) provide sufficient spatial contrast for a retrieval of ...

  7. The Evolution of the Surface of Symmetry of the Interplanetary Dust from 24° to 5° Elongation

    NASA Astrophysics Data System (ADS)

    Stenborg, Guillermo; Howard, Russell A.

    2017-10-01

    The white-light STEREO/SECCHI images include light scattered by dust in orbit about the Sun (the F-corona). We analyzed the evolution of the symmetry axis of the F-corona between 2007 and 2012 in the elongation range covered by the STEREO-A/HI-1 instrument (4°-24° elongation) to characterize the plane of symmetry of the zodiacal dust cloud. The symmetry axes both above and below the ecliptic plane were derived separately without assuming any particular functional form. No noticeable time dependence was observed. However, we did find an evolution with elongation of both the inclination I and the ascending node {{{Ω }}}A of the inferred plane of symmetry. Both parameters appeared fairly constant in the outer half of the elongation range studied (I=˜ 3\\buildrel{\\circ}\\over{.} 7,{{{Ω }}}A=˜ 83^\\circ ; values close to those of Venus’s orbit). Then, they start to evolve, becoming I=˜ 6^\\circ (I.e., a trend toward the solar equatorial plane) and {{{Ω }}}A=˜ 57^\\circ at about 5° elongation. This variation indicates that the zodiacal dust cloud exhibits a warped plane of symmetry, with an estimated center of symmetry at about 0.5 {R}⊙ from the Sun’s center on the side of the heliosphere containing Jupiter. We found a marginal difference between the inclination of the axes below and above the ecliptic. This is suggestive of an increased dust density distribution at certain fixed longitudes, which could be explained by the dust deposition of Kreutz Sun-grazing comets. We conjecture that the circumsolar dust is mainly affected by gravitational forces, other forces becoming dominant only where the more rapid changes occur.

  8. Colour dependence of zodiacal light models

    NASA Technical Reports Server (NTRS)

    Giese, R. H.; Hanner, M. S.; Leinert, C.

    1973-01-01

    Colour models of the zodiacal light in the ecliptic have been calculated for both dielectric and metallic particles in the sub-micron and micron size range. Two colour ratios were computed, a blue ratio and a red ratio. The models with a size distribution proportional to s to the -2.5 power ds (where s is the particle radius) generally show a colour close to the solar colour and almost independent of elongation. Especially in the blue colour ratio there is generally no significant dependence on the lower cutoff size (0.1-1 micron). The main feature of absorbing particles is a reddening at small elongations. The models for size distributions proportional to s to the -4 power ds show larger departures from solar colour and more variation with model parameters. Colour measurements, including red and near infra-red, therefore are useful to distinguish between flat and steep size spectra and to verify the presence of slightly absorbing particles.

  9. Measurements of cloud condensation nuclei activity and droplet activation kinetics of fresh unprocessed regional dust samples and minerals

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Sokolik, I. N.; Nenes, A.

    2011-04-01

    This study reports laboratory measurements of cloud condensation nuclei (CCN) activity and droplet activation kinetics of aerosols dry generated from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. Based on the observed dependence of critical supersaturation, sc, with particle dry diameter, Ddry, we found that FHH (Frenkel, Halsey and Hill) adsorption activation theory is a far more suitable framework for describing fresh dust CCN activity than Köhler theory. One set of FHH parameters (AFHH ∼ 2.25 ± 0.75, BFHH ∼ 1.20 ± 0.10) can adequately reproduce the measured CCN activity for all species considered, and also explains the large range of hygroscopicities reported in the literature. Based on a threshold droplet growth analysis, mineral dust aerosols were found to display retarded activation kinetics compared to ammonium sulfate. Comprehensive simulations of mineral dust activation and growth in the CCN instrument suggest that this retardation is equivalent to a reduction of the water vapor uptake coefficient (relative to that for calibration ammonium sulfate aerosol) by 30-80%. These results suggest that dust particles do not require deliquescent material to act as CCN in the atmosphere.

  10. Measurements of cloud condensation nuclei activity and droplet activation kinetics of fresh unprocessed regional dust samples and minerals

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Sokolik, I. N.; Nenes, A.

    2010-12-01

    This study reports laboratory measurements of cloud condensation nuclei (CCN) activity and droplet activation kinetics of aerosols dry-generated from clays, calcite, quartz, and desert soil samples from Northern Africa, East Asia/China, and Northern America. Based on the observed dependence of critical supersaturation, sc, with particle dry diameter, Ddry, we find that FHH adsorption activation theory is a far more suitable framework for describing fresh dust CCN activity than Köhler theory. One set of FHH parameters (AFFH ~ 2.25 ± 0.75, BFFH ~ 1.20 ± 0.10) can adequately reproduce the measured CCN activity for all species considered, and also explains the large range of hygroscopicities reported in the literature. Based on threshold droplet growth analysis, mineral dust aerosols were found to display retarded activation kinetics compared to ammonium sulfate. Comprehensive simulations of mineral dust activation and growth in the CCN instrument suggest that this retardation is equivalent to a reduction of the water vapor uptake coefficient (relative to that for calibration ammonium sulfate aerosol) by 30-80%. These results suggest that dust particles do not require deliquescent material to act as CCN in the atmosphere.

  11. Examination of the potential impacts of dust and pollution aerosol acting as cloud nucleating aerosol on water resources in the Colorado River Basin

    NASA Astrophysics Data System (ADS)

    Jha, Vandana

    In this study we examine the cumulative effect of dust acting as cloud nucleating aerosol (cloud condensation nuclei (CCN), giant cloud condensation nuclei (GCCN), and ice nuclei (IN)) along with anthropogenic aerosol pollution acting primarily as CCN, over the entire Colorado Rocky Mountains from the months of October to April in the year 2004-2005; the snow year. This ˜6.5 months analysis provides a range of snowfall totals and variability in dust and anthropogenic aerosol pollution. The specific objectives of this research is to quantify the impacts of both dust and pollution aerosols on wintertime precipitation in the Colorado Mountains using the Regional Atmospheric Modeling System (RAMS). In general, dust enhances precipitation primarily by acting as IN, while aerosol pollution reduces water resources in the CRB via the so-called "spill-over" effect, by enhancing cloud droplet concentrations and reducing riming rates. Dust is more episodic and aerosol pollution is more pervasive throughout the winter season. Combined response to dust and aerosol pollution is a net reduction of water resources in the CRB. The question is by how much are those water resources affected? Our best estimate is that total winter-season precipitation loss for for the CRB the 2004-2005 winter season due to the combined influence of aerosol pollution and dust is 5,380,00 acre-feet of water. Sensitivity studies for different cases have also been run for the specific cases in 2004-2005 winter season to analyze the impact of changing dust and aerosol ratios on precipitation in the Colorado River Basin. The dust is varied from 3 to 10 times in the experiments and the response is found to be non monotonic and depends on various environmental factors. The sensitivity studies show that adding dust in a wet system increases precipitation when IN affects are dominant. For a relatively dry system high concentrations of dust can result in over-seeding the clouds and reductions in precipitation

  12. Dust clouds around red giant stars - Evidence of sublimating comet disks?

    NASA Technical Reports Server (NTRS)

    Matese, John J.; Whitmire, Daniel P.; Reynolds, Ray T.

    1989-01-01

    The dust production by disk comets around intermediate mass stars evolving into red giants is studied, focusing on AGB supergiants. The model of Iben and Renzini (1983) is used to study the observed dust mass loss for AGB stars. An expression is obtained for the comet disk net dust production rate and values of the radius and black body temperature corresponding to peak sublimation are calculated for a range of stellar masses. Also, the fractional amount of dust released from a cometesimal disk during a classical nova outburst is estimated.

  13. Water vapor, water-ice clouds, and dust in the North Polar Region

    NASA Technical Reports Server (NTRS)

    Tamppari, Leslie K.; Smith, Michael D.; Bass, Deborah S.; Hale, Amy S.

    2006-01-01

    The behavior of water vapor, water-ice and dust in the Martian atmosphere is important for understanding the overall Martian climate system, which is characterized by three main cycles: water, including water-ice, dust, and CO2. Understanding these cycles will lend insight into the behavior of the atmospheric dynamics, the atmosphere's ability to transport dust, water-ice, and vapor to different parts of the planet, and how that ability changes as a function of dust and water-ice loading.

  14. Semidirect Dynamical and Radiative Impact of North African Dust Transport on Lower Tropospheric Clouds over the Subtropical North Atlantic in CESM 1.0

    SciT

    DeFlorio, Mike; Ghan, Steven J.; Singh, Balwinder

    This study uses a century length pre-industrial climate simulation by the Community Earth System Model (CESM 1.0) to explore statistical relationships between dust, clouds and atmospheric circulation, and to suggest a dynamical, rather than microphysical, mechanism linking subtropical North Atlantic lower tropospheric cloud cover with North African dust transport. The length of the run allows us to account for interannual variability of dust emissions and transport downstream of North Africa in the model. CESM’s mean climatology and probability distribution of aerosol optical depth in this region agrees well with available AERONET observations. In addition, CESM shows strong seasonal cycles ofmore » dust burden and lower tropospheric cloud fraction, with maximum values occurring during boreal summer, when a strong correlation between these two variables exists downstream of North Africa over the subtropical North Atlantic. Calculations of Estimated Inversion Strength (EIS) and composites of EIS on high and low downstream North Africa dust months during boreal summer reveal that dust is likely increasing inversion strength over this region due to both solar absorption and reflection. We find no evidence for a microphysical link between dust and lower tropospheric clouds in this region. These results yield new insight over an extensive period of time into the complex relationship between North African dust and lower tropospheric clouds over the open ocean, which has previously been hindered by spatiotemporal constraints of observations. Our findings lay a framework for future analyses using sub-monthly data over regions with different underlying dynamics.« less

  15. Saharan dust as a causal factor of hemispheric asymmetry in aerosols and cloud cover over the tropical Atlantic Ocean

    DOE PAGES

    Kishcha, Pavel; Da Sliva, Arlindo; Starobinets, Boris; ...

    2015-07-09

    Meridional distribution of aerosol optical thickness (AOT) over the tropical Atlantic Ocean (30°N – 30°S) was analyzed to assess seasonal variations of meridional AOT asymmetry. Ten-year MERRA Aerosol Reanalysis (MERRAero) data (July 2002 – June 2012) confirms that the Sahara desert emits a significant amount of dust into the atmosphere over the Atlantic Ocean. Only over the Atlantic Ocean did MERRAero show that desert dust dominates other aerosol species and is responsible for meridional aerosol asymmetry between the tropical North and South Atlantic. Over the 10-year period under consideration, both MISR measurements and MERRAero data showed a pronounced meridional AOTmore » asymmetry. The meridional AOT asymmetry, characterized by the hemispheric ratio (RAOT) of AOT averaged separately over the North and over the South Atlantic, was about 1.7. Seasonally, meridional AOT asymmetry over the Atlantic was the most pronounced between March and July, when dust presence is maximal (RAOT ranged from 2 to 2.4). There was no noticeable meridional aerosol asymmetry in total AOT from September to October. During this period the contribution of carbonaceous aerosols to total AOT in the South Atlantic was comparable to the contribution of dust aerosols to total AOT in the North Atlantic. During the same 10-year period, MODIS cloud fraction (CF) data showed that there was no noticeable asymmetry in meridional CF distribution in different seasons (the hemispheric ratio of CF ranged from 1.0 to 1.2). MODIS CF data illustrated significant cloud cover (CF of 0.7 – 0.9) with limited precipitation ability along the Saharan Air Layer.« less

  16. 72. 451 MADISON AVENUE, GRAND STAIR, ZODIAC CLOCK WITH DECORATIVE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    72. 451 MADISON AVENUE, GRAND STAIR, ZODIAC CLOCK WITH DECORATIVE CARVING BY STANFORD WHITE AND AUGUSTUS SAINT-GAUDENS - Villard Houses, 451-457 Madison Avenue & 24 East Fifty-first Street, New York County, NY

  17. The Primeval Zodiac: Its Social, Religious, and Mythological Background

    NASA Astrophysics Data System (ADS)

    Verderame, L.

    2009-08-01

    In this brief paper we try to draw the lines of the possible development of the originary iconographic and symbolic repertoire of the Mesopotamian zodiac, which through the Greeks was adopted in the Western world.

  18. Constraining the Dust Opacity Law in Three Small and Isolated Molecular Clouds

    SciT

    Webb, K. A.; Thanjavur, K.; Di Francesco, J.

    Density profiles of isolated cores derived from thermal dust continuum emission rely on models of dust properties, such as mass opacity, that are poorly constrained. With complementary measures from near-infrared extinction maps, we can assess the reliability of commonly used dust models. In this work, we compare Herschel -derived maps of the optical depth with equivalent maps derived from CFHT WIRCAM near-infrared observations for three isolated cores: CB 68, L 429, and L 1552. We assess the dust opacities provided from four models: OH1a, OH5a, Orm1, and Orm4. Although the consistency of the models differs between the three sources, themore » results suggest that the optical properties of dust in the envelopes of the cores are best described by either silicate and bare graphite grains (e.g., Orm1) or carbonaceous grains with some coagulation and either thin or no ice mantles (e.g., OH5a). None of the models, however, individually produced the most consistent optical depth maps for every source. The results suggest that either the dust in the cores is not well-described by any one dust property model, the application of the dust models cannot be extended beyond the very center of the cores, or more complex SED fitting functions are necessary.« less

  19. Optimization of high-inclination orbits using planetary flybys for a zodiacal light-imaging mission

    NASA Astrophysics Data System (ADS)

    Soto, Gabriel; Lloyd, James; Savransky, Dmitry; Grogan, Keith; Sinha, Amlan

    2017-09-01

    The zodiacal light caused by interplanetary dust grains is the second-most luminous source in the solar system. The dust grains coalesce into structures reminiscent of early solar system formation; their composition has been predicted through simulations and some edge-on observations but better data is required to validate them. Scattered light from these dust grains presents challenges to exoplanet imaging missions: resolution of their stellar environment is hindered by exozodiacal emissions and therefore sets the size and scope of these imaging missions. Understanding the composition of this interplanetary dust in our solar system requires an imaging mission from a vantage point above the ecliptic plane. The high surface brightness of the zodiacal light requires only a small aperture with moderate sensitivity; therefore a 3cm camera is enough to meet the science goals of the mission at an orbital height of 0.1AU above the ecliptic. A 6U CubeSat is the target mass for this mission which will be a secondary payload detaching from an existing interplanetary mission. Planetary flybys are utilized to produce most of the plane change Δv deep space corrective maneuvers are implemented to optimize each planetary flyby. We developed an algorithm which determines the minimum Δv required to place the CubeSat on a transfer orbit to a planet's sphere of influence and maximizes the resultant orbital height with respect to the ecliptic plane. The satellite could reach an orbital height of 0.22 AU with an Earth gravity assist in late 2024 by boarding the Europa Clipper mission.

  20. Recent studies of the optical properties of dust and cloud particles in the Mars atmosphere and the interannual frequency of global dust storms

    NASA Technical Reports Server (NTRS)

    Clancy, R. T.; Lee, S. W.; Muhleman, D. O.

    1991-01-01

    The results of research with two distinctly separate sets of observations yield new information on the optical properties of particulate scatterers in the Mars atmosphere, and on the interannual variability of the abundance of such scatterers in the Mars atmosphere. The first set of observations were taken by the IRTM (Infrared Thermal Mapper) instrument onboard the Viking Orbiters, during the period 1976 to 1980. Several hundred emission phase function (EPF) sequences were obtained over the Viking mission, in which the IRTM visual brightness channel observed the same area of surface/atmosphere as the spacecraft passed overhead. The 1 to 2 percent accuracy of calibration and the phase-angle coverage that characterizes these data make them ideally suited to determining both the optical depths and optical properties of dust and cloud scatterers in the Mars atmosphere versus latitude, longitude, seasons (L sub s), and surface elevation over the extended period of Viking observations. The EPF data were analyzed with a multiple scattering radiative transfer code to determine dust single scattering albedos which are distinctly higher than indicated by the Viking Lander observations. The second set of observations regard ground-based observations of the 1.3 to 2.6 mm rotational transitions of CO in the Martian atmosphere. The low-to-mid latitude average of the atmospheric temperature profile (0 to 70 km altitude) were derived from a number of such observations over the 1980 to 1990 period.

  1. Cosmic-rays, gas, and dust in nearby anticentre clouds. II. Interstellar phase transitions and the dark neutral medium

    NASA Astrophysics Data System (ADS)

    Remy, Q.; Grenier, I. A.; Marshall, D. J.; Casandjian, J. M.

    2018-03-01

    Aim. H I 21-cm and 12CO 2.6-mm line emissions trace the atomic and molecular gas phases, respectively, but they miss most of the opaque H I and diffuse H2 present in the dark neutral medium (DNM) at the transition between the H I-bright and CO-bright regions. Jointly probing H I, CO, and DNM gas, we aim to constrain the threshold of the H I-H2 transition in visual extinction, AV, and in total hydrogen column densities, NHtot. We also aim to measure gas mass fractions in the different phases and to test their relation to cloud properties. Methods: We have used dust optical depth measurements at 353 GHz, γ-ray maps at GeV energies, and H I and CO line data to trace the gas column densities and map the DNM in nearby clouds toward the Galactic anticentre and Chamaeleon regions. We have selected a subset of 15 individual clouds, from diffuse to star-forming structures, in order to study the different phases across each cloud and to probe changes from cloud to cloud. Results: The atomic fraction of the total hydrogen column density is observed to decrease in the (0.6-1) × 1021 cm-2 range in NHtot (AV ≈ 0.4 mag) because of the formation of H2 molecules. The onset of detectable CO intensities varies by only a factor of 4 from cloud to cloud, between 0.6 × 1021 cm-2 and 2.5 × 1021 cm-2 in total gas column density. We observe larger H2 column densities than linearly inferred from the CO intensities at AV > 3 mag because of the large CO optical thickness; the additional H2 mass in this regime represents on average 20% of the CO-inferred molecular mass. In the DNM envelopes, we find that the fraction of diffuse CO-dark H2 in the molecular column densities decreases with increasing AV in a cloud. For a half molecular DNM, the fraction decreases from more than 80% at 0.4 mag to less than 20% beyond 2 mag. In mass, the DNM fraction varies with the cloud properties. Clouds with low peak CO intensities exhibit large CO-dark H2 fractions in molecular mass, in particular the

  2. Inerting of magnesium dust cloud with Ar, N2 and CO2.

    PubMed

    Li, G; Yuan, C M; Fu, Y; Zhong, Y P; Chen, B Z

    2009-10-15

    Experiments were conducted on the inerting of magnesium dust with N(2), CO(2), and Ar. Comparing the maximum explosion pressure, maximum rate of pressure rise, and limiting oxygen concentration with different inertants, it was determined that Ar is not the best inert gas under all conditions as commonly believed. N(2) was more effective than Ar as an inertant. CO(2) provided more inerting effect than either Ar and N(2) in low magnesium dust concentrations, although explosibility was increased at higher dust concentrations. Both N(2) and CO(2) as inerting agents showed higher LOC values than Ar. These results indicated that N(2) is a more economical inerting gas than Ar for the tested coarse magnesium dust.

  3. Results of observations of the dust distribution in the F-corona of the sun

    NASA Astrophysics Data System (ADS)

    Shestakova, L. I.; Demchenko, B. I.

    2016-03-01

    The results of modeling of the distribution of dust in the circumsolar zone are presented. The dust distribution was retrieved from observations of the line-of-sight velocities in the F-corona to the distances of 7-11 solar radii during the total eclipses of the Sun in different years: on July 31, 1981; August 11, 1991; March 29, 2006; and August 1, 2008. Comparison of the results has shown that the dust composition varies from year to year and the dust is dynamically nonuniform. In addition to the dust related to the zodiacal cloud and concentrating to the ecliptic plane, the dust of retrograde motion and the ejections and accretion in the polar regions are observed. From the results of observations of eclipses on July 31, 1981, August 11, 1991, and August 1, 2008, the east-west asymmetry in a sign of the line-of-sight velocities was detected: they are negative to the east of the Sun and positive to the west. Such distribution of the velocities is indicative of the nearecliptic orbital dust motion, whose direction coincides with that of the motion of the planets. In the course of the eclipse of March 29, 2006, almost no dynamical connection with the zodiacal cloud was found. At the same time, the direction, where the observed velocities are largest in value and opposite in sign on opposite sides of the Sun, was determined, which provides evidence of the orbital motion deviating from the ecliptic plane. The results of observations in 2006 reveal a clear genetic connection of the observed orbital motion of dust with the parent comets of the Kreutz family found near the Sun close to the eclipse date. The velocities observed near the symmetry line in the plane of the sky grow by absolute value with increasing the elongation, which may take place, if the line of sight croßses an empty zone that is free of dust. The modeling of the data of observations near the symmetry plane allowed the parameters of the dust distribution near the sublimation zone to be obtained. In

  4. 3D dust clouds (Yukawa Balls) in strongly coupled dusty plasmas

    SciT

    Melzer, A.; Passvogel, M.; Miksch, T.

    2010-06-16

    Three-dimensional finite systems of charged dust particles confined to concentric spherical shells in a dusty plasma, so-called 'Yukawa balls', have been studied with respect to their static and dynamic properties. Here, we review the charging of particles in a dusty plasma discharge by computer simulations and the respective particle arrangements. The normal mode spectrum of Yukawa balls is measured from the 3D thermal Brownian motion of the dust particles around their equilibrium positions.

  5. Clouds

    2010-09-14

    Clouds are common near the north polar caps throughout the spring and summer. The clouds typically cause a haze over the extensive dune fields. This image from NASA Mars Odyssey shows the edge of the cloud front.

  6. A new look at dust and clouds in the Mars atmosphere - Analysis of emission-phase-function sequences from global Viking IRTM observations

    NASA Technical Reports Server (NTRS)

    Clancy, R. T.; Lee, Steven W.

    1991-01-01

    The present analysis of emission-phase function (EPF) observations from the IR thermal mapper aboard the Viking Orbiter encompasses polar latitudes, and Viking Lander sites, and spans a wide range of solar longitudes. A multiple scattering radiative transfer model which incorporates a bidirectional phase function for the surface and atmospheric scattering by dust and clouds yields surface albedos and dust and ice optical properties and optical depths for the variety of Mars conditions. It is possible to fit all analyzed EPF sequences corresponding to dust scattering with an albedo of 0.92, rather than the 0.86 given by Pollack et al. on the bases of Viking Lander observations.

  7. The Zodiacal Exoplanets in Time (ZEIT) Survey

    NASA Astrophysics Data System (ADS)

    Mann, Andrew; Gaidos, Eric; Newton, Elisabeth R.; Rizzuto, Aaron C.; Vanderburg, Andrew; Mace, Gregory N.; Kraus, Adam L.

    2017-01-01

    Planets and their host stars evolve with time, and the first few hundred million years are thought to be the most formative. However, the majority of known exoplanets orbit stars older than the timescales of interest (>1 Gyr). We have launched the Zodiacal Exoplanets in Time (ZEIT) survey with the goal of identifying and characterizing young (<1 Gyr) transiting planets. To this end, we have utilized high-precision photometry of nearby young clusters and stellar associations taken as part of the K2 mission. Thus far we have discovered transiting planets in the Hyades and Praesepe clusters (˜800 Myr), and the Upper Scorpius OB association (˜11 Myr), but interestingly none in the Pleiades (˜125 Myr). These discoveries can be used to set limits on the migration timescale, estimate atmosphere loss around young planets, and provide independent tests of pre-main sequence stellar models. Here I overview some key science results from our survey and briefly discuss our plans to identify more young planetary systems.

  8. Laboratory study of the effect of oxalic acid on the cloud condensation nuclei activity of mineral dust aerosol

    NASA Astrophysics Data System (ADS)

    Gierlus, Kelly M.; Laskina, Olga; Abernathy, Tricia L.; Grassian, Vicki H.

    2012-01-01

    Dicarboxylic acids, which make up a significant portion of the atmospheric organic aerosol, are emitted directly through biomass burning as well as produced through the oxidation of volatile organic compounds. Oxalic acid, the most abundant of the dicarboxylic acids, has been shown by recent field studies to be present in mineral dust aerosol particles. The presence of these internally mixed organic compounds can alter the water absorption and cloud condensation nuclei (CCN) abilities of mineral particles in the Earth's atmosphere. The University of Iowa's Multi-Analysis Aerosol Reactor System ( MAARS) was used to measure the CCN activity of internally mixed particles that were generated from a mixture of either calcite or polystyrene latex spheres (PSLs) in an aqueous solution of oxalic acid. Although PSL is not a mineral dust component, it is used here as a non-reactive, insoluble particle. CCN measurements indicate that the internally mixed oxalate/calcite particles showed nearly identical CCN activity compared to the original calcite particles whereas oxalic acid/PSL internally mixed particles showed much greater CCN activity compared to PSL particles alone. This difference is due to the reaction of calcite with oxalic acid, which produces a relatively insoluble calcium oxalate coating on the particle surface and not a soluble coating as it does on the PSL particle. Our results suggest that atmospheric processing of mineral dust aerosol through heterogeneous processes will likely depend on the mineralogy and the specific chemistry involved. Increase in the CCN activity by incorporation of oxalic acid are only expected for unreactive insoluble dust particles that form a soluble coating.

  9. Link between interplanetary & cometary dust: Polarimetric observations and space studies with Rosetta & Eye-Sat

    NASA Astrophysics Data System (ADS)

    Levasseur-Regourd, Anny-Chantal; Gaboriaud, Alain; Buil, Christian; Ressouche, Antoine; Lasue, J.; Palun, Adrien; Apper, Fabien; Elmaleh, Marc

    in 2016 [7]. Its main purpose is to study the zodiacal light intensity and polarization from a Sun-synchronous orbit, for the first time at the high spatial resolution of 1° over a wide portion of the sky and at four different wavelengths (in the visible and near-IR domains). The instrumental choices and new on-board technologies will be summarized, together with the results that may be expected on local properties of the interplanetary dust particles and thus on their similarities and differences with cometary dust particles. Support from CNES is warmly acknowledged. [1] Leinert, C., Bowyer, S., Haikala, L.K., et al. The 1997 reference of diffuse night sky brightness, Astron. Astrophys. Supp., 127, 1-99, 1998. [2] Levasseur-Regourd, A.C., Mann, I., Dumont, R., et al. Optical and thermal properties of interplanetary dust. In Interplanetary dust (Grün, E. et al. Eds), 57-94, Springer-Verlag, Berlin, 2001. [3] Lasue, J., Levasseur-Regourd, A.C., Fray, N., et al. Inferring the interplanetary dust properties from remote observations and simulations, Astron. Astrophys., 473, 641-649, 2007. [4] Nesvorny, D., Jenniskens, P., Levison, H.F., et al. Cometary origin of the zodiacal cloud and carbonaceous micrometeorites: implications for hot debris disks. Astrophys. J. 713, 816-836, 2010. [5] Levasseur-Regourd, A.C., Mukai, T., Lasue, J., et al. Physical properties of cometary and interplanetary dust, Planet. Space Sci., 55, 1010-1020, 2007. [6] Hadamcik, E., Sen, A.K., Levasseur-Regourd, A.C., et al., Astron. Astrophys., 517, A86, 2010. [7] CNES internal report. Eye-Sat end of phase A internal review, EYESAT-PR-0-022-CNES, 2013.

  10. FRAGMENTATION AND EVOLUTION OF MOLECULAR CLOUDS. II. THE EFFECT OF DUST HEATING

    SciT

    Urban, Andrea; Evans, Neal J.; Martel, Hugo

    2010-02-20

    We investigate the effect of heating by luminosity sources in a simulation of clustered star formation. Our heating method involves a simplified continuum radiative transfer method that calculates the dust temperature. The gas temperature is set by the dust temperature. We present the results of four simulations; two simulations assume an isothermal equation of state and the two other simulations include dust heating. We investigate two mass regimes, i.e., 84 M{sub sun} and 671 M{sub sun}, using these two different energetics algorithms. The mass functions for the isothermal simulations and simulations that include dust heating are drastically different. In themore » isothermal simulation, we do not form any objects with masses above 1 M{sub sun}. However, the simulation with dust heating, while missing some of the low-mass objects, forms high-mass objects ({approx}20 M{sub sun}) which have a distribution similar to the Salpeter initial mass function. The envelope density profiles around the stars formed in our simulation match observed values around isolated, low-mass star-forming cores. We find the accretion rates to be highly variable and, on average, increasing with final stellar mass. By including radiative feedback from stars in a cluster-scale simulation, we have determined that it is a very important effect which drastically affects the mass function and yields important insights into the formation of massive stars.« less

  11. Improvement in Clouds and the Earth's Radiant Energy System/Surface and Atmosphere Radiation Budget Dust Aerosol Properties, Effects on Surface Validation of Clouds and Radiative Swath

    SciT

    Rutan, D.; Rose, F.; Charlock, T.P.

    2005-03-18

    Within the Clouds and the Earth's Radiant Energy System (CERES) science team (Wielicki et al. 1996), the Surface and Atmospheric Radiation Budget (SARB) group is tasked with calculating vertical profiles of heating rates, globally, and continuously, beneath CERES footprint observations of Top of Atmosphere (TOA) fluxes. This is accomplished using a fast radiative transfer code originally developed by Qiang Fu and Kuo-Nan Liou (Fu and Liou 1993) and subsequently highly modified by the SARB team. Details on the code and its inputs can be found in Kato et al. (2005) and Rose and Charlock (2002). Among the many required inputsmore » is characterization of the vertical column profile of aerosols beneath each footprint. To do this SARB combines aerosol optical depth information from the moderate-resolution imaging spectroradiometer (MODIS) instrument along with aerosol constituents specified by the Model for Atmosphere and Chemical Transport (MATCH) of Collins et al. (2001), and aerosol properties (e.g. single scatter albedo and asymmetry parameter) from Tegen and Lacis (1996) and OPAC (Hess et al. 1998). The publicly available files that include these flux profiles, called the Clouds and Radiative Swath (CRS) data product, available from the Langley Atmospheric Sciences Data Center (http://eosweb.larc.nasa.gov/). As various versions of the code are completed, publishable results are named ''Editions.'' After CRS Edition 2A was finalized it was found that dust aerosols were too absorptive. Dust aerosols have subsequently been modified using a new set of properties developed by Andy Lacis and results have been released in CRS Edition 2B. This paper discusses the effects of changing desert dust aerosol properties, which can be significant for the radiation budget in mid ocean, a few thousand kilometers from the source regions. Resulting changes are validated via comparison of surface observed fluxes from the Saudi Solar Village surface site (Myers et al. 1999), and the E

  12. African dust particles and their impact on the solar energy budget in a Caribbean tropical montane cloud forest

    NASA Astrophysics Data System (ADS)

    Rivera, F. A.; Mayol-Bracero, O. L.; Torres-Delgado, E.

    2017-12-01

    To understand the impact of aerosols over the atmospheric energy budget it is essential to identify their size and chemical properties. Atmospheric aerosols emitted, for example, from African dust storms, directly affect climate by altering the dynamics of cloud formation and by reducing the amount of radiation reaching vegetation and the soil surface. In this project, we seek to improve our understanding of the variations in the concentrations of African dust and the role it might play in the energy budget at a Tropical Montane Cloud Forest (TMCF). Concentrations of particulate matter with diameters equal or less than 10µm (PM10) and aerosol optical properties (scattering and absorption) for years 2013 and 2014 were studied in northeastern Puerto Rico at the nature reserve of Cabezas de San Juan (CSJ). At CSJ we used an Integrating Nephelometer to measure light scattering at three wavelengths (450, 550 and 700 nm) and calculated the Scattering Angstrom Exponent (SAE), a measure inversely related to the size of the aerosol particle. We also used the Continuous Light Absorption Photometer (CLAP) to measure the light absorption at three wavelengths (450, 550 and 700). Visibility (meters) and radiation (total solar, UV and IR irradiation) were studied at the TMCF of Pico del Este (PE). PM10 data from stations at Cataño, Guaynabo, and Fajardo were also obtained. The PM10 data were used to study the variation in aerosol concentrations during the year and to study whether there was an effect on the incoming solar radiation. The periods under the influence of African dust were identified using the spectral coefficients measured at CSJ and the air mass back trajectories using the HYSPLIT model. During the summer period, an increase in PM10 concentrations, related to African Dust incursions, was observed. Preliminary results suggest that, for 2013 and 2014, in the presence of high concentrations of PM10 and with low SAE, the total radiation at PE decreased. This could be

  13. Infrared Spectroscopy of HR 4796A's Bright Outer Cometary Ring + Tenuous Inner Hot Dust Cloud

    NASA Astrophysics Data System (ADS)

    Lisse, C. M.; Sitko, M. L.; Marengo, M.; Vervack, R. J., Jr.; Fernandez, Y. R.; Mittal, T.; Chen, C. H.

    2017-11-01

    We have obtained new NASA/IRTF SpeX spectra of the HR 4796A debris ring system. We find a unique red excess flux that extends out to ˜9 μm in Spitzer IRS spectra, where thermal emission from cold, ˜100 K dust from the system’s ring at ˜75 au takes over. Matching imaging ring photometry, we find the excess consists of NIR reflectance from the ring, which is as red as that of old, processed comet nuclei, plus a tenuous thermal emission component from close-in, T ˜ 850 K circumstellar material evincing an organic/silicate emission feature complex at 7-13 μm. Unusual, emission-like features due to atomic Si, S, Ca, and Sr were found at 0.96-1.07 μm, likely sourced by rocky dust evaporating in the 850 K component. An empirical cometary dust phase function can reproduce the scattered light excess and 1:5 balance of scattered versus thermal energy for the ring with optical depth < τ > ≥slant 0.10 in an 8 au wide belt of 4 au vertical height and M dust > 0.1-0.7 M Mars. Our results are consistent with HR 4796A, consisting of a narrow shepherded ring of devolatilized cometary material associated with multiple rocky planetesimal subcores and a small steady stream of dust inflowing from this belt to a rock sublimation zone at ˜1 au from the primary. These subcores were built from comets that have been actively emitting large, reddish dust for >0.4 Myr at ˜100 K, the temperature at which cometary activity onset is seen in our solar system.

  14. Molecules and dust in the Large Magellanic Cloud: new colour classifications for post-Main-Sequence stars

    NASA Astrophysics Data System (ADS)

    Markwick-Kemper, Ciska; Leisenring, Jarron; Meixner, Margaret; van Dyk, Schuyler; Szczerba, Ryszard

    In the Large Magellanic Cloud (LMC), as in the Milky Way, dust formation predominantly occurs in the circumstellar environments of evolved stars. The process of dust condensation is not fully understood, and investigating the dust condensation sequence in the low metallicity environment of the LMC (about half of the solar metallicity), may yield additional insights in the dust condensation process. Topics to be studied include the final condensation products, the correlation of the condensation sequence with evolutionary status of the star, degree of crystallinity of the silicates and ratio of carbon-rich dust producing stars. The composition and properties of dust are most easily studied using infrared spectroscopy, and using the high sensitivity of the Infrared Spectrograph (IRS) on board of Spitzer, we were able to observe the thermal emission from circumstellar dust of these stars individually. A sample of 63 post-Main-Sequence stars were selected, using their 2MASS/MSX colours (Egan et al. 2001). We aimed to cover all post-Main-Sequence evolutionary stages, to make an inventory of the dust condensation products, while we placed a certain emphasis on oxygen-rich AGB stars with a intermediate mass-loss rate, to study the existence of a threshold mass-loss rate above which crystalline silicates are observed (Kemper et al. 2001). Here we will present the observed spectra, along with their spectral classification. We find that a large fraction of the stars we observed exhibit spectral features of carbon-rich dust and molecules, such as SiC, C2H2 and MgS. In fact we find that many of these stars are previously classified as oxygen-rich AGB stars, or as OH/IR stars based on their NIR/MIR colours (Egan et al. 2001). These colours are determined for Galactic samples, while in the LMC sample, stars with a carbon-rich chemistry in their outflows occupy a much larger region of the various colour-colour diagrams. In addition, a large fraction of the sample show amorphous

  15. Research approach and first results on agglomerate compaction in protoplanetary dust simulation in the Cloud Manipulation System

    NASA Astrophysics Data System (ADS)

    Vedernikov, Andrei; Blum, Jurgen; Ingo Von Borstel, Olaf; Schraepler, Rainer; Balapanov, Daniyar; Cecere, Anselmo

    2016-07-01

    Nanometre and micrometre-sized solid particles are ubiquitous in space and on Earth - from galaxies, interstellar space, protoplanetary and debris disks to planetary rings and atmospheres, planetary surfaces, comets, interplanetary space, Earth's atmosphere. Apparently, the most intriguing problem in the picture of the formation of planets is the transition from individual microscopic dust grains to kilometre-sized planetesimals. Revealing the mechanisms of this transition is one of the main tasks of the European Space Agency's project Interaction in Cosmic and Atmospheric Particle Systems (ICAPS). It was found that Brownian motion driven agglomeration could not provide the transition within reasonable time scale. As a result, at this stage top scientific goals shifted towards forced agglomeration and concentration of particles, targeting revealing the onset of compaction, experimental study of the evolution of fractal dimensions, size and mass distribution, occurrence of bouncing. The main tasks comprise 1) development of the rapid agglomeration model 2) development of the experimental facilities creating big fractal-type agglomerates from 10 to 1000 μm from a cloud of micrometre-size grains; 3) experimental realization of the rapid agglomeration in microgravity and ground conditions; and 4) in situ investigation of the morphology, mobility, mechanical and optical properties of the free-floating agglomerates, including investigation of thermophoresis, photophoresis of the agglomerates and of the two-phase flow phenomena. To solve the experimental part of the tasks we developed a Cloud Manipulation System, realized as a breadboard (CMS BB) for long duration microgravity platforms and a simplified laboratory version (CMS LV) mostly oriented on short duration microgravity and ground tests. The new system is based on the use of thermophoresis, most favourable for cloud manipulation without creating additional particle-particle forces in the cloud with a possibility

  16. A survey of carbon monoxide emission in dark clouds. [cosmic dust

    NASA Technical Reports Server (NTRS)

    Dickman, R. L.

    1975-01-01

    Results are reported of a CO and (C-13)O survey of 68 dark clouds from the Lynds catalog. CO was detected in 63 of the 64 sources in which it was searched for, and the (C-13)O line was seen in 52 of 55 clouds. There is a rather narrow distribution of CO peak line radiation temperatures about a mean of 6 K; this may reflect the presence of a roughly uniform kinetic temperature of 9.5 K in the sources. Despite the probably subthermal excitation temperature of the (C-13)O transition observed, derived (C-13)O column densities are most likely good to within a factor of 2. Typical CO column densities for the clouds surveyed are 5 x 10 to the 17-th power per sq cm, assuming a terrestrial carbon isotope ratio. All 68 clouds have previously been studied by Dieter in 6-cm H2CO absorption; a comparison of line widths shows the (C-13)O lines to generally be wider than their formaldehyde counterparts. Possible explanations of this fact in terms of internal cloud motions are discussed.

  17. Evolution of trace elements in the planetary boundary layer in southern China: Effects of dust storms and aerosol-cloud interactions

    NASA Astrophysics Data System (ADS)

    Li, Tao; Wang, Yan; Zhou, Jie; Wang, Tao; Ding, Aijun; Nie, Wei; Xue, Likun; Wang, Xinfeng; Wang, Wenxing

    2017-03-01

    Aerosols and cloud water were analyzed at a mountaintop in the planetary boundary layer in southern China during March-May 2009, when two Asian dust storms occurred, to investigate the effects of aerosol-cloud interactions (ACIs) on chemical evolution of atmospheric trace elements. Fe, Al, and Zn predominated in both coarse and fine aerosols, followed by high concentrations of toxic Pb, As, and Cd. Most of these aerosol trace elements, which were affected by dust storms, exhibited various increases in concentrations but consistent decreases in solubility. Zn, Fe, Al, and Pb were the most abundant trace elements in cloud water. The trace element concentrations exhibited logarithmic inverse relationships with the cloud liquid water content and were found highly pH dependent with minimum concentrations at the threshold of pH 5.0. The calculation of Visual MINTEQ model showed that 80.7-96.3% of Fe(II), Zn(II), Pb(II), and Cu(II) existed in divalent free ions, while 71.7% of Fe(III) and 71.5% of Al(III) were complexed by oxalate and fluoride, respectively. ACIs could markedly change the speciation distributions of trace elements in cloud water by pH modification. The in-cloud scavenging of aerosol trace elements likely reached a peak after the first 2-3 h of cloud processing, with scavenging ratios between 0.12 for Cr and 0.57 for Pb. The increases of the trace element solubility (4-33%) were determined in both in-cloud aerosols and postcloud aerosols. These results indicated the significant importance of aerosol-cloud interactions to the evolution of trace elements during the first several cloud condensation/evaporation cycles.

  18. Nulling interferometry: impact of exozodiacal clouds on the performance of future life-finding space missions

    NASA Astrophysics Data System (ADS)

    Defrère, D.; Absil, O.; den Hartog, R.; Hanot, C.; Stark, C.

    2010-01-01

    Context. Earth-sized planets around nearby stars are being detected for the first time by ground-based radial velocity and space-based transit surveys. This milestone is opening the path toward the definition of instruments able to directly detect the light from these planets, with the identification of bio-signatures as one of the main objectives. In that respect, both the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) have identified nulling interferometry as one of the most promising techniques. The ability to study distant planets will however depend on the amount of exozodiacal dust in the habitable zone of the target stars. Aims: We assess the impact of exozodiacal clouds on the performance of an infrared nulling interferometer in the Emma X-array configuration. The first part of the study is dedicated to the effect of the disc brightness on the number of targets that can be surveyed and studied by spectroscopy during the mission lifetime. In the second part, we address the impact of asymmetric structures in the discs such as clumps and offset which can potentially mimic the planetary signal. Methods: We use the DarwinSIM software which was designed and validated to study the performance of space-based nulling interferometers. The software has been adapted to handle images of exozodiacal discs and to compute the corresponding demodulated signal. Results: For the nominal mission architecture with 2-m aperture telescopes, centrally symmetric exozodiacal dust discs about 100 times denser than the solar zodiacal cloud can be tolerated in order to survey at least 150 targets during the mission lifetime. Considering modeled resonant structures created by an Earth-like planet orbiting at 1 AU around a Sun-like star, we show that this tolerable dust density goes down to about 15 times the solar zodiacal density for face-on systems and decreases with the disc inclination. Conclusions: Whereas the disc brightness only affects

  19. China Dust

    Atmospheric Science Data Center

    2013-04-16

    ... SpectroRadiometer (MISR) nadir-camera images of eastern China compare a somewhat hazy summer view from July 9, 2000 (left) with a ... arid and sparsely vegetated surfaces of Mongolia and western China pick up large quantities of yellow dust. Airborne dust clouds from the ...

  20. Teeth and numerology from zodiac signs. A correlative study.

    PubMed

    Kudva, S; Bhat, A P

    2000-01-01

    Comparative anatomical descriptions have been time and again mentioned in the literature. Based on these aspects, an attempt is made to correlate the morphological features of the human teeth, the zodiac sun signs and numerology. This unique study (first ever of its kind) is also done with a purpose as to whether a particular 'Zodiac Sunsign' or numerology can predict about an individual dental health, the same way the future predictions are being made. It was quite interesting to note that there are few definite attributable dental morphological traits and health to the specific sun signs and numerology.

  1. Research studies using OSO-6 zodiacal light experiment data

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The results of research studies on the OSO-6 zodiacal light experiment, conducted during the period from May 1976 to October 1977 are described. A discussion is included of the instrument performance and the empirical calibrations developed. Main areas of the research performed, i.e., (1) zodiacal light variation analysis; (2) integrated starlight and diffuse galactic light; and (3) earth/moon libration region counterglow, are covered. Considerable data processing was performed during these studies and it is summarized. Recommendations for future research to complete the interim results are given.

  2. The Coupled Roles of Dust and Clouds in the Mars Climate

    NASA Technical Reports Server (NTRS)

    Clancy, R. Todd

    2000-01-01

    During the period October 1997 to September 1999 we obtained and analyzed over 100 millimeter-wave observations of Mars atmospheric CO line absorption for atmospheric temperature profiles. These measurements extend through one full Mars year (solar longitudes L(sub S) of 190 deg in 1997 to 180 deg in 1999) and coincide with atmospheric temperature profile and dust column measurements front the Thermal Emission Spectrometer (TES) experiment on board the Mars Global Surveyor (MGS) spacecraft. A comparison of Mars atmospheric temperatures retrieved by these distinct methods provides the first opportunity to place the long-term (1982-1999) millimeter retrievals of Mars atmospheric temperatures within the context of contemporaneous, spatially mapped spacecraft, observations. Profile comparisons of 0-30 km altitude atmospheric temperatures retrieved with the two techniques agree typically to within the 5 K calibration accuracy of the millimeter observations. At the 0.5 mbar pressure level (approximately 25 km altitude) the 30N/30S average for TES infrared temperatures and the disk-averaged millimeter temperatures are also well correlated in their seasonal and dust-storm-related variations over the 1997-1999 period. This period includes the Noachis Terra regional dust storm, which led to very abrupt heating (approximately 15 K at 0.5 mbar) of the global Mars atmosphere at L(sub S)=224 deg in 1997 [Christensen et al., 1998; Conrath et al., this issue; Smith et al., this issue]. Much colder (10-20 K) global atmospheric temperatures were observed during the 1997 versus 1977 perihelion periods (L(sub S)=200 deg-330 deg), consistent with the much (2 to 8 times) lower global dust loading of the atmosphere during the 1997 perihelion dust storm season versus the Viking period of the 1977a,b storms. The 1998-1999 Mars atmosphere revealed by both the millimeter and TES observations is also 10-15 K colder than presented by the Viking climatology during the aphelion season (L(sub S

  3. The Use of OMPS Near Real Time Products in Volcanic Cloud Risk Mitigation and Smoke/Dust Air Quality Assessments

    NASA Astrophysics Data System (ADS)

    Seftor, C. J.; Krotkov, N. A.; McPeters, R. D.; Li, J. Y.; Durbin, P. B.

    2015-12-01

    Near real time (NRT) SO2 and aerosol index (AI) imagery from Aura's Ozone Monitoring Instrument (OMI) has proven invaluable in mitigating the risk posed to air traffic by SO2 and ash clouds from volcanic eruptions. The OMI products, generated as part of NASA's Land, Atmosphere Near real-time Capability for EOS (LANCE) NRT system and available through LANCE and both NOAA's NESDIS and ESA's Support to Aviation Control Service (SACS) portals, are used to monitor the current location of volcanic clouds and to provide input into Volcanic Ash (VA) advisory forecasts. NRT products have recently been developed using data from the Ozone Mapping and Profiler Suite onboard the Suomi NPP platform; they are currently being made available through the SACS portal and will shortly be incorporated into the LANCE NRT system. We will show examples of the use of OMPS NRT SO2 and AI imagery to monitor recent volcanic eruption events. We will also demonstrate the usefulness of OMPS AI imagery to detect and track dust storms and smoke from fires, and how this information can be used to forecast their impact on air quality in areas far removed from their source. Finally, we will show SO2 and AI imagery generated from our OMPS Direct Broadcast data to highlight the capability of our real time system.

  4. Simulating Mars' Dust Cycle with a Mars General Circulation Model: Effects of Water Ice Cloud Formation on Dust Lifting Strength and Seasonality

    NASA Technical Reports Server (NTRS)

    Kahre, Melinda A.; Haberle, Robert; Hollingsworth, Jeffery L.

    2012-01-01

    The dust cycle is critically important for the current climate of Mars. The radiative effects of dust impact the thermal and dynamical state of the atmosphere [1,2,3]. Although dust is present in the Martian atmosphere throughout the year, the level of dustiness varies with season. The atmosphere is generally the dustiest during northern fall and winter and the least dusty during northern spring and summer [4]. Dust particles are lifted into the atmosphere by dust storms that range in size from meters to thousands of kilometers across [5]. Regional storm activity is enhanced before northern winter solstice (Ls200 degrees - 240 degrees), and after northern solstice (Ls305 degrees - 340 degrees ), which produces elevated atmospheric dust loadings during these periods [5,6,7]. These pre- and post- solstice increases in dust loading are thought to be associated with transient eddy activity in the northern hemisphere with cross-equatorial transport of dust leading to enhanced dust lifting in the southern hemisphere [6]. Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles [8,9,10]. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading.

  5. Experimental demonstration of plasma-drag acceleration of a dust cloud to hypervelocities.

    PubMed

    Ticoş, C M; Wang, Zhehui; Wurden, G A; Kline, J L; Montgomery, D S; Dorf, L A; Shukla, P K

    2008-04-18

    Simultaneous acceleration of hundreds of dust particles to hypervelocities by collimated plasma flows ejected from a coaxial gun is demonstrated. Graphite and diamond grains with radii between 5 and 30 microm, and flying at speeds up to 3.7 km/s, have been recorded with a high-speed camera. The observations agree well with a model for plasma-drag acceleration of microparticles much larger than the plasma screening length.

  6. Observed changes in limb clouds immediately prior to the onset of planet-encircling dust storms

    NASA Technical Reports Server (NTRS)

    Martin, L. J.; James, P. B.; Zurek, R. W.

    1992-01-01

    Of the several size and nomenclature groupings of Martian dust storms, it is the plane-encircling or truly runaway dust storms that are of most concern to both the theoreticians and mission planners. Once believed to be regularly seasonal, it is now known that they are not annual occurrences and that the few we know about occurred within at least one-third of Mars' seasonal cycle. We cannot confirm that any were observed before 1956, and not one has been observed since 1982 (the classification of that event as 'encircling' is an interpretation of observation from a single point on the planet's surface). If these storms occur in cycles, we do not know the lengths or causes of the cycles. Regional and local dust storms occur more frequently and throughout the Martian year, but the underlying question is how do some become runaways, encircling the planet, while the others die out, usually within a few days. An investigation of this topic is presented.

  7. Environmental Effects of an Impact-Generated Dust Cloud: Implications for the Cretaceous-Tertiary Extinctions

    NASA Astrophysics Data System (ADS)

    Pollack, James B.; Toon, Owen B.; Ackerman, Thomas P.; McKay, Christopher P.; Turco, Richard P.

    1983-01-01

    A model of the evolution and radiative effects of a debris cloud from a hypothesized impact event at the Cretaceous-Tertiary boundary suggests that the cloud could have reduced the amount of light at the earth's surface below that required for photosynthesis for several months and, for a somewhat shorter interval, even below that needed for many animals to see. For 6 months to 1 year, the surface would cool; the oceans would cool only a few degrees Celsius at most, but the continents might cool a maximum of 40 Kelvin. Extinctions in the ocean may have been caused primarily by the temporary cessation of photosynthesis, but those on land may have been primarily induced by a combination of lowered temperatures and reduced light.

  8. Environmental effects of an impact-generated dust cloud - Implications for the Cretaceous-Tertiary extinctions

    NASA Technical Reports Server (NTRS)

    Pollack, J. B.; Toon, O. B.; Ackerman, T. P.; Mckay, C. P.; Turco, R. P.

    1983-01-01

    A model of the evolution and radiative effects of a debris cloud from a hypothesized impact event at the Cretaceous-Tertiary boundary suggests that the cloud could have reduced the amount of light at the earth's surface below that required for photosynthesis for several months and, for a somewhat shorter interval, even below that needed for many animals to see. For 6 months to 1 year, the surface would cool; the oceans could cool only a few degrees Celsius at most, but the continents might cool a maximum of 40 Kelvin. Extinctions in the ocean may have been caused primarily by the temporary cessation of photosynthesis, but those on land may have been primarily induced by a combination of lowered temperatures and reduced light.

  9. Ten-color Gegenschein-zodiacal light photometer. [onboard Skylab

    NASA Technical Reports Server (NTRS)

    Sparrow, J. G.; Weinberg, J. L.; Hahn, R. C.

    1977-01-01

    A ten-color Fabry photometer was used during Skylab missions SL-2 and SL-3 to measure sky brightness and polarization associated with zodiacal light, background starlight, F region airglow, and spacecraft corona. A brief description is given of the design, calibration, and performance of the instrument.

  10. Dust Cloud Modeling and Propagation Effects for Radar and Communications Codes

    DTIC Science & Technology

    1978-11-01

    particles can be described by a power law probabi 1it Y d i st r i ut i on with a power exponent of 4. Four is a typical value for dust particlIs from...loose unconsolidated soils such as desert alluviun, blust ,eera ted from a nuclear cratering explosion in rock and cohes ive soil s haN pO,,e r exponent ...da p = power law exponent amin = minimum particle diameter in the distribution (cm) a = maximum particle diameter in the distribution (cm).max The log

  11. Reactive oxygen species formed in aqueous mixtures of secondary organic aerosols and mineral dust influencing cloud chemistry and public health in the Anthropocene.

    PubMed

    Tong, Haijie; Lakey, Pascale S J; Arangio, Andrea M; Socorro, Joanna; Kampf, Christopher J; Berkemeier, Thomas; Brune, William H; Pöschl, Ulrich; Shiraiwa, Manabu

    2017-08-24

    Mineral dust and secondary organic aerosols (SOA) account for a major fraction of atmospheric particulate matter, affecting climate, air quality and public health. How mineral dust interacts with SOA to influence cloud chemistry and public health, however, is not well understood. Here, we investigated the formation of reactive oxygen species (ROS), which are key species of atmospheric and physiological chemistry, in aqueous mixtures of SOA and mineral dust by applying electron paramagnetic resonance (EPR) spectrometry in combination with a spin-trapping technique, liquid chromatography-tandem mass spectrometry (LC-MS/MS), and a kinetic model. We found that substantial amounts of ROS including OH, superoxide as well as carbon- and oxygen-centred organic radicals can be formed in aqueous mixtures of isoprene, α-pinene, naphthalene SOA and various kinds of mineral dust (ripidolite, montmorillonite, kaolinite, palygorskite, and Saharan dust). The molar yields of total radicals were ∼0.02-0.5% at 295 K, which showed higher values at 310 K, upon 254 nm UV exposure, and under low pH (<3) conditions. ROS formation can be explained by the decomposition of organic hydroperoxides, which are a prominent fraction of SOA, through interactions with water and Fenton-like reactions with dissolved transition metal ions. Our findings imply that the chemical reactivity and aging of SOA particles can be enhanced upon interaction with mineral dust in deliquesced particles or cloud/fog droplets. SOA decomposition could be comparably important to the classical Fenton reaction of H 2 O 2 with Fe 2+ and that SOA can be the main source of OH radicals in aqueous droplets at low concentrations of H 2 O 2 and Fe 2+ . In the human respiratory tract, the inhalation and deposition of SOA and mineral dust can also lead to the release of ROS, which may contribute to oxidative stress and play an important role in the adverse health effects of atmospheric aerosols in the Anthropocene.

  12. KENNEDY SPACE CENTER, FLA. - On Launch Pad 39A, clouds of dust float away from the Mobile Launcher Platform, which is undergoing sandblasting to remove corrosion before repainting. Routine maintenance includes sandblasting and repainting as preventive means to minimize corrosion.

    2003-09-12

    KENNEDY SPACE CENTER, FLA. - On Launch Pad 39A, clouds of dust float away from the Mobile Launcher Platform, which is undergoing sandblasting to remove corrosion before repainting. Routine maintenance includes sandblasting and repainting as preventive means to minimize corrosion.

  13. Evolution of Cometary Dust Particles to the Orbit of the Earth: Particle Size, Shape, and Mutual Collisions

    NASA Astrophysics Data System (ADS)

    Yang, Hongu; Ishiguro, Masateru

    2018-02-01

    In this study, we numerically investigated the orbital evolution of cometary dust particles, with special consideration of the initial size–frequency distribution (SFD) and different evolutionary tracks according to the initial orbit and particle shape. We found that close encounters with planets (mostly Jupiter) are the dominating factor determining the orbital evolution of dust particles. Therefore, the lifetimes of cometary dust particles (∼250,000 yr) are shorter than the Poynting–Robertson lifetime, and only a small fraction of large cometary dust particles can be transferred into orbits with small semimajor axes. The exceptions are dust particles from 2P/Encke and, potentially, active asteroids that have little interaction with Jupiter. We also found that the effects of dust shape, mass density, and SFD were not critical in the total mass supply rate to the interplanetary dust particle (IDP) cloud complex when these quantities are confined by observations of zodiacal light brightness and SFD around the Earth’s orbit. When we incorporate a population of fluffy aggregates discovered in the Earth’s stratosphere and the coma of 67P/Churyumov–Gerasimenko within the initial ejection, the initial SFD measured at the comae of comets (67P and 81P/Wild 2) can produce the observed SFD around the Earth’s orbit. Considering the above effects, we derived the probability of mutual collisions among dust particles within the IDP cloud for the first time in a direct manner via numerical simulation and concluded that mutual collisions can mostly be ignored.

  14. Evolution of the Edgeworth-Kuiper Belt and Kuiperoidal Dust

    NASA Astrophysics Data System (ADS)

    Ozernoy, L. M.; Ipatov, S. I.

    Evolution of orbits of Edgeworth-Kuiper belt objects (EKBOs) under the gravitational influence of the giant planets has been studied by a number of authors (e.g., Duncan & Levison; Budd; Ozernoy, Gorkavyi & Taidakova). Here we show that the gravitational interactions of EKBOs can also play a certain role in their orbital evolution. For instance, during the last 4 Gyr as many as several percents of EKBOs could change their semimajor axes by more than 1 AU due to close encounters with other EKBOs. Even small variations in orbital elements of EKBOs caused by their mutual collisions coupled with the mutual gravitational influence can cause large variations in the orbital elements due to the gravitational influence of planets. About 6% of Neptune-crossers can reach the orbit of the Earth, with the average time in Earth-crossing orbits of about 5× 103 yr. The portion of former EKBOs now moving in Earth-crossing orbits can exceed 20% of all Earth-crossers. Evaporation of the volatile material from the EKBOs surfaces, due to mutual EKBO collisions, along with the Solar wind and the heating by the Sun, are the sources of the dust in the outer Solar system. The evolution and structure of the interplanetary dust cloud computed, in some approximations, by Gorkavyi, Ozernoy, Mather, & Taidakova offers a preliminary 3-D physical model of the cloud, which includes three dust components (asteroidal, cometary, and kuiperoidal), which is fairly consistent with the available data of Pioneer and Voyager dust detectors and contribution of the zodiacal light into the COBE/DIRBE data. We acknowledge support of this work by NASA grant NAG5-10776, the Russian Federal Program ``Astronomy'' (section 1.9.4.1), RFBR (01-02-17540), and INTAS (00-240).

  15. Connecting LADEE LDEX Observations of the Moon's dust cloud to the temporal and selenographic variability produced by micrometeoroid impacts from Jupiter Family Comets

    NASA Astrophysics Data System (ADS)

    Janches, D.; Pokorny, P.; Sarantos, M.; Nesvorny, D.

    2017-12-01

    Recent observations by the Lunar Dust Experiment (LDEX) on board NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) were perceived to indicate an unbalanced influence of meteoroids impacting from the Helion and the Anti-Helion directions. These observations were interpreted without proper consideration of the dynamical characteristics of the meteoroid environment and its spatio-temporal influence on the Moon's surface. In this work, a dynamical model of meteoroids originating from Jupiter Family Comets is utilized to model the secondary dust ejecta cloud engulfing the Moon. It is shown that the combination of the dynamical properties of these meteoroids, together with the orbital geometry of LADEE, introduce a bias in the observations and causes LADEE LDEX to be more sensitive to the Helion source. This effect must be considered in order to draw accurate conclusions regarding the meteoroid environment and its influence on the Moon's surface.

  16. Overview for the reanalysis of Mariner 9 UV spectrometer data for ozone, cloud, and dust abundances, and their interaction over climate timescales

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1992-01-01

    Mariner 9 UV spectrometer data were reinverted for the ozone abundance, cloud abundance, dust abundance, and polar-cap albedo. The original reduction of the spectra ignored the presence of atmospheric dust and clouds, even though their abundance is substantial and can mask appreciable amounts of ozone if not accounted for (Lindner, 1988). The Mariner 9 ozone data has been used as a benchmark in all theoretical models of atmospheric composition, escape, and photochemistry. A second objective is to examine the data for the interrelationship of the ozone cycle, dust cycle, and cloud cycle, on an annual, inter-annual, and climatic basis, testing predictions by Lindner (1988). This also has implications for many terrestrial ozone studies, such as the ozone hole, acid rain, and ozone-smog. A third objective is to evaluate the efficacy of the reflectance spectroscopy technique at retrieving the ozone abundance on Mars. This would be useful for planning ozone observations on future Mars missions or the terrestrial troposphere.

  17. The fertilizing role of African dust in the Amazon rainforest: A first multiyear assessment based on data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations

    NASA Astrophysics Data System (ADS)

    Yu, Hongbin; Chin, Mian; Yuan, Tianle; Bian, Huisheng; Remer, Lorraine A.; Prospero, Joseph M.; Omar, Ali; Winker, David; Yang, Yuekui; Zhang, Yan; Zhang, Zhibo; Zhao, Chun

    2015-03-01

    The productivity of the Amazon rainforest is constrained by the availability of nutrients, in particular phosphorus (P). Deposition of long-range transported African dust is recognized as a potentially important but poorly quantified source of phosphorus. This study provides a first multiyear satellite-based estimate of dust deposition into the Amazon Basin using three-dimensional (3-D) aerosol measurements over 2007-2013 from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). The 7 year average of dust deposition into the Amazon Basin is estimated to be 28 (8-48) Tg a-1 or 29 (8-50) kg ha-1 a-1. The dust deposition shows significant interannual variation that is negatively correlated with the prior-year rainfall in the Sahel. The CALIOP-based multiyear mean estimate of dust deposition matches better with estimates from in situ measurements and model simulations than a previous satellite-based estimate does. The closer agreement benefits from a more realistic geographic definition of the Amazon Basin and inclusion of meridional dust transport calculation in addition to the 3-D nature of CALIOP aerosol measurements. The imported dust could provide about 0.022 (0.006-0.037) Tg P of phosphorus per year, equivalent to 23 (7-39) g P ha-1 a-1 to fertilize the Amazon rainforest. This out-of-basin phosphorus input is comparable to the hydrological loss of phosphorus from the basin, suggesting an important role of African dust in preventing phosphorus depletion on timescales of decades to centuries.

  18. DETECTION OF REMNANT DUST CLOUD ASSOCIATED WITH THE 2007 OUTBURST OF 17P/HOLMES

    SciT

    Ishiguro, Masateru; Kim, Yoonyoung; Kwon, Yuna G.

    2016-01-20

    This article reports a new optical observation of 17P/Holmes one orbital period after the historical outburst event in 2007. We detected not only a common dust tail near the nucleus but also a long narrow structure that extended along the position angle 274.°6 ± 0.°1 beyond the field of view (FOV) of the Kiso Wide Field Camera, i.e., >0.°2 eastward and >2.°0 westward from the nuclear position. The width of the structure decreased westward with increasing distance from the nucleus. We obtained the total cross section of the long extended structure in the FOV, C{sub FOV} = (2.3 ± 0.5) × 10{sup 10} m{sup 2}. From themore » position angle, morphology, and mass, we concluded that the long narrow structure consists of materials ejected during the 2007 outburst. On the basis of the dynamical behavior of dust grains in the solar radiation field, we estimated that the long narrow structure would be composed of 1 mm–1 cm grains having an ejection velocity of >50 m s{sup −1}. The velocity was more than one order of magnitude faster than that of millimeter–centimeter grains from typical comets around a heliocentric distance r{sub h} of 2.5 AU. We considered that sudden sublimation of a large amount of water-ice (≈10{sup 30} mol s{sup −1}) would be responsible for the high ejection velocity. We finally estimated a total mass of M{sub TOT} = (4–8) × 10{sup 11} kg and a total kinetic energy of E{sub TOT} = (1–6) × 10{sup 15} J for the 2007 outburst ejecta, which are consistent with those of previous studies that were conducted soon after the outburst.« less

  19. Interstellar Dust: Contributed Papers

    NASA Technical Reports Server (NTRS)

    Tielens, Alexander G. G. M. (Editor); Allamandola, Louis J. (Editor)

    1989-01-01

    A coherent picture of the dust composition and its physical characteristics in the various phases of the interstellar medium was the central theme. Topics addressed included: dust in diffuse interstellar medium; overidentified infrared emission features; dust in dense clouds; dust in galaxies; optical properties of dust grains; interstellar dust models; interstellar dust and the solar system; dust formation and destruction; UV, visible, and IR observations of interstellar extinction; and quantum-statistical calculations of IR emission from highly vibrationally excited polycyclic aromatic hydrocarbon (PAH) molecules.

  20. SIGNATURES OF RECENT ASTEROID DISRUPTIONS IN THE FORMATION AND EVOLUTION OF SOLAR SYSTEM DUST BANDS

    SciT

    Kehoe, A. J. Espy; Colwell, J. E.; Kehoe, T. J. J.

    We have performed detailed dynamical modeling of the structure of a faint dust band observed in coadded InfraRed Astronomical Satellite data at an ecliptic latitude of 17° that convincingly demonstrates that it is the result of a relatively recent (significantly less than 1 Ma) disruption of an asteroid and is still in the process of forming. We show here that young dust bands retain information on the size distribution and cross-sectional area of dust released in the original asteroid disruption, before it is lost to orbital and collisional decay. We find that the Emilkowalski cluster is the source of thismore » partial band and that the dust released in the disruption would correspond to a regolith layer ∼3 m deep on the ∼10 km diameter source body's surface. The dust in this band is described by a cumulative size-distribution inverse power-law index with a lower bound of 2.1 (implying domination of cross-sectional area by small particles) for dust particles with diameters ranging from a few μm up to a few cm. The coadded observations show that the thermal emission of the dust band structure is dominated by large (mm–cm size) particles. We find that dust particle ejection velocities need to be a few times the escape velocity of the Emilkowalski cluster source body to provide a good fit to the inclination dispersion of the observations. We discuss the implications that such a significant release of material during a disruption has for the temporal evolution of the structure, composition, and magnitude of the zodiacal cloud.« less

  1. Results of measurements with the Planetary Fourier Spectrometer onboard Mars Express: Clouds and dust at the end of southern summer. A comparison with OMEGA images

    NASA Astrophysics Data System (ADS)

    Zasova, L. V.; Formisano, V.; Moroz, V. I.; Bibring, J.-P.; Grassi, D.; Ignatiev, N. I.; Giuranna, M.; Bellucci, G.; Altieri, F.; Blecka, M.; Gnedykh, V. N.; Grigoriev, A. V.; Lellouch, E.; Mattana, A.; Maturilli, A.; Moshkin, B. E.; Nikolsky, Yu. V.; Patsaev, D. V.; Piccioni, G.; Ratai, M.; Saggin, B.; Fonti, S.; Khatuntsev, I. V.; Hirsh, H.; Ekonomov, A. P.

    2006-07-01

    We discuss the results of measurements made with the Planetary Fourier Spectrometer (PFS) onboard the Mars Express spacecraft. The data were obtained in the beginning of the mission and correspond to the end of summer in the southern hemisphere of Mars ( L s ˜ 340°). Three orbits are considered, two of which passed through volcanoes Olympus and Ascraeus Mons (the height above the surface is about +20 km), while the third orbit intersects lowland Hellas (-7 km). The influence of the relief on the properties of the aerosol observed is demonstrated: clouds of water ice with a visual optical thickness of 0.1-0.5 were observed above volcanoes, while only dust was found during the observations (close in time) along the orbit passing through Hellas in low and middle latitudes. This dust is homogeneously mixed with gas and has a reduced optical thickness of 0.25±0.05 (at v = 1100 cm-1). In addition to orographic clouds, ice clouds were observed in this season in the northern polar region. The clouds seen in the images obtained simultaneously by the mapping spectrometer OMEGA confirm the PFS results. Temperature inversion is discovered in the north polar hood below the level 1 mbar with a temperature maximum at about 0.6 mbar. This inversion is associated with descending movements in the Hadley cell.

  2. Polarization of the zodiacal light - First results from Skylab

    NASA Technical Reports Server (NTRS)

    Sparrow, J. G.; Weinberg, J. L.; Hahn, R. C.

    1976-01-01

    A brief description is given of the Skylab ten color photoelectric photometer and the programs of measurements made during Skylab missions SL-2 and SL-3. Results obtained on the polarized brightness of zodiacal light at five points on the antisolar hemisphere are discussed and compared with other published data for the north celestial pole, south ecliptic pole, at elongation 90 degrees on the ecliptic, and at two places near the north galactic pole.

  3. The Chevroches zodiacal cap and its Burgundy relations

    NASA Astrophysics Data System (ADS)

    Devevey, Frédéric; Vernou, Christian; Rousseau, Aurélie

    2011-06-01

    The excavation of an unexplored secondary agglomeration in Chevroches (France), from 2001 to 2002 has led to the discovery of a bronze dome of a type unknown in the Ancient world. It is inscribed with three lines in Greek transcribing Egyptian and Roman months, and the twelve signs of the Zodiac. This paper presents the first observations and some other finds from similar objects in Burgundy.

  4. Dynamics of Dust Particles Released from Oort Cloud Comets and Their Contribution to Radar Meteors

    NASA Technical Reports Server (NTRS)

    Nesvorny, David; Vokrouhlicky, David; Pokorny, Petr; Janches, Diego

    2012-01-01

    The Oort Cloud Comets (OCCs), exemplified by the Great Comet of 1997 (Hale-Bopp), are occasional visitors from the heatless periphery of the solar system. Previous works hypothesized that a great majority of OCCs must physically disrupt after one or two passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC meteoroids can be found in the existing meteor radar data. We find that OCC particles with diameters D < or approx. 10 microns are blown out from the solar system by radiation pressure, while those with D > or approx. 1 mm have a very low Earth-impact probability. The intermediate particle sizes, D approx. 100 microns represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a approx. 1 AU. They are expected to produce meteors with radiants near the apex of the Earth s orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex meteors, except for the eccentricity distribution, which is more skewed toward e approx. 1 in our model. Finally, we propose an explanation for the long-standing problem in meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits.

  5. Division F Commission 22: Meteors, Meteorites, and Interplanetary Dust

    NASA Astrophysics Data System (ADS)

    Jenniskens, Peter; Borovička, Jiří; Watanabe, Jun-Ichi; Jopek, Tadeusz; Abe, Shinsuke; Consolmagno, Guy J.; Ishiguro, Masateru; Janches, Diego; Ryabova, Galina O.; Vaubaillon, Jérémie; Zhu, Jin

    2016-04-01

    Commission 22 (Meteors, Meteorites and Interplanetary Dust) was established at the first IAU General Assembly held in Rome in 1922, with William Frederick Denning as its first President. Denning was an accountant by profession, but as an amateur astronomer he contributed extensively to meteor science. Commission 22 thus established a pattern that has continued to this day that non-professional astronomers were welcomed and valued and could play a significant role in its affairs. The field of meteors, meteorites and interplanetary dust has played a disproportional role in the astronomical perception of the general public through the majestic displays of our annual meteor showers. Those in the field deployed many techniques uncommon in other fields of astronomy, studying the ``vermin of space'', the small solid bodies that pervade interplanetary space and impact Earth's atmosphere, the surface of the Moon, and that of our satellites in orbit. Over time, the field has tackled a wide array of problems, from predicting the encounter with meteoroid streams, to the origin of our meteorites and the nature of the zodiacal cloud. Commission 22 has played an important role in organizing the field through dedicated meetings, a data centre, and working groups that developed professional-amateur relationships and that organized the nomenclature of meteor showers. The contribution of Commission 22 to the field is perhaps most readily seen in the work of the presidents that followed in the footsteps of Denning.

  6. HST Imaging of Dust Structures and Stars in the Ram Pressure Stripped Virgo Spirals NGC 4402 and NGC 4522: Stripped from the Outside In with Dense Cloud Decoupling

    NASA Astrophysics Data System (ADS)

    Abramson, A.; Kenney, J.; Crowl, H.; Tal, T.

    2016-08-01

    We describe and constrain the origins of interstellar medium (ISM) structures likely created by ongoing intracluster medium (ICM) ram pressure stripping in two Virgo Cluster spirals, NGC 4522 and NGC 4402, using Hubble Space Telescope (HST) BVI images of dust extinction and stars, as well as supplementary H I, Hα, and radio continuum images. With a spatial resolution of ˜10 pc in the HST images, this is the highest-resolution study to date of the physical processes that occur during an ICM-ISM ram pressure stripping interaction, ram pressure stripping's effects on the multi-phase, multi-density ISM, and the formation and evolution of ram-pressure-stripped tails. In dust extinction, we view the leading side of NGC 4402 and the trailing side of NGC 4522, and so we see distinct types of features in both. In both galaxies, we identify some regions where dense clouds are decoupling or have decoupled and others where it appears that kiloparsec-sized sections of the ISM are moving coherently. NGC 4522 has experienced stronger, more recent pressure and has the “jellyfish” morphology characteristic of some ram-pressure-stripped galaxies. Its stripped tail extends up from the disk plane in continuous upturns of dust and stars curving up to ˜2 kpc above the disk plane. On the other side of the galaxy, there is a kinematically and morphologically distinct extraplanar arm of young, blue stars and ISM above a mostly stripped portion of the disk, and between it and the disk plane are decoupled dust clouds that have not been completely stripped. The leading side of NGC 4402 contains two kiloparsec-scale linear dust filaments with complex substructure that have partially decoupled from the surrounding ISM. NGC 4402 also contains long dust ridges, suggesting that large parts of the ISM are being pushed out at once. Both galaxies contain long ridges of polarized radio continuum emission indicating the presence of large-scale, ordered magnetic fields. We propose that magnetic

  7. HST IMAGING OF DUST STRUCTURES AND STARS IN THE RAM PRESSURE STRIPPED VIRGO SPIRALS NGC 4402 AND NGC 4522: STRIPPED FROM THE OUTSIDE IN WITH DENSE CLOUD DECOUPLING

    SciT

    Abramson, A.; Kenney, J.; Crowl, H.

    We describe and constrain the origins of interstellar medium (ISM) structures likely created by ongoing intracluster medium (ICM) ram pressure stripping in two Virgo Cluster spirals, NGC 4522 and NGC 4402, using Hubble Space Telescope (HST) BVI images of dust extinction and stars, as well as supplementary H i, H α , and radio continuum images. With a spatial resolution of ∼10 pc in the HST images, this is the highest-resolution study to date of the physical processes that occur during an ICM–ISM ram pressure stripping interaction, ram pressure stripping's effects on the multi-phase, multi-density ISM, and the formation andmore » evolution of ram-pressure-stripped tails. In dust extinction, we view the leading side of NGC 4402 and the trailing side of NGC 4522, and so we see distinct types of features in both. In both galaxies, we identify some regions where dense clouds are decoupling or have decoupled and others where it appears that kiloparsec-sized sections of the ISM are moving coherently. NGC 4522 has experienced stronger, more recent pressure and has the “jellyfish” morphology characteristic of some ram-pressure-stripped galaxies. Its stripped tail extends up from the disk plane in continuous upturns of dust and stars curving up to ∼2 kpc above the disk plane. On the other side of the galaxy, there is a kinematically and morphologically distinct extraplanar arm of young, blue stars and ISM above a mostly stripped portion of the disk, and between it and the disk plane are decoupled dust clouds that have not been completely stripped. The leading side of NGC 4402 contains two kiloparsec-scale linear dust filaments with complex substructure that have partially decoupled from the surrounding ISM. NGC 4402 also contains long dust ridges, suggesting that large parts of the ISM are being pushed out at once. Both galaxies contain long ridges of polarized radio continuum emission indicating the presence of large-scale, ordered magnetic fields. We propose

  8. Observations of the zodiacal light from the ecliptic to the poles.

    NASA Technical Reports Server (NTRS)

    Sparrow, J. G.; Ney, E. P.

    1972-01-01

    The brightness and polarization of the zodiacal light have been measured from the satellite OSO-5, using two photometers of effective wavelengths 4180 and 6820 A. The satellite configuration restricts the observations to ecliptic longitudes close to 90 deg, but measurements have been made from the ecliptic to the poles. On the ecliptic, the intensity of the zodiacal light was found to be 117 S10 (blue) and 315 S10 (red) with polarizations of 16.5 and 15 per cent, respectively. At the ecliptic poles the zodiacal intensity was 35 S10 (blue) with 20 per cent polarization. No temporal changes in zodiacal light have been found nor any significant differences in the intensities in the two hemispheres. The direction of polarization of the zodiacal light has been shown to be H-pass radial.

  9. A Near-Infrared Spectrometer to Measure Zodiacal Light Absorption Spectrum

    NASA Technical Reports Server (NTRS)

    Kutyrev, A. S.; Arendt, R.; Dwek, E.; Kimble, R.; Moseley, S. H.; Rapchun, D.; Silverberg, R. F.

    2010-01-01

    We have developed a high throughput infrared spectrometer for zodiacal light fraunhofer lines measurements. The instrument is based on a cryogenic dual silicon Fabry-Perot etalon which is designed to achieve high signal to noise Fraunhofer line profile measurements. Very large aperture silicon Fabry-Perot etalons and fast camera optics make these measurements possible. The results of the absorption line profile measurements will provide a model free measure of the zodiacal Light intensity in the near infrared. The knowledge of the zodiacal light brightness is crucial for accurate subtraction of zodiacal light foreground for accurate measure of the extragalactic background light after the subtraction of zodiacal light foreground. We present the final design of the instrument and the first results of its performance.

  10. H I, CO, and Planck/IRAS dust properties in the high latitude cloud complex, MBM 53, 54, 55 and HLCG 92 – 35. Possible evidence for an optically thick H I envelope around the CO clouds

    SciT

    Fukui, Yasuo; Okamoto, Ryuji; Kaji, Ryohei

    We present an analysis of the H I and CO gas in conjunction with the Planck/IRAS submillimeter/far-infrared dust properties toward the most outstanding high latitude clouds MBM 53, 54, 55 and HLCG 92 – 35 at b = –30° to – 45°. The CO emission, dust opacity at 353 GHz (τ{sub 353}), and dust temperature (T {sub d}) show generally good spatial correspondence. On the other hand, the correspondence between the H I emission and the dust properties is less clear than in CO. The integrated H I intensity W{sub H} {sub I} and τ{sub 353} show a large scattermore » with a correlation coefficient of ∼0.6 for a T {sub d} range from 16 K to 22 K. We find, however, that W{sub H} {sub I} and τ{sub 353} show better correlation for smaller ranges of T {sub d} every 0.5 K, generally with a correlation coefficient of 0.7-0.9. We set up a hypothesis that the H I gas associated with the highest T {sub d} ≥ 21.5 K is optically thin, whereas the H I emission is generally optically thick for T {sub d} lower than 21.5 K. We have determined a relationship for the optically thin H I gas between atomic hydrogen column density and τ{sub 353}, N{sub H} {sub I} (cm{sup −2})=(1.5×10{sup 26})⋅τ{sub 353}, under the assumption that the dust properties are uniform and we have applied this to estimate N{sub H} {sub I} from τ{sub 353} for the whole cloud. N{sub H} {sub I} was then used to solve for T {sub s} and τ{sub H} {sub I} over the region. The result shows that the H I is dominated by optically thick gas having a low spin temperature of 20-40 K and a density of 40-160 cm{sup –3}. The H I envelope has a total mass of ∼1.2 × 10{sup 4} M {sub ☉}, an order of magnitude larger than that of the CO clouds. The H I envelope properties derived by this method do not rule out a mixture of H I and H{sub 2} in the dark gas, but we present indirect evidence that most of the gas mass is in the atomic state.« less

  11. Dust in brown dwarfs and extra-solar planets. I. Chemical composition and spectral appearance of quasi-static cloud layers

    NASA Astrophysics Data System (ADS)

    Helling, Ch.; Woitke, P.; Thi, W.-F.

    2008-07-01

    Aims: Brown dwarfs are covered by dust cloud layers which cause inhomogeneous surface features and move below the observable τ = 1 level during the object's evolution. The cloud layers have a strong influence on the structure and spectral appearance of brown dwarfs and extra-solar planets, e.g. by providing high local opacities and by removing condensable elements from the atmosphere causing a sub-solar metalicity in the atmosphere. We aim at understanding the formation of cloud layers in quasi-static substellar atmospheres that consist of dirty grains composed of numerous small islands of different solid condensates. Methods: The time-dependent description is a kinetic model describing nucleation, growth and evaporation. It is extended to treat gravitational settling and is applied to the static-stationary case of substellar model atmospheres. From the solution of the dust moments, we determine the grain size distribution function approximately which, together with the calculated material volume fractions, provides the basis for applying effective medium theory and Mie theory to calculate the opacities of the composite dust grains. Results: The cloud particles in brown dwarfs and hot giant-gas planets are found to be small in the high atmospheric layers (a ≈ 0.01 μm), and are composed of a rich mixture of all considered condensates, in particular MgSiO3[s], Mg2SiO4[s] and SiO2[s]. As the particles settle downward, they increase in size and reach several 100 μm in the deepest layers. The more volatile parts of the grains evaporate and the particles stepwise purify to form composite particles of high-temperature condensates in the deeper layers, mainly made of Fe[s] and Al2O3[s]. The gas phase abundances of the elements involved in the dust formation process vary by orders of magnitudes throughout the atmosphere. The grain size distribution is found to be relatively broad in the upper atmospheric layers but strongly peaked in the deeper layers. This reflects

  12. Prehistory of Zodiac Dating: Three Strata of Upper Paleolithic Constellations

    NASA Astrophysics Data System (ADS)

    Gurshtein, Alex A.

    A pattern of archaic proto-constellations is extracted from Aratus' "The Phaenomena" didactic poem list according to a size criterion elaborated earlier, and their symbolism is analyzed. As a result of this approach three celestial symbolical strata are discovered to be probably a reflection of the symbols for the Lower, the Middle and the Upper Worlds; the Under-World creatures have a water character, the Middle World ones are mostly anthropomorphic and flying beings are for the Upper World. The strata excerpted from Aratus' sky seems to be in agreement with the well-known Babylonian division into three god pathways for Ea (Enki), Anu and Enlil. There is a possibility of dating the pattern discovered because of precession's strong influence as far back as 16 thousand years, the result being supported by the comparison of different star group mean sizes. The archaic constellation pattern under consideration is a reasonable background of symbolical meanings for the first Zodiacal generation quartet (7.5 thousand years old) examined by the author previously. The enormous size of the Argo constellation (Ship of Argo and his Argonauts) as well as the large sizes of other southern constellations are explained as due to the existence of an accumulation zone near the South celestial pole. Some extra correlations between the reconstruction proposed and cultural data available are discussed. The paper is the second part of the investigation "On the Origin of the Zodiacal constellations" published in Vistas in Astronomy, vol.36, pp.171-190, 1993.

  13. Relations Between Cloud Condensation Nuclei And Aerosol Optical Properties Relevant to Remote Sensing: Airborne Measurements in Biomass Burning, Pollution and Dust Aerosol Over North America

    NASA Astrophysics Data System (ADS)

    Shinozuka, Y.; Clarke, A.; Howell, S.; Kapustin, V.; McNaughton, C.; Zhou, J.; Decarlo, P.; Jimenez, J.; Roberts, G.; Tomlinson, J.; Collins, D.

    2008-12-01

    Remote sensing of the concentration of cloud condensation nuclei (CCN) would help investigate the indirect effect of tropospheric aerosols on clouds and climate. In order to assess its feasibility, this paper evaluates the spectral-based retrieval technique for aerosol number and seeks one for aerosol solubility, using in-situ aircraft measurements of aerosol size distribution, chemical composition, hygroscopicity, CCN activity and optical properties. Our statistical analysis reveals that the CCN concentration over Mexico can be optically determined to a relative error of <20%, smaller than that for the mainland US and the surrounding oceans (~a factor of 2). Mexico's advantage is four-fold. Firstly, many particles originating from the lightly regulated industrial combustion and biomass burning are large enough to significantly affect light extinction, elevating the correlation between extinction and CCN number in absence of substantial dust. Secondly, the generally low ambient humidity near the major aerosol sources limits the error in the estimated response of particle extinction to humidity changes. Thirdly, because many CCN contain black carbon, light absorption also provides a measure of the CCN concentration. Fourthly, the organic fraction of volatile mass of submicron particles (OMF) is anti-correlated with the wavelength dependence of extinction due to preferential anion uptake by coarse dust, which provides a potential tool for remote-sensing OMF and the particle solubility.

  14. Experimental investigations of the minimum ignition energy and the minimum ignition temperature of inert and combustible dust cloud mixtures.

    PubMed

    Addai, Emmanuel Kwasi; Gabel, Dieter; Krause, Ulrich

    2016-04-15

    The risks associated with dust explosions still exist in industries that either process or handle combustible dust. This explosion risk could be prevented or mitigated by applying the principle of inherent safety (moderation). This is achieved by adding an inert material to a highly combustible material in order to decrease the ignition sensitivity of the combustible dust. The presented paper deals with the experimental investigation of the influence of adding an inert dust on the minimum ignition energy and the minimum ignition temperature of the combustible/inert dust mixtures. The experimental investigation was done in two laboratory scale equipment: the Hartmann apparatus and the Godbert-Greenwald furnace for the minimum ignition energy and the minimum ignition temperature test respectively. This was achieved by mixing various amounts of three inert materials (magnesium oxide, ammonium sulphate and sand) and six combustible dusts (brown coal, lycopodium, toner, niacin, corn starch and high density polyethylene). Generally, increasing the inert materials concentration increases the minimum ignition energy as well as the minimum ignition temperatures until a threshold is reached where no ignition was obtained. The permissible range for the inert mixture to minimize the ignition risk lies between 60 to 80%. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Planck intermediate results: XXIX. All-sky dust modelling with Planck, IRAS, and WISE observations

    DOE PAGES

    Ade, P. A. R.; Aghanim, N.; Alves, M. I. R.; ...

    2016-02-09

    In this paper, we present all-sky modelling of the high resolution Planck, IRAS, and WISE infrared (IR) observations using the physical dust model presented by Draine & Li in 2007 (DL, ApJ, 657, 810). We study the performance and results of this model, and discuss implications for future dust modelling. The present work extends the DL dust modelling carried out on nearby galaxies using Herschel and Spitzer data to Galactic dust emission. We employ the DL dust model to generate maps of the dust mass surface density Σ Md, the dust optical extinction A V, and the starlight intensity heatingmore » the bulk of the dust, parametrized by U min. The DL model reproduces the observed spectral energy distribution (SED) satisfactorily over most of the sky, with small deviations in the inner Galactic disk and in low ecliptic latitude areas, presumably due to zodiacal light contamination. In the Andromeda galaxy (M31), the present dust mass estimates agree remarkably well (within 10%) with DL estimates based on independent Spitzer and Herschel data. We compare the DL optical extinction A V for the diffuse interstellar medium (ISM) with optical estimates for approximately 2 × 10 5 quasi-stellar objects (QSOs) observed inthe Sloan Digital Sky Survey (SDSS). The DL A V estimates are larger than those determined towards QSOs by a factor of about 2, which depends on U min. The DL fitting parameter U min, effectively determined by the wavelength where the SED peaks, appears to trace variations in the far-IR opacity of the dust grains per unit A V, and not only in the starlight intensity. These results show that some of the physical assumptions of the DL model will need to be revised. To circumvent the model deficiency, we propose an empirical renormalization of the DL A V estimate, dependent of U min, which compensates for the systematic differences found with QSO observations. This renormalization, made to match the A V estimates towards QSOs, also brings into agreement the DL A

  16. Zodiacal light and the asteroid belt - The view from Pioneer 10

    NASA Technical Reports Server (NTRS)

    Hanner, M. S.; Weinberg, J. L.; Deshields, L. M., II; Green, B. A.; Toller, G. N.

    1974-01-01

    Brightnesses measured by the Pioneer 10 imaging photopolarimeter in two regions of sky were compared on sky maps at sun-spacecraft distances from 2.4 to 4.8 AU to determine the spatial extent of the zodiacal light. Data in the ecliptic at elongations greater than 90 deg show negligible contribution to the zodiacal light beyond 3.3 AU, the 2:1 Jupiter resonance. The zodiacal light brightness at 2.4 AU is less than 10% of that observed at 1 AU.

  17. The Lunar Dust Environment

    NASA Astrophysics Data System (ADS)

    Szalay, Jamey Robert

    Planetary bodies throughout the solar system are continually bombarded by dust particles, largely originating from cometary activities and asteroidal collisions. Surfaces of bodies with thick atmospheres, such as Venus, Earth, Mars and Titan are mostly protected from incoming dust impacts as these particles ablate in their atmospheres as 'shooting stars'. However, the majority of bodies in the solar system have no appreciable atmosphere and their surfaces are directly exposed to the flux of high speed dust grains. Impacts onto solid surfaces in space generate charged and neutral gas clouds, as well as solid secondary ejecta dust particles. Gravitationally bound ejecta clouds forming dust exospheres were recognized by in situ dust instruments around the icy moons of Jupiter and Saturn, and had not yet been observed near bodies with refractory regolith surfaces before NASA's Lunar Dust and Environment Explorer (LADEE) mission. In this thesis, we first present the measurements taken by the Lunar Dust Explorer (LDEX), aboard LADEE, which discovered a permanently present, asymmetric dust cloud surrounding the Moon. The global characteristics of the lunar dust cloud are discussed as a function of a variety of variables such as altitude, solar longitude, local time, and lunar phase. These results are compared with models for lunar dust cloud generation. Second, we present an analysis of the groupings of impacts measured by LDEX, which represent detections of dense ejecta plumes above the lunar surface. These measurements are put in the context of understanding the response of the lunar surface to meteoroid bombardment and how to use other airless bodies in the solar system as detectors for their local meteoroid environment. Third, we present the first in-situ dust measurements taken over the lunar sunrise terminator. Having found no excess of small grains in this region, we discuss its implications for the putative population of electrostatically lofted dust.

  18. R associations. VI - The reddening law in dust clouds and the nature of early-type emission stars in nebulosity from a study of five associations

    NASA Technical Reports Server (NTRS)

    Herbst, W.; Warner, J. W.; Miller, D. P.; Herzog, A.

    1982-01-01

    Positions, identification charts, UBVRIKLMN photometry and spectral types are given for stars, illuminating reflection nebulae that are visible on the POSS prints, which have been identified in five associations. With a ratio of total to selective extinction of 4.2, the reddening law applicable to the dust clouds in which the stars are embedded is steeper than normal. The five associations exhibit 18 early-type stars with circumstellar shells, of which those with spectral types earlier than B5 characteristically have weak IR excesses, in contrast to the strong excesses indicative of circumstellar dust, of later-type stars. Color-magnitude charts show a distribution lying above the ZAMS by up to about 2 mag for both the circumstellar shell stars and those classified as rapid rotators. It is suggested that (1) rapid rotation accounts for the scatter in the color-magnitude diagram, and (2) many of the nebulous early-type emission-line stars are rapid rotators rather than pre-main sequence objects.

  19. Cauchy horizon stability in a collapsing spherical dust cloud: II. Energy bounds for test fields and odd-parity gravitational perturbations

    NASA Astrophysics Data System (ADS)

    Ortiz, Néstor; Sarbach, Olivier

    2018-01-01

    We analyze the stability of the Cauchy horizon associated with a globally naked, shell-focussing singularity arising from the complete gravitational collapse of a spherical dust cloud. In a previous work, we have studied the dynamics of spherical test scalar fields on such a background. In particular, we proved that such fields cannot develop any divergences which propagate along the Cauchy horizon. In the present work, we extend our analysis to the more general case of test fields without symmetries and to linearized gravitational perturbations with odd parity. To this purpose, we first consider test fields possessing a divergence-free stress-energy tensor satisfying the dominant energy condition, and we prove that a suitable energy norm is uniformly bounded in the domain of dependence of the initial slice. In particular, this result implies that free-falling observers co-moving with the dust particles measure a finite energy of the field, even as they cross the Cauchy horizon at points lying arbitrarily close to the central singularity. Next, for the case of Klein–Gordon fields, we derive point-wise bounds from our energy estimates which imply that the scalar field cannot diverge at the Cauchy horizon, except possibly at the central singular point. Finally, we analyze the behaviour of odd-parity, linear gravitational and dust perturbations of the collapsing spacetime. Similarly to the scalar field case, we prove that the relevant gauge-invariant combinations of the metric perturbations stay bounded away from the central singularity, implying that no divergences can propagate in the vacuum region. Our results are in accordance with previous numerical studies and analytic work in the self-similar case.

  20. Mathematical modeling of velocity and number density profiles of particles across the flame propagation through a micro-iron dust cloud.

    PubMed

    Bidabadi, Mehdi; Haghiri, Ali; Rahbari, Alireza

    2010-04-15

    In this study, an attempt has been made to analytically investigate the concentration and velocity profiles of particles across flame propagation through a micro-iron dust cloud. In the first step, Lagrangian particle equation of motion during upward flame propagation in a vertical duct is employed and then forces acting upon the particle, such as thermophoretic force (resulted from the temperature gradient), gravitation and buoyancy are introduced; and consequently, the velocity profile as a function of the distance from the leading edge of the combustion zone is extracted. In the resumption, a control volume above the leading edge of the combustion zone is considered and the change in the particle number density in this control volume is obtained via the balance of particle mass fluxes passing through it. This study explains that the particle concentration at the leading edge of the combustion zone is more than the particle agglomeration in a distance far from the flame front. This increase in the particle aggregation above the combustion zone has a remarkable effect on the lower flammability limits of combustible particle cloud. It is worth noticing that the velocity and particle concentration profiles show a reasonable compatibility with the experimental data. 2009 Elsevier B.V. All rights reserved.

  1. Size Dependence of Dust Distribution around the Earth Orbit

    NASA Astrophysics Data System (ADS)

    Ueda, Takahiro; Kobayashi, Hiroshi; Takeuchi, Taku; Ishihara, Daisuke; Kondo, Toru; Kaneda, Hidehiro

    2017-05-01

    In the solar system, interplanetary dust particles (IDPs) originating mainly from asteroid collisions and cometary activities drift to Earth orbit due to Poynting-Robertson drag. We analyzed the thermal emission from IDPs that was observed by the first Japanese infrared astronomical satellite, AKARI. The observed surface brightness in the trailing direction of the Earth orbit is 3.7% greater than that in the leading direction in the 9 μm band and 3.0% in the 18 μm band. In order to reveal dust properties causing leading-trailing surface brightness asymmetry, we numerically integrated orbits of the Sun, the Earth, and a dust particle as a restricted three-body problem including radiation from the Sun. The initial orbits of particles are determined according to the orbits of main-belt asteroids or Jupiter-family comets. Orbital trapping in mean motion resonances results in a significant leading-trailing asymmetry so that intermediate sized dust (˜10-100 μm) produces a greater asymmetry than zodiacal light. The leading-trailing surface brightness difference integrated over the size distribution of the asteroidal dust is obtained to be 27.7% and 25.3% in the 9 μm and 18 μm bands, respectively. In contrast, the brightness difference for cometary dust is calculated as 3.6% and 3.1% in the 9 μm and 18 μm bands, respectively, if the maximum dust radius is set to be s max = 3000 μm. Taking into account these values and their errors, we conclude that the contribution of asteroidal dust to the zodiacal infrared emission is less than ˜10%, while cometary dust of the order of 1 mm mainly accounts for the zodiacal light in infrared.

  2. Size Dependence of Dust Distribution around the Earth Orbit

    SciT

    Ueda, Takahiro; Takeuchi, Taku; Kobayashi, Hiroshi

    In the solar system, interplanetary dust particles (IDPs) originating mainly from asteroid collisions and cometary activities drift to Earth orbit due to Poynting–Robertson drag. We analyzed the thermal emission from IDPs that was observed by the first Japanese infrared astronomical satellite, AKARI . The observed surface brightness in the trailing direction of the Earth orbit is 3.7% greater than that in the leading direction in the 9 μ m band and 3.0% in the 18 μ m band. In order to reveal dust properties causing leading–trailing surface brightness asymmetry, we numerically integrated orbits of the Sun, the Earth, and amore » dust particle as a restricted three-body problem including radiation from the Sun. The initial orbits of particles are determined according to the orbits of main-belt asteroids or Jupiter-family comets. Orbital trapping in mean motion resonances results in a significant leading–trailing asymmetry so that intermediate sized dust (∼10–100 μ m) produces a greater asymmetry than zodiacal light. The leading–trailing surface brightness difference integrated over the size distribution of the asteroidal dust is obtained to be 27.7% and 25.3% in the 9 μ m and 18 μ m bands, respectively. In contrast, the brightness difference for cometary dust is calculated as 3.6% and 3.1% in the 9 μ m and 18 μ m bands, respectively, if the maximum dust radius is set to be s {sub max} = 3000 μ m. Taking into account these values and their errors, we conclude that the contribution of asteroidal dust to the zodiacal infrared emission is less than ∼10%, while cometary dust of the order of 1 mm mainly accounts for the zodiacal light in infrared.« less

  3. Interstellar and Cometary Dust

    NASA Technical Reports Server (NTRS)

    Mathis, John S.

    1997-01-01

    'Interstellar dust' forms a continuum of materials with differing properties which I divide into three classes on the basis of observations: (a) diffuse dust, in the low-density interstellar medium; (b) outer-cloud dust, observed in stars close enough to the outer edges of molecular clouds to be observed in the optical and ultraviolet regions of the spectrum, and (c) inner-cloud dust, deep within the cores of molecular clouds, and observed only in the infrared by means of absorption bands of C-H, C=O, 0-H, C(triple bond)N, etc. There is a surprising regularity of the extinction laws between diffuse- and outer-cloud dust. The entire mean extinction law from infrared through the observable ultraviolet spectrum can be characterized by a single parameter. There are real deviations from this mean law, larger than observational uncertainties, but they are much smaller than differences of the mean laws in diffuse- and outer-cloud dust. This fact shows that there are processes which operate over the entire distribution of grain sizes, and which change size distributions extremely efficiently. There is no evidence for mantles on grains in local diffuse and outer-cloud dust. The only published spectra of the star VI Cyg 12, the best candidate for showing mantles, does not show the 3.4 micro-m band which appreciable mantles would produce. Grains are larger in outer-cloud dust than diffuse dust because of coagulation, not accretion of extensive mantles. Core-mantle grains favored by J. M. Greenberg and collaborators, and composite grains of Mathis and Whiffen (1989), are discussed more extensively (naturally, I prefer the latter). The composite grains are fluffy and consist of silicates, amorphous carbon, and some graphite in the same grain. Grains deep within molecular clouds but before any processing within the solar system are presumably formed from the accretion of icy mantles on and within the coagulated outer-cloud grains. They should contain a mineral

  4. Velocity Distributions of Interplanetary Dust Derived from Astronomical Sky Spectra

    NASA Astrophysics Data System (ADS)

    Huestis, D. L.; Ali, S.; Cosby, P. C.; Slanger, T. G.

    2001-11-01

    Characterization of interplanetary dust is important for understanding the creation by accretion of planets and moons, the development of planetary atmospheres, and, potentially, for the initiation of prebiotic chemistry. The recent COBE mission has provided a profile in ecliptic coordinates of the distribution of interplanetary dust particles through their thermal infrared emission. Additional information about interplanetary dust can be extracted from its visible spectrum of scattered sunlight, called Zodiacal Light. Night sky spectra taken at large-aperture telescopes using high-resolution echelle spectrographs reveal Fraunhofer absorption features in the Zodiacal Light spectrum of scattered sunlight, a nuisance in subtraction from the spectrum of the extraterrestrial object under investigation. We are analyzing the intensity modulations and Doppler shifts of solar Fraunhofer absorption lines in the Zodiacal Light component of sky spectra, donated by collaborating astronomers using Keck/HIRES and other high-performance astronomical facilities. Our objectives include velocity distributions of interplanetary dust and improved separation of terrestrial and extraterrestrial sources in sky spectra. Participation of S. Ali was made possible by a grant from the NSF Physics Research Experiences for Undergraduates (REU) program.

  5. The Dust-to-Gas Ratio in the Damped Ly alpha Clouds Towards the Gravitationally Lensed QSO 0957+561

    NASA Technical Reports Server (NTRS)

    Zuo, Lin; Beaver, E. A.; Burbidge, E. Margaret; Cohen, Ross D.; Junkkarinen, Vesa T.; Lyons, R. W.

    1997-01-01

    We present HST/FOS spectra of the two bright images (A and B) of the gravitationally lensed QSO 0957+561 in the wavelength range 2200-3300 A. We find that the absorption system (Z(sub abs)) = 1.3911) near z(sub em) is a weak, damped Ly alpha system with strong Ly alpha absorption lines seen in both images. However, the H(I) column densities are different, with the line of sight to image A intersecting a larger column density. The continuum shapes of the two spectra differ in the sense that the flux level of image A increases more slowly toward shorter wavelengths than that of image B. We explain this as the result of differential reddening by dust grains in the damped Ly alpha absorber. A direct outcome of this explanation is a determination of the dust-to-gas ratio, k, in the damped Ly alpha system. We derive k = 0.55 + 0.18 for a simple 1/lambda extinction law and k = 0.31 + 0.10 for the Galactic extinction curve. For gravitationally lensed systems with damped Ly alpha absorbers, our method is a powerful tool for determining the values and dispersion of k, and the shapes of extinction curves, especially in the FUV and EUV regions. We compare our results with previous work.

  6. Global dust cycle

    NASA Astrophysics Data System (ADS)

    Ridgwell, Andy

    Dust, micron to submicron particles and mostly comprising soil mineral fragments, affects a multitude of climatic and biogeochemical processes during its journey from its sources on land to sinks on land and in the ocean. Suspended in the atmosphere, the presence of dust can alter both shortwave and longwave radiation balances, enhance cloud nucleation, and affect photochemical reaction rates. Deposited to the land surface, dust has beneficial impacts on soil quality but detrimental implications for human health. At the interface of surface ocean and lower atmosphere, dust deposited to seawater supplies plankton with the essential micronutrient iron and hence provides an important control on marine ecosystems. This chapter reviews these various roles of dust in the Earth system; summarizes the factors controlling the production, transport, and deposition of dust; and, because the causes and consequences of dust are interlinked via climate and atmospheric CO2, discusses the potential importance of dusty feedback in past and future climate change.

  7. Dust in the Solar System - Properties and Origins

    NASA Technical Reports Server (NTRS)

    Messenger, Scott; Keller, Lindsay; Nakamura-Messenger, Keiko

    2013-01-01

    Interplanetary dust pervades the inner Solar System, giving rise to a prominent glow above the horizon at sunrise and sunset known as the zodiacal light. This dust derives from the disintegration of comets as they approach the Sun and from collisions among main-belt asteroids. The Earth accretes roughly 4x10(exp 6) kg/year of 1 - 1,000 micron dust particles as they spiral into the Sun under the influence of Poynting-Robertson drag and solar wind drag. Samples of these grains have been collected from deep sea sediments, Antarctic ice and by high-altitude aircraft and balloon flights. Interplanetary dust particles (IDPs) collected in the stratosphere have been classified by their IR spectra into olivine, pyroxene, and hydrated silicate-dominated classes. Most IDPs have bulk major and minor element abundances that are similar to carbonaceous chondrite meteorites. Hydrated silicate-rich IDPs are thought to derive from asteroids based on their mineralogy and low atmospheric entry velocities estimated from peak temperatures reached during atmospheric entry. Anhydrous IDPs are typically aggregates of 0.1 - approx. 1 micron Mg-rich olivine and pyroxene, amorphous silicates (GEMS), Fe, Nisulfides and rare spinel and oxides bound together by carbonaceous material. These IDPs are often argued to derive from comets based on compositional similarities and high atmospheric entry velocities that imply high eccentricity orbits. Infrared spectra obtained from anhydrous IDPs closely match remote IR spectra obtained from comets. The most primitive (anhydrous) IDPs appear to have escaped the parent-body thermal and aqueous alteration that has affected meteorites. These samples thus consist entirely of grains that formed in the ancient solar nebula and pre-solar interstellar and circumstellar environments. Isotopic studies of IDPs have identified silicate stardust grains that formed in the outflows of red giant and asymptotic giant branch stars and supernovae]. These stardust grains

  8. Voyages of the Zodiac, an Impenitent Traveller across Lands and Ages

    NASA Astrophysics Data System (ADS)

    Belmonte, Juan Antonio

    2015-05-01

    The zodiac is one of humankind's oldest astronomical heritages. Indeed, it has a long history and had an impressive cultural influence in the past that could be traced from the steppes of Mesopotamia to the wilderness of the Roman frontiers in Great Britain. In the present essay, we will discuss the origin of the zodiacal constellations in ancient Mesopotamia from their possible prehistoric ancestors in the pre-ceramic context of the 10,000-year-old site of Göbleki Tepe. Later on, we will discuss the role that the zodiac played in the development of the new cult established by King Antiochos I of Commagene in his hierothesion at Nemrud Dag, where a planetary conjunction in Leo has played a role in the clues to understand the enigmas of such an impressive monument. This will be followed by the analysis of its southwards travel to the Valley of the Nile, where we will study the famous Zodiac of Dendera. Then we will travel westwards to discuss the astronomical aspects of a new religion where astronomical eras and the zodiac ought to play a most relevant role, Mithraism. Finally, new ideas for future research in this most interesting topic will briefly be sketched.

  9. A CMB foreground study in WMAP data: Extragalactic point sources and zodiacal light emission

    NASA Astrophysics Data System (ADS)

    Chen, Xi

    , separately, in comparison to t 0.40 from the WMAP catalogs. Our source catalogs are a good supplement to the existing WMAP source catalogs, and the method itself is proven to be both complementary to and competitive with all the current source finding techniques in WMAP maps. Scattered light and thermal emission from the interplanetary dust (IPD) within our Solar System are major contributors to the diffuse sky brightness at most infrared wavelengths. For wavelengths longer than 3.5 mm, the thermal emission of the IPD dominates over scattering, and the emission is often referred to as the Zodiacal Light Emission (ZLE). To set a limit of ZLE contribution to the WMAP data, we have performed a simultaneous fit of the yearly WMAP time-ordered data to the time variation of ZLE predicted by the DIRBE IPD model (Kelsallet al. 1998) evaluated at 240 mm, plus [cursive l] = 1 - 4 CMB components. It is found that although this fitting procedure can successfully recover the CMB dipole to a 0.5% accuracy, it is not sensitive enough to determine the ZLE signal nor the other multipole moments very accurately.

  10. FAR-ULTRAVIOLET DUST ALBEDO MEASUREMENTS IN THE UPPER SCORPIUS CLOUD USING THE SPINR SOUNDING ROCKET EXPERIMENT

    SciT

    Lewis, N. K.; Cook, T. A.; Wilton, K. P.

    2009-11-20

    The Spectrograph for Photometric Imaging with Numeric Reconstruction sounding rocket experiment was launched on 2000 August 4 to record far-ultraviolet (912-1450 A) spectral and spatial information for the giant reflection nebula in the Upper Scorpius region. The data were divided into three arbitrary bandpasses (912-1029 A, 1030-1200 A, and 1235-1450 A) for which stellar and nebular flux levels were derived. These flux measurements were used to constrain a radiative transfer model and to determine the dust albedo for the Upper Scorpius region. The resulting albedos were 0.28 +- 0.07 for the 912-1029 A bandpass, 0.33 +- 0.07 for the 1030-1200more » A bandpass, and 0.77 +- 0.13 for the 1235-1450 A bandpass.« less

  11. CHANGE OF MAGNETIC FIELD-GAS ALIGNMENT AT THE GRAVITY-DRIVEN ALFVÉNIC TRANSITION IN MOLECULAR CLOUDS: IMPLICATIONS FOR DUST POLARIZATION OBSERVATIONS

    SciT

    Chen, Che-Yu; King, Patrick K.; Li, Zhi-Yun

    Diffuse striations in molecular clouds are preferentially aligned with local magnetic fields, whereas dense filaments tend to be perpendicular to them. When and why this transition occurs remain uncertain. To explore the physics behind this transition, we compute the histogram of relative orientation (HRO) between the density gradient and the magnetic field in three-dimensional magnetohydrodynamic (MHD) simulations of prestellar core formation in shock-compressed regions within giant molecular clouds. We find that, in the magnetically dominated (sub-Alfvénic) post-shock region, the gas structure is preferentially aligned with the local magnetic field. For overdense sub-regions with super-Alfvénic gas, their elongation becomes preferentially perpendicularmore » to the local magnetic field. The transition occurs when self-gravitating gas gains enough kinetic energy from the gravitational acceleration to overcome the magnetic support against the cross-field contraction, which results in a power-law increase of the field strength with density. Similar results can be drawn from HROs in projected two-dimensional maps with integrated column densities and synthetic polarized dust emission. We quantitatively analyze our simulated polarization properties, and interpret the reduced polarization fraction at high column densities as the result of increased distortion of magnetic field directions in trans- or super-Alfvénic gas. Furthermore, we introduce measures of the inclination and tangledness of the magnetic field along the line of sight as the controlling factors of the polarization fraction. Observations of the polarization fraction and angle dispersion can therefore be utilized in studying local magnetic field morphology in star-forming regions.« less

  12. Dust devils on Mars

    NASA Astrophysics Data System (ADS)

    Thomas, P.; Gierasch, P. J.

    1985-10-01

    Viking Orbiter photographic imagery has confirmed the occurrence of dust devils on Mars. The images were of small bright clouds with long, tapered shadows viewed from a nearly-nadir angle. Spectra of the features were consistent with dust and not condensates. A maximum height of 6.8 km and width of 1 km were measured. The dust devils appeared on smooth planes, and had average dimensions of 2 km height and 200 m diam, carrying 3000 kg of dust. The data may be of use in interpreting convective processes on earth.

  13. Spitzer SAGE-Spec: Near infrared spectroscopy, dust shells, and cool envelopes in extreme Large Magellanic Cloud asymptotic giant branch stars

    SciT

    Blum, R. D.; Srinivasan, S.; Kemper, F.

    2014-11-01

    K-band spectra are presented for a sample of 39 Spitzer Infrared Spectrograph (IRS) SAGE-Spec sources in the Large Magellanic Cloud. The spectra exhibit characteristics in very good agreement with their positions in the near-infrared—Spitzer color-magnitude diagrams and their properties as deduced from the Spitzer IRS spectra. Specifically, the near-infrared spectra show strong atomic and molecular features representative of oxygen-rich and carbon-rich asymptotic giant branch stars, respectively. A small subset of stars was chosen from the luminous and red extreme ''tip'' of the color-magnitude diagram. These objects have properties consistent with dusty envelopes but also cool, carbon-rich ''stellar'' cores. Modest amountsmore » of dust mass loss combine with the stellar spectral energy distribution to make these objects appear extreme in their near-infrared and mid-infrared colors. One object in our sample, HV 915, a known post-asymptotic giant branch star of the RV Tau type, exhibits CO 2.3 μm band head emission consistent with previous work that demonstrates that the object has a circumstellar disk.« less

  14. Interstellar Gas-phase Element Depletions in the Small Magellanic Cloud: A Guide to Correcting for Dust in QSO Absorption Line Systems

    SciT

    Jenkins, Edward B.; Wallerstein, George, E-mail: ebj@astro.princeton.edu, E-mail: walleg@u.washington.edu

    We present data on the gas-phase abundances for 9 different elements in the interstellar medium of the Small Magellanic Cloud (SMC), based on the strengths of ultraviolet absorption features over relevant velocities in the spectra of 18 stars within the SMC. From this information and the total abundances defined by the element fractions in young stars in the SMC, we construct a general interpretation on how these elements condense into solid form onto dust grains. As a group, the elements Si, S, Cr, Fe, Ni, and Zn exhibit depletion sequences similar to those in the local part of our Galaxymore » defined by Jenkins. The elements Mg and Ti deplete less rapidly in the SMC than in the Milky Way, and Mn depletes more rapidly. We speculate that these differences might be explained by the different chemical affinities to different existing grain substrates. For instance, there is evidence that the mass fractions of polycyclic aromatic hydrocarbons in the SMC are significantly lower than those in the Milky Way. We propose that the depletion sequences that we observed for the SMC may provide a better model for interpreting the element abundances in low-metallicity Damped Lyman Alpha (DLA) and sub-DLA absorption systems that are recorded in the spectra of distant quasars and gamma-ray burst afterglows.« less

  15. The influence of the Chinese zodiac on fertility in Hong Kong SAR.

    PubMed

    Yip, Paul S F; Lee, Joseph; Cheung, Y B

    2002-11-01

    The annual total of births in Hong Kong SAR fell substantially in the past 20 years; hence the total fertility rate (TFR) followed the downward trend and dropped to a low of 0.9 below replacement level in 2000. Despite the long-term downward trend, short-run increases in the annual total of births and the TFR were exhibited. Such temporary fertility increases are identified in the Dragon Years of 1988 and 2000. The phenomenon of fertility changes associated with zodiacal animal years is examined in this paper with a view to gaining some insight into whether Chinese cultural preferences and folklore beliefs might have influenced prospective parents' reproductive behaviour. The paper explains the underlying philosophy of the Chinese astrological tradition and discusses how zodiacal preferences affect fertility between 1976 and 2000. The paper also explores why zodiacal influences on Chinese fertility before 1976 did not exist. It is unquestionable that the Dragon Year preference exerts an influence on fertility of modern Chinese populations through zodiacal birth-timing motivations. Birth rate rise in the Dragon Year is due to changes in timing of births that will have little effect on cumulative fertility.

  16. Skylab experiment SO73: Gegenschein/zodiacal light. [electrophotometry of surface brightness and polarization

    NASA Technical Reports Server (NTRS)

    Weinberg, J. L.

    1976-01-01

    A 10 color photoelectric polarimeter was used to measure the surface brightness and polarization associated with zodiacal light, background starlight, and spacecraft corona during each of the Skylab missions. Fixed position and sky scanning observations were obtained during Skylab missions SL-2 and SL-3 at 10 wavelenghts between 4000A and 8200A. Initial results from the fixed-position data are presented on the spacecraft corona and on the polarized brightness of the zodiacal light. Included among the fixed position regions that were observed are the north celestial pole, south ecliptic pole, two regions near the north galactic pole, and 90 deg from the sun in the ecliptic. The polarized brightness of the zodiacal light was found to have the color of the sun at each of these positions. Because previous observations found the total brightness to have the color of the sun from the near ultraviolet out to 2.4 micrometers, the degree of polarization of the zodiacal light is independent of wavelength from 4000A to 8200A.

  17. Interstellar Gas-phase Element Depletions in the Small Magellanic Cloud: A Guide to Correcting for Dust in QSO Absorption Line Systems

    NASA Astrophysics Data System (ADS)

    Jenkins, Edward B.; Wallerstein, George

    2017-04-01

    We present data on the gas-phase abundances for 9 different elements in the interstellar medium of the Small Magellanic Cloud (SMC), based on the strengths of ultraviolet absorption features over relevant velocities in the spectra of 18 stars within the SMC. From this information and the total abundances defined by the element fractions in young stars in the SMC, we construct a general interpretation on how these elements condense into solid form onto dust grains. As a group, the elements Si, S, Cr, Fe, Ni, and Zn exhibit depletion sequences similar to those in the local part of our Galaxy defined by Jenkins. The elements Mg and Ti deplete less rapidly in the SMC than in the Milky Way, and Mn depletes more rapidly. We speculate that these differences might be explained by the different chemical affinities to different existing grain substrates. For instance, there is evidence that the mass fractions of polycyclic aromatic hydrocarbons in the SMC are significantly lower than those in the Milky Way. We propose that the depletion sequences that we observed for the SMC may provide a better model for interpreting the element abundances in low-metallicity Damped Lyman Alpha (DLA) and sub-DLA absorption systems that are recorded in the spectra of distant quasars and gamma-ray burst afterglows. Based on observations with the NASA/ESA Hubble Space Telescope and additional data obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Associations of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. These observations are associated with program nr. 13778.

  18. Lidar Ratios for Dust Aerosols Derived From Retrievals of CALIPSO Visible Extinction Profiles Constrained by Optical Depths from MODIS-Aqua and CALIPSO/CloudSat Ocean Surface Reflectance Measurements

    NASA Technical Reports Server (NTRS)

    Young, Stuart A.; Josset, Damien B.; Vaughan, Mark A.

    2010-01-01

    CALIPSO's (Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations) analysis algorithms generally require the use of tabulated values of the lidar ratio in order to retrieve aerosol extinction and optical depth from measured profiles of attenuated backscatter. However, for any given time or location, the lidar ratio for a given aerosol type can differ from the tabulated value. To gain some insight as to the extent of the variability, we here calculate the lidar ratio for dust aerosols using aerosol optical depth constraints from two sources. Daytime measurements are constrained using Level 2, Collection 5, 550-nm aerosol optical depth measurements made over the ocean by the MODIS (Moderate Resolution Imaging Spectroradiometer) on board the Aqua satellite, which flies in formation with CALIPSO. We also retrieve lidar ratios from night-time profiles constrained by aerosol column optical depths obtained by analysis of CALIPSO and CloudSat backscatter signals from the ocean surface.

  19. Stellar Ontogeny: From Dust...

    ERIC Educational Resources Information Center

    MOSAIC, 1978

    1978-01-01

    Discusses the process of star formation. Infrared and radio astronomy, particularly microwave astronomy is used to provide information on different stages of stellar formation. The role of dust and gas which swirl through the interstellar regions of a galaxy and the collapse of a cloud in star formation are also presented. (HM)

  20. Cloud Interactions

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 1 July 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth.

    Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms.

    This image was acquired during mid-spring near the North Pole. The linear water-ice clouds are now regional in extent and often interact with neighboring cloud system, as seen in this image. The bottom of the image shows how the interaction can destroy the linear nature. While the surface is still visible through most of the clouds, there is evidence that dust is also starting to enter the atmosphere.

    Image information: VIS instrument. Latitude 68.4, Longitude 258.8 East (101.2 West). 38 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration

  1. Dust agglomeration

    NASA Technical Reports Server (NTRS)

    2000-01-01

    John Marshall, an investigator at Ames Research Center and a principal investigator in the microgravity fluid physics program, is studying the adhesion and cohesion of particles in order to shed light on how granular systems behave. These systems include everything from giant dust clouds that form planets to tiny compressed pellets, such as the ones you swallow as tablets. This knowledge should help us control the grains, dust, and powders that we encounter or use on a daily basis. Marshall investigated electrostatic charge in microgravity on the first and second U.S. Microgravity Laboratory shuttle missions to see how grains aggregate, or stick together. With gravity's effects eliminated on orbit, Marshall found that the grains of sand that behaved ever so freely on Earth now behaved like flour. They would just glom together in clumps and were quite difficult to disperse. That led to an understanding of the prevalence of the electrostatic forces. The granules wanted to aggregate as little chains, like little hairs, and stack end to end. Some of the chains had 20 or 30 grains. This phenomenon indicated that another force, what Marshall believes to be an electrostatic dipole, was at work.(The diagram on the right emphasizes the aggregating particles in the photo on the left, taken during the USML-2 mission in 1995.)

  2. World cup soccer players tend to be born with sun and moon in adjacent zodiacal signs

    PubMed Central

    Verhulst, J

    2000-01-01

    The ecliptic elongation of the moon with respect to the sun does not show uniform distribution on the birth dates of the 704 soccer players selected for the 1998 World Cup. However, a uniform distribution is expected on astronomical grounds. The World Cup players show a very pronounced tendency (p = 0.00001) to be born on days when the sun and moon are in adjacent zodiacal signs. Key Words: soccer; World Cup; astrology; moon PMID:11131239

  3. The Martian Dust Cycle: Observations and Modeling

    NASA Technical Reports Server (NTRS)

    Kahre, Melinda A.

    2013-01-01

    The dust cycle is critically important for Mars' current climate system. Suspended atmospheric dust affects the radiative balance of the atmosphere, and thus greatly influences the thermal and dynamical state of the atmosphere. Evidence for the presence of dust in the Martian atmosphere can be traced back to yellow clouds telescopically observed as early as the early 19th century. The Mariner 9 orbiter arrived at Mars in November of 1971 to find a planet completely enshrouded in airborne dust. Since that time, the exchange of dust between the planet's surface and atmosphere and the role of airborne dust on Mars' weather and climate has been studied using observations and numerical models. The goal of this talk is to give an overview of the observations and to discuss the successes and challenges associated with modeling the dust cycle. Dust raising events on Mars range in size from meters to hundreds of kilometers. During some years, regional storms merge to produce hemispheric or planet encircling dust clouds that obscure the surface and raise atmospheric temperatures by tens of kelvin. The interannual variability of planet encircling dust storms is poorly understood. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. A low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading are generally observed: one peak occurs before northern winter solstice and one peak occurs after northern winter solstice. Numerical modeling studies attempting to interactively simulate the Martian dust cycle with general circulation models (GCMs) include the lifting, transport, and sedimentation of radiatively active dust. Two dust lifting processes are commonly represented in

  4. Dust storm off Western Africa

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The impacts of Saharan dust storms reach far beyond Africa. Wind-swept deserts spill airborne dust particles out over the Atlantic Ocean where they can enter trade winds bound for Central and North America and the Caribbean. This Moderate Resolution Imaging Spectroradiometer (MODIS) image shows a dust storm casting an opaque cloud of cloud across the Canary Islands and the Atlantic Ocean west of Africa on June 30, 2002. In general it takes between 5 and 7 days for such an event to cross the Atlantic. The dust has been shown to introduce foreign bacteria and fungi that have damaged reef ecosystems and have even been hypothesized as a cause of increasing occurrences of respiratory complaints in places like Florida, where the amount of Saharan dust reaching the state has been increasing over the past 25 years.

  5. Microparticle impact calibration of the Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) onboard the solar power sail demonstrator IKAROS

    NASA Astrophysics Data System (ADS)

    Hirai, Takayuki; Cole, Michael J.; Fujii, Masayuki; Hasegawa, Sunao; Iwai, Takeo; Kobayashi, Masanori; Srama, Ralf; Yano, Hajime

    2014-10-01

    The Arrayed Large-Area Dust Detectors in INterplanetary space (ALADDIN) is an array of polyvinylidene fluoride (PVDF) based dust detectors aboard the solar power sail demonstrator named IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). The total sensor area of ALADDIN (0.54 m2) is the world's largest among the past PVDF-based dust detectors. IKAROS was launched in May 2010 and then ALADDIN measured cosmic dust impacts for 16 months while orbiting around between 0.7 and 1.1 AU. The main scientific objective of ALADDIN is to reveal number density of ≥10-μm-sized dust in the zodiacal cloud with much higher time-space resolution than that achieved by any past in-situ measurements. The distribution of ≥10-μm-sized dust can be also observed mainly with the light scattering by optical instruments. This paper gives the scientific objectives, the instrumental description, and the results of microparticle impact calibration of ALADDIN conducted in ground laboratories. For the calibration tests we used Van de Graaf accelerators (VdG), two-stage light gas guns (LGG), and a nano-second pulsed Nd:YAG laser (nsPL). Through these experiments, we obtained depolarization charge signal caused by hypervelocity impacts or laser irradiation using the flight spare of 20-μm-thick PVDF sensor and the electronics box of ALADDIN. In the VdG experiment we accelerated iron, carbon, and silver microparticles at 1-30 km/s, while in the LGG experiment we performed to shoot 100's-μm-sized particles of soda-lime glass and stainless steel at 3-7 km/s as single projectile. For interpolation to ≥10-μm size, we irradiated infrared laser at the energy of 15-20 mJ directly onto the PVDF sensor. From the signal analysis, we developed a calibration law for estimation of masses of impacted dust particles. The dynamic range of ALADDIN corresponds from 9×10-14 kg to 2×10-10 kg (4-56 μm in diameter at density of 2.0 g/cm3) at the expected impact velocity of 10 km/s at 1 AU

  6. Glow and Dust in Plasma Boundaries

    NASA Astrophysics Data System (ADS)

    Land, Victor; Douglass, Angela; Qiao, Ke; Zhang, Zhuanhao; Matthews, Lorin S.; Hyde, Truell

    2013-04-01

    The sheath region is probed in different complex plasma experiments using dust particles in addition to measurement of the optical emission originating from the plasma. The local maximum in optical emission coincides with the breaking of quasi-neutrality at the sheath boundary as indicated by the vertical force profile reconstructed from dust particle trajectories, as well as by the local onset of dust density waves in high density dust clouds suspended in a dielectric box.

  7. Ion- and dust-acoustic instabilities in dusty plasmas

    NASA Technical Reports Server (NTRS)

    Rosenberg, M.

    1993-01-01

    Dust ion-acoustic and dust-acoustic instabilities in dusty plasmas are investigated using a standard Vlasov approach. Possible applications of these instabilities to various cosmic environments, including protostellar clouds and planetary rings, are briefly discussed.

  8. Martian Clouds

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 28 June 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth.

    Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms.

    This image was acquired during early spring near the North Pole. The linear 'ripples' are transparent water-ice clouds. This linear form is typical for polar clouds. The black regions on the margins of this image are areas of saturation caused by the build up of scattered light from the bright polar material during the long image exposure.

    Image information: VIS instrument. Latitude 68.1, Longitude 147.9 East (212.1 West). 38 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS

  9. Coupling Mars' Dust and Water Cycles: Effects on Dust Lifting Vigor, Spatial Extent and Seasonality

    NASA Technical Reports Server (NTRS)

    Kahre, M. A.; Hollingsworth, J. L.; Haberle, R. M.; Montmessin, F.

    2012-01-01

    The dust cycle is an important component of Mars' current climate system. Airborne dust affects the radiative balance of the atmosphere, thus greatly influencing the thermal and dynamical state of the atmosphere. Dust raising events on Mars occur at spatial scales ranging from meters to planet-wide. Although the occurrence and season of large regional and global dust storms are highly variable from one year to the next, there are many features of the dust cycle that occur year after year. Generally, a low-level dust haze is maintained during northern spring and summer, while elevated levels of atmospheric dust occur during northern autumn and winter. During years without global-scale dust storms, two peaks in total dust loading were observed by MGS/TES: one peak occurred before northern winter solstice at Ls 200-240, and one peak occurred after northern winter solstice at L(sub s) 305-340. These maxima in dust loading are thought to be associated with transient eddy activity in the northern hemisphere, which has been observed to maximize pre- and post-solstice. Interactive dust cycle studies with Mars General Circulation Models (MGCMs) have included the lifting, transport, and sedimentation of radiatively active dust. Although the predicted global dust loadings from these simulations capture some aspects of the observed dust cycle, there are marked differences between the simulated and observed dust cycles. Most notably, the maximum dust loading is robustly predicted by models to occur near northern winter solstice and is due to dust lifting associated with down slope flows on the flanks of the Hellas basin. Thus far, models have had difficulty simulating the observed pre- and post- solstice peaks in dust loading. Interactive dust cycle studies typically have not included the formation of water ice clouds or their radiative effects. Water ice clouds can influence the dust cycle by scavenging dust from atmosphere and by interacting with solar and infrared radiation

  10. Cloud Front

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA02171 Cloud Front

    These clouds formed in the south polar region. The faintness of the cloud system likely indicates that these are mainly ice clouds, with relatively little dust content.

    Image information: VIS instrument. Latitude -86.7N, Longitude 212.3E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  11. Condition for dust evacuation from the first galaxies

    NASA Astrophysics Data System (ADS)

    Fukushima, Hajime; Yajima, Hidenobu; Omukai, Kazuyuki

    2018-06-01

    Dust enables low-mass stars to form from low-metallicity gas by inducing fragmentation of clouds via cooling by thermal emission. Dust may, however, be evacuated from star-forming clouds due to the radiation force from massive stars. We study here the condition for dust evacuation by comparing the dust evacuation time with the time of cloud destruction due to either expansion of H II regions or supernovae. The cloud destruction time has a weak dependence on cloud radius, while the dust evacuation time is shorter for a cloud with a smaller radius. Dust evacuation, thus, occurs in compact star-forming clouds whose column density is NH ≃ 1024-1026 cm-2. The critical halo mass above which dust evacuation occurs is lower for higher formation red shift, e.g. ˜109 M⊙ at red shift z ˜ 3 and ˜107 M⊙ at z ˜ 9. In addition, the metallicity of the gas should be less than ˜10-2 Z⊙, otherwise attenuation by dust reduces the radiation force significantly. From the dust-evacuated gas, massive stars are likely to form, even with a metallicity above ˜10-5 Z⊙, the critical value for low-mass star formation due to dust cooling. This can explain the dearth of ultra-metal-poor stars with a metallicity lower than ˜10-4 Z⊙.

  12. Theory of Dust Voids in Plasmas

    NASA Technical Reports Server (NTRS)

    Goree, J.; Morfill, G. E.; Tsytovich, V. N.; Vladimirov, S. V.

    1999-01-01

    Dusty plasmas in a gas discharge often feature a stable void, i.e., a dust-free region inside the dust cloud. This occurs under conditions relevant to both plasma processing discharges and plasma crystal experiments. The void results from a balance of the electrostatic and ion drag forces on a dust particle. The ion drag force is driven by a flow of ions outward from an ionization source and toward the surrounding dust cloud, which has a negative space charge. In equilibrium the force balance for dust particles requires that the boundary with the dust cloud be sharp, provided that the particles are cold and monodispersive. Numerical solutions of the one-dimensional nonlinear fluid equations are carried out including dust charging and dust-neutral collisions, but not ion-neutral collisions. The regions of parameter space that allow stable void equilibria are identified. There is a minimum ionization rate that can sustain a void. Spatial profiles of plasma parameters in the void are reported. In the absence of ion-neutral collisions, the ion flow enters the dust cloud's edge at Mach number M = 1. Phase diagrams for expanding or contracting voids reveal a stationary point corresponding to a single stable equilibrium void size, provided the ionization rate is constant. Large voids contract and small voids expand until they attain this stationary void size. On the other hand, if the ionization rate is not constant, the void size can oscillate. Results are compared to recent laboratory and microgravity experiments.

  13. Dust particle radial confinement in a dc glow discharge.

    PubMed

    Sukhinin, G I; Fedoseev, A V; Antipov, S N; Petrov, O F; Fortov, V E

    2013-01-01

    A self-consistent nonlocal model of the positive column of a dc glow discharge with dust particles is presented. Radial distributions of plasma parameters and the dust component in an axially homogeneous glow discharge are considered. The model is based on the solution of a nonlocal Boltzmann equation for the electron energy distribution function, drift-diffusion equations for ions, and the Poisson equation for a self-consistent electric field. The radial distribution of dust particle density in a dust cloud was fixed as a given steplike function or was chosen according to an equilibrium Boltzmann distribution. The balance of electron and ion production in argon ionization by an electron impact and their losses on the dust particle surface and on the discharge tube walls is taken into account. The interrelation of discharge plasma and the dust cloud is studied in a self-consistent way, and the radial distributions of the discharge plasma and dust particle parameters are obtained. It is shown that the influence of the dust cloud on the discharge plasma has a nonlocal behavior, e.g., density and charge distributions in the dust cloud substantially depend on the plasma parameters outside the dust cloud. As a result of a self-consistent evolution of plasma parameters to equilibrium steady-state conditions, ionization and recombination rates become equal to each other, electron and ion radial fluxes become equal to zero, and the radial component of electric field is expelled from the dust cloud.

  14. Variations between Dust and Gas in the Diffuse Interstellar Medium. III. Changes in Dust Properties

    NASA Astrophysics Data System (ADS)

    Reach, William T.; Bernard, Jean-Philippe; Jarrett, Thomas H.; Heiles, Carl

    2017-12-01

    We study infrared emission of 17 isolated, diffuse clouds with masses of order {10}2 {M}ȯ to test the hypothesis that grain property variations cause the apparently low gas-to-dust ratios that have been measured in those clouds. Maps of the clouds were constructed from Wide-field Infrared Survey Explorer (WISE) data and directly compared with the maps of dust optical depth from Planck. The mid-infrared emission per unit dust optical depth has a significant trend toward lower values at higher optical depths. The trend can be quantitatively explained by the extinction of starlight within the clouds. The relative amounts of polycyclic aromatic hydrocarbon and very small grains traced by WISE, compared with large grains tracked by Planck, are consistent with being constant. The temperature of the large grains significantly decreases for clouds with larger dust optical depth; this trend is partially due to dust property variations, but is primarily due to extinction of starlight. We updated the prediction for molecular hydrogen column density, taking into account variations in dust properties, and find it can explain the observed dust optical depth per unit gas column density. Thus, the low gas-to-dust ratios in the clouds are most likely due to “dark gas” that is molecular hydrogen.

  15. LADEE Search for a Dust Exosphere: A Historical Perspective

    NASA Technical Reports Server (NTRS)

    Glenar, D. A.; Stubbs, T. J.; Elphic, R.

    2014-01-01

    The LADEE search for exospheric dust is strongly motivated by putative detections of forward-scattered sunlight from exospheric dust grains which were observed during the Apollo era. This dust population, if it exists, has been associated with charging and transport of dust near the terminators. It is likely that the concentration of these dust grains is governed by a saltation mechanism originated by micrometeoroid impacts, which are the source of the more tenuous ejecta cloud.

  16. VizieR Online Data Catalog: XZ Catalog of Zodiacal Stars (XZ80Q) (Herald, 2003)

    NASA Astrophysics Data System (ADS)

    Herald, D.

    2003-11-01

    The XZ catalog was created at the U.S. Naval Observatory in 1977 by Richard Schmidt and Tom Van Flandern, primarily for the purpose of generating predictions of lunar occultations, and for analyzing timings of these events. It was designed to include all stars within 6d 40' of the ecliptic (the "Zodiac"), which is as far as the Moon's limb can ever get as seen from anywhere on the Earth's surface, leaving some margin for stellar proper motions and change in the obliquity of the ecliptic over the course of three centuries. The original version contained 32,221 entries; since that time, many changes have been made in succeeding versions, including better positions and proper motions, and the elimination and addition of stars. Details about the history of XZ catalog can be found in the "doc.txt" file. The XZ80Q revision has been developed from XZ80P, which was created by Mitsuru Soma. It is now complete over the Zodiac for stars down to visual magnitude 12.0. The "xz80q.dat" file contains the list of stars making the catalog; additional files provide details about double and variable stars included in the XZ80Q. The catalog includes also lists of the various existing names of the stars. (11 data files).

  17. The evolution of the zodiac in the context of ancient oriental history

    NASA Astrophysics Data System (ADS)

    Gurshtein, Alex A.

    The dates for the second (ca. 2700 B.C. to within 250 years) and the third ecliptical quartets (ca. 1200 B.C. to within 400 years) evaluated earlier are considered in the context of ancient Egyptian history. The origin of the second quartet coincides with the Great Pyramids and the initiation of the Egyptian solar, or so-called "civil" calendar, the first of such a type in the world. The third quartet is concurrent with the solar conversion of Amenhotep IV (Akhenaton) and takes place at the finale of the great Sothic period of 1461 years after the initiation of the solar calendar. It is argued that the Great Pyramids seem to be monuments to the Sun-god built in honor of the Egyptians having reached an understanding of the Sun's track upon the starry background, Akhenaton's conversion being in a direct connection with the original Pyramids' ideology. This paper is the third part of a single investigation. The first two parts "On the Origin of the Zodiacal Constellations" and "Prehistory of Zodiac Dating: Three Strata of Upper Paleolithic Constellations" were published in Vistas in Astronomy in 1993 and 1995.

  18. Wood Dust

    Cancer.gov

    Learn about wood dust, which can raise the risk of cancers of the paranasal sinuses and nasal cavity. High amounts of wood dust are produced in sawmills, and in the furniture-making, cabinet-making, and carpentry industries.

  19. Parameterizing the interstellar dust temperature

    NASA Astrophysics Data System (ADS)

    Hocuk, S.; Szűcs, L.; Caselli, P.; Cazaux, S.; Spaans, M.; Esplugues, G. B.

    2017-08-01

    The temperature of interstellar dust particles is of great importance to astronomers. It plays a crucial role in the thermodynamics of interstellar clouds, because of the gas-dust collisional coupling. It is also a key parameter in astrochemical studies that governs the rate at which molecules form on dust. In 3D (magneto)hydrodynamic simulations often a simple expression for the dust temperature is adopted, because of computational constraints, while astrochemical modelers tend to keep the dust temperature constant over a large range of parameter space. Our aim is to provide an easy-to-use parametric expression for the dust temperature as a function of visual extinction (AV) and to shed light on the critical dependencies of the dust temperature on the grain composition. We obtain an expression for the dust temperature by semi-analytically solving the dust thermal balance for different types of grains and compare to a collection of recent observational measurements. We also explore the effect of ices on the dust temperature. Our results show that a mixed carbonaceous-silicate type dust with a high carbon volume fraction matches the observations best. We find that ice formation allows the dust to be warmer by up to 15% at high optical depths (AV> 20 mag) in the interstellar medium. Our parametric expression for the dust temperature is presented as Td = [ 11 + 5.7 × tanh(0.61 - log 10(AV) ]χuv1/5.9, where χuv is in units of the Draine (1978, ApJS, 36, 595) UV field.

  20. Cosmic dust

    NASA Technical Reports Server (NTRS)

    Brownlee, Donald E.; Sandford, Scott A.

    1992-01-01

    Dust is a ubiquitous component of our galaxy and the solar system. The collection and analysis of extraterrestrial dust particles is important to exobiology because it provides information about the sources of biogenically significant elements and compounds that accumulated in distant regions of the solar nebula and that were later accreted on the planets. The topics discussed include the following: general properties of interplanetary dust; the carbonaceous component of interplanetary dust particles; and the presence of an interstellar component.

  1. Dust Storm in Southern California

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Along historic Route 66, just southeast of the little town of Amboy, California, lies a dried-up lake. Dry lakebeds are good sources of two things: salt and dust. In this image, the now-parched Bristol Lake offers up both. On April 12, 2007, dust storms menaced the area around Amboy. To the northwest, near Newberry Springs, California, dust hampered visibility and led to a multi-car collision on Interstate 40, killing two people and injuring several others. The same day, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite captured this image of a dust storm in the dry remains of Bristol Lake. Many small dust clouds boil up from the ground surface, casting their shadows to the northwest. A bright white cloud floating over the dust also throws its shadow onto the ground below. East of the dust storm are salt works that stand out from the surrounding landscape thanks to their straight lines and sharp angles. Dark ground surfaces alternate with mined white salt in a network of stripes. When lakes evaporate, chemicals that had been dissolved in the water stay behind, making dry lake beds an ideal place to find heavy concentrations of minerals, including salt. Besides the salt works, something else appears in stark contrast to this arid place. Lush green fields of irrigated crops appear in the east. Besides their color, their orderly arrangement reveals their human-made origin.

  2. Flying Through Dust From Asteroids

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-11-01

    How can we tell what an asteroid is made of? Until now, weve relied on remote spectral observations, though NASAs recently launched OSIRIS-REx mission may soon change this by landing on an asteroid and returning with a sample.But what if we could learn more about the asteroids near Earth without needing to land on each one? It turns out that we can by flying through their dust.The aerogel dust collector of the Stardust mission. [NASA/JPL/Caltech]Ejected CluesWhen an airless body is impacted by the meteoroids prevalent throughout our solar system, ejecta from the body are flung into the space around it. In the case of small objects like asteroids, their gravitational pull is so weak that most of the ejected material escapes, forming a surrounding cloud of dust.By flying a spacecraft through this cloud, we could perform chemical analysis of the dust, thereby determining the asteroids composition. We could even capture some of the dust during a flyby (for example, by using an aerogel collector like in the Stardust mission) and bring it back home to analyze.So whats the best place to fly a dust-analyzing or -collecting spacecraft? To answer this, we need to know what the typical distribution of dust is around a near-Earth asteroid (NEA) a problem that scientists Jamey Szalay (Southwest Research Institute) and Mihly Hornyi (University of Colorado Boulder) address in a recent study.The colors show the density distribution for dust grains larger than 0.3 m around a body with a 10-km radius. The distribution is asymmetric, with higher densities on the apex side, shown here in the +y direction. [Szalay Hornyi 2016]Moon as a LaboratoryTo determine typical dust distributions around NEAs, Szalay and Hornyi first look at the distribution of dust around our own Moon, caused by the same barrage of meteorites wed expect to impact NEAs. The Moons dust cloud was measured in situ in 2013 and 2014 by the Lunar Dust Experiment (LDEX) on board the Lunar Atmosphere and Dust Environment

  3. Fingerprints in the Dust

    NASA Technical Reports Server (NTRS)

    2001-01-01

    These MISR nadir-camera images of eastern China compare a somewhat hazy summer view from July 9, 2000 (left) with a spectacularly dusty spring view from April 7, 2001 (middle). The left-hand and middle images are from Terra orbits 2967 and 6928, respectively, and extend from central Manchuria near the top to portions of North and South Korea at the bottom. They are approximately 380 kilometers in width.

    Asia's desert areas are prone to soil erosion, as underground water tables are lowered by prolonged drought and by industrial and agricultural water use. Heavy winds blowing eastward across the arid and sparsely vegetated surfaces of Mongolia and western China pick up large quantities of yellow dust. Airborne dust clouds from the April 2001 storm blew across the Pacific Ocean and were carried as far as North America. The minerals transported in this manner are believed to provide nutrients for both oceanic and land ecosystems.

    According to the Xinhua News Agency in China, nearly one million tons of Gobi Desert dust blow into Beijing each year. During a similar dust outbreak last year, the Associated Press reported that the visibility in Beijing had been reduced the point where buildings were barely visible across city streets, and airline schedules were significantly disrupted. The dust has also been implicated in adverse health effects such as respiratory discomfort and eye irritation.

    The image on the right is a higher resolution MISR nadir-camera view of a portion of the April 7, 2001 dust cloud. It covers an area roughly 250 kilometers wide by 470 kilometers high. When viewed at full magnification, a number of atmospheric wave features, like the ridges and valleys of a fingerprint, are apparent. These are probably induced by surface topography, which can disturb the wind flow. A few small cumulus clouds are also visible, and are casting shadows on the thick lower dust layer.

    Analyses of images such as these constitute one phase of MISR

  4. Migration of Interplanetary Dust and Comets

    NASA Astrophysics Data System (ADS)

    Ipatov, S. I.; Mather, J. C.

    Our studies of migration of interplanetary dust and comets were based on the results of integration of the orbital evolution of 15,000 dust particles and 30,000 Jupiter-family comets (JFCs) [1-3]. For asteroidal and cometary particles, the values of the ratio β between the radiation pressure force and the gravitational force varied from <0.0004 to 0.4. For silicates, such values correspond to particle diameters between >1000 and 1 microns. The probability of a collision of a dust particle started from an asteroid or JFC with the Earth during a lifetime of the particle was maximum at diameter d ˜100 microns. For particles started from asteroids and comet 10P, this maximum probability was ˜0.01. Different studies of migration of dust particles and small bodies testify that the fraction of cometary dust particles of the overall dust population inside Saturn's orbit is considerable and can be dominant: (1) Cometary dust particles produced both inside and outside Jupiter's orbit are needed to explain the observed constant number density of dust particles at 3-18 AU. The number density of migrating trans-Neptunian particles near Jupiter's orbit is smaller by a factor of several than that beyond Saturn's orbit. Only a small fraction of asteroidal particles can get outside Jupiter's orbit. (2) Some (less than 0.1%) JFCs can reach typical near-Earth object orbits and remain there for millions of years. Dynamical lifetimes of most of the former JFCs that have typical near-Earth object orbits are about 106 -109 yr, so during most of these times they were extinct comets. Such former comets could disintegrate and produce a lot of mini-comets and dust. (3) Comparison of the velocities of zodiacal dust particles (velocities of MgI line) based on the distributions of particles over their orbital elements obtained in our runs [3-4] with the velocities obtained at the WHAM observations shows that only asteroidal dust particles cannot explain these observations, and particles

  5. Dust Streams from Tunisia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    On October 6, 2001, the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) captured this true-color image of a large dust storm blowing northeastward across the Mediterranean Sea from Tunisia. According to Joseph Prospero, professor of atmospheric science at the University of Miami, there is an unusual arc-shaped 'front' to the dust cloud. The storm's shape suggests that the source of the dust is rather small and that the meteorology driving it rather unusual. The dust seems to be coming out of the wadis, dry lakebeds and riverbeds, at the base of the Tell Atlas Mountains in northern Tunisia and eastern Algeria. The dust appears to be blowing toward the island of Sicily, Italy (toward the upper righthand corner). Also notice there is a relatively thin plume of smoke emanating eastward from the top of Mount Etna on Sicily. Image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  6. Southern Clouds

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03026 Southern Clouds

    This image shows a system of clouds just off the margin of the South Polar cap. Taken during the summer season, these clouds contain both water-ice and dust.

    Image information: VIS instrument. Latitude 80.2S, Longitude 57.6E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  7. Maintaining the Background Dust Opacity During Northern Hemisphere Summer Mars Using Wind Stress Based Dust Lifting

    NASA Astrophysics Data System (ADS)

    Jha, V.; Kahre, M. A.

    2017-12-01

    The Mars atmosphere has low levels of dust during Northern Hemisphere (NH) spring and summer (the non-dusty season) and increased levels during NH autumn and winter (the dusty season). In the absence of regional or global storms, dust devils and local storms maintain a background minimum dust loading during the non-dusty season. While observational surveys and Global Climate Model (GCM) studies suggest that dust devils are likely to be major contributors to the background haze during NH spring and summer, a complete understanding of the relative contribution of dust devils and local dust storms has not yet been achieved. We present preliminary results from an investigation that focuses on the effects of radiatively active water ice clouds on dust lifting processes during these seasons. Water ice clouds are known to affect atmospheric temperatures directly by absorption and emission of thermal infrared radiation and indirectly through dynamical feedbacks. Our goal is to understand how clouds affect the contribution by local (wind stress) dust storms to the background dust haze during NH spring and summer. The primary tool for this work is the NASA Ames Mars GCM, which contains physical parameterizations for a fully interactive dust cycle. Three simulations that included wind stress dust lifting were executed for a period of 5 Martian years: a case that included no cloud formation, a case that included radiatively inert cloud formation and a case that included radiatively active cloud (RAC) formation. Results show that when radiatively active clouds are included, the clouds in the aphelion cloud belt radiatively heat the atmosphere aloft in the tropics (Figure 1). This heating produces a stronger overturning circulation, which in turn produces an enhanced low-level flow in the Hadley cell return branch. The stronger low-level flow drives higher surface stresses and increased dust lifting in those locations. We examine how realistic these simulated results are by

  8. The S sub 10 /V/ unit of surface brightness. [for zodiacal light measurement

    NASA Technical Reports Server (NTRS)

    Sparrow, J. G.; Weinberg, J. L.

    1976-01-01

    Some discrepancies in the use of the unit of zodiacal light measurements - S sub 10 (V), which is the equivalent number of tenth magnitude stars of solar spectral type per square degree - are discussed. It is suggested that: (1) the S sub 10 (V) unit be understood to represent 10th magnitude solar (G2V) stars per square degree at mean solar distance, (2) the V refers to the visual color in the UBV system defined by Johnson and Morgan (1953), (3) the apparent solar visual magnitude be taken as -26.73 and the B-V index as .63, (4) the solar spectral irradiance values of Labs and Neckel (1970) be used, and (5) when using Vega as a standard to obtain brightnesses in S sub 10 (V), +.04 be used as its magnitude at all wavelengths and the irradiance values of Hayes and Latham (1975) be used.

  9. Dust near luminous ultraviolet stars

    NASA Technical Reports Server (NTRS)

    Henry, Richard C.

    1993-01-01

    This report describes research activities related to the Infrared Astronomical Satellite (IRAS) sky survey. About 745 luminous stars were examined for the presence of interstellar dust heated by a nearby star. The 'cirrus' discovered by IRAS is thermal radiation from interstellar dust at moderate and high galactic latitudes. The IRAS locates the dust which must (at some level) scatter ultraviolet starlight, although it was expected that thermal emission would be found around virtually every star, most stars shown no detectable emission. And the emission found is not uniform. It is not that the star is embedded in 'an interstellar medium', but rather what is found are discrete clouds that are heated by starlight. An exception is the dearth of clouds near the very hottest stars, implying that the very hottest stars play an active role with respect to destroying or substantially modifying the dust clouds over time. The other possibility is simply that the hottest stars are located in regions lacking in dust, which is counter-intuitive. A bibliography of related journal articles is attached.

  10. Prebiotic chemistry in clouds

    NASA Technical Reports Server (NTRS)

    Oberbeck, Verne R.; Marshall, John; Shen, Thomas

    1991-01-01

    The chemical evolution hypothesis of Woese (1979), according to which prebiotic reactions occurred rapidly in droplets in giant atmospheric reflux columns was criticized by Scherer (1985). This paper proposes a mechanism for prebiotic chemistry in clouds that answers Scherer's concerns and supports Woese's hypothesis. According to this mechanism, rapid prebiotic chemical evolution was facilitated on the primordial earth by cycles of condensation and evaporation of cloud drops containing clay condensation nuclei and nonvolatile monomers. For example, amino acids supplied by, or synthesized during entry of meteorites, comets, and interplanetary dust, would have been scavenged by cloud drops containing clay condensation nuclei and would be polymerized within cloud systems during cycles of condensation, freezing, melting, and evaporation of cloud drops.

  11. ADONIS Discovers Dust Disk around a Star with a Planet

    NASA Astrophysics Data System (ADS)

    2000-10-01

    Zodiacal Light in the iota Horologii Extrasolar Planetary System Retraction (August 2001) The presumed detection of a dust disk around iota Horologii, presented in this Press Release, has been found to be due to an instrumental artefact and is therefore not real. This is the conclusion reached by the astronomers working with the ADONIS Adaptive Optics instrument, following a series of extremely careful tests. In September 2000, iota Horologii - a star which was found earlier by radial velocity measurements to be orbited by a planetary companion - was observed by ADONIS, the adaptive optics system at the ESO 3.6-m telescope. These observations showed an elliptically shaped excess emission around this star when comparing with two reference stars. Such an excess, if real, can only be explained by the presence of a dust disk around this star. A series of new observations - again with the ADONIS system - have not confirmed the previous results. The search for dust disks around stars is a very difficult observational task, because the star is much brighter than the faint extended emission of a dust disk, It is therefore necessary to block the light of the star by means of a so-called coronographic mask. But even this is not sufficient - it is also necessary to subtract the remaining "light-wings" from the star (i.e., the pattern that results from the stray light in the telescope and camera). For this purpose, a "reference" star assumed to be without excess emission is always observed before and after each observation of the "target" star. The light pattern observed for the "reference" star (the standard Point-Spread-Function) is then used to remove numerically the pattern of the "target" star, thereby isolating any additional light that may come from a circumstellar disk. For this analysis, it is crucial that the Point-Spread-Function remains unchanged during the observation of the reference and target stars. In fact, for each observation of the target star, at least two

  12. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, D.´niel; Lauretta, Dante S.

    2014-02-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  13. Dynamics and Distribution of Interplanetary Dust

    NASA Astrophysics Data System (ADS)

    Ipatov, S. I.; Mather, J. C.

    2005-08-01

    We integrated the orbital evolution of 12,000 asteroidal, cometary, and trans-Neptunian dust particles, under the gravitational influence of planets, Poynting-Robertson drag, radiation pressure, and solar wind drag (Annals of the New York Academy of Sciences, v. 1017, 66-80, 2004; Advances in Space Research, in press, 2005). The orbital evolution of 30,000 Jupiter-family comets (JFCs) was also integrated (Annals of the New York Academy of Sciences, v. 1017, 46-65, 2004). For asteroidal and cometary particles, the values of the ratio β between the radiation pressure force and the gravitational force varied from <0.0004 to 0.4 (for silicates, such values correspond to particle diameters between >1000 and 1 microns). The considered cometary particles started from comets 2P, 10P, and 39P. The probability of a collision of an asteroidal or cometary dust particle with the Earth during a lifetime of the particle was maximum at diameter about 100 microns; this is in accordance with cratering records. Our different studies of migration of dust particles and small bodies testify that the fraction of cometary dust particles of the overall dust population inside Saturn's orbit is considerable and can be dominant: (1) Some JFCs can reach orbits entirely located inside Jupiter's orbit and remain in such orbits for millions of years. Such former comets could disintegrate during millions of years and produce a lot of mini-comets and dust. (2) The spatial density of migrating trans-Neptunian particles near Jupiter's orbit is smaller by a factor of several than that beyond Saturn's orbit. Only a small fraction of asteroidal particles can migrate outside Jupiter's orbit. Therefore cometary dust particles are needed to explain the observed constant spatial density of dust particles at 3-18 AU from the Sun. (3) Comparison of the velocities of zodiacal dust particles obtained in our runs with the observations of velocities of these particles made by Reynolds et al. (Ap.J., 2004, v. 612

  14. Cometary Dust

    NASA Astrophysics Data System (ADS)

    Levasseur-Regourd, Anny-Chantal; Agarwal, Jessica; Cottin, Hervé; Engrand, Cécile; Flynn, George; Fulle, Marco; Gombosi, Tamas; Langevin, Yves; Lasue, Jérémie; Mannel, Thurid; Merouane, Sihane; Poch, Olivier; Thomas, Nicolas; Westphal, Andrew

    2018-04-01

    This review presents our understanding of cometary dust at the end of 2017. For decades, insight about the dust ejected by nuclei of comets had stemmed from remote observations from Earth or Earth's orbit, and from flybys, including the samples of dust returned to Earth for laboratory studies by the Stardust return capsule. The long-duration Rosetta mission has recently provided a huge and unique amount of data, obtained using numerous instruments, including innovative dust instruments, over a wide range of distances from the Sun and from the nucleus. The diverse approaches available to study dust in comets, together with the related theoretical and experimental studies, provide evidence of the composition and physical properties of dust particles, e.g., the presence of a large fraction of carbon in macromolecules, and of aggregates on a wide range of scales. The results have opened vivid discussions on the variety of dust-release processes and on the diversity of dust properties in comets, as well as on the formation of cometary dust, and on its presence in the near-Earth interplanetary medium. These discussions stress the significance of future explorations as a way to decipher the formation and evolution of our Solar System.

  15. Plasma-Based Detector of Outer-Space Dust Particles

    NASA Technical Reports Server (NTRS)

    Tsurutani, Bruce; Brinza, David E.; Henry, Michael D.; Clay, Douglas R.

    2006-01-01

    A report presents a concept for an instrument to be flown in outer space, where it would detect dust particles - especially those associated with comets. The instrument would include a flat plate that would intercept the dust particles. The anticipated spacecraft/dust-particle relative speeds are so high that the impingement of a dust particle on the plate would generate a plasma cloud. Simple electric dipole sensors located equidistantly along the circumference of the plate would detect the dust particle indirectly by detecting the plasma cloud. The location of the dust hit could be estimated from the timing of the detection pulses of the different dipoles. The mass and composition of the dust particle could be estimated from the shapes and durations of the pulses from the dipoles. In comparison with other instruments for detecting hypervelocity dust particles, the proposed instrument offers advantages of robustness, large collection area, and simplicity.

  16. Dust That's Worth Keeping

    SciT

    Hazi, A

    2006-01-25

    Images taken of interstellar space often display a colorful canvas of portions of the electromagnetic spectrum. Dispersed throughout the images are interstellar clouds of dust and gas--remnants ejected from stars and supernovae over billions and billions of years. For more than 40 years, astronomers have observed that interstellar dust exhibits a consistent effect at a spectral wavelength of 2,175 angstroms, the equivalent of 5.7 electronvolts in energy on the electromagnetic spectrum. At this wavelength, light from stars is absorbed by dust in the interstellar medium, blocking the stars light from reaching Earth. The 2,175-angstrom feature, which looks like a bumpmore » on spectra, is the strongest ultraviolet-visible light spectral signature of interstellar dust and is visible along nearly every observational line of sight. Scientists have sought to solve the mystery of what causes the 2,175-angstrom feature by reproducing the effect in the laboratory. They speculated a number of possibilities, including fullerenes (buckyballs), nanodiamonds, and even interstellar organisms. However, none of these materials fits the data for the unique spectral feature. Limitations in the energy and spatial resolution achievable with electron microscopes and ion microprobes--the two main instruments used to study samples of dust--have also prevented scientists from finding the answer. A collaborative effort led by Livermore physicist John Bradley and funded by the National Aeronautics and Space Administration (NASA) has used a new-generation transmission electron microscope (TEM) and nanoscale ion microprobe to unlock the mystery. The Livermore group includes physicists Zu Rong Dai, Ian Hutcheon, Peter Weber, and Sasa Bajt and postdoctoral researchers Hope Ishii, Giles Graham, and Julie Smith. They collaborated with the University of California at Davis (UCD), Lawrence Berkeley National Laboratory, Washington University's Laboratory for Space Sciences in St. Louis, and NASA

  17. Dust That's Worth Keeping

    NASA Technical Reports Server (NTRS)

    Hazi, A.

    2006-01-01

    Images taken of interstellar space often display a colorful canvas of portions of the electromagnetic spectrum. Dispersed throughout the images are interstellar clouds of dust and gas--remnants ejected from stars and supernovae over billions and billions of years. For more than 40 years, astronomers have observed that interstellar dust exhibits a consistent effect at a spectral wavelength of 2,175 angstroms, the equivalent of 5.7 electronvolts in energy on the electromagnetic spectrum. At this wavelength, light from stars is absorbed by dust in the interstellar medium, blocking the stars light from reaching Earth. The 2,175-angstrom feature, which looks like a bump on spectra, is the strongest ultraviolet-visible light spectral signature of interstellar dust and is visible along nearly every observational line of sight. Scientists have sought to solve the mystery of what causes the 2,175-angstrom feature by reproducing the effect in the laboratory. They speculated a number of possibilities, including fullerenes (buckyballs), nanodiamonds, and even interstellar organisms. However, none of these materials fits the data for the unique spectral feature. Limitations in the energy and spatial resolution achievable with electron microscopes and ion microprobes--the two main instruments used to study samples of dust--have also prevented scientists from finding the answer. A collaborative effort led by Livermore physicist John Bradley and funded by the National Aeronautics and Space Administration (NASA) has used a new-generation transmission electron microscope (TEM) and nanoscale ion microprobe to unlock the mystery. The Livermore group includes physicists Zu Rong Dai, Ian Hutcheon, Peter Weber, and Sasa Bajt and postdoctoral researchers Hope Ishii, Giles Graham, and Julie Smith. They collaborated with the University of California at Davis (UCD), Lawrence Berkeley National Laboratory, Washington University's Laboratory for Space Sciences in St. Louis, and NASA's Ames

  18. CO observations of dark clouds in Lupus

    NASA Technical Reports Server (NTRS)

    Murphy, D. C.; Cohen, R.; May, J.

    1986-01-01

    C-12O observations covering 170 square degrees toward the southern T Association Lupus have revealed the presence of an extended physically related complex of dark clouds which have recently formed low mass stars. The estimated mass of the clouds (about 30,000 solar masses) is comparable to that of the nearby Ophiuchus dust clouds. The Lupus clouds are projected onto a gap between two subgroups of the Scorpio-Centaurus OB association suggesting that this long accepted subgrouping may require reinterpretation.

  19. The Fate of Saharan Dust Across the Atlantic and Implications for a Central American Dust Barrier

    NASA Technical Reports Server (NTRS)

    Nowottnick, E.; Colarco, P.; da Silva, A.; Hlavka, D.; McGill, M.

    2011-01-01

    Saharan dust was observed over the Caribbean basin during the summer 2007 NASA Tropical Composition, Cloud, and Climate Coupling (TC4) field experiment. Airborne Cloud Physics Lidar (CPL) and satellite observations from MODIS suggest a barrier to dust transport across Central America into the eastern Pacific. We use the NASA GEOS-5 atmospheric transport model with online aerosol tracers to perform simulations of the TC4 time period in order to understand the nature of this barrier. Our simulations are driven by the Modem Era Retrospective-Analysis for Research and Applications (MERRA) meteorological analyses. We evaluate our baseline simulated dust distributions using MODIS and CALIOP satellite and ground-based AERONET sun photometer observations. GEOS-5 reproduces the observed location, magnitude, and timing of major dust events, but our baseline simulation does not develop as strong a barrier to dust transport across Central America as observations suggest. Analysis of the dust transport dynamics and lost processes suggest that while both mechanisms play a role in defining the dust transport barrier, loss processes by wet removal of dust are about twice as important as transport. Sensitivity analyses with our model showed that the dust barrier would not exist without convective scavenging over the Caribbean. The best agreement between our model and the observations was obtained when dust wet removal was parameterized to be more aggressive, treating the dust as we do hydrophilic aerosols.

  20. Numerical Prediction of Dust. Chapter 10

    NASA Technical Reports Server (NTRS)

    Benedetti, Angela; Baldasano, J. M.; Basart, S.; Benincasa, F.; Boucher, O.; Brooks, M.; Chen, J. P.; Colarco, P. R.; Gong, S.; Huneeus, N.; hide

    2013-01-01

    Covers the whole breadth of mineral dust research, from a scientific perspective Presents interdisciplinary work including results from field campaigns, satellite observations, laboratory studies, computer modelling and theoretical studies Explores the role of dust as a player and recorder of environmental change This volume presents state-of-the-art research about mineral dust, including results from field campaigns, satellite observations, laboratory studies, computer modelling and theoretical studies. Dust research is a new, dynamic and fast-growing area of science and due to its multiple roles in the Earth system, dust has become a fascinating topic for many scientific disciplines. Aspects of dust research covered in this book reach from timescales of minutes (as with dust devils, cloud processes, and radiation) to millennia (as with loess formation and oceanic sediments), making dust both a player and recorder of environmental change. The book is structured in four main parts that explore characteristics of dust, the global dust cycle, impacts of dust on the Earth system, and dust as a climate indicator. The chapters in these parts provide a comprehensive, detailed overview of this highly interdisciplinary subject. The contributions presented here cover dust from source to sink and describe all the processes dust particles undergo while travelling through the atmosphere. Chapters explore how dust is lifted and transported, how it affects radiation, clouds, regional circulations, precipitation and chemical processes in the atmosphere, and how it deteriorates air quality. The book explores how dust is removed from the atmosphere by gravitational settling, turbulence or precipitation, how iron contained in dust fertilizes terrestrial and marine ecosystems, and about the role that dust plays in human health. We learn how dust is observed, simulated using computer models and forecast. The book also details the role of dust deposits for climate reconstructions

  1. The influence of lunar phases and zodiac sign 'Leo' on perioperative complications and outcome in elective spine surgery.

    PubMed

    Joswig, Holger; Stienen, Martin N; Hock, Carolin; Hildebrandt, Gerhard; Surbeck, Werner

    2016-06-01

    Many people believe that the moon has an influence on daily life, and some even request elective surgery dates depending on the moon calendar. The aim of this study was to assess the influence of 'unfavorable' lunar or zodiac constellations on perioperative complications and outcome in elective surgery for degenerative disc disease. Retrospective database analysis including 924 patients. Using uni- and multivariate logistic regression, the likelihood for intraoperative complications and re-do surgeries as well as the clinical outcomes at 4 weeks was analyzed for surgeries performed during the waxing moon, full moon, and dates when the moon passed through the zodiac sign 'Leo.' In multivariate analysis, patients operated on during the waxing moon were 1.54 times as likely as patients who were operated on during the waning moon to suffer from an intraoperative complication (OR 1.54, 95 % CI 1.07-2.21, p = 0.019). In contrast, there was a trend toward fewer re-do surgeries for surgery during the waxing moon (OR 0.51, 95 % CI 0.23-1.16, p = 0.109), while the 4-week responder status was similar (OR 0.73, 95 % CI 0.47-1.14, p = 0.169). A full moon and the zodiac sign Leo did not increase the likelihood for complications, re-do surgeries or unfavorable outcomes. We found no influence of 'unfavorable' lunar or zodiac constellations on the 4-week responder status or the revision rate that would justify a moon calendar-based selection approach to elective spine surgery dates. However, the fact that patients undergoing surgery during the waxing moon were more likely to suffer from an intraoperative complication is a surprising curiosity and defies our ability to find a rational explanation.

  2. Saharan Dust on the Move

    2017-12-08

    A piece of Africa—actually lots of them—began to arrive in the Americas in June 2014. On June 23, a lengthy river of dust from western Africa began to push across the Atlantic Ocean on easterly winds. A week later, the influx of dust was affecting air quality as far away as the southeastern United States. This composite image, made with data from the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP, shows dust heading west toward South America and the Gulf of Mexico on June 25, 2014. The dust flowed roughly parallel to a line of clouds in the intertropical convergence zone, an area near the equator where the trade winds come together and rain and clouds are common. In imagery captured by the Moderate Resolution Imaging Spectroradiometer (MODIS), the dust appeared to be streaming from Mauritania, Senegal, and Western Sahara, though some of it may have originated in countries farther to the east. Saharan dust has a range of impacts on ecosystems downwind. Each year, dust events like the one pictured here deliver about 40 million tons of dust from the Sahara to the Amazon River Basin. The minerals in the dust replenish nutrients in rainforest soils, which are continually depleted by drenching, tropical rains. Research focused on peat soils in the Everglades show that African dust has been arriving regularly in South Florida for thousands of years as well. In some instances, the impacts are harmful. Infusion of Saharan dust, for instance, can have a negative impact on air quality in the Americas. And scientists have linked African dust to outbreaks of certain types of toxic algal blooms in the Gulf of Mexico and southern Florida. Read more: 1.usa.gov/1snkzmS NASA images by Norman Kuring, NASA’s Ocean Color web. Caption by Adam Voiland. Credit: NASA Earth Observatory NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and

  3. Microgravity combustion of dust suspensions

    NASA Technical Reports Server (NTRS)

    Lee, John H. S.; Peraldi, Olivier; Knystautas, Rom

    1993-01-01

    Unlike the combustion of homogeneous gas mixtures, there are practically no reliable fundamental data (i.e., laminar burning velocity, flammability limits, quenching distance, minimum ignition energy) for the combustion of heterogeneous dust suspensions. Even the equilibrium thermodynamic data such as the constant pressure volume combustion pressure and the constant pressure adiabatic flame temperature are not accurately known for dust mixtures. This is mainly due to the problem of gravity sedimentation. In normal gravity, turbulence, convective flow, electric and acoustic fields are required to maintain a dust in suspension. These external influences have a dominating effect on the combustion processes. Microgravity offers a unique environment where a quiescent dust cloud can in principle be maintained for a sufficiently long duration for almost all combustion experiments (dust suspensions are inherently unstable due to Brownian motion and particle aggregation). Thus, the microgravity duration provided by drop towers, parabolic flights, and the space shuttle, can all be exploited for different kinds of dust combustion experiments. The present paper describes some recent studies on microgravity combustion of dust suspension carried out on the KC-135 and the Caravelle aircraft. The results reported are obtained from three parabolic flight campaigns.

  4. Experiments on Dust Grain Charging

    NASA Technical Reports Server (NTRS)

    Abbas, M. N.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; West, E. A.

    2004-01-01

    Dust particles in various astrophysical environments are charged by a variety of mechanisms generally involving collisional processes with other charged particles and photoelectric emission with UV radiation from nearby sources. The sign and the magnitude of the particle charge are determined by the competition between the charging processes by UV radiation and collisions with charged particles. Knowledge of the particle charges and equilibrium potentials is important for understanding of a number of physical processes. The charge of a dust grain is thus a fundamental parameter that influences the physics of dusty plasmas, processes in the interplanetary medium and interstellar medium, interstellar dust clouds, planetary rings, cometary and outer atmospheres of planets etc. In this paper we present some results of experiments on charging of dust grains carried out on a laboratory facility capable levitating micron size dust grains in an electrodynamic balance in simulated space environments. The charging/discharging experiments were carried out by exposing the dust grains to energetic electron beams and UV radiation. Photoelectric efficiencies and yields of micron size dust grains of SiO2, and lunar simulates obtained from NASA-JSC will be presented.

  5. Allergies, asthma, and dust

    MedlinePlus

    Reactive airway disease - dust; Bronchial asthma - dust; Triggers - dust ... Things that make allergies or asthma worse are called triggers. Dust is a common trigger. When your asthma or allergies become worse due to dust, you are ...

  6. Spring Dust Storm Smothers Beijing

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A few days earlier than usual, a large, dense plume of dust blew southward and eastward from the desert plains of Mongolia-quite smothering to the residents of Beijing. Citizens of northeastern China call this annual event the 'shachenbao,' or 'dust cloud tempest.' However, the tempest normally occurs during the spring time. The dust storm hit Beijing on Friday night, March 15, and began coating everything with a fine, pale brown layer of grit. The region is quite dry; a problem some believe has been exacerbated by decades of deforestation. According to Chinese government estimates, roughly 1 million tons of desert dust and sand blow into Beijing each year. This true-color image was made using two adjacent swaths (click to see the full image) of data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), flying aboard the OrbView-2 satellite, on March 17, 2002. The massive dust storm (brownish pixels) can easily be distinguished from clouds (bright white pixels) as it blows across northern Japan and eastward toward the open Pacific Ocean. The black regions are gaps between SeaWiFS' viewing swaths and represent areas where no data were collected. Image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  7. Dust near luminous ultraviolet stars

    NASA Technical Reports Server (NTRS)

    Henry, Richard C.

    1992-01-01

    More than 700 luminous stars in the infrared astronomical satellite (IRAS) Skyflux plates were examined for the presence of dust heated by a nearby star. This dust may be distinguished from the ubiquitous cool cirrus by its higher temperature and thus enhanced 60 micron emission. More than 120 dust clouds were found around only 106 of the stars with a volume filling factor of 0.006 and an intercloud separation of 46 pc. A region of dust smoothly distributed through the volume of space heated by the star could not be found and hence an upper limit of 0.05 cm(exp -3) is placed on the equivalent gas density in the intercloud regions. The clouds have an average density of 0.22 cm(exp -3) and a radius of 1.9 pc, albeit with wide variations in their properties. Two different scale heights of 140 and 540 pc were found. This was interpreted as evidence for different distributions of dust in and out of the galactic disk.

  8. Clouds in the Martian Atmosphere

    NASA Astrophysics Data System (ADS)

    Määttänen, Anni; Montmessin, Franck

    2018-01-01

    Although resembling an extremely dry desert, planet Mars hosts clouds in its atmosphere. Every day somewhere on the planet a part of the tiny amount of water vapor held by the atmosphere can condense as ice crystals to form cirrus-type clouds. The existence of water ice clouds has been known for a long time, and they have been studied for decades, leading to the establishment of a well-known climatology and understanding of their formation and properties. Despite their thinness, they have a clear impact on the atmospheric temperatures, thus affecting the Martian climate. Another, more exotic type of clouds forms as well on Mars. The atmospheric temperatures can plunge to such frigid values that the major gaseous component of the atmosphere, CO2, condenses as ice crystals. These clouds form in the cold polar night where they also contribute to the formation of the CO2 ice polar cap, and also in the mesosphere at very high altitudes, near the edge of space, analogously to the noctilucent clouds on Earth. The mesospheric clouds are a fairly recent discovery and have put our understanding of the Martian atmosphere to a test. On Mars, cloud crystals form on ice nuclei, mostly provided by the omnipresent dust. Thus, the clouds link the three major climatic cycles: those of the two major volatiles, H2O and CO2; and that of dust, which is a major climatic agent itself.

  9. Wet Dust Deposition Across Texas, USA

    NASA Astrophysics Data System (ADS)

    Collins, J. D., Jr.; Ponette-González, A.; Gill, T. E.; Glass, G. A.; Weathers, K. C.

    2016-12-01

    Atmospheric dust deposition is of critical importance in terrestrial biogeochemical cycles, supplying essential limiting nutrients, such as calcium and phosphorus as well as pollutants, such as lead, to ecosystems. Dust particles are delivered to terrestrial ecosystems directly as dry deposition or in precipitation (wet deposition) as a result of rainout (particles incorporated into cloud droplets) and washout (particles that collide with raindrops as they fall). Compared to dry deposition, wet dust deposition (dissolved + particulate) is a poorly understood yet potentially significant pathway for dust input, especially in humid regions. We quantified wet dust deposition to two National Atmospheric Deposition Monitoring (NADP) sites across Texas-one in west (Guadalupe Mountains) and one in east (near Houston) Texas-with contrasting climate/dust regimes and land cover. We focused on 2012 during one of the most severe droughts in Texas since 1895. Dust event days (DEDs) were identified using meteorological data for stations within 150 km of the NADP sites where wet deposition was sampled weekly. DEDs were defined using the following criteria: visibility <10 km, <30% relative humidity, and wind speed >50 km, supplemented with other Saharan dust incursion and dust observations. A total of 34 DEDs (20 sample weeks) were identified for the west and 5 DEDs (4 sample weeks) for the east Texas sites. Bulk elemental composition of washout particles is analyzed using Particle Induced X-ray Emission (PIXE) spectroscopy and X-ray Fluorescence (XRF) spectroscopy. Using these data, we will examine differences in the chemical composition of rainwater and aerosol particles filtered from rain samples for dust versus non-dust event days at each study site. Deposition fluxes for dust and non-dust event weeks are also compared. Quantifying the magnitude of wet dust deposition is necessary to improve evaluation of dust impacts on biogeochemical cycles.

  10. Formation and dissociation of dust molecules in dusty plasma

    NASA Astrophysics Data System (ADS)

    Yan, Jia; Feng, Fan; Liu, Fucheng; Dong, Lifang; He, Yafeng

    2016-09-01

    Dust molecules are observed in a dusty plasma experiment. By using measurements with high spatial resolution, the formation and dissociation of the dust molecules are studied. The ion cloud in the wake of an upper dust grain attracts the lower dust grain nearby. When the interparticle distance between the upper dust grain and the lower one is less than a critical value, the two dust grains would form a dust molecule. The upper dust grain always leads the lower one as they travel. When the interparticle distance between them is larger than the critical value, the dust molecule would dissociate. Project supported by the National Natural Science Foundation of China (Grant Nos. 11205044 and 11405042), the Natural Science Foundation of Hebei Province, China (Grant Nos. A2011201006 and A2012201015), the Research Foundation of Education Bureau of Hebei Province, China (Grant No. Y2012009), the Program for Young Principal Investigators of Hebei Province, China, and the Midwest Universities Comprehensive Strength Promotion Project, China.

  11. Towards a Full-sky, High-resolution Dust Extinction Map with WISE and Planck

    NASA Astrophysics Data System (ADS)

    Meisner, Aaron M.; Finkbeiner, D. P.

    2014-01-01

    We have recently completed a custom processing of the entire WISE 12 micron All-sky imaging data set. The result is a full-sky map of diffuse, mid-infrared Galactic dust emission with angular resolution of 15 arcseconds, and with contaminating artifacts such as compact sources removed. At the same time, the 2013 Planck HFI maps represent a complementary data set in the far-infrared, with zero-point relatively immune to zodiacal contamination and angular resolution superior to previous full-sky data sets at similar frequencies. Taken together, these WISE and Planck data products present an opportunity to improve upon the SFD (1998) dust extinction map, by virtue of enhanced angular resolution and potentially better-controlled systematics on large scales. We describe our continuing efforts to construct and test high-resolution dust extinction and temperature maps based on our custom WISE processing and Planck HFI data.

  12. Molecular clouds in galaxies with different Z - Fragmentation of diffuse clouds driven by opacity

    NASA Technical Reports Server (NTRS)

    Franco, Jose; Cox, Donald P.

    1986-01-01

    Molecular clouds are formed from diffuse interstellar clouds when the external ultraviolet radiation field is prevented from penetrating into the cloud. The opacity is provided mainly by dust grains and the required column density to the cloud center is larger than about 5 x 10 to the 20th (solar Z/Z)/sq cm. This high-opacity criterion could have a significant impact on the radial trends observed in spiral galaxies, and on the distinctions between spiral and dwarf irregular galaxies.

  13. X-Ray Dust Tomography: Mapping the Galaxy one X-ray Transient at a Time

    NASA Astrophysics Data System (ADS)

    Heinz, Sebastian; Corrales, Lia

    2018-01-01

    Tomography using X-ray light echoes from dust scattering by interstellar clouds is an accurate tool to study the line-of-sight distribution of dust. It can be used to measure distances to molecular clouds and X-ray sources, it can map Galactic structure in dust, and it can be used for precision measurements of dust composition and grain size distribution. Necessary conditions for observing echoes include a suitable X-ray lightcurve and sufficient dust column density to the source. I will discuss a tool set for studying dust echoes and show results obtained for some of the brightest echoes detected to date.

  14. Integrative Analysis of Desert Dust Size and Abundance Suggests Less Dust Climate Cooling

    NASA Technical Reports Server (NTRS)

    Kok, Jasper F.; Ridley, David A.; Zhou, Qing; Miller, Ron L.; Zhao, Chun; Heald, Colette L.; Ward, Daniel S.; Albani, Samuel; Haustein, Karsten

    2017-01-01

    Desert dust aerosols affect Earths global energy balance through interactions with radiation, clouds, and ecosystems. But the magnitudes of these effects are so uncertain that it remains unclear whether atmospheric dust has a net warming or cooling effect on global climate. Consequently, it is still uncertain whether large changes in atmospheric dust loading over the past century have slowed or accelerated anthropogenic climate change, and the climate impact of possible future alterations in dust loading is similarly disputed. Here we use an integrative analysis of dust aerosol sizes and abundance to constrain the climatic impact of dust through direct interactions with radiation. Using a combination of observational, experimental, and model data, we find that atmospheric dust is substantially coarser than represented in current climate models. Since coarse dust warms global climate, the dust direct radiative effect (DRE) is likely less cooling than the 0.4 W m superscript 2 estimated by models in a current ensemble. We constrain the dust DRE to -0.20 (-0.48 to +0.20) W m superscript 2, which suggests that the dust DRE produces only about half the cooling that current models estimate, and raises the possibility that dust DRE is actually net warming the planet.

  15. UV extinction properties of carina nebular dust

    NASA Technical Reports Server (NTRS)

    Massa, Derck

    1993-01-01

    I have performed an analysis of the UV extinction by dust along the line of sight to the young open cluster Tr 16. The observed curves are parameterized in order to extract quantitative information about the structure of the curves. Furthermore, by constructing differential extinction curves, obtained by differencing curves for stars which lie within a few arc seconds of each other on the sky, I was able to obtain a curve which is free of the effects of foreground extinction, and represents the extinction by the dust in the Tr 16 molecular cloud. I then show that this curve is nearly identical to one due to dust in the Orion molecular cloud. This result shows that dust in the Carina arm exhibits the same behavior as that in the local arm.

  16. Desert dust suppressing precipitation: A possible desertification feedback loop

    PubMed Central

    Rosenfeld, Daniel; Rudich, Yinon; Lahav, Ronen

    2001-01-01

    The effect of desert dust on cloud properties and precipitation has so far been studied solely by using theoretical models, which predict that rainfall would be enhanced. Here we present observations showing the contrary; the effect of dust on cloud properties is to inhibit precipitation. Using satellite and aircraft observations we show that clouds forming within desert dust contain small droplets and produce little precipitation by drop coalescence. Measurement of the size distribution and the chemical analysis of individual Saharan dust particles collected in such a dust storm suggest a possible mechanism for the diminished rainfall. The detrimental impact of dust on rainfall is smaller than that caused by smoke from biomass burning or anthropogenic air pollution, but the large abundance of desert dust in the atmosphere renders it important. The reduction of precipitation from clouds affected by desert dust can cause drier soil, which in turn raises more dust, thus providing a possible feedback loop to further decrease precipitation. Furthermore, anthropogenic changes of land use exposing the topsoil can initiate such a desertification feedback process. PMID:11353821

  17. Asian dust events of April 1998

    Husar, R.B.; Tratt, D.M.; Schichtel, B.A.; Falke, S.R.; Li, F.; Jaffe, D.; Gasso, S.; Gill, T.; Laulainen, N.S.; Lu, F.; Reheis, M.C.; Chun, Y.; Westphal, D.; Holben, B.N.; Gueymard, C.; McKendry, I.; Kuring, N.; Feldman, G.C.; McClain, C.; Frouin, R.J.; Merrill, J.; DuBois, D.; Vignola, F.; Murayama, T.; Nickovic, S.; Wilson, W.E.; Sassen, K.; Sugimoto, N.; Malm, W.C.

    2001-01-01

    On April 15 and 19, 1998, two intense dust storms were generated over the Gobi desert by springtime low-pressure systems descending from the northwest. The windblown dust was detected and its evolution followed by its yellow color on SeaWiFS satellite images, routine surface-based monitoring, and through serendipitous observations. The April 15 dust cloud was recirculating, and it was removed by a precipitating weather system over east Asia. The April 19 dust cloud crossed the Pacific Ocean in 5 days, subsided to the surface along the mountain ranges between British Columbia and California, and impacted severely the optical and the concentration environments of the region. In east Asia the dust clouds increased the albedo over the cloudless ocean and land by up to 10-20%, but it reduced the near-UV cloud reflectance, causing a yellow coloration of all surfaces. The yellow colored backscattering by the dust eludes a plausible explanation using simple Mie theory with constant refractive index. Over the West Coast the dust layer has increased the spectrally uniform optical depth to about 0.4, reduced the direct solar radiation by 30-40%, doubled the diffuse radiation, and caused a whitish discoloration of the blue sky. On April 29 the average excess surface-level dust aerosol concentration over the valleys of the West Coast was about 20-50 ??g/m3 with local peaks >100 ??g/m3. The dust mass mean diameter was 2-3 ??m, and the dust chemical fingerprints were evident throughout the West Coast and extended to Minnesota. The April 1998 dust event has impacted the surface aerosol concentration 2-4 times more than any other dust event since 1988. The dust events were observed and interpreted by an ad hoc international web-based virtual community. It would be useful to set up a community-supported web-based infrastructure to monitor the global aerosol pattern for such extreme aerosol events, to alert and to inform the interested communities, and to facilitate collaborative

  18. Mapping the circumsolar dust ring near the orbit of Venus

    NASA Astrophysics Data System (ADS)

    Jones, M. H.; Bewsher, D.; Brown, D. S.

    2017-05-01

    Synoptic images obtained from the HI-2 instrument on STEREO-A and -B between 2007 and 2014 have been used to further investigate the circumsolar dust ring at the orbit of Venus that was reported by Jones et al. (2013). The analysis is based on high signal-to-noise ratio photometry of the zodiacal light, using data acquired over 10-day intervals, followed by a process of extracting spatial variability on scales up to about 6.5°. The resulting images provide information about the structure of the ring at the location where it is viewed tangentially. We identify 65 usable data sets that comprise about 11% of the available HI-2 data. Analysis of these images show that the orientation of the ring appears to be different to that of the orbit of Venus, with an inclination of 2.1° and longitude of ascending node of 68.5°. We map the variation of ring density parameters in a frame of reference that is co-rotating with Venus and find a pattern suggestive of dust in a 3: 2 orbital resonance. However, the location of the maxima of dust densities is not as expected from theoretical models, and there is some evidence that the dust density distribution in the ring has a pattern speed that differs from the mean motion of Venus.

  19. Alanine aminotransferase and mortality in patients with type 2 diabetes (ZODIAC-38).

    PubMed

    Deetman, Petronella E; Alkhalaf, Alaa; Landman, Gijs W D; Groenier, Klaas H; Kootstra-Ros, Jenny E; Navis, Gerjan; Bilo, Henk J G; Kleefstra, Nanne; Bakker, Stephan J L

    2015-08-01

    Combined data suggest a bimodal association of alanine aminotransferase (ALT) with mortality in the general population. Little is known about the association of ALT with mortality in patients with type 2 diabetes. We therefore investigated the association of ALT with all-cause, cardiovascular and noncardiovascular mortality in patients with type 2 diabetes. A prospective study was performed in patients with type 2 diabetes, treated in primary care, participating in the Zwolle Outpatient Diabetes project Integrating Available Care (ZODIAC) study. Cox regression analyses were performed to determine the associations of log2 -transformed baseline ALT with all-cause, cardiovascular and noncardiovascular mortality. In 1187 patients with type 2 diabetes (67 ± 12 years, 45% female), ALT levels were 11 (8-16) U/L. During median follow-up for 11.1 (6.1-14.0) years, 553 (47%) patients died, with 238 (20%) attributable to cardiovascular causes. Overall, ALT was inversely associated with all-cause mortality (hazard ratio [HR] 0.81; 95% confidence interval [CI] 0.72-0.92), independently of potential confounders. This was less attributable to cardiovascular mortality (HR 0.87; 95% CI 0.72-1.05), than to noncardiovascular mortality (HR 0.77; 95% CI 0.65-0.90). Despite the overall inverse association of ALT with mortality, it appeared that a bimodal association with all-cause mortality was present with increasing risk for levels of ALT above normal (P = 0.003). In patients with type 2 diabetes, low levels of ALT are associated with an increased risk of all-cause mortality, in particular noncardiovascular mortality, compared to normal levels of ALT, while risk again starts to increase when levels are above normal. © 2015 Stichting European Society for Clinical Investigation Journal Foundation.

  20. Dust Ejection Induced by Small Meteoroids Impacting Martian Surface

    NASA Technical Reports Server (NTRS)

    Shuvalov, Valery

    2001-01-01

    The objective of this study is numerical modeling of meteoroid impact on the martian surface and determination of the resulting dust cloud parameters. Additional information is contained in the original extended abstract.

  1. Venus Clouds: A dirty hydrochloric acid model

    NASA Technical Reports Server (NTRS)

    Hapke, B.

    1971-01-01

    The spectral and polarization data for Venus are consistent with micron-sized, aerosol cloud particles of hydrochloric acid containing soluble and insoluble iron compounds, whose source could be volcanic or crustal dust. The ultraviolet features could arise from variations in the Fe-HCl concentration in the cloud particles.

  2. Extrasolar comets: The origin of dust in exozodiacal disks?

    NASA Astrophysics Data System (ADS)

    Marboeuf, U.; Bonsor, A.; Augereau, J.-C.

    2016-11-01

    Comets have been invoked in numerous studies as a potentially important source of dust and gas around stars, but none has studied the thermo-physical evolution, out-gassing rate, and dust ejection of these objects in such stellar systems. In this paper we investigate the thermo-physical evolution of comets in exo-planetary systems in order to provide valuable theoretical data required to interpret observations of gas and dust. We use a quasi-3D model of cometary nucleus to study the thermo-physical evolution of comets evolving around a single star from 0.1 to 50 AU, whose homogeneous luminosity varies from 0.1 to 70L⊙. This paper provides thermal evolution, physical alteration, mass ejection, lifetimes, and the rate of dust and water gas mass productions for comets as a function of the distance to the star and stellar luminosity. Results show significant physical changes to comets at high stellar luminosities. The mass loss per revolution and the lifetime of comets depend on their initial size, orbital parameters and follow a power law with stellar luminosity. The models are presented in such a manner that they can be readily applied to any planetary system. By considering the examples of the Solar System, Vega and HD 69830, we show that dust grains released from sublimating comets have the potential to create the observed (exo)zodiacal emission. We show that observations can be reproduced by 1 to 2 massive comets or by a large number of comets whose orbits approach close to the star. Our conclusions depend on the stellar luminosity and the uncertain lifetime of the dust grains. We find, as in previous studies, that exozodiacal dust disks can only survive if replenished by a population of typically sized comets renewed from a large and cold reservoir of cometary bodies beyond the water ice line. These comets could reach the inner regions of the planetary system following scattering by a (giant) planet.

  3. Ice nucleation by soil dust compared to desert dust aerosols

    NASA Astrophysics Data System (ADS)

    Moehler, O.; Steinke, I.; Ullrich, R.; Höhler, K.; Schiebel, T.; Hoose, C.; Funk, R.

    2015-12-01

    A minor fraction of atmospheric aerosol particles, so-called ice-nucleating particles (INPs), initiates the formation of the ice phase in tropospheric clouds and thereby markedly influences the Earth's weather and climate systems. Whether an aerosol particle acts as an INP depends on its size, morphology and chemical compositions. The INP fraction of certain aerosol types also strongly depends on the temperature and the relative humidity. Because both desert dust and soil dust aerosols typically comprise a variety of different particles, it is difficult to assess and predict their contribution to the atmospheric INP abundance. This requires both accurate modelling of the sources and atmospheric distribution of atmospheric dust components and detailed investigations of their ice nucleation activities. The latter can be achieved in laboratory experiments and parameterized for use in weather and climate models as a function of temperature and particle surface area, a parameter called ice-nucleation active site (INAS) density. Concerning ice nucleation activity studies, the soil dust is of particular interest because it contains a significant fraction of organics and biological components, both with the potential for contributing to the atmospheric INP abundance at relatively high temperatures compared to mineral components. First laboratory ice nucleation experiments with a few soil dust samples indicated their INP fraction to be comparable or slightly enhanced to that of desert dust. We have used the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud simulation chamber to study the immersion freezing ability of four different arable soil dusts, sampled in Germany, China and Argentina. For temperatures higher than about -20°C, we found the INP fraction of aerosols generated from these samples by a dry dispersion technique to be significantly higher compared to various desert dust aerosols also investigated in AIDA experiments. In this contribution, we

  4. The Continuous Monitoring of Desert Dust using an Infrared-based Dust Detection and Retrieval Method

    NASA Technical Reports Server (NTRS)

    Duda, David P.; Minnis, Patrick; Trepte, Qing; Sun-Mack, Sunny

    2006-01-01

    Airborne dust and sand are significant aerosol sources that can impact the atmospheric and surface radiation budgets. Because airborne dust affects visibility and air quality, it is desirable to monitor the location and concentrations of this aerosol for transportation and public health. Although aerosol retrievals have been derived for many years using visible and near-infrared reflectance measurements from satellites, the detection and quantification of dust from these channels is problematic over bright surfaces, or when dust concentrations are large. In addition, aerosol retrievals from polar orbiting satellites lack the ability to monitor the progression and sources of dust storms. As a complement to current aerosol dust retrieval algorithms, multi-spectral thermal infrared (8-12 micron) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Meteosat-8 Spinning Enhanced Visible and Infrared Imager (SEVIRI) are used in the development of a prototype dust detection method and dust property retrieval that can monitor the progress of Saharan dust fields continuously, both night and day. The dust detection method is incorporated into the processing of CERES (Clouds and the Earth s Radiant Energy System) aerosol retrievals to produce dust property retrievals. Both MODIS (from Terra and Aqua) and SEVERI data are used to develop the method.

  5. The US Naval Observatory Zodiacal Zone Catalog (Douglas and Harrington 1990): Documentation for the machine-readable version

    NASA Technical Reports Server (NTRS)

    Warren, Wayne H., Jr.

    1990-01-01

    The machine readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The Zodiacal Zone Catalog is a catalog of positions and proper motions for stars in the magnitude range where m sub v is between 4 and 10, lying within 16 deg of the ecliptic and north of declination -30 deg. The catalog contains positions and proper motions, at epoch, for equator and equinox J2000.0, magnitudes and spectral types taken mostly from the Smithsonian Astrophysical Observatory Star Catalog, and reference positions and proper motions for equinox and epoch B1950.0.

  6. African Dust Aerosols as Atmospheric Ice Nuclei

    NASA Technical Reports Server (NTRS)

    DeMott, Paul J.; Brooks, Sarah D.; Prenni, Anthony J.; Kreidenweis, Sonia M.; Sassen, Kenneth; Poellot, Michael; Rogers, David C.; Baumgardner, Darrel

    2003-01-01

    Measurements of the ice nucleating ability of aerosol particles in air masses over Florida having sources from North Africa support the potential importance of dust aerosols for indirectly affecting cloud properties and climate. The concentrations of ice nuclei within dust layers at particle sizes below 1 pn exceeded 1/cu cm; the highest ever reported with our device at temperatures warmer than homogeneous freezing conditions. These measurements add to previous direct and indirect evidence of the ice nucleation efficiency of desert dust aerosols, but also confirm their contribution to ice nuclei populations at great distances from source regions.

  7. Full-sky, High-resolution Maps of Interstellar Dust

    NASA Astrophysics Data System (ADS)

    Meisner, Aaron Michael

    We present full-sky, high-resolution maps of interstellar dust based on data from the Wide-field Infrared Survey Explorer (WISE) and Planck missions. We describe our custom processing of the entire WISE 12 micron All-Sky imaging data set, and present the resulting 15 arcsecond resolution, full-sky map of diffuse Galactic dust emission, free of compact sources and other contaminating artifacts. Our derived 12 micron dust map offers angular resolution far superior to that of all other existing full-sky, infrared dust emission maps, revealing a wealth of small-scale filamentary structure. We also apply the Finkbeiner et al. (1999) two-component thermal dust emission model to the Planck HFI maps. We derive full-sky 6.1 arcminute resolution maps of dust optical depth and temperature by fitting this two-component model to Planck 217-857 GHz along with DIRBE/IRAS 100 micron data. In doing so, we obtain the first ever full-sky 100-3000 GHz Planck-based thermal dust emission model, as well as a dust temperature correction with ~10 times enhanced angular resolution relative to DIRBE-based temperature maps. Analyzing the joint Planck/DIRBE dust spectrum, we show that two-component models provide a better fit to the 100-3000 GHz emission than do single-MBB models, though by a lesser margin than found by Finkbeiner et al. (1999) based on FIRAS and DIRBE. We find that, in diffuse sky regions, our two-component 100-217 GHz predictions are on average accurate to within 2.2%, while extrapolating the Planck Collaboration (2013) single-MBB model systematically underpredicts emission by 18.8% at 100 GHz, 12.6% at 143 GHz and 7.9% at 217 GHz. We calibrate our two-component optical depth to reddening, and compare with reddening estimates based on stellar spectra. We find the dominant systematic problems in our temperature/reddening maps to be zodiacal light on large angular scales and the cosmic infrared background anisotropy on small angular scales. Future work will focus on combining

  8. A simplified Suomi NPP VIIRS dust detection algorithm

    NASA Astrophysics Data System (ADS)

    Yang, Yikun; Sun, Lin; Zhu, Jinshan; Wei, Jing; Su, Qinghua; Sun, Wenxiao; Liu, Fangwei; Shu, Meiyan

    2017-11-01

    Due to the complex characteristics of dust and sparse ground-based monitoring stations, dust monitoring is facing severe challenges, especially in dust storm-prone areas. Aim at constructing a high-precision dust storm detection model, a pixel database, consisted of dusts over a variety of typical feature types such as cloud, vegetation, Gobi and ice/snow, was constructed, and their distributions of reflectance and Brightness Temperatures (BT) were analysed, based on which, a new Simplified Dust Detection Algorithm (SDDA) for the Suomi National Polar-Orbiting Partnership Visible infrared Imaging Radiometer (NPP VIIRS) is proposed. NPP VIIRS images covering the northern China and Mongolian regions, where features serious dust storms, were selected to perform the dust detection experiments. The monitoring results were compared with the true colour composite images, and results showed that most of the dust areas can be accurately detected, except for fragmented thin dusts over bright surfaces. The dust ground-based measurements obtained from the Meteorological Information Comprehensive Analysis and Process System (MICAPS) and the Ozone Monitoring Instrument Aerosol Index (OMI AI) products were selected for comparison purposes. Results showed that the dust monitoring results agreed well in the spatial distribution with OMI AI dust products and the MICAPS ground-measured data with an average high accuracy of 83.10%. The SDDA is relatively robust and can realize automatic monitoring for dust storms.

  9. Dust grains from the heart of supernovae

    NASA Astrophysics Data System (ADS)

    Bocchio, Marco; Marassi, Stefania; Schneider, Raffaella; Bianchi, Simone; Limongi, Marco; Chieffi, A.

    2016-06-01

    Dust grains are classically thought to form in the winds of asymptotic giant branch (AGB) stars. However, there is increasing evidence today for dust formation in supernovae (SNe). To establish the relative importance of these two classes of stellar sources of dust, it is important to know the fraction of freshly formed dust in SN ejecta that is able to survive the passage of the reverse shock and be injected in the interstellar medium. We have developed a new code (GRASH_Rev) which follows the newly-formed dust evolution throughout the supernova explosion until the merging of the forward shock with the circumstellar ISM. We have considered four well studied SNe in the Milky Way and Large Magellanic Cloud: SN1987A, CasA, the Crab Nebula, and N49. For all the simulated models, we find good agreement with observations and estimate that between 1 and 8% of the observed mass will survive, leading to a SN dust production rate of (3.9± 3.7)×10^(-4) MM_{⊙})/yr in the Milky Way. This value is one order of magnitude larger than the dust production rate by AGB stars but insufficient to counterbalance the dust destruction by SNe, therefore requiring dust accretion in the gas phase.

  10. Testing the sensitivity of past climates to the indirect effects of dust

    NASA Astrophysics Data System (ADS)

    Sagoo, Navjit; Storelvmo, Trude

    2017-06-01

    Mineral dust particles are important ice nuclei (IN) and as such indirectly impact Earth's radiative balance via the properties of cold clouds. Using the Community Earth System Model version 1.0.6, and Community Atmosphere Model version 5.1, and a new empirical parameterization for ice nucleation on dust particles, we investigate the radiative forcing induced by dust IN for different dust loadings. Dust emissions are representative of global conditions for the Last Glacial Maximum and the mid-Pliocene Warm Period. Increased dust leads to smaller and more numerous ice crystals in mixed phase clouds, impacting cloud opacity, lifetime, and precipitation. This increases the shortwave cloud radiative forcing, resulting in significant surface temperature cooling and polar amplification—which is underestimated in existing studies relative to paleoclimate archives. Large hydrological changes occur and are linked to an enhanced dynamical response. We conclude that dust indirect effects could potentially have a significant impact on the model-data mismatch that exists for paleoclimates.Plain Language SummaryMineral <span class="hlt">dust</span> and climate are closely linked, with large fluctuations in <span class="hlt">dust</span> deposition recorded in geological archives. Dusty conditions are generally associated with cold, glacial periods and low <span class="hlt">dust</span> with warmer climates. The direct effects of <span class="hlt">dust</span> on the climate (absorbing and reflecting radiation) are well understood; however, the indirect effects of <span class="hlt">dust</span> on climate have been overlooked. <span class="hlt">Dust</span> indirectly impacts the climate through its role as ice nuclei; the presence of <span class="hlt">dust</span> makes it easier for ice to form in a <span class="hlt">cloud</span>. We explore the indirect effects of <span class="hlt">dust</span> in climates with different <span class="hlt">dust</span> loading from the present by conducting a climate modeling study in which <span class="hlt">dust</span> are able to act as ice nuclei. Including <span class="hlt">dust</span> indirect effects increases the sensitivity of our model to changes in <span class="hlt">dust</span> emission. Increasing <span class="hlt">dust</span> impacts ice</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900045348&hterms=1101&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231101','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900045348&hterms=1101&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3D%2526%25231101"><span>Physical conditions in molecular <span class="hlt">clouds</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Evans, Neal J., II</p> <p>1989-01-01</p> <p>Recent developments have complicated the picture of the physical conditions in molecular <span class="hlt">clouds</span>. The discoveries of widespread emission from high-J lines of CD and 12-micron IRAS emission have revealed the presence of considerably hotter gas and <span class="hlt">dust</span> near the surfaces of molecular <span class="hlt">clouds</span>. These components can complicate interpretation of the bulk of the <span class="hlt">cloud</span> gas. Commonly assumed relations between column density or mean density and <span class="hlt">cloud</span> size are called into question by conflicting results and by consideration of selection effects. Analysis of density and density structure through molecular excitation has shown that very high densities exist in star formation regions, but unresolved structure and possible chemical effects complicate the interpretation. High resolution far-IR and submillimeter observations offer a complementary approach and are beginning to test theoretical predictions of density gradients in <span class="hlt">clouds</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A21K2302Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A21K2302Y"><span>Identification of <span class="hlt">dust</span> source regions and <span class="hlt">dust</span> emission trends across North Africa and the Middle East using MISR satellite observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Y.; Kalashnikova, O. V.; Garay, M. J.; Notaro, M.</p> <p>2017-12-01</p> <p>Global arid and semi-arid regions supply 1100 to 5000 Tg of Aeolian <span class="hlt">dust</span> to the atmosphere each year, primarily from North Africa and secondarily from the Middle East. Previous <span class="hlt">dust</span> source identification methods, based on either remotely-sensed aerosol optical depth (AOD) or <span class="hlt">dust</span> activity, yield distinct <span class="hlt">dust</span> source maps, largely due to the limitations in each method and remote-sensing product. Here we apply a novel motion-based method for <span class="hlt">dust</span> source identification. <span class="hlt">Dust</span> plume thickness and motion vectors from Multi-angle Imaging SpectroRadiometer (MISR) <span class="hlt">Cloud</span> Motion Vector Product (CMVP) are examined to identify the regions with high frequency of fast moving-<span class="hlt">dust</span> plumes, by season. According to MISR CMVP, Bodele depression is the most important <span class="hlt">dust</span> source across North Africa, consistent with previous studies. Seasonal variability of <span class="hlt">dust</span> emission across the North Africa is largely driven by climatology of wind and precipitation, featuring the influence of Sharav Cyclone and western African monsoon. In the Middle East, Iraq, Kuwait, and eastern Saudi Arabia are identified as <span class="hlt">dust</span> source regions, especially during summer months, when the Middle Eastern Shamal wind is active. Furthermore, <span class="hlt">dust</span> emission trend at each <span class="hlt">dust</span> source are diagnosed from the motion-based <span class="hlt">dust</span> source dataset. Increase in <span class="hlt">dust</span> emission from the Fertile Crescent, Sahel, and eastern African <span class="hlt">dust</span> sources are identified from MISR CMVP, implying potential contribution from these <span class="hlt">dust</span> sources to the upward trend in AOD and <span class="hlt">dust</span> AOD over the Middle East in the 21st century. By comparing with various <span class="hlt">dust</span> source identification studies, we conclude that the motion-based identification of <span class="hlt">dust</span> sources is an encouraging alternative and compliment to the AOD-only source identification method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950041632&hterms=cloud+database&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcloud%2Bdatabase','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950041632&hterms=cloud+database&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dcloud%2Bdatabase"><span>IRAS images of nearby dark <span class="hlt">clouds</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wood, Douglas O. S.; Myers, Philip C.; Daugherty, Debra A.</p> <p>1994-01-01</p> <p>We have investigated approximately 100 nearby molecular <span class="hlt">clouds</span> using the extensive, all-sky database of IRAS. The <span class="hlt">clouds</span> in this study cover a wide range of physical properties including visual extinction, size, mass, degree of isolation, homogeneity and morphology. IRAS 100 and 60 micron co-added images were used to calculate the 100 micron optical depth of <span class="hlt">dust</span> in the <span class="hlt">clouds</span>. These images of <span class="hlt">dust</span> optical depth compare very well with (12)CO and (13)CO observations, and can be related to H2 column density. From the optical depth images we locate the edges of dark <span class="hlt">clouds</span> and the dense cores inside them. We have identified a total of 43 `IRAS <span class="hlt">clouds</span>' (regions with A(sub v) greater than 2) which contain a total of 255 `IRAS cores' (regions with A(sub v) greater than 4) and we catalog their physical properties. We find that the <span class="hlt">clouds</span> are remarkably filamentary, and that the cores within the <span class="hlt">clouds</span> are often distributed along the filaments. The largest cores are usually connected to other large cores by filaments. We have developed selection criteria to search the IRAS Point Source Catalog for stars that are likely to be associated with the <span class="hlt">clouds</span> and we catalog the IRAS sources in each <span class="hlt">cloud</span> or core. Optically visible stars associated with the <span class="hlt">clouds</span> have been identified from the Herbig and Bell catalog. From these data we characterize the physical properties of the <span class="hlt">clouds</span> including their star-formation efficiency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/40458','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/40458"><span>The influence of an extensive <span class="hlt">dust</span> event on snow chemistry in the southern Rocky Mountains</span></a></p> <p><a target="_blank" href=""></a></p> <p>Charles Rhoades; Kelly Elder; E. Greene</p> <p>2010-01-01</p> <p>In mid-February 2006, windstorms in Arizona, Utah, and western Colorado generated a <span class="hlt">dust</span> <span class="hlt">cloud</span> that distributed a layer of <span class="hlt">dust</span> across the surface of the snowpack throughout much of the Colorado Rockies; it remained visible throughout the winter. We compared the chemical composition of snowfall and snowpack collected during and after the <span class="hlt">dust</span> deposition event with pre-...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740011343','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740011343"><span>Cosmic <span class="hlt">dust</span> in the atmosphere and in the interplanetary space at 1 AU today and in the early solar system</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fechtig, H.</p> <p>1973-01-01</p> <p>A description of techniques used in recent experiments to detect and analyze cosmic <span class="hlt">dust</span> and micrometeorites is given and the results both from the study of lunar crater statistics and from in situ measurements are reviewed. The results from lunar crater statistics show an agreement with the results obtained from in situ measurements in interplanetary space and derived from <span class="hlt">zodiacal</span> light measurements. The near earth results show an enhancement in the flux numbers. This can be caused either by secondary lunar debris or by disintegration of low density fireballs in the outer atmosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730019028','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730019028"><span>Skylab experiment performance evaluation manual. Appendix T: Experiment T027/S073 contamination measurement, photometer and Gegenschein/<span class="hlt">zodiacal</span> light (MSFC)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Meyers, J. E.</p> <p>1973-01-01</p> <p>A series of analyses for Experiment T027/S073, contamination measurement, photometer and gegenschein/<span class="hlt">zodiacal</span> light (MSFC), to be used for evaluating the performance of the Skylab corollary experiments under preflight, inflight, and post-flight conditons is presented. Experiment contingency plan workaround procedure and malfunction analyses are presented in order to assist in making the experiment operationally successful.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016cosp...41E.835H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016cosp...41E.835H"><span>Summary of the results from the Lunar <span class="hlt">Dust</span> Experiment (LDEX) onboard the Lunar Atmosphere and <span class="hlt">Dust</span> Environment (LADEE) Mission</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Horanyi, Mihaly</p> <p>2016-07-01</p> <p>The Lunar <span class="hlt">Dust</span> Experiment (LDEX) onboard the Lunar Atmosphere and <span class="hlt">Dust</span> Environment Explorer (LADEE) mission (9/2013 - 4/2014) discovered a permanently present <span class="hlt">dust</span> <span class="hlt">cloud</span> engulfing the Moon. The size, velocity, and density distributions of the <span class="hlt">dust</span> particles are consistent with ejecta <span class="hlt">clouds</span> generated from the continual bombardment of the lunar surface by sporadic interplanetary <span class="hlt">dust</span> particles. Intermittent density enhancements were observed during several of the annual meteoroid streams, especially during the Geminids. LDEX found no evidence of the expected density enhancements over the terminators where electrostatic processes were predicted to efficiently loft small grains. LDEX is an impact ionization <span class="hlt">dust</span> detector, it captures coincident signals and full waveforms to reliably identify <span class="hlt">dust</span> impacts. LDEX recorded average impact rates of approximately 1 and 0.1 hits/minute of particles with impact charges of q > 0.5 and q > 5 fC, corresponding to particles with radii of a > 0.3 and a> 0.7~μm, respectively. Several of the yearly meteor showers generated sustained elevated levels of impact rates, especially if their radiant direction intersected the lunar surface near the equatorial plane, greatly enhancing the probability of crossing their ejecta plumes. The characteristic velocities of <span class="hlt">dust</span> particles in the <span class="hlt">cloud</span> are on the order of ~100 m/s which we neglect compared to the typical spacecraft speeds of 1.6 km/s. Hence, with the knowledge of the spacecraft orbit and attitude, impact rates can be directly turned into particle densities as functions of time and position. LDEX observations are the first to identify the ejecta <span class="hlt">clouds</span> around the Moon sustained by the continual bombardment of interplanetary <span class="hlt">dust</span> particles. Most of the <span class="hlt">dust</span> particles generated in impacts have insufficient energy to escape and follow ballistic orbits, returning to the surface, 'gardening' the regolith. Similar ejecta <span class="hlt">clouds</span> are expected to engulf all airless planetary objects, including</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010371','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010371"><span>Global Analysis of Aerosol Properties Above <span class="hlt">Clouds</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Waquet, F.; Peers, F.; Ducos, F.; Goloub, P.; Platnick, S. E.; Riedi, J.; Tanre, D.; Thieuleux, F.</p> <p>2013-01-01</p> <p>The seasonal and spatial varability of Aerosol Above <span class="hlt">Cloud</span> (AAC) properties are derived from passive satellite data for the year 2008. A significant amount of aerosols are transported above liquid water <span class="hlt">clouds</span> on the global scale. For particles in the fine mode (i.e., radius smaller than 0.3 m), including both clear sky and AAC retrievals increases the global mean aerosol optical thickness by 25(+/- 6%). The two main regions with man-made AAC are the tropical Southeast Atlantic, for biomass burning aerosols, and the North Pacific, mainly for pollutants. Man-made AAC are also detected over the Arctic during the spring. Mineral <span class="hlt">dust</span> particles are detected above <span class="hlt">clouds</span> within the so-called <span class="hlt">dust</span> belt region (5-40 N). AAC may cause a warming effect and bias the retrieval of the <span class="hlt">cloud</span> properties. This study will then help to better quantify the impacts of aerosols on <span class="hlt">clouds</span> and climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20090005026&hterms=If+world+asteroid&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DIf%2Bworld%2Basteroid','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20090005026&hterms=If+world+asteroid&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DIf%2Bworld%2Basteroid"><span>Detecting Exoplanets with the New Worlds Observer: The Problem of Exozodiacal <span class="hlt">Dust</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Roberge, A.; Noecker, M. C.; Glassman, T. M.; Oakley, P.; Turnbull, M. C.</p> <p>2009-01-01</p> <p><span class="hlt">Dust</span> coming from asteroids and comets will strongly affect direct imaging and characterization of terrestrial planets in the Habitable Zones of nearby stars. Such <span class="hlt">dust</span> in the Solar System is called the <span class="hlt">zodiacal</span> <span class="hlt">dust</span> (or 'zodi' for short). Higher levels of similar <span class="hlt">dust</span> are seen around many nearby stars, confined in disks called debris disks. Future high-contrast images of an Earth-like exoplanet will very likely be background-limited by light scattered of both the local Solar System zodi and the circumstellar <span class="hlt">dust</span> in the extrasolar system (the exozodiacal <span class="hlt">dust</span>). Clumps in the exozodiacal <span class="hlt">dust</span>, which are expected in planet-hosting systems, may also be a source of confusion. Here we discuss the problems associated with imaging an Earth-like planet in the presence of unknown levels of exozodiacal <span class="hlt">dust</span>. Basic formulae for the exoplanet imaging exposure time as function of star, exoplanet, zodi, exozodi, and telescope parameters will be presented. To examine the behavior of these formulae, we apply them to the New Worlds Observer (NWO) mission. NWO is a proposed 4-meter UV/optical/near-IR telescope, with a free flying starshade to suppress the light from a nearby star and achieve the high contrast needed for detection and characterization of a terrestrial planet in the star's Habitable Zone. We find that NWO can accomplish its science goals even if exozodiacal <span class="hlt">dust</span> levels are typically much higher than the Solar System zodi level. Finally, we highlight a few additional problems relating to exozodiacal <span class="hlt">dust</span> that have yet to be solved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1398167-overview-mineral-dust-modeling-over-east-asia','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1398167-overview-mineral-dust-modeling-over-east-asia"><span>An overview of mineral <span class="hlt">dust</span> modeling over East Asia</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciT</a></p> <p>Chen, Siyu; Huang, Jianping; Qian, Yun</p> <p></p> <p><span class="hlt">Dust</span> aerosol, one of the most abundant aerosol species in the atmosphere, has significant impacts on the energy balance and climatic feedback of the Earth system through its influence on solar and terrestrial radiation as well as <span class="hlt">clouds</span>. East Asia is the one of prominent regions of <span class="hlt">dust</span> generation. The East Asia <span class="hlt">dust</span> life cycle and associated radiative and climatic effects are the outstanding science issues in understanding climate change at regional and even global scale. In the past decades, numerous <span class="hlt">dust</span> models have been developed and applied to comprehend a series of <span class="hlt">dust</span>-related processes studies, including emission, transport, andmore » deposition, and to understand the effects of <span class="hlt">dust</span> aerosol on the radiation and climate over East Asian. In this paper, we review the recent achievements and progresses in East Asian <span class="hlt">dust</span> modeling research and discuss the potential challenges in future studies.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1014755','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1014755"><span><span class="hlt">Cloud</span> Computing</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2010-04-29</p> <p><span class="hlt">Cloud</span> Computing   The answer, my friend, is blowing in the wind.   The answer is blowing in the wind. 1Bingue ‐ Cook  <span class="hlt">Cloud</span>   Computing  STSC 2010... <span class="hlt">Cloud</span>   Computing  STSC 2010 Objectives • Define the <span class="hlt">cloud</span>    • Risks of  <span class="hlt">cloud</span>   computing f l d i• Essence o  c ou  comput ng • Deployed <span class="hlt">clouds</span> in DoD 3Bingue...Cook  <span class="hlt">Cloud</span>   Computing  STSC 2010 Definitions of <span class="hlt">Cloud</span> Computing       <span class="hlt">Cloud</span>   computing  is a model for enabling  b d d ku</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21713579','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21713579"><span>Popular belief meets surgical reality: impact of lunar phases, Friday the 13th and <span class="hlt">zodiac</span> signs on emergency operations and intraoperative blood loss.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schuld, Jochen; Slotta, Jan E; Schuld, Simone; Kollmar, Otto; Schilling, Martin K; Richter, Sven</p> <p>2011-09-01</p> <p>The influence of superstition, moon calendars, and popular belief on evidence-based medicine is stunning. More than 40% of medical staff is convinced that lunar phases can affect human behavior. The idea that Friday the 13th is associated with adverse events and bad luck is deep-rooted in the population of Western industrial countries. The aim of the present study was to test the hypothesis that these myths are transferable to real-life surgery. We analyzed the extent to which moon phases, <span class="hlt">zodiac</span> signs, and Friday the 13th influence blood loss, emergency frequency, and intestinal perforations by evaluating the operation records of all 27,914 consecutive patients of our institution undergoing general, visceral, or vascular surgery between August 2001 and August 2010. Dates of surgery were allocated to lunar phases and to <span class="hlt">zodiac</span> signs, as well as to Friday the 13th. A total of 111 lunar cycles and 15 Fridays the 13th occurred within the 3,281-day observation period. Patients' characteristics did not differ in lunar phases, <span class="hlt">zodiac</span> signs, or Fridays the 13th. Full moon phases, the presence of Friday the 13th, and <span class="hlt">zodiac</span> signs influenced neither intraoperative blood loss nor emergency frequency. No statistical peaks regarding perforated aortic aneurysms and gastrointestinal perforations were found on full moon or Friday the 13th. Scientific analysis of our data does not support the belief that moon phases, <span class="hlt">zodiac</span> signs, or Friday 13th influence surgical blood loss and emergency frequency. Our data indicate that such beliefs are myths far beyond reality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17333517','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17333517"><span>Lunar phases and <span class="hlt">zodiac</span> signs do not influence quality of radical cystectomy--a statistical analysis of 452 patients with invasive bladder cancer.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>May, Matthias; Braun, Kay-Patrick; Helke, Christian; Richter, Willi; Vogler, Horst; Hoschke, Bernd; Siegsmund, Michael</p> <p>2007-01-01</p> <p>To determine the influence of the lunar phases and the position of the moon in the <span class="hlt">zodiac</span> on the frequency of complications and the survival of bladder cancer patients after radical cystectomy. It has been postulated that radical cystectomy performed during the waxing moon, or particularly at full moon, or at the <span class="hlt">zodiac</span> sign Libra is associated with a poorer outcome. We tested this hypothesis by evaluating the progression-free survival, the complication rate and the re-operation rate for 452 consecutive patients after radical cystectomy. In this retrospective review, the dates of surgery were allocated to the lunar phases and the <span class="hlt">zodiac</span> signs. Based on these classifications, the patients were placed in groups which combined the lunar phase laws and differentiated between evidently unfavorable (full moon or waxing moon and/or the <span class="hlt">zodiac</span> sign Libra; assigned to group 1) and favorable periods for surgery (new moon or waning moon and other signs of the <span class="hlt">zodiac</span> apart from Libra; assigned to group 2). The mean follow-up was 49 months (range 0-158 months). A total of 244 patients (54%) were operated during an unfavorable period (group 1) and 208 (46%) patients during the auspicious period (group 2). The mean age, gender and kind of urinary derivation did not differ significantly in the two groups. Pathological tumor stages were evenly distributed according to the lunar phase groups (P = 0.713). We found no significant differences in the perioperative mortality rates, early re-operation rates, early complications, and late complications across the two groups. No significant differences in progression-free survival were observed when timing of cystectomy during the lunar cycle was considered (P = 0.231). Our analysis demonstrated no predictable influence of the lunar phase on survival or complications. Although this was not a prospective randomized trial, the statistical magnitude of the results do not support any recommendations for scheduling patients for radical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140016979','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140016979"><span>Far-Reaching Impacts of African <span class="hlt">Dust</span>- A Calipso Perspective</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yu, Hongbin; Chin, Mian; Yuan, Tianle; Bian, Huisheng; Prospero, Joseph; Omar, Ali; Remer, Lorraine; Winker, David; Yang, Yuekui; Zhang, Yan; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20140016979'); toggleEditAbsImage('author_20140016979_show'); toggleEditAbsImage('author_20140016979_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20140016979_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20140016979_hide"></p> <p>2014-01-01</p> <p>African <span class="hlt">dust</span> can transport across the tropical Atlantic and reach the Amazon basin, exerting far-reaching impacts on climate in downwind regions. The transported <span class="hlt">dust</span> influences the surface-atmosphere interactions and <span class="hlt">cloud</span> and precipitation processes through perturbing the surface radiative budget and atmospheric radiative heating and acting as <span class="hlt">cloud</span> condensation nuclei and ice nuclei. <span class="hlt">Dust</span> also influences biogeochemical cycle and climate through providing nutrients vital to the productivity of ocean biomass and Amazon forests. Assessing these climate impacts relies on an accurate quantification of <span class="hlt">dust</span> transport and deposition. Currently model simulations show extremely large diversity, which calls for a need of observational constraints. Kaufman et al. (2005) estimated from MODIS aerosol measurements that about 144 Tg of <span class="hlt">dust</span> is deposited into the tropical Atlantic and 50 Tg of <span class="hlt">dust</span> into the Amazon in 2001. This estimated <span class="hlt">dust</span> import to Amazon is a factor of 3-4 higher than other observations and models. However, several studies have argued that the oversimplified characterization of <span class="hlt">dust</span> vertical profile in the study would have introduced large uncertainty and very likely a high bias. In this study we quantify the trans-Atlantic <span class="hlt">dust</span> transport and deposition by using 7 years (2007-2013) observations from CALIPSO lidar. CALIPSO acquires high-resolution aerosol extinction and depolarization profiles in both <span class="hlt">cloud</span>-free and above-<span class="hlt">cloud</span> conditions. The unique CALIPSO capability of profiling aerosols above <span class="hlt">clouds</span> offers an unprecedented opportunity of examining uncertainties associated with the use of MODIS clear-sky data. <span class="hlt">Dust</span> is separated from other types of aerosols using the depolarization measurements. We estimated that on the basis of 7-year average, 118142 Tg of <span class="hlt">dust</span> is deposited into the tropical Atlantic and 3860 Tg of <span class="hlt">dust</span> into the Amazon basin. Substantial interannual variations are observed during the period, with the maximum to minimum ratio of about 1</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006ERL.....1a1001R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006ERL.....1a1001R"><span>PERSPECTIVE: <span class="hlt">Dust</span>, fertilization and sources</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Remer, Lorraine A.</p> <p>2006-11-01</p> <p>Aerosols, tiny suspended particles in the atmosphere, play an important role in modifying the Earth's energy balance and are essential for the formation of <span class="hlt">cloud</span> droplets. Suspended <span class="hlt">dust</span> particles lifted from the world's arid regions by strong winds contain essential minerals that can be transported great distances and deposited into the ocean or on other continents where productivity is limited by lack of usable minerals [1]. <span class="hlt">Dust</span> can transport pathogens as well as minerals great distance, contributing to the spread of human and agricultural diseases, and a portion of <span class="hlt">dust</span> can be attributed to human activity suggesting that <span class="hlt">dust</span> radiative effects should be included in estimates of anthropogenic climate forcing. The greenish and brownish tints in figure 1 show the wide extent of monthly mean mineral <span class="hlt">dust</span> transport, as viewed by the MODerate resolution Imaging Spectroradiometer (MODIS) satellite sensor. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite Figure 1. The monthly mean global aerosol system for February 2006 from the MODIS aboard the Terra satellite. The brighter the color, the greater the aerosol loading. Red and reddish tints indicate aerosol dominated by small particles created primarily from combustion processes. Green and brownish tints indicate larger particles created from wind-driven processes, usually transported desert <span class="hlt">dust</span>. Note the bright green band at the southern edge of the Saharan desert, the reddish band it must cross if transported to the southwest and the long brownish transport path as it crosses the Atlantic to South America. Image courtesy of the NASA Earth Observatory (http://earthobservatory.nasa.gov). Even though qualitatively we recognize the extent and importance of <span class="hlt">dust</span> transport and the role that it plays in fertilizing nutrient-limited regions, there is much that is still unknown. We are just now beginning to quantify the amount of <span class="hlt">dust</span> that exits one continental region and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACP....1511653H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACP....1511653H"><span>Detection of anthropogenic <span class="hlt">dust</span> using CALIPSO lidar measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, J. P.; Liu, J. J.; Chen, B.; Nasiri, S. L.</p> <p>2015-10-01</p> <p>Anthropogenic <span class="hlt">dusts</span> are those produced by human activities on disturbed soils, which are mainly cropland, pastureland, and urbanized regions, and are a subset of the total <span class="hlt">dust</span> load which includes natural sources from desert regions. Our knowledge of anthropogenic <span class="hlt">dusts</span> is still very limited due to a lack of data. To understand the contribution of anthropogenic <span class="hlt">dust</span> to the total global <span class="hlt">dust</span> load, it is important to identify it apart from total <span class="hlt">dust</span>. In this study, a new technique for distinguishing anthropogenic <span class="hlt">dust</span> from natural <span class="hlt">dust</span> is proposed by using <span class="hlt">Cloud</span>-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) <span class="hlt">dust</span> and planetary boundary layer (PBL) height retrievals along with a land use data set. Using this technique, the global distribution of <span class="hlt">dust</span> is analyzed and the relative contribution of anthropogenic and natural <span class="hlt">dust</span> sources to regional and global emissions are estimated. Results reveal that local anthropogenic <span class="hlt">dust</span> aerosol due to human activity, such as agriculture, industrial activity, transportation, and overgrazing, accounts for about 25 % of the global continental <span class="hlt">dust</span> load. Of these anthropogenic <span class="hlt">dust</span> aerosols, more than 53 % come from semi-arid and semi-wet regions. Annual mean anthropogenic <span class="hlt">dust</span> column burden (DCB) values range from 0.42 g m-2, with a maximum in India, to 0.12 g m-2, with a minimum in North America. A better understanding of anthropogenic <span class="hlt">dust</span> emission will enable us to focus on human activities in these critical regions and with such knowledge we will be more able to improve global <span class="hlt">dust</span> models and to explore the effects of anthropogenic emission on radiative forcing, climate change, and air quality in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACPD...1510163H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACPD...1510163H"><span>Detection of anthropogenic <span class="hlt">dust</span> using CALIPSO lidar measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, J.; Liu, J.; Chen, B.; Nasiri, S. L.</p> <p>2015-04-01</p> <p>Anthropogenic <span class="hlt">dusts</span> are those produced by human activities on disturbed soils, which are mainly cropland, pasture, and urbanized regions and are a subset of the total <span class="hlt">dust</span> load which includes natural sources from desert regions. Our knowledge of anthropogenic <span class="hlt">dusts</span> is still very limited due to a lack of data on source distribution and magnitude, and on their effect on radiative forcing which may be comparable to other anthropogenic aerosols. To understand the contribution of anthropogenic <span class="hlt">dust</span> to the total global <span class="hlt">dust</span> load and its effect on radiative transfer and climate, it is important to identify them from total <span class="hlt">dust</span>. In this study, a new technique for distinguishing anthropogenic <span class="hlt">dust</span> from natural <span class="hlt">dust</span> is proposed by using <span class="hlt">Cloud</span>-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) <span class="hlt">dust</span> and planetary boundary layer (PBL) height retrievals along with a land use dataset. Using this technique, the global distribution of <span class="hlt">dust</span> is analyzed and the relative contribution of anthropogenic and natural <span class="hlt">dust</span> sources to regional and global emissions are estimated. Results reveal that local anthropogenic <span class="hlt">dust</span> aerosol due to human activity, such as agriculture, industrial activity, transportation, and overgrazing, accounts for about 25% of the global continental <span class="hlt">dust</span> load. Of these anthropogenic <span class="hlt">dust</span> aerosols, more than 53% come from semi-arid and semi-wet regions. Annual mean anthropogenic <span class="hlt">dust</span> column burden (DCB) values range from 0.42 g m-2 with a maximum in India to 0.12 g m-2 with a minimum in North America. A better understanding of anthropogenic <span class="hlt">dust</span> emission will enable us to focus on human activities in these critical regions and with such knowledge we will be better able to improve global <span class="hlt">dust</span> models and to explore the effects of anthropogenic emission on radiative forcing, climate change and air quality in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvD..95j3511P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvD..95j3511P"><span>Line-of-sight extrapolation noise in <span class="hlt">dust</span> polarization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Poh, Jason; Dodelson, Scott</p> <p>2017-05-01</p> <p>The B-modes of polarization at frequencies ranging from 50-1000 GHz are produced by Galactic <span class="hlt">dust</span>, lensing of primordial E-modes in the cosmic microwave background (CMB) by intervening large scale structure, and possibly by primordial B-modes in the CMB imprinted by gravitational waves produced during inflation. The conventional method used to separate the <span class="hlt">dust</span> component of the signal is to assume that the signal at high frequencies (e.g. 350 GHz) is due solely to <span class="hlt">dust</span> and then extrapolate the signal down to a lower frequency (e.g. 150 GHz) using the measured scaling of the polarized <span class="hlt">dust</span> signal amplitude with frequency. For typical Galactic thermal <span class="hlt">dust</span> temperatures of ˜20 K , these frequencies are not fully in the Rayleigh-Jeans limit. Therefore, deviations in the <span class="hlt">dust</span> <span class="hlt">cloud</span> temperatures from <span class="hlt">cloud</span> to <span class="hlt">cloud</span> will lead to different scaling factors for <span class="hlt">clouds</span> of different temperatures. Hence, when multiple <span class="hlt">clouds</span> of different temperatures and polarization angles contribute to the integrated line-of-sight polarization signal, the relative contribution of individual <span class="hlt">clouds</span> to the integrated signal can change between frequencies. This can cause the integrated signal to be decorrelated in both amplitude and direction when extrapolating in frequency. Here we carry out a Monte Carlo analysis on the impact of this line-of-sight extrapolation noise on a greybody <span class="hlt">dust</span> model consistent with Planck and Pan-STARRS observations, enabling us to quantify its effect. Using results from the Planck experiment, we find that this effect is small, more than an order of magnitude smaller than the current uncertainties. However, line-of-sight extrapolation noise may be a significant source of uncertainty in future low-noise primordial B-mode experiments. Scaling from Planck results, we find that accounting for this uncertainty becomes potentially important when experiments are sensitive to primordial B-mode signals with amplitude r ≲0.0015 in the greybody <span class="hlt">dust</span> models considered in this</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22614007-positive-column-glow-discharge-neon-charged-dust-grains-review','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22614007-positive-column-glow-discharge-neon-charged-dust-grains-review"><span>Positive column of a glow discharge in neon with charged <span class="hlt">dust</span> grains (a review)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciT</a></p> <p>Polyakov, D. N., E-mail: cryolab@ihed.ras.ru; Shumova, V. V.; Vasilyak, L. M.</p> <p></p> <p>The effect of charged micron-size <span class="hlt">dust</span> grains (microparticles) on the electric parameters of the positive column of a low-pressure dc glow discharge in neon has been studied experimentally and numerically. Numerical analysis is carried out in the diffusion-drift approximation with allowance for the interaction of <span class="hlt">dust</span> grains with metastable neon atoms. In a discharge with a <span class="hlt">dust</span> grain <span class="hlt">cloud</span>, the longitudinal electric field increases. As the number density of <span class="hlt">dust</span> grains in an axisymmetric cylindrical <span class="hlt">dust</span> <span class="hlt">cloud</span> rises, the growth of the electric field saturates. It is shown that the contribution of metastable atoms to ionization is higher in amore » discharge with <span class="hlt">dust</span> grains, in spite of the quenching of metastable atoms on <span class="hlt">dust</span> grains. The processes of charging of <span class="hlt">dust</span> grains and the <span class="hlt">dust</span> <span class="hlt">cloud</span> are considered. As the number density of <span class="hlt">dust</span> grains rises, their charge decreases, while the space charge of the <span class="hlt">dust</span> <span class="hlt">cloud</span> increases. The results obtained can be used in plasma technologies involving microparticles.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://images.nasa.gov/#/details-PIA04930.html','SCIGOVIMAGE-NASA'); return false;" href="https://images.nasa.gov/#/details-PIA04930.html"><span><span class="hlt">Clouds</span> Near Mie Crater</span></a></p> <p><a target="_blank" href=""></a></p> <p></p> <p>2003-12-13</p> <p>Mie Crater, a large basin formed by asteroid or comet impact in Utopia Planitia, lies at the center of this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) red wide angle image. The crater is approximately 104 km (65 mi) across. To the east and southeast (toward the lower right) of Mie, in this 5 December 2003 view, are <span class="hlt">clouds</span> of <span class="hlt">dust</span> and water ice kicked up by local <span class="hlt">dust</span> storm activity. It is mid-winter in the northern hemisphere of Mars, a time when passing storms are common on the northern plains of the red planet. Sunlight illuminates this image from the lower left; Mie Crater is located at 48.5°N, 220.3°W. Viking 2 landed west/southwest of Mie Crater, off the left edge of this image, in September 1976. http://photojournal.jpl.nasa.gov/catalog/PIA04930</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPSC...10..846S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPSC...10..846S"><span>In situ <span class="hlt">dust</span> measurements by the Cassini Cosmic <span class="hlt">Dust</span> Analyzer in 2014 and beyond</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Srama, R.</p> <p>2015-10-01</p> <p>Today, the German-lead Cosmic <span class="hlt">Dust</span> Analyser (CDA) is operated continuously for 11 years in orbit around Saturn. Many discoveries like the Saturn nanodust streams or the large extended Ering were achieved. CDA provided unique results regarding Enceladus, his plume and the liquid water below the icy crust. In 2014 and 2015 CDA focuses on extended inclination and equatorial scans of the ring particle densities. Furthermore, scans are performed of the Pallene and Helene regions. Special attention is also given to the search of the <span class="hlt">dust</span> <span class="hlt">cloud</span> around Dione and to the Titan region. Long integration times are needed in order to characterize the flux and composition of exogenous <span class="hlt">dust</span> (including interstellar <span class="hlt">dust</span>) or possible retrograde <span class="hlt">dust</span> particles. Finally, dedicated observation campaigns focus on the coupling of nanodust streams to Saturn's magnetosphere and the search of possible periodicities in the stream data. Saturn's rotation frequency was identified in the impact rate of nanodust particles at a Saturn distance of 40 Saturn radii. A special geometry in 2014-065 lead to an occultation of the <span class="hlt">dust</span> stream by the moon Titan and its atmosphere when Titan crossed the line-of-sight between Saturn and Cassini. Here, CDA pointed towards Saturn for the measurement of stream particles. Around closest approach when Cassini was behind Titan, the flux of stream particles went down to zero (Fig. 1). This "<span class="hlt">dust</span> occultation" is a new method to analyse the properties of the stream particles (speed, composition, mass) or the properties of Titans atmosphere (density). Furthermore, the particle trajectories can be constrained for a better analysis of their origin. In the final three years CDA performs exogenous and interstellar <span class="hlt">dust</span> campaigns, studies of the composition and origin of Saturn's main rings by unique ring ejecta measurements, long-duration nano-<span class="hlt">dust</span> stream observations, high-resolution maps of small moon orbit crossings, studies of the <span class="hlt">dust</span> <span class="hlt">cloud</span> around Dione and studies</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005DPS....37.1901M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005DPS....37.1901M"><span>A History of the Martian <span class="hlt">Dust</span> Storms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McKim, R. J.</p> <p>2005-08-01</p> <p>The author reviews historical observations of Martian <span class="hlt">dust</span> storms from the earliest telescopic records up to the present day (see R.J.McKim, Telescopic Martian <span class="hlt">Dust</span> Storms: A Narrative and Catalogue, Memoirs of the British Astronomical Association, volume 44, 1999 (166 pp)). The earliest record begins with Maraldi in 1704. The term ``yellow <span class="hlt">cloud</span>" was coined by Burton (1879). The first event which attracted much attention was the regional <span class="hlt">dust</span> storm of 1894 October-November. The first planet-encircling event was that of 1909. The daily evolution of <span class="hlt">dust</span> storms began to be studied in 1911; photography would not help until 1922. Other milestones in our understanding of the phenomenon are illustrated and explained. The telescopic literature is littered with errors of fact and interpretation, and the author describes some of the pitfalls and successes in the analysis of old telescopic records.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/987911','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/987911"><span><span class="hlt">Cloud</span> Computing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciT</a></p> <p>Pete Beckman and Ian Foster</p> <p></p> <p>Chicago Matters: Beyond Burnham (WTTW). Chicago has become a world center of "<span class="hlt">cloud</span> computing." Argonne experts Pete Beckman and Ian Foster explain what "<span class="hlt">cloud</span> computing" is and how you probably already use it on a daily basis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AAS...22525614M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AAS...22525614M"><span>A 100-3000 GHz model of thermal <span class="hlt">dust</span> emission observed by Planck, DIRBE and IRAS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meisner, Aaron M.; Finkbeiner, Douglas P.</p> <p>2015-01-01</p> <p>We apply the Finkbeiner et al. (1999) two-component thermal <span class="hlt">dust</span> emission model to the Planck HFI maps. This parametrization of the far-infrared <span class="hlt">dust</span> spectrum as the sum of two modified blackbodies serves as an important alternative to the commonly adopted single modified blackbody (MBB) <span class="hlt">dust</span> emission model. Analyzing the joint Planck/DIRBE <span class="hlt">dust</span> spectrum, we show that two-component models provide a better fit to the 100-3000 GHz emission than do single-MBB models, though by a lesser margin than found by Finkbeiner et al. (1999) based on FIRAS and DIRBE. We also derive full-sky 6.1' resolution maps of <span class="hlt">dust</span> optical depth and temperature by fitting the two-component model to Planck 217-857 GHz along with DIRBE/IRAS 100μm data. Because our two-component model matches the <span class="hlt">dust</span> spectrum near its peak, accounts for the spectrum's flattening at millimeter wavelengths, and specifies <span class="hlt">dust</span> temperature at 6.1' FWHM, our model provides reliable, high-resolution thermal <span class="hlt">dust</span> emission foreground predictions from 100 to 3000 GHz. We find that, in diffuse sky regions, our two-component 100-217 GHz predictions are on average accurate to within 2.2%, while extrapolating the Planck Collaboration (2013) single-MBB model systematically underpredicts emission by 18.8% at 100 GHz, 12.6% at 143 GHz and 7.9% at 217 GHz. We calibrate our two-component optical depth to reddening, and compare with reddening estimates based on stellar spectra. We find the dominant systematic problems in our temperature/reddening maps to be <span class="hlt">zodiacal</span> light on large angular scales and the cosmic infrared background anistropy on small angular scales. We have recently released maps and associated software utilities for obtaining thermal <span class="hlt">dust</span> emission and reddening predictions using our Planck-based two-component model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA10019&hterms=gemstones&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgemstones','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA10019&hterms=gemstones&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dgemstones"><span><span class="hlt">Dust</span> in the Quasar Wind (Artist Concept)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2007-01-01</p> <p><p/> Dusty grains -- including tiny specks of the minerals found in the gemstones peridot, sapphires and rubies -- can be seen blowing in the winds of a quasar, or active black hole, in this artist's concept. The quasar is at the center of a distant galaxy. <p/> Astronomers using NASA's Spitzer Space Telescope found evidence that such quasar winds might have forged these dusty particles in the very early universe. The findings are another clue in an ongoing cosmic mystery: where did all the <span class="hlt">dust</span> in our young universe come from? <p/> <span class="hlt">Dust</span> is crucial for efficient star formation as it allows the giant <span class="hlt">clouds</span> where stars are born to cool quickly and collapse into new stars. Once a star has formed, <span class="hlt">dust</span> is also needed to make planets and living creatures. <span class="hlt">Dust</span> has been seen as far back as when the universe was less than a tenth of its current age, but how did it get there? Most <span class="hlt">dust</span> in our current epoch forms in the winds of evolved stars that did not exist when the universe was young. <p/> Theorists had predicted that winds from quasars growing in the centers of distant galaxies might be a source of this <span class="hlt">dust</span>. While the environment close to a quasar is too hot for large molecules like <span class="hlt">dust</span> grains to survive, <span class="hlt">dust</span> has been found in the cooler, outer regions. Astronomers now have evidence that <span class="hlt">dust</span> is created in these outer winds. <p/> Using Spitzer's infrared spectrograph instrument, scientists found a wealth of <span class="hlt">dust</span> grains in a quasar called PG2112+059 located at the center of a galaxy 8 billion light-years away. The grains - including corundum (sapphires and rubies); forsterite (peridot); and periclase (naturally occurring in marble) - are not typically found in galaxies without quasars, suggesting they might have been freshly formed in the quasar's winds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880002221','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880002221"><span>Composition, structure and chemistry of interstellar <span class="hlt">dust</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tielens, Alexander G. G. M.; Allamandola, Louis J.</p> <p>1986-01-01</p> <p>The observational constraints on the composition of the interstellar <span class="hlt">dust</span> are analyzed. The <span class="hlt">dust</span> in the diffuse interstellar medium consists of a mixture of stardust (amorphous silicates, amorphous carbon, polycyclic aromatic hydrocarbons, and graphite) and interstellar medium <span class="hlt">dust</span> (organic refractory material). Stardust seems to dominate in the local diffuse interstellar medium. Inside molecular <span class="hlt">clouds</span>, however, icy grain mantles are also important. The structural differences between crystalline and amorphous materials, which lead to differences in the optical properties, are discussed. The astrophysical consequences are briefly examined. The physical principles of grain surface chemistry are discussed and applied to the formation of molecular hydrogen and icy grain mantles inside dense molecular <span class="hlt">clouds</span>. Transformation of these icy grain mantles into the organic refractory <span class="hlt">dust</span> component observed in the diffuse interstellar medium requires ultraviolet sources inside molecular <span class="hlt">clouds</span> as well as radical diffusion promoted by transient heating of the mantle. The latter process also returns a considerable fraction of the molecules in the grain mantle to the gas phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009RMxAC..35...25R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009RMxAC..35...25R"><span>The terminal Velocity of the Deep Impact <span class="hlt">dust</span> Ejecta</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rengel, M.; Küppers, M.; Keller, H. U.; Gutierrez, P.; Hviid, S. F.</p> <p>2009-05-01</p> <p>The collision of the projectile released from NASA Deep Impact spacecraft on the nucleus of comet 9P/Tempel 1 generated a hot plume. Afterwards ejecta were created, and material moved slowly in a form of a <span class="hlt">dust</span> <span class="hlt">cloud</span>, which dissipated during several days after the impact. Here we report a study about the distribution of terminal velocities of the particles ejected by the impact. This is performed by the development and application of an ill-conditioned inverse problem approach. We model the light-curves as seen by the Narrow Angle Camera (NAC) of OSIRIS onboard the ESA spacecraft Rosetta, and we compare them with the OSIRIS observations. Terminal velocities are derived using a maximum likelihood estimator. The <span class="hlt">dust</span> velocity distribution is well constrained, and peaks at around 220 m s^{-1}, which is in good agreement with published estimates of the expansion velocities of the <span class="hlt">dust</span> <span class="hlt">cloud</span>. Measured and modeled velocity of the <span class="hlt">dust</span> <span class="hlt">cloud</span> suggests that the impact ejecta were quickly accelerated by the gas in the cometary coma. This analysis provides a more thorough understanding of the properties (velocity and mass of <span class="hlt">dust</span>) of the Deep Impact <span class="hlt">dust</span> <span class="hlt">cloud</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PPCF...50l4022G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PPCF...50l4022G"><span>Simulation of <span class="hlt">dust</span> voids in complex plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goedheer, W. J.; Land, V.</p> <p>2008-12-01</p> <p>In dusty radio-frequency (RF) discharges under micro-gravity conditions often a void is observed, a <span class="hlt">dust</span> free region in the discharge center. This void is generated by the drag of the positive ions pulled out of the discharge by the electric field. We have developed a hydrodynamic model for dusty RF discharges in argon to study the behaviour of the void and the interaction between the <span class="hlt">dust</span> and the plasma background. The model is based on a recently developed theory for the ion drag force and the charging of the <span class="hlt">dust</span>. With this model, we studied the plasma inside the void and obtained an understanding of the way it is sustained by heat generated in the surrounding <span class="hlt">dust</span> <span class="hlt">cloud</span>. When this heating mechanism is suppressed by lowering the RF power, the plasma density inside the void decreases, even below the level where the void collapses, as was recently shown in experiments on board the International Space Station. In this paper we present results of simulations of this collapse. At reduced power levels the collapsed central <span class="hlt">cloud</span> behaves as an electronegative plasma with corresponding low time-averaged electric fields. This enables the creation of relatively homogeneous Yukawa balls, containing more than 100 000 particles. On earth, thermophoresis can be used to balance gravity and obtain similar <span class="hlt">dust</span> distributions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.A44B..07K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.A44B..07K"><span>Aerosol-<span class="hlt">Cloud</span> Interactions and <span class="hlt">Cloud</span> Microphysical Properties in the Asir Region of Saudi Arabia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kucera, P. A.; Axisa, D.; Burger, R. P.; Li, R.; Collins, D. R.; Freney, E. J.; Buseck, P. R.</p> <p>2009-12-01</p> <p>In recent advertent and inadvertent weather modification studies, a considerable effort has been made to understand the impact of varying aerosol properties and concentration on <span class="hlt">cloud</span> properties. Significant uncertainties exist with aerosol-<span class="hlt">cloud</span> interactions for which complex microphysical processes link the aerosol and <span class="hlt">cloud</span> properties. Under almost all environmental conditions, increased aerosol concentrations within polluted air masses will enhance <span class="hlt">cloud</span> droplet concentration relative to that in unperturbed regions. The interaction between <span class="hlt">dust</span> particles and <span class="hlt">clouds</span> are significant, yet the conditions in which <span class="hlt">dust</span> particles become <span class="hlt">cloud</span> condensation nuclei (CCN) are uncertain. In order to quantify this aerosol effect on <span class="hlt">clouds</span> and precipitation, a field campaign was launched in the Asir region, located adjacent to the Red Sea in the southwest region of Saudi Arabia. Ground measurements of aerosol size distributions, hygroscopic growth factors, CCN concentrations as well as aircraft measurements of <span class="hlt">cloud</span> hydrometeor size distributions were observed in the Asir region in August 2009. The presentation will include a summary of the analysis and results with a focus on aerosol-<span class="hlt">cloud</span> interactions and <span class="hlt">cloud</span> microphysical properties observed during the convective season in the Asir region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......409A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......409A"><span>Evaluating the impact of above-<span class="hlt">cloud</span> aerosols on <span class="hlt">cloud</span> optical depth retrievals from MODIS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alfaro, Ricardo</p> <p></p> <p>Using two different operational Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) <span class="hlt">cloud</span> optical depth (COD) retrievals (visible and shortwave infrared), the impacts of above-<span class="hlt">cloud</span> absorbing aerosols on the standard COD retrievals are evaluated. For fine-mode aerosol particles, aerosol optical depth (AOD) values diminish sharply from the visible to the shortwave infrared channels. Thus, a suppressed above-<span class="hlt">cloud</span> particle radiance aliasing effect occurs for COD retrievals using shortwave infrared channels. Aerosol Index (AI) from the spatially and temporally collocated Ozone Monitoring Instrument (OMI) are used to identify above-<span class="hlt">cloud</span> aerosol particle loading over the southern Atlantic Ocean, including both smoke and <span class="hlt">dust</span> from the African sub-continent. MODIS and OMI Collocated <span class="hlt">Cloud</span>-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data are used to constrain <span class="hlt">cloud</span> phase and provide contextual above-<span class="hlt">cloud</span> AOD values. The frequency of occurrence of above-<span class="hlt">cloud</span> aerosols is depicted on a global scale for the spring and summer seasons from OMI and CALIOP, thus indicating the significance of the problem. Seasonal frequencies for smoke-over-<span class="hlt">cloud</span> off the southwestern Africa coastline reach 20--50% in boreal summer. We find a corresponding low COD bias of 10--20% for standard MODIS COD retrievals when averaged OMI AI are larger than 1.0. No such bias is found over the Saharan <span class="hlt">dust</span> outflow region off northern Africa, since both MODIS visible and shortwave in channels are vulnerable to <span class="hlt">dust</span> particle aliasing, and thus a COD impact cannot be isolated with this method. A similar result is found for a smaller domain, in the Gulf of Tonkin region, from smoke advection over marine stratocumulus <span class="hlt">clouds</span> and outflow into the northern South China Sea in spring. This study shows the necessity of accounting for the above-<span class="hlt">cloud</span> aerosol events for future studies using standard MODIS <span class="hlt">cloud</span> products in biomass burning outflow regions, through the use of</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRD..119.5410A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRD..119.5410A"><span>Evaluating the impact of aerosol particles above <span class="hlt">cloud</span> on <span class="hlt">cloud</span> optical depth retrievals from MODIS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alfaro-Contreras, Ricardo; Zhang, Jianglong; Campbell, James R.; Holz, Robert E.; Reid, Jeffrey S.</p> <p>2014-05-01</p> <p>Using two different operational Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) <span class="hlt">cloud</span> optical depth (COD) retrievals (0.86 versus 1.6 µm), we evaluate the impact of above-<span class="hlt">cloud</span> smoke aerosol particles on near-IR (0.86 µm) COD retrievals. Aerosol Index (AI) from the collocated Ozone Monitoring Instrument (OMI) are used to identify above-<span class="hlt">cloud</span> aerosol particle loading over the southern Atlantic Ocean, including both smoke and <span class="hlt">dust</span> from the African subcontinent. Collocated <span class="hlt">Cloud</span>-Aerosol Lidar and Infrared Pathfinder Satellite Observation data constrain <span class="hlt">cloud</span> phase and provide contextual above-<span class="hlt">cloud</span> aerosol optical depth. The frequency of occurrence of above-<span class="hlt">cloud</span> aerosol events is depicted on a global scale for the spring and summer seasons from OMI and <span class="hlt">Cloud</span> Aerosol Lidar with Orthogonal Polarization. Seasonal frequencies for smoke-over-<span class="hlt">cloud</span> off the southwestern Africa coastline reach 20-50% in boreal summer. We find a corresponding low COD bias of 10-20% for standard MODIS COD retrievals when averaged OMI AI are larger than 1. No such bias is found over the Saharan <span class="hlt">dust</span> outflow region off northern Africa, since both MODIS 0.86 and 1.6 µm channels are vulnerable to radiance attenuation due to <span class="hlt">dust</span> particles. A similar result is found for a smaller domain, in the Gulf of Tonkin region, from smoke advection over marine stratocumulus <span class="hlt">clouds</span> and outflow into the northern South China Sea in spring. This study shows the necessity of accounting for the above-<span class="hlt">cloud</span> aerosol events for future studies using standard MODIS <span class="hlt">cloud</span> products in biomass burning outflow regions, through the use of collocated OMI AI and supplementary MODIS 1.6 µm COD products.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23004877','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23004877"><span>Self-confinement of finite <span class="hlt">dust</span> clusters in isotropic plasmas.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Miloshevsky, G V; Hassanein, A</p> <p>2012-05-01</p> <p>Finite two-dimensional <span class="hlt">dust</span> clusters are systems of a small number of charged grains. The self-confinement of <span class="hlt">dust</span> clusters in isotropic plasmas is studied using the particle-in-cell method. The energetically favorable configurations of grains in plasma are found that are due to the kinetic effects of plasma ions and electrons. The self-confinement phenomenon is attributed to the change in the plasma composition within a <span class="hlt">dust</span> cluster resulting in grain attraction mediated by plasma ions. This is a self-consistent state of a <span class="hlt">dust</span> cluster in which grain's repulsion is compensated by the reduced charge and floating potential on grains, overlapped ion <span class="hlt">clouds</span>, and depleted electrons within a cluster. The common potential well is formed trapping <span class="hlt">dust</span> clusters in the confined state. These results provide both valuable insights and a different perspective to the classical view on the formation of boundary-free <span class="hlt">dust</span> clusters in isotropic plasmas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/864831','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/864831"><span><span class="hlt">Dust</span> feed mechanism</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Milliman, Edward M.</p> <p>1984-01-01</p> <p>The invention is a <span class="hlt">dust</span> feed device for delivery of a uniform supply of <span class="hlt">dust</span> for long periods of time to an aerosolizing means for production of a <span class="hlt">dust</span> suspension. The device utilizes at least two tandem containers having spiral brushes within the containers which transport the <span class="hlt">dust</span> from a supply to the aerosolizer means.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA462009','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA462009"><span>A Post-AGB Star in the Small Magellanic <span class="hlt">Cloud</span> Observed with the Spitzer Infrared Spectrograph</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2006-10-23</p> <p>spectral features, MSX SMC 029, in the Small Magellanic <span class="hlt">Cloud</span> (SMC) usimg the low-resolution modules of the Infrared Spectrograph on the Spitzer Space ...029, in the Small Magellanic <span class="hlt">Cloud</span> (SMC) using the low-resolution modules of the Infrared Spectrograph on the Spitzer Space Telescope. A cool <span class="hlt">dust</span>... outer atmosphere expands and pulsates, pushing gas away from the star where it can cool and condense into <span class="hlt">dust</span> grains. The resulting circumstellar <span class="hlt">dust</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997ApJ...478..536P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997ApJ...478..536P"><span><span class="hlt">Dust</span> in High-Redshift Galaxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pettini, Max; King, David L.; Smith, Linda J.; Hunstead, Richard W.</p> <p>1997-03-01</p> <p>Measurements of Zn and Cr abundances in 18 damped Lyα systems (DLAs) at absorption redshifts zabs = 0.692-3.390 (but mostly between zabs ~= 2 and 3) show that metals and <span class="hlt">dust</span> are much less abundant in high-redshift galaxies than in the Milky Way today. Typically, [Zn/H] ~= -1.2 as Zn tracks Fe closely in Galactic stars of all metallicities and is only lightly depleted onto interstellar grains, we conclude that the overall degree of metal enrichment of damped Lyα galaxies ~13.5 Gyr ago (H0 = 50 km s-1 Mpc-1, q0 = 0.05) was ~1/15 solar. Values of [Cr/Zn] span the range from ~=0 to <~ - 0.65 which we interpret as evidence for selective depletion of Cr onto <span class="hlt">dust</span> in some DLAs. On average Cr and other refractory elements are depleted by only a factor of ~2, significantly less than in local interstellar <span class="hlt">clouds</span>. We propose that this reflects an overall lower abundance of <span class="hlt">dust</span>--which may be related to the lower metallicities, likely higher temperature of the ISM and higher supernova rates in these young galaxies--rather than an ``exotic'' composition of <span class="hlt">dust</span> grains. Combining a metallicity ZDLA ~= 1/15 Z⊙ with a <span class="hlt">dust</span>-to-metals ratio ~1/2 of that in local interstellar <span class="hlt">clouds</span>, we deduce that the ``typical'' <span class="hlt">dust</span>-to-gas ratio in damped Lyα galaxies is ~1/30 of the Milky Way value. This amount of <span class="hlt">dust</span> will introduce an extinction at 1500 Å of only A1500 ~ 0.1 in the spectra of background QSOs. Similarly, we expect little reddening of the broad spectral energy distribution of the high-z field galaxies now being found routinely by deep imaging surveys. Even such trace amounts of <span class="hlt">dust</span>, however, can explain the weakness of Lyα emission from star-forming regions. We stress the approximate nature of such general statements; in reality, the range of metallicities and <span class="hlt">dust</span> depletions encountered indicates that some sight lines through high-redshift galaxies may be essentially <span class="hlt">dust</span>-free, while others could suffer detectable extinction. Finally, we show that, despite claims to the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A13K..02Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A13K..02Z"><span>Observational evidence for the aerosol impact on ice <span class="hlt">cloud</span> properties regulated by <span class="hlt">cloud</span>/aerosol types</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, B.; Gu, Y.; Liou, K. N.; Jiang, J. H.; Li, Q.; Liu, X.; Huang, L.; Wang, Y.; Su, H.</p> <p>2017-12-01</p> <p>The interactions between aerosols and ice <span class="hlt">clouds</span> (consisting only of ice) represent one of the largest uncertainties in global radiative forcing from pre-industrial time to the present. The observational evidence for the aerosol impact on ice <span class="hlt">cloud</span> properties has been quite limited and showed conflicting results, partly because previous observational studies did not consider the distinct features of different ice <span class="hlt">cloud</span> and aerosol types. Using 9-year satellite observations, we find that, for ice <span class="hlt">clouds</span> generated from deep convection, <span class="hlt">cloud</span> thickness, <span class="hlt">cloud</span> optical thickness (COT), and ice <span class="hlt">cloud</span> fraction increase and decrease with small-to-moderate and high aerosol loadings, respectively. For in-situ formed ice <span class="hlt">clouds</span>, however, the preceding <span class="hlt">cloud</span> properties increase monotonically and more sharply with aerosol loadings. The case is more complicated for ice crystal effective radius (Rei). For both convection-generated and in-situ ice <span class="hlt">clouds</span>, the responses of Rei to aerosol loadings are modulated by water vapor amount in conjunction with several other meteorological parameters, but the sensitivities of Rei to aerosols under the same water vapor amount differ remarkably between the two ice <span class="hlt">cloud</span> types. As a result, overall Rei slightly increases with aerosol loading for convection-generated ice <span class="hlt">clouds</span>, but decreases for in-situ ice <span class="hlt">clouds</span>. When aerosols are decomposed into different types, an increase in the loading of smoke aerosols generally leads to a decrease in COT of convection-generated ice <span class="hlt">clouds</span>, while the reverse is true for <span class="hlt">dust</span> and anthropogenic pollution. In contrast, an increase in the loading of any aerosol type can significantly enhance COT of in-situ ice <span class="hlt">clouds</span>. The modulation of the aerosol impacts by <span class="hlt">cloud</span>/aerosol types is demonstrated and reproduced by simulations using the Weather Research and Forecasting (WRF) model. Adequate and accurate representations of the impact of different <span class="hlt">cloud</span>/aerosol types in climate models are crucial for reducing the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A13K..02Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A13K..02Z"><span>Observational evidence for the aerosol impact on ice <span class="hlt">cloud</span> properties regulated by <span class="hlt">cloud</span>/aerosol types</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, B.; Gu, Y.; Liou, K. N.; Jiang, J. H.; Li, Q.; Liu, X.; Huang, L.; Wang, Y.; Su, H.</p> <p>2016-12-01</p> <p>The interactions between aerosols and ice <span class="hlt">clouds</span> (consisting only of ice) represent one of the largest uncertainties in global radiative forcing from pre-industrial time to the present. The observational evidence for the aerosol impact on ice <span class="hlt">cloud</span> properties has been quite limited and showed conflicting results, partly because previous observational studies did not consider the distinct features of different ice <span class="hlt">cloud</span> and aerosol types. Using 9-year satellite observations, we find that, for ice <span class="hlt">clouds</span> generated from deep convection, <span class="hlt">cloud</span> thickness, <span class="hlt">cloud</span> optical thickness (COT), and ice <span class="hlt">cloud</span> fraction increase and decrease with small-to-moderate and high aerosol loadings, respectively. For in-situ formed ice <span class="hlt">clouds</span>, however, the preceding <span class="hlt">cloud</span> properties increase monotonically and more sharply with aerosol loadings. The case is more complicated for ice crystal effective radius (Rei). For both convection-generated and in-situ ice <span class="hlt">clouds</span>, the responses of Rei to aerosol loadings are modulated by water vapor amount in conjunction with several other meteorological parameters, but the sensitivities of Rei to aerosols under the same water vapor amount differ remarkably between the two ice <span class="hlt">cloud</span> types. As a result, overall Rei slightly increases with aerosol loading for convection-generated ice <span class="hlt">clouds</span>, but decreases for in-situ ice <span class="hlt">clouds</span>. When aerosols are decomposed into different types, an increase in the loading of smoke aerosols generally leads to a decrease in COT of convection-generated ice <span class="hlt">clouds</span>, while the reverse is true for <span class="hlt">dust</span> and anthropogenic pollution. In contrast, an increase in the loading of any aerosol type can significantly enhance COT of in-situ ice <span class="hlt">clouds</span>. The modulation of the aerosol impacts by <span class="hlt">cloud</span>/aerosol types is demonstrated and reproduced by simulations using the Weather Research and Forecasting (WRF) model. Adequate and accurate representations of the impact of different <span class="hlt">cloud</span>/aerosol types in climate models are crucial for reducing the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA06449&hterms=cloud+technology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dcloud%2Btechnology','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA06449&hterms=cloud+technology&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dcloud%2Btechnology"><span><span class="hlt">Cloud</span>-Ground Interaction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2004-01-01</p> <p>[figure removed for brevity, see original site] <p/> Released 30 June 2004 The atmosphere of Mars is a dynamic system. Water-ice <span class="hlt">clouds</span>, fog, and hazes can make imaging the surface from space difficult. <span class="hlt">Dust</span> storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in <span class="hlt">cloud</span> and <span class="hlt">dust</span> storm development and growth. <p/> Eons of atmospheric <span class="hlt">dust</span> storm activity has left its mark on the surface of Mars. <span class="hlt">Dust</span> carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms. <p/> This image of the North Polar water-ice <span class="hlt">clouds</span> shows how surface topography can affect the linear form. Notice that the crater at the bottom of the image is causing a deflection in the linear form. <p/> Image information: VIS instrument. Latitude 68.4, Longitude 100.7 East (259.3 West). 38 meter/pixel resolution. <p/> Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. <p/> NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ISPAr.XL1c..85B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ISPAr.XL1c..85B"><span>Using Aerosol Reflectance for <span class="hlt">Dust</span> Detection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bahramvash Shams, S.; Mohammadzade, A.</p> <p>2013-09-01</p> <p>In this study we propose an approach for <span class="hlt">dust</span> detection by aerosol reflectance over arid and urban region in clear sky condition. In urban and arid areas surface reflectance in red and infrared spectral is bright and hence shorter wavelength is required for this detections. Main step of our approach can be mentioned as: <span class="hlt">cloud</span> mask for excluding cloudy pixels from our calculation, calculate Rayleigh path radiance, construct a surface reflectance data base, estimate aerosol reflectance, detect <span class="hlt">dust</span> aerosol, <span class="hlt">dust</span> detection and evaluations of <span class="hlt">dust</span> detection. Spectral with wavelength 0.66, 0.55, 0.47 μm has been used in our <span class="hlt">dust</span> detection. Estimating surface reflectance is the most challenging step of obtaining aerosol reflectance from top of atmosphere (TOA) reflectance. Hence for surface estimation we had created a surface reflectance database of 0.05 degree latitude by 0.05 degree longitude resolution by using minimum reflectivity technique (MRT). In order to evaluate our <span class="hlt">dust</span> detection algorithm MODIS aerosol product MOD04 and common <span class="hlt">dust</span> detection method named Brightness Temperature Difference (BTD) had been used. We had implemented this method to Moderate Resolution Imaging Spectroradiometer (MODIS) image of part of Iran (7 degree latitude and 8 degree longitude) spring 2005 <span class="hlt">dust</span> phenomenon from April to June. This study uses MODIS LIB calibrated reflectance high spatial resolution (500 m) MOD02Hkm on TERRA spacecraft. Hence our <span class="hlt">dust</span> detection spatial resolution will be higher spatial resolution than MODIS aerosol product MOD04 which has 10 × 10 km2 and BTD resolution is 1 km due to the band 29 (8.7 μm), 31 (11 μm), and 32 (12 μm) spatial resolutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.P41G1997D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.P41G1997D"><span>Laboratory investigation of <span class="hlt">dust</span> impacts on antennas in space</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drake, K.; Gruen, E.; Malaspina, D.; Sternovsky, Z.</p> <p>2013-12-01</p> <p>We are performing calibration measurements in our laboratory using a <span class="hlt">dust</span> accelerator to understand the mechanisms how <span class="hlt">dust</span> impact generated plasma <span class="hlt">clouds</span> couple into electric field antennas on spacecraft. The S/WAVES electric field instruments on board the twin STEREO spacecraft observed short duration (milliseconds), large amplitude (> 15 mV) voltage spikes associated with the impact of high velocity <span class="hlt">dust</span> particles on the spacecraft [St. Cyr et al., 2009, MeyerVernet et al, 2009a, Zaslavsky et al., 2012]. These sharp spikes have been attributed to plasma <span class="hlt">clouds</span> generated by the impact ionization of high velocity <span class="hlt">dust</span> particles. The high count rate has lead to the interpretation that S/WAVES is detecting nanometer sized <span class="hlt">dust</span> particles (nano-<span class="hlt">dust</span>) generated in the inner solar system and accelerated to close to solar wind velocities before impacting the spacecraft at 1 AU. The S/WAVES nano-<span class="hlt">dust</span> interpretation is currently based on an incomplete understanding of the charge generated from relevant materials and the coupling mechanism between the plasma <span class="hlt">cloud</span> and the electric field instrument. Calibration measurements are performed at the <span class="hlt">dust</span> accelerator facility at the University of Colorado to investigate the effect of various impact parameters on the signals measured by the electric field instrument. The <span class="hlt">dust</span> accelerator facility allows experimental control over target materials, size (micron to sub-micron), and velocity (1-60 km/s) of impacting <span class="hlt">dust</span> particles, geometry of the impact, the ';spacecraft' potential, and the presence or absence of photoelectrons, allowing each coupling factor to be isolated and quantified. As the first step in this effort, we measure the impact charge generation for materials relevant for the STEREO spacecraft.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080047968&hterms=fine+dust&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfine%2Bdust','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080047968&hterms=fine+dust&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfine%2Bdust"><span>Lunar <span class="hlt">Dust</span> Charging by Photoelectric Emissions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abbas, M. M.; Tankosic, D.; Craven, P. D.; Spann, J. F.; LeClair, A.; West, E. A.</p> <p>2007-01-01</p> <p>The lunar surface is covered with a thick layer of sub-micron/micron size <span class="hlt">dust</span> grains formed by meteoritic impact over billions of years. The fine <span class="hlt">dust</span> grains are levitated and transported on the lunar surface, as indicated by the transient <span class="hlt">dust</span> <span class="hlt">clouds</span> observed over the lunar horizon during the Apollo 17 mission. Theoretical models suggest that the <span class="hlt">dust</span> grains on the lunar surface are charged by the solar ultraviolet (UV) radiation as well as the solar wind. Even without any physical activity, the <span class="hlt">dust</span> grains are levitated by electrostatic fields and transported away from the surface in the near vacuum environment of the Moon. The current <span class="hlt">dust</span> charging and levitation models, however, do not fully explain the observed phenomena. Since the abundance of <span class="hlt">dust</span> on the Moon's surface with its observed adhesive characteristics has the potential of severe impact on human habitat and operations and lifetime of a variety of equipment, it is necessary to investigate the charging properties and the lunar <span class="hlt">dust</span> phenomena in order to develop appropriate mitigating strategies. Photoelectric emission induced by the solar UV radiation with photon energies higher than the work function (WF) of the grain materials is recognized to be the dominant process for charging of the lunar <span class="hlt">dust</span>, and requires measurements of the photoelectric yields to determine the charging and equilibrium potentials of individual <span class="hlt">dust</span> grains. In this paper, we present the first laboratory measurements of the photoelectric efficiencies and yields of individual sub-micron/micron size <span class="hlt">dust</span> grains selected from sample returns of Apollo 17 and Luna-24 missions as well as similar size <span class="hlt">dust</span> grains from the JSC-1 simulants. The measurements were made on a laboratory facility based on an electrodynamic balance that permits a variety of experiments to be conducted on individual sub-micron/micron size <span class="hlt">dust</span> grains in simulated space environments. The photoelectric emission measurements indicate grain size dependence with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007P%26SS...55..953A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007P%26SS...55..953A"><span>Lunar <span class="hlt">dust</span> charging by photoelectric emissions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abbas, M. M.; Tankosic, D.; Craven, P. D.; Spann, J. F.; LeClair, A.; West, E. A.</p> <p>2007-05-01</p> <p>The lunar surface is covered with a thick layer of sub-micron/micron size <span class="hlt">dust</span> grains formed by meteoritic impact over billions of years. The fine <span class="hlt">dust</span> grains are levitated and transported on the lunar surface, as indicated by the transient <span class="hlt">dust</span> <span class="hlt">clouds</span> observed over the lunar horizon during the Apollo 17 mission. Theoretical models suggest that the <span class="hlt">dust</span> grains on the lunar surface are charged by the solar ultraviolet (UV) radiation as well as the solar wind. Even without any physical activity, the <span class="hlt">dust</span> grains are levitated by electrostatic fields and transported away from the surface in the near vacuum environment of the Moon. The current <span class="hlt">dust</span> charging and levitation models, however, do not fully explain the observed phenomena. Since the abundance of <span class="hlt">dust</span> on the Moon's surface with its observed adhesive characteristics has the potential of severe impact on human habitat and operations and lifetime of a variety of equipment, it is necessary to investigate the charging properties and the lunar <span class="hlt">dust</span> phenomena in order to develop appropriate mitigating strategies. Photoelectric emission induced by the solar UV radiation with photon energies higher than the work function (WF) of the grain materials is recognized to be the dominant process for charging of the lunar <span class="hlt">dust</span>, and requires measurements of the photoelectric yields to determine the charging and equilibrium potentials of individual <span class="hlt">dust</span> grains. In this paper, we present the first laboratory measurements of the photoelectric efficiencies and yields of individual sub-micron/micron size <span class="hlt">dust</span> grains selected from sample returns of Apollo 17 and Luna-24 missions as well as similar size <span class="hlt">dust</span> grains from the JSC-1 simulants. The measurements were made on a laboratory facility based on an electrodynamic balance that permits a variety of experiments to be conducted on individual sub-micron/micron size <span class="hlt">dust</span> grains in simulated space environments. The photoelectric emission measurements indicate grain size dependence with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070014798','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070014798"><span>Lunar <span class="hlt">Dust</span> Charging by Photoelectric Emissions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abbas, M. M.; Tankosic, D.; Craven, P. D.; Spann, J. F.; LeClair, A.; West, E. A.</p> <p>2007-01-01</p> <p>The lunar surface is covered with a thick layer of sub-micron/micron size <span class="hlt">dust</span> grains formed by meteoritic impact over billions of years. The fine <span class="hlt">dust</span> grains are levitated and transported on the lunar surface, as indicated by the transient <span class="hlt">dust</span> <span class="hlt">clouds</span> observed over the lunar horizon during the Apollo 17 mission. Theoretical models suggest that the <span class="hlt">dust</span> grains on the lunar surface are charged by the solar UV radiation as well as the solar wind. Even without any physical activity, the <span class="hlt">dust</span> grains are levitated by electrostatic fields and transported away from the surface in the near vacuum environment of the Moon. The current <span class="hlt">dust</span> charging and levitation models, however, do not fully explain the observed phenomena. Since the abundance of <span class="hlt">dust</span> on the Moon s surface with its observed adhesive characteristics has the potential of severe impact on human habitat and operations and lifetime of a variety of equipment, it is necessary to investigate the charging properties and the lunar <span class="hlt">dust</span> phenomena in order to develop appropriate mitigating strategies. Photoelectric emission induced by the solar UV radiation with photon energies higher than the work function of the grain materials is recognized to be the dominant process for charging of the lunar <span class="hlt">dust</span>, and requires measurements of the photoelectric yields to determine the charging and equilibrium potentials of individual <span class="hlt">dust</span> grains. In this paper, we present the first laboratory measurements of the photoelectric efficiencies and yields of individual sub-micron/micron size <span class="hlt">dust</span> grains selected from sample returns of Apollo 17, and Luna 24 missions, as well as similar size <span class="hlt">dust</span> grains from the JSC-1 simulants. The measurements were made on a laboratory facility based on an electrodynamic balance that permits a variety of experiments to be conducted on individual sub-micron/micron size <span class="hlt">dust</span> grains in simulated space environments. The photoelectric emission measurements indicate grain size dependence with the yield</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA03470&hterms=benefits+cloud&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dbenefits%2Bcloud','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA03470&hterms=benefits+cloud&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dbenefits%2Bcloud"><span>Arsia Mons Spiral <span class="hlt">Cloud</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p><p/> One of the benefits of the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) Extended Mission is the opportunity to observe how the planet's weather changes during a second full martian year. This picture of Arsia Mons was taken June 19, 2001; southern spring equinox occurred the same day. Arsia Mons is a volcano nearly large enough to cover the state of New Mexico. On this particular day (the first day of Spring), the MOC wide angle cameras documented an unusual spiral-shaped <span class="hlt">cloud</span> within the 110 km (68 mi) diameter caldera--the summit crater--of the giant volcano. Because the <span class="hlt">cloud</span> is bright both in the red and blue images acquired by the wide angle cameras, it probably consisted mostly of fine <span class="hlt">dust</span> grains. The <span class="hlt">cloud</span>'s spin may have been induced by winds off the inner slopes of the volcano's caldera walls resulting from the temperature differences between the walls and the caldera floor, or by a vortex as winds blew up and over the caldera. Similar spiral <span class="hlt">clouds</span> were seen inside the caldera for several days; we don't know if this was a single <span class="hlt">cloud</span> that persisted throughout that time or one that regenerated each afternoon. Sunlight illuminates this scene from the left/upper left.<p/>Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A21E0128K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A21E0128K"><span>Mixed Calcium <span class="hlt">Dust</span> and Carbonaceous Particles from Asia Contributing to Precipitation Changes in California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kristensen, L.; Cornwell, G.; Sedlacek, A. J., III; Prather, K. A.</p> <p>2016-12-01</p> <p>Mineral <span class="hlt">dust</span> particles can serve as <span class="hlt">cloud</span> condensation nuclei (CCN), with enhanced CCN activity observed when the <span class="hlt">dust</span> is mixed with additional soluble species. Long range atmospheric transport can change the composition of <span class="hlt">dust</span> particles through aging, <span class="hlt">cloud</span> processing and mixing with other particles. The CalWater2 campaign measured single particles and <span class="hlt">cloud</span> dynamics to investigate the influence aerosols have on the hydrological cycle in California. An Aircraft Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to characterize and identify single particles within <span class="hlt">clouds</span> potentially acting as ice and <span class="hlt">cloud</span> nuclei. Two matching flights over California's mountains in March 2015 detected significantly different particle types that resulted in different precipitation totals. Calcium <span class="hlt">dust</span> dominated the particle composition during the first flight which had an observed decrease in orographic precipitation. Particle composition and air mass back trajectories indicate an Asian desert origin. The calcium <span class="hlt">dust</span> particles contained secondary acids, in particular oxalic acid, acquired during transport from Asia to California. This chemical processing likely increased the solubility of the <span class="hlt">dust</span>, enabling the particles to act as more effective CCN. The chemical composition also showed oligomeric carbonaceous species were mixed with the calcium <span class="hlt">dust</span> particles, potentially further increasing the solubility the particles. A single particle soot photometer (SP2) measured black carbon concurrently and returned intense incandescence when calcium <span class="hlt">dust</span> was present, confirming the calcium <span class="hlt">dust</span> particles were internally mixed with a carbonaceous species. <span class="hlt">Dust</span> particles were greatly reduced during the second flight with local biomass burning particles the dominant type. Observed precipitation in California were within forecast levels during the second flight. These single particle measurements from CalWater2 show that <span class="hlt">dust</span> particles from Asia can affect <span class="hlt">cloud</span> process and thus</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1132660-corrigendum-aerosol-impacts-california-winter-clouds-precipitation-during-calwater-local-pollution-versus-long-range-transported-dust-published-atmos-chem-phys','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1132660-corrigendum-aerosol-impacts-california-winter-clouds-precipitation-during-calwater-local-pollution-versus-long-range-transported-dust-published-atmos-chem-phys"><span>Corrigendum to Aerosol impacts on California winter <span class="hlt">clouds</span> and precipitation during CalWater 2011: local pollution versus long-range transported <span class="hlt">dust</span> published in Atmos. Chem. Phys., 14, 81–101, 2014</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciT</a></p> <p>Fan, Jiwen; Leung, Lai-Yung R.; DeMott, Paul J.</p> <p>2014-05-01</p> <p>In the paper “Aerosol impacts on California winter <span class="hlt">clouds</span> and precipitation during CalWater 2011: local pollution versus long-range transported dust” by J. Fan et al., wrong versions of Fig. 8 and Fig. 12 were published. Please find the correct figures below.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AAS...23135001M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AAS...23135001M"><span>Looking for <span class="hlt">Dust</span>-Scattering Light Echoes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mills, Brianna; Heinz, Sebastian; Corrales, Lia</p> <p>2018-01-01</p> <p>Galactic X-ray transient sources such as neutron stars or black holes sometimes undergo an outburst in X-rays. Ring structures have been observed around three such sources, produced by the X-ray photons being scattered by interstellar <span class="hlt">dust</span> grains along our line of sight. These <span class="hlt">dust</span>-scattering light echoes have proven to be a useful tool for measuring and constraining Galactic distances, mapping the <span class="hlt">dust</span> structure of the Milky Way, and determining the <span class="hlt">dust</span> composition in the <span class="hlt">clouds</span> producing the echo. Detectable light echoes require a sufficient quantity of <span class="hlt">dust</span> along our line of sight, as well as bright, short-lived Galactic X-ray flares. Using data from the Monitor of All-Sky X-ray Image (MAXI) on-board the International Space Station, we ran a peak finding algorithm in Python to look for characteristic flare events. Each flare was characterized by its fluence, the integrated flux of the flare over time. We measured the distribution of flare fluences to show how many observably bright flares were recorded by MAXI. This work provides a parent set for <span class="hlt">dust</span> echo searches in archival X-ray data and will inform observing strategies with current and future X-ray missions such as Athena and Lynx.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=GL-2002-001592&hterms=movement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmovement','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=GL-2002-001592&hterms=movement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dmovement"><span>Computer Model Predicts the Movement of <span class="hlt">Dust</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2002-01-01</p> <p>A new computer model of the atmosphere can now actually pinpoint where global <span class="hlt">dust</span> events come from, and can project where they're going. The model may help scientists better evaluate the impact of <span class="hlt">dust</span> on human health, climate, ocean carbon cycles, ecosystems, and atmospheric chemistry. Also, by seeing where <span class="hlt">dust</span> originates and where it blows people with respiratory problems can get advanced warning of approaching <span class="hlt">dust</span> <span class="hlt">clouds</span>. 'The model is physically more realistic than previous ones,' said Mian Chin, a co-author of the study and an Earth and atmospheric scientist at Georgia Tech and the Goddard Space Flight Center (GSFC) in Greenbelt, Md. 'It is able to reproduce the short term day-to-day variations and long term inter-annual variations of <span class="hlt">dust</span> concentrations and distributions that are measured from field experiments and observed from satellites.' The above images show both aerosols measured from space (left) and the movement of aerosols predicted by computer model for the same date (right). For more information, read New Computer Model Tracks and Predicts Paths Of Earth's <span class="hlt">Dust</span> Images courtesy Paul Giroux, Georgia Tech/NASA Goddard Space Flight Center</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.5490K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.5490K"><span>Poleward transport of Saharan <span class="hlt">dust</span> initiated by a Saharan cyclone.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karam Francis, Diana Bou; Chaboureau, Jean-Pierre; Cuesta, Juan</p> <p>2016-04-01</p> <p>To enhance the understanding of the role of Saharan mineral <span class="hlt">dust</span> in the Arctic climate system, this study focuses on <span class="hlt">dust</span> emission and poleward transport associated with an intense Saharan cyclone that occurred over North Africa in early April 2011. Satellites observations at high spatio-temporal resolution are used in this study in order to characterize qualitatively (using MSG-SEVIRI and CALIPSO/<span class="hlt">Cloud</span>Sat) and quantitatively (using MODIS and OMI) the <span class="hlt">dust</span> activity over North Africa associated with the Saharan cyclone as well as the transport of <span class="hlt">dust</span> toward the northern pole. Beside the observations, a simulation at high resolution is performed using the MesoNh model in order to estimation the <span class="hlt">dust</span> load transported northward and to evaluate the <span class="hlt">dust</span> deposition north to 60°N and its impact on the Albedo. In this study, we identify in new and important mechanism for the transpo