Science.gov

Sample records for icy grain analog

  1. Measurements of Polyatomic Molecule Formation on an Icy Grain Analog Using Fast Atoms

    NASA Technical Reports Server (NTRS)

    Chutjian, A.; Madsunkov, S.; Shortt, B. J.; MacAskill, J. A.; Darrach, M. R.

    2006-01-01

    Carbon dioxide has been produced from the impact of a monoenergetic O(P-3) beam upon a surface cooled to 4.8 K and covered with a CO ice. Using temperature-programmed desorption and mass spectrometer detection, we have detected increasing amounts of CO2 formation with O(P-3) energies of 2, 5, 10, and 14 eV. This is the first measurement of polyatomic molecule formation on a surface with superthermal atoms. The goal of this work is to detect other polyatomic species, such as CH3OH, which can be formed under conditions that simulate the grain temperature, surface coverage, and superthermal atoms present in shock-heated circumstellar and interstellar regions.

  2. Building Small Icy Bodies: the Process of Icy Grain Aggregation

    NASA Astrophysics Data System (ADS)

    Fraser, Helen Jane; Hill, Catherine Rachel; Blum, Jurgen; Heisselmann, Daniel

    2015-08-01

    The material remaining in proto-planetary disks provides the ingredients from which planetessimals, and eventually comets, asteroids and planets (including their ring and moon systems) evolve. Aggregation processes are thought to proceed much more rapidly beyond snow-lines in such disks, aided by icy mantles on dust grains, but we do not know nano- and micron-scale dust combines to kilometer-sizes. Recent ALMA observations have proven the existence of snow lines in other proto-planetary systems (Qi et al Science (2013)), so it is by studying icy collisions in the laboratory that we can begin to understand the assembly of the icy bodies in our Solar System.Icy particles (between 4.7 and 10.8 mm in diameter) were collided at relative collision velocities of 0.27 - 0.51 m s-1, at 131 - 160 K, under microgravity conditions using a purpose-built experiment (Salter et al Rev Sci Inst (2010)). Bouncing was observed in the majority of collisions, across a full range of normalized impact parameters (b/R = 0.0-1.0). Coefficients of restitution were evenly spread between 0.08 and 0.65 with an average value of 0.36, leading to a minimum of 58% of translational energy being lost in the collision. The range of coefficients of restitution was attributed to the surface roughness of the particles. Analysis of particle rotation showed that up to 17% of the energy of the particles before the collision was converted into rotational energy. Temperature did not affect the coefficients of restitution over the range studied (Hill et all A&A (2015a)). The effects of chemical composition on the collisional outcomes were also studied, at relative particle impact velocities between 0.01 and 0.19 ms-1, temperatures between 131 and 160 K and a pressure of around 10-5 mbar. Overall the collisional properties of the icy particles were unchanged (Hill et al A&A (2015b)).The implications of these experimental results will be discussed in terms of our understanding of the formation and evolution of

  3. Quantum chemical protocols for modeling reactions and spectra in astrophysical ice analogs: the challenging case of the C⁺ + H₂O reaction in icy grain mantles.

    PubMed

    Woon, David E

    2015-11-21

    Icy grain mantles that accrete on refractory dust particles in the very cold interstellar medium or beyond the snow line in protoplanetary disks serve as minute incubators for heterogeneous chemistry. Ice mantle chemistry can differ significantly from the gas phase chemistry that occurs in these environments and is often richer. Modeling ices and their chemistry is a challenging task for quantum theoretical methods, but theory promises insight into these systems that is difficult to attain with experiments. Density functional theory (DFT) is predominately employed for modeling reactions in icy grain mantles due to its favorable scalability, but DFT has limitations that risk undercutting its reliability for this task. In this work, basic protocols are proposed for identifying the degree to which DFT methods are able to reproduce experimental or higher level theoretical results for the fundamental interactions upon which ice mantle chemistry depends, including both reactive interactions and non-reactive scaffolding interactions. The exemplar of this study is the reaction of C(+) with H2O, where substantial methodological differences are found in the prediction of gas phase relative energetics for stationary points (about 10 kcal mol(-1) for the C-O bond energy of the H2OC(+) intermediate), which in turn casts doubt about employing it to treat the C(+) + H2O reaction on an ice surface. However, careful explorations demonstrate that B3LYP with small correlation consistent basis sets performs in a sufficiently reliable manner to justify using it to identify plausible chemical pathways, where the dominant products were found to be neutral HOC and the CO(-) anion plus one and two H3O(+) cations, respectively. Predicted vibrational and electronic spectra are presented that would serve to verify or disconfirm the pathways; the latter were computed with time-dependent DFT. Conclusions are compared with those of a recent similar study by McBride and coworkers (J. Phys. Chem

  4. Quantum chemical protocols for modeling reactions and spectra in astrophysical ice analogs: the challenging case of the C⁺ + H₂O reaction in icy grain mantles.

    PubMed

    Woon, David E

    2015-11-21

    Icy grain mantles that accrete on refractory dust particles in the very cold interstellar medium or beyond the snow line in protoplanetary disks serve as minute incubators for heterogeneous chemistry. Ice mantle chemistry can differ significantly from the gas phase chemistry that occurs in these environments and is often richer. Modeling ices and their chemistry is a challenging task for quantum theoretical methods, but theory promises insight into these systems that is difficult to attain with experiments. Density functional theory (DFT) is predominately employed for modeling reactions in icy grain mantles due to its favorable scalability, but DFT has limitations that risk undercutting its reliability for this task. In this work, basic protocols are proposed for identifying the degree to which DFT methods are able to reproduce experimental or higher level theoretical results for the fundamental interactions upon which ice mantle chemistry depends, including both reactive interactions and non-reactive scaffolding interactions. The exemplar of this study is the reaction of C(+) with H2O, where substantial methodological differences are found in the prediction of gas phase relative energetics for stationary points (about 10 kcal mol(-1) for the C-O bond energy of the H2OC(+) intermediate), which in turn casts doubt about employing it to treat the C(+) + H2O reaction on an ice surface. However, careful explorations demonstrate that B3LYP with small correlation consistent basis sets performs in a sufficiently reliable manner to justify using it to identify plausible chemical pathways, where the dominant products were found to be neutral HOC and the CO(-) anion plus one and two H3O(+) cations, respectively. Predicted vibrational and electronic spectra are presented that would serve to verify or disconfirm the pathways; the latter were computed with time-dependent DFT. Conclusions are compared with those of a recent similar study by McBride and coworkers (J. Phys. Chem

  5. Thermal Conductivity Measurements on Icy Satellite Analogs

    NASA Technical Reports Server (NTRS)

    Javeed, Aurya; Barmatz, Martin; Zhong, Fang; Choukroun, Mathieu

    2012-01-01

    With regard to planetary science, NASA aspires to: "Advance scientific knowledge of the origin and history of the solar system, the potential for life elsewhere, and the hazards and resources present as humans explore space". In pursuit of such an end, the Galileo and Cassini missions garnered spectral data of icy satellite surfaces implicative of the satellites' structure and material composition. The potential for geophysical modeling afforded by this information, coupled with the plausibility of life on icy satellites, has pushed Jupiter's Europa along with Saturn's Enceladus and Titan toward the fore of NASA's planetary focus. Understanding the evolution of, and the present processes at work on, the aforementioned satellites falls squarely in-line with NASA's cited goal.

  6. Vaporization in comets - The icy grain halo of Comet West

    NASA Technical Reports Server (NTRS)

    Ahearn, M. F.; Cowan, J. J.

    1980-01-01

    The variation with heliocentric distance of the production rates of various species in Comet West (1975n = 1976 VI) is explained with a cometary model consisting of a CO2 dominated nucleus plus a halo of icy grains of H2O or clathrate hydrate. It is concluded that the parents of CN and C3 are released primarily from the nucleus but that the parent of C2 is released primarily from the halo of icy grains.

  7. Formation of ions and radicals from icy grains in comets

    NASA Technical Reports Server (NTRS)

    Jackson, William M.

    1992-01-01

    Two theoretical models for the formation of radicals from ice grains are examined to determine if this can explain the jets in comets. It is shown that the production rates for these radicals by the photolysis of molecules in the icy grains are not high enough to explain the jets. A new mechanism is proposed involving the release of cations and anions in the gas phase as the icy mantle surrounding the grains is evaporated. Solar visible radiation can then form radicals by photodetachment of the electrons from these anions. The production rate of radicals formed in this manner is in accord with the production rates of the observed radicals.

  8. Explosive desorption of icy grain mantles in dense clouds

    NASA Technical Reports Server (NTRS)

    Schutte, W. A.; Greenberg, J. M.

    1991-01-01

    The cycling of the condensible material in dense clouds between the gas phase and the icy grain mantles is investigated. In the model studied, desorption of the ice occurs due to grain mantle explosions when photochemically stored energy is released after transient heating by a cosmic ray particle. It is shown that, depending on the grain size distribution in dense clouds, explosive desorption can maintain up to about eight percent of the carbon in the form of CO in the gas phase at typical cloud densities.

  9. EVOLUTION OF SIZE DISTRIBUTION OF ICY GRAINS BY SUBLIMATION AND CONDENSATION

    SciTech Connect

    Kuroiwa, Takuto; Sirono, Sin-iti

    2011-09-20

    In the outer part of a protoplanetary disk, dust grains consist of silicate core covered by an ice mantle. A temporal heating event in the disk results in sublimation of the ice mantle. After the end of the heating event, as the temperature decreases, H{sub 2}O molecules recondense on the surface of the dust grain. Ultimately, the dust grain is covered by an ice mantle. Because the equilibrium vapor pressure on the grain surface decreases with the grain size, a large grain grows faster than a small grain. As a result, the size of an icy dust grain changes as a result of the heating event. The change in size also affects the mechanical properties of the dust aggregates formed by the icy grains. In this paper, we investigated the evolution of the size distribution of icy dust grains during sublimation and condensation. We found that the size evolution of icy grains can be divided into two stages. In the first stage, the icy grains grow through condensation of H{sub 2}O molecules. In the second stage, the size of grains changes further as H{sub 2}O molecules are transferred between icy grains while the surrounding gas condenses. The size distribution of the icy dust grains becomes bimodal, with a small number of relatively large grains and many small grains without an icy mantle. Possible effects of the size change on the evolution of icy dust aggregates are discussed.

  10. Formation of ions and radicals from icy grains in comets

    NASA Technical Reports Server (NTRS)

    Jackson, William M.; Gerth, Christopher; Hendricks, Charles

    1991-01-01

    Ion and radical formation in comets are thought to occur primarily by photodissociation of gas phase molecules. Experimental evidence and theoretical calculations are presented that show that some of the radical and ions can come directly from ice grains. The experimental evidence suggest that if the frozen molecules on the surface of grains undergo direct dissociation then they may be able to release radicals directly in the gas phase. If the molecules undergo predissociation it is unlikely that they will release radicals in the gas phase since they should be quenched. Calculations of this direct photodissociation mechanism further indicate that even if the parent molecule undergoes direct dissociation, the yield will not be high enough to explain the rays structure in comets unless the radicals are stored in the grains and then released when the grain evaporates. Calculations were also performed to determine the maximum number of ions that can be stored in an icy grain's radius. This number is compared with the ratio of the ion to neutral molecular density. The comparison suggests that some of the ions observed near the nucleus of the comet could have originally been present in the cometary nucleus. It is also pointed out that the presence of these ions in icy grains could lead to radical formation via electron recombination. Finally, an avalanche process was evaluated as another means of producing ions in comets.

  11. Laboratory permittivity measurements of icy planetary analogs in the millimeter and submillimeter domains, in relation with JUICE mission.

    NASA Astrophysics Data System (ADS)

    Brouet, Y.; Jacob, K.; Murk, A.; Poch, O.; Pommerol, A.; Thomas, N.; Levasseur-Regourd, A. C.

    2015-12-01

    The European Space Agency's JUpiter ICy moons Explorer (JUICE) spacecraft is planned for launch in 2022 and arrival at Jupiter in 2030. It will observe the planet Jupiter and three of its largest moons, Ganymede, Callisto and Europa. One instrument on the JUICE spacecraft is the Sub-millimeter Wave Instrument (SWI), which will measure brightness temperatures from Jupiter's stratosphere and troposphere, and from subsurfaces of Jupiter's icy moons. In the baseline configuration SWI consists of two tunable sub-millimeter wave receivers operating from 530 to 625 GHz. As an alternative one of the receivers could cover the range of 1080 and 1275 GHz. Inversion models are strongly dependent on the knowledge of the complex relative permittivity (hereafter permittivity) of the target material to retrieve the physical properties of the subsurface (e.g. [1][2]). We set up a laboratory experiment allowing us to perform reproducible measurements of the complex scattering parameters S11 and S21 in the ranges of 70 to 110 GHz, of 100 to 160 GHz, of 140 to 220 GHz, of 140 to 220 GHz and of 510 to 715 GHz. These scattering parameters can be used to retrieve the permittivity of icy analogs of the surfaces and subsurfaces of Jupiter's icy moons in order to prepare the data interpretation of SWI [3]. The measurements are performed under laboratory conditions with a quasi-optical bench (Institute of Applied Physics, University of Bern). The icy analogs that we prepare in the Laboratory for Outflow Studies of Sublimating Materials (LOSSy, Physics Institute, University of Bern), include two different porous water ice samples composed of fine-grained ice particles with a size range of 4 to 6 microns and ice particles with a size range of 50 to 100 microns [4][5]; and possibly CO2 ice. We will present the general experimental set-up and the first results in the context to prepare the data interpretation of SWI. [1] Ulaby, F. T., Long, D. G., 2014. Microwave radar and radiometric remote

  12. Sublimating icy planetesimals as the source of nucleation seeds for grain condensation in classical novae

    NASA Technical Reports Server (NTRS)

    Matese, John J.; Whitmire, D. P.; Reynolds, R. T.

    1989-01-01

    The problem of grain nucleation during novae outbursts is a major obstacle to our understanding of dust formation in these systems. How nucleation seeds can form in the hostile post-outburst environment remains an unresolved matter. It is suggested that the material for seeding the condensation of ejecta outflow is stored in a primordial disk of icy planetesimals surrounding the system. Evidence is presented that the requisite number of nucleation seeds can be released by sublimation of the planetesimals during outbursts.

  13. Evidence for Chemical Processing of Precometary Icy Grains In Circumstellar Environments of Pre-Main-Sequence Stars

    NASA Technical Reports Server (NTRS)

    Teglier, Stephen C.; Weintraub, David A.; Rettig, Terrence W.; Pendleton, Yvonne J.; Whittet, Douglas C.; Kulesa, Craig A.

    1995-01-01

    We report the detection of a broad absorption feature near 2166 cm-1 in the spectrum of the Taurus cloud source Elias 18. This pre-main-sequence source is the second in Taurus, the third in our survey, and the fifth known in the sky to show the broad 2166 cm-1 absorption feature. Of equal importance, this feature is not seen toward several other embedded sources in our survey, nor is it seen toward the source Elias 16, located behind the Taurus cloud. Laboratory experiments with interstellar ice analogs show that such a feature is associated with a complex C=-N containing compound [called X(C=-N)] that results from high-energy processing (ultraviolet irradiation or ion bombardment) of simple ice components into more complex, organic components, We find a nonlinear anticorrelation between the abundance of X(C=-N) and frozen CO in non- polar lattices. We find no correlation between the abundance of X(C=-N) and frozen CO in polar lattices. Because the abundances of frozen CO and H20 are strongly correlated with each other and with visual extinction toward sources embedded in and located behind the Taurus molecular cloud, these ice components usually are associated with intracloud material. Our results indicate that X(C=-N) molecules result from chemical processing of dust grains dominated by nonpolar icy mantles in the local environments of pre-main- sequence stars. Such processing of icy grains in the early solar system may be an important source of organic compounds observed in minor solar system bodies. The delivery of these organic compounds to the surface of the primitive Earth through comet impacts may have provided the raw materials for prebiotic chemistry.

  14. Microwave continuum radiation from comet Kohoutek 1973f - Emission from the icy-grain halo

    NASA Technical Reports Server (NTRS)

    Hobbs, R. W.; Brandt, J. C.; Maran, S. P.; Webster, W. J., Jr.; Swamy, K. S. K.

    1975-01-01

    Cometary emission was measured at 3.71 cm on January 10-11, 1974. A possible detection at 2.8 cm and an upper limit at 11.1 cm are also reported. Interferometer measurements at 3.71 cm show that the angular diameter is less than 1.4 arc sec or less than 850 km at the comet. The corresponding disk brightness temperature is greater than 313 + or - 80 K. The radiation presumably originates in the icy-grain halo postulated by Delsemme.

  15. Modelling of the sublimation of icy grains in the coma of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Gicquel, A.; Vincent, J.-B.; Shi, X.; Sierks, H.; Rose, M.; Güttler, C.; Tubiana, C.

    2015-10-01

    The ESA (European Space Agency) Rosetta spacecraft was launched on 2 March 2004, to reach comet 67P/Churyumov-Gerasimenko in August 2014. Since March 2014, images of the nucleus and the coma (gas and dust) of the comet have been acquired by the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) camera system [1] using both, the wide angle camera (WAC) and the narrow angle camera (NAC). The orbiter will be maintained in the vicinity of the comet until perihelion (Rh=1.3 AU) or even until Rh=1.8 AU post-perihelion (December 2015). Nineteen months of uninterrupted, close-up observations of the gas and dust coma will be obtained and will help to characterize the evolution of comet gas and dust activity during its approach to the Sun. Indeed, for the first time, we will follow the development of a comet's coma from a close distance. Also the study of the dust-gas interaction in the coma will highlight the sublimation of icy grains. Even if the sublimation of icy grains is known, it is not yet integrated in a complete dust-gas model. We are using the Direct Simulation Monte Carlo (DSMC) method to study the gas flow close to the nucleus. The code called PI-DSMC (www.pidsmc. com) can simulate millions of molecules for multiple species.When the gas flow is simulated, we inject the dust particle with a zero velocity and we take into account the 3 forces acting on the grains in a cometary environment (drag force, gravity and radiative pressure). We used the DLL (Dynamic Link Library) model to integrate the sublimation of icy grains in the gas flowand allow studying the effect of the additional gas on the dust particle trajectories. For a quantitative analysis of the sublimation of icy, outflowing grains we will consider an ensemble of grains of various radii with different compositions [2] The evolution of the grains, once they are ejected into the coma, depends on their initial size, their composition and the heliocentric distance (because the temperature of

  16. Prebiotic chemistry in icy grain mantles in space. An experimental and observational approach.

    PubMed

    Muñoz Caro, Guillermo M; Dartois, Emmanuel

    2013-03-01

    A compendium of different solid carbonaceous materials detected in space is presented, focussing on the search for organic matter of prebiotic interest. This journey takes us from the carbon grains likely formed in the atmospheres of evolved stars to organic grain mantles made from ice processing thought to be present in dense interstellar clouds and circumstellar regions, making a stop in solar system objects that could have delivered organic species to the early Earth. The most abundant carbon materials detected to date in space appear to be of little biological relevance. On the other hand, organic refractory residues, made in the laboratory from UV-photoprocessing followed by warm-up of interstellar ice analogs, are a hydrocarbon material rich in O and N containing chemical compounds that could act as initiators of prebiotic chemistry. A similar material might be present in dust grains inside dense clouds or circumstellar regions, some comets, and as a minor component in carbonaceous chondrites. We use infrared spectroscopy as a tool to spot organic refractory matter in various space environments. The delivery of organic materials via comets, (micro-) meteorites, and interplanetary dust particles to the primitive Earth might have contributed as a starting material for prebiotic chemistry. To test this hypothesis, it is first essential to characterize the composition of exogenous organic matter.

  17. Prebiotic chemistry in icy grain mantles in space. An experimental and observational approach.

    PubMed

    Muñoz Caro, Guillermo M; Dartois, Emmanuel

    2013-03-01

    A compendium of different solid carbonaceous materials detected in space is presented, focussing on the search for organic matter of prebiotic interest. This journey takes us from the carbon grains likely formed in the atmospheres of evolved stars to organic grain mantles made from ice processing thought to be present in dense interstellar clouds and circumstellar regions, making a stop in solar system objects that could have delivered organic species to the early Earth. The most abundant carbon materials detected to date in space appear to be of little biological relevance. On the other hand, organic refractory residues, made in the laboratory from UV-photoprocessing followed by warm-up of interstellar ice analogs, are a hydrocarbon material rich in O and N containing chemical compounds that could act as initiators of prebiotic chemistry. A similar material might be present in dust grains inside dense clouds or circumstellar regions, some comets, and as a minor component in carbonaceous chondrites. We use infrared spectroscopy as a tool to spot organic refractory matter in various space environments. The delivery of organic materials via comets, (micro-) meteorites, and interplanetary dust particles to the primitive Earth might have contributed as a starting material for prebiotic chemistry. To test this hypothesis, it is first essential to characterize the composition of exogenous organic matter. PMID:23340705

  18. THE UPTAKE OF INTERSTELLAR GASEOUS CO INTO ICY GRAIN MANTLES IN A QUIESCENT DARK CLOUD

    SciTech Connect

    Whittet, D. C. B.; Goldsmith, P. F.; Pineda, J. L.

    2010-09-01

    Data from the Five College Radio Astronomy Observatory CO Mapping Survey of the Taurus molecular cloud are combined with extinction data for a sample of 292 background field stars to investigate the uptake of CO from the gas to icy grain mantles on dust within the cloud. On the assumption that the reservoir of CO in the ices is represented well by the combined abundances of solid CO and solid CO{sub 2} (which forms by oxidation of CO on the dust), we find that the total column density (gas + solid) correlates tightly with visual extinction (A{sub V}) over the range 5 mag < A{sub V} < 30 mag, i.e., up to the highest extinctions covered by our sample. The mean depletion of gas-phase CO, expressed as {delta}(CO) = N(CO){sub ice}/N(CO){sub total}, increases monotonically from negligible levels for A{sub V} {approx}< 5 to {approx} 0.3 at A{sub V} = 10 and {approx} 0.6 at A{sub V} = 30. As these results refer to line-of-sight averages, they must be considered lower limits to the actual depletion at loci deep within the cloud, which may approach unity. We show that it is plausible for such high levels of depletion to be reached in dense cores on timescales {approx}0.6 Myr, comparable with their expected lifetimes. Dispersal of cores during star formation may be effective in maintaining observable levels of gaseous CO on the longer timescales estimated for the age of the cloud.

  19. Grain sizes, surface areas, and porosities of vapor-deposited H2O ices used to simulate planetary icy surfaces.

    PubMed

    Boxe, C S; Bodsgard, B R; Smythe, W; Leu, M T

    2007-05-15

    Mean grain sizes and specific surface areas (SSAs) of ice substrates formed by vapor deposition at low temperatures are of importance in simulating external surfaces of icy satellites in the solar system. Environmental scanning electron microscopy (ESEM) was used to obtain granule sizes and to observe the phase of ice granules prepared on borosilicate, silicon, and metallic plates. Ices prepared at a temperature lower than 140 K appear to be amorphous, and their granule sizes are typically submicrometer. At slightly warmer temperatures, near 180-200 K, ice films are composed of either hexagonal or cubic granules with sizes up to a few micrometers. When briefly annealed to even warmer temperatures, ice granule sizes approach approximately 10 microm. SSAs of ice substrates were determined from BET (Brunauer, Emmett, and Teller) analysis of gas adsorption isotherms in the temperature range from 83.5 to 261 K. SSAs decrease drastically from 102 m2/g at 83.5 K to 0.87 m2/g at 150 K and further decrease slowly to 0.22 m2/g at 261 K, suggesting that the transition from amorphous to crystalline forms occurs at approximately 150 K. The overall decrease in SSAs is primarily due to metamorphism and sintering. These results are comparable to recent field and laboratory measurements. Possible implications for theoretical models of icy satellites of outer planets using remote sensing techniques are also discussed. PMID:17306289

  20. Ion-Ice Astrochemistry: Barrierless Low-Energy Deposition Pathways to HCOOH, CH3OH, and CO2 on Icy Grain Mantles from Precursor Cations

    NASA Technical Reports Server (NTRS)

    Woon, David E.

    2011-01-01

    A new family of very favorable reaction pathways is explored involving the deposition of ions on icy grain mantles with very low energies. Quantum chemical cluster calculations at the MP2/6-31+G** level in 4H2O clusters and at the B3LYP/6-31+G** level in 17H2O clusters indicate that HCO+ and CH3 + are able to react spontaneously with one of the water molecules in the cluster to form protonated formic acid (HCOOH2 +) and protonated methanol (CH3OH2 +), respectively. It is furthermore found that these initial adducts spontaneously transfer their excess protons to the cluster to form neutral formic acid and methanol, plus solvated hydronium, H3O+. In the final case, if a CO molecule is bound to the surface of the cluster, OH+ may react with it to form protonated carbon dioxide (HCO2 +), which then loses its proton to yield CO2 and H3O+. In the present model, all of these processes were found to occur with no barriers. Discussion includes the analogous gas phase processes, which have been considered in previous studies, as well as the competitive abstraction pathway for HCO(+) + H2O.

  1. The Effects of Cracking on the Surface Potential of Icy Grains in Saturn’s E-Ring: Laboratory Studies

    NASA Astrophysics Data System (ADS)

    Bu, Caixia; Bahr, David A.; Dukes, Catherine A.; Baragiola, Raúl A.

    2016-07-01

    Within Saturn's E-ring, dust grains are coated by water vapor co-released with ice grains from the geyser-like eruptions of Enceladus. These ice-coated grains have intrinsic surface potential and interact synergistically with the ions and electrons of Saturn's magnetospheric plasmas. We perform laboratory experiments to investigate the effects of water-ice growth on the surface potential, using amorphous solid water (ASW) films. We estimate the growth of the surface potential to be ˜‑2.5 mV (Earth) yr‑1 and ‑112 mV yr‑1 for E-ring grains at ˜4.5R s and 3.95R s outside Enceladus’s plume, respectively. In addition, our measurements show that the linear relationship between the surface potential and the film thickness, as described in previous studies, has an upper limit, where the film spontaneously cracks above a porosity-dependent critical thickness. Heating of the cracked films with (and without) deposited charge shows that significant positive (and negative) surface potentials are retained at temperatures above 110 K, contrary to the minimal values (roughly zero) for thin, transparent ASW films. The significant surface potentials observed on micron-scale cracked ice films after thermal cycling, ‑(5–20) V, are consistent with Cassini measurements, which indicate a negative charge of up to ‑5 V for E-ring dust particles at ˜5R s. Therefore, the native grain surface potential resulting from water-vapor coating must be included in modeling studies of interactions between E-ring icy surfaces and Saturn's magnetospheric plasma.

  2. The Effects of Cracking on the Surface Potential of Icy Grains in Saturn’s E-Ring: Laboratory Studies

    NASA Astrophysics Data System (ADS)

    Bu, Caixia; Bahr, David A.; Dukes, Catherine A.; Baragiola, Raúl A.

    2016-07-01

    Within Saturn's E-ring, dust grains are coated by water vapor co-released with ice grains from the geyser-like eruptions of Enceladus. These ice-coated grains have intrinsic surface potential and interact synergistically with the ions and electrons of Saturn's magnetospheric plasmas. We perform laboratory experiments to investigate the effects of water-ice growth on the surface potential, using amorphous solid water (ASW) films. We estimate the growth of the surface potential to be ˜-2.5 mV (Earth) yr-1 and -112 mV yr-1 for E-ring grains at ˜4.5R s and 3.95R s outside Enceladus’s plume, respectively. In addition, our measurements show that the linear relationship between the surface potential and the film thickness, as described in previous studies, has an upper limit, where the film spontaneously cracks above a porosity-dependent critical thickness. Heating of the cracked films with (and without) deposited charge shows that significant positive (and negative) surface potentials are retained at temperatures above 110 K, contrary to the minimal values (roughly zero) for thin, transparent ASW films. The significant surface potentials observed on micron-scale cracked ice films after thermal cycling, -(5-20) V, are consistent with Cassini measurements, which indicate a negative charge of up to -5 V for E-ring dust particles at ˜5R s. Therefore, the native grain surface potential resulting from water-vapor coating must be included in modeling studies of interactions between E-ring icy surfaces and Saturn's magnetospheric plasma.

  3. Sublimation and reformation of icy grains in the primitive solar nebula

    NASA Technical Reports Server (NTRS)

    Lunine, Jonathan I.; Engel, Steffi; Rizk, Bashar; Horanyi, Mihaly

    1991-01-01

    The quantity of water ice that sublimates during the free fall of grains into the solar nebula from a surrounding interstellar cloud varies from over 90 percent of the grain mass as 30 AU from the nebular center to less than 10 percent at more than 100 AU. Virtually all the water that is sublimated ultimately recondenses, since the cold nebular gas lying beyond 10 AU is unable to hold more than a small portion as vapor. The return of most of the gas to solid phase near the nebular ambient temperature, of about 50 K, may result in at least two grain populations consisting, in one case, of unaltered interstellar grains which did not undergo sublimation, and in the other of water ice which cocondensed with more volatile gases at nebular ambient temperatures to yield volatile-rich amorphous phases.

  4. FORMATION OF FORMALDEHYDE AND CARBON DIOXIDE ON AN ICY GRAIN ANALOG USING FAST HYDROGEN ATOMS

    SciTech Connect

    Madzunkov, S. M.; MacAskill, J. A.; Chutjian, A.; Darrach, M. R.; Vidali, G.; Shortt, B. J.

    2009-05-20

    Formaldehyde (H{sub 2}CO) and carbon dioxide (CO{sub 2}) were produced in collisions of a superthermal, 3 eV beam of H({sup 2}S) atoms with CO molecules adsorbed on a gold surface at 4.8 K. The reaction-generated products were detected and analyzed using the techniques of temperature programmed desorption (TPD), quadrupole mass spectrometry, and a novel application of the Metropolis algorithm, random-walk procedure to identify the unique fractionation patterns of H{sub 2}CO and CO{sub 2} from the patterns of other species such as N{sub 2}, CO, and H{sub 2}O embedded in the CO blanket and devolved in the TPD/mass spectrometry process. Reaction sequences are given to account for the formation of H{sub 2}CO and CO{sub 2}.

  5. Herschel-resolved Outer Belts of Two-belt Debris Disks—Evidence of Icy Grains

    NASA Astrophysics Data System (ADS)

    Morales, F. Y.; Bryden, G.; Werner, M. W.; Stapelfeldt, K. R.

    2016-11-01

    We present dual-band Herschel/PACS imaging for 59 main-sequence stars with known warm dust (T warm ∼ 200 K), characterized by Spitzer. Of 57 debris disks detected at Herschel wavelengths (70 and/or 100 and 160 μm), about half have spectral energy distributions (SEDs) that suggest two-ring disk architectures mirroring that of the asteroid–Kuiper Belt geometry; the rest are consistent with single belts of warm, asteroidal material. Herschel observations spatially resolve the outer/cold dust component around 14 A-type and 4 solar-type stars with two-belt systems, 15 of which for the first time. Resolved disks are typically observed with radii >100 AU, larger than expected from a simple blackbody fit. Despite the absence of narrow spectral features for ice, we find that the shape of the continuum, combined with resolved outer/cold dust locations, can help constrain the grain size distribution and hint at the dust’s composition for each resolved system. Based on the combined Spitzer/IRS+Multiband Imaging Photometer (5-to-70 μm) and Herschel/PACS (70-to-160 μm) data set, and under the assumption of idealized spherical grains, we find that over half of resolved outer/cold belts are best fit with a mixed ice/rock composition. Minimum grain sizes are most often equal to the expected radiative blowout limit, regardless of composition. Three of four resolved systems around the solar-type stars, however, tend to have larger minimum grains compared to expectation from blowout (f MB = a min/a BOS ∼ 5). We also probe the disk architecture of 39 Herschel-unresolved systems by modeling their SEDs uniformly, and find them to be consistent with 31 single- and 8 two-belt debris systems. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia, with important participation from NASA.

  6. Laboratory Annealing Experiments Of Refractory Silicate Grain Analogs Using Differential Scanning Calorimetry

    NASA Technical Reports Server (NTRS)

    Kimura, Yuki; Nuth, Joseph A., III; Tsukamota, Katsuo; Kaito, Chihiro

    2010-01-01

    Exothermic reactions during the annealing of laboratory synthesized amorphous magnesium-bearing silicate particles used as grain analogs of cosmic dust were detected by differential scanning calorimetry (DSC) in air. With infrared spectroscopy and transmission electron microscopy, we show that cosmic dust could possibly undergo fusion to larger particles, with oxidation of magnesium silicide and crystallization of forsterite as exothermic reactions in the early solar system. The reactions begin at approximately 425, approximately 625, and approximately 1000 K, respectively, and the reaction energies (enthalpies) are at least 727, 4151, and 160.22 J per gram, respectively. During the crystallization of forsterite particles, the spectral evolution of the 10 micrometer feature from amorphous to crystalline was observed to begin at lower temperature than the crystallization temperature of 1003 K. During spectral evolution at lower temperature, nucleation and/or the formation of nanocrystallites of forsterite at the surface of the grain analogs was observed.

  7. FORMATION OF CARBON DIOXIDE, METHANOL, ETHANOL, AND FORMIC ACID ON AN ICY GRAIN ANALOG USING FAST OXYGEN ATOMS

    SciTech Connect

    Madzunkov, S. M.; MacAskill, J. A.; Chutjian, A.

    2010-03-20

    Carbon dioxide (CO{sub 2}), methanol (CH{sub 3}OH), ethanol (CH{sub 3}CH{sub 2}OH), and formic acid (HCOOH) have been formed in collisions of a superthermal, 9 eV beam of O({sup 3} P) atoms with CH{sub 4} molecules, with an over coat of CO molecules, adsorbed on a gold surface at 4.8 K. The products are detected using temperature programmed-desorption and quadrupole mass spectrometry. Identification of the species is carried out through use of the Metropolis random walk algorithm as constrained by the fractionation patterns of the detected species. Relative formation yields are reported and reaction sequences are given to account for possible formation routes.

  8. The Structure of Ice Nanoclusters and Thin-films of Water Ice: Implications for Icy Grains in Cold Molecular Clouds

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance; Blake, David; Uffindell, Christine; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The cubic to hexagonal phase transformation in water ice (I(sub c) yields I(sub h)) is used to measure the extent to which surface structure and impurities control bulk properties. In pure crystalline (I(sub c)) water ice nanoclusters and in thin-films of impure water ice, I(sub c) yields I(sub h) occurs at lower temperatures than in thin-films of pure water ice. The disordered surface of the 20 nm diameter nanoclusters promotes transformations or reactions which would otherwise be kinetically hindered. Likewise, impurities such as methanol introduce defects into the ice network, thereby allowing sluggish structural transitions to proceed. Such surface-related phenomena play an important role in promoting chemical reactions on interstellar ice grains within cold molecular clouds, where the first organic compounds are formed.

  9. Olivine in terminal particles of Stardust aerogel tracks and analogous grains in chondrite matrix

    NASA Astrophysics Data System (ADS)

    Frank, David R.; Zolensky, Michael E.; Le, Loan

    2014-10-01

    The dearth of both major and minor element analyses of anhydrous silicate phases in chondrite matrix has thus far hindered their comparison to the Wild 2 samples. We present 68 analyses of olivine (Fa0-97) in the coarse-grained terminal particles of Stardust aerogel tracks and a comprehensive dataset (>103 analyses) of analogous olivine grains (5-30 μm) isolated in CI, CM, CR, CH, CO, CV3-oxidized, CV3-reduced, C3-ungrouped (Acfer 094 and Ningqiang), L/LL 3.0-4, EH3, and Kakangari chondrite matrix. These compositions reveal that Wild 2 likely accreted a diverse assortment of material that was radially transported from various carbonaceous and ordinary chondrite-forming regions. The Wild 2 olivine includes amoeboid olivine aggregates (AOAs), refractory forsterite, type I and type II chondrule fragments and/or microchondrules, and rare relict grain compositions. In addition, we have identified one terminal particle that has no known compositional analog in the meteorite record and may be a signature of low-temperature, aqueous processing in the Kuiper Belt. The generally low Cr content of FeO-rich olivine in the Stardust samples indicates that they underwent mild thermal metamorphism, akin to a petrologic grade of 3.05-3.15.

  10. Interstellar silicate analogs for grain-surface reaction experiments: Gas-phase condensation and characterization of the silicate dust grains

    SciTech Connect

    Sabri, T.; Jäger, C.; Gavilan, L.; Lemaire, J. L.; Vidali, G.; Henning, T.

    2014-01-10

    Amorphous, astrophysically relevant silicates were prepared by laser ablation of siliceous targets and subsequent quenching of the evaporated atoms and clusters in a helium/oxygen gas atmosphere. The described gas-phase condensation method can be used to synthesize homogeneous and astrophysically relevant silicates with different compositions ranging from nonstoichiometric magnesium iron silicates to pyroxene- and olivine-type stoichiometry. Analytical tools have been used to characterize the morphology, composition, and spectral properties of the condensates. The nanometer-sized silicate condensates represent a new family of cosmic dust analogs that can generally be used for laboratory studies of cosmic processes related to condensation, processing, and destruction of cosmic dust in different astrophysical environments. The well-characterized silicates comprising amorphous Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4}, as well as the corresponding crystalline silicates forsterite and fayalite, produced by thermal annealing of the amorphous condensates, have been used as real grain surfaces for H{sub 2} formation experiments. A specifically developed ultra-high vacuum apparatus has been used for the investigation of molecule formation experiments. The results of these molecular formation experiments on differently structured Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4} described in this paper will be the topic of the next paper of this series.

  11. Survival of refractory presolar grain analogs during Stardust-like impact into Al foils: Implications for Wild 2 presolar grain abundances and study of the cometary fine fraction

    NASA Astrophysics Data System (ADS)

    Croat, T. K.; Floss, C.; Haas, B. A.; Burchell, M. J.; Kearsley, A. T.

    2015-08-01

    We present results of FIB-TEM studies of 12 Stardust analog Al foil craters which were created by firing refractory Si and Ti carbide and nitride grains into Al foils at 6.05 km s-1 with a light-gas gun to simulate capture of cometary grains by the Stardust mission. These foils were prepared primarily to understand the low presolar grain abundances (both SiC and silicates) measured by SIMS in Stardust Al foil samples. Our results demonstrate the intact survival of submicron SiC, TiC, TiN, and less-refractory Si3N4 grains. In small (<2 μm) craters that are formed by single grain impacts, the entire impacting crystalline grain is often preserved intact with minimal modification. While they also survive in crystalline form, grains at the bottom of larger craters (>5 μm) are typically fragmented and are somewhat flattened in the direction of impact due to partial melting and/or plastic deformation. The low presolar grain abundance estimates derived from SIMS measurements of large craters (mostly >50 μm) likely result from greater modification of these impactors (i.e., melting and isotopic dilution), due to higher peak temperatures/pressures in these crater impacts. The better survivability of grains in smaller craters suggests that more accurate presolar grain estimates may be achievable through measurement of such craters. It also suggests small craters can provide a complementary method of study of the Wild 2 fine fraction, especially for refractory CAI-like minerals.

  12. ICI Showcase House Prototype

    SciTech Connect

    2009-02-16

    Building Science Corporation collaborated with ICI Homes in Daytona Beach, FL on a 2008 prototype Showcase House that demonstrates the energy efficiency and durability upgrades that ICI currently promotes through its in-house efficiency program called EFactor.

  13. Laboratory Experiments on Rotation and Alignment of the Analogs of Interstellar Dust Grains by Radiation

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Gallagher, D. L.; West, E. A.; Weingartner, J. C.; Witherow, W. K.; Tielens, A. G. G. M.

    2004-01-01

    The processes and mechanisms involved in the rotation and alignment of interstellar dust grains have been of great interest in astrophysics ever since the surprising discovery of the polarization of starlight more than half a century ago. Numerous theories, detailed mathematical models and numerical studies of grain rotation and alignment with respect to the Galactic magnetic field have been presented in the literature. In particular, the subject of grain rotation and alignment by radiative torques has been shown to be of particular interest in recent years. However, despite many investigations, a satisfactory theoretical understanding of the processes involved in grain rotation and alignment has not been achieved. As there appears to be no experimental data available on this subject, we have carried out some unique experiments to illuminate the processes involved in rotation of dust grains in the interstellar medium. In this paper we present the results of some preliminary laboratory experiments on the rotation of individual micron/submicron size nonspherical dust grains levitated in an electrodynamic balance evacuated to pressures of approximately 10(exp -3) to 10(exp -5) torr. The particles are illuminated by laser light at 5320 Angstroms, and the grain rotation rates are obtained by analyzing the low frequency (approximately 0-100 kHz) signal of the scattered light detected by a photodiode detector. The rotation rates are compared with simple theoretical models to retrieve some basic rotational parameters. The results are examined in the light of the current theories of alignment.

  14. Photoelectric Emission Measurements on the Analogs of Individual Cosmic Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Tankosic, D.; Craven, P. D.; Spann, J. F.; LeClair, A.; West, E. A.; Weingartner, J. C.; Tielens, A. G. G. M.; Nuth, J. a.; Camata, R. P.

    2006-01-01

    The photoelectric emission process is considered to be the dominant mechanism for charging of cosmic dust grains in many astrophysical environments. The grain charge and equilibrium potentials play an important role in the dynamical and physical processes that include heating of the neutral gas in the interstellar medium, coagulation processes in the dust clouds, and levitation and dynamical processes in the interplanetary medium and planetary surfaces and rings. An accurate evaluation of photoelectric emission processes requires knowledge of the photoelectric yields of individual dust grains of astrophysical composition as opposed to the values obtained from measurements on flat surfaces of bulk materials, as it is generally assumed on theoretical considerations that the yields for the small grains are much different from the bulk values. We present laboratory measurements of the photoelectric yields of individual dust grains of silica, olivine, and graphite of approx. 0.09-5 micrometer radii levitated in an electrodynamic balance and illuminated with ultraviolet radiation at 120-160 nm wavelengths. The measured yields are found to be substantially higher than the bulk values given in the literature and indicate a size dependence with larger particles having order-of-magnitude higher values than for submicron-size grains.

  15. Laboratory Experiments on Rotation and Alignment of the Analogs of Interstellar Dust Grains by Radiation

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Gallagher, D. L.; West, E. A.; Weingartner, J. C.; Witherow, W. K.; Tielens, A. G. G. M.

    2004-01-01

    The processes and mechanisms involved in the rotation and alignment of interstellar dust grains have been of great interest in astrophysics ever since the surprising discovery of the polarization of starlight more than half a century ago. Numerous theories, detailed mathematical models, and numerical studies of grain rotation and alignment with respect to the Galactic magnetic field have been presented in the literature. In particular, the subject of grain rotation and alignment by radiative torques has been shown to be of particular interest in recent years. However, despite many investigations, a satisfactory theoretical understanding of the processes involved in subject, we have carried out some unique experiments to illuminate the processes involved in the rotation of dust grains in the interstellar medium. In this paper we present the results of some preliminary laboratory experiments on the rotation of individual micron/submicron-sized, nonspherical dust grains levitated in an electrodynamic balance evacuated to pressures of approximately 10(exp -3) to 10(exp -5) torr. The particles are illuminated by laser light at 5320 A, and the grain rotation rates are obtained by analyzing the low-frequency (approximately 0 - 100 kHz) signal of the scattered light detected by a photodiode detector. The rotation rates are compared with simple theoretical models to retrieve some basic rotational parameters. The results are examined in light of the current theories of alignment.

  16. A study of the icy tails of the distant comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1975-01-01

    Properties are studied of the icy grain model for the tails of comets Baade 1955 VI and Haro-Chavira 1956 I, which have large perihelion distances. The general profiles and orientations of the tails are compared with a set of synchrones, or theoretical trajectories of particles ejected from a cometary nucleus at given instants of time. Several features observed in these comets are shown to be explained by the icy grain model, including jet activity in the coma and no appreciable broadening of the tail with increasing distance from the nucleus. It is demonstrated that the transition region between 2 and 3 AU, where water snow begins to experience rapid evaporation, has a significant effect on the dynamics of icy tails. It is suggested that the icy grains constituting these cometary tails may carry fine particles of meteoric dust which are released when the grains begin to disintegrate by evaporation.

  17. Phototelectric Emission Measurements on the Analogs of Individual Cosmic Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, Mian M.; Tankosic, D.; Craven, P. D.; Spann, J. F.; LeClair, A.; West, E. A.; Weingartner, J. C.; Tielens, A. G. G. M.; Nuth, J. A.; Camata, R. P.; Gerakines, P. A.

    2005-01-01

    The photoelectric emission process is considered to be the dominant mechanism for charging of cosmic dust grains in many astrophysical environments. The grain charge and the equilibrium potentials play an important role in the dynamical and physical processes that include heating of the neutral gas in the interstellar medium, coagulation processes in the dust clouds, and levitation and dynamical processes in the interplanetary medium and planetary surfaces and rings. An accurate evaluation of photoelectric emission processes requires knowledge of the photoelectric yields of individual dust grains of astrophysical composition as opposed to the values obtained from measurements on flat surfaces of bulk materials, as it is generally assumed on theoretical considerations that the yields for the small grains are much higher than the bulk values. We present laboratory measurements of the photoelectric yields of individual dust grains of silica, olivine, and graphite of approximately 0.09 to 8 microns radii levitated in an electrodynamic balance and illuminated with W radiation at 120 to 160 nm wavelengths. The measured values and the size dependence of the yields are found to be substantially different from the bulk values given in the literature.

  18. Survival of Submicron Refractory Presolar Grains in Stardust and Stardust Analog Craters

    NASA Astrophysics Data System (ADS)

    Croat, T. K.; Floss, C.; Kearsley, A. T.; Burchell, M. J.

    2013-09-01

    FIB-TEM studies of Stardust analog craters demonstrate intact survival of refractory minerals (such as TiC, TiN and SiC). The Al craters resulting from submicron projectiles show physical properties somewhat different from those of larger projectiles.

  19. Will Organic Synthesis Within Icy Grains or on Dust Surfaces in the Primitive Solar Nebula Completely Erase the Effects of Photochemical Self Shielding?

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A., III; Johnson, Natasha M.

    2012-01-01

    There are at least 3 separate photochemical self-shielding models with different degrees of commonality. All of these models rely on the selective absorption of (12))C(16)O dissociative photons as the radiation source penetrates through the gas allowing the production of reactive O-17 and O-18 atoms within a specific volume. Each model also assumes that the undissociated C(16)O is stable and does not participate in the chemistry of nebular dust grains. In what follows we will argue that this last, very important assumption is simply not true despite the very high energy of the CO molecular bond.

  20. Geology of icy satellites

    NASA Technical Reports Server (NTRS)

    Mckinnon, W. B.

    1985-01-01

    The geology of the major icy satellites of Jupiter, Saturn, Uranus, and Neptune is discussed in terms of the four major processes that shape icy satellite surfaces: impact cratering, volcanism, tectonism, and interactions with planetary magnetospheres and solar radiation. The role of these processes in creating the differences that exist among the satellites, in particular the orderly progression of geological properties in the Jovian satellites, is emphasized. Important questions left open after the Voyager missions are summarized.

  1. Reflectance Spectra of Regolith Analogs in the middle-IR: Influence of Grain Size

    NASA Astrophysics Data System (ADS)

    Le Bras, A.

    1999-09-01

    Reflectance spectroscopy of asteroids permits to infer the mineral composition of their surface. Since spectral mineral features are sensitive to surface parameters such as grain size, regolith compactness, temperature, maturity,... the interpretation of remote-sensing asteroids spectra is not easy nor unique. Asteroids family members show a continuous dispersion of their spectral characteristics (Doressoudiram et al., 1997) which seems to be due first to a compositional variation but also to some space weathering processes. Space weathering may contribute to the spectral dispersion of the smallest S-type asteroids too. New laboratory spectra are required in order to understand the influence of surface parameters and space weathering effects, and to interpret the recent high-spectral resolution observations from ISO. We started an experimental program at Institut d'Astrophysique Spatiale (Orsay, France), using the 2.5-120 microns interferometer spectrometer, to study the influence of surface parameters on mineral features. First, we study grain size effects with two types of terrestrial rocks: anorthosite (bright) and basalt (dark) in the 2-40 microns range. In a second part, we will extend our experiments to other samples (meteorites and asteroid-like mixtures), and to the visible and NIR range. We present the experimental setup and the preliminary results obtained for 6 different grain size ranges with basalt and anorthosite.

  2. Icy Collisions - Planet Building beyond the snowline

    NASA Astrophysics Data System (ADS)

    Gaertner, Sabrina; Hill, Catherine; Heisselmann, Daniel; Blum, Juergen; Fraser, Helen

    2015-11-01

    Collisions of small icy and dust particles beyond the “snow-line” are a key step in planet formation. Whilst the physical forces that underpin the aggregation of the smallest grains (van der Waals) and the largest planetessimals (gravity) are well understood, the processes involving mm - cm sized particles remain a mystery.In a unique set of experiments, we investigated low velocity collisions of dust and icy particles in this size range under microgravity conditions - utilizing parabolic flight (e.g. Salter 2009, Hill 2015 (a) & (b)). Experiments were performed at cryogenic temperatures (below 140 K) for icy aggregates and ambient as well as cryogenic temperatures (80 - 220 K) for dust aggregates.The kinetic analysis of the observed collisions of different aggregate types in different shapes and sizes revealed astonishing results - as the collisional properties of all investigated particles differ strongly from the usual assumptions in models of planet formation.Here, we present a summary of the results on the collisions of icy particles as well as first results on the collisions of dust aggregates. Focus will be on the coefficient of restitution, which measures the loss of translational energy in bouncing collisions and is a key parameter in models of planet formation.

  3. Icy Satellites Impactor Probes for the Jovian Icy Moons Orbiter

    NASA Technical Reports Server (NTRS)

    Shirley, J. H.; Zimmerman, W. F.; Strauss, W.; Ivlev, R.; Duong, T.; Hunter, D.; Slimko, E.; Nacaise, F.; Archer, E.; Nesmith, B.

    2003-01-01

    We present a preliminary design and mission description for Icy Satellites Impactor Probes (IPS). This design addresses two of the scientific themes of this Icy Galilean Satellites Forum: Surface Chemistry and Geophysics, and Interior Structures. Impactor probes may also make significant contributions in the areas of surface geology and mineralogy.

  4. Interstellar grain chemistry and organic molecules

    NASA Technical Reports Server (NTRS)

    Allamandola, L. J.; Sandford, S. A.

    1990-01-01

    The detection of prominant infrared absorption bands at 3250, 2170, 2138, 1670 and 1470 cm(-1) (3.08, 4.61, 4.677, 5.99 and 6.80 micron m) associated with molecular clouds show that mixed molecular (icy) grain mantles are an important component of the interstellar dust in the dense interstellar medium. These ices, which contain many organic molecules, may also be the production site of the more complex organic grain mantles detected in the diffuse interstellar medium. Theoretical calculations employing gas phase as well as grain surface reactions predict that the ices should be dominated only by the simple molecules H2O, H2CO, N2, CO, O2, NH3, CH4, possibly CH3OH, and their deuterated counterparts. However, spectroscopic observations in the 2500 to 1250 cm(-1)(4 to 8 micron m) range show substantial variation from source reactions alone. By comparing these astronomical spectra with the spectra of laboratory-produced analogs of interstellar ices, one can determine the composition and abundance of the materials frozen on the grains in dense clouds. Experiments are described in which the chemical evolution of an interstellar ice analog is determined during irradiation and subsequent warm-up. Particular attention is paid to the types of moderately complex organic materials produced during these experiments which are likely to be present in interstellar grains and cometary ices.

  5. Scattering properties of natural snow and frost - Comparison with icy satellite photometry

    NASA Technical Reports Server (NTRS)

    Verbiscer, Anne J.; Veverka, Joseph

    1990-01-01

    The Hapke (1986) equation is presently fit to ascertain the single-scattering albedo of the icy satellites of Uranus and Neptune and the one-term Henyey-Greenstein particle-phase function g for each of the Middleton and Mungall (1952) goniophotometric data samples. There emerge both very high single-scattering albedos and strongly forward-scattering particle phase functions; while these are in keeping with Mie theory-based theoretical considerations, they contrast with the observed backscattering behavior of icy satellites. It is suggested the icy satellite frost grains are aggregated into particles of complex texture, which produce the unusual backscattering behavior.

  6. Environmental Change in Icy Moons

    NASA Astrophysics Data System (ADS)

    Pappalardo, R. T.; Vance, S.

    2014-12-01

    There is strong evidence that subsurface oceans could exist within several of the outer solar system's ice-rich moons, at Jupiter (Europa, Ganymede, and Callisto), Saturn (Enceladus and Titan), and Neptune (Triton). If liquid water is indeed available in these subsurface environments, then the availability of chemical energy becomes the greatest limitation on whether icy worlds could harbor life. Of these moons, the largest (Ganymede, Callisto, and Titan) are expected to harbor oceans deep within, and high-pressure H2O ice phases are expected farther beneath those deep oceans. In contrast, the oceans of smaller icy worlds—Europa, Enceladus, and Triton—are plausibly in direct contact with rock below. Given that serpentinization or other water-rock geochemical activity could supply reductants directly to their oceans, these icy worlds have the greatest chance to support present-day microbial life. Each of these three icy worlds displays spectacular resurfaced terrains that are very young (crater retention ages ~10s Myr and younger), with their internal activity linked to extremes in tidal heating today and/or in the geologically recent past. However, the degree of their tidal heating may have changed greatly over time. Europa is believed to experience cyclical tidal heating and activity; Enceladus may have experienced cyclical activity or a geologically recent pulse of activity; Triton may have experienced extreme tidal heating upon its capture and orbital circularization. Such dynamic pasts would pose challenges for any life within. We consider the possible effects of severe swings in the activity level of icy worlds, specifically the implications for delivery of chemical energy to their subsurface oceans.

  7. Habitability potential of icy moons

    NASA Astrophysics Data System (ADS)

    Coustenis, A.; Solomonidou, A.; Bampasidis, G.; Hirtzig, M.; Sohl, F.; Hussmann, H.; Kyriakopoulos, K.; Seymour, K.; Bratsolis, E.; Moussas, X.

    2012-09-01

    The satellites of Jupiter and Saturn have been revealed as extremely astrobiologically interesting bodies presenting promising conditions for habitability and the development and/or maintenance of life. Titan and Enceladus, Saturn's satellites, were found by the Cassini-Huygens mission to possess active organic chemistries with seasonal variations, unique geological features and possibly internal liquid water oceans, among other. Additionally, Jupiter's Europa and Ganymede show indications of harboring liquid water oceans under their icy crusts, which may be in direct contact with a silicate mantle floor and kept warm through time by tidally generated heat. All of these environments satisfy many of the "classical" criteria for habitability (liquid water, energy sources to sustain metabolism and "nutrients" over a period of time long enough to allow the development of life). In order to study the habitability of icy moons around giant planets, we look at the atmosphere-surface-interior connections with their similarities with the Earth as a starting point [1]. The discovery of the water jets on Enceladus, the possibility for cryovolcanic processes on Titan and the hypothetically active mantle of Europa suggest that icy moons around giant planets may well contain subsurface oceans.

  8. Technologies for Icy Bodies Access

    NASA Technical Reports Server (NTRS)

    Carsey, F. D.; Anderson, F. S.; French, L. C.; Green, J. R.; Jones, J. A.; Lane, A. L.; Leger, P. C.; Zimmerman, W. F.

    2001-01-01

    Recent events in planetary exploration have profoundly changed the way both space scientists and the public regard the solar system and our place in it. These events include the Galileo data suggesting subsurface oceans in the Jovian system, ever stronger suggestions of near-surface water on Mars, as well as the complex structure observed for the Mars polar caps. And, of course, interest in icy cometary bodies is as old as humankind. Finally, the Mars north polar cap may conceivably cover and protect an ancient ocean floor, an obvious candidate ancient or extant habitat. In short, our interest in searching for life embraced early on the search for liquid water, and that has led us to an additional appreciation for water ice as both a commonplace partner with liquid water and as an issue to be addressed in the exploration of a host of interesting sites. In general, the spectrum of specialized technology for space exploration has not yet been broadened to include the requirements brought about by exploration of icy sites. We argue that technologies for access, operations, and science in icy solar system sites must be examined and their prioritized development initiated in order to successfully plan missions to these compelling sites over the next two decades. Additional information is contained in the original extended abstract.

  9. Failure strength of icy lithospheres

    NASA Technical Reports Server (NTRS)

    Golombek, M. P.; Banerdt, W. B.

    1987-01-01

    Lithospheric strengths derived from friction on pre-existing fractures and ductile flow laws show that the tensile strength of intact ice under applicable conditions is actually an order of magnitude stronger than widely assumed. It is demonstrated that this strength is everywhere greater than that required to initiate frictional sliding on pre-existing fractures and faults. Because the tensile strength of intact ice increases markedly with confining pressure, it actually exceeds the frictional strength at all depths. Thus, icy lithospheres will fail by frictional slip along pre-existing fractures at yeild stresses greater than previously assumed rather than opening tensile cracks in intact ice.

  10. Antarctic analogs for Enceladus

    NASA Astrophysics Data System (ADS)

    Murray, A. E.; Andersen, D. T.; McKay, C. P.

    2014-12-01

    Enceladus is a new world for Astrobiology. The Cassini discovery of the icy plume emanating from the South Polar region indicates an active world, where detection of water, organics, sodium, and nano-particle silica in the plume strongly suggests that the source is a subsurface salty ocean reservoir. Recent gravity data from Cassini confirms the presence of a regional sea extending north to 50°S. An ocean habitat under a thick ice cover is perhaps a recurring theme in the Outer Solar System, but what makes Enceladus unique is that the plume jetting out into space is carrying samples of this ocean. Therefore, through the study of Enceladus' plumes we can gain new insights not only of a possible habitable world in the Solar Systems, but also about the formation and evolution of other icy-satellites. Cassini has been able to fly through this plume - effectively sampling the ocean. It is time to plan for future missions that do more detailed analyses, possibly return samples back to Earth and search for evidence of life. To help prepare for such missions, the need for earth-based analog environments is essential for logistical, methodological (life detection) and theoretical development. We have undertaken studies of two terrestrial environments that are close analogs to Enceladus' ocean: Lake Vida and Lake Untersee - two ice-sealed Antarctic lakes that represent physical, chemical and possibly biological analogs for Enceladus. By studying the diverse biology and physical and chemical constraints to life in these two unique lakes we will begin to understand the potential habitability of Enceladus and other icy moons, including possible sources of nutrients and energy, which together with liquid water are the key ingredients for life. Analog research such as this will also enable us to develop and test new strategies to search for evidence of life on Enceladus.

  11. The tectonics of icy satellites

    NASA Astrophysics Data System (ADS)

    Murchie, S. L.

    The formation of tectonic structures on icy satellites may have resulted from one or more of several geologic processes: global volume change due to internal temperature change, H2O-ice phase changes, or ice-silicate differentiation; mantle convection driven by thermal or compositional heterogeneities; tidal deformation; and impact-related processes including formation of fracture systems, seismic disruption of areas antipodal to impact sites, basin collapse, and global reorientation. Observed tectonic structures and their associated volcanic deposits are classified herein into six basic assemblages: (1) pervasive troughs and scarps occurring at globally coherent orientations; (2) throughgoing troughs and bands of troughs, generally associated with volcanic materials; (3) linear to curvilinear ridges; (4) volcanically modified systems of concentric and radial scarps and furrows; (5) regional volcanic and tectonic centers; and (6) grooved terrain intimately associated with light-colored volcanic deposits. Comparison of these assemblages with predicted manifestations of different geologic processes may lead to some understanding of the relationship of volcanic and tectonic features to the endogenic and exogenic processes that have affected icy satellites.

  12. ICI optical data storage tape

    NASA Technical Reports Server (NTRS)

    Mclean, Robert A.; Duffy, Joseph F.

    1991-01-01

    Optical data storage tape is now a commercial reality. The world's first successful development of a digital optical tape system is complete. This is based on the Creo 1003 optical tape recorder with ICI 1012 write-once optical tape media. Several other optical tape drive development programs are underway, including one using the IBM 3480 style cartridge at LaserTape Systems. In order to understand the significance and potential of this step change in recording technology, it is useful to review the historical progress of optical storage. This has been slow to encroach on magnetic storage, and has not made any serious dent on the world's mountains of paper and microfilm. Some of the reasons for this are the long time needed for applications developers, systems integrators, and end users to take advantage of the potential storage capacity; access time and data transfer rate have traditionally been too slow for high-performance applications; and optical disk media has been expensive compared with magnetic tape. ICI's strategy in response to these concerns was to concentrate its efforts on flexible optical media; in particular optical tape. The manufacturing achievements, media characteristics, and media lifetime of optical media are discussed.

  13. Cryogenic Property Measurements on Icy Compositions with Application to Solar System Ices

    NASA Astrophysics Data System (ADS)

    Hays, C.; Castillo-Rogez, J.; Barmatz, M.; Mitchell, K.

    2007-08-01

    Introduction and Science Motivation:We present the motivations, objectives, and preliminary experimental results for a new experimental cryo-ices initiative launched at JPL. The main motivation for this work is to fully appreciate the discoveries made by the Cassini-Huygens and Galileo missions, to prepare for the Dawn and New Horizons missions, and to look forward to potential missions to Europa, Enceladus, and Titan. This work is a joint effort among experimentalists and theorists at JPL, in collaboration with specialists in icy material properties the world over. Experimental Approach: A range of experiments are being devised which will improve our ability to model ice-rock body internal evolution and geological processes using modern synthesis and characterization techniques under cryogenic conditions. Initial experiments will involve pure water, methanol-water, ammonia-water, and ammoniawater- methanol mixtures, relevant to a range of icy satellites and processes. Ammonia is considered to play an important role in Titan cryovolcanism, whereas methanol is chosen as an experimental analog due to its ease-of-use in the laboratory. Where beneficial, we will determine basic thermophysical properties and phase diagrams using a Differential Scanning Calorimeter. Solids.We plan to analyze samples from terrestrial glaciers, which are relevant to both the terrestrial and planetary geology and geophysical communities. Terrestrial glaciers appear as realistic analogs for modeling processes taking place in the outer icy shells of icy satellites. These results will better enable us to predict the long-term evolution of terrestrial glaciers and ice shelves. Also, we will synthesize specimens with controlled microstructures by using equilibrium and non-equilibrium synthesis methods. Equilibrium methods, e.g., conventional (slow) freezing in a mold, will provide microstructural length scales in the range 0.2 to 1 mm (with and without preferred orientation, e.g., columnar

  14. The SCITEAS experiment: Optical characterizations of sublimating icy planetary analogues

    NASA Astrophysics Data System (ADS)

    Pommerol, A.; Jost, B.; Poch, O.; El-Maarry, M. R.; Vuitel, B.; Thomas, N.

    2015-05-01

    We have designed and built a laboratory facility to investigate the spectro-photometric and morphologic properties of different types of ice-bearing planetary surface analogs and follow their evolution upon exposure to a low pressure and low temperature environment. The results obtained with this experiment are used to verify and improve our interpretations of current optical remote-sensing datasets. They also provide valuable information for the development and operation of future optical instruments. The Simulation Chamber for Imaging the Temporal Evolution of Analogue Samples (SCITEAS) is a small thermal vacuum chamber equipped with a variety of ports and feedthroughs that permit both in-situ and remote characterizations as well as interacting with the sample. A large quartz window located directly above the sample is used to observe its surface from outside with a set of visible and near-infrared cameras. The sample holder can be easily and quickly inserted and removed from the chamber and is compatible with the other measurement facilities of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern. We report here on the results of two of the first experiments performed in the SCITEAS chamber. In the first experiment, fine-grained water ice mixed with dark organic and mineral matter was left to sublime in vacuum and at low temperature, simulating the evolution of the surface of a comet nucleus approaching the Sun. We observed and characterized the formation and evolution of a crust of refractory organic and mineral matter at the surface of the sample and linked the evolution of its structure and texture to its spectro-photometric properties. In the second experiment, a frozen soil was prepared by freezing a mixture of smectite mineral and water. The sample was then left to sublime for 6 h to simulate the loss of volatiles from icy soil at high latitudes on Mars. Colour images were produced using the definitions of the

  15. Electron irradiation effects in icy regoliths: The PacMan anomalies at Saturn

    NASA Astrophysics Data System (ADS)

    Schaible, Micah; Johnson, Robert E.; Zhigilei, Leo

    2016-10-01

    The anomalous regions identified on the leading hemispheres of the icy Saturnian moons, colloquially known as the 'PacMan' features, were found to have larger thermal inertia than the surrounding regions. The locations of the anomalies were shown to closely match the expected deposition profile of high energy (~ MeV) electrons moving counter rotational to the moons, suggesting an energetic source to drive their formation. Here we consider the mechanisms by which electron radiation can produce changes in the thermal conductivity of an icy regolith and compare estimates obtained from theoretical and experimental results with the measured thermal inertia and grain impact resurfacing rates on the icy moons.Electron interactions with the grains can both create and anneal defects in the crystalline lattice, and deposited energy drives molecular diffusion. Mobilized molecules accumulate in the contact region between grains due to the surface energy minimum, thus increasing the contact volume or 'sintering' the grains. Previously developed sintering rate equations and measured electron energy distributions near the icy moons were used to estimate the timescale for the energetic electrons to increase the contact volume sufficiently to produce the enhanced thermal conductivity of the anomalous regions. In order to properly constrain the sintering calculations, molecular dynamics (MD) simulations of electron interactions in water ice were carried out to determine the number and diffusion length of excited molecules. Water molecules were artificially excited both in a water ice bulk and near a grain surface, and several ice polymorphs relevant to ice grain formation in outer solar system conditions were considered. Comparing the estimated sintering timescales to micrometeorite resurfacing rates indicates that grains must be small (~5um) and/or irregularly shaped with a high defect density in the contact regions. Since there is some disagreement in these grains sizes and

  16. 2.7- to 4.1-micron spectrophotometry of icy satellites of Saturn and Jupiter

    NASA Technical Reports Server (NTRS)

    Lebofsky, L. A.; Feierberg, M. A.

    1985-01-01

    Spectrophotometry is presented in the 2.7-4.1 micrometer spectral region for icy satellites of Saturn (Tethys, Dione, Rhea, Iapetus and Hyperion) and Jupiter (Europa, Ganymede and Callisto). The 3.6-micrometer reflectance peak characteristic of fine-grained water ice is observed prominently on the satellites of Saturn, faintly on the leading side of Europa, and not at all on Ganymede, Callisto or the dark side of Iapetus. The spectral reflectances of these icy satellites may be affected by their equilibrium surface temperatures and magnetospheric effects.

  17. ICI/BASF PP for acrylics swap

    SciTech Connect

    Alperowicz, N.

    1993-01-27

    ICI (London) and BASF (Ludwigshafen) have announced their long-awaited polypropylene (PP) for acrylics swap deal. ICI is buying BASF's European acrylic resin business, and the German firm will acquire ICI's European PP operations. The deal is due for completion by mid-1993, subject to regulatory approvals. BASF, hitherto a small-scale PP producer, doubles capacity to 600,000 m.t./year and moves up the European PP league to number three, behind Himont and Shell. BASF, whose process is used in the plants, secures a foothold in the UK PP market, where Shell - planning a merger with Himont - is the only other producer, with 170,000 m.t./year. ICI's purchase involves BASF's Resart GmbH and Critesa SA subsidiaries, located at Mainz, Germany and near Barcelona, Spain, respectively. The business - which will add about [Brit pounds]60 million ($93 million) to ICI Acrylics [Brit pounds]300-million revenues - employs 400 people, who will transfer to ICI.

  18. THE SINTERING REGION OF ICY DUST AGGREGATES IN A PROTOPLANETARY NEBULA

    SciTech Connect

    Sirono, Sin-iti

    2011-07-10

    Icy grain aggregates are formed in the outer region of a protoplanetary nebula. The infall of these aggregates to the central star is due to gas drag, and their temperature increases as the infall proceeds. The icy molecules on the grain move to the neck where the grains get connected through sublimation and condensation of the molecules. This process is called sintering. As the sintering proceeds, the mechanical strength of the neck changes considerably, strongly affecting the collisional evolution of the aggregates. The timescale required for sintering is determined in this study, based on which the region where the sintering proceeds within a prescribed timescale is obtained. It is found that the region covers a substantial fraction of the protoplanetary nebula, and the location of the region depends on the temperature distribution inside the nebula. If the aggregate is stirred up and the temperature of the aggregate increases temporally, the sintering region spreads to the whole nebula.

  19. Exchange processes from the deep interior to the surface of icy moons

    NASA Astrophysics Data System (ADS)

    Grasset, O.

    present dynamics of icy surfaces: erosion, tectonics and cryovolcanism. This second topic is devoted to the description of the surface features. A synthesis of what has been seen in the jovian system and a presentation of what is now discovered in the saturnian system might be useful. 3) Internal processes: dynamics of icy mantles. Many works have been done specifically for icy moons (rheology of icy mantles, heating modes, effect of ice composition, internal activity of small moons, internal oceans,. . . ). Icy mantles present so many different convective processes, depending on parameters such as the ice composition, the heating mode, . . . , that a full review of the recent progress on the subject is required. 4) Physics and chemistry of ices: experimental constraints on hydrates, clathrates and organics. Nothing can be done without experimental data. Thermodynamical constraints, phase diagrams, but also mechanical properties of icy materials are required for constraining all models. Many progress have been made these last five years, especially for clathrate structures so important in the case of Titan. A review of these progresses is required. 5) Earth analogs: a tool for understanding surface/ internal features. Tectonic and volcanic features on icy moons are sometimes confronted to Earth structures. This procedure is very interesting. While materials are different (on Earth the melt is lighter than the rock, but on icy moons it is the contrary), tectonic and volcanic features can be very similar. Our good understanding of the Earth can be very useful for describing the processes responsible of tectonic/volcanic features on the moons. Discussing around the five themes described above may provide some constraints on open questions such as the characteristics of liquid layers within icy moons, the cryovolcanism on Titan, the resurfacing of Europa, the composition of Titan's surface, and the activity on Enceladus. 2

  20. Cryovolcanism on the icy satellites

    USGS Publications Warehouse

    Kargel, J.S.

    1994-01-01

    Evidence of past cryovolcanism is widespread and extremely varied on the icy satellites. Some cryovolcanic landscapes, notably on Triton, are similar to many silicate volcanic terrains, including what appear to be volcanic rifts, calderas and solidified lava lakes, flow fields, breached cinder cones or stratovolcanoes, viscous lava domes, and sinuous rilles. Most other satellites have terrains that are different in the important respect that no obvious volcanoes are present. The preserved record of cryovolcanism generally is believed to have formed by eruptions of aqueous solutions and slurries. Even Triton's volcanic crust, which is covered by nitrogen-rich frost, is probably dominated by water ice. Nonpolar and weakly polar molecular liquids (mainly N2, CH4, CO, CO2, and Ar), may originate by decomposition of gas-clathrate hydrates and may have been erupted on some icy satellites, but without water these substances do not form rigid solids that are stable against sublimation or melting over geologic time. Triton's plumes, active at the time of Voyager 2's flyby, may consist of multicomponent nonpolar gas mixtures. The plumes may be volcanogenic fumaroles or geyserlike emissions powered by deep internal heating, and, thus, the plumes may be indicating an interior that is still cryomagmatically active; or Triton's plumes may be powered by solar heating of translucent ices very near the surface. The Uranian and Neptunian satellites Miranda, Ariel, and Triton have flow deposits that are hundreds to thousands of meters thick (implying highly viscous lavas); by contrast, the Jovian and Saturnian satellites generally have plains-forming deposits composed of relatively thin flows whose thicknesses have not been resolved in Voyager images (thus implying relatively low-viscosity lavas). One possible explanation for this inferred rheological distinction involves a difference in volatile composition of the Uranian and Neptunian satellites on one hand and of the Jovian and

  1. Cryovolcanism on the icy satellites

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.

    1994-01-01

    Evidence of past cryovolcanism is widespread and extremely varied on the icy satellites. Some cryovolcanic landscapes, notably on Triton, are similar to many silicate volcanic terrains, including what appear to be volcanic rifts, calderas and solidified lava lakes, flow fields, breached cinder cones or stratovolcanoes, viscous lava domes, and sinuous rilles. Most other satellites have terrains that are different in the important respect that no obvious volcanoes are present. The preserved record of cryovolcanism generally is believed to have formed by eruptions of aqueous solutions and slurries. Even Triton's volcanic crust, which is covered by nitrogen-rich frost, is probably dominated by water ice. Nonpolar and weakly polar molecular liquids (mainly N2, CH4, CO, CO2, and Ar), may originate by decomposition of gas-clathrate hydrates and may have been erupted on some icy satellites, but without water these substances do not form rigid solids that are stable against sublimation or melting over geologic time. Triton's plumes, active at the time of Voyager 2's flyby, may consist of multicomponent nonpolar gas mixtures. The plumes may be volcanogenic fumaroles or geyserlike emissions powered by deep internal heating, and, thus, the plumes may be indicating an interior that is still cryomagmatically active; or Triton's plumes may be powered by solar heating of translucent ices very near the surface. The Uranian and Neptunian satellites Miranda, Ariel, and Triton have flow deposits that are hundreds to thousands of meters thick (implying highly viscous lavas); by contrast, the Jovian and Saturnian satellites generally have plains-forming deposits composed of relatively thin flows whose thicknesses have not been resolved in Voyager images (thus implying relatively low-viscosity lavas). One possible explanation for this inferred rheological distinction involves a difference in volatile composition of the Uranian and Neptunian satellites on one hand and of the Jovian and

  2. The Scattering Properties of Natural Terrestrial Snows versus Icy Satellite Surfaces

    NASA Technical Reports Server (NTRS)

    Domingue, Deborah; Hartman, Beth; Verbiscer, Anne

    1997-01-01

    Our comparisons of the single particle scattering behavior of terrestrial snows and icy satellite regoliths to the laboratory particle scattering measurements of McGuire and Hapke demonstrate that the differences between icy satellite regoliths and their terrestrial counterparts are due to particle structures and textures. Terrestrial snow particle structures define a region in the single particle scattering function parameter space separate from the regions defined by the McGuire and Hapke artificial laboratory particles. The particle structures and textures of the grains composing icy satellites regoliths are not simple or uniform but consist of a variety of particle structure and texture types, some of which may be a combination of the particle types investigated by McGuire and Hapke.

  3. Heavy ion irradiation of astrophysical ice analogs

    NASA Astrophysics Data System (ADS)

    Duarte, Eduardo Seperuelo; Domaracka, Alicja; Boduch, Philippe; Rothard, Hermann; Balanzat, Emmanuel; Dartois, Emmanuel; Pilling, Sergio; Farenzena, Lucio; da Silveira, Enio Frota

    Icy grain mantles consist of small molecules containing hydrogen, carbon, oxygen and nitrogen atoms (e.g. H2O, CO, CO2, NH3). Such ices, present in different astrophysical environments (giant planets satellites, comets, dense clouds, and protoplanetary disks), are subjected to irradiation of different energetic particles: UV radiation, ion bombardment (solar and stellar wind as well as galactic cosmic rays), and secondary electrons due to cosmic ray ionization of H2. The interaction of these particles with astrophysical ice analogs has been the object of research over the last decades. However, there is a lack of information on the effects induced by the heavy ion component of cosmic rays in the electronic energy loss regime. The aim of the present work is to simulate of the astrophysical environment where ice mantles are exposed to the heavy ion cosmic ray irradiation. Sample ice films at 13K were irradiated by nickel ions with energies in the 1-10 MeV/u range and analyzed by means of FTIR spectrometry. Nickel ions were used because their energy deposition is similar to that deposited by iron ions, which are particularly abundant cosmic rays amongst the heaviest ones. In this work the effects caused by nickel ions on condensed gases are studied (destruction and production of molecules as well as associated cross sections, sputtering yields) and compared with respective values for light ions and UV photons.

  4. Interstellar and Planetary Analogs in the Laboratory

    NASA Technical Reports Server (NTRS)

    Salama, Farid

    2013-01-01

    We present and discuss the unique capabilities of the laboratory facility, COSmIC, that was developed at NASA Ames to investigate the interaction of ionizing radiation (UV, charged particles) with molecular species (neutral molecules, radicals and ions) and carbonaceous grains in the Solar System and in the Interstellar Medium (ISM). COSmIC stands for Cosmic Simulation Chamber, a laboratory chamber where interstellar and planetary analogs are generated, processed and analyzed. It is composed of a pulsed discharge nozzle (PDN) expansion that generates a free jet supersonic expansion in a plasma cavity coupled to two ultrahigh-sensitivity, complementary in situ diagnostics: a cavity ring down spectroscopy (CRDS) system for photonic detection and a Reflectron time-of-flight mass spectrometer (ReTOF-MS) for mass detection. This setup allows the study of molecules, ions and solids under the low temperature and high vacuum conditions that are required to simulate some interstellar, circumstellar and planetary physical environments providing new fundamental insights on the molecular level into the processes that are critical to the chemistry in the ISM, circumstellar and planet forming regions, and on icy objects in the Solar System. Recent laboratory results that were obtained using COSmIC will be discussed, in particular the progress that have been achieved in monitoring in the laboratory the formation of solid particles from their gas-phase molecular precursors in environments as varied as circumstellar outflow and planetary atmospheres.

  5. OASIS: Organics Analyzer for Sampling Icy Surfaces

    NASA Technical Reports Server (NTRS)

    Getty, S. A.; Dworkin, J. P.; Glavin, D. P.; Martin, M.; Zheng, Y.; Balvin, M.; Southard, A. E.; Ferrance, J.; Malespin, C.

    2012-01-01

    Liquid chromatography mass spectrometry (LC-MS) is a well established laboratory technique for detecting and analyzing organic molecules. This approach has been especially fruitful in the analysis of nucleobases, amino acids, and establishing chirol ratios [1 -3]. We are developing OASIS, Organics Analyzer for Sampling Icy Surfaces, for future in situ landed missions to astrochemically important icy bodies, such as asteroids, comets, and icy moons. The OASIS design employs a microfabricated, on-chip analytical column to chromatographically separate liquid ana1ytes using known LC stationary phase chemistries. The elution products are then interfaced through electrospray ionization (ESI) and analyzed by a time-of-flight mass spectrometer (TOF-MS). A particular advantage of this design is its suitability for microgravity environments, such as for a primitive small body.

  6. Lunar Analog

    NASA Technical Reports Server (NTRS)

    Cromwell, Ronita L.

    2009-01-01

    In this viewgraph presentation, a ground-based lunar analog is developed for the return of manned space flight to the Moon. The contents include: 1) Digital Astronaut; 2) Bed Design; 3) Lunar Analog Feasibility Study; 4) Preliminary Data; 5) Pre-pilot Study; 6) Selection of Stockings; 7) Lunar Analog Pilot Study; 8) Bed Design for Lunar Analog Pilot.

  7. Observations of the icy universe.

    NASA Astrophysics Data System (ADS)

    Boogert, A. C. Adwin; Gerakines, Perry A.; Whittet, Douglas C. B.

    2015-08-01

    Freeze-out of the gas-phase elements onto cold grains in dense interstellar and circumstellar media builds up ice mantles consisting of molecules that are mostly formed in situ (H2O, NH3, CO2, CO, CH3OH, and more). This review summarizes the detected infrared spectroscopic ice features and compares the abundances across Galactic, extragalactic, and Solar System environments. A tremendous amount of information is contained in the ice band profiles. Laboratory experiments play a critical role in the analysis of the observations. Strong evidence is found for distinct ice formation stages, separated by CO freeze-out at high densities. The ice bands have proven to be excellent probes of the thermal history of their environment. The evidence for the long-held idea that processing of ices by energetic photons and cosmic rays produces complex molecules is weak. Recent state-of-the-art observations show promise for much progress in this area with planned infrared facilities.

  8. Fluffy dust forms icy planetesimals by static compression

    NASA Astrophysics Data System (ADS)

    Kataoka, Akimasa; Tanaka, Hidekazu; Okuzumi, Satoshi; Wada, Koji

    2013-09-01

    Context. Several barriers have been proposed in planetesimal formation theory: bouncing, fragmentation, and radial drift problems. Understanding the structure evolution of dust aggregates is a key in planetesimal formation. Dust grains become fluffy by coagulation in protoplanetary disks. However, once they are fluffy, they are not sufficiently compressed by collisional compression to form compact planetesimals. Aims: We aim to reveal the pathway of dust structure evolution from dust grains to compact planetesimals. Methods: Using the compressive strength formula, we analytically investigate how fluffy dust aggregates are compressed by static compression due to ram pressure of the disk gas and self-gravity of the aggregates in protoplanetary disks. Results: We reveal the pathway of the porosity evolution from dust grains via fluffy aggregates to form planetesimals, circumventing the barriers in planetesimal formation. The aggregates are compressed by the disk gas to a density of 10-3 g/cm3 in coagulation, which is more compact than is the case with collisional compression. Then, they are compressed more by self-gravity to 10-1 g/cm3 when the radius is 10 km. Although the gas compression decelerates the growth, the aggregates grow rapidly enough to avoid the radial drift barrier when the orbital radius is ≲6 AU in a typical disk. Conclusions: We propose a fluffy dust growth scenario from grains to planetesimals. It enables icy planetesimal formation in a wide range beyond the snowline in protoplanetary disks. This result proposes a concrete initial condition of planetesimals for the later stages of the planet formation.

  9. Atmospheric/Exospheric Characteristics of Icy Satellites

    NASA Astrophysics Data System (ADS)

    Coustenis, A.; Tokano, T.; Burger, M. H.; Cassidy, T. A.; Lopes, R. M.; Lorenz, R. D.; Retherford, K. D.; Schubert, G.

    2010-06-01

    The atmospheres/exospheres of icy satellites greatly vary from one to the next in terms of density, composition, structure or steadiness. Titan is the only icy satellite with a dense atmosphere comparable in many ways to that of the Earth’s atmosphere. Titan’s atmosphere prevents the surface from direct interaction with the plasma environment, but gives rise to Earth-like exchanges of energy, matter and momentum. The atmospheres of other satellites are tenuous. Enceladus’ atmosphere manifests itself in a large water vapor plume emanating from surface cracks near the south pole. Io’s SO2 atmosphere originates from volcanoes. Europa’s tenuous O2 atmosphere is produced by intense radiation bombardment. This chapter reviews the characteristics of the atmospheres of Titan, Enceladus, Io and Europa based on observations.

  10. The Jupiter Icy Moons Orbiter reference trajectory

    NASA Technical Reports Server (NTRS)

    Whiffen, Gregory J.; Lam, Try

    2006-01-01

    The proposed NASA Jupiter Icy Moons Orbiter (JIMO) mission would have used a single spacecraft to orbit Callisto, Ganymede, and Europa in succession. The enormous Delta-Velocity required for this mission (nearly [25 km/s]) would necessitate the use of very high efficiency electric propulsion. The trajectory created for the proposed baseline JIMO mission may be the most complex trajectory ever designed. This paper describes the current reference trajectory in detail and describes the processes that were used to construct it.

  11. Convection in Icy Satellites: Implications for Habitability and Planetary Protection

    NASA Technical Reports Server (NTRS)

    Barr, A. C.; Pappalardo, R. T.

    2004-01-01

    Solid-state convection and endogenic resurfacing in the outer ice shells of the icy Galilean satellites (especially Europa) may contribute to the habitability of their internal oceans and to the detectability of any biospheres by spacecraft. If convection occurs in an ice I layer, fluid motions are confined beneath a thick stagnant lid of cold, immobile ice that is too stiff to participate in convection. The thickness of the stagnant lid varies from 30 to 50% of the total thickness of the ice shell, depending on the grain size of ice. Upward convective motions deliver approximately 10(exp 9) to 10(exp 13) kg yr(sup -1) of ice to the base of the stagnant lid, where resurfacing events driven by compositional or tidal effects (such as the formation of domes or ridges on Europa, or formation of grooved terrain on Ganymede) may deliver materials from the stagnant lid onto the surface. Conversely, downward convective motions deliver the same mass of ice from the base of the stagnant lid to the bottom of the satellites ice shells. Materials from the satellites surfaces may be delivered to their oceans by downward convective motions if material from the surface can reach the base of the stagnant lid during resurfacing events. Triggering convection from an initially conductive ice shell requires modest amplitude (a few to tens of kelvins) temperature anomalies to soften the ice to permit convection, which may require tidal heating. Therefore, tidal heating, compositional buoyancy, and solid-state convection in combination may be required to permit mass transport between the surfaces and oceans of icy satellites. Callisto and probably Ganymede have thick stagnant lids with geologically inactive surfaces today, so forward contamination of their surfaces is not a significant issue. Active convection and breaching of the stagnant lid is a possibility on Europa today, so is of relevance to planetary protection policy.

  12. Investigating Saturn's Icy Moons using HST/STIS

    NASA Astrophysics Data System (ADS)

    Hendrix, A. R.; Noll, K. S.; Spencer, J. R.

    2015-12-01

    The inner moons of Saturn - Mimas, Enceladus, Tethys, Dione and Rhea - exhibit remarkable large-scale albedo and color variations. These trends can be linked to a combination of the unique exogenic processes occurring the Saturn system, including E-ring grain bombardment and charged particle bombardment. One of the fascinating characteristics of the Saturn system is that the icy satellites, though their surface compositions are dominated by water ice, are spectrally red - they are absorbing in the ultraviolet-visible wavelength region (wavelengths <~550 nm) - a spectral feature not typical of pure water ice. In fact, the existing data show that in the UV, absorptions appear to be present superimposed on the overall red slope. Thus, though Cassini instruments have learned much about the surfaces of the icy moons, a basic question that remains is: What is their surface composition and what are the species or processes that cause these UV absorptions? Cassini's spectral coverage is lacking in precisely the near-UV wavelength regime in which the satellites appear to absorb most strongly. To resolve this issue and determine some understanding of the surface species present, we have obtained data using HST/STIS (Space Telescope Imaging Spectrograph). We have utilized the STIS G230L detector to obtain high SNR spectra in the 180-320 nm region along with short G430L exposures to obtain spectra in the 320-570 nm range, to completely fill in the Cassini gap in spectral coverage. Full-disk measurements have been made of the trailing and leading hemispheres of Mimas, Dione and Rhea; a spectrum of Enceladus was also obtained. We report on the results. In particular, we discuss implications for the presence of ammonia, ozone and organics.

  13. UV-IR Spectra of the Icy Saturnian Satellites

    NASA Astrophysics Data System (ADS)

    Hendrix, A. R.; Filacchione, G.; Schenk, P.; Clark, R. N.; Cuzzi, J. N.; Noll, K. S.; Spencer, J. R.

    2014-12-01

    Cassini's multi-instrument suite allows simultaneous observations of the icy satellites of Saturn over a wide range of wavelengths. We present composite UV-IR spectra (0.1-5 microns) of the leading and trailing hemispheres of the icy moons using data from Cassini supplemented with spectra from Hubble Space Telescope (STIS). We use data of Mimas, Enceladus, Tethys, Dione and Rhea from the Ultraviolet Imaging Spectrograph (UVIS), the Imaging Subsystem (ISS) and the Visual-Near Infrared Mapping Spectrometer (VIMS) taken during simultaneous measurements, or using similar observational geometries. The well-studied phase curve behaviors of the satellites are utilized to readily combine Earth-based STIS data with the Cassini datasets to create composite spectra. Focusing primarily on the UV-visible region so far, we find that the spectra of all satellites are bright and spectrally relatively flat at visible wavelengths longer than 500-600 nm; shortward of 500-600 nm the surfaces become absorbing with wavelength, resulting in reddish spectra. The satellites exhibit flattish-to-bowl-shaped spectra in the ~200-350 nm range and demonstrate the 165 nm water ice absorption edge, in varying strengths. These composite spectra are used to study the system-wide surface compositions of the satellites to understand large-scale exogenic effects (e.g., E-ring grain bombardment and radiolytic processing) at a variety of regolith sensing depths, and in particular to study implications for the presence and distribution of organics, ammonia, and other non-H2O-ice species in the system.

  14. Space Environmental Erosion of Polar Icy Regolith

    NASA Technical Reports Server (NTRS)

    Farrell, William M.; Killen, R. M.; Vondrak, R. R.; Hurley, D. M.; Stubbs, T. J.; Delory, G. T.; Halekas, J. S.; Zimmerman, M. I.

    2011-01-01

    While regions at the floors of permanently shadowed polar craters are isolated from direct sunlight, these regions are still exposed to the harsh space environment, including the interplanetary Lyman-a background, meteoric impacts, and obstacle-affected solar wind. We demonstrate that each of these processes can act to erode the polar icy regolith located at or near the surface along the crater floor. The Lyman-a background can remove/erode the icy-regolith via photon stimulated desorption [1], meteoric impacts can vaporize the regolith [2], and redirected solar wind ions can sputter the ice-regolith mix [3]. As an example we shall examine in detail the inflow of solar wind ions and electrons into polar craters, One might expect such ions to flow horizontally over the crater top (see Figure). However, we find that plasma ambipolar processes act to deflect passing ions into the craters [3]. We examine this plasma process and determine the ion flux as a function of position across a notional crater floor. We demonstrate that inflowing solar wind ions can indeed create sputtering along the crater floor, effectively eroding the surface. Erosion time scales rrom sputtering will be presented. We shall also consider the effect of impact vaporization on buried icy-regolith regions. There will also be a discussion of solar wind electrons that enter into the PSR, demonstrating that these also have the ability rree surface-bound atoms via electron stimulated desorption processes [l].

  15. High energy electron processing of icy regoliths on Saturn's moons

    NASA Astrophysics Data System (ADS)

    Schaible, Micah; Johnson, Robert E.

    2015-11-01

    A unique space weathering phenomenon has been identified on several icy Saturnian moons. Cassini revealed anomalous lens shaped regions in both optical and thermal wavelengths, colloquially known as the 'PacMan' feature, which are centered on the leading hemispheres and approximately symmetric about the equators. In particular, the Cassini InfraRed Spectrometer (CIRS) measurements of thermal emission in the mid-IR showed that surface temperature variations during a diurnal cycle were smaller inside the anomalous regions. The locations of the anomalies were shown to closely match the expected deposition profile of high energy (~ MeV) electrons moving counter rotational to the moons, suggesting an energetic source to drive their formation. However, the mechanisms by which thermal conductivity enhancement occur lack quantitative comparison with theoretical and experimental results.Electron interactions with the grains can excite molecules, which, if near enough to an intergrain contact, can cause atoms or molecules to migrate into the contact region, thus increasing the contact volume or 'sintering' the grains. Sintering improves the thermal contact between grains, leading to increased effective thermal conductivity of the regolith. Equations previously developed to describe material behavior in nuclear reactor were used to estimate the timescale for the energetic electrons to increase the contact volume sufficiently to describe the enhanced thermal conductivity of the anomalous regions. In order to properly constrain the sintering calculations, the unique electron energy distribution measured in the vicinity of each of the moons was used in the calculations, and molecular dynamics simulations of excited electrons in water ice were carried out to determine the length scale for an average electron excitation or ionization event. This length scale determines the distance from the primary reaction at which electrons can still be mobilized to move into the contact region

  16. Laboratory Reference Spectroscopy of Icy Satellite Candidate Surface Materials (Invited)

    NASA Astrophysics Data System (ADS)

    Dalton, J. B.; Jamieson, C. S.; Shirley, J. H.; Pitman, K. M.; Kariya, M.; Crandall, P.

    2013-12-01

    The bulk of our knowledge of icy satellite composition continues to be derived from ultraviolet, visible and infrared remote sensing observations. Interpretation of remote sensing observations relies on availability of laboratory reference spectra of candidate surface materials. These are compared directly to observations, or incorporated into models to generate synthetic spectra representing mixtures of the candidate materials. Spectral measurements for the study of icy satellites must be taken under appropriate conditions (cf. Dalton, 2010; also http://mos.seti.org/icyworldspectra.html for a database of compounds) of temperature (typically 50 to 150 K), pressure (from 10-9 to 10-3 Torr), viewing geometry, (i.e., reflectance), and optical depth (must manifest near infrared bands but avoid saturation in the mid-infrared fundamentals). The Planetary Ice Characterization Laboratory (PICL) is being developed at JPL to provide robust reference spectra for icy satellite surface materials. These include sulfate hydrates, hydrated and hydroxylated minerals, and both organic and inorganic volatile ices. Spectral measurements are performed using an Analytical Spectral Devices FR3 portable grating spectrometer from .35 to 2.5 microns, and a Thermo-Nicolet 6500 Fourier-Transform InfraRed (FTIR) spectrometer from 1.25 to 20 microns. These are interfaced with the Basic Extraterrestrial Environment Simulation Testbed (BEEST), a vacuum chamber capable of pressures below 10-9 Torr with a closed loop liquid helium cryostat with custom heating element capable of temperatures from 30-800 Kelvins. To generate optical constants (real and imaginary index of refraction) for use in nonlinear mixing models (i.e., Hapke, 1981 and Shkuratov, 1999), samples are ground and sieved to six different size fractions or deposited at varying rates to provide a range of grain sizes for optical constants calculations based on subtractive Kramers-Kronig combined with Hapke forward modeling (Dalton and

  17. Icy Schwedeneck field may provide reference

    SciTech Connect

    Not Available

    1985-05-01

    Situated in an icy region of the Baltic Sea, Germany's first offshore field may provide the nation with the reference needed to encroach the arctic market. Production began last winter from one platform in the Schwedeneck-See field, located about three miles off the Baltic Coast. Total reserves have been estimated at more than 18 million bbl. Yearly production by the end of 1986 has been estimated at 294,000 bbl. The first two production platforms were installed in late 1983 in water depths ranging from 50 to 80 ft. Because of the ice hazards inherent in the Baltic, the platforms are concrete designed with steel decks.

  18. Survivability of bacteria ejected from icy surfaces after hypervelocity impact.

    PubMed

    Burchell, Mark J; Galloway, James A; Bunch, Alan W; Brandão, Pedro F B

    2003-02-01

    Both the Saturnian and Jovian systems contain satellites with icy surfaces. If life exists on any of these icy bodies (in putative subsurface oceans for example) then the possibility exists for transfer of life from icy body to icy body. This is an application of the idea of Panspermia, wherein life migrates naturally through space. A possible mechanism would be that life, here taken as bacteria, could become frozen in the icy surface of one body. If a high-speed impact occurred on that surface, ejecta containing the bacteria could be thrown into space. It could then migrate around the local region of space until it arrived at a second icy body in another high-speed impact. In this paper we consider some of the necessary steps for such a process to occur, concentrating on the ejection of ice bearing bacteria in the initial impact, and on what happens when bacteria laden projectiles hit an icy surface. Laboratory experiments using high-speed impacts with a light gas gun show that obtaining icy ejecta with viable bacterial loads is straightforward. In addition to demonstrating the viability of the bacteria carried on the ejecta, we have also measured the angular and size distribution of the ejecta produced in hypervelocity impacts on ice. We have however been unsuccessful at transferring viable bacteria to icy surfaces from bacteria laden projectiles impacting at hypervelocities. PMID:12967273

  19. Survivability of bacteria ejected from icy surfaces after hypervelocity impact.

    PubMed

    Burchell, Mark J; Galloway, James A; Bunch, Alan W; Brandão, Pedro F B

    2003-02-01

    Both the Saturnian and Jovian systems contain satellites with icy surfaces. If life exists on any of these icy bodies (in putative subsurface oceans for example) then the possibility exists for transfer of life from icy body to icy body. This is an application of the idea of Panspermia, wherein life migrates naturally through space. A possible mechanism would be that life, here taken as bacteria, could become frozen in the icy surface of one body. If a high-speed impact occurred on that surface, ejecta containing the bacteria could be thrown into space. It could then migrate around the local region of space until it arrived at a second icy body in another high-speed impact. In this paper we consider some of the necessary steps for such a process to occur, concentrating on the ejection of ice bearing bacteria in the initial impact, and on what happens when bacteria laden projectiles hit an icy surface. Laboratory experiments using high-speed impacts with a light gas gun show that obtaining icy ejecta with viable bacterial loads is straightforward. In addition to demonstrating the viability of the bacteria carried on the ejecta, we have also measured the angular and size distribution of the ejecta produced in hypervelocity impacts on ice. We have however been unsuccessful at transferring viable bacteria to icy surfaces from bacteria laden projectiles impacting at hypervelocities.

  20. Discovering New Compounds on Icy Moon Surfaces with Mid-Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Young, C. L.; Wray, J. J.; Hand, K. P.; Poston, M.; Carlson, R. W.; Clark, R. N.; Spencer, J. R.; Jennings, D. E.

    2015-12-01

    Spectroscopy of icy satellite surfaces can aid us in understanding sources and sinks of material in the outer solar system. The spectral complexity of the Saturnian satellite system as seen in reflected sunlight suggests additional complexity may be present at mid-infrared wavelengths from which unique compositional information can be gleaned [1]. Yet to date, Cassini Composite Infrared Spectrometer (CIRS) surface compositional studies have received little attention. We are investigating the value of mid-infrared spectroscopy for identifying non-H2O constituents of icy moon surfaces. On Iapetus' dark terrain, we find an emissivity feature at ~855 cm-1 and a possible doublet at 660 and 690 cm-1 that do not correspond to any known instrument artifacts [2]. We attribute the 855 cm-1feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths [3]. Silicates on the dark terrains of Saturn's icy moons have been suspected for decades, but there have been no definitive detections until now. Because peaks can shift depending on temperature, pressure, and grain size, measurements at Iapetus-like conditions are necessary for more positive feature identifications [e.g., 4]. We measured the vacuum (P<3x10-8 torr) and low temperature (125 K) mid-infrared spectra of various fine-grained powdered silicates. We find that some of these materials do have emissivity features near 855 cm-1and match the doublet. Identifying a specific silicate would provide clues into the origin and implications of the dark material in the Saturnian system. We also report on our ongoing exploration of the CIRS icy moon dataset and plans for additional future measurements in JPL's Icy Worlds Simulation Lab. [1] Flasar, F. M., et al. (2004), Space Sci Rev, 115, 169. [2] Young, C.L., et al. (in review), ApJ Lett. [3] Christensen, P. R., et al. (2004), Sci, 306, 1733. [4] Wray, J. J., et al. (2014), DPS 46th Meeting, Vol. 46.

  1. Identifying new surface constituents of icy moons using mid-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Young, Cindy L.; Wray, James J.; Hand, Kevin P.; Poston, Michael J.; Carlson, Robert W.; Clark, Roger N.; Spencer, John R.; Jennings, Donald E.

    2015-11-01

    Spectroscopic compositional studies of the icy satellites can help us to better understand the formation and evolution of material in the outer solar system. The spectral complexity of the Saturnian satellite system as seen in reflected visible light suggests additional complexity may be present at mid-infrared wavelengths from which unique compositional information can be gleaned [1]. In addition, the mid-infrared is the region of the stronger fundamental diagnostic vibrational modes of many compounds. However, Cassini Composite Infrared Spectrometer (CIRS) surface compositional studies have received little attention to date.We are exploring the suitability of mid-infrared spectroscopy for discovering non-H2O compounds on icy moon surfaces. On the dark terrain of Iapetus, we find an emissivity feature at ~855 cm-1 and a potential doublet at 660 and 690 cm-1 that do not correspond to any known instrument artifacts [2]. We attribute the 855 cm-1 feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths [3]. Although silicates on the dark terrains of Saturn’s icy moons have been suspected for decades, there have been no definitive prior detections. Serpentines measured at ambient conditions have features near 855 cm-1 and 660 cm-1 [4]. However, peaks can shift depending on temperature, pressure, and grain size, so measurements at Iapetus-like conditions are necessary for more positive identifications [e.g., 5].We measured the vacuum, low temperature (125 K) spectra of various fine-grained powdered silicates. We find that some of these materials do have emissivity features near 855 cm-1 and match the doublet. Identifying a specific silicate would provide clues into the sources and sinks of the dark material in the Saturnian system. We report on our ongoing exploration of the CIRS icy moon dataset and plans for future measurements in JPL’s Icy Worlds Simulation Lab.[1] Flasar, F

  2. Shock synthesis of amino acids from impacting cometary and icy planet surface analogues

    NASA Astrophysics Data System (ADS)

    Martins, Zita; Price, Mark C.; Goldman, Nir; Sephton, Mark A.; Burchell, Mark J.

    2013-12-01

    Comets are known to harbour simple ices and the organic precursors of the building blocks of proteins--amino acids--that are essential to life. Indeed, glycine, the simplest amino acid, was recently confirmed to be present on comet 81P/Wild-2 from samples returned by NASA's Stardust spacecraft. Impacts of icy bodies (such as comets) onto rocky surfaces, and, equally, impacts of rocky bodies onto icy surfaces (such as the jovian and saturnian satellites), could have been responsible for the manufacture of these complex organic molecules through a process of shock synthesis. Here we present laboratory experiments in which we shocked ice mixtures analogous to those found in a comet with a steel projectile fired at high velocities in a light gas gun to test whether amino acids could be produced. We found that the hypervelocity impact shock of a typical comet ice mixture produced several amino acids after hydrolysis. These include equal amounts of D- and L-alanine, and the non-protein amino acids α-aminoisobutyric acid and isovaline as well as their precursors. Our findings suggest a pathway for the synthetic production of the components of proteins within our Solar System, and thus a potential pathway towards life through icy impacts.

  3. Porosity and the ecology of icy satellites

    NASA Technical Reports Server (NTRS)

    Croft, Steven K.

    1993-01-01

    The case for a significant role for porosity in the structure and evolution of icy bodies in the Solar System has been difficult to establish. We present a relevant new data set and a series of structure models including a mechanical compression, not thermal creep, model for porosity that accounts satisfactorily for observed densities, moments of inertia, geologic activity, and sizes of tectonic features on icy satellites. Several types of observational data sets have been used to infer significant porosity, but until recently, alternative explanations have been preferred. Our first area of concern is the occurrence of cryovolcanism as a function of satellite radius; simple radiogenic heating models of icy satellites suggest minimum radii for melting and surface cryovolcanism to be 400 to 500 km, yet inferred melt deposits are seen on satellites half that size. One possible explanation is a deep, low conductivity regolith which lowers conductivity and raises internal temperatures, but other possibilities include tidal heating or crustal compositions of low conductivity. Our second area of concern is the occurrence and magnitude of tectonic strain; tectonic structures have been seen on icy satellites as small as Mimas and Proteus. The structures are almost exclusively extensional, with only a few possible compression Al features, and inferred global strains are on the order of 1 percent expansion. Expansions of this order in small bodies like Mimas and prevention of late compressional tectonics due to formation of ice mantles in larger bodies like Rhea are attained only in structure models including low-conductivity, and thus possibly high porosity, crusts. Thirdly, inferred moments of inertia less than 0.4 in Mimas and Tethys can be explained by high-porosity crusts, but also by differentiation of a high density core. Finally, the relatively low densities of smaller satellites like Mimas and Miranda relative to larger neighbors can be explained by deep porosity

  4. Semi-brittle behavior of a multi-phase crust and its influence on the tectonics of icy satellites

    NASA Astrophysics Data System (ADS)

    McCarthy, Christine; Cooper, Reid F.

    2010-05-01

    Our ability to observe and interpret reasonably the tectonics of icy satellites hinges on our understanding of the viscoelastic and plastic rheologies and microstructural evolution of the material comprising their icy outer shells. The morphological diversity observed on the surfaces of the satellites may be due in part to the rheological influence of the various cryominerals that are present in addition to water ice on many of these icy bodies. Our experimental investigation explores the affects of secondary minerals on the phase behavior and physical properties (both plastic and anelastic) of ice at conditions approaching those of the icy satellites. Using uniaxial compression creep experiments (T = 230-250K; P = 0.1 and 50 MPa), we characterize the transient and steady-state deformation behaviors of eutectic aggregates (made via crystallization of liquid solution) of ice-I and MgSO4•11H2O ("MS11"; meridianiite) and compare them to the deformation behaviors of pure polycrystalline ice-I tested at the same conditions on the same apparatus. The ice/hydrate aggregates display a higher sensitivity to stress than does pure polycrystalline ice at the same conditions. One significant role that the second phase plays in ductile deformation is to pin grain growth, keeping grain sizes small and deformation within the grain/colony size sensitive creep regime. The mechanical and microstructural observations from this study indicate that the hydrate phase, which is distinctly stronger than pure ice, additionally offers a framework of support that resists ductile deformation at low stresses; the aggregates display at least an order of magnitude higher effective viscosity than do samples of pure polycrystalline ice at the same conditions up to 6MPa. At higher stresses, however, the hydrate phase promotes semi-brittle flow and cavitation, both of which are forms of strain weakening. Semi-brittle flow in the icy shell of a planetary body would decrease the depth to the brittle

  5. IPPF Co-operative Information Service (ICIS). November 1977.

    ERIC Educational Resources Information Center

    International Planned Parenthood Federation, London (England).

    This ICIS bulletin replaces the formal Library Bulletin of the International Planned Parenthood Federation (IPPF). It represents the integration of a bibliographic information network. Entries in ICIS are classified according to the following nine categories: (0) General Reference; (1) IPPF; (2) Family Planning and Health Care; (3) Biomedical…

  6. IPPF Co-operative Information Service (ICIS). May 1977.

    ERIC Educational Resources Information Center

    International Planned Parenthood Federation, London (England).

    The pooling of documentation service resources has resulted in the creation of an International Planned Parenthood Federation (IPPF) integrated bibliographic information system. Thus, the former Library Bulletin has become IPPF Cooperative Information Service (ICIS). This is the first such publication. Entries in ICIS are classified according to…

  7. Radiation Induced Chemistry of Icy Surfaces: Laboratory Simulations

    NASA Technical Reports Server (NTRS)

    Gudipati, Murthy S.; Lignell, Antti; Li, Irene; Yang, Rui; Jacovi, Ronen

    2011-01-01

    We will discuss laboratory experiments designed to enhance our understanding the chemical processes on icy solar system bodies, enable interpretation of in-situ and remote-sensing data, and help future missions to icy solar system bodies, such as comets, Europa, Ganymede, Enceladus etc.

  8. The Fatigue of Water Ice: Insight into the Tectonic Resurfacing of Tidally Deformed Icy Satellites

    NASA Astrophysics Data System (ADS)

    Hammond, N. P.; Barr, A. C.; Hirth, G.; Cooper, R. F.

    2015-12-01

    Fatigue is a process that causes materials to weaken during cyclic loading and experience brittle failure at much lower applied stresses. We perform laboratory experiments to study the fatigue behavior of water ice at conditions relevant to the surfaces of icy satellites, to test the hypothesis that the lithospheres of some icy satellites are weakened by fatigue. Many icy moons of the outer solar system, such as Europa and Enceladus, experience cyclic stresses driven by tidal forces from their parent planet. Stresses generated by tides and other physical processes, such as solid-state convection of the ice shell, are weak compared to laboratory derived yield stress values of ice. The surface geology on many icy moons, however, suggests that these processes are capable of deforming the surface, suggesting that their surfaces may have been weakened. During fatigue, microcracks slowly grow under the action of cyclic loads. Cracks grow until the stress intensity reaches a critical value and the sample fractures. The rate of microcrack growth varies with material, temperature, and loading frequency, but under most conditions the growth rate can be characterized by Paris' Law. We use a servo-hydraulic loading machine to perform cyclic 4-point bending tests on polycrystalline ice samples to measure the rate of fatigue crack growth. Ice samples are formed using the standard ice method in a sample mold with dimensions of 10x4x2 cm with an average grain size of 1.2 mm. An initial flaw is cut into the sample and loaded such that the flaw experiences the maximum tensile stress in the sample. Our initial experiments were performed at T=223 K, loading frequencies of 0.5 Hz, and stress intensities ranging from 0.3 to 0.8 of the plane-strain fracture toughness. Sample compliance is used to estimate crack length according to analytical solutions [1]. Experiments show an increase in compliance with time, consistent with substantial subcritical crack growth. Future experiments will

  9. Low Force Penetration of Icy Regolith

    NASA Technical Reports Server (NTRS)

    Mantovani, J. G.; Galloway, G. M.; Zacny, K.

    2016-01-01

    A percussive cone penetrometer measures the strength of granular material by using percussion to deliver mechanical energy into the material. A percussive cone penetrometer was used in this study to penetrate a regolith ice mixture by breaking up ice and decompacting the regolith. As compared to a static cone penetrometer, percussion allows low reaction forces to push a penetrometer probe tip more easily into dry regolith in a low gravity environment from a planetary surface rover or a landed spacecraft. A percussive cone penetrates icy regolith at ice concentrations that a static cone cannot penetrate. In this study, the percussive penetrator was able to penetrate material under 65 N of down-force which could not be penetrated using a static cone under full body weight. This paper discusses using a percussive cone penetrometer to discern changes in the concentration of water-ice in a mixture of lunar regolith simulant and ice to a depth of one meter. The rate of penetration was found to be a function of the ice content and was not significantly affected by the down-force. The test results demonstrate that this method may be ideal for a small platform in a reduced gravity environment. However, there are some cases where the system may not be able to penetrate the icy regolith, and there is some risk of the probe tip becoming stuck so that it cannot be retracted. It is also shown that a percussive cone penetrometer could be used to prospect for water ice in regolith at concentrations as high as 8 by weight.

  10. The Icy Cold Heart of Pluto

    NASA Astrophysics Data System (ADS)

    Hamilton, Douglas P.

    2015-11-01

    The locations of large deposits of frozen volatiles on planetary surfaces are largely coincident with areas receiving the minimum annual influx of solar energy; familiar examples include the polar caps of Earth and Mars. For planets tilted by more than 45 degrees, however, the poles actually receive more energy than some other latitudes. Pluto, with its current obliquity of 119 degrees, has minima in its average annual insolation at +/- 27 degrees latitude, with ~1.5% more energy flux going to the equator and ~15% more to the poles. Remarkably, the fraction of annual solar energy incident on different latitudes depends only on the obliquity of the planet and not on any of its orbital parameters.Over millions of years, Pluto's obliquity varies sinusoidally from 102-126 degrees, significantly affecting the latitudinal profile of solar energy deposition. Roughly 1Myr ago, the poles received 15% more energy that today while the equator received 13% less. The energy flux to latitudes between 25-35 degrees is far more stable, remaining low over the presumably billions of years since Pluto acquired its current spin properties. Like the poles at Earth, these mid latitudes on Pluto should be favored for the long-term deposition of volatile ices. This is, indeed, the location of the bright icy heart of Pluto, Sputnik Planum.Reflected light and emitted thermal radiation from Charon increases annual insolation to one side of Pluto by of order 0.02%. Although small, the bulk of the energy is delivered at night to Pluto's cold equatorial regions. Furthermore, Charon's thermal infrared radiation is easily absorbed by icy deposits on Pluto, slowing deposition and facilitating sublimation of volatiles. We argue that the slight but persistent preference for ices to form and survive in the anti-Charon Pluto's heart.

  11. Heliosheath Space Environment Interactions with Icy Bodies in the Outermost Solar System

    NASA Technical Reports Server (NTRS)

    Cooper, John F.; Hill, Matthew E.; Richardson, John D.; Sturner, Steven J.

    2006-01-01

    The Voyager 1 and 2 spacecraft are exploring the space environment of the outermost solar system at the same time that earth-based astronomy continues to discover new icy bodies, one larger than Pluto, in the transitional region outward from the Classical Kuiper Belt to the Inner Oort Cloud. Some of the Scattered Disk Objects in this region periodically pass through the heliosheath, entered by Voyager 1 in Dec. 2004 and later expected to be reached by Voyager 2, and out even beyond the heliopause into the Very Local Interstellar Medium. The less energetic heliosheath ions, important for implantation and sputtering processes, are abundant near and beyond the termination shock inner boundary, but the source region of the more penetrating anomalous cosmic ray component has not yet been found. Advantageous for modeling of icy body interactions, the measured heliosheath flux spectra are relatively more stable within this new regime of isotropic compressional magnetic turbulence than in the upstream heliospheric environment. The deepest interactions and resultant radiation-induced chemistry arise from the inwardly diffusing component of the galactic cosmic ray ions with significant intensity modulation also arising in the heliosheath beyond Voyager 1. Surface gardening by high-velocity impacts of smaller bodies (e.g., fragments of previous KBO collisions) and dust is a further space weathering process setting the time scales for long term exposure of different regolith layers to the ion irradiation. Sputtering and ionization of impact ejecta grains may provide a substantial feedback of pickup ions for multiple cycles of heliosheath acceleration and icy body interaction. Thus the space weathering interactions are potentially of interest not only for effects on sensible surface composition of the icy bodies but also for evolution of the heliosheath plasma energetic ion, and neutral emission environment.

  12. Habitability potential of icy moons: a comparative study

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Coustenis, Athena; Encrenaz, Thérèse; Sohl, Frank; Hussmann, Hauke; Bampasidis, Georgios; Wagner, Frank; Raulin, François; Schulze-Makuch, Dirk; Lopes, Rosaly

    2014-05-01

    Looking for habitable conditions in the outer solar system our research focuses on the natural satellites rather than the planets themselves. Indeed, the habitable zone as traditionally defined may be larger than originally con-ceived. The strong gravitational pull caused by the giant planets may produce enough energy to sufficiently heat the interiors of orbiting icy moons. The outer solar system satellites then provide a conceptual basis within which new theories for understanding habitability can be constructed. Measurements from the ground but also by the Voyager, Galileo and the Cassini spacecrafts revealed the potential of these satellites in this context, and our understanding of habitability in the solar system and beyond can be greatly enhanced by investigating several of these bodies together [1]. Their environments seem to satisfy many of the "classical" criteria for habitability (liquid water, energy sources to sustain metabolism and chemical compounds that can be used as nutrients over a period of time long enough to allow the development of life). Indeed, several of the moons show promising conditions for habitability and the de-velopment and/or maintenance of life. Europa, Callisto and Ganymede may be hiding, under their icy crust, putative undersurface liquid water oceans [3] which, in the case of Europa [2], may be in direct contact with a silicate mantle floor and kept warm by tidally generated heat [4]. Titan and Enceladus, Saturn's satellites, were found by the Cassini-Huygens mission to possess active organic chemistries with seasonal variations, unique geological features and possibly internal liquid water oceans. Titan's rigid crust and the probable existence of a subsurface ocean create an analogy with terrestrial-type plate tectonics, at least surficial [5], while Enceladus' plumes find an analogue in gey-sers. As revealed by Cassini the liquid hydrocarbon lakes [6] distributed mainly at polar latitudes on Titan are ideal isolated

  13. Flow and fracture of ices, with application to icy satellites (Invited)

    NASA Astrophysics Data System (ADS)

    Durham, W. B.; Stern, L. A.; Pathare, A.; Golding, N.

    2013-12-01

    Exploration of the outer planets and their satellites by spacecraft over the past 4 decades has revealed that the prevailing low temperatures in the outer solar system have not produced "dead" cryoworlds of generic appearance. Rather, there is an extraordinary diversity in average densities, presence/absence and compositions of atmospheres and planetary rings, average albedos and their seasonal changes, near-surface compositions, and surface records of impact cratering and endogenic tectonic and igneous processes. One reason for this diversity is that the icy minerals present in abundance on many of these worlds are now or once were at significant fractions of their melting temperatures. Hence, a host of thermally activated processes related to endogenic activity (such as crystal defect migration, mass diffusion, surface transport, solid-solid changes of state, and partial melting) may occur that can enable inelastic flow on the surfaces and in the interiors of these bodies. Planetary manifestations include viscous crater relaxation in ice-rich terrain, cryovolcanism, the presence of a stable subsurface ocean, and the effects of solid-ice convection in deep interiors. We make the connection between theoretical mechanisms of deformation and planetary geology through laboratory experiment. Specifically, we develop quantitative constitutive flow laws (strain rate vs. stress) that describe the effects of relevant environmental variables (hydrostatic pressure, temperature, phase composition, chemical impurities). Our findings speak to topics including (1) the behavior of an outer ice I layer, its thickness, the depth to which a stagnant lid might extend, and possibility of wholesale overturn; (2) softening effects of dissolved species such as ammonia and perchlorate; (3) hardening effects of enclathration and of rock dust; and (4) effects of grain size on strength and factors affecting grain size. Other applications of lab data include dynamics of the deep interiors of

  14. Analog earthquakes

    SciTech Connect

    Hofmann, R.B.

    1995-09-01

    Analogs are used to understand complex or poorly understood phenomena for which little data may be available at the actual repository site. Earthquakes are complex phenomena, and they can have a large number of effects on the natural system, as well as on engineered structures. Instrumental data close to the source of large earthquakes are rarely obtained. The rare events for which measurements are available may be used, with modfications, as analogs for potential large earthquakes at sites where no earthquake data are available. In the following, several examples of nuclear reactor and liquified natural gas facility siting are discussed. A potential use of analog earthquakes is proposed for a high-level nuclear waste (HLW) repository.

  15. Radical formation in the coma from photodissociation of ice grains

    NASA Technical Reports Server (NTRS)

    Jackson, William M.; Gerth, Christopher

    1990-01-01

    Long ago visual observations of comets suggested that there are jets in comets but it has only been recently that A'Hearn et al. have proven that some of these jets are due to emission from the CN radical. Recent studies in the lab have shown that CN radicals can be ejected directly into the gas phase from the photolysis of frozen vapors if the parent molecular has been excited to repulsive excited state. This later observation suggests that the jets that have been observed may be due to photodissociation of icy grains in the coma. A theory of radical formation from icy grains is presented. It is shown that direct formation of free radicals in the coma is an effective way to produce radicals from icy grains in the coma. The model predicts that icy grains could produce from 6 to 800,000 OH radicals/s per grain depending upon whether the radius of the grain is 0.3 to 100 micron.

  16. Chemical Composition of Icy Satellite Surfaces

    NASA Astrophysics Data System (ADS)

    Dalton, J. B.; Cruikshank, D. P.; Stephan, K.; McCord, T. B.; Coustenis, A.; Carlson, R. W.; Coradini, A.

    2010-06-01

    Much of our knowledge of planetary surface composition is derived from remote sensing over the ultraviolet through infrared wavelength ranges. Telescopic observations and, in the past few decades, spacecraft mission observations have led to the discovery of many surface materials, from rock-forming minerals to water ice to exotic volatiles and organic compounds. Identifying surface materials and mapping their distributions allows us to constrain interior processes such as cryovolcanism and aqueous geochemistry. The recent progress in understanding of icy satellite surface composition has been aided by the evolving capabilities of spacecraft missions, advances in detector technology, and laboratory studies of candidate surface compounds. Pioneers 10 and 11, Voyagers I and II, Galileo, Cassini and the New Horizons mission have all made significant contributions. Dalton (Space Sci. Rev., 2010, this issue) summarizes the major constituents found or inferred to exist on the surfaces of the icy satellites (cf. Table 1 from Dalton, Space Sci. Rev., 2010, this issue), and the spectral coverage and resolution of many of the spacecraft instruments that have revolutionized our understanding (cf. Table 2 from Dalton, Space Sci. Rev., 2010, this issue). While much has been gained from these missions, telescopic observations also continue to provide important constraints on surface compositions, especially for those bodies that have not yet been visited by spacecraft, such as Kuiper Belt Objects (KBOs), trans-Neptunian Objects (TNOs), Centaurs, the classical planet Pluto and its moon, Charon. In this chapter, we will discuss the major satellites of the outer solar system, the materials believed to make up their surfaces, and the history of some of these discoveries. Formation scenarios and subsequent evolution will be described, with particular attention to the processes that drive surface chemistry and exchange with interiors. Major similarities and differences between the

  17. Grain alignment by ferromagnetic impurities

    NASA Technical Reports Server (NTRS)

    Mathis, J. S.

    1986-01-01

    The observed wavelength dependence of linear polarization, and its variation from region to region can be explained by the following assumptions. Interstellar grains resemble interplanetary grains, in that they are composed of collections of small particles coagulated together into elongated masses. A fraction of the small particles are ferromagnetic. Presumably these are either metallic Fe or magnetite, Fe3O4. If and only if a large grain contains one or more magnetic particles is the grain aligned in the galactic magnetic field. The magnetic particles stick only to silicate grains because of chemical similarities, or (equivalently) any pure carbon grains in the diffuse interstellar medium (ISM) are too spherical to produce polarization. Grains in dense regions, such as the outer parts of molecular clouds, are larger than those in the diffuse ISM because of coagulation of the grains rather than accretion of icy mantles. These regions are known to have larger than normal values of lambda (max), the wavelength of the maximum of linear polarization. The above assumptions are sufficient to allow the calculation of the wavelength dependence of the polarization.

  18. Low Force Icy Regolith Penetration Technology

    NASA Technical Reports Server (NTRS)

    Metzger, P. T.; Galloway, G. M.; Mantovani, J. G.; Zacny, K.; Zacny, Kris; Craft, Jack

    2011-01-01

    Recent data from the Moon, including LCROSS data, indicate large quantities of water ice and other volatiles frozen into the soil in the permanently shadowed craters near the poles. If verified and exploited, these volatiles will revolutionize spaceflight as an inexpensive source of propellants and other consumables outside Earth's gravity well. This report discusses a preliminary investigation of a method to insert a sensor through such a soiVice mixture to verify the presence, nature, and concentration of the ice. It uses percussion to deliver mechanical energy into the frozen mixture, breaking up the ice and decompacting the soil so that only low reaction forces are required from a rover or spacecraft to push the sensor downward. The tests demonstrate that this method may be ideal for a small platform in lunar gravity. However, there are some cases where the system may not be able to penetrate the icy soil, and there is some risk ofthe sensor becoming stuck so that it cannot be retracted, so further work is needed. A companion project (ISDS for Water Detection on the Lunar Surface) has performed preliminary investigation of a dielectric/thermal sensor for use with this system.

  19. Towards Coupled Modelling of Accretion and Water-Rock Differentiation of Icy Worlds

    NASA Astrophysics Data System (ADS)

    Neumann, Wladimir Otto; Breuer, Doris; Spohn, Tilman

    2015-08-01

    The early Solar system produced a variety of bodies with different properties. Among the small bodies, objects that contain notable amounts of water ice (Ceres, icy satellites) are of particular interest. Water-rock separation on such worlds is probable and has been confirmed in some cases. Heating by 26Al and 60Fe suffices to produce liquid water (T>273 K) even in km-sized seeds during the early accretion of icy worlds.Assuming accretion of ice and dust, the rheology is dominated by one of the two components, depending on their proportions. Two differentiation regimes arise: (a) Upon melting of an icy matrix, the dust grains settle via Stokes flow; (b) Upon melting of ice in a rocky matrix, water ascends through the matrix via Darcy flow. Prior to ice melting, porosity is reduced by creep of ice. However, there are leftover pores filled with gas. For (a) the differentiation scheme is not affected. For (b) ice melting increases the porosity of the matrix. Only a part of the void space will be filled with water. Water will percolate if the matrix (1) deforms sufficiently to close the pores filled with gas and (2) deforms further to squeeze the water out of the matrix. Temperatures of up to 700 K are needed for this. Thus, water will first migrate downwards filling the pores, vacated previously by gas. After that, it will either remain in suspension until the matrix deforms and then percolate, or will vaporise first and then fill the pores with the vapour. Subsequent matrix deformation will mobilise the vapour. On its way to the surface water will form in the cooler layers.The differentiation starts during the accretion. At the end of the accretion, a pre-differentiated structure around the centre is possible, leading to a reallocation of the heat sources and changing the temperature profile. The evolution path varies with the growth rate assumed.We couple porosity loss and water-rock differentiation of an accreting icy object in an adaptive-grid 1D numerical model

  20. Why Icy Cliffs are Stressed Out and Falling to Pieces

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Sori, M. M.; Russell, P.; Pathare, A.; Becerra, P.; Molaro, J.; Sutton, S.; Mellon, M. T.; HiRISE Team

    2016-09-01

    Steep, icy, north polar cliffs are actively retreating through fracturing and blockfalls and additionally are scoured clean of dust by avalanches each spring. We explain this activity through modeling of thermoelastic stresses.

  1. Triptycene analogs

    NASA Technical Reports Server (NTRS)

    Hua, Duy (Inventor); Perchellet, Jean-Pierre (Inventor)

    2004-01-01

    This invention provides analogs of triptycene which are useful as anticancer drugs, as well as for other uses. The potency of these compounds is in a similar magnitude as daunomycin, a currently used anticancer drug. Each compound of the invention produces one or more desired effects (blocking nucleoside transport, inhibiting nucleic acid or protein syntheses, decreasing the proliferation and viability of cancer cells, inducing DNA fragmentation or retaining their effectiveness against multidrug-resistant tumor cells).

  2. Mid-infrared spectroscopy to better characterize icy moon surface compositions

    NASA Astrophysics Data System (ADS)

    Young, Cindy L.; Wray, James J.; Hand, Kevin P.; Poston, Michael; Carlson, Robert W.; Clark, Roger Nelson; Spencer, John R.; Jennings, Donald

    2016-10-01

    Previous spectroscopy work on icy moons has focused primarily on the visible and near-IR portion of the spectrum due to challenges presented by a low signal to noise ratio at the longer wavelengths. However, the mid-IR is the region of the strongest fundamental vibrations of many important types of molecules (e.g., organics) and has the potential to reveal unique compositional information [1]. We use the wealth of data that is now available from Cassini's Composite Infrared Spectrometer (CIRS) to average spectra over similar regions to improve the signal to noise, helping to reveal spectral features never before observed.Our initial work has already led to the detection and tentative laboratory identification of the first spectral features observed for any icy moon in the mid-IR [2]. On Iapetus' dark terrain, we found an emissivity feature at ~855 cm-1 and a possible doublet at 660 and 690 cm-1 that does not correspond to any known instrument artifacts. We attributed the 855 cm-1 feature to fine-grained silicates, similar to those found in dust on Mars and in meteorites, which are nearly featureless at shorter wavelengths [e.g., 3, 4]. Silicates on the dark terrains of Saturn's icy moons have been suspected for decades, but there have been no definitive detections until this work.We measured the vacuum, low temperature mid-IR spectra of various fine-grained powdered silicates, including Mg-rich serpentines, often present in meteorites. Some of these materials do have emissivity features near 855 cm-1 and exhibit a doublet. Presently, we are continuing to comb the CIRS icy moon database for spectral features (particularly focusing on the warmer surfaces in the Saturn system) and are performing further vacuum chamber measurements to experiment with more sample types and ice/sample mixtures to determine the impacts of changing conditions in the chamber on features. We are also working to understand how surface porosity and mixing with various darkening agents may

  3. Laboratory Infrared Spectroscopy to Identify New Compounds on Icy Moon Surfaces

    NASA Astrophysics Data System (ADS)

    Wray, James J.; Young, Cindy L.; Hand, Kevin P.; Poston, Michael J.; Carlson, Robert W.; Clark, Roger N.; Spencer, John R.; Jennings, Donald E.

    2014-11-01

    We are exploring the value of mid-infrared spectroscopy for identifying non-H2O constituents of icy moon surfaces. Recently we reported evidence for a new emissivity feature identified on Iapetus using Cassini’s Composite Infrared Spectrometer [1]. This 11.7 μm feature is consistent with emissivity minima (transparency features) of very fine-grained silicates. Its position and shape may be diagnostic of silicate type, but most lab data at these wavelengths have been acquired using coarser grains and/or at Earth surface pressures and temperatures. Infrared spectra can change substantially under low-temperature, vacuum conditions [e.g., 2,3].We prepared sieved (<0.4 mm) and very fine-grained (few μm) powders of six different silicates and measured their VNIR (0.35-2.5 μm) reflectance spectra under ambient air, and mid-IR (1.2-20 μm) spectra in a purged N2 glovebox. All silicates exhibited mid-IR transparency features (and loss of other features) in micronized form that were not observed for the coarser grain sizes. Muscovite, a phyllosilicate mineral possibly similar to those tentatively identified on Europa [4], provided the closest match to Iapetus in the mid-IR--although clear VNIR features of muscovite have not been identified on Iapetus [5]--and therefore we measured muscovite across the same wavelength range under Iapetus-like conditions (T=125 K, P<3x10^-8 torr). We will report on our ongoing analysis and plans for additional future measurements in JPL’s Icy Worlds Simulation Lab. [1] Young, C.L., et al. (2014), Workshop on the Habitability of Icy Worlds, Abstract #4038.[2] Logan, L.M., et al. (1973), J. Geophys. Res., 78(23), 4983-5003.[3] Donaldson Hanna, K.L., et al. (2012), J. Geophys. Res., 117, E00H05.[4] Shirley, J.H., et al. (2013), AGU Fall Meeting, Abstract #P54A-07.[5] Clark, R.N., et al. (2012), Icarus, 218, 831-860.

  4. Geologic Landforms and Processes on Icy Satellites

    NASA Technical Reports Server (NTRS)

    Schenk, Paul M.; Moore, Jeffrey M.

    1998-01-01

    During the first reconaissence of the satellites of the outer solar system conducted by the Voyager missions (1979-1989), a surprising diversity of unusual geologic landforms were observed, in some cases with bewildering complexity (e.g., Triton). Impact features were certainly expected but the variety of volcanic, diapiric, tectonic, impact, and erosional landforms was only remotely suggested by some early theoretical works. These diagnostic features are manifestations of the internal composition, thermal history, and dynamical evolution of these bodies. It is the job of the geologist to interpret the morphology, stratigraphy, and composition of these deposits and structures to ascertain what materials were mobilized in the interior, in what amount, and the mechanism and cause of their mobilization. In this chapter, we review what is know about these features and what constraints can be placed on composition and thermal history. Particular emphasis is placed on volcanic features, as these are most directly related to satellite composition and thermal history. The surface spectra, high albedos, and low bulk densities of the satellites of the outer solar system indicate that water and other ices are abundant on these bodies, particularly on their surfaces. Ices, particularly water ice, are less dense than silicates and will tend to float and form crusts during differentiation or partial melting of the interior. Ices therefore take the place of silicates as 'crust-forming' minerals and dominate geologic processes on icy satellites. Melted ices form magma bodies, and sometimes are extruded as lavas, an unusual but still valid perspective for terrestrial geologists. The unusual properties of some ices, including their low melting temperatures, and low strengths (as well as the decrease in density on the freezing of water ice), will ultimately be very important in interpreting this record.

  5. Saturn and 4 Icy Moons, Enhanced Color

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This enhanced-color picture shows Saturn, its rings, and four of its icy satellites. Three satellites (Tethys, Dione, and Rhea) are visible against the darkness of space, and another smaller satellite (Mimas) is visible against Saturn's cloud tops very near the left horizon and just below the rings. The dark shadows of Mimas and Tethys are also visible on Saturn's cloud tops, and the shadow of Saturn is seen across part of the rings. Saturn, second in size only to Jupiter in our Solar System, is 120,660 km (75,000 mi) in diameter at its equator (the ring plane) but, because of its rapid spin, Saturn is 10% smaller measured through its poles. Saturn's rings are composed mostly of ice particles ranging from microscopic dust to boulders in size. These particles orbit Saturn in a vast disk that is a mere 100 meters (330 feet) or so thick. The rings' thinness contrasts with their huge diameter--for instance 272,400 km (169,000 mi) for the outer part of the bright A ring, the outermost ring visible here. The pronounced concentric gap in the rings, the Cassini Division (named after its discoverer), is a 3500-km wide region (2200 mi, almost the width of the United States) that is much less populated with ring particles than the brighter B and A rings to either side of the gap. The rings also show some enigmatic radial structure ('spokes'), particularly at left. This image was synthesized from images taken in Voyager's orange, blue, and ultraviolet filters and was processed to create an exaggerated false color.

  6. The Cold and Icy Heart of Pluto

    NASA Astrophysics Data System (ADS)

    Hamilton, D. P.

    2015-12-01

    The locations of large deposits of frozen volatiles on planetary surfaces are largely coincident with areas receiving the minimum annual influx of solar energy. Thus we have the familiar polar caps of Earth and Mars, but cold equatorial regions for planets with obliquities between 54 and 126 degrees. Furthermore, for tilts between 45-66 degrees and 114-135 degrees the minimum incident energy occurs neither at the pole nor the equator. We find that the annual average insolation is always symmetric about Pluto's equator and is fully independent of the relative locations of the planet's pericenter and equinoxes. Remarkably, this symmetry holds for arbitrary orbital eccentricities and obliquities, and so we provide a short proof in the margin of this abstract. The current obliquity of Pluto is 119 degrees, giving it minima in average annual insolation at +/- 27 degrees latitude, with ~1.5% more flux to the equator and ~15% more to the poles. But the obliquity of Pluto also varies sinusoidally from 102-126 degrees and so, over the past million years, Pluto's annual equatorial and polar fluxes have changed by +15% and -13%, respectively. Interestingly, the energy flux received by latitudes between 25-35 degrees remains nearly constant over the presumably billions of years since Pluto acquired its current orbit and spin properties. Thus these latitudes are continuously cold and should be favored for the long-term deposition of volatile ices; the bright heart of Pluto, Sputnik Planum, extends not coincidentally across these latitudes. Reflected light and emitted thermal radiation from Charon increases annual insolation to one side of Pluto by of order 0.02%. Although small, the bulk of the energy is delivered at night to Pluto's cold equatorial regions. Furthermore, Charon's thermal IR is delivered very efficiently to icy deposits. Over billions of years, ices have preferentially formed and survived in the anti-Charon hemisphere.

  7. Geologic Evolution of Saturn's Icy Moon Tethys

    NASA Astrophysics Data System (ADS)

    Wagner, Roland; Stephan, K.; Schmedemann, N.; Roatsch, T.; Kersten, E.; Neukum, G.; Porco, C. C.

    2013-10-01

    Tethys, 1072 km in diameter, is a mid-sized icy moon of Saturn imaged for the first time in two Voyager flybys [1][2][3]. Since July 2004, its surface has been imaged by the Cassini ISS cameras at resolutions between 200 and 500 m/pxl. We present results from our ongoing work to define and map geologic units in camera images obtained preferentially during Cassini’s Equinox and Solstice mission phases. In the majority of Tethys’ surface area a densely cratered plains unit [1][2][3][this work] is abundant. The prominent graben system of Ithaca Chasma is mapped as fractured cratered plains. Impact crater and basin materials can be subdivided into three degradational classes. Odysseus is a fresh large impact basin younger than Ithaca Chasma according to crater counts [4]. Heavily degraded craters and basins occur in the densely cratered plains unit. A smooth, less densely cratered plains unit in the trailing hemisphere was previously identified by [2] but mapping of its boundaries is difficult due to varying viewing geometries of ISS images. To the south of Odysseus, we identified a cratered plains unit not seen in Voyager data, characterized by remnants of highly degraded large craters superimposed by younger fresher craters with a lower crater density compared to the densely cratered plains unit. Its distinct linear northern contact with the densely cratered plains suggests a tectonic origin. Sets of minor fractures can be distinguished in the densely cratered plains, and locally, features of mass wasting can be observed. References: [1] Smith B. A. et al. (1981), Science 212, 163-191. [2] Smith B. A. et al. (1982), Science 215, 504-537. [3] Moore J. M. and Ahern J. L. (1983), JGR 88 (suppl.), A577-A584. [4] Giese B. et al. (2007), GRL 34, doi:10.1029/2007GL031467.

  8. Phoebe and the Icy Saturnian Satellites: Implications for Satellite Origins

    NASA Astrophysics Data System (ADS)

    Mosqueira, I.; Estrada, P. R.

    2004-11-01

    Phoebe's retrograde, eccentric and inclined orbit marks it as an object captured from heliocentric orbit. Accordingly, its composition may be indicative of its origin in the solar nebula. Analogous arguments have been made extensively in connection with the origin of Pluto-Charon (see, e.g., McKinnon et al. 1997) as well as Triton (McKinnon and Mueller 1989). Indeed, the demarcation between nebula and subnebula objects has led a number of workers (see, e.g., Johnson et al. 1987; Lunine et al. 1993; Podolak et al. 1993) to argue that the regular satellites of the giant planets did not derive the bulk of their material directly from heliocentric orbit. The recent Cassini flyby of Phoebe has yielded a mass for this object of GM = 0.5527 ± 0.001 km3/s2 Jacobson et al. 2004 (this conference). Its density of 1.6 g/cm3 indicates a rock to ice ratio of at least 50 % (Porco et al. 2004; Science, to be submitted). Phoebe's high rock/ice ratio when compared to the icy Saturnian satellites reinforces the argument that Phoebe is an object that formed in heliocentric orbit and became captured. Yet, given that it may be misleading to lump together satellites with quite different formation histories, we refine the comparison on the basis of models for regular satellite formation. Because it derives condensables directly from heliocentric orbit and fails to consider planetesimals, the model of Canup and Ward (2002) does not provide a context for understanding such compositional differences. We will therefore discuss two models of satellite formation we are developing, which differ mainly in their treatment of turbulence (decaying vs steady). In both models the inner (located inside Titan's orbit), icy Saturnian satellites represent a second generation of objects. Mosqueira and Estrada (2003a,b) has these satellites forming 104-10^5 years after Titan as the disk became optically thin and water rich due to preferential gas drag loss of silicates as Saturn cooled. On the other hand

  9. Phoebe and the Icy Saturnian Satellites: Implications for Satellite Origins

    NASA Astrophysics Data System (ADS)

    Mosqueira, I.; Estrada, P. R.

    2004-12-01

    Phoebe's retrograde, eccentric and inclined orbit marks it as an object captured from heliocentric orbit. Accordingly, its composition may be indicative of its origin in the solar nebula. Analogous arguments have been made extensively in connection with the origin of Pluto-Charon (see, e.g., McKinnon et al. 1997) as well as Triton (McKinnon and Mueller 1989). Indeed, the demarcation between nebula and subnebula objects has led a number of workers (see, e.g., Johnson et al. 1987; Lunine et al. 1993; Podolak et al. 1993) to argue that the regular satellites of the giant planets did not derive the bulk of their material directly from heliocentric orbit. The recent Cassini flyby of Phoebe has yielded a mass for this object of GM = 0.5527 ± 0.001 km3/s2 Jacobson et al. 2004. Its density of 1.6 g/cm3 indicates a rock to ice ratio of at least 50 % (Porco et al. 2004; Science, to be submitted). Phoebe's high rock/ice ratio when compared to the icy Saturnian satellites reinforces the argument that Phoebe is an object that formed in heliocentric orbit and became captured. Yet, given that it may be misleading to lump together satellites with quite different formation histories, we refine the comparison on the basis of models for regular satellite formation. Because it derives condensables directly from heliocentric orbit and fails to consider planetesimals, the model of Canup and Ward (2002) does not provide a context for understanding such compositional differences. We will therefore discuss two models of satellite formation we are developing, which differ mainly in their treatment of turbulence (decaying vs steady). In both models the inner (located inside Titan's orbit), icy Saturnian satellites represent a second generation of objects. Mosqueira and Estrada (2003a,b) has these satellites forming 104-10^5 years after Titan as the disk became optically thin and water rich due to preferential gas drag loss of silicates as Saturn cooled. On the other hand, the gas

  10. Sublimation from icy jets as a probe of the interstellar volatile content of comets.

    PubMed

    Blake, G A; Qi, C; Hogerheijde, M R; Gurwell, M A; Muhleman, D O

    1999-03-18

    Comets are some of the most primitive bodies left over from the Solar System's early history. They may preserve both interstellar material and material from the proto-solar nebula, and so studies of their volatile components can provide clues about the evolution of gases and ices, as a collapsing molecular cloud transforms into a mature planetary system. Previous observations of emission from rotational transitions in molecules have averaged over large areas of the inner coma, and therefore include both molecules that sublimed from the nucleus and those that result from subsequent chemical processes in the coma Here we present high-resolution observations of emission from the molecules HNC, DCN and HDO associated with comet Hale-Bopp. Our data reveal arc-like structures-icy jets-offset from (but close to) the nucleus. The measured abundance ratios on 1-3" scales are substantially different from those on larger scales, and cannot be accounted for by models of chemical processes in the coma; they are, however, similar to the values observed in the cores of dense interstellar clouds and young stellar objects. We therefore propose that sublimation from millimetre-sized icy grains ejected from the nucleus provides access to relatively unaltered volatiles. The D/H ratios inferred from our data suggest that, by mass, Hale-Bopp (and by inference the outer regions of the early solar nebula) consists of > or =15-40% of largely unprocessed interstellar material.

  11. Icy outbursts from comet 67P/Churyumov-Gerasimenko as observed by the Alice FUV spectrograph

    NASA Astrophysics Data System (ADS)

    Steffl, Andrew Joseph; A'Hearn, Michael F.; Bertaux, Jean-Loup; Feaga, Lori M.; Feldman, Paul D.; Noonan, John; Parker, Joel Wm.; Schindhelm, Eric; Stern, S. Alan; Weaver, Harold A.

    2016-10-01

    Since the Rosetta spacecraft's historic rendezvous with 67P/Churyumov-Gerasimenko on 6 August 2014, the Alice far-ultraviolet spectrograph (700-2050Å) has monitored gas and dust emissions from the comet. During this time, Alice has observed several large dust outbursts. During such outbursts, the brightness of sunlight reflected from dust can increase by almost two orders of magnitude on timescales of a few tens of minutes. Typically, the reflectance spectrum of dust is very similar to that of the pre-perihelion nucleus: dark and relatively featureless with a blue spectral slope. However, a subset of the dust outbursts show a markedly different character with dust that is bright--in some cases brighter than the sunlit nucleus itself-- and displaying a strong absorption feature around 1700Å, characteristic of water ice. In such outbursts, the observed "dust" is likely to consist primarily of icy grains. We focus on two of these icy outbursts that occurred on 10 July 2015 and 13 September 2015 showing spectra from before, during, and after the events and comparing them to spectra of the nucleus obtained contemporaneously and from several months before and after perihelion.

  12. Contributions of icy planetesimals to the Earth's early atmosphere.

    PubMed

    Owen, T C; Bar-Nun, A

    2001-01-01

    Laboratory experiments on the trapping of gases by ice forming at low temperatures implicate comets as major carriers of the heavy noble gases to the inner planets. These icy planetesimals may also have brought the nitrogen compounds that ultimately produced atmospheric N2. However, if the sample of three comets analyzed so far is typical, the Earth's oceans cannot have been produced by comets alone, they require an additional source of water with low D/H. The highly fractionated neon in the Earth's atmosphere may also indicate the importance of non-icy carriers of volatiles. The most important additional carrier is probably the rocky material comprising the bulk of the mass of these planets. Venus may require a contribution from icy planetesimals formed at the low temperatures characteristic of the Kuiper Belt. PMID:11599179

  13. Morphology and Scaling of Ejecta Deposits on Icy Satellites

    NASA Technical Reports Server (NTRS)

    Schenk, Paul M.; Ridolfi, Francis J.; Bredekamp, Joe (Technical Monitor)

    2002-01-01

    Continuous ejecta deposits on Ganymede consist of two major units, or facies: a thick inner hummocky pedestal facies, and a relatively thin outer radially scoured facies defined also by the inner limit of the secondary crater field. Both ejecta facies have a well-defined power-law relationship to crater diameter for craters ranging from 15 to approx. 600 km across. This relationship can be used to estimate the nominal crater diameter for impact features on icy satellites (such as palimpsests and multiring basins) for which the crater rim is no longer recognizable. Ejecta deposits have also been mapped on 4 other icy satellites. Although morphologically similar to eject deposits on the Moon, ejecta deposits for smaller craters are generally significantly broader in extent on the icy satellites, in apparent defiance of predictions of self-similarity. A greater degree of rim collapse and enlargement on the Moon may explain the observed difference.

  14. Potential Biospheres of the icy world in our solar systems

    NASA Astrophysics Data System (ADS)

    de Vera, Jean-Pierre Paul; Baqué, Mickael

    2016-04-01

    The challenge in astrobiology and planetary research in the near future is to realize space missions to study the habitability of Mars and the icy moons of the Jovian and Saturnian systems. Mars is an interesting object to search for habitable environments and for fossilized (and potentially present) life because of its past water driven wet history. On the other hand the Jovian moon Europa and the Saturnian moon Enceladus are promising candidates, where liquid water oceans beneath the surface are expected. These oceans can be habitable environments and the next challenge is to search there for present life. Some examples on potential biospheres and their biosignatures in Mars-like environments and in environmental conditions with reference to the icy moons will be given, which might exist in such kind of icy environments.

  15. The Saturn System's Icy Satellites: New Results from Cassini

    NASA Technical Reports Server (NTRS)

    Lopes-Gautier, Rosaly M.; Buratti, Bonnie; Hendrix, A. R.

    2008-01-01

    Cassini-Huygens is a multidisciplinary, international planetary mission consisting of an orbiting spacecraft and a probe. The Huygens probe successfully landed on Titan's surface on January 14, 2005, while the orbiter has performed observations of Saturn, its rings, satellites, and magnetosphere since it entered orbit around Saturn on July 1, 2004. The Cassini mission has been prolific in its scientific discoveries about the Saturn system. In this special section, we present new mission results with a focus on the 'icy satellites,' which we define as all Saturn's moons with the exception of Titan. The results included in this section have come out of the Cassini SOST--Satellites Orbiter Science Team--a multi-instrument and multidiscipline group that works together to better understand the icy satellites and their interactions with Saturn and its rings. Other papers included in this issue present ground-based observations and interior modeling of these icy moons.

  16. Rifting and Faulting on icy Satellites

    NASA Astrophysics Data System (ADS)

    Nimmo, F.

    2003-12-01

    Two kinds of rifting have been identified on the icy Galilean satellites [1,2]. Europa possesses ˜10~km wide extensional bands, characterized by very high degrees of local extension, internal deformation on a lengthscale of ˜~100~m, and a general resemblance to mid-ocean ridges on Earth [3]. Ganymede has ˜100~km wide areas of grooved terrain, characterized by km-scale tilted fault blocks [4,5], lower degrees of local extension (stretching factor <1.6 [5]) and a general resemblance to continental rifts on Earth [1]. The characteristic spacing of faults on Europa and Ganymede has been used to infer the depth to the brittle-ductile transition (BDT), which depends on the strain rate and the shell thickness [4,6]. Here I present another constraint on these quantities, obtained by considering the circumstances under which narrow (Europa-style) or wide (Ganymede-style) rifts may form. The model is based on an analysis of terrestrial continent rifting [7]. When an ice shell is extended, the thermal gradient increases and it becomes weaker, favouring further extension. The extension also gives rise to lateral shell thickness variations, which oppose further extension. However, these lateral thickness variations may be removed if the base of the ice shell can flow rapidly. If lateral flow is rapid, narrow zones of extension and high stretching factors are generated. If lateral flow is slow, wider rifts and lower stretching factors are favoured. Thick ice shells or high strain rates favour narrow rifts; thin ice shells or low strain rates favour wide rifts. The existence of wide rifts on Ganymede is consistent with a conductive shell thickness of 4-8~km at the time of rifting, and agrees with previous estimates of strain rates [8]. To produce narrow rifting and the inferred BDT depth on Europa requires a larger shell thickness (8-20~km) and a strain rate >= 10-15~s-1. Based on the likely shell thicknesses, the inferred strain rates for Europa and Ganymede can be explained

  17. ICI and Penspen in Nigerian and Qatari methanol deals

    SciTech Connect

    Alperowicz, N.

    1992-03-11

    The U.K. consulting and engineering company Penspen Ltd. (London) has signed a second joint venture agreement in Qatar and has selected the ICI (London) methanol process. The technology will also be used in a world-scale methanol plant in Nigeria that Penspen is helping to set up. Under the first agreement, signed on January 1 with Qatar General Petroleum Corp. (QGPC), a 50/50 venture is being formed to build a $370-million, 2,000-m.t./day methanol plant at Umm Said. ICI will provide its low-pressure technology and help market 75% of the output. Completion is due late 1994.

  18. Asteroid Icy Regolith Excavation and Volatile Capture Project

    NASA Technical Reports Server (NTRS)

    Zeitlin, Nancy; Mantovani, James; Swanger, Adam; Townsend, Ivan

    2015-01-01

    Icy regolith simulants will be produced in a relevant vacuum environment using various minerals, including hydrated minerals, that are found in C-type meteorites and in other types of planetary regolith. This will allow us to characterize the mechanical strength of the icy regolith as a function of ice content using penetration, excavation, and sample capture devices. The results of this study will benefit engineers in designing efficient regolith excavators and ISRU processing systems for future exploration missions to asteroids and other planetary bodies.

  19. Synthesis and characterization of peptides after high-energy impact on the icy matrix: Preliminary step for further UV-induced formation

    NASA Astrophysics Data System (ADS)

    Gontareva, Natalia B.; Kuzicheva, Evgenia A.; Shelegedin, Vladimir N.

    2009-04-01

    In the interstellar medium, the most probable source of organic molecules could be non-equilibrium processes driven by photons, cosmic rays, shock waves and solid bodies' collisions. The dense cold phase of ISM host icy dust grains - important chemical catalyst during its life cycle. Such particles consist of mineral core composed by silicate or olivine admixed with metal sulfides and oxides, with the water-icy envelope containing organic molecules. Organic molecules in the ISM evolve and become later incorporated in solar system material (comets and meteorites). The formation of polypeptides from single amino acids was traced in simulation experiments representing the inner structure of icy dust grains. Experimental chamber was irradiated at subzero temperatures at the dosage of 2.54 kRad/min. Solid frozen solutions of Gly and Phe were taken as the experimental samples inserted into the metal tube kept at subzero temperatures in the presence of liquid nitrogen. Formation of di- and tri-peptides was demonstrated after applying mass-spectrometry and high performance liquid chromatography (HPLC) techniques. Having polypeptides within the icy matrix, dust grains with ice mantles are transported to warm, dense and active protostellar regions, where ultraviolet irradiation may become important and alter the grain composition. Furthermore UVC radiation may contribute to the formation of additional amounts of polypeptides, since short-wave photons are totally adsorbed by a thin outer layer. This presumption coincides with our previous investigations concerning UV impact on prebiotic formation of the main biological molecules. Combination of two irradiation types in different stages of interstellar flight could compensate the effects of low reagents concentration and temperature. Since the primordial Earth had no atmosphere, the natural carriers could get freely onto its surface and thus raise the concentration of organic molecules.

  20. Novel in situ chemical sensing technologies for icy environments

    NASA Astrophysics Data System (ADS)

    Wadham, Jemma; Mowlem, Matthew; Beaton, Alex; Bagshaw, Elizabeth; Lamarche-Gagnon, Guillaume; Telling, Jon; Hawkings, Jon; Tranter, Martyn

    2016-04-01

    A dramatic development in subglacial science in recent decades has been the considerable international effort aimed at improving understanding of the hidden subglacial aquatic environments beneath ice sheets. These include a diverse range of lakes, rivers, shallow and deep sediments. Technology challenges associated with the exploration of these and other icy environments are substantial because of their remote nature, extreme conditions and the requirement for sterile/clean access and sampling. In situ sensors provide an alternative to sample recovery and return for monitoring in situ conditions and are available for many analytes, but they are frequently unsuitable for deployment in icy environments. Low temperatures, freeze-thaw cycles, remote locations, low concentration and low ionic strength meltwaters challenge technologies designed for non cryospheric systems. The UK NERC- funded DELVE programme (DeEveLopment and Validation of in situ chemical sensors for icy Ecosystems) was launched with the goal of developing and testing the first suite of geochemical sensors for icy ecosystems, with a focus on redox sensitive species and dissolved nutrients. All sensors were subject to testing at low temperatures, including freeze-thaw cycling, and the response to low concentration and low ionic strength was quantified. Here we report high resolution, continuous data derived from a suite of biogeochemical sensors which were deployed to a large proglacial river draining the Greenland Ice Sheet during the 2015 melt season. These data show that these sensors have strong potential for more challenging deployment to the basal regions of ice sheets.

  1. IPPF Co-operative Information Service (ICIS). February 1978.

    ERIC Educational Resources Information Center

    International Planned Parenthood Federation, London (England).

    This publication is a catalogue of document descriptions that may be of use to national family planning/population organizations. The International Planned Parenthood Federation (IPPF) Cooperative Information Service (ICIS) has developed this quarterly series as a service to population documentation centers so that these centers can acquire the…

  2. Neutral atmosphere near the icy surface of Jupiter's moon Ganymede

    NASA Astrophysics Data System (ADS)

    Shematovich, V. I.

    2016-07-01

    The paper discusses the formation and dynamics of the rarefied gas envelope near the icy surface of Jupiter's moon Ganymede. Being the most massive icy moon, Ganymede can form a rarefied exosphere with a relatively dense near-surface layer. The main parent component of the gas shell is water vapor, which enters the atmosphere due to thermal degassing, nonthermal radiolysis, and other active processes and phenomena on the moon's icy surface. A numerical kinetic simulation is performed to investigate, at the molecular level, the formation, chemical evolution, and dynamics of the mainly H2O- and O2-dominant rarefied gas envelopes. The ionization processes in these rarefied gas envelopes are due to exposure to ultraviolet radiation from the Sun and the magnetospheric plasma. The chemical diversity of the icy moon's gas envelope is attributed to the primary action of ultraviolet solar photons and plasma electrons on the rarefied gas in the H2O- or O2-dominant atmosphere. The model is used to calculate the formation and development of the chemical diversity in the relatively dense near-surface envelope of Ganymede, where an important contribution comes from collisions between parent molecules and the products of their photolysis and radiolysis.

  3. The interesting case of the Iota-Cygnids (525 ICY)

    NASA Astrophysics Data System (ADS)

    Andreić, Željko; Šegon, Damir; Vida, Denis; Novoselnik, Filip; Skokić, Ivica

    2014-01-01

    One of the showers recently reported by the Croatian Meteor Network, the Iota-Cygnids (525 ICY), is described. From the 40 available orbits, the mean orbit of the shower and some other parameters were obtained. The Iota-Cygnids were detected from October 16 (Sol.Lon. = 203◦) to November, 19th (Sol.Lon. = 237◦), with a slightly higher activity around October 31 (Sol.Lon. = 218◦). The possible parent body is Asteroid 2001 SS287, with DSH = 0.16, indicating that 525 ICY is probably asteroidal in origin. However, a few more asteroids have DSH < 0.20, so the question of the parent body requires a more detailed study to be solved. In depth analysis of IAU MDC has found two showers that are quite similar to the 525 ICY: 83 OCG and 282 DCY. By gathering additional data outside the IAU MDC, we found out that 282 DCY is a rediscovery of 83 OCG. Also, 525 ICY is identical to 83 OCG, but this fact was not recognized before, probably due to incorrect coordinates for the 83 OCG radiant in the IAU MDC database and the lack of information about the activity period of the showers in the IAU MDC database.

  4. Workshop on Europa's Icy Shell: Past, Present, and Future

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This volume contains abstracts that have been accepted for presentation at the workshop on Europa's Icy Shell: Past, Present, and Future, February 6-8,2004, Houston, Texas. Administration and publications support for this meeting were provided by the staff of the Publications and Program Services Department at the Lunar and Planetary Institute.

  5. Forum on Concepts and Approaches for Jupiter Icy Moons Orbiter

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The papers presented at this conference primarily discuss instruments and techniques for conducting science on Jupiter's icy moons, and geologic processes on the moons themselves. Remote sensing of satellites, cratering on satellites, and ice on the surface of Europa are given particular attention. Some papers discuss Jupiter's atmosphere, or exobiology.

  6. 9 CFR 83.5 - Interstate Certificate of Inspection (ICI).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Interstate Certificate of Inspection (ICI). 83.5 Section 83.5 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE INTERSTATE TRANSPORTATION OF ANIMALS (INCLUDING POULTRY) AND ANIMAL PRODUCTS...

  7. Organic Synthesis in Simulated Interstellar Ice Analogs

    NASA Technical Reports Server (NTRS)

    Dworkin, Jason P.; Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Deamer, David W.; Elsila, Jamie; Zare, Richard N.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    Comets and carbonaceous micrometeorites may have been significant sources of organic compounds on the early Earth. Ices on grains in interstellar dense molecular clouds contain a variety of simple molecules as well as aromatic molecules of various sizes. While in these clouds the icy grains are processed by ultraviolet light and cosmic radiation which produces more complex organic molecules. ID We have run laboratory simulations to identify the types of molecules which could have been generated photolytically in pre-cometary ices. Experiments were conducted by forming various realistic interstellar mixed-molecular ices with and without polycyclic aromatic hydrocarbons (PAHs) at approx. 10 K under high vacuum irradiated with LTV light from a hydrogen plasma lamp: The residue that remained after warming to room temperature was analyzed by HPLC, and by laser desorption mass spectrometry. The residue contains several classes of compounds which may be of prebiotic significance.

  8. Organic Synthesis in Simulated Interstellar Ice Analogs

    NASA Technical Reports Server (NTRS)

    Dworkin, Jason P.; Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Deamer, David W.; Elsila, Jamie; Zare, Richard N.

    2001-01-01

    Comets and carbonaceous micrometeorites may have been significant sources of organic compounds on the early Earth. Ices on grains in interstellar dense molecular clouds contain a variety of simple molecules as well as aromatic molecules of various sizes. While in these clouds the icy grains are processed by ultraviolet light and cosmic radiation which produces more complex organic molecules. We have run laboratory simulations to identify the types of molecules which could have been generated photolytically in pre-cometary ices. Experiments were conducted by forming various realistic interstellar mixed-molecular ices with and without polycyclic aromatic hydrocarbons (PAHs) at approx. 10 K under high vacuum irradiated with UV light from a hydrogen plasma lamp. The residue that remained after warming to room temperature was analyzed by HPLC, and by laser desorption mass spectrometry. The residue contains several classes of compounds which may be of prebiotic significance.

  9. Analysis of Cassini UVIS Far Ultraviolet Reflectance Spectra to Constrain the Non-Ice Material in Saturn’s Rings and Icy Moons

    NASA Astrophysics Data System (ADS)

    Bradley, Eric Todd; Colwell, J. E.; Esposito, L. W.; Hendrix, A. R.

    2012-10-01

    The FUV spectra of Saturn’s icy ring particles and moons show the presence of an absorbing constituent that presumably is delivered to the system via micrometeoroid bombardment. Understanding the properties of the non-icy material plays into broader questions regarding the age and evolution of the rings. The FUV spectrum contains a water ice absorption edge at 165 nm. The reflectance shortward of the water ice absorption edge is determined by the composition and abundance of the non-icy material whereas the reflectance longward of the absorption edge is determined by both water ice and non-icy material. We have taken two approaches to constrain the properties of the non-ice component of the rings using FUV spectra taken by the Cassini UVIS. In one approach we compare the ring particle Bond albedo, A0, to spectral models with varying abundances and compositions of non-ice components. We first determine A0, across the water ice absorption edge using the classical Chandrasekhar radiative transfer model for the C Ring and Cassini Division with the scattering function replaced by a self-gravity wake model for the A and B rings. We then compare the retrieved values of A0, to spectral models of intimate mixtures where the free parameters are the fractional abundances of the ice and non-ice constituents, grain size, and grain asymmetry parameter for scattering. In the second approach we compare FUV color ratios (180/155 nm) across Saturn’s rings, as well as to icy moons, in order to investigate relative variations in water ice abundance in these objects. We find that A0, longward of the absorption edge peaks in the outer B ring and reaches a minimum in the C Ring and Cassini Division, consistent with the purest water ice being found in the B Ring and the most polluted in the C Ring and Cassini Division.

  10. Fingering phenomena during grain-grain displacement

    NASA Astrophysics Data System (ADS)

    Mello, Nathália M. P.; Paiva, Humberto A.; Combe, G.; Atman, A. P. F.

    2016-05-01

    Spontaneous formation of fingered patterns during the displacement of dense granular assemblies was experimentally reported few years ago, in a radial Hele-Shaw cell. Here, by means of discrete element simulations, we have recovered the experimental findings and extended the original study to explore the control parameters space. In particular, using assemblies of grains with different geometries (monodisperse, bidisperse, or polydisperse), we measured the macroscopic stress tensor in the samples in order to confirm some conjectures proposed in analogy with Saffman-Taylor viscous fingering phenomena for immiscible fluids. Considering an axial setup which allows to control the discharge of grains and to follow the trajectory and the pressure gradient along the displacing interface, we have applied the Darcy law for laminar flow in fluids in order to measure an "effective viscosity" for each assembly combination, in an attempt to mimic variation of the viscosity ratio between the injected/displaced fluids in the Saffman-Taylor experiment. The results corroborate the analogy with the viscous fluids displacement, with the bidisperse assembly corresponding to the less viscous geometry. But, differently to fluid case, granular fingers only develop for a specific combination of displaced/injected geometries, and we have demonstrated that it is always related with the formation of a force chain network along the finger direction.

  11. 76 FR 45226 - Lynn Canal/Icy Straits Resource Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-28

    ... Forest Service Lynn Canal/Icy Straits Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Lynn Canal/Icy Straits Resource Advisory Committee will meet in Juneau... Mendenhall Loop Road, Juneau, Alaska. Send written comments to Lynn Canal/Icy Straits Resource...

  12. 76 FR 28950 - Lynn Canal/Icy Straits Resource Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-19

    ... Forest Service Lynn Canal/Icy Straits Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Lynn Canal/Icy Straits Resource Advisory Committee will hold a... teleconference. Send written comments to Lynn Canal/Icy Straits Resource Advisory Committee, c/o...

  13. Compositions of Oceans on Icy Solar System Bodies (Invited)

    NASA Astrophysics Data System (ADS)

    Zolotov, M. Y.

    2010-12-01

    Interior oceans may exist on at least several solar system bodies: Europa, Enceladus, Ganymede, Titan and Triton. Compositions of the oceans could reflect bulk chemistries on the bodies, degree and timing of differendentition, current temperature and pressure conditions, and chemical exchanges between icy shells, liquid layers, and suboceanic solids (rocks, sediments, ices and clathrates). Observational signs are sparse and modeling is the major approach to evaluate oceanic compositions. On Europa, a presence of S(VI) species and CO2 at endogenic surface features [1] suggests sulfates and C species (organic and/or inorganic) in the ocean. The detection of NaCl and Na2CO3/NaHCO3-bearing grains emitted from Enceladus [2] implies the dominance of Na, Cl and carbonate/bicarbonate ions in the past and/or present alkaline fluids in the interior. These observations are consistent with independent models for water-rock interaction [3]. Evaluated low contents of other elements (Mg, Fe, Ca, K, S, P, etc.) in initial oceanic waters [3] are accounted for by low solubilities of minerals deposited from water solutions (serpentine, saponite, magnetite, carbonates, sulfides and phosphates). Oceanic redox states are affected by the composition of accreted ices and rocks, hydrogen production through oxidation of solids (mainly Fe-Ni metal) by water and an efficiency of H2 escape. Formation of a sulfate-bearing ocean (as on Europa) through oxidation of sulfides could have been driven by radiolytically-formed oxidants (H2O2, O2), high-temperature (>500 K) hydrothermal activity and H2 escape. Formation of sulfate facilitates leaching of Mg from minerals leading to the Mg-SO4-Na-Cl ocean. Although some of these factors could have played roles on the Galilean satellites, formation of sulfate-bearing oceans beyond Jupiter is unlikely. Accretion of cometary-type ices on moons allows an existence of water-methanol-ammonia liquids at ~153 K, although ammonia could have been sequestered in

  14. Studies of solid carbon dioxide in interstellar ice analogs subject to thermal processing

    NASA Astrophysics Data System (ADS)

    White, Douglas W.

    2010-09-01

    Solid CO2 has been detected in many lines of sight in the interstellar medium from infrared observatories. Spectral profiles from space-based observatories have suggested that CO2 on icy grain mantles is mixed with other common molecules such as H2O and CH 3OH in interstellar regions and that thermal annealing has occurred. The vibrational mode at 658 cm-1 (15.2 mum) is suspected to be a powerful diagnostic tool as to the composition of species on icy grain mantles as well as thermal histories. However, previous studies have not systematically investigated ice composition and temperature. Laboratory spectra of interstellar ice analogs have been created in this study order to better understand the physical properties of solid CO2 in these interstellar environments. Existing databases of ice composition studies and effects of ice thermal history were updated in this study to include a more systematic approach. The 658 cm-1 (15.2 mum) bending mode feature of CO2 is examined here and the subsequent astrophysical implications stated. In the first set of experiments, 47 mixtures of H2O,CH3OH, andCO2 were slowly warmed and mid-infrared absorption spectra were recorded at 5K intervals. The second set of experiments involved examining the CO2 bending mode feature of 10 different CO2-containing ice mixtures at different temperatures where ice segregation was suspected. In these experiments, the ice mixtures were slowly heated to the desired temperature for increasing time intervals before cooling down and recording mid-IR absorption spectra. These studies may be used to analyze IR data from space-based observatories such as the Spitzer Space Telescope Infrared Spectrograph as well other future IR observations of the interstellar medium. Finally, mass spectroscopy measurements were taken from temperature programmed desorption (TPD) experiments performed on several binary mixtures of H2O + CO2 and CH 3OH + CO2. Physical properties such as desorption energy of CO2 can be

  15. High Latitude Scintillations during the ICI-4 Rocket Campaign.

    NASA Astrophysics Data System (ADS)

    Patra, S.; Moen, J.

    2015-12-01

    We present the first results from the Norwegian ICI-4 sounding rocket campaign in February 2015. The ICI-4 was launched into F-region auroral blobs from the Andøya Space Center. The multi needle langmuir probe (m-NLP) on board the rocket sampled the ionospheric density structures at a sub-meter spatial resolution. A multi-phase screen model has been developed to estimate the scintillations from the density measurements acquired on-board spacecrafts. The phase screen model is validated and the comparison of the estimated values with scintillations measured by ground receivers during the campaign will be presented. A combination of scintillation receivers in Svalbard and surrounding areas as well as all sky imagers at Ny Ålesund, Longyerbyen, and Skibotn are used to improve the performance of the model.

  16. Laboratory Simulations of Ammonia-Rich Oceans in Icy Worlds

    NASA Technical Reports Server (NTRS)

    Vance, S. D.; Brown, J. M.

    2011-01-01

    Improved equations of state for ammonia-water solutions are important for properly understanding the interiors of large icy satellites hosting deep interior oceans. Titan is the primary example of such a world, but water-rich dwarf planets Measurements of solution density are now possible at relevant pressures (above approx. 250 megapascals) using the Simulator for Icy World Interiors. Analysis of sound velocity measurements in aqueous magnesium sulfate obtained in our laboratory, shows a correction on the order of 5% to 700 megapascals (7 kilobar) from -20 to 100 C and to 3 m (approx. 30 percentage by weight) concentration. Accurate prediction of density as a function of pressure, temperature, and ammonia concentration are needed for interpretation of remote observations to address questions of interior liquid layer depth, composition, and fluid dynamics.

  17. Crustal failure on icy Moons from a strong tidal encounter

    NASA Astrophysics Data System (ADS)

    Quillen, Alice C.; Giannella, David; Shaw, John G.; Ebinger, Cynthia

    2016-09-01

    Close tidal encounters among large planetesimals and Moons should have been more common than grazing or normal impacts. Using a mass spring model within an N-body simulation, we simulate the deformation of the surface of an elastic spherical body caused by a close parabolic tidal encounter with a body that has similar mass as that of the primary body. Such an encounter can induce sufficient stress on the surface to cause brittle failure of an icy crust and simulated fractures can extend a large fraction of the radius of body. Strong tidal encounters may be responsible for the formation of long graben complexes and chasmata in ancient terrain of icy Moons such as Dione, Tethys, Ariel and Charon.

  18. EVAPORATION OF ICY PLANETESIMALS DUE TO BOW SHOCKS

    SciTech Connect

    Tanaka, Kyoko K.; Yamamoto, Tetsuo; Tanaka, Hidekazu; Miura, Hitoshi; Nagasawa, Makiko; Nakamoto, Taishi

    2013-02-20

    We present the novel concept of evaporation of planetesimals as a result of bow shocks associated with planetesimals orbiting with supersonic velocities relative to the gas in a protoplanetary disk. We evaluate the evaporation rates of the planetesimals based on a simple model describing planetesimal heating and evaporation by the bow shock. We find that icy planetesimals with radius {approx}>100 km evaporate efficiently even outside the snow line in the stage of planetary oligarchic growth, where strong bow shocks are produced by gravitational perturbations from protoplanets. The obtained results suggest that the formation of gas giant planets is suppressed owing to insufficient accretion of icy planetesimals onto the protoplanet within the {approx}<5 AU disk region.

  19. Jupiter Icy Moons Tidal Signatures and Ocean Mapping from Orbit

    NASA Technical Reports Server (NTRS)

    Wu, X.; Bar-Server, Y. E.; Folkner, W. M.; Williams, J. G.; Zumberge, J. F.

    2003-01-01

    Following the Galileo spacecraft encounters with Europa, Ganymede, and Callisto, evidence emerged suggesting that these Galilean moons of Jupiter may have liquid oceans underneath their icy shells. Detection of the oceans on one or all three moons will have profound implications on probability of life beyond the Earth. The icy satellites also have tidal environments that are among the strongest in the solar system. The leading time-varying tidal forcing term on the surface of Europa is at least 9 times larger than those on the inner planets. Tidal forcing on the surfaces of Ganymede and Callisto are about 10% and 7%, respectively, of that on Europa. Since a planetary body with internal fluid deforms more than an otherwise solid body, tidal measurements offer exciting opportunities to detect the oceans.

  20. Grain size-sensitive creep in ice II

    USGS Publications Warehouse

    Kubo, T.; Durham, W.B.; Stern, L.A.; Kirby, S.H.

    2006-01-01

    Rheological experiments on fine-grained water ice II at low strain rates reveal a creep mechanism that dominates at conditions of low stress. Using cryogenic scanning electron microscopy, we observed that a change in stress exponent from 5 to 2.5 correlates strongly with a decrease in grain size from about 40 to 6 micrometers. The grain size-sensitive creep of ice II demonstrated here plausibly dominates plastic strain at the low-stress conditions in the interior of medium- to large-sized icy moons of the outer solar system.

  1. Grain size-sensitive creep in ice II.

    PubMed

    Kubo, Tomoaki; Durham, William B; Stern, Laura A; Kirby, Stephen H

    2006-03-01

    Rheological experiments on fine-grained water ice II at low strain rates reveal a creep mechanism that dominates at conditions of low stress. Using cryogenic scanning electron microscopy, we observed that a change in stress exponent from 5 to 2.5 correlates strongly with a decrease in grain size from about 40 to 6 micrometers. The grain size-sensitive creep of ice II demonstrated here plausibly dominates plastic strain at the low-stress conditions in the interior of medium- to large-sized icy moons of the outer solar system. PMID:16513977

  2. Grain size-sensitive creep in ice II.

    PubMed

    Kubo, Tomoaki; Durham, William B; Stern, Laura A; Kirby, Stephen H

    2006-03-01

    Rheological experiments on fine-grained water ice II at low strain rates reveal a creep mechanism that dominates at conditions of low stress. Using cryogenic scanning electron microscopy, we observed that a change in stress exponent from 5 to 2.5 correlates strongly with a decrease in grain size from about 40 to 6 micrometers. The grain size-sensitive creep of ice II demonstrated here plausibly dominates plastic strain at the low-stress conditions in the interior of medium- to large-sized icy moons of the outer solar system.

  3. JUICE: A European Mission to Jupiter and its Icy Moons

    NASA Astrophysics Data System (ADS)

    Witasse, O.; Altobelli, N.; Barabash, S.; Bruzzone, L.; Dougherty, M.; Erd, C.; Fletcher, L.; Gladstone, R.; Grasset, O.; Gurvits, L.; Hartogh, P.; Hussmann, H.; Iess, I.; Langevin, Y.; Palumbo, P.; Piccioni, G.; Sarri, G.; Titov, D.; Wahlund, J.-E.

    2015-10-01

    JUICE -JUpiter ICy moons Explorer -is the first large mission in the ESA Cosmic Vision 2015-2025 programme[1]. The mission was selected in May 2012 and adopted in November 2014. The implementation phase starts in July 2015, following the selection of the prime industrial contractor. Planned for launch in June 2022 and arrival at Jupiter in October 2029, it will spend at least three years making detailed observations of Jupiter and three of its largest moons, Ganymede, Callisto and Europa.

  4. Icy Soil Acquisition Device for the 2007 Phoenix Mars Lander

    NASA Technical Reports Server (NTRS)

    Chu, Philip; Wilson, Jack; Davis, Kiel; Shiraishi, Lori; Burke, Kevin

    2008-01-01

    The Icy Soil Acquisition Device is a first of its kind mechanism that is designed to acquire ice-bearing soil from the surface of the Martian polar region and transfer the samples to analytical instruments, playing a critical role in the potential discovery of existing water on Mars. The device incorporates a number of novel features that further the state of the art in spacecraft design for harsh environments, sample acquisition and handling, and high-speed low torque mechanism design.

  5. Space Weathering on Icy Satellites in the Outer Solar System

    NASA Technical Reports Server (NTRS)

    Clark, R. N.; Perlman, Z.; Pearson, N.; Cruikshank, D. P.

    2014-01-01

    Space weathering produces well-known optical effects in silicate minerals in the inner Solar System, for example, on the Moon. Space weathering from solar wind and UV (ultraviolet radiation) is expected to be significantly weaker in the outer Solar System simply because intensities are low. However, cosmic rays and micrometeoroid bombardment would be similar to first order. That, combined with the much higher volatility of icy surfaces means there is the potential for space weathering on icy outer Solar System surfaces to show optical effects. The Cassini spacecraft orbiting Saturn is providing evidence for space weathering on icy bodies. The Cassini Visible and Infrared Mapping Spectrometer (VIMS) instrument has spatially mapped satellite surfaces and the rings from 0.35-5 microns and the Ultraviolet Imaging Spectrograph (UVIS) instrument from 0.1 to 0.2 microns. These data have sampled a complex mixing space between H2O ice and non-ice components and they show some common spectral properties. Similarly, spectra of the icy Galilean satellites and satellites in the Uranian system have some commonality in spectral properties with those in the Saturn system. The UV absorber is spectrally similar on many surfaces. VIMS has identified CO2, H2 and trace organics in varying abundances on Saturn's satellites. We postulate that through the spatial relationships of some of these compounds that they are created and destroyed through space weathering effects. For example, the trapped H2 and CO2 observed by VIMS in regions with high concentrations of dark material may in part be space weathering products from the destruction of H2O and organic molecules. The dark material, particularly on Iapetus which has the highest concentration in the Saturn system, is well matched by space-weathered silicates in the .4 to 2.6 micron range, and the spectral shapes closely match those of the most mature lunar soils, another indicator of space weathered material.

  6. SIZE AND SURFACE AREA OF ICY DUST AGGREGATES AFTER A HEATING EVENT AT A PROTOPLANETARY NEBULA

    SciTech Connect

    Sirono, Sin-iti

    2013-03-01

    The activity of a young star rises abruptly during an FU Orionis outburst. This event causes a temporary temperature increase in the protoplanetary nebula. H{sub 2}O icy grains are sublimated by this event, and silicate cores embedded inside the ice are ejected. During the high-temperature phase, the silicate grains coagulate to form silicate core aggregates. After the heating event, the temperature drops, and the ice recondenses onto the aggregates. I determined numerically the size distribution of the ice-covered aggregates. The size of the aggregates exceeds 10 {mu}m around the snow line. Because of the migration of the ice to large aggregates, only a small fraction of the silicate core aggregate is covered with H{sub 2}O ice. After the heating event, the surface of an ice-covered aggregate is totally covered by silicate core aggregates. This might reduce the fragmentation velocity of aggregates when they collide. It is possible that the covering silicate cores shield the UV radiation field which induces photodissociation of H{sub 2}O ice. This effect may cause the shortage of cold H{sub 2}O vapor observed by Herschel.

  7. Analog current mode analog/digital converter

    NASA Technical Reports Server (NTRS)

    Hadidi, Khayrollah (Inventor)

    1996-01-01

    An improved subranging or comparator circuit is provided for an analog-to-digital converter. As a subranging circuit, the circuit produces a residual signal representing the difference between an analog input signal and an analog of a digital representation. This is achieved by subdividing the digital representation into two or more parts and subtracting from the analog input signal analogs of each of the individual digital portions. In another aspect of the present invention, the subranging circuit comprises two sets of differential input pairs in which the transconductance of one differential input pair is scaled relative to the transconductance of the other differential input pair. As a consequence, the same resistor string may be used for two different digital-to-analog converters of the subranging circuit.

  8. Photometric properties of Mars soils analogs

    USGS Publications Warehouse

    Pommerol, A.; Thomas, N.; Jost, B.; Beck, P.; Okubo, C.; McEwen, A.S.

    2013-01-01

    We have measured the bidirectional reflectance of analogs of dry, wet, and frozen Martian soils over a wide range of phase angles in the visible spectral range. All samples were produced from two geologic samples: the standard JSC Mars-1 soil simulant and Hawaiian basaltic sand. In a first step, experiments were conducted with the dry samples to investigate the effects of surface texture. Comparisons with results independently obtained by different teams with similar samples showed a satisfying reproducibility of the photometric measurements as well as a noticeable influence of surface textures resulting from different sample preparation procedures. In a second step, water was introduced to produce wet and frozen samples and their photometry investigated. Optical microscope images of the samples provided information about their microtexture. Liquid water, even in relatively low amount, resulted in the disappearance of the backscattering peak and the appearance of a forward-scattering peak whose intensity increases with the amount of water. Specular reflections only appeared when water was present in an amount large enough to allow water to form a film at the surface of the sample. Icy samples showed a wide variability of photometric properties depending on the physical properties of the water ice. We discuss the implications of these measurements in terms of the expected photometric behavior of the Martian surface, from equatorial to circum-polar regions. In particular, we propose some simple photometric criteria to improve the identification of wet and/or icy soils from multiple observations under different geometries.

  9. Shallow normal fault slopes on Saturnian icy satellites

    NASA Astrophysics Data System (ADS)

    Beddingfield, Chloe B.; Burr, Devon M.; Dunne, William M.

    2015-12-01

    Fault dips are a function of the coefficient of internal friction, μi, of the lithospheric material. Laboratory deformation experiments of H2O ice at conditions applicable to icy bodies yield 0 ≤ μi ≤ 0.55 such that normal faults dip between 45° and 59°. We tested the hypothesis that normal faults on icy bodies reflect these values by using digital elevation models to examine geometries of large extensional systems on three Saturnian satellites. Analyzed faults within Ithaca Chasma on Tethys and Avaiki Chasmata on Rhea all exhibit shallower-than-predicted topographic slopes across the fault scarp, which we term "fault slopes." A scarp of Padua Chasmata within Dione's Wispy Terrain also has a shallow fault slope, although three others that make up Palatine Chasmata exhibit steeper slopes as predicted. We infer that viscous relaxation is the most viable explanation for these shallow fault slopes, and we model the potential role of viscous relaxation in creating shallow slopes. Our modeling results support formation of these normal faults with steep dips consistent with deformation experiments, followed by their relaxation due to lithospheric heating events related to radionuclide decay. The steepest fault slopes in this terrain yield 0 ≤ μi ≤ 0.73 for Dione's lithospheric ice, which overlaps the dip range predicted from experiments. Results of this work suggest that viscous relaxation substantially affected fault slopes on Tethys, Rhea, and Dione. By implication, these processes may have also affected fault geometries on other icy satellites.

  10. Impact Craters on Jupiter's Icy Moons as Astrobiological Targets

    NASA Astrophysics Data System (ADS)

    Bierhaus, E. B.; Lipps, J. H.

    2004-12-01

    Impact craters are prime astrobiological targets on icy moons with possible subsurface oceans. Craters are natural probes to subsurface materials; hence may sequester biologic signatures such as whole organisms, fossils, biochemicals, biomarkers, and biotextures. Craters expose a stratigraphic record. The closer to the crater center, the more deep-seated is the excavated material. All craters provide samples of the crust in the walls, overturned ice, and ejecta. Larger craters excavate deep interior ice in the central peaks, which may arise at the interface between solid ice and liquid water. The largest craters possess concentric rings, and flat floors that may be frozen water from under the icy shell that might expose information about the water column. Craters immediately deliver sub-surface materials to the surface, in contrast to endogenic processes (e.g. Europa) that likely operate over days to thousands or more years. The slower endogenic processes allow any extant life proactively to migrate from their habitats to other marginal regions or to die and degrade. Craters also offer unique habitats. A sub-surface "lens" of melt remains beneath the crater floor for up to thousands of years after impact. Life could rapidly exploit and abandon these habitats as they form and disappear, so these sub-surface melt-lenses may serve as rich - albeit temporary - locales of biological activity or repositories for fossils as they freeze. Although Europa displays the best evidence for a global ocean of the three icy Galilean satellites, Ganymede and Callisto also may have liquid water beneath their icy crusts. Ganymede, at least, bears evidence of an extensive geological history, which may have provided energy and habitats for biological processes. Though briny oceans (if they exist) are deeper beneath the icy crusts on Ganymede and Callisto than on Europa, the investigative principle largely remains the same. However, excavation to the deeply buried water requires larger

  11. Icy Dwarf Planets: Colored popsicles in the Solar System

    NASA Astrophysics Data System (ADS)

    Pinilla-Alonso, Noemi

    2015-08-01

    In 1992 the discovery of 1992 QB1 was the starting signal of a race to characterize the trans-Neptunian belt. The detection of icy “asteroids”, similar to Pluto, in the outer Solar System had been largely hypothesized but it had also being an elusive goal. This belt was considered by the planetary scientists as the icy promised land, the largest reservoir of primordial ices in the Solar System.From 1992 to 2005 about 1000 trans-Neptunian objects and Centaurs had been discovered and a lot of “first ever” science had been published: 1996 TO66, first ever detection of the water ice bands in a TNO's spectrum; 1998 WW31, first detection of a binary; first estimation of size and albedo from thermal and visible observations, Varuna; discovery of Sedna, at that moment “the coldest most distant place known in the Solar System”2005 was the year of the discovery of three large TNOs: (136108) Haumea, (136472) Makemake and (136199) Eris (a.k.a 2003 EL61, 2005 FY9 and 2003 UB313). These three big guys entered the schoolyard showing off as colored popsicles and making a clear statement: “We are special”, and sure they are!The discovery of these large TNOs resulted in 2006 in the adoption by the IAU of a new definition of planet and in the introduction of a new category of minor bodies: the “dwarf planets”. With only three members at this moment (although this can change anytime) the exclusive club of the icy dwarf planets is formed by the TNOs at the higher end of the size distribution. By virtue of their size and low surface temperatures, these bodies can retain most of their original inventory of ices. As a consequence, their visible and near-infrared spectra show evidences of water ice, nitrogen, methane and longer chains of hydrocarbons. Moreover, they have high geometric albedo in the visible. Also the accretional and radiogenic heating for these bodies was likely more than sufficient to have caused their internal differentiation.In this talk we will

  12. Experimental constraints on the chemical evolution of icy satellites

    SciTech Connect

    Scott, H P; Williams, Q; Ryerson, F J

    2000-01-18

    The inferred internal structure of large icy satellites hinges on the degree to which their rock component has been hydrated: this is due to the low density of hydrated silicates relative to anhydrous silicates. Accordingly, interior models of icy satellites have varied greatly in their estimates of ice thickness due to uncertainties in the density of the underlying rock. Furthermore, as both H{sub 2}O (potentially liquid) and organic materials are likely to be present, icy moons have been postulated to be possible hosts for extraterrestrial life; therefore, the stability of organic material under relevant hydrothermal conditions is an important issue. For example, Ganymede, Titan, and Triton are similar in that high pressure hydrothermal processing of silicates has likely been important in their chemical evolution. With mean densities between 1.8 and 2.1 g/cm{sup 3}, compositional models of these bodies incorporate approximately 50--80% silicate minerals by weight, with ices constituting the remaining mass. Moment of inertia constraints on the internal structure of Ganymede demonstrate that differentiation between rock and ice has occurred: such differentiation has also likely occurred in Titan and Triton. During accretion and differentiation (which could be ongoing), the silicate fraction of their interiors would have interacted with aqueous fluids at moderate to high temperatures and pressures. Indeed, a strong magnetic field appears to be generated by Ganymede implying that interior temperatures are high enough (in excess of 1,000 K) to maintain a liquid iron alloy in this satellite. High temperature/pressure hydrothermal processing at rock-water interfaces would profoundly influence the bulk mineralogy and internal structure of these bodies: the degree of hydration of the rocky fraction of these bodies has been a source of ongoing uncertainty. Surprisingly few phase equilibria data exist for compositions of relevance to hydrothermal interactions on icy

  13. Grain boundaries

    SciTech Connect

    Balluffi, R.W.; Bristowe, P.D.

    1991-01-01

    The present document is a progress report describing the work accomplished to date during the second year of our four-year grant (February 15, 1990--February 14, 1994) to study grain boundaries. The research was focused on the following three major efforts: Study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; study of short-circuit diffusion along grain boundaries; and development of a Thin-film Deposition/Bonding Apparatus for the manufacture of high purity bicrystals.

  14. Interstellar chemical differentiation across grain sizes

    NASA Astrophysics Data System (ADS)

    Ge, J. X.; He, J. H.; Li, Aigen

    2016-07-01

    In this work, we investigate the effects of ion accretion and size-dependent dust temperatures on the abundances of both gas-phase and grain-surface species. While past work has assumed a constant areal density for icy species, we show that this assumption is invalid and the chemical differentiation over grain sizes is significant. We use a gas-grain chemical code to demonstrate this numerically for two typical interstellar conditions: a dark cloud (DC) and a cold neutral medium (CNM). It is shown that, although the grain-size distribution variation (but with the total grain surface area unchanged) has little effect on the gas-phase abundances, it can alter the abundances of some surface species by up to ∼2-4 orders of magnitude. The areal densities of ice species are larger on smaller grains in the DC model as a consequence of ion accretion. However, the surface areal density evolution tracks are more complex in the CNM model due to the combined effects of ion accretion and dust temperature variation. The surface areal density differences between the smallest ( ∼ 0.01 μm) and the biggest ( ∼ 0.2 μm) grains can reach ∼1 and ∼5 orders of magnitude in the DC and CNM models, respectively.

  15. Modeling Spectra of Icy Satellites and Cometary Icy Particles Using Multi-Sphere T-Matrix Code

    NASA Astrophysics Data System (ADS)

    Kolokolova, Ludmilla; Mackowski, Daniel; Pitman, Karly M.; Joseph, Emily C. S.; Buratti, Bonnie J.; Protopapa, Silvia; Kelley, Michael S.

    2016-10-01

    The Multi-Sphere T-matrix code (MSTM) allows rigorous computations of characteristics of the light scattered by a cluster of spherical particles. It was introduced to the scientific community in 1996 (Mackowski & Mishchenko, 1996, JOSA A, 13, 2266). Later it was put online and became one of the most popular codes to study photopolarimetric properties of aggregated particles. Later versions of this code, especially its parallelized version MSTM3 (Mackowski & Mishchenko, 2011, JQSRT, 112, 2182), were used to compute angular and wavelength dependence of the intensity and polarization of light scattered by aggregates of up to 4000 constituent particles (Kolokolova & Mackowski, 2012, JQSRT, 113, 2567). The version MSTM4 considers large thick slabs of spheres (Mackowski, 2014, Proc. of the Workshop ``Scattering by aggregates``, Bremen, Germany, March 2014, Th. Wriedt & Yu. Eremin, Eds., 6) and is significantly different from the earlier versions. It adopts a Discrete Fourier Convolution, implemented using a Fast Fourier Transform, for evaluation of the exciting field. MSTM4 is able to treat dozens of thousands of spheres and is about 100 times faster than the MSTM3 code. This allows us not only to compute the light scattering properties of a large number of electromagnetically interacting constituent particles, but also to perform multi-wavelength and multi-angular computations using computer resources with rather reasonable CPU and computer memory. We used MSTM4 to model near-infrared spectra of icy satellites of Saturn (Rhea, Dione, and Tethys data from Cassini VIMS), and of icy particles observed in the coma of comet 103P/Hartley 2 (data from EPOXI/DI HRII). Results of our modeling show that in the case of icy satellites the best fit to the observed spectra is provided by regolith made of spheres of radius ~1 micron with a porosity in the range 85% - 95%, which slightly varies for the different satellites. Fitting the spectra of the cometary icy particles requires icy

  16. Cometary grains

    NASA Technical Reports Server (NTRS)

    Baum, William A.; Kreidl, Tobias J.; Schleicher, David G.

    1992-01-01

    CCD observations of cometary comas in the spectral continuum are reported. Radial brightness profiles of 14 comets and isophotal maps of three are presented. For 10 of the 14, the azimuthally averaged brightness in the vicinity of the nucleus falls off faster than rho exp -1, where rho is the projected radial distance from the nucleus in the plane of the sky. Simple modeling is used to show that radiation pressure alone cannot account for the observed departures from rho exp -1; it is postulated that the grains fade, i.e., decrease in albedo or size, while they glow outward. For only three of the comets no evidence was found of any grain fading at all. Cases with the most rapid grain fading occurred at small heliocentric distances, but so did some of the cases with no fading, from which large intrinsic differences from comet to comet in the nature of the grain population are inferred.

  17. Interstellar grains

    NASA Technical Reports Server (NTRS)

    Snow, T. P.

    1986-01-01

    There are few aspects of interstellar grains that can be unambiguously defined. Very little can be said that is independent of models or presuppositions; hence issues are raised and questions categorized, rather than providing definitive answers. The questions are issues fall into three general areas; the general physical and chemical nature of the grains; the processes by which they are formed and destroyed; and future observational approaches.

  18. Thermal Conductive Heat Transfer and Partial Melting of Volatiles in Icy Moons, Asteroids, and Kuiper Belt Objects (Invited)

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Furfaro, R.

    2013-12-01

    these processes result in transient thermal states and hence rapid evolution of icy body interiors. Interesting heat-flow phenomena (approximated as steady-state thermal states) have been modeled in volatile-rich main belt asteroids, Io, Europa, Enceladus, Titan, Pluto, and Makemake (2005 FY9). Thermal conditions can activate geologic processes, but the occurrence of geologic activity can fundamentally alter the thermal conductivity and elasticity of icy objects, which then further affects the distribution and type of subsequent geologic activity. For example, cryoclastic volcanism on Enceladus can increase solid-state greenhouse heating of the upper crust, reduce thermal conductivity, and increase retention of heat and spur further cryovolcanism. Sulfur extrusion on Io can produce low-thermal-conductivity flows, high thermal gradients, basal melting of the flows, and lateral extrusion and spreading of the flows or formation of solid-crusted lava lakes. Impact formation of regoliths and fine-grained dust deposits on large asteroids may generate local variations in thermal gradients. Interior heating and geologic activity can either (1) emplace low-conductivity materials on the surface and cause further interior heating, or (2) drive metamorphism, sintering, and volatile loss, and increase thermal conductivity and cool the object. Thus, the type and distribution of present-day geologic activity on icy worlds is dependent on geologic history. Geology begets geology.

  19. Photodesorption from low-temperature water ice in interstellar and circumsolar grains.

    PubMed

    Westley, M S; Baragiola, R A; Johnson, R E; Baratta, G A

    1995-02-01

    Dust grains in the interstellar medium and the outer Solar System commonly have a coating of water ice, which affects their optical properties and surface chemistry. The thickness of these icy mantles may be determined in part by the extent of photodesorption (photosputtering) by background ultraviolet radiation. But this process is poorly understood, with theoretical estimates of the photodesorption rate spanning several orders of magnitude. Here we report measurements of the absolute ultraviolet photodesorption yield of low-temperature water ice. Our results indicate that the rate of photodesorption is appreciable. In particular, it can account for the absence of icy mantles on grains in diffuse interstellar clouds, it exceeds solar-wind ion erosion and sublimation in the outer Solar System, and it is important in determining the lifetimes of icy mantles in dense molecular clouds.

  20. Surface Penetrating Radar Simulations for Jupiter's Icy Moons

    NASA Technical Reports Server (NTRS)

    Markus, Thorsten; Gogineni, S. P.; Green, J. L.; Reinisch, B. W.; Song, P.; Fung, S. F.; Benson, R. F.; Taylor, W. W. L.; Cooper, F.

    2003-01-01

    The icy moons of Jupiter (Europa, Callisto, and Ganymede) are of similar overall composition but show different surface features as a result of different sub-surface processes. Furthermore, each of these moons could have a liquid ocean of water buried underneath the icy crust, but their depth can only be speculated. For Europa, estimates put the thickness of the ice shell anywhere between 2-30 km, with'a few models predicting up to 100 km. Much of the uncertainties are due to the largely unknown temperature gradients and levels of water impurities across different surface layers. One of the most important geological processes is the possible transportation of heat by ice convection. If the ice is convecting, then an upper limit of about 20 km is set for the depth of the ocean underneath. Convection leads to a sharp increase in temperature followed by a thick region of nearly constant temperature. If ice is not convecting, then an exponentially increasing temperature profile is expected. The crust is thought to be a mixture of ice and rock, and although the exact percentage of rock is not known, it is expected to be low. Additionally, the ice crust could contain salt, similar to sea ice on Earth. The exact amount of salt and how that amount changes with depth is also unknown. In preparation for the Jupiter Icy Moons Orbiter (JIMO) mission, we performed simulations for a surface-penetrating radar investigating signatures for different possible surface and sub-surface structures of these moons in order to estimate the applicability of using radar with a frequency range between 1 and 50 MHz. This includes simulations of power requirements, attenuation losses, layer resolutions for scenarios with and without the presence of a liquid ocean underneath the ice, cases of convecting and non-convecting ice, different impurities within the ice, and different surface roughnesses.

  1. Europa's Icy Shell: A Bridge Between Its Surface and Ocean

    NASA Technical Reports Server (NTRS)

    Schenk, Paul; Mimmo, Francis; Prockter, Louise

    2004-01-01

    Europa, a Moon-sized, ice-covered satellite of Jupiter, is second only to Mars in its astrobiological potential. Beneath the icy surface, an ocean up to 150 km deep is thought to exist, providing a potential habitat for life,and a tempting target for future space missions. The Galileo mission to the Jovian system recently ended, but there are already long-range plans to send much more capable spacecraft,such as the proposed Jupiter Icy Moons Orbiter (JIMO), to take a closer look at Europa and her siblings, Ganymede and Callisto, some time in the next two decades. Europak outer icy shell is the only interface between this putative ocean and the surface, but many aspects of this shell are presently poorly understood; in particular, its composition, thickness, deformational history, and mechanical properties. To discuss the ice shell and our current understanding of it, 78 scientists from the terrestrial and planetary science communities in the United States and Europe gathered for a 3-day workshop hosted by the Lunar and Planetary Institute in Houston in February. A key goal was to bring researchers from disparate disciplines together to discuss the importance and limitations of available data on Europa with a post-Galileo perspective. The workshop featured 2 days of reviews and contributed talks on the composition, physical properties, stratigraphy, tectonics, and future exploration of the ice shell and underlying ocean. The final morning included an extended discussion period, moderated by a panel of noted experts, highlighting outstanding questions and areas requiring future research.

  2. Modeling Radar Scatter from Icy and Young Rough Lunar Craters

    NASA Technical Reports Server (NTRS)

    Thompson, Thomas (Tommy); Ustinov, Eugene; Spudis, Paul; Fessler, Brian

    2012-01-01

    For lunar orbital synthetic aperture radars, such as the Chandrayaan Mini-RF operating at S- band (13-cm) wavelength and the Lunar Reconnaissance Orbiter Mini-RF operating at S- band and X-band (3-cm) wavelengths, it is important to understand the radar backscattering characteristics of the icy and young, rough craters. Assuming a mixing model consisting of diffuse and quasi-specular scattering components, we have modeled the opposite-sense circular (OC) and same-sense circular (SC) backscattering characteristics. The specular component, consisting of only OC echoes, represents the echoes from the surface and subsurface layers that are oriented perpendicular to the radar's line-of-sight. The diffuse component, consisting of both SC and OC echoes, represents the echoes associated with either rocks or ice. Also, diffuse echoes have backscatter that is proportional to the cosine of the incidence angle. We modeled how these two (specular and diffuse) radar scattering components could be modulated by factors such as surface roughness associated with young craters. We also modeled how ice radar scattering components could be modulated by a thin regolith covering, and/or by the situation where ice occupies small patches within a larger radar pixel. We tested this modeling by examining 4 nonpolar craters and 12 polar craters using LRO Mini-RF data. Results indicate that icy and young rough craters can be distinguished based upon their SC enhancements (Alpha) and OC enhancements (Gamma). In addition, we also examined the craters that have unusual circular polarization ratios (CPRs) that likely result from a double bounce mode of scattering. Blocky fresh craters, icy craters, and craters exhibiting double bounce scattering can be separated based on the values of Alpha, Gamma, the ratio of Alpha/Gamma and the weighted sum of Alpha and Gamma.

  3. Sounding of Icy Galilean Satellites by Surface Observatories

    NASA Technical Reports Server (NTRS)

    Khurana, K. K.; Banerdt, W. B.; Johnson, T. V.; Russell, C. T.; Kivelson, M. G.; Davis, P. M.; Vidale, J. E.

    2001-01-01

    Several independent geological and geophysical investigations suggest that Europa and Ganymede contain subsurface oceans. Using Jupiter's rotating magnetic field as a primary signal, the magnetometer experiment onboard Galileo has measured secondary induction signals emanating from Europa, Ganymede, and surprisingly Callisto. The strong electromagnetic induction from these moons suggests that large global electrical conductors are located just below their icy crusts. A detailed analysis reveals that global salty oceans with salinity similar to the Earth's ocean and thicknesses in the range of approx. 6-100 kms can explain the induction observed by the Galileo magnetometer. Additional information is contained in the original extended abstract.

  4. Evolution of topography on comets. II - Icy craters and trenches

    NASA Astrophysics Data System (ADS)

    Colwell, J. E.; Jakosky, B. M.; Sandor, B. J.; Stern, S. A.

    1990-05-01

    The determination of the effects of topography on the sublimation rates of comets and other icy bodies is presently approached via a model of ice heating and sublimation from topographical features. The energy balance equation is solved for cylindrical trenches and spherical craters; the model encompasses shadowing, solar heating, the trapping of thermal radiation and sublimed gas molecules, and reflection of sunlight within the cavity. Generally, an enhancement is found in the net sublimation rate for trenches and craters farther from the sun than some critical distance which depends on the albedo.

  5. A Power Conversion Concept for the Jupiter Icy Moons Orbiter

    NASA Technical Reports Server (NTRS)

    Mason, Lee S.

    2003-01-01

    The Jupiter Icy Moons Orbiter (JIMO) is a bold new mission under development by the Office of Space Science at NASA Headquarters. ITMO is examining the potential of Nuclear Electric Propulsion (NEP) technology to efficiently deliver scientific payloads to three Jovian moons: Callisto, Ganymede, and Europa. A critical element of the NEP vehicle is the reactor power system, consisting of the nuclear reactor, power conversion, heat rejection, and power management and distribution (PMAD). The emphasis of this paper is on the non-nuclear elements of the reactor power system.

  6. Ion pick-up near the icy Galilean satellites

    NASA Astrophysics Data System (ADS)

    Volwerk, M.; Khurana, K. K.

    2010-12-01

    The ion pick-up near the icy Galilean satellites is studied using ion cyclotron waves. Using Galileo magnetometer data, we show evidence for the existence of ion cyclotron waves, which are generated by pick-up of freshly ionized particles. Near Europa, in the wake various kinds of ions are detected, which were already predicted to be present on the moon. Upstream of the moon there is evidence for water ion pick-up, which could facilitate the slow down of the plasma flow. Ganymede shows evidence for either water or oxygen pick up on the flanks of the magnetosphere. Callisto shows indication of hydrogen pick-up from its atmosphere.

  7. Radioactive Decay - An Analog.

    ERIC Educational Resources Information Center

    McGeachy, Frank

    1988-01-01

    Presents an analog of radioactive decay that allows the student to grasp the concept of half life and the exponential nature of the decay process. The analog is devised to use small, colored, plastic poker chips or counters. Provides the typical data and a graph which supports the analog. (YP)

  8. Investigation of Celestial Solid Analogs

    NASA Technical Reports Server (NTRS)

    Sievers, A. J.

    2003-01-01

    Our far infrared studies of both hydrophobic and hydrophilic aerogel grains have demonstrated that the mm and sub-mm wave absorption produced by the fundamental two level systems (TLS) mechanism represents a more significant contribution for these open grain structures than for bulk amorphous silicate grains. We found that the region with the anomalous temperature dependence of the spectral index due to the TLS excitations can extend in a fluffy material up to 80 per cm, which is well beyond its typical upper limit for bulk glasses. Currently there is no theoretical explanation for this surprising result. The effects of reduced dimensionality on the optical properties of carbonaceous grains have been studied with a systematic investigation of carbon aerogels. This spectroscopic approach has permitted a more reliable determination of the single grain mass normalized absorption coefficient based on the experimentally determined characteristics of the fluffy material rather than on first principles calculations involving the bulk properties of the substance. Our finding is that the electrical connectivity of the material is the main factor affecting its far infrared absorption coefficient. Another one of the main constituents of the interstellar dust, amorphous ice, has been investigated in the mm-wave region both in the high (HDA) and low (LDA) density amorphous phases and as a function of impurities. We found that doping either phase with ionic (LiCl) or molecular (methanol) impurities decreases the difference in the mm-wave absorption coefficient between the HDA and LDA ice phases so that the HDA spectrum can be used as an analog for impure ice absorption in the far infrared spectral region.

  9. Measurements of the organic composition of cometary grains with the COSIMA TOF-SIMS instrument onboard the ROSETTA spacecraft

    NASA Astrophysics Data System (ADS)

    Cottin, H.; Le Roy, L.; Briani, G.; Bardyn, A.; Briois, C.; Fray, N.; Thirkell, L.; Engrand, C.; Hilchenbach, M.

    2013-12-01

    , polycyclic aromatic hydrocarbons, amino acids...) has been prepared on ground instruments similar to the space COSIMA instrument. We also tested the analytical capabilities of COSIMA on laboratory analogs of cometary organic matter synthesized from heating and/or photolysis of icy mixtures (inspired from the classical Greenberg yellow stuff experiments), as well as on natural proxy such as insoluble organic matter from carbonaceous chondrites (Murchison & Orgueil) and kerogen. This talk will show the hopes and limitations in term of analytical capabilities of the COSIMA instrument, and the expected science return for our understanding of the origin of comets and their astrobiological relevance.

  10. Interplanetary Dust Particles as Samples of Icy Asteroids

    NASA Astrophysics Data System (ADS)

    Vernazza, P.; Marsset, M.; Beck, P.; Binzel, R. P.; Birlan, M.; Brunetto, R.; Demeo, F. E.; Djouadi, Z.; Dumas, C.; Merouane, S.; Mousis, O.; Zanda, B.

    2015-06-01

    Meteorites have long been considered as reflections of the compositional diversity of main belt asteroids and consequently they have been used to decipher their origin, formation, and evolution. However, while some meteorites are known to sample the surfaces of metallic, rocky and hydrated asteroids (about one-third of the mass of the belt), the low-density icy asteroids (C-, P-, and D-types), representing the rest of the main belt, appear to be unsampled in our meteorite collections. Here we provide conclusive evidence that the surface compositions of these icy bodies are compatible with those of the most common extraterrestrial materials (by mass), namely anhydrous interplanetary dust particles (IDPs). Given that these particles are quite different from known meteorites, it follows that the composition of the asteroid belt consists largely of more friable material not well represented by the cohesive meteorites in our collections. In the light of our current understanding of the early dynamical evolution of the solar system, meteorites likely sample bodies formed in the inner region of the solar system (0.5-4 AU) whereas chondritic porous IDPs sample bodies that formed in the outer region (>5 AU).

  11. Prebiotic chemistry within a simple impacting icy mixture.

    PubMed

    Goldman, Nir; Tamblyn, Isaac

    2013-06-20

    We present results of prebiotic organic synthesis in shock compressed mixtures of simple ices from quantum molecular dynamics (MD) simulations extended to close to equilibrium time scales. Given the likelihood of an inhospitable prebiotic atmosphere on early Earth, it is possible that impact processes of comets or other icy bodies were a source of prebiotic chemical compounds on the primitive planet. We observe that moderate shock pressures and temperatures within a CO2-rich icy mixture (36 GPa and 2800 K) produce a number of nitrogen containing heterocycles, which dissociate to form functionalized aromatic hydrocarbons upon expansion and cooling to ambient conditions. In contrast, higher shock conditions (48-60 GPa, 3700-4800 K) resulted in the synthesis of long carbon-chain molecules, CH4, and formaldehyde. All shock compression simulations at these conditions have produced significant quantities of simple C-N bonded compounds such as HCN, HNC, and HNCO upon expansion and cooling to ambient conditions. Our results elucidate a mechanism for impact synthesis of prebiotic molecules at realistic impact conditions that is independent of external constraints such as the presence of a catalyst, illuminating UV radiation, or pre-existing conditions on a planet. PMID:23639050

  12. The icy Jovian satellites after the Galileo mission

    NASA Astrophysics Data System (ADS)

    Greenberg, Richard

    2010-03-01

    The icy satellites of Jupiter, Callisto, Ganymede, Europa and Amalthea have diverse and remarkable characteristics. Their initial compositions were determined by conditions in the circum-Jovian nebula, just as the planets' initial properties were governed by their formation within the circumsolar nebula. The satellites subsequently evolved under the complex interplay of orbital and geophysical processes, especially the effects of orbital resonances, tides, internal differentiation and heat. The history and character of the satellites can be inferred from consideration of the formation of planets and the satellites, from studies of their plausible orbital evolution, from measurements of geophysical properties, especially gravitational and magnetic fields, from observations of the compositions and geological structure of their surfaces and from theoretical modeling of the processes that connect these lines of evidence. The three large icy satellites probably contain significant liquid water: Europa has a deep liquid water ocean under a thin surface layer of ice; Ganymede and Callisto likely have relatively thin liquid water layers deep below their surfaces. Models of formation are challenged by the surprising properties of the outermost and innermost of the group: Callisto is partially differentiated, with rock and ice mixed through much of its interior; and tiny Amalthea also appears to be largely composed of ice. Each of the four moons is fascinating in its own right, and the ensemble provides a powerful set of constraints on the processes that led to their formation and evolution.

  13. BENZENE FORMATION ON INTERSTELLAR ICY MANTLES CONTAINING PROPARGYL ALCOHOL

    SciTech Connect

    Sivaraman, B.; Mukherjee, R.; Subramanian, K. P.; Banerjee, S. B.

    2015-01-10

    Propargyl alcohol (CHCCH{sub 2}OH) is a known stable isomer of the propenal (CH{sub 2}CHCHO) molecule that was reported to be present in the interstellar medium (ISM). At astrochemical conditions in the laboratory, icy layers of propargyl alcohol grown at 85 K were irradiated by 2 keV electrons and probed by a Fourier Transform InfraRed spectrometer in the mid-infrared (IR) region, 4000-500 cm{sup –1}. Propargyl alcohol ice under astrochemical conditions was studied for the first time; therefore, IR spectra of reported amorphous (85 K) and crystalline (180 K) propargyl alcohol ices can be used to detect its presence in the ISM. Moreover, our experiments clearly show benzene (C{sub 6}H{sub 6}) formation to be the major product from propargyl alcohol irradiation, confirming the role of propargyl radicals (C{sub 3}H{sub 3}) formed from propargyl alcohol dissociation that was long expected based on theoretical modeling to effectively synthesize C{sub 6}H{sub 6} in the interstellar icy mantles.

  14. Oceans and Internal Structures of the Large Icy Satellites

    NASA Astrophysics Data System (ADS)

    Vance, S.; Brown, J.; Choukroun, M.; Sotin, C.

    2013-12-01

    We predict water ice freezing and constrain geothermal gradients in the interiors of the large icy satellites Ganymede, Callisto, and Titan using thermodynamic and phase-boundary data for MgSO4 and ammonia solutions, including new results for ammonia. Accounting for available measurements of gravitational moments of inertia leads to estimates of the depths to silicate boundaries. In the case of Ganymede we also compute the size of an iron-bearing core. The new equations of state allow us to assess the influence of ocean salinity on the thickness of layers of ice I-III-V-VI in the interiors of these objects, and on associated ocean dynamics. Ocean compositions with salt and ammonia have less high-pressure ice, and can exist in the presence of ice III. In some model oceans high-pressure ice phases become buoyant relative to surrounding fluids, implying frazil-like upward snows, interlayered liquids and ices, and fluids in direct contact with rock. We discuss the relative roles of dissolved constituents in the large icy satellites, the consequences for their habitability, and prospects of future missions for testing these predictions. Schematic of interior structure for Ganymede showing dense fluids under high pressure ices and directly in contact with rock. We use available thermodynamic properties for relevant fluids and solids materials us to calculate self-consistent depths for the various layers (approximate values shown here).

  15. Benzene Formation on Interstellar Icy Mantles Containing Propargyl Alcohol

    NASA Astrophysics Data System (ADS)

    Sivaraman, B.; Mukherjee, R.; Subramanian, K. P.; Banerjee, S. B.

    2015-01-01

    Propargyl alcohol (CHCCH2OH) is a known stable isomer of the propenal (CH2CHCHO) molecule that was reported to be present in the interstellar medium (ISM). At astrochemical conditions in the laboratory, icy layers of propargyl alcohol grown at 85 K were irradiated by 2 keV electrons and probed by a Fourier Transform InfraRed spectrometer in the mid-infrared (IR) region, 4000-500 cm-1. Propargyl alcohol ice under astrochemical conditions was studied for the first time; therefore, IR spectra of reported amorphous (85 K) and crystalline (180 K) propargyl alcohol ices can be used to detect its presence in the ISM. Moreover, our experiments clearly show benzene (C6H6) formation to be the major product from propargyl alcohol irradiation, confirming the role of propargyl radicals (C3H3) formed from propargyl alcohol dissociation that was long expected based on theoretical modeling to effectively synthesize C6H6 in the interstellar icy mantles.

  16. Very High Resolution Image of Icy Cliffs on Europa

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This image, taken by the camera onboard NASA's Galileo spacecraft, is a very high resolution view of the Conamara Chaos region on Jupiter's moon Europa. It shows an area where icy plates have been broken apart and moved around laterally. The top of this image is dominated by corrugated plateaus ending in icy cliffs over a hundred meters (a few hundred feet) high. Debris piled at the base of the cliffs can be resolved down to blocks the size of a house. A fracture that runs horizontally across and just below the center of the Europa image is about the width of a freeway.

    North is to the top right of the image, and the sun illuminates the surface from the east. The image is centered at approximately 9 degrees north latitude and 274 degrees west longitude. The image covers an area approximately 1.7 kilometers by 4 kilometers (1 mile by 2.5 miles). The resolution is 9 meters (30 feet) per picture element. This image was taken on December 16, 1997 at a range of 900 kilometers (540 miles) by Galileo's solid state imaging system.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

  17. Chemical Processes in the Icy Plumes of Enceladus

    NASA Astrophysics Data System (ADS)

    Boice, D. C.; Goldstein, R.

    2012-12-01

    The icy plumes from Saturn's moon Enceladus are unusual phenomena that have raised several challenging questions about the relationship of this small satellite to its surrounding environment. In addition, they offer a unique window to probe the interior structure and composition of this icy satellite. Measurements of the neutral and ion composition of the plumes by instruments aboard Cassini reveal the presence of water group species, nitrogen-bearing molecules, and other species that are the major volatiles in cometary ices. Our cometary coma model with chemistry (SUISEI) has been adapted to study this problem. SUISEI produces abundances of the gas species; velocities of the bulk gas, light atomic and molecular hydrogen with escape, and electrons; gas and electron temperatures; column densities to facilitate comparison with observations; energy budget quantities; attenuation of the solar irradiance; and other quantities that can be related readily to the in situ measurements. Likely ion-molecule chemistry and other issues are discussed to gain a perspective on our current understanding of Enceladus. Acknowledgements: We acknowledge funding and support from the SwRI Internal Research and Development Program, the NASA Cassini (CAPS) Mission, and the NSF Planetary Astronomy Program.

  18. Experimental impact shock chemistry on planetary icy satellites

    NASA Astrophysics Data System (ADS)

    Nna-Mvondo, Delphine; Khare, Bishun; Ishihara, Tomoko; McKay, Christopher P.

    2008-04-01

    We present new experimental results on impact shock chemistry into icy satellites of the outer planets. Icy mixtures of pure water ice with CO 2, Na 2CO 3, CH 3OH, and CH 3OH/(NH 4) 2SO 4 at 77 K were ablated with a powerful pulsed laser—a new technique used to simulate shock processes which can occur during impacts. New products were identified by GC-MS and FTIR analyses after laser ablation. Our results show that hydrogen peroxide is formed in irradiated H 2O/CO 2 ices with a final concentration of 0.23%. CO and CH 3OH were also detected as main products. The laser ablation of frozen H 2O/Na 2CO 3 generates only CO and CO 2 as destruction products from the salt. Pulsed irradiation of water ice containing methanol leads also to the formation of CO and CO 2, generates methane and more complex molecules containing carbonyl groups like acetaldehyde, acetone, methyl formate, and a diether, dimethyl formal. The last three compounds are also produced when adding ammonium sulfate to H 2O/CH 3OH ice, but acetone is more abundant. The formation of two hydrocarbons, CH 4 and C 2H 6 is observed as well as the production of three nitrogen compounds, nitrous oxide, hydrogen cyanide, and acetonitrile.

  19. Emergence of Habitable Environments in Icy World Interiors

    NASA Astrophysics Data System (ADS)

    Neveu, Marc

    2016-07-01

    Finding habitable worlds is a key driver of solar system exploration. Many solar system missions seek environments providing liquid water, energy, and nutrients, the three ingredients necessary to sustain life [1]. Such environments include hydrothermal systems, spatially confined systems where hot aqueous fluid circulates through rock by convection. Hydrothermal activity may be widespread in the solar system. Most solar system worlds larger than 200 km in radius are icy moons and dwarf planets, likely composed of an icy, cometary mantle surrounding a rocky, chondritic core [2]. By improving an icy world evolution code [3] to include the effects of core fracturing and hydrothermal circulation, I show that several icy moons and dwarf planets likely have undergone extensive water-rock interaction [4,5]. This supports observations of aqueous products on their surfaces [6,7]. I simulated the alteration of chondritic rock [8] by pure water or fluid of cometary composition [9] to show that aqueous alteration feeds back on geophysical evolution: it modifies the fluid antifreeze content, affecting its persistence over geological timescales; and the distribution of radionuclides, whose decay is a chief heat source on dwarf planets [10]. Hydrothermal circulation also efficiently transports heat from the core into the ocean, thereby increasing ocean persistence [4]. Thus, these coupled geophysical-geochemical models provide a comprehensive picture of icy world evolution and the emergence of liquid environments in chemical disequilibrium with underlying rock in their interiors. Habitable settings also require a suitable supply of bioessential elements; but what constitutes "suitable"? I sought to quantify the bulk elemental composition of hydrothermal microbial communities, collected in hot spring sediments and mats at Yellowstone National Park, USA. To do so, one must minimize the contribution of non-biological material to the samples analyzed. This was achieved using a

  20. Comparative relief-forming potential of rocky terrestrial planets and icy saturnian satellites

    NASA Astrophysics Data System (ADS)

    Kochemasov, G. G.

    2009-04-01

    Comparative relief-forming potential of rocky terrestrial planets and icy saturnian satellites. G. Kochemasov IGEM of the Russian Academy of Sciences, Moscow, Russia, kochem.36@mail.ru The wave planetology [1-3 & others] states that "orbits make structures". Its third theorem ("Celestial bodies are granular") is to say that sizes of tectonic granules are inversely proportional to orbital frequencies: higher frequency - smaller granule, and vice versa, lower frequency - larger granule. Thus, Mercury is very fine-grained, Venus fine-grained, Earth medium-grained, Mars coarse-grained. The following row of granule sizes confirms it: Mercury πR/16, Venus πR/6, Earth πR/4, Mars πR/2 (R-a planet radius). A geometrical model of this presents a circle with inscribed in it standing waves: for Mercury 16 waves, for Venus 6 waves, for Earth 4 waves (a cross!), for Mars 2 waves [4]. This geometrization is rather descriptive as it shows how waves amplitudes increase with the Solar distance and oscillations around a circle (wave heights) can be measured [5]. These heights are as follows: Mercury 2πR/64.08, Venus 2πR/24.34, Earth 2πR/16.44, Mars 2πR/8.8. These heights reduced to the Earth's one (taken as 1) are as follows: Mercury 0.256, Venus 0.675, Earth 1.0, Mars 1.868. Now we are looking at the real relief ranges (spans). They are as follows in km: Mercury ~5 (a bit less than 5 km according to one laser altimetry profile by Messenger spacecraft in 2007), Venus ~14, Earth ~20, Mars ~30. This last figure may be increased by heights of collapsed cones of huge marcian volcanoes having calderas radii 40-50 km and presumed slope angle 5-6 degrees that gives additional 4-5 km for the martian relief range making it ~35 km. Taking the Earth range as 1, one gets the following row of relative heights: Mercury 0.25, Venus 0.7, Earth 1.0, Mars 1.75. Comparing two rows of relative heights (theoretic and real) one sees that they are rather similar: Mercury 0.256 (0.25), Venus 0

  1. An Icy Kuiper Belt Around the Young Solar-type Star HD 181327

    NASA Technical Reports Server (NTRS)

    Lebreton, J.; Augereau, J.-C.; Thi, W.-F.; Roberge, A.; Donaldson, J; Schneider, G.; Maddison, S. T.; Menard, F.; Riviere-Marichalar, P.; Matthews, G. S.; Kamp, I.; Pinte, C.; Dent, W. R. F.; Barrado, D.; Duchene, G.; Gonzalez, J.-F.; Grady C. A.; Meeus,G.; Pantin, E.; Williams, J. P.; Woitke, P.

    2012-01-01

    Context. HD 181327 is a young main sequence F5/F6 V star belonging to the Beta Pictoris moving group (age approx.. 12 Myr). It harbors an optically thin belt of circumstellar material at radius approx.. 90 AU, presumed to result from collisions in a population of unseen planetesimals. Aims. We aim to study the dust properties in the belt in details, and to constrain the gas-to-dust ratio. Methods. We obtained far-infrared photometric observations of HD 181327 with the PACS instrument onboard the Herschel Space Observatory, complemented by new 3.2 mm observations carried with the ATCA array. The geometry of the belt is constrained with newly reduced HST/NICMOS scattered light images that allow the degeneracy between the disk geometry and the dust properties to be broken. We then use the radiative transfer code GRaTeR to compute a large grid of models, and we identify the grain models that best reproduce the spectral energy distribution (SED) through a Bayesian analysis. We attempt to detect the oxygen and ionized carbon fine-structure lines with Herschel/PACS spectroscopy, providing observables to our photochemical code ProDiMo. Results. The HST observations confirm that the dust is confined in a narrow belt. The continuum is detected with Herschel/PACS completing nicely the SED in the far-infrared. The disk is marginally resolved with both PACS and ATCA. A medium integration of the gas spectral lines only provides upper limits on the [OI] and [CII] line fluxes.We show that the HD 181327 dust disk consists of micron-sized grains of porous amorphous silicates and carbonaceous material surrounded by an important layer of ice, for a total dust mass of approx.. 0.05 Solar Mass (in grains up to 1 mm). We discuss evidences that the grains consists of fluffy aggregates. The upper limits on the gas atomic lines do not provide unambiguous constraints: only if the PAH abundance is high, the gas mass must be lower than approx. 17 Solar Mass. Conclusions. Despite the weak

  2. Dielectric properties of Jovian satellite ice analogs for subsurface radar exploration: A review

    NASA Astrophysics Data System (ADS)

    Pettinelli, Elena; Cosciotti, Barbara; Di Paolo, Federico; Lauro, Sebastian Emanuel; Mattei, Elisabetta; Orosei, Roberto; Vannaroni, Giuliano

    2015-09-01

    The first European mission dedicated to the exploration of Jupiter and its icy moons (JUpiter ICy moons Explorer—JUICE) will be launched in 2022 and will reach its final destination in 2030. The main goals of this mission are to understand the internal structure of the icy crusts of three Galilean satellites (Europa, Ganymede, and Callisto) and, ultimately, to detect Europa's subsurface ocean, which is believed to be the closest to the surface among those hypothesized to exist on these moons. JUICE will be equipped with the 9 MHz subsurface-penetrating radar RIME (Radar for Icy Moon Exploration), which is designed to image the ice down to a depth of 9 km. Moreover, a parallel mission to Europa, which will host onboard REASON (Radar for Europa Assessment and Sounding: Ocean to Near-surface) equipped with 9MHz and 60MHz antennas, has been recently approved by NASA. The success of these experiments strongly relies on the accurate prediction of the radar performance and on the optimal processing and interpretation of radar echoes that, in turn, depend on the dielectric properties of the materials composing the icy satellite crusts. In the present review we report a complete range of potential ice types that may occur on these icy satellites to understand how they may affect the results of the proposed missions. First, we discuss the experimental results on pure and doped water ice in the framework of the Jaccard theory, highlighting the critical aspects in terms of a lack of standard laboratory procedures and inconsistency in data interpretation. We then describe the dielectric behavior of extraterrestrial ice analogs like hydrates and icy mixtures, carbon dioxide ice and ammonia ice. Building on this review, we have selected the most suitable data to compute dielectric attenuation, velocity, vertical resolution, and reflection coefficients for such icy moon environments, with the final goal being to estimate the potential capabilities of the radar missions as a

  3. 76 FR 21330 - Lynn Canal/Icy Straits Resource Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-15

    ... Forest Service Lynn Canal/Icy Straits Resource Advisory Committee AGENCY: Forest Service, USDA. ACTION: Notice of meeting. SUMMARY: The Lynn Canal/Icy Straits Resource Advisory Committee will meet in Juneau... National Monument Office, 8510 Mendenhall Loop Road, Juneau, Alaska. Send written comments to Lynn...

  4. Cost-Effective Icy Bodies Exploration using Small Satellite Missions

    NASA Technical Reports Server (NTRS)

    Jonsson, Jonas; Mauro, David; Stupl, Jan; Nayak, Michael; Aziz, Jonathan; Cohen, Aaron; Colaprete, Anthony; Dono-Perez, Andres; Frost, Chad; Klamm, Benjamin; McCafferty, Julian; McKay, Chris; Sears, Derek; Soulage, Michael; Swenson, Jason; Weston, Sasha; Yang Yang, Fan

    2015-01-01

    It has long been known that Saturn's moon Enceladus is expelling water-rich plumes into space, providing passing spacecraft with a window into what is hidden underneath its frozen crust. Recent discoveries indicate that similar events could also occur on other bodies in the solar system, such as Jupiter's moon Europa and the dwarf planet Ceres in the asteroid belt. These plumes provide a possible giant leap forward in the search for organics and assessing habitability beyond Earth, stepping stones toward the long-term goal of finding extraterrestrial life. The United States Congress recently requested mission designs to Europa, to fit within a cost cap of $1B, much less than previous mission designs' estimates. Here, innovative cost-effective small spacecraft designs for the deep-space exploration of these icy worlds, using new and emerging enabling technologies, and how to explore the outer solar system on a budget below the cost horizon of a flagship mission, are investigated. Science requirements, instruments selection, rendezvous trajectories, and spacecraft designs are some topics detailed. The mission concepts revolve around a comparably small-sized and low-cost Plume Chaser spacecraft, instrumented to characterize the vapor constituents encountered on its trajectory. In the event that a plume is not encountered, an ejecta plume can be artificially created by a companion spacecraft, the Plume Maker, on the target body at a location timed with the passage of the Plume Chaser spacecraft. Especially in the case of Ceres, such a mission could be a great complimentary mission to Dawn, as well as a possible future Europa Clipper mission. The comparably small volume of the spacecraft enables a launch to GTO as a secondary payload, providing multiple launch opportunities per year. Plume Maker's design is nearly identical to the Plume Chaser, and fits within the constraints for a secondary payload launch. The cost-effectiveness of small spacecraft missions enables the

  5. The Global Contribution of Secondary Craters on the Icy Satellites

    NASA Astrophysics Data System (ADS)

    Hoogenboom, T.; Johnson, K. E.; Schenk, P.

    2014-12-01

    At present, surface ages of bodies in the Outer Solar System are determined only from crater size-frequency distributions (a method dependent on an understanding of the projectile populations responsible for impact craters in these planetary systems). To derive accurate ages using impact craters, the impactor population must be understood. Impact craters in the Outer Solar System can be primary, secondary or sesquinary. The contribution of secondary craters to the overall population has recently become a "topic of interest." Our objective is to better understand the contribution of dispersed secondary craters to the small crater populations, and ultimately that of small comets to the projectile flux on icy satellites in general. We measure the diameters of obvious secondary craters (determined by e.g. irregular crater shape, small size, clustering) formed by all primary craters on Ganymede for which we have sufficiently high resolution data to map secondary craters. Primary craters mapped range from approximately 40 km to 210 km. Image resolution ranges from 45 to 440 m/pixel. Bright terrain on Ganymede is our primary focus. These resurfaced terrains have relatively low crater densities and serve as a basis for characterizing secondary populations as a function of primary size on an icy body for the first time. Although focusing on Ganymede, we also investigate secondary crater size, frequency, distribution, and formation, as well as secondary crater chain formation on icy satellites throughout the Saturnian and Jovian systems principally Rhea. We compare our results to similar studies of secondary cratering on the Moon and Mercury. Using Galileo and Voyager data, we have identified approximately 3,400 secondary craters on Ganymede. In some cases, we measured crater density as a function of distance from a primary crater. Because of the limitations of the Galileo data, it is necessary to extrapolate from small data sets to the global population of secondary craters

  6. JUICE: A European Mission to Jupiter and its Icy Moons

    NASA Astrophysics Data System (ADS)

    Grasset, Olivier; Witasse, Olivier; Barabash, Stas; Brandt, Pontus; Bruzzone, Lorenzo; Bunce, Emma; Cecconi, Baptiste; Cavalié, Thibault; Cimo, Giuseppe; Coustenis, Athena; Cremonese, Gabriele; Dougherty, Michele; Fletcher, Leigh N.; Gladstone, Randy; Gurvits, Leonid; Hartogh, Paul; Hoffmann, Holger; Hussmann, Hauke; Iess, Luciano; Jaumann, Ralf; Kasaba, Yasumasa; Kaspi, Yohai; Krupp, Norbert; Langevin, Yves; Mueller-Wodarg, Ingo; Palumbo, Pasquale; Piccioni, Giuseppe; Plaut, Jeffrey; Poulet, Francois; Roatsch, Thomas; Retherford, Kurt D.; Rothkaehl, Hanna; Stevenson, David J.; Tosi, Federico; Van Hoolst, Tim; Wahlund, Jan-Erik; Wurz, Peter; Altobelli, Nicolas; Accomazzo, A.; Boutonnet, Arnaud; Erd, Christian; Vallat, Claire

    2016-10-01

    JUICE - JUpiter ICy moons Explorer - is the first large mission in the ESA Cosmic Vision programme [1]. The implementation phase started in July 2015. JUICE will arrive at Jupiter in October 2029, and will spend 3 years characterizing the Jovian system, the planet itself, its giant magnetosphere, and the giant icy moons: Ganymede, Callisto and Europa. JUICE will then orbit Ganymede.The first goal of JUICE is to explore the habitable zone around Jupiter [2]. Ganymede is a high-priority target because it provides a unique laboratory for analyzing the nature, evolution and habitability of icy worlds, including the characteristics of subsurface oceans, and because it possesses unique magnetic fields and plasma interactions with the environment. On Europa, the focus will be on recently active zones, where the composition, surface and subsurface features (including putative water reservoirs) will be characterized. Callisto will be explored as a witness of the early Solar System.JUICE will also explore the Jupiter system as an archetype of gas giants. The circulation, meteorology, chemistry and structure of the Jovian atmosphere will be studied from the cloud tops to the thermosphere and ionosphere. JUICE will investigate the 3D properties of the magnetodisc, and study the coupling processes within the magnetosphere, ionosphere and thermosphere. The mission also focuses on characterizing the processes that influence surface and space environments of the moons.The payload consists of 10 instruments plus a ground-based experiment (PRIDE) to better constrain the S/C position. A remote sensing package includes imaging (JANUS) and spectral-imaging capabilities from UV to sub-mm wavelengths (UVS, MAJIS, SWI). A geophysical package consists of a laser altimeter (GALA) and a radar sounder (RIME) for exploring the moons, and a radio science experiment (3GM) to probe the atmospheres and to determine the gravity fields. The in situ package comprises a suite to study plasma and

  7. Analog, still without fear

    NASA Astrophysics Data System (ADS)

    Delagrange, A. D.

    1984-09-01

    This report is an update of one issued in 1977 which predicted that the predicted death of analog circuitry (also called linear) would not occur; in fact, the patient appeared remarkably healthy. The report proved correct. We have the same situation again today: the same predictions and counter-prediction. Each year brings significant advances in the field of analog integrated circuitry. Many of the traditional arguments against analog circuitry are no longer valid. This report attempts to summarize what is available now, and what can (and cannot) be done with analog integrated circuits. It defines analog and makes some comparisons with digital. The most common types of analog integrated circuits are then listed and discussed. Lastly, some design and trouble-shooting hints are given, and the state-of-the-art is discussed.

  8. Saturn's icy satellites investigated by Cassini-VIMS. II. Results at the end of nominal mission

    USGS Publications Warehouse

    Filacchione, G.; Capaccioni, F.; Clark, R.N.; Cuzzi, J.N.; Cruikshank, D.P.; Coradini, A.; Cerroni, P.; Nicholson, P.D.; McCord, T.B.; Brown, R.H.; Buratti, B.J.; Tosi, F.; Nelson, R.M.; Jaumann, R.; Stephan, K.

    2010-01-01

    We report the detailed analysis of the spectrophotometric properties of Saturn's icy satellites as derived by full-disk observations obtained by visual and infrared mapping spectrometer (VIMS) experiment aboard Cassini. In this paper, we have extended the coverage until the end of the Cassini's nominal mission (June 1st 2008), while a previous paper (Filacchione, G., and 28 colleagues [2007]. Icarus 186, 259-290, hereby referred to as Paper I) reported the preliminary results of this study. During the four years of nominal mission, VIMS has observed the entire population of Saturn's icy satellites allowing us to make a comparative analysis of the VIS-NIR spectral properties of the major satellites (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus) and irregular moons (Atlas, Prometheus, Pandora, Janus, Epimetheus, Telesto, Calypso, Phoebe). The results we discuss here are derived from the entire dataset available at June 2008 which consists of 1417 full-disk observations acquired from a variety of distances and inclinations from the equatorial plane, with different phase angles and hemispheric coverage. The most important spectrophotometric indicators (as defined in Paper I: I/F continua at 0.55 ??m, 1.822 ??m and 3.547 ??m, visible spectral slopes, water and carbon dioxide bands depths and positions) are calculated for each observation in order to investigate the disk-integrated composition of the satellites, the distribution of water ice respect to "contaminants" abundances and typical regolith grain properties. These quantities vary from the almost pure water ice surfaces of Enceladus and Calypso to the organic and carbon dioxide rich Hyperion, Iapetus and Phoebe. Janus visible colors are intermediate between these two classes having a slightly positive spectral slope. These results could help to decipher the origins and evolutionary history of the minor moons of the Saturn's system. We introduce a polar representation of the spectrophotometric

  9. Interpretation of spectrophotometric surface properties of comet 67P/Churyumov-Gerasimenko by laboratory simulations of cometary analogs

    NASA Astrophysics Data System (ADS)

    Jost, Bernhard; Pommerol, Antoine; Poch, Olivier; Carrasco, Nathalie; Szopa, Cyril; Thomas, Nicolas

    2015-11-01

    The OSIRIS imaging system [1] onboard European Space Agency’s Rosetta mission has been orbiting the comet 67P/Churyumov-Gerasimenko (67P) since August 2014. It provides an enormous quantity of high resolution images of the nucleus in the visible spectral range. 67P revealed an unexpected diversity of complex surface structures and spectral properties have also been measured [2].To better interpret this data, a profound knowledge of laboratory analogs of cometary surfaces is essential. For this reason we have set up the LOSSy laboratory (Laboratory for Outflow Studies of Sublimating Materials) to study the spectrophotometric properties of ice-bearing cometary nucleus analogs. The main focus lies on the characterization of the surface evolution under simulated space conditions. The laboratory is equipped with two facilities: the PHIRE-2 radio-goniometer [3], designed to measure the bidirectional visible reflectance of samples under a wide range of geometries and the SCITEAS simulation chamber [4], designed to study the evolution of icy samples subliming under low pressure/temperature conditions by hyperspectral imaging in the VIS-NIR range. Different microscopes complement the two facilities.We present laboratory data of different types of fine grained ice particles mixed with non-volatile components (complex organic matter and minerals). As the ice sublimes, a deposition lag of non-volatile constituents is built-up on top of the ice, possibly mimic a cometary surface. The bidirectional reflectance of the samples have been characterized before and after the sublimation process.A comparison of our laboratory findings with recent OSIRIS data [5] will be presented.[1] Keller, H. U., et al., 2007, Space Sci. Rev., 128, 26[2] Thomas, N. , 2015, Science, 347, Issue 6220, aaa0440[3] Jost, B., submitted, Icarus[4] Pommerol, A., et al., 2015. Planet Space Sci 109:106-122.[5] Fornasier, S., et al., in press. Icarus, arXiv:1505.06888

  10. Nonvolatile Analog Memory

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C. (Inventor)

    2007-01-01

    A nonvolatile analog memory uses pairs of ferroelectric field effect transistors (FFETs). Each pair is defined by a first FFET and a second FFET. When an analog value is to be stored in one of the pairs, the first FFET has a saturation voltage applied thereto, and the second FFET has a storage voltage applied thereto that is indicative of the analog value. The saturation and storage voltages decay over time in accordance with a known decay function that is used to recover the original analog value when the pair of FFETs is read.

  11. Analog synthetic biology.

    PubMed

    Sarpeshkar, R

    2014-03-28

    We analyse the pros and cons of analog versus digital computation in living cells. Our analysis is based on fundamental laws of noise in gene and protein expression, which set limits on the energy, time, space, molecular count and part-count resources needed to compute at a given level of precision. We conclude that analog computation is significantly more efficient in its use of resources than deterministic digital computation even at relatively high levels of precision in the cell. Based on this analysis, we conclude that synthetic biology must use analog, collective analog, probabilistic and hybrid analog-digital computational approaches; otherwise, even relatively simple synthetic computations in cells such as addition will exceed energy and molecular-count budgets. We present schematics for efficiently representing analog DNA-protein computation in cells. Analog electronic flow in subthreshold transistors and analog molecular flux in chemical reactions obey Boltzmann exponential laws of thermodynamics and are described by astoundingly similar logarithmic electrochemical potentials. Therefore, cytomorphic circuits can help to map circuit designs between electronic and biochemical domains. We review recent work that uses positive-feedback linearization circuits to architect wide-dynamic-range logarithmic analog computation in Escherichia coli using three transcription factors, nearly two orders of magnitude more efficient in parts than prior digital implementations. PMID:24567476

  12. Thermo-Chemical Convection in Europa's Icy Shell with Salinity

    NASA Technical Reports Server (NTRS)

    Han, L.; Showman, A. P.

    2005-01-01

    Europa's icy surface displays numerous pits, uplifts, and chaos terrains that have been suggested to result from solid-state thermal convection in the ice shell, perhaps aided by partial melting. However, numerical simulations of thermal convection show that plumes have insufficient buoyancy to produce surface deformation. Here we present numerical simulations of thermochemical convection to test the hypothesis that convection with salinity can produce Europa's pits and domes. Our simulations show that domes (200-300 m) and pits (300-400 m) comparable to the observations can be produced in an ice shell of 15 km thick with 5-10% compositional density variation if the maximum viscosity is less than 10(exp 18) Pa sec. Additional information is included in the original extended abstract.

  13. The long-period librations of large synchronous icy moons

    NASA Astrophysics Data System (ADS)

    Yseboodt, Marie; Van Hoolst, Tim

    2014-11-01

    A moon in synchronous rotation has longitudinal librations because of its non-spherical mass distribution and its elliptical orbit around the planet. We study the long-period librations of the Galilean satellites and Titan and include deformation effects and the existence of a subsurface ocean. We take into account the fact that the orbit is not keplerian and has other periodicities than the main period of orbital motion around Jupiter or Saturn due to perturbations by the Sun, other planets and moons. An orbital theory is used to compute the orbital perturbations due to these other bodies. For Titan we also take into account the large atmospheric torque at the semi-annual period of Saturn around the Sun.We numerically evaluate the amplitude and phase of the long-period librations for many interior structure models of the icy moons constrained by the mass, radius and gravity field.

  14. Mobility of icy sand packs, with application to Martian permafrost

    USGS Publications Warehouse

    Durham, W.B.; Pathare, A.V.; Stern, L.A.; Lenferink, H.J.

    2009-01-01

    [1] The physical state of water on Mars has fundamental ramifications for both climatology and astrobiology. The widespread presence of "softened" Martian landforms (such as impact craters) can be attributed to viscous creep of subsurface ground ice. We present laboratory experiments designed to determine the minimum amount of ice necessary to mobilize topography within Martian permafrost. Our results show that the jammed-to-mobile transition of icy sand packs neither occurs at fixed ice content nor is dependent on temperature or stress, but instead correlates strongly with the maximum dry packing density of the sand component. Viscosity also changes rapidly near the mobility transition. The results suggest a potentially lower minimum volatile inventory for the impact-pulverized megaregolith of Mars. Furthermore, the long-term preservation of partially relaxed craters implies that the ice content of Martian permafrost has remained close to that at the mobility transition throughout Martian history. Copyright 2009 by the American Geophysical Union.

  15. Compositional Remote Sensing of Icy Planets and Satellites Beyond Jupiter

    NASA Technical Reports Server (NTRS)

    Roush, Ted L.

    2002-01-01

    The peak of the solar energy distribution occurs at visual wavelengths and falls off rapidly in the infrared. This fact, improvements in infrared detector technology, and the low surface temperatures for most icy objects in the outer solar system have resulted in the bulk of telescopic and spacecraft observations being performed at visual and near-infrared wavelengths. Such observations, begun in the early 1970's and continuing to present, have provided compositional information regarding the surfaces of the satellites of Saturn and Uranus, Neptune's moon Triton, Pluto, Pluto's moon Charon, Centaur objects, and Kuiper belt objects. Because the incident sunlight penetrates the surface and interacts with the materials present there, the measured reflected sunlight contains information regarding the surface materials, and the ratio of the reflected to incident sunlight provides a mechanism of identifying the materials that are present.

  16. Dynamical tides in icy satellites with subsurface oceans

    NASA Astrophysics Data System (ADS)

    Beuthe, M.; Rivoldini, A.; Trinh, A.; Van Hoolst, T.

    2015-10-01

    Subsurface oceans are a generic feature of large icy bodies, if not now, then at some point in their past evolution. Various datasets already point to the existence of oceans within Europa, Ganymede, Callisto, Titan,Enceladus, and Mimas, while other bodies like Ceres,Pluto, and Triton await their turn. Subsurface oceans partially decouple the crust and thus greatly enhance tidal effect, unless the crust is very thick and hard. Dynamical effects are usually neglected when computing tidal deformations of solid bodies. It is well known,however, that various oscillation modes have a ma- jor impact on tidal dissipation within shallow surface oceans [1]. We show here that the dynamical Love numbers of a non-rotating body exhibit a simple resonant behavior if the ocean is very shallow. We also examine how the resonance is affected by rotation.

  17. A Holographic Microscope for Detection of Microorganisms on Icy Worlds

    NASA Astrophysics Data System (ADS)

    Lindensmith, C. A.; Nadeau, J. L.; Deming, J. W.; Showalter, G. M.; Rider, S.; Bedrossian, M.

    2015-12-01

    Holography is a well-established imaging technique that uses the interference of light to record and reproduce three-dimensional images of objects. Its use began in the 1960s with the invention of the laser. Digital holographic microscopy (DHM) has several advantages over ordinary imaging microscopy which make it ideal for field and astrobiology use, including no need for focus or scanning so that instruments are readily made autonomous. DHM can produce simultaneous bright-field and quantitative phase-contrast images of the same field, providing additional information about transparent objects, e.g., refractive index and/or thickness; thus it inherently supports effective label-free imaging. We have built a fieldable DHM for detection of microorganisms in bodies of water and in brines collected from sea ice. Ice that appears solid to the eye contains interconnected brine-filled microscopic pores and veins which are occupied by populations of prokaryotes and eukaryotes. The presence of life in "solid" ice has important implications for exploration of icy worlds, where it is unlikely that the first missions will be able to access the subsurface oceans. Using this new instrument, we examined several dozen samples from three different sites around Nuuk, Greenland. In all samples, mixed populations of both prokaryotic and eukaryotic microorganisms were observed. Many of the organisms were motile immediately upon extraction from sea ice, and others became motile after warming or addition of sugars and/or amino acids. Meaningful motility was readily distinguished from turbulence or fluid flow. The spatial resolution of the instrument was better than 1 μm, leading to unambiguous recognition of subcellular structures in eukaryotes, including nuclei and chloroplasts. We present mission scenrios for both orbiters and landers in which DHM may be used as a valuable complement to chemical-based life detection techniques for discovery of cellular life on icy worlds.

  18. Saturn's icy satellites and rings investigated by Cassini-VIMS: III - Radial compositional variability

    NASA Astrophysics Data System (ADS)

    Filacchione, G.; Capaccioni, F.; Ciarniello, M.; Clark, R. N.; Cuzzi, J. N.; Nicholson, P. D.; Cruikshank, D. P.; Hedman, M. M.; Buratti, B. J.; Lunine, J. I.; Soderblom, L. A.; Tosi, F.; Cerroni, P.; Brown, R. H.; McCord, T. B.; Jaumann, R.; Stephan, K.; Baines, K. H.; Flamini, E.

    2012-08-01

    In the last few years Cassini-VIMS, the Visible and Infrared Mapping Spectrometer, returned to us a comprehensive view of the Saturn's icy satellites and rings. After having analyzed the satellites' spectral properties (Filacchione, G., Capaccioni, F., McCord, T.B., Coradini, A., Cerroni, P., Bellucci, G., Tosi, F., D'Aversa, E., Formisano, V., Brown, R.H., Baines, K.H., Bibring, J.P., Buratti, B.J., Clark, R.N., Combes, M., Cruikshank, D.P., Drossart, P., Jaumann, R., Langevin, Y., Matson, D.L., Mennella, V., Nelson, R.M., Nicholson, P.D., Sicardy, B., Sotin, C., Hansen, G., Hibbitts, K., Showalter, M., Newman, S. [2007]. Icarus 186, 259-290, paper I) and their distribution across the satellites' hemispheres (Filacchione, G., Capaccioni, F., Clark, R.N., Cuzzi, J.N., Cruikshank, D.P., Coradini, A., Cerroni, P., Nicholson, P.D., McCord, T.B., Brown, R.H., Buratti, B.J., Tosi, F., Nelson, R.M., Jaumann, R., Stephan, K. [2010]. Icarus 206, 507-523, paper II), we proceed in this paper to investigate the radial variability of icy satellites (principal and minor) and main rings average spectral properties. This analysis is done by using 2264 disk-integrated observations of the satellites and a 12 × 700 pixels-wide rings radial mosaic acquired with a spatial resolution of about 125 km/pixel. Using different VIS and IR spectral indicators, e.g. spectral slopes and band depths, we perform a comparative analysis of these data aimed to measure the distribution of water ice and red contaminant materials across Saturn's system. The average surface regolith grain sizes are estimated with different indicators through comparison with laboratory and synthetic spectra. These measurements highlight very striking differences in the population here analyzed, which vary from the almost uncontaminated and water ice-rich surfaces of Enceladus and Calypso to the metal/organic-rich and red surfaces of Iapetus' leading hemisphere and Phoebe. Rings spectra appear more red than the icy

  19. Sputtering processes - Erosion and chemical change. [Magnetospheric ion bombardment of planetary atmospheric ice grains

    SciTech Connect

    Johnson, R.E.; Lanzerotti, L.J.; Brown, W.L.

    1984-01-01

    Laboratory data and models of sputter-induced erosion and chemical alterations in ice films are reviewed and the results are applied to icy grains and satellites exposed to magnetospheric ion bombardment. It is shown that the source of the plasma in the inner magnetosphere of Saturn is likely to be the sputter erosion of the icy objects in this region and the sputter erosion and possible stabilization of the E-ring are considered. Ion-induced polymerization is discussed as a source of the darkened rings of Uranus. 78 references.

  20. Thermal formation of methylammonium methylcarbamate in interstellar ice analogs: a glycine salt precursor under VUV irradiation

    NASA Astrophysics Data System (ADS)

    Duvernay, Fabrice; Borget, Fabien; Bossa, Jean-Baptiste; Theule, Patrice; Dhendecourt, Louis; Chiavassa, Thierry

    Dust grains in the interstellar medium (ISM) play an important role in dense molecular clouds chemistry of providing a surface (catalyst) upon which atoms and molecules can freeze out, forming icy mantles. Dense molecular clouds are characterized by low temperature (10 -50 K) and represent the birth sites of stars. After a gravitationnal breakdown, a part of the dense molecular cloud collapses toward the formation of star and subsequently a protoplanetary disk from which planets, asteroids and comets will appear. During this evolution, interstellar or-ganic material inside ices undergoes different range of chemical alterations (thermal cycling process, ultraviolet photons, electron scattering and cosmic rays irradiation) hence increasing the molecular complexity before their incorporation inside precometary ices. To date, it is supposed that comets could have delivered to the early Earth the organic materials essential to a prebiotic chemistry, one of the prerequisites toward the origin of living systems. The for-mation of prebiotical molecules such as the simplest amino acids (glycine) is proposed in this current study mainly based on laboratory experiments simulating the chemistry occuring on ices within protostellar environments. Infrared spectroscopy and mass spectroscopy are used to monitor the thermal formation of glycine isomer form: the methylammonium methylcarbamate [CH3NH3+][CH3NHCOO-] in interstellar ice analogs made up of two astrophysical relevant molecules: carbon dioxide (CO2) and methylamine (CH3NH2). Using infrared spectroscopy, we study the photochemical behaviour of a pure sample of methylammonium methylcarbamate under vacuum ultraviolet (VUV) field. We show that a glycine isomer salt could readily enter into the composition of ices in colder region of protostellar environments. Upon ultraviolet irra-diation, this latter can undergo an isomerization process induced by photons yielding a glycine salt: the methylammonium glycinate [CH3NH3+][NH2CH2

  1. Interstellar grains within interstellar grains

    NASA Technical Reports Server (NTRS)

    Bernatowicz, Thomas J.; Amari, Sachiko; Zinner, Ernst K.; Lewis, Roy S.

    1991-01-01

    Five interstellar graphite spherules extracted from the Murchison carbonaceous meteorite are studied. The isotopic and elemental compositions of individual particles are investigated with the help of an ion microprobe, and this analysis is augmented with structural studies of ultrathin sections of the grain interiors by transmission electron microscopy. As a result, the following procedure for the formation of the interstellar graphite spherule bearing TiC crystals is inferred: (1) high-temperature nucleation and rapid growth of the graphitic carbon spherule in the atmosphere of a carbon-rich star, (2) nucleation and growth of TiC crystals during continued growth of the graphitic spherule and the accretion of TiC onto the spherule, (3) quenching of the graphite growth process by depletion of C or by isolation of the spherule before other grain types could condense.

  2. Hydraulic Capacitor Analogy

    ERIC Educational Resources Information Center

    Baser, Mustafa

    2007-01-01

    Students have difficulties in physics because of the abstract nature of concepts and principles. One of the effective methods for overcoming students' difficulties is the use of analogies to visualize abstract concepts to promote conceptual understanding. According to Iding, analogies are consistent with the tenets of constructivist learning…

  3. Analog synthetic biology

    PubMed Central

    Sarpeshkar, R.

    2014-01-01

    We analyse the pros and cons of analog versus digital computation in living cells. Our analysis is based on fundamental laws of noise in gene and protein expression, which set limits on the energy, time, space, molecular count and part-count resources needed to compute at a given level of precision. We conclude that analog computation is significantly more efficient in its use of resources than deterministic digital computation even at relatively high levels of precision in the cell. Based on this analysis, we conclude that synthetic biology must use analog, collective analog, probabilistic and hybrid analog–digital computational approaches; otherwise, even relatively simple synthetic computations in cells such as addition will exceed energy and molecular-count budgets. We present schematics for efficiently representing analog DNA–protein computation in cells. Analog electronic flow in subthreshold transistors and analog molecular flux in chemical reactions obey Boltzmann exponential laws of thermodynamics and are described by astoundingly similar logarithmic electrochemical potentials. Therefore, cytomorphic circuits can help to map circuit designs between electronic and biochemical domains. We review recent work that uses positive-feedback linearization circuits to architect wide-dynamic-range logarithmic analog computation in Escherichia coli using three transcription factors, nearly two orders of magnitude more efficient in parts than prior digital implementations. PMID:24567476

  4. Challenges in Using Analogies

    ERIC Educational Resources Information Center

    Lin, Shih-Yin; Singh, Chandralekha

    2011-01-01

    Learning physics requires understanding the applicability of fundamental principles in a variety of contexts that share deep features. One way to help students learn physics is via analogical reasoning. Students can be taught to make an analogy between situations that are more familiar or easier to understand and another situation where the same…

  5. An Icy Kuiper-Belt Around the Young Solar-Type Star HD 181327

    NASA Technical Reports Server (NTRS)

    Lebreton, J.; Augereau, J.-C.; Thi, W.-F.; Roberge, A.; Donaldson, J.; Schneider, G.; Maddison, S. T.; Menard, F.; Riviere-Marichalar, P.; Mathews, G. S.; Kamp, I.; Pinte, C.; Dent, W. R. F.; Barrado, D.; Duchene, G.; Gonzalez, J.-F.; Grady, C. A.; Meeus, G.; Pantin, E.; Williams, J. P.; Woitke, P.

    2011-01-01

    HD 181327 is a young Main Sequence F5/F6 V star belonging to the Beta Pictoris moving group (age approx 12 Myr). It harbors an optically thin belt of circumstellar material at approx90 AU, presumed to result from collisions in a populat.ion of unseen planetesimals. Aims. We aim to study the dust properties in the belt in great details, and to constrain the gas-to-dust ratio. Methods. We obtained far-IR photometric observations of HD 181327 with the PACS instrument onboard the Herschel Space Observatory, complemented by new 3.2 nun observations carried with the ATCA array. The geometry of the belt is constrained with newly reduced HST /NICMOS scattered light images that break the degeneracy between the disk geometry and the dust properties. We then use the radiative transfer code GRaTer to compute a large grid of dust models, and we apply a Bayesian inference method to identify the grain models that best reproduce the SED. We attempt to detect the oxygen and ionized carbon fine-structure lines with Herschel/PACS spectroscopy, providing observables to our photochemical code ProDiMo. Results. The HST observations confirm that the dust is confined in a narrow belt. The continuum is detected with Herschel/PACS completing nicely the SED in the far-infrared. The disk is marginally resolved with both PACS and ATCA. A medium integration of the gas spectral lines only provides upper limits on the [OI] and [CII] line fluxes. We show that the HD 181327 dust disk consists of micron-sized grains of porous amorphous silicates and carbonaceous material surrounded by an import.ant layer of ice for a total dust mass of approx 0.05 stellar Mass. We discuss evidences that the grains consists of fluffy aggregates. The upper limits on the gas atomic lines do not provide unambiguous constraints: only if the PAH abundance is high, the gas mass must be lower than approx 17 Stellar Mass Conclusions. Despite the weak constraints on the gas disk, the age of HD 181327 and the properties of the

  6. Polymerization of Building Blocks of Life on Europa and Other Icy Moons.

    PubMed

    Kimura, Jun; Kitadai, Norio

    2015-06-01

    The outer Solar System may provide a potential habitat for extraterrestrial life. Remote sensing data from the Galileo spacecraft suggest that the jovian icy moons--Europa, Ganymede, and possibly Callisto--may harbor liquid water oceans underneath their icy crusts. Although compositional information required for the discussion of habitability is limited because of significantly restricted observation data, organic molecules are ubiquitous in the Universe. Recently, in situ spacecraft measurements and experiments suggest that amino acids can be formed abiotically on interstellar ices and comets. These amino acids could be continuously delivered by meteorite or comet impacts to icy moons. Here, we show that polymerization of organic monomers, in particular amino acids and nucleotides, could proceed spontaneously in the cold environment of icy moons, in particular the jovian icy moon Europa as a typical example, based on thermodynamic calculations, though kinetics of formation are not addressed. Observed surface temperature on Europa is 120 and 80 K in the equatorial region and polar region, respectively. At such low temperatures, Gibbs energies of polymerization become negative, and the estimated thermal structure of the icy crust should contain a shallow region (i.e., at a depth of only a few kilometers) favorable for polymerization. Investigation of the possibility of organic monomer polymerization on icy moons could provide good constraints on the origin and early evolution of extraterrestrial life. PMID:26060981

  7. Polymerization of Building Blocks of Life on Europa and Other Icy Moons.

    PubMed

    Kimura, Jun; Kitadai, Norio

    2015-06-01

    The outer Solar System may provide a potential habitat for extraterrestrial life. Remote sensing data from the Galileo spacecraft suggest that the jovian icy moons--Europa, Ganymede, and possibly Callisto--may harbor liquid water oceans underneath their icy crusts. Although compositional information required for the discussion of habitability is limited because of significantly restricted observation data, organic molecules are ubiquitous in the Universe. Recently, in situ spacecraft measurements and experiments suggest that amino acids can be formed abiotically on interstellar ices and comets. These amino acids could be continuously delivered by meteorite or comet impacts to icy moons. Here, we show that polymerization of organic monomers, in particular amino acids and nucleotides, could proceed spontaneously in the cold environment of icy moons, in particular the jovian icy moon Europa as a typical example, based on thermodynamic calculations, though kinetics of formation are not addressed. Observed surface temperature on Europa is 120 and 80 K in the equatorial region and polar region, respectively. At such low temperatures, Gibbs energies of polymerization become negative, and the estimated thermal structure of the icy crust should contain a shallow region (i.e., at a depth of only a few kilometers) favorable for polymerization. Investigation of the possibility of organic monomer polymerization on icy moons could provide good constraints on the origin and early evolution of extraterrestrial life.

  8. Polymerization of Building Blocks of Life on Europa and Other Icy Moons

    NASA Astrophysics Data System (ADS)

    Kimura, Jun; Kitadai, Norio

    2015-06-01

    The outer solar system may provide a potential habitat for extraterrestrial life. Remote sensing data from the Galileo spacecraft suggest that the jovian icy moons, Europa, Ganymede, and possibly Callisto, may harbor liquid water oceans underneath their icy crusts. Although compositional information required for the discussion of habitability is limited because of significantly restricted observation data, organic molecules are ubiquitous in the universe. Recently, in-situ spacecraft measurements and experiments suggest that amino acids can be formed abiotically on interstellar ices and comets. These amino acids could be continuously delivered by meteorite or comet impacts to icy moons. Here, we show that polymerization of organic monomers, in particular amino acids and nucleotides, could proceed spontaneously in the cold environment of icy moons, in particular the Jovian icy moon Europa as a typical example, based on thermodynamic calculations, though kinetics of formation are not addressed. Observed surface temperature on Europa is 120 and 80 K in the equatorial region and polar region, respectively. At such low temperatures, Gibbs energies of polymerization become negative, and the estimated thermal structure of the icy crust should contain a shallow region (i.e., at a depth of only a few kilometers) favorable for polymerization. Investigation of the possibility of organic monomer polymerization on icy moons could provide good constraints on the origin and early evolution of extraterrestrial life.

  9. Polymerization of Building Blocks of Life on Europa and Other Icy Moons

    PubMed Central

    Kitadai, Norio

    2015-01-01

    Abstract The outer Solar System may provide a potential habitat for extraterrestrial life. Remote sensing data from the Galileo spacecraft suggest that the jovian icy moons—Europa, Ganymede, and possibly Callisto—may harbor liquid water oceans underneath their icy crusts. Although compositional information required for the discussion of habitability is limited because of significantly restricted observation data, organic molecules are ubiquitous in the Universe. Recently, in situ spacecraft measurements and experiments suggest that amino acids can be formed abiotically on interstellar ices and comets. These amino acids could be continuously delivered by meteorite or comet impacts to icy moons. Here, we show that polymerization of organic monomers, in particular amino acids and nucleotides, could proceed spontaneously in the cold environment of icy moons, in particular the jovian icy moon Europa as a typical example, based on thermodynamic calculations, though kinetics of formation are not addressed. Observed surface temperature on Europa is 120 and 80 K in the equatorial region and polar region, respectively. At such low temperatures, Gibbs energies of polymerization become negative, and the estimated thermal structure of the icy crust should contain a shallow region (i.e., at a depth of only a few kilometers) favorable for polymerization. Investigation of the possibility of organic monomer polymerization on icy moons could provide good constraints on the origin and early evolution of extraterrestrial life. Key Words: Planetary science—Europa—Planetary habitability and biosignatures—Extraterrestrial life—Extraterrestrial organic compounds. Astrobiology 15, 430–441. PMID:26060981

  10. Comparative relief-forming potential of rocky terrestrial planets and icy saturnian satellites

    NASA Astrophysics Data System (ADS)

    Kochemasov, G. G.

    2009-04-01

    Comparative relief-forming potential of rocky terrestrial planets and icy saturnian satellites. G. Kochemasov IGEM of the Russian Academy of Sciences, Moscow, Russia, kochem.36@mail.ru The wave planetology [1-3 & others] states that "orbits make structures". Its third theorem ("Celestial bodies are granular") is to say that sizes of tectonic granules are inversely proportional to orbital frequencies: higher frequency - smaller granule, and vice versa, lower frequency - larger granule. Thus, Mercury is very fine-grained, Venus fine-grained, Earth medium-grained, Mars coarse-grained. The following row of granule sizes confirms it: Mercury πR/16, Venus πR/6, Earth πR/4, Mars πR/2 (R-a planet radius). A geometrical model of this presents a circle with inscribed in it standing waves: for Mercury 16 waves, for Venus 6 waves, for Earth 4 waves (a cross!), for Mars 2 waves [4]. This geometrization is rather descriptive as it shows how waves amplitudes increase with the Solar distance and oscillations around a circle (wave heights) can be measured [5]. These heights are as follows: Mercury 2πR/64.08, Venus 2πR/24.34, Earth 2πR/16.44, Mars 2πR/8.8. These heights reduced to the Earth's one (taken as 1) are as follows: Mercury 0.256, Venus 0.675, Earth 1.0, Mars 1.868. Now we are looking at the real relief ranges (spans). They are as follows in km: Mercury ~5 (a bit less than 5 km according to one laser altimetry profile by Messenger spacecraft in 2007), Venus ~14, Earth ~20, Mars ~30. This last figure may be increased by heights of collapsed cones of huge marcian volcanoes having calderas radii 40-50 km and presumed slope angle 5-6 degrees that gives additional 4-5 km for the martian relief range making it ~35 km. Taking the Earth range as 1, one gets the following row of relative heights: Mercury 0.25, Venus 0.7, Earth 1.0, Mars 1.75. Comparing two rows of relative heights (theoretic and real) one sees that they are rather similar: Mercury 0.256 (0.25), Venus 0

  11. Comparative study of icy patches on comet nuclei

    NASA Astrophysics Data System (ADS)

    Oklay, Nilda; Pommerol, Antoine; Barucci, Maria Antonietta; Sunshine, Jessica; Sierks, Holger; Pajola, Maurizio

    2016-07-01

    Cometary missions Deep Impact, EPOXI and Rosetta investigated the nuclei of comets 9P/Tempel 1, 103P/Hartley 2 and 67P/Churyumov-Gerasimenko respectively. Bright patches were observed on the surfaces of each of these three comets [1-5]. Of these, the surface of 67P is mapped at the highest spatial resolution via narrow angle camera (NAC) of the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS, [6]) on board the Rosetta spacecraft. OSIRIS NAC is equipped with twelve filters covering the wavelength range of 250 nm to 1000 nm. Various filters combinations are used during surface mapping. With high spatial resolution data of comet 67P, three types of bright features were detected on the comet surface: Clustered, isolated and bright boulders [2]. In the visible spectral range, clustered bright features on comet 67P display bluer spectral slopes than the average surface [2, 4] while isolated bright features on comet 67P have flat spectra [4]. Icy patches observed on the surface of comets 9P and 103P display bluer spectral slopes than the average surface [1, 5]. Clustered and isolated bright features are blue in the RGB composites generated by using the images taken in NIR, visible and NUV wavelengths [2, 4]. This is valid for the icy patches observed on comets 9P and 103P [1, 5]. Spectroscopic observations of bright patches on comets 9P and 103P confirmed the existence of water [1, 5]. There were more than a hundred of bright features detected on the northern hemisphere of comet 67P [2]. Analysis of those features from both multispectral data and spectroscopic data is an ongoing work. Water ice is detected in eight of the bright features so far [7]. Additionally, spectroscopic observations of two clustered bright features on the surface of comet 67P revealed the existence of water ice [3]. The spectral properties of one of the icy patches were studied by [4] using OSIRIS NAC images and compared with the spectral properties of the active regions observed

  12. Jupiter Icy Moons Explorer: mission status after the Definition Phase

    NASA Astrophysics Data System (ADS)

    Titov, Dmitri; Barabash, Stas; Bruzzone, Lorenzo; Dougherty, Michele; Erd, Christian; Fletcher, Leigh; Gare, Philippe; Gladstone, Randall; Grasset, Olivier; Gurvits, Leonid; Hartogh, Paul; Hussmann, Hauke; Iess, Luciano; Jaumann, Ralf; Langevin, Yves; Palumbo, Pasquale; Piccioni, Giuseppe; Sarri, Giuseppe; Wahlund, Jan-Erik; Witasse, Olivier

    2015-04-01

    JUpiter ICy moons Explorer (JUICE), the ESA first large-class mission within the Cosmic Vision Program 2015-2025, was adopted in November 2014. The mission will perform detailed investigations of Jupiter and its system with particular emphasis on Ganymede as a planetary body and potential habitat. The overarching theme for JUICE is: The emergence of habitable worlds around gas giants. At Ganymede, the mission will characterize in detail the ocean layers; provide topographical, geological and compositional mapping of the surface; study the physical properties of the icy crusts; characterize the internal mass distribution, investigate the exosphere; study Ganymede's intrinsic magnetic field and its interactions with the Jovian magnetosphere. For Europa, the focus will be on the non-ice chemistry, understanding the formation of surface features and subsurface sounding of the icy crust over recently active regions. Callisto will be explored as a witness of the early solar system. JUICE will perform a multidisciplinary investigation of the Jupiter system as an archetype for gas giants. The circulation, meteorology, chemistry and structure of the Jovian atmosphere will be studied from the cloud tops to the thermosphere. The focus in Jupiter's magnetosphere will include an investigation of the three dimensional properties of the magnetodisc and in-depth study of the coupling processes within the magnetosphere, ionosphere and thermosphere. Aurora and radio emissions will be elucidated. JUICE will study the moons' interactions with the magnetosphere, gravitational coupling and long-term tidal evolution of the Galilean satellites. JUICE highly capable scientific payload includes 10 state-of-the-art instruments onboard the spacecraft plus one experiment that uses the spacecraft telecommunication system with ground-based radio telescopes. The remote sensing package includes a high-resolution multi-band visible imager (JANUS) and spectro-imaging capabilities from the

  13. Meat analog: a review.

    PubMed

    Malav, O P; Talukder, S; Gokulakrishnan, P; Chand, S

    2015-01-01

    The health-conscious consumers are in search of nutritious and convenient food item which can be best suited in their busy life. The vegetarianism is the key for the search of such food which resembles the meat in respect of nutrition and sensory characters, but not of animal origin and contains vegetable or its modified form, this is the point when meat analog evolved out and gets shape. The consumers gets full satisfaction by consumption of meat analog due to its typical meaty texture, appearance and the flavor which are being imparted during the skilled production of meat analog. The supplement of protein in vegetarian diet through meat alike food can be fulfilled by incorporating protein-rich vegetative food grade materials in meat analog and by adopting proper technological process which can promote the proper fabrication of meat analog with acceptable meat like texture, appearance, flavor, etc. The easily available vegetables, cereals, and pulses in India have great advantages and prospects to be used in food products and it can improve the nutritional and functional characters of the food items. The various form and functional characters of food items are available world over and attracts the meat technologists and the food processors to bring some innovativeness in meat analog and its presentation and marketability so that the acceptability of meat analog can be overgrown by the consumers.

  14. Sodium Salts in Ice Grains from Enceladus

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Kempf, S.; Schmidt, J.; Brillantov, N.; Abel, B.; Beinsen, A.; Buck, U.; Srama, R.

    2009-04-01

    One key requirement for the formation of life precursors on Enceladus, is liquid water below its icy surface. Although measurements and model calculations for Enceladus plume source suggest temperatures close to the melting point, direct evidence for liquid water has not been produced so far. We present compositional measurements by Cassini's dust detector of ice particles emitted from Saturn's cryo-volcanic moon Enceladus into the E ring. Since sodium is considered as crucial indicator for an Enceladus ocean, our detection of sodium salts within the grains provide the first evidence for mineral enriched liquid water below the moon's icy surface. In nearly all particles detected in situ by the Cosmic Dust Analyser (CDA) aboard the Cassini spacecraft, we found sodium (Na) in varying concentrations. Most spectra also show potassium (K) in lower abundance. In mass spectra that are particularly sodium rich, sodium salts (like NaCl and NaHCO3) are identified as Na bearing components. This is only possible if the plume source is liquid water that is or has been in contact with the rocky material of Enceladus' core. The abundance of minerals as well as the inferred basic pH value of those grains exhibit a compelling similarity with the predicted composition of an Enceladus ocean. The Na-rich ice particles likely are frozen ocean droplets expelled through the plumes into the E ring. From the compositional analysis, models for grain production and ejection can be derived which give new insights in plume dynamics and subsurface processes. They also allow the refinement of models for a water-rock-interaction at the bottom of the liquid layer.

  15. Icy Satellite Science Today and in Cassini's Final Three Years

    NASA Astrophysics Data System (ADS)

    Buratti, B. J.

    2014-12-01

    The Cassini Mission has turned our view of Saturn's icy moons from scientific sketches to fully realized worlds. Among the major discoveries are: Activity on Enceladus and associated plumes that originate in small hot spots on its south pole and that appear to be modulated by tidal forces; a liquid subsurface water ocean on Enceladus that is a habitable environment; several new moons; debris rings associated with moons; a unique equatorial ridge on Iapetus; the identity of new constituents on the moons including carbon dioxide ice on most of them and polycyclic aromatic hydrocarbons (PAHs)on Iapetus; differentiated or partially differentiated interiors; nano-iron on the surfaces of the moons and in the rings; volatile segregation on Iapetus and Hyperion; and a bewildering array of geologic processes on the small moons. But our new view of these icy worlds has spawned new questions. Among these unanswered questions are: How variable are the plumes? Have any other moons had activity similar to that on Enceladus and did it continue up to the recent past? How much dust do the moons contribute to the region around Saturn? What caused the ridge on Iapetus? What are the interiors of the moons like? How differentiated and compensated are they? Five additional targeted flybys, two of Dione and three of Enceladus, have been designed to answer these questions and will be implemented during the remainder of the Solstice Mission. The Dione flybys both include gravity passes to determine its state of differentiation. One of the flybys is optimized to measure the fields and particle environment around Dione. One of the two remote-sensing flybys of Enceladus will scrutinize the south polar region to further understand the size, temperature, and variability of the emitting areas, while the other will observe the north pole to determine why it is so different from the south. The third Enceladus flyby involves an unprecedented pass less than 50 km above the surface into the midst of

  16. Defining the Contribution of Fragmentation to Icy World Geology

    NASA Astrophysics Data System (ADS)

    Walker, C. C.; Schmidt, B. E.

    2014-12-01

    The fracture and failure of the outer planet satellites' icy shells are not only an observable record of stress and activity throughout their evolution, they are also key mechanisms in the interaction of surface and subsurface material and thus crucial aspects of the study of crustal overturn and ice shell habitability. Recent work suggests that Europa's chaos terrain formation may include a collapse phase, with the eventual appearance of the chaos terrain determined in part by fracture density in the ice. Similarly, Enceladus' subdued south polar terrain is now known to exist above a trapped south polar sea. With this in mind, the work to be presented combines fractal analysis and a novel fragmentation physics model to characterize the transition from fractured ice to fragmented/collapsed ice and thus, implications for crustal overturn in Europa's ice shell using terrestrial glaciological studies to develop and test plausible processes. While intuition may suggest that ice "explosions" and simple elastic crack propagation are different, a fast-propagating fracture or other abrupt shift to the status quo (e.g., thinned shell) of the system is in effect very similar, as damage radiates through the system. In studying the size distribution of fragments in Europa's chaos regions, it is possible to back out physical properties of the ice, e.g., material strength, cohesion properties and most importantly, energy necessary to create such a fragmentation event. Fragmentation theory describes the breakage of a body into several pieces. When integrated, our models of crack propagation and fragmentation account for the three modes of fracturing: initiation, propagation, and interaction, and allows for characterization of the energy necessary for fragmented topography (e.g., chaos) to form within an ice shell to better understand the implications for surface overturn. We have modeled fracture formation and coalescence into fragments that results in a similar distribution to

  17. The alteration of icy samples during sample acquisition

    NASA Astrophysics Data System (ADS)

    Mungas, G.; Bearman, G.; Beegle, L. W.; Hecht, M.; Peters, G. H.; Glucoft, J.; Strothers, K.

    2006-12-01

    Valid in situ scientific studies require both that samples be analyzed in as pristine condition as possible and that any modification from the pristine to the sampled state be well understood. While samples with low to high ice concentration are critical for the study of astrobiology and geology, they pose problems with respect to the sample acquisition, preparation and distribution systems (SPAD) upon which the analytical instruments depend. Most significant of the processes that occur during SPAD is sublimation or melting caused by thermal loading from drilling, coring, etc. as well as exposure to a dry low pressure ambient environment. These processes can alter the sample, as well as generating, meta-stable liquid water that can refreeze in the sample transfer mechanisms, interfering with proper operation and creating cross-contamination. We have investigated and quantified loss of volatiles such as H2O, CO, CO2, and organics contained within icy and powdered samples when acquired, processed and transferred. During development of the MSL rock crusher, for example, ice was observed to pressure-fuse and stick to the side even at -70C. We have investigated sublimation from sample acquisition at Martian temperature and pressure for a samples ranging from 10 to 100 water/dirt ratios. Using the RASP that will be on Phoenix, we have measured sublimation of ice during excavation at Martian pressure and find that the sublimation losses can range from 10 to 50 percent water. It is the thermal conductivity of the soil that determines local heat transport, and how much of the sample acquisition energy is wicked away into the soil and how much goes into the sample. Modeling of sample acquisition methods requires measurement of these parameters. There is a two phase model for thermal conductivity as a function of dirt/ice ratio but it needed to be validated. We used an ASTM method for measuring thermal conductivity and implemented it in the laboratory. The major conclusion is

  18. Radiation Synthesis of New Molecules on Jupiter's Icy Satellites

    NASA Technical Reports Server (NTRS)

    Moore, M. H.; Hudson, R. L.; Carlson, R. W.

    2003-01-01

    Spectra of Jupiter's icy satellites reveal surfaces dominated by water-ice, minor amounts of SO2 and CO2, and (for Europa) H2O2 along with hydrated materials. Jovian magnetospheric ions (protons, sulfur, and oxygen) and electrons significantly modify the chemical composition of these moons' surfaces in times ranging from a few years for Europa to thousands of years for Callisto at micrometer depths. Appropriate laboratory studies examining relevant volatile and non-volatile materials under low-temperature radiation conditions can provide information on likely radiation chemical mechanisms, on the stability and evolution of species, and on new species awaiting detection. Although the molecules detected on the icy moons are relatively simple, predicting their responses to radiation in space remains difficult. One problem is that there is a dearth of fundamental data examining solid-phase reactions. Our laboratory experiments have focused on infrared studies (2.5 to 25 microns) of a few simple irradiated ices. We have measured the spectra of proton-irradiated H2O ice containing SO2, H2S, and/or CO2. Ices with H2O/SO2 or H2O/H2S ratios of 3 and 30 have been irradiated at 86 K, 110 K, and 132 K. In irradiated H2O + SO2 ices new ions have been identified: SO4(-2), HSO4(-) and H3O(+). After warming to 260 K the residual spectrum is similar to that of H2SO4. Ices with H2O + H2S form SO2. After warming to 175 K, the residual sample matches the spectrum of hydrated H2SO4. H2O + CO2 ice forms carbonic acid, H2CO3 which is stable to temperatures near 230 K. In addition, OCS has been detected in irradiated ices containing H2O + SO2 + CO2. The radiation half-life of SO2 and H2S in H2O has been calculated. Our results give compelling evidence for the presence of new species awaiting detection. Future experiments will examine the signatures of these ices and hydrated materials in the 1 to 5 micron region, where possible weaker overtone bands may occur. In addition, absolute

  19. Planetary protection for the Jupiter Icy Moons Orbiter

    NASA Astrophysics Data System (ADS)

    Gershman, R.; Kohlhase, C.; Koukol, R.

    NASA is developing plans for an ambitious mission to orbit three planet-sized moons of Jupiter -- Callisto, Ganymede and Europa -- which may harbor vast oceans beneath their icy surfaces. The mission, called the Jupiter Icy Moons Orbiter (JIMO), would orbit each of these moons for extensive investigations of their makeup, their history and their potential for sustaining life. JIMO has been identified as the first space science mission to potentially incorporate the revolutionary nuclear power and propulsion capability being developed by NASA's Project Prometheus. Planetary protection (PP) requirements for JIMO are expected to be based on a recommendation by the Space Studies Board (SSB) of the U.S. National Research Council that in any one mission the probability of contaminating a Europan ocean with a viable Earth organism should be less than 10-4. The SSB stated that calculation of this probability should, as a minimum, take into account the following: bioburden at launch, cruise survival of the organisms, organism survival in the radiation environment adjacent to Europa, probability of landing at a geologically active site on Europa, the mechanisms of transfer of the organisms to the Europan subsurface, and organism survival and proliferation before, during, and after subsurface transfer. This presentation reports on preliminary assessment of these factors by the JIMO Project and on work in progress aimed at finding a design capable of meeting planetary protection goals for Europa with the lowest cost and risk impacts for the project. This design will potentially include: credit for sterilizing effects of in-flight radiation, pre-launch sterilization with isolation from recontamination for spacecraft elements protected from the radiation environment, identification of quarantine orbits within the Jovian system providing long term stability, providing high system reliability against failure modes that could lead to surface impact, and assuring separation of the

  20. Analogs from LEO: Mapping Earth Observations to Planetary Science & Astrobiology. (Invited)

    NASA Astrophysics Data System (ADS)

    Hand, K. P.; Painter, T. H.

    2010-12-01

    If, as Charles Lyell articulated ‘the present is the key to the past’ for terrestrial geology, then perhaps by extension the Earth, our planet, is the key to understanding other planets. This is the basic premise behind planetary analogs. Many planetary science missions, however, utilize orbiters and are therefore constrained to remote sensing. This is the reverse of how we developed our understanding of Earth’s environments; remote sensing is a relatively new tool for understanding environments and processes on Earth. Here we present several cases and comparisons between Earth’s cryosphere and icy worlds of the outer Solar System (e.g. Europa, Titan, and Enceladus), where much of our knowledge is limited to remote observations (the sole exception being the Huygens probe to Titan). Three regions are considered: glaciers in the Sierra Nevada, the permafrost lakes of Alaska’s North Slope, and spreading centers of the ocean floor. Two key issues are examined: 1) successes and limitations for understanding processes that shape icy worlds, and 2) successes and limitations for assessing the habitability of icy worlds from orbit. Finally, technological considerations for future orbiting mission to icy worlds are presented.

  1. Simulations of mechanical failure in ice: Implications of terrestrial fracture models as applied to they icy satellites of the outer solar system

    NASA Astrophysics Data System (ADS)

    Walker, C. C.; Bassis, J. N.

    2011-12-01

    At the South Pole of Enceladus, a small icy moon orbiting Saturn, is a heavily fractured ice plain surrounded by a nearly-circular mountain range. Remarkably, the Cassini orbiter detected jets of water emanating from the icy shell and into space, originating from 4 parallel "tiger stripe" rifts within the center of the ice plain. The tiger stripes imaged on Enceladus are morphologically similar to rifts observed to form under extensional stress regimes in terrestrial ice shelves; the putative subsurface ocean hypothesized beneath the icy shell strengthens the analogy that their formation may have similar mechanical origins. Past studies have also suggested that the tiger stripes are the result of a process similar to that of mid-ocean ridge spreading on the Earth, but it remains to be seen whether or not such motion is consistent with the mountainous features seen at the circular cliff-like boundary of the region. In an attempt to understand the formation of these tiger stripes and their relationship to the observed mountain chains, we apply a conceptual model in which the ice is considered to be less like a continuous fluid body and, instead, behaves like a granular material made up of discrete blocks of ice. The tidal forces on the small moon tug on the shell enough that it has been cracked many times over, motivating the assumption that the ice exists in a continuum between wholly intact ice and highly pre-fractured ice. We employ several experimental setups with the intention of mapping the deformation of the south polar segment of the shell, to determine the processes that may contribute to its observed morphological state. These setups range from large scale topographical models, e.g., simulating the build up of mountains and processes that lead to overall elevation differences in the region, to small-scale, and focus on the more detailed level of fracturing. We explore our ice-shelf rifting analogy by modeling both icy moon fracturing and ice shelf rifting

  2. Challenges in Using Analogies

    NASA Astrophysics Data System (ADS)

    Lin, Shih-Yin; Singh, Chandralekha

    2011-11-01

    Learning physics requires understanding the applicability of fundamental principles in a variety of contexts that share deep features.1-7 One way to help students learn physics is via analogical reasoning. Students can be taught to make an analogy between situations that are more familiar or easier to understand and another situation where the same physics principle is involved but that is more difficult to handle. Here, we examine introductory physics students' ability to use analogies in solving problems involving Newton's second law. Students enrolled in an algebra-based introductory physics course were given a solved problem involving tension in a rope and were then asked to solve another problem for which the physics is very similar but involved a frictional force. They were asked to point out the similarities between the two problems and then use the analogy to solve the friction problem.

  3. Fatty acid analogs

    DOEpatents

    Elmaleh, David R.; Livni, Eli

    1985-01-01

    In one aspect, a radioactively labeled analog of a fatty acid which is capable of being taken up by mammalian tissue and which exhibits an in vivo beta-oxidation rate below that with a corresponding radioactively labeled fatty acid.

  4. Synthesis of novel ICIE16/BSG and ICIE16/BSG-NITRI bioglasses and description of ionic release kinetics upon immersion in SBF fluid: Effect of nitridation.

    PubMed

    Orgaz, Felipe; Amat, Daniel; Szycht, Olga; Dzika, Aleksandra; Barba, Flora; Becerra, José; Santos-Ruiz, Leonor

    2016-03-01

    A novel bioactive glass scaffold ICIE16/BSG has been prepared from a mixture of two different melt-derived glasses: a silicate bioglass (ICIE16) and a borosilicate bioglass (BSG). Combined processing techniques (gel casting and foam replication) were used to form three-dimensional, interconnected porous monolith scaffolds (Orgaz et al., 2016) [1]. They were then nitrided with a hot ammonia flow as described in (Aleixandre et al., 1973) [3] and (Nieto, 1984) [4] to synthesize the ICIE16/BSG-NITRI bioglass (Orgaz et al., 2016) [1]. Herein we present a flow chart summarizing the forming process, plus images of the resulting scaffold after sintering and drying. Bioactivity was characterized in vitro by immersion in simulated body fluid (SBF) for up to seven days. Data of ionic release kinetics upon SBF immersion are presented. PMID:26858981

  5. Synthesis of novel ICIE16/BSG and ICIE16/BSG-NITRI bioglasses and description of ionic release kinetics upon immersion in SBF fluid: Effect of nitridation.

    PubMed

    Orgaz, Felipe; Amat, Daniel; Szycht, Olga; Dzika, Aleksandra; Barba, Flora; Becerra, José; Santos-Ruiz, Leonor

    2016-03-01

    A novel bioactive glass scaffold ICIE16/BSG has been prepared from a mixture of two different melt-derived glasses: a silicate bioglass (ICIE16) and a borosilicate bioglass (BSG). Combined processing techniques (gel casting and foam replication) were used to form three-dimensional, interconnected porous monolith scaffolds (Orgaz et al., 2016) [1]. They were then nitrided with a hot ammonia flow as described in (Aleixandre et al., 1973) [3] and (Nieto, 1984) [4] to synthesize the ICIE16/BSG-NITRI bioglass (Orgaz et al., 2016) [1]. Herein we present a flow chart summarizing the forming process, plus images of the resulting scaffold after sintering and drying. Bioactivity was characterized in vitro by immersion in simulated body fluid (SBF) for up to seven days. Data of ionic release kinetics upon SBF immersion are presented.

  6. Synthesis of novel ICIE16/BSG and ICIE16/BSG-NITRI bioglasses and description of ionic release kinetics upon immersion in SBF fluid: Effect of nitridation

    PubMed Central

    Orgaz, Felipe; Amat, Daniel; Szycht, Olga; Dzika, Aleksandra; Barba, Flora; Becerra, José; Santos-Ruiz, Leonor

    2015-01-01

    A novel bioactive glass scaffold ICIE16/BSG has been prepared from a mixture of two different melt-derived glasses: a silicate bioglass (ICIE16) and a borosilicate bioglass (BSG). Combined processing techniques (gel casting and foam replication) were used to form three-dimensional, interconnected porous monolith scaffolds (Orgaz et al., 2016) [1]. They were then nitrided with a hot ammonia flow as described in (Aleixandre et al., 1973) [3] and (Nieto, 1984) [4] to synthesize the ICIE16/BSG-NITRI bioglass (Orgaz et al., 2016) [1]. Herein we present a flow chart summarizing the forming process, plus images of the resulting scaffold after sintering and drying. Bioactivity was characterized in vitro by immersion in simulated body fluid (SBF) for up to seven days. Data of ionic release kinetics upon SBF immersion are presented. PMID:26858981

  7. Plume Collection Strategies for Icy World Sample Return

    NASA Technical Reports Server (NTRS)

    Neveu, M.; Glavin, D. P.; Tsou, P.; Anbar, A. D.; Williams, P.

    2015-01-01

    Three icy worlds in the solar system display evidence of pluming activity. Water vapor and ice particles emanate from cracks near the south pole of Saturn's moon Enceladus. The plume gas contains simple hydrocarbons that could be fragments of larger, more complex organics. More recently, observations using the Hubble and Herschel space telescopes have hinted at transient water vapor plumes at Jupiter's moon Europa and the dwarf planet Ceres. Plume materials may be ejected directly from possible sub-surface oceans, at least on Enceladus. In such oceans, liquid water, organics, and energy may co-exist, making these environments habitable. The venting of habitable ocean material into space provides a unique opportunity to capture this material during a relatively simple flyby mission and return it to Earth. Plume collection strategies should enable investigations of evidence for life in the returned samples via laboratory analyses of the structure, distribution, isotopic composition, and chirality of the chemical components (including biomolecules) of plume materials. Here, we discuss approaches for the collection of dust and volatiles during flybys through Enceladus' plume, based on Cassini results and lessons learned from the Stardust comet sample return mission. We also highlight areas where sample collector and containment technology development and testing may be needed for future plume sample return missions.

  8. Large Collisions on Icy and Rocky Bodies with Strength

    NASA Astrophysics Data System (ADS)

    Davies, E.; Stewart, S. T.

    2015-12-01

    Here, we investigate the outcome of collisions between icy-rocky planetary embryos with strength. In the inner solar system, impacts between embryos are hypothesized to generate crustal dichotomies on global scales, e.g., the Borealis Basin on Mars. In the Kuiper Belt, such global scale collisions differ from the inner solar system in important ways. First, bodies are less massive and their mutual collision velocities are smaller in amplitude compared to the inner solar system. As a result, the amount of direct shock heating is small and very localized. Strength is an important factor because shear heating is a process that can deposit energy more deeply into the final body. With a small gravitational potential, the post impact shape of the body may exhibit features related to residual strength. The variety of possible post-impact structures depends on the pre-impact thermal state and level of differentiation of the silicate-ice mixture and impact conditions. Here, we focus on collisions scenarios proposed for the origin of the Pluto system using the CTH shock physics code. We report on the magnitude of thermal processing and residual strength for varying assumptions about initial conditions.

  9. A Power Conversion Concept for the Jupiter Icy Moons Orbiter

    NASA Technical Reports Server (NTRS)

    Mason, Lee S.

    2003-01-01

    The Jupiter Icy Moons Orbiter (JIMO) mission is currently under study by the Office of Space Science under the Project Prometheus Program. JIMO is examining the use of Nuclear Electric Propulsion (NEP) to carry scientific payloads to three Jovian moons. A potential power system concept includes dual 100 kWe Brayton converters, a deployable pumped loop heat rejection subsystem, and a 400 Vac Power Management and Distribution (PMAD) bus. Many trades were performed in aniving at this candidate power system concept. System-level studies examined design and off-design operating modes, determined startup requirements, evaluated subsystem redundancy options, and quantified the mass and radiator area of reactor power systems from 20 to 200 kWe. In the Brayton converter subsystem, studies were performed to investigate converter packaging options, and assess the induced torque effects on spacecraft dynamics due to rotating machinery. In the heat rejection subsystem, design trades were conducted on heat transport approaches, material and fluid options, and deployed radiator geometries. In the PMAD subsystem, the overall electrical architecture was defined and trade studies examined distribution approaches, voltage levels, and cabling options.

  10. Lunar and Planetary Science XXXV: Icy Worlds: Moving and Grooving

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Reports from the conference session entitled Icy Worlds: Moving and Grooving, include:Mass Anomalies on Ganymede; Europan Chaos and Lenticulae: A Synthesis of Size, Spacing, and Areal Density Analyses; Thermal and Topographic Tests of Europa Chaos Formation Models; Flexure of Europa s Lithosphere Due to Ridge-Loading; Ridges on Europa: Origin by Incremental Ice-Wedging ; Convergent Boundaries on Europa: a Numerical Approach to Euler Pole Analysis and Its' Implications for Plate Reconstruction; Numerical Simulations of Subsolidus Convection in the Ice Shell of Europa: Implications for the Thermal Evolution and Present State; Effects of Plasticity on Convection in an Ice Shell: Implications for Europa; Non-Newtonian Convection and Compositional Buoyancy: Advances in Modeling Convection and Dome Formation on Europa; Convective Instability in Ice I: Application to Callisto and Ganymede; Crater Size Distributions on Callisto: A Galileo SSI Summary; Neutron Diffraction Studies of Planetary Ices; and H2O2 Synthesis Induced by Irradiation of H2O with Energetic H+ and Ar+ Ions at Various Temperatures.

  11. Methane and Nitrogen Abundances on the Icy Dwarf Planet Makemake

    NASA Astrophysics Data System (ADS)

    Tegler, Stephen C.; Grundy, William M.; Dillingham, Randy; Fish, Derek; Hendler, Nathan; Sufflebeam, Terry

    2014-11-01

    We present an optical spectrum of the icy dwarf planet Makemake from the MMT 6.5 meter telescope and Red Channel Spectrograph (6250 - 9800 angstroms; 3.5 angstroms per pixel; exposure time 7h 30m) on Mt. Hopkins, AZ. In addition, we present laboratory transmission spectra over similar wavelengths of methane-nitrogen ice mixtures from the Astrophysical Ice Laboratory in the Department of Physics and Astronomy at Northern Arizona University. By anchoring our analysis with the methane-nitrogen phase diagram of Prokhvatilov and Yantsevich (1983, Sov. J. Low Temp. Phys., 9, 94), and comparing methane bands in our Makemake spectrum and methane bands in our laboratory spectra, we are able to make the first quantitative estimate of Makemake's methane and nitrogen abundances. We compare Makemake’s abundances with our previously derived abundances for Triton, Pluto, and Eris (see Tegler et al., 2012, ApJ, 751, 76). We gratefully acknowledge support from the NASA Solar Systems Observations and Solar System Workings programs. We thank Steward Observatory for the consistent allocation of telescope time.

  12. Global multispectral mosaics of the icy Galilean satellites

    NASA Technical Reports Server (NTRS)

    Johnson, T. V.; Mosher, J. A.; Kupferman, P.; Soderblom, L. A.; Danielson, G. E.; Cook, A. F.

    1983-01-01

    Multispectral mosaics of the three icy Galilean satellites have been produced from low- to moderate-resolution Voyager images. The digital image data have been calibrated using preflight and in-flight calibration data, and reduced to normal albedos for four-color band passes, centered at 0.35, 0.41, 0.48, and 0.59 microns. The individual images have been geometrically corrected, mosaiked, and presented in a normal cylindrical map projection at a uniform scale of 8 km/pixel. Preliminary analysis of the normal albedo data shows that (1) the darkest terrains on the satellites are the dark regions on Callisto, (2) the brightest regions are bright plains regions on Europa and bright, fresh craters on Ganymede, (3) bright craters on Ganymede and its dark, cratered regions are both significantly brighter than comparable terrains on Callisto, and (4) Europa exhibits several distinct spectral units, with regions on the trailing hemisphere having lower relative ultraviolet spectral reflectance than areas on the leading hemisphere. This is consistent with proposals that Io-related plasma impact on Europa's trailing side has altered its optical properties.

  13. 10 years of mapping the icy saturnian satellites

    NASA Astrophysics Data System (ADS)

    Roatsch, Thomas; Kersten, Elke; Matz, Klaus-Dieter; Porco, Carolyn

    2014-05-01

    The Cassini spacecraft started its tour through the Saturnian system in July 2004. The Imaging Science Subsystem onboard the orbiter con-sists of a high-resolution Narrow Angle Camera (NAC) with a focal length of 2000 mm and a Wide Angle Camera (WAC) with a focal length of 200 mm [1]. One of the main objectives of the Cassini mission is to investigate the icy Saturnian satellites. These satellites were imaged in many flybys during the no-minal mission between 2004 and 2008. The imaging campaign continued during the first extended mission (''Equinox mission'') between 2008 and 2010 and continues during the current second extended mission (''Solstice mission''). It is now possible to image also the Northern parts of the Icy satellites which were not illuminated during the nominal mission. Mosaicking: The image data processing chain con-sists of the same steps as described in [2]: radiometric calibration, geometric correction, map projection, and mosaicking. Spacecraft position and camera pointing data are available in the form of SPICE kernels (http://naif.jpl.nasa.gov). While the orbit information is sufficiently accurate to be used directly for mapping purposes, the pointing information must be corrected using limb fits (semi-controlled mosaics) or by photo-grammetric bundle adjustment (controlled mosaics). The coordinate system adopted by the Cassini mis-sion for satellite mapping is the IAU ''planetographic'' system, consisting of planetographic latitude and posi-tive West longitude. The surface position of the prime meridian as defined by the IAU cartography working group [3] is defined by small craters. New values for the rotational parameter W0 which defines the location of the prime meridian at January 1, 2000 were calcula-ted based on the high-resolution mosaics to be consis-tent with this definition [4] and approved by the IAU [3]. Cartographic maps: Three different quadrangle schemes were used for the generation of the maps and the atlases [5]: • A

  14. FGF growth factor analogs

    DOEpatents

    Zamora, Paul O.; Pena, Louis A.; Lin, Xinhua; Takahashi, Kazuyuki

    2012-07-24

    The present invention provides a fibroblast growth factor heparin-binding analog of the formula: ##STR00001## where R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, X, Y and Z are as defined, pharmaceutical compositions, coating compositions and medical devices including the fibroblast growth factor heparin-binding analog of the foregoing formula, and methods and uses thereof.

  15. Sublimating grains model of cometary coma.

    NASA Astrophysics Data System (ADS)

    Faggi, S.; Tozzi, G. P.; Brucato, J. R.

    Billion years of space weathering produces a crust of organic matter (see e.g. Kanuchova et al. 2012) that will be released when a comet enter for the first time in the inner Solar System. New comets, coming form the Oort Colud at their first passage close to the Sun, are particularly important because they are not differentiated by the Solar radiation and they are supposed to have a large quantity of ice organic matter close to the surface. When a comet approach to the Sun, its activity is driven by the sublimation of these nucleus ices: if the heliocentric distances, R_H , is greater than 3 AU the sublimation of CO and CO_2 ices is the main source of comet activity, otherwise at shorter distances, the sublimation of water become the most important mechanism of activity. These gases, escaping from the nucleus, drag in the coma grains that can be refractory dust (silicates, carbon), water ice and/or organic ices. Oort comets at their first passage in the inner Solar System, should produce an halo of organic or water icy particles. Our group has been monitoring new, inbound, bright Oort comets (C/2011 F1, C/2012 S1, C/2012 K1, C/2013 V5, C/2012 F3, C/2013 US10, C/2013 X1) to search for these icy grains. The method consists in detecting the cloud of sublimating grains in the inner coma by using the Sigma Af function (Tozzi et al. 2007) directly from images. However this over-population of grains, beside the sublimation, can be also due to short time activity (outburst) or too big grains expanding at very slow velocity, as it has been found in comet 67P/C-G (Tozzi eta al, 2011, A&A, 531, 54). To disentangle between the phenomena it is necessary to monitor the comet both at short timescale, for the outbursts (by repeating the observations after few nights), and at long term (weeks-months). If the cloud does not expand with the decreasing of the heliocentric distance there is high probability that we are in presence of organic and/or water ice grains. We can disentangle

  16. Gravito-electromagnetic analogies

    NASA Astrophysics Data System (ADS)

    Costa, L. Filipe O.; Natário, José

    2014-10-01

    We reexamine and further develop different gravito-electromagnetic (GEM) analogies found in the literature, and clarify the connection between them. Special emphasis is placed in two exact physical analogies: the analogy based on inertial fields from the so-called "1+3 formalism", and the analogy based on tidal tensors. Both are reformulated, extended and generalized. We write in both formalisms the Maxwell and the full exact Einstein field equations with sources, plus the algebraic Bianchi identities, which are cast as the source-free equations for the gravitational field. New results within each approach are unveiled. The well known analogy between linearized gravity and electromagnetism in Lorentz frames is obtained as a limiting case of the exact ones. The formal analogies between the Maxwell and Weyl tensors are also discussed, and, together with insight from the other approaches, used to physically interpret gravitational radiation. The precise conditions under which a similarity between gravity and electromagnetism occurs are discussed, and we conclude by summarizing the main outcome of each approach.

  17. Modelling the Internal Structure and Evolution of Small Icy Bodies of the Solar System

    NASA Astrophysics Data System (ADS)

    Prialnik, D.

    2016-08-01

    The evolution of the internal structure of icy bodies of the solar system is simulated by numerical codes. The results are compared to available observations. The activity of comets and the differentiated structure of large bodies can be explained.

  18. GRAIN SORTING IN COMETARY DUST FROM THE OUTER SOLAR NEBULA

    SciTech Connect

    Wozniakiewicz, P. J.; Bradley, J. P.; Ishii, H. A.; Brownlee, D. E.; Kearsley, A. T.; Burchell, M. J.; Price, M. C.

    2012-12-01

    Most young stars are surrounded by a disk of gas and dust. Close to the hot stars, amorphous dust grains from the parent molecular cloud are reprocessed into crystals that are then distributed throughout the accretion disk. In some disks, there is a reduction in crystalline grain size with heliocentric distance from the star. We investigated crystalline grain size distributions in chondritic porous (CP) interplanetary dust particles (IDPs) believed to be from small, icy bodies that accreted in outer regions of the solar nebula. The grains are Mg-rich silicates and Fe-rich sulfides, the two most abundant minerals in CP IDPs. We find that they are predominantly <0.25 {mu}m in radius with a mean grain size that varies from one CP IDP to another. We report a size-density relationship between the silicates and sulfides. A similar size-density relationship between much larger silicate and sulfide grains in meteorites from the asteroid belt is ascribed to aerodynamic sorting. Since the silicate and sulfide grains in CP IDPs are theoretically too small for aerodynamic sorting, their size-density relationship may be due to another process capable of sorting small grains.

  19. Electrical Circuits and Water Analogies

    ERIC Educational Resources Information Center

    Smith, Frederick A.; Wilson, Jerry D.

    1974-01-01

    Briefly describes water analogies for electrical circuits and presents plans for the construction of apparatus to demonstrate these analogies. Demonstrations include series circuits, parallel circuits, and capacitors. (GS)

  20. Grain growth and experimental deformation of fine-grained ice aggregates

    NASA Astrophysics Data System (ADS)

    Diebold, Sabrina; de Bresser, Hans; Spiers, Chris; Durham, William B.; Stern, Laura

    2010-05-01

    Ice is one of the most abundant materials in our solar system. It is the principal constituent of most of the moons of the outer solar system. Thus, the flow behavior of ice is of great interest when studying geodynamic processes on icy moons. Grain growth is an elementary process that is assumed to be important in the ice sheet layering of planetary moons, where temperatures 100-273 K exist. We concentrate on the questions to what extent grain growth may influence the evolution of strength of deforming ice and if the grain growth process is independent or dependent of deformation. The answers to these questions will help us to quantitatively test the hypothesis that the progressive evolution of the grain (crystal) size distribution of deforming and recrystallizing ice directly affects its rheological behaviour in terms of composite grain-size-sensitive (GSS) and grain-size-insensitive (GSI) creep, and that this might, after time, result in a steady state balance between mechanisms of GSS and GSI creep. We performed static grain growth experiments at different temperatures and a pressure (P) of 1 atm, and deformation experiments at P = 30-100 MPa starting in the GSS-creep field. The starting material ice Ih has a grain size < 2 μm and was generated by a special pressure-release technique described by Stern et al. (1997) resulting in dense ice aggregates. The ice grains of the polycrystalline starting samples were randomly oriented and the material has a porosity of < 0.5%. For the grain growth tests a Hart Scientific temperature bath was filled with d-Limonene as cooling medium. The ice specimens were put into sealed alumina cylinders. For the grain growth tests, temperatures (T) between 213 K and 268 K were chosen. The durations of these tests varied between one day and two weeks. For the deformation experiments, temperatures of > 170 K and strain rates between 10-8 s-1 and 10-4 s-1 were chosen. Grain sizes, grain size distributions and grain topologies were

  1. Phloem transport of arsenic species from flag leaf to grain during grain filling

    SciTech Connect

    Carey, Anne-Marie; Norton, Gareth J.; Deacon, Claire; Scheckel, Kirk G.; Lombi, Enzo; Punshon, Tracy; Guerinot, Mary Lou; Lanzirotti, Antonio; Newville, Matt; Choi, Yongseong; Price, Adam H.; Meharg, Andrew A.

    2011-09-20

    Strategies to reduce arsenic (As) in rice grain, below concentrations that represent a serious human health concern, require that the mechanisms of As accumulation within grain be established. Therefore, retranslocation of As species from flag leaves into filling rice grain was investigated. Arsenic species were delivered through cut flag leaves during grain fill. Spatial unloading within grains was investigated using synchrotron X-ray fluorescence (SXRF) microtomography. Additionally, the effect of germanic acid (a silicic acid analog) on grain As accumulation in arsenite-treated panicles was examined. Dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were extremely efficiently retranslocated from flag leaves to rice grain; arsenate was poorly retranslocated, and was rapidly reduced to arsenite within flag leaves; arsenite displayed no retranslocation. Within grains, DMA rapidly dispersed while MMA and inorganic As remained close to the entry point. Germanic acid addition did not affect grain As in arsenite-treated panicles. Three-dimensional SXRF microtomography gave further information on arsenite localization in the ovular vascular trace (OVT) of rice grains. These results demonstrate that inorganic As is poorly remobilized, while organic species are readily remobilized, from leaves to grain. Stem translocation of inorganic As may not rely solely on silicic acid transporters.

  2. Phloem Transport of Arsenic Species from Flag Leaf to Grain During Grain Filling

    SciTech Connect

    A Carey; G Norton; C Deacon; K Scheckel; E Lombi; T Punshon; M Guerinot; A Lanzirotti; M Newville; et al.

    2011-12-31

    Strategies to reduce arsenic (As) in rice grain, below concentrations that represent a serious human health concern, require that the mechanisms of As accumulation within grain be established. Therefore, retranslocation of As species from flag leaves into filling rice grain was investigated. Arsenic species were delivered through cut flag leaves during grain fill. Spatial unloading within grains was investigated using synchrotron X-ray fluorescence (SXRF) microtomography. Additionally, the effect of germanic acid (a silicic acid analog) on grain As accumulation in arsenite-treated panicles was examined. Dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were extremely efficiently retranslocated from flag leaves to rice grain; arsenate was poorly retranslocated, and was rapidly reduced to arsenite within flag leaves; arsenite displayed no retranslocation. Within grains, DMA rapidly dispersed while MMA and inorganic As remained close to the entry point. Germanic acid addition did not affect grain As in arsenite-treated panicles. Three-dimensional SXRF microtomography gave further information on arsenite localization in the ovular vascular trace (OVT) of rice grains. These results demonstrate that inorganic As is poorly remobilized, while organic species are readily remobilized, from leaves to grain. Stem translocation of inorganic As may not rely solely on silicic acid transporters.

  3. Search for Evidence of Life in Icy Bodies - Enceladus Sample Return Mission Concept

    NASA Astrophysics Data System (ADS)

    Kanik, Isik

    2016-07-01

    Beyond Earth, are there modern habitats elsewhere in the Solar System with necessary conditions, organic matter, water, energy, and nutrients to sustain life, and do organisms live there now? Water dominates the composition of Icy Worlds. Since life follows water on Earth, life might exist in Icy Worlds. Enceladus, as an icy world, appears to satisfy the necessary conditions for life, based on detailed examination by the Cassini spacecraft. Careful chemical characterization of plume materials is the most direct way to determine if this habitable environment is inhabited, and, if not, why not. This characterization requires laboratory analysis of returned samples. Finding and confirming new found life require comprehensive sample analyses collected from icy bodies such as Enceladus. In this presentation, we argue that sample return is necessary because the search for biomarkers is too complex and too "path dependent" to be conducted in situ. The habitability of Icy worlds such as Enceladus and Europa the accessibility of samples in the plume make this types of missions a high priority for astrobiology. Our mission concept, called "LIFE", will follow up on recent discoveries by conducting a more detailed in situ investigation of the organics in the plume and by returning samples to Earth for a search for biomarkers as evidence of life - or perhaps only prebiotic evolution. Sample return missions from icy world can be very costly; however, given the existence of a plume (as for Enceladus), the cost of returning samples can be substantially reduced by a flyby sample return.

  4. Core Shadow Zones of Terrestrial Planets and Icy Moons

    NASA Astrophysics Data System (ADS)

    Sohl, F.; Knapmeyer, M.; Gassner, L.; Lange, C.; Wagner, F. W.

    2011-12-01

    The internal dynamics of a planetary core is strongly dependent on its total radius. The volume/surface ratio of a planetary core is linked directly to the outgoing heat flux, which is also an indicator for the element partition between the surrounding mantle and the core. The determination of the core radius is thus an elementary step to better understand the origin and evolution of a planetary body. An observable that has been shown to serve as indicator for core size is the extent of the seismological (P-wave-) core shadow. It appears that the variation of seismic velocities with depth is dominated by quadratic terms, if not an essentially depth independent velocity can be assumed. The observed and predicted core shadow extents of many terrestrial planet models, computed as function of the relative core radius, thus align closely to the analytically derived function for objects with constant velocity profiles. The heavier solar system terrestrial planets, especially Venus and Earth, show the largest deviation from the relation between core radius and shadow width that holds for small bodies. For terrestrial planets more massive than Earth, as found for several exoplanets, the increasing internal pressure would cause increased curvature of tentative seismic rays and thus a more pronounced excursion from the relation for bodies with depth-independent elastic parameters. For Titan, a geophysical network has been suggested as a follow up to the highly successful Cassini-Huygens mission that is currently orbiting Saturn. Titan belongs to the class of weakly differentiated icy moons, which consist of an icy crust, underlain by a deep internal ocean and a central ice-rock body. Unlike any other moon in the solar system, Titan has a thick atmosphere that gives rise to surface processes resembling those on Earth. The goal of the proposed network is an improved understanding of the interactions between atmosphere, surficial ice and a putative subsurface water ocean. Key

  5. Internal Structure and Dynamics of Icy Satellites (Invited)

    NASA Astrophysics Data System (ADS)

    Spohn, T.

    2009-12-01

    The icy satellites of the giant planets have a wide variety of compositions as indicated by their average densities. The compositions range from almost completely ice as in the case of Tethys to mostly silicate rock as in the case of Europa. The present knowledge about the structure and interior dynamics of these satellites, unfortunately, remains speculative. For the icy Galilean satellites, the Moment of Inertia (MoI) factors are well constrained but only under the assumption that the satellites are in hydrostatic equilibrium. Satellite Doppler-tracking data on the Saturnian satellite Rhea also allow constraints on its interior structure. Of these satellites, Ganymede and Europa are likely to be fully differentiated with water/ice outer layers, rocky mantles and iron cores. Callisto appears to be incompletely differentiated with an ice shell overlying an ice-rock core. Rhea is undifferentiated or partly differentiated. The water/ice shell of Europa is comparatively thin, about 150km thick. It is agreed to be mostly liquid water with an a few tens of kilometer thick ice lid. The water/ice layer on Ganymede should have a thickness of roughly 1/3 of the surface radius. It likely contains a liquid water ocean that stretches from a depth of some tens to a hundred kilometers to a depth of around two hundred kilometers. The depth extent of this ocean is, however, not well constrained and depends on the composition of the ice, and its heat transfer properties. Magnetic induction signals at Callisto suggest that this satellite also has an ocean similar to Ganymede. While the presence of oceans are relatively well understood for Europa and Ganymede from heat balance considerations and the water ice phase diagram understanding Callisto’s ocean is more challenging. In particular, considering its incomplete differentiation status. Little is yet known about the interior structure of Titan - for which sufficiently accurate gravity data are still not available - and Triton

  6. Division of Icy Bodies into Groups Based on Surface Properties

    NASA Astrophysics Data System (ADS)

    Schaefer, Bradley E.; Rabinowitz, D. L.; Tourtellottte, S. W.

    2008-09-01

    We propose the division of the icy bodies in the outer Solar System into five groups based on their surface properties. This division can be equivalently made by three definitions involving: size/orbit/color; measured surface properties; the physical mechanisms that reprocess the surfaces. Our first group is the Small/Red bodies (including the red Centaurs, Kuiper Belt Objects, and Scattered Disk Objects) which are 1.5 mag. These surfaces all have albedo <16; percent, and have lost their volatile ices by Jeans escape with cosmic rays reddening the remaining ices. Our second group is the Small/Gray bodies (including the gray Centaurs, Scattered Disk Objects, and Trojans) which are <800; km in diameter and with B-R<1.5 mag. These surfaces all have very low albedo (<6; percent) because their surface ices have been lost due to heating by the Sun at some time in their past orbital history leaving only their original rocky material to cover the surface. Our third group is the Intermediate bodies (Quaoar, Orcus, and Charon) with diameters 800-1400 km. Their surfaces have lost some of the volatile ices (methane and nitrogen in particular) to Jeans escape, while the remaining ices contain ammonia and crystalline water ice with some cryovolcanism. Our fourth group is the Large bodies (Pluto, Eris, Sedna, Triton, and 2005 FY9) with diameters >1400; km. These bodies are large enough to support active cryovolcanism plus seasonal frost formation/sublimation and are large enough so that the methane and nitrogen ices dominate because they have not been lost to Jeans escape. Our fifth group is the Collisional bodies (including the 2003 EL61 collisional family) which all have similar orbits. Their surfaces all have very neutral colors, low opposition surges, and relatively high albedos, because the volatile ices were all lost during the collision leaving a young surface with only water ice.

  7. Saturn and 4 Icy Moons in Natural Color

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This approximate natural-color image shows Saturn, its rings, and four of its icy satellites. Three satellites (Tethys, Dione, and Rhea) are visible against the darkness of space, and another smaller satellite (Mimas) is visible against Saturn's cloud tops very near the left horizon and just below the rings. The dark shadows of Mimas and Tethys are also visible on Saturn's cloud tops, and the shadow of Saturn is seen across part of the rings. Saturn, second in size only to Jupiter in our Solar System, is 120,660 km (75,000 mi) in diameter at its equator (the ring plane) but, because of its rapid spin, Saturn is 10% smaller measured through its poles. Saturn's rings are composed mostly of ice particles ranging from microscopic dust to boulders in size. These particles orbit Saturn in a vast disk that is a mere 100 meters (330 feet) or so thick. The rings' thinness contrasts with their huge diameter--for instance 272,400 km (169,000 mi) for the outer part of the bright A ring, the outermost ring visible here. The pronounced concentric gap in the rings, the Cassini Division (named after its discoverer), is a 3500-km wide region (2200 mi, almost the width of the United States) that is much less populated with ring particles than the brighter B and A rings to either side of the gap. The rings also show some enigmatic radial structure ('spokes'), particularly at left. This image was synthesized from images taken in Voyager's blue and violet filters and was processed to recreate an approximately natural color and contrast.

  8. New Approach to Icy Satellite Tidal Response Modeling

    NASA Astrophysics Data System (ADS)

    Castillo-Rogez, Julie

    2009-09-01

    Based on the experimental determination of ice anelasticity over a wide frequency range, as well as previous studies of ice primary creep, Castillo-Rogez et al. (2009) inferred that, in most situations, the response of planetary ices to tidal stress is anelastic. As a result, tidal models assuming a viscoelastic, Maxwellian response can lead to erroneous estimates of tidal dissipation by several orders of magnitude. Numerous measurements show that the transient response of rock and ice during primary creep can be fitted with the Andrade model. Measurements of the response of ice to cyclic stress also demonstrate that the Andrade model can accurately match the ice attenuation behavior observed for a wide range of frequencies encompassing satellites tides. Input to the Andrade model can be inferred from the frequency-dependence of the attenuation observed in the transient regime. It also requires a good understanding of the nature and properties of the microstructural features involved in the internal friction. Fortunately, numerous laboratory measurements have been reported in the literature for a variety of deformation regimes. Thus it is possible to make an educated guess about the ice attenuation behavior expected as a function of context. I will introduce a preliminary version of a new dissipation model applicable to icy satellites and present the measurement roadmap undertaken in the JPL Planetary Tides Simulation Facility to establish empirical forms of the Andrade model as a function of temperature, stress, composition, microstructure and its evolution with time, over a frequency range that encompasses the anelastic and viscoelastic regimes of a variety of ices. Acknowledgement: This work has been conducted at the Jet Propulsion Laboratory, Caltech under a contract with NASA. Government sponsorship acknowledged. JPL Research and Technology Development program acknowledged.

  9. Chemistry and Spectroscopy of Frozen Chloride Salts on Icy Bodies

    NASA Astrophysics Data System (ADS)

    Johnson, Paul; Thomas, Elena C.; Hodyss, Robert; Vu, Tuan; Choukroun, Mathieu

    2016-10-01

    Currently, our understanding of the chemical composition of Europa's surface is our best means of inferring constraints on the subsurface ocean composition and its subsequent habitability. The bulk of our knowledge of Europa surface chemistry can be traced to near infrared spectra recorded by the Near Infrared Mapping Spectrometer on the Galileo spacecraft. However, the usefulness of this and other remote sensing data is limited by the availability of spectral libraries of candidate materials under relevant conditions (temperature, thermal/radiation history, etc.). Chloride salts are expected to exist on the surface of Europa, and other icy bodies, based on geochemical predictions of the ocean composition. In order to help improve our understanding of Europa's surface composition, we have conducted a study of frozen chloride-salt brines prepared under simulated Europa surface conditions (vacuum, temperature, and UV irradiation) using both near IR and Raman spectroscopies. Specifically, Raman spectroscopy was used to determine the hydration states of various chloride salts as a function of temperature. Near IR spectroscopy of identically prepared samples was used to provide reference reflectance spectra of the identified hydrated salts. Our results indicate that at temperatures ranging from 80 K to 233 K, hydrohalite is formed from the freezing of NaCl brines, while the freezing of KCl solutions does not form KCl hydrates. In addition, the freezing of MgCl2 solutions forms a stable hexahydrate, and the freezing of CaCl2 solutions forms a hexahydrate, a tetrahydrate, and a dihydrate. Dehydration of the salts was observed as temperatures were increased, leading to a succession of hydration states in the case of CaCl2.

  10. Whole Grains and Fiber

    MedlinePlus

    ... fiber. Some examples of refined grains are wheat flour, enriched bread and white rice. Most refined grains are enriched , which means that ... grains. Some examples of enriched grains are wheat flour, enriched bread and white rice. Eating whole grains provides important health benefits: Many ...

  11. Electrical analogous in viscoelasticity

    NASA Astrophysics Data System (ADS)

    Ala, Guido; Di Paola, Mario; Francomano, Elisa; Li, Yan; Pinnola, Francesco P.

    2014-07-01

    In this paper, electrical analogous models of fractional hereditary materials are introduced. Based on recent works by the authors, mechanical models of materials viscoelasticity behavior are firstly approached by using fractional mathematical operators. Viscoelastic models have elastic and viscous components which are obtained by combining springs and dashpots. Various arrangements of these elements can be used, and all of these viscoelastic models can be equivalently modeled as electrical circuits, where the spring and dashpot are analogous to the capacitance and resistance, respectively. The proposed models are validated by using modal analysis. Moreover, a comparison with numerical experiments based on finite difference time domain method shows that, for long time simulations, the correct time behavior can be obtained only with modal analysis. The use of electrical analogous in viscoelasticity can better reveal the real behavior of fractional hereditary materials.

  12. Analogical Reasoning in Geometry Education

    ERIC Educational Resources Information Center

    Magdas, Ioana

    2015-01-01

    The analogical reasoning isn't used only in mathematics but also in everyday life. In this article we approach the analogical reasoning in Geometry Education. The novelty of this article is a classification of geometrical analogies by reasoning type and their exemplification. Our classification includes: analogies for understanding and setting a…

  13. Digital and analog communication systems

    NASA Technical Reports Server (NTRS)

    Shanmugam, K. S.

    1979-01-01

    The book presents an introductory treatment of digital and analog communication systems with emphasis on digital systems. Attention is given to the following topics: systems and signal analysis, random signal theory, information and channel capacity, baseband data transmission, analog signal transmission, noise in analog communication systems, digital carrier modulation schemes, error control coding, and the digital transmission of analog signals.

  14. Enantiomeric Excesses Induced in Amino Acids by Ultraviolet Circularly Polarized Light Irradiation of Extraterrestrial Ice Analogs: A Possible Source of Asymmetry for Prebiotic Chemistry

    NASA Astrophysics Data System (ADS)

    Modica, Paola; Meinert, Cornelia; de Marcellus, Pierre; Nahon, Laurent; Meierhenrich, Uwe J.; Le Sergeant d'Hendecourt, Louis

    2014-06-01

    The discovery of meteoritic amino acids with enantiomeric excesses of the L-form (ee L) has suggested that extraterrestrial organic materials may have contributed to prebiotic chemistry and directed the initial occurrence of the ee L that further led to homochirality of amino acids on Earth. A proposed mechanism for the origin of ee L in meteorites involves an asymmetric photochemistry of extraterrestrial ices by UV circularly polarized light (CPL). We have performed the asymmetric synthesis of amino acids on achiral extraterrestrial ice analogs by VUV CPL, investigating the chiral asymmetry transfer at two different evolutionary stages at which the analogs were irradiated (regular ices and/or organic residues) and at two different photon energies (6.6 and 10.2 eV). We identify 16 distinct amino acids and precisely measure the L-enantiomeric excesses using the enantioselective GC × GC-TOFMS technique in five of them: α-alanine, 2,3-diaminopropionic acid, 2-aminobutyric acid, valine, and norvaline, with values ranging from ee L = -0.20% ± 0.14% to ee L = -2.54% ± 0.28%. The sign of the induced ee L depends on the helicity and the energy of CPL, but not on the evolutionary stage of the samples, and is the same for all five considered amino acids. Our results support an astrophysical scenario in which the solar system was formed in a high-mass star-forming region where icy grains were irradiated during the protoplanetary phase by an external source of CPL of a given helicity and a dominant energy, inducing a stereo-specific photochemistry.

  15. Enantiomeric excesses induced in amino acids by ultraviolet circularly polarized light irradiation of extraterrestrial ice analogs: A possible source of asymmetry for prebiotic chemistry

    SciTech Connect

    Modica, Paola; De Marcellus, Pierre; D'Hendecourt, Louis Le Sergeant; Meinert, Cornelia; Meierhenrich, Uwe J.; Nahon, Laurent E-mail: ldh@ias.u-psud.fr

    2014-06-10

    The discovery of meteoritic amino acids with enantiomeric excesses of the L-form (ee {sub L}) has suggested that extraterrestrial organic materials may have contributed to prebiotic chemistry and directed the initial occurrence of the ee {sub L} that further led to homochirality of amino acids on Earth. A proposed mechanism for the origin of ee {sub L} in meteorites involves an asymmetric photochemistry of extraterrestrial ices by UV circularly polarized light (CPL). We have performed the asymmetric synthesis of amino acids on achiral extraterrestrial ice analogs by VUV CPL, investigating the chiral asymmetry transfer at two different evolutionary stages at which the analogs were irradiated (regular ices and/or organic residues) and at two different photon energies (6.6 and 10.2 eV). We identify 16 distinct amino acids and precisely measure the L-enantiomeric excesses using the enantioselective GC × GC-TOFMS technique in five of them: α-alanine, 2,3-diaminopropionic acid, 2-aminobutyric acid, valine, and norvaline, with values ranging from ee {sub L} = –0.20% ± 0.14% to ee {sub L} = –2.54% ± 0.28%. The sign of the induced ee {sub L} depends on the helicity and the energy of CPL, but not on the evolutionary stage of the samples, and is the same for all five considered amino acids. Our results support an astrophysical scenario in which the solar system was formed in a high-mass star-forming region where icy grains were irradiated during the protoplanetary phase by an external source of CPL of a given helicity and a dominant energy, inducing a stereo-specific photochemistry.

  16. Between ice and gas: CO2 on the icy satellites of Jupiter and Saturn

    NASA Astrophysics Data System (ADS)

    Hibbitts, C.

    2010-12-01

    CO2 exists in the surfaces of the icy Galilean and Saturnian satellites [1-6], yet despite its discovery over a decade ago on Ganymede, and five years ago on the Saturnian satellites, its nature is still debated [7]. On the Galilean satellites Callisto and Ganymede, the CO2 that is detected is bound to, or trapped within, the non-ice materials that prevent it from sublimating or otherwise escaping from the surface. On Europa, it resides within both the ice and nonice materials [8,9]. While greater abundances of CO2 may exist in the interiors of these moons, or small amounts may be continually created through particle bombardment of the surface, the observed CO2 is only a trace material, with a few hundred molecules responsible for the deepest absorption features and an estimated molar abundance of 0.1% [2; 10-12]. Yet its presence may provide essential clues to processes that shape the surfaces of the moon [13] and potentially key to understanding the composition of potential oceans in the subsurfaces. We continue measurements of the infrared properties associated with CO2 adsorbed onto nonice materials under pressures and at temperatures relevant to these icy satellites using bidirectional reflectance spectroscopy from ~ 1.5 to 5.5 μm. Previous measurements, using transmission spectroscopy, demonstrated both a compositional and a temperature dependence on the spectral signature of adsorbed CO2 [14]. Bidirectional spectroscopy enables detection of lower concentrations of adsorbate on fine-grained materials such as clays due to their large surface area to volume ratios and thus large surface areas that may be covered by adsorbate [15]. The effectiveness of transmission spectroscopy was also limited by the strong absorption of light within the pressed sample and its impermeability, which limited the coverage by adsorbate to the pellet’s outer surface. All measurements demonstrate that CO2 adsorbs onto montmorillonite clays, possibly due to its quadrupole moment

  17. Radar Sounding for Planetary Subsurface Exploration: Translating the Mars Experience to Jupiter's Icy Moons

    NASA Astrophysics Data System (ADS)

    Plaut, J.

    2015-12-01

    Exploration of the subsurface of Mars using radar sounding began with MARSIS (Mars Advanced Radar for Subsurface and Ionospheric Sounding) on Mars Express in 2005 and continued with SHARAD (Shallow Radar) on Mars Reconnaissance Orbiter in 2006. These instruments have been operating continuously since, providing a rich legacy of science return and observational experience in the highly variable environments and target sets at Mars. New missions to the icy moons of Jupiter, ESA's JUICE (Jupiter Icy Moon Explorer) and NASA's Europa Mission, will both carry radar sounders to probe the subsurface of several of the icy moons (Ganymede, Europa and Callisto by JUICE; Europa by the Europa Mission). The success of the Mars sounders demonstrated the scientific value of the technique and provided confidence that sounding of the icy moons is a promising endeavor. Icy targets at Mars have proven especially amenable to penetration by radar sounding. The polar layered deposits of Mars have been probed to their base (2-4 km deep) by MARSIS, operating at frequencies of 1.3-5.5 MHz. SHARAD, operating with a wider bandwidth at 15-25 MHz, provides higher vertical resolution that allows detection and imaging of fine details of interior layering in the ice deposits. The sounder planned for the Europa mission, REASON (Radar for Europa Assessment and Sounding, Ocean to Near-Surface), will utilize simultaneous dual frequency signals to obtain complementary deep sounding and high-vertical-resolution shallow observations. Co-located observations by MARSIS and SHARAD also demonstrate that high surface roughness (relative to the radar wavelength) affects the strength of the penetrating signals, and thus the capability to detect deep or low-contrast subsurface interfaces. The icy moon sounders' wavelengths were selected, in part, to mitigate against this degradation of signals by the anticipated rough surfaces of Jupiter's moons. This paper will discusss these and other examples of lessons

  18. Analogy, explanation, and proof

    PubMed Central

    Hummel, John E.; Licato, John; Bringsjord, Selmer

    2014-01-01

    People are habitual explanation generators. At its most mundane, our propensity to explain allows us to infer that we should not drink milk that smells sour; at the other extreme, it allows us to establish facts (e.g., theorems in mathematical logic) whose truth was not even known prior to the existence of the explanation (proof). What do the cognitive operations underlying the inference that the milk is sour have in common with the proof that, say, the square root of two is irrational? Our ability to generate explanations bears striking similarities to our ability to make analogies. Both reflect a capacity to generate inferences and generalizations that go beyond the featural similarities between a novel problem and familiar problems in terms of which the novel problem may be understood. However, a notable difference between analogy-making and explanation-generation is that the former is a process in which a single source situation is used to reason about a single target, whereas the latter often requires the reasoner to integrate multiple sources of knowledge. This seemingly small difference poses a challenge to the task of marshaling our understanding of analogical reasoning to understanding explanation. We describe a model of explanation, derived from a model of analogy, adapted to permit systematic violations of this one-to-one mapping constraint. Simulation results demonstrate that the resulting model can generate explanations for novel explananda and that, like the explanations generated by human reasoners, these explanations vary in their coherence. PMID:25414655

  19. Arterial Pressure Analog.

    ERIC Educational Resources Information Center

    Heusner, A. A.; Tracy, M. L.

    1980-01-01

    Describes a simple hydraulic analog which allows students to explore some physical aspects of the cardiovascular system and provides them with a means to visualize and conceptualize these basic principles. Simulates the behavior of arterial pressure in response to changes in heart rate, stroke volume, arterial compliance, and peripheral…

  20. Quantum Analog Computing

    NASA Technical Reports Server (NTRS)

    Zak, M.

    1998-01-01

    Quantum analog computing is based upon similarity between mathematical formalism of quantum mechanics and phenomena to be computed. It exploits a dynamical convergence of several competing phenomena to an attractor which can represent an externum of a function, an image, a solution to a system of ODE, or a stochastic process.

  1. Reasoning through Instructional Analogies

    ERIC Educational Resources Information Center

    Kapon, Shulamit; diSessa, Andrea A.

    2012-01-01

    This article aims to account for students' assessments of the plausibility and applicability of analogical explanations, and individual differences in these assessments, by analyzing properties of students' underlying knowledge systems. We developed a model of explanation and change in explanation focusing on knowledge elements that provide a…

  2. How Analogy Drives Physics

    SciTech Connect

    Hofstadter, Doug

    2004-05-05

    Many new ideas in theoretical physics come from analogies to older ideas in physics. For instance, the abstract notion of 'isospin' (or isotopic spin) originated in the prior concept of 'spin' (quantized angular momentum); likewise, the concept of 'phonon' (quantum of sound, or quantized collective excitation of a crystal) was based on the prior concept of 'photon' (quantum of light, or quantized element of the electromagnetic field). But these two examples, far from being exceptions, in fact represent the bread and butter of inventive thinking in physics. In a nutshell, intraphysics analogy-making -- borrowing by analogy with something already known in another area of physics -- is central to the progress of physics. The aim of this talk is to reveal the pervasiveness -- indeed, the indispensability -- of this kind of semi-irrational, wholly intuitive type of thinking (as opposed to more deductive mathematical inference) in the mental activity known as 'doing physics'. Speculations as to why wild analogical leaps are so crucial to the act of discovery in physics (as opposed to other disciplines) will be offered.

  3. Analog signal isolation techniques

    SciTech Connect

    Beadle, E.R.

    1992-12-31

    This paper discusses several techniques for isolating analog signals in an accelerator environment. The techniques presented here encompass isolation amplifiers, voltage-to-frequency converters (VIFCs), transformers, optocouplers, discrete fiber optics, and commercial fiber optic links. Included within the presentation of each method are the design issues that must be considered when selecting the isolation method for a specific application.

  4. Analog signal isolation techniques

    SciTech Connect

    Beadle, E.R.

    1992-01-01

    This paper discusses several techniques for isolating analog signals in an accelerator environment. The techniques presented here encompass isolation amplifiers, voltage-to-frequency converters (VIFCs), transformers, optocouplers, discrete fiber optics, and commercial fiber optic links. Included within the presentation of each method are the design issues that must be considered when selecting the isolation method for a specific application.

  5. Lunar magnetism, space weathering, and icy satellite interiors

    NASA Astrophysics Data System (ADS)

    Hemingway, Douglas

    An enduring mystery since Apollo is that, in spite of the Moon's lack of a global magnetic field, the surface is nevertheless dotted with regional magnetic fields strong enough to be detected from orbit. Did the Moon once have an intrinsic global field that magnetized parts of the crust but has since decayed away? This is a question of fundamental importance to understanding the formation and evolution of solid planetary bodies, and yet it remains unanswered due in part to limitations in our knowledge of these crustal magnetic anomalies. Adding to the puzzle, many of these magnetic anomalies are accompanied by enigmatic optical features, known as swirls, which may hold the key to understanding "space weathering"---a process by which airless bodies change color over time due to exposure to solar wind and micrometeoroids. Here we show both that swirl morphology provides information about the structure of the underlying magnetic sources, and that the color of the lunar surface varies systematically with latitude in a way that allows us to distinguish between the effects of solar wind ion and micrometeoroid bombardment, addressing a decades-old problem in remote sensing, and aiding in the interpretation of the spectra of airless bodies throughout the solar system. The remarkable diversity of the outer solar system's satellites provides important clues about the formation and evolution of the solar system. Many of the satellites have surprisingly young surfaces, owing in some cases to on-going geologic activity. Moreover, the existence of subsurface oceans within some of the satellites raises the intriguing possibility of extant habitable environments in the outer solar system. Determining the properties of their ice shells and the structures of their deep interiors places fundamental constraints on how the icy satellites formed and evolved, and on what governs their behavior today. Using gravity and topography data from Cassini, we develop analytical models showing

  6. The Origins and Evolution of Molecules in Icy Solids

    NASA Technical Reports Server (NTRS)

    Hudson, Reggie L.; Moore, Marla H.

    2010-01-01

    Astronomical observations of the past few decades have revealed the existence of a variety of molecules in extraterrestrial ices. These molecules include H2O, CO, and CO2, and organics such as CH4, CH30H, and C2H6. Some ices are dominated by polar molecules, while non-polar species appear to dominate others. Observations, mainly in the radio and IR regions, have allowed the inference of other solid-phase molecules whose formation remains difficult to explain by gas-phase chemistry alone. Several laboratory research groups have reported on extensive experiments on the solid-phase reaction chemistry of icy materials, generally as initiated by either ionizing radiation or vacuum-UV photons. These experiments not only permit molecular identifications to be made from astronomical observations, but also allow predictions of yet unidentified molecules. This laboratory approach has evolved over more than 30 years with much of the earliest work focusing on complex mixtures thought to represent either cometary or interstellar ices. Although those early experiments documented a rich solid-state photo- and radiation chemistry, they revealed few details of reactions for particular molecules, partly due to the multi-component nature of the samples. Since then, model systems have been examined that allow the chemistry of individual species and specific reactions to be probed. Reactions involving most of the smaller astronomical molecules have now been studied and specific processes identified. Current laboratory work suggests that a variety of reactions occur in extraterrestrial ices, including acid-base processes, radical dimerizations, proton transfers, oxidations, reductions, and isomerizations. This workshop presentation will focus on chemical reactions relevant to solar system and interstellar ices. While most of the work will be drawn from that to which the speaker has contributed, results from other laboratories also will be included. Suggestions for future studies will be

  7. Iceless Icy Moons: Is the Nice Model In Trouble?

    NASA Astrophysics Data System (ADS)

    Dones, Henry C. Luke; Levison, H. F.

    2012-05-01

    Nimmo and Korycansky (2012; henceforth NK12) stated that if the outer Solar System underwent a Late Heavy Bombardment (LHB) in the Nice model, the mass striking the icy satellites at speeds up to tens of km/s would have vaporized so much ice that moons such as Mimas, Enceladus, and Miranda would have been devolatilized. NK12's possible explanations of this apparent discrepancy with observations include (1) the mass influx was a factor of 10 less than that in the Nice model; (2) the mass distribution of the impactors was top-heavy, so that luck might have saved some of the moons from suffering large, vapor-removing impacts; or (3) the inner moons formed after the LHB. NK12 calculated the mass influx onto the satellites from the lunar impact rate estimated by Gomes et al. (2005) and scaling factors calculated by Zahnle et al. (1998, 2003; also see Barr and Canup 2010). Production of vapor in hypervelocity impacts is calculated from Kraus et al. (2011). Our preliminary results show that there is about an order-of-magnitude uncertainty in the mass striking the satellites during the LHB, with NK12's estimate at the upper end of the range. We will discuss how the mass influx depends on the velocity and mass distributions of the impactors. The Nice model lives. We thank the NASA Lunar Science Institute (http://lunarscience.nasa.gov/) for support. Barr, A.C., Canup, R.M., Nature Geoscience 3, 164-167 (2010). Gomes, R., Levison, H.F., Tsiganis, K., Morbidelli, A., Nature 435, 466-469 (2005). Kraus, R.G., Senft, L.E., Stewart, S.T., Icarus 214, 724-738 (2011). Nimmo, F., Korycansky, D.G., Icarus, in press, http://www.sciencedirect.com/science/article/pii/S0019103512000310 (2012). Zahnle, K., Dones, L., Levison, H.F., Icarus 136, 202-222 (1998). Zahnle, K., Schenk, P., Levison, H.F., Dones, L., Icarus 163, 263-289 (2003).

  8. Cryovolcanic Conduit Evolution and Eruption on Icy Satellites

    NASA Astrophysics Data System (ADS)

    Mitchell, K. L.

    2014-12-01

    In silicate volcanism, such as on Earth or Io, eruptions typically result from fracture formation caused by interaction of tectonic stresses with inflating, pressurized magma sources, leading to transport of melt through an evolving conduit. On icy satellites the paradigm may be similar, resulting from some combination of tidal stresses and expansion of freezing water within, or near the base of, an ice shell. Such a fracture will result in eruption if mass continuity can be established, with buoyancy aided by exsolution and expansion of dissolved volatiles. After onset, conduit shape evolves due to: (1) shear-stresses or frictional erosional; (2) wallrock "bursting" due to massive wall stresses; (3) wall melting or condensation of particles due to heat transfer; or (4) changes in applied stresses. Preliminary thermodynamic and fluid mechanical analysis suggests some initial cooling during ascent resulting from exsolution and expansion of volatiles, thermally buffered by freezing, Conduit contraction may occur, and so evolution towards a deep, gas-filled plume chamber is difficult to accommodate without evoking a co-incidental process. Conduit flaring occurs near the surface where velocities are greatest, enhancing erosion. Here, viscous dissipative heating exceeds adiabatic cooling, and so some boiling (a few wt%) may occur. In contrast with silicate volcanism, decompression to below the triple point will occur within conduit, vent or jet, resulting in rapid freezing and boiling of the remaining water at a 6.8:1 ratio. Subsequent isentropic or adiabatic expansion within erupting jets may result in a few percent net of condensation or sublimation. These effects combined lead to ~4:1-7:1 solid:vapor ratios in the jet for most eruption conditions. These figures are consistent with the ~6:1 inferred in Enceladus' jets, supporting the hypothesis that the Enceladus plume draws from a subsurface body of liquids through a conduit. Similar results are anticipated if

  9. Interpretation of surface properties of comet 67P/Churyumov-Gerasimenko using bidirectional reflectance studies of laboratory cometary analogs

    NASA Astrophysics Data System (ADS)

    Jost, Bernhard; Pommerol, Antoine; Poch, Olivier; Fornasier, Sonia; Hasselmann, Pedro Henrique; Feller, Clément; Carrasco, Nathalie; Szopa, Cyril; Thomas, Nicolas

    2016-10-01

    The European Space Agency's Rosetta mission has been orbiting the nucleus of comet 67P/Churyumov-Gerasimenko (67P) for more than 2 years. An enormous quantity of surface data at variable spatial resolution and over a wide range of the electromagnetic spectrum has been acquired by a series of complementary instruments during this period. The long accompany time allowed characterization and comparison of spectrophotometric properties in the pre- and post-perihelion phase.A profound knowledge of laboratory analogues of cometary surfaces is essential for interpreting remote sensing data. The LOSSy laboratory (Laboratory for Outflow Studies of Sublimating Materials) at the University of Bern was set up to study the spectrophotometric properties of ice-bearing cometary nucleus analogs. The laboratory is equipped with two instruments: the PHIRE-2 radio-goniometer [2], designed to measure the bidirectional visible reflectance of samples under a wide range of geometries and the SCITEAS simulation chamber [3], designed to study the evolution of icy samples subliming under low pressure/temperature conditions by hyperspectral imaging in the VIS-NIR range.We present reflectance data of various well characterized and reproducible mixtures of fine grained ice particles, tholins, and carbonaceous compounds that we systematically compare to the phase curves, albedo, spectrum and phase reddening observed by Rosetta at 67P [4].Our results allow us setting a lower limit of a few micrometers on the dust particle size and demonstrate that meter-sized bright patches have to be relatively dust free at small scale. Further we show that the most porous samples (p≈80%) best match the phase curve of 67P.[1] Keller, H. U., et al., 2007, Space Sci. Rev. 128, 26[2] Jost, B., et al., 2016. Icarus 264, 109-131.[3] Pommerol, A., et al., 2015. Planet Space Sci 109, 106-122.[4] Fornasier, S., et al., 2015. A&A 583, A30.

  10. Modeling KBOs Charon, Orcus and Salacia by means of a new equation of state for porous icy bodies

    NASA Astrophysics Data System (ADS)

    Malamud, U.; Prialnik, D.

    2015-10-01

    We use a one-dimensional adaptive-grid thermal evolution code to model intermediate sized Kuiper belt objects Charon, Orcus and Salacia and compare their measured bulk densities with those resulting from evolutionary calculations at the end of 4.6 Gyr. Our model assumes an initial homogeneous composition of mixed ice and rock, and follows the multiphase flow of water through the porous rocky medium, consequent differentiation and aqueous chemical alterations in the rock. Heating sources include long-lived radionuclides, serpentinization reactions, release of gravitational potential energy due to compaction, and crystallization of amorphous ice. The density profile is calculated by assuming hydrostatic equilibrium to be maintained through changes in composition, pressure and temperature. To this purpose, we construct an equation of state suitable for porous icy bodies with radii of a few hundred km, based on the best available empirical studies of ice and rock compaction, and on comparisons with rock porosities in Earth analog and Solar System silicates. We show that the observed bulk densities can be reproduced by assuming the same set of initial and physical parameters, including the same rock/ice mass ratio for all three bodies. We conclude that the mass of the object uniquely determines the evolution of porosity, and thus explains the observed differences in bulk density. The final structure of all three objects is differentiated, with an inner rocky core, and outer ice-enriched mantle. The degree of differentiation, too, is determined by the object's mass.

  11. A Submersible, Off-Axis Holographic Microscope for Detection of Microbial Motility and Morphology in Aqueous and Icy Environments.

    PubMed

    Lindensmith, Christian A; Rider, Stephanie; Bedrossian, Manuel; Wallace, J Kent; Serabyn, Eugene; Showalter, G Max; Deming, Jody W; Nadeau, Jay L

    2016-01-01

    Sea ice is an analog environment for several of astrobiology's near-term targets: Mars, Europa, Enceladus, and perhaps other Jovian or Saturnian moons. Microorganisms, both eukaryotic and prokaryotic, remain active within brine channels inside the ice, making it unnecessary to penetrate through to liquid water below in order to detect life. We have developed a submersible digital holographic microscope (DHM) that is capable of resolving individual bacterial cells, and demonstrated its utility for immediately imaging samples taken directly from sea ice at several locations near Nuuk, Greenland. In all samples, the appearance and motility of eukaryotes were conclusive signs of life. The appearance of prokaryotic cells alone was not sufficient to confirm life, but when prokaryotic motility occurred, it was rapid and conclusive. Warming the samples to above-freezing temperatures or supplementing with serine increased the number of motile cells and the speed of motility; supplementing with serine also stimulated chemotaxis. These results show that DHM is a useful technique for detection of active organisms in extreme environments, and that motility may be used as a biosignature in the liquid brines that persist in ice. These findings have important implications for the design of missions to icy environments and suggest ways in which DHM imaging may be integrated with chemical life-detection suites in order to create more conclusive life detection packages.

  12. Properties of filamentary sublimation residues from dispersions of clay in ice. [on Martian poles, comet nuclei, and icy satellites

    NASA Technical Reports Server (NTRS)

    Saunders, R. S.; Parker, T. J.; Stephens, J. B.; Fanale, F. P.; Sutton, S.

    1986-01-01

    Results are reported from experimental studies of the formation of ice mixed with mineral particles in an effort to simulate similar processes on natural surfaces such as at the Martian poles, on comet nuclei and on icy satellites. The study consisted of low-pressure, low-temperature sublimations of water ice from dilutions of water-clay (montmorillonite and Cabosil) dispersions of various component ratios. Liquid dispersions were sprayed into liquid nitrogen to form droplets at about -50 C. Both clay-water dispersions left a filamentary residue on the bottom of the Dewar after the water ice had sublimated off. The residue was studied with optical and SEM microscopy, the latter method revealing a high electrical conductivity in the residue. The results suggest that the sublimation of the water ice can leave a surface crust, which may be analogous to processes at the Martian poles and on comet nuclei. The process could proceed by the attachment of water molecules to salt crystals during the hottest part of the Martian year. The residue remaining was found to remain stable up to 370 C, be porous, and remain resilient, which could allow it to insulate ice bodies such as comets in space.

  13. A Submersible, Off-Axis Holographic Microscope for Detection of Microbial Motility and Morphology in Aqueous and Icy Environments.

    PubMed

    Lindensmith, Christian A; Rider, Stephanie; Bedrossian, Manuel; Wallace, J Kent; Serabyn, Eugene; Showalter, G Max; Deming, Jody W; Nadeau, Jay L

    2016-01-01

    Sea ice is an analog environment for several of astrobiology's near-term targets: Mars, Europa, Enceladus, and perhaps other Jovian or Saturnian moons. Microorganisms, both eukaryotic and prokaryotic, remain active within brine channels inside the ice, making it unnecessary to penetrate through to liquid water below in order to detect life. We have developed a submersible digital holographic microscope (DHM) that is capable of resolving individual bacterial cells, and demonstrated its utility for immediately imaging samples taken directly from sea ice at several locations near Nuuk, Greenland. In all samples, the appearance and motility of eukaryotes were conclusive signs of life. The appearance of prokaryotic cells alone was not sufficient to confirm life, but when prokaryotic motility occurred, it was rapid and conclusive. Warming the samples to above-freezing temperatures or supplementing with serine increased the number of motile cells and the speed of motility; supplementing with serine also stimulated chemotaxis. These results show that DHM is a useful technique for detection of active organisms in extreme environments, and that motility may be used as a biosignature in the liquid brines that persist in ice. These findings have important implications for the design of missions to icy environments and suggest ways in which DHM imaging may be integrated with chemical life-detection suites in order to create more conclusive life detection packages. PMID:26812683

  14. A Submersible, Off-Axis Holographic Microscope for Detection of Microbial Motility and Morphology in Aqueous and Icy Environments

    PubMed Central

    Lindensmith, Christian A.; Rider, Stephanie; Bedrossian, Manuel; Wallace, J. Kent; Serabyn, Eugene; Showalter, G. Max; Deming, Jody W.; Nadeau, Jay L.

    2016-01-01

    Sea ice is an analog environment for several of astrobiology’s near-term targets: Mars, Europa, Enceladus, and perhaps other Jovian or Saturnian moons. Microorganisms, both eukaryotic and prokaryotic, remain active within brine channels inside the ice, making it unnecessary to penetrate through to liquid water below in order to detect life. We have developed a submersible digital holographic microscope (DHM) that is capable of resolving individual bacterial cells, and demonstrated its utility for immediately imaging samples taken directly from sea ice at several locations near Nuuk, Greenland. In all samples, the appearance and motility of eukaryotes were conclusive signs of life. The appearance of prokaryotic cells alone was not sufficient to confirm life, but when prokaryotic motility occurred, it was rapid and conclusive. Warming the samples to above-freezing temperatures or supplementing with serine increased the number of motile cells and the speed of motility; supplementing with serine also stimulated chemotaxis. These results show that DHM is a useful technique for detection of active organisms in extreme environments, and that motility may be used as a biosignature in the liquid brines that persist in ice. These findings have important implications for the design of missions to icy environments and suggest ways in which DHM imaging may be integrated with chemical life-detection suites in order to create more conclusive life detection packages. PMID:26812683

  15. Modeling Kuiper belt objects Charon, Orcus and Salacia by means of a new equation of state for porous icy bodies

    NASA Astrophysics Data System (ADS)

    Malamud, Uri; Prialnik, Dina

    2015-01-01

    We use a one-dimensional adaptive-grid thermal evolution code to model Kuiper belt objects Charon, Orcus and Salacia and compare their measured bulk densities with those resulting from evolutionary calculations at the end of 4.6 Gyr. Our model assumes an initial homogeneous composition of mixed ice and rock, and follows the multiphase flow of water through the porous rocky medium, consequent differentiation and aqueous chemical alterations in the rock. Heating sources include long-lived radionuclides, serpentinization reactions, release of gravitational potential energy due to compaction, and crystallization of amorphous ice. The density profile is calculated by assuming hydrostatic equilibrium to be maintained through changes in composition, pressure and temperature. To this purpose, we construct an equation of state suitable for porous icy bodies with radii of a few hundred km, based on the best available empirical studies of ice and rock compaction, and on comparisons with rock porosities in Earth analog and Solar System silicates. We show that the observed bulk densities can be reproduced by assuming the same set of initial and physical parameters, including the same rock/ice mass ratio for all three bodies. We conclude that the mass of the object uniquely determines the evolution of porosity, and thus explains the observed differences in bulk density. The final structure of all three objects is differentiated, with an inner rocky core, and outer ice-enriched mantle. The degree of differentiation, too, is determined by the object's mass.

  16. TERRESTRIAL PLANET FORMATION THROUGH ACCRETION OF SUBLIMATING ICY PLANETESIMALS IN A COLD NEBULA

    SciTech Connect

    Machida, Ryosuke; Abe, Yutaka

    2010-06-20

    Most of the theories of the solar system formation stand on the assumption that the formation of planetesimals occurs in a transparent (i.e., optically thin) nebula, in which H{sub 2}O ice is unstable at the formation region of the terrestrial planet due to direct stellar irradiation. However, in the astronomical context, it is confirmed by both observations and numerical models that protoplanetary disks are initially opaque (i.e., optically thick) owing to floating small dust particles, and the interior of the disk is colder than the transparent disk. If planetesimals are formed in the opaque cold nebula, they should be mainly composed of H{sub 2}O ice, even at the formation region of terrestrial planets. Abundant icy material would help the formation of planetesimals through enhancement of the dust amount. Icy planetesimals start sublimation when the protoplanetary disk gets transparent through clearance of small dust particles. Here, we investigated the consequence of such icy planetesimal formation through numerical simulations of the competition between the sublimation and accretion of icy planetesimals. It was shown that various types of planets ranging from rocky planets to water-ball planets can be formed inside the location of the snow line of a transparent disk depending on the disk mass and the time evolution of disk transparency. We found size-dependent water content of icy planetesimals, which suggests potential difference in the redox state between meteorites and terrestrial planets at the same distance from the central star.

  17. Modelling Ocean Dissipation in Icy Satellites: A Comparison of Linear and Quadratic Friction

    NASA Astrophysics Data System (ADS)

    Hay, H.; Matsuyama, I.

    2015-12-01

    Although subsurface oceans are confirmed in Europa, Ganymede, Callisto, and strongly suspected in Enceladus and Titan, the exact mechanism required to heat and maintain these liquid reservoirs over Solar System history remains a mystery. Radiogenic heating can supply enough energy for large satellites whereas tidal dissipation provides the best explanation for the presence of oceans in small icy satellites. The amount of thermal energy actually contributed to the interiors of these icy satellites through oceanic tidal dissipation is largely unquantified. Presented here is a numerical model that builds upon previous work for quantifying tidally dissipated energy in the subsurface oceans of the icy satellites. Recent semi-analytical models (Tyler, 2008 and Matsuyama, 2014) have solved the Laplace Tidal Equations to estimate the time averaged energy flux over an orbital period in icy satellite oceans, neglecting the presence of a solid icy shell. These models are only able to consider linear Rayleigh friction. The numerical model presented here is compared to one of these semi-analytical models, finding excellent agreement between velocity and displacement solutions for all three terms to the tidal potential. Time averaged energy flux is within 2-6% of the analytical values. Quadratic (bottom) friction is then incorporated into the model, replacing linear friction. This approach is commonly applied to terrestrial ocean dissipation studies where dissipation scales nonlinearly with velocity. A suite of simulations are also run for the quadratic friction case which are then compared to and analysed against recent scaling laws developed by Chen and Nimmo (2013).

  18. The dust halo of Saturn's largest icy moon, Rhea.

    PubMed

    Jones, G H; Roussos, E; Krupp, N; Beckmann, U; Coates, A J; Crary, F; Dandouras, I; Dikarev, V; Dougherty, M K; Garnier, P; Hansen, C J; Hendrix, A R; Hospodarsky, G B; Johnson, R E; Kempf, S; Khurana, K K; Krimigis, S M; Krüger, H; Kurth, W S; Lagg, A; McAndrews, H J; Mitchell, D G; Paranicas, C; Postberg, F; Russell, C T; Saur, J; Seiss, M; Spahn, F; Srama, R; Strobel, D F; Tokar, R; Wahlund, J-E; Wilson, R J; Woch, J; Young, D

    2008-03-01

    Saturn's moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn's magnetosphere. The Cassini spacecraft's in situ observations reveal that energetic electrons are depleted in the moon's vicinity. The absence of a substantial exosphere implies that Rhea's magnetospheric interaction region, rather than being exclusively induced by sputtered gas and its products, likely contains solid material that can absorb magnetospheric particles. Combined observations from several instruments suggest that this material is in the form of grains and boulders up to several decimetres in size and orbits Rhea as an equatorial debris disk. Within this disk may reside denser, discrete rings or arcs of material.

  19. Grain Handling and Storage.

    ERIC Educational Resources Information Center

    Harris, Troy G.; Minor, John

    This text for a secondary- or postecondary-level course in grain handling and storage contains ten chapters. Chapter titles are (1) Introduction to Grain Handling and Storage, (2) Elevator Safety, (3) Grain Grading and Seed Identification, (4) Moisture Control, (5) Insect and Rodent Control, (6) Grain Inventory Control, (7) Elevator Maintenance,…

  20. Grain Grading and Handling.

    ERIC Educational Resources Information Center

    Rendleman, Matt; Legacy, James

    This publication provides an introduction to grain grading and handling for adult students in vocational and technical education programs. Organized in five chapters, the booklet provides a brief overview of the jobs performed at a grain elevator and of the techniques used to grade grain. The first chapter introduces the grain industry and…

  1. Terrestrial Spaceflight Analogs: Antarctica

    NASA Technical Reports Server (NTRS)

    Crucian, Brian

    2013-01-01

    Alterations in immune cell distribution and function, circadian misalignment, stress and latent viral reactivation appear to persist during Antarctic winterover at Concordia Station. Some of these changes are similar to those observed in Astronauts, either during or immediately following spaceflight. Others are unique to the Concordia analog. Based on some initial immune data and environmental conditions, Concordia winterover may be an appropriate analog for some flight-associated immune system changes and mission stress effects. An ongoing smaller control study at Neumayer III will address the influence of the hypoxic variable. Changes were observed in the peripheral blood leukocyte distribution consistent with immune mobilization, and similar to those observed during spaceflight. Alterations in cytokine production profiles were observed during winterover that are distinct from those observed during spaceflight, but potentially consistent with those observed during persistent hypobaric hypoxia. The reactivation of latent herpesviruses was observed during overwinter/isolation, that is consistently associated with dysregulation in immune function.

  2. Laboratory studies on the rheology of cryogenic slurries with implications for icy satellites

    NASA Astrophysics Data System (ADS)

    Carey, Elizabeth; Mitchell, Karl; Choukroun, Mathieu; Zhong, Fang

    2015-04-01

    Interpretation of Cassini RADAR and VIMS data has suggested some landforms on Titan may be due to effusive cryovolcanic processes that created cones, craters and flows. High-resolution Voyager 2 images of Triton also show strong evidence of cryovolcanic features. Fundamental to modeling of cryovolcanic features is the understanding of the rheological properties of cryogenic icy slurries in a thermodynamic and fluid mechanical context, i.e., how they deform and flow or stall under an applied stress. A series of measurements were performed on methanol-water mixtures and ammonia-water mixtures. We measured the rheology of the slurries as a function of temperature and strain rate, which revealed development of yield stress-like behaviors, shear-rate dependence, and thixotropic behavior, even at relatively low crystal fractions. Visualization of icy slurries supports the current hypothesis that crystallization dominates rheological properties. We shall discuss these findings and their implications for cryovolcanism on icy satellites.

  3. Kidnapping small icy asteroids in Earth near encounter to harbour life and to deflect trajectory

    NASA Astrophysics Data System (ADS)

    Fargion, Daniele

    2016-07-01

    The inter-planetary flight for human being is under danger because of unscreened and lethal solar flare radioactive showers. The screening of the astronauts by huge superconducting magnetic fields is unrealistic by many reasons. On the contrary the ability to reach nearby icy asteroids, to harbour there a complete undergound room where ecological life systems are first set, this goal may offer a later natural and safe currier for future human stations and enterprise. The need to deflect such a small size (a few thousands tons objects) maybe achieved by micro nuclear engines able to dig the asteroid icy skin, to heat and propel the soil by a synchronous jet engine array, bending and driving it to any desired trajectories. The need for such a wide collection of icy asteroid stations, often in a robotic ibernated state, it will offer the safe help station, raft in the wide space sea, where to collect material or energy in long human planetary travels.

  4. Analog storage integrated circuit

    DOEpatents

    Walker, J. T.; Larsen, R. S.; Shapiro, S. L.

    1989-01-01

    A high speed data storage array is defined utilizing a unique cell design for high speed sampling of a rapidly changing signal. Each cell of the array includes two input gates between the signal input and a storage capacitor. The gates are controlled by a high speed row clock and low speed column clock so that the instantaneous analog value of the signal is only sampled and stored by each cell on coincidence of the two clocks.

  5. Analog storage integrated circuit

    DOEpatents

    Walker, J.T.; Larsen, R.S.; Shapiro, S.L.

    1989-03-07

    A high speed data storage array is defined utilizing a unique cell design for high speed sampling of a rapidly changing signal. Each cell of the array includes two input gates between the signal input and a storage capacitor. The gates are controlled by a high speed row clock and low speed column clock so that the instantaneous analog value of the signal is only sampled and stored by each cell on coincidence of the two clocks. 6 figs.

  6. Application of mud volcanism for rocky and icy planetary bodies

    NASA Astrophysics Data System (ADS)

    Bradak, B.; Kereszturi, A.

    In this work we review our current knowledge on the two basic kinds of mud volcanism on Earth and its application to planetary environments. We emphasize the processes at the newly discovered submarine giant blueschit mud volcanoes around subductuion zones as a useful analogy for several processes on planetary surfaces. Because of the tectonically compressed environment where gas and liquid release cause diapiric rising of "mud" bodies without extremely high temperature, these are good models for several processes on the following planetary bodies: 1. volcanoes build up by low viscosity lavas on Venus, 2. subsurface water-clathrate decomposition driven break up of liquified matters on Mars, 3. pseudovolcanic cones on Mars, 4. cryo-like volcanoes on Mars, 5. cryovolcanism and diapiric model for the origin of the chaotic terrains on Europa, 6. origin of cantaloupe terrain and possible connection of explosive volcanism with insolation on Triton.

  7. Regional geology and stratigraphy of Saturn's icy moon Tethys

    NASA Astrophysics Data System (ADS)

    Wagner, Roland; Stephan, Katrin; Schmedemann, Nico; Roatsch, Thomas; Kersten, Elke; Neukum, Gerhard; Porco, Carolyn C.

    2013-04-01

    Tethys, with a diameter of 1060 km one of the 6 mid-sized icy moons of Saturn, was imaged for the first time in the early 1980ies by the cameras aboard the two Voyager spacecraft at resolutions of 1 km/pxl and lower [1][2][3]. These images show that most of Tethys is densely cratered and displays two major landmarks: the ~ 400 km large impact structure Odysseus and the huge graben system of Ithaca Chasma [1][2]. Since July 2004, Cassini has been in orbit about Saturn and has made several close passes at Tethys, providing an almost complete global image coverage at regional scale (200 - 500 m/pxl). However, varying viewing geometries between images taken during different orbits still impede the identification and mapping of geologic units. In this work we present an update of Tethys' regional geology and stratigraphy, based on Cassini ISS images. Crater distribution measurements, by us and in comparison with measurements of other groups [4], are used to support stratigraphic findings. Most of Tethys' surface consists of a hilly, rugged, heavily cratered plains unit, as identified in Voyager images [1][2][3]. A smooth, less densely cratered plains unit in the trailing hemisphere was previously observed by [2] which is also identifiable in Cassini ISS, but its exact boundaries are difficult to map due to varying viewing geometries of ISS observations. Another sparsely cratered plains unit not seen in Voyager images can be located to the south of Odysseus. It features remnants of highly degraded large craters superimposed by younger fresher craters with a lower crater density compared to the heavily cratered plains. Its distinct linear northern contact with the heavily cratered plains suggests an origin related to tectonism. Again, varying viewing conditions hamper to map the exact boundaries of this unit. The prominent graben system of Ithaca Chasma represents fractured cratered plains. The high resolution of Cassini ISS images reveals that tectonism on Tethys is more

  8. The promise of analog computation

    NASA Astrophysics Data System (ADS)

    MacLennan, B. J.

    2014-10-01

    Future computing paradigms and technologies will have to be more like the physical processes by which they are realized, and because these processes are primarily continuous, post-Moore's law computing will involve an increased use of analog computation. Traditionally analog computers have computed ordinary differential equations of time, but analog field computation permits massively parallel temporal integration of partial differential equations. In principle many different physical media - not just electronics - can be exploited to implement the basic operations of analog computing, a small number of which are sufficient to approximate a wide variety of analog computations, thus providing a basis for universal analog computation and general-purpose analog computers. The contentious issue of the computational power of analog computers is addressed best on its own terms, rather by asking it within the context of Church-Turing computation, which distorts the relevant questions and their answers.

  9. Experimental techniques to study clathrate hydrates in the context of giant icy moons

    NASA Astrophysics Data System (ADS)

    Le Menn, E.; Bezacier, L.; Bollengier, O.; Oancea, A.; Grasset, O.; Tobie, G.

    2012-09-01

    Gas clathrate hydrates probably play a key role in the storage and transport of gas compounds in water-rich environments, especially for icy moons [1]. In order to understand how they may affect the exchange processes in these objects, a series of experiments has been set up to realise controlled synthesis of mixted gas hydrates, to perform infrared and Raman diagnostics, and to constrain their phase diagram. Experiments cover a wide pressure range, from 10-2 mbar up to 30 GPa and are focused on three gas compounds of high interest for the icy satellites of the outer solar system: methane, carbon dioxide and nitrogen.

  10. An Overview of the Jupiter Icy Moons Orbiter (JIMO) Mission, Environments, and Materials Challenges

    NASA Technical Reports Server (NTRS)

    Edwards, Dave

    2012-01-01

    Congress authorized NASA's Prometheus Project in February 2003, with the first Prometheus mission slated to explore the icy moons of Jupiter with the following main objectives: (1) Develop a nuclear reactor that would provide unprecedented levels of power and show that it could be processed safely and operated reliably in space for long-duration. (2) Explore the three icy moons of Jupiter -- Callisto, Ganymede, and Europa -- and return science data that would meet the scientific goals as set forth in the Decadal Survey Report of the National Academy of Sciences.

  11. The ICI-WARM Non-Proprietary Regional Frequency Analysis Tool Using the Method Of L-Moments

    NASA Astrophysics Data System (ADS)

    Giovannettone, J. P.; Wright, M. J.

    2011-12-01

    The International Center for Integrated Water Resources Management (ICI-WaRM) is currently developing a non-proprietary Regional Frequency Analysis (RFA) tool to be used to answer the following questions: "How rare is the current drought?", "How likely is it that the drought will end in X months?", "How large a drought should we plan for?", and "How rare is the drought of record?". The method of L-moments is used, which is analogous to using regular moments except they are calculated using equations that represent linear combinations of the sample data elements. The advantages are increased robustness with respect to outliers, the ability to characterize a wider range of frequency distributions, and less bias. Sites are first lumped into homogeneous regions. Regional L-moments and rainfall frequency distributions are estimated. Individual site statistics can then be obtained by multiplying the regional growth curve by the site's average annual rainfall. This method allows the inclusion of sites with short record lengths, few rain gage stations, missing data, and/or higher variability due to topography. An example is given in Fig. 1, which shows an attempt to fit a GEV distribution to an individual site's growth curve (Fig. 1a) compared to an improved fit of the GEV to the growth curve of the corresponding homogeneous region (Fig. 1b), particularly within the portion of the curve that represents extreme events. The location of the 100-year event is shown on each graph for reference purposes. In addition to GEV, the software can attempt to fit 13 other frequency distributions. The end products of the ICI-WaRM Regional Frequency Analysis tool include estimates of the intensity of rainfall events for individual sites and rainfall intensity probably maps for a particular region for any rain event frequency, duration, and starting month. Current and future applications of this software include an attempt to construct a continental drought atlas of South America (a

  12. The dust halo of Saturn's largest icy moon, Rhea.

    PubMed

    Jones, G H; Roussos, E; Krupp, N; Beckmann, U; Coates, A J; Crary, F; Dandouras, I; Dikarev, V; Dougherty, M K; Garnier, P; Hansen, C J; Hendrix, A R; Hospodarsky, G B; Johnson, R E; Kempf, S; Khurana, K K; Krimigis, S M; Krüger, H; Kurth, W S; Lagg, A; McAndrews, H J; Mitchell, D G; Paranicas, C; Postberg, F; Russell, C T; Saur, J; Seiss, M; Spahn, F; Srama, R; Strobel, D F; Tokar, R; Wahlund, J-E; Wilson, R J; Woch, J; Young, D

    2008-03-01

    Saturn's moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn's magnetosphere. The Cassini spacecraft's in situ observations reveal that energetic electrons are depleted in the moon's vicinity. The absence of a substantial exosphere implies that Rhea's magnetospheric interaction region, rather than being exclusively induced by sputtered gas and its products, likely contains solid material that can absorb magnetospheric particles. Combined observations from several instruments suggest that this material is in the form of grains and boulders up to several decimetres in size and orbits Rhea as an equatorial debris disk. Within this disk may reside denser, discrete rings or arcs of material. PMID:18323452

  13. Ultraviolet Photometric Parameters of the Icy Galilean Satellites

    NASA Technical Reports Server (NTRS)

    Hendrix, Amanda R.; Domingue, Deborah L.; King, Kimberly

    2002-01-01

    The Galilean satellites are each phase-locked with Jupiter, so that one hemisphere (the Jovian hemisphere centered on 0 deg longitude) is always facing Jupiter. The leading hemisphere is centered on 90 deg W longitude, while the central longitude of the trailing hemisphere is 270 deg W. Because Jupiter's magnetosphere corotates at a rate faster than the orbital speed of the moons, the satellites' trailing hemispheres are affected by magnetospheric particle bombardment. Some effects are implantation of magnetospheric ions, sputtering, erosion and grain size alteration. The leading hemispheres of these moons are more dominantly affected by micrometeorite bombardment, while the Jovian hemispheres may be affected by dust and/or neutral wind particles streaming out radially from Io and its torus.

  14. Extension of volcanic forcing data back to 100 BC using the Analog method

    NASA Astrophysics Data System (ADS)

    Wagner, Sebastian; Zorita, Eduardo

    2013-04-01

    Present reconstructions of volcanic forcing to be used for climate simulations so far extend back until 500 AD for stratospheric aerosol sulphate injection (Gao et al., 2008), and back until 800 AD for aerosol optical depth and effective radius (Crowley et al. 2012; ICI5 data set). Here, we aim to extent the volcanic data set of Crowley et al. (2012) back to 100 BC. This data sets originally starts in 800 AD, for aerosol optical depth and effective radius. The method we apply is the Analog method, using information in the already existing reconstruction and extending it back in time by using information of long volcanic sulphate contained in Greenland and Antarctic Ice cores published in previous studies. The reconstruction of the volcanic forcing in first millennium is based on the search of analogs in the second millennium. The pool of analogs includes the ICI5 data set for the period 800-2000 AD. The basic philosophy is to find volcanic events with the same or similar magnitude in terms of volcanic sulphate deposition in Greenland and Antarctic ice cores. For the Northern Hemisphere the estimated maximum total stratospheric sulphate loading from Zielinski (1995) is used. For the Southern Hemisphere the Plummer et al. (2012) data set and the Ferris et al. (2011) data set are used in terms of sulphate deposition. To ensure that the volcanic event was large enough in magnitude, a certain threshold is applied to the analog selection. The extension, i.e. the analog search, is carried out separately for the four different latitudinal bands of the ICI5 data set. The method can be applied when better records than the Zielinski et al. (1995), record for the Northern Hemisphere become available. The analogs are selected based on the comparison between the information contained in the ice cores in the pre-800 AD period and post-800 AD period. For each event in the pre-800 AD period (the target), the most similar event (the analog) in the post-800 AD pool in terms of ice

  15. IMPULSIVE SPOT HEATING AND THERMAL EXPLOSION OF INTERSTELLAR GRAINS REVISITED

    SciTech Connect

    Ivlev, A. V.; Röcker, T. B.; Vasyunin, A.; Caselli, P.

    2015-05-20

    The problem of the impulsive heating of dust grains in cold, dense interstellar clouds is revisited theoretically with the aim of better understanding the leading mechanisms of the explosive desorption of icy mantles. We rigorously show that if the heating of a reactive medium occurs within a sufficiently localized spot (e.g., the heating of mantles by cosmic rays (CRs)), then the subsequent thermal evolution is characterized by a single dimensionless number λ. This number identifies a bifurcation between two distinct regimes: when λ exceeds a critical value (threshold), the heat equation exhibits the explosive solution, i.e., the thermal (chemical) explosion is triggered. Otherwise, thermal diffusion causes the deposited heat to spread over the entire grain—this regime is commonly known as whole-grain heating. The theory allows us to find a critical combination of physical parameters that govern the explosion of icy mantles due to impulsive spot heating. In particular, our calculations suggest that heavy CR species (e.g., iron ions) colliding with dust are able to trigger the explosion. Based on recently calculated local CR spectra, we estimate the expected rate of explosive desorption. The efficiency of the desorption, which in principle affects all solid species independent of their binding energy, is shown to be comparable to other CR desorption mechanisms typically considered in the literature. Also, the theory allows us to estimate the maximum abundances of reactive species that may be stored in the mantles, which provides important constraints on the available astrochemical models.

  16. Saturn’s icy satellites investigated by Cassini-VIMS. II. Results at the end of nominal mission

    NASA Astrophysics Data System (ADS)

    Filacchione, G.; Capaccioni, F.; Clark, R. N.; Cuzzi, J. N.; Cruikshank, D. P.; Coradini, A.; Cerroni, P.; Nicholson, P. D.; McCord, T. B.; Brown, R. H.; Buratti, B. J.; Tosi, F.; Nelson, R. M.; Jaumann, R.; Stephan, K.

    2010-04-01

    We report the detailed analysis of the spectrophotometric properties of Saturn's icy satellites as derived by full-disk observations obtained by visual and infrared mapping spectrometer (VIMS) experiment aboard Cassini. In this paper, we have extended the coverage until the end of the Cassini's nominal mission (June 1st 2008), while a previous paper ( Filacchione, G., and 28 colleagues [2007]. Icarus 186, 259-290, hereby referred to as Paper I) reported the preliminary results of this study. During the four years of nominal mission, VIMS has observed the entire population of Saturn's icy satellites allowing us to make a comparative analysis of the VIS-NIR spectral properties of the major satellites (Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus) and irregular moons (Atlas, Prometheus, Pandora, Janus, Epimetheus, Telesto, Calypso, Phoebe). The results we discuss here are derived from the entire dataset available at June 2008 which consists of 1417 full-disk observations acquired from a variety of distances and inclinations from the equatorial plane, with different phase angles and hemispheric coverage. The most important spectrophotometric indicators (as defined in Paper I: I/ F continua at 0.55 μm, 1.822 μm and 3.547 μm, visible spectral slopes, water and carbon dioxide bands depths and positions) are calculated for each observation in order to investigate the disk-integrated composition of the satellites, the distribution of water ice respect to "contaminants" abundances and typical regolith grain properties. These quantities vary from the almost pure water ice surfaces of Enceladus and Calypso to the organic and carbon dioxide rich Hyperion, Iapetus and Phoebe. Janus visible colors are intermediate between these two classes having a slightly positive spectral slope. These results could help to decipher the origins and evolutionary history of the minor moons of the Saturn's system. We introduce a polar representation of the spectrophotometric

  17. Neural Analog Information Processing

    NASA Astrophysics Data System (ADS)

    Hecht-Nielsen, Robert

    1982-07-01

    Neural Analog Information Processing (NAIP) is an effort to develop general purpose pattern classification architectures based upon biological information processing principles. This paper gives an overview of NAIP and its relationship to the previous work in neural modeling from which its fundamental principles are derived. It also presents a theorem concerning the stability of response of a slab (a two dimensional array of identical simple processing units) to time-invariant (spatial) patterns. An experiment (via computer emulation) demonstrating classification of a spatial pattern by a simple, but complete NAIP architecture is described. A concept for hardware implementation of NAIP architectures is briefly discussed.

  18. Impact fracture experiments simulating interstellar grain-grain collisions

    NASA Technical Reports Server (NTRS)

    Freund, Friedemann; Chang, Sherwood; Dickinson, J. Thomas

    1990-01-01

    Oxide and silicate grains condensing during the early phases of the formation of the solar system or in the outflow of stars are exposed to high partial pressures of the low-z elements H, C, N and O and their simple gaseous compounds. Though refractory minerals are nominally anhydrous and non-carbonate, if they crystallize in the presence of H2O, N2 and CO or CO2 gases, they dissolve traces of the gaseous components. The question arises: How does the presence of dissolved gases or gas components manifest itself when grain-grain collisions occur. What are the gases emitted when grains are shattered during a collision event. Researchers report on fracture experiments in ultrahigh vacuum (UHV, approximately less than 10 to the -8th power mbar) designed to measure (by means of a quadrupole mass spectrometer, QMS, with microns to ms time resolution) the emission of gases and vapors during and after impact (up to 1.5 sec). Two terrestrial materials were chosen which represent structural and compositional extremes: olivine (San Carlos, AZ), a densely packed Mg-Fe(2+) silicate from the upper mantle, available as 6 to 12 mm single crystals, and obsidian (Oregon), a structurally open, alkaline-SiO2-rich volcanic glass. In the olivine crystals OH- groups have been identified spectroscopically, as well as H2 molecules. Obsidian is a water-rich glass containing OH- besides H2O molecules. Olivine from the mantle often contains CO2, either as CO2-rich fluid in fluid inclusions or structurally dissolved or both. By analogy to synthetic glasses CO2 in the obsidian may be present in form of CO2 molecules in voids of molecular dimensions, or as carbonate anions, CO3(2-). No organic molecules have been detected spectroscopically in either material. Results indicate that refractory oxide/silicates which contain dissolved traces of the H2O and CO/CO2 components but no spectroscopically detectable traces of organics may release complex H-C-O (possibly H-C-N-O) molecules upon fracture

  19. A passive low frequency instrument for radio wave sounding the subsurface oceans of the Jovian icy moons: An instrument concept

    NASA Astrophysics Data System (ADS)

    Hartogh, P.; Ilyushin, Ya. A.

    2016-10-01

    Exploration of subsurface oceans on Jovian icy moons is a key issue of the icy moons' geology. Electromagnetic wave propagation is the only way to probe their icy mantles from the orbit. In the present paper, a principal concept of a passive interferometric instrument for deep sounding of the icy moons' crust is proposed. Its working principle is measuring and correlating Jupiter's radio wave emissions with reflections from the deep sub-surface of the icy moons. A number of the functional aspects of the proposed experiment are studied, in particular, impact of the wave scattering on the surface terrain on the instrument performance and digital sampling of the noisy signal. Results of the test of the laboratory prototype of the instrument are also presented in the paper.

  20. It's Far, It's Small, It's Cool: It's an Icy Exoplanet!

    NASA Astrophysics Data System (ADS)

    2006-01-01

    Using a network of telescopes scattered across the globe, including the Danish 1.54m telescope at ESO La Silla (Chile), astronomers [1] discovered a new extrasolar planet significantly more Earth-like than any other planet found so far. The planet, which is only about 5 times as massive as the Earth, circles its parent star in about 10 years. It is the least massive exoplanet around an ordinary star detected so far and also the coolest [2]. The planet most certainly has a rocky/icy surface. Its discovery marks a groundbreaking result in the search for planets that support life. ESO PR Photo 03a/06 ESO PR Photo 03a/06 Artist's Impression of the Newly Found Exoplanet The new planet, designated by the unglamorous identifier of OGLE-2005-BLG-390Lb, orbits a red star five times less massive than the Sun and located at a distance of about 20,000 light years, not far from the centre of our Milky Way galaxy. Its relatively cool parent star and large orbit implies that the likely surface temperature of the planet is 220 degrees Centigrade below zero, too cold for liquid water. It is likely to have a thin atmosphere, like the Earth, but its rocky surface is probably deeply buried beneath frozen oceans. It may therefore more closely resemble a more massive version of Pluto, rather than the rocky inner planets like Earth and Venus. "This planet is actually the first and only planet that has been discovered so far that is in agreement with the theories for how our Solar System formed ", said Uffe Gråe Jørgensen (Niels Bohr Institute, Copenhagen, Denmark), member of the team. The favoured theoretical explanation for the formation of planetary systems proposes that solid 'planetesimals' accumulate to build up planetary cores, which then accrete nebular gas - to form giant planets - if they are sufficiently massive. Around red dwarfs, the most common stars of our Galaxy, this model favours the formation of Earth- to Neptune-mass planets being between 1 and 10 times the Earth

  1. Hypothetical Inverted Critical Zones for Subsurface Biospheres on Desert Planets and Icy Ocean Worlds

    NASA Astrophysics Data System (ADS)

    Boston, P. J.

    2015-10-01

    Earth as a model for cave habitable real-estate does not encompass other possibilities including desert planets like Mars, or icy ocean worlds viewed as planetary-scale water-filled caves in water ice bedrock which will have inverted Critical Zones.

  2. Experimental Facilities to Synthesize and Study Clathrate Hydrates: Applications to Icy Moons

    NASA Astrophysics Data System (ADS)

    Le Menn, E.; Nna Mvondo, D.; Bezacier, L.; Bollengier, O.; Grasset, O.; Tobie, G.

    2014-02-01

    A series of experimental investigations are being carried out on mixed CH4-N2 and CH4-CO2 clathrate hydrates, compounds of high interest for icy moons. First results on their phase diagram and their infrared and Raman signatures will be presented.

  3. Concurrent Validity of the "Working with Others Scale" of the ICIS Employment Interview System

    ERIC Educational Resources Information Center

    Cassidy, Martha W.

    2011-01-01

    The purpose of this study was to determine if the Working with Others Scale from the American Association of School Personnel Administrators (AASPA) Interactive Computer Interview System (ICIS) was a valid predictor of practicing teachers' interpersonal skills and abilities to work well with colleagues. Participants in the study were all employed…

  4. Channel Estimation and ISI/ICI Cancellation for MIMO-OFDM Systems with Insufficient Cyclic Prefix

    NASA Astrophysics Data System (ADS)

    Chiu, Yi-Jen; Chen, Chien-Sheng; Chang, Ting-Wei

    In multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, the multipath components whose delays exceed cyclic prefix (CP) cause inter-symbol interference (ISI) and inter-carrier interference (ICI), which may degrade system performance severely. In this paper, we propose a joint channel estimation and ISI/ICI cancellation scheme in which a limited CP is used in a trade-off against high-rate performance in MIMO-OFDM systems. A channel estimation scheme based on the criterion of Expectation-Maximization (EM) algorithm can be proposed through the use of a training symbol. The EM algorithm uses an iterative procedure to estimate channel parameters and can estimate channel impulse response (CIR) accurately enough to mitigate ISI/ICI influences. Through the accurate CIR estimation, an efficient method has been developed to counteract ISI/ICI influences in signal detection in the case where the inserted CP length is less than the CIR length. Simulation results show that the proposed method can significantly enhance the overall MIMO-OFDM system performance after only a few iterations.

  5. Inverse theory resolution analysis in planning radio science gravity investigations of icy moons

    NASA Astrophysics Data System (ADS)

    Ganse, A.; Vance, S.

    2014-12-01

    The nature of an icy satellite's interior relates fundamentally to its composition, thermal structure, formation and evolution history, and prospects for supporting life. Gravity measurements via radio Doppler information during spacecraft flybys constitute an important tool to infer gross interior structure. Liquid water and ice layers have previously been inferred for the interiors of Jupiter's icy satellites Europa, Ganymede, and Callisto on the basis of magnetic field measurements by the Galileo probe. On Europa and Callisto induced magnetic field signatures measured by the Galileo probe provided strong evidence for an ionic aqueous ocean. Among the chief goals of the proposed Europa Clipper mission in returning to Europa is characterizing the structure of the moon's icy shell. A geophysical inverse theory resolution analysis can be calculated at the pre-measurement mission planning stage, contributing planning considerations from the point of view of the search for mass anomalies in the ice shell (meteorites or diapiric upwellings) or near the H2O/rock interface (seamounts). The analysis allows us to assess the location-varying resolution of an icy moon's interior density anomaly distribution that can be estimated from radio Doppler measurements. It considers the tradeoff between the resolution of the estimated density anomaly distribution and its estimation uncertainty, and investigates issues in distinguishing between ocean anomalies (e.g., seamounts) and mass anomalies within or near the surface of the ice layer. We apply the resolution analysis to proposed Europa Clipper trajectories and past Galileo spacecraft trajectories about Europa and Ganymede.

  6. Astrobiological and Geological Implications of Convective Transport in Icy Outer Planet Satellites

    NASA Technical Reports Server (NTRS)

    Pappalardo, Robert T.; Zhong, Shi-Jie; Barr, Amy

    2005-01-01

    The oceans of large icy outer planet satellites are prime targets in the search for extraterrestrial life in our solar system. The goal of our project has been to develop models of ice convection in order to understand convection as an astrobiologically relevant transport mechanism within icy satellites, especially Europa. These models provide valuable constraints on modes of surface deformation and thus the implications of satellite surface geology for astrobiology, and for planetary protection. Over the term of this project, significant progress has been made in three areas: (1) the initiation of convection in large icy satellites, which we find probably requires tidal heating; (2) the relationship of surface features on Europa to internal ice convection, including the likely role of low-melting-temperature impurities; and (3) the effectiveness of convection as an agent of icy satellite surface-ocean material exchange, which seems most plausible if tidal heating, compositional buoyancy, and solid-state convection work in combination. Descriptions of associated publications include: 3 published papers (including contributions to 1 review chapter), 1 manuscript in revision, 1 manuscript in preparation (currently being completed under separate funding), and 1 published popular article. A myriad of conference abstracts have also been published, and only those from the past year are listed.

  7. Fulfilling the Mission of ICIE: Industry and Institutions Develop Collaborative Programs.

    ERIC Educational Resources Information Center

    Swaffield, Bruce C.

    1999-01-01

    Examines trends in the increasing partnerships between industry and institutions of higher education in light of the mission and activities of the International Council for Innovation in Higher Education (ICIE). Cites examples of such partnerships involving various industries and types of institutions. Stresses the need for colleges and…

  8. JUpiter ICy Moons Explorer (JUICE): The ESA L1 Mission to the Jupiter System

    NASA Astrophysics Data System (ADS)

    Dougherty, M. K.; Grasset, O.; Erd, C.; Titov, D.; Bunce, E.; Coustenis, A.; Blanc, M.; Coates, A.; Drossart, P.; Fletcher, L.; Hussmann, H.; Jaumann, R.; Krupp, N.; Prieto-Ballesteros, O.; Tortora, P.; Tosi, F.; Van Hoolst, T.

    2012-10-01

    The Jupiter Icy Moons Explorer (JUICE) mission has recently been selected by ESA as the first large mission within the Cosmic Visions 2015-2025 plan. We will introduce the mission that is being developed to thoroughly explore the Jupiter system with focus on the largest satellite, Ganymede.

  9. Antarctic Space Analog Program

    NASA Technical Reports Server (NTRS)

    Palinkas, Lawrence A; Gunderson, E. K. Eric; Johnson, Jeffrey C.; Holland, Albert W.

    1998-01-01

    The primary aim of this project was to examine group dynamics and individual performance in extreme, isolated environments and identify human factors requirements for long-duration space missions using data collected in an analog environment. Specifically, we wished to determine: 1) the characteristics of social relations in small groups of individuals living and working together in extreme, isolated environments, and 2) the environmental, social and psychological determinants of performance effectiveness in such groups. These two issues were examined in six interrelated studies using data collected in small, isolated research stations in Antarctica from 1963 to the present. Results from these six studies indicated that behavior and performance on long-duration space flights is likely to be seasonal or cyclical, situational, social, and salutogenic in nature. The project responded to two NASA program emphases for FY 1997 as described in the NRA: 1) the primary emphasis of the Behavior and Performance Program on determining long-term individual and group performance responses to space, identifying critical factors affecting those responses and understanding underlying mechanisms involved in behavior and performance, and developing and using ground-based models and analogs for studying space-related behavior and performance; and 2) the emphasis of the Data Analysis Program on extended data analysis. Results from the study were used to develop recommendations for the design and development of pre-flight crew training and in-flight psychological countermeasures for long-duration manned space missions.

  10. The Radar for Icy Moon Exploration (RIME) on the JUICE Mission

    NASA Astrophysics Data System (ADS)

    Bruzzone, L.; Plaut, J.; Alberti, G.; Blankenship, D. D.; Bovolo, F.; Campbell, B. A.; Castelletti, D.; Gim, Y.; Ilisei, A. M.; Kofman, W. W.; Komatsu, G.; McKinnon, W. B.; Mitri, G.; Moussessian, A.; Notarnicola, C.; Orosei, R.; Patterson, G. W.; Pettinelli, E.; Plettemeier, D.

    2015-12-01

    The Radar for Icy Moon Exploration (RIME) is one of the main instruments included in the JUpiter ICy moons Explorer (JUICE) ESA mission. It is a radar sounder designed for studying the subsurface geology and geophysics of Galilean icy moons (i.e., Ganymede, Europa and Callisto) and for detecting possible subsurface water. RIME is designed for penetration of the icy moons up to a depth of 9 km. Two main operation scenarios are foreseen for RIME: i) flyby observations of Europa, Ganymede and Callisto (from a distance of 1000 km to the closest approach of about 400 km); and ii) circular orbital observations around Ganymede at 500 km of altitude. According to these scenarios, RIME is designed to explore the icy shell of the Galilean icy satellites by characterizing the wide range of compositional, thermal, and structural variation found in the subsurface of these moons. RIME observations will profile the ice shells of the Galilean icy satellites with specific focus on Ganymede given the circular orbital phase. The acquired measures will provide geological context on hemispheric (thousands of km), regional (hundreds of km with multiple overlaps), and targeted (tens of km) scales appropriate for a variety of hypothesis tests. RIME will operate in a single frequency band, centred at 9 MHz. The frequency was selected as the result of extensive study of penetration capabilities, surface roughness of the moons, Jovian radio noise, antenna accommodation, and system design. The 9 MHz frequency provides penetration capabilities and mitigation of surface scattering (which can cause signal loss and clutter issues), at the expense of mapping coverage, as it is likely to obtain high SNR observations only on the anti-Jovian side of the target moons. The RIME antenna is a 16 m dipole. The chirp pulse bandwidth is up to 3 MHz, which provides vertical resolution of about 50 m in ice after side lobe weighting. RIME will also operate with 1 MHz bandwidth to reduce data volume when

  11. It's Far, It's Small, It's Cool: It's an Icy Exoplanet!

    NASA Astrophysics Data System (ADS)

    2006-01-01

    Using a network of telescopes scattered across the globe, including the Danish 1.54m telescope at ESO La Silla (Chile), astronomers [1] discovered a new extrasolar planet significantly more Earth-like than any other planet found so far. The planet, which is only about 5 times as massive as the Earth, circles its parent star in about 10 years. It is the least massive exoplanet around an ordinary star detected so far and also the coolest [2]. The planet most certainly has a rocky/icy surface. Its discovery marks a groundbreaking result in the search for planets that support life. ESO PR Photo 03a/06 ESO PR Photo 03a/06 Artist's Impression of the Newly Found Exoplanet The new planet, designated by the unglamorous identifier of OGLE-2005-BLG-390Lb, orbits a red star five times less massive than the Sun and located at a distance of about 20,000 light years, not far from the centre of our Milky Way galaxy. Its relatively cool parent star and large orbit implies that the likely surface temperature of the planet is 220 degrees Centigrade below zero, too cold for liquid water. It is likely to have a thin atmosphere, like the Earth, but its rocky surface is probably deeply buried beneath frozen oceans. It may therefore more closely resemble a more massive version of Pluto, rather than the rocky inner planets like Earth and Venus. "This planet is actually the first and only planet that has been discovered so far that is in agreement with the theories for how our Solar System formed ", said Uffe Gråe Jørgensen (Niels Bohr Institute, Copenhagen, Denmark), member of the team. The favoured theoretical explanation for the formation of planetary systems proposes that solid 'planetesimals' accumulate to build up planetary cores, which then accrete nebular gas - to form giant planets - if they are sufficiently massive. Around red dwarfs, the most common stars of our Galaxy, this model favours the formation of Earth- to Neptune-mass planets being between 1 and 10 times the Earth

  12. Heating and melting of small icy satellites by the decay of 26Al

    NASA Technical Reports Server (NTRS)

    Prialnik, D.; Bar-Nun, A.; Owen, T. (Principal Investigator)

    1990-01-01

    We study the effect of radiogenic heating due to 26Al on the thermal evolution of small icy satellites. Our object is to find the extent of internal melting as a function of the satellite radius and of the initial 26Al abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of approximately 10(6) yr (comparable with the lifetime of 26Al). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of 40K, 232Th, 235U, 238U, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10(9) yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. Our main conclusion is that the initial 26Al abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, approximately 7 x 10(-7) by mass). We find, for example, that an initial 26Al mass fraction of approximately 4 x 10(-8) is sufficient for melting almost completely icy spheres with radii of 800 km, typical of the larger icy planetary satellites. We also find that for any given 26Al abundance, there is a narrow range of radii below which only marginal melting occurs and above which most of the ice melts (and refreezes later). Since extensive melting may have important consequences, such as differentiation, gas release, and volcanic activity, the effect of 26Al should be included in future studies of satellite interiors.

  13. Heating and melting of small icy satellites by the decay of 26Al.

    PubMed

    Prialnik, D; Bar-Nun, A

    1990-05-20

    We study the effect of radiogenic heating due to 26Al on the thermal evolution of small icy satellites. Our object is to find the extent of internal melting as a function of the satellite radius and of the initial 26Al abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of approximately 10(6) yr (comparable with the lifetime of 26Al). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of 40K, 232Th, 235U, 238U, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10(9) yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. Our main conclusion is that the initial 26Al abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, approximately 7 x 10(-7) by mass). We find, for example, that an initial 26Al mass fraction of approximately 4 x 10(-8) is sufficient for melting almost completely icy spheres with radii of 800 km, typical of the larger icy planetary satellites. We also find that for any given 26Al abundance, there is a narrow range of radii below which only marginal melting occurs and above which most of the ice melts (and refreezes later). Since extensive melting may have important consequences, such as differentiation, gas release, and volcanic activity, the effect of 26Al should be included in future studies of satellite interiors.

  14. Marketing Farm Grain Crops.

    ERIC Educational Resources Information Center

    Ridenour, Harlan E.

    This vocational agriculture curriculum on grain marketing contains three parts: teacher guide, student manual, and student workbook. All three are coordinated and cross-referenced. The course is designed to give students of grain marketing a thorough background in the subject and provide practical help in developing grain marketing strategies for…

  15. Vorticity in analog gravity

    NASA Astrophysics Data System (ADS)

    Cropp, Bethan; Liberati, Stefano; Turcati, Rodrigo

    2016-06-01

    In the analog gravity framework, the acoustic disturbances in a moving fluid can be described by an equation of motion identical to a relativistic scalar massless field propagating in curved space-time. This description is possible only when the fluid under consideration is barotropic, inviscid, and irrotational. In this case, the propagation of the perturbations is governed by an acoustic metric that depends algebrically on the local speed of sound, density, and the background flow velocity, the latter assumed to be vorticity-free. In this work we provide a straightforward extension in order to go beyond the irrotational constraint. Using a charged—relativistic and nonrelativistic—Bose-Einstein condensate as a physical system, we show that in the low-momentum limit and performing the eikonal approximation we can derive a d’Alembertian equation of motion for the charged phonons where the emergent acoustic metric depends on flow velocity in the presence of vorticity.

  16. Mars inflatable greenhouse analog.

    PubMed

    Sadler, Philip D; Giacomelli, Gene A

    2002-01-01

    Light intensities on the Martian surface can possibly support a bioregenerative life support system (BLSS) utilizing natural sunlight for hydroponic crop production, if a suitable controlled environment can be provided. Inflatable clear membrane structures offer low mass, are more easily transported than a rigid structure, and are good candidates for providing a suitable controlled environment for crop production. Cable culture is one hydroponic growing system that can take advantage of the beneficial attributes of the inflatable structure. An analog of a Mars inflatable greenhouse can provide researchers data on issues such as crew time requirements for operation, productivity for BLSS, human factors, and much more at a reasonable cost. This is a description of one such design.

  17. Mars inflatable greenhouse analog.

    PubMed

    Sadler, Philip D; Giacomelli, Gene A

    2002-01-01

    Light intensities on the Martian surface can possibly support a bioregenerative life support system (BLSS) utilizing natural sunlight for hydroponic crop production, if a suitable controlled environment can be provided. Inflatable clear membrane structures offer low mass, are more easily transported than a rigid structure, and are good candidates for providing a suitable controlled environment for crop production. Cable culture is one hydroponic growing system that can take advantage of the beneficial attributes of the inflatable structure. An analog of a Mars inflatable greenhouse can provide researchers data on issues such as crew time requirements for operation, productivity for BLSS, human factors, and much more at a reasonable cost. This is a description of one such design. PMID:11987303

  18. Analog and digital signal processing

    NASA Astrophysics Data System (ADS)

    Baher, H.

    The techniques of signal processing in both the analog and digital domains are addressed in a fashion suitable for undergraduate courses in modern electrical engineering. The topics considered include: spectral analysis of continuous and discrete signals, analysis of continuous and discrete systems and networks using transform methods, design of analog and digital filters, digitization of analog signals, power spectrum estimation of stochastic signals, FFT algorithms, finite word-length effects in digital signal processes, linear estimation, and adaptive filtering.

  19. Low-velocity impacts into cryogenic icy regolith

    NASA Astrophysics Data System (ADS)

    Brisset, Julie; Colwell, Josh E.; Dove, Adrienne; Rascon, Allison; Mohammed, Nadia; Cox, Christopher

    2016-10-01

    The first stages of planet formation take place in the protoplanetary disk (PPD), where µm-sized dust grains accrete into km-sized planetesimals. In the current discussion on the processes involved in accretion beyond the cm scale, the size distribution of the particles colliding at low speeds (a few m/s) inside the PPD is thought to play an important role. A few larger bodies that survived bouncing and fragmentation collisions accumulate the fine dust residue of the erosion and fragmentation of other particles that were destroyed in more energetic collisions. A significant component of this dust on bodies farther out in the PPD will be composed of ices.We have carried out a series of experiments to study the ejecta mass-velocity distribution from impacts of cm-scale particles into granular media at speeds below 3 m/s in both microgravity and 1-g conditions in vacuo and room temperature. Aggregate-aggregate collision experiments have shown bouncing and fragmentation at speeds above ~ 1 m/s. However, most planetesimal formation occurred beyond the frost line and at much lower temperatures than our earlier experiments. We have performed impact experiments at 1-g into JSC-1 lunar regolith simulant at low temperatures (<150 K) with water ice particles mixed into the JSC-1 sample. We varied the impact energy and the water ice content of the sample and measured the ejecta mass-velocity distribution as well as the final crater size. Our goal is to determine if the cryogenic temperature and the presence of water ice in the regolith affects the dynamic response to low-velocity impacts and the production of regolith. We will present the results of the cryogenic impacts and compare them to the study performed at room temperature without water ice. The inclusion of water ice into the target sample is a first step towards better understanding the influence of the presence of water ice in the production of ejecta in response to low-velocity impacts. We will discuss the

  20. Beta 1- and beta 2-adrenoceptor antagonist activities of ICI-215001, a putative beta 3-adrenoceptor agonist.

    PubMed Central

    Tesfamariam, B.; Allen, G. T.

    1994-01-01

    1. The present study was undertaken to characterize the beta 3-adrenoceptor agonist activity of ICI-215001 and to determine whether it exhibits additional activities on beta 1- and beta 2-adrenoceptors in isolated spontaneously beating atrium, trachea and ileum of guinea-pig. 2. In guinea-pig atrium, isoprenaline, a non-selective beta-adrenoceptor agonist, caused concentration-dependent, positive chronotropic effects that were inhibited by atenolol, a selective beta 1-antagonist. ICI-215001 also competitively antagonized the increase in heart rate caused by isoprenaline. 3. ICI-215001 exhibited low intrinsic activity at increasing the beating rate of atrium and no activity on resting or induced tone of tracheal strips. 4. In strips of guinea-pig trachea, contracted submaximally with carbachol, isoprenaline, caused concentration-dependent relaxations. Both ICI-118551, a selective beta 2-adrenoceptor antagonist, and ICI-215001 competitively inhibited the relaxations caused by isoprenaline. 5. In isolated strips of guinea-pig ileum longitudinal smooth muscle contracted with histamine, isoprenaline and ICI-215001 caused relaxations which were inhibited by alprenolol, a beta-adrenoceptor antagonist with modest affinity for beta 3-adrenoceptors, but were resistant to ICI-118551 and atenolol. 6. These results indicate that ICI-215001 exhibits beta 3-adrenoceptor agonist activity as demonstrated by relaxations mediated via atypical beta-adrenoceptors in the longitudinal smooth muscle of guinea-pig ileum. Further, the studies demonstrate that ICI-215001 can act as an antagonist at beta 1- and beta 2-adrenoceptors in situations where its intrinsic agonist activity is low. PMID:7913381

  1. [Analogies and analogy research in technical biology and bionics].

    PubMed

    Nachtigall, Werner

    2010-01-01

    The procedural approaches of Technical Biology and Bionics are characterized, and analogy research is identified as their common basis. The actual creative aspect in bionical research lies in recognizing and exploiting technically oriented analogies underlying a specific biological prototype to indicate a specific technical application.

  2. FET comparator detects analog signal levels without loading analog device

    NASA Technical Reports Server (NTRS)

    Wallace, H. L.

    1966-01-01

    FET comparator circuit detects discrete analog computer output levels without excessively loading the output amplifier of the computer. An FET common source amplifier is coupled by a differential amplifier to a bistable transistor flip-flop. This circuit provides a digital output for analog voltages above or below a predetermined level.

  3. FREE TRANSLATIONAL OSCILLATIONS OF ICY BODIES WITH A SUBSURFACE OCEAN USING A VARIATIONAL APPROACH

    SciTech Connect

    Escapa, A.; Fukushima, T.

    2011-03-15

    We analyze the influence of the interior structure of an icy body with an internal ocean on the relative translational motions of its solid constituents. We consider an isolated body differentiated into three homogeneous layers with spherical symmetry: an external ice-I layer, a subsurface ammonia-water ocean, and a rocky inner core. This composition represents icy bodies such as Europa, Titania, Oberon, and Triton, as well as Pluto, Eris, Sedna, and 2004 DW. We construct the equations of motion by assuming that the solid constituents are rigid and that the ocean is an ideal fluid, the internal motion being characterized by the relative translations of the solids and the induced flow in the fluid. Then we determine the dynamics of the icy body using the methods of analytical mechanics, that is, we compute the kinetic energy and the gravitational potential energy, and obtain the Lagrangian function. The resulting solution of the Lagrange equations shows that the solid layers perform translational oscillations of different amplitudes with respect to the barycenter of the body. We derive the dependence of the frequency of the free oscillations of the system on the characteristics of each layer, expressing the period of the oscillations as a function of the densities and masses of the ocean and the rocky inner core, and the mass of the icy body. We apply these results to previously developed subsurface models and obtain numerical values for the period and the ratio between the amplitudes of the translational oscillations of the solid components. The features obtained are quite different from the cases of Earth and Mercury. Our analytical formulas satisfactorily explain the source of these differences. When models of the same icy body, compatible with the existence of an internal ocean, differ in the thickness of the ice-I layer, their associated periods experience a relative variation of at least 10%. In particular, the different models for Titania and Oberon exhibit a

  4. Laboratory Simulated Impact Shock on Ices relevant to Planetary icy Bodies

    NASA Astrophysics Data System (ADS)

    Nna Mvondo, D.; Khare, B. N.; McKay, C. P.; Ishihara, T.

    2006-12-01

    Several icy satellites of the outer planets show impact cratering features and it is recognised that this process may have played a crucial role in the formation and evolution of icy bodies. The effect of impact by extraterrestrial objects into the surface is commonly related to physical changes. Most of the research applied to impacts on ices has been developed to study and understand the cratering formation process and their physical, geophysical characteristics. Chemical changes and synthesis occurring on icy planetary surfaces are generally explained by the influence of UV photons and high-energy charged particles on ices. Nonetheless, impact process onto ices could be a source of local or global endogenic process and could be especially advantageous as an efficient energy source for driving interesting chemistry. Impacts can ensure that icy surfaces are eventually exposed, for a limited period of time, to aqueous melt in impact craters and ejecta and one can imagine that impurities included in the ice may undergo hydrolysis and other reactions under such conditions. Upon impact, the kinetic energy of the bolide is transferred to the ground liberating a great deal of stress energy which could initiate in situ a diverse series of chemical reactions in the fracture zone beneath the crater (Borucki et al., 2002; Jones and Lewis, 1987). Here we present a new approach testing in laboratory the chemistry conducted by impacts into planetary ices and we report the first experimental results. We have irradiated with a powerful pulsed laser icy mixtures of pure water ices containing CO2, Na2CO3, CH3OH and CH3OH / (NH4)2SO4 at 77K. GC-MS and FTIR analyses show that hydrogen peroxide, carbon monoxide and methanol are formed in irradiated H2O / CO2 ices. Ice containing sodium carbonate generates under simulated impact CO and CO2 which are also produced in impacted H2O / CH3OH and H2O / CH3OH / (NH4)2SO4 ices. But, in both latter icy mixtures, methane and more complex

  5. Compositional Impact of Io Volcanic Emissions on Jupiter's Magnetosphere and the Icy Galilean Moons

    NASA Technical Reports Server (NTRS)

    Cooper, John; Fegley, Bruce; Lipatov, Alexander; Richardson, John; Sittler, Edward

    2011-01-01

    The magnetospheric ion population of Jupiter is dominated by the 1000 kg/s of iogenic material constantly ejected by IO volcanism as neutral gas (approx. 1 kg/s goes out as high speed dust grains), subsequent atmospheric losses to the IO torus, and radial transport of torus ions throughout the magnetosphere. As that magnetosphere is greatly distended in radial size by the iogenic plasma loading, so are surfaces of the other Galilean moons also significantly, and perhaps even dominantly, affected by iogenic plasma bombardment, e.g. at the level up to 0.2 kg/s heavy ions (mostly O and S) onto Europa as per local plasma ion measurements. In comparison, cometary impacts onto IO deliver about 0.02 kg/s of impact ejecta to Europa via ballistic transfer through the Jupiter system. The magnetosphere of this system operates as a powerful engine to produce and transport ions from the IO source to the surfaces of these other moons, and any future orbiter missions to these moons must account for surface distributions of the iogenic material and its chemical effects before real assessments can be made of sensible chemical materials otherwise arising from primordial formation and subsequent evolution of these moons. This is a fundamental problem of space weathering that must be addressed for all planetary bodies with thin atmospheres and direct surface exposure to their space plasma environments. Long-standing debates from Galileo Orbiter measurements about the origins of hydrate sulfates at Europa present examples of this problem, as to whether the sulfates arise from oceanic minerals or from iogenic sulfur chemistry. Any orbiter or landed mission to Europa for astrobiological investigations would further need to separate the potential chemical biosignatures of life or its precursors from the highly abundant background of iogenic material. Although no single ion carries a tag identifying it as of iogenic or other origin, the elemental abundance distributions of ions to be

  6. Ion processing of ices and the origin of SO2 and O3 on the icy surfaces of the icy jovian satellites

    NASA Astrophysics Data System (ADS)

    Boduch, P.; Brunetto, R.; Ding, J. J.; Domaracka, A.; Kaňuchová, Z.; Palumbo, M. E.; Rothard, H.; Strazzulla, G.

    2016-10-01

    We present new experimental results relative to 144 keV S9+ or Ar9+ ion implantation in targets made of oxygen rich frozen gases (O2, CO2) and mixtures with water ice. Spectra in the UV (200-400 nm) range have been obtained before and after implantation. The targets have been selected because they can be representative of the parent molecules from which SO2 and O3, observed to be present on the surfaces of Jupiter's icy Moons, could be formed due to radiolysis induced by the abundant magnetospheric ions. The results indicate that sulfur dioxide is not detectable after sulfur implantation in oxygen bearing species. Ozone is formed after argon and sulfur ion implantation. Sulfur implantation in O2 and CO2 targets also induces the formation of a band centered at about 255 nm (that we tentatively attribute to SO3- radicals). In the mixtures with water the band appears initially at the same wavelength and shifts to about 247 nm at higher ion fluences possibly indicating the formation of sulfite (HSO3-) ions. An absorption band observed on Ganymede is well fitted by using three components: ozone, sulfite ions and a not identified component having an absorption band centered at 298 nm. In all of the studied cases ion implantation produces a spectral reddening over the investigated spectral range (200-400 nm) that well mimics the observed spectral slopes of Jupiter's icy satellites.

  7. Refractory Organic Compounds in Enceladus' Ice Grains and Hydrothermal Activity

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Khawaja, N.; Hsu, H. W.; Sekine, Y.; Shibuya, T.

    2015-12-01

    Cassini's Cosmic Dust Analyzer (CDA) generates time-of-flight mass spectra of individual grains impinging on the instruments target-plate. Following the analysis of salt rich ice grains emitted by Enceladus that indicated a salt-water ocean in contact with the moon's rocky core [1,2] a recent CDA analysis of nano-phase silica particles pointed at hydrothermal activity at the moon's rock/water interface [3]. The results imply temperatures above 80 - 90°C and alkaline pH values around 10 reminiscent of alkaline hydrothermal vents on Earth like the Lost City Hydrothermal Field. In this context the compositional analysis of organic components in CDA mass spectra of the ejected ice grains is of particular relevance. A multitude of volatile organic species has already been identified in the gas component of the plume [4]. As expected, we find more complex organic molecules in ice grains than in the gas indicating aromatic species, amines, and carbonyl group species. The composition of organic-bearing ice grains displays a great diversity indicating a variety of different organic species in varying concentrations. Recent spatially resolved CDA in situ measurements inside Enceladus' plume indicate that these organic compounds are especially frequent in 'young' ice grains that have just been ejected by high velocity jets. We investigate the implications of our findings with respect to ice grain formation at the water surface and inside the icy vents. We constrain the generation of organic compounds at the rock/water interface in the light of hydrothermal activity and the potential for the formation of life precursor molecules in Enceladus' ocean. Ref:[1] Postberg et al., Nature 459, 1098-1101 (2009). [2] Postberg et al., Nature 474, 620-622 (2011). [3]. Hsu, Postberg, Sekine et al., Nature, 519, 207-210 (2015). [4] Waite et al., Nature 460, 487-490 (2009).

  8. Producing and Recognizing Analogical Relations

    ERIC Educational Resources Information Center

    Lipkens, Regina; Hayes, Steven C.

    2009-01-01

    Analogical reasoning is an important component of intelligent behavior, and a key test of any approach to human language and cognition. Only a limited amount of empirical work has been conducted from a behavior analytic point of view, most of that within Relational Frame Theory (RFT), which views analogy as a matter of deriving relations among…

  9. Drawing Analogies in Environmental Education

    ERIC Educational Resources Information Center

    Affifi, Ramsey

    2014-01-01

    Reconsidering the origin, process, and outcomes of analogy-making suggests practices for environmental educators who strive to disengage humans from the isolating illusions of dichotomizing frameworks. We can view analogies as outcomes of developmental processes within which human subjectivity is but an element, threading our sense of self back…

  10. Natural analog studies: Licensing perspective

    SciTech Connect

    Bradbury, J.W.

    1995-09-01

    This report describes the licensing perspective of the term {open_quotes}natural analog studies{close_quotes} as used in CFR Part 60. It describes the misunderstandings related to its definition which has become evident during discussions at the U.S Nuclear Regulatory Commission meetings and tries to clarify the appropriate applications of natural analog studies to aspects of repository site characterization.

  11. Testing of Icy-Soil Sample Delivery in Simulated Martian Conditions (Animation)

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for animation

    This movie clip shows testing under simulated Mars conditions on Earth in preparation for NASA's Phoenix Mars Lander using its robotic arm for delivering a sample to the doors of a laboratory oven.

    The icy soil used in the testing flowed easily from the scoop during all tests at Martian temperatures. On Mars, icy soil has stuck to the scoop, a surprise that may be related to composition of the soil at the landing site.

    This testing was done at Honeybee Robotics Spacecraft Mechanisms Corp., New York, which supplied the Phoenix scoop.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASAaE(TM)s Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  12. Crustal Failure in Large Icy Bodies from a Strong Tidal Encounter

    NASA Astrophysics Data System (ADS)

    Quillen, Alice C.; Giannella, David; Shaw, John

    2015-11-01

    Close tidal encounters among large planetesimals and satellites are more common than grazing or direct impacts. Using a mass spring model simulation, we look at the deformation of the surface of an elastic spherical body caused by a nearly parabolic close tidal encounter with a body that has mass similar to that of the primary body. We delineate a regime for tidal encounters that induce sufficient stress on the surface for brittle failure of an icy crust. Simulated cracks caused by extension of the crust extend a large fraction of the radius of body. Tidal encounters give an alternative mechanism for formation of long graben complexes and chasma on icy satellites such as Dione, Tethys, Ariel and Charon.

  13. Distinct Aqueous and Hydrocarbon Cryovolcanism on Titan and Other Icy Satellites (Invited)

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.; Furfaro, R.; Candelaria, P.

    2010-12-01

    Almost as soon as low-temperature solar nebula condensation sequences were first computed, it was realized that icy satellites have an internal heat source in long-lived radioactivities and could undergo differentiation; furthermore, freezing-point depressants, such as ammonia, and apolar gases, such as methane, could enable icy satellites to undergo aqueous cryovolcanism. The subsequent recognition of tidal and gravitational potential energy sources increased expectations for cryovolcanism. Voyager imaging and discovery of apparent cryovolcanic landforms—best exhibited by Triton, more ambiguous elsewhere-- motivated studies of the phase relations, phase densities and other thermodynamic properties, solid- and liquid-state rheologies, and possible cryovolcanic eruptive behaviors and landform characteristics. Ironically, the closer we examined Jovian icy moons with Galileo, the rarer cryovolcanic landforms appeared to be, with only a few compelling and very well characterized cases found mainly on Europa. Compelling examples of effusive cryovolcanism mainly occupied local topographic lows, whereas cases not in low spots tended to exhibit signs of explosive emplacement. Spectacular evidence of explosive cryovolcanism or geyser-like behavior was found by Cassini on Enceladus, but most other icy Saturnian moons did not reveal any compelling indicators of eruptions. Titan has so far been a mixed case, where some indicators of cryovolcanism have been reported, but there is scant compelling evidence for the process. We think that the sparseness of compelling effusive cryovolcanic features on icy satellites is because free, unreacted ammonia is less common than previously thought, and the main aqueous liquids are salt-water solutions denser than ice I; hence, they tend not to erupt, or they erupt only if driven by gas exsolution; even then, a thin ice shell and high heat flow is needed to allow aqueous liquids near enough to the surface to erupt. On satellites with thick

  14. Icy Galilean satellite reflectance spectra - Less ice on Ganymede and Callisto?

    NASA Technical Reports Server (NTRS)

    Spencer, John R.

    1987-01-01

    An evaluation of reflectance spectra of the icy Galilean satellites, taking account of the depth of the 3-micron fundamental water ice absorption feature and the shorter wavelength bands, suggests lower ice abundances for Ganymede and Callistro than previously supposed, provided that the ice is segregated from the nonicy material. Data are consistent with a 50 percent areal coverage of ice on Ganymede and 10 percent on Callistro, the rest of the surface being covered by carbonaceous chondrite-like material with strong 3-micron absorption due to bound water. The analysis indicates a homogeneous icy surface for Europa, and the possible presence on all three objects of small quantities of surface sulfuric acid.

  15. Titan's Impact Cratering Record: Erosion of Ganymedean (and other) Craters on a Wet Icy Landscape

    NASA Astrophysics Data System (ADS)

    Schenk, P.; Moore, J.; Howard, A.

    2012-04-01

    We examine the cratering record of Titan from the perspective of icy satellites undergoing persistent landscape erosion. First we evaluate whether Ganymede (and Callisto) or the smaller low-gravity neighboring icy satellites of Saturn are the proper reference standard for evaluating Titan’s impact crater morphologies, using topographic and morphometric measurements (Schenk, 2002; Schenk et al. (2004) and unpublished data). The special case of Titan’s largest crater, Minrva, is addressed through analysis of large impact basins such as Gilgamesh, Lofn, Odysseus and Turgis. Second, we employ a sophisticated landscape evolution and modification model developed for study of martian and other planetary landforms (e.g., Howard, 2007). This technique applies mass redistribution principles due to erosion by impact, fluvial and hydrological processes to a planetary landscape. The primary advantage of our technique is the possession of a limited but crucial body of areal digital elevation models (DEMs) of Ganymede (and Callisto) impact craters as well as global DEM mapping of Saturn’s midsize icy satellites, in combination with the ability to simulate rainfall and redeposition of granular material to determine whether Ganymede craters can be eroded to resemble Titan craters and the degree of erosion required. References: Howard, A. D., “Simulating the development of martian highland landscapes through the interaction of impact cratering, fluvial erosion, and variable hydrologic forcing”, Geomorphology, 91, 332-363, 2007. Schenk, P. "Thickness constraints on the icy shells of the galilean satellites from impact crater shapes". Nature, 417, 419-421, 2002. Schenk, P.M., et al. "Ages and interiors: the cratering record of the Galilean satellites". In: Jupiter: The Planet, Satellites, and Magnetosphere, Cambridge University Press, Cambridge, UK, pp. 427-456, 2004.

  16. Efficacy of a rubber outsole with a hybrid surface pattern for preventing slips on icy surfaces.

    PubMed

    Yamaguchi, Takeshi; Hsu, Jennifer; Li, Yue; Maki, Brian E

    2015-11-01

    Conventional winter-safety footwear devices, such as crampons, can be effective in preventing slips on icy surfaces but the protruding studs can lead to other problems such as trips. A new hybrid (rough and smooth) rubber outsole was designed to provide high slip resistance without use of protruding studs or asperities. In the present study, we examined the slip resistance of the hybrid rubber outsole on both dry (-10 °C) and wet (0 °C) icy surfaces, in comparison to three conventional strap-on winter anti-slip devices: 1) metal coils ("Yaktrax Walker"), 2) gritted (sandpaper-like) straps ("Rough Grip"), and 3) crampons ("Altagrips-Lite"). Drag tests were performed to measure static (SCOF) and dynamic (DCOF) coefficients of friction, and gait trials were conducted on both level and sloped ice surfaces (16 participants). The drag-test results showed relatively high SCOF (≧0.37) and DCOF (≧0.31) values for the hybrid rubber sole, at both temperatures. The other three footwear types exhibited lower DCOF values (0.06-0.20) when compared with the hybrid rubber sole at 0 °C (p < 0.01). Slips were more frequent when wearing the metal coils, in comparison to the other footwear types, when descending a slope at -10 °C (6% of trials vs 0%; p < 0.05). There were no other significant footwear-related differences in slip frequency, distance or velocity. These results indicate that the slip-resistance of the hybrid rubber sole on icy surfaces was comparable to conventional anti-slip footwear devices. Given the likely advantages of the hybrid rubber sole (less susceptibility to tripping, better slip resistance on non-icy surfaces), this type of sole should contribute to a decrease in fall accidents; however, further research is needed to confirm its effectiveness under a wider range of test conditions.

  17. Impact of coastal processes on resource development with an example from Icy Bay, Alaska

    USGS Publications Warehouse

    Molnia, Bruce F.

    1978-01-01

    The coastline of Alaska is dynamic and continually readjusting to changes in the many processes that operate in the coastal zone. Because of this dynamic nature, special consideration must be made in planning for development, and. caution must be exercised in site selection for facilities to be emplaced in the coastal zone. All types of coastal processes from continuously active normal processes to the low frequency-high intensity rare event must be considered. Site-specific evaluation-s considering the broad range of possible processes must precede initiation of development. An example of the relation between coastal processes and a proposed resource treatment facility is presented for Icy Bay, Alaska. Icy Bay is the only sheltered bay near many of the offshore tracts leased for petroleum exploration in the 1976 northern Gulf of Alaska OCS (Outer Continental Shelf) lease sale. Consequently, it has been selected as a primary onshore staging site for the support of offshore exploration and development. The environment of Icy Bay has many potentially hazardous features, including a submarine moraine at the bay mouth and actively calving glaciers at the bay's head which produce many icebergs. But most significant from the point of view of locating onshore facilities and pipeline corridors are the high rates of shoreline erosion and sediment deposition. If pipelines or any onshore staging facilities are to be placed in the coastal areas of Icy Bay, then the dynamic changes in shoreline position must be considered so that man-made structures will not be eroded away or be silted in before the completion of development.

  18. Tidal dissipation in the large icy satellites: implications for their thermal evolution.

    NASA Astrophysics Data System (ADS)

    Tobie, G.; Mocquet, A.; Sotin, C.

    2003-04-01

    Tidal dissipation is a large heat source that controls the thermal evolution of several bodies of the Solar system, notably Europa and Titan. In order to investigate how tidal heating affects the present and past thermal states of these icy satellites, we perform numerical calculations of tidal dissipation distribution for different internal structures and different viscoelastic properties of their interiors. The numerical method is developed after the elastic formulation of free spheroidal oscillations of a compressible self-gravitating planet and adapted to a tidally forced viscoelastic response of the body. We test systematically the dependence of tidal dissipation on the rheological parameters namely, the viscosity eta, the shear modulus μ, and the bulk modulus K, as well as on the orbital parameters, i.e. the eccentricity e and the forcing frequency ω. The effects of tidal dissipation on heat balance in the outer icy layers are investigated with a 2D thermal convection model. We show that the tidal dissipation in the icy layers of Europa and Titan is very large, and that it allows for the long-term existence of a subsurface ocean below a convective ice I layer. We are also investigating thermal evolution models of the rocky core to address the question of tidal dissipation in the silicates. Although tidal dissipation in the rocky core is not required for an ocean to exist, it may provide an additional heating source for seafloor volcanism to occur. In addition, we show that the tidal dissipation in a floating icy layer mainly depends on its viscous structure and that the lateral viscosity variations modify the local dissipation and the value of the global dissipation up to 30%.

  19. Power-Conversion Concept Designed for the Jupiter Icy Moons Orbiter

    NASA Technical Reports Server (NTRS)

    Mason, Lee S.

    2004-01-01

    The Jupiter Icy Moons Orbiter (JIMO) is a bold new mission being developed by NASA's Office of Space Science under Project Prometheus. JIMO is examining the potential of nuclear electric propulsion (NEP) technology to efficiently deliver scientific payloads to three of Jupiter's moons: Callisto, Ganymede, and Europa. A critical element of the NEP spacecraft is the space reactor power system (SRPS), consisting of the nuclear reactor, power conversion, heat rejection, and power management and distribution (PMAD).

  20. Brine Pockets in the Icy Shell on Europa: Distribution, Chemistry, and Habitability

    NASA Technical Reports Server (NTRS)

    Zolotov, M. Yu; Shock, E. L.; Barr, A. C.; Pappalardo, R. T.

    2004-01-01

    On Earth, sea ice is rich in brine, salt, and gas inclusions that form through capturing of seawater during ice formation. Cooling of the ice over time leads to sequential freezing of captured sea-water, precipitation of salts, exsolution of gases, and formation of brine channels and pockets. Distribution and composition of brines in sea ice depend on the rate of ice formation, vertical temperature gradient, and the age of the ice. With aging, the abundance of brine pockets decreases through downward migration. De- spite low temperatures and elevated salinities, brines in sea ice provide a habitat for photosynthetic and chemosynthetic organisms. On Europa, brine pockets and channels could exist in the icy shell that may be from a few km to a few tens of km thick and is probably underlain by a water ocean. If the icy shell is relatively thick, convection could develop, affecting the temperature pattern in the ice. To predict the distribution and chemistry of brine pockets in the icy shell we have combined numerical models of the temperature distribution within a convecting shell, a model for oceanic chemistry, and a model for freezing of Europan oceanic water. Possible effects of brine and gas inclusions on ice rheology and tectonics are discussed.

  1. Heating and melting of small icy satellites by the decay of Al-26

    SciTech Connect

    Prialnik, D.; Bar-Nun, A. )

    1990-05-01

    The effect of radiogenic heating due to Al-26 on the thermal evolution of small icy satellites is studied. The object is to find the extent of internal melting as a function of the satellite radius and of the initial Al-26 abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of about 10 to the 6th yr (comparable with the lifetime of Al-26). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of K-40, Th-232, U-235, and U-238, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10 to the 9th yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. The main conclusion is that the initial Al-26 abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, about 7 x 10 to the -7th by mass). 34 refs.

  2. Thickness Constraints on the Icy Shells of the Galilean Satellites from a Comparison of Crater Shapes

    NASA Technical Reports Server (NTRS)

    Schenk, Paul M.

    2002-01-01

    A thin outer ice shell on Jupiter's large moon Europa would imply easy exchange between the surface and any organic or biotic material in its putative subsurface ocean. The thickness of the outer ice shell is poorly constrained, however, with model-dependent estimates ranging from a few kilometers of depths of impact craters on Europa, Ganymede and Callisto that reveal two anomalous transitions in crater shape with diameter. The first transition is probably related to temperature-dependent ductility of the crust at shallow depths (7-8 km on Europa). The second transition is attributed to the influence of subsurface oceans on all three satellites, which constrains Europa's icy shell to be at least 19 km thick. The icy lithospheres of Ganymede and Callisto are equally ice-rich, but Europa's icy shell has a thermal structure about 0.25-0.5 times the thickness of Ganymede's or Callisto's shells, depending on epoch. The appearances of the craters on Europa are inconsistent with thin-ice-shell models and indicate that exchange of oceanic and surface material could be difficult.

  3. Subsurface Water Oceans on Icy Satellites: Chemical Composition and Exchange Processes

    NASA Astrophysics Data System (ADS)

    Sohl, Frank; Choukroun, Mathieu; Kargel, Jeffrey; Kimura, Jun; Pappalardo, Robert; Vance, Steve; Zolotov, Mikhail

    2010-06-01

    The state of knowledge about the structure and composition of icy satellite interiors has been significantly extended by combining direct measurements from spacecraft, laboratory experiments, and theoretical modeling. The existence of potentially habitable liquid water reservoirs on icy satellites is dependent on the radiogenic heating of the rock component, additional contributions such as the dissipation of tidal energy, the efficiency of heat transfer to the surface, and the presence of substances that deplete the freezing point of liquid water. This review summarizes the chemical evolution of subsurface liquid water oceans, taking into account a number of chemical processes occuring in aqueous environments and partly related to material exchange with the deep interior. Of interest are processes occuring at the transitions from the liquid water layer to the ice layers above and below, involving the possible formation of clathrate hydrates and high-pressure ices on large icy satellites. In contrast, water-rock exchange is important for the chemical evolution of the liquid water layer if the latter is in contact with ocean floor rock on small satellites. The composition of oceanic floor deposits depends on ambient physical conditions and ocean chemistry, and their evolutions through time. In turn, physical properties of the ocean floor affect the circulation of oceanic water and related thermal effects due to tidally-induced porous flow and aqueous alteration of ocean floor rock.

  4. Preliminary Design of ICI-based Multimedia for Reconceptualizing Electric Conceptions at Universitas Pendidikan Indonesia

    NASA Astrophysics Data System (ADS)

    Samsudin, A.; Suhandi, A.; Rusdiana, D.; Kaniawati, I.

    2016-08-01

    Interactive Conceptual Instruction (ICI) based Multimedia has been developed to represent the electric concepts turn into more real and meaningful learning. The initial design of ICI based multimedia is a multimedia computer that allows users to explore the entire electric concepts in terms of the existing conceptual and practical. Pre-service physics teachers should be provided with the learning that could optimize the conceptions held by re-conceptualizing concepts in Basic Physics II, especially the concepts about electricity. To collect and to analyze the data genuinely and comprehensively, researchers utilized a developing method of ADDIE which has comprehensive steps: analyzing, design, development, implementation, and evaluation. The ADDIE developing steps has been utilized to describe comprehensively from the phase of analysis program up until the evaluation program. Based on data analysis, it can be concluded that ICI-based multimedia could effectively increase the pre-service physics teachers’ understanding on electric conceptions for re-conceptualizing electric conceptions at Universitas Pendidikan Indonesia.

  5. Thermal Conductivity Measurements on consolidated Soil Analogs

    NASA Astrophysics Data System (ADS)

    Seiferlin, K.; Heimberg, M.; Thomas, N.

    2007-08-01

    Heat transport in porous media such as soils and regolith is significantly reduced compared to the properties of compact samples of the same material. The bottle neck for solid state heat transport is the contact area between adjacent grains. For "dry" and unconsolidated materials the contact areas and thus the thermal conductivity are extremely small. Sintering and cementation are two processes that can increase the cross section of interstitial bonds signifcantly. On Mars, cementation can be caused by condensation of water or carbon dioxide ice from the vapor phase, or from salts and minerals that fall out from aqueous solutions. We produced several artificially cemented samples, using small glass beads of uniform size as soil analog. The cementation is achieved by initially molten wax that is mixed with the glass beads while liqiud. The wax freezes preferably at the contact points between grains, thus minimizing surface energy, and consolidates the samples. The thermal conductivity of these samples is then measured in vacuum. We present the results of these measurements and compare them with theoretical models. The observed range of thermal conductivity values can explain some, but not all of the variations in thermal intertia that can be seen in TES remote sensing data.

  6. Evaluation of ICI D7114, a putative stimulant of brown adipocytes, on histamine-contracted guinea-pig ileum.

    PubMed Central

    Growcott, J. W.; Wilson, C.; Holloway, B.; Mainwaring, S.

    1993-01-01

    1. Experiments were performed to characterize the effects of the novel brown adipocyte stimulant, ICI D7114, in the guinea-pig isolated ileum, right atrium and tracheal chain. In the ileum, agonist-induced inhibition of the contractile response to either histamine or prostaglandin E2 (PGE2) was assessed, along with effects on resting rate in the atrium and resting tone in the tracheal chain. In the latter two preparations, antagonism of isoprenaline-induced responses by ICI D7114 was also assessed. 2. Inhibitory responses were obtained in the ileum to ICI D7114, isoprenaline, BRL37344, and noradrenaline. The responses to ICI D7114, isoprenaline and BRL37344 were resistant to blockade with propranolol (5 microM), naloxone (1 microM), methysergide (0.1 microM), cimetidine, indomethacin and 8-phenyltheophylline (all 10 microM). These responses to isoprenaline, in the presence of propranolol (5 microM), were competitively antagonized by alprenolol (1-100 microM) with a pA2 value of 6.44. The responses to ICI D7114 and BRL37344 were antagonized by single concentrations of alprenolol (1 microM) with apparent pKB values of 6.53 and 6.57 respectively. These data indicate an effect of ICI D7114 at the atypical beta-adrenoceptor in the guinea-pig ileum. 3. The order and relative potency of agonists at the atypical beta-adrenoceptor was BRL37344 (4) < isoprenaline (1) = ICI D7114 (1.1) > noradrenaline (0.5). 4. ICI D7114 (1 nM - 10 microM) caused no significant change in the rate of beating or the resting tone of the guinea-pig right atrium or tracheal chain respectively.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8104647

  7. Origins of GEMS Grains

    NASA Technical Reports Server (NTRS)

    Messenger, S.; Walker, R. M.

    2012-01-01

    Interplanetary dust particles (IDPs) collected in the Earth s stratosphere contain high abundances of submicrometer amorphous silicates known as GEMS grains. From their birth as condensates in the outflows of oxygen-rich evolved stars, processing in interstellar space, and incorporation into disks around new stars, amorphous silicates predominate in most astrophysical environments. Amorphous silicates were a major building block of our Solar System and are prominent in infrared spectra of comets. Anhydrous interplanetary dust particles (IDPs) thought to derive from comets contain abundant amorphous silicates known as GEMS (glass with embedded metal and sulfides) grains. GEMS grains have been proposed to be isotopically and chemically homogenized interstellar amorphous silicate dust. We evaluated this hypothesis through coordinated chemical and isotopic analyses of GEMS grains in a suite of IDPs to constrain their origins. GEMS grains show order of magnitude variations in Mg, Fe, Ca, and S abundances. GEMS grains do not match the average element abundances inferred for ISM dust containing on average, too little Mg, Fe, and Ca, and too much S. GEMS grains have complementary compositions to the crystalline components in IDPs suggesting that they formed from the same reservoir. We did not observe any unequivocal microstructural or chemical evidence that GEMS grains experienced prolonged exposure to radiation. We identified four GEMS grains having O isotopic compositions that point to origins in red giant branch or asymptotic giant branch stars and supernovae. Based on their O isotopic compositions, we estimate that 1-6% of GEMS grains are surviving circumstellar grains. The remaining 94-99% of GEMS grains have O isotopic compositions that are indistinguishable from terrestrial materials and carbonaceous chondrites. These isotopically solar GEMS grains either formed in the Solar System or were completely homogenized in the interstellar medium (ISM). However, the

  8. Current Status of Japanese Participation to Jupiter Icy Moons Explorer "JUICE"

    NASA Astrophysics Data System (ADS)

    Saito, Y.; Sasaki, S.; Kimura, J.; Tohara, K.; Fujimoto, M.; Sekine, Y.

    2015-12-01

    JUICE is an ESA's L-class mission to Explore Jupiter Icy Moons. The science objectives of JUICE is to understand (1) emergence of habitable worlds around gas giants and (2) Jupiter system as an archetype for gas giants. JUICE was mission adopted in November 2014. JUICE will be launched by Arian-5. After 7.5 years of interplanetary transfer and Earth-Venus-Earth-Earth gravity assists JUICE will be inserted into an orbit around Jupiter in January 2030. JUICE will make observation of all the three Jupiter icy Moons that potentially have subsurface ocean under the icy crust. After inserted into Ganymede orbit in 2032, JUICE will make detailed observation of the largest Icy Moon in the solar system. Three Japanese groups were selected to provide part of the three science instruments RPWI, GALA, and PEP/JNA. Two Japanese groups were also selected as science Co-I of two instrument groups JANUS and J-MAG. JUICE is the first mission for ISAS/JAXA to participate to foreign large science mission as a junior partner who will provide part of the science instruments. Taking into account all the data to be obtained by 5 instruments that JUICE-JAPAN will participate, Japanese team will be able to contribute to most of the major science objectives relating with planet Jupiter (JANUS), Jupiter magnetosphere (PEP/JNA, RPWI, and J-MAG), and Icy Moons (GALA, J-MAG, and JANUS). JUICE-JAPAN Working Group (WG) was established in September 2013. JUICE-JAPAN WG submitted a proposal for ISAS/JAXA small project in February 2014. JUICE-JAPAN WG passed the MDR in September 2014. JUICE-JAPAN passed the ISAS SRR that was held in April 2015 and also passed the ISAS project preparation review that was held in May 2015. Currently JUICE-JAPAN is an ISAS pre-project. In the future, SDR is scheduled in the end of 2015, PDR is scheduled in 2016 and CDR is scheduled in 2017. JUICE is a long-term mission that will be completed about 20 years from now. It is quite important to take place a necessary change

  9. Fractal analysis on Enceladus: a global ocean underneath the icy crust

    NASA Astrophysics Data System (ADS)

    Lucchetti, Alice; Pozzobon, Riccardo; Mazzarini, Francesco; Cremonese, Gabriele; Simioni, Emanuele; Massironi, Matteo

    2016-04-01

    Plumes of water have been observed erupting from Enceladus' south polar terrain providing direct evidence of a reservoir of liquid below the surface, that could be considered global or just a small body of water concentrated at its south pole. Gravity data collected during the spacecraft's several close flyby over the south polar region determined that the icy shell above the liquid ocean must be 30-40 km thick extending from the south pole up to 50°S (Iess et al. 2014). The hypothesis of a global ocean beneath the icy crust has been raised even in a recent paper of Thomas et al. (2015) thanks to the measurements of the very slight wobble that Enceladus displays as it orbits Saturn. In this work we support the hypothesis of the presence of an ocean layer using the fractal percolation theory. This method allowed us to estimate the icy shell thickness values in different regions of Enceladus from the south polar terrain up to the north pole. The spatial distribution of fractures on Enceladus has been analyzed in terms of their self-similar clustering and a two-point correlation method was used to measure the fractal dimension of the fractures population (Mazzarini, 2004, 2010). A self-similar clustering of fractures is characterized by a correlation coefficient with a size range defined by a lower and upper cut-off, that represent a mechanical discontinuity and the thickness of the fractured icy crust, thus connected to the liquid reservoir. We mapped the fractures on Enceladus surface based on April 2010 global mosaic from Cassini mission and applied the fractal method firstly to the south polar terrain finding indeed a fractal correlation of fractures and providing an ice shell thickness of ~40 km. Then, we analyzed fractures of four different regions around the equator and around the north pole inferring an overall ice shell thickness ranging from 35 to 45 km. Our results are in agreement with the gravity observations (Iess et al., 2014) and the mechanical models

  10. Sulfonimidamide analogs of oncolytic sulfonylureas.

    PubMed

    Toth, J E; Grindey, G B; Ehlhardt, W J; Ray, J E; Boder, G B; Bewley, J R; Klingerman, K K; Gates, S B; Rinzel, S M; Schultz, R M; Weir, L C; Worzalla, J F

    1997-03-14

    A series of sulfonimidamide analogs of the oncolytic diarylsulfonylureas was synthesized and evaluated for (1) in vitro cytotoxicity against CEM cells, (2) in vivo antitumor activity against subaxillary implanted 6C3HED lymphosarcoma, and (3) metabolic breakdown to the o-sulfate of p-chloroaniline. The separated enantiomers of one sulfonimidamide analog displayed very different activities in the in vivo screening model. In general, several analogs demonstrated excellent growth inhibitory activity in the 6C3HED model when dosed orally or intraperitoneally. A correlative structure-activity relationship to the oncolytic sulfonylureas was not apparent.

  11. Interstellar Dust Grain Alignment

    NASA Astrophysics Data System (ADS)

    Andersson, B.-G.; Lazarian, A.; Vaillancourt, John E.

    2015-08-01

    Interstellar polarization at optical-to-infrared wavelengths is known to arise from asymmetric dust grains aligned with the magnetic field. This effect provides a potentially powerful probe of magnetic field structure and strength if the details of the grain alignment can be reliably understood. Theory and observations have recently converged on a quantitative, predictive description of interstellar grain alignment based on radiative processes. The development of a general, analytical model for this radiative alignment torque (RAT) theory has allowed specific, testable predictions for realistic interstellar conditions. We outline the theoretical and observational arguments in favor of RAT alignment, as well as reasons the "classical" paramagnetic alignment mechanism is unlikely to work, except possibly for the very smallest grains. With further detailed characterization of the RAT mechanism, grain alignment and polarimetry promise to not only better constrain the interstellar magnetic field but also provide new information on the dust characteristics.

  12. Synthesis of Large Molecules in Cometary Ice Analogs: Physical Properties

    NASA Astrophysics Data System (ADS)

    Dworkin, Jason; Sandford, S. A.; Allamandola, L. J.; Deamer, D. W.; Gillette, S. J.; Zare, R. N.

    Comets and carbonaceous micrometeorites may have been important sources of volatiles on the early Earth; their organic composition may therefore be related to the origin of life. Ices on grains in molecular clouds contain a variety of simple molecules. Within the cloud and especially the presolar nebula, these icy grains would have been photoprocessed by ultraviolet light to produce more complex molecules. We are investigating the molecules that could have been generated in precometary ices. Experiments were conducted by forming a realistic interstellar ice (H_2^O, CH_3H, NH_3 and CO) at ~10 K under high vacuum irradiated UV by a hydrogen plasma lamp. The residue remaining after warming to room temperature was analyzed by HPLC and by several mass spectrometric methods. This material contains a variety of complex compounds with MS profiles resembling those found in IDPs and meteorites. Surface tension measurements show that an amphiphilic component is also present. These species do not appear in various controls or in unphotolyzed samples. In other experiments, the residues were dispersed in aqueous media for microscopy. The organic material forms 10-40 micrometer droplets that fluoresce (300-450 nm) under UV excitation and appear strikingly similar to those produced by extracts of the Murchison meteorite. Together, these results suggest a link between organic material synthesized on cold grains photochemically and compounds that may have contributed to the organic inventory of the primitive Earth. The amphiphilic properties of such compounds permit self-assembly into the membranous boundary structures required for the first forms of cellular life.

  13. Evaluating countermeasures in spaceflight analogs.

    PubMed

    Ploutz-Snyder, Lori

    2016-04-15

    Countermeasures are defined as solutions to prevent the undesirable physiologic outcomes associated with spaceflight. Spaceflight analogs provide a valuable opportunity for the evaluation of countermeasures because they allow for the evaluation of more subjects, more experimental control, and are considerably less expensive than actual spaceflight. The various human analogs have differing strengths and weaknesses with respect to the development and evaluation of countermeasures. The human analogs are briefly reviewed with a focus on their suitability for countermeasure evaluation. Bed rest is the most commonly used analog for evaluating countermeasures. While countermeasures are typically developed to target one or maybe two particular physiologic issues, it is increasingly important to evaluate all of the organ systems to discern whether they might be unintended consequences on nontargeted tissues. In preparation for Mars exploration it will be necessary to fully integrate countermeasures to protect all organ systems. The synergistic and antagonistic effects of multiple countermeasures needs to be the focus of future work. PMID:26662054

  14. Introduction to Analog Field Testing

    NASA Video Gallery

    NASA tests systems and operational concepts in analog environments, which include locations underwater, in the arctic, on terrestrial impact craters, in the desert, and on the International Space S...

  15. Flight Analogs (Bed Rest Research)

    NASA Video Gallery

    Flight Analogs / Bed Rest Research Projects provide NASA with a ground based research platform to complement space research. By mimicking the conditions of weightlessness in the human body here on ...

  16. Evaluation of ICI D7114, a putative stimulant of brown adipocytes, on histamine-contracted guinea-pig ileum.

    PubMed

    Growcott, J W; Wilson, C; Holloway, B; Mainwaring, S

    1993-08-01

    1. Experiments were performed to characterize the effects of the novel brown adipocyte stimulant, ICI D7114, in the guinea-pig isolated ileum, right atrium and tracheal chain. In the ileum, agonist-induced inhibition of the contractile response to either histamine or prostaglandin E2 (PGE2) was assessed, along with effects on resting rate in the atrium and resting tone in the tracheal chain. In the latter two preparations, antagonism of isoprenaline-induced responses by ICI D7114 was also assessed. 2. Inhibitory responses were obtained in the ileum to ICI D7114, isoprenaline, BRL37344, and noradrenaline. The responses to ICI D7114, isoprenaline and BRL37344 were resistant to blockade with propranolol (5 microM), naloxone (1 microM), methysergide (0.1 microM), cimetidine, indomethacin and 8-phenyltheophylline (all 10 microM). These responses to isoprenaline, in the presence of propranolol (5 microM), were competitively antagonized by alprenolol (1-100 microM) with a pA2 value of 6.44. The responses to ICI D7114 and BRL37344 were antagonized by single concentrations of alprenolol (1 microM) with apparent pKB values of 6.53 and 6.57 respectively. These data indicate an effect of ICI D7114 at the atypical beta-adrenoceptor in the guinea-pig ileum. 3. The order and relative potency of agonists at the atypical beta-adrenoceptor was BRL37344 (4) < isoprenaline (1) = ICI D7114 (1.1) > noradrenaline (0.5). 4. ICI D7114 (1 nM - 10 microM) caused no significant change in the rate of beating or the resting tone of the guinea-pig right atrium or tracheal chain respectively. It did, however, cause selective blockade of the responses to isoprenaline in these tissues (apparent pKB values 7.63 and 5.85 in atrium and tracheal chain respectively). Responses to histamine (atrium) and aminophylline (tracheal chain) were not significantly affected by 10 microM ICI D7114.5. These results demonstrate that ICI D7114 possesses selective agonist activity at atypical beta-adrenoceptors in the

  17. The Robustness of Acoustic Analogies

    NASA Technical Reports Server (NTRS)

    Freund, J. B.; Lele, S. K.; Wei, M.

    2004-01-01

    Acoustic analogies for the prediction of flow noise are exact rearrangements of the flow equations N(right arrow q) = 0 into a nominal sound source S(right arrow q) and sound propagation operator L such that L(right arrow q) = S(right arrow q). In practice, the sound source is typically modeled and the propagation operator inverted to make predictions. Since the rearrangement is exact, any sufficiently accurate model of the source will yield the correct sound, so other factors must determine the merits of any particular formulation. Using data from a two-dimensional mixing layer direct numerical simulation (DNS), we evaluate the robustness of two analogy formulations to different errors intentionally introduced into the source. The motivation is that since S can not be perfectly modeled, analogies that are less sensitive to errors in S are preferable. Our assessment is made within the framework of Goldstein's generalized acoustic analogy, in which different choices of a base flow used in constructing L give different sources S and thus different analogies. A uniform base flow yields a Lighthill-like analogy, which we evaluate against a formulation in which the base flow is the actual mean flow of the DNS. The more complex mean flow formulation is found to be significantly more robust to errors in the energetic turbulent fluctuations, but its advantage is less pronounced when errors are made in the smaller scales.

  18. Habitability of the giant icy moons: current knowledge and future insights from the JUICE mission

    NASA Astrophysics Data System (ADS)

    Grasset, O.; Prieto-Ballesteros, O.; Titov, D.; Erd, C.; Bunce, E.; Coustenis, A.; Blanc, M.; Coates, A.; Fletcher, L.; van Hoolst, T.; Hussmann, H.; Jaumann, R.; Krupp, N.; Tortora, P.; Tosi, F.; Wielders, A.

    2012-09-01

    Large satellites of gas giants, at orbits beyond the snow-line, such as Jupiter or Saturn, can contain a large amount of water (almost 45% in mass). Hydrospheres are extremely thick, ~600 km for Ganymede and Callisto, and may possess liquid layers below the icy crust. Thus, the Galilean satellites provide a conceptual basis within which new theories for understanding habitability can be constructed. Measurements from the Voyager and Galileo spacecraft revealed the potential of these satellites in this context. The JUpiter Icy moons Explorer (JUICE) will greatly enhance our understanding of their potential habitability. It is known, even at Earth where life mostly depends on solar energy, that habitats exist deep in the oceans in eternal darkness feeding on chemical energy. Aqueous layers are suspected below the icy crusts of the moons, which possess similar physical characteristics than Earth's deep oceans. Since they are certainly very stable through time, and because complex chemistry and energy sources may be available, life may have originated within such subsurface habitats despite the hostile surface conditions. Liquid water reservoirs have been proposed on Ganymede, Europa and Callisto from geophysical models, based on Galileo observations. These oceans that are covered by ice shells exist independently of the input of stellar energy, and are located well outside the conventional habitable zone of the Sun. Considering the pressure range encountered within the icy moons, four different scenarios can be defined. These result from varying thicknesses of the water ice layers and the liquid ocean with respect to the silicate floor (Figure 1). Case 2 in Figure 1 is highly probable for the largest moons (Ganymede and Callisto), while case 3 is more probable for Europa and smaller icy moons if they host liquid reservoirs such as has been discovered at Enceladus. Europa's ocean is unique because it may be in contact with the rock layer. This substrate may be

  19. Folding of Pollen Grains

    NASA Astrophysics Data System (ADS)

    Katifori, Eleni; Alben, Silas; Cerda, Enrique; Nelson, David; Dumais, Jacques

    2008-03-01

    At dehiscence, which occurs when the anther reaches maturity and opens, pollen grains dehydrate and their volume is reduced. The pollen wall deforms to accommodate the volume loss, and the deformation pathway depends on the initial turgid pollen grain geometry and the mechanical properties of the pollen wall. We demonstrate, using both experimental and theoretical approaches, that the design of the apertures (areas on the pollen wall where the stretching and the bending modulus are reduced) is critical for controlling the folding pattern, and ensures the pollen grain viability. An excellent fit to the experiments is obtained using a discretized version of the theory of thin elastic shells.

  20. Convection in grain refining

    NASA Technical Reports Server (NTRS)

    Flemings, M. C.; Szekely, J.

    1982-01-01

    The relationship between fluid flow phenomena, nucleation, and grain refinement in solidifying metals both in the presence and in the absence of a gravitational field was investigated. The reduction of grain size in hard-to-process melts; the effects of undercooling on structure in solidification processes, including rapid solidification processing; and control of this undercooling to improve structures of solidified melts are considered. Grain refining and supercooling thermal modeling of the solidification process, and heat and fluid flow phenomena in the levitated metal droplets are described.

  1. The (impossible?) formation of acetaldehyde on the grain surfaces: insights from quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Enrique-Romero, J.; Rimola, A.; Ceccarelli, C.; Balucani, N.

    2016-06-01

    Complex Organic Molecules (COMs) have been detected in the interstellar medium (ISM). However, it is not clear whether their synthesis occurs on the icy surfaces of interstellar grains or via a series of gas-phase reactions. As a test case of the COMs synthesis in the ISM, we present new quantum chemical calculations on the formation of acetaldehyde (CH3CHO) from the coupling of the HCO and CH3 radicals, both in gas phase and on water ice surfaces. The binding energies of HCO and CH3 on the amorphous water ice were also computed (2333 and 734 K, respectively). Results indicate that, in gas phase, the products could be either CH3CHO, CH4 + CO, or CH3OCH, depending on the relative orientation of the two radicals. However, on the amorphous water ice, only the CH4 + CO product is possible due to the geometrical constraints imposed by the water ice surface. Therefore, acetaldehyde cannot be synthesized by the CH3 + HCO coupling on the icy grains. We discuss the implications of these results and other cases, such as ethylene glycol and dimethyl ether, in which similar situations can occur, suggesting that formation of these molecules on the grain surfaces might be unlikely.

  2. Sodium Salts in Ice Grains from Enceladus' Plumes: Evidence for an Ocean below the Moon's Surface

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Kempf, S.; Schmidt, J.; Brillantov, N.; Beinsen, A.; Abel, B.; Buck, U.; Srama, R.

    2008-12-01

    One key requirement for the formation of life on Enceladus, is liquid water below its icy surface. Although measurements and model calculations for Enceladus plume source suggest temperatures close to the melting point, direct evidence for liquid water has not been produced so far. We present compositional measurements by Cassini's dust detector of ice particles emitted from Saturn's cryo-volcanic moon Enceladus into the E ring. Since sodium is considered as crucial tracer for an Enceladus ocean, our detection of sodium salts within the grains provide the first evidence for mineral enriched liquid water below the moon's icy surface. In nearly all particles detected in situ by the Cosmic Dust Analyser (CDA) aboard the Cassini spacecraft, we found sodium (Na) in varying concentrations. Most spectra also show potassium (K) in lower abundance. In mass spectra that are particularly sodium rich, sodium salts (like NaCl and NaHCO3) are identified as Na bearing components. This is only possible if the plume source is liquid water that is or has been in contact with the rocky material of Enceladus' core. The abundance of minerals as well as the inferred basic pH value of those grains exhibit a compelling similarity with the predicted composition of an Enceladus ocean. As for terrestrial oceans, sodium (Na+) and chloride (Cl-) are expected to be the most abundant components, followed by hydrogen carbonate (HCO3-). From the compositional analysis, models for grain production and ejection can be derived which give new insights into dynamic, subsurface processes.

  3. Kansas Agents Study Grain Marketing

    ERIC Educational Resources Information Center

    Schoeff, Robert W.

    1973-01-01

    Author is an extension specialist in feed and grain marketing for Kansas State University. He describes a tour set up to educate members of the Kansas Grain and Feed Dealers' Association in the area of grain marketing and exporting. (GB)

  4. Relative astrobiological potential of irradiated icy bodies in the solar system

    NASA Astrophysics Data System (ADS)

    Cooper, John

    A common factor uniting icy moons with either putative subsurface oceans or evident cryo-volcanic activity is that these reside in the magnetospheres of the giant planets. Interestingly, the two known active moons, Enceladus and Triton, are not in the giant planet magnetosphere with the most extreme radiation, that of Jupiter. Either such radiation has little connection to activity, or else it might have an inhibiting effect at extreme levels such as at Europa. The astrobiological potential of Europa is generally thought to be the highest of the three Galilean icy moons, mainly since the putative global ocean would be closest to the surface, and yet there is little evidence for any significant abundance of organics at the surface. In contrast, ac-tive Enceladus clearly does have easily detectable abundances of simple hydrocarbons and may also have subsurface liquid water. The relatively shorter lifetimes with respect to radilolytic destruction might explain absence of surface organics on Europa, but the lack of gas-driven activity there also suggests absence of redox chemistry important to life as we know it. In the context of a model for gas produced by oxidation processes from radiolytic oxidants, Cooper et al. (Plan. Sp. Sci., 2009) earlier suggested that Europa, enveloped in a surface-bound oxygen atmosphere not detectably present at Enceladus, could be in an extreme state of oxidation to the limit that organics could not survive anywhere in the outer ice crust or underlying ocean. Could that mean that astrobiological potential is higher on Enceladus and even on Triton than on Europa? It is also noted that bright large Kuiper Belt Objects such as Eris may have icy surfaces continually replenished by cryovolcanism and hence might also have potentially significant astrobiological potential.

  5. A 1-D evolutionary model for icy satellites, applied to Enceladus

    NASA Astrophysics Data System (ADS)

    Malamud, Uri; Prialnik, Dina

    2016-04-01

    We develop a long-term 1-D evolution model for icy satellites that couples multiple processes: water migration and differentiation, geochemical reactions and silicate phase transitions, compaction by self-gravity, and ablation. The model further considers the following energy sources and sinks: tidal heating, radiogenic heating, geochemical energy released by serpentinization or absorbed by mineral dehydration, gravitational energy and insolation, and heat transport by conduction, convection, and advection. We apply the model to Enceladus, by guessing the initial conditions that would render a structure compatible with present-day observations, assuming the initial structure to have been homogeneous. Assuming the satellite has been losing water continually along its evolution, we postulate that it was formed as a more massive, more icy and more porous satellite, and gradually transformed into its present day state due to sustained long-term tidal heating. We consider several initial compositions and evolution scenarios and follow the evolution for the age of the Solar System, testing the present day model results against the available observational constraints. Our model shows the present configuration to be differentiated into a pure icy mantle, several tens of km thick, overlying a rocky core, composed of dehydrated rock at the center and hydrated rock in the outer part. For Enceladus, it predicts a higher rock/ice mass ratio than previously assumed and a thinner ice mantle, compatible with recent estimates based on gravity field measurements. Although, obviously, the model cannot be used to explain local phenomena, it sheds light on the internal structure invoked in explanations of localized features and activities.

  6. Ultraviolet photolysis of amino acids on the surface of icy Solar System bodies

    NASA Astrophysics Data System (ADS)

    Johnson, Paul V.; Hodyss, Robert; Chernow, Victoria F.; Lipscomb, Dawn M.; Goguen, Jay D.

    2012-11-01

    The icy worlds of the outer Solar System are of significant astrobiological interests due, in large part, to the evidence of liquid water beneath the surfaces of a number of jovian and saturnian satellites. Many of these surfaces are subject to various levels of particle and photon radiation. If molecular compounds of biological origin are present in the surface ice layer (originating either in situ or delivered from a subsurface aqueous environment), can they be detected as evidence of biological activity, or do they decompose too rapidly in the surface radiation environment? We present a wavelength resolved study of the ultraviolet photolysis of glycine and phenylalanine to address this question. Studying these reactions at multiple discreet wavelengths distinguishes the present work from previous matrix isolation studies using hydrogen flow lamps and continuum sources by resolving the important contribution of photons with energies much lower than Lyman-α (121.6 nm). We find that although the half-lives of glycine and phenylalanine are essentially identical at 147 nm, they diverge at 206 nm and diverge significantly at 254 nm with glycine having longer half-lives at these longer wavelengths. Scaling the results to account for the wavelength dependent variation in solar irradiance shows that despite the reduction of photon energies in the 200-250 nm range, versus 147 nm, it is the longer wavelengths that will dominate the destruction of amino acids in icy surfaces. It seems unlikely that organics can survive long enough on the surface of an icy planetary body to be detected without being frequently replenished from a shielded source such as a subsurface ocean.

  7. Relict grains in chondrules

    NASA Technical Reports Server (NTRS)

    Rambaldi, E. R.

    1981-01-01

    Attention is given to the fact that a significant fraction of the chondrules from ordinary chondrites contain silicate grains that survived the chondrule formation process without melting. Typically, these grains consist of coarse olivine, rarely orthopyroxene, crystals located in the core of chondrules and displaying a zoning that is inconsistent with crystallization from a silicate melt. It is noted that the relict grains still preserve the imprint of processes that occurred in the solar nebula and, in some cases, may include the isotopic record of interstellar grains. Information is presented on the chondrule precursor materials and the process of chondrule formation which was acquired by a compositional and textural study of three of the most unequilibrated type 3 ordinary chondrites.

  8. Efficacy of a rubber outsole with a hybrid surface pattern for preventing slips on icy surfaces.

    PubMed

    Yamaguchi, Takeshi; Hsu, Jennifer; Li, Yue; Maki, Brian E

    2015-11-01

    Conventional winter-safety footwear devices, such as crampons, can be effective in preventing slips on icy surfaces but the protruding studs can lead to other problems such as trips. A new hybrid (rough and smooth) rubber outsole was designed to provide high slip resistance without use of protruding studs or asperities. In the present study, we examined the slip resistance of the hybrid rubber outsole on both dry (-10 °C) and wet (0 °C) icy surfaces, in comparison to three conventional strap-on winter anti-slip devices: 1) metal coils ("Yaktrax Walker"), 2) gritted (sandpaper-like) straps ("Rough Grip"), and 3) crampons ("Altagrips-Lite"). Drag tests were performed to measure static (SCOF) and dynamic (DCOF) coefficients of friction, and gait trials were conducted on both level and sloped ice surfaces (16 participants). The drag-test results showed relatively high SCOF (≧0.37) and DCOF (≧0.31) values for the hybrid rubber sole, at both temperatures. The other three footwear types exhibited lower DCOF values (0.06-0.20) when compared with the hybrid rubber sole at 0 °C (p < 0.01). Slips were more frequent when wearing the metal coils, in comparison to the other footwear types, when descending a slope at -10 °C (6% of trials vs 0%; p < 0.05). There were no other significant footwear-related differences in slip frequency, distance or velocity. These results indicate that the slip-resistance of the hybrid rubber sole on icy surfaces was comparable to conventional anti-slip footwear devices. Given the likely advantages of the hybrid rubber sole (less susceptibility to tripping, better slip resistance on non-icy surfaces), this type of sole should contribute to a decrease in fall accidents; however, further research is needed to confirm its effectiveness under a wider range of test conditions. PMID:26154199

  9. State and velocity distributions of Cl atoms produced in the photodissociation of ICI at 237 nm

    NASA Astrophysics Data System (ADS)

    Ni, Chi-Kung; Flynn, George W.

    1993-07-01

    Photofragment spectroscopy of ICI molecules photodissociated at 237 nm is studied by 2 + 1 resonance-enhanced multi-photon ionization and time of flight techniques. Doppler profiles of the chlorine atom fragments in two spin—orbit states show that chlorine atoms in the ground state, 2P 3/2, are produced from a perpendicular dissociative transition, and chlorine atoms in the excited state, 2P 1/2, arise from a parallel transition. The possible electronically excited states leading to dissociation in both the perpendicular and parallel cases are considered.

  10. Shock vaporization and the accretion of the icy satellites of Jupiter and Saturn

    NASA Technical Reports Server (NTRS)

    Ahrens, T. J.; Okeefe, J. D.

    1985-01-01

    The known properties of water and ice over a wide range of pressures and temperatures are applied to describe constraints on the shock vaporization processes for water and ice in the solar system. In particular, the role of impact vaporization acting during the formation of the Jovian and Saturnian satellites is examined in an attempt to explain the observed density in terms of composition of these rock and ice objects. A possible model of accretion of icy satellites is considered which predicts that the amount of ice devolatilization is related to planetary size.

  11. Onset of convection and differentiation in the hydrated cores of icy moons.

    NASA Astrophysics Data System (ADS)

    Sotin, Christophe; Reynard, Bruno

    2013-04-01

    The Galileo mission to Jupiter and the Cassini/Huygens mission to Saturn have revealed that the three large Jovian icy moons and Titan, Saturn's largest satellite, are at least partly differentiated. Their normalized moments of inertia are smaller than 2/5, which is the value for undifferentiated moons. We present new simulations of the thermal evolution, dehydration process, differentiation, and onset of convection in the hydrated cores of large icy satellites. The motivation is to investigate whether convection can start before dehydration starts in the cores. Such a process would prevent differentiation. The viscosity of antigorite, the hydrated silicate supposed to compose the hydrated cores, is strongly non-Newtonian and weakly temperature-dependent. The cores are volumetrically heated by natural radioactivity. We have adapted the theory developed for non-Newtonian fluids heated from below [1] to the case of volumetrically heated fluids. A recent review [2] of the physical parameters relevant to the thermal evolution of hydrated cores made of antigorite provides values quite different from those used in previous studies [3,4], which seriously modifies the results of previous simulations including the predicted present interior structure of the large icy satellites. The numerical simulations presented in this study suggest that the inner part of the hydrated core of icy moons would dehydrate for a large range of parameters, the most important of which is the amount of 40K. The outer core would remain hydrated. It is shown that convection could start in the outer core for large values of internal heating. Implications for subsequent thermal evolution are being investigated. [1] Solomatov V.S. (1995) Scaling of temperature and stressdependent viscosity convection; Phys. Fluids 7, 266; doi: 10.1063/1.868624. [2] Reynard B. (2012) Serpentine in active subduction zones. Lithos, doi: 10.1016/j.lithos.2012.10.012 [3] Grinrod P.M., A.D. Fortes, F. Nimmo, D.L. Feltham

  12. Radio Sounding Techniques for the Galilean Icy Moons and their Jovian Magnetospheric Environment

    NASA Technical Reports Server (NTRS)

    Green, James L.; Markus, Thursten; Fung, Shing F.; Benson, Robert F.; Reinich, Bodo W.; Song, Paul; Gogineni, S. Prasad; Cooper, John F.; Taylor, William W. L.; Garcia, Leonard

    2004-01-01

    Radio sounding of the Earth's topside ionosphere and magnetosphere is a proven technique from geospace missions such as the International Satellites for Ionospheric Studies (ISIS) and the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE). Application of this technique to Jupiter's icy moons and the surrounding Jovian magnetosphere will provide unique remote sensing observations of the plasma and magnetic field environments and the subsurface conductivities, of Europa, Ganymede, and Callisto. Spatial structures of ionospheric plasma above the surfaces of the moons vary in response to magnetic-field perturbations from (1) magnetospheric plasma flows, (2) ionospheric currents from ionization of sputtered surface material, and (3) induced electric currents in salty subsurface oceans and from the plasma flows and ionospheric currents themselves. Radio sounding from 3 kHz to 10 MHz can provide the global electron densities necessary for the extraction of the oceanic current signals and supplements in-situ plasma and magnetic field measurements. While radio sounding requires high transmitter power for subsurface sounding, little power is needed to probe the electron density and magnetic field intensity near the spacecraft. For subsurface sounding, reflections occur at changes in the dielectric index, e.g., at the interfaces between two different phases of water or between water and soil. Variations in sub-surface conductivity of the icy moons can be investigated by radio sounding in the frequency range from 10 MHz to 50 MHz, allowing the determination of the presence of density and solid-liquid phase boundaries associated with oceans and related structures in overlying ice crusts. The detection of subsurface oceans underneath the icy crusts of the Jovian moons is one of the primary objectives of the Jupiter Icy Moons Orbiter (JIMO) mission. Preliminary modeling results show that return signals are clearly distinguishable be&een an ice crust with a thickness of

  13. Electric Propulsion Technology Development for the Jupiter Icy Moons Orbiter Project

    NASA Technical Reports Server (NTRS)

    2004-01-01

    During 2004, the Jupiter Icy Moons Orbiter project, a part of NASA's Project Prometheus, continued efforts to develop electric propulsion technologies. These technologies addressed the challenges of propelling a spacecraft to several moons of Jupiter. Specific challenges include high power, high specific impulse, long lived ion thrusters, high power/high voltage power processors, accurate feed systems, and large propellant storage systems. Critical component work included high voltage insulators and isolators as well as ensuring that the thruster materials and components could operate in the substantial Jupiter radiation environment. A review of these developments along with future plans is discussed.

  14. Large Impact Features on Saturn's Middle-sized Icy Satellites: Global Image Mosaics and Topography

    NASA Technical Reports Server (NTRS)

    Schenk, P. M.; Moore, J. M.; McKinnon, W. B.

    2003-01-01

    With the approach of Cassini to the Saturn system, attention naturally focuses on the planet, its rings and Titan, but the Saturn system is also populated by a number of smaller satellites. The seven middle-sized icy satellites, along with those of Uranus, (between 400 and 1500 km wide) are distinctly different geophysically and geologically from their much larger Galilean-class brethren [e.g., 1]. Topographic mapping of these bodies is a critical part of understanding their geologic evolution. Here we describe our recent efforts to map the topography of these satellites using Voyager data.

  15. Technology for a Thermo-chemical Ice Penetrator for Icy Moons

    NASA Astrophysics Data System (ADS)

    Arenberg, Jonathan; Harpole, George; Zamel, James; Sen, Bashwar; Lee, Greg; Ross, Floyd; Retherford, Kurt D.

    2016-10-01

    The ability to place sensors or to take samples below the ice surface enables a wide variety of potential scientific investigations. Penetrating an ice cap can be accomplished via a mechanical drill, laser drill, kinetic impactor, or heated penetrator. This poster reports on the development of technology for the latter most option, namely a self-heated probe driven by an exothermic chemical reaction: a Thermo-chemical ice penetrator (TChIP). Our penetrator design employs a eutectic mix of alkali metals that produce an exothermic reaction upon contact with an icy surface. This reaction increases once the ice starts melting, so no external power is required. This technology is inspired by a classified Cold-War era program developed at Northrop Grumman for the US Navy. Terrestrial demonstration of this technology took place in the Arctic; however, this device cannot be considered high TRL for application at the icy moons of the solar system due to the environmental differences between Earth's Arctic and the icy moons. These differences demand a TChIP design specific to these cold, low mass, airless worlds. It is expected that this model of TChIP performance will be complex, incorporating all of the forces on the penetrator, gravity, the thermo-chemistry at the interface between penetrator and ice, and multi-phase heat and mass transport, and hydrodynamics. Our initial efforts are aimed at the development of a validated set of tools and simulations to predict the performance of the penetrator for both the environment found on these icy moons and for a terrestrial environment. The purpose of the inclusion of the terrestrial environment is to aid in model validation. Once developed and validated, our models will allow us to design penetrators for a specific scientific application on a specific body. This poster discusses the range of scientific investigations that are enabled by TChIP. We also introduce the development plan to advance TChIP to the point where it can be

  16. Chronic pelvic pain syndrome/bladder pain syndrome: taking stock, looking ahead: ICI-RS 2011.

    PubMed

    Hanno, Philip; Andersson, Karl Eric; Birder, Lori; Elneil, Suzy; Kanai, Anthony; Pontari, Michel

    2012-03-01

    This review reflects the presentations and subsequent discussions at the International consultation on Incontinence Research Society's annual meeting. It updates the current definitions and diagnostic and treatment algorithms for bladder pain syndrome and chronic pelvic pain syndrome (non-bacterial prostatitis), highlights some specific basic research findings from discussion participants, looks at what we can hope to eventually learn from a large multicenter National Institutes of Health study, reviews future research pathways as articulated by the National Urologic Research Agenda of the American Urological Association and others, discusses recent therapeutic efforts, and concludes with discussion points from the ICI-RS meeting.

  17. Grains in galactic haloes.

    NASA Astrophysics Data System (ADS)

    Ferrara, A.; Barsella, B.; Ferrini, F.; Greenberg, J. M.; Aiello, S.

    1989-12-01

    The authors considered the effect of extensive forces on dust grains subjected to the light and matter distribution of the spiral galaxy NGC 3198. They have shown that the combined force on a small particle located above the plane of a galactic disk may be either attractive or repulsive depending on a variety of parameters. The authors present here the preliminary results of the study of the motion of a dust grain for NGC 3198.

  18. All-optical analog comparator.

    PubMed

    Li, Pu; Yi, Xiaogang; Liu, Xianglian; Zhao, Dongliang; Zhao, Yongpeng; Wang, Yuncai

    2016-01-01

    An analog comparator is one of the core units in all-optical analog-to-digital conversion (AO-ADC) systems, which digitizes different amplitude levels into two levels of logical '1' or '0' by comparing with a defined decision threshold. Although various outstanding photonic ADC approaches have been reported, almost all of them necessitate an electrical comparator to carry out this binarization. The use of an electrical comparator is in contradiction to the aim of developing all-optical devices. In this work, we propose a new concept of an all-optical analog comparator and numerically demonstrate an implementation based on a quarter-wavelength-shifted distributed feedback laser diode (QWS DFB-LD) with multiple quantum well (MQW) structures. Our results show that the all-optical comparator is very well suited for true AO-ADCs, enabling the whole digital conversion from an analog optical signal (continuous-time signal or discrete pulse signal) to a binary representation totally in the optical domain. In particular, this all-optical analog comparator possesses a low threshold power (several mW), high extinction ratio (up to 40 dB), fast operation rate (of the order of tens of Gb/s) and a step-like transfer function.

  19. Crows spontaneously exhibit analogical reasoning.

    PubMed

    Smirnova, Anna; Zorina, Zoya; Obozova, Tanya; Wasserman, Edward

    2015-01-19

    Analogical reasoning is vital to advanced cognition and behavioral adaptation. Many theorists deem analogical thinking to be uniquely human and to be foundational to categorization, creative problem solving, and scientific discovery. Comparative psychologists have long been interested in the species generality of analogical reasoning, but they initially found it difficult to obtain empirical support for such thinking in nonhuman animals (for pioneering efforts, see [2, 3]). Researchers have since mustered considerable evidence and argument that relational matching-to-sample (RMTS) effectively captures the essence of analogy, in which the relevant logical arguments are presented visually. In RMTS, choice of test pair BB would be correct if the sample pair were AA, whereas choice of test pair EF would be correct if the sample pair were CD. Critically, no items in the correct test pair physically match items in the sample pair, thus demanding that only relational sameness or differentness is available to support accurate choice responding. Initial evidence suggested that only humans and apes can successfully learn RMTS with pairs of sample and test items; however, monkeys have subsequently done so. Here, we report that crows too exhibit relational matching behavior. Even more importantly, crows spontaneously display relational responding without ever having been trained on RMTS; they had only been trained on identity matching-to-sample (IMTS). Such robust and uninstructed relational matching behavior represents the most convincing evidence yet of analogical reasoning in a nonprimate species, as apes alone have spontaneously exhibited RMTS behavior after only IMTS training.

  20. All-optical analog comparator

    NASA Astrophysics Data System (ADS)

    Li, Pu; Yi, Xiaogang; Liu, Xianglian; Zhao, Dongliang; Zhao, Yongpeng; Wang, Yuncai

    2016-08-01

    An analog comparator is one of the core units in all-optical analog-to-digital conversion (AO-ADC) systems, which digitizes different amplitude levels into two levels of logical ‘1’ or ‘0’ by comparing with a defined decision threshold. Although various outstanding photonic ADC approaches have been reported, almost all of them necessitate an electrical comparator to carry out this binarization. The use of an electrical comparator is in contradiction to the aim of developing all-optical devices. In this work, we propose a new concept of an all-optical analog comparator and numerically demonstrate an implementation based on a quarter-wavelength-shifted distributed feedback laser diode (QWS DFB-LD) with multiple quantum well (MQW) structures. Our results show that the all-optical comparator is very well suited for true AO-ADCs, enabling the whole digital conversion from an analog optical signal (continuous-time signal or discrete pulse signal) to a binary representation totally in the optical domain. In particular, this all-optical analog comparator possesses a low threshold power (several mW), high extinction ratio (up to 40 dB), fast operation rate (of the order of tens of Gb/s) and a step-like transfer function.

  1. All-optical analog comparator

    PubMed Central

    Li, Pu; Yi, Xiaogang; Liu, Xianglian; Zhao, Dongliang; Zhao, Yongpeng; Wang, Yuncai

    2016-01-01

    An analog comparator is one of the core units in all-optical analog-to-digital conversion (AO-ADC) systems, which digitizes different amplitude levels into two levels of logical ‘1’ or ‘0’ by comparing with a defined decision threshold. Although various outstanding photonic ADC approaches have been reported, almost all of them necessitate an electrical comparator to carry out this binarization. The use of an electrical comparator is in contradiction to the aim of developing all-optical devices. In this work, we propose a new concept of an all-optical analog comparator and numerically demonstrate an implementation based on a quarter-wavelength-shifted distributed feedback laser diode (QWS DFB-LD) with multiple quantum well (MQW) structures. Our results show that the all-optical comparator is very well suited for true AO-ADCs, enabling the whole digital conversion from an analog optical signal (continuous-time signal or discrete pulse signal) to a binary representation totally in the optical domain. In particular, this all-optical analog comparator possesses a low threshold power (several mW), high extinction ratio (up to 40 dB), fast operation rate (of the order of tens of Gb/s) and a step-like transfer function. PMID:27550874

  2. All-optical analog comparator.

    PubMed

    Li, Pu; Yi, Xiaogang; Liu, Xianglian; Zhao, Dongliang; Zhao, Yongpeng; Wang, Yuncai

    2016-01-01

    An analog comparator is one of the core units in all-optical analog-to-digital conversion (AO-ADC) systems, which digitizes different amplitude levels into two levels of logical '1' or '0' by comparing with a defined decision threshold. Although various outstanding photonic ADC approaches have been reported, almost all of them necessitate an electrical comparator to carry out this binarization. The use of an electrical comparator is in contradiction to the aim of developing all-optical devices. In this work, we propose a new concept of an all-optical analog comparator and numerically demonstrate an implementation based on a quarter-wavelength-shifted distributed feedback laser diode (QWS DFB-LD) with multiple quantum well (MQW) structures. Our results show that the all-optical comparator is very well suited for true AO-ADCs, enabling the whole digital conversion from an analog optical signal (continuous-time signal or discrete pulse signal) to a binary representation totally in the optical domain. In particular, this all-optical analog comparator possesses a low threshold power (several mW), high extinction ratio (up to 40 dB), fast operation rate (of the order of tens of Gb/s) and a step-like transfer function. PMID:27550874

  3. Crows spontaneously exhibit analogical reasoning.

    PubMed

    Smirnova, Anna; Zorina, Zoya; Obozova, Tanya; Wasserman, Edward

    2015-01-19

    Analogical reasoning is vital to advanced cognition and behavioral adaptation. Many theorists deem analogical thinking to be uniquely human and to be foundational to categorization, creative problem solving, and scientific discovery. Comparative psychologists have long been interested in the species generality of analogical reasoning, but they initially found it difficult to obtain empirical support for such thinking in nonhuman animals (for pioneering efforts, see [2, 3]). Researchers have since mustered considerable evidence and argument that relational matching-to-sample (RMTS) effectively captures the essence of analogy, in which the relevant logical arguments are presented visually. In RMTS, choice of test pair BB would be correct if the sample pair were AA, whereas choice of test pair EF would be correct if the sample pair were CD. Critically, no items in the correct test pair physically match items in the sample pair, thus demanding that only relational sameness or differentness is available to support accurate choice responding. Initial evidence suggested that only humans and apes can successfully learn RMTS with pairs of sample and test items; however, monkeys have subsequently done so. Here, we report that crows too exhibit relational matching behavior. Even more importantly, crows spontaneously display relational responding without ever having been trained on RMTS; they had only been trained on identity matching-to-sample (IMTS). Such robust and uninstructed relational matching behavior represents the most convincing evidence yet of analogical reasoning in a nonprimate species, as apes alone have spontaneously exhibited RMTS behavior after only IMTS training. PMID:25532894

  4. Are polymers suitable rock analogs?

    NASA Astrophysics Data System (ADS)

    ten Grotenhuis, Saskia M.; Piazolo, Sandra; Pakula, T.; Passchier, Cees W.; Bons, Paul D.

    2002-05-01

    To evaluate if a polymer is suitable for analog modeling, it is essential to know the rheological properties of the material. Polymers used in analog modeling exhibit a complex rheological behavior; only part of which has been taken into account in most modeling studies. The mechanical behavior is strongly dependent on strain rate and temperature, and is characterized by specific dependencies of the storage and loss moduli, related to the elasticity and viscosity, on the deformation rate (frequency). We have measured the storage and loss moduli at a broad range of strain rates and strains, using an oscillatory parallel-disk rheometer. Investigated materials are polydimethylsiloxane (PDMS), mixtures of PDMS and BaSO 4 (filler), Rhodorsil Gomme and mixtures of Rhodorsil Gomme and plastilina, all commonly used in analog experiments. Our measurements show that the rheological properties of mixtures of plastilina and Rhodorsil Gomme depend on its deformation history. Therefore, these mixtures are problematic for analog modeling. For mixtures of PDMS and BaSO 4, the significance of the elastic component increases with increasing filler content, and accordingly, these mixtures have a limited application for modeling of viscous deformation. Pure PDMS and Rhodorsil Gomme exhibit Newtonian flow behavior at strain rates commonly used in analog modeling.

  5. An investigation into the cardiac and pulmonary beta-adrenoceptor blocking activity of ICI 66,082 in man.

    PubMed

    Marlin, G E; Kumana, C R; Kaye, C M; Smith, D M; Turner, P

    1975-04-01

    1 Oral ICI 66,082 (200 mg) or water (control treatment) were each administered to six healthy volunteers. 2 The heart rate (HR) and peak flow rate (PFR) were measured at rest and during vigorous exercise before and at intervals up to 24 h after each treatment. 3 ICI 66,082 produced significant reductions in exercise HR at all times compared with the changes after the control treatment (P less than 0.001), whereas with resting HR, corresponding significant reductions only occurred at 2,3 and 4 h (P less than 0.05). 4 Although there was no change in resting PFR, significant reductions in exercise PFR, compared with the changes after the control treatment, occurred at all times excepting at 2 h after ICI 66,082 (P less than 0.025). 5 The findings are consistent with ICI 66,082 possessing partial cardioselectivity. 6 Plasma levels and renal excretion of the drug were determined. Urinary recovery was variable which, together with the plasma concentration/effect relationships obtained, raise the possibility that ICI 66,082 is metabolized in man. PMID:1234497

  6. An investigation into the cardiac and pulmonary beta-adrenoceptor blocking activity of ICI 66,082 in man.

    PubMed

    Marlin, G E; Kumana, C R; Kaye, C M; Smith, D M; Turner, P

    1975-04-01

    1 Oral ICI 66,082 (200 mg) or water (control treatment) were each administered to six healthy volunteers. 2 The heart rate (HR) and peak flow rate (PFR) were measured at rest and during vigorous exercise before and at intervals up to 24 h after each treatment. 3 ICI 66,082 produced significant reductions in exercise HR at all times compared with the changes after the control treatment (P less than 0.001), whereas with resting HR, corresponding significant reductions only occurred at 2,3 and 4 h (P less than 0.05). 4 Although there was no change in resting PFR, significant reductions in exercise PFR, compared with the changes after the control treatment, occurred at all times excepting at 2 h after ICI 66,082 (P less than 0.025). 5 The findings are consistent with ICI 66,082 possessing partial cardioselectivity. 6 Plasma levels and renal excretion of the drug were determined. Urinary recovery was variable which, together with the plasma concentration/effect relationships obtained, raise the possibility that ICI 66,082 is metabolized in man.

  7. An investigation into the cardiac and pulmonary beta-adrenoceptor blocking activity of ICI 66,082 in man.

    PubMed Central

    Marlin, G E; Kumana, C R; Kaye, C M; Smith, D M; Turner, P

    1975-01-01

    1 Oral ICI 66,082 (200 mg) or water (control treatment) were each administered to six healthy volunteers. 2 The heart rate (HR) and peak flow rate (PFR) were measured at rest and during vigorous exercise before and at intervals up to 24 h after each treatment. 3 ICI 66,082 produced significant reductions in exercise HR at all times compared with the changes after the control treatment (P less than 0.001), whereas with resting HR, corresponding significant reductions only occurred at 2,3 and 4 h (P less than 0.05). 4 Although there was no change in resting PFR, significant reductions in exercise PFR, compared with the changes after the control treatment, occurred at all times excepting at 2 h after ICI 66,082 (P less than 0.025). 5 The findings are consistent with ICI 66,082 possessing partial cardioselectivity. 6 Plasma levels and renal excretion of the drug were determined. Urinary recovery was variable which, together with the plasma concentration/effect relationships obtained, raise the possibility that ICI 66,082 is metabolized in man. PMID:1234497

  8. Testing Grain Surface Chemistry in Star Forming Regions

    NASA Astrophysics Data System (ADS)

    Keane, Jacqueline; Boogert, Adwin

    2008-03-01

    The key chemical reactions that produce the first generation ice mantles in dense molecular clouds are still poorly known. Within cold, dense clouds, species formed in the gas and on the grain surfaces will stick to the grains and form icy mantles. However, during star-formation, materials in the general cloud medium are subjected to numerous chemical and physical processes that are driven mostly by thermal and energetic radiation. The comparison between background stars and protostars is a proven excellent tool for this purpose. By comparing observed interstellar solid state abundances with models of grain surface chemistry it is possible to elucidate the efficiency and hence relevancy of a number of chemical reactions, in particular the CO_2 formation pathways. In part because of Spitzer, significant progress has been made towards understanding the various effects of these radiation processes on the ices around a large sample of high- and low-mass protostars. First results suggest that two different CO2 formation pathways play a role in these harsh environments. Though which reaction initially dominated the chemistry is unknown due to the numerous physical processes. Unfortunately, only a small sample of background field stars have been observed, most notably Taurus. In Taurus, only one reaction pathway appears to be efficient in quiescent regions, but this result is sample limited. We propose to take low resolution spectra from 5 to 22 microns along the line of sight toward 31 field stars behind the LDN 673 molecular cloud. Differences in near-IR ice chemistry have already been observed and we will use these mid-infrared data to provide more stringent constraints on chemical models of grain surface chemistry. With this sample it is possible to address fundamental questions in astrochemistry: what are the dominant grain surface chemistry pathways? What is the composition of the first generation ice mantles in molecular clouds?

  9. Grain Surface Chemistry and the Composition of Interstellar Ices

    NASA Technical Reports Server (NTRS)

    Tielens, A. G. G. M.

    2006-01-01

    Submicron sized dust grains are an important component of the interstellar medium. In particular they provide surface where active chemistry can take place. At the low temperatures (-10 K) of the interstellar medium, colliding gas phase species will stick, diffuse, react, and form an icy mantle on these dust grains. This talk will review the principles of grain surface chemistry and delineate important grain surface routes, focusing on reactions involving H, D, and O among each other and with molecules such as CO. Interstellar ice mantles can be studied through the fundamental vibrations of molecular species in the mid-infrared spectra of sources embedded in or located behind dense molecular clouds. Analysis of this type of data has provided a complex view of the composition of these ices and the processes involved. Specifically, besides grain surface chemistry, the composition of interstellar ices is also affected by thermal processing due to nearby newly formed stars. This leads to segregation between different ice components as well as outgassing. The latter results in the formation of a so-called Hot Core region with a gas phase composition dominated by evaporated mantle species. Studies of such regions provide thus a different view on the ice composition and the chemical processes involved. Interstellar ices can also be processed by FUV photons and high energy cosmic ray ions. Cosmic ray processing likely dominates the return of accreted species to the gas phase where further gas phase reactions can take place. These different chemical routes towards molecular complexity in molecular clouds and particularly regions of star formation will be discussed.

  10. Deformation behavior of ultra-fine-grained copper

    SciTech Connect

    Valiev, R.Z.; Lian, J.; Nazarov, A.A.; Baudelet, B. . Genie Physique et Mecanique des Materiaux); Kozlov, E.V.; Ivanov, Yu.F. . Dept. of Physics)

    1994-07-01

    Mechanical behavior and structural changes, such as the evolution of grain and dislocation structures and the formation of slip lines and grain-boundary-sliding traces, of a submicron-grained (SMG) copper during room-temperature compression have been studies. It is suggested that the absorption of dislocations into grain boundaries (GBs) is due to the migration and sliding of some highly non-equilibrium GBs during the deformation process and is influenced by high level internal stresses. From this point of view, the unusual behavior of SMG copper, in particular, the high yielding and flow stresses, the absence of strain hardening, high plasticity and low strain rate sensitivity, are explained. Analogies of the mechanical behavior of SMG copper with mechanical properties of metallic materials at large plastic strains in stage 4 are discussed.

  11. Solid-State Spectroscopy: Silicates & Carbonaceous Grains

    NASA Astrophysics Data System (ADS)

    Jager, C.; Mutschke, H.; Henning, T.; Huisken, F.

    2011-05-01

    Cosmic dust grains prove their existence by interstellar extinction curves, IR spectra, and elemental depletion patterns. They influence the heating rate of the gas via the photo-electric effect and the formation rate of molecular hydrogen as well as other more complex organic molecules being formed on their surfaces. Dust grains, well mixed with gas, absorb and scatter stellar light and reemit the absorbed energy at infrared and millimeter wavelengths. For the interpretation of these data, the spectral properties of cosmic dust in a broad wavelength range are required. These spectral data can be obtained by measurements of dust analogs prepared in the laboratory. The application of formation techniques that come close to astrophysical formation conditions such as gas-phase condensations and the study of dust processing by energy-rich irradiation are necessary to produce astrophysically realistic cosmic dust analogs. A detailed characterization of the physical and chemical structure of the laboratory produced materials has to precede the measurements of the spectral properties. The qualitative improvement of the spectral data measured in the laboratory including spectroscopic measurements at low temperatures and absorption spectroscopy of aerosol particles helps to improve the interpretation of dust observations in various astrophysical environments and to gain more information on astrophysical processes such as star and planet formation.

  12. Natural analogs for Yucca Mountain

    SciTech Connect

    Murphy, W.M.

    1995-11-01

    High-level radioactive waste in the US, spent fuels from commercial reactors and nuclear materials generated by defense activities, will remain potentially hazardous for thousands of years. Demonstrable long-term stability of certain geologic and geochemical systems motivates and sustains the concept that high-level waste can be safely isolated in geologic repositories for requisite periods of time. Each geologic repository is unique in its properties and performance with reguard to isolation of nuclear wastes. Studies of processes analogous to waste-form alteration and radioelement transport in environments analogous to Yucca Mountain are being conducted at two sites, described in this article to illustrate uses of natural analog data: the Nopal I uranium deposit in the Sierra Pena Blanca, Mexico, and the Akrotiri archaeological site on the island of Santorini, Greece.

  13. Test Wiseness and Analogy Test Performance

    ERIC Educational Resources Information Center

    Moore, James C.

    1971-01-01

    Subjects received self instruction on how to approach analogy questions. Instruction was directed toward knowledge of the general format of analogy questions in standarized tests and the 15 types of relationships commonly asked for in analogy questions. An analogies post-test showed a significant effect for the group. (Author)

  14. Analogies in Science and Science Teaching

    ERIC Educational Resources Information Center

    Brown, Simon; Salter, Susan

    2010-01-01

    Analogies are often used in science, but students may not appreciate their significance, and so the analogies can be misunderstood or discounted. For this reason, educationalists often express concern about the use of analogies in teaching. Given the important place of analogies in the discourse of science, it is necessary that students are…

  15. Multilateral Collaborations in Analog Research

    NASA Technical Reports Server (NTRS)

    Cromwell, R. l.

    2016-01-01

    International collaborations in studies utilizing ground-based space flight analogs are an effective means for answering research questions common to participating agencies. These collaborations bring together worldwide experts to solve important space research questions. By collaborating unnecessary duplication of science is reduced, and the efficiency of analog use is improved. These studies also share resources among agencies for cost effective solutions to study implementation. Recently, NASA has engaged in collaborations with international partners at a variety of analog sites. The NASA Human Exploration Research Analog (HERA) is currently hosting investigator studies from NASA and from the German Space Agency (DLR). These isolation studies will answer questions in the areas of team cohesion, sleep and circadian rhythms, and neurobehavioral correlates to function. Planning for the next HERA campaign is underway as proposal selections are being made from the International Life Sciences Research Announcement (ILSRA). Studies selected from the ILSRA will be conducted across 4 HERA missions in 2017. NASA is planning collaborative studies with DLR at the :envihab facility in Cologne, Germany. Investigations were recently selected to study the effects of 0.5% CO2 exposure over 30 days of bed rest. These studies will help to determine the fidelity of this ground-based analog for studying the visual impairment intracranial pressure syndrome. NASA is also planning a multilateral collaboration at :envihab with DLR and the European Space Agency (ESA) to examine artificial gravity as a countermeasure to mitigate the effects of 60 days of bed rest. NASA is also considering collaborations with the Russian Institute for Biomedical Problems (IBMP) in studies that will utilize their Ground-based Experimental Facility (NEK). The NEK is comprised of 4 interconnected modules and a Martian surface simulator. This isolation analog can support 3 -10 crew members for long duration

  16. On the onset of convection and differentiation in the hydrated cores of icy moons

    NASA Astrophysics Data System (ADS)

    Sotin, C.; Reynard, B.

    2012-09-01

    We will present new simulations of the thermal evolution, dehydration process, differentiation, and onset of convection in the hydrated cores of large icy satellites. The motivation is to investigate whether convection can start before dehydration starts in the cores. Such a process would prevent differentiation. The viscosity of antigorite, the hydrated silicate supposed to compose the hydrated cores, is strongly non-Newtonian and weakly temperature-dependent. The cores are volumetrically heated by natural radioactivity. We have adapted the theory developed by Solomatov (1995) [1] for non-Newtonian fluids heated from below to the case of volumetrically heated fluids. A recent review [2] of the physical parameters relevant to the thermal evolution of hydrated cores made of antigorite provides values quite different from those used in previous studies [3,4], which seriously modifies the results of previous simulations including the predicted present interior structure of the large icy satellites. One key parameter is the amount of potassium present in the hydrated silicates. This study investigates ratios of K/U that span a broad range from earthlike to solar. It is shown that convection can start but is limited to the outer layer of the hydrated core. In the center, temperatures are large enough for dehydration to start.

  17. The ammonia-water system and the chemical differentiation of icy satellites

    USGS Publications Warehouse

    Hogenboom, D.L.; Kargel, J.S.; Consolmagno, G.J.; Holden, T.C.; Lee, L.; Buyyounouski, M.

    1997-01-01

    We report the discovery of the first high-pressure polymorphs of ammonia hydrates: ammonia monohydrate II and ammonia dihydrate II. The subsolidus transitions and melting curves of these substances are shown by their volume-temperature functions; uncalibrated calorimetry corroborates these phase changes. From 20 to 300 MPa ammonia dihydrate and ice melt at a eutectic to form water-rich liquids; at lower and higher pressures, ammonia dihydrate melts incongruently to ammonia-rich liquids. The new data are consistent with independently known thermodynamic parameters of the ammonia-water system. These results fill in an important region of pressure-temperature space not previously studied; a body of previous data reported by other investigators covers a complementary region (higher pressures), but in the light of the new data those earlier results now appear to have been misinterpreted. We show that a suitable reinterpretation of the previous data supports the identification of at least one high-pressure polymorph of each compound. The behavior of the system H2O-NH3in many ways follows that of MgO-SiO2, and the roles of ammonia-water in icy satellite evolution may parallel those of magnesium silicates in Earth's structure, volcanism, and deep mantle tectonism. Pressure-related effects, including a pressure influence on the ammonia content of cryomagmas, might be significant in determining some potentially observable aspects of cryovolcanic morphologies, surface compositions, and interior structures of icy satellites. ?? 1997 Academic Press.

  18. Impact jetting of water ice, with application to the accretion of icy planetesimals and Pluto

    NASA Technical Reports Server (NTRS)

    Mckinnon, William B.

    1989-01-01

    Jetting can occur during oblique impacts of water-ice bodies at relative velocities as low as 500 m/sec, because of the low Hugoniot elastic limit and high compressibility of ice compared to rock. In jetted ice, incipient melting, complete melting, and incipient vaporization occur, upon release to low pressure, at impact velocities of 1.3, 2.0, and 2.7 km/sec, respectively, much less than the 3.4, 4.4, and 5.3 km/sec, required in head-on collisions. Uncertainties in the shock equation-of-state may allow complete melting during jetting of relative velocities as low as 1.2 km/sec. Because jet speeds exceed impact speeds during the accretion of icy bodies greater than a few 100 km in radius, there may be a significant loss of icy material. Thus, jetting during a Charon-forming collision (and not vaporization) may account for Pluto-Charon's relatively large rock/ice ratio, should the C/O ratio of the solar nebula turn out to be too low to sufficiently raise the rock/ice ratio of outer solar nebula condensates by formation of noncondensable CO.

  19. Preliminary Measurements on the Mechanical Properties of Clathrate Hydrates with Implications for the Internal Dynamics of Icy Satellites

    NASA Astrophysics Data System (ADS)

    Choukroun, M.; Barmatz, M. B.; Castillo, J. C.; Sotin, C.

    2008-12-01

    Surface features potentially associated with cryovolcanism have been identified on Titan, and the processes taking place beneath the surface are likely associated with the dissociation of clathrate hydrates and the release of methane. On Enceladus, the South Pole plume discovered by the Cassini-Huygens mission contains a large proportion of volatiles, in amounts consistent with models of clathrate hydrates dissociation at depth (Kieffer et al., Science 314, 1764-1766, 2006). The stability of clathrate hydrates is relatively well constrained in pure and mixed gas systems (e.g., Sloan, Clathrate hydrates of natural gases, Marcel Dekker, New York, 1998). Recent measurements of clathrate destabilization in presence of ammonia, a likely component of Titan's interior, led to the development of a new model of cryovolcanism (Choukroun et al., Lunar Planet. Sci. Conf., #1837, Houston, 2008). Internal dynamics relies on ice convection at depth on Titan and Enceladus (e.g., Tobie et al., Icarus 175, 496-502, 2005), and on relatively large tidal stresses on Enceladus. Clathrates are expected to destabilize when subject to stress (Durham et al., J. Geophys. Res. 108 (B4), 2182, 2003). Therefore, addressing the mechanical properties of clathrate hydrates in these environments is a necessary step toward better understanding cryovolcanic processes. We have developed a new apparatus for growing clathrate hydrates samples with controlled geometry, composition, and grain size. This system consists of a high-pressure autoclave and a cooling system and supports gas pressures up to 500 bars, and temperatures within the range -50 - 150 °C. We have started the production of clathrate hydrates of CH4, CO2, and N2 with this system, with the purpose to test their mechanical properties using an Instron compression system (Castillo-Rogez et al., submitted to J. Geophys. Res.; Castillo-Rogez et al., this meeting). We will present initial measurements on the creep response and on the

  20. Crater formation and modification on the icy satellites of Uranus and Saturn - Depth/diameter and central peak occurrence

    NASA Technical Reports Server (NTRS)

    Schenk, Paul M.

    1989-01-01

    Fresh crater shapes, in particular crater depth/diameter ratios d/D, have been measured for craters on nine of the icy satellites. Crater depths were determined from photoclinometry plus some shallow measurements. Interior morphology, including rimwall slope, was also examined from photoclinometry profiles. Central peak statistics and the characteristic break in slope of d/D curves were determined in order to estimate the transition diameter from simple to complex craters. Crater morphology and transition diameters on the icy satellites were then compared with crater morphology on the terrestrial rocky planets in order to separate or evaluate the relative importance and similarity of surface gravity and target characteristics in controlling crater formation and modification in icy and rocky targets. Estimates of effective rheologies of the target materials were also obtained based on morphologic changes.

  1. Impact of Universal Plasma and Energetic Particle Processes on Icy Bodies of the Kuiper Belt and the Oort Cloud

    NASA Technical Reports Server (NTRS)

    Cooper, John F.; Richardson, J. D.; Hill, M. E.; Sturner, S. J.

    2008-01-01

    Modeling of space plasma and energetic particle interactions with icy bodies of the outer solar system is simplified when there is commonality of the underlying source, acceleration, and transport processes in spatially distinct regions from the supersonic heliosphere through the heliosheath into the local interstellar medium (LISM). Current trends in the Voyager heliosheath measurements suggest strong commonality to processes in the LISM. The Fisk-Gloeckler "universal" spectrum at suprathermal energies apparently plays a strong role in coupling the plasma and high energy particle regimes in the spatial and energetic transitions from the outer heliosphere to the LISM. Dominant processes in consecutive energy regimes project to varying effects versus irradiation depth on exposed upper surfaces of airless small icy bodies and to upper atmospheres of larger bodies such as Titan and Pluto. Relative absence of the universal suprathermal spectrum in the mid-heliospheric region of the classical Kuiper Belt may profoundly affect surface color diversity of icy bodies in this region.

  2. Organics Analyzer for Sampling Icy Surfaces: A liquid chromatograph-mass spectrometer for future in situ small body missions

    NASA Astrophysics Data System (ADS)

    Getty, Stephanie A.; Dworkin, Jason P.; Glavin, Daniel P.; Martin, Mildred; Zheng, Yun; Balvin, Manuel; Southard, Adrian E.; Feng, Steven; Ferrance, Jerome; Kotecki, Carl; Malespin, Charles; Mahaffy, Paul R.

    Liquid chromatography mass spectrometry (LC-MS) is an important laboratory technique for the detection and analysis of organic molecules with high sensitivity and selectivity. This approach has been especially fruitful in the analysis of nucleobases, amino acids, and measuring amino acid enantiomeric ratios in extraterrestrial materials. We are developing OASIS, Organics Analyzer for Sampling Icy Surfaces, for in situ analysis on future landed missions to astrochemically important icy bodies, such as asteroids, comets, and icy moons. The OASIS design employs a microfabricated, on-chip analytical column to chromatographically separate liquid analytes using known LC stationary phase chemistries. The elution products are then interfaced through spray ionization and analyzed by a time-of-flight mass spectrometer (TOF-MS). A particular advantage of our design is its suitability for microgravity environments, such as for a primitive small body.

  3. The effects of thermogenic agents on hindlimb oxygen consumption in the dog: ICI D7114 and noradrenaline.

    PubMed

    Gainer, J L; Briscoe, M G; Holloway, B R

    1993-01-15

    The thermogenic action of beta-adrenoceptor agonists may be due, in part, to increased metabolism in skeletal muscle. Previous results suggest that vasoconstriction is also necessary, and that the effect can be blocked by vasodilators. Both noradrenaline and the beta-3 agonist, ICI D7114, were studied using two dog hindlimb protocols. During constant perfusion conditions, ICI D7114 caused a significant increase in hindlimb oxygen consumption although it is a vasodilator. Noradrenaline resulted in a smaller rise in oxygen consumption, and produced a marked vasoconstriction. Both noradrenaline and ICI D7114 resulted in decreased oxygen consumption when the blood flow was allowed to vary in response to the drug treatment. The results suggest that changes in tissue oxygen consumption caused by beta-agonists are not related to vasomotion. PMID:8094057

  4. Terrestrial analogs for space exploration habitation systems

    NASA Technical Reports Server (NTRS)

    Campbell, Paul D.; Brown, Jeri W.

    1992-01-01

    The Space Exploration Initiative (SEI) can use early earth-based analogs to simulate many aspects of space flight missions and system operation. These analogs can thus provide information supporting future missions to the moon and to Mars. A study was performed to investigate the potential of terrestrial analogs in simulating human space exploration missions. The study resulted in preliminary requirements and concepts for analog habitation systems, and further study in this area is necessary for SEI terrestrial analog development.

  5. Ionization chemistry in the H2O-dominant atmospheres of the icy moons

    NASA Astrophysics Data System (ADS)

    Shematovich, V. I.; Johnson, R. E.

    2007-08-01

    The main pathways of the ionization chemistry for pure H2O- and mixed H2O+O2+CO2+NH3+CH4 atmospheres which are representative for neutral and ionized atmospheres of the icy bodies in the Jovian and Saturnian systems are discussed. The gaseous envelopes of the icy moons of the giant planets are formed usually due to the surface radiolysis by the solar UV radiation and energetic magnetospheric plasma (Johnson, 1990). The standard astrochemical UMIST2005 (UDFA05) network is used to infer the main chemical pathways of ionization chemistry in the pure or with admixtures of other volatile molecules water vapor atmospheres. In case of the H2O- dominant atmosphere the parent H2O molecules are easily dissociated and ionized by the solar UVradiation and the energetic magnetospheric electrons. These impact processes result in the formation of the secondary neutral and ionized products - chemically active radicals O and OH, and H+, H2+, O+, OH+, and H2O+ ions. Secondary ions have admixture abundances in the H2O-dominant atmospheres, because they are efficiently transformed to H3O+ hydroxonium ions in the fast ion-molecular reactions. The major H3O+ hydroxonium ion does not chemically interact with other neutrals, and is destroyed in the dissociative recombination with thermal electrons mainly reproducing the chemically simple H, H2, O, and OH species. In case of the mixed H2O+O2-dominant atmosphere corresponding to the near-surface atmospheres of icy moons (Shematovich et al., 2005), the ionization chemistry results in the formation of the second major ion O2+ - because ion of molecular oxygen has the lower ionization potential comparing with other parent species -H2, H2O, CO2. The H+, O+, OH+, and H2O+ ions can be easily converted to O2+ ions through the ion-molecular reactions. In case of significant admixture of molecular hydrogen it is possible to transfer the O2+ ions to the O2H+ ions through the fast reaction with H2 and further to the H3O+ ions through the ion

  6. JUpiter ICy moons Explorer (juice): AN ESA L-Class Mission Candidate to the Jupiter System

    NASA Astrophysics Data System (ADS)

    Dougherty, M. K.; Grasset, O.; Erd, C.; Titov, D.; Bunce, E. J.; Coustenis, A.; Blanc, M.; Coates, A. J.; Drossart, P.; Fletcher, L.; Hussmann, H.; Jaumann, R.; Krupp, N.; Prieto-Ballesteros, O.; Tortora, P.; Tosi, F.; Van Hoolst, T.

    2012-04-01

    The overarching theme for JUICE is: The emergence of habitable worlds around gas giants. Humankind wonders whether the origin of life is unique to the Earth or if it occurs elsewhere in our Solar System or beyond. To answer this question, even though the mechanisms by which life originated on Earth are not yet clearly understood, one can assume that the necessary conditions involve the simultaneous presence of organic compounds, trace elements, water, energy sources and a relative stability of the environment over time. JUICE will address the question: Are there current habitats elsewhere in the Solar System with the necessary conditions (water, biological essential elements, energy and stability) to sustain life? The spatial extent and evolution of habitable zones within the Solar System are critical elements in the development and sustainment of life, as well as in addressing the question of whether life developed on Earth alone or whether it was developed in other Solar System environments and was then imported to Earth. The focus of JUICE is to characterise the conditions that may have led to the emergence of habitable environments among the Jovian icy satellites, with special emphasis on the three ocean-bearing worlds, Ganymede, Europa, and Callisto. Ganymede is identified for detailed investigation since it provides a natural laboratory for analysis of the nature, evolution and potential habitability of icy worlds in general, but also because of the role it plays within the system of Galilean satellites, and its unique magnetic and plasma interactions with the surrounding Jovian environment. For Europa, where two targeted flybys are planned, the focus will be on the chemistry essential to life, including organic molecules, and on understanding the formation of surface features and the composition of the non water-ice material, leading to the identification and characterisation of candidate sites for future in situ exploration. Furthermore, JUICE will provide

  7. X-ray diffraction studies of shocked lunar analogs

    NASA Technical Reports Server (NTRS)

    Hanss, R. E.

    1979-01-01

    The X-ray diffraction experiments on shocked rock and mineral analogs of particular significance to lunar geology are described. Materials naturally shocked by meteorite impact, nuclear-shocked, or artificially shocked in a flat plate accelerator were utilized. Four areas were outlined for investigation: powder diffractometer studies of shocked single crystal silicate minerals (quartz, orthoclase, oligoclase, pyroxene), powder diffractometer studies of shocked polycrystalline monomineralic samples (dunite), Debye-Scherrer studies of single grains of shocked granodiorite, and powder diffractometer studies of shocked whole rock samples. Quantitative interpretation of peak shock pressures experienced by materials found in lunar or terrestrial impact structures is presented.

  8. Analog Input Data Acquisition Software

    NASA Technical Reports Server (NTRS)

    Arens, Ellen

    2009-01-01

    DAQ Master Software allows users to easily set up a system to monitor up to five analog input channels and save the data after acquisition. This program was written in LabVIEW 8.0, and requires the LabVIEW runtime engine 8.0 to run the executable.

  9. Geometrical Analogies in Mathematics Lessons

    ERIC Educational Resources Information Center

    Eid, Wolfram

    2007-01-01

    A typical form of thinking to approach problem solutions humanly is thinking in analogous structures. Therefore school, especially mathematical lessons should help to form and to develop corresponding heuristic abilities of the pupils. In the contribution, a summary of possibilities of mathematics lessons regarding this shall particularly be…

  10. Analogy of the Cell Project

    ERIC Educational Resources Information Center

    Science Scope, 2005

    2005-01-01

    In this project, students compare the makeup of a cell to an everyday working unit or system. They create a three-dimensional object that represents their analogy. For example, students could create a car motor or manufacturing plant. (Of course, this is totally hand-created by them, so it can be a homemade re-creation of a system, not an actual…

  11. Analog Simulation of a Laser.

    ERIC Educational Resources Information Center

    Kessler, Gary

    1982-01-01

    Presents an analog simulation of laser properties (finding time evolution of the intensity of a ruby laser pulse) which serves as the basis of a three-four hour laboratory experiment. Includes programs for solution to rate equations of a three-level laser and production of a giant pulse in a ruby laser. (Author/SK)

  12. Algicidal Activity of Stilbene Analogs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As part of our continuing search for natural product and natural product-based compounds for the control of off-flavor in catfish, a total of twenty nine stilbene analogs were synthesized and evaluated for algicidal activity against the 2-methylisoborneol (MIB)-producing cyanobacterium Oscillatoria ...

  13. Paper Analogies Enhance Biology Teaching.

    ERIC Educational Resources Information Center

    Stencel, John E.

    1997-01-01

    Describes how to use paper analogies as models to illustrate various concepts in biology, human anatomy, and physiology classes. Models include biochemical paper models, protein papergrams, a paper model of early brain development, and a 3-D paper model of a eukaryotic cell. (AIM)

  14. Mathematical Analogy and Metaphorical Insight

    ERIC Educational Resources Information Center

    Zwicky, Jan

    2010-01-01

    How are we to understand the power of certain literary metaphors? The author argues that the apprehension of good metaphors is importantly similar to the apprehension of fruitful mathematical analogies: both involve a structural realignment of vision. The author then explores consequences of this claim, drawing conceptually significant parallels…

  15. Understanding & Teaching Genetics Using Analogies

    ERIC Educational Resources Information Center

    Woody, Scott; Himelblau, Ed

    2013-01-01

    We present a collection of analogies that are intended to help students better understand the foreign and often nuanced vocabulary of the genetics curriculum. Why is it called the "wild type"? What is the difference between a locus, a gene, and an allele? What is the functional (versus a rule-based) distinction between dominant and…

  16. International Alligator Rivers Analog Project

    SciTech Connect

    Bichard, G.F.

    1988-01-01

    The Australian Nuclear Science and Technology Organization (ANSTO), the Japan Atomic Energy Research Institute, the Swedish Nuclear Power Inspectorate, the U.K. Department of the Environment, the US Nuclear Regulatory Commission (NRC), and the Power Reactor and Nuclear Fuel Development Corporation of Japan are participating under the aegis of the Nuclear Energy Agency in the International Alligator Rivers Analog Project. The project has a duration of 3 yr, starting in 1988. The project has grown out of a research program on uranium ore bodies as analogs of high-level waste (HLW) repositories undertaken by ANSTO supported by the NRC. A primary objective of the project is to develop an approach to radionuclide transport model validation that may be used by the participants to support assessments of the safety of radioactive waste repositories. The approach involves integrating mathematical and physical modeling with hydrological and geochemical field and laboratory investigations of the analog site. The Koongarra uranium ore body has been chosen as the analog site because it has a secondary ore body that has formed over the past million years as a result of leaching by groundwater flowing through fractures in the primary ore body.

  17. Electrical analog to projectile motion

    NASA Astrophysics Data System (ADS)

    Vondracek, Mark

    1998-04-01

    This article describes an electrical analog to traditional projectile problems given in high school and introductory college classes. It also discusses the importance of stressing the understanding of physical laws and principles to students, and that the physics behind a problem is more important than being able to memorize and use various equations.

  18. Analogy between Thermodynamics and Mechanics.

    ERIC Educational Resources Information Center

    Peterson, Mark A.

    1979-01-01

    Establishes and illustrates a formal analogy between the motion of a particle and the "motion" of the equilibrium state of a homogeneous system in a quasistatic process. The purpose is to show that there is a much larger set of natural coordinate transformations in thermodynamics. (GA)

  19. Bayesian Analogy with Relational Transformations

    ERIC Educational Resources Information Center

    Lu, Hongjing; Chen, Dawn; Holyoak, Keith J.

    2012-01-01

    How can humans acquire relational representations that enable analogical inference and other forms of high-level reasoning? Using comparative relations as a model domain, we explore the possibility that bottom-up learning mechanisms applied to objects coded as feature vectors can yield representations of relations sufficient to solve analogy…

  20. The Identity Consolidation Inventory (ICI): development and application of a questionnaire for assessing the structuralization of individual identity.

    PubMed

    Samuel, Steven; Akhtar, Salman

    2009-03-01

    This paper describes the author's effort to develop a self-rating scale to measure the consolidation of identity in a given individual. It describes the construction of the 35-item Identity Consolidation Inventory (ICI) and, as an appendix to the paper, includes the final version of this questionnaire. The scale's reliability and validity are demonstrated via its administration to 238 normal controls, 80 individuals with Borderline Personality Disorder and 13 subjects with Dissociative Identity Disorder ("multiple personality"). The clinical and research usefulness of ICI lies in the realm of discerning the syndrome of identity diffusion that underlies all severe personality disorders.

  1. Grains in galactic haloes

    NASA Technical Reports Server (NTRS)

    Ferrara, Andrea; Barsella, Bruno; Ferrini, F.; Greenberg, J. Mayo; Aiello, Santi

    1989-01-01

    Researchers considered the effect of extensive forces on dust grains subjected to the light and matter distribution of a spiral galaxy (Greenberg et al. (1987), Ferrini et al. (1987), Barsella et al (1988). Researchers showed that the combined force on a small particle located above the plane of a galactic disk may be either attractive or repulsive depending on a variety of parameters. They found, for example, that graphite grains from 20 nm to 250 nm radius are expelled from a typical galaxy, while silicates and other forms of dielectrics, after initial expulsion, may settle in potential minimum within the halo. They discuss only the statistical behavior of the forces for 17 galaxies whose luminosity and matter distribution in the disk, bulge and halo components are reasonably well known. The preliminary results of the study of the motion of a dust grain for NGC 3198 are given.

  2. Composite circumstellar dust grains

    NASA Astrophysics Data System (ADS)

    Gupta, Ranjan; Vaidya, Dipak B.; Dutta, Rajeshwari

    2016-10-01

    We calculate the absorption efficiencies of composite silicate grains with inclusions of graphite and silicon carbide in the spectral range 5-25 μm. We study the variation in absorption profiles with volume fractions of inclusions. In particular we study the variation in the wavelength of peak absorption at 10 and 18 μm. We also study the variation of the absorption of porous silicate grains. We use the absorption efficiencies to calculate the infrared flux at various dust temperatures and compare with the observed infrared emission flux from the circumstellar dust around some M-type and asymptotic giant branch stars obtained from IRAS and a few stars from Spitzer satellite. We interpret the observed data in terms of the circumstellar dust grain sizes, shape, composition and dust temperature.

  3. Grain quality inspection system

    NASA Technical Reports Server (NTRS)

    Flood, C. A., Jr.; Singletow, D. P.; James, S. N.

    1979-01-01

    A review of grain quality indicators and measurement methods was conducted in order to assess the feasibility of using remote sensing technology to develop a continuous monitoring system for use during grain transfer operations. Most detection methods were found to be too slow or too expensive to be incorporated into the normal inspection procedure of a grain elevator on a continuous basis. Two indicators, moisture content and broken corn and foreign material, show potential for automation and are of an economic value. A microprocessor based system which utilizes commercially available electronic moisture meter was developed and tested. A method for automating BCFM measurement is described. A complete system description is presented along with performance test results.

  4. 279 - Xanes Studies on UV-Irradiated Interstellar Ice Analogs: A Comparison to STARDUST Samples

    NASA Technical Reports Server (NTRS)

    Milam, Stefanie N.; Cody, George D.; Kilcoyne, A. L. David; Nuevo, Michel; Sandford, Scott A.; Stroud, Rhonda M.; DeGregorio, Bradley T.

    2010-01-01

    We present C-, N-, and O-XANES (X-ray Absorption Near-Edge Spectroscopy) results of organic residues produced in the laboratory from the UV irradiation of astrophysical ice analogs containing H20, CO, CH30H, NH31 in order to mimic processes that may occur in cold icy bodies of the outer Solar System, particularly in comets, Such analyses showed that laboratory-formed organic residues mainly consist of a solid phase and an oily phase. C-XANES analysis of the solid phase suggests a rich distribution of organic functionalities, among which carbonyl groups, C=C bonds, and alcohols are present. Results from N-XANES indicate the possible presence of amide, amine, and nitrile groups, The O-XANES spectra confirmed the a-bearing groups, These results are compared with the XANES spectra obtained from STARDUST cometary samples,

  5. Impact of Self-Explanation and Analogical Comparison Support on Learning Processes, Motivation, Metacognition, and Transfer

    NASA Astrophysics Data System (ADS)

    Richey, J. Elizabeth

    Research examining analogical comparison and self-explanation has produced a robust set of findings about learning and transfer supported by each instructional technique. However, it is unclear how the types of knowledge generated through each technique differ, which has important implications for cognitive theory as well as instructional practice. I conducted a pair of experiments to directly compare the effects of instructional prompts supporting self-explanation, analogical comparison, and the study of instructional explanations across a number of fine-grained learning process, motivation, metacognition, and transfer measures. Experiment 1 explored these questions using sequence extrapolation problems, and results showed no differences between self-explanation and analogical comparison support conditions on any measure. Experiment 2 explored the same questions in a science domain. I evaluated condition effects on transfer outcomes; self-reported self-explanation, analogical comparison, and metacognitive processes; and achievement goals. I also examined relations between transfer and self-reported processes and goals. Receiving materials with analogical comparison support and reporting greater levels of analogical comparison were both associated with worse transfer performance, while reporting greater levels of self-explanation was associated with better performance. Learners' self-reports of self-explanation and analogical comparison were not related to condition assignment, suggesting that the questionnaires did not measure the same processes promoted by the intervention, or that individual differences in processing are robust even when learners are instructed to engage in self-explanation or analogical comparison.

  6. Charging of interplanetary grains

    NASA Technical Reports Server (NTRS)

    Baragiola, R. A.; Johnson, R. E.; Newcomb, John L.

    1995-01-01

    The objective of this program is to quantify, by laboratory experiments, the charging of ices and other insulators subject to irradiation with electrons, ions and ultraviolet photons and to model special conditions based on the data. The system and conditions to be studied are those relevant for charging of dust in magnetospheric plasmas. The measurements are supplemented by computer simulations of charging or grains under a variety of conditions. Our work for this period involved experiments on water ice, improved models of charging of ice grains for Saturn's E-ring, and the construction of apparatus for electron impact studies and measurements of electron energy distributions.

  7. Radiative Grain Alignment

    NASA Astrophysics Data System (ADS)

    Andersson, B. G.

    2015-12-01

    Polarization due to aligned dust grains was discovered in the interstellar medium more than 60 years ago. A quantitative, observationally well tested theory of the phenomenon has finally emerged in the last decade, promising not only an improved understanding of interstellar magnetic fields, but new tools for studying the dust environments and grain characteristics. This Radiative Alignment Torque (RAT) theory also has many potential applications in solar system physics, including for comet dust characteristics. I will review the main aspects of the theory and the observational tests performed to date, as well as some of the new possibilities for using polarization as a tool to study dust and its environment, with RAT alignment.

  8. Grain optical properties

    NASA Technical Reports Server (NTRS)

    Hanner, Martha

    1988-01-01

    The optical properties of small grains provide the link between the infrared observations presented in Chapter 1 and the dust composition described in Chapter 3. In this session, the optical properties were discussed from the viewpoint of modeling the emission from the dust coma and the scattering in order to draw inference about the dust size distribution and composition. The optical properties are applied to the analysis of the infrared data in several ways, and these different uses should be kept in mind when judging the validity of the methods for applying optical constants to real grains.

  9. Multiple age components in individual molybdenite grains

    USGS Publications Warehouse

    Aleinikoff, John N.; Creaser, Robert A.; Lowers, Heather; Magee, Charles W.; Grauch, Richard I.

    2012-01-01

    Re–Os geochronology of fractions composed of unsized, coarse, and fine molybdenite from a pod of unusual monazite–xenotime gneiss within a granulite facies paragneiss, Hudson Highlands, NY, yielded dates of 950.5 ± 2.5, 953.8 ± 2.6, and 941.2 ± 2.6 Ma, respectively. These dates are not recorded by co-existing zircon, monazite, or xenotime. SEM–BSE imagery of thin sections and separated grains reveals that most molybdenite grains are composed of core and rim plates that are approximately perpendicular. Rim material invaded cores, forming irregular contacts, probably reflecting dissolution/reprecipitation. EPMA and LA-ICP-MS analyses show that cores and rims have different trace element concentrations (for example, cores are relatively enriched in W). On the basis of inclusions of zircon with metamorphic overgrowths, we conclude that molybdenite cores and rims formed after high-grade regional metamorphism. The discovery of cores and rims in individual molybdenite grains is analogous to multi-component U-Pb geochronometers such as zircon, monazite, and titanite; thus, molybdenite should be carefully examined before dating to ensure that the requirement of age homogeneity is fulfilled.

  10. Grain-damage hysteresis and plate tectonic states

    NASA Astrophysics Data System (ADS)

    Bercovici, David; Ricard, Yanick

    2016-04-01

    Shear localization in the lithosphere is an essential ingredient for understanding how and why plate tectonics is generated from mantle convection on terrestrial planets. The theoretical model for grain-damage and pinning in two-phase polycrystalline rocks provides a frame-work for understanding lithospheric shear weakening and plate-generation, and is consistent with laboratory and field observations of mylonites. Grain size evolves through the competition between coarsening, which drives grain-growth, and damage, which drives grain reduction. The interface between crystalline phases controls Zener pinning, which impedes grain growth. Damage to the interface enhances the Zener pinning effect, which then reduces grain-size, forcing the rheology into the grain-size-dependent diffusion creep regime. This process thus allows damage and rheological weakening to co-exist, providing a necessary positive self-weakening feedback. Moreover, because pinning inhibits grain-growth it promotes shear-zone longevity and plate-boundary inheritance. However, the suppression of interface damage at low interface curvature (wherein inter-grain mixing is inefficient and other energy sinks of deformational work are potentially more facile) causes a hysteresis effect, in which three possible equilibrium grain-sizes for a given stress coexist: (1) a stable, large-grain, weakly-deforming state, (2) a stable, small-grain, rapidly-deforming state analogous to ultramylonites, and (3) an unstable, intermediate grain-size state perhaps comparable to protomylonites. A comparison of the model to field data suggests that shear-localized zones of small-grain mylonites and ultra-mylonites exist at a lower stress than the co-existing large-grain porphyroclasts, rather than, as predicted by paleopiezometers or paleowattmeters, at a much higher stress; this interpretation of field data thus allows localization to relieve instead of accumulate stress. The model also predicts that a lithosphere that

  11. Laboratory Spectra of CO2 Vibrational Modes in Planetary Ice Analogs

    NASA Technical Reports Server (NTRS)

    White, Douglas; Mastrapa, Rachel M.; Sandford, Scott

    2012-01-01

    Laboratory spectra have shown that CO2 is a powerful diagnostic tool for analyzing infrared data from remote observations, as it has been detected on icy moons in the outer Solar System as well as dust grain surfaces in the interstellar medium (ISM). IR absorption band profiles of CO2 within ice mixtures containing H2O and CH3OH change with respect to temperature and mixture ratios. In this particular study, the CO2 asymmetric stretching mode near 4.3 m (2350 cm (exp-1)), overtone mode near 1.97 m (5080 cm (exp-1)), and the combination bands near 2.7 m (3700 cm (exp-1)), 2.8 m (3600 cm (exp-1)), and 2.02 m (4960 cm (exp -1)), are systematically observed in different mixtures with H2O and CH3OH in temperature ranges from 15K to 150 K. Additionally, some high-temperature deposits (T greater than 50 K) of H2O, CH3OH, and CO2 ice mixtures were performed. These data may then be used to interpret infrared observational data obtained from icy surfaces in the outer Solar System and beyond.

  12. Grain boundary curvature and grain growth kinetics with particle pinning

    NASA Astrophysics Data System (ADS)

    Shahandeh, Sina; Militzer, Matthias

    2013-08-01

    Second-phase particles are used extensively in design of polycrystalline materials to control the grain size. According to Zener's theory, a distribution of particles creates a pinning pressure on a moving grain boundary. As a result, a limiting grain size is observed, but the effect of pinning on the detail of grain growth kinetics is less known. The influence of the particles on the microstructure occurs in multiple length scales, established by particle radius and the grain size. In this article, we use a meso-scale phase-field model that simulates grain growth in the presence of a uniform pinning pressure. The curvature of the grain boundary network is measured to determine the driving pressure of grain growth in 2D and 3D systems. It was observed that the grain growth continues, even under conditions where the average driving pressure is smaller than the pinning pressure. The limiting grain size is reached when the maximum of driving pressure distribution in the structure is equal to the pinning pressure. This results in a limiting grain size, larger than the one predicted by conventional models, and further analysis shows consistency with experimental observations. A physical model is proposed for the kinetics of grain growth using parameters based on the curvature analysis of the grain boundaries. This model can describe the simulated grain growth kinetics.

  13. Estimations on the Interior of Small Icy Bodies in the Solar System

    NASA Astrophysics Data System (ADS)

    Taubner, Ruth-Sophie; Leitner, Johannes J.; Firneis, Maria G.; Hitzenberger, Regina

    2014-05-01

    During the last decade small icy bodies have become more and more important for the search for potential habitats in the Solar System. This development was primarily attributable to the indications for Europa's subsurface ocean (e.g., Carr et al., 1998) and the detection of Enceladus' plume (Porco et al., 2006). These observations showed that liquid water can exist under certain circumstances even far beyond the classical habitable zone (Kasting et al., 1993). Additionally, the subsurface water reservoirs may contain a significant amount of ammonia which causes the fluid to stay liquid even below 0°C. If liquid water is in contact with the rocky layer, erosion or similar interaction processes will take place and enrich the water with possible nutrients for potential life forms in this habitat. Therefore, especially the water/rock boundary zone seems highly interesting for astrobiological studies. We developed a three and four layer model for the interior of small icy bodies, i.e. icy moons, TNOs, and asteroids as small as 200 km in radius. The simulations are based on three different scenarios which consider the diverse interior structures of three selected prototype satellites (Io, Europa, and Titan). On average, the water layer represents approximately 20 % of the bodies' radii for the Europa- and Titan-like model. In contrast, for the Io-like scenario, in which we do not include a global subsurface ocean, just Io, the Moon, Vesta, and Hygiea fit into the model. This may indicate that water/ice-regions or even liquid water shells are far more common in the Solar System than previously assumed. Furthermore, we estimate the bodies' dimensionless moment of inertia and compare our results to observed values as far as they are available. Moreover, the physical conditions at the bottom of the bodies' potential subsurface ocean and the thickness of each layer will be estimated. This study will give us a good overview about the distribution of potential liquid water

  14. Thermodynamic Equations of State for Aqueous Solutions Applied to Deep Icy Satellite and Exoplanet Oceans

    NASA Astrophysics Data System (ADS)

    Vance, S.; Brown, J. M.; Bollengier, O.; Journaux, B.; Sotin, C.; Choukroun, M.; Barnes, R.

    2014-12-01

    Supporting life in icy world or exoplanet oceans may require global seafloor chemical reactions between water and rock. Such interactions have been regarded as limited in larger icy worlds such as Ganymede and Titan, where ocean depths approach 800 km and GPa pressures (>10katm). If the oceans are composed of pure water, such conditions are consistent with the presence of dense ice phases V and VI that cover the rocky seafloor. Exoplanets with oceans can obtain pressures sufficient to generate ices VII and VIII. We have previously demonstrated temperature gradients in such oceans on the order of 20 K or more, resulting from fluid compressibility in a deep adiabatic ocean based on our experimental work. Accounting for increases in density for highly saline oceans leads to the possibility of oceans perched under and between high pressure ices. Ammonia has the opposite effect, instead decreasing ocean density, as reported by others and confirmed by our laboratory measurements in the ammonia water system. Here we report on the completed equation of state for aqueous ammonia derived from our prior measurements and optimized global b-spline fitting methods We use recent diamond anvil cell measurements for water and ammonia to extend the equation of state to 400°C and beyond 2 GPa, temperatures and pressures applicable to icy worlds and exoplanets. Densities show much less temperature dependence but comparabe high-pressure derivatives to previously published ammonia-water properties derived for application to Titan (Croft et al. 1988). Thermal expansion is in better agreement with the more self-consistent equation of state of Tillner-Roth and Friend (1998). We also describe development of a planetary NaCl equation of state using recent measurements of phase boundaries and sound speeds. We examine implications of realistic ocean-ice thermodynamics for Titan and exoplanet interiors using the methodology recently applied to Ganymede for oceans dominated by MgSO4. High

  15. Photon-induced electro-chemical processes in airless icy bodies analogues

    NASA Astrophysics Data System (ADS)

    Marchione, Demian; Gudipati, Murthy

    2016-10-01

    Previous laboratory studies have shown that radiation-induced ionization of impurities in water-rich ices drives the formation of ionized species resulting in charge generation and accumulation in ices [1-3]. It is expected that some of these impurity ions are decomposed into smaller volatile species and ejected into the vacuum. These processes are relevant to the chemical composition of the near-surface tenuous (thin) atmosphere of icy bodies such as the Jovian satellites like Europa.Our work aims at investigating photocurrents from organic impurity embedded water ices of several microns thick and understanding how these measurements correlate with the desorption of volatiles during UV and electron irradiation. These experiments are performed in an ultrahigh vacuum chamber around Europa's surface temperature (100 – 150 K) conditions using a low-pressure hydrogen flow-discharge lamp emitting primarily at Lyα (121.6 nm), a 2 keV electron source, and a substrate-less electrode. Photoionization of organic impurities in the water matrix results in charge pair (electron and ion) separation within the ice, and hence in detectable currents that are measured as a function of the applied bias and the temperature (5 K – 200 K). Photodesorption products are also identified by a quadrupole mass spectrometer (QMS) and correlated with conductivity measurements. We will discuss these results in the context of expected Europa's surface photoconductivity and near-surface volatile production.References:[1] M. S. Gudipati, and L. J. Allamandola, Astrophysical Journal Letters, 2003, 596(2), L195-L198.[2] M. S. Gudipati, Journal of Physical Chemistry A, 2004, 108(20), 4412-4419.[3] S. H. Cuylle, L. J. Allamandola, and H. Linnartz, Astronomy and Astrophysics, 2014, 562, A22.This work has been carried out at Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration, and funded by NASA under Planetary

  16. Icy Galilean Satellites: Radar Echoes Due to a Coherent Backscatter Effect

    NASA Astrophysics Data System (ADS)

    Black, G. J.; Campbell, D. B.; Nicholson, P. D.

    1997-07-01

    We have modeled the radar scattering properties of Europa, Ganymede, and Callisto using a vector formulation of the coherent backscatter effect [1]. At wavelengths of 3.5 cm and 12.6 cm, the specific radar cross sections [2] of the icy Galilean satellites are not only an order of magnitude larger than those of typical inner Solar System targets, but also greater than unity, indicating that these icy surfaces preferentially backscatter. Even more unusual is that the icy surface reflection mechanism largely preserves the incident polarization. At 70 cm wavelength the cross sections of Europa, Ganymede, and Callisto are lower than those measured at the shorter wavelengths by factors of 4-10, while the polarization ratios appear to remain at high values [3]. In order to explain the radar data several possible mechanisms have been proposed by various workers, all of which are based on the fact that the surfaces and upper layers of these moons are mainly water ice. Water ice at the low temperatures found on these objects is a poor absorber of radio-wavelength radiation, permitting the radar signal to penetrate more efficiently into the surface than is possible with silicate compositions. We have adapted a model of the coherent backscatter effect [1] to explain the observed wavelength dependence of the radar cross sections. Since the subsurface attenuation coefficient can be quite small, the presence of embedded wavelength-scale scatterers may result in this particular multiple-scattering process, thus enhancing the echo near exact backscatter as well as preserving the incident polarization. By assuming Mie scatterers that are distributed in size as a power law, we fit the observed wavelength variations in cross section and polarization properties. Model parameters that best reproduce the data indicate that the scattering layers are on the order of ten meters thick. The scatterer size distributions follow fairly steep power laws, with the maximum scatterer sizes falling

  17. Edible grain legumes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Edible grain legumes including dry bean, dry pea, chickpeas, and lentils, have served as important sources of protein for human diets for thousands of years. In the US, these crops are predominately produced for export markets. The objective of this study was to examine yield gains in these crops ov...

  18. On Organic Material in E Ring Ice Grains

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Khawaja, N.; Reviol, R.; Nölle, L.; Klenner, F.; Hsu, H. W.; Horanyi, M.

    2015-12-01

    Pure water ice dominates the composition of the micron and sub-micron sized dust particles in Saturn's E-ring, a ring constantly replenished by active ice jets of the moon Enceladus [1]. Details about the composition of this tenuous, optically thin ring can only be constrained by in situ measurements. The Cosmic Dust Analyzer (CDA) onboard Cassini investigates the composition of these grains by cationic time-of-flight mass spectra of individual ice grains hitting the instruments target surface. From these spectra three compositional types of E ring ice grains have been identified previously [2,3]: Type-1: Almost pure water, Type-2: Enriched in organics, and Type-3: Enriched in salt. Unlike Type-1 and 3, organic-enriched Type-2 spectra have not yet been investigated in depth. Here we report the first detailed compositional analysis of this type. The spectra analysis is supported by a large-scale laboratory ground campaign yielding a library of analogue spectra for organic material embedded in a water ice matrix. In contrast to Type 1 and 3, Type-2 spectra display a great compositional diversity, which indicates varying contributions of several organic species. So far we have identified characteristic fragment patterns of at least three classes of organic compounds: aromatic species, amines, and carbonyl group species. Work is in progress to quantify concentrations of the identified species and to assign yet un-specified organic mass lines in Type 2 spectra. Due to the dynamical evolution of the orbital elements of E ring grains a large fraction collides with the icy moons embedded in the E ring. Therefore, the organic components identified by CDA can accumulate on the surfaces of these bodies over time. Ref: :[1]Kempf et al., Icarus-206, 2010. [2]Postberg et al., Nature-459, 2009. [3]Postberg et al., Icarus-193, 2008.

  19. Hemispheric and Topographic Asymmetry of Magnetospheric Particle Irradiation for Icy Moon Surfaces

    NASA Technical Reports Server (NTRS)

    Cooper, John F.; Sturner, S. J.

    2007-01-01

    All surfaces of icy moons without significant atmospheres, i.e. all except Titan in the giant planet systems, are irradiated by hot plasma and more energetic charged particles from the local magnetospheric environments. This irradiation can significantly impact the chemical composition, albedo, and detectable presence of signs of life on the sensible surfaces, while also limiting lifetimes and science operations of orbital spacecraft for extreme radiation environments as at Europa. Planning of surface remote sensing and lander operations, and interpretation of remote sensing and in-situ measurements, should include consideration of natural shielding afforded by the body of the moon, by any intrinsic or induced magnetic fields as at Ganyrnede, and by topographic structures.

  20. Cassini finds an oxygen-carbon dioxide atmosphere at Saturn's icy moon Rhea.

    PubMed

    Teolis, B D; Jones, G H; Miles, P F; Tokar, R L; Magee, B A; Waite, J H; Roussos, E; Young, D T; Crary, F J; Coates, A J; Johnson, R E; Tseng, W-L; Baragiola, R A

    2010-12-24

    The flyby measurements of the Cassini spacecraft at Saturn's moon Rhea reveal a tenuous oxygen (O(2))-carbon dioxide (CO(2)) atmosphere. The atmosphere appears to be sustained by chemical decomposition of the surface water ice under irradiation from Saturn's magnetospheric plasma. This in situ detection of an oxidizing atmosphere is consistent with remote observations of other icy bodies, such as Jupiter's moons Europa and Ganymede, and suggestive of a reservoir of radiolytic O(2) locked within Rhea's ice. The presence of CO(2) suggests radiolysis reactions between surface oxidants and organics or sputtering and/or outgassing of CO(2) endogenic to Rhea's ice. Observations of outflowing positive and negative ions give evidence for pickup ionization as a major atmospheric loss mechanism.

  1. Infrared Spectral Studies of the Thermally-Driven Chemistry Present on Icy Satellites

    NASA Technical Reports Server (NTRS)

    Loeffler, Mark J.; Hudson, Reggie L.

    2012-01-01

    Remote sensing of Jupiters icy satellites has revealed that even though their surfaces arc composed mostly of water ice, molecules such as SO2, CO2, H2O2. O2, and O3 also are present. On Europa, a high radiation flux is believed to play a role in the formation of many of the minor species detected, and numerous laboratory studies have been devoted to explore this hypothesis. In this presentation we will discuss some of our recent research on another alteration pathway, thermally-driven chemical reactions, which are also important for understanding the chemical evolution of Europa's surface and sub-surface ices. We will focus on the infrared spectra of and reactions between H2O, SO2 and H2O2, at 80 - 130 K.

  2. The Early Climate History of Mars: "Warm and Wet" or "Cold and Icy"?

    NASA Astrophysics Data System (ADS)

    Head, James

    2013-04-01

    The Amazonian climate (last ~66% of history) was much like today, a cold and dry climate regime, characterized by the latitudinal migration of surface ice in response to variations in spin-axis/orbital parameters. But what characterized the Noachian climate (first ~20% of history)? Some data support a "warm and wet" early Mars, but this evidence has been challenged. New models of early Mars climate (Forget, Wordsworth et al.) find that for atmospheric pressures greater than a few hundred millibars, surface temperatures vary with altitude due to atmosphere-surface thermal coupling: an adiabatic cooling effect (ACE) results in deposition of snow and ice at high altitudes, in contrast to Amazonian conditions. Without other warming mechanisms, no combination of parameters lead to mean annual surface temperatures (MAT) consistent with widespread liquid water anywhere on the planet. The ACE causes southern highland region temperatures to fall significantly below the global average leading to a "Noachian Icy Highlands" scenario: Water is transported to the highlands from low-lying regions due to the ACE and snows out to form an extended H2O ice cap at the southern pole, and altitude-dependent snow and ice deposits down to lower southern latitudes. Could the predictions of this "Noachian Icy Highlands" model be consistent with the many lines of evidence traditionally cited for a "warm, wet" early Mars? Perturbing this predominant Noachian environment with punctuated impacts and volcanism/greenhouse gases would lead to raising of global surface temperatures toward the melting point of water, with the following consequences: 1) ice above the surface ice stability line undergoes rapid altitude/latitude dependent warming during each Mars summer; 2) meltwater runoff from the continuous ice sheet drains and flows downslope to the edge of the ice sheet, where meltwater channels encounter cratered terrain, forming closed-basin and open-basin lakes; 3) seasonal top-down heating and

  3. OGLE-2005-BLG-390Lb - Gravity Reveals First Cool Rocky/icy Exoplanet

    NASA Astrophysics Data System (ADS)

    Dominik, Martin

    2008-09-01

    Gravitational microlensing is currently the only technique capable of detecting exoplanets down to Earth mass that share their evolutionary history with potentially habitable planets. A network of five 1m-class optical telescopes distributed in longitude around the southern hemisphere enables PLANET (Probing Lensing Anomalies NETwork) to characterize such planets in observed deviations, lasting from hours to days, to ongoing microlensing events. Since 2005, PLANET operates a common microlensing campaign with RoboNet-l.O, a network of UK-built robotic 2m-telescopes. We report the discovery of OGLE-2005-BLG-390Lb, with a mass of 3-10 Earth masses orbiting an M-dwarf at about 3 AU the first cool rocky/icy exoplanet. This provides the first observational hint that planets like Earth are common in the Universe. Royal Society University Research Fellow on behalf of the PLANET and RoboNet collaborations.

  4. Chemical Schemes for Surface Modification of Icy Satellites: A Road Map

    NASA Technical Reports Server (NTRS)

    Delitsky, Mona L.; Lane, Arthur L.

    1997-01-01

    The icy Galilean satellites of Jupiter are subject to magnetospheric plasma ion bombardment, which induces chemical changes within the ice. The possible detection of CO2 on the surface of Ganymede by the Galileo spacecraft makes for a more complicated chemistry and increases the number of chemical compounds that may then be present. We outline chemical schemes for the irradiation of pure and mixed ices H2O/CO2 and suggest species which observers may detect on Europa, Ganymede, and Callisto, such as C3O2, H2CO3, H2O2, CO3, HO2, CO, H2CO, CH2CO, as well as K2O, KOH, and SO3, from plasma implantation. Column abundances of compounds in the ice are calculated using a specified energy input and G values (yield per 100 eV).

  5. Analysis of Thrust Vectoring Capabilities for the Jupiter Icy Moons Orbiter

    NASA Technical Reports Server (NTRS)

    Quadrelli, Marco B .; Gromov, Konstantin; Murray, Emmanuell

    2005-01-01

    A strategy to mitigate the impact of the trajectory design of the Jupiter Icy Moons Orbiter (JIMO) on the attitude control design is described in this paper. This paper shows how the thrust vectoring control torques, i.e. the torques required to steer the vehicle, depend on various parameters (thrust magnitude, thrust pod articulation angles, and thrust moment arms). Rather than using the entire reaction control system (RCS) system to steer the spacecraft, we investigate the potential utilization of only thrust vectoring of the main ion engines for the required attitude control to follow the representative trajectory. This study has identified some segments of the representative trajectory where the required control torque may exceed the designed ion engine capability, and how the proposed mitigation strategy succeeds in reducing the attitude control torques to within the existing capability.

  6. Geology of the Icy Galilean Satellites: Understanding Crustal Processes and Geologic Histories Through the JIMO Mission

    NASA Technical Reports Server (NTRS)

    Figueredo, P. H.; Tanaka, K.; Senske, D.; Greeley, R.

    2003-01-01

    Knowledge of the geology, style and time history of crustal processes on the icy Galilean satellites is necessary to understanding how these bodies formed and evolved. Data from the Galileo mission have provided a basis for detailed geologic and geo- physical analysis. Due to constrained downlink, Galileo Solid State Imaging (SSI) data consisted of global coverage at a -1 km/pixel ground sampling and representative, widely spaced regional maps at -200 m/pixel. These two data sets provide a general means to extrapolate units identified at higher resolution to lower resolution data. A sampling of key sites at much higher resolution (10s of m/pixel) allows evaluation of processes on local scales. We are currently producing the first global geological map of Europa using Galileo global and regional-scale data. This work is demonstrating the necessity and utility of planet-wide contiguous image coverage at global, regional, and local scales.

  7. Titan and other icy satellites - Dielectric properties of constituent materials and implications for radar sounding

    NASA Technical Reports Server (NTRS)

    Thompson, W. Reid; Squyres, Steven W.

    1990-01-01

    Radar sounding observations of Titan and the other outer solar system icy satellites have been conducted in order to ascertain the materials present, their dielectric properties, and the degree of radar signal penetration. Deep penetration is possible at long wavelengths, while strong reflections may occur due to pockets or layers of H2O-NH3 solution. Attention is given to the case of Titan, using models to calculate radar reflection S/N ratios; the models involve H2O ice covered by a 100-m thick layer of organic sediments that are overlain by an ocean of liquid CH4-C2H6-N2. At 13.6-cm wavelength, a greater-than-10 dB S/N is computed from the ocean-sediment and sediment-ice interfaces, suggesting that the geology of Titan may be investigated by such a sounding mode despite deep ocean coverage of the satellite.

  8. ICI D7114: a novel selective adrenoceptor agonist of brown fat and thermogenesis.

    PubMed

    Holloway, B R; Howe, R; Rao, B S; Stribling, D

    1992-01-01

    Increasing energy expenditure by treatment with thermogenic drugs is not new, but available drugs have suffered from the problem of lack of selectivity. In the last decade two key findings have allowed the development of selective thermogenic drugs that have promise in the treatment of obesity. 1) The recognition that brown adipose tissue (BAT) plays a role in compensatory increases in energy expenditure has allowed an approach directed at a target organ. 2) The demonstration showing that increases in the activity of BAT may be modulated by an atypical (beta 3) adrenoceptor has led to the development of a new peripherally acting beta-adrenoceptor agonist ICI D7114, which stimulates thermogenesis at doses that have little effect on beta 1 or beta 2 adrenoceptors. Treatment with the compound activates BAT and thermogenesis even in species and situations where the intrinsic capacity is low. 3) The compound has beneficial effects in animal models of obesity and disturbed glucose and lipid homeostasis. PMID:1345891

  9. Battery hydrometer with analog output

    SciTech Connect

    Patis, B.L.

    1982-09-21

    There is disclosed a battery hydrometer for providing an analog electrical signal having a magnitude related to the specific gravity of a battery electrolyte. The hydrometer includes a source of radiation for providing a detectable beam of radiation and a piston member arranged to be submerged within the electrolyte and to intercept and modulate the beam of radiation in response to the specific gravity of the electrolyte. The piston member is suspended within the electrolyte by a spring which exerts a compressive force upon the piston member against which the electrolyte must act. The hydrometer further includes a radiation detector aligned with the radiation source for providing an analog electrical signal having a magnitude responsive to the modulated beam of radiation.

  10. Analog Nonvolatile Computer Memory Circuits

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd

    2007-01-01

    In nonvolatile random-access memory (RAM) circuits of a proposed type, digital data would be stored in analog form in ferroelectric field-effect transistors (FFETs). This type of memory circuit would offer advantages over prior volatile and nonvolatile types: In a conventional complementary metal oxide/semiconductor static RAM, six transistors must be used to store one bit, and storage is volatile in that data are lost when power is turned off. In a conventional dynamic RAM, three transistors must be used to store one bit, and the stored bit must be refreshed every few milliseconds. In contrast, in a RAM according to the proposal, data would be retained when power was turned off, each memory cell would contain only two FFETs, and the cell could store multiple bits (the exact number of bits depending on the specific design). Conventional flash memory circuits afford nonvolatile storage, but they operate at reading and writing times of the order of thousands of conventional computer memory reading and writing times and, hence, are suitable for use only as off-line storage devices. In addition, flash memories cease to function after limited numbers of writing cycles. The proposed memory circuits would not be subject to either of these limitations. Prior developmental nonvolatile ferroelectric memories are limited to one bit per cell, whereas, as stated above, the proposed memories would not be so limited. The design of a memory circuit according to the proposal must reflect the fact that FFET storage is only partly nonvolatile, in that the signal stored in an FFET decays gradually over time. (Retention times of some advanced FFETs exceed ten years.) Instead of storing a single bit of data as either a positively or negatively saturated state in a ferroelectric device, each memory cell according to the proposal would store two values. The two FFETs in each cell would be denoted the storage FFET and the control FFET. The storage FFET would store an analog signal value

  11. Classical Analog to Entanglement Reversibility

    NASA Astrophysics Data System (ADS)

    Chitambar, Eric; Fortescue, Ben; Hsieh, Min-Hsiu

    2015-08-01

    In this Letter we study the problem of secrecy reversibility. This asks when two honest parties can distill secret bits from some tripartite distribution pX Y Z and transform secret bits back into pX Y Z at equal rates using local operation and public communication. This is the classical analog to the well-studied problem of reversibly concentrating and diluting entanglement in a quantum state. We identify the structure of distributions possessing reversible secrecy when one of the honest parties holds a binary distribution, and it is possible that all reversible distributions have this form. These distributions are more general than what is obtained by simply constructing a classical analog to the family of quantum states known to have reversible entanglement. An indispensable tool used in our analysis is a conditional form of the Gács-Körner common information.

  12. Troughs in Ice Sheets and Other Icy Deposits on Mars: Analysis of Their Radiative Balance

    NASA Technical Reports Server (NTRS)

    Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, H. J.

    2000-01-01

    It has long been known that groove-like structures in glaciers and ice sheets can trap more incoming solar radiation than is the case for a 'normal' flat, smooth surface. In this presentation, we shall describe the radiative regimes of typical scarps and troughs on icy surfaces of Mars, and suggest how these features originate and evolve through time. The basis of our analysis is the radiation balance model presented by Pfeffer and Bretherton. Their model considers the visible band radiation regime of a V-shaped groove on a terrestrial ice surface, and shows that absorbed energy can be enhanced by up to 50 percent for grooves with small opening angles and with typical polar values of the solar zenith angle. Our work extends this model by considering: (a) departures from V-shaped geometry, (b) both englacial and surficial dust and debris, and (c) the infrared spectrum. We apply the extended model to various features on the Martian surface, including the spiral-like scarps on the Northern and Southern ice sheets, the large-scale chasms (e.g., Chasm Borealis), and groove-like lineations on valley floors thought to be filled with mixtures of dust and icy substances. In conjunction with study of valley-closure experiments, we suggest that spiral-like scarps and chasms are stable features of the Martian climate regime. We also suggest that further study of scarps and chasms may shed light on the composition (i.e., relative proportions of water ice, carbon-dioxide ice and dust) of the Martian ice sheets and valley fills.

  13. The Other Chemistry of the Jovian Icy Satellites - Low Energy and Sulfurous

    NASA Technical Reports Server (NTRS)

    Hudson, Reggie L.; Loeffler, M. J.; Moore, M. H.

    2010-01-01

    Spectra of Jupiter's icy satellites reveal surfaces dominated by H2O-ice with minor amounts of SO2 and other materials. The co-existence of H2O and SO2 in surfaces exposed to jovian magnetospheric radiation suggests that sulfuric acid (H2SO4) also could be present. This was noted by Carlson et al. (1999), who supported this suggestion with assignments of near-IR bands in Europa spectra to hydrated H2SO4. Laboratory experiments since have demonstrated radiolytically-driven syntheses in S- and SO2-containing H2O-Ices (Carlson et al., 2002; Moore et al., 2006). In the Cosmic Ice Laboratory, we recently have investigated the thermal chemistry of SO2 trapped in H2O-ice. IR spectra of H2O + SO2 mixtures recorded at 10 to 230 K were used to follow low-temperature reactions in the absence of radiation effects. No SO2 reactions were found at 10 K, but warming to more-relevant Europa temperatures produced both HSO3(-) and S2O5(2-). Added NH3 shifted the product composition toward SO3(2-) and away from the other ions. We find that H2O and SO2 react to produce sulfur oxyanions, such as bisulfite, that as much as 30% of the SO2 can be consumed through this reaction, and that the products remain in the ice when the temperature is lowered, indicating that these reactions are irreversible. Our results suggest that thermally-induced reactions can alter the chemistry at and below the surfaces of the icy satellites in the jovian system.

  14. Performance enhancement of wireless mobile adhoc networks through improved error correction and ICI cancellation

    NASA Astrophysics Data System (ADS)

    Sabir, Zeeshan; Babar, M. Inayatullah; Shah, Syed Waqar

    2012-12-01

    Mobile adhoc network (MANET) refers to an arrangement of wireless mobile nodes that have the tendency of dynamically and freely self-organizing into temporary and arbitrary network topologies. Orthogonal frequency division multiplexing (OFDM) is the foremost choice for MANET system designers at the Physical Layer due to its inherent property of high data rate transmission that corresponds to its lofty spectrum efficiency. The downside of OFDM includes its sensitivity to synchronization errors (frequency offsets and symbol time). Most of the present day techniques employing OFDM for data transmission support mobility as one of the primary features. This mobility causes small frequency offsets due to the production of Doppler frequencies. It results in intercarrier interference (ICI) which degrades the signal quality due to a crosstalk between the subcarriers of OFDM symbol. An efficient frequency-domain block-type pilot-assisted ICI mitigation scheme is proposed in this article which nullifies the effect of channel frequency offsets from the received OFDM symbols. Second problem addressed in this article is the noise effect induced by different sources into the received symbol increasing its bit error rate and making it unsuitable for many applications. Forward-error-correcting turbo codes have been employed into the proposed model which adds redundant bits into the system which are later used for error detection and correction purpose. At the receiver end, maximum a posteriori (MAP) decoding algorithm is implemented using two component MAP decoders. These decoders tend to exchange interleaved extrinsic soft information among each other in the form of log likelihood ratio improving the previous estimate regarding the decoded bit in each iteration.

  15. Global Topographic Mapping Of Saturn's Midsize Icy Satellites: System-wide Thermal And Impact Effects

    NASA Astrophysics Data System (ADS)

    Schenk, Paul M.

    2010-10-01

    Cassini stereo coverage of Saturn's 6 largest midsized icy satellites has been used to produce the first global topographic maps of major icy bodies. All except Iapetus have dynamic topography of -5 to +5 km (excepting the largest basins). Apparently all except Iapetus have been topographically reset by global heating events capable of erasing or preventing the 10's of kilometers of regional relief observed on that outer moon. In contrast to Tethys, Dione features no deep large basins and exhibits lower relief generally, and extensive crater relaxation specifically. Apparently Dione remained hot even longer than Tethys, despite geologic and topographic evidence for smooth volcanic-style plains and tectonic disruption on both satellites. No deep basins are evident on Rhea either. On Rhea, the leading side features a generally much smoother texture at length-scales of 100 km than does the (faulted) trailing hemisphere, suggesting that the leading hemisphere also experienced more pervasive heating than the trailing. On Mimas, an irregular region near the antipode to Herschel exhibits lower crater depths than elsewhere, a possible signature of seismic focusing of the type seen on Mercury. Basin disruption effects appear to be limited. The most prominent occur around Evander (Dione) and southeast of Odysseus (Tethys) , where radial "gouge” erased the preexisting cratering record in favor of much smaller densely packed craters in an annulus around the basin which terminates at a circumferential ridge up to 2 km high! This may be a ring structure or distal ejecta ridge. Radial grooves may also occur near ancient relaxed basins on Dione and Rhea. Grooves 2-3 km deep on Mimas extend nearly globally but their relationship to Herschel is uncertain. Enceladus topography is dominated by pervasive resurfacing and by large-scale depressions (or dimples) that are plausibly due to isostatic variations in shell thickness.

  16. The Potential for Oceans Within Icy Outer Planetary Bodies - A Comparative Study

    NASA Astrophysics Data System (ADS)

    England, C.

    2002-09-01

    Several outer planetary moons and related bodies are investigated for their likelihood of containing an aqueous (i.e.; a water-dominated) layer between an assumed rocky core and icy mantle. A steady-state thermal analysis of differentiated bodies is used to estimate temperature profiles in their interiors prior to the formation of such a layer. This analysis assumes radiogenic heating at chondritic rates localized in a rocky core, a two-layer composite sphere, and non-convective heat transfer in the mantle. The largest bodies such as Ganymede, Titan and Callisto, should have substantial subsurface oceans. Intermediate-sized bodies such as Triton, Europa and Pluto, are likely to have aqueous strata, but of a reduced extent. Smaller bodies such as Titania, Rhea, Oberon and Iapetus, may have aqueous core-mantle interfaces, but only if other heat sources such as tidal dissipation or warming from past epochs are important. A Trans-Neptunian Object with radius of 910 km and a density of 1725 kg/m3 is the smallest that may have an aqueous seam at present day. Bodies having as small a radius as 539 km may have had melted layers in past epochs, or even currently if present day rates of radiogenic heating have been underestimated. If the radiogenic heating rate is closer to that of in-situ lunar samples (i.e.; about twice the chondritic rate), then oceans may be common in the outer Solar System. A descriptive criterion is proposed that describes the likelihood of the existence of an aqueous layer based on a pre-melt temperature calculated at the rock-ice interface. The steady-state two-layer analysis provides a language by which primitive icy bodies can be better understood.

  17. Precision Navigation of Cassini Images Using Rings, Icy Satellites, and Fuzzy Bodies

    NASA Astrophysics Data System (ADS)

    French, Robert S.; Showalter, Mark R.; Gordon, Mitchell K.

    2016-10-01

    Before images from the Cassini spacecraft can be analyzed, errors in the published pointing information (up to ~110 pixels for the Imaging Science Subsystem Narrow Angle Camera) must be corrected so that the line of sight vector for each pixel is known. This complicated and labor-intensive process involves matching the image contents with known features such as stars, rings, or moons. Metadata, such as lighting geometry or ring radius and longitude, must be computed for each pixel as well. Both steps require mastering the SPICE toolkit, a highly capable piece of software with a steep learning curve. Only after these steps are completed can the actual scientific investigation begin.We have embarked on a three-year project to perform these steps for all 400,000+ Cassini ISS images as well as images taken by the VIMS, UVIS, and CIRS instruments. The result will be a series of SPICE kernels that include accurate pointing information and a series of backplanes that include precomputed metadata for each pixel. All data will be made public through the PDS Ring-Moon Systems Node (http://www.pds-rings.seti.org). We expect this project to dramatically decrease the time required for scientists to analyze Cassini data.In a previous poster (French et al. 2014, DPS #46, 422.01) we discussed our progress navigating images using stars, simple ring models, and well-defined icy bodies. In this poster we will report on our current progress including the use of more sophisticated ring models, navigation of "fuzzy" bodies such as Titan and Saturn, and use of crater matching on high-resolution images of the icy satellites.

  18. Mass Movement and Landform Degradation on the Icy Galilean Satellites: Results of the Galileo Nominal Mission

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.; Asphaug, Erik; Morrison, David; Spencer, John R.; Chapman, Clark R.; Bierhaus, Beau; Sullivan, Robert J.; Chuang, Frank C.; Klemaszewski, James E.; Greeley, Ronald

    1999-01-01

    The Galileo mission has revealed remarkable evidence of mass movement and landform degradation on the icy Galilean satellites of Jupiter. Weakening of surface materials coupled with mass movement reduces the topographic relief of landforms by moving surface materials down-slope. Throughout the Galileo orbiter nominal mission we have studied all known forms of mass movement and landform degradation of the icy galilean satellites, of which Callisto, by far, displays the most degraded surface. Callisto exhibits discrete mass movements that are larger and apparently more common than seen elsewhere. Most degradation on Ganymede appears consistent with sliding or slumping, impact erosion, and regolith evolution. Sliding or slumping is also observed at very small (100 m) scale on Europa. Sputter ablation, while probably playing some role in the evolution of Ganymede's and Callisto's debris layers, appears to be less important than other processes. Sputter ablation might play a significant role on Europa only if that satellite's surface is significantly older than 10(exp 8) years, far older than crater statistics indicate. Impact erosion and regolith formation on Europa are probably minimal, as implied by the low density of small craters there. Impact erosion and regolith formation may be important on the dark terrains of Ganymede, though some surfaces on this satellite may be modified by sublimation-degradation. While impact erosion and regolith formation are expected to operate with the same vigor on Callisto as on Ganymede, most of the areas examined at high resolution on Callisto have an appearance that implies that some additional process is at work, most likely sublimation-driven landform modification and mass wasting. The extent of surface degradation ascribed to sublimation on the outer two Galilean satellites implies that an ice more volatile than H2O is probably involved.

  19. Impact jetting water ice, with application to the accretion of icy planetesimals and Pluto

    SciTech Connect

    McKinnon, W.B. )

    1989-11-01

    Jetting can occur during oblique impacts of water ice bodies at relative velocities at low as {approximately}500 m s{sup {minus}1}, because of the low Hugoniot elastic limit and high compressibility of ice compared to rock. In jetted ice, incipient melting, complete melting, and incipient vaporization occur, upon release to low pressure, at impact velocities of 1.3, 2.0, and 2.7 km s{sup {minus}1}, respectively, much less than the 3.4, 4.4, and 5.3 km s{sup {minus}1} required in head-on collisions. Uncertainties in the shock equation-of-state may allow complete melting during jetting at relative velocities as low as 1.2 km s{sup {minus}1}. Because jet speeds exceed impact speeds, often by a factor of several, during the accretion of icy bodies greater than a few 100 km in radius there any be a significant loss of icy material. This is more true if the accreting body is large enough to differentiate so that its surface layers are closer to pure ice in composition, and especially true if bodies of comparable size are involved, which emphasizes the obliqueness of the collision. The author suggests that it is jetting during a Charon-forming collision (and not vaporization) that may account for Pluto-Charon's relatively large rock/ice ratio, should the C/O ratio of the solar nebula turn out too low to sufficiently raise the rock/ice ratio of outer solar nebula condensates by formation of non-condensable CO.

  20. A 1-D evolutionary model for icy satellites, applied to Enceladus

    NASA Astrophysics Data System (ADS)

    Prialnik, Dina; Malamud, Uri

    2015-11-01

    A 1-D long-term evolution code for icy satellites is presented, which couples multiple processes: water migration, geochemical reactions, water and silicate phase transitions, crystallization, compaction by self-gravity, and ablation. The code takes into account various energy sources: tidal heating, radiogenic heating, geochemical energy released by serpentinization or absorbed by mineral dehydration, gravitational energy, and insolation. It includes heat transport by conduction, convection, and advection.The code is applied to Enceladus, by guessing the initial conditions that would render a structure compatible with present-day observations, and adopting a homogeneous initial structure. Assuming that the satellite has been losing water continually along its evolution, it follows that it was formed as a more massive, more ice-rich and more porous object, and gradually transformed into its present day state, due to sustained tidal heating. Several initial compositions and evolution scenarios are considered, and the evolution is simulated for the age of the Solar System. The results corresponding to the present configuration are confronted with the available observational constraints. The present configuration is shown to be differentiated into a pure icy mantle, several tens of km thick, overlying a rocky core, composed of dehydrated rock in the central part and hydrated rock in the outer part. Such a differentiated structure is obtained not only for Enceladus, but for other medium size ice-rich bodies as well.Predictions for Enceladus are a higher rock/ice mass ratio than previously assumed, and a thinner ice mantle, compatible with recent estimates based on gravity field measurements. Although, obviously, the 1-D model cannot be used to explain local phenomena, it sheds light on the internal structure invoked in explanations of localized features and activities.

  1. Effect of ICI 118551 on bronchial beta-adrenoceptor function and exercise heart rate in normal man.

    PubMed Central

    Tattersfield, A E; Cragg, D J

    1983-01-01

    To determine whether the beta 2-selectivity of ICI 118551 extended to human airways, we measured bronchial beta-adrenoceptor blockade and the reduction in exercise heart rate in six normal subjects on different occasions after ingestion of ICI 118551 20 or 50 mg, propranolol 40 mg or placebo in random order. Bronchial beta-adrenoceptor blockade after each active drug was measured as the displacement of the airway dose-response curve to salbutamol and expressed as a dose ratio. Exercise heart rate was measured during the fifth minute of steady state exercise at 70% of the subject's maximum work load. The mean dose ratios for the salbutamol airway dose-response curves following ICI 118551 20 and 50 mg and propranolol 40 mg were 11, 55 and 48 respectively. The mean reductions in exercise heart rate for the three drugs were 0.6, 6.6 and 16.6% respectively. These results confirm that the beta 2-selectivity of ICI 118551 includes airway beta 2-adrenoceptors in man. PMID:6140938

  2. Organic synthesis via irradiation and warming of ice grains in the solar nebula.

    PubMed

    Ciesla, Fred J; Sandford, Scott A

    2012-04-27

    Complex organic compounds, including many important to life on Earth, are commonly found in meteoritic and cometary samples, though their origins remain a mystery. We examined whether such molecules could be produced within the solar nebula by tracking the dynamical evolution of ice grains in the nebula and recording the environments to which they were exposed. We found that icy grains originating in the outer disk, where temperatures were less than 30 kelvin, experienced ultraviolet irradiation exposures and thermal warming similar to that which has been shown to produce complex organics in laboratory experiments. These results imply that organic compounds are natural by-products of protoplanetary disk evolution and should be important ingredients in the formation of all planetary systems, including our own. PMID:22461502

  3. Organic Synthesis via Irradiation and Warming of Ice Grains in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Ciesla, Fred J.; Sanford, Scott A.

    2012-01-01

    Complex organic compounds, including many important to life on Earth, are commonly found in meteoritic and cometary samples, though their origins remain a mystery. We examined whether such molecules could be produced within the solar nebula by tracking the dynamical evolution of ice grains in the nebula and recording the environments they were exposed to. We found that icy grains originating in the outer disk, where temperatures were less than 30 K, experienced UV irradiation exposures and thermal warming similar to that which has been shown to produce complex organics in laboratory experiments. These results imply that organic compounds are natural byproducts of protoplanetary disk evolution and should be important ingredients in the formation of all planetary systems, including our own.

  4. Uterine blood flow responses to ICI 182 780 in ovariectomized oestradiol-17β-treated, intact follicular and pregnant sheep

    PubMed Central

    Magness, Ronald R; Phernetton, Terrance M; Gibson, Tiffini C; Chen, Dong-bao

    2005-01-01

    Oestrogen dramatically increases uterine blood flow (UBF) in ovariectomized (Ovx) ewes. Both the follicular phase and pregnancy are normal physiological states with elevated levels of circulating oestrogen. ICI 182 780 is a pure steroidal oestrogen receptor (ER) antagonist that blocks oestrogenic actions in oestrogen-responsive tissue. We hypothesized that an ER-mediated mechanism is responsible for in vivo rises in UBF in physiological states of high oestrogen. The purpose of the study was to examine the effect of an ER antagonist on exogenous and endogenous oestradiol-17β (E2β)-mediated elevations in UBF. Sheep were surgically instrumented with bilateral uterine artery blood flow transducers, and uterine and femoral artery catheters. Ovx animals (n = 8) were infused with vehicle (35% ethanol) or ICI 182 780 (0.1–3.0 μg min−1) into one uterine artery for 10 min before and 50 min after E2β was given (1 μg kg−1i.v. bolus) and UBF was recorded for an additional hour. Intact, cycling sheep were synchronized to the follicular phase using progesterone, prostaglandin F2α(PGF2α) and pregnant mare serum gonadotrophin (PMSG). When peri-ovulatory rises in UBF reached near peak levels, ICI 182 780 (1 or 2 μg (ml uterine blood flow)−1) was infused unilaterally (n = 4 sheep). Ewes in the last stages of pregnancy (late pregnant ewes) were also given ICI 182 780 (0.23–2.0 μg (ml uterine blood flow)−1; 60 min infusion) into one uterine artery (n = 8 sheep). In Ovx sheep, local infusion of ICI 182 780 did not alter systemic cardiovascular parameters, such as mean arterial blood pressure or heart rate; however, it maximally decreased ipsilateral, but not contralateral, UBF vasodilatory responses to exogenous E2β by ∼55–60% (P < 0.01). In two models of elevated endogenous E2β, local ICI 182 780 infusion inhibited the elevated UBF seen in follicular phase and late pregnant ewes in a time-dependent manner by ∼60% and 37%, respectively; ipsilateral

  5. Dust grain charging in a wake of other grains

    SciTech Connect

    Miloch, W. J.; Block, D.

    2012-12-15

    The charging of dust grain in the wake of another grains in sonic and supersonic collisionless plasma flows is studied by numerical simulations. We consider two grains aligned with the flow, as well as dust chains and multiple grain arrangements. It is found that the dust charge depends significantly on the flow speed, distance between the grains, and the grain arrangement. For two and three grains aligned, the charges on downstream grains depend linearly on the flow velocity and intergrain distance. The simulations are carried out with DiP3D, a three dimensional particle-in-cell code with both electrons and ions represented as numerical particles [W. J. Miloch et al., Phys. Plasmas 17, 103703 (2010)].

  6. THz time-domain spectroscopy of mixed CO2-CH3OH interstellar ice analogs.

    PubMed

    McGuire, Brett A; Ioppolo, Sergio; Allodi, Marco A; Blake, Geoffrey A

    2016-07-27

    The icy mantles of interstellar dust grains are the birthplaces of the primordial prebiotic molecular inventory that may eventually seed nascent solar systems and the planets and planetesimals that form therein. Here, we present a study of two of the most abundant species in these ices after water: carbon dioxide (CO2) and methanol (CH3OH), using TeraHertz (THz) time-domain spectroscopy and mid-infrared spectroscopy. We study pure and mixed-ices of these species, and demonstrate the power of the THz region of the spectrum to elucidate the long-range structure (i.e. crystalline versus amorphous) of the ice, the degree of segregation of these species within the ice, and the thermal history of the species within the ice. Finally, we comment on the utility of the THz transitions arising from these ices for use in astronomical observations of interstellar ices.

  7. Thermal analog device reduces machining errors

    NASA Technical Reports Server (NTRS)

    Mcclure, E. R.

    1972-01-01

    Thermal analog devices predict thermal expansion and contraction of machine structures subjected to various heat inputs. Analog devices correct positioning of machine tools to compensate for distortion of machine frame.

  8. Simple Electronic Analog of a Josephson Junction.

    ERIC Educational Resources Information Center

    Henry, R. W.; And Others

    1981-01-01

    Demonstrates that an electronic Josephson junction analog constructed from three integrated circuits plus an external reference oscillator can exhibit many of the circuit phenomena of a real Josephson junction. Includes computer and other applications of the analog. (Author/SK)

  9. Basic Electricity--a Novel Analogy.

    ERIC Educational Resources Information Center

    Grant, Richard

    1996-01-01

    Uses the analogy of water flow to introduce concepts in basic electricity. Presents a demonstration that uses this analogy to help students grasp the relationship between current, voltage, and resistance. (JRH)

  10. Coherent Backscattering Effect in Icy Satellites: Model, Cassini VIMS, and Ground-Based Near-Infrared Spectra

    NASA Astrophysics Data System (ADS)

    Pitman, Karly M.; Kolokolova, L.; Verbiscer, A. J.

    2013-10-01

    Compositional mapping of icy satellite surfaces is usually based on correlating spectral absorption band depths with the abundance of ice/non-ice species and/or particle size alone. However, absorption band depths and shapes also depend on observation geometry, specifically the solar phase angle α. The constructive interference of light that is responsible for the coherent backscattering effect (CBE) should significantly alter the interpretation of spacecraft spectra obtained at α < 2 degrees in particular (Helfenstein et al. 1997 Icarus 128, 2-14), but the magnitude of the CBE on band depth has not yet been quantified or studied in detail. In this work, we explore the relationship between α, spectral band depth and shape caused by CBE for both Cassini Visual & Infrared Mapping Spectrometer (VIMS) and ground-based near-infrared observations of bright and dark satellites. We report numerical CBE modeling performed using the publicly available multisphere T-matrix (MSTM) computer code to simulate the change in absorption bands with the solar phase angle seen in the spectra of icy bodies. We compare these models to Cassini VIMS extracted I/F spectra for selected icy satellites (e.g., Rhea, Iapetus, Enceladus) as well as ground-based λ = 0.9 - 2.4 μm spectra of Tethys, Dione, Iapetus, Rhea, and Enceladus acquired using Triplespec (R=3000) at Apache Point Observatory, New Mexico. Such results ultimately place limits on the size and packing fraction of icy satellite regolith particles and aid in interpretations of the structure, composition, and evolution of icy satellites. This work is supported by NASA’s Outer Planets Research program (NNX12AM76G; PI Pitman), Planetary Astronomy program (NNX09AD06G; PI Verbiscer), and NASA’s Advanced Supercomputing Division. Calibrated Cassini VIMS data cubes appear courtesy of B. J. Buratti and the Cassini VIMS team.

  11. Hegel, Analogy, and Extraterrestrial Life

    NASA Astrophysics Data System (ADS)

    Ross, Joseph T.

    Georg Wilhelm Friedrich Hegel rejected the possibility of life outside of the Earth, according to several scholars of extraterrestrial life. Their position is that the solar system and specifically the planet Earth is the unique place in the cosmos where life, intelligence, and rationality can be. The present study offers a very different interpretation of Hegel's statements about the place of life on Earth by suggesting that, although Hegel did not believe that there were other solar systems where rationality is present, he did in fact suggest that planets in general, not the Earth exclusively, have life and possibly also intelligent inhabitants. Analogical syllogisms are superficial, according to Hegel, insofar as they try to conclude that there is life on the Moon even though there is no evidence of water or air on that body. Similar analogical arguments for life on the Sun made by Johann Elert Bode and William Herschel were considered by Hegel to be equally superficial. Analogical arguments were also used by astronomers and philosophers to suggest that life could be found on other planets in our solar system. Hegel offers no critique of analogical arguments for life on other planets, and in fact Hegel believed that life would be found on other planets. Planets, after all, have meteorological processes and therefore are "living" according to his philosophical account, unlike the Moon, Sun, and comets. Whereas William Herschel was already finding great similarities between the Sun and the stars and had extended these similarities to the property of having planets or being themselves inhabitable worlds, Hegel rejected this analogy. The Sun and stars have some properties in common, but for Hegel one cannot conclude from these similarities to the necessity that stars have planets. Hegel's arguments against the presence of life in the solar system were not directed against other planets, but rather against the Sun and Moon, both of which he said have a different

  12. Grain rotation mediated by grain boundary dislocations in nanocrystalline platinum

    PubMed Central

    Wang, Lihua; Teng, Jiao; Liu, Pan; Hirata, Akihiko; Ma, En; Zhang, Ze; Chen, Mingwei; Han, Xiaodong

    2014-01-01

    Grain rotation is a well-known phenomenon during high (homologous) temperature deformation and recrystallization of polycrystalline materials. In recent years, grain rotation has also been proposed as a plasticity mechanism at low temperatures (for example, room temperature for metals), especially for nanocrystalline grains with diameter d less than ~15 nm. Here, in tensile-loaded Pt thin films under a high-resolution transmission electron microscope, we show that the plasticity mechanism transitions from cross-grain dislocation glide in larger grains (d>6 nm) to a mode of coordinated rotation of multiple grains for grains with d<6 nm. The mechanism underlying the grain rotation is dislocation climb at the grain boundary, rather than grain boundary sliding or diffusional creep. Our atomic-scale images demonstrate directly that the evolution of the misorientation angle between neighbouring grains can be quantitatively accounted for by the change of the Frank–Bilby dislocation content in the grain boundary. PMID:25030380

  13. Science Teachers' Analogical Reasoning

    ERIC Educational Resources Information Center

    Mozzer, Nilmara Braga; Justi, Rosária

    2013-01-01

    Analogies can play a relevant role in students' learning. However, for the effective use of analogies, teachers should not only have a well-prepared repertoire of validated analogies, which could serve as bridges between the students' prior knowledge and the scientific knowledge they desire them to understand, but also know how to…

  14. History of Presolar Grains

    NASA Technical Reports Server (NTRS)

    Bernatowicz, Thomas J.

    2005-01-01

    Papers on the History of Presolar Grains. This has been a very productive period in which much of the laboratory work conducted in the previous year and during this funding cycle were brought to completion. In the last year we have published or submitted for peer review 4 research papers, 4 review papers, and 11 abstracts in research areas supported under this grant. Brief synopses of the results of the research papers are presented, followed by short summaries of the topics discussed in the review papers. Several areas of research are of course being actively pursued, and the appended list of abstracts gives citations to this ongoing work. In a paper submitted to the Astrophysical Journal, the results of an investigation into the physical conditions in the mass outflows of asymptotic giant branch (AGB) carbon stars that are required for the formation of micron-sized presolar graphite grains, with and without previously formed internal crystals of titanium carbide (TIC) are reported.

  15. FINE GRAIN NUCLEAR EMULSION

    DOEpatents

    Oliver, A.J.

    1962-04-24

    A method of preparing nuclear track emulsions having mean grain sizes less than 0.1 microns is described. The method comprises adding silver nitrate to potassium bromide at a rate at which there is always a constant, critical excess of silver ions. For minimum size grains, the silver ion concentration is maintained at the critical level of about pAg 2.0 to 5.0 during prectpitation, pAg being defined as the negative logarithm of the silver ion concentration. It is preferred to eliminate the excess silver at the conclusion of the precipitation steps. The emulsion is processed by methods in all other respects generally similar to the methods of the prior art. (AEC)

  16. Isotropic Monte Carlo Grain Growth

    2013-04-25

    IMCGG performs Monte Carlo simulations of normal grain growth in metals on a hexagonal grid in two dimensions with periodic boundary conditions. This may be performed with either an isotropic or a misorientation - and incliantion-dependent grain boundary energy.

  17. Rumen degradation and availability of various amounts of liquid methionine hydroxy analog in lactating dairy cows.

    PubMed

    Koenig, K M; Rode, L M; Knight, C D; Vázquez-Añón, M

    2002-04-01

    Ruminal escape of various amounts of methionine hydroxy analog [D,L-2-hydroxy-4-(methylthio)-butanoic acid (HMB)] was measured in an experiment designed as a 4 x 4 Latin square using four lactating dairy cows with cannula in the rumen and duodenum. The cows were fed a diet composed of corn silage, alfalfa haylage, rolled barley grain, canola meal, and blood meal, three times per day. The cows were fed the liquid analog each day for 1 wk before the experiment was started. On the day of the experiment, each cow received an intraruminal bolus dose of 0, 25, or 50 g of the liquid analog (Alimet feed supplement, 88% HMB) or 51.2 g of a dry calcium salt of the analog (86% HMB; MHA) mixed with 0.5 kg of ground barley grain. A liquid phase marker (Co-EDTA) was administered as a bolus dose into the rumen at the time of administration of the methionine hydroxy analogs. Rumen and duodenal contents, and blood serum were collected at 0, 1, 3, 6, 9, 12, and 24 h relative to the time of dosing. Rumen and duodenal samples were analyzed for Co and HMB, and serum was analyzed for free methionine. Fractional rate constants for the passage of the liquid marker (k(p)) and the decline of HMB concentration in the rumen (k(rHMB)) were determined by nonlinear regression. Liquid passage from the rumen was similar among the four analog treatments (0.136 +/- 0.012/h; mean +/- SEM). Ruminal escape of HMB as a percentage of the dose (100% x k(p)/k(rHMB)) did not differ between cows receiving 25, 50, and 51.2 g of the methionine analogs (42.5, 41.0, and 34.9 +/- 9.0%, respectively) and averaged 39.5%. Duodenal appearance of HMB as a percentage also did not differ between cows receiving 25, 50, and 51.2 g of the methionine analogs (16.2, 26.8, and 22.7%, respectively) and averaged 22%. Omasal absorption of HMB was variable ranging from 12.3 to 26.3% and averaged 17.6%. Serum methionine concentration peaked at 3 and 6 h after dosing and increased in proportion to the amount of the analog

  18. Tírez Lake as a Terrestrial Analog of Europa

    NASA Astrophysics Data System (ADS)

    Prieto-Ballesteros, Olga; Rodríguez, Nuria; Kargel, Jeffrey S.; Kessler, Carola González; Amils, Ricardo; Remolar, David Fernández

    2003-12-01

    Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa's ocean. The proposal is based on the comparison of the hydrogeochemistry of Tírez Lake with the geochemical features of the alteration mineralogy of meteoritic precursors and with Galileo's Near Infrared Mapping Spectrometer data on Europa's surface. To validate the astrobiological potential of Tírez Lake as an analog of Europa, different hydrogeochemical, mineral, and microbial analyses were performed. Experimental and theoretical modeling helped to understand the crystallization pathways that may occur in Europa's crust. Calculations about the oxidation state of the hypothetical Europan ocean were estimated to support the sulfate-rich neutral liquid model as the origin of Europa's observed hydrated minerals and to facilitate their comparison with Tírez's hydrogeochemistry. Hydrogeochemical and mineralogical analyses showed that Tírez waters corresponded to Mg-Na-SO4-Cl brines with epsomite, hexahydrite, and halite as end members. A preliminary microbial ecology characterization identified two different microbial domains: a photosynthetically sustained community represented by planktonic/benthonic forms and microbial mat communities, and a subsurficial anaerobic realm in which chemolithotrophy predominates. Fluorescence in situ hybridization has been used to characterize the prokaryotic diversity of the system. The subsurficial community seemed to be dominated by sulfate-reducing bacteria and methanogens. Frozen Tírez brines were analyzed by Fourier-transform infrared techniques providing spectra similar to those reported previously using pure components and to the Galileo spectral data. Calorimetric measurements of Tírez brines showed pathways and phase metastability for magnesium sulfate and sodium chloride crystallization that may aid in understanding the processes involved in the formation of Europa's icy crust. The use of fluorescence hybridization techniques for

  19. Tírez lake as a terrestrial analog of Europa.

    PubMed

    Prieto-Ballesteros, Olga; Rodríguez, Nuria; Kargel, Jeffrey S; Kessler, Carola González; Amils, Ricardo; Remolar, David Fernández

    2003-01-01

    Tírez Lake (La Mancha, central Spain) is proposed as a terrestrial analogue of Europa's ocean. The proposal is based on the comparison of the hydrogeochemistry of Tírez Lake with the geochemical features of the alteration mineralogy of meteoritic precursors and with Galileo's Near Infrared Mapping Spectrometer data on Europa's surface. To validate the astrobiological potential of Tírez Lake as an analog of Europa, different hydrogeochemical, mineral, and microbial analyses were performed. Experimental and theoretical modeling helped to understand the crystallization pathways that may occur in Europa's crust. Calculations about the oxidation state of the hypothetical Europan ocean were estimated to support the sulfate-rich neutral liquid model as the origin of Europa's observed hydrated minerals and to facilitate their comparison with Tírez's hydrogeochemistry. Hydrogeochemical and mineralogical analyses showed that Tírez waters corresponded to Mg-Na-SO(4)-Cl brines with epsomite, hexahydrite, and halite as end members. A preliminary microbial ecology characterization identified two different microbial domains: a photosynthetically sustained community represented by planktonic/benthonic forms and microbial mat communities, and a subsurficial anaerobic realm in which chemolithotrophy predominates. Fluorescence in situ hybridization has been used to characterize the prokaryotic diversity of the system. The subsurficial community seemed to be dominated by sulfate-reducing bacteria and methanogens. Frozen Tírez brines were analyzed by Fourier-transform infrared techniques providing spectra similar to those reported previously using pure components and to the Galileo spectral data. Calorimetric measurements of Tírez brines showed pathways and phase metastability for magnesium sulfate and sodium chloride crystallization that may aid in understanding the processes involved in the formation of Europa's icy crust. The use of fluorescence hybridization techniques for

  20. Storing Peanuts in Grain Bags

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was executed to determine the potential of storing farmers stock peanuts and shelled peanuts for crushing in hermetically sealed grain bags. The objectives of the study were to evaluate equipment for loading and unloading the grain bags, the capacity of the grain bags, and the changes in qu...

  1. Grain-grain interaction in stationary dusty plasma

    SciTech Connect

    Lampe, Martin; Joyce, Glenn

    2015-02-15

    We present a particle-in-cell simulation study of the steady-state interaction between two stationary dust grains in uniform stationary plasma. Both the electrostatic force and the shadowing force on the grains are calculated explicitly. The electrostatic force is always repulsive. For two grains of the same size, the electrostatic force is very nearly equal to the shielded electric field due to a single isolated grain, acting on the charge of the other grain. For two grains of unequal size, the electrostatic force on the smaller grain is smaller than the isolated-grain field, and the force on the larger grain is larger than the isolated-grain field. In all cases, the attractive shadowing force exceeds the repulsive electrostatic force when the grain separation d is greater than an equilibrium separation d{sub 0}. d{sub 0} is found to be between 6λ{sub D} and 9λ{sub D} in all cases. The binding energy is estimated to be between 19 eV and 900 eV for various cases.

  2. Electrical Evolution of a Dust Plume from a Low Energy Lunar Impact: A Model Analog to LCROSS

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Stubbs, T. J.; Jackson, T. L.; Colaprete, A.; Heldmann, J. L.; Schultz, P. H.; Killen, R. M.; Delory, G. T.; Halekas, J. S.; Marshall, J. R.; Zimmerman, M. I.; Collier, M. R.; Vondrak, R. R.

    2011-01-01

    A Monte Carlo test particle model was developed that simulates the charge evolution of micron and sub-micron sized dust grains ejected upon low-energy impact of a moderate-size object onto a lunar polar crater floor. Our analog is the LCROSS impact into Cabeus crater. Our primary objective is to model grain discharging as the plume propagates upwards from shadowed crater into sunlight.

  3. Special Grain Boundaries in Ultrafine-Grained Tungsten.

    PubMed

    Dudka, O V; Ksenofontov, V A; Sadanov, E V; Starchenko, I V; Mazilova, T I; Mikhailovskij, I M

    2016-12-01

    Field ion microscopy and computer simulation were used for the study of an atomic structure high-angle grain boundary in hard-drawn ultrafine-grained tungsten wire. These boundaries with special misorientations are beyond the scope of the coincident site lattice model. It was demonstrated that the special non-coincident grain boundaries are the plane-matching boundaries, and rigid-body displacements of adjacent nanograins are normal to the <110> misorientation axis. The vectors of rigid-body translations of grains are described by broad asymmetric statistical distribution. Mathematical modeling showed that special incommensurate boundaries with one grain oriented along the {211} plane have comparatively high cohesive energies. The grain-boundary dislocations ½<110> were revealed and studied at the line of local mismatch of {110} atomic planes of adjacent grains. PMID:27416905

  4. Special Grain Boundaries in Ultrafine-Grained Tungsten

    NASA Astrophysics Data System (ADS)

    Dudka, O. V.; Ksenofontov, V. A.; Sadanov, E. V.; Starchenko, I. V.; Mazilova, T. I.; Mikhailovskij, I. M.

    2016-07-01

    Field ion microscopy and computer simulation were used for the study of an atomic structure high-angle grain boundary in hard-drawn ultrafine-grained tungsten wire. These boundaries with special misorientations are beyond the scope of the coincident site lattice model. It was demonstrated that the special non-coincident grain boundaries are the plane-matching boundaries, and rigid-body displacements of adjacent nanograins are normal to the <110> misorientation axis. The vectors of rigid-body translations of grains are described by broad asymmetric statistical distribution. Mathematical modeling showed that special incommensurate boundaries with one grain oriented along the {211} plane have comparatively high cohesive energies. The grain-boundary dislocations ½<110> were revealed and studied at the line of local mismatch of {110} atomic planes of adjacent grains.

  5. Visual homing in analog hardware.

    PubMed

    Möller, R

    1999-10-01

    Insects of several species rely on visual landmarks for returning to important locations in their environment. The "average landmark vector model" is a parsimonious model which reproduces some aspects of the visual homing behavior of bees and ants. To gain insights in the structure and complexity of the neural apparatus that might underly the navigational capabilities of these animals, the average landmark vector model was implemented in analog hardware and used to control a mobile robot. The experiments demonstrate that the apparently complex task of visual homing might be realized by simple and mostly peripheral neural circuits in insect brains.

  6. Classical analog of quantum phase

    SciTech Connect

    Ord, G.N.

    1992-07-01

    A modified version of the Feynman relativistic chessboard model (FCM) is investigated in which the paths involved are spirals in the space-time. Portions of the paths in which the particle`s proper time is reversed are interpreted in terms of antiparticles. With this intepretation the particle-antiparticle field produced by such trajectories provides a classical analog of the phase associated with particle paths in the unmodified FCM. It is shwon that in the nonrelativistic limit the resulting kernel is the correct Dirac propagator and that particle-antiparticle symmetry is in this case responsible for quantum interference. 7 refs., 3 figs.

  7. Comet Grains: Their IR Emission and Their Relation to ISM Grains

    NASA Technical Reports Server (NTRS)

    Wooden, Diane H.; DeVincenzi, Donald (Technical Monitor)

    2002-01-01

    deduced abundance of crystalline silicates in comet dust. An insufficient source of ISM Mg-rich crystals leads to the inference that most Mg-rich crystals in comets are primitive grains processed in the early solar nebula prior to their incorporation into comets. Mg-rich crystals may condense in the hot (approx. 1450 K), inner zones of the early solar nebula and then travel large radial distances out to the comet-forming zone. On the other hand, Mg-rich silicate crystals may be ISM amorphous silicates annealed at approx. 1000 K and radially distributed out to the comet-forming zone or annealed in nebular shocks at approx. 5 - 10 AU. Determining the relative abundance of amorphous and crystalline silicates in comets probes the relative contributions of ISM grains and primitive grains to small, icy bodies in the solar system. The life cycle of dust from its stardust origins through the ISM to its incorporation into comets is discussed.

  8. Identification of Organics in Ice Grains from Enceladus

    NASA Astrophysics Data System (ADS)

    Khawaja, N.; Postberg, F.; Reviol, R.; Nölle, L.; Klenner, F.; Srama, R.

    2015-12-01

    The Cosmic Dust Analyzer (CDA) aboard the Cassini spacecraft performs in-situ measurements of the chemical composition of icy dust grains impinging onto the target surface. The instrument recorded cationic Time-of-Flight (ToF) mass spectra of organic-bearing ice grains emitted from Enceladus at different impact velocities causing different molecular fragmentation patterns [1,2]. Here we present a detailed analysis of these spectra (Type-2) to identify the composition of organic material embedded in Enceladus ice grains. The organic compounds display a great compositional diversity, which indicates varying contributions of several organic species. The spectra analysis is supported by a large-scale laboratory ground campaign yielding a library of analogue spectra for organic material embedded in a water ice matrix. To mimic the identified pattern of cationic fragments in organic enriched spectra we use a laboratory setup: Infrared Free Liquid MALDI ToF Mass Spectrometer (IR-FL-MALDI-ToF-MS). An infrared laser is used to disperse a liquid micro-beam of a water-solution to get cationic fragments. The laser energy is adjusted to simulate different impact velocities of ice particles on CDA [3]. So far we have identified characteristic fragment patterns of at least three classes of organic molecules: (i) aromatic species, (ii) amines, and (iii) carbonyl group species. (i) ice grains containing aromatic species are identified by a series of characteristic aromatic fragment cations (ii) ice grains containing amines are identified by a pronounced ammonium cation and (iii) ice grains containing carbonyl compounds are specified by a characteristic acylium cation in conjunction with certain others mass lines. Besides aromatic, amine and carbonyl species, Type-2 spectra also show contributions from other, yet un-specified, organic species. Typically, fragment cations of aromatic compounds are stable at impact velocities up-to 15km/s whereas cations of amines and carbonyl species

  9. Grain-size-induced weakening of H2O ices I and II and associated anisotropic recrystallization

    USGS Publications Warehouse

    Stern, L.A.; Durham, W.B.; Kirby, S.H.

    1997-01-01

    Grain-size-dependent flow mechanisms tend to be favored over dislocation creep at low differential stresses and can potentially influence the rheology of low-stress, low-strain rate environments such as those of planetary interiors. We experimentally investigated the effect of reduced grain size on the solid-state flow of water ice I, a principal component of the asthenospheres of many icy moons of the outer solar system, using techniques new to studies of this deformation regime. We fabricated fully dense ice samples of approximate grain size 2 ?? 1 ??m by transforming "standard" ice I samples of 250 ?? 50 ??m grain size to the higher-pressure phase ice II, deforming them in the ice II field, and then rapidly releasing the pressure deep into the ice I stability field. At T ??? 200 K, slow growth and rapid nucleation of ice I combine to produce a fine grain size. Constant-strain rate deformation tests conducted on these samples show that deformation rates are less stress sensitive than for standard ice and that the fine-grained material is markedly weaker than standard ice, particularly during the transient approach to steady state deformation. Scanning electron microscope examination of the deformed fine-grained ice samples revealed an unusual microstructure dominated by platelike grains that grew normal to the compression direction, with c axes preferentially oriented parallel to compression. In samples tested at T ??? 220 K the elongation of the grains is so pronounced that the samples appear finely banded, with aspect ratios of grains approaching 50:1. The anisotropic growth of these crystallographically oriented neoblasts likely contributes to progressive work hardening observed during the transient stage of deformation. We have also documented remarkably similar microstructural development and weak mechanical behavior in fine-grained ice samples partially transformed and deformed in the ice II field.

  10. New Cassini RADAR Results for Iapetus and Saturn's Other Icy Satellites

    NASA Astrophysics Data System (ADS)

    Ostro, S.; West, R.; Wye, L.; Janssen, M.; Paillou, P.; Stiles, B.; Kelleher, K.; Anderson, Y.; Boehmer, R.; Callahan, P.; Gim, Y.; Hamilton, G.; Johnson, W.; Veeramachaneni, C.; Cassini RADAR Team

    2007-12-01

    During the past two years, radar tracks on the icy satellites have more than doubled the number of observations reported by Ostro et al. (2006, Icarus 183, 479-490). Our scatterometry has now yielded estimates of the 2.2-cm- wavelength radar albedo in the same linear (SL) polarization as transmitted for Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus, and Phoebe. Our tracks have sampled widely separated subradar locations on most of the satellites, in some cases using beams comparable to or larger than the target's disc and in others using beams significantly smaller than the disc. Hence we can begin to assess the dispersion in these objects' distributions of radar reflectivity. The 2.2-cm SL radar albedo varies by at least several tens of percent on at least Dione, Rhea, Enceladus, and Iapetus. For Enceladus, a scatterometric observation centered on (29 S, 243 W) with a beamwidth of 1.2 Enceladus diameters gives the largest disc-integrated SL radar albedo obtained at any wavelength for any solar system object (including Europa), probably because of the extreme purity of at least the uppermost few decimeters of the water-ice regolith on much of the hemisphere facing the radar. For Iapetus, multi-beam, disc-resolved measurements disclose that the disparity in the 2.2-cm SL radar albedos between the optically bright and dark terrains is greater than that inferred by Ostro et al. (2006). During the Iapetus 49 flyby shortly after this meeting's abstract deadline, radar observations will include SAR imaging with 2-to-12-km surface resolution covering much of the visible disc, using beam sizes of about 120 km (less than one tenth of an Iapetus diameter), plus a short altimetric measurement with 35-m range resolution. The radar imaging will be mostly of the optically dark terrain and will include tracks across the equatorial ridge and the largest impact structures in Cassini Regio. The Iapetus SAR images will be the first of an icy satellite for which high

  11. Tectonics of Icy Moons: A Tale of Oceans and Orbital Dynamics

    NASA Astrophysics Data System (ADS)

    Kattenhorn, Simon

    2010-05-01

    Icy moons of the outer solar system commonly experience eccentric orbits that impart daily tidal stresses to the outer ice layer. Depending on the orbital dynamics and configuration of the moons and their host planets, these stresses may or may not be sufficiently large to deform the ice layer. Although the stresses are typically very small, many icy moons exhibit pervasively tectonized surfaces, replete with fractures, faults, and significant topography (e.g., Europa, Ganymede, Enceladus, Dione, Titan, Miranda, Ariel, Titania, Triton). Deformation may be driven by various means (e.g., orbital recession, polar wander, ice shell thickening), but tidal deformation is particularly important and is enhanced if an outer ice layer is decoupled from an underlying liquid ocean. The tidal response of the ocean creates tidal bulges in the ice layer that oscillate longitudinally and in amplitude during the orbital period. The resultant diurnal tidal stress field (perhaps 10s of kPa) rotates throughout the orbit. Any fractures growing in this time frame should thus be curved (e.g., Europa's cycloidal cracks, which have been cited as the smoking gun for a subsurface ocean). Long lineaments should accumulate strike-slip offsets in such a stress field, as occurs on Europa and perhaps Enceladus. The progressive development of ice ridges to either side of central cracks may result from this shearing process. A decoupled ice layer also permits faster than synchronous rotation of the ice layer, which may allow several MPa of stress to accrue, perhaps explaining long lineaments on Europa. It is unclear if Europa continues to be tectonically active, especially given apparent ice shell thickening that would have muted the tidal response through time. Nonetheless, subtle troughs across Europa's surface crosscut all other features and may indicate some degree of ongoing activity. In contrast, active tectonics on Enceladus is implied by ongoing geyser-like eruptions of water-ice from

  12. Very High Resolution Image of Icy Cliffs on Europa and Similar Scales on Earth (Providence, RI)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The top image is a very high resolution view of the Conamara Chaos region on Jupiter's moon Europa, showing an area where icy plates have been broken apart and moved around laterally. The top of this image is dominated by corrugated plateaus ending in icy cliffs over a hundred meters (a few hundred feet) high. Debris piled at the base of the cliffs. The bottom image is an aerial photograph of downtown Providence, Rhode Island at the same scale. The bright white circular feature in the top center of the Providence image is an indoor hockey rink, and one can find many craters in the Europa image about the same size. Blocks of debris which have fallen from the cliffs on the Europa image are about the same size as houses seen in the Providence image, and the largest blocks are almost as large as the Rhode Island state capitol building (large white building in upper left of Providence image). A fracture that runs horizontally across the center of the Europa image is about the same width as the freeway which runs along the bottom of the Providence image.

    North is to the top right of the Europa image, and the sun illuminates the surface from the east. The Europa image is centered at approximately 9 degrees north latitude and 274 degrees west longitude. The images each cover an area approximately 1.7 kilometers by 4 kilometers (1 mile by 2.5 miles). The resolution is 9 meters (30 feet) per picture element. The Europa image was taken on December 16, 1997 at a range of 900 kilometers (540 miles) by the solid state imaging system on NASA's Galileo spacecraft.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/ galileo.

  13. Theoretical studies of the radar properties of the icy Galilean moons of Jupiter

    NASA Technical Reports Server (NTRS)

    Eshleman, Von R.

    1993-01-01

    The icy Galilean satellites of Jupiter - Europa, Ganymede, and Callisto - have unusual radar scattering properties compared with those of the terrestrial planets or Earth's Moon. There are three main features of the data that distinguish these targets: (1) the radar cross-section normalized by the geometrical cross-section is an order of magnitude larger than that of any terrestrial planet; (2) the reflected power is almost evenly distributed between two orthogonal polarizations with more power being returned in the same circular polarization as was transmitted whereas virtually all of the power returned from the terrestrial planets is contained in the opposite circular polarization to the one that was transmitted; and (3) the echo power spectra have a broad shape indicating a nearly uniformly radar-bright surface in contrast to the spectra from the terrestrial planets that contain a strong quasi-specular component from the vicinity of the sub-radar point and very little reflected power from the rest of the surface. The normalized radar cross-sections decrease as the areal water ice coverage decreases from Europa to Ganymede to Callisto. Recently, radar echoes from the polar caps of Mars and Mercury, and from Saturn's satellite Titan imply similarly strong cross-sections and have classically unexpected polarization properties and it is also thought that this is due to the presence of ice on the surface. A model called the radar glory model is analyzed and it is shown that the main features of the radar echoes calculated from this model agree well with the observations from all three icy Galilean satellites. This model involves long radar paths in the ice below the surface and special structures in which the refractive index decreases abruptly at a hemispherical boundary. It is not known whether such structures exist or how they could be created, but possible scenarios can be imagined such as the formation of an impact crater followed by deposition of a frost layer

  14. Swash mark and grain flow

    USGS Publications Warehouse

    Sallenger,, Asbury H.

    1981-01-01

    Swash marks composed entirely of coarse sand are commonly found on coarse-sand beaches. These swash marks are 10 to 30 centimeters in width and a few millimeters to one centimeter in height. Previous observations, mostly on finer-sand beaches, indicate swash marks are seldom over a few millimeters in height and are commonly composed of material readily floated by surface tension (e.g., mica flakes and shell fragments). Swash marks composed of coarse sand have both fining seaward and fining with depth trends in grain size. Apparently, the leading margin of a wave upwash drives a highly concentrated flow of grains in which both grain size and grain velocity decrease with depth. Therefore, large grains are transported at greater velocities than are smaller grains. Thus, at the maximum advance of an upwash, a swash mark is deposited which has the observed fining seaward and fining with depth trends in grain size.

  15. Icy satellites of Saturn: disk-integrated observations of the brightness opposition surge at low phase angles

    NASA Astrophysics Data System (ADS)

    Kulyk, I.; Jockers, K.

    2007-08-01

    The surfaces of most atmosphereless bodies exhibit two interesting optical phenomena at small phase angles, namely a strong brightness increase and negative values of the degree of linear polarization. Of particular interest is the appearance a nonlinear growth of the surface brightness and a second narrow minimum of polarization at phase angles less than 1-3°. These features of brightness and polarization in the narrow phase angle range near opposition are called the photometric and polarimetric opposition effects. These phenomena have attracted increased attention from the perspective of theories of light scattering in random media and their application to the determination of properties of the upper optically active regolith layers on the atmosphereless bodies. However, up to now photometric and especially polarimetric observations conducted at small phase angles are rare. In order to enlarge the amount of available observational data we have conducted photopolarimetric observations of the major icy Saturnian satellites. The observations were performed at the 2m-telescope of the Bulgarian National Observatory with the Two-Channel Focal Reducer of the Bulgarian Academy of Sciences built at the Max-Planck-Institute for Solar System Science. This instrument incorporates a two-channel imaging polarimeter which can be used in coronagraph setup. The light of Saturn and its rings is almost fully absorbed by a black glass and its diffraction pattern is eliminated by a Lyot stop. The photopolarimeter records intensity and degree of polarization of the satellites in two colors simultaneously. In this study, we present the first results of the disk-integrated photometry of Enceladus, Tethys, Dione, and Rhea in the red (center wavelength 694 nm, FWHM 79 nm) and near-infrared (center wavelength 888.5 nm, FWHM 29 nm, methane absorption band) spectral bands at phase angles between 5.6° and 0.01°. The resulting magnitudes can be represented as a sum of two terms, one

  16. Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on boardRosetta

    NASA Astrophysics Data System (ADS)

    Gicquel, A.; Vincent, J.-B.; Agarwal, J.; A'Hearn, M. F.; Bertini, I.; Bodewits, D.; Sierks, H.; Lin, Z.-Y.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Barucci, M. A.; Bertaux, J.-L.; Besse, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; Deller, J.; De Cecco, M.; Frattin, E.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann, M.; Hu, X.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez; Lowry, S.; Marzari, F.; Masoumzadeh, N.; Massironi, M.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Pommerol, A.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.

    2016-11-01

    Beginning in March 2014, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analyzed the dust monitoring observations shortly after the southern vernal equinox on May 30 and 31, 2015 with the WAC at the heliocentric distance Rh = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this article was that through the sublimation of the aggregates of dirty grains (radius a between 5 microm and 50 microm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data we needed to inject a number of aggregates between 8.5 x $10^{13}$ and 8.5 x $10^{10}$ for a = 5 microm and 50 microm respectively, or an initial mass of $H_2O$ ice around 22kg.

  17. Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras onboard Rosetta.

    NASA Astrophysics Data System (ADS)

    Gicquel, A.; Vincent, J.-B.; Agarwal, J.; A'Hearn, M. F.; Bertini, I.; Bodewits, D.; Sierks, H.; Lin, Z.-Y.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Barucci, M. A.; Bertaux, J.-L.; Besse, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; Deller, J.; De Cecco, M.; Frattin, E.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann, M.; Hu, X.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez; Lowry, S.; Marzari, F.; Masoumzadeh, N.; Massironi, M.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Pommerol, A.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.

    2016-08-01

    Beginning in March 2014, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analyzed the dust monitoring observations shortly after the southern vernal equinox on May 30 and 31, 2015 with the WAC at the heliocentric distance R_h = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this article was that through the sublimation of the aggregates of dirty grains (radius a between 5μm and 50μm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data we needed to inject a number of aggregates between 8.5 × 1013 and 8.5 × 1010 for a = 5μm and 50μm respectively, or an initial mass of H_2O ice around 22kg.

  18. Non-water-ice constituents in the surface material of the icy Galilean satellites from the Galileo near-infrared mapping spectrometer investigation

    USGS Publications Warehouse

    McCord, T.B.; Hansen, G.B.; Clark, R.N.; Martin, P.D.; Hibbitts, C.A.; Fanale, F.P.; Granahan, J.C.; Segura, M.; Matson, D.L.; Johnson, T.V.; Carlson, R.W.; Smythe, W.D.; Danielson, G.E.

    1998-01-01

    We present evidence for several non-ice constituents in the surface material of the icy Galilean satellites, using the reflectance spectra returned by the Galileo near infrared mapping spectrometer (NIMS) experiment. Five new absorption features are described at 3.4, 3.88, 4.05, 4.25, and 4.57 ??m for Callisto and Ganymede, and some seem to exist for Europa as well. The four absorption bands strong enough to be mapped on Callisto and Ganymede are each spatially distributed in different ways, indicating different materials are responsible for each absorption. The spatial distributions are correlated at the local level in complex ways with surface features and in some cases show global patterns. Suggested candidate spectrally active groups, perhaps within larger molecules, producing the five absorptions include C-H, S-H, SO2, CO2, and C???N. Organic material like tholins are candidates for the 4.57- and 3.4-??m features. We suggest, based on spectroscopic evidence, that CO2 is present as a form which does not allow rotational modes and that SO2 is present neither as a frost nor a free gas. The CO2, SO2, and perhaps cyanogen (4.57 ??m) may be present as very small collections of molecules within the crystal structure, perhaps following models for radiation damage and/or for comet and interstellar grain formation at low temperatures. Some of the dark material on these surfaces may be created by radiation damage of the CO2 and other carbon-bearing species and the formation of graphite. These spectra suggest a complex chemistry within the surface materials and an important role for non-ice materials in the evolution of the satellite surfaces. Copyright 1998 by the American Geophysical Union.

  19. Lunar and Planetary Science XXXV: Presolar Grains

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Topics discussed include: Presolar Silicate Grains; Presolar Silicates from Primitivr Chondrites; Oxygen and Magnesium Isotopic Ratios of Presolar Spinel Grains; Study of Two New Presolar Grains from Bishunpur Ordinary Chondrite; Extinct Technetium in Presolar Grains; etc.

  20. Cosmic dust analog simulation in a microgravity environment: The STARDUST program

    NASA Technical Reports Server (NTRS)

    Ferguson, F.; Lilleleht, L. U.; Nuth, J.; Stephens, J. R.; Bussoletti, E.; Carotenuto, L.; Colangeli, L.; Dell'aversana, P.; Mele, F.; Mennella, V.

    1995-01-01

    We have undertaken a project called STARDUST which is a collaboration with Italian and American investigators. The goals of this program are to study the condensation and coagulation of refractory materials from the vapor and to study the properties of the resulting grains as analogs to cosmic dust particles. To reduce thermal convective currents and to develop valuable experience in designing an experiment for the Gas-Grain Simulation Facility aboard Space Station, Freedom we have built and flown a new chamber to study these processes under periods of microgravity available on NASA's KC-135 Research Aircraft. Preliminary results from flights with magnesium and zinc are discussed.