Science.gov

Sample records for main belt comets

  1. Are the main belt comets, comets?

    NASA Astrophysics Data System (ADS)

    Licandro, Javier; Campins, Humberto

    We present the visible spectrum of asteroid-comet transition object 133P/Elst-Pizarro (7968), the first member of the new population of objects called Main Belt Comets (Hsieh & Jewitt 2006). The spectrum was obtained with the 4.2m William Herschel Telescope at the “Roque de los Muchachos” observatory. The orbital elements of 133P place it within the Themis collisional family, but the observed cometary activity during it last 3 perihelion passages also suggest a possible origin in the trans-Neptunian belt or the Oort Cloud, the known sources of comets. We found a clear similarity between our spectrum of 133P and those of other members of the Themis family such as 62 Erato, and a strong contrast with those of cometary nuclei, such as 162P/Siding-Spring. This spectral comparison leads us to conclude that 133P is unlikely to have a cometary origin. This conclusion is strengthened by spectral similarities with activated near-Earth asteroid 3200 Phaethon, and suggest that there are activated asteroids in the near-Earth asteroid and main belt populations with similar surface properties.

  2. A binary main-belt comet.

    PubMed

    Agarwal, Jessica; Jewitt, David; Mutchler, Max; Weaver, Harold; Larson, Stephen

    2017-09-20

    Asteroids are primitive Solar System bodies that evolve both collisionally and through disruptions arising from rapid rotation. These processes can lead to the formation of binary asteroids and to the release of dust, both directly and, in some cases, through uncovering frozen volatiles. In a subset of the asteroids called main-belt comets, the sublimation of excavated volatiles causes transient comet-like activity. Torques exerted by sublimation measurably influence the spin rates of active comets and might lead to the splitting of bilobate comet nuclei. The kilometre-sized main-belt asteroid 288P (300163) showed activity for several months around its perihelion 2011 (ref. 11), suspected to be sustained by the sublimation of water ice and supported by rapid rotation, while at least one component rotates slowly with a period of 16 hours (ref. 14). The object 288P is part of a young family of at least 11 asteroids that formed from a precursor about 10 kilometres in diameter during a shattering collision 7.5 million years ago. Here we report that 288P is a binary main-belt comet. It is different from the known asteroid binaries in its combination of wide separation, near-equal component size, high eccentricity and comet-like activity. The observations also provide strong support for sublimation as the driver of activity in 288P and show that sublimation torques may play an important part in binary orbit evolution.

  3. A binary main-belt comet

    NASA Astrophysics Data System (ADS)

    Agarwal, Jessica; Jewitt, David; Mutchler, Max; Weaver, Harold; Larson, Stephen

    2017-09-01

    Asteroids are primitive Solar System bodies that evolve both collisionally and through disruptions arising from rapid rotation. These processes can lead to the formation of binary asteroids and to the release of dust, both directly and, in some cases, through uncovering frozen volatiles. In a subset of the asteroids called main-belt comets, the sublimation of excavated volatiles causes transient comet-like activity. Torques exerted by sublimation measurably influence the spin rates of active comets and might lead to the splitting of bilobate comet nuclei. The kilometre-sized main-belt asteroid 288P (300163) showed activity for several months around its perihelion 2011 (ref. 11), suspected to be sustained by the sublimation of water ice and supported by rapid rotation, while at least one component rotates slowly with a period of 16 hours (ref. 14). The object 288P is part of a young family of at least 11 asteroids that formed from a precursor about 10 kilometres in diameter during a shattering collision 7.5 million years ago. Here we report that 288P is a binary main-belt comet. It is different from the known asteroid binaries in its combination of wide separation, near-equal component size, high eccentricity and comet-like activity. The observations also provide strong support for sublimation as the driver of activity in 288P and show that sublimation torques may play an important part in binary orbit evolution.

  4. A population of comets in the main asteroid belt.

    PubMed

    Hsieh, Henry H; Jewitt, David

    2006-04-28

    Comets are icy bodies that sublimate and become active when close to the Sun. They are believed to originate in two cold reservoirs beyond the orbit of Neptune: the Kuiper Belt (equilibrium temperatures of approximately 40 kelvin) and the Oort Cloud (approximately 10 kelvin). We present optical data showing the existence of a population of comets originating in a third reservoir: the main asteroid belt. The main-belt comets are unlike the Kuiper Belt and Oort Cloud comets in that they likely formed where they currently reside and may be collisionally activated. The existence of the main-belt comets lends new support to the idea that main-belt objects could be a major source of terrestrial water.

  5. Assessing the Main-Belt Comet Population with Comet Hunters

    NASA Astrophysics Data System (ADS)

    Schwamb, Megan E.; Hsieh, Henry H.; Zhang, Zhi-Wei; Chen, Ying-Tung; Lintott, Chris; Wang, Shiang-Yu; Mishra, Ishan

    2017-01-01

    Cometary activity in the asteroid belt is a recent discovery. Evidence suggests recent collisions play a role excavating subsurface water ice in these Main Belt Comets (MBCs). MBCs may be an alternative source of Earth’s water. The properties and origins of the MBCs remain elusive. To date ~15 MBCs are known, but only with many tens to 100s of MBCs can we fully explore this new reservoir and its implications for the early Earth.Automated routines identify cometary objects by comparing the point spread functions (PSFs) of moving objects to background stars. This approach may miss cometary activity with low-level dust comae or trails that are too weak or extended to affect an object's near-nucleus PSF profile. Direct visual inspection of moving objects by survey team members can often catch such unusual objects, but such an approach is impractical for the largest surveys to date, and will only become more intractable with the next generation wide-field surveys.With the Internet, tens of thousands of people can be engaged in the scientific process. With this citizen science approach, the combined assessment of many non-experts often equals or rivals that of a trained expert and in many cases outperforms automated algorithms. The Comet Hunters (http://www.comethunters.org) project enlists the public to search for MBCs in data from the Hyper Suprime-Cam (HSC) wide survey. HSC is to date the largest field-of-view camera (covering a 1.5 degree diameter circle on sky) on a 8-10-m class telescope. The HSC wide survey provides the sensitivity to detect cometary activity at lower levels than have been possible for previous surveys.We will give an overview of the Comet Hunters project. We will present the results from the first ~10,000 HSC asteroids searched and provide an estimate on the frequency of cometary activity in the Main Asteroid beltAcknowledgements: This work uses data generated via the Zooniverse.org platform, development of which was supported by a Global

  6. Activating main belt comets by collisions

    NASA Astrophysics Data System (ADS)

    Maindl, T. I.; Haghighipour, N.; Schäfer, C.; Speith, R.

    2016-02-01

    Since their identification as a new class of bodies by Hsieh and Jewitt in 2006 active asteroids (or Main Belt Comets, MBCs) have attracted a great deal of interest. Given that sublimation of volatile material (presumably water-ice) drives MBC activity, these bodies are probable candidates for delivering a significant amount of Earth's water. Dynamical studies suggest in-situ formation of MBCs as the remnants of the break-up of large icy asteroids. Also, collisions between MBCs and small objects might have exposed sub-surface water-ice triggering the cometary activity of these bodies. In order to advance the effort of understanding the nature of MBC activation, we have investigated these collision processes by simulating the impacts in detail using a smooth particle hydrodynamics (SPH) approach that includes material strength and fracture models. Our simulations cover a range of impact velocities (between 0.5 km/s and 5.3 km/s) and angles, allowing m-sized impactors to erode enough of an MBC's surface to expose volatiles and trigger its activation. We also varied the material strength of the active asteroid's surface to study its influence on crater depths and shapes. As expected, depending on the impact energy, impact angle, and MBC's material strength we observe different crater depths. Across all scenarios however, our results show that the crater depths do not exceed a few meters. This implies that if the activity of MBCs is due to sublimating water-ice, ice has to exist in no deeper than a few meters from the surface.

  7. Active Asteroids: Main-Belt Comets and Disrupted Asteroids

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.

    2016-10-01

    The study of active asteroids has attracted a great deal of interest in recent years since the recognition of main-belt comets (which orbit in the main asteroid belt, but exhibit comet-like activity due to the sublimation of volatile ices) as a new class of comets in 2006, and the discovery of the first disrupted asteroids (which, unlike MBCs, exhibit comet-like activity due to a physical disruption such as an impact or rotational destabilization, not sublimation) in 2010. In this paper, I will briefly discuss key areas of interest in the study of active asteroids.

  8. Triggering Comet-Like Activity of Main Belt Comets

    NASA Astrophysics Data System (ADS)

    Haghighipour, N.; Maindl, T. I.; Schäfer, C.; Speith, R.; Dvorak, R.

    2016-01-01

    Main Belt Comets (MBCs) have attracted a great deal of interest since their identification as a new class of bodies by Hsieh and Jewitt in 2006. Much of this interest is due to the implication that MBC activity is driven by the sublimation of volatile material (presumed to be water-ice) presenting these bodies as probable candidates for the delivery of a significant fraction of Earth's water. Results of the studies of the dynamics of MBCs suggest that these objects might have formed in-situ as the remnants of the break-up of large icy asteroids. Simulations also show that collisions among MBCs and small objects could have played an important role in triggering the cometary activity of these bodies. Such collisions might have exposed sub-surface water-ice which sublimated and created thin atmospheres and tails around MBCs. In order to drive the effort of understanding the nature of the activation of MBCs, we have investigated these collision processes by simulating the impacts in detail using a smooth particle hydrodynamics (SPH) approach that includes material strength and fracture models. We have carried out simulations for a range of impact velocities and angles, allowing m-sized impactors to erode enough of an MBC's surface to expose volatiles and trigger its activation. Impact velocities were varied between 0.5 km/s and 5.3 km/s, and the projectile radius was chosen to be 1 m. As expected, we observe significantly different crater depths depending on the impact energy, impact angle, and MBC's material strength. Results show that for all values of impact velocity and angle, crater depths are only a few meters, implying that if the activity of MBCs is due to the sublimation of water-ice, ice has to exist in no deeper than a few meters from the surface. We present details of our simulations and discuss the implications of their results.

  9. Triggering Comet-Like Activities of Main Belt Comets

    NASA Astrophysics Data System (ADS)

    Haghighipour, Nader; Maindl, Thomas; Dvorak, Rudolf; Schäfer, Christoph; Speith, Roland

    2015-08-01

    Main-belt comets (MBCs) have attracted a great deal of interest since their identification as a new class of bodies by Hsieh and Jewitt in 2006. Much of this interest is due to the implication that MBC activity is driven by the sublimation of volatile material (presumed to be water-ice) presenting these bodies as probable candidates for the delivery of a significant fraction of Earth’s water. Results of the studies of the dynamics of MBCs suggest that these objects might have formed in-situ as the remnants of the break-up of large icy asteroids. Simulations also show that collisions among MBCs and small objects could have played an important role in triggering the cometary activity of these bodies. Such collisions might have exposed sub-surface water-ice which sublimated and created thin atmospheres and tails around MBCs. In order to drive the effort of understanding the nature of the activation of MBCs, we have investigated these collision processes by simulating the impacts in detail using a smoothed particle hydrodynamics (SPH) approach that includes material strength and fracture models. We have carried out simulations for a range of impact velocities and angles, allowing m-sized impactors to erode enough of an MBC’s surface to trigger its activation. Impact velocities were varied between 2.5 km/s and 5.3 km/s, and the projectile radii were chosen to be 0.5 and 1 m. As expected, we observe significantly different crater depths depending on the impact energy, impact angle, and MBC’s material strength. Our simulations point to a clearly notable spread in the aggregated crater depths due to different impact angles and water-ice contents causing deeper craters due to less overall material strength. Results show that for all values of impact velocity and angle, crater depths are only a few meters, implying that, as suggested by Schorghofer (2008), if the activity of MBCs is due to the sublimation of water-ice, water has to exist in no deeper than a few meters

  10. MAIN-BELT COMET P/2008 R1 (GARRADD)

    SciTech Connect

    Jewitt, David; Yang Bin; Haghighipour, Nader E-mail: yangbin@ifa.hawaii.edu

    2009-05-15

    We present a study of the newly discovered main-belt comet P/2008 R1 (Garradd), an object with the dynamical characteristics of an asteroid and the physical characteristics of a comet. Photometry sets a limit to the effective radius of the nucleus at r{sub e} < 0.7 km (red geometric albedo 0.05 assumed). The coma shows a secular fading in our data caused by the escape of dust particles from the near-nucleus environment. The optical reflection spectrum is a nearly neutral continuum devoid of gaseous emission lines, from which we derive a limit to the cyanide (CN) radical production rate of Q {sub CN}< 1.4 x 10{sup 23} s{sup -1} and infer a mass-loss rate <1.5 kg s{sup -1} at the time of our observations. Unlike the first-reported main-belt comets, P/2008 R1 is not dynamically stable. The nearby 8:3 mean-motion resonance with Jupiter induces dynamical instability on timescales 20-30 Myr. Hence, we conclude that P/2008 R1 has recently arrived from a more stable source elsewhere. The high Tisserand parameter of the orbit (in fact, with T{sub J} = 3.216 it is the highest of any comet) points to a source in the asteroid belt itself, instead of in the Kuiper belt (putative source of the Jupiter family comets). We infer that P/2008 R1 is an icy body from the outer asteroid belt in which sublimation has been triggered by rising temperatures resulting from a decreasing perihelion distance.

  11. MAIN-BELT COMET 238P/READ REVISITED

    SciTech Connect

    Hsieh, Henry H.; Meech, Karen J.; Pittichova, Jana E-mail: meech@ifa.hawaii.edu

    2011-07-20

    We present a series of observations of the return of activity in main-belt comet (MBC) 238P/Read. Using data obtained in 2010 July and August when 238P appeared to be largely inactive, we find best-fit IAU phase function parameters of H = 19.05 {+-} 0.05 mag, corresponding to a nucleus radius of r{sub n} {approx} 0.4 km (assuming an albedo of p{sub R} = 0.05), and G = -0.03 {+-} 0.05. Observations from 2010 September onward show a clear rise in activity, causing both a notable change in visible morphology and increasing photometric excesses beyond what would be expected based on bare nucleus observations. By the end of the observing period reported on here, the dust mass in the coma shows indications of reaching a level comparable to that observed in 2005, but further observations are highly encouraged once 238P again becomes observable from Earth in mid-2011 to confirm whether this level of activity is achieved, or if the comet shows a noticeable drop in activity strength compared with 2005. Comet 238P is now the second MBC (after 133P/Elst-Pizarro) observed to exhibit recurrent activity, providing strong corroboration for the conclusion that it is a true comet whose active episodes are driven by sublimation of volatile ice.

  12. MAIN-BELT COMET P/2012 T1 (PANSTARRS)

    SciTech Connect

    Hsieh, Henry H.; Kaluna, Heather M.; Yang Bin; Haghighipour, Nader; Micheli, Marco; Denneau, Larry; Jedicke, Robert; Kleyna, Jan; Veres, Peter; Wainscoat, Richard J.; Ansdell, Megan; Elliott, Garrett T.; Keane, Jacqueline V.; Meech, Karen J.; Riesen, Timm E.; Sonnett, Sarah; Novakovic, Bojan; Fitzsimmons, Alan; Moskovitz, Nicholas A.; Sheppard, Scott S.; and others

    2013-07-01

    We present initial results from observations and numerical analyses aimed at characterizing the main-belt comet P/2012 T1 (PANSTARRS). Optical monitoring observations were made between 2012 October and 2013 February using the University of Hawaii 2.2 m telescope, the Keck I telescope, the Baade and Clay Magellan telescopes, Faulkes Telescope South, the Perkins Telescope at Lowell Observatory, and the Southern Astrophysical Research Telescope. The object's intrinsic brightness approximately doubles from the time of its discovery in early October until mid-November and then decreases by {approx}60% between late December and early February, similar to photometric behavior exhibited by several other main-belt comets and unlike that exhibited by disrupted asteroid (596) Scheila. We also used Keck to conduct spectroscopic searches for CN emission as well as absorption at 0.7 {mu}m that could indicate the presence of hydrated minerals, finding an upper limit CN production rate of Q{sub CN} < 1.5 Multiplication-Sign 10{sup 23} mol s{sup -1}, from which we infer a water production rate of Q{sub H{sub 2O}}<5 Multiplication-Sign 10{sup 25} mol s{sup -1}, and no evidence of the presence of hydrated minerals. Numerical simulations indicate that P/2012 T1 is largely dynamically stable for >100 Myr and is unlikely to be a recently implanted interloper from the outer solar system, while a search for potential asteroid family associations reveals that it is dynamically linked to the {approx}155 Myr old Lixiaohua asteroid family.

  13. Castalia: A European Mission to a Main Belt Comet

    NASA Astrophysics Data System (ADS)

    Snodgrass, Colin; Castalia mission science Team

    2013-10-01

    Main Belt Comets (MBCs) are a newly identified population, with stable asteroid-like orbits in the outer main belt and a comet-like appearance. It is believed that they survived the age of the solar system in a dormant state and that their activity occurred only recently. Water ice is the only volatile expected to survive, and only when buried under an insulating surface. Excavation by impact could bring the water ice (closer) to the surface and trigger the start of MBC activity. The specific science goals of the Castalia mission are: 1. Characterize a new Solar System family, the MBCs, by in-situ investigation 2. Understand the physics of activity on MBCs 3. Directly detect water in the asteroid belt 4. Test if MBCs are a viable source for Earth’s water 5. Use MBCs as tracers of planetary system formation and evolution These goals can be achieved by a spacecraft designed to rendezvous with and orbit an MBC for some months, arriving before the active period begins for mapping before directly sampling the gas and dust released during the active phase. Given the low level of activity of MBCs, and the expectation that their activity comes from only a localized patch on the surface, the orbiting spacecraft will have to be able to maintain a very close orbit over extended periods - the Castalia plan envisages an orbiter capable of ‘hovering’ autonomously at distances of only a few km from the surface of the MBC. The straw-man instrument payload is made up of: - Visible and near-infrared spectral imager - Thermal infrared imager - Radio science - Dust impact detector - Dust composition analyzer - Neutral/ion mass spectrometer - Magnetometer - Plasma package In addition to this, the option of a surface science package is being considered. At the moment MBC 133P/Elst-Pizarro is the best-known target for such a mission. A design study for the Castalia mission has been carried out in partnership between the science team, DLR and OHB Systems. This study looked at

  14. Main-belt Comet P/2012 T1 (PANSTARRS)

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Kaluna, Heather M.; Novaković, Bojan; Yang, Bin; Haghighipour, Nader; Micheli, Marco; Denneau, Larry; Fitzsimmons, Alan; Jedicke, Robert; Kleyna, Jan; Vereš, Peter; Wainscoat, Richard J.; Ansdell, Megan; Elliott, Garrett T.; Keane, Jacqueline V.; Meech, Karen J.; Moskovitz, Nicholas A.; Riesen, Timm E.; Sheppard, Scott S.; Sonnett, Sarah; Tholen, David J.; Urban, Laurie; Kaiser, Nick; Chambers, K. C.; Burgett, William S.; Magnier, Eugene A.; Morgan, Jeffrey S.; Price, Paul A.

    2013-07-01

    We present initial results from observations and numerical analyses aimed at characterizing the main-belt comet P/2012 T1 (PANSTARRS). Optical monitoring observations were made between 2012 October and 2013 February using the University of Hawaii 2.2 m telescope, the Keck I telescope, the Baade and Clay Magellan telescopes, Faulkes Telescope South, the Perkins Telescope at Lowell Observatory, and the Southern Astrophysical Research Telescope. The object's intrinsic brightness approximately doubles from the time of its discovery in early October until mid-November and then decreases by ~60% between late December and early February, similar to photometric behavior exhibited by several other main-belt comets and unlike that exhibited by disrupted asteroid (596) Scheila. We also used Keck to conduct spectroscopic searches for CN emission as well as absorption at 0.7 μm that could indicate the presence of hydrated minerals, finding an upper limit CN production rate of Q CN < 1.5 × 1023 mol s-1, from which we infer a water production rate of Q_H_2O<5\\times 10^{25} mol s-1, and no evidence of the presence of hydrated minerals. Numerical simulations indicate that P/2012 T1 is largely dynamically stable for >100 Myr and is unlikely to be a recently implanted interloper from the outer solar system, while a search for potential asteroid family associations reveals that it is dynamically linked to the ~155 Myr old Lixiaohua asteroid family. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, and made possible by the generous financial support of the W. M. Keck Foundation, the Magellan Telescopes located at Las Campanas Observatory, Chile, and the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inova

  15. Castalia - A Mission to a Main Belt Comet

    NASA Astrophysics Data System (ADS)

    Jones, G. H.; Snodgrass, C.

    2015-10-01

    Main Belt Comets (MBCs), or Active Asteroids, constitute a newly identified class of solar system objects. They have stable, asteroid-like orbits and some exhibit a recurrent comet-like appearance. It is believed that they survived the age of the solarsystem in a dormant state and that their current ice sublimation driven activity only began recently. Buried water ice is the only volatile expected to survive under an insulating surface. Excavation by an impact can expose the ice and trigger the start of MBC activity. We present the case for a mission to one of these objects. The specific science goals of the Castalia mission are: 1. Characterize a new Solar System family, the MBCs, by in-situ investigation 2. Understand the physics of activity on MBCs 3. Directly sample water in the asteroid belt and test if MBCs are a viable source for Earth's water 4. Use the observed structure of an MBC as a tracer of planetary system formation and evolution. These goals can be achieved by a spacecraft designed to rendezvous with and orbit an MBC for a time interval of some months, arriving before the active period for mapping and then sampling the gas and dust released during the active phase. Given the low level of activity of MBCs, and the expectation that their activity comes from only a localized patch on the surface, the orbiting spacecraft will have to be able to maintain a very close orbit over extended periods - the Castalia plan envisages an orbiter capable of 'hovering' autonomously at distances of only a few km from the surface of the MBC. The strawman payload comprises a Visible and near-infrared spectral imager, Thermal infrared imager, Radio science,Subsurface radar, Dust impact detector, Dust composition analyser, Neutral/ion mass spectrometer, Magnetometer, and Plasma package. In addition to this, a surface science package is being considered. At the moment, MBC 133P/Elst Pizarro is the bestknown target for such a mission. A design study for the Castalia mission

  16. Castalia - European Mission to a Main Belt Comet

    NASA Astrophysics Data System (ADS)

    Hilchenbach, M.

    2013-12-01

    Main Belt Comets (MBCs) are a recently identified new solar system population with stable asteroid-like orbits and a comet-like appearance. It is believed that they survived the age of the solar system in a dormant state and that their activity occurred only recently. Buried water ice is the only volatile expected to survive under an insulating surface. Excavation by an impact might expose the ice and trigger the start of MBC activity. The specific science goals of the Castalia mission are: 1. Characterize a new Solar System family, the MBCs, by in-situ investigation 2. Understand the physics of activity on MBCs 3. Directly detect water in the asteroid belt 4. Test if MBCs are a viable source for Earth's water 5. Use MBCs as tracers of planetary system formation and evolution These goals can be achieved by a spacecraft designed to rendezvous with and orbit an MBC for a time interval of some months, arriving before the active period for mapping and then directly sampling the gas and dust released during the active phase. Given the low level of activity of MBCs, and the expectation that their activity comes from only a localized patch on the surface, the orbiting spacecraft will have to be able to maintain a very close orbit over extended periods - the Castalia plan envisages an orbiter capable of ';hovering' autonomously at distances of only a few km from the surface of the MBC. The straw-man instrument payload is made up of: - Visible and near-infrared spectral imager - Thermal infrared imager - Radio science - Dust impact detector - Dust composition analyzer - Neutral/ion mass spectrometer - Magnetometer - Plasma package In addition to this, the option of a surface science package is being considered. At the moment MBC 133P/Elst-Pizarro is the best-known target for such a mission. A design study for the Castalia mission has been carried out in partnership between the science team, DLR and OHB Systems. This study looked at possible missions to 133P with launch

  17. Castalia - A European Mission to a Main Belt Comet

    NASA Astrophysics Data System (ADS)

    Hilchenbach, Martin

    2014-05-01

    Main Belt Comets (MBCs) are a recently identified new solar system population with stable asteroid-like orbits and a comet-like appearance. It is believed that they survived the age of the solar system in a dormant state and that their activity occurred only recently. Buried water ice is the only volatile expected to survive under an insulating surface. Excavation by an impact might expose the ice and trigger the start of MBC activity. Mission goals: Castalia is a science mission to an MBC with the goal to illuminate their mysteries (namely the activity), to decipher the messages of MBCs from the formation period of the planetary system and to explore possible their links to Earth. The specific science goals of the mission are: (1) Characterize a new Solar System family, the MBCs, by in-situ investigation (2) Understand the physics of activity on MBCs (3) Directly detect water in the asteroid belt (4) Test if MBCs are a viable source for Earth's water (5)Use MBCs as tracers of planetary system formation and evolution Mission profile: These goals can be achieved by a spacecraft designed to rendezvous with and orbit an MBC for a time interval of some months to a year, arriving before the active period for mapping and then directly sampling the gas and dust released during the active phase. Given the low level of activity of MBCs, and the expectation that their activity comes from only a localized patch on the surface, the orbiting spacecraft will have to be able to maintain a very close orbit over extended periods - the Castalia plan envisages an orbiter capable of 'hovering' autonomously at distances of only a few km from the surface of the MBC. Scientific payload: The strawman instrument payload is made up of: - Visible and near-infrared spectral imager - Thermal infrared imager - Radars for deep and shallow penetration depths - Radio science - Dust impact detector - Dust composition analyzer - Neutral/ion mass spectrometer - Magnetometer - Plasma package. In

  18. Castalia - A European Mission to a Main Belt Comet

    NASA Astrophysics Data System (ADS)

    Prialnik, Dina

    Main Belt Comets (MBCs) are a recently identified new solar system population with stable asteroid-like orbits and a comet-like appearance. It is believed that they survived the age of the Solar System in a dormant state and that their activity occurred only recently. Buried water ice is the only volatile expected to survive under an insulating surface. Excavation by an impact might expose the ice and trigger the start of MBC activity. Castalia is a science mission to an MBC with the goal to illuminate their mysteries (namely, the activity), to decipher the messages of MBCs from the formation period of the planetary system and to explore their possible links to Earth. The specific science goals of the mission are: (1) Characterize a new Solar System family, the MBCs, by in-situ investigation (2) Understand the physics of activity on MBCs (3) Directly sample primordial water in the asteroid belt (4) Test if MBCs are a viable source for Earth's water (5) Use MBCs as tracers of planetary system formation and evolution. Mission profile: These goals can be achieved by a spacecraft designed to randezvous with an MBC and orbit it for a time interval of some months to a year, arriving before the active period for mapping, and then directly sampling the gas and dust released during the active phase. Given the low level of activity of MBCs, and the expectation that their activity comes from only a localized patch on the surface, the orbiting spacecraft will have to be able to maintain a very close orbit over extended periods of time. The Castalia mission envisages an orbiter capable of 'hovering' autonomously at distances of only a few km from the surface of the MBC. Scientific payload: the straw an instrument payload is made up of: (a) Visible and near-infrared spectral imager; (b) Thermal infrared imager; (c) Radars for deep and shallow penetration depths; Radio science; (d) Dust impact detector; (e) Dust composition analyses; Neutral/ion mass spectrometer; (f

  19. Castalia - A Mission to a Main Belt Comet

    NASA Astrophysics Data System (ADS)

    Jones, G. H.

    2014-12-01

    Main Belt Comets (MBCs), or Active Asteroids, constitute a newly identified class of solar system objects. They have stable, asteroid-like orbits and some exhibit a recurrent comet-like appearance. It is believed that they survived the age of the solar system in a dormant state and that their current ice sublimation driven activity only began recently. Buried water ice is the only volatile expected to survive under an insulating surface. Excavation by an impact can expose the ice and trigger the start of MBC activity. We present the case for a mission to one of these objects, to be submitted to the European Space Agency's current call for an M-class mission. The specific science goals of the Castalia mission are: 1. Characterize a new Solar System family, the MBCs, by in-situ investigation 2. Understand the physics of activity on MBCs 3. Directly sample water in the asteroid belt and test if MBCs are a viable source for Earth's water 4. Use the observed structure of an MBC as a tracer of planetary system formation and evolution. These goals can be achieved by a spacecraft designed to rendezvous with and orbit an MBC for a time interval of some months, arriving before the active period for mapping and then sampling the gas and dust released during the active phase. Given the low level of activity of MBCs, and the expectation that their activity comes from only a localized patch on the surface, the orbiting spacecraft will have to be able to maintain a very close orbit over extended periods - the Castalia plan envisages an orbiter capable of 'hovering' autonomously at distances of only a few km from the surface of the MBC. The strawman payload comprises a Visible and near-infrared spectral imager, Thermal infrared imager, Radio science, Subsurface radar, Dust impact detector, Dust composition analyser, Neutral/ion mass spectrometer, Magnetometer, and Plasma package. In addition to this, a surface science package is being considered. At the moment, MBC 133P

  20. Castalia --- a European Mission to a main-belt comet

    NASA Astrophysics Data System (ADS)

    Boehnhardt, H.; Castalia Study Science Team

    2014-07-01

    Main Belt Comets (MBCs) are a new solar system population with stable asteroid-like orbits and a comet-like appearance. It is believed that they survived the age of the solar system in a dormant state and that their activity occurred only recently. Buried water ice is the only volatile expected to survive under an insulating surface. Excavation by an impact might expose the ice and trigger the start of MBC activity. Castalia is a science mission to an MBC with the goal to illuminate their mysteries, to decipher the messages of MBCs from the formation period of the planetary system and to explore their possible links to Earth. The specific science goals of the mission are: (1) Characterize a new Solar System family, the MBCs, by in-situ investigation (2) Understand the physics of activity on MBCs (3) Directly sample primordial water in the asteroid belt (4) Test if MBCs are a viable source for Earth's water (5) Use MBCs as tracers of planetary system formation and evolution. Mission profile: These goals can be achieved by a spacecraft designed to rendezvous with an MBC and orbit it for a time interval of some months to a year, arriving before the active period for mapping and then directly sampling the gas and dust released during the active phase. Given the low level of activity of MBCs, and the expectation that their activity comes from only a localized patch on the surface, the orbiting spacecraft will have to be able to maintain a very close orbit over extended periods - the Castalia plan envisages an orbiter capable of ''hovering'' autonomously at distances of only a few km from the surface of the MBC. Scientific payload: The strawman instrument payload is made up of: Visible and near-infrared spectral imager; Thermal infrared imager; Radars for deep and shallow penetration depths; Radio science; Dust impact detector; Dust composition analyzer; Neutral/ion mass spectrometer; Magnetometer; Plasma package. In addition to this, the option of a surface science

  1. Potential Jupiter-Family comet contamination of the main asteroid belt

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Haghighipour, Nader

    2016-10-01

    We present the results of "snapshot" numerical integrations of test particles representing comet-like and asteroid-like objects in the inner Solar System aimed at investigating the short-term dynamical evolution of objects close to the dynamical boundary between asteroids and comets as defined by the Tisserand parameter with respect to Jupiter, TJ (i.e., TJ = 3). As expected, we find that TJ for individual test particles is not always a reliable indicator of initial orbit types. Furthermore, we find that a few percent of test particles with comet-like starting elements (i.e., similar to those of Jupiter-family comets) reach main-belt-like orbits (at least temporarily) during our 2 Myr integrations, even without the inclusion of non-gravitational forces, apparently via a combination of gravitational interactions with the terrestrial planets and temporary trapping by mean-motion resonances with Jupiter. We estimate that the fraction of real Jupiter-family comets occasionally reaching main-belt-like orbits on Myr timescales could be on the order of ∼ 0.1-1%, although the fraction that remain on such orbits for appreciable lengths of time is certainly far lower. For this reason, the number of JFC-like interlopers in the main-belt population at any given time is likely to be small, but still non-zero, a finding with significant implications for efforts to use apparently icy yet dynamically asteroidal main-belt comets as tracers of the primordial distribution of volatile material in the inner Solar System. The test particles with comet-like starting orbital elements that transition onto main-belt-like orbits in our integrations appear to be largely prevented from reaching low eccentricity, low inclination orbits, suggesting that the real-world population of main-belt objects with both low eccentricities and inclinations may be largely free of this potential occasional Jupiter-family comet contamination. We therefore find that low-eccentricity, low-inclination main-belt

  2. THE NUCLEUS OF MAIN-BELT COMET 259P/GARRADD

    SciTech Connect

    MacLennan, Eric M.; Hsieh, Henry H. E-mail: emaclenn@utk.edu

    2012-10-10

    We present observations of the main-belt comet 259P/Garradd, previously known as P/2008 R1 (Garradd), obtained in 2011 and 2012 using the Gemini North Telescope on Mauna Kea in Hawaii and the SOAR telescope at Cerro Pachon in Chile, with the goal of computing the object's phase function and nucleus size. We find an absolute magnitude of H{sub R} = 19.71 {+-} 0.05 mag and slope parameter of G{sub R} = -0.08 {+-} 0.05 for the inactive nucleus, corresponding to an effective nucleus radius of r{sub e} = 0.30 {+-} 0.02 km, assuming an R-band albedo of p{sub R} = 0.05. We also revisit observations reported for 259P while it was active in 2008 to quantify the dust mass loss and compare the object with other known main-belt comets.

  3. The main-belt comets: The Pan-STARRS1 perspective

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Denneau, Larry; Wainscoat, Richard J.; Schörghofer, Norbert; Bolin, Bryce; Fitzsimmons, Alan; Jedicke, Robert; Kleyna, Jan; Micheli, Marco; Vereš, Peter; Kaiser, Nicholas; Chambers, Kenneth C.; Burgett, William S.; Flewelling, Heather; Hodapp, Klaus W.; Magnier, Eugene A.; Morgan, Jeffrey S.; Price, Paul A.; Tonry, John L.; Waters, Christopher

    2015-03-01

    We analyze a set of 760 475 observations of 333 026 unique main-belt objects obtained by the Pan-STARRS1 (PS1) survey telescope between 2012 May 20 and 2013 November 9, a period during which PS1 discovered two main-belt comets, P/2012 T1 (PANSTARRS) and P/2013 R3 (Catalina-PANSTARRS). PS1 comet detection procedures currently consist of the comparison of the point spread functions (PSFs) of moving objects to those of reference stars, and the flagging of objects that show anomalously large radial PSF widths for human evaluation and possible observational follow-up. Based on the number of missed discovery opportunities among comets discovered by other observers, we estimate an upper limit comet discovery efficiency rate of ∼70% for PS1. Additional analyses that could improve comet discovery yields in future surveys include linear PSF analysis, modeling of trailed stellar PSFs for comparison to trailed moving object PSFs, searches for azimuthally localized activity, comparison of point-source-optimized photometry to extended-source-optimized photometry, searches for photometric excesses in objects with known absolute magnitudes, and crowd-sourcing. Analysis of the discovery statistics of the PS1 survey indicates an expected fraction of 59 MBCs per 106 outer main-belt asteroids (corresponding to a total expected population of ∼140 MBCs among the outer main-belt asteroid population with absolute magnitudes of 12 main-belt asteroids (corresponding to a total of ∼230 MBCs), assuming a detection efficiency of 50%. We note however that significantly more sensitive future surveys (particularly those utilizing larger aperture telescopes) could detect many more MBCs than estimated here. Examination of the orbital element distribution of all known MBCs reveals an excess of high eccentricities (0.1 < e < 0.3) relative to the background asteroid population. Theoretical calculations show that, given these

  4. The search for main-belt comets: The Pan-STARRS1 perspective

    NASA Astrophysics Data System (ADS)

    Hsieh, H.; Denneau, L.; Wainscoat, R.; Jedicke, R.; Schorghofer, N.; Micheli, M.; Veres, P.; Kleyna, J.; Bolin, B.

    2014-07-01

    In recent years, an increasing number of objects have been discovered in the main asteroid belt that exhibit comet-like activity. Some instances of activity are believed to result from sublimation of volatile sub-surface ice, and the objects exhibiting this type of activity have come to be known as main-belt comets (MBCs; Hsieh & Jewitt 2006). For most MBCs, the presence of gas is only inferred from visible dust emission, although water vapor outgassing has recently been directly detected from (1) Ceres (Kuppers et al. 2014), indicating that water sublimation on MBCs could also be possible. In other instances, comet-like dust emission has been found to result from impacts onto otherwise inert objects, rotational disruption, or a combination of effects (cf., Jewitt 2012). In these cases, the objects can be referred to as disrupted asteroids. Collectively, MBCs and disrupted asteroids are known as active asteroids. MBCs have attracted interest in astrobiology due to theoretical studies indicating that material from the asteroid belt region could have been a significant primordial source of the water and other volatiles on the Earth. Icy asteroids also contain some of the least altered material from the inner protosolar disk still in existence today, presenting us with opportunities to learn about the earliest stages of our solar system's formation. The added bonus of the MBCs' relatively close proximity in the asteroid belt means that in situ spacecraft studies are entirely feasible using present-day technology. Pan-STARRS1 (PS1) is a wide-field synoptic survey telescope located on Halekala in Hawaii. It employs a 3.2×3.2 deg 1.4 gigapixel camera and uses an SDSS-like filter system. As of 2014 March 31, the Pan-STARRS1 survey has discovered three MBCs --- P/2006 VW139, P/2012 T1 (PANSTARRS), and P/2013 R3 (Catalina-PANSTARRS) --- as well as one disrupted asteroid (P/2013 P5 (PANSTARRS)), two active Centaurs, 33 Jupiter-family comets, and 17 long-period comets. For

  5. The Hawaii trails project: comet-hunting in the main asteroid belt

    NASA Astrophysics Data System (ADS)

    Hsieh, H. H.

    2009-10-01

    Context: The mysterious solar system object 133P/(7968) Elst-Pizarro is dynamically asteroidal, yet displays recurrent comet-like dust emission. Two scenarios were hypothesized to explain this unusual behavior: 1) 133P is a classical comet from the outer solar system that has evolved onto a main-belt orbit or 2) 133P is a dynamically ordinary main-belt asteroid on which subsurface ice has recently been exposed. If 1) is correct, the expected rarity of a dynamical transition onto an asteroidal orbit implies that 133P could be alone in the main belt. In contrast, if 2) is correct, other icy main-belt objects should exist and could also exhibit cometary activity. Aims: Believing 133P to be a dynamically ordinary, yet icy main-belt asteroid, I set out to test the primary prediction of the hypothesis: that 133P-like objects should be common and could be found by an appropriately designed observational survey. Methods: I conducted just such a survey - the Hawaii Trails Project - of selected main-belt asteroids in a search for objects displaying cometary activity. Optical observations were made of targets selected from among the Themis, Koronis, and Veritas asteroid families, the Karin asteroid cluster, and low-inclination, kilometer-scale outer-belt asteroids, using the Lulin 1.0 m, small and moderate aperture research telescope system (SMARTS) 1.0 m, University of Hawaii 2.2 m, southern astrophysical research (SOAR) 4.1 m, Gemini North 8.1 m, Subaru 8.2 m, and Keck I 10 m telescopes. Results: I made 657 observations of 599 asteroids, discovering one active object now known as 176P/LINEAR, leading to the identification of the new cometary class of main-belt comets (MBCs). These results suggest that there could be ~100 currently active MBCs among low-inclination, kilometer-scale outer-belt asteroids. Physically and statistically, MBC activity is consistent with initiation by meter-sized impactors. The estimated rate of impacts and sizes of resulting active sites, however

  6. THE EXTRAORDINARY MULTI-TAILED MAIN-BELT COMET P/2013 P5

    SciTech Connect

    Jewitt, David; Agarwal, Jessica; Weaver, Harold; Mutchler, Max; Larson, Stephen

    2013-11-20

    Hubble Space Telescope observations of main-belt comet P/2013 P5 reveal an extraordinary system of six dust tails that distinguish this object from any other. Observations two weeks apart show dramatic morphological change in the tails while providing no evidence for secular fading of the object as a whole. Each tail is associated with a unique ejection date, revealing continued, episodic mass loss from the 0.24 ± 0.04 km radius nucleus over the last five months. As an inner-belt asteroid and probable Flora family member, the object is likely to be highly metamorphosed and unlikely to contain ice. The protracted period of dust release appears inconsistent with an impact origin, but may be compatible with a body that is losing mass through a rotational instability. We suggest that P/2013 P5 has been accelerated to breakup speed by radiation torques.

  7. The Near-Earth Object Population: Connections to Comets, Main-Belt Asteroids, and Meteorites

    NASA Astrophysics Data System (ADS)

    Binzel, R. P.; Reddy, V.; Dunn, T. L.

    Near-Earth objects (NEOs) owe their origins to both the main-belt asteroids and comets. They include (by definition) precursors for all meteorite samples. Thus understanding NEO connections is central to the modern study of small bodies in our solar system and serves as the principal focus of this chapter. Herein we also briefly highlight how the proximity of near-Earth objects enables detailed study of the smallest known and most accessible natural objects in space, and we provide links to other chapters addressing these aspects more fully. The success of Japan's Hayabusa mission sample return yields a definitive link between the most common class of near-Earth asteroids and one of the most common meteorites, a watershed whose ground truth enables a deeper level of understanding and new questions. We can now investigate the near-Earth population to pinpoint specific main-belt source regions for broad taxonomic classes and specific meteorite types in addition to estimating the extinct comet contribution. Spectral properties combined with long-term orbital modeling reveal a strong role played by planetary encounters to resurface (and likely reshape) many objects. Outstanding puzzles remain for many of the newly revealed details; their resolution will generate new insights to the basic physical processes governing small bodies.

  8. The Nucleus of Main-belt Comet 259P/Garradd

    NASA Astrophysics Data System (ADS)

    MacLennan, Eric M.; Hsieh, Henry H.

    2012-10-01

    We present observations of the main-belt comet 259P/Garradd, previously known as P/2008 R1 (Garradd), obtained in 2011 and 2012 using the Gemini North Telescope on Mauna Kea in Hawaii and the SOAR telescope at Cerro Pachon in Chile, with the goal of computing the object's phase function and nucleus size. We find an absolute magnitude of HR = 19.71 ± 0.05 mag and slope parameter of GR = -0.08 ± 0.05 for the inactive nucleus, corresponding to an effective nucleus radius of re = 0.30 ± 0.02 km, assuming an R-band albedo of pR = 0.05. We also revisit observations reported for 259P while it was active in 2008 to quantify the dust mass loss and compare the object with other known main-belt comets. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

  9. Deep wide-field imaging of main belt comets and asteroids

    NASA Astrophysics Data System (ADS)

    Rajagopal, Jayadev; Jewitt, David; Ridgway, Susan

    2014-02-01

    We propose to continue a deep imaging study, using the pODI optical imager on the WIYN telescope, of selected regions of the main asteroid belt that contain a known main-belt comet (MBC). An MBC is an asteroid that shows evidence of significant mass loss, seen as transient, comet- like tails and comae. In 2013, we were awarded 4 nights over the two semesters and obtained high-impact wide-field, deep images of two new MBCs, P/2010 A2 and P/2013 P5, to study their origins. In addition, we use the considerable pODI field-of-view to search for direct evidence of very low-level mass-loss activity in the sample of main belt asteroids that will also be detected. Asteroids could be repositories of primordial water and a supply for volatiles on earth. In order to test this possibility (suggested by the recent TALCS asteroid survey at CFHT) and further characterize the mass-loss in known MBC activity, we will observe ~ 25- arcminute fields around ~ 3 known MBCs to significantly deeper levels than TALCS with better resolution. More than half of the 2013A allocation was lost to weather. We request 4 nights in 2014A. With this additional time we are confident of reaching publishable results on low level mass-loss and on the evolution of the activity in known MBCs. We will follow the secular evolution of P/2010 A2. And, as in the previous two semesters, we hope to add a spectacular wide-field deep image of a new MBC.

  10. Comets Captured in the Main Asteroid Belt: Evidence for a Lost Neptune-Like Planet

    NASA Astrophysics Data System (ADS)

    Bottke, W. F., Jr.

    2016-12-01

    The Nice model describes a family of solutions where the giant planets started in a different configuration, experienced a dynamical instability, and reached their final configuration via interactions with a sea of leftover comet-like planetesimals. The most successful version of this model assumes there were five planets between 5-20 AU: Jupiter, Saturn, Uranus, Neptune, and a Neptune-like body. The extra Neptune-like body was ejected via a Jupiter encounter but not before it helped populate stable niches with disk planetesimals across the Solar System (e.g., Trojans, irregular satellites). Here we use numerical simulations to show that the Neptune-like body directly interacted with the main belt for several tens of thousands of years, enough to help capture numerous disk planetesimals into the asteroid belt and the first-order mean motion resonances with Jupiter. We find our model runs produce the right proportion of large P- and D-type asteroids in the inner, central, and outer main belt, while also populating the Hilda and Thule populations in Jupiter's 3/2 and 4/3 resonances. For example, in the central main belt between 2.5-2.8 AU, we predict the largest P/D types should be 180 ± 25 km, compared to the D 177 km diameter P-type (409) Aspasia, while there should be 20 (+20, -10) D > 150 km bodies, compared to 17 known such bodies. Our model does produce a factor of a few overabundance of D > 10 km P/D-types in the main belt, though this mismatch is likely explained by removal mechanisms not yet explored (e.g., thermal destruction of D > 10 km disk planetesimals en route to the inner solar system, collision evolution in the main belt over 4 Gyr, dynamical losses in the main belt via Yarkovsky thermal forces over 4 Gyr). Overall, our five-planet instability model not only reproduces the major trends identified by Levison et al. (2009), but it also provides a more satisfying match to constraints. Accordingly, it provides us with strong supporting evidence that

  11. SUBLIMATION-DRIVEN ACTIVITY IN MAIN-BELT COMET 313P/GIBBS

    SciTech Connect

    Hsieh, Henry H.; Hainaut, Olivier; Novaković, Bojan; Bolin, Bryce; Denneau, Larry; Haghighipour, Nader; Kleyna, Jan; Meech, Karen J.; Schunova, Eva; Wainscoat, Richard J.; Fitzsimmons, Alan; Kokotanekova, Rosita; Snodgrass, Colin; Lacerda, Pedro; Micheli, Marco; Moskovitz, Nick; Wasserman, Lawrence; Waszczak, Adam

    2015-02-10

    We present an observational and dynamical study of newly discovered main-belt comet 313P/Gibbs. We find that the object is clearly active both in observations obtained in 2014 and in precovery observations obtained in 2003 by the Sloan Digital Sky Survey, strongly suggesting that its activity is sublimation-driven. This conclusion is supported by a photometric analysis showing an increase in the total brightness of the comet over the 2014 observing period, and dust modeling results showing that the dust emission persists over at least three months during both active periods, where we find start dates for emission no later than 2003 July 24 ± 10 for the 2003 active period and 2014 July 28 ± 10 for the 2014 active period. From serendipitous observations by the Subaru Telescope in 2004 when the object was apparently inactive, we estimate that the nucleus has an absolute R-band magnitude of H{sub R} = 17.1 ± 0.3, corresponding to an effective nucleus radius of r{sub e} ∼ 1.00 ± 0.15 km. The object’s faintness at that time means we cannot rule out the presence of activity, and so this computed radius should be considered an upper limit. We find that 313P’s orbit is intrinsically chaotic, having a Lyapunov time of T{sub l} = 12,000 yr and being located near two three-body mean-motion resonances with Jupiter and Saturn, 11J-1S-5A and 10J+12S-7A, yet appears stable over >50 Myr in an apparent example of stable chaos. We furthermore find that 313P is the second main-belt comet, after P/2012 T1 (PANSTARRS), to belong to the ∼155 Myr old Lixiaohua asteroid family.

  12. Discovery of Main-belt Comet P/2006 VW139 by Pan-STARRS1

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Yang, Bin; Haghighipour, Nader; Kaluna, Heather M.; Fitzsimmons, Alan; Denneau, Larry; Novaković, Bojan; Jedicke, Robert; Wainscoat, Richard J.; Armstrong, James D.; Duddy, Samuel R.; Lowry, Stephen C.; Trujillo, Chadwick A.; Micheli, Marco; Keane, Jacqueline V.; Urban, Laurie; Riesen, Timm; Meech, Karen J.; Abe, Shinsuke; Cheng, Yu-Chi; Chen, Wen-Ping; Granvik, Mikael; Grav, Tommy; Ip, Wing-Huen; Kinoshita, Daisuke; Kleyna, Jan; Lacerda, Pedro; Lister, Tim; Milani, Andrea; Tholen, David J.; Vereš, Peter; Lisse, Carey M.; Kelley, Michael S.; Fernández, Yanga R.; Bhatt, Bhuwan C.; Sahu, Devendra K.; Kaiser, Nick; Chambers, K. C.; Hodapp, Klaus W.; Magnier, Eugene A.; Price, Paul A.; Tonry, John L.

    2012-03-01

    The main-belt asteroid (300163) 2006 VW139 (later designated P/2006 VW139) was discovered to exhibit comet-like activity by the Pan-STARRS1 (PS1) survey telescope using automated point-spread-function analyses performed by PS1's Moving Object Processing System. Deep follow-up observations show both a short (~10'') antisolar dust tail and a longer (~60'') dust trail aligned with the object's orbit plane, similar to the morphology observed for another main-belt comet (MBC), P/2010 R2 (La Sagra), and other well-established comets, implying the action of a long-lived, sublimation-driven emission event. Photometry showing the brightness of the near-nucleus coma remaining constant over ~30 days provides further evidence for this object's cometary nature, suggesting it is in fact an MBC, and not a disrupted asteroid. A spectroscopic search for CN emission was unsuccessful, though we find an upper limit CN production rate of Q CN < 1.3 × 1024 mol s-1, from which we infer a water production rate of Q_H_2O<10^{26} mol s-1. We also find an approximately linear optical spectral slope of 7.2%/1000 Å, similar to other cometary dust comae. Numerical simulations indicate that P/2006 VW139 is dynamically stable for >100 Myr, while a search for a potential asteroid family around the object reveals a cluster of 24 asteroids within a cutoff distance of 68 m s-1. At 70 m s-1, this cluster merges with the Themis family, suggesting that it could be similar to the Beagle family to which another MBC, 133P/Elst-Pizarro, belongs.

  13. Sublimation-Driven Activity in Main-Belt Comet 313p/Gibbs

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Hainaut, Olivier; Novaković, Bojan; Bolin, Bryce; Denneau, Larry; Fitzsimmons, Alan; Haghighipour, Nader; Kleyna, Jan; Kokotanekova, Rosita; Lacerda, Pedro; Meech, Karen J.; Micheli, Marco; Moskovitz, Nick; Schunova, Eva; Snodgrass, Colin; Wainscoat, Richard J.; Wasserman, Lawrence; Waszczak, Adam

    2015-02-01

    We present an observational and dynamical study of newly discovered main-belt comet 313P/Gibbs. We find that the object is clearly active both in observations obtained in 2014 and in precovery observations obtained in 2003 by the Sloan Digital Sky Survey, strongly suggesting that its activity is sublimation-driven. This conclusion is supported by a photometric analysis showing an increase in the total brightness of the comet over the 2014 observing period, and dust modeling results showing that the dust emission persists over at least three months during both active periods, where we find start dates for emission no later than 2003 July 24 ± 10 for the 2003 active period and 2014 July 28 ± 10 for the 2014 active period. From serendipitous observations by the Subaru Telescope in 2004 when the object was apparently inactive, we estimate that the nucleus has an absolute R-band magnitude of HR = 17.1 ± 0.3, corresponding to an effective nucleus radius of re ∼ 1.00 ± 0.15 km. The object’s faintness at that time means we cannot rule out the presence of activity, and so this computed radius should be considered an upper limit. We find that 313P’s orbit is intrinsically chaotic, having a Lyapunov time of Tl = 12,000 yr and being located near two three-body mean-motion resonances with Jupiter and Saturn, 11J-1S-5A and 10J+12S-7A, yet appears stable over >50 Myr in an apparent example of stable chaos. We furthermore find that 313P is the second main-belt comet, after P/2012 T1 (PANSTARRS), to belong to the ∼155 Myr old Lixiaohua asteroid family.

  14. Comet Hunters: A Citizen Science Project to Search for Comets in the Main Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Schwamb, Megan Elizabeth; Zhang, Zhi-Wei; Chen, Ying-Tung; Wang, Shiang-Yu; Lintott, Chris

    2016-10-01

    Fully automated detection of comets in wide-field surveys remains a challenge, as even highly successful comet-finding surveys like Pan-STARRS rely on a combination of both automated flagging algorithms and vetting by human eyes. To take advantage of the long-noted superiority of the human eye over computer algorithms in certain types of pattern recognition, particularly when dealing with a range of target morphologies of interest, we have created a citizen science website with the aim of allowing the general public to aid in the search for active asteroids, which are objects that occupy dynamically asteroidal orbits yet exhibit comet-like dust emission due to sublimation, impact disruption, rotational destabilization, or other effects. Located at comethunters.org, the Comet Hunters website was built using the Zooniverse Project Builder (https://www.zooniverse.org/lab), and displays images of known asteroids obtained either from archival data obtained between 1999 and 2014 by the Suprime-Cam wide-field imager mounted on the 8-m Subaru telescope on Mauna Kea in Hawaii, or more contemporary data obtained by the Hyper Suprime-Cam (HSC) wide-field imager also on the Subaru Telescope as part of the ongoing HSC Subaru Strategic Program (SSP) survey. By using observations from such a large-aperture telescope, most of which have never been searched for solar system objects, much less cometary ones, we expect that volunteers should be able to make genuinely scientifically significant discoveries, and also provide valuable insights into the potential and challenges of searching for comets in the LSST era. To date, over 13,000 registered volunteers have contributed 350,000 classifications. We will discuss the design and construction of the Comet Hunters website, and also discuss early results from the project.This work uses data generated via the Zooniverse.org platform, development of which was supported by a Global Impact Award from Google, and by the Alfred P. Sloan

  15. Observational and Dynamical Characterization of Main-belt Comet P/2010 R2 (La Sagra)

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Yang, Bin; Haghighipour, Nader; Novaković, Bojan; Jedicke, Robert; Wainscoat, Richard J.; Denneau, Larry; Abe, Shinsuke; Chen, Wen-Ping; Fitzsimmons, Alan; Granvik, Mikael; Grav, Tommy; Ip, Wing; Kaluna, Heather M.; Kinoshita, Daisuke; Kleyna, Jan; Knight, Matthew M.; Lacerda, Pedro; Lisse, Carey M.; Maclennan, Eric; Meech, Karen J.; Micheli, Marco; Milani, Andrea; Pittichová, Jana; Schunova, Eva; Tholen, David J.; Wasserman, Lawrence H.; Burgett, William S.; Chambers, K. C.; Heasley, Jim N.; Kaiser, Nick; Magnier, Eugene A.; Morgan, Jeffrey S.; Price, Paul A.; Jørgensen, Uffe G.; Dominik, Martin; Hinse, Tobias; Sahu, Kailash; Snodgrass, Colin

    2012-05-01

    We present observations of the recently discovered comet-like main-belt object P/2010 R2 (La Sagra) obtained by Pan-STARRS1 and the Faulkes Telescope-North on Haleakala in Hawaii, the University of Hawaii 2.2 m, Gemini-North, and Keck I telescopes on Mauna Kea, the Danish 1.54 m telescope (operated by the MiNDSTEp consortium) at La Silla, and the Isaac Newton Telescope on La Palma. An antisolar dust tail is observed to be present from 2010 August through 2011 February, while a dust trail aligned with the object's orbit plane is also observed from 2010 December through 2011 August. Assuming typical phase darkening behavior, P/La Sagra is seen to increase in brightness by >1 mag between 2010 August and December, suggesting that dust production is ongoing over this period. These results strongly suggest that the observed activity is cometary in nature (i.e., driven by the sublimation of volatile material), and that P/La Sagra is therefore the most recent main-belt comet to be discovered. We find an approximate absolute magnitude for the nucleus of HR = 17.9 ± 0.2 mag, corresponding to a nucleus radius of ~0.7 km, assuming an albedo of p = 0.05. Comparing the observed scattering surface areas of the dust coma to that of the nucleus when P/La Sagra was active, we find dust-to-nucleus area ratios of Ad /AN = 30-60, comparable to those computed for fellow main-belt comets 238P/Read and P/2008 R1 (Garradd), and one to two orders of magnitude larger than for two other main-belt comets (133P/Elst-Pizarro and 176P/LINEAR). Using optical spectroscopy to search for CN emission, we do not detect any conclusive evidence of sublimation products (i.e., gas emission), finding an upper limit CN production rate of Q CN < 6 × 1023 mol s-1, from which we infer an H2O production rate of Q_H_2O\\,{<}\\,10^{26} mol s-1. Numerical simulations indicate that P/La Sagra is dynamically stable for >100 Myr, suggesting that it is likely native to its current location and that its composition is

  16. OBSERVATIONAL AND DYNAMICAL CHARACTERIZATION OF MAIN-BELT COMET P/2010 R2 (La Sagra)

    SciTech Connect

    Hsieh, Henry H.; Yang Bin; Haghighipour, Nader; Jedicke, Robert; Wainscoat, Richard J.; Denneau, Larry; Kaluna, Heather M.; Kleyna, Jan; Novakovic, Bojan; Abe, Shinsuke; Chen Wenping; Ip, Wing; Kinoshita, Daisuke; Fitzsimmons, Alan; Lacerda, Pedro; Granvik, Mikael; Grav, Tommy; Knight, Matthew M.; Lisse, Carey M.; Maclennan, Eric; and others

    2012-05-15

    We present observations of the recently discovered comet-like main-belt object P/2010 R2 (La Sagra) obtained by Pan-STARRS1 and the Faulkes Telescope-North on Haleakala in Hawaii, the University of Hawaii 2.2 m, Gemini-North, and Keck I telescopes on Mauna Kea, the Danish 1.54 m telescope (operated by the MiNDSTEp consortium) at La Silla, and the Isaac Newton Telescope on La Palma. An antisolar dust tail is observed to be present from 2010 August through 2011 February, while a dust trail aligned with the object's orbit plane is also observed from 2010 December through 2011 August. Assuming typical phase darkening behavior, P/La Sagra is seen to increase in brightness by >1 mag between 2010 August and December, suggesting that dust production is ongoing over this period. These results strongly suggest that the observed activity is cometary in nature (i.e., driven by the sublimation of volatile material), and that P/La Sagra is therefore the most recent main-belt comet to be discovered. We find an approximate absolute magnitude for the nucleus of H{sub R} = 17.9 {+-} 0.2 mag, corresponding to a nucleus radius of {approx}0.7 km, assuming an albedo of p = 0.05. Comparing the observed scattering surface areas of the dust coma to that of the nucleus when P/La Sagra was active, we find dust-to-nucleus area ratios of A{sub d} /A{sub N} = 30-60, comparable to those computed for fellow main-belt comets 238P/Read and P/2008 R1 (Garradd), and one to two orders of magnitude larger than for two other main-belt comets (133P/Elst-Pizarro and 176P/LINEAR). Using optical spectroscopy to search for CN emission, we do not detect any conclusive evidence of sublimation products (i.e., gas emission), finding an upper limit CN production rate of Q{sub CN} < 6 Multiplication-Sign 10{sup 23} mol s{sup -1}, from which we infer an H{sub 2}O production rate of Q{sub H{sub 2O}} < 10{sup 26} mol s{sup -1}. Numerical simulations indicate that P/La Sagra is dynamically stable for >100 Myr

  17. WATER-ICE-DRIVEN ACTIVITY ON MAIN-BELT COMET P/2010 A2 (LINEAR)?

    SciTech Connect

    Moreno, F.; Ortiz, J. L.; Cabrera-Lavers, A.; Augusteijn, T.; Liimets, T.; Lindberg, J. E.; Pursimo, T.; RodrIguez-Gil, P.; Vaduvescu, O.

    2010-08-01

    The dust ejecta of Main-Belt Comet P/2010 A2 (LINEAR) have been observed with several telescopes at the Observatorio del Roque de los Muchachos on La Palma, Spain. Application of an inverse dust tail Monte Carlo method to the images of the dust ejecta from the object indicates that a sustained, likely water-ice-driven, activity over some eight months is the mechanism responsible for the formation of the observed tail. The total amount of the dust released is estimated to be 5 x 10{sup 7} kg, which represents about 0.3% of the nucleus mass. While the event could have been triggered by a collision, this cannot be determined from the currently available data.

  18. OPTICAL AND DYNAMICAL CHARACTERIZATION OF COMET-LIKE MAIN-BELT ASTEROID (596) SCHEILA

    SciTech Connect

    Hsieh, Henry H.; Yang Bin; Haghighipour, Nader E-mail: yangbin@ifa.hawaii.edu

    2012-01-01

    We present observations and a dynamical analysis of the comet-like main-belt object, (596) Scheila. V-band photometry obtained on UT 2010 December 12 indicates that Scheila's dust cloud has a scattering cross-section {approx}1.4 times larger than that of the nucleus, corresponding to a dust mass of M{sub d} {approx} 3 Multiplication-Sign 10{sup 7} kg. V-R color measurements indicate that both the nucleus and dust are redder than the Sun, with no significant color differences between the dust cloud's northern and southern plumes. We also undertake an ultimately unsuccessful search for CN emission, where we find CN and H{sub 2}O production rates of Q{sub CN} < 9 Multiplication-Sign 10{sup 23} s{sup -1} and Q{sub H{sub 2O}}<10{sup 27} s{sup -1}. Numerical simulations indicate that Scheila is dynamically stable for >100 Myr, suggesting that it is likely native to its current location. We also find that it does not belong to a dynamical asteroid family of any significance. We consider sublimation-driven scenarios that could produce the appearance of multiple plumes of dust emission, but reject them as being physically implausible. Instead, we concur with previous studies that the unusual morphology of Scheila's dust cloud is most simply explained by a single oblique impact, meaning that this object is likely not a main-belt comet but is instead the second disrupted asteroid after P/2010 A2 (LINEAR) to be discovered.

  19. The nucleus of main-belt Comet P/2010 R2 (La Sagra)

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.

    2014-11-01

    We present recent observations of main-belt comet P/2010 R2 (La Sagra) obtained using the Gemini North telescope on five nights in late 2011 and early 2013 during portions of the object's orbit when dust emission was expected to be minimal or absent. We find that P/La Sagra continues to exhibit a faint dust trail aligned with its orbit plane as late as 2011 December 31, while no activity is observed by the time of our next observations on 2013 March 3, shortly before aphelion. Using only photometry measured when the comet was observed to be inactive, we find best-fit IAU phase function parameters of HR=18.4±0.2mag and G =0.17±0.10 , corresponding to an effective nucleus radius of rN=0.55±0.05km (assuming pR=0.05 ). We revisit photometry obtained when P/La Sagra was observed to be active in 2010 using our revised determination of the object's nucleus size, finding a peak dust-to-nucleus mass ratio of Md/MN=(5.8±1.6)×10-4 , corresponding to an estimated total peak dust mass of Md=(5.3±1.5)×108kg . We also compute the inferred peak total active surface area and active surface fraction for P/La Sagra, finding Aact∼5×104m2 and fact∼0.01 , respectively. Finally, we discuss P/La Sagra's upcoming perihelion passage, particularly focusing on the available opportunities to conduct follow-up observations in order to search for recurrent activity and, if recurrent activity is present, to search for changes in P/La Sagra's activity strength on successive orbit passages that should provide insights into the evolution of MBC activity over time.

  20. Albedos of Main-Belt Comets 133P/Elst-Pizarro and 176P/LINEAR

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Jewitt, David; Fernández, Yanga R.

    2009-04-01

    We present the determination of the geometric R-band albedos of two main-belt comet (MBC) nuclei based on data from the Spitzer Space Telescope and a number of ground-based optical facilities. For 133P/Elst-Pizarro, we find an albedo of pR = 0.05 ± 0.02 and an effective radius of re = 1.9 ± 0.3 km (estimated semiaxes of a ~ 2.3 km and b ~ 1.6 km). For 176P/LINEAR, we find an albedo of pR = 0.06 ± 0.02 and an effective radius of re = 2.0 ± 0.2 km (estimated semiaxes of a ~ 2.6 km and b ~ 1.5 km). In terms of albedo, 133P and 176P are similar to each other and are typical of other Themis family asteroids, C-class asteroids, and other comet nuclei. We find no indication that 133P and 176P are compositionally unique among other dynamically similar (but inactive) members of the Themis family, in agreement with previous assertions that the two objects most likely formed in situ. We also note that low albedo (pR < 0.075) remains a consistent feature of all cometary (i.e., icy) bodies, whether they originate in the inner solar system (the MBCs) or in the outer solar system (all other comets). This work makes use of observations made with the Spitzer Space Telescope (Programs 3119 and 30678), which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration (NASA). Additionally, some data presented herein were obtained at the W. M. Keck Observatory that is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. Some data presented herein were also obtained at ESO facilities at La Silla under program ID 081.C-0822(A).

  1. THE DUST ENVIRONMENT OF MAIN-BELT COMET P/2012 T1 (PANSTARRS)

    SciTech Connect

    Moreno, F.; Pozuelos, F.

    2013-06-20

    The Main-Belt Comet P/2012 T1 (PANSTARRS) has been imaged using the 10.4 m Gran Telescopio Canarias and the 4.2 m William Herschel Telescope at six epochs in the period from 2012 November to 2013 February, with the aim of monitoring its dust environment. The dust tails' brightness and morphology are best interpreted in terms of a model of sustained dust emission spanning four to six months. The total dust mass ejected is estimated at {approx}6-25 Multiplication-Sign 10{sup 6} kg. We assume a time-independent power-law size distribution function, with particles in the micrometer to centimeter size range. Based on the quality of the fits to the isophote fields, an anisotropic emission pattern is favored against an isotropic one, in which the particle ejection is concentrated toward high latitudes ({+-}45 Degree-Sign to {+-}90 Degree-Sign ) in a high-obliquity object (I = 80 Degree-Sign ). This seasonally driven ejection behavior, along with the modeled particle ejection velocities, are in remarkable agreement to those we found for P/2010 R2 (La Sagra).

  2. ON THE DUST ENVIRONMENT OF MAIN-BELT COMET 313 P/Gibbs

    SciTech Connect

    Pozuelos, F. J.; Moreno, F.

    2015-06-10

    We present observations carried out using the 10.4 m Gran Telescopio Canarias and an interpretative model of the dust environment of activated asteroid 313 P/Gibbs. We discuss three different models relating to different values of the dust parameters, i.e., dust loss rate, maximum and minimum sizes of particles, power index of the size distribution, and emission pattern. The best model corresponds to an isotropic emission of particles which started on August 1. The sizes of grains were in the range of 0.1−2000 μm, with velocities for 100 μm particles between 0.4−1.9 m s{sup −1}, with a dust production rate in the range of 0.2−0.8 kg s{sup −1}. The dust tails’ brightnesses and morphologies are best interpreted in terms of a model of sustained and low dust emission driven by water-ice sublimation, spanning since 2014 August 1, and triggered by a short impulsive event. This event produced an emission of small particles of about 0.1 μm with velocities of ∼4 m s{sup −1}. From our model we deduce that the activity of this main-belt comet continued for at least four months since activation.

  3. THE DUST ENVIRONMENT OF MAIN-BELT COMET P/2010 R2 (LA SAGRA)

    SciTech Connect

    Moreno, F.; Lara, L. M.; Ortiz, J. L.; De Leon, J.; Molina, A.

    2011-09-01

    We present a model of the dust environment of Main-Belt Comet P/2010 R2 (La Sagra) from images acquired during the period 2010 October-2011 January. The tails are best simulated by anisotropic ejection models, with emission concentrated near the nucleus south pole, the spin axis having an obliquity near 90{sup 0}, indicative of a possible seasonally driven behavior. The dust mass loss rate increases rapidly shortly before perihelion, reaching a maximum value of {approx}4 kg s{sup -1}, and maintaining a sustained, cometary-like, activity of about 3-4 kg s{sup -1} up to at least 200 days after perihelion, the date of the latest observation. The size distribution function is characterized by particles in the 5 x 10{sup -4} cm to 1 cm radius range, assuming a time-constant power-law distribution with an index of -3.5. The ejection velocities are compatible with water-ice sublimation activity at the heliocentric distance of 2.7 AU, with values of 10-20 cm s{sup -1} for particle radius of 1 cm, and inverse square root dependence on particle size, typical of hydrodynamical gas drag.

  4. Hubble space telescope investigation of main-belt comet 133P/Elst-Pizarro

    SciTech Connect

    Jewitt, David; Ishiguro, Masateru; Weaver, Harold; Agarwal, Jessica; Mutchler, Max; Larson, Steven

    2014-05-01

    We report new observations of the prototype main-belt comet (active asteroid) 133P/Elst-Pizarro taken at high angular resolution using the Hubble Space Telescope. The object has three main components: (1) a point-like nucleus; (2) a long, narrow antisolar dust tail; and (3) a short, sunward anti-tail. There is no resolved coma. The nucleus has a mean absolute magnitude H{sub V} = 15.70 ± 0.10 and a light curve range ΔV = 0.42 mag, the latter corresponding to projected dimensions 3.6 × 5.4 km (axis ratio 1.5:1) at the previously measured geometric albedo of 0.05 ± 0.02. We explored a range of continuous and impulsive emission models to simultaneously fit the measured surface brightness profile, width, and position angle of the antisolar tail. Preferred fits invoke protracted emission, over a period of 150 days or less, of dust grains following a differential power-law size distribution with index 3.25 ≤q ≤ 3.5 and with a wide range of sizes. Ultra-low surface brightness dust projected in the sunward direction is a remnant from emission activity occurring in previous orbits, and consists of the largest (≥cm-sized) particles. Ejection velocities of one-micron-sized particles are comparable to the ∼1.8 m s{sup –1} gravitational escape speed of the nucleus, while larger particles are released at speeds less than the gravitational escape velocity. The observations are consistent with, but do not prove, a hybrid hypothesis in which mass loss is driven by gas drag from the sublimation of near-surface water ice, but escape is aided by centripetal acceleration from the rotation of the elongated nucleus. No plausible alternative hypothesis has been identified.

  5. PHYSICAL PROPERTIES OF MAIN-BELT COMET 176P/LINEAR

    SciTech Connect

    Hsieh, Henry H.; Ishiguro, Masateru; Lacerda, Pedro; Jewitt, David E-mail: p.lacerda@qub.ac.uk E-mail: jewitt@ucla.edu

    2011-07-15

    We present a physical characterization of comet 176P/LINEAR, the third discovered member of the new class of main-belt comets, which exhibit cometary activity but are dynamically indistinguishable from main-belt asteroids. Observations show the object exhibiting a fan-shaped tail for at least one month in late 2005, but then becoming inactive in early 2006. During this active period, we measure broadband colors of B - V = 0.63 {+-} 0.02, V - R = 0.35 {+-} 0.02, and R - I = 0.31 {+-} 0.04. Using data from when the object was observed to be inactive, we derive best-fit IAU phase function parameters of H = 15.10 {+-} 0.05 mag and G = 0.15 {+-} 0.10, and best-fit linear phase function parameters of m(1, 1, 0) = 15.35 {+-} 0.05 mag and {beta} = 0.038 {+-} 0.005 mag deg{sup -1}. From this baseline phase function, we find that 176P exhibits a mean photometric excess of {approx}30% during its active period, implying an approximate total coma dust mass of M{sub d} {approx} (7.2 {+-} 3.6) x 10{sup 4} kg. From inactive data obtained in early 2007, we find a rotation period of P{sub rot} = 22.23 {+-} 0.01 hr and a peak-to-trough photometric range of {Delta}m {approx} 0.7 mag. Phasing our photometric data from 176P's 2005 active period to this rotation period, we find that the nucleus exhibits a significantly smaller photometric range than in 2007 that cannot be accounted for by coma damping effects, and as such, are attributed by us to viewing geometry effects. A detailed analysis of these geometric effects showed that 176P is likely to be a highly elongated object with an axis ratio of 1.8 < b/a < 2.1, an orbital obliquity of {epsilon} {approx} 60{sup 0}, and a solstice position at a true anomaly of {nu}{sub o} = 20{sup 0} {+-} 20{sup 0}. Numerical modeling of 176P's dust emission found that its activity can only be reproduced by asymmetric dust emission, such as a cometary jet. We find plausible fits to our observations using models assuming {approx}10 {mu}m dust particles

  6. Testing the comet nature of main belt comets. The spectra of 133P/Elst-Pizarro and 176P/LINEAR

    NASA Astrophysics Data System (ADS)

    Licandro, J.; Campins, H.; Tozzi, G. P.; de León, J.; Pinilla-Alonso, N.; Boehnhardt, H.; Hainaut, O. R.

    2011-08-01

    Context. Dynamically, 133P/Elst-Pizarro and 176P/LINEAR are main belt asteroids, likely members of the Themis collisional family, and unlikely of cometary origin. They have been observed with cometary-like tails, which may be produced by water-ice sublimation. They are part of a small group of objects called Main Belt Comets (MBCs, Hsieh & Jewitt 2006). Aims: We attempt to determine if these MBCs have spectral properties compatible with those of comet nuclei or with other Themis family asteroids. Methods: We present the visible spectrum of MBCs 133P and 176P, as well as three Themis family asteroids: (62) Erato, (379) Huenna and (383) Janina, obtained in 2007 using three telescopes at "El Roque de los Muchachos" Observatory, in La Palma, Spain, and the 8 m Kueyen (UT2) VLT telescope at Cerro Paranal, Chile. The spectra of the MBCs are compared with those of the Themis family asteroids, comets, likely "dormant" comets and asteroids with past cometary-like activity in the near-Earth (NEA) population. As 133P was observed active, we also look for the prominent CN emission around 0.38 μm typically observed in comets, to test if the activity is produced by the sublimation of volatiles. Results: The spectra of 133P and 176P resemble best those of B-type asteroid and are very similar to those of Themis family members and another activated asteroid in the near-Earth asteroid population, (3200) Phaethon. On the other hand, these spectra are significantly different from the spectrum of comet 162P/Siding-Spring and most of the observed cometary nuclei. CN gas emission is not detected in the spectrum of 133P. We determine an upper limit for the CN production rate Q(CN) = 1.3 × 1021 mol/s, three orders of magnitude lower than the Q(CN) of Jupiter family comets observed at similar heliocentric distances. Conclusions: The spectra of 133P/Elst-Pizarro and 176P/LINEAR confirm that they are likely members of the Themis family of asteroids, fragments that probably retained

  7. Physical Properties of Main-belt Comet 176P/LINEAR

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Ishiguro, Masateru; Lacerda, Pedro; Jewitt, David

    2011-07-01

    We present a physical characterization of comet 176P/LINEAR, the third discovered member of the new class of main-belt comets, which exhibit cometary activity but are dynamically indistinguishable from main-belt asteroids. Observations show the object exhibiting a fan-shaped tail for at least one month in late 2005, but then becoming inactive in early 2006. During this active period, we measure broadband colors of B - V = 0.63 ± 0.02, V - R = 0.35 ± 0.02, and R - I = 0.31 ± 0.04. Using data from when the object was observed to be inactive, we derive best-fit IAU phase function parameters of H = 15.10 ± 0.05 mag and G = 0.15 ± 0.10, and best-fit linear phase function parameters of m(1, 1, 0) = 15.35 ± 0.05 mag and β = 0.038 ± 0.005 mag deg-1. From this baseline phase function, we find that 176P exhibits a mean photometric excess of ~30% during its active period, implying an approximate total coma dust mass of Md ~ (7.2 ± 3.6) × 104 kg. From inactive data obtained in early 2007, we find a rotation period of P rot = 22.23 ± 0.01 hr and a peak-to-trough photometric range of Δm ~ 0.7 mag. Phasing our photometric data from 176P's 2005 active period to this rotation period, we find that the nucleus exhibits a significantly smaller photometric range than in 2007 that cannot be accounted for by coma damping effects, and as such, are attributed by us to viewing geometry effects. A detailed analysis of these geometric effects showed that 176P is likely to be a highly elongated object with an axis ratio of 1.8 < b/a < 2.1, an orbital obliquity of ɛ ~ 60°, and a solstice position at a true anomaly of ν o = 20° ± 20°. Numerical modeling of 176P's dust emission found that its activity can only be reproduced by asymmetric dust emission, such as a cometary jet. We find plausible fits to our observations using models assuming ~10 μm dust particles continuously emitted over the period during which 176P was observed to be active, and a jet direction of 180° <~

  8. Origin of the Main-Belt Comets: Formed In-Situ or Interlopers from the Outer Solar System?

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Haghighipour, Nader

    2014-11-01

    Since the discovery of the first main-belt comet (MBC), 133P/Elst-Pizarro, the dynamical origin of cometary objects in the asteroid belt has been the subject of great interest. The comet-like activity of MBCs appears to be driven by the sublimation of water ice, which is intriguing given studies showing that icy objects from the asteroid belt region could have been a significant primordial source of terrestrial water. However, while dynamical modeling of the first three known MBCs (Haghighipour, 2009, M&PS, 44, 1863-1869) favored in-situ formation as the most probable scenario for the origin of these objects, the possibility that MBCs could be interlopers from the outer solar system has never been definitively ruled out. The Tisserand parameter with respect to Jupiter, T_J, is commonly used to characterize the dynamical origin of a small solar system object. Asteroids believed to have formed in situ in the asteroid belt generally have T_J>3 and comets which are presumed to have formed in the outer solar system generally have T_J<3. All of the known MBCs have T_J>3, suggesting that they formed in situ, but we are interested in investigating whether objects with T_J<3 can in fact evolve onto stable main-belt orbits with T_J>3. We have studied this issue by integrating the orbits of a large number of test particles with T_J values close to 3 (2.8 < T_J < 3.2) in order to observe what happens to particles close to the canonical T_J=3 boundary between asteroids and comets. We confirm that T_J=3 is not a hard boundary, as we find objects with T_J < 3 that are dynamically stable over timescales longer than typical cometary dynamical lifetimes, as well as objects with T_J > 3 that are dynamically unstable over typical cometary dynamical lifetimes. Intriguingly, we also find that a small fraction of particles with T_J < 3 do in fact evolve onto orbits similar to those of certain known MBCs, specifically those with large eccentricities or inclinations. This suggests that an

  9. X-shooter search for outgassing from main belt comet P/2012 T1 (Pan-STARRS)

    NASA Astrophysics Data System (ADS)

    Snodgrass, C.; Yang, B.; Fitzsimmons, A.

    2017-09-01

    Context. Main belt comets are a recently identified population of minor bodies with stable asteroid-like orbits but cometary appearances. Sublimation of water ice is the most likely mechanism for their recurrent activity (i.e. dust tails and dust comae), although there has been no direct detection of gas. These peculiar objects could hold the key to the origin of water on Earth. Aims: In this paper we present a search for the gas responsible for lifting dust from P/2012 T1 (Pan-STARRS), and review previous attempts at such measurements. To date such searches have mainly been indirect, looking for the common cometary gas CN rather than gasses related to water itself. Methods: We use the VLT and X-shooter to search for emission from OH in the UV, a direct dissociation product of water. Results: We do not detect any emission lines, and place an upper limit on water production rate from P/2012 T1 of 8-9 × 1025 molecules s-1. This is similar to limits derived from observations using the Herschel space telescope. Conclusions: We conclude that the best current facilities are incapable of detecting water emission at the exceptionally low levels required to produce the observed activity in main belt comets. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 290.C-5007(A).

  10. DISCOVERY OF MAIN-BELT COMET P/2006 VW{sub 139} BY Pan-STARRS1

    SciTech Connect

    Hsieh, Henry H.; Yang Bin; Haghighipour, Nader; Kaluna, Heather M.; Denneau, Larry; Jedicke, Robert; Wainscoat, Richard J.; Armstrong, James D.; Micheli, Marco; Keane, Jacqueline V.; Urban, Laurie; Riesen, Timm; Meech, Karen J.; Fitzsimmons, Alan; Novakovic, Bojan; Duddy, Samuel R.; Lowry, Stephen C.; Trujillo, Chadwick A.; Abe, Shinsuke; Cheng, Yu-Chi; and others

    2012-03-20

    The main-belt asteroid (300163) 2006 VW{sub 139} (later designated P/2006 VW{sub 139}) was discovered to exhibit comet-like activity by the Pan-STARRS1 (PS1) survey telescope using automated point-spread-function analyses performed by PS1's Moving Object Processing System. Deep follow-up observations show both a short ({approx}10'') antisolar dust tail and a longer ({approx}60'') dust trail aligned with the object's orbit plane, similar to the morphology observed for another main-belt comet (MBC), P/2010 R2 (La Sagra), and other well-established comets, implying the action of a long-lived, sublimation-driven emission event. Photometry showing the brightness of the near-nucleus coma remaining constant over {approx}30 days provides further evidence for this object's cometary nature, suggesting it is in fact an MBC, and not a disrupted asteroid. A spectroscopic search for CN emission was unsuccessful, though we find an upper limit CN production rate of Q{sub CN} < 1.3 Multiplication-Sign 10{sup 24} mol s{sup -1}, from which we infer a water production rate of Q{sub H{sub 2O}}<10{sup 26} mol s{sup -1}. We also find an approximately linear optical spectral slope of 7.2%/1000 A, similar to other cometary dust comae. Numerical simulations indicate that P/2006 VW{sub 139} is dynamically stable for >100 Myr, while a search for a potential asteroid family around the object reveals a cluster of 24 asteroids within a cutoff distance of 68 m s{sup -1}. At 70 m s{sup -1}, this cluster merges with the Themis family, suggesting that it could be similar to the Beagle family to which another MBC, 133P/Elst-Pizarro, belongs.

  11. The “Main-Belt Comets” are not comets, nor active asteroids; they are temporary shaken asteroids

    NASA Astrophysics Data System (ADS)

    Tancredi, Gonzalo

    2015-08-01

    Several objects in asteroidal orbits have presented comaes and tails similar to the ones presented by comets for short period of times. There are at present 16 objects in this group. Several hypotheses have been proposed to explain the activity of this object [Jewitt 2012]. Among them, the most accepted scenario for many objects is the ice sublimation and the ejection of dust, in a similar way as the cometary activity. Therefore several authors have coined these objects “Main Belt Comets” [Hsieh & Jewitt 2006]. Nevertheless, in some cases, some authors have concluded that the ejection of dust must be due to an impact.We propose an alternative model for the formation of the dusty comaes and tails.The impact of a small body against a larger one initially produces a crater and the ejection of dust at high velocity (>100 m/s). The dust is rapidly dispersed and it should be only observable just after the impact. In addition the impact generates a shock wave, which propagates to the body interior. The asteroid is globally shaken. Material is ejected at low velocities from the entire surface, similar to the low escape velocities at the surface. The particles move away from the asteroid due to the solar radiation pressure, forming the thin tails aligned with the orbital plane. These tails could persist for various months, as they have been seen in these objects.In addition, chunks of rock could be ejected in suborbital flights lasting for days; which, at return they would induce a new low-velocity ejection of particles. This process can explain some of the long-lasting events.The recurrence of the activity for some objects could be explained due to the collision with a dense meteor shower present in the main-belt.The so-called “Main Belt Comets” could be explained with a hypothesis that does not require the presence of ice on the surface of these objects. We also do not favor the term “Activated asteroids”, because it implies some kind of endogenous process

  12. CONSTRAINTS ON THE PHYSICAL PROPERTIES OF MAIN BELT COMET P/2013 R3 FROM ITS BREAKUP EVENT

    SciTech Connect

    Hirabayashi, Masatoshi; Sánchez, Diego Paul; Gabriel, Travis; Scheeres, Daniel J.

    2014-07-01

    Jewitt et al. recently reported that main belt comet P/2013 R3 experienced a breakup, probably due to rotational disruption, with its components separating on mutually hyperbolic orbits. We propose a technique for constraining physical properties of the proto-body, especially the initial spin period and cohesive strength, as a function of the body's estimated size and density. The breakup conditions are developed by combining mutual orbit dynamics of the smaller components and the failure condition of the proto-body. Given a proto-body with a bulk density ranging from 1000 kg m{sup –3} to 1500 kg m{sup –3} (a typical range of the bulk density of C-type asteroids), we obtain possible values of the cohesive strength (40-210 Pa) and the initial spin state (0.48-1.9 hr). From this result, we conclude that although the proto-body could have been a rubble pile, it was likely spinning beyond its gravitational binding limit and would have needed cohesive strength to hold itself together. Additional observations of P/2013 R3 will enable stronger constraints on this event, and the present technique will be able to give more precise estimates of its internal structure.

  13. DETERMINATION OF AN UPPER LIMIT FOR THE WATER OUTGASSING RATE OF MAIN-BELT COMET P/2012 T1 (PANSTARRS)

    SciTech Connect

    O'Rourke, L.; Teyssier, D.; Kueppers, M.; Snodgrass, C.; De Val-Borro, M.; Hartogh, P.; Biver, N.; Bockelee-Morvan, D.; Hsieh, H.; Micheli, M.; Fernandez, Y.

    2013-09-01

    A new Main-Belt Comet (MBC) P/2012 T1 (PANSTARRS) was discovered on 2012 October 6, approximately one month after its perihelion, by the Pan-STARRS1 survey based in Hawaii. It displayed cometary activity upon its discovery with one hypothesis being that the activity was driven by sublimation of ices; as a result, we searched for emission assumed to be driven by the sublimation of subsurface ices. Our search was of the H{sub 2}O 1{sub 10}-1{sub 01} ground state rotational line at 557 GHz from P/2012 T1 (PANSTARRS) with the Heterodyne Instrument for the Far Infrared on board the Herschel Space Observatory on 2013 January 16, when the object was at a heliocentric distance of 2.504 AU and a geocentric distance of 2.064 AU. Perihelion was in early 2012 September at a distance of 2.411 AU. While no H{sub 2}O line emission was detected in our observations, we were able to derive sensitive 3{sigma} upper limits for the water production rate and column density of <7.63 Multiplication-Sign 10{sup 25} molecules s{sup -1} and of <1.61 Multiplication-Sign 10{sup 11} cm{sup -2}, respectively. An observation taken on 2013 January 15 using the Very Large Telescope found the MBC to be active during the Herschel observation, suggesting that any ongoing sublimation due to subsurface ice was lower than our upper limit.

  14. Constraints on the Physical Properties of Main Belt Comet P/2013 R3 from its Breakup Event

    NASA Astrophysics Data System (ADS)

    Hirabayashi, Masatoshi; Scheeres, Daniel J.; Sánchez, Diego P.; Gabriel, Travis

    2014-11-01

    Main belt comet P/2013 R3 recently experienced a breakup, probably due to rotational disruption. From October through December 2013 its small components, with effective radii of 0.2-0.5 km, were observed to be escaping with a dispersion velocity of 0.2-0.5 m/s (Jewitt et al., Apj Letters 784, L8, 2014). This study develops and applies a technique for constraining the physical properties of the proto-body. The proto-body is assumed to be a uniformly rotating biaxial ellipsoid. To model this breakup event, we develop a combined analysis for the failure condition of the proto-body during its structural breakup phase and of the mutual orbit dynamics of the small components during its dynamics phase. To model the structural breakup phase we use structural analysis. Since a uniformly rotating ellipsoid with cohesion may fail across the central cross section first, we apply the Davidsson method (Davidsson, Icarus 149, 375-383, 2001) that considered the failure condition to be characterized by the yield condition of the averaged stress over the cross section. For the dynamics phase, we consider the energy conservation during this event. Calculation of the total energy requires consideration of the shape change due to the breakup phase, and we derive it without approximation (Scheeres, CMDA 89, 127-140, 2004). These phases can be combined based on the assumption that the initial spin period is equal to the spin period when the proto-body starts the structural breakup phase. Given a proto-body with a bulk density ranging from 1000 kg/m3 to 1500 kg/m3 (a typical range of bulk density for C-type asteroids), we obtain possible values of the cohesion (40 - 210 Pa) and the initial spin state (0.48 - 1.9 hr). We conclude that although the proto-body could have been a rubble pile, it was likely spinning beyond its gravitational binding limit and would have needed cohesive strength to hold itself together. If additional observations of P/2013 R3 are carried out, the present

  15. The contribution of comets in Near-Earth Object and Main Belt populations and the role of collisions in the physical properties of members of these populations.

    NASA Astrophysics Data System (ADS)

    Michel, P.

    2008-09-01

    The population of Near-Earth Objects (NEOs) is composed of small bodies of various origins. Groundbased observational programs have been developed to perform their inventory and to determine their physical properties. However, these observations contain many biases and the total population of NEOs with diameters down to a few hundreds of meters has not been identified yet. In recent years, the main sources of NEOs have been characterized [1]. Most of these bodies come from the asteroid main belt and the Jupiter-family comets and their source regions are linked to transport mechanisms (mean motion and secular resonances, slow diffusion mechanisms) to the NEO-space. It has then been possible to construct a complete model of the steady-state orbital, size and albedo distribution of NEOs and to determine the level of contribution of each of their sources, including the contribution of Jupiter-family comets. However, nothing is known regarding the contribution of longperiod comets. Physical observations have been conducted in order to identify potential dormant or extinct comets among small bodies in the NEO population and to determine the fraction of "comet candidates within the total NEO population. Combining the results of these observations with our model of NEO population to evaluate source region probabilities [1], it was found that 8 +/- 5% of the total asteroid-like NEO population may have originated as comets from the outer Solar System [2]. In the population of Main Belt (MB) asteroids, three members are known to display transient comet-like physical characteristics, including prolonged periods of dust emission leading to the formation of radiation pressure-swept tails [3]. These physical properties are most naturally explained as the result of sub-limation of near-surface ice from what are, dynamically, mainbelt asteroids (hence the name "main-belt comets" (MBCs) or, equivalently "icy asteroids"). No pausible dynamical path to the asteroid belt from the

  16. The Dynamics Of Inner Solar System Bodies With 2.8 < Tj < 3.2 And The Implications For The Origin Of Main-Belt Comets

    NASA Astrophysics Data System (ADS)

    Haghighipour, Nader; Hsieh, Henry H.

    2014-05-01

    Main-belt comets (MBCs) have attracted a great deal of interest since their identification as a new class of bodies by Hsieh and Jewitt in 2006. Much of this interest is due to the implication that MBC activity is driven by the sublimation of volatile material (presumed to be water ice) presenting these bodies as probable candidates for the delivery of a significant fraction of the Earth’s water. An interesting characteristic of these objects is that while similar to comets, they have comae and dusty tails, they resemble asteroids, dynamically (i.e., their Tisserand numbers with respect to Jupiter, Tj, are larger than 3). The Tisserand parameter is a conserved quantity in the restricted three-body problem, and the Tisserand parameter with respect to Jupiter is frequently used to distinguish between asteroids (Tj>3), which are thought to be stable on Gyr timescales, and comets (Tj<3), which are thought to have dynamical lifetimes on the order of 10^5-10^6 yr before colliding with the Sun or being ejected from the solar system. Since the solar system is of course significantly more complex than the idealized three-body system assumed in the derivation of the Tisserand parameter, however, the boundary line between asteroids and comets is in fact not as distinct as the common use of the Tisserand parameter would suggest. We studied the dynamical evolution of test particles with Tisserand numbers ranging from 2.8 to 3.2 to explore the behavior of solar system objects (such as MBCs) with Tj values close to the canonical asteroid-comet boundary of 3. We find, as expected, that Tj is not a hard boundary between asteroids and comets, and that we can expect to find objects that are dynamically stable (over the time period of integrations) with Tj<3 as well as objects that are dynamically unstable with Tj>3. Dynamical stability can be seen to be a function of not just Tj, but also other orbital elements such as the eccentricity and aphelion distance. We will report on the

  17. Exploring Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Sykes, M. V.; Larson, S. M.; Whiteley, R.; Fink, U.; Jedicke, R.; Emery, J.; Fevig, R.; Kelley, M.; Harris, A. W.; Ostro, S.; Reed, K.; Binzel, R. P.; Rivkin, A.; Magri, C.; Bottke, W.; Durda, D.; Walker, R.; Davis, D.; Hartmann, W. K.; Sears, D.; Yano, H.; Granahan, J.; Storrs, A.; Bus, S. J.; Bell, J. F.; Tholen, D.; Cellino, A.

    2001-11-01

    Terrestrial planet formation in the main asteroid belt was interrupted when growing protoplanets became sufficiently massive to gravitationally perturb the local population, causing bodies to collide with increased energy, thus ending accretion and commencing fragmentation and disruption. Few of these protoplanets are thought to have survived unshattered (e.g., Ceres, Vesta, Pallas), leaving a main belt population dominated by fragments of fragments, and significantly depleted of mass as a consequence of dynamical scattering. Yet, these fragments retain a record of the early steps of planet formation and evolution, as well as a record of early solar system conditions and the primordial composition gradient in that region. By exploring main belt asteroids through groundbased observations and spacecraft, modeling and theoretical work, we seek ultimately to recover this information. A single mission to a single target is not sufficient to address, in isolation, these questions. They require a foundation of robust, broad, and continuing groundbased, theoretical, and modeling programs. Such work is funded at a small fraction of a typical mission cost through the NASA Research and Analysis Program. Therefore, within the context of planetary decadal study recommendations to NASA, highest priority needs to be given to maintaining and growing a healthy R&A program over the next ten years and beyond. Missions also have an important role to play. An Earth orbiting remote sensing mission needs to be considered as a means of collecting important data for a large fraction of all main belt asteroids above a sub-kilometer diameter (while also realizing synergistic benefits to astrophysics). Missions to specific main belt targets can provide important new insights and leverage new understanding of existing data, models, and theories, but target definition (and corresponding instrument complement) is critical and must be based on our existing knowledge of these very diverse objects

  18. A SHORT-DURATION EVENT AS THE CAUSE OF DUST EJECTION FROM MAIN-BELT COMET P/2012 F5 (GIBBS)

    SciTech Connect

    Moreno, F.

    2012-12-10

    We present observations and an interpretative model of the dust environment of the Main-Belt Comet P/2010 F5 (Gibbs). The narrow dust trails observed can be interpreted unequivocally as an impulsive event that took place around 2011 July 1 with an uncertainty of {+-}10 days, and a duration of less than a day, possibly of the order of a few hours. The best Monte Carlo dust model fits to the observed trail brightness imply ejection velocities in the range 8-10 cm s{sup -1} for particle sizes between 30 cm and 130 {mu}m. This weak dependence of velocity on size contrasts with that expected from ice sublimation and agrees with that found recently for (596) Scheila, a likely impacted asteroid. The particles seen in the trail are found to follow a power-law size distribution of index Almost-Equal-To -3.7. Assuming that the slowest particles were ejected at the escape velocity of the nucleus, its size is constrained to about 200-300 m in diameter. The total ejected dust mass is {approx}> 5 Multiplication-Sign 10{sup 8} kg, which represents approximately 4%-20% of the nucleus mass.

  19. The location of Asteroidal Belt Comets (ABCs), in a comet's evolutionary diagram: The Lazarus Comets

    NASA Astrophysics Data System (ADS)

    Ferrín, Ignacio; Zuluaga, Jorge; Cuartas, Pablo

    2013-09-01

    There is a group of newly recognized asteroids in the main belt that are exhibiting cometary characteristics. We will call them Asteroidal Belt Comets or ABCs for short. The surprising property of these objects is that their orbits are entirely asteroidal while their behaviour is entirely cometary, with Tisserand invariants larger than 3.0, while all Jupiter family comets have Tisserand invariants smaller than 3.0. An analysis of their orbital and physical properties has resulted in the following conclusion. (1) We define the `detached group (DG)' as those objects that exhibit cometary characteristics (sublimating water) and have aphelion distances Q < 4.5 au. The DG contains all the ABCs traditionally recognized, plus a few other members not traditionally recognized like 2P and 107P. With the above definition there are 11 members of the ABC group: 2P, 107P, 133P, 176P, 233P, 238P, C/2008 R1, C/2010 R2, 2011 CR42, 3200 and 300163 = 2006 VW139. And there are three members of the collisioned asteroids, CA, P/2010 A2, 596 Scheila and P/2012 F5 Gibbs. (2) In the literature a common reason for activity is interplanetary collisions. Active objects sublimate ices except for the CA that have exhibited dust tails due to collisions and 3200 Phaethon activated by solar wind sputtering. In this work, we will trace the origin of activity to a diminution of their perihelion distances, a hypothesis that has not been previously explored in the literature. (3) We have calibrated the blackbody (colour) temperature of comets versus perihelion distance, R, regardless of class. We find T = 325 ± 5 K/√R. (4) Using a mathematical model of the thermal wave we calculate the thickness of the crust or dust layer on comet nuclei. We find a thickness of 2.0 ± 0.5 m for comet 107P, 4.7 ± 1.2 m for comet 133P and 1.9 ± 0.5 m for a sample of nine comets. Note the small errors. (5) We have located three ABCs in an evolutionary diagram of Remaining Revolutions (RR) versus Water-Budget Age (WB

  20. Super-Comet or Big Asteroid Belt?

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1: Spectrograph of HD 69830

    This graph of data from NASA's Spitzer Space Telescope demonstrates that the dust around a nearby star called HD 69830 (upper line) has a very similar composition to that of Comet Hale-Bopp. Spitzer spotted large amounts of this dust in the inner portion of the HD 69830 system.

    The bumps and dips seen in these data, or spectra, represent the 'fingerprints' of various minerals. Spectra are created when an instrument called a spectrograph spreads light out into its basic parts, like a prism turning sunlight into a rainbow. These particular spectra reveal the presence of the silicate mineral called olivine, and more specifically, a type of olivine called forsterite, which is pictured in the inset box. Forsterite is a bright-green gem found on Earth, on the 'Green Sand Beach' of Hawaii among other places; and in space, in comets and asteroids.

    Because the dust around HD 69830 has a very similar make-up to that of Comet Hale-Bopp, astronomers speculate that it might be coming from a giant comet nearly the size of Pluto. Such a comet may have been knocked into the inner solar system of HD 69830, where it is now leaving in its wake a trail of evaporated dust.

    Nonetheless, astronomers say the odds that Spitzer has caught a 'super-comet' spiraling in toward its star - an unusual and relatively short-lived event - are slim. Instead, they favor the theory that the observed dust is actually the result of asteroids banging together in a massive asteroid belt.

    The data of HD 69830's dust were taken by Spitzer's infrared spectrograph. The data of Comet Hale-Bopp were taken by the European Space Agency's Infrared Observatory Satellite. The picture of forsterite comes courtesy of Dr. George Rossman, California Institute of Technology, Pasadena.

  1. Super-Comet or Big Asteroid Belt?

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1: Spectrograph of HD 69830

    This graph of data from NASA's Spitzer Space Telescope demonstrates that the dust around a nearby star called HD 69830 (upper line) has a very similar composition to that of Comet Hale-Bopp. Spitzer spotted large amounts of this dust in the inner portion of the HD 69830 system.

    The bumps and dips seen in these data, or spectra, represent the 'fingerprints' of various minerals. Spectra are created when an instrument called a spectrograph spreads light out into its basic parts, like a prism turning sunlight into a rainbow. These particular spectra reveal the presence of the silicate mineral called olivine, and more specifically, a type of olivine called forsterite, which is pictured in the inset box. Forsterite is a bright-green gem found on Earth, on the 'Green Sand Beach' of Hawaii among other places; and in space, in comets and asteroids.

    Because the dust around HD 69830 has a very similar make-up to that of Comet Hale-Bopp, astronomers speculate that it might be coming from a giant comet nearly the size of Pluto. Such a comet may have been knocked into the inner solar system of HD 69830, where it is now leaving in its wake a trail of evaporated dust.

    Nonetheless, astronomers say the odds that Spitzer has caught a 'super-comet' spiraling in toward its star - an unusual and relatively short-lived event - are slim. Instead, they favor the theory that the observed dust is actually the result of asteroids banging together in a massive asteroid belt.

    The data of HD 69830's dust were taken by Spitzer's infrared spectrograph. The data of Comet Hale-Bopp were taken by the European Space Agency's Infrared Observatory Satellite. The picture of forsterite comes courtesy of Dr. George Rossman, California Institute of Technology, Pasadena.

  2. OORT-Cloud and Kuiper-Belt Comets

    NASA Technical Reports Server (NTRS)

    Whipple, Fred L.

    1998-01-01

    This paper follows the broadly accepted theory that Oort-Cloud Comets originated in the Solar Nebula in the general region where the major planets, Jupiter and Saturn, were formed while the Kuiper-Belt Comets originated farther out where the temperatures were lower. The Oort-Cloud Comets are identified orbitally by long periods and random inclinations and, including the Halley-type comets, comets with a Tisserand Criterion less than 2.0. Kuiper-Belt comets are identified by short periods, usually much less than 200 years, and small inclinations to the ecliptic. Here two criteria for comet activity are found to separate the two classes of comets. These quantities NG1 and NG2, were intended to measure theoretical nongravitaional effects on comet orbits. They are only, mildly successful in correlations with observed cases of measured non-gravitational forces. But, in fact, their variations with perihelion distance separate the two classes of comets. The results are consistent with the theory that the activity or intrinsic brightness of Oort-Cloud Comets fall off faster with increasing perihelion distance that does the intrinsic brightness of short-period Kuiper-Belt Comets.

  3. The Kuiper belt and the solar system's comet disk.

    PubMed

    Gladman, Brett

    2005-01-07

    Our planetary system is embedded in a small-body disk of asteroids and comets, vestigial remnants of the original planetesimal population that formed the planets. Once formed, those planets dispersed most of the remaining small bodies. Outside of Neptune, this process has left our Kuiper belt and built the Oort cloud, as well as emplacing comets into several other identifiable structures. The orbits in these structures indicate that our outer solar system's comet disk was shaped by a variety of different physical processes, which teach us about how the giant planets formed. Recent work has shown that the scattered disk is the most likely source of short-period comets. Moreover, a growing body of evidence indicates that the sculpting of the Kuiper belt region may have involved large-scale planetary migration, the presence of other rogue planetary objects in the disk, and/or the close passage of other stars in the Sun's birth cluster.

  4. The Kuiper Belt and the Solar System's Comet Disk

    NASA Astrophysics Data System (ADS)

    Gladman, Brett

    2005-01-01

    Our planetary system is embedded in a small-body disk of asteroids and comets, vestigial remnants of the original planetesimal population that formed the planets. Once formed, those planets dispersed most of the remaining small bodies. Outside of Neptune, this process has left our Kuiper belt and built the Oort cloud, as well as emplacing comets into several other identifiable structures. The orbits in these structures indicate that our outer solar system's comet disk was shaped by a variety of different physical processes, which teach us about how the giant planets formed. Recent work has shown that the scattered disk is the most likely source of short-period comets. Moreover, a growing body of evidence indicates that the sculpting of the Kuiper belt region may have involved large-scale planetary migration, the presence of other rogue planetary objects in the disk, and/or the close passage of other stars in the Sun's birth cluster.

  5. Eccentricity distribution in the main asteroid belt

    NASA Astrophysics Data System (ADS)

    Malhotra, Renu; Wang, Xianyu

    2017-03-01

    The observationally complete sample of the main belt asteroids now spans more than two orders of magnitude in size and numbers more than 64 000 (excluding collisional family members). We undertook an analysis of asteroids' eccentricities and their interpretation with simple physical models. We find that a century old conclusion that the asteroids' eccentricities follow a Rayleigh distribution holds for the osculating eccentricities of large asteroids, but the proper eccentricities deviate from a Rayleigh distribution; there is a deficit of eccentricities smaller than ∼0.1 and an excess of larger eccentricities. We further find that the proper eccentricities do not depend significantly on asteroid size but have strong dependence on heliocentric distance; the outer asteroid belt follows a Rayleigh distribution, but the inner belt is strikingly different. Eccentricities in the inner belt can be modelled as a vector sum of a primordial eccentricity vector of random orientation and magnitude drawn from a Rayleigh distribution of parameter ∼0.06, and an excitation of random phase and magnitude ∼0.13. These results imply that when a late dynamical excitation of the asteroids occurred, it was independent of asteroid size and was stronger in the inner belt than in the outer belt. We discuss implications for the primordial asteroid belt and suggest that the observationally complete sample size of main belt asteroids is large enough that more sophisticated model-fitting of the eccentricities is warranted and could serve to test alternative theoretical models of the dynamical excitation history of asteroids and its links to the migration history of the giant planets.

  6. Lightcurve Analysis for Ten Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Casalnuovo, Giovanni Battista

    2017-07-01

    Photometric observations of ten main-belt asteroids, 2854 Rawson, 3113 Chizhevskij, 5318 Dientzenhofer, (5563) 1991 VZ1, 7143 Haramura, 10421 Dalmatin, (11386) 1998 TA18, (18429) 1994 AO1, (23496) 1991 VN3, and (31782) 1999 KM6 were made at the Eurac Observatory (MPC C62). Results of lightcurve analysis are presented.

  7. How to install main belts efficiently

    SciTech Connect

    Ketz, J.

    1985-03-01

    Belt conveyors and mine cars form an integral part of the connecting link between an underground working area and the preparation plant. Problems in the link are sometimes neglected while attention is centered on the face. Eventually the neglect may cause the mine to shut down because its operating costs are too high. Mine operators can reduce the chances of such a calamity by correctly installing one of those key links, the main haulage belt conveyors. The following recommendations are based on the author's engineering experience in deep mines. The drive is the heart of the belt conveyor. Five components must be installed properly so that the mechanics can fine tune the belt conveyor drive. A concrete base is essential for a main haulage conveyor projected to be in service for more than 10 years. Beams with 6-in.-wide flanges should be welded to rails embedded in the concrete base. The drive is welded to the 6-in. beams for a permanent installation, and the beams allow dust to be cleaned from under the drive.

  8. The evolution of water in carbonaceous main belt asteroids

    NASA Astrophysics Data System (ADS)

    Kaluna, Heather Maria

    2015-09-01

    Astronomical signatures of water in the asteroid belt are found in the form of aqueously altered minerals and main-belt comets (MBCs). When paired with cosmochemical studies of meteorites, observations of aqueously altered minerals and MBCs may provide us with a way to constrain the availability of water during asteroid parent body accretion and thus constrain the position of the snow line in the early solar system. However, space weathering processes reduce our ability to accurately characterize asteroid compositions and match them with meteorite analogs. The goal of this dissertation is to study the role of water in space weathering processes, search for space weathering trends among C-complex asteroids, and characterize the mineralogy of two C-complex asteroid families. We simulate micrometeorite bombardment of C-complex minerals through the laser irradiation of Mg and Fe-end member phyllosilicates. We find that the minerals lizardite and cronstedtite show both an increase and decrease in spectral slopes as a function of irradiation. However, the overall spectral trends of these two minerals are notably different, and space weathering trends may vary with the degree of aqueous alteration experienced by an asteroid parent body. Our data show that dehydration of hydrous minerals is not necessary for space weathering processes to be effective. We conducted an extensive telescopic survey of the Beagle and Themis asteroid families, and obtained one of the most comprehensive visible and near-infrared data sets on these asteroids to date. Our data suggest space weathering of C-complex asteroids occurs primarily at visible wavelengths, and results in an increase in spectral slopes and a decrease in albedo with age. Lastly, we explore the evolution of water ice in the main belt comet 133P/Elst-Pizarro. We use photometry data along with lightcurve inversion to constrain the pole orientation of 133P/Elst-Pizarro. We use the resulting obliquity (≥75°) to model the

  9. Escape of asteroids from the main belt

    NASA Astrophysics Data System (ADS)

    Granvik, Mikael; Morbidelli, Alessandro; Vokrouhlický, David; Bottke, William F.; Nesvorný, David; Jedicke, Robert

    2017-02-01

    Aims: We locate escape routes from the main asteroid belt, particularly into the near-Earth-object (NEO) region, and estimate the relative fluxes for different escape routes as a function of object size under the influence of the Yarkovsky semimajor-axis drift. Methods: We integrated the orbits of 78 355 known and 14 094 cloned main-belt objects and Cybele and Hilda asteroids (hereafter collectively called MBOs) for 100 Myr and recorded the characteristics of the escaping objects. The selected sample of MBOs with perihelion distance q > 1.3 au and semimajor axis a < 4.1 au is essentially complete, with an absolute magnitude limit ranging from HV < 15.9 in the inner belt (a < 2.5 au) to HV < 14.4 in the outer belt (2.5 au < a < 4.1 au). We modeled the semimajor-axis drift caused by the Yarkovsky force and assigned four different sizes (diameters of 0.1, 0.3, 1.0, and 3.0 km) and random spin obliquities (either 0 deg or 180 deg) for each test asteroid. Results: We find more than ten obvious escape routes from the asteroid belt to the NEO region, and they typically coincide with low-order mean-motion resonances with Jupiter and secular resonances. The locations of the escape routes are independent of the semimajor-axis drift rate and thus are also independent of the asteroid diameter. The locations of the escape routes are likewise unaffected when we added a model for Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) cycles coupled with secular evolution of the rotation pole as a result of the solar gravitational torque. A Yarkovsky-only model predicts a flux of asteroids entering the NEO region that is too high compared to the observationally constrained flux, and the discrepancy grows larger for smaller asteroids. A combined Yarkovsky and YORP model predicts a flux of small NEOs that is approximately a factor of 5 too low compared to an observationally constrained estimate. This suggests that the characteristic timescale of the YORP cycle is longer than our canonical

  10. Period Determination of Six Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Ferrero, Andrea

    2014-07-01

    Observations of six main-belt asteroids (MBA) produced lightcurve parameters of: 487 Venetia, P = 13.34 ± 0.01 h, A = 0.20 mag; 684 Hildburg, P = 15.89 ± 0.01 h, A = 0.22 mag; 772 Tanete, P = 8.629 ± 0.001 h, A = 0.18 mag.; 1181 Lilith, P = 15.04 ± 0.01 h, A = 0.11 mag.; 1246 Chaka, P = 25.44 ± 0.01 h, A = 0.25 mag.; and 2834 Christy Carol, P = 12.79 ± 0.01 h, A = 0.39 mag.

  11. Inner main belt asteroids in Slivan states?

    NASA Astrophysics Data System (ADS)

    Vraštil, J.; Vokrouhlický, D.

    2015-07-01

    Context. The spin state of ten asteroids in the Koronis family has previously been determined. Surprisingly, all four asteroids with prograde rotation were shown to have spin axes nearly parallel in the inertial space. All asteroids with retrograde rotation had large obliquities and rotation periods that were either short or long. The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect has been demonstrated to be able to explain all these peculiar facts. In particular, the effect causes the spin axes of the prograde rotators to be captured in a secular spin-orbit resonance known as Cassini state 2, a configuration dubbed "Slivan state". Aims: It has been proposed based on an analysis of a sample of asteroids in the Flora family that Slivan states might also exist in this region of the main belt. This is surprising because convergence of the proper frequency s and the planetary frequency s6 was assumed to prevent Slivan states in this zone. We therefore investigated the possibility of a long-term stable capture in the Slivan state in the inner part of the main belt and among the asteroids previously observed. Methods: We used the swift integrator to determine the orbital evolution of selected asteroids in the inner part of the main belt. We also implemented our own secular spin propagator into the swift code to efficiently analyze their spin evolution. Results: Our experiments show that the previously suggested Slivan states of the Flora-region asteroids are marginally stable for only a small range of the flattening parameter Δ. Either the observed spins are close to the Slivan state by chance, or additional dynamical effects that were so far not taken into account change their evolution. We find that only the asteroids with very low-inclination orbits (lower than ≃4°, for instance) could follow a similar evolution path as the Koronis members and be captured in their spin state into the Slivan state. A greater number of asteroids in the inner main-belt Massalia

  12. Asteroids, comets, Kuiper Belt objects, meteors: the ACM (AKM) 2002 perspective

    NASA Astrophysics Data System (ADS)

    Binzel, Richard P.

    2002-11-01

    An impressionistic overview is given on the state of science of Asteroider, Kometer, Meteorer (AKM), where the Swedish spelling is adopted in recognition of the origin of the ACM conference series. Asteroider (asteroids) are a field that has come of age to the point of asking sophisticated geological and geophysical questions based on dedicated spacecraft missions. Kometer (comets) are coming of age with a strong international emphasis toward new comet missions and ever increasing sophistication of Earth-based observations. K also stands for Kuiper belt objects, a field that wasn't invented when our conference series began but whose inclusion we embrace and recognize as being integral to our science. (Hence the recommendation that we adopt the moniker AKM to proclaim fully our inclusivity) KBOs are an emerging field, perhaps analogous to a fast growing child. The presently known number of KBOs is comparable to the number of known main-belt asteroids in 1900, suggesting that we are just beginning to learn about this region. Meteorer (meteors) is a rejuvenated field that has enjoyed spectacular recent successes in detailed predictions of the Leonid shower and in just recently recording the fall and recovering the Neuschwanstein meteorite. The future outlook portends the greatest advancement in K (kometer and KBOs) with broad interdisciplinary implications.

  13. Detecting Mass Loss in Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Sandberg, Erik; Rajagopal, Jayadev; Ridgway, Susan E.; Kotulla, Ralf C.; Valdes, Francisco; Allen, Lori

    2016-01-01

    Sandberg, E., Rajagopal, J., Ridgway, S.E, Kotulla, R., Valdes, F., Allen, L.The Dark Energy Camera (DECam) on the 4m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO) is being used for a survey of Near Earth Objects (NEOs). Here we attempt to identify mass loss in main belt asteroids (MBAs) from these data. A primary motivation is to understand the role that asteroids may play in supplying dust and gas for debris disks. This work focuses on finding methods to automatically pick out asteroids that have qualities indicating possible mass loss. Two methods were chosen: looking for flux above a certain threshold in the asteroid's radial profile, and comparing its PSF to that of a point source. After sifting through 490 asteroids, several have passed these tests and should be followed up with a more rigorous analysis.Sandberg was supported by the NOAO/KPNO Research Experience for Undergraduates (REU) Program which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829)

  14. On future opportunities to observe gravitational scattering of main belt asteroids into NEO source regions

    NASA Astrophysics Data System (ADS)

    Ivantsov, A.; Eggl, S.; Hestroffer, D.; Thuillot, W.

    2014-12-01

    Physical and orbital properties of the current NEO population can be explained when one assumes that their primary origin lies in the asteroid main-belt and Jupiter-family comet (P<20 years) regions (Bottke et al. 2000a, 2002; Greenstreet et al. 2012; Mainzer et al. 2012). Orbital resonances with the Gas Giants within the main-belt which cause strong eccentricity-pumping are transport mechanisms that can carry main belt asteroids into the inner Solar System. Two well known resonances in this respect are the 2:1 and 3:1 mean-motion resonance with Jupiter as well as the nu 5 and nu 6 secular resonances. Since the average life-time of asteroids in resonances is much shorter than the age of the Solar System, a constant flux of asteroids into resonant regions is necessary in order to sustain the observed NEO population (Morbidelli et al. 2002).

  15. Search for Water in Outer Main Belt Based on AKARI Asteroid Catalog

    NASA Astrophysics Data System (ADS)

    Usui, Fumihiko

    2012-06-01

    We propose a program to search water ice on the surface of asteroids in the outer main belt regions, which have high albedo measured with AKARI. The distribution of water in the main belt provides important information to understanding of the formation and evolution of the solar system, because water is a good indicator of temperature in the early solar nebula. The existence of water ice is a hot topic in the solar system studies today. Water ice is recently found in the outer region of the main asteroid belt and some of them are linked to the main belt comets. Brand-new albedo data brought by AKARI opens the possibility of detection of water ice on the C-type asteroids. Here we propose to make the spectroscopic observations with the Subaru telescope in the near-infrared wavelengths to detect water ice on these high-albedo C-type asteroids. Thanks to a large aperture of Subaru telescope and a high altitude of Mauna Kea, it can be only possible to observe a weak signal of the existence of water on the surface of asteroids with a certain S/N. In addition, using the imaging data taken prior to IRCS spectroscopic mode, we intend to seek any comet-like activities by investigating diffuseness of the asteroids, which can be detected by comparing the observed point-spread functions with those of field stars.

  16. Aqueous alteration on main-belt asteroids

    NASA Astrophysics Data System (ADS)

    Fornasier, S.; Lantz, C.; Barucci, M.; Lazzarin, M.

    2014-07-01

    The study of aqueous alteration is particularly important for unraveling the processes occurring during the earliest times in Solar System history, as it can give information both on the thermal processes and on the localization of water sources in the asteroid belt, and for the associated astrobiological implications. The aqueous alteration process produces the low temperature (< 320 K) chemical alteration of materials by liquid water which acts as a solvent and produces materials like phyllosilicates, sulphates, oxides, carbonates, and hydroxides. This means that liquid water was present in the primordial asteroids, produced by the melting of water ice by heating sources, very probably by ^{26}Al decay. Hydrated minerals have been found mainly on Mars surface, on primitive main-belt asteroids (C, G, B, F, and P-type, following the classification scheme by Tholen, 1984) and possibly also on few transneptunian objects. Reflectance spectroscopy of aqueous altered asteroids shows absorption features in the 0.6-0.9 and 2.5-3.5-micron regions, which are diagnostic of, or associated with, hydrated minerals. In this work, we investigate the aqueous alteration process on a large sample of 600 visible spectra of C-complex asteroids available in the literature. We analyzed all these spectra in a similar way to characterize the absorption-band parameters (band center, depth, and width) and spectral slope, and to look for possible correlations between the aqueous alteration process and the asteroids taxonomic classes, orbital elements, heliocentric distances, albedo, and sizes. We find that 4.6 % of P, 7.7 % of F, 9.8 % of B, 50.5 % of C, and 100 % of the G-type asteroids have absorption bands in the visible region due to hydrated silicates. Our analysis shows that the aqueous alteration sequence starts from the P-type objects, practically unaltered, and increases through the P → F → B → C → G asteroids, these last being widely aqueously altered, strengthening thus

  17. The evolution of comets in the Oort cloud and Kuiper belt.

    PubMed

    Alan Stern, S

    2003-08-07

    Comets are remnants from the time when the outer planets formed, approximately 4-4.5 billion years ago. They have been in storage since then in the Oort cloud and Kuiper belt-distant regions that are so cold and sparsely populated that it was long thought that comets approaching the Sun were pristine samples from the time of Solar System formation. It is now recognized, however, that a variety of subtle but important evolutionary mechanisms operate on comets during their long storage, so they can no longer be regarded as wholly pristine.

  18. Migration of Matter from the Edgeworth-Kuiper and Main Asteroid Belts to the Earth

    NASA Technical Reports Server (NTRS)

    Ipatov. S. I.; Oegerle, William (Technical Monitor)

    2002-01-01

    The main asteroid belt (MAB), the Edgeworth-Kuiper belt (EKB), and comets belong to the main sources of dust in the Solar System. Most of Jupiter-family comets came from the EKB. Comets can be distracted due to close encounters with planets and the Sun, collisions with small bodies, a nd internal forces. We support the Eneev's idea that the largest objects in the ELB and MAB could be formed directly by the compression of rarefied dust condensations of the protoplanetary cloud but not by the accretion of small (for example, 1-km) planetesimals. The total mass of planetesimals that entered the EKB from the feeding zone of the giant planets during their accumulation could exceed tens of Earth's masses. These planetesimals increased eccentricities of 'local' trans-Neptunian objects (TNOs) and swept most of these TNOs. A small portion of such planetesimals could left beyond Neptune's orbit in highly eccentric orbits. The results of previous investigations of migration and collisional evolution of minor bodies were summarized. Mainly our recent results are presented.

  19. 32. photographer unknown undated AGGREGATE PLANT SHOWING MAIN BELT CONVEYOR ...

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

    32. photographer unknown undated AGGREGATE PLANT SHOWING MAIN BELT CONVEYOR UNITS AND STORAGE UNIT. - Bonneville Project, Columbia River, 1 mile Northeast of Exit 40, off Interstate 84, Bonneville, Multnomah County, OR

  20. The Collisional Evolution of the Main Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Bottke, W. F.; Brož, M.; O'Brien, D. P.; Campo Bagatin, A.; Morbidelli, A.; Marchi, S.

    Collisional and dynamical models of the main asteroid belt allow us to glean insights into planetesimal- and planet-formation scenarios as well as how the main belt reached its current state. Here we discuss many of the processes affecting asteroidal evolution and the constraints that can be used to test collisional model results. We argue the main belt's wavy size-frequency distribution for diameter D < 100-km asteroids is increasingly a byproduct of comminution as one goes to smaller sizes, with its shape a fossil-like remnant of a violent early epoch. Most D > 100-km asteroids, however, are primordial, with their physical properties set by planetesimal formation and accretion processes. The main-belt size distribution as a whole has evolved into a collisional steady state, and it has possibly been in that state for billions of years. Asteroid families provide a critical historical record of main-belt collisions. The heavily depleted and largely dispersed "ghost families," however, may hold the key to understanding what happened in the primordial days of the main belt. New asteroidal fragments are steadily created by both collisions and mass shedding events via YORP spinup processes. A fraction of this population, in the form of D < 30 km fragments, go on to escape the main belt via the Yarkovsky/YORP effects and gravitational resonances, thereby creating a quasi-steady-state population of planet-crossing and near-Earth asteroids. These populations go on to bombard all inner solar system worlds. By carefully interpreting the cratering records they produce, it is possible to constrain how portions of the main-belt population have evolved with time.

  1. Dynamical studies of Centaurs and their sources: interactions with the Main Belt

    NASA Astrophysics Data System (ADS)

    Galiazzo, Mattia; Carruba, Valerio; Wiegert, Paul

    2015-08-01

    Centaurs are objects whose orbits are found between those of the giant planets. Their main source is presumed to be the Trans-Neptunian objects (TNOs), and they are among the sources of Near-Earth Objects. Their dynamical evolution is heavily influenced by close encounters with giant planets and some of them were most likely scattered into their current orbits. After experiencing close encounters with the giant planets, Centaurs may have their eccentricity increased to values large enough to reach the main belt (a<3.8 au) and even the region of the Near-Earth asteroids, with a perihelion, (q<1.3 au). Some may become short-period comets and a fraction falls into the Sun or become sun-grazers. In this work we propose to investigate the interactions of dynamically evolving Centaurs and other members of the outer Solar System (i.e. Plutinos and Trans-Neptunian objects which cross the orbit of Neptune) with main belt asteroids to determine if chaotic scattering caused by close encounters and impacts may have played (and/or still play) a role in the dynamical evolution of the main belt. Preliminary results show already that TNOs (larger than 100 km size) are capable of reaching the inner solar system and may cross the main belt several times during an interval of time at least of ~10 kyrs. Centaurs such as 1995 S1 can generate significant deflections to the orbits of main belt asteroids after close encounters. In particular, we plan to investigate if close encounters with large (diameters larger than 100 km) outer Solar System bodies could have been responsible for the scattering of V-type asteroids from the Vesta family beyond the 3J:1 mean motion resonance, into the central and outer main belt.

  2. A Search for 23rd Magnitude Kuiper Belt Comets

    NASA Technical Reports Server (NTRS)

    Luu, Jane

    1997-01-01

    The goal of the project was to identify a statistically significant sample of large (200 km-sized) Kuiper Belt Objects (KBOs), by covering 10 sq. degrees of the sky to a red limiting magnitude m(sub R) = 23. This work differs from, but builds on, previous surveys of the outer solar system in that it will cover a large area to a limiting magnitude that is deep enough to guarantee positive results. The proposed work should provide us with a significant number of 200 km-size KBOs (approx. 20 are expected) for subsequent studies. Such a sample is crucial if we are to investigate the statistical properties of the Belt and its members. It was modified the original research strategy to accommodate unanticipated problems such as the urgent need for follow-up observations,the original goal was still reached: we have substantially increased the number of Kuiper Belt Objects brighter than 23rd mag.

  3. The fossilized size distribution of the main asteroid belt

    NASA Astrophysics Data System (ADS)

    Bottke, William F.; Durda, Daniel D.; Nesvorný, David; Jedicke, Robert; Morbidelli, Alessandro; Vokrouhlický, David; Levison, Hal

    2005-05-01

    Planet formation models suggest the primordial main belt experienced a short but intense period of collisional evolution shortly after the formation of planetary embryos. This period is believed to have lasted until Jupiter reached its full size, when dynamical processes (e.g., sweeping resonances, excitation via planetary embryos) ejected most planetesimals from the main belt zone. The few planetesimals left behind continued to undergo comminution at a reduced rate until the present day. We investigated how this scenario affects the main belt size distribution over Solar System history using a collisional evolution model (CoEM) that accounts for these events. CoEM does not explicitly include results from dynamical models, but instead treats the unknown size of the primordial main belt and the nature/timing of its dynamical depletion using innovative but approximate methods. Model constraints were provided by the observed size frequency distribution of the asteroid belt, the observed population of asteroid families, the cratered surface of differentiated Asteroid (4) Vesta, and the relatively constant crater production rate of the Earth and Moon over the last 3 Gyr. Using CoEM, we solved for both the shape of the initial main belt size distribution after accretion and the asteroid disruption scaling law QD∗. In contrast to previous efforts, we find our derived QD∗ function is very similar to results produced by numerical hydrocode simulations of asteroid impacts. Our best fit results suggest the asteroid belt experienced as much comminution over its early history as it has since it reached its low-mass state approximately 3.9-4.5 Ga. These results suggest the main belt's wavy-shaped size-frequency distribution is a "fossil" from this violent early epoch. We find that most diameter D≳120 km asteroids are primordial, with their physical properties likely determined during the accretion epoch. Conversely, most smaller asteroids are byproducts of fragmentation

  4. 32. DETAIL OF MAIN DRIVE WHEELS AND BELT TENSIONING DEVICE ...

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

    32. DETAIL OF MAIN DRIVE WHEELS AND BELT TENSIONING DEVICE OF MAIN POWER TRAIN, LOOKING SOUTHEAST, LOOKING FORM BEHIND THE CLASSIFIER. THESE WHEELS DROVE THE BULL WHEELS ON THE STAMP BATTERIES ABOVE. THE TENSIONING DEVICE AT CENTER RIGHT CONTROLLED THE SPEED OF THE STAMPS. - Skidoo Mine, Park Route 38 (Skidoo Road), Death Valley Junction, Inyo County, CA

  5. An anomalous basaltic meteorite from the innermost main belt.

    PubMed

    Bland, Philip A; Spurny, Pavel; Towner, Martin C; Bevan, Alex W R; Singleton, Andrew T; Bottke, William F; Greenwood, Richard C; Chesley, Steven R; Shrbeny, Lukas; Borovicka, Jiri; Ceplecha, Zdenek; McClafferty, Terence P; Vaughan, David; Benedix, Gretchen K; Deacon, Geoff; Howard, Kieren T; Franchi, Ian A; Hough, Robert M

    2009-09-18

    Triangulated observations of fireballs allow us to determine orbits and fall positions for meteorites. The great majority of basaltic meteorites are derived from the asteroid 4 Vesta. We report on a recent fall that has orbital properties and an oxygen isotope composition that suggest a distinct parent body. Although its orbit was almost entirely contained within Earth's orbit, modeling indicates that it originated from the innermost main belt. Because the meteorite parent body would likely be classified as a V-type asteroid, V-type precursors for basaltic meteorites unrelated to Vesta may reside in the inner main belt. This starting location is in agreement with predictions of a planetesimal evolution model that postulates the formation of differentiated asteroids in the terrestrial planet region, with surviving fragments concentrated in the innermost main belt.

  6. Photometry and Lightcurve Analysis of 7 Main-Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Violante, R.; Leake, M. A.

    2012-12-01

    We report the synodic periods and lightcurves for three main-belt asteroids and provide lightcurves for four other main-belt asteroids. 676 Melitta has a period of 8.35 ± 0.05 hours, with an amplitude of 0.056 ± 0.026 magnitude; 688 Melanie has a period of 16.10 ± 0.05 hours, and an amplitude of 0.091 ± 0.019 magnitude; 1677 Tycho Brahe has a period of 3.89 ± 0.06 hours, and an amplitude of 0.564 ± 0.011 magnitude.

  7. Photometry and Lightcurve Analysis of 7 Main-Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Violante, Renata; Leake, M. A.

    2013-01-01

    We report the synodic periods and lightcurves for three main-belt asteroids and provide lightcurves for four other main-belt asteroids. 676 Melitta has a period of 8.35 ± 0.05 hours, with an amplitude of 0.056 ± 0.026 magnitude; 688 Melanie has a period of 16.10 ± 0.05 hours, and an amplitude of 0.091 ± 0.019 magnitude; 1677 Tycho Brahe has a period of 3.89 ± 0.06 hours, and an amplitude of 0.564 ± 0.011 magnitude.

  8. The Size Frequency Distribution of Small Main-Belt Asteroids

    NASA Technical Reports Server (NTRS)

    Burt, Brian J.; Trilling, David E.; Hines, Dean C.; Stapelfeldt, Karl R.; Rebull, Luisa M.; Fuentes, Cesar I.; Hulsebus, Alan

    2012-01-01

    The asteroid size distribution informs us about the formation and composition of the Solar System. We build on our previous work in which we harvest serendipitously observed data of the Taurus region and measure the brightness and size distributions of Main-belt asteroids. This is accomplished with the highly sensitive MIPS 24 micron channel. We expect to catalog 104 asteroids, giving us a statistically significant data set. Results from this investigation will allow us to characterize the total population of small, Main-belt asteroids. Here we will present new results on the completeness of our study; on the presence of size distribution variations with inclination and radial distance in the belt; and early result on other archival fields.

  9. Reddy Main Belt Asteroid Spectra V1.0

    NASA Astrophysics Data System (ADS)

    Reddy, V.; Sanchez, J. A.

    2016-08-01

    This data set contains low-resolution (R 150) near-infrared (0.7-2.5 microns) spectra of 90 main belt asteroids observed with the SpeX instrument on the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai'i. This data set archives reduced, calibrated spectra of targets of opportunity observed from 2001 to 2012.

  10. Lightcurve Analysis for Seven Main-belt Asteroids

    NASA Astrophysics Data System (ADS)

    Casalnuovo, Giovanni Battitsa

    2015-04-01

    Photometric observations of seven main-belt asteroids were made at the Eurac Observatory (C62 in Bolzano- Italy) in 2014: 1983 Bok, 2634 James Bradley, 4252 Godwin, 5116 Korsor, 10597 (1996 TR10), 52505 (1996 FD4), and 53247 (1999 DE2).

  11. Lightcurve Observations of Nine Main-belt Asteroids

    NASA Astrophysics Data System (ADS)

    Warell, Johan

    2017-10-01

    Photometric observations of nine main-belt asteroids were obtained in 2014-2016. The selected objects all had unusually favourable apparitions. Lightcurves and rotation periods are presented for 1911 Schubart, 2042 Sitarski, 2383 Bradley, 3000 Leonardo, 4974 Elford, 5471 Tunguska, 8679 Tingstäde, (16206) 2000 CL39 and (24691) 1990 RH3.

  12. 5m Main Belt Asteroid Population Estimation Using Vesta Imagery

    NASA Astrophysics Data System (ADS)

    Rynders, Michael; Trilling, David E.

    2016-10-01

    The Main Belt is the largest source of Near-Earth asteroids, but objects <~3 km in diametercannot be reliably detected through conventional means and their number and distribution must be extrapolated. However, craters as small as 50 meters can be seen in the Dawn Framing Camera images from the 2012 mission to Vesta. Since craters of this size are formed by ~5 meter asteroids, counting craters on Vesta allows us to measure the size distribution of asteroids down to sizes that have previously been inaccessible by several orders of magnitude. In the imagery 50m craters were ~2 pixels wide and presented a challenge to reliably count. To validate and calibrate the efficiency and accuracy of counting craters only pixels wide, an experiment was carried out by counting large craters at artificially degraded resolutions. This produced an efficiency curve that was combined with the census of craters >2 pixels in diameter that were counted in a 33km 2 region to give a crater density. By knowing the crater density and making some reasonable assumptions about the orbital distribution of asteroids and the age of Vesta's surface, an estimate of the population of small asteroids in the inner main belt was made. It was found that the inner region of the main asteroid belt contains approximately 20 billion asteroids larger than 5 m. These results agree well with the measured inner Main Belt Size distribution derived by the Wide-field Infrared Survey Explorer, WISE (Masiero et al. 2011).

  13. On enigmatic properties of the main belt asteroids

    NASA Astrophysics Data System (ADS)

    Kochemasov, G.

    Two properties of the main belt asteroids still bother planetologists: why they are mainly of an oblong shape and why the larger bodies rotate faster than the smaller ones. According to the excepted impact theory constantly produced fragments should be rather more or less of equal dimensions. Larger bodies are more difficult to make rotating by hits than the smaller ones. The comparative wave planetology states that "orbits make structures". It means that as all celestial bodies move in non-round keplerian elliptic (and parabolic) orbits with periodically changing accelerations they are subjected to an action of inertia-gravity waves causing body warpings. These warpings in rotating bodies (but all celestial bodies rotate!) acquire stationary character and 4 ortho- and diagonal directions. An interference of these waves produces uprising (+), subsiding (-) and neutral (0) tectonic blocks size of which depends on the warping wavelengths. The fundamental wave 1 long 2πR makes one hemisphere to rise (bulge) and the opposite one to fall (press in) - this two-segment construction is the ubiquitous tectonic dichotomy. The first overtone wave 2 long πR is responsible for tectonic sectoring complicating the dichotomic segments. This already rather complicated structural picture is further complicated by a warping action of individual waves lengths of which are inversely proportional to orbital frequencies : higher frequency - smaller wave and , vice versa, lower frequency - larger waves. These waves produce tectonic granulation, granule size being a half of a wavelength. All terrestrial planets and the belt asteroids according to their orb. fr. are strictly arranged in the following row of granule sizes: Mercury πR/16, Venus πR/6, Earth πR/4, Mars πR/2, asteroids πR/1. The waves lengths and amplitudes increase with the solar distance, their warping action accordingly increases. If Mercury, Venus and Earth are more or less globular, Mars is already elliptical because

  14. Near-infrared spectra of high-albedo outer main-belt asteroids

    SciTech Connect

    Kasuga, Toshihiro; Shirahata, Mai; Usui, Fumihiko; Kuroda, Daisuke; Ootsubo, Takafumi; Okamura, Natsuko; Hasegawa, Sunao

    2015-02-01

    Most outer main-belt asteroids have low albedos because of their carbonaceouslike bodies. However, infrared satellite surveys have revealed that some asteroids have high albedos, which may suggest the presence of unusual surface minerals for those primitive objects. We present new near-infrared (1.1–2.5 μm) spectra of four outer main-belt asteroids with albedos ≥ 0.1. The C-complex asteroids (555) Norma and (2542) Calpurnia are featureless and have (50%–60%) amorphous Mg pyroxenes that might explain the high albedos. Asteroids (701) Oriola (which is a C-complex asteroid) and (2670) Chuvashia (a D/T-type or M-type asteroid) show possible broad absorption bands (1.5–2.1 μm). The feature can be reproduced by either Mg-rich amorphous pyroxene (with 50%–60% and 80%–95% Mg, respectively) or orthopyroxene (crystalline silicate), which might be responsible for the high albedos. No absorption features of water ice (near 1.5 and 2.0 μm) are detected in the objects. We discuss the origin of high albedo components in the outer main-belt asteroids and their physical relations to comets.

  15. Jupiter family comets in near-Earth orbits: Are some of them interlopers from the asteroid belt?

    NASA Astrophysics Data System (ADS)

    Fernández, Julio A.; Sosa, Andrea

    2015-12-01

    We analyze a sample of 58 Jupiter family comets (JFCs) in near-Earth orbits, defined as those whose perihelion distances at the time of discovery were qdisc < 1.3 au. In our definition JFCs have Tisserand parameters 2 < T < 3 and orbital periods P < 20 yr. We integrated the orbits of these objects, plus 50 clones for each one of them, for 104 yr in the past and in the future. We find that most of them move on highly unstable orbits, having fallen in their current near-Earth orbits in the recent past, going from less than one hundred years to a few thousands years. They experience frequent close encounters with Jupiter down to distances ≲ 0.1 au. This is the expected behavior for comets whose limited physical lifetimes in the near-Earth region make them unlikely to survive there for more than about a few hundred revolutions. In this sense the orbits of most JFCs are typically "cometary", and they should be regarded as newcomers in the near-Earth region. Yet, a minor fraction of JFCs (less than about one third) are found to move on stable orbits for the past ∼ 104 yr, and in some cases are found to continue to be stable at 5 × 104 yr in the past. They also avoid very close encounters with Jupiter. Their orbital behavior is very similar to that of NEAs in cometary orbits. While "typical" JFCs in unstable orbits probably come from the trans-Neptunian region, the minor group of JFCs in asteroidal orbits may come from the main asteroid belt, like the NEAs. The asteroidal JFCs may have a more consolidated structure and a higher mineral content than that of comets coming from the trans-Neptunian belt or the Oort cloud, which could explain their much longer physical lifetimes in the near-Earth region. In particular, we mention comets 66P/du Toit, 162P/Siding Spring, 169P/NEAT, 182P/LONEOS, 189P/NEAT, 249P/LINEAR, 300P/Catalina, and P/2003 T12 (SOHO) as the most likely candidates to have an origin in the main asteroid belt. Another interesting case is 207P/NEAT, which

  16. On the spatial distribution of main belt asteroids

    NASA Astrophysics Data System (ADS)

    Souami, D.; Lemaitre, A.; Souchay, J.

    2014-12-01

    We investigate here the distribution of main belt asteroids in the space with respect to the ecliptic-equinox J2000. We identify and confirm a sinusoidal behaviour of this distribution, which disappears when the inclination is given with respect to Jupiter's orbital plane, or with respect to the invariable plane (IP). This behaviour is explained by planetary secular effects, mainly due to Jupiter. Furthermore, we identify three different orbital behaviours that explain the density distribution in this space.

  17. Comets

    NASA Astrophysics Data System (ADS)

    Brownlee, D. E.

    2003-12-01

    Comets are surviving members of a formerly vast distribution of solid bodies that formed in the cold regions of the solar nebula. Cometary bodies escaped incorporation into planets and ejection from the solar system and they have been stored in two distant reservoirs, the Oort cloud and the Kuiper Belt, for most of the age of the solar system. Observed comets appear to have formed between 5 AU and 55 AU. From a cosmochemical viewpoint, comets are particularly interesting bodies because they are preserved samples of the solar nebula's cold ice-bearing regions that occupied 99% of the areal extent of the solar nebula disk. All comets formed beyond the "snow line" of the nebula, where the conditions were cold enough for water ice to condense, but they formed from environments that significantly differed in temperature. Some formed in the comparatively "warm" regions near Jupiter where the nebular temperature may have been greater than 120 K and others clearly formed beyond Neptune where temperatures may have been less than 30 K (Bell et al., 1997). Although comets are the best-preserved materials from the early solar system, they should be a mix of nebular and presolar materials that accreted over a vast range of distances from the Sun in environments that differed in temperature, pressure, and accretional conditions such as impact speed.Comets, by conventional definition, are unstable near the Sun; they contain highly volatile ices that vigorously sublime within 2-3 AU of the Sun. When heated, they release gas and solids due to "cometary activity," a series of processes usually detected from afar by the presence of a coma of gas and dust surrounding the cometary nucleus and or elongated tails composed of dust and gas. Active comets clearly have not been severely modified by the moderate to extreme heating that has affected all other solar system materials, including planets, moons, and even the asteroids that produced the most primitive meteorites. Comets have been

  18. WISE/NEOWISE OBSERVATIONS OF ACTIVE BODIES IN THE MAIN BELT

    SciTech Connect

    Bauer, James M.; Mainzer, A. K.; Masiero, Joseph R.; Blauvelt, Erin K.; Cherry, De'Andre; Grav, Tommy; Walker, Russell G.; McMillan, Robert S.; Scotti, James V.; Fernandez, Yan R.; Kramer, Emily; Meech, Karen J.; Tholen, David J.; Riesen, Timm; Urban, Laurie; Khayat, Alain; Lisse, Carey M.; Cutri, Roc M.; Dailey, John W.; Pearman, George; Collaboration: WISE Team; and others

    2012-03-01

    We report results based on mid-infrared photometry of five active main belt objects (AMBOs) detected by the Wide-field Infrared Survey Explorer (WISE) spacecraft. Four of these bodies, P/2010 R2 (La Sagra), 133P/Elst-Pizarro, (596) Scheila, and 176P/LINEAR, showed no signs of activity at the time of the observations, allowing the WISE detections to place firm constraints on their diameters and albedos. Geometric albedos were in the range of a few percent, and on the order of other measured comet nuclei. P/2010 A2 was observed on 2010 April 2-3, three months after its peak activity. Photometry of the coma at 12 and 22 {mu}m combined with ground-based visible-wavelength measurements provides constraints on the dust particle mass distribution (PMD), dlog n/dlog m, yielding power-law slope values of {alpha} = -0.5 {+-} 0.1. This PMD is considerably more shallow than that found for other comets, in particular inbound particle fluence during the Stardust encounter of comet 81P/Wild 2. It is similar to the PMD seen for 9P/Tempel 1 in the immediate aftermath of the Deep Impact experiment. Upper limits for CO{sub 2} and CO production are also provided for each AMBO and compared with revised production numbers for WISE observations of 103P/Hartley 2.

  19. Comets

    NASA Technical Reports Server (NTRS)

    Feldman, P. D.

    2006-01-01

    Spectroscopy of comets, in the X-ray and far-ultraviolet from space, and in the near infrared and millimeter from the ground, have revealed a wealth of new information, particularly about the molecular constituents that make up the volatile fraction of the comet s nucleus. Interpretation of these data requires not only proper wavelengths for identification but also information about the photolytic and excitation processes at temperatures typical of the inner coma (70-100 K) that lead to the observed spectral signatures. Several examples, mainly from Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope spectra of comets observed during the last few years, will be given to illustrate some of the current issues.

  20. A record of planet migration in the main asteroid belt.

    PubMed

    Minton, David A; Malhotra, Renu

    2009-02-26

    The main asteroid belt lies between the orbits of Mars and Jupiter, but the region is not uniformly filled with asteroids. There are gaps, known as the Kirkwood gaps, in distinct locations that are associated with orbital resonances with the giant planets; asteroids placed in these locations will follow chaotic orbits and be removed. Here we show that the observed distribution of main belt asteroids does not fill uniformly even those regions that are dynamically stable over the age of the Solar System. We find a pattern of excess depletion of asteroids, particularly just outward of the Kirkwood gaps associated with the 5:2, the 7:3 and the 2:1 Jovian resonances. These features are not accounted for by planetary perturbations in the current structure of the Solar System, but are consistent with dynamical ejection of asteroids by the sweeping of gravitational resonances during the migration of Jupiter and Saturn approximately 4 Gyr ago.

  1. Low-frequency Slivan states in the outer main belt?

    NASA Astrophysics Data System (ADS)

    Vraštil, J.; Vokrouhlický, D.

    2016-02-01

    Context. Spin states of several main belt asteroids have been recently found to reside in what is called the Slivan state, namely a secular spin-orbit resonance with the s6 mode of their orbital precession in space. Aims: We examine a possibility of the Slivan states of asteroids with other than orbital s6 precession frequency. Methods: The asteroids' orbital and spin states are numerically propagated using well-tested computer codes. We select parameter space favorable for the Slivan-state capture with the s7 frequency mode of the orbital precession. The stability of these states is numerically verified. Results: We find that asteroid (184) Dejopeja has a spin state captured in (or very nearly) the Slivan state with the s7 orbital frequency. In general, such a situation may favorably occur for low-inclination orbits in the outermost part of the main asteroid belt. We expect these states to be common among the Themis family members.

  2. Stable Slivan states in the inner main belt?

    NASA Astrophysics Data System (ADS)

    Vraštil, J.; Vokrouhlický, D.

    2014-07-01

    Slivan~(2002) derived spin states for ten asteroids in the Koronis family residing in the outer main belt. Surprisingly, all four asteroids with prograde sense of rotation were shown to have spin axes nearly parallel in the inertial space. All asteroids with retrograde sense of rotation had large obliquities and rotation periods either short or long. Vokrouhlický et al.~(2003) developed a model capable to explain this peculiar setup. Its key element was a capture in spin- orbital resonance (Cassini state 2) with planetary frequency s_6 assisted by evolution due to the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. These resonant configurations were dubbed ''Slivan states''. In this work, we analyze whether Slivan states can exist elsewhere in the main belt, focusing on its inner part (heliocentric distance < 2.5 au). We find that long-term stable Slivan states can indeed exist in this part of the main belt provided that the orbital inclination is low enough. This is because the low inclination allows for the separation of the Cassini zones associated with the proper frequency s and the planetary frequency s_6. As an example, the spin state of (20)~Massalia may be located inside, or very close, to a Slivan state. On the other hand, the orbital inclination of the members in the Flora family, or the region nearby, exceeds a critical value to maintain long-term stability of the Slivan states. For that reason, the spin states recently determined by Kryszczyńska~(2013) for a couple of asteroids in this innermost part of the main belt are not similar to the Slivan states in the Koronis family. Still, their proximity to the Cassini state of the s_6 frequency may require an explanation.

  3. Rotation Period Determination of Four Main-belt Asteroids

    NASA Astrophysics Data System (ADS)

    Ferrero, Andrea

    2016-10-01

    Observations of four main-belt asteroids (MBA) revealed the following rotation periods and lightcurve amplitudes: 3861 Lorenz, P = 11.91 ± 0.01 h, A = 0.28 mag; 6173 Jimwestphal P = 2.908 ± 0.001 h, A = 0.41 mag; 10259 Osipovyurij, P = 6.356 ± 0.001 h, A = 0.30 mag; 29470 Higgs, P = 36.31 ± 0.01 h, A = 0.48 mag.

  4. Rotational Period of Three Main-belt Asteroids

    NASA Astrophysics Data System (ADS)

    Ferrro, Andrea

    2017-04-01

    CCD photometric observations of three main-belt asteroids were made to find the synodic period and amplitude of their lightcurves: 1264 Letaba, P = 33.27 ± 0.01 h, A = 0.15 mag; 2407 Haug, P = 6.162 ± 0.002 h, A = 0.32 mag; and 5464 Weller, P = 3.288 ± 0.002 h, A = 0.35 mag.

  5. Low-energy multiple rendezvous of main belt asteroids

    NASA Technical Reports Server (NTRS)

    Penzo, Paul A.; Bender, David F.

    1992-01-01

    An approach to multiple asteroid rendezvous missions to the main belt region is proposed. In this approach key information which consists of a launch date and delta V can be generated for all possible pairs of asteroids satisfying specific constraints. This information is made available on a computer file for 1000 numbered asteroids with reasonable assumptions, limitations, and approximations to limit the computer requirements and the size of the data file.

  6. Rotation Periods for Three Main-belt Asteroids

    NASA Astrophysics Data System (ADS)

    Franco, Lorenzo; Baj, Giorgio; Tinella, Vito; Bachini, Mauro; Succi, Giacomo; Casalnuovo, Giovanni Battista; Bacci, Paolo

    2017-10-01

    Photometric observations of three main-belt asteroids were made from Italy in order to determine their synodic rotation periods. For 1022 Olympiada the period is 3.834 ± 0.001 hr, amplitude 0.66 mag. For 1602 Indiana the results are 2.601 ± 0.001 hr and 0.16 mag. and for 2501 Lohja we report 3.809 ± 0.001 hr and 0.44 mag.

  7. A photoelectric lightcurve survey of small main belt asteroids

    NASA Technical Reports Server (NTRS)

    Binzel, R. P.; Mulholland, J. D.

    1983-01-01

    A survey to obtain photoelectric lightcurves of small main-belt asteroids was conducted from November 1981 to April 1982 using the 0.91- and 2.1-m telescopes at the University of Texas McDonald Observatory. A total of 18 main-belt asteroids having estimated dimaters under 30 km were observed with over half of these being smaller than 15 km. Rotational periods were determined or estimated from multiple nights of observation for nearly all of these yielding a sample of 17 small main-belt asteroids which is believed to be free of observational selection effects. All but two of these objects were investigated for very short periods in the range of 1 min to 2 hr using power spectrum analysis of a continuous set of integrations. No evidence for such short periods was seen in this sample. Rotationally averaged B(1,0) magnitudes were determined for most of the surveyed asteroids, allowing diameter estimates to be made. Imposing the suspected selection effects of photogaphic photometry on the results of this survey gives excellent agreement with the results from that technique. This shows that the inability of photographic photometry to obtain results for many asteroids is indeed due to the rotational parameter of those asteroids.

  8. Non-Vestoid candidates in the inner Main Belt

    NASA Astrophysics Data System (ADS)

    Moskovitz, Nicholas; Oszkiewicz, Dagmara; Skiff, Brian; Kankiewicz, Pawel; Licandro, Javier; Galiazzo, Mattia; Zeilinger, Werner

    2016-10-01

    Most Howardite-Eucrite-Diogenite (HED) meteorites (analogues to V-type asteroids) are thought to originate from asteroid (4) Vesta. However some HEDs show distinct oxygen isotope ratios and therefore are thought to originate from other asteroids. In this study we try to identify asteroids that may represent parent bodies of those mismatching HEDs. In particular the origin of the anomalous Bunburra Rockhole meteorite was traced back to the inner main asteroid belt, showing that there might be asteroids that are not genetically linked to the asteroid (4) Vesta (the main source of V-type asteroids and HED meteorites) in the inner main belt. In this work we identify V-type asteroids outside the dynamical Vesta family whose rotational properties (retrograde vs prograde rotation) suggest the direction of Yarkovsky drift that sets them apart from typical Vestoids and Vesta fugitives. Specificly Nesvorny et al. 2008 simulated escapes paths from the Vesta family and showed that typical Vesta fugitives in the inner main asteroid belt at semi-major axis a < 2.3 AU have to have retrograde rotations and physical and thermal parameters that maximize the Yarkovsky force in order to evolve to scattered orbits within 1-2 Gys (age of the Vesta collisional family). Therefore large asteroids outside the Vesta family and with a < 2.3 AU and having thermal and rotational properties minimizing the Yarkovsky drift or showing Yarkovsky drift direction towards (4) Vesta are the best candidates for non-Vestoidal V-type asteroids and therefore parent bodies of anomalous HED. In this study we have performed accurate photometric observations and determined sense of rotation for several asteroids testing their links to Vesta and anomalous HED. We have found several potential non-Vestoid candidates. Those objects have to be studied in more detail to fully confirm their link to anomalous HEDs.

  9. Constraints on impact rates in the pluto-charon system and the population of the Kuiper comet belt

    SciTech Connect

    Weissman, P.R. ); Dobrovolskis, A.R. ); Stern, S.A. )

    1989-11-01

    Impact rates in the Pluto-Charon system are dominated by comets from the proposed Kuiper Belt, 30 to 50 AU from the Sun. Such collisions excite the eccentricity of Charon's orbit, which then decays due to tidal dissipation. Charon's eccentricity approaches a quasi-steady state, which can be used to constrain the total number and mass of comets in the Kuiper Belt. Unfortunately, the current upper limit on Charon's orbital eccentricity must be reduced by more than a factor of ten before useful constraints can be set.

  10. Constraints on impact rates in the Pluto-Charon system and the population of the Kuiper comet belt

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.; Dobrovolskis, Anthony R.; Stern, S. Alan

    1989-01-01

    Impact rates in the Pluto-Charon system are dominated by comets from the proposed Kuiper Belt, 30 to 50 AU from the sun. Such collisions excite the eccentricity of Charon's orbit, which then decays due to tidal dissipation. Charon's eccentricity approaches a quasi-steady state, which can be used to constrain the total number and mass of comets in the Kuiper Belt. Unfortunately, the current upper limit on Charon's orbital eccentricity must be reduced by more than a factor of ten before useful constraints can be set.

  11. On the oldest asteroid families in the main belt

    NASA Astrophysics Data System (ADS)

    Carruba, V.; Nesvorný, D.; Aljbaae, S.; Domingos, R. C.; Huaman, M.

    2016-06-01

    Asteroid families are groups of minor bodies produced by high-velocity collisions. After the initial dispersions of the parent bodies fragments, their orbits evolve because of several gravitational and non-gravitational effects, such as diffusion in mean-motion resonances, Yarkovsky and Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effects, close encounters of collisions, etc. The subsequent dynamical evolution of asteroid family members may cause some of the original fragments to travel beyond the conventional limits of the asteroid family. Eventually, the whole family will dynamically disperse and no longer be recognizable. A natural question that may arise concerns the time-scales for dispersion of large families. In particular, what is the oldest still recognizable family in the main belt? Are there any families that may date from the late stages of the late heavy bombardment and that could provide clues on our understanding of the primitive Solar system? In this work, we investigate the dynamical stability of seven of the allegedly oldest families in the asteroid main belt. Our results show that none of the seven studied families has a nominally mean estimated age older than 2.7 Gyr, assuming standard values for the parameters describing the strength of the Yarkovsky force. Most `paleo-families' that formed between 2.7 and 3.8 Gyr would be characterized by a very shallow size-frequency distribution, and could be recognizable only if located in a dynamically less active region (such as that of the Koronis family). V-type asteroids in the central main belt could be compatible with a formation from a paleo-Eunomia family.

  12. The chemical structure of the Main-Belt

    NASA Astrophysics Data System (ADS)

    Carry, Benoit; DeMeo, Francesca

    2015-08-01

    The asteroid main belt between Mars and Jupiter holds evidences from the early Solar System history. The original chemical stratification of the accretion disk has been scrambled by planetary migrations, resulting in a radial mixing of compositions. Since the 1970s, spectral surveys have characterized the surface compositions of the largest members first, then of smaller bodies, slowly tapering into the size-frequency distribution. These surveys led to major discoveries, including the succession of dominating taxonomic classes along heliocentric distances, stained by the presence of interlopers in this over-arching structure. In the 2000s, these results have sustained the emergence of the current paradigm of Solar System formation: the Nice model, in which planets migrated from their formation locations to their current orbits.Since then, all-sky surveys in the visible and mid-infrared, the Sloan Digital Sky Survey and NASA WISE mission, have observed tens of thousands of asteroids, allowing characterization of their surface composition and estimation of their diameter. Simultaneously, our knowledge on asteroid density greatly improved: the sample of density determinations presented a tenfold increase. Such a rich dataset opened the possibility to scrutinize asteroid compositions to smaller sizes and to study the distribution of material in the main belt by mass, rather than by numbers. The picture resulting from these data go back over the previous view, and the few interlopers seem to be rule. The large scale structure seen on the largest bodies holds, but mixing increases at smaller sizes. This detailed picture supports the main results from recent dynamical models of planetary migration and radial mixing of smaller bodies, albeit several observed structures remain yet to be explained: numerous primitive D-type in the inner belt, apparently missing mantle counterpart (A-types) to the crustal and iron core-like (V- and M-types) material.Observational evidences

  13. Main results on asteroids and comets returned from the Herschel mission

    NASA Astrophysics Data System (ADS)

    Mueller, Thomas; Vilenius, Esa

    The Herschel Space Observatory was designed to observe the 'cool universe' in the far-IR wavelength range. During the operational phase between May 2009 and April 2013 the main focus was on the exploration of the formation of galaxies and stars, but also many solar system objects were studied in detail. Several space-mission targets like Bennu (OSIRIS-REx), 1999 JU _{3} (Hayabusa-2), Lutetia (Rosetta), Ceres and Vesta (DAWN) were observed at far-infrared wavelengths with the Herschel instruments. These thermal emission studies provide information which is complementary to the in-situ or flyby data and help to derive physical properties and to understand thermal processes. The results can be applied to many similar objects which are not included in interplanetary mission studies, but easily accessible by remote observations. Trans-Neptunian objects (TNO) and Centaurs have their thermal emission peak at Herschel's far-IR wavelength range and about 130 TNOs have been characterized as part of the Herschel Open Time Key programm "TNOs are Cool!". The newly derived physical and thermal properties show the large diversity in the outer solar system. TNO densities, albedos, or size distributions are important ingredients for testing formation and evolution scenarios. We will present the results of dedicated photometric and spectroscopic studies of prominent near-Earth, main-belt, and trans-Neptunian objects, as well as selected comets. Highlights of the Herschel mission are the finding of water on Ceres, the Earth-like D/H ratio of comet Hartley-2 and the detailed picture of the trans-Neptunian population with implications also for models describing the migration of the giant planets about 4 billion years ago.

  14. Subaru Main Belt Asteroid Survey (SMBAS)—Size and color distributions of small main-belt asteroids

    NASA Astrophysics Data System (ADS)

    Yoshida, F.; Nakamura, T.

    2007-06-01

    Since February, 2001, we have been conducting a series of survey observations to investigate the physical property of very small Main Belt Asteroids (sub-km MBAs) using the Subaru prime-focus camera (Suprime-Cam) attached to the 8.2 m Subaru telescope. We call our surveys "SMBAS: Subaru Main-Belt Asteroids Survey". This paper presents the results of the second SMBAS (SMBAS-II) which was performed in October 2001. In SMBAS-II, a˜4.0deg2 sky area near the opposition and near the ecliptic was surveyed with the R- and B-bands. We detected 1838 moving objects up to R˜25mag. In SMBAS-II, we could not determine the exact orbits of the objects, because of the short observational arc of only ˜40min. Instead, we statistically estimated the semi-major axis ( a) of each moving object from its apparent sky-motion vector assuming its circular orbit and then, we used the a's to select MBAs and to estimate their absolute magnitudes ( H). The limiting magnitude of SMBAS-II for MBAs was R˜24.2 mag. It corresponds to H˜20 mag at the outer edge of main belt. Thus, assuming their mean albedos, down to D˜0.3 km of S-type asteroids and 0.6 km of C-type asteroids were detected in SMBAS-II. We found that the slopes ( b) of the cumulative size distribution (CSD) (i.e. N(>D)∝D, D: diameter) for sub-km MBAs ranging from 0.6 to 1 km in diameter is 1.29±0.02. Our b value (1.29) is much shallower than those ( ˜ 1.8) of the Palomer Leiden Survey (PLS) [van Houten, C.J., van Houten, G.I., Herget, P., Gehrels, T., 1970. The Palomar-Leiden survey of faint minor planets. Astr. Astrophys. Suppl. 2, 339-448] and Spacewatch surveys [Jedicke, R., Metcalfe, T.S., 1998. The orbital and absolute magnitude distributions of main belt asteroids. Icarus 131, 245-260.] for larger asteroids ( D>5 km) and almost consistent with that (1.3) of SDSS [Ivezić, Ž., Tabachnik, S., Rafikov, R., Lupton, R.H., Quinn, T., Hammergren, M., Eyer, L., Chu, J., Armstrong, J.C., Fan, X., Finlator, K., Geballe, T

  15. Near-Infrared Spectroscopy of 12 Outer Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Takir, Driss; Emery, J. P.

    2010-10-01

    We have begun a project to quantify the degree of aqueous alteration in CM carbonaceous chondrites, obtain spectra of these chondrites, and measure spectra of possibly related outer Main Belt asteroids in order to explore the nature of aqueous alteration on these asteroids. In this first stage of the project, we will present the near-infrared (NIR) spectra of 12 outer Main Belt asteroids (2.59 < a < 3.96 AU). The asteroids include, 10 Hygiea, 76 Friea, 91 Aegina, 107 Camila, 104 Klymene, 121 Hemione, 153 Hilda, 308 Polyxo, 334 Chicago, 361 Bononia, 401 Ottilia, and 790 Pretoria. We collected the spectra of these asteroids between April 2009 and April 2010, using the long wavelength cross-dispersed (LXD) mode (1.9-4.1-µm) of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF). We also observed some of these asteroids with the prism mode (0.8-2.5-µm). For data reduction, we used Spextool, a set of Interactive Data Language routines provided by the IRTF. Except for 91 Aegina, all observed asteroids exhibit an absorption feature near 3-µm, which is attributed to hydrated minerals and/or H2O ice. The hydrated mineral features on these asteroids show two different band shapes, weak "rounded” H2O-like absorption band and deeper "checkmark” OH-like absorption band. The former band shape is much more common in our sample than the latter band shape.

  16. Near-infrared Spectroscopy Of Outer Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Takir, Driss; Emery, J.

    2009-09-01

    We have recently begun a spectral survey of the outer Main Belt population (3.2 AU < a < 4.6 AU), using near-infrared spectroscopy (0.8-2.5 μm). The objective of this survey is to search for signatures of H2O, organics, hydrated silicates, and/or anhydrous silicates on this group of asteroids. Studying the outer Main Belt asteroids will allow us to better understand the dynamical evolution of the Solar System and provide crucial constrains on nebular composition. Our first observing run, using the SpeX spectrograph/imager at the NASA IRTF, took place remotely form the University of Tennessee Knoxville on the nights of April 15, 16, and 17, 2009 (UT). More observing runs will be conducted this year and the beginning of next year. The initial data reduction process reveals that some of these asteroids exhibit weak and strong absorption features. We will present some of these initial spectra and results.

  17. Recent Arecibo Radar Observations of Main-Belt Asteroids.

    NASA Astrophysics Data System (ADS)

    Shepard, Michael K.; Howell, Ellen; Nolan, Michael; Taylor, Patrick; Springmann, Alessondra; Giorgini, Jon; Benner, Lance; Magri, Christopher

    2014-11-01

    We recently observed main-belt asteroids 12 Victoria (Tholen S-class, Bus L-class), 246 Asporina (A-class), and 2035 Stearns with the S-band (12 cm) Arecibo radar. Signal-to-noise ratios for Asporina and Stearns were only strong enough for continuous-wave (CW) analysis. Signal-to-noise ratios for Victoria were high enough for delay-Doppler imaging. Stearns exhibited a high radar polarization ratio of unity, higher than any other main-belt E-class, but similar to near-Earth E-class asteroids [Benner et al. Icarus 198, 294-304, 2008; Shepard et al. Icarus 215, 547-551, 2011]. The A-class asteroids show spectral absorption features consistent with olivine and have been suggested as the source of pallasite meteorites or the rare brachinites [Cruikshank and Hartmann, Science 223, 281-283, 1984]. The radar cross-section measured for Asporina leads to a radar albedo estimate of 0.11, suggesting a low near-surface bulk density, and by inference, a low metal content. This suggests that the brachinites are a better analog for Asporina than the iron-rich pallasites. Victoria has been observed by radar in the past and the continuous-wave echoes suggest it has a large concavity or is a contact binary [Mitchell et al. Icarus 118, 105-131, 1995]. Our new imaging observations should determine which is more likely.

  18. Photometry of Main Belt and Trojan asteroids with K2

    NASA Astrophysics Data System (ADS)

    Szabó, Gyula; Kiss, Csaba; Pal, Andras; Szabo, Robert

    2016-10-01

    Due to the failure of the second reaction wheel, a new mission was conceived for the otherwise healthy Kepler space telescope. In the course of the K2 Mission, the telescope is staring at the plane of the Ecliptic, hence thousands of Solar System bodies cross the K2 fields, usually causing extra noise in the highly accurate photometric data.We could measure the first continuous asteroid light curves, covering several days wthout interruption, that has been unprecedented to date. We studied the K2 superstamps covering the M35 and Neptune/Nereid fields observed in the long cadence (29.4-min sampling) mode. Asteroid light curves are generated by applying elongated apertures. We investigated the photometric precision that the K2 Mission can deliver on moving Solar System bodies, and determined the first uninterrupted optical light curves of main-belt and Trojan asteroids. We use thed Lomb-Scargle method to find periodicities due to rotation.We derived K2 light curves of 924 main-belt asteroids in the M35 field, and 96 in the path of Neptune and Nereid. Due to the faintness of the asteroids and the high density of stars in the M35 field, 4.0% of the asteroids with at least 12 data points show clear periodicities or trend signalling a long rotational period, as opposed to 15.9% in the less crowded Neptune field. We found that the duty cycle of the observations had to reach ˜ 60% in order to successfully recover rotational periods.The derived period-amplitude diagram is consistent to the known distribution of Main Belt asteroids. For Trojan asteroids, the contribution of our 56 objects with newly determined precise period and amplitude is in the order of all previously known asteroids. The comparison with earth-based determinations showed a previous bias toward short periods and has also proven that asteroid periods >20 hour can be unreliable in a few cases because of daylight time and diurnal calibrations. These biases are avoided from the space. We present an unbiased

  19. HIGH ECLIPTIC LATITUDE SURVEY FOR SMALL MAIN-BELT ASTEROIDS

    SciTech Connect

    Terai, Tsuyoshi; Takahashi, Jun; Itoh, Yoichi

    2013-11-01

    Main-belt asteroids have been continuously colliding with one another since they were formed. Their size distribution is primarily determined by the size dependence of asteroid strength against catastrophic impacts. The strength scaling law as a function of body size could depend on collision velocity, but the relationship remains unknown, especially under hypervelocity collisions comparable to 10 km s{sup –1}. We present a wide-field imaging survey at an ecliptic latitude of about 25° for investigating the size distribution of small main-belt asteroids that have highly inclined orbits. The analysis technique allowing for efficient asteroid detections and high-accuracy photometric measurements provides sufficient sample data to estimate the size distribution of sub-kilometer asteroids with inclinations larger than 14°. The best-fit power-law slopes of the cumulative size distribution are 1.25 ± 0.03 in the diameter range of 0.6-1.0 km and 1.84 ± 0.27 in 1.0-3.0 km. We provide a simple size distribution model that takes into consideration the oscillations of the power-law slope due to the transition from the gravity-scaled regime to the strength-scaled regime. We find that the high-inclination population has a shallow slope of the primary components of the size distribution compared to the low-inclination populations. The asteroid population exposed to hypervelocity impacts undergoes collisional processes where large bodies have a higher disruptive strength and longer lifespan relative to tiny bodies than the ecliptic asteroids.

  20. Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt.

    PubMed

    de Vries, B L; Acke, B; Blommaert, J A D L; Waelkens, C; Waters, L B F M; Vandenbussche, B; Min, M; Olofsson, G; Dominik, C; Decin, L; Barlow, M J; Brandeker, A; Di Francesco, J; Glauser, A M; Greaves, J; Harvey, P M; Holland, W S; Ivison, R J; Liseau, R; Pantin, E E; Pilbratt, G L; Royer, P; Sibthorpe, B

    2012-10-04

    Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets. Collisions between such bodies produce small dust particles, the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg(2-2x)Fe(2x)SiO(4)) has been done for the protoplanetary disk HD 100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids (x ≈ 0.29). In the cold outskirts of the β Pictoris system, an analogue to the young Solar System, olivine crystals were detected but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets. Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of β Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01 ± 0.001) and show that they make up 3.6 ± 1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System, even though β Pictoris is more massive and more luminous and has a different planetary system architecture.

  1. Main characteristics of the COMET/COMRADE experiments

    NASA Technical Reports Server (NTRS)

    Borg, J.; Bibring, J.-P.; Maag, Carl R.

    1994-01-01

    Both the COMET (Collection en Orbite de Matiere Extra Terrestre) and the COMRADE (Collection of Micrometeorites, Residue and Debris Ejecta) programs are developed to the collection and analysis of the particles of various origins orbiting around the Earth at low altitudes (between approx. 300 and approx. 500 km). The COMET experiment is more specifically designed to be flown for a short period of time (a few days), in concordance with a meteor stream crossing the Earth. Thus, it results in a considerable enrichment in the collection of grains related to a given comet. The COMRADE experiment has been selected as a proposal for long-duration flights (a few months), in order to gain information on all sizes of particles present on low Earth orbits, including submicrometer grains. It has been accepted by ESA authorities for use on the EURECA 2 platform. The objectives of these studies are multiple. The use of passive detectors gives access to the chemical and isotopical properties of the grains in the micrometer size range, by analyzing either the particle remnant mixed with the target material, or the intact particle captured in a specific low-density material. The particle remnants of the micrometer-sized extraterrestrial grains, having impacted on purposely designed metallic collectors, are identified for complete and detailed chemical, isotopic, and organic analysis, thereby determining grain composition as well as the existence of organic and inorganic molecules, to be related with the possible cometary origin of the grains. Micrometer/submicrometer dust grains are also captured in a manner that ensures minimal particle degradation. The captured intact particles are returned to Earth for complete and detailed chemical, isotopic, spectral, mineralogical, and organic analysis.

  2. New insights into main belt asteroid collisional lifetimes

    NASA Astrophysics Data System (ADS)

    Henych, Tomas; Holsapple, Keith

    2016-10-01

    We are developing a new Monte Carlo code to study the collisional and spin evolution of main belt asteroids. A byproduct is information on asteroid lifetimes. We find new interpretations and values of those lifetimes.In the conventional approach, the "collisional lifetime" is measured by the time when an asteroid is struck by an impactor large enough to remove one-half of the target's mass. That event is called a catastrophic disruption (CD). From an assumed population of impactors and Poisson statistics, one can estimate the largest expected impactor to impact in a given time interval to get its expected collisional lifetime. However, our Monte Carlo simulations give lifetimes that are distinctly shorter. That raises questions about the basic definition of catastrophic disruption.During its presence in the main belt, many other asteroids of all sizes continually strike a target asteroid. Before the CD one happens, there are many small impacts, and a few less than but not equal to the CD one. Each impact erodes the target asteroid. Very commonly, it is eroded to a much smaller mass before some CD event. We will present examples.So what shall we define as its collisional lifetime? Should it be the time for which its mass is reduced to one-half of its original mass, irrespective of how that happened, perhaps from many impacts? Or when any single impact reduces its mass to one-half of its original mass? Or when a single impact reduces it to one-half of its current mass?We propose that collisional lifetime is defined as the time at which it reaches 50% of its original mass, from any combination of small and/or large events. We use cratering and ejecta scaling formulas (e.g. Holsapple, 1993, Housen and Holsapple, 2011) to calculate the eroded mass history of the target for a history of impactors and calculate the outcome of any impact using the current size. In the gravity regime, the eroded body is easier to disrupt. We will present our lifetime estimates and those of

  3. Non-Vestoid candidate asteroids in the inner main belt

    NASA Astrophysics Data System (ADS)

    Oszkiewicz, Dagmara A.; Skiff, Brian A.; Moskovitz, Nick; Kankiewicz, Paweł; Marciniak, Anna; Licandro, Javier; Galiazzo, Mattia A.; Zeilinger, Werner W.

    2017-03-01

    Context. Most howardite-eucrite-diogenite (HED) meteorites (analogues to V-type asteroids) are thought to originate from the asteroid (4) Vesta. However some HEDs show distinct oxygen isotope ratios and therefore are thought to originate from other asteroids. In this study we try to identify asteroids that may represent parent bodies of those mismatching HEDs. Aims: The main goal of this study is to test the hypothesis that there might be V-type asteroids in the inner main asteroid belt unrelated to (4) Vesta. In order to evolve outside the Vesta family and became Vesta fugitives, asteroids should produce the correct Yarkovsky drift. The direction of which is dependent on asteroid sense of rotation. Therefore we focus on determining sense of rotation for asteroids outside the Vesta family to better understand their origin. Methods: We performed photometric observations using the 1.1 m and 1.8 m telescopes at Lowell Observatory to determine rotational synodic periods of selected objects before, at, and after opposition. Prograde rotators show a minimum in synodic period at opposition while retrograde rotators show a maximum. This is known as the "drifting minima" method. Changes in the rotational period are on the order of seconds and fractions of seconds and depend on the rotational pole of the object and the asteroid-observer-Sun geometry at opposition. Results: We have determined sense of rotation for eight asteroids and retrieved spin states for three objects from literature. For one asteroid we were not able to determine the sense of rotation. In total our sample includes 11 V-type asteroids and one S-type (test object). We have revised rotation periods for three objects. Five V-types in our sample can be explained by migration from the Vesta family. Two show spin states that are inconsistent with migration from Vesta. The origin of the remaining objects is ambiguous. Conclusions: We found two objects with rotations inconsistent with migration from Vesta

  4. A late Miocene dust shower from the break-up of an asteroid in the main belt.

    PubMed

    Farley, Kenneth A; Vokrouhlický, David; Bottke, William F; Nesvorný, David

    2006-01-19

    Throughout the history of the Solar System, Earth has been bombarded by interplanetary dust particles (IDPs), which are asteroid and comet fragments of diameter approximately 1-1,000 microm. The IDP flux is believed to be in quasi-steady state: particles created by episodic main belt collisions or cometary fragmentation replace those removed by comminution, dynamical ejection, and planetary or solar impact. Because IDPs are rich in 3He, seafloor sediment 3He concentrations provide a unique means of probing the major events that have affected the IDP flux and its source bodies over geological timescales. Here we report that collisional disruption of the >150-km-diameter asteroid that created the Veritas family 8.3 +/- 0.5 Myr ago also produced a transient increase in the flux of interplanetary dust-derived 3He. The increase began at 8.2 +/- 0.1 Myr ago, reached a maximum of approximately 4 times pre-event levels, and dissipated over approximately 1.5 Myr. The terrestrial IDP accretion rate was overwhelmingly dominated by Veritas family fragments during the late Miocene. No other event of this magnitude over the past approximately 10(8) yr has been deduced from main belt asteroid orbits. One remarkably similar event is present in the 3He record 35 Myr ago, but its origin by comet shower or asteroid collision remains uncertain.

  5. The Main Asteroid Belt: The Crossroads of the Solar System

    NASA Astrophysics Data System (ADS)

    Michel, Patrick

    2015-08-01

    Orbiting the Sun between Mars and Jupiter, main belt asteroids are leftover planetary building blocks that never accreted enough material to become planets. They are therefore keys to understanding how the Solar System formed and evolved. They may also provide clues to the origin of life, as similar bodies may have delivered organics and water to the early Earth.Strong associations between asteroids and meteorites emerged thanks to multi-technique observations, modeling, in situ and sample return analyses. Spacecraft images revolutionized our knowledge of these small worlds. Asteroids are stunning in their diversity in terms of physical properties. Their gravity varies by more orders of magnitude than its variation among the terrestrial planets, including the Moon. Each rendezvous with an asteroid thus turned our geological understanding on its head as each asteroid is affected in different ways by a variety of processes such as landslides, faulting, and impact cratering. Composition also varies, from ice-rich to lunar-like to chondritic.Nearly every asteroid we see today, whether of primitive or evolved compositions, is the product of a complex history involving accretion and one or more episodes of catastrophic disruption that sometimes resulted in families of smaller asteroids that have distinct and indicative petrogenic relationships. These families provide the best data to study the impact disruption process at scales far larger than those accessible in laboratory. Tens, perhaps hundreds, of early asteroids grew large enough to thermally differentiate. Their traces are scattered pieces of their metal-rich cores and, more rarely, their mantles and crusts.Asteroids represent stages on the rocky road to planet formation. They have great stories to tell about the formation and evolution of our Solar System as well as other planetary systems: asteroid belts seem common around Sun-like stars. We will review our current knowledge on their properties, their link to

  6. The dust-to-ices ratio in comets and Kuiper belt objects

    NASA Astrophysics Data System (ADS)

    Fulle, M.; Della Corte, V.; Rotundi, A.; Green, S. F.; Accolla, M.; Colangeli, L.; Ferrari, M.; Ivanovski, S.; Sordini, R.; Zakharov, V.

    2017-07-01

    Comet 67P/Churyumov-Gerasimenko (67P hereinafter) is characterized by a dust transfer from the southern hemi-nucleus to the night-side northern dust deposits, which constrains the dust-to-ices mass ratio inside the nucleus to values a factor of 2 larger than that provided by the lost mass of gas and non-volatiles. This applies to all comets because the gas density in all night comae cannot prevent the dust fallback. Taking into account Grain Impact Analyser and Dust Accumulator (GIADA) data collected during the entire Rosetta mission, we update the average dust bulk density to ρ {}{}_D = 785_{-115}^{+520} kg m-3 that, coupled to the 67P nucleus bulk density, confirms an average dust-to-ices mass ratio δ = 7.5 inside 67P. The improved dust densities are consistent with a mixture of (20 ± 8) per cent of ices, (4 ± 1) per cent of Fe sulphides, (22 ± 2) per cent of silicates and (54 ± 5) per cent of hydrocarbons, on average volume abundances. These values correspond to solar chemical abundances, as suggested by the elemental C/Fe ratio observed in 67P. The ice content in 67P matches that inferred in Kuiper belt objects, (20 ± 12) per cent on average volume abundance and suggests a water content in all trans-Neptunian objects lower than in CI chondrites. The 67P icy pebbles and the dust collected by GIADA have a microporosity of (49 ± 5) and (59 ± 8) per cent, respectively.

  7. Comet Odyssey: Comet Nucleus Orbiter

    NASA Astrophysics Data System (ADS)

    Weissman, P. R.; Smythe, W. D.; Spitz, S. J.; Bernard, D. E.; Bailey, R. W.

    2004-11-01

    Comet Odyssey is a comet nucleus orbiter mission, proposed to NASA's Discovery program in 2004. The goal of the mission is to completely characterize a cometary nucleus, both physically and compositionally, as can only be done during an extended rendezvous and not with a fast flyby. Comet Odyssey will launch in October 2009 on a Delta II 7925 and use a solar-electric powered spacecraft to effect a rendezvous with periodic comet 46P/Wirtanen in October 2013. Arrival is 96 days after perihelion at a heliocentric distance of 1.61 AU. Comet Odyssey's science payload includes narrow- and wide-angle CCD cameras, an infrared thermal imager, a gas chromatograph/mass spectrometer, an XRD/XRF dust compositional analyzer, and a dust counter and accumulation sensors. The Comet Odyssey spacecraft implementation uses a high heritage approach of flight proven and redundant hardware. The 3-engine ion propulsion subsystem is derived from that on Dawn but includes the capability for multi-engine thrusting. Comet Odyssey will approach the Wirtanen nucleus and make repeated slow flybys through the active cometary coma for a period of three months. It will then be placed in a ˜100-km radius orbit around the nucleus, with a plan to eventually orbit at 40-km altitude or less. From that altitude the narrow-angle camera will map the entire nucleus surface at 1 meter/pixel and the thermal imager will map at 19 meter/pixel. The orbital portion of the nominal mission will last 4.5 months, following the comet outward from the Sun to 3.3 AU as the comet evolves from an active to a quiescent state. En route to P/Wirtanen, the Comet Odyssey spacecraft will perform a close flyby of the 200-km diameter, G-type, main belt asteroid 19 Fortuna in January 2012 and make appropriate remote sensing observations.

  8. ORBITS, MASSES, AND EVOLUTION OF MAIN BELT TRIPLE (87) SYLVIA

    SciTech Connect

    Fang, Julia; Margot, Jean-Luc; Rojo, Patricio

    2012-08-15

    Sylvia is a triple asteroid system located in the main belt. We report new adaptive optics observations of this system that extend the baseline of existing astrometric observations to a decade. We present the first fully dynamical three-body model for this system by fitting to all available astrometric measurements. This model simultaneously fits for individual masses, orbits, and primary oblateness. We find that Sylvia is composed of a dominant central mass surrounded by two satellites orbiting at 706.5 {+-} 2.5 km and 1357 {+-} 4.0 km, i.e., about 5 and nearly 10 primary radii. We derive individual masses of 1.484{sup +0.016}{sub -0.014} Multiplication-Sign 10{sup 19} kg for the primary (corresponding to a density of 1.29 {+-} 0.39 g cm{sup -3}), 7.33{sup +4.7}{sub -2.3} Multiplication-Sign 10{sup 14} kg for the inner satellite, and 9.32{sup +20.7}{sub -8.3} Multiplication-Sign 10{sup 14} kg for the outer satellite. The oblateness of the primary induces substantial precession and the J{sub 2} value can be constrained to the range of 0.0985-0.1. The orbits of the satellites are relatively circular with eccentricities less than 0.04. The spin axis of the primary body and the orbital poles of both satellites are all aligned within about 2 deg of each other, indicating a nearly coplanar configuration and suggestive of satellite formation in or near the equatorial plane of the primary. We also investigate the past orbital evolution of the system by simulating the effects of a recent passage through 3:1 mean-motion eccentricity-type resonances. In some scenarios this allow us to place constraints on interior structure and past eccentricities.

  9. Spectro-dynamical asteroid families in the main belt

    NASA Astrophysics Data System (ADS)

    Bus, S.

    2014-07-01

    their V-type spectra that is related to the strength of the 1-micron absorption band. This spectral offset between the two groupings is consistent with the color differences observed in the Rheasilvia and Venenia impact basins on Vesta [6]. The same level of analysis used to determine the structure of the Vesta family is now being applied to all families in the main belt. An update on results, including a final count of asteroid families identified in this search, will be presented.

  10. Basaltic asteroids in the main belt: Spectral and mineralogical characterization

    NASA Astrophysics Data System (ADS)

    De Sanctis, M.; Migliorini, A.; Lazzaro, D.; Ammannito, E.

    2014-07-01

    Most of the basaltic asteroids are thought to be fragments of Vesta, forming its dynamical family, but few others do not appear to have a clear dynamical link, suggesting, thus, the existence of other basaltic parent bodies. Excluding Vesta and its family, the lack of intact differentiated asteroids introduces a strong constraint to the formation scenario of basaltic material. The spectral investigation of the basaltic asteroids in the main belt can help in understanding if there are V-type asteroids that show a differing mineralogy with respect to Vesta and its family members. We present new NIR reflectance spectra of V-type candidate asteroids obtained at the 3.6-m Telescopio Nazionale Galileo covering the spectral range 0.7 to 2.5 microns. The observed objects were selected from diverse datasets of putative V-type asteroids in order to characterize them, and hence better understand their relationship with Vesta. All the spectra of the asteroids here reported show two prominent absorption features at 1 and 2 microns that are typical of V-class objects, indicating that the methods based on the photometric surveys to infer the basaltic asteroid distribution are quite robust. The spectra of these asteroids are examined and compared to those of Vesta and the HED meteorites, for which Vesta is believed to be the parent body, and other V-type asteroids previously observed. To enlarge the data set and increase the statistical significance of the analysis, we included the data presented in our previous articles (De Sanctis et al., 2011ab). It is important to note that all these objects have been observed at the same telescope with the same instrumental set up. We derive spectral parameters from the NIR spectra to infer mineralogical information on the observed asteroids. The V-type asteroids here examined show a large variability of band parameters. These parameters have been compared with those of the HED meteorites and with the parameters derived for Vesta using the

  11. Response of Jupiter's Electron Belt to a Comet-like Impact

    NASA Astrophysics Data System (ADS)

    Santos-Costa, D.; Bolton, S. J.; Sault, R. J.; Thorne, R. M.; Levin, S.

    2010-12-01

    Jupiter's strong magnetic field contributes to populate the Jovian magnetosphere with very energetic electrons in its innermost region, resulting in an observed synchrotron radio emission above the galactic noise level. With the little amount of existing in-situ data for the radiation zones, radio measurements provide the only method for currently investigating Jupiter's relativistic electron distribution, constraining theoretical models of processes responsible for particle distributions and the origins of their dynamics. In the present paper, the contribution of a comet-like impact to observed variations of Jupiter’s radiation-belt emission on time-scales of days to weeks with the VLA in 2009 is discussed. During the third week of July, ground-based measurements at different radio bands confirmed that a large projectile had struck Jupiter’s atmosphere. Our VLA data analysis of synchrotron emission shows that a steep enhancement of the brightness distributions was observed during the same period. The increase in the synchrotron emission actually went on for a couple of weeks before gradually fading in August. The intensity variations of the radio emission during the weeks that followed the July 2009 impact are first interpreted by the longitudinal expansion of the impact-related synchrotron hot spot originally located at the Jupiter System III longitude of 305 degrees. We then demonstrate that the combining effect of adiabatic transport with the occurrence of energy resonance near the moon Amalthea is a comprehensive explanation for understanding why the radiation at L_rad ~ 1.4 Rj is responding to the dynamics of ~ 10-MeV energy electrons trapped at L_impact ~ 3.3 Rj. By considering different origins of adiabatic radial transport, we further show that particles transport from L_impact to L_rad can take a few days to a couple of weeks. The travel time depends on which source of fluctuations was the most effective during the middle of 2009. A period of temporal

  12. Comets

    NASA Image and Video Library

    Did you know that comets seen streaking across the night sky may have brought the building blocks of life to our planet billions of years ago? Join NASA in learning more about these fascinating obj...

  13. Discovery and characteristics of the rapidly rotating active asteroid (62412) 2000 SY178 in the main belt

    SciTech Connect

    Sheppard, Scott S.; Trujillo, Chadwick

    2015-02-01

    We report a new active asteroid in the main belt of asteroids between Mars and Jupiter. Object (62412) 2000 SY178 exhibited a tail in images collected during our survey for objects beyond the Kuiper Belt using the Dark Energy Camera on the CTIO 4 m telescope. We obtained broadband colors of 62412 at the Magellan Telescope, which, along with 62412's low albedo, suggests it is a C-type asteroid. 62412's orbital dynamics and color strongly correlate with the Hygiea family in the outer main belt, making it the first active asteroid known in this heavily populated family. We also find 62412 to have a very short rotation period of 3.33 ± 0.01 hours from a double-peaked light curve with a maximum peak-to-peak amplitude of 0.45 ± 0.01 mag. We identify 62412 as the fastest known rotator of the Hygiea family and the nearby Themis family of similar composition, which contains several known main belt comets. The activity on 62412 was seen over one year after perihelion passage in its 5.6 year orbit. 62412 has the highest perihelion and one of the most circular orbits known for any active asteroid. The observed activity is probably linked to 62412's rapid rotation, which is near the critical period for break-up. The fast spin rate may also change the shape and shift material around 62412's surface, possibly exposing buried ice. Assuming 62412 is a strengthless rubble pile, we find the density of 62412 to be around 1500 kg m{sup −3}.

  14. Lunar and Planetary Science XXXV: Asteroids, Meteors, Comets

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session Asteroids, Meteors, Comets includes the following topics: 1) Where Some Asteroid Parent Bodies; 2) The Collisional Evolution of the Main Belt Population; 3) On Origin of Ecliptic Families of Periodic Comets; 4) Mineralogy and Petrology of Laser Irradiated Carbonaceous Chondrite Mighei; and 5) Interaction of the Gould Belt and the Earth.

  15. Lunar and Planetary Science XXXV: Asteroids, Meteors, Comets

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session Asteroids, Meteors, Comets includes the following topics: 1) Where Some Asteroid Parent Bodies; 2) The Collisional Evolution of the Main Belt Population; 3) On Origin of Ecliptic Families of Periodic Comets; 4) Mineralogy and Petrology of Laser Irradiated Carbonaceous Chondrite Mighei; and 5) Interaction of the Gould Belt and the Earth.

  16. Albedo distribution of main-belt asteroids based on IRAS, AKARI, and WISE

    NASA Astrophysics Data System (ADS)

    Usui, F.; Hasegawa, S.; Ishiguro, M.; Mueller, T.; Ootsubo, T.

    2014-07-01

    Presently, the number of asteroids is known to be more than 630,000, and more than 90 % of asteroids with known orbital elements are classified as main-belt asteroids (MBAs). The spatial distribution of compositions among MBAs is of particular interest, because the main belt is the largest reservoir of asteroids in the solar system. Asteroids are thought to be the remnants of planetesimals formed in the early solar system, and allow us to study the formation and evolution of asteroids, origin of meteoroids and the near-Earth asteroids, as well as the formation of the solar system. Size and albedo are one of the most basic physical quantities of asteroid. Knowledge of size and albedo is essential in many aspects of asteroid research, such as the chemical composition and mineralogy, the size-frequency distribution of dynamical families and populations of asteroids, and the relationship between small bodies in the outer solar system and comets. Several techniques have been developed to determine the size of asteroids; by direct imaging with the Hubble Space Telescope or large ground-based telescopes with adaptive optics, radar observations, speckle interferometry, stellar occultation combined with lightcurve inversion techniques, and spacecraft flyby / rendezvous / sample return. One of the most effective methods for measuring asteroid size and albedo indirectly is through the use of radiometry, which combines information of the thermal emission (infrared flux) and the reflected sunlight (absolute magnitude). This method can provide unique data for asteroid size and albedo. Using radiometric measurements, a large number of objects can be observed in a short period of time, providing coherent data for large populations of asteroids within the asteroid belt. Infrared observations can be made still better under ideal circumstances, from space. The first space-borne infrared telescope is the Infrared Astronomical Satellite (IRAS; [1]), launched in 1983 and performed a

  17. Influence of the Centaurs and TNOs on the main belt and its families

    NASA Astrophysics Data System (ADS)

    Galiazzo, Mattia A.; Wiegert, Paul; Aljbaae, Safwan

    2016-12-01

    Centaurs are objects whose orbits are found between those of the giant planets. They are supposed to originate mainly from the Trans-Neptunian objects, and they are among the sources of Near-Earth Objects. Trans-Neptunian Objects (TNOs) cross Neptune's orbit and produce the Centaurs. We investigate their interactions with main belt asteroids to determine if chaotic scattering caused by close encounters and impacts by these bodies may have played a role in the dynamical evolution of the main belt. We find that Centaurs and TNOs that reach the inner Solar System can modify the orbits of main belt asteroids, though only if their mass is of the order of 10^{-9} m_{⊙} for single encounters or, one order less in case of multiple close encounters. Centaurs and TNOs are unlikely to have significantly dispersed young asteroid families in the main belt, but they could have perturbed some old asteroid families. Current main belt asteroids that originated as Centaurs or Trans-Neptunian Objects may lie in the outer belt with short lifetime ≤ 4 My, most likely between 2.8 and 3.2 au at larger eccentricities than typical of main belt asteroids.

  18. Dynamical evolution of V-type photometric candidates in the central and outer main belt asteroids

    NASA Astrophysics Data System (ADS)

    Carruba, V.; Huaman, M.

    2014-07-01

    V-type asteroids are associated with basaltic composition, and are supposed to be fragments of crust of differentiated objects. Most V-type asteroids in the main belt are found in the inner main belt, and are either current members of the Vesta dynamical family (Vestoids), or past members that drifted away. However, several V-type photometric candidates have been recently identified in the central and outer main belt. The origin of this large population of V-type objects is not well understood, since it seems unlikely that Vestoids crossing the 3:1 and 5:2 mean-motion resonance with Jupiter could account for the whole observed population. In this work, we investigated a possible origin of the bodies from local sources, such as the parent bodies of the Eunomia, Merxia, and Agnia asteroid families in the central main belt, and Dembowska, Eos and Magnya asteroid families in the outer main belt. Our results show that dynamical evolution from the parent bodies of the Eunomia and Merxia/Agnia families on timescales of 2 Gyr or more could be responsible for the current orbital location of most of the V-type photometric candidates in the central main belt. Studies for the outer main belt are currently in progress. by the FAPESP (grant 2011/19863-3) and CAPES (grant 15029-12-3) funding agencies.

  19. Collision rates and impact velocities in the Main Asteroid Belt

    NASA Technical Reports Server (NTRS)

    Farinella, Paolo; Davis, Donald R.

    1992-01-01

    Wetherill's (1967) algorithm is presently used to compute the mutual collision probabilities and impact velocities of a set of 682 asteroids with large-than-50-km radius representative of a bias-free sample of asteroid orbits. While collision probabilities are nearly independent of eccentricities, a significant decrease is associated with larger inclinations. Collisional velocities grow steeply with orbital eccentricity and inclination, but with curiously small variation across the asteroid belt. Family asteroids are noted to undergo collisions with other family members 2-3 times more often than with nonmembers.

  20. Detection of Exocometary CO within the 440 Myr Old Fomalhaut Belt: A Similar CO+CO2 Ice Abundance in Exocomets and Solar System Comets

    NASA Astrophysics Data System (ADS)

    Matrà, L.; MacGregor, M. A.; Kalas, P.; Wyatt, M. C.; Kennedy, G. M.; Wilner, D. J.; Duchene, G.; Hughes, A. M.; Pan, M.; Shannon, A.; Clampin, M.; Fitzgerald, M. P.; Graham, J. R.; Holland, W. S.; Panić, O.; Su, K. Y. L.

    2017-06-01

    Recent Atacama Large Millimeter/submillimeter Array observations present mounting evidence for the presence of exocometary gas released within Kuiper Belt analogs around nearby main-sequence stars. This represents a unique opportunity to study their ice reservoir at the younger ages when volatile delivery to planets is most likely to occur. We here present the detection of CO J = 2-1 emission colocated with dust emission from the cometary belt in the 440 Myr old Fomalhaut system. Through spectrospatial filtering, we achieve a 5.4σ detection and determine that the ring's sky-projected rotation axis matches that of the star. The CO mass derived ((0.65{--}42)× {10}-7 {M}\\oplus ) is the lowest of any circumstellar disk detected to date and must be of exocometary origin. Using a steady-state model, we estimate the CO+CO2 mass fraction of exocomets around Fomalhaut to be between 4.6% and 76%, consistent with solar system comets and the two other belts known to host exocometary gas. This is the first indication of a similarity in cometary compositions across planetary systems that may be linked to their formation scenario and is consistent with direct interstellar medium inheritance. In addition, we find tentative evidence that (49+/- 27)% of the detected flux originates from a region near the eccentric belt's pericenter. If confirmed, the latter may be explained through a recent impact event or CO pericenter glow due to exocometary release within a steady-state collisional cascade. In the latter scenario, we show how the azimuthal dependence of the CO release rate leads to asymmetries in gas observations of eccentric exocometary belts.

  1. Near-Infrared Albedos of Main Belt Asteroids and Families from NEOWISE

    NASA Astrophysics Data System (ADS)

    Masiero, Joseph R.; Grav, T.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; Sonnett, S.

    2014-11-01

    We present new results from revised thermal models of Main Belt asteroids in the NEOWISE dataset, focusing on the 3.4- and 4.6-micron albedos of asteroids and asteroid families. We show that the Main Belt is well described by three unique 3.4-micron albedo groups, tracing to the C-complex, S-complex, and K-type asteroids. Among large asteroid families, the Eos family shows a reflectance behavior that is unique in the Main Belt, matching the K-type albedo group. This work is described in detail in a recently published article in the Astrophysical Journal.

  2. Comets

    NASA Astrophysics Data System (ADS)

    Barbieri, Cesare; Bertini, Ivano

    2017-08-01

    The paper reviews properties of comets, from historical sightings and interpretations, to contemporary ground- and space-based knowledge. The importance of comets in understanding the present Solar System and its dynamical, physical and chemical evolution, their relationship with other minor bodies, their possible role for the very early phases of our Earth, will be examined. Emphasis will be on the results of the recently completed European Rosetta mission to comet 67P/Churyumov-Gerasimenko, in particular those by OSIRIS, its imaging system. It is fair to say that Rosetta's results represent a most important step in the development of cometary science, whose full implications start just to surface and will be fully appreciated over several more years.

  3. P/2010 A2 LINEAR. I. An impact in the asteroid main belt

    NASA Astrophysics Data System (ADS)

    Hainaut, O. R.; Kleyna, J.; Sarid, G.; Hermalyn, B.; Zenn, A.; Meech, K. J.; Schultz, P. H.; Hsieh, H.; Trancho, G.; Pittichová, J.; Yang, B.

    2012-01-01

    Comet P/2010 A2 LINEAR is an object on an asteroidal orbit within the inner main belt, therefore a good candidate for membership with the main belt comet family. It was observed with several telescopes (ESO New Technology Telescope, La Silla, Chile; Gemini North, Mauna Kea, Hawaii; University of Hawaii 2.2 m, Mauna Kea, Hawaii) from 14 Jan. until 19 Feb. 2010 in order to characterize and monitor it and its very unusual dust tail, which appears almost fully detached from the nucleus; the head of the tail includes two narrow arcs forming a cross. No evolution was observed during the span of the observations. Observations obtained during the Earth orbital plane crossing allowed an examination of the out-of-plane 3D structure of the tail. The immediate surroundings of the nucleus were found dust-free, which allowed an estimate of the nucleus radius of 80-90 m, assuming an albedo p = 0.11 and a phase correction with G = 0.15 (values typical for S-type asteroids). A model of the thermal evolution indicates that such a small nucleus could not maintain any ice content for more than a few million years on its current orbit, ruling out ice sublimation dust ejection mechanism. Rotational spin-up and electrostatic dust levitations were also rejected, leaving an impact with a smaller body as the favoured hypothesis. This is further supported by the analysis of the tail structure. Finston-Probstein dynamical dust modelling indicates the tail was produced by a single burst of dust emission. More advanced models (described in detail in a companion paper), independently indicate that this burst populated a hollow cone with a half-opening angle α ~ 40° and with an ejection velocity vmax ~ 0.2 m s-1, where the small dust grains fill the observed tail, while the arcs are foreshortened sections of the burst cone. The dust grains in the tail are measured to have radii between a = 1-20 mm, with a differential size distribution proportional to a-3.44 ± 0.08. The dust contained in the

  4. Optical spectroscopy and photometry of main-belt asteroids with a high orbital inclination

    NASA Astrophysics Data System (ADS)

    Iwai, Aya; Itoh, Yoichi; Terai, Tsuyoshi; Gupta, Ranjan; Sen, Asoke; Takahashi, Jun

    2017-02-01

    We carried out low-resolution optical spectroscopy of 51 main-belt asteroids, most of which have highly-inclined orbits. They are selected from D-type candidates in the SDSS-MOC 4 catalog. Using the University of Hawaii 2.2 m telescope and the Inter-University Centre for Astronomy and Astrophysics 2 m telescope in India, we determined the spectral types of 38 asteroids. Among them, eight asteroids were classified as D-type asteroids. Fractions of D-type asteroids are 3.0+/-1.1 for low orbital inclination main-belt asteroids and 7.3+/-2.0 for high orbital inclination main-belt asteroids. The results of our study indicate that some D-type asteroids were formed within the ecliptic region between the main belt and Jupiter, and were then perturbed by Jupiter.

  5. A Collisional Model of the "Pristine Zone" of the Main Asteroid Belt and the Dynamics of LHB Families Located There

    NASA Astrophysics Data System (ADS)

    Broz, Miroslav; Cibulkova, H.; Rehak, M.

    2012-10-01

    Modifying the Boulder code (Morbidelli et al. 2009), we construct a new collisional model of the Main Asteroid Belt, which is divided to six parts (inner, middle, outer, pristine zone, Cybele region and high-inclination region) in order to study relations between them and check the number of families observed in each of them. We focus on the so-called "pristine zone" between 2.825 and 2.955 AU - bounded by the 5:2 and 7:3 resonances with Jupiter - because this region is relatively empty and we may thus spot very old/eroded families. We model long-term dynamical and collisional evolution of the Itha family (around the asteroid (918) Itha) and we interpreted it as an old, dispersed and comminutioned cluster, likely dated back to the Late Heavy Bombardment 3.8 Gyr ago. We thus extend our collisional models and include the effects of the LHB too. In the framework of the Nice model, the flux of comets during the LHB is mostly controlled by the original size-freqeuncy distribution of the cometary disk beyond Neptune and a rate at which comets disrupt when they approach the Sun. To this point we provide a related discussion of various cometary disruption laws.

  6. Comets

    NASA Technical Reports Server (NTRS)

    Wilkening, L. L. (Editor); Matthews, M. S. (Editor)

    1982-01-01

    Vacuum ultraviolet observations from sounding rockets and satellite observatories of the gaseous comae of several comets are reviewed. The earliest of these led to discovery of the hydrogen envelope extending for millions of km from the nucleus. Subsequent observations of H I Lyman alpha, the OH (0,0 band and the oxygen resonance triplet provided strong evidence for the water-ice model of the cometary nucleus. Several species were discovered in the coma including C, C(+), CO, S, and CS. High resolution spectroscopy and the spatial variation of the observed emissions provide means to elucidate the production and excitation mechanisms of these species. The similarity of the spectra of the half dozen comets observed to date argues for a common, homogeneous composition (with the exception of dust and CO) of the cometary ice and a minimal effect on the neutral species due to molecular collisions in the inner coma.

  7. Evolution and detectability of comet clouds during post-main-sequence stellar evolution

    NASA Technical Reports Server (NTRS)

    Stern, S. Alan; Brandt, John C.; Shull, J. Michael

    1990-01-01

    The destruction of volatile-rich comet disks and Oort-type clouds around luminous post-main-sequence stars is modeled. The models are in agreement with several aspects of existing observations of water and complex molecules in the envelopes of giant and supergiant stars. If confirmed, these results would establish the common existence of Oort-type clouds around other stars and would constitute indirect evidence for sites of past planetary formation.

  8. Evolution and detectability of comet clouds during post-main-sequence stellar evolution

    NASA Technical Reports Server (NTRS)

    Stern, S. Alan; Brandt, John C.; Shull, J. Michael

    1990-01-01

    The destruction of volatile-rich comet disks and Oort-type clouds around luminous post-main-sequence stars is modeled. The models are in agreement with several aspects of existing observations of water and complex molecules in the envelopes of giant and supergiant stars. If confirmed, these results would establish the common existence of Oort-type clouds around other stars and would constitute indirect evidence for sites of past planetary formation.

  9. Reconstructing the spin distributions of main-belt asteroids

    NASA Astrophysics Data System (ADS)

    Holsapple, K.

    2014-07-01

    INTRODUCTION: We now have spin data for almost six thousand asteroids, each value being a result of that asteroid's history. Some features of that distribution are now evident. The gravity spin limit at the period of about 2.3 h for asteroids with a diameter greater than a few kilometers is well established (Harris 1996, Pravec and Harris 2000, Holsapple 2001, and others). The strength of smaller asteroids as inferred from the ''fast spinners'' has been presented by Holsapple (2007), Sanchez and Scheeres (2014), and others. Several statistical analyses of the database have been presented (e.g., Pravec and Harris 2002). Here that database is used as a means of investigating the prior history of the asteroid belt. THEORETICAL APPROACHES: A way to understand the data is to attempt to reproduce it using theoretical models and numerical simulations of the physics of the processes that created it. Such studies have evolved since McAdoo and Burns (1973) first suggested collisions as a source of the spins; they include Davis et al. (1979), Dobrovolskis and Burns (1984), Harris (1979), Davis et al. (1989), Farinella et al. (1992), Henych and Pravec (2013), and others. These analyses are based upon averaging the effects of a number of individual impacts into a given target asteroid. I retrace the path and analyses of those authors in this work, but make important modifications and updates. The primary elements introduced in those prior studies include: 1) a population of asteroids in a given space; 2) a distribution of impact velocities and angles; 3) the efficiency of angular-momentum transfer in an impact; 4) the loss or gain of mass and angular inertia; 5) the amount, direction, and speed of the cratering ejecta. The characteristics of the ejecta are especially important: they determine the ''angular-momentum drain'' first identified by Dobrovolskis and Burns (1984). It is caused by the preferential escape of ejecta in the downrange spin direction. Here I revisit, update

  10. Some results of exploration of comet 67P/Churyumov-Gerasimenko - the main target of the Rosetta space mission

    NASA Astrophysics Data System (ADS)

    Churyumov, K. I.

    The short period comet 67P/Churyumov-Gerasimenko from the Jupiter comet family is selected as main target of the European space mission Rosetta. In September 1969 the three collaborators of expedition of Kyiv Shevchenko University went to the Alma-Ata Astrophysical Institute to conduct a survey of short period and new comets. The main result of the expedition was the discovery of the new short period comet 67P on Oct. 22 ,1969 on the five plates obtained by Klim Churyumov and Svetlana Gerasimenko Sept. 9, 11 and 21, 1969 with the help of 50-cm f/2.4 Maksutov telescope in Alam-Ata. The astronomer Nikolay Belyaev from Saint-Petersbourg showed the comet followed an elliptical orbit. The fact that the comet had a close encounter with Jupiter in 1959 very important because only after this encounter comet 67P could be discovered in 1969 with the help of terrestrial telescopes. The comparison of comet 67P/Churyumov-Gerasimenko's light curve in its 1982-1983 apparition and the curve of the solar activity indices changes that are reduced to the comet`s center shows that the variations of the comet's brightness rather well correlate with the changes of the solar indices. On the basis of photometric processing of the two photographic images of comet 67P obtained in Nizhny Arkhyz with the help of the 6- BTA reflector of SAO of RAS some physical parameters of the comet plasma tail (coefficients of diffusion D?? , Dbot and induction of magnetic field B) were determined. (Jan. 12.105, 1983 UT: D??=5.07× 1014div 1.21× 1015 cm2/s, Dbot =5.73× 1013div 1.37× 1014 cm2/s, B=46div 111 nT; Jan. 13.124, 1983 UT: D??=4.67× 1014div 1.14× 1015 cm2/s, Dbot =4.30× 1013div 1.05× 1014 cm2/s, B=55div 134 nT). The obtained upper estimates of induction of the magnetic field B≅ 111 nT for Jan. 12,1983 and B≅ 134 nT for Jan. 13,1983 probably surpass real values of B in the cometary plasma tail. I think that this peculiarity of magnetic fields in plasma tail of comet 67P is tight connected

  11. MAIN BELT ASTEROIDS WITH WISE/NEOWISE. I. PRELIMINARY ALBEDOS AND DIAMETERS

    SciTech Connect

    Masiero, Joseph R.; Mainzer, A. K.; Bauer, J. M.; Eisenhardt, P. R. M.; DeBaun, E.; Elsbury, D.; Gautier, T. IV; Gomillion, S.; Wilkins, A.; Cutri, R. M.; Dailey, J.; McMillan, R. S.; Spahr, T. B.; Skrutskie, M. F.; Tholen, D.; Walker, R. G.; Wright, E. L.

    2011-11-10

    We present initial results from the Wide-field Infrared Survey Explorer (WISE), a four-band all-sky thermal infrared survey that produces data well suited for measuring the physical properties of asteroids, and the NEOWISE enhancement to the WISE mission allowing for detailed study of solar system objects. Using a NEATM thermal model fitting routine, we compute diameters for over 100,000 Main Belt asteroids from their IR thermal flux, with errors better than 10%. We then incorporate literature values of visible measurements (in the form of the H absolute magnitude) to determine albedos. Using these data we investigate the albedo and diameter distributions of the Main Belt. As observed previously, we find a change in the average albedo when comparing the inner, middle, and outer portions of the Main Belt. We also confirm that the albedo distribution of each region is strongly bimodal. We observe groupings of objects with similar albedos in regions of the Main Belt associated with dynamical breakup families. Asteroid families typically show a characteristic albedo for all members, but there are notable exceptions to this. This paper is the first look at the Main Belt asteroids in the WISE data, and only represents the preliminary, observed raw size, and albedo distributions for the populations considered. These distributions are subject to survey biases inherent to the NEOWISE data set and cannot yet be interpreted as describing the true populations; the debiased size and albedo distributions will be the subject of the next paper in this series.

  12. Albedo Properties of Small (0.5 to 20 km) Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Ryan, Erin L.; Woodward, C. E.

    2010-01-01

    Serendipitous observations of main belt asteroids by the Spitzer Space Telescope have enabled determination of main belt asteroid albedos and diameters for targets as small as 0.5 km (eg., Ryan et al. 2009, AJ, 137, 5134). We have used multi-epoch data at 5.8, 8.0 and 24 microns from the MIPSGAL and Taurus Legacy Surveys to obtain diameters and albedos for a sample of approximately 2000 main belt asteroids. Using STM and NEATM, we have obtained diameters ranging from 0.5 to 30 km and albedos ranging from 0.02 to 0.5. Results of this program reveal an albedo distribution that is more diverse in range than the albedo distribution seen in the IRAS and MSX surveys. This diversity may reflect effects of space weathering reddening which is selectively reddening larger asteroids. This reddening effect may reinforce the findings from accretion models that indicate that asteroids in the early solar system were 100 km and larger (Morbidelli et al., 2009, Icarus, in press), by suggesting that the larger asteroids are indeed the oldest members of the main belt. We will present results on the albedo distribution as a function of semi-major axis and new analysis of the mean albedo of dynamical families within the main belt. Support for this work provided in part by a National Science Foundation grant AST-0706980 to the University of Minnesota.

  13. Dynamical evolution of V-type asteroids in the central main belt

    NASA Astrophysics Data System (ADS)

    Carruba, V.; Huaman, M. E.; Domingos, R. C.; Santos, C. R. Dos; Souami, D.

    2014-04-01

    V-type asteroids are associated with basaltic composition, and are supposed to be fragments of crust of differentiated objects. Most V-type asteroids in the main belt are found in the inner main belt, and are either current members of the Vesta dynamical family (Vestoids), or past members that drifted away. However, several V-type photometric candidates have been recently identified in the central and outer main belt. The origin of this large population of V-type objects is not well understood. Since it seems unlikely that Vestoids crossing the 3J:-1A mean-motion resonance with Jupiter could account for the whole population of V-type asteroids in the central and outer main belt, origin from local sources, such as the parent bodies of the Eunomia, and of the Merxia and Agnia asteroid families, has been proposed as an alternative mechanism. In this work, we investigated the dynamical evolution of the V-type photometric candidates in the central main belt, under the effect of gravitational and non-gravitational forces. Our results show that dynamical evolution from the parent bodies of the Eunomia and Merxia/Agnia families on time-scales of 2 Byr or more could be responsible for the current orbital location of most of the low-inclined V-type asteroids.

  14. Imaging polarimetry of comet 73P/Schwassmann-Wachmann 3 main fragments during its 2006 apparition

    NASA Astrophysics Data System (ADS)

    Hadamcik, E.; Levasseur-Regourd, A. C.

    2016-04-01

    We have observed the dust ejected by parts of the nucleus (so-called fragments or components) of comet 73 P/Schwassmann-Wachmann 3 during seven consecutive nights from 2006, April 27 to May 3 by imaging polarimetry using the 0.8 m telescope at OHP (Observatoire de Haute-Provence, France). Three fragments were observed, B and C main fragments on all nights and G fragment on two nights at 24 h interval. Fragment C, which almost behaves as a normal comet, presents some night-to-night evolution on polarization maps together with some sunward-jets morphology. Fragment B, as noticed by numerous observers, continues to fragment, with clues to the presence of large secondary fragments, tailward on the intensity images; an increase of activity is noticed on May 2. Jets and fans are observed sunward, with a larger extension in fragment C than in B. Fragment G is fainter and, as fragment B, it continues to fragment. A short sunward jet is detected on the rotational gradient image together with an important tailward structure. The integrated polarization for the two main fragments is typical of polarization of high-Pmax comets. An important evolution is observed from night-to-night on the polarization maps. Fragment C presents, in two nights at 48 h interval, a lower polarization in the inner coma, neither observed in the intermediate night nor later. A high polarization is also observed on the two sides of the lower polarization regions. In fragment B, the regions around the secondary fragments have a higher polarization than the surrounding coma, They are easily detected in the treated intensity images. As usually, the polarization increases when the phase angle increases. Numerous observers have found similar chemical compositions for the two main fragments together with differences in their optical properties, suggesting heterogeneities in the physical properties during the aggregation of the original nucleus and/or changes after the ejection of dust particles.

  15. COLOR DEPENDENCE IN THE SIZE DISTRIBUTION OF MAIN BELT ASTEROIDS REVISITED

    SciTech Connect

    August, Tyler M.; Wiegert, Paul A.

    2013-06-15

    The size distribution of the asteroid belt is examined with 16956 main belt asteroids detected in data taken from the Canada-France-Hawaii Telescope Legacy Survey in two filters (g' and r'). The cumulative H (absolute magnitude) distribution is examined in both filters, and both match well to simple power laws down to H = 17, with slopes in rough agreement with those reported the literature. This implies that disruptive collisions between asteroids are gravitationally dominated down to at least this size, and probably sub-kilometer scales. The slopes of these distributions appear shallower in the outer belt than the inner belt, and the g' distributions appear slightly steeper than the r'. The slope shallowing in the outer belt may reflect a real compositional difference: the inner asteroid belt has been suggested to consist mostly of stony and/or metallic S-type asteroids, whereas carbonaceous C-types are thought to be more prevalent further from the Sun. No waves are seen in the size distribution above H = 15. Since waves are expected to be produced at the transition from gravitationally-dominated to internal strength-dominated collisions, their absence here may imply that the transition occurs at sub-kilometer scales, much smaller than the H = 17 (diameter {approx} 1.6 km) cutoff of this study.

  16. Color Dependence in the Size Distribution of Main Belt Asteroids Revisited

    NASA Astrophysics Data System (ADS)

    August, Tyler M.; Wiegert, Paul A.

    2013-06-01

    The size distribution of the asteroid belt is examined with 16956 main belt asteroids detected in data taken from the Canada-France-Hawaii Telescope Legacy Survey in two filters (g' and r'). The cumulative H (absolute magnitude) distribution is examined in both filters, and both match well to simple power laws down to H = 17, with slopes in rough agreement with those reported the literature. This implies that disruptive collisions between asteroids are gravitationally dominated down to at least this size, and probably sub-kilometer scales. The slopes of these distributions appear shallower in the outer belt than the inner belt, and the g' distributions appear slightly steeper than the r'. The slope shallowing in the outer belt may reflect a real compositional difference: the inner asteroid belt has been suggested to consist mostly of stony and/or metallic S-type asteroids, whereas carbonaceous C-types are thought to be more prevalent further from the Sun. No waves are seen in the size distribution above H = 15. Since waves are expected to be produced at the transition from gravitationally-dominated to internal strength-dominated collisions, their absence here may imply that the transition occurs at sub-kilometer scales, much smaller than the H = 17 (diameter ~ 1.6 km) cutoff of this study.

  17. Period Determination of Main-belt Asteroid (26274) 1998 RH75

    NASA Astrophysics Data System (ADS)

    Brown, Johnny Eugene, Jr.; Linder, Tyler; Puckett, Andrew; Holmes, Robert

    2017-04-01

    Photometric observations of the inner main-belt asteroid (26274) 1998 RH75 were made on three nights in 2016 March. Analysis gave a bimodal lightcurve with a synodic period of 3.1296 ± 0.0001 h and amplitude of 0.55 ± 0.02 mag.

  18. Multi-Zone Simulations of the Collisional Evolution of Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Granata, V.; Marzari, F.; Davis, D. R.; Paolicchi, P.; Vanzani, V.

    2011-03-01

    We have adapted the planet building code, a multizone code, to study the collisional evolution of asteroids in the main belt. In this way the effects of resonances and Yarkowski's drift are statistically included and we can estimate the flux of bodies into NEO orbits.

  19. Density and Axis-size Relationship of Five Main-belt Asteroids: 2017 January - March

    NASA Astrophysics Data System (ADS)

    Aznar Macias, Amadeo

    2017-07-01

    Despite many decades of minor planet studies focused on external and dynamical properties, there are still hundreds of asteroids that have never been measured. Presented here are the results of photometric analysis applied to five main-belt asteroids. In addition to calculating rotation period, axis ratios assuming a simple ellipsoidal shape and the estimated minimum density of each asteroid are reported.

  20. Discovery and Exploration of Comet 67P/CHURYUMOV-GERASIMENKO - the Main Target of the Rosetta Space Mission

    NASA Astrophysics Data System (ADS)

    Churyumov, K. I.

    2006-08-01

    The short period comet 67P/Churyumov-Gerasimenko from the Jupiter comet family is selected as main target of the European space mission Rosetta. In September 1969 the three collaborators of expedition of Kyiv Shevchenko University went to the Alma-Ata Astrophysical Institute to conduct a survey of short period and new comets. The main result of the expedition was the discovery of the new short period comet 67P on Oct. 22 ,1969 on the five plates obtained by Klim Churyumov and Svetlana Gerasimenko Sept. 9, 11 and 21, 1969 with the help of 50-cm f/2.4 Maksutov telescope in Alam-Ata. The comparison of comet 67P/ Churyumov-Gerasimenko's light curve in its 1982-1983 apparition and the curve of the solar activity indices changes that are reduced to the comet`s center shows that the variations of the comet's brightness rather well correlate with the changes of the solar indices. On the basis of photometric processing of the two photographic images of comet 67P obtained in Nizhny Arkhyz with the help of the 6- BTA reflector of SAO of RAS some physical parameters of the comet plasma tail (coefficients of diffusion D[||], D[????]and induction of magnetic field B) were determined. (Jan. 12.105, 1983 UT: D[||]=5.07×10^14±1.21 ×10^15 cm^2/s, D[?]=5.73×10^13±1.37×10^14 cm^2/s, B=46±111 nT; Jan. 13.124, 1983 UT: D[||]=4.67×10^14÷1.14 ×10^15 cm^2/s, D[?]=4.30×10^13±1.05×10^14 cm^2/s, B=55±134 nT). The obtained upper estimates of induction of the magnetic field B ≈ 111 nT for Jan. 12,1983 and B ≈ 134 nT for Jan. 13,1983 probably surpass real values of B in the cometary plasma tail. I think that this peculiarity of magnetic fields in plasma tail of comet 67P is tight connected with the magnetic properties of the surface layers of the cometary nucleus. I hope that this problem will be successful solved with the help of the device ROMAP installed on the ROSETTA Lander when it will land on the comet 67P nucleus in 2014.

  1. STIS Coronagraphic Imaging of Fomalhaut: Main Belt Structure and the Orbit of Fomalhaut b

    NASA Technical Reports Server (NTRS)

    Kalas, Paul; Graham, James R.; Fitzgerald, Michael P.; Clampin, Mark

    2013-01-01

    We present new optical coronagraphic data of Fomalhaut obtained with HST/STIS in 2010 and 2012. Fomalhaut b is recovered at both epochs to high significance. The observations include the discoveries of tenuous nebulosity beyond the main dust belt detected to at least 209AU projected radius, and a approx. 50AU wide azimuthal gap in the belt northward of Fomalhaut b. The two epochs of Space Telescope Imaging Spectrograph (STIS) photometry exclude optical variability greater than 35%. A Markov chain Monte Carlo analysis demonstrates that the orbit of Fomalhaut b is highly eccentric, with e = 0.8 +/- 0.1, a = 177 +/- 68AU, and q = 32 +/- 24AU. Fomalhaut b is apsidally aligned with the belt and 90% of allowed orbits have mutual inclination <=36 deg. Fomalhaut b's orbit is belt crossing in the sky plane projection, but only 12% of possible orbits have ascending or descending nodes within a 25AU wide belt annulus. The high eccentricity invokes a dynamical history where Fomalhaut b may have experienced a significant dynamical interaction with a hypothetical planet Fomalhaut c, and the current orbital configuration may be relatively short-lived. The Tisserand parameter with respect to a hypothetical Fomalhaut planet at 30AU or 120AU lies in the range 2-3, similar to highly eccentric dwarf planets in our solar system. We argue that Fomalhaut b's minimum mass is that of a dwarf planet in order for a circumplanetary satellite system to remain bound to a sufficient radius from the planet to be consistent with the dust scattered light hypothesis. In the coplanar case, Fomalhaut b will collide with the main belt around 2032, and the subsequent emergent phenomena may help determine its physical nature.

  2. STIS CORONAGRAPHIC IMAGING OF FOMALHAUT: MAIN BELT STRUCTURE AND THE ORBIT OF FOMALHAUT b

    SciTech Connect

    Kalas, Paul; Graham, James R.; Fitzgerald, Michael P.; Clampin, Mark

    2013-09-20

    We present new optical coronagraphic data of Fomalhaut obtained with HST/STIS in 2010 and 2012. Fomalhaut b is recovered at both epochs to high significance. The observations include the discoveries of tenuous nebulosity beyond the main dust belt detected to at least 209 AU projected radius, and a ∼50 AU wide azimuthal gap in the belt northward of Fomalhaut b. The two epochs of Space Telescope Imaging Spectrograph (STIS) photometry exclude optical variability greater than 35%. A Markov chain Monte Carlo analysis demonstrates that the orbit of Fomalhaut b is highly eccentric, with e = 0.8 ± 0.1, a = 177 ± 68 AU, and q = 32 ± 24 AU. Fomalhaut b is apsidally aligned with the belt and 90% of allowed orbits have mutual inclination ≤36°. Fomalhaut b's orbit is belt crossing in the sky plane projection, but only 12% of possible orbits have ascending or descending nodes within a 25 AU wide belt annulus. The high eccentricity invokes a dynamical history where Fomalhaut b may have experienced a significant dynamical interaction with a hypothetical planet Fomalhaut c, and the current orbital configuration may be relatively short-lived. The Tisserand parameter with respect to a hypothetical Fomalhaut planet at 30 AU or 120 AU lies in the range 2-3, similar to highly eccentric dwarf planets in our solar system. We argue that Fomalhaut b's minimum mass is that of a dwarf planet in order for a circumplanetary satellite system to remain bound to a sufficient radius from the planet to be consistent with the dust scattered light hypothesis. In the coplanar case, Fomalhaut b will collide with the main belt around 2032, and the subsequent emergent phenomena may help determine its physical nature.

  3. Re-examining the main asteroid belt as the primary source of ancient lunar craters

    NASA Astrophysics Data System (ADS)

    Minton, David A.; Richardson, James E.; Fassett, Caleb I.

    2015-02-01

    It has been hypothesized that the impactors that created the majority of the observable craters on the ancient lunar highlands were derived from the main asteroid belt in such a way that preserved their size-frequency distribution (Strom, R.G., Malhotra, R., Ito, T., Yoshida, F., Kring, D.A. [2005]. Science 309, 1847-1850). A more limited version of this hypothesis, dubbed the E-belt hypothesis, postulates that a destabilized contiguous inner extension of the main asteroid belt produced a bombardment limited to those craters younger than Nectaris basin (Bottke, W.F., Vokrouhlický, D., Minton, D., Nesvorný, D., Morbidelli, A., Brasser, R., Simonson, B., Levison, H.F. [2012]. Nature 485, 78-81). We investigate these hypotheses with a Monte Carlo code called the Cratered Terrain Evolution Model (CTEM), which models the topography of a terrain that has experienced bombardment due to an input impactor population. We detail our effort to calibrate the code with a human crater counter. We also take advantage of recent advances in understanding the scaling relationships between impactor size (Di ) and final crater size (Dc ) for basin-sized impact craters (Dc>300km ) in order to use large impact basins as a constraint on the ancient impactor population of the Moon. We find that matching the observed number of lunar highlands craters with Dc≃100km requires that the total number of impacting asteroids with Di>10km be no fewer than 4×10-6km-2 . However, this required mass of impactors has <1% chance of producing only a single basin larger than the ∼1200 km Imbrium basin; instead, these simulations are likely to produce more large basins than are observed on the Moon. This difficulty in reproducing the lunar highlands cratering record with a main asteroid belt SFD arises because the main belt is relatively abundant in the objects that produce these "megabasins" that are larger than Imbrium. We also find that the main asteroid belt SFD has <16% chance of producing

  4. APIES: A mission for the exploration of the main asteroid belt using a swarm of microsatellites

    NASA Astrophysics Data System (ADS)

    D'Arrigo, P.; Santandrea, S.

    2006-10-01

    APIES (Asteroid Population Investigation and Exploration Swarm) is a mission developed by EADS Astrium in response to a European Space Agency (ESA) Call for Ideas for "swarm" missions, based on the utilization of a large number of spacecraft working cooperatively to achieve the mission objectives. The APIES baseline concept is centred on a "swarm" of 19 BElt Explorer (BEE) identical microsatellites, weighing less than 45 kg each, including their scientific payload, visiting over 100 Main Belt asteroids in multiple flybys. The BEEs are carried to the asteroid belt by a Hub and Interplanetary VEhicle (HIVE), a conventional spacecraft launched with a Soyuz-Fregat rocket, using solar electric propulsion for the transfer to the asteroid belt and acting as communication hub and control centre for the mission after the swarm deployment. Using the latest advances in systems miniaturization, propulsion, onboard autonomy and communications, the APIES mission can achieve its ambitious goal within the framework of a standard ESA mission, representing a novel mission concept example, whose feasibility is essentially linked to the use of microsatellite technology, enabling the achievement of science objectives unattainable with conventional spacecraft.

  5. Origins and Asteroid Main-Belt Stratigraphy for H-, L-, LL-Chondrite Meteorites

    NASA Astrophysics Data System (ADS)

    Binzel, Richard; DeMeo, Francesca; Burbine, Thomas; Polishook, David; Birlan, Mirel

    2016-10-01

    We trace the origins of ordinary chondrite meteorites to their main-belt sources using their (presumably) larger counterparts observable as near-Earth asteroids (NEAs). We find the ordinary chondrite stratigraphy in the main belt to be LL, H, L (increasing distance from the Sun). We derive this result using spectral information from more than 1000 near-Earth asteroids [1]. Our methodology is to correlate each NEA's main-belt source region [2] with its modeled mineralogy [3]. We find LL chondrites predominantly originate from the inner edge of the asteroid belt (nu6 region at 2.1 AU), H chondrites from the 3:1 resonance region (2.5 AU), and the L chondrites from the outer belt 5:2 resonance region (2.8 AU). Each of these source regions has been cited by previous researchers [e.g. 4, 5, 6], but this work uses an independent methodology that simultaneously solves for the LL, H, L stratigraphy. We seek feedback from the planetary origins and meteoritical communities on the viability or implications of this stratrigraphy.Methodology: Spectroscopic and taxonomic data are from the NASA IRTF MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) [1]. For each near-Earth asteroid, we use the Bottke source model [2] to assign a probability that the object is derived from five different main-belt source regions. For each spectrum, we apply the Shkuratov model [3] for radiative transfer within compositional mixing to derive estimates for the ol / (ol+px) ratio (and its uncertainty). The Bottke source region model [2] and the Shkuratov mineralogic model [3] each deliver a probability distribution. For each NEA, we convolve its source region probability distribution with its meteorite class distribution to yield a likelihood for where that class originates. Acknowledgements: This work supported by the National Science Foundation Grant 0907766 and NASA Grant NNX10AG27G.References: [1] Binzel et al. (2005), LPSC XXXVI, 36.1817. [2] Bottke et al. (2002). Icarus 156, 399. [3

  6. Photometric Observations of Main-belt Asteroids 656 Beagle and 2649 Oongaq

    NASA Astrophysics Data System (ADS)

    Sonka, Adrian Bruno; Popescu, Marcel; Nedelcu, Dan Alin

    2016-01-01

    We present photometric observations for two main-belt asteroids, 656 Beagle and 2649 Oongaq, carried out at Astronomical Institute of Romanian Academy between 2014 September and 2015 March. For 656 Beagle, we found a synodic rotation period of 7.034 ± 0.003 h and for 2649 Oongaq a synodic rotation period of 7.789 ± 0.006 h. Both are in good agreement with recent results.

  7. Period Determination of Four Main-belt Asteroids in Mid-2013

    NASA Astrophysics Data System (ADS)

    Ferrero, Andrea

    2014-01-01

    Observations of four main-belt asteroids (MBA) produced lightcurve parameters of: 1030 Vitja, P = 6.332 ± 0.001 h, A = 0.21 mag; 1058 Grubba, P = 46.30 ± 0.01 h, A = 0.24 mag; 1486 Marilyn, P = 4.568 ± 0.001 h, A = 0.42 mag.; and 3255 Tholen, P = 2.947 ± 0.001 h, A = 0.11 mag.

  8. VizieR Online Data Catalog: Main-belt asteroids optical light curves (Szabo+, 2016)

    NASA Astrophysics Data System (ADS)

    Szabo, R.; Pal, A.; Sarneczky, K.; Szabo, Gy. M.; Molnar, L.; Kiss, L. L.; Hanyecz, O.; Plachy, E.; Kiss, Cs.

    2016-09-01

    These files contain the photometric measurements of main-belt asteroids observed with the Kepler space telescope during the K2 Mission in the fields of the open cluster M35 and the Neptune/Nereid. Additionally, the observational data (start time, end time, length of observations, duty cycle, brightness) are listed, as well as rotational period and amplitude values determined from the K2 observations, where available. (6 data files).

  9. Photometric Observations of Main-belt Asteroids 1990 Pilcher and 8443 Svecica

    NASA Astrophysics Data System (ADS)

    Brincat, Stephen M.; Grech, Winston

    2017-10-01

    We report on photometric observations of two main-belt asteroids, 1990 Pilcher and 8443 Svecica, that were acquired from 2017 March to May. We found the synodic rotation period of 1990 Pilcher as 2.842 ± 0.001 h and amplitude of 0.08 ± 0.03 mag and of 8443 Svecica as 20.998 ± 0.001 h and amplitude of 0.62 ± 0.03 mag.

  10. Preliminary Analysis of WISE/NEOWISE 3-band Cryogenic and Post-Cryogenic Observations of Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Cabrera, Mario; Masiero, J. R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Nugent, C.

    2013-01-01

    After the Wide-field Infrared Survey Explorer (WISE) satellite ran out of its telescope-cooling cryogen, operations were continued for an additional four months to survey for asteroids. During the fully cryogenic portion of the mission, WISE was operating at four different wavebands centered at W1 = 3.4 μm, W2 = 4.6 μm, W3 = 12 μm, and W4 = 22 μm. When the inner cryogen tank was exhausted, the two wavebands (W3 and W4) that detected the longer wavelengths were lost, and the telescope continued to survey the sky in the remaining two wavebands. While bands W3 and W4 were of particular interest for solar system science due to their sensitivity to thermal emission from minor planets, the W2 band nevertheless was dominated by thermal emission for many asteroids. W1 was mainly sensitive to reflected sunlight for Main Belt asteroids. Infrared imaging is vital to be able to determine physical properties of asteroids and comets such as their diameter with a much better accuracy than by using visible light alone. During the Post-Cryogenic Survey phase, WISE observed some of the same objects as it did during the fully cryogenic phase, as well as objects that it had not observed before. The main objective of this project is to compare the Post-Cryogenic Survey data with the fully cryogenic data of overlapping objects to determine the accuracy of calculated properties from the Post-Cryogenic Survey data. In doing so, we have been able to establish that the diameters and albedos calculated for objects observed during the Post-Cryogenic Survey phase have an accuracy of about +/- 20% and +/- 40% respectively.

  11. Effect of rotational disruption on the size-frequency distribution of the Main Belt asteroid population

    NASA Astrophysics Data System (ADS)

    Jacobson, Seth A.; Marzari, Francesco; Rossi, Alessandro; Scheeres, Daniel J.; Davis, Donald R.

    2014-03-01

    The size distribution of small asteroids in the Main Belt is assumed to be determined by an equilibrium between the creation of new bodies out of the impact debris of larger asteroids and the destruction of small asteroids by collisions with smaller projectiles. However, for a diameter less than 6 km, we find that YORP-induced rotational disruption significantly contributes to the erosion even exceeding the effects of collisional fragmentation. Including this additional grinding mechanism in a collision evolution model for the asteroid belt, we generate size-frequency distributions from either an accretional or an `Asteroids were born big' initial size-frequency distribution that are consistent with observations reported in Gladman et al. Rotational disruption is a new mechanism that must be included in all future collisional evolution models of asteroids.

  12. A six-part collisional model of the main asteroid belt

    NASA Astrophysics Data System (ADS)

    Cibulková, H.; Brož, M.; Benavidez, P. G.

    2014-10-01

    In this work, we construct a new model for the collisional evolution of the main asteroid belt. Our goals are to test the scaling law of Benz and Asphaug (Benz, W., Asphaug, E. [1999]. Icarus, 142, 5-20) and ascertain if it can be used for the whole belt. We want to find initial size-frequency distributions (SFDs) for the considered six parts of the belt (inner, middle, “pristine”, outer, Cybele zone, high-inclination region) and to verify if the number of synthetic asteroid families created during the simulation matches the number of observed families as well. We used new observational data from the WISE satellite (Masiero et al., 2011) to construct the observed SFDs. We simulate mutual collisions of asteroids with a modified version of the Boulder code (Morbidelli, A., et al. [2009]. Icarus, 204, 558-573), where the results of hydrodynamic (SPH) simulations of Durda et al. (Durda, D.D., et al. [2007]. Icarus, 498-516) and Benavidez et al. (Benavidez, P.G., et al. [2012]. 219, 57-76) are included. Because material characteristics can significantly affect breakups, we created two models - for monolithic asteroids and for rubble-piles. To explain the observed SFDs in the size range D=1 to 10 km we have to also account for dynamical depletion due to the Yarkovsky effect. The assumption of (purely) rubble-pile asteroids leads to a significantly worse fit to the observed data, so that we can conclude that majority of main-belt asteroids are rather monolithic. Our work may also serve as a motivation for further SPH simulations of disruptions of smaller targets (with a parent body size of the order of 1 km).

  13. Dynamics of Main Belt Comets: Implications for Their Origin and Formation Mechanism

    NASA Astrophysics Data System (ADS)

    Haghighipour, N.; Hsieh, H. H.

    2012-05-01

    To determine the origin of MBCs P/2006 VW139 and P/2010 R2 we have carried out an extensive study of the dynamical evolution of these bodies and a large number of their clones. Results suggest that these objects are native to their current locations.

  14. HUBBLE SPACE TELESCOPE OBSERVATIONS OF MAIN-BELT COMET (596) SCHEILA

    SciTech Connect

    Jewitt, David; Weaver, Harold; Mutchler, Max; Larson, Stephen; Agarwal, Jessica

    2011-05-20

    We present Hubble Space Telescope Observations of (596) Scheila during its recent dust outburst. The nucleus remained point-like with absolute magnitude H{sub V} = 8.85 {+-} 0.02 in our data, equal to the pre-outburst value, with no secondary fragments of diameter {>=}100 m (for assumed albedos 0.04). We find a coma having a peak scattering cross section {approx}2.2x10{sup 4} km{sup 2}, corresponding to a mass in micron-sized particles of {approx}4x10{sup 7} kg. The particles are deflected by solar radiation pressure on projected spatial scales {approx}2x10{sup 4} km, in the sunward direction, and swept from the vicinity of the nucleus on timescales of weeks. The coma fades by {approx}30% between observations on UT 2010 December 27 and 2011 January 4. The observed mass loss is inconsistent with an origin either by rotational instability of the nucleus or by electrostatic ejection of regolith charged by sunlight. Dust ejection could be caused by the sudden but unexplained exposure of buried ice. However, the data are most simply explained by the impact, at {approx}5 km s{sup -1}, of a previously unknown asteroid {approx}35 m in diameter.

  15. TAOS: Taiwan-American Occultation Survey of Comet-Sized Objects in the Kuiper Belt

    NASA Technical Reports Server (NTRS)

    Lissauer, Jack; DeVincenzi, Donald (Technical Monitor)

    1999-01-01

    Several dozen minor planets with radii greater than 100 km have been detected beyond Neptune using large telescopes. The TAOS project is to measure directly the number of these KBOs (Kuiper Belt Objects) down to the typical size of cometary nuclei (a few km) and out as far as approximately 100 AU from the Sun. Because of their large distance, small sizes and presumed low albedos, these target objects are extremely faint. Three 50 cm wide field robotic telescopes with 2048 x 2048 CCD cameras will be deployed along a 7 km east-west baseline in or near Jade Mountain National Park in Taiwan. They will monitor approximately 3000 stars for occultations by KBOs in a coincidence mode, so that the sequence and timing of the three separate blinkings can be used to distinguish real events from false alarms. Follow-up imaging observations using large telescopes will yield albedos and orbits for some of the larger objects detected by TAOS. A fourth telescope on a north-south spur to refine the size information on occulting GABON is also being contemplated.

  16. TAOS: Taiwan-American Occultation Survey of Comet-Sized Objects in the Kuiper Belt

    NASA Technical Reports Server (NTRS)

    Lissauer, Jack; DeVincenzi, Donald (Technical Monitor)

    1999-01-01

    Several dozen minor planets with radii greater than 100 km have been detected beyond Neptune using large telescopes. The TAOS project is to measure directly the number of these KBOs (Kuiper Belt Objects) down to the typical size of cometary nuclei (a few km) and out as far as approximately 100 AU from the Sun. Because of their large distance, small sizes and presumed low albedos, these target objects are extremely faint. Three 50 cm wide field robotic telescopes with 2048 x 2048 CCD cameras will be deployed along a 7 km east-west baseline in or near Jade Mountain National Park in Taiwan. They will monitor approximately 3000 stars for occultations by KBOs in a coincidence mode, so that the sequence and timing of the three separate blinkings can be used to distinguish real events from false alarms. Follow-up imaging observations using large telescopes will yield albedos and orbits for some of the larger objects detected by TAOS. A fourth telescope on a north-south spur to refine the size information on occulting GABON is also being contemplated.

  17. Transpression as the main deformational event in an Archaean greenstone belt, northeastern Minnesota

    NASA Technical Reports Server (NTRS)

    Hudleston, P. J.; Schultz-Ela, D.; Bauer, R. L.; Southwick, D. L.

    1986-01-01

    Deformed and metamorphosed sedimentary and volcanic rocks of the Vermilion district constitute an Archean greenstone belt trending east-west between higher grade rocks of the Vermilion Granitic Complex to the north and the Giants Range batholith to the south. Metamorphic grade is low throughout, being lowest in the center of the belt (chlorite zone of the greenschist facies). All the measured strain, a cleavage or schistosity, and a mineral lineation in this belt are attributed to the main phase of deformation D sub 2 that followed an earlier nappe-forming event D sub 1, which left little evidence of penetrative fabric. Previous work assumed that the D sub 2 deformation resulted from north-south compression across the district. It is now believed that a significant component of this deformation resulted from dextral shear across the whole region. Thus the Vermilion fault, a late-state largely strike-slip structure that bounds the Vermilion district to the north, may simply be the latest, most brittle expression of a shear regime that was much more widespread in space and time. Features that are indicative of shear include ductile shear zones with sigmoidal foliation patterns, highly schistose zones with the development of shear bands, feldspar clasts or pyrite cubes with asymmetric pressure shadows, and the fact that the asymmetry of the F sub 2 folds is predominantly Z for at least 15 km south of the Vermilion fault.

  18. A new 6-part collisional model of the Main Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Broz, Miroslav; Cibulkova, H.

    2013-10-01

    In this work, we constructed a new model for the collisional evolution of the Main Asteroid Belt. Our goals are to test the scaling law from the work of Benz & Asphaug (1999) and ascertain if it can be used for the whole belt. We want to find initial size-frequency distributions (SFDs) for the considered six parts of the belt, and to verify if the number of asteroid families created during the simulation matches the number of observed families as well. We used new observational data from the WISE satellite (Masiero et al., 2011) to construct the observed SFDs. We simulated mutual collisions of asteroids with a modified Boulder code (Morbidelli et al., 2009), in which the results of hydrodynamic (SPH) simulations from the work of Durda et al. (2007) are included. Because material characteristics can affect breakups, we created two models - for monolithic asteroids and for rubble-piles (Benavidez et al., 2012). To explain the observed SFDs in the size range D = 1 to 10 km we have to also account for dynamical depletion due to the Yarkovsky effect. Our work may also serve as a motivation for further SPH simulations of disruptions of smaller targets (parent body size of the order of 1 km). The work of MB was supported by grant GACR 13-013085 of the Czech Science Foundation and the Research Programme MSM0021620860 of the Czech Ministry of Education.

  19. Early Evolution of the Main Belt Informed by the Compositional Diversity of Basaltic Asteroids

    NASA Astrophysics Data System (ADS)

    Leith, Thomas; Moskovitz, Nicholas; Mayne, Rhiannon; DeMeo, Francesca; Takir, Driss

    2015-11-01

    We present near-infrared (0.78-2.45 micron) reflectance spectra for eight outer main belt (a > 2.5 AU) asteroids that have been taxonomically classified as V-types based on visible wavelength data. Three of these objects are spectrally distinct from all classifications in the Bus-DeMeo spectral catalogue, and thus could represent either spectral end members of the V-type taxonomic class or a small population of a new spectral type. The remainder of the sample are classified as V- or R-type. All of these asteroids are dynamically distinct from the Vestoid family, implying that they originated from differentiated planetesimals which have since been destroyed or ejected from the solar system. The 1- and 2-μm band centers of all objects, determined using Modified Gaussian Model fits, were compared to those of 47 Vestoids and fifteen HED meteorites of known composition. Formulas relating Band 1 and Band 2 centers to the pyroxene mineralogies of these asteroids were derived from the sample of HED meteorites and used to determine the Fs numbers of all asteroids. The Fs numbers of the five outer belt V- and R-type asteroids are, on average, between five and ten molar percent lower than those of the Vestoids, implying that these objects formed in a more reducing environment than Vesta. Given the complex evolution of oxygen fugacity in the solar nebula, these compositional results suggest that these outer belt basaltic asteroids formed either interior to Vesta and were later scattered to the outer belt or formed at a later epoch than Vesta.

  20. SECULAR RESONANCE SWEEPING OF THE MAIN ASTEROID BELT DURING PLANET MIGRATION

    SciTech Connect

    Minton, David A.; Malhotra, Renu E-mail: renu@lpl.arizona.edu

    2011-05-01

    We calculate the eccentricity excitation of asteroids produced by the sweeping {nu}{sub 6} secular resonance during the epoch of planetesimal-driven giant planet migration in the early history of the solar system. We derive analytical expressions for the magnitude of the eccentricity change and its dependence on the sweep rate and on planetary parameters; the {nu}{sub 6} sweeping leads to either an increase or a decrease of eccentricity depending on an asteroid's initial orbit. Based on the slowest rate of {nu}{sub 6} sweeping that allows a remnant asteroid belt to survive, we derive a lower limit on Saturn's migration speed of {approx}0.15 AU Myr{sup -1} during the era that the {nu}{sub 6} resonance swept through the inner asteroid belt (semimajor axis range 2.1-2.8 AU). This rate limit is for Saturn's current eccentricity and scales with the square of its eccentricity; the limit on Saturn's migration rate could be lower if its eccentricity were lower during its migration. Applied to an ensemble of fictitious asteroids, our calculations show that a prior single-peaked distribution of asteroid eccentricities would be transformed into a double-peaked distribution due to the sweeping of the {nu}{sub 6} resonance. Examination of the orbital data of main belt asteroids reveals that the proper eccentricities of the known bright (H {<=} 10.8) asteroids may be consistent with a double-peaked distribution. If so, our theoretical analysis then yields two possible solutions for the migration rate of Saturn and for the dynamical states of the pre-migration asteroid belt: a dynamically cold state (single-peaked eccentricity distribution with mean of {approx}0.05) linked with Saturn's migration speed {approx}4 AU Myr{sup -1} or a dynamically hot state (single-peaked eccentricity distribution with mean of {approx}0.3) linked with Saturn's migration speed {approx}0.8 AU Myr{sup -1}.

  1. Investigating The Spectral Diversity Of V-type Asteroids In The Inner Main Belt

    NASA Astrophysics Data System (ADS)

    Moskovitz, Nicholas; Burbine, T. H.; Mayne, R.; Bus, S. J.; Willman, M.; Jedicke, R.; Gaidos, E.

    2008-09-01

    Spectroscopic (Binzel & Xu, 1993), dynamical (Zappala et al., 1990) and morphological (Thomas et al., 1997) evidence suggests that the Vestoids are a population of basaltic asteroids that were ejected from the surface of Vesta as a consequence of a large family-forming impact. Over time these fragments have migrated via the Yarkovsky effect (Bottke et al., 2001) and interaction with secular resonances (Carruba et al., 2005) to large orbital distances from Vesta. However, Nesvorny et al. (2008) suggest that regions of high (i > 9 deg.) and low inclination (i < 4 deg.) in the inner Main Belt cannot be populated by a significant number of Vestoids. Thus, the recent identification of numerous V-type asteroids in these regions (Moskovitz et al., 2008; Roig & Gil-Hutton, 2006) raises two interesting possibilities: (1) they originated from a differentiated parent body other than Vesta, or (2) they originated from Vesta before the primary family forming impact and before the Late Heavy Bombardment when resonance sweeping dynamically excited the Main Belt. The possibility of a unique parent body or an older surface implies that the surface mineralogy of these objects may be distinct from that of "ordinary” Vestoids. In consideration of these issues we present new spectra and analysis for a variety of V-type asteroids throughout the inner Main Belt (a < 2.5 AU) with a particular focus on objects that have large values of delta-v (Zappala et al., 1996) relative to Vesta. Our analysis includes a search for trends in the spectral properties of these objects as a function of orbital distance from Vesta and an attempt to link these spectral properties to the petrology of meteorite samples using both band analysis techniques (Burbine et al., 2007) and MGM analysis (Sunshine et al., 1990). This work is supported by a NASA GSRP fellowship.

  2. A low-density M-type asteroid in the main belt.

    PubMed

    Margot, J L; Brown, M E

    2003-06-20

    The orbital parameters of a satellite revolving around 22 Kalliope indicate that the bulk density of this main-belt asteroid is 2.37 +/- 0.4 grams per cubic centimeter. M-type asteroids such as Kalliope are thought to be the disrupted metallic cores of differentiated bodies. The low-density indicates that Kalliope cannot be predominantly composed of metal and may be composed of chondritic material with approximately 30% porosity. The satellite orbit is circular, suggesting that Kalliope and its satellite have different internal structures and tidal dissipation rates. The satellite may be an aggregate of impact ejecta from an earlier collision with Kalliope.

  3. Capture of Trans-Neptunian Planetesimals in the Main Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Vokrouhlický, David; Bottke, William F.; Nesvorný, David

    2016-08-01

    The orbital evolution of the giant planets after nebular gas was eliminated from the Solar System but before the planets reached their final configuration was driven by interactions with a vast sea of leftover planetesimals. Several variants of planetary migration with this kind of system architecture have been proposed. Here, we focus on a highly successful case, which assumes that there were once five planets in the outer Solar System in a stable configuration: Jupiter, Saturn, Uranus, Neptune, and a Neptune-like body. Beyond these planets existed a primordial disk containing thousands of Pluto-sized bodies, ˜50 million D > 100 km bodies, and a multitude of smaller bodies. This system eventually went through a dynamical instability that scattered the planetesimals and allowed the planets to encounter one another. The extra Neptune-like body was ejected via a Jupiter encounter, but not before it helped to populate stable niches with disk planetesimals across the Solar System. Here, we investigate how interactions between the fifth giant planet, Jupiter, and disk planetesimals helped to capture disk planetesimals into both the asteroid belt and first-order mean-motion resonances with Jupiter. Using numerical simulations, we find that our model produces the right proportion of P- and D-type asteroids in the inner, central, and outer main belt, while also populating the Hilda and Thule regions in Jupiter’s 3/2 and 4/3 resonances. Moreover, the largest observed P/D types in each sub-population are an excellent fit to our captured population results (within uncertainties). The model produces a factor of ˜10 overabundance of diameter D > 10 km P/D types in the main belt, but this mismatch can likely be explained by various removal mechanisms (e.g., collision evolution over 4 Gyr, dynamical losses via Yarkovsky thermal forces over 4 Gyr, thermal destruction of the planetesimals en route to the inner solar system). Overall, our instability model provides a more

  4. APIES: a mission for the exploration of the main asteroid belt using a swarm of microspacecraft

    NASA Astrophysics Data System (ADS)

    D'Arrigo, P.; Santandrea, S.

    2003-11-01

    APIES (Asteroid Population Investigation & Exploration Swarm) is a mission developed by EADS Astrium in response to the European Space Agency (ESA) recent Invitation to Tender for "swarm" missions, based on the utilisation of a large number of spacecraft working cooperatively to achieve the mission objectives. APIES, currently in its Feasibility Study Phase, is intended to be the first interplanetary swarm mission, designed to explore the asteroid main belt. This is one of the least known parts of the Solar System, yet holding vital information about its evolution and planet formation. APIES aims to characterize a statistically significant sample of asteroids, exploring the main belt in great detail, measuring mass & density and imaging over 100 of these objects, at a stroke more than doubling the number of Solar System bodies visited by man-made spacecraft. Using the latest advances in systems miniaturization, propulsion, onboard autonomy and communications, the APIES mission can achieve these ambitious goals within the framework of a standard ESA mission. The currently ongoing Mission Feasibility Study is part of the General Studies Programme (GSP) of ESA, whose purpose is to evaluate novel missions, concepts, methods, and to identify their research and development needs beyond the programmes currently running.

  5. The kilometer-sized Main Belt asteroid population revealed by Spitzer

    NASA Astrophysics Data System (ADS)

    Ryan, E. L.; Mizuno, D. R.; Shenoy, S. S.; Woodward, C. E.; Carey, S. J.; Noriega-Crespo, A.; Kraemer, K. E.; Price, S. D.

    2015-06-01

    Aims: Multi-epoch Spitzer Space Telescope 24 μm data is utilized from the MIPSGAL and Taurus Legacy surveys to detect asteroids based on their relative motion. Methods: Infrared detections are matched to known asteroids and average diameters and albedos are derived using the near Earth asteroid thermal model (NEATM) for 1865 asteroids ranging in size from 0.2 to 169 km. A small subsample of these objects was also detected by IRAS or MSX and the single wavelength albedo and diameter fits derived from these data are within the uncertainties of the IRAS and/or MSX derived albedos and diameters and available occultation diameters, which demonstrates the robustness of our technique. Results: The mean geometric albedo of the small Main Belt asteroids in this sample is pV = 0.134 with a sample standard deviation of 0.106. The albedo distribution of this sample is far more diverse than the IRAS or MSX samples. The cumulative size-frequency distribution of asteroids in the Main Belt at small diameters is directly derived and a 3σ deviation from the fitted size-frequency distribution slope is found near 8 km. Completeness limits of the optical and infrared surveys are discussed. Tables 1-3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A42

  6. The Sub-Kilometer Asteroid Diameter Survey II: The debiased size distribution of main belt asteroids

    NASA Astrophysics Data System (ADS)

    Jedicke, R.; Gladman, B.; Davis, D.; Petit, J.-M.

    2011-10-01

    The Sub-Kilometer Asteroid Diameter Survey (SKADS, [1]) imaged ˜8.6 square degrees of sky and detected 1277 main belt asteroids to a limiting magnitude of R˜23 (at which the efficiency is 50%). SKADS was performed in both V and R filters and allows a probabilistic assignment of an albedo, and therefore diameter, to each object. By planting synthetic objects directly into the images we have determined the moving object detection efficiency as a function of their rate and direction of motion and their apparent magnitude on each of the six survey nights. The surveying pattern was designed to provide recovery of the asteroids over intervals of >6 days and therefore provides a good orbit, distance and absolute magnitude for each of the objects. We have performed a high-resolution, high-accuracy simulation of the multi-night surveying procedure to compute the observational selection effects as a function of semi-major axis, eccentricity, inclination and absolute magnitude (see Figure 1). We will present the results of this simulation and provide the observationally corrected distributions of main belt objects as a function of their orbital parameters, absolute magnitude and diameter.

  7. Main-belt asteroids with WISE/NEOWISE: Near-infrared albedos

    SciTech Connect

    Masiero, Joseph R.; Mainzer, A. K.; Nugent, C. R.; Bauer, J. M.; Stevenson, R.; Sonnett, S.

    2014-08-20

    We present revised near-infrared albedo fits of 2835 main-belt asteroids observed by WISE/NEOWISE over the course of its fully cryogenic survey in 2010. These fits are derived from reflected-light near-infrared images taken simultaneously with thermal emission measurements, allowing for more accurate measurements of the near-infrared albedos than is possible for visible albedo measurements. Because our sample requires reflected light measurements, it undersamples small, low-albedo asteroids, as well as those with blue spectral slopes across the wavelengths investigated. We find that the main belt separates into three distinct groups of 6%, 16%, and 40% reflectance at 3.4 μm. Conversely, the 4.6 μm albedo distribution spans the full range of possible values with no clear grouping. Asteroid families show a narrow distribution of 3.4 μm albedos within each family that map to one of the three observed groupings, with the (221) Eos family being the sole family associated with the 16% reflectance 3.4 μm albedo group. We show that near-infrared albedos derived from simultaneous thermal emission and reflected light measurements are important indicators of asteroid taxonomy and can identify interesting targets for spectroscopic follow-up.

  8. MAIN-BELT ASTEROIDS IN THE K2 ENGINEERING FIELD OF VIEW

    SciTech Connect

    Szabó, R.; Sárneczky, K.; Szabó, Gy. M.; Pál, A.; Kiss, Cs. P.; Kiss, L. L.; Csák, B.; Illés, L.; Rácz, G.

    2015-03-15

    Unlike NASA’s original Kepler Discovery Mission, the renewed K2 Mission will target the plane of the Ecliptic, observing each field for approximately 75 days. This will bring new opportunities and challenges, in particular the presence of a large number of main-belt asteroids that will contaminate the photometry. The large pixel size makes K2 data susceptible to the effects of apparent minor planet encounters. Here, we investigate the effects of asteroid encounters on photometric precision using a subsample of the K2 engineering data taken in 2014 February. We show examples of asteroid contamination to facilitate their recognition and distinguish these events from other error sources. We conclude that main-belt asteroids will have considerable effects on K2 photometry of a large number of photometric targets during the Mission that will have to be taken into account. These results will be readily applicable for future space photometric missions applying large-format CCDs, such as TESS and PLATO.

  9. MARS Gravity-Assist to Improve Missions towards Main-Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Casalino, Lorenzo; Colasurdo, Guido

    fain-belt asteroids are one of the keys to the investigation of the processes that lead to the solar electric propulsion (SEP) with ion thrusters is a mature technology for the exploration of the bolar system. NASA is currently planning the DAWN mission towards two asteroids of the main s with Vesta in 2010 and Ceres in 2014. A mission to an asteroid of the main belt requires a large velocity increment (V) and the use of high-specific-impulse thrusters, such as ion thrusters, p m ovides a large improvement of the payload and, consequently, of the scientific return of the of this kind of trajectory is a non-trivial task, since many local optima exist and performance can be improved by increasing the trip-time and the number of revolutions around the sun, in order to use t the propellant only in the most favorable positions (namely, perihelia, aphelia and nodes) along the Mars is midway between the Earth and the main belt; even though its gravity is quite small, a gravity assist from Mars can remarkably improve the trajectory performance and is considered in this paper. p he authors use an indirect optimization procedure based on the theory of optimal control. The Mars) spheres of influence is neglected; the equations of motion are therefore integrated only in the heliocentric reference frame, whereas the flyby is treated as a discontinuity of the spacecraft's velocity. The paper analyzes trajectories, which exploit chemical propulsion to escape from the E variable-power, constant-specific-impulse propulsion system is assumed. The optimization procedure provides departure, flyby and arrival dates, the hyperbolic excess velocity on leaving the t arth's sphere of influence, which must be provided by the chemical propulsion system, and the E e ass at rendezvous, when the trip time is assigned. As far as the thrust magnitude is concerned, m either full-thrust arcs or coast arcs are required, and the procedure provides the times to switch the g low and the spacecraft

  10. Uninterrupted optical light curves of main-belt asteroids from the K2 mission

    NASA Astrophysics Data System (ADS)

    Szabó, R.; Pál, A.; Sárneczky, K.; Szabó, Gy. M.; Molnár, L.; Kiss, L. L.; Hanyecz, O.; Plachy, E.; Kiss, Cs.

    2016-11-01

    Context. Because the second reaction wheel failed, a new mission was conceived for the otherwise healthy Kepler space telescope. In the course of the K2 mission, the telescope is staring at the plane of the Ecliptic. Thousands of solar system bodies therefore cross the K2 fields and usually cause additional noise in the highly accurate photometric data. Aims: We here follow the principle that some person's noise is another person's signal and investigate the possibility of deriving continuous asteroid light curves. This is the first such endeavor. In general, we are interested in the photometric precision that the K2 mission can deliver on moving solar system bodies. In particular, we investigate space photometric optical light curves of main-belt asteroids. Methods: We studied the K2 superstamps that cover the fields of M35, and Neptune together with Nereid, which were observed in the long-cadence mode (29.4 min sampling). Asteroid light curves were generated by applying elongated apertures. We used the Lomb-Scargle method to determine periodicities that are due to rotation. Results: We derived K2 light curves of 924 main-belt asteroids in the M35 field and 96 in the path of Neptune and Nereid. The light curves are quasi-continuous and several days long. K2 observations are sensitive to longer rotational periods than typical ground-based surveys. Rotational periods are derived for 26 main-belt asteroids for the first time. The asteroid sample is dominated by faint objects (>20 mag). Owing to the faintness of the asteroids and the high density of stars in the M35 field, only 4.0% of the asteroids with at least 12 data points show clear periodicities or trends that signal a long rotational period, as opposed to 15.9% in the less crowded Neptune field. We found that the duty cycle of the observations had to reach 60% to successfully recover rotational periods. Full Tables 1-4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130

  11. Observational constraints on the catastrophic disruption rate of small main belt asteroids

    NASA Astrophysics Data System (ADS)

    Denneau, Larry; Jedicke, Robert; Fitzsimmons, Alan; Hsieh, Henry; Kleyna, Jan; Granvik, Mikael; Micheli, Marco; Spahr, T.; Vereš, Peter; Wainscoat, Richard; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Flewelling, H.; Huber, M. E.; Kaiser, N.; Morgan, J. S.; Tonry, J. L.

    2015-01-01

    We have calculated 90% confidence limits on the steady-state rate of catastrophic disruptions of main belt asteroids in terms of the absolute magnitude at which one catastrophic disruption occurs per year (H0CL) as a function of the post-disruption increase in brightness (Δm) and subsequent brightness decay rate (τ). The confidence limits were calculated using the brightest unknown main belt asteroid (V = 18.5) detected with the Pan-STARRS1 (Pan-STARRS1) telescope. We measured the Pan-STARRS1's catastrophic disruption detection efficiency over a 453-day interval using the Pan-STARRS moving object processing system (MOPS) and a simple model for the catastrophic disruption event's photometric behavior in a small aperture centered on the catastrophic disruption event. We then calculated the H0CL contours in the ranges from 0.5 mag < Δm < 20 mag and 0.001 magd-1 < τ < 10 magd-1 encompassing measured values from known cratering and disruption events and our model's predictions. Our simplistic catastrophic disruption model suggests that Δm ∼ 20 mag and 0.01 magd-1 ≲ τ ≲ 0.1 magd-1 which would imply that H0 ≳ 28 -strongly inconsistent with H0,B2005 = 23.26 ± 0.02 predicted by Bottke et al. (Bottke, W.F., Durda, D.D., Nesvorný, D., Jedicke, R., Morbidelli, A., Vokrouhlický, D., Levison, H.F. [2005]. Icarus, 179, 63-94.) using purely collisional models. However, if we assume that H0 =H0,B2005 our results constrain 11.0 mag ≲ Δm ≲ 12.4 mag , inconsistent with our simplistic impact-generated catastrophic disruption model. We postulate that the solution to the discrepancy is that > 99 % of main belt catastrophic disruptions in the size range to which this study was sensitive (∼100 m) are not impact-generated, but are instead due to fainter rotational breakups, of which the recent discoveries of disrupted asteroids P/2013 P5 and P/2013 R3 are probable examples. We estimate that current and upcoming asteroid surveys may discover up to 10 catastrophic

  12. Aqueous alteration on main belt primitive asteroids: Results from visible spectroscopy

    NASA Astrophysics Data System (ADS)

    Fornasier, S.; Lantz, C.; Barucci, M. A.; Lazzarin, M.

    2014-05-01

    This work focuses on the study of the aqueous alteration process which acted in the main belt and produced hydrated minerals on the altered asteroids. Hydrated minerals have been found mainly on Mars surface, on main belt primitive asteroids and possibly also on few TNOs. These materials have been produced by hydration of pristine anhydrous silicates during the aqueous alteration process, that, to be active, needed the presence of liquid water under low temperature conditions (below 320 K) to chemically alter the minerals. The aqueous alteration is particularly important for unraveling the processes occurring during the earliest times of the Solar System history, as it can give information both on the asteroids thermal evolution and on the localization of water sources in the asteroid belt. To investigate this process, we present reflected light spectral observations in the visible region (0.4-0.94 μm) of 80 asteroids belonging to the primitive classes C (prevalently), G, F, B and P, following the Tholen (Tholen, D.J. [1984]. Ph.D. Dissertation, University of Arizona, Tucson). classification scheme. We find that about 65% of the C-type and all the G-type asteroids investigated reveal features suggesting the presence of hydrous materials, mainly a band centered around 0.7 μm, while we do not find evidence of hydrated materials in the other low albedo asteroids (B, F, and P) investigated. We combine the present observations with the visible spectra of asteroids available in the literature for a total of 600 primitive main belt asteroids. We analyze all these spectra in a similar way to characterize the absorption band parameters (band center, depth and width) and spectral slope, and to look for possible correlations between the aqueous alteration process and the asteroids taxonomic classes, orbital elements, heliocentric distances, albedo and sizes. Our analysis shows that the aqueous alteration sequence starts from the P-type objects, practically unaltered, and

  13. First known Terrestrial Impact of a Binary Asteroid from a Main Belt Breakup Event

    PubMed Central

    Ormö, Jens; Sturkell, Erik; Alwmark, Carl; Melosh, Jay

    2014-01-01

    Approximately 470 million years ago one of the largest cosmic catastrophes occurred in our solar system since the accretion of the planets. A 200-km large asteroid was disrupted by a collision in the Main Asteroid Belt, which spawned fragments into Earth crossing orbits. This had tremendous consequences for the meteorite production and cratering rate during several millions of years following the event. The 7.5-km wide Lockne crater, central Sweden, is known to be a member of this family. We here provide evidence that Lockne and its nearby companion, the 0.7-km diameter, contemporaneous, Målingen crater, formed by the impact of a binary, presumably ‘rubble pile’ asteroid. This newly discovered crater doublet provides a unique reference for impacts by combined, and poorly consolidated projectiles, as well as for the development of binary asteroids. PMID:25340551

  14. First known terrestrial impact of a binary asteroid from a main belt breakup event.

    PubMed

    Ormö, Jens; Sturkell, Erik; Alwmark, Carl; Melosh, Jay

    2014-10-23

    Approximately 470 million years ago one of the largest cosmic catastrophes occurred in our solar system since the accretion of the planets. A 200-km large asteroid was disrupted by a collision in the Main Asteroid Belt, which spawned fragments into Earth crossing orbits. This had tremendous consequences for the meteorite production and cratering rate during several millions of years following the event. The 7.5-km wide Lockne crater, central Sweden, is known to be a member of this family. We here provide evidence that Lockne and its nearby companion, the 0.7-km diameter, contemporaneous, Målingen crater, formed by the impact of a binary, presumably 'rubble pile' asteroid. This newly discovered crater doublet provides a unique reference for impacts by combined, and poorly consolidated projectiles, as well as for the development of binary asteroids.

  15. V lightcurves and B-V colours of main-belt asteroids

    NASA Astrophysics Data System (ADS)

    Blanco, C.; Riccioli, D.

    To obtain asteroid photometric lightcurves sufficiently covered to yield the elements necessary to apply the methods for computing their rotational parameters and shape, an observational campaign of main-belt asteroids was undertaken at the Astronomy Institute of Catania University. During more than 40 observational runs, made since 1992 at the M.G. Fracastoro station of Catania Astrophysical Observatory, the lightcurves of more than a hundred asteroids were constructed and the values of rotational axis orientation and of the axes ratio of 50 objects were computed. We present the V lightcurves, the B-V colour, the found values of the synodical rotational period and the lightcurves amplitude of 56 Melete, 95 Arethusa, 138 Tolosa, 198 Ampella, 212 Medea, 286 Iclea, 432 Pythia, 509 Iolanda, 568 Cheruskia, 674 Rachele, 860 Ursina, 1369 Ostanina and 1469 Linzia. The characteristic of the lightcurves and the period values are discussed in comparison with the ones reported in the literature.

  16. A Non-Gravitational Effect and Spin Orientation of Kilometre-Sized Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Kazantsev, A. M.; Kazantseva, L.

    2016-09-01

    Determining spin directions of asteroids - a rather difficult task Today, only about 200 asteroids have identified spin orientations. For some asteroids it can determine the spin directions by precise calculations of the evolution of the orbits. Numerical calculations of the orbital evolution of the MBA asteroids from 2005 to 2016 were carried out. The calculation results analysis leads to the conclusion that in our days an influence of non-gravitational effects (NGE) of cometary nature becomes apparent in motion of a significant portion (at least 5%) of the main belt asteroids up to 40 km. Such NGE causes the increase of the semi-major axes of orbits of the low-albedo asteroids with respect to the semi-major axes of orbits of bodies with the large albedos. Change an asteroid semi-major axis should depend on the spin direction. Therefore the calculations may indicate on the spin direction (prograde or retrograde) for several tens of asteroids.

  17. The Main-belt Asteroid and NEO Tour with Imaging and Spectroscopy (MANTIS)

    NASA Astrophysics Data System (ADS)

    Rivkin, A.; Cohen, B. A.; Barnouin, O. S.; Chabot, N. L.; Ernst, C. M.; Klima, R. L.; Helbert, J.; Sternovsky, Z.

    2015-12-01

    The asteroids preserve information from the earliest times in solar system history, with compositions in the population reflecting the material in the solar nebula and experiencing a wide range of temperatures. Today they experience ongoing processes, some of which are shared with larger bodies but some of which are unique to their size regime. They are critical to humanity's future as potential threats, resource sites, and targets for human visitation. However, over twenty years since the first spacecraft encounters with asteroids, they remain poorly understood. The mission we propose here, the Main-belt Asteroid and NEO Tour with Imaging and Spectroscopy (MANTIS), explores the diversity of asteroids to understand our solar system's past history, its present processes, and future opportunities and hazards. MANTIS addresses many of NASA's highest priorities as laid out in its 2014 Science Plan and provides additional benefit to the Planetary Defense and Human Exploration communities via a low-risk, cost-effective tour of the near-Earth and inner asteroid belt. MANTIS visits the materials that witnessed solar system formation and its earliest history, addressing the NASA goal of exploring and observing the objects in the solar system to understand how they formed and evolve. MANTIS measures OH, water, and organic materials via several complementary techniques, visiting and sampling objects known to have hydrated minerals and addressing the NASA goal of improving our understanding of the origin and evolution of life on Earth. MANTIS studies the geology and geophysics of nine diverse asteroids, with compositions ranging from water-rich to metallic, representatives of both binary and non-binary asteroids, and sizes covering over two orders of magnitude, providing unique information about the chemical and physical processes shaping the asteroids, addressing the NASA goal of advancing the understanding of how the chemical and physical processes in our solar system

  18. Albedo, Size and Taxonomy of the Small Body Populations Outside the Main Belt

    NASA Astrophysics Data System (ADS)

    Grav, Tommy; Mainzer, Amy; Bauer, James; Masiero, Joseph R.; Cutri, Roc; Nugent, Carrie; Sonnett, Sarah; Kramer, Emily A.

    2015-11-01

    Using the data from the WISE/NEOWISE mission we have derived albedo and size distributions of ~1200 Cybeles, ~1000 Hildas, ~1700 Jovian Trojans and a dozen irregular satellites of Jupiter and Saturn. These data increases by an order of magnitude our knowledge of the makeup of the small body populations between the Main Belt and Saturn. We find that all these populations are dominated by low albedo objects, with only the Cybeles (with less than 10%) having any significant fraction of possible interloper objects with albedo higher than 15%. Using the near-infrared albedos (in the 3.4 and 4.6μm bands, denoted W1 and W2 respectively) we were able to derive the taxonomic classifications of the largest objects in each population, showing that they are dominated by surfaces that are similar to C-, P- and D-type asteroids. The dominance of these dark, primitive surfaces indicate two possible formation scenarios. These small body populations may have been formed in situ beyond the snow line, potentially serving as bodies that can provide significant insight into the composition of the early Solar Nebula in the region of the current Giant Planets. Alternatively, they may be captured bodies that were perturbed from the region outside the Giant Planets as the planets migrated during the early stages of Solar System formation. This allows for insight into the composition of the Trans-Neptunian population by study of populations that are significantly closer, brighter and more accessible. The low percentages of potentially higher albedo, stony objects common in the Main Asteroid Belt indicates that only a few of these objects have embedded themselves into these populations, potentially imposing significant constraints on the migration of Jupiter inside its current orbit.

  19. Masses of asteroids and the total mass of the main asteroid belt

    NASA Astrophysics Data System (ADS)

    Vladimirovna Pitjeva, Elena; Petrovich Pitjev, Nikolay

    2015-08-01

    The renovated database of observations of planets and spacecraft, as well as asteroid data have been used for estimation of masses of asteroids and the total mass of main asteroid belt from their perturbations on motion of solar system bodies. The direct dynamical mass estimations were obtained for about 30 largest asteroids by their gravitation impacts on other bodies. The masses of other large asteroids were estimated by their diameters and evaluated densities. The total contribution of all remaining small asteroids is modeled as a gravitational force from uniform two-dimensional ring with the constant mass distribution in the ecliptic plane. The work was based on the new version of the EPM2014 ephemerides of IAA RAS using more than 800000 positional observations (mostly radar ones) of planets and spacecraft obtained in 1913-2014. For the first time, the two-dimensional asteroid annulus with dimensions corresponding to its observable width has been used instead of one-dimensional ring which applied for modeling perturbation of small asteroids in our previous versions of EPM ephemerides. As a result, the accuracy of the mass of the two-dimensional asteroid annulus has increased by 6 times; orbits of all planets have improved distinctly, in particular, the formal uncertainties of the semi-major axes of the planets decreased by two times. The total mass of the main asteroid belt has been found: Mbelt = (12.25 ± 0.19)×10-10MSun. ≈ 2.5 MCeres.Moreover, the estimation of the total mass of Trans-Neptunian Objects (TNO) including the known masses of 30 largest TNO, Pluto and the evaluated mass of the TNO ring (with a radius of 43 au) was obtained:592×10-10 MSun (or 125 MCeres).

  20. A search for subkilometer-sized ordinary chondrite like asteroids in the main-belt

    NASA Astrophysics Data System (ADS)

    Lin, H. W.; Yoshida, Fumi; Chen, Y. T.; Ip, W. H.; Chang, C. K.

    2015-07-01

    The size-dependent effects of asteroids on surface regolith and collisional lifetimes suggest that small asteroids are younger than large asteroids. In this study, we performed multicolor main-belt asteroid (MBA) survey by Subaru telescope/Suprime-Cam to search for subkilometer-sized ordinary chondrite (Q-type) like MBAs. The total survey area was 1.5 deg2 near ecliptic plane and close to the opposition. We detected 150 MBAs with 4 bands (B, V, R, I) in this survey. The range of absolute magnitude of detected asteroids was between 13 and 22 magnitude, which is equivalent to the size range of kilometer to sub-kilometer diameter in MBAs. From this observation, 75 of 150 MBAs with color uncertainty less than 0.1 were used in the spectral type analysis, and two possible Q-type asteroids were detected. This mean that the Q-type to S-type ratio in MBAs is <0.05. Meanwhile, the Q/S ratio in near Earth asteroids (NEAs) has been estimated to be 0.5-2 (Binzel, R.P. et al. [2004]. Icarus 107, 259-224; Dandy, C.L., Fitzsimmins, A., Collander-Brown, S.J. [2003]. Icarus 163, 363-373). Therefore, Q-type NEAs might be delivered from the main belt region with weathered, S-type surface into near Earth region and then obtain their Q-type, non-weathered surface after undergoing re-surfacing process there. The resurfacing mechanisms could be: 1. dispersal of surface material by tidal effect during planetary encounters (Binzel, R.P. et al. [2010]. Nature 463, 331-334; Nesvorný, D. et al. [2010]. Icarus 209, 510-519), 2. the YORP spin-up induced rotational-fission (Polishook, D. et al. [2014]. Icarus 233, 9-26) or surface re-arrangement, or 3. thermal degradation (Delbo, M. et al. [2014]. Nature 508, 233-236).

  1. Albedo, Size and Taxonomy of the Small Body Populations Outside the Main Belt

    NASA Astrophysics Data System (ADS)

    Grav, Tommy; Mainzer, A.; Bauer, J. M.; Masiero, J. R.; Nugent, C. R.; Stevenson, R. A.

    2013-10-01

    Using the data from the WISE/NEOWISE mission we have derived albedo and size distribution of more than ~1200 Cybeles, ~1000 Hildas, ~1700 Jovian Trojans and a dozen irregular satellites of Jupiter and Saturn. This dataset increases by an order of magnitude our knowledge of the makeup of the small body populations between the Main Belt and Saturn. We find that all these populations are dominated by low albedo objects, with only the Cybele and Hilda populations having a small (less than 10% among the Cybeles and less than 1% among the Hildas, Trojans and irregular satellites) fraction of objects with albedos higher than 15%. Using the near-infrared albedos (in the 3.4 and 4.6 micron bands) we were also able to derive the taxonomic classifications of the largest objects in each populations, showing that they are dominated by C-, P- and D-type surfaces. The dominance of these dark bodies indicate two possible formation scenarios. The small body populations may have been formed in situ beyond the snow line, potentially serving as primitive bodies that can provide significant insight into the composition of the early Solar Nebula in the region of the Giant Planets. Alternatively, they may be captured bodies that were perturbed from the region outside the Giant Planets as the planets migrated during the early stages of Solar System formation. This allows for insight into the composition of the Trans-Neptunian population by study of populations that are closer, brighter and more accessible. The low percentages of the more stony objects common in the Main Asteroid Belt indicates that few of these objects were embedded in the populations, imposing significant constraints on the migration of Jupiter inside its current orbit.

  2. Results from the Herschel Gould Belt Survey in the Ophiuchus Main Cloud

    NASA Astrophysics Data System (ADS)

    Ladjelate, Bilal; André, Philippe; Könyves, Vera; Men'shchikov, Alexander

    2015-08-01

    Results from the Herschel Gould Belt Survey in the Ophiuchus Main CloudThe Ophiuchus Molecular Cloud is a well documented star-forming cloud located ~140 pc from the Sun. It is therefore an excellent laboratory for dense core search and classification. Harbouring low-mass star formation, its protostellar population have been studied for about three decades from the near infrared to the millimeter and radio range.As part of the Herschel Gould Belt Survey (http://www.herschel.fr/cea/gouldbelt/), extensive submillimeter images of the Ophiuchus Main Cloud (L1688) were produced and a deep census of both prestellar cores and young protostars was obtained using the multi-scale, multi-wavelength source extraction algorithm, getsources (Mensh'chikov et al. 2012).About 300 starless cores were extracted, including ~100 candidates gravitationally bound prestellar cores. The prestellar cores are primarily found in high column density filamentary structures above AV~7. Based on these data we discuss, the properties of the prestellar core mass function (CMF) as well as its variations in the various clumps of the cloud. The peak of the prestellar CMF appears to be close to 0.3 Solar masses in L1688.Conceptually, the low-mass end of the prestellar CMF is populated by pre-brown dwarf cores, the prototype of which is Oph-B11, a 20 Jovian masses object identified with SCUBA and IRAM (Greaves et al. 2003, André et al. 2012). Our Herschel census of dense cores in L1688 contains a few other candidate ultra low-mass cores under the hydrogen-burning limit (0.08 M⊙) which will be discussed.

  3. Variations in Jupiter's Radiation Belts and Synchrotron Radiation as a Result of the Impacts of Comet Shoemaker-Levy/9

    NASA Technical Reports Server (NTRS)

    Bolton, S.; Gulkis, S.; Klein, M.; Thorne, R. M.

    1995-01-01

    Changes to Jupiter's synchrotron radiation following the impact of Comet Shoemaker-Levy/9 are reported. Also, the consequences are reported for three possible mechanisms that might have caused those changes.

  4. 30 CFR 75.1101 - Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Deluge-type water sprays, foam generators; main... Fire Protection § 75.1101 Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives. Deluge-type water sprays or foam generators automatically actuated by rise in temperature, or...

  5. 30 CFR 75.1101 - Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Deluge-type water sprays, foam generators; main... Fire Protection § 75.1101 Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives. Deluge-type water sprays or foam generators automatically actuated by rise in temperature, or...

  6. 30 CFR 75.1101 - Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Deluge-type water sprays, foam generators; main... Fire Protection § 75.1101 Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives. Deluge-type water sprays or foam generators automatically actuated by rise in temperature, or...

  7. 30 CFR 75.1101 - Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Deluge-type water sprays, foam generators; main... Fire Protection § 75.1101 Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives. Deluge-type water sprays or foam generators automatically actuated by rise in temperature, or...

  8. 30 CFR 75.1101 - Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Deluge-type water sprays, foam generators; main... Fire Protection § 75.1101 Deluge-type water sprays, foam generators; main and secondary belt-conveyor drives. Deluge-type water sprays or foam generators automatically actuated by rise in temperature, or...

  9. Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey.

    PubMed

    Marchis, F; Kaasalainen, M; Hom, E F Y; Berthier, J; Enriquez, J; Hestroffer, D; Le Mignant, D; de Pater, I

    2006-11-01

    This paper presents results from a high spatial resolution survey of 33 main-belt asteroids with diameters >40 km using the Keck II Adaptive Optics (AO) facility. Five of these (45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra) were confirmed to have satellite. Assuming the same albedo as the primary, these moonlets are relatively small (∼5% of the primary size) suggesting that they are fragments captured after a disruptive collision of a parent body or captured ejecta due to an impact. For each asteroid, we have estimated the minimum size of a moonlet that can positively detected within the Hill sphere of the system by estimating and modeling a 2-σ detection profile: in average on the data set, a moonlet located at 2/100 × R(Hill) (1/4 × R(Hill)) with a diameter larger than 6 km (4 km) would have been unambiguously seen. The apparent size and shape of each asteroid was estimated after deconvolution using a new algorithm called AIDA. The mean diameter for the majority of asteroids is in good agreement with IRAS radiometric measurements, though for asteroids with a D < 200 km, it is underestimated on average by 6-8%. Most asteroids had a size ratio that was very close to those determined by lightcurve measurements. One observation of 104 Klymene suggests it has a bifurcated shape. The bi-lobed shape of 121 Hermione described in Marchis et al. [Marchis, F., Hestroffer, D., Descamps, P., Berthier, J., Laver, C., de Pater, I., 2005c. Icarus 178, 450-464] was confirmed after deconvolution. The ratio of contact binaries in our survey, which is limited to asteroids larger than 40 km, is surprisingly high (∼6%), suggesting that a non-single configuration is common in the main-belt. Several asteroids have been analyzed with lightcurve inversions. We compared lightcurve inversion models for plane-of-sky predictions with the observed images (9 Metis, 52 Europa, 87 Sylvia, 130 Elektra, 192 Nausikaa, and 423 Diotima, 511 Davida). The AO images allowed us to

  10. Phase II of the Small Main-Belt Asteroid Spectroscopic Survey. A Feature-Based Taxonomy

    NASA Astrophysics Data System (ADS)

    Bus, Schelte J.; Binzel, Richard P.

    2002-07-01

    The second phase of the Small Main-belt Asteroid Spectroscopic Survey (SMASSII) produced an internally consistent set of visible-wavelength charge-coupled device (CCD) spectra for 1447 asteroids (Bus and Binzel 2002, Icarus, ). These data provide a basis for developing a new asteroid taxonomy that utilizes more of the information contained in CCD spectra. Here we construct a classification system that builds on the robust framework provided by existing asteroid taxonomies. In particular, we define three major groupings (the S-, C-, and X-complexes) that adhere to the classical definitions of the S-, C-, and X-type asteroids. A total of 26 classes are defined, based on the presence or absence of specific spectral features. Definitions and boundary parameters are provided for each class, allowing new spectral observations to be placed in this system. Of these 26 classes, 12 bear familiar single-letter designations that follow previous conventions: A, B, C, D, K, O, Q, R, S, T, V, and X. A new L-class is introduced to describe 35 objects with spectra having a steep UV slope shortward of 0.75 μm, but which are relatively flat longward of 0.75 μm. Asteroids with intermediate spectral characteristics are assigned multiletter designations: Cb, Cg, Cgh, Ch, Ld, Sa, Sk, Sl, Sq, Sr, Xc, Xe, and Xk. Members of the Cgh- and Ch-classes have spectra containing a 0.7-μm feature that is generally attributed to hydration. Although previously considered featureless, CCD observations reveal distinct features of varying strengths in the spectra of asteroids in the X-complex, thus allowing the Xc-, Xe-, and Xk-classes to be established. Most notably, the spectra of Xe-type asteroids contain an absorption feature centered near 0.49 μm that may be associated with troilite. Several new members are identified for previously unique or sparsely populated classes: 12 A-types, 3 O-types, and 3 R-types. Q-types are common within the near-Earth asteroid population but remain unobserved in

  11. Toward an understanding of phyllosilicate mineralogy in the outer main asteroid belt

    NASA Astrophysics Data System (ADS)

    Takir, Driss; Emery, Joshua P.; McSween, Harry Y.

    2015-09-01

    Proposed mineralogical linkages between CM/CI carbonaceous chondrites and outer Main Belt asteroids remain uncertain due to a dearth of diagnostic absorptions in visible and near-infrared (∼0.4-2.5 μm) spectra of the two sets of objects. Absorptions near 3 μm in both sets hold promise for illuminating the potential linkages. Spectral comparisons of meteorites and asteroids have been challenging because meteorite spectra have usually been acquired in ambient terrestrial environments, and hence were contaminated by atmospheric water. In this study, we compare near-infrared spectra of chondrites measured in the laboratory under asteroid-like conditions (Takir, D. et al. [2013]. Meteorit. Planet. Sci. 48, 1618-1637) and spectra of asteroids measured with the long-wavelength cross-dispersed (LXD: 1.9-4.2-μm) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF) (Takir, D., Emery, J.P. [2012]. Icarus 219, 641-654). Using the 3-μm band shape, we find that spectral Group 2 CM and CI (Ivuna) chondrites are possible meteorite analogs for asteroids with the sharp 3-μm features, which are predominately located in the 2.5 < a < 3.3 AU region. Spectral Group 2 CM chondrites contain phyllosilicate phases intermediate between endmembers Fe-serpentine and Mg-serpentine, with a petrological subtype ranging from 2.2 to 2.1 (Takir, D. et al. [2013]. Meteorit. Planet. Sci. 48, 1618-1637). No meteorite match was found for asteroids showing a rounded 3-μm feature, which tend to be located farther from the Sun (3.0 < a < 4.0 AU), or for asteroids with distinctive spectra like 1 Ceres or 52 Europa. The study of the 3-μm band in meteorites and asteroids has implications for the understanding of phyllosilicate mineralogy and its distribution in the outer Main Belt region.

  12. Shape, size and multiplicity of main-belt asteroids I. Keck Adaptive Optics survey

    PubMed Central

    Marchis, F.; Kaasalainen, M.; Hom, E.F.Y.; Berthier, J.; Enriquez, J.; Hestroffer, D.; Le Mignant, D.; de Pater, I.

    2008-01-01

    This paper presents results from a high spatial resolution survey of 33 main-belt asteroids with diameters >40 km using the Keck II Adaptive Optics (AO) facility. Five of these (45 Eugenia, 87 Sylvia, 107 Camilla, 121 Hermione, 130 Elektra) were confirmed to have satellite. Assuming the same albedo as the primary, these moonlets are relatively small (∼5% of the primary size) suggesting that they are fragments captured after a disruptive collision of a parent body or captured ejecta due to an impact. For each asteroid, we have estimated the minimum size of a moonlet that can positively detected within the Hill sphere of the system by estimating and modeling a 2-σ detection profile: in average on the data set, a moonlet located at 2/100 × RHill (1/4 × RHill) with a diameter larger than 6 km (4 km) would have been unambiguously seen. The apparent size and shape of each asteroid was estimated after deconvolution using a new algorithm called AIDA. The mean diameter for the majority of asteroids is in good agreement with IRAS radiometric measurements, though for asteroids with a D < 200 km, it is underestimated on average by 6–8%. Most asteroids had a size ratio that was very close to those determined by lightcurve measurements. One observation of 104 Klymene suggests it has a bifurcated shape. The bi-lobed shape of 121 Hermione described in Marchis et al. [Marchis, F., Hestroffer, D., Descamps, P., Berthier, J., Laver, C., de Pater, I., 2005c. Icarus 178, 450–464] was confirmed after deconvolution. The ratio of contact binaries in our survey, which is limited to asteroids larger than 40 km, is surprisingly high (∼6%), suggesting that a non-single configuration is common in the main-belt. Several asteroids have been analyzed with lightcurve inversions. We compared lightcurve inversion models for plane-of-sky predictions with the observed images (9 Metis, 52 Europa, 87 Sylvia, 130 Elektra, 192 Nausikaa, and 423 Diotima, 511 Davida). The AO images allowed us to

  13. Spectral and mineralogical characterization of inner main-belt V-type asteroids

    NASA Astrophysics Data System (ADS)

    de Sanctis, M. C.; Migliorini, A.; Luzia Jasmin, F.; Lazzaro, D.; Filacchione, G.; Marchi, S.; Ammannito, E.; Capria, M. T.

    2011-09-01

    Context. V-type asteroids in the inner main belt are thought to be genetically related to (4) Vesta as collisional fragments. We investigate their relationship with Vesta observing putative V-type asteroids. Aims: The aim of this work is to observe candidate V-type asteroids, selected in different regions of the inner main belt, to characterize them and hence better understand their relationship with (4) Vesta. Methods: We present new NIR reflectance spectra of 18 V-type candidate asteroids, selected from datasets of possible V-type asteroids. The data were obtained at the 3.6 m Telescopio Nazionale Galileo, covering the spectral range 0.7 to 2.5 μm. We derive spectral parameters from NIR spectra to infer mineralogical information of the observed asteroids. The spectra of these asteroids are examined and compared to those of Howardite-Eucrite-Diogenite meteorites (HED), of which (4) Vesta is believed to be the parent body, and other V-type asteroids observed during previous campaigns. To enlarge the data set and increase the statistical significance of the analysis, we included the data presented in our previous article, obtaining a final data set of 41 V-type asteroids. Results: The V-type asteroids examined here show a higher variability of band parameters with respect to HEDs values, as for (4) Vesta. This result indicates that (4) Vesta and V-type asteroids have mineralogies that are not completely represented in the HEDs collection. Conclusions: An important finding is that some of the observed asteroids show spectral characteristics similar to diogenites, a result that may have relevant implications on their origin. Moreover, most of the diogenitic asteroids are not members of the Vesta classical family. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Centro Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the

  14. Evidence for a source of H chondrites in the outer main asteroid belt

    NASA Astrophysics Data System (ADS)

    Nedelcu, D. A.; Birlan, M.; Popescu, M.; Bădescu, O.; Pricopi, D.

    2014-07-01

    Aims: In this paper we report near-infrared spectroscopic observations of one of the largest potentially hazardous asteroids, (214869) 2007 PA8. Mineralogical analysis of this object was followed by the investigation of the dynamical delivery mechanism from its probable source region, based on long-term numerical integrations. Methods: The spectrum of (214869) 2007 PA8 was analysed using the positions of 1 μm and 2 μm bands and by curve-matching with RELAB meteorites spectra. Its dynamical evolution was investigated by means of a 200 000-year numerical integration in the past of 1275 clones followed to the source region. Results: (214869) 2007 PA8 has a very young surface with a composition more akin to H chondrites than to any other type of ordinary chondrite. It arrived from the outer Main Belt in the near-Earth space via the 5:2 mean motion resonance with Jupiter by eccentricity pumping. Identification of its source region far from (6) Hebe raises the possibility of the existence of a second parent body of the H chondrites that has a radically different post-accretion history. Future spectroscopic surveys in the 5:2 resonance region will most likely discover other asteroids with an H chondrite composition. Figure 2 is available in electronic form at http://www.aanda.org

  15. The recent breakup of an asteroid in the main-belt region.

    PubMed

    Nesvorný, David; Bottke, William F; Dones, Luke; Levison, Harold F

    2002-06-13

    The present population of asteroids in the main belt is largely the result of many past collisions. Ideally, the asteroid fragments resulting from each impact event could help us understand the large-scale collisions that shaped the planets during early epochs. Most known asteroid fragment families, however, are very old and have therefore undergone significant collisional and dynamical evolution since their formation. This evolution has masked the properties of the original collisions. Here we report the discovery of a family of asteroids that formed in a disruption event only 5.8 +/- 0.2 million years ago, and which has subsequently undergone little dynamical and collisional evolution. We identified 39 fragments, two of which are large and comparable in size (diameters of approximately 19 and approximately 14 km), with the remainder exhibiting a continuum of sizes in the range 2-7 km. The low measured ejection velocities suggest that gravitational re-accumulation after a collision may be a common feature of asteroid evolution. Moreover, these data can be used to check numerical models of larger-scale collisions.

  16. Parameters of Rotation and Shapes of Main-belt Asteroids from APT Observatory Group: Second Quarter 2016

    NASA Astrophysics Data System (ADS)

    Aznar Macias, Amadeo

    2016-10-01

    Using observations made during the second quarter of 2016, the rotation periods and the semi-axis a/b ratio of the projected shape for six main-belt asteroids were determined: 238 Hypatia, 1603 Neva, 1859 Kovalevskaya, 4170 Semmelweis, 3002 Delasalle, and (31013) 1996 DR.

  17. Distribution of spin-axes longitudes and shape elongations of main-belt asteroids

    NASA Astrophysics Data System (ADS)

    Cibulková, H.; Ďurech, J.; Vokrouhlický, D.; Kaasalainen, M.; Oszkiewicz, D. A.

    2016-11-01

    Context. Large all-sky surveys provide us with a lot of photometric data that are sparse in time (typically a few measurements per night) and can be potentially used for the determination of shapes and rotational states of asteroids. The method generally used to derive these parameters is the light curve inversion. However, for most asteroids their sparse data are not accurate enough to derive a unique model and the light curve inversion method is thus not very efficient. Aims: To fully utilize photometry sparse in time, we developed a new simplified model and applied it on the data from the Lowell photometric database. Our aim was to derive spin axis orientations and shape elongations of asteroids and to find out if there are some differences in distributions of these parameters for selected subpopulations. Methods: We modeled asteroids as geometrically scattering triaxial ellipsoids. Observed values of mean brightness and the dispersion of brightness were compared with computed values obtained from the parameters of the model, i.e., the ecliptical longitude λ and latitude β of the pole and the ratios a/b, b/c of axes of the ellipsoid. These parameters were optimized to get the best agreement with the observation. Results: We found that the distribution of λ for main-belt asteroids is not uniform and is dependent on the inclination of the orbit. Surprisingly, the nonuniformity of λ distribution is larger for asteroids residing on low-inclination orbits. We also studied distributions of a/b for several groups of asteroids and found that small asteroids (D< 25 km) are on average more elongated than large ones.

  18. Polarimetric survey of main-belt asteroids⋆. III. Results for 33 X-type objects

    NASA Astrophysics Data System (ADS)

    Cañada-Assandri, M.; Gil-Hutton, R.; Benavidez, P.

    2012-06-01

    Aims: We present results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (Casleo), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained with the Torino and CASPROF polarimeters at the 2.15 m telescope. The Torino polarimeter is an instrument that allows the simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results: The survey began in 2003, and up to 2009 data of a sample of more than 170 asteroids were obtained. In this paper the results for 33 X-type objects are presented, several of them are being polarimetrically observed for the first time. Using these data we found polarization curves and polarimetric parameters for different groups among this taxonomic class and that there are objects with very different albedo in the sub-classes of the X taxonomic complex. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A11

  19. A possible YORP effect on C and S Main Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Carbognani, A.

    2011-01-01

    A rotating frequency analysis in a previous paper, showed that two samples of C and S-type asteroids belonging to the Main Belt, but not to any families, present two different values for the transition diameter to a Maxwellian distribution of the rotation frequency, respectively 48 and 33 km. In this paper, after a more detailed statistical analysis, aiming to verify that the result is physically relevant, we found a better estimate for the transition diameter, respectively D C = 44 ± 2 km and D S = 30 ± 1 km. The ratio between these estimated transition diameters, D C/ D S = 1.5 ± 0.1, can be supported with the help of the YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) effect, although other physical causes cannot be completely ruled out. In this paper we have derived a simple scaling law for YORP which, taking into account the different average heliocentric distance, the bulk density, the albedo and the asteroid "asymmetry surface factor", has enabled us to reasonably justify the ratio between the diameters transition of C-type and S-type asteroids. The same scaling law can be used to estimate a new ratio between the bulk densities of S and C asteroids samples (giving ρ S/ ρ C ≈ 2.9 ± 0.3), and can explain why the asteroids near the transition diameter have about the same absolute magnitude. For C-type asteroids, using the found density ratio and other estimates of S-type density, it is also possible to estimate an average bulk density equal to 0.9 ± 0.1 g cm -3, a value compatible with icy composition. The suggested explanation for the difference of the transition diameters is a plausible hypothesis, consistent with the data, but it needs to be studied more in depth with further observations.

  20. Pole and shape of (1459) Magnya, the outer main belt basaltic asteroid

    NASA Astrophysics Data System (ADS)

    Silva, J. S.; Lazzaro, D.

    2015-08-01

    Context. The basaltic asteroid (1459) Magnya is, to date, the only confirmed example of this kind of asteroid in the outer main belt (Lazzaro et al. 2000). It might be a rare surviving fragment from a larger, differentiated, and subsequently disrupted object most probably unrelated to (4) Vesta. Aims: We derive the direction of the pole and the shape of asteroid (1459) Magnya in order to increase the knowledge of the body's physical properties. In particular, these two properties are useful to characterize which regions of the body are being sampled by spectral observations at distinct epochs and telescopes and to better assess the degree of surface homogeneity of (1459) Magnya. Methods: An observational campaign of (1459) Magnya was set up to determine its pole and shape from photometric lightcurves of the asteroid. These lightcurves were acquired at diverse telescopes and observatories from 2002 to 2014. Additional data from the literature was added, and a method of inversion was applied. Results: The obtained pole of asteroid (1459) Magnya is given by the ecliptic coordinates λ = 159 ± 10° and β = -75 ± 10°. The asteroid is modeled by a slightly elongated ellipsoid, rotating along the smallest axis with a period of 4.679100 ± 0.000005 h. The derived direction of the pole was used to compute the viewing geometry of the spectroscopic observations of (1459) Magnya obtained by various authors and indicates the necessity of new visible and near-infrared observations in order to correctly assess the degree of homogeneity of its surface. Based on observations made at the Observatório do Pico dos Dias/LNA, and at the Observatório Astronômico do Sertão de Itaparica/ON.

  1. Precise Distances for Main-belt Asteroids in Only Two Nights

    NASA Astrophysics Data System (ADS)

    Heinze, Aren N.; Metchev, Stanimir

    2015-10-01

    We present a method for calculating precise distances to asteroids using only two nights of data from a single location—far too little for an orbit—by exploiting the angular reflex motion of the asteroids due to Earth’s axial rotation. We refer to this as the rotational reflex velocity method. While the concept is simple and well-known, it has not been previously exploited for surveys of main belt asteroids (MBAs). We offer a mathematical development, estimates of the errors of the approximation, and a demonstration using a sample of 197 asteroids observed for two nights with a small, 0.9-m telescope. This demonstration used digital tracking to enhance detection sensitivity for faint asteroids, but our distance determination works with any detection method. Forty-eight asteroids in our sample had known orbits prior to our observations, and for these we demonstrate a mean fractional error of only 1.6% between the distances we calculate and those given in ephemerides from the Minor Planet Center. In contrast to our two-night results, distance determination by fitting approximate orbits requires observations spanning 7-10 nights. Once an asteroid’s distance is known, its absolute magnitude and size (given a statistically estimated albedo) may immediately be calculated. Our method will therefore greatly enhance the efficiency with which 4m and larger telescopes can probe the size distribution of small (e.g., 100 m) MBAs. This distribution remains poorly known, yet encodes information about the collisional evolution of the asteroid belt—and hence the history of the Solar System.

  2. The Evolution of the Grand Tack's Main Belt through the Solar System's Age

    NASA Astrophysics Data System (ADS)

    Deienno, Rogerio; Gomes, Rodney S.; Morbidelli, Alessandro; Walsh, Kevin J.; Nesvorny, David

    2015-05-01

    The Asteroid Belt is marked by the mixture of physical properties among its members, as well as its peculiar distribution of orbital eccentricities and inclinations. Formation models of the Asteroid Belt show that its formation is strongly linked to the process of terrestrial planet formation. The Grand Tack model presents a possible solution to the conundrum of reconciling the small mass of Mars with the properties of the Asteroid Belt, providing also a scenario for understanding the mixture of physical properties of the Belt objects. Regarding the orbital distribution of these objects, the Grand Tack model achieved good agreement with the observed inclination distribution, but failed in relation to the eccentricities, which are systematically skewed towards too large values at the end of the dynamical phase described by the Grand Tack model. Here, we evaluate the evolution of the orbital characteristics of the Asteroid Belt from the end of the phase described by the Grand Tack model, throughout the subsequent evolution of the Solar System. Our results show the concrete possibility that the eccentricity distribution after the Grand Tack phase is consistent with the current distribution. Finally, favorable and unfavorable issues faced by the Grand Tack model will be discussed, together with the influence of the primordial eccentricities of Jupiter and Saturn. Acknowledgement: FAPESP.

  3. Is the Grand Tack model compatible with the orbital distribution of main belt asteroids?

    NASA Astrophysics Data System (ADS)

    Deienno, Rogerio; Gomes, Rodney S.; Walsh, Kevin J.; Morbidelli, Alessandro; Nesvorný, David

    2016-07-01

    The Asteroid Belt is characterized by the radial mixing of bodies with different physical properties, a very low mass compared to Minimum Mass Solar Nebula expectations and has an excited orbital distribution, with eccentricities and inclinations covering the entire range of values allowed by the constraints of dynamical stability. Models of the evolution of the Asteroid Belt show that the origin of its structure is strongly linked to the process of terrestrial planet formation. The Grand Tack model presents a possible solution to the conundrum of reconciling the small mass of Mars with the properties of the Asteroid Belt, including the mass depletion, radial mixing and orbital excitation. However, while the inclination distribution produced in the Grand Tack model is in good agreement with the one observed, the eccentricity distribution is skewed towards values larger than those found today. Here, we evaluate the evolution of the orbital properties of the Asteroid Belt from the end of the Grand Tack model (at the end of the gas nebula phase when planets emerge from the dispersing gas disk), throughout the subsequent evolution of the Solar System including an instability of the Giant Planets approximately 400 Myr later. Before the instability, the terrestrial planets were modeled on dynamically cold orbits with Jupiter and Saturn locked in a 3:2 mean motion resonance. The model continues for an additional 4.1 Gyr after the giant planet instability. Our results show that the eccentricity distribution obtained in the Grand Tack model evolves towards one very similar to that currently observed, and the semimajor axis distribution does the same. The inclination distribution remains nearly unchanged with a slight preference for depletion at low inclination; this leads to the conclusion that the inclination distribution at the end of the Grand Tack is a bit over-excited. Also, we constrain the primordial eccentricities of Jupiter and Saturn, which have a major influence

  4. A population of Main Belt Asteroids co-orbiting with Ceres and Vesta

    NASA Astrophysics Data System (ADS)

    Christou, Apostolos A.; Wiegert, Paul

    2012-01-01

    We have carried out a search for Main Belt Asteroids (MBAs) co-orbiting with the large MBA Vesta and the dwarf planet Ceres. Through improving the search criteria used in Christou (Christou, A.A. [2000b]. Astron. Astrophys. 356, L71-L74) and numerical integrations of candidate coorbitals, we have identified approximately 51 (44) objects currently in co-orbital libration with Ceres (Vesta). We show that these form part of a larger population of transient coorbitals; 129 (94) MBAs undergo episodes of co-orbital libration with Ceres (Vesta) within a 2 Myr interval centred on the present. The lifetime in the resonance is typically a few times ˜10 5 yr but can exceed 2 × 10 6 yr. The variational properties of the orbits of several co-orbitals were examined. It was found that their present states with respect to the secondary are well determined but knowledge of it is lost typically after ˜2 × 10 5 yr. Objects initially deeper into the coorbital region maintain their coorbital state for longer. Using the model of Namouni et al. (Namouni, F., Christou, A.A., Murray, C.D. [1999]. Phys. Rev. Lett. 83, 2506-2509) we show that their dynamics are similar to those of temporary coorbital NEAs of the Earth and Venus. As in that case, the lifetime of resonant libration is dictated by planetary secular perturbations, the inherent chaoticity of the orbits and close encounters with massive objects other than the secondary. In particular we present evidence that, while in the coorbital state, close encounters with the secondary are generally avoided and that Ceres affects the stability of tadpole librators of Vesta. Finally we demonstrate the existence of Quasi-Satellite orbiters of both Ceres and Vesta and conclude that decametre-sized objects detected in the vicinity of Vesta by the DAWN mission may, in fact, belong to this dynamical class rather than be bona-fide (i.e. Keplerian) satellites of Vesta.

  5. The LXD-mode Main-Belt/NEO Observing Program (LMNOP): Results

    NASA Astrophysics Data System (ADS)

    Rivkin, A.; Howell, E.; Emery, J.

    2014-07-01

    The spectral region beyond 2.5 μ m is rich with spectral features due to OH, water, and organic materials. For many low-albedo objects, it hosts the only detectable absorption bands. For this reason, astronomical observations of asteroids at these wavelengths are critical to understanding their nature, even though such observations can be difficult due to the Earth's atmosphere [1]. Since 2002, we have been obtaining data in the 2--4 μ m region using the SpeX instrument on the IRTF in ''LXD mode'' [2]. While not originally designed as a survey, we call the collection of individual projects that we have completed over the years the ''LXD-mode Main- belt/NEO Observing Program'' (LMNOP). At the time of the upgrade of the SpeX instrument earlier in 2014, 390 observations of 210 different asteroids have been observed in the LMNOP. We have focused on C-complex asteroids (53 % of targets), but the survey also includes significant numbers of targets in the X complex (24 %) and S complex (11 %). The SpeX upgrade, with an associated break in observing and a need to change the reduction pipeline for future data, marks a convenient time to mark the end of this phase of the LMNOP. The data collected has already been used to determine the surface compositional variation on Ceres [3-4], Lutetia [5], and Vesta [6], and to discover water ice frost on the surface of Themis [7]. Analysis is now moving forward into studies of compositional variation on Pallas and Hygiea, among other objects. The data is also being analyzed to study the links between the Ch-class asteroids and the CM meteorites, and to calculate the amount of water/OH implied by the asteroid spectra. We will present results from the LMNOP dataset, including in-depth studies of individual objects, interpretations of taxonomic groups, and the beginnings of a taxonomic system in the 3-μ m range itself.

  6. The breakup of a main-belt asteroid 450 thousand years ago.

    PubMed

    Nesvorný, David; Vokrouhlický, David; Bottke, William F

    2006-06-09

    Collisions in the asteroid belt frequently lead to catastrophic breakups, where more than half of the target's mass is ejected into space. Several dozen large asteroids have been disrupted by impacts over the past several billion years. These impact events have produced groups of fragments with similar orbits called asteroid families. Here we report the discovery of a very young asteroid family around the object 1270 Datura. Our work takes advantage of a method for identification of recent breakups in the asteroid belt using catalogs of osculating (i.e., instantaneous) asteroid orbits. The very young families show up in these catalogs as clusters in a five-dimensional space of osculating orbital elements.

  7. Comet Schwassmann-Wachmann I

    NASA Technical Reports Server (NTRS)

    2003-01-01

    velocities, they appear to move relative to the comet and background stars, thereby producing a slight elongated appearance. The Spitzer data have allowed astronomers to use thermal measurements, which reduce the uncertainties of visible-light albedo (reflectivity) measurements, to determine their size. With diameters of 1.4 and 3.0 kilometers, these are the smallest main-belt asteroids yet measured by infrared means.

  8. Physical parameters and morphology of comet 67P/Churyumov-Gerasimenko - a main target of Rosetta space mission

    NASA Astrophysics Data System (ADS)

    Churyumov, Klim; Kleshchonok, Valery; Mozgova, Alyona

    Rosetta, a European space vehicle was head to the icy nucleus of the short period comet 67P/Churyumov-Gerasimenko on 2 March, 2004 from cosmodrome Kouru. On 20 Jan. 2014, Rosetta after 10 years of flight and 31-month sleep has been woke up succesfully and now will approche to the icy nucleus of comet Churyumov-Gerasimenko and pass away into orbit around the cometary nucleus. In November 2014 the Philae probe will be sent from Rosetta on the nucleus of comet 67P to study the relict matter of the Solar system. Comet 67P was discovered by the Kyiv astronomers Klim Churyumov and Svitlana Gerasimenko on 22 October 1969 on the five photographic plates exponed with the help of 50-cm Maksutov’s reflector of the Alma-Ata Astrophysical Institute on 9, 11 and 21 Sept. 1969. First 5 exact positions of comet were sent to Dr Brian Marsden. Dr B.Marsden showed it was new comet. The comet had an apparent magnitude of 13 and a faint tail about 1 arcmin in length at position angle 280 degrees. The astronomer Nikolay Belyaev from Saint-Petersbourg calculated that the comet followed an elliptical orbit. In 1982 it had the close encounter with the Earth at 0.3910 A.U. On the basis of the observations of comet 67P obtained in Nizhny Arkhyz with the help of the 6- BTA reflector of SAO of RAS some physical parameters of its comet plasma tail (coefficients of diffusion Dp(parallel) , Ds(perpendicular) and induction of magnetic field B) were determined. Other results of exploration of comet 67P (its polarisation, spectral observations, the light curve and morphology) in different apparitions are discussed.

  9. Outer Belt Electron Dropout during St. Patrick's Day storm in 2015: SSC Induced Dropout Echoes and Main-Phase Dropout

    NASA Astrophysics Data System (ADS)

    Hao, Y.; Zong, Q.; Zhou, X.; Fu, S.

    2016-12-01

    Mechanisms of radiation belt electron flux dropout are of fundamental interest in magnetosphere dynamics. In this study, we analyse the strong flux dropout of outer belt MeV electrons observed by Van Allen Probes during the largest geomagnetic storm of the last decade. The dropout is found to be composed of two phases: the dropout echoes induced by the interplanetary shock in front of the CME and the total flux dropout at the shrinking outer boundary of the radiation belt during the main phase of the storm. As the first case of dispersionless dropout echoes, REPT observations show clear 90o pitch angle dependence and also indicate that the dropout echoes originate from duskside magnetosphere. Both of those characters observed are consistent with our previous remote sensing results. During the main phase, pitch angle distributions of MeV electrons at nightside near the dropout edge are measured to be isotropic rather than butterfly-shaped. Such pitch angle distributions suggest mechanism of MeV electrons besides magnetopause shadowing. Observations of magnetic field, hot plasma and plasma density indicate the coexistence of the dropout edge and a nightside near-earth taillike structure. Further comparison between MeV electron gyro-radius and local field line curvature suggests that strong curvature scattering occurs at the dropout edge, which may lead to precipitation of those MeV electrons.

  10. Quasi-Static and Dynamic Response Characteristics of F-4 Bias-Ply and Radial-Belted Main Gear Tires

    NASA Technical Reports Server (NTRS)

    Davis, Pamela A.

    1997-01-01

    An investigation was conducted at Langley Research Center to determine the quasi-static and dynamic response characteristics of F-4 military fighter 30x11.5-14.5/26PR bias-ply and radial-belted main gear tires. Tire properties were measured by the application of vertical, lateral, and fore-and-aft loads. Mass moment-of-inertia data were also obtained. The results of the study include quasi-static load-deflection curves, free-vibration time-history plots, energy loss associated with hysteresis, stiffness and damping characteristics, footprint geometry, and inertia properties of each type of tire. The difference between bias-ply and radial-belted tire construction is given, as well as the advantages and disadvantages of each tire design. Three simple damping models representing viscous, structural, and Coulomb friction are presented and compared with the experimental data. The conclusions discussed contain a summary of test observations.

  11. VizieR Online Data Catalog: Spectroscopy of main-belt Ch/Cgh-type asteroids (Vernazza+, 2016)

    NASA Astrophysics Data System (ADS)

    Vernazza, P.; Marsset, M.; Beck, P.; Binzel, R. P.; Birlan, M.; Cloutis, E. A.; DeMeo, F. E.; Dumas, C.; Hiroi, T.

    2016-09-01

    We conducted an extensive spectroscopic survey in the near-infrared range of 70 main-belt Ch/Cgh-type asteroids and 4 Ch/Cgh-type families and combined these measurements with available visible wavelength spectra. New data presented here are near-infrared asteroid spectral measurements for Ch- and Cgh-type asteroids from 0.7-2.5μm obtained using SpeX, the low- to medium-resolution near-IR spectrograph and imager on the 3m NASA InfraRed Telescope Facility (IRTF) located on Mauna Kea, HI. Observing runs were conducted remotely primarily from the Observatory of Paris-Meudon, France between 2010 April and 2012 January. The spectrograph SpeX, combined with a 0.8*15arcsec slit, was used in the low-resolution prism mode for acquisition of the spectra in the 0.7-2.5μm wavelength range. In order to monitor the high luminosity and variability of the sky in the near-IR, the telescope was moved along the slit during the acquisition of the data so as to obtain a sequence of spectra located at two different positions (A and B) on the array. In addition, we complemented our data set with additional near-infrared spectra retrieved from the Small Main-Belt Asteroid Spectroscopic Survey (SMASS) database (http://smass.mit.edu/). Combining these near-infrared measurements with available visible wavelength spectra (Bus, 1999PhDT........50B; Lazzaro et al., 2004Icar..172..179L) allows for the first time an extensive visible and near-infrared (VNIR) spectral database of main-belt Ch and Cgh types with D>45km (78% or 49/63 of all Ch and Cgh types listed in SMASS; see Table1). (1 data file).

  12. Lightcurve Analysis for Nine Main-belt Asteroids. Rotation Period and Physical Parameters from APT Observatory Group: 2016 October-December

    NASA Astrophysics Data System (ADS)

    Aznar Macias, Amadeo

    2017-04-01

    Lightcurves of nine main-belt asteroids (MBA) obtained at APT-Observatory Group from 2016 October- December were analyzed for rotation period, amplitude and physical parameters (axis size relationship).

  13. Nine Galileo Views in Natural Color of Main-Belt Asteroid Ida

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This set of color images of asteroid 243 Ida was taken by the imaging system on the Galileo spacecraft as it approached and raced past the asteroid on August 28, 1993. These images were taken through the 4100-angstrom (violet), 7560-angstrom (infrared) and 9680- angstrom (infrared) filters and have been processed to show Ida as it would appear to the eye in approximately natural color. The stark shadows portray Ida's irregular shape, which changes its silhouetted outline when seen from different angles. More subtle shadings reveal surface topography (such as craters) and differences in the physical state and composition of the soil ('regolith'). Analysis of the images show that Ida is 58 kilometers long and 23 kilometers wide (36 x 14 miles). Ida is the first asteroid discovered to have a natural satellite, Dactyl (not shown here). Both Ida and Dactyl are heavily cratered by impacts with smaller asteroids and comets, including some of the same populations of small objects that bombard Earth. These data, combined with reflectance spectra from Galileo's near-infrared mapping spectrometer, may allow scientists to determine whether Ida is a relatively unaltered primitive object made of material condensed from the primordial Solar Nebula at the origin of the Solar System or whether it has been altered by strong heating--evidence interpreted so far suggests that Ida is a piece of a larger object that has been severely heated. Whereas heating and melting of large planets is well understood, the cause of heating of small asteroids is more enigmatic--it may have involved exotic processes that occurred only for a short time after the birth of the Sun and its planets.

  14. Characteristics and large bulk density of the C-type main-belt triple asteroid (93) Minerva

    NASA Astrophysics Data System (ADS)

    Marchis, F.; Vachier, F.; Ďurech, J.; Enriquez, J. E.; Harris, A. W.; Dalba, P. A.; Berthier, J.; Emery, J. P.; Bouy, H.; Melbourne, J.; Stockton, A.; Fassnacht, C. D.; Dupuy, T. J.; Strajnic, J.

    2013-05-01

    From a set of adaptive optics (AO) observations collected with the W.M. Keck telescope between August and September 2009, we derived the orbital parameters of the most recently discovered satellites of the large C-type asteroid (93) Minerva. The satellites of Minerva, which are approximately 3 and 4 km in diameter, orbit very close to the primary (˜5 and ˜8 × Rp and ˜1% and ˜2% × RHill) in a circular manner, sharing common characteristics with most of the triple asteroid systems in the main-belt. Combining these AO observations with lightcurve data collected since 1980 and two stellar occultations in 2010 and 2011, we removed the ambiguity of the pole solution of Minerva's primary and showed that it has an almost regular shape with an equivalent diameter Deq = 154 ± 6 km in agreement with IRAS observations. The surprisingly high bulk density of 1.75 ± 0.30 g/cm3 for this C-type asteroid, suggests that this taxonomic class is composed of asteroids with different compositions, For instance, Minerva could be made of the same material as dry CR, CO, and CV meteorites. We discuss possible scenarios on the origin of the system and conclude that future observations may shine light on the nature and composition of this fifth known triple main-belt asteroid.

  15. Distant Comets in the Early Solar System

    NASA Technical Reports Server (NTRS)

    Meech, Karen J.

    2000-01-01

    The main goal of this project is to physically characterize the small outer solar system bodies. An understanding of the dynamics and physical properties of the outer solar system small bodies is currently one of planetary science's highest priorities. The measurement of the size distributions of these bodies will help constrain the early mass of the outer solar system as well as lead to an understanding of the collisional and accretional processes. A study of the physical properties of the small outer solar system bodies in comparison with comets in the inner solar system and in the Kuiper Belt will give us information about the nebular volatile distribution and small body surface processing. We will increase the database of comet nucleus sizes making it statistically meaningful (for both Short-Period and Centaur comets) to compare with those of the Trans-Neptunian Objects. In addition, we are proposing to do active ground-based observations in preparation for several upcoming space missions.

  16. ALBEDO PROPERTIES OF MAIN BELT ASTEROIDS BASED ON THE ALL-SKY SURVEY OF THE INFRARED ASTRONOMICAL SATELLITE AKARI

    SciTech Connect

    Usui, Fumihiko; Hasegawa, Sunao; Matsuhara, Hideo; Kasuga, Toshihiro; Ishiguro, Masateru; Kuroda, Daisuke; Mueller, Thomas G.; Ootsubo, Takafumi

    2013-01-01

    We present an analysis of the albedo properties of main belt asteroids (MBAs) detected by the All-Sky Survey of the infrared astronomical satellite AKARI. The characteristics of 5120 asteroids detected by the survey, including their sizes and albedos, were cataloged in the Asteroid Catalog Using AKARI (AcuA). Size and albedo measurements were based on the standard thermal model, using inputs of infrared fluxes and absolute magnitudes measured at optical wavelengths. MBAs, which account for 4722 of the 5120 AcuA asteroids, have semimajor axes of 2.06-3.27 AU, except for the near-Earth asteroids. AcuA provides a complete data set of all MBAs brighter than the absolute magnitude of H < 10.3, which corresponds to the diameter of d > 20 km. We confirmed that the albedo distribution of the MBAs is strongly bimodal as was already known from the past observations, and that the bimodal distribution occurs not only in the total population, but also within inner, middle, and outer regions of the main belt. The bimodal distribution in each group consists of low-albedo components in C-type asteroids and high-albedo components in S-type asteroids. We found that the small asteroids have much more variety in albedo than the large asteroids. In spite of the albedo transition process like space weathering, the heliocentric distribution of the mean albedo of asteroids in each taxonomic type is nearly flat. The mean albedo of the total, on the other hand, gradually decreases with an increase in semimajor axis. This can be explained by the compositional ratio of taxonomic types; that is, the proportion of dark asteroids such as C- and D-types increases, while that of bright asteroids such as S-type decreases, with increasing heliocentric distance. The heliocentric distributions of X-subclasses: E-, M-, and P-types, which can be divided based on albedo values, are also examined. P-types, which are the major component in X-types, are distributed throughout the main belt regions, and the

  17. Where Do Comets Come From?

    ERIC Educational Resources Information Center

    Van Flandern, Tom

    1982-01-01

    Proposes a new origin for comets in the solar system, namely, that comets originated in the breakup of a body orbiting the sun in or near the present location of the asteroid belt in the relatively recent past. Predictions related to the theory are discussed. (Author/JN)

  18. Where Do Comets Come From?

    ERIC Educational Resources Information Center

    Van Flandern, Tom

    1982-01-01

    Proposes a new origin for comets in the solar system, namely, that comets originated in the breakup of a body orbiting the sun in or near the present location of the asteroid belt in the relatively recent past. Predictions related to the theory are discussed. (Author/JN)

  19. Polarimetric survey of main-belt asteroids. V. The unusual polarimetric behavior of V-type asteroids

    NASA Astrophysics Data System (ADS)

    Gil-Hutton, R.; López-Sisterna, C.; Calandra, M. F.

    2017-03-01

    Aims: We present the results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained using the CASPROF and CASPOL polarimeters at the 2.15 m telescope. The CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation and CASPOL is a polarimeter based on a CCD detector, which allows us to observe fainter objects with better signal-to-noise ratio. Results: The survey began in 1995 and data on a large sample of asteroids were obtained until 2012. A second period began in 2013 using a polarimeter with a more sensitive detector in order to study small asteroids, families, and special taxonomic groups. We obtained 55 polarimetric measurements for 28 V-type main belt asteroids, all of them polarimetrically observed for the first time. The data obtained in this survey let us find polarimetric parameters for (1459) Magnya and for a group of 11 small V-type objects with similar polarimetric behavior. These polarization curves are unusual since they show a shallow minimum and a small inversion angle in comparison with (4) Vesta, although they have a steeper slope at α0. This polarimetric behavior could be explained by differences in the regoliths of these asteroids. The observations of (2579) Spartacus, and perhaps also (3944) Halliday, indicate a inversion angle larger than 24-25°. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.

  20. Effects of YORP-induced rotational fission on the small size end of the Main Belt asteroid size distribution

    NASA Astrophysics Data System (ADS)

    Rossi, Alessandro; Jacobson, S.; Marzari, F.; Scheeres, D.; Davis, D. R.

    2013-10-01

    From the results of a comprehensive asteroid population evolution model, we conclude that the YORP-induced rotational fission hypothesis has strong repercussions for the small size end of the Main Belt asteroid size frequency distribution. These results are consistent with observed asteroid population statistics. The foundation of this model is the asteroid rotation model of Marzari et al. (2011), which incorporates both the YORP effect and collisional evolution. This work adds to that model the rotational fission hypothesis (i.e. when the rotation rate exceeds a critical value, erosion and binary formation occur). The YORP effect timescale for large asteroids with diameters D > ~6 km is longer than the collision timescale in the Main Belt, thus the frequency of large asteroids is determined by a collisional equilibrium (e.g. Bottke 2005), but for small asteroids with diameters D < ~6 km, the asteroid population evolution model confirms that YORP-induced rotational fission destroys small asteroids more frequently than collisions. Therefore, the frequency of these small asteroids is determined by an equilibrium between the creation of new asteroids out of the impact debris of larger asteroids and the destruction of these asteroids by YORP-induced rotational fission. By introducing a new source of destruction that varies strongly with size, YORP-induced rotational fission alters the slope of the size frequency distribution. Using the outputs of the asteroid population evolution model and a 1-D collision evolution model, we can generate this new size frequency distribution and it matches the change in slope observed by the SKADS survey (Gladman 2009). This agreement is achieved with both an accretional power-law or a truncated “Asteroids were Born Big” size frequency distribution (Weidenschilling 2010, Morbidelli 2009).

  1. Hilda family contribution to the Jupiter Family Comets (JFC)

    NASA Astrophysics Data System (ADS)

    di Sisto, R. P.; Brunini, A.; Dirani, L. D.; Orellana, R. B.

    The distinction between asteroids and comets, is based in their observational qualities rather than in their orbital characteristics. Comets show activity when they reach the interior Solar System. Asteroids from the outer Belt, may have compound of the same volatile material, dust and organic molecules than comets, but they didn't approach enough to the Sun, to show activity. From the compositional point of view, it is a bit arbitrary or at least difficult to distinguish between asteroids from the external main belt and comets. The firsts may be very similar to comets, or at least be objects of intermediate characteristics. The Hildas asteroids, in 3:2 mean motion with Jupiter, have great quantity of volatiles. The main source of Jupiter Family Comets (JFC) is the transneptunian region, but less than 10 % of them comes from the Troyan swarms. In this article we study the Hilda family as another probable source of JFC. We perform numerical simulations and follow the dynamical evolution of Hildas escaped from the resonance. From the 391 particles that escaped from the resonance, 386 (98.7 %) live at least for 1000 years as JFC. The mean life time in this zone is 1.4 × 106 years. The escape rate of an Hilda asteroid, with diameter D greater than 1 km. Is 1.1 × 10-4, so, there is 65 Hildas with D > 1km. (the typical size of a comet) in the JFC region. Therefore, the contribution of Hilda asteroids to the population of comets is important.

  2. Distribution of spin axes and shape elongations of main-belt asteroids

    NASA Astrophysics Data System (ADS)

    Cibulkova, Helena; Durech, Josef; Vokrouhlicky, David; Kaasalainen, Mikko; Oszkiewicz, Dagmara Anna

    2016-10-01

    Photometric data that are sparse in time (typically few measurements per night over ~15 years) are a potential source of information about shapes and rotational states of asteroids. However, currently available data are usually not accurate enough to derive a unique sidereal rotation period and corresponding shape model by the lightcurve inversion method. To fully utilize sparse-in-time data, we have developed a new simplified model that provides an approximate solution for the orientation of the spin axis (λ, β) and ratios of axes of the ellipsoid, a/b, b/c (asteroids are modelled as geometrically scattering triaxial ellipsoids). The observed values of mean brightness (over one apparition) and the dispersion of brightness are compared with values computed from the model parameters (λ, β, a, b, setting c=1) which are optimized to get the best agreement. The model was applied on the data from Lowell photometric database. We found that the distribution of pole ecliptic longitude λ is nonuniform and that this nonuniformity is larger for asteroids with low inclination of their orbits. The second main result is that small asteroids (D<25 km) are on average more elongated (a/b ~ 1.6) than the large ones (for D>50 km the mean value of a/b is 1.3).

  3. Comet nucleus and asteroid sample return missions

    NASA Technical Reports Server (NTRS)

    Melton, Robert G.; Thompson, Roger C.; Starchville, Thomas F., Jr.; Adams, C.; Aldo, A.; Dobson, K.; Flotta, C.; Gagliardino, J.; Lear, M.; Mcmillan, C.

    1992-01-01

    During the 1991-92 academic year, the Pennsylvania State University has developed three sample return missions: one to the nucleus of comet Wild 2, one to the asteroid Eros, and one to three asteroids located in the Main Belt. The primary objective of the comet nucleus sample return mission is to rendezvous with a short period comet and acquire a 10 kg sample for return to Earth. Upon rendezvous with the comet, a tethered coring and sampler drill will contact the surface and extract a two-meter core sample from the target site. Before the spacecraft returns to Earth, a monitoring penetrator containing scientific instruments will be deployed for gathering long-term data about the comet. A single asteroid sample return mission to the asteroid 433 Eros (chosen for proximity and launch opportunities) will extract a sample from the asteroid surface for return to Earth. To limit overall mission cost, most of the mission design uses current technologies, except the sampler drill design. The multiple asteroid sample return mission could best be characterized through its use of future technology including an optical communications system, a nuclear power reactor, and a low-thrust propulsion system. A low-thrust trajectory optimization code (QuickTop 2) obtained from the NASA LeRC helped in planning the size of major subsystem components, as well as the trajectory between targets.

  4. Orbital evolution of dust particles from comets and asteroids

    NASA Technical Reports Server (NTRS)

    Jackson, A. A.; Zook, H. A.

    1992-01-01

    Results are presented from a computer simulation in which dust grains of three different sizes were released at perihelion passage from each of (1) 15 main belt asteroids, (2) 15 short-period comets with perihelion greater than 1 AU, and (3) 5 such comets with perihelion less than 1 AU. The evolving-orbit calculations for each of the dust rains include the effects of solar and planetary gravity, radiation pressure, Poynting-Robertson drag, and solar wind drag. It is noted that when dust grains evolve to intersection with the earth's orbit, they retain orbital characteristics indicative of their origins.

  5. Orbital evolution of dust particles from comets and asteroids

    NASA Astrophysics Data System (ADS)

    Jackson, A. A.; Zook, H. A.

    1992-05-01

    Results are presented from a computer simulation in which dust grains of three different sizes were released at perihelion passage from each of (1) 15 main belt asteroids, (2) 15 short-period comets with perihelion greater than 1 AU, and (3) 5 such comets with perihelion less than 1 AU. The evolving-orbit calculations for each of the dust rains include the effects of solar and planetary gravity, radiation pressure, Poynting-Robertson drag, and solar wind drag. It is noted that when dust grains evolve to intersection with the earth's orbit, they retain orbital characteristics indicative of their origins.

  6. Secular orbital evolution of Jupiter family comets

    NASA Astrophysics Data System (ADS)

    Rickman, H.; Gabryszewski, R.; Wajer, P.; Wiśniowski, T.; Wójcikowski, K.; Szutowicz, S.; Valsecchi, G. B.; Morbidelli, A.

    2017-02-01

    Context. The issue of the long term dynamics of Jupiter family comets (JFCs) involves uncertain assumptions about the physical evolution and lifetimes of these comets. Contrary to what is often assumed, real effects of secular dynamics cannot be excluded and therefore merit investigation. Aims: We use a random sample of late heavy bombardment cometary projectiles to study the long-term dynamics of JFCs by a Monte Carlo approach. In a steady-state picture of the Jupiter family, we investigate the orbital distribution of JFCs, including rarely visited domains like retrograde orbits or orbits within the outer parts of the asteroid main belt. Methods: We integrate 100 000 objects over a maximum of 100 000 orbital revolutions including the Sun, a comet, and four giant planets. Considering the steady-state number of JFCs to be proportional to the total time spent in the respective orbital domain, we derive the capture rate based on observed JFCs with small perihelia and large nuclei. We consider a purely dynamical model and one where the nuclei are eroded by ice sublimation. Results: The JFC inclination distribution is incompatible with our erosional model. This may imply that a new type of comet evolution model is necessary. Considering that comets may live for a long time, we show that JFCs can evolve into retrograde orbits as well as asteroidal orbits in the outer main belt or Cybele regions. The steady-state capture rate into the Jupiter family is consistent with 1 × 109 scattered disk objects with diameters D > 2 km. Conclusions: Our excited scattered disk makes it difficult to explain the JFC inclination distribution, unless the physical evolution of JFCs is more intricate than assumed in standard, erosional models. Independent of this, the population size of the Jupiter family is consistent with a relatively low-mass scattered disk.

  7. CCD scanning for asteroids and comets

    NASA Technical Reports Server (NTRS)

    Gehrels, T.; Mcmillan, R. S.

    1986-01-01

    A change coupled device (CCD) is used in a scanning mode to find new asteroids and recover known asteroids and comet nuclei. Current scientific programs include recovery of asteroids and comet nuclei requested by the Minor Planet Center (MPC), discovery of new asteroids in the main belt and of unusual orbital types, and follow-up astrometry of selected new asteroids discovered. The routine six sigma limiting visual magnitude is 19.6 and slightly more than a square degree is scanned three times every 90 minutes of observing time during the fortnight centered on New Moon. Semiautomatic software for detection of moving objects is in routine use; angular speeds as low as 11.0 arcseconds per hour were distinguished from the effects of the Earth's atmosphere on the field of view. A typical set of three 29-minute scans near the opposition point along the ecliptic typically nets at least 5 new main-belt asteroids down to magnitude 19.6. In 18 observing runs (months) 43 asteroids were recovered, astrometric and photometric data on 59 new asteroids were reported, 10 new asteroids with orbital elements were consolidated, and photometry and positions of 22 comets were reported.

  8. Comets. [IUE

    NASA Technical Reports Server (NTRS)

    Ahearn, Michael F.

    1988-01-01

    The IUE was used to study comets including the first dynamically new comet to approach closer than 3 AU. Differences between old and new comets are studied. Results relevant to the nature of cometary nuclei are discussed. Identification of species in the spectra; relative abundances; variability of comets; and comet mass are considered.

  9. PRELIMINARY ANALYSIS OF WISE/NEOWISE 3-BAND CRYOGENIC AND POST-CRYOGENIC OBSERVATIONS OF MAIN BELT ASTEROIDS

    SciTech Connect

    Masiero, Joseph R.; Mainzer, A. K.; Bauer, J. M.; Cabrera, M. S.; Cutri, R. M.; Nugent, C.

    2012-11-01

    We present preliminary diameters and albedos for 13511 Main Belt asteroids (MBAs) that were observed during the 3-Band Cryo phase of the Wide-field Infrared Survey Explorer (WISE; after the outer cryogen tank was exhausted) and as part of the NEOWISE Post-Cryo Survey (after the inner cryogen tank was exhausted). With a reduced or complete loss of sensitivity in the two long wavelength channels of WISE, the uncertainty in our fitted diameters and albedos is increased to {approx}20% for diameter and {approx}40% for albedo. Diameter fits using only the 3.4 and 4.6 {mu}m channels are shown to be dependent on the literature optical H absolute magnitudes. These data allow us to increase the number of size estimates for large MBAs which have been identified as members of dynamical families. We present thermal fits for 14 asteroids previously identified as the parents of a dynamical family that were not observed during the fully cryogenic mission.

  10. Perspectives on Comets, Comet-like Asteroids, and Their Predisposition to Provide an Environment That Is Friendly to Life.

    PubMed

    Bosiek, Katharina; Hausmann, Michael; Hildenbrand, Georg

    2016-04-01

    In recent years, studies have shown that there are many similarities between comets and asteroids. In some cases, it cannot even be determined to which of these groups an object belongs. This is especially true for objects found beyond the main asteroid belt. Because of the lack of comet fragments, more progress has been made concerning the chemical composition of asteroids. In particular, the SMASSII classification establishes a link between the reflecting spectra and chemical composition of asteroids and meteorites. To find clues for the chemical structure of comets, the parameters of all known asteroids of the SMASSII classification were compared to those of comet groups like the Encke-type comets, the Jupiter-family comets, and the Halley-type comets, as well as comet-like objects like the damocloids and the centaurs. Fifty-six SMASSII objects similar to comets were found and are categorized as comet-like asteroids in this work. Aside from the chemistry, it is assumed that the available energy on these celestial bodies plays an important role concerning habitability. For the determination of the available energy, the effective temperature was calculated. Additionally, the size of these objects was considered in order to evaluate the possibility of a liquid water core, which provides an environment that is more likely to support processes necessary to create the building blocks of life. Further study of such objects could be notable for the period of the Late Heavy Bombardment and could therefore provide important implications for our understanding of the inner workings of the prebiotic evolution within the Solar System since the beginning.

  11. Perspectives on Comets, Comet-like Asteroids, and Their Predisposition to Provide an Environment That Is Friendly to Life

    NASA Astrophysics Data System (ADS)

    Bosiek, Katharina; Hausmann, Michael; Hildenbrand, Georg

    2016-04-01

    In recent years, studies have shown that there are many similarities between comets and asteroids. In some cases, it cannot even be determined to which of these groups an object belongs. This is especially true for objects found beyond the main asteroid belt. Because of the lack of comet fragments, more progress has been made concerning the chemical composition of asteroids. In particular, the SMASSII classification establishes a link between the reflecting spectra and chemical composition of asteroids and meteorites. To find clues for the chemical structure of comets, the parameters of all known asteroids of the SMASSII classification were compared to those of comet groups like the Encke-type comets, the Jupiter-family comets, and the Halley-type comets, as well as comet-like objects like the damocloids and the centaurs. Fifty-six SMASSII objects similar to comets were found and are categorized as comet-like asteroids in this work. Aside from the chemistry, it is assumed that the available energy on these celestial bodies plays an important role concerning habitability. For the determination of the available energy, the effective temperature was calculated. Additionally, the size of these objects was considered in order to evaluate the possibility of a liquid water core, which provides an environment that is more likely to support processes necessary to create the building blocks of life. Further study of such objects could be notable for the period of the Late Heavy Bombardment and could therefore provide important implications for our understanding of the inner workings of the prebiotic evolution within the Solar System since the beginning.

  12. Comets in the near-Earth object population

    NASA Astrophysics Data System (ADS)

    DeMeo, Francesca; Binzel, Richard P.

    2008-04-01

    Because the lifespan of near-Earth objects (NEOs) is shorter than the age of the Solar System, these objects originate elsewhere. Their most likely sources are the main asteroid belt and comets. Through physical observations we seek to identify potential dormant or extinct comets among "asteroids" catalogued as NEOs and thereby determine the fraction of "comet candidates" within the total NEO population. Both discovery statistics and dynamical models indicate that candidate cometary objects in near-Earth space are predominantly found among those having a jovian Tisserand parameter T<3. Therefore, we seek to identify comet candidates among asteroid-like NEOs using three criteria: T<3, spectral parameters (C, D, T, or P taxonomic types), and/or low (<0.075) albedos. We present new observations for 20 NEOs having T<3, consisting of visible spectra, near-infrared spectra, and/or albedo measurements obtained using the NASA Infrared Telescope Facility, the Kitt Peak National Observatory 4 m, and the Magellan Observatory 6.5-m. Four of our "asteroid" targets have been subsequently confirmed as low activity comets. Thus our sample includes spectra of the nuclei of Comets 2002 EX12 = 169P (NEAT), 2001 WF2 = 182P (LONEOS), 2003 WY25 = D/1891 W1 (Blanplain), and Halley Family Comet 2006 HR30 = P/2006 HR30 (Siding Spring). From the available literature, we tabulate physical properties for 55 NEOs having T<3, and after accounting for possible bias effects, we estimate that 54±10% of NEOs in T<3 orbits have "comet-like" spectra or albedos. Bias corrected discovery statistics [Stuart, J.S., Binzel, R.P., 2004. Icarus 170, 295-311] estimate 30±5% of the entire NEO population resides in orbits having T<3. Combining these two factors suggests that 16±5% of the total discovered "asteroid-like" NEO population has "comet-like" dynamical and physical properties. Outer main-belt asteroids typically have similar taxonomic and albedo properties as our "comet candidates." Using the model

  13. Polarimetric survey of main-belt asteroids. IV. New results from the first epoch of the CASLEO survey

    NASA Astrophysics Data System (ADS)

    Gil-Hutton, R.; Cellino, A.; Bendjoya, Ph.

    2014-09-01

    Aims: We present results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained using the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results: The survey began in 1995, and until 2012 data on a large sample of asteroids were obtained. We here present and analyze the unpublished results for 129 asteroids of different taxonomic types, 56 which were polarimetrically observed for the first time. We find that the asteroids (402) Chloe and (729) Watsonia are Barbarians, and asteroid (269) Justitia shows a phase - polarization curve that seems to have a small inversion angle. Data obtained in UBVRI colors allow us to sketch an analysis of the wavelength dependence of the degree of linear polarization for 31 asteroids, in spite of some large error bars in some cases. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/569/A122

  14. Polarimetric survey of main-belt asteroids. II. Results for 58 B- and C-type objects

    NASA Astrophysics Data System (ADS)

    Gil-Hutton, R.; Cañada-Assandri, M.

    2012-03-01

    Aims: We present results of a polarimetric survey of main-belt asteroids at Complejo Astronómico el Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. Methods: The data were obtained with the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results: The survey began in 2003, and up to 2009 data on a sample of more than 170 asteroids were obtained. In this paper the results for 58 B- and C-type objects are presented, most of them polarimetrically observed for the first time. Using these data we find phase-polarization curves and polarimetric parameters for these taxonomic classes. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Tables 1 and 2 are available in electronic form at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/539/A115

  15. Polarimetric survey of main-belt asteroids. I. Results for fifty seven S-, L-, and K-type objects

    NASA Astrophysics Data System (ADS)

    Gil-Hutton, R.; Cañada-Assandri, M.

    2011-05-01

    Aims: We present the first results of a polarimetric survey of main-belt asteroids at Complejo Astronómico El Leoncito (Casleo), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties, similar to those shown by the asteroid (234) Barbara. Methods: The data were obtained with the Torino and CASPROF polarimeters at the 2.15 m telescope. The Torino polarimeter is an instrument that allows the simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation. Results: The survey began in 2003, and up to 2009 data on a sample of more than 170 asteroids were obtained. In this paper the results of 57 S-, L-, and K-type objects are presented, most of them are being polarimetrically observed for the first time. Using these data we find phase-polarization curves and polarimetric parameters for these taxonomic classes. Furthermore, we also find two candidates, (397) Vienna and (458) Hercynia, that could have a phase-polarization curve with a large inversion angle. Based on observations carried out at the Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the National Universities of La Plata, Córdoba, and San Juan.Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/A+A/529/A86

  16. MEST-a special orbit of dark comet

    NASA Astrophysics Data System (ADS)

    Cao, Dayong

    2013-04-01

    ``Like mass attract, like energy repel each other.'' A mass-energy oscillation can produce a mass-energy wave which can build up a mass-energy field like a space-time field of the mass-energy, because the space-time is frequency and amplitude square. The Big Bang system has an energy center which makes a repulsive gravity and a negative curvature like dark energy. But a light has the space-time of itself. When a light travels in the universe, its quantum space-time will convert to a universal space-time. It will cause Hubble's red shift by itself. So we need find a new balance system of the flat universe. The Sun and Tyche-dark hole build up a system by a conversation of mass-energy and space-time. The dark hole and the dark comet (like a kind of antimatter or Dark matter) are mainly space-time while mass-energy is ancillary. They have their space-time center which is different from a mass-energy center of the solar system, which is mainly mass-energy while space-time is ancillary. The dark comets belt is around the dark hole. When the dark hole goes near the solar system, it will take the dark comets belt and the asteroids belt to impact planets. With a mass-energy and space-time coordinates, a relationship between the sun and the dark hole decides a special elliptical orbit both of a dark comet and asteroid who will hit on the solar system. We need use a space-time effect to change the orbit of dark hole, dark comet and asteroid which will impact our earth to avoid next impaction. A little asteroid hit on the ground of Russia on Feb. 15th, 2013. It authenticates my supposition that ``their new impaction will come in 20 years.''

  17. MID-INFRARED PHOTOMETRIC ANALYSIS OF MAIN BELT ASTEROIDS: A TECHNIQUE FOR COLOR-COLOR DIFFERENTIATION FROM BACKGROUND ASTROPHYSICAL SOURCES

    SciTech Connect

    Bhattacharya, B.; Helou, G.; Noriega-Crespo, A.; Surace, J.; Capak, P.; Grillmair, C.; Rebull, L. M.; Penprase, B. E.; Meadows, V. S.; Salvato, M.; Aussel, H.; Ilbert, O.; Le Floc'h, E.; Looper, D.; Granvik, M.; Sanders, D. B.; Giorgini, J. D.; Hagen, A.; Reach, W. T.

    2010-09-01

    The Spitzer Space Telescope routinely detects asteroids in astrophysical observations near the ecliptic plane. For the galactic or extragalactic astronomer, these solar system bodies can introduce appreciable uncertainty into the source identification process. We discuss an infrared color discrimination tool that may be used to distinguish between solar system objects and extrasolar sources. We employ four Spitzer Legacy data sets, the First Look Survey-Ecliptic Plane Component (FLS-EPC), SCOSMOS, SWIRE, and GOODS. We use the Standard Thermal Model to derive FLS-EPC main belt asteroid (MBA) diameters of 1-4 km for the numbered asteroids in our sample and note that several of our solar system sources may have fainter absolute magnitude values than previously thought. A number of the MBAs are detected at flux densities as low as a few tens of {mu}Jy at 3.6 {mu}m. As the FLS-EPC provides the only 3.6-24.0 {mu}m observations of individual asteroids to date, we are able to use this data set to carry out a detailed study of asteroid color in comparison to astrophysical sources observed by SCOSMOS, SWIRE, and GOODS. Both SCOSMOS and SWIRE have identified a significant number of asteroids in their data, and we investigate the effectiveness of using relative color to distinguish between asteroids and background objects. We find a notable difference in color in the IRAC 3.6-8.0 mm and MIPS 24 {mu}m bands between the majority of MBAs, stars, galaxies, and active galactic nuclei, though this variation is less significant when comparing fluxes in individual bands. We find median colors for the FLS-EPC asteroids to be [F(5.8/3.6), F(8.0/4.5), F(24/8)] = (4.9 {+-} 1.8, 8.9 {+-} 7.4, 6.4 {+-} 2.3). Finally, we consider the utility of this technique for other mid-infrared observations that are sensitive to near-Earth objects, MBAs, and trans-Neptunian objects. We consider the potential of using color to differentiate between solar system and background sources for several space

  18. Epsilon Eridani Inner Asteroid Belt

    NASA Image and Video Library

    2017-09-14

    SCI2017_0004: Artist's illustration of the Epsilon Eridani system showing Epsilon Eridani b, right foreground, a Jupiter-mass planet orbiting its parent star at the outside edge of an asteroid belt. In the background can be seen another narrow asteroid or comet belt plus an outermost belt similar in size to our solar system's Kuiper Belt. The similarity of the structure of the Epsilon Eridani system to our solar system is remarkable, although Epsilon Eridani is much younger than our sun. SOFIA observations confirmed the existence of the asteroid belt adjacent to the orbit of the Jovian planet. Credit: NASA/SOFIA/Lynette Cook

  19. Seat Belt Usage in Injured Car Occupants: Injury Patterns, Severity and Outcome After Two Main Car Accident Mechanisms in Kashan, Iran, 2012

    PubMed Central

    Mohammadzadeh, Mahdi; Paravar, Mohammad; Mirzadeh, Azadeh Sadat; Mohammadzadeh, Javad; Mahdian, Soroush

    2015-01-01

    Background: Road traffic accidents (RTAs) are the main public health problems in Iran. The seat belts, which are vehicle safety devices, are imperative to reduce the risk of severe injuries and mortality. Objectives: The aim of the study was to evaluate injury patterns, severity and outcome among belted and unbelted car occupants who were injured in car accidents. Patients and Methods: This cross-sectional prospective study was performed on all car occupants injured in RTAs (n = 822) who were transported to hospital and hospitalized for more than 24 hours from March 2012 to March 2013. Demographic profile of the patients, including age, gender, position in the vehicle, the use of seat belts, type of car crashes, injured body regions, revised trauma score (RTS), Glasgow coma score (GCS), duration of hospital stay and mortality rate were analyzed by descriptive analysis, chi-square and independent t-test. P < 0.05 was considered significant. Results: A total of 560 patients used seat belts (68.1%). The unbelted occupants were younger (28 years vs. 38 years) and had more frequently sustained head, abdomen and multiple injuries (P = 0.01, P = 0.01 and P = 0.009, respectively). Also, these patients had significantly lower GCS and elongated hospitalization and higher death rate (P = 0.001, P = 0.001 and P = 0.05, respectively). Tendency of severe head trauma and low RTS and death were increased in unbelted occupants in car rollover accident mechanisms (P = 0.001, P = 0.01 and P = 0.008, respectively). Conclusions: During car crashes, especially car rollover, unbelted occupants are more likely to sustain multiple severe injuries and death. Law enforcement of the seat belt usage for all occupants (front and rear seat) is obligatory to reduce severe injuries sustained as a result of car accidents, especially in vehicles with low safety. PMID:26064867

  20. HIGH-ALBEDO C-COMPLEX ASTEROIDS IN THE OUTER MAIN BELT: THE NEAR-INFRARED SPECTRA

    SciTech Connect

    Kasuga, Toshihiro; Usui, Fumihiko; Hasegawa, Sunao; Ootsubo, Takafumi; Kuroda, Daisuke

    2013-07-01

    Primitive, outer-belt asteroids are generally of low albedo, reflecting carbonaceous compositions like those of CI and CM meteorites. However, a few outer-belt asteroids having high albedos are known, suggesting the presence of unusually reflective surface minerals or, conceivably, even exposed water ice. Here, we present near-infrared (1.1-2.5 {mu}m) spectra of four outer-belt C-complex asteroids with albedos {>=}0.1. We find no absorption features characteristic of water ice (near 1.5 and 2.0 {mu}m) in the objects. Intimate mixture models set limits to the water ice by weight {<=}2%. Asteroids (723) Hammonia and (936) Kunigunde are featureless and have (60%-95%) amorphous Mg pyroxenes that might explain the high albedos. Asteroid (1276) Ucclia also shows a featureless reflection spectrum with (50%-60%) amorphous Mg pyroxenes. Asteroid (1576) Fabiola shows a possible weak, broad absorption band (1.5-2.1 {mu}m). The feature can be reproduced by (80%) amorphous Mg pyroxenes or orthopyroxene (crystalline silicate), either of which is likely to cause its high albedo. We discuss the origin of high-albedo components in primitive asteroids.

  1. High-albedo C-complex Asteroids in the Outer Main Belt: The Near-infrared Spectra

    NASA Astrophysics Data System (ADS)

    Kasuga, Toshihiro; Usui, Fumihiko; Ootsubo, Takafumi; Hasegawa, Sunao; Kuroda, Daisuke

    2013-07-01

    Primitive, outer-belt asteroids are generally of low albedo, reflecting carbonaceous compositions like those of CI and CM meteorites. However, a few outer-belt asteroids having high albedos are known, suggesting the presence of unusually reflective surface minerals or, conceivably, even exposed water ice. Here, we present near-infrared (1.1-2.5 μm) spectra of four outer-belt C-complex asteroids with albedos >=0.1. We find no absorption features characteristic of water ice (near 1.5 and 2.0 μm) in the objects. Intimate mixture models set limits to the water ice by weight <=2%. Asteroids (723) Hammonia and (936) Kunigunde are featureless and have (60%-95%) amorphous Mg pyroxenes that might explain the high albedos. Asteroid (1276) Ucclia also shows a featureless reflection spectrum with (50%-60%) amorphous Mg pyroxenes. Asteroid (1576) Fabiola shows a possible weak, broad absorption band (1.5-2.1 μm). The feature can be reproduced by (80%) amorphous Mg pyroxenes or orthopyroxene (crystalline silicate), either of which is likely to cause its high albedo. We discuss the origin of high-albedo components in primitive asteroids.

  2. Basalt here, basalt there: Constraining the basaltic nature of eight Vp-type asteroids in the inner and outer main asteroid belt

    NASA Astrophysics Data System (ADS)

    Hardersen, Paul Scott; Reddy, Vishnu

    2016-10-01

    The distribution and abundance of basaltic material in the main asteroid belt has multiple implications that impact our understanding of the physical and thermal conditions that existed in the inner solar system during the formation epoch about 4.6 Gyr ago. Subjects impacted by a more accurate basaltic asteroid inventory include the efficacy of current inner solar system heating model predictions (Al-26 and T Tauri induction heating), the existence of differentiated parent bodies other than (4) Vesta, the dispersion efficiency of Vestoids by YORP forces, and the predictive ability of the V-taxonomy in predicting a basaltic surface composition. This work reports on a continuation of an effort to better constrain the basaltic asteroid population in the main asteroid belt with the goal of observing about 650 Vp-type asteroids. This work focuses on two populations: a) those Vp-classified asteroids (Carvano et al., 2010) in the spatial vicinity of (4) Vesta (candidate Vestoids) in the inner main belt, and b) Vp-classified asteroids in the outer main belt beyond 2.5 AU. Thus far, 23 Vp-type asteroids and candidate Vestoids have been observed and analyzed, which are all strongly suggestive of a basaltic surface composition (Hardersen et al., 2014, 2015, 2016 (in preparation)). However, unpublished work is beginning to show that the Vp taxonomic class is less accurate in its ability to identify basaltic surface compositions in outer-belt Vp-type asteroids. We report here on an additional set of Vp-type asteroids that were observed at the NASA Infrared Telescope Facility (IRTF) in December 2015 and January 2016. All observations were obtained with the SpeX spectrograph in prism mode with spectral range from 0.7 to 2.5 microns. They include (4900) Maymelou, (7302) 1993 CQ, (9064) Johndavies, (9531) Jean-Luc, (11341) Babbage, (17480) 1991 PE10, (20171) 1996 WC2, and (25849) 2000 ET107. We present average near-infrared (NIR) reflectance spectra of each asteroid, determine the

  3. Atlas of Great Comets

    NASA Astrophysics Data System (ADS)

    Stoyan, Ronald; Dunlop, Storm

    2015-01-01

    Foreword; Using this book; Part I. Introduction: Cometary beliefs and fears; Comets in art; Comets in literature and poetry; Comets in science; Cometary science today; Great comets in antiquity; Great comets of the Middle Ages; Part II. The 30 Greatest Comets of Modern Times: The Great Comet of 1471; Comet Halley 1531; The Great Comet of 1556; The Great Comet of 1577; Comet Halley, 1607; The Great Comet of 1618; The Great Comet of 1664; Comet Kirch, 1680; Comet Halley, 1682; The Great Comet of 1744; Comet Halley, 1759; Comet Messier, 1769; Comet Flaugergues, 1811; Comet Halley, 1835; The Great March Comet of 1843; Comet Donati, 1858; Comet Tebbutt, 1861; The Great September Comet of 1882; The Great January Comet of 1910; Comet Halley, 1910; Comet Arend-Roland, 1956; Comet Ikeya-Seki, 1965; Comet Bennett, 1970; Comet Kohoutek, 1973-4; Comet West, 1976; Comet Halley, 1986; Comet Shoemaker-Levy 9, 1994; Comet Hyakutake, 1996; Comet Hale-Bopp, 1997; Comet McNaught, 2007; Part III. Appendices; Table of comet data; Glossary; References; Photo credits; Index.

  4. Size and Perihelion Distribution of S and Q-type Asteroid Spectral Slopes from the Near Earth Region Through the Main Belt

    NASA Astrophysics Data System (ADS)

    Graves, Kevin; Minton, David A.; Hirabayashi, Masatoshi; Carry, Benoit; DeMeo, Francesca E.

    2016-10-01

    High resolution spectral observations of small S-type and Q-type Near Earth Asteroids (NEAs) have shown two important trends. The spectral slope of these asteroids, which is a good indication of the amount of space weathering the surface has received, has been shown to decrease with decreasing perihelion and size. Specifically, these trends show that there are less weathered surfaces at low perihelion and small sizes. With recent results from all-sky surveys such as the Sloan Digital Sky Survey's (SDSS) Moving Object Catalog, we have gained an additional data set to test the presence of these trends in the NEAs as well as the Mars Crossers (MCs) and the Main Belt. We use an analog to the spectral slope in the SDSS data which is the slope through the g', r' and i' filters, known as the gri-slope, to investigate the amount of weathering that is present among small asteroids throughout the inner solar system. We find that the trend of the gri-slope decreases with decreasing size at nearly the same rate in the Main Belt as in the MC and NEA regions. We propose that these results suggest a ubiquitous presence of Q-types and S-types with low spectral slopes at small sizes throughout the inner solar system, from the Main Belt to the NEA region. Additionally, we suggest that the trend of decreasing spectral slope with perihelion may only be valid at perihelia of approximately less than 1 AU. These results suggest a change in the interpretation for the formation of Q-type asteroids. Planetary encounters may help to explain the high fraction of Q-types at low perihelia, but another process which is present everywhere must also be refreshing the surfaces of these asteroids. We suggest the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect as a possible mechanism.

  5. Great Comets

    NASA Astrophysics Data System (ADS)

    Burnham, Robert

    2000-05-01

    Spectacular and mysterious objects that come and go in the night sky, comets have dwelt in our popular culture for untold ages. As remnants from the formation of the Solar system, they are objects of key scientific research and space missions. As one of nature's most potent and dramatic dangers, they pose a threat to our safety--and yet they were the origin of our oceans and perhaps even life itself. This beautifully illustrated book tells the story of the biggest and most awe-inspiring of all comets: those that have earned the title "Great." Robert Burnham focuses on the Great comets Hyakutake in 1996 and Hale-Bopp in 1997, which gripped attention worldwide because, for many, they were the first comets ever seen. He places these two recent comets in the context of their predecessors from past ages, among them the famous Comet Halley. Great Comets explains the exciting new discoveries that have come from these magnificent objects and profiles the spaceprobes to comets due for launch in the next few years. The book even takes a peek behind Hollywood's science-fiction fantasies to assess the real risks humanity faces from potential impacts of both comets and asteroids. For everyone interested in astronomy, this exciting book reveals the secrets of the Great Comets and provides essential tools for keeping up to date with comet discoveries in the future. Robert Burnham has been an amateur astronomer since the mid-1950s. He has been a senior editor of Astronomy magazine (1986-88) and is the author of many books and CD-ROMS, including Comet Hale-Bopp: Find and Enjoy the Great Comet and Comet Explorer.

  6. Cometary Volatiles and the Origin of Comets

    NASA Technical Reports Server (NTRS)

    A'Hearn, Michael F.; Feaga, Lori M.; Keller, H. Uwe; Kawakita, Hideyo; Hampton, Donald L.; Kissel, Jochen; Klaasen, Kenneth P.; McFadden, Lucy A.; Meech, Karen J.; Schultz, Peter H.; Sunshine, Jessica M.; Thomas, Peter C.; Veverka, Joseph; Yeomans, Donald K.; Besse, Sebastien; Bodewits, Dennis; Farnham, Tony L.; Groussin, Olivier; Kelley, Michael S.; Lisse, Carey M.; Merlin, Frederic; Protopapa, Silvia; Wellnitz, Dennis D.

    2012-01-01

    We describe recent results on the CO/C02/H2O composition of comets and compare these with models of the protoplanetary disk. We argue that the cometary observations require reactions on grain surfaces to convert CO to CO2 and also require formation between the CO and CO2 snow lines. This then requires very early mixing of cometesimals in the protoplanetary disk analogous to the mixing described for the asteroid belt by Walsh and Morbidelli. We suggest that most comets formed in the region of the giant planets. the traditional source of the Oort-cloud comets but not of the Jupiter-family comets

  7. Mostly Dormant Comets and their Disintegration into Meteoroid Streams: A Review

    NASA Astrophysics Data System (ADS)

    Jenniskens, Peter

    2008-06-01

    The history of associating meteor showers with asteroidal-looking objects is long, dating to before the 1983 discovery that 3200 Phaethon moves among the Geminids. Only since the more recent recognition that 2003 EH1 moves among the Quadrantids are we certain that dormant comets are associated with meteoroid streams. Since that time, many orphan streams have found parent bodies among the newly discovered Near Earth Objects. The seven established associations pertain mostly to showers in eccentric or highly inclined orbits. At least 35 other objects are tentatively linked to streams in less inclined orbits that are more difficult to distinguish from those of asteroids. There is mounting evidence that the streams originated from discrete breakup events, rather than long episodes of gradual water vapor outgassing. If all these associations can be confirmed, they represent a significant fraction of all dormant comets that are in near-Earth orbits, suggesting that dormant comets break at least as frequently as the lifetime of the streams. I find that most pertain to NEOs that have not yet fully decoupled from Jupiter. The picture that is emerging is one of rapid disintegration of comets after being captured by Jupiter, and consequently, that objects such as 3200 Phaethon most likely originated from among the most primitive asteroids in the main belt, instead. They too decay mostly by disintegration into comet fragments and meteoroid streams. The disintegration of dormant comets is likely the main source of our meteor showers and the main supply of dust to the zodiacal cloud.

  8. Results of Observations of Occultations of Stars by Main-Belt and Trojan Asteroids, and the Promise of Gaia

    NASA Astrophysics Data System (ADS)

    Dunham, David W.; Herald, David Russell; Preston, Steven; Loader, Brian; Bixby Dunham, Joan

    2016-10-01

    objects of the highest scientific interest, including some comets.

  9. The nature of comet-asteroid transition object (3200) Phaethon

    NASA Astrophysics Data System (ADS)

    Licandro, J.; Campins, H.; Mothé-Diniz, T.; Pinilla-Alonso, N.; de León, J.

    2007-01-01

    Context: The study of asteroids that present sporadic cometary activity is of fundamental importance to address several astronomical problems including the end states of comet nuclei, the abundance of water in main belt asteroids, and its role as a possible source of terrestial water. Aims: We studied the composition of the surface of asteroid (3200) Phaethon, a paradigmatic case of asteroid-comet transition object, in order to determine its cometary or asteroidal nature. Methods: We report visible and near infrared spectra covering the 0.35-2.4 μm spectral range, obtained with the 4.2 m William Herschel Telescope, the 2.5 m Nordic Optical Telescope, and the Italian 3.58 m Telescopio Nazionale Galileo at "El Roque de los Muchachos" Observatory (La Palma, Spain). Our spectrum is compared with those of meteorite samples and man-made mineral mixtures to determine possible components, modeled using multiple scattering formulations, and also compared with the spectra of comet nuclei and other comet-asteroid transitional objects. Results: Phaethon's spectrum does not show any sharp structure and has a negative slope at wavelengths >0.43 μm, consistent with B-type asteroids. Below 0.43 μm the reflectance decreases. The spectral shape is similar to that of aqueously altered CI/CM meteorites and of hydrated minerals. A surface composition with hydrated silicates is also suggested by the models. A possible spectral variability in the UV is suggested by the avaliable spectra, and is compatible with a slightly different abundance of hydrated silicates. Finally, Phaethon's spectrum shows important differences with the few comet nuclei properly observed at these wavelengths and is similar to the spectra of other peculiar comet-asteroid transition objects. Conclusions: .The spectral properties and dynamical properties of (3200) Phaethon support an asteroidal nature rather than a cometary one. Phaethon is more likely an "activated" asteroid, similar to the population of

  10. YORP and collisional shaping of the sub-populations, rotation rate and size-frequency distributions in the main-belt

    NASA Astrophysics Data System (ADS)

    Rossi, A.; Marzari, F.; Scheeres, D.; Jacobson, S.; Davis, D.

    In the last several years a comprehensive asteroid-population-evolution model was developed incorporating both the YORP effect and collisional evolution \\citep{rossi_2009}, \\citep{marz_2011}, \\citep{jac_mnras}. From the results of this model we were able to match the observed main belt rotation rate distribution and to give a first plausible explanation of the observed excess of slow rotators, through a random walk-like evolution of the spin, induced by repeated collisions with small projectiles. Moreover, adding to the model the rotational fission hypothesis (i.e. when the rotation rate exceeds a critical value, erosion and binary formation occur; \\citealt{sch_2007}) and binary-asteroid evolution \\citep{jac_sch}, we first showed that the YORP-induced rotational-fission hypothesis has strong repercussions for the small size end of the main-belt asteroid size-frequency distribution. We also concluded that this hypothesis is consistent with observed asteroid-population statistics and with the observed sub-populations of binary asteroids, asteroid pairs and contact binaries. An overview of the results obtained, the modelling uncertainties and the ongoing work will be given.

  11. Comet or Asteroid?

    NASA Astrophysics Data System (ADS)

    1997-11-01

    /1996n2pw.html - Are They Comets or Asteroids? (adapted version of article by Stuart J. Goldman in Sky & Telescope, November 1996) * http://cfa-www.harvard.edu/~graff/pressreleases/1996PW.html - Two Unusual Objects: 1996 PW and C/1996 N2 (Press information from the Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, Massachusetts, U.S.A.) * Abstract of research article : Origin and Evolution of the Unusual Object 1996 PW: Asteroids from the Oort Cloud? by Paul R. Weissman and Harold F. Levison * Abstract of research article : The Main Asteroid Belt - Comet Graveyard or Nursery? by Mark Hammergren * Preprint of research article : The Lightcurve and Colours of Unusual Minor Planet 1996 PW by J.K. Davies et al. This Press Release is accompanied by ESO PR Photo 31a/97 [JPG, 120k] , ESO PR Photo 31b/97 [JPG, 45k] and ESO PR Photo 31c/97 [JPG, 52k]. A larger version of ESO PR Photo 31c/97 [JPG, 384k] is also available. They may be reproduced, if credit is given to the European Southern Observatory. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ).

  12. Anatomy of a Busted Comet

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Poster Version (Figure 1)

    NASA's Spitzer Space Telescope captured the picture on the left of comet Holmes in March 2008, five months after the comet suddenly erupted and brightened a millionfold overnight. The contrast of the picture has been enhanced on the right to show the anatomy of the comet.

    Every six years, comet 17P/Holmes speeds away from Jupiter and heads inward toward the sun, traveling the same route typically without incident. However, twice in the last 116 years, in November 1892 and October 2007, comet Holmes mysteriously exploded as it approached the asteroid belt. Astronomers still do not know the cause of these eruptions.

    Spitzer's infrared picture at left hand side of figure 1, reveals fine dust particles that make up the outer shell, or coma, of the comet. The nucleus of the comet is within the bright whitish spot in the center, while the yellow area shows solid particles that were blown from the comet in the explosion. The comet is headed away from the sun, which lies beyond the right-hand side of figure 1.

    The contrast-enhanced picture on the right shows the comet's outer shell, and strange filaments, or streamers, of dust. The streamers and shell are a yet another mystery surrounding comet Holmes. Scientists had initially suspected that the streamers were small dust particles ejected from fragments of the nucleus, or from hyerpactive jets on the nucleus, during the October 2007 explosion. If so, both the streamers and the shell should have shifted their orientation as the comet followed its orbit around the sun. Radiation pressure from the sun should have swept the material back and away from it. But pictures of comet Holmes taken by Spitzer over time show the streamers and shell in the same configuration, and not pointing away from the sun. The observations have left astronomers stumped.

    The horizontal line seen in the contrast-enhanced picture is a trail of debris

  13. Anatomy of a Busted Comet

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Poster Version (Figure 1)

    NASA's Spitzer Space Telescope captured the picture on the left of comet Holmes in March 2008, five months after the comet suddenly erupted and brightened a millionfold overnight. The contrast of the picture has been enhanced on the right to show the anatomy of the comet.

    Every six years, comet 17P/Holmes speeds away from Jupiter and heads inward toward the sun, traveling the same route typically without incident. However, twice in the last 116 years, in November 1892 and October 2007, comet Holmes mysteriously exploded as it approached the asteroid belt. Astronomers still do not know the cause of these eruptions.

    Spitzer's infrared picture at left hand side of figure 1, reveals fine dust particles that make up the outer shell, or coma, of the comet. The nucleus of the comet is within the bright whitish spot in the center, while the yellow area shows solid particles that were blown from the comet in the explosion. The comet is headed away from the sun, which lies beyond the right-hand side of figure 1.

    The contrast-enhanced picture on the right shows the comet's outer shell, and strange filaments, or streamers, of dust. The streamers and shell are a yet another mystery surrounding comet Holmes. Scientists had initially suspected that the streamers were small dust particles ejected from fragments of the nucleus, or from hyerpactive jets on the nucleus, during the October 2007 explosion. If so, both the streamers and the shell should have shifted their orientation as the comet followed its orbit around the sun. Radiation pressure from the sun should have swept the material back and away from it. But pictures of comet Holmes taken by Spitzer over time show the streamers and shell in the same configuration, and not pointing away from the sun. The observations have left astronomers stumped.

    The horizontal line seen in the contrast-enhanced picture is a trail of debris

  14. COLOR SYSTEMATICS OF COMETS AND RELATED BODIES

    SciTech Connect

    Jewitt, David

    2015-12-15

    Most comets are volatile-rich bodies that have recently entered the inner solar system following long-term storage in the Kuiper belt and the Oort cloud reservoirs. These reservoirs feed several distinct, short-lived “small body” populations. Here, we present new measurements of the optical colors of cometary and comet-related bodies including long-period (Oort cloud) comets, Damocloids (probable inactive nuclei of long-period comets) and Centaurs (recent escapees from the Kuiper belt and precursors to the Jupiter family comets). We combine the new measurements with published data on short-period comets, Jovian Trojans and Kuiper belt objects to examine the color systematics of the comet-related populations. We find that the mean optical colors of the dust in short-period and long-period comets are identical within the uncertainties of measurement, as are the colors of the dust and of the underlying nuclei. These populations show no evidence for scattering by optically small particles or for compositional gradients, even at the largest distances from the Sun, and no evidence for ultrared matter. Consistent with earlier work, ultrared surfaces are common in the Kuiper belt and on the Centaurs, but not in other small body populations, suggesting that this material is hidden or destroyed upon entry to the inner solar system. The onset of activity in the Centaurs and the disappearance of the ultrared matter in this population begin at about the same perihelion distance (∼10 AU), suggesting that the two are related. Blanketing of primordial surface materials by the fallback of sub-orbital ejecta, for which we calculate a very short timescale, is the likely mechanism. The same process should operate on any mass-losing body, explaining the absence of ultrared surface material in the entire comet population.

  15. Halley's Comet.

    ERIC Educational Resources Information Center

    Carey, Tom

    1985-01-01

    Provides tips for viewing Comet Halley in the Northeast including best viewing dates from November 1985-January 1986. Discusses going south to view the comet in March-April 1986 and gives specific information about accommodations for the Halley Rally in Everglades National Park, southernmost site in the contiguous 48 states. (JHZ)

  16. Halley's Comet.

    ERIC Educational Resources Information Center

    Carey, Tom

    1985-01-01

    Provides tips for viewing Comet Halley in the Northeast including best viewing dates from November 1985-January 1986. Discusses going south to view the comet in March-April 1986 and gives specific information about accommodations for the Halley Rally in Everglades National Park, southernmost site in the contiguous 48 states. (JHZ)

  17. Gas, Dust, and Nuclei: Cometary Types in the Largest IR Survey of Comets.

    NASA Astrophysics Data System (ADS)

    Bauer, James; Kramer, Emily; Mainzer, Amy; Grav, Tommy; Masiero, Joseph; Stevenson, Rachel; Nugent, Carrie; Sonnett, Sarah

    2015-08-01

    Space-based infrared (IR) surveys of objects have the potential to yield rich data sets for any particular class of small body. Thermal IR measurements often yield the most fundamental of astrophysical properties, the object’s size. When these data are synergistically combined with shorter-wavelength observations, the albedos of these bodies can be determined. The interpretation of IR observations of cometary bodies are more complicated, since their activity may obscure the bare surfaces of their nuclei. Yet space-based IR surveys provide the opportunity to observe this emitted dust and gas at wavelengths and sensitivities not possible from the ground.With the 163 comets detected during the WISE prime mission, and the more than 60 comets seen in the first year of data since the NEOWISE reactivated mission, the combined sample represents the largest survey of comets in the mid-IR. These data of over 200 comets provide dust particle size constraints and dust reflectance measurements, as well as nucleus size measurements. They are sensitive to the presence of the rarely observed gas species, CO2, directly detectable only from above the Earth’s atmosphere, and to the presence of CO emission, which is difficult to view from the ground. The data contain large samples of major cometary types (long-period and short-period comets), as well as smaller samples of Halley-type comets, Main Belt comets, and Near Earth comets, observed at multiple epochs, and so provide an unprecedentedly comprehensive view of the different comet populations.

  18. The World of Comets

    NASA Astrophysics Data System (ADS)

    Guillemin, Amédée; Glaisher, James

    2010-10-01

    1. Beliefs and superstitions relative to comets; 2. Cometary astronomy up to the time of Newton; 3. The motions and orbits of comets; 4. Periodical comets; 5. Periodical comets; 6. The world of comets and cometary systems; 7. Physical and chemical constitution of comets; 8. Physical transformations of comets; 9. Mass and density of comets; 10. The light of comets; 11. Theory of cometary phenomena; 12. Comets and shooting stars; 13. Comets and the earth; 14. Physical influences of comets; 15. Some questions about comets; Tables.

  19. Dating slate belts using 40Ar/39Ar geochronology and zircon ages from crosscutting plutons: A case study from east-central Maine, USA

    NASA Astrophysics Data System (ADS)

    Ghanem, Hind; Kunk, Michael J.; Ludman, Allan; Bish, David L.; Wintsch, Robert P.

    2016-12-01

    We report the ages of cleavage development in a normally intractable lower greenschist facies slate belt, the Central Maine-Aroostook-Matapedia belt in east-central Maine. We have attacked this problem by identifying the minimum ages of muscovite in a regional Acadian cleavage (S1) and in a local ductile fault zone cleavage (S2) using 40Ar/39Ar geochronology and the ages of crosscutting plutons. Our success stems from the regional low-grade metamorphism of the rocks in which each crystallization event preserves a40Ar/39Ar crystallization age and not a cooling age. Evidence for recrystallization via a pressure solution mechanism comes from truncations of detrital, authigenic, and in some rocks S1 muscovite and chlorite grains by new cleavage-forming muscovite and chlorite grains. Low-blank furnace age spectra from meta-arkosic and slaty rocks climb from moderate temperature Devonian age-steps dominated by cleavage-forming muscovite to Ordovician age-steps dominated by a detrital muscovite component. S1- and S2-cleaved rocks were hornfelsed by granitoids of ∼407 and 377 Ma, respectively. The combination of these minimum ages with the maximum metamorphic crystallization ages establishes narrow constraints on the timing of these two cleavage-forming events, ∼410 Ma (S1) and ∼380 Ma (S2). These two events coincide in time with a change in the plate convergence kinematics from the arrival of the Avalon terrane (Acadian orogeny), to a right-lateral transpression arrival of the Meguma terrane in the Neoacadian orogeny.

  20. THERMAL SHADOWS AND COMPOSITIONAL STRUCTURE IN COMET NUCLEI

    SciTech Connect

    Guilbert-Lepoutre, Aurelie; Jewitt, David E-mail: jewitt@ucla.edu

    2011-12-10

    We use a fully three-dimensional thermal evolution model to examine the effects of a non-uniform surface albedo on the subsurface thermal structure of comets. Surface albedo markings cast 'thermal shadows' with strong lateral thermal gradients. Corresponding compositional gradients can be strong, especially if the crystallization of amorphous water ice is triggered in the hottest regions. We show that the spatial extent of the structure depends mainly on the obliquity, thermal conductivity, and heliocentric distance. In some circumstances, subsurface structure caused by the thermal shadows of surface features can be maintained for more than 10 Myr, the median transport time from the Kuiper Belt to the inner solar system. Non-uniform compositional structure can be an evolutionary product and does not necessarily imply that comets consist of building blocks accumulated in different regions of the protoplanetary disk.

  1. Mosaic of CCDs to Survey for Asteroids and Comets

    NASA Technical Reports Server (NTRS)

    McMillan, Robert S.

    2002-01-01

    Spacewatch searches for asteroids and comets ranging in location from near-Earth space to regions beyond the orbit of Neptune. We are studying Earth-approaching asteroids, main belt asteroids, comets, Centaurs, and TNOs, as well as the interrelationships of these classes and their bearing on the origin and evolution of the solar system. Spacewatch is described at http://www. lpl. arizona. edu/spacewatch/index.html. The Spacewatch Project has been discovering Earth-approaching asteroids (EAs) steadily and has used the results aggressively to estimate the statistical properties of the EA population. This grant funded Spacewatch to develop and implement a mosaic of CCD imaging detectors for the 0.9-m telescope, to increase that telescope's rate of coverage of sky area while preserving its limiting magnitude.

  2. The state of knowledge concerning the Kuiper belt

    NASA Technical Reports Server (NTRS)

    Levison, Harold F.

    1992-01-01

    The arguments for and against the idea that most short-period comets originate in the Kuiper belt are discussed. Observational constraints on the distribution of mass in the Kuiper belt are reviewed as well as a model of the physical conditions that now exist. Finally, predictions from this model about the detectability of the Kuiper belt are compared to optical surveys.

  3. Conveyor belt plow for ideal belt cleaning

    SciTech Connect

    Michaelsen, W.J.

    1982-05-01

    The accumulation of excess material around the return drum of a conveyor arises from an inefficient belt plow. The frequency with which this problem occurs would indicate a design problem rather than faulty installation or negligent maintenance. The reasons for the poor operation of the plow become obvious after applying basic physical principles. Simple and cheap improvements can be implemented to improve plow performance. To be effective, a plow should be installed either near the tail end, to protect the return drum, or ahead of the automatic belt tensioning device, to prevent spillage from falling onto the take-up pulley. In order to perform well, the scraping blade of the plow must be in continuous contact with the belt across its full width, having contact pressure as uniform as possible. It has been proven, though, that uniform contact pressure cannot be achieved under operating conditions with the standard arrangement shown in Figure 1. There are two solutions to this problem which can be carried out in most mine workshops and help reduce belt downtime. All too often an ineffective plow allows material to be needlessly trapped against the belt, causing excessive wear and, ultimately, tearing the belt. Even with highly experienced belt crews, a short stoppage in the main belt can have serious effects throughout the mine. An efficient plow means a cleaner running belt.

  4. Late Triassic granites from Bangka, Indonesia: A continuation of the Main Range granite province of the South-East Asian Tin Belt

    NASA Astrophysics Data System (ADS)

    Ng, Samuel Wai-Pan; Whitehouse, Martin J.; Roselee, Muhammad H.; Teschner, Claudia; Murtadha, Sayed; Oliver, Grahame J. H.; Ghani, Azman A.; Chang, Su-Chin

    2017-05-01

    The South-East Asian Tin Belt is one of the most tin-productive regions in the world. It comprises three north-south oriented granite provinces, of which the arc-related Eastern granite province and the collision-related Main Range granite province run across Thailand, Singapore, and Indonesia. These tin-producing granite provinces with different mineral assemblages are separated by Paleo-Tethyan sutures exposed in Thailand and Malaysia. The Eastern Province is usually characterised by granites with biotite ± hornblende. Main Range granites are sometimes characterised by the presence of biotite ± muscovite. However, the physical boundary between the two types of granite is not well-defined on the Indonesian Tin Islands, because the Paleo-Tethyan suture is not exposed on land there. Both hornblende-bearing (previously interpreted as I-type) and hornblende-barren (previously interpreted as S-type) granites are apparently randomly distributed on the Indonesian Tin Islands. Granites exposed on Bangka, the largest and southernmost Tin Island, no matter whether they are hornblende-bearing or hornblende-barren, are geochemically similar to Malaysian Main Range granites. The average ɛNd(t) value obtained from the granites from Bangka (average ɛNd(t) = -8.2) falls within the range of the Main Range Province (-9.6 to -5.4). These granites have SIMS zircon U-Pb ages of ca. 225 Ma and ca. 220 Ma, respectively that are both within the period of Main Range magmatism (∼226-201 Ma) in the Peninsular Malaysia. We suggest that the granites exposed on Bangka represent the continuation of the Main Range Province, and that the Paleo-Tethyan suture lies to the east of the island.

  5. Ways of Changing the Number and Size Distribution of Ecliptic Comets

    NASA Astrophysics Data System (ADS)

    Dones, Henry C. Luke; Womack, Maria; Alvarellos, Jose; Bierhaus, Edward B.; Bottke, William; Hamill, Patrick; Nesvorny, David; Robbins, Stuart J.; Zahnle, Kevin

    2017-06-01

    The existence of the Kuiper Belt was proposed because of the need for a low-inclination source for the Jupiter-family comets (JFCs). Indeed, the Kuiper Belt is thought to be the main reservoir of ecliptic comets (ECs), which include the JFCs and Centaurs. Ironically, we still do not know whether the belt, specifically its Scattered Disk, provides an adequate source for the ECs (Volk and Malhotra 2008). ECs are also thought to be the main source of Sun-orbiting impactors on the regular moons of the giant planets (Zahnle et al. 2003 [Z03]). Some models of the cometary orbital distribution used by Z03 and others to estimate impact rates assume comets are indestructible; in fact, many cometssplit, sometimes far from the Sun (Fernández 2009). Assuming shatterproof comets may lead to incorrect results for cometary orbital distributions. Other models impose a physical lifetime for bodies that approach within ~3 AU of the Sun, where sublimation of water ice begins, after which a comet is assumed to be dormant or disrupted (Nesvorný et al. 2017). In reality, some comets (e.g., 29P, Hale-Bopp) are active due to volatiles such as CO and CO2 beyond the orbit of Jupiter (Womack et al. 2017). 174P/Echeclus underwent a 7-magnitude outburst 13 AU from the Sun (Rousselot et al. 2016), and CO emission was recently detected from Echeclus at 6 AU (Wierzchos et al. 2017). We will estimate the effects of several mechanisms on the number and size distribution of comet nuclei as a function of distance from the Sun, including cometary activity and spontaneous disruption; tidal disruption by a giant planet, as happened for Shoemaker-Levy 9; and tidal disruption of binaries, which are numerous among "cold classical" Kuiper Belt Objects (Fraser et al. 2017). We thank the Cassini Data Analysis Program for support.Fernández Y (2009). Planet. Space. Sci. 57, 1218.Fraser WC, et al. (2017). Nat. Astron. 1, 0088.Nesvorný D, et al. (2017). In preparation.Rousselot P, et al. (2016). MNRAS 462, S

  6. Halley's Comet

    NASA Technical Reports Server (NTRS)

    Newburn, R. L., Jr.; Yeomans, D. K.

    1982-01-01

    Since 240 B.C., Chinese observers have documented a nearly unbroken record of scientifically useful observations of Periodic Comet Halley (P/Halley). Investigations of the comet's motion by Western astronomers are discussed, taking into account the first successful prediction of a cometary return by Halley (1705), computations conducted by Rosenberger (1830), and studies performed by Cowell and Crommelin (1910). Comet Halley's motion and nongravitational forces are considered along with meteor showers associated with P/Halley. The physical properties of P/Halley are examined, giving attention to the visual observations, the light curve of P/Halley, the coma, the tails, direct photographs, spectrograms, and the emission spectrum of P/Halley. Other subjects explored are related to the cometary nucleus, the mass of P/Halley, the rotation period and axial inclination, the composition, a nominal model of P/Halley's coma, and plans for investigations in connection with the coming apparition of Comet Halley.

  7. Sketching Comets

    NASA Astrophysics Data System (ADS)

    Perez, Jeremy

    Comets add a sense of surprise and freshness to the predictability and seeming timelessness of the visible cosmos. Some of these mists of dust and fl uorescing gas sail through the inner solar system at regular intervals, such as the famous comet 1P/Halley. Many other comets are discovered yearly as they make their first observed descent to our vicinity. Depending on their distance, composition, and intrinsic brightness, comets can present a variety of appearances—from almost stellar objects, to soft round patches, to majestic, tailed plumes that are sometimes visible to the naked eye. Because these are fl eeting, transitory objects, time spent observing and sketching them is all the more precious.

  8. Comet culture

    NASA Astrophysics Data System (ADS)

    Lusher, Rebekah

    2011-10-01

    Rebekah Lusher describes an exhibition in the new Caroline Lucretia Gallery at the Herschel Museum of Astronomy in Bath: Omens and Inspirations: Ice, Dust and Fire - the Story of the Great Comet of 1811.

  9. Platinum-group elements in alpine-type ultramafic rocks and related chromite ores of the main ophiolite belt of the Urals

    NASA Astrophysics Data System (ADS)

    Volchenko, Yu. A.; Koroteev, V. A.; Neustroeva, I. I.

    2009-04-01

    On the basis of a representative collection of ultramafic rocks and chromite ores and a series of technological samples from the largest (Central and Western) deposits in the Rai-Iz massif of the Polar Urals and the Almaz-Zhemchuzhina and Poiskovy deposits in the Kempirsai massif of the southern Urals, the distribution and speciation of platinum-group elements (PGE) in various type sections of mafic-ultramafic massifs of the Main ophiolite belt of the Urals have been studied. Spectral-chemical and spectrophotometric analyses were carried out to estimate PGE in 700 samples of ultramafic rocks and chromite ores; 400 analyses of minerals from rocks, ores, and concentrates and 100 analyses of PGE minerals (PGM) in chromite ores and concentrates were performed using an electron microprobe. Near-chondritic and nonchondritic PGE patterns in chromitebearing sections have been identified. PGE mineralization has been established to occur in chromite ore from all parts of the mafic-ultramafic massifs in the Main ophiolite belt of the Urals. The PGE deposits and occurrences discovered therein are attributed to four types (Kraka, Kempirsai, Nurali-Upper Neiva, and Shandasha), which are different in mode of geological occurrence, geochemical specialization, and placer-forming capability. Fluid-bearing minerals of the pargasite-edenite series have been identified for the first time in the matrix of chromite ore of the Kempirsai massif (the Almaz-Zhemchuzhina deposit) and Voikar-Syn’ya massif (the Kershor deposit). The PGE grade in various types of chromite ore ranges from 0.1-0.2 to 1-2 g/t or higher. According to technological sampling, the average PGE grade in the largest deposits of the southeastern ore field of the Kempirsai massif is 0.5-0.7 g/t. Due to the occurrence of most PGE as PGM 10-100 mm in size and the proved feasibility of their recovery into nickel alloys, chromites of the Kempirsai massif can be considered a complex ore with elevated and locally high Os, Ir

  10. A Post-Stardust Mission View of Jupiter Family Comets

    NASA Technical Reports Server (NTRS)

    Zolensky, M.

    2011-01-01

    Before the Stardust Mission, many persons (including the mission team) believed that comet nuclei would be geologically boring objects. Most believed that comet nucleus mineralogy would be close or identical to the chondritic interplanetary dust particles (IDPs), or perhaps contain mainly amorphous nebular condensates or that comets might even be composed mainly of preserved presolar material [1]. Amazingly, the results for Comet Wild 2 (a Jupiter class comet) were entirely different. Whether this particular comet will ultimately be shown to be typical or atypical will not be known for a rather long time, so we describe our new view of comets from the rather limited perspective of this single mission.

  11. Dating slate belts using 40Ar/39Ar geochronology and zircon ages from crosscutting plutons: A case study from east-central Maine, USA

    NASA Astrophysics Data System (ADS)

    Ghanem, Hind; Kunk, Michael; Ludman, Allan; Bish, David; Wintsch, Robert

    2016-04-01

    Determining the tectonic significance of slate belts is a persistent problem in many orogenic belts because of the lack of time constraints on the age of deposition and the age(s) of cleavages. We have solved this problem in east-central Maine where the ages of the regional Acadian cleavage (S1) and local ductile fault zone cleavage (S2) were both constrained using 40Ar/39Ar geochronology and the ages of crosscutting plutons. Applying 40Ar/39Ar geochronology to rocks with multiple generations of muscovite was possible because each cleavage-forming muscovite records a crystallization age rather than a cooling age due to the low grade of regional metamorphism. Evidence for metamorphic crystallization in rocks dominated by regional Acadian cleavage (S1) comes from the truncations of detrital and authigenic muscovite and chlorite grains by new muscovite and chlorite grains that define the S1 foliation. In rocks that display two foliations, the evidence comes from the truncations of chlorite and muscovite grains defining all earlier fabrics by new muscovite grains in the younger folia (S2). Step-heating experiments using the 40Ar/39Ar technique on twelve samples all yielded sigmoidal age spectra. The low-temperature steps produced a hump in the age spectra, indicating 39Ar recoil into adjacent interlayered chlorite grains, the latter interlayering confirmed by back-scattered electron imaging. Continuing steps climbed steadily from those with minimum apparent ages as young as ~381 Ma to steps with maximum ages as old as 466 Ma. The samples with the lowest minimum apparent age steps are those in which the S2 cleavage-forming mica population dominates. In contrast, the oldest apparent age steps are from samples that have the highest modal abundance of detrital micas. The Middle Ordovician age of the maximum age steps is interpreted to be the minimum cooling age of the detrital micas. The minimum 40Ar/39Ar age steps of muscovite in the samples that display only S1 cleavage

  12. Comet Radar Explorer

    NASA Astrophysics Data System (ADS)

    Asphaug, Erik; CORE Science Team

    2010-10-01

    Comet Radar Explorer (CORE) is a low cost mission that uses sounding radar to image the 3D internal structure of the nucleus of Jupiter-family comet (JFC) Tempel 2. Believed to originate in the Kuiper Belt, JFCs are among the most primitive bodies in the inner solar system. CORE operates a 5 and 15 MHz Radar Reflection Imager from close orbit about the nucleus of Tempel 2, obtaining a dense network of echoes that are used to map its interior dielectric contrasts to high resolution (ង m) and resolve the dielectric constants to  m throughout the 16x8x9 km nucleus. The resulting clear images of internal structure and composition reveal how the nucleus was formed and how it has evolved. Radiometric tracking of the spacecraft orbit results in an interior mass distribution that constrains the radar-based models of interior composition. High-resolution visible and infrared color images provide the surface and exterior boundary conditions for interior models and hypotheses. They present the geology and morphology of the nucleus surface at meter-scales, and also the time-evolving activity, structure and composition of the inner coma. By making deep connections from interior to exterior, the data CORE provides will answer fundamental questions about the earliest stages of planetesimal evolution and planet formation, and lay the foundation for a comet nucleus sample return mission. CORE is led by Prof. Erik Asphaug of the University of California, Santa Cruz and is managed by JPL. It benefits from key scientific and payload contributions by ASI and CNES. The international science team has been assembled on the basis of their key involvement in past and ongoing missions to comets, and in Mars radar missions, and for their expertise in radar data analysis.

  13. Ground-Based Centimeter, Millimeter, and Submillimeter Observations of Recent Comets

    NASA Technical Reports Server (NTRS)

    Milam, S. N.; Chuang, Y.-L.; Charnley, S. B.; Kuan, Y. -J.; Villanueva, G. L.; Coulson, I. M.; Remijan. A. R.

    2012-01-01

    Comets provide important clues to the physical and chemical processes that occurred during the formation and early evolution of the Solar System, and could also have been important for initiating prebiotic chemistry on the early Earth [I]. Comets are comprised of molecular ices, that may be pristine interstellar remnants of Solar System formation, along with high-temperature crystalline silicate dust that is indicative of a more thermally varied history in the protosolar nebula [2]. Comparing abundances of cometary parent volatiles, and isotopic fractionation ratios, to those found in the interstellar medium, in disks around young stars, and between cometary families, is vital to understanding planetary system formation and the processing history experienced by organic matter in the so-called interstellar-comet connection [3]. In the classical picture, the long-period comets probably formed in the nebular disk across the giant planet formation region (5-40 AU) with the majority of them originating from the Uranus-Neptune region. They were subsequently scattered out to the Oort Cloud (OC) by Jupiter. The short-period comets (also known as ecliptic or Jupiter Family Comets - JFC) reside mainly in the Edgeworth-Kuiper belt where they were formed. Given the gradient in physical conditions expected across this region of the nebula, chemical diversity in this comet population is to be expected [4,5]. We have conducted observations of comets I 03P/Hartley 2 (JFC) and C/2009 PI (Garradd) (OC), at primarily millimeter and submillimeter wavelengths, to determine important cosmogonic quantities, such as the ortho:para ratio and isotope ratios, as well as probe the origin of cometary organics and if they vary between the two dynamic reservoirs.

  14. Rosetta Comet Spreads its Jets

    NASA Image and Video Library

    2014-10-24

    This image was taken by the Optical, Spectroscopic, and Infrared Remote Imaging System, Rosetta main onboard scientific imaging system, on Sept. 10, 2014. Jets of cometary activity can be seen along almost the entire body of the comet.

  15. The Lockne - Målingen doublet impacts, the result of a binary asteroid from the 470 Ma Main Asteroid Belt event

    NASA Astrophysics Data System (ADS)

    Sturkell, E. C.; Ormo, J.; Alwmark, C.; Melosh, H., IV

    2015-12-01

    Approximately 470 million years ago one of the largest cosmic catastrophes occurred in our solar system since the accretion of the planets. A 200-km large asteroid was disrupted by a collision in the Main Asteroid Belt (MAB), which spawned fragments into Earth crossing orbits. This had tremendous consequences for the meteorite production and cratering rate during several millions of years following the event. The 7.5-km wide Lockne crater, central Sweden, is known to be a member of this family. The 600 m large Lockne asteroid was a binary and had a companion in space by a smaller 150 m satellite. The recent discovery of the nearby, 0.7-km diameter, synchronous Målingen crater suggests it to form a doublet impact structure together with the larger Lockne crater, and as we will show here, most likely by a binary, 'rubble pile' asteroid. Despite observational evidence that about 16% of the Near Earth Asteroids (NEA's) are binary, only a handful of the approximately 188 known craters on Earth have been suggested as potential doublets. The stratigraphic and geographic relationship with Lockne suggests the Lockne and Målingen craters to be the first described doublet impact structure by a binary asteroid into a marine-target setting. In addition, the precise dating of the Lockne-Målingen impact in relation to the MAB breakup event provides a hands-on reference for studies of the formation of binaries from asteroid breakup events.

  16. The binary Kuiper-belt object 1998 WW31.

    PubMed

    Veillet, Christian; Parker, Joel Wm; Griffin, Ian; Marsden, Brian; Doressoundiram, Alain; Buie, Marc; Tholen, David J; Connelley, Michael; Holman, Matthew J

    2002-04-18

    The recent discovery of a binary asteroid during a spacecraft fly-by generated keen interest, because the orbital parameters of binaries can provide measures of the masses, and mutual eclipses could allow us to determine individual sizes and bulk densities. Several binary near-Earth, main-belt and Trojan asteroids have subsequently been discovered. The Kuiper belt-the region of space extending from Neptune (at 30 astronomical units) to well over 100 AU and believed to be the source of new short-period comets-has become a fascinating new window onto the formation of our Solar System since the first member object, not counting Pluto, was discovered in 1992 (ref. 13). Here we report that the Kuiper-belt object 1998 WW31 is binary with a highly eccentric orbit (eccentricity e approximately 0.8) and a long period (about 570 days), very different from the Pluto/Charon system, which was hitherto the only previously known binary in the Kuiper belt. Assuming a density in the range of 1 to 2 g cm-3, the albedo of the binary components is between 0.05 and 0.08, close to the value of 0.04 generally assumed for Kuiper-belt objects.

  17. Ramifications of a Divot in the Kuiper Belt's Size Distribution

    NASA Astrophysics Data System (ADS)

    Gladman, Brett; Shankman, C.; Kaib, N.; Kavelaars, J.; Petit, J.

    2012-10-01

    Our recent detection (see Shankman et al., this meeting) of a divot in the distribution of numbers of Scattering TNOs as a function of absolute magnitude would, if extended to all Kuiper Belt sub-populations, simultaneously explain several outstanding curiosities in the literature. We examine these puzzles in the context of our proposed divot scenario and provide a cohesive picture of the "hot" Trans-Neptunian populations (the scattering, inner belt, hot main belt, outer/detached, and resonant populations). We explore the observed rollover in the Kuiper Belt's luminosity function, the "missing" Neptune Trojans, the source of the Jupiter Family Comets, and patterns seen in the hot/cold ratio as a function of magnitude. Our interpretation is that a detected divot is a preserved relic of the size distribution made by planetesimal formation, now "frozen in" to portions of the Kuiper Belt which share a "hot" orbital inclination distribution. This research was supported by the Canadian National Sciences and Engineering Research Council.

  18. Comet ISON

    NASA Image and Video Library

    2013-11-23

    ISS038-E-007980 (23 Nov. 2013) --- A close inspection of this image, photographed by one of the Expedition 38 crew members aboard the International Space Station, reveals a pin-head sized view of an object which is actually the comet ISON, seen just to the right of center and a little below center in the frame. Hardware components of the orbital outpost and Earth's atmosphere above the horizon take up most of the image. Most of the other bright dots in the sky are heavenly bodies. The comet is distinguishable by its tail.

  19. The comet rendezvous asteroid flyby mission: A status report

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.; Neugebauer, Marcia

    1991-01-01

    The Comet Rendezvous Asteroid Flyby (CRAF) mission received a new start in fiscal year 1990. CRAF will match orbits with an active short-period comet and follow it around the Sun, making scientific measurements of the nucleus, coma, and tail. The Imaging system will map the nucleus surface at a resolution of 1 meter/line-pair or better, while Visible and Infrared Mapping Spectrometer (VIMS) and Thermal Infrared Radiometer Experiment (TIREX) will produce spectral and thermal maps of the surface. Onboard instruments will collect cometary dust, ice, and gases and perform elemental and molecular analysis. A suite of fields and particles instruments will observe the solar wind interaction with the cometary atmosphere and tail. Radio tracking of the spacecraft will provide an accurate measure of the nucleus mass and higher harmonics in the comet's gravity field. En route to the comet, the spacecraft will make a close flyby of a large asteroid, preferably a primitive type from the outer main belt. Observations at the asteroid include remote sensing mapping of the surface, detection of any solar wind interaction observable at the flyby distance, and measurement of the asteroid mass to better than 10 percent accuracy. Detailed design of the CRAF spacecraft is currently underway at the Jet Propulsion Laboratory (JPL). Recent mass growth has necessitated a switch to Venus-Earth gravity assist type trajectories, similar to that used by the Galileo spacecraft. These trajectories require longer flight times from launch to rendezvous with the target comet. The details of the current baseline mission, spacecraft design, and instrument payload will be reviewed.

  20. NASA returns rocks from a comet.

    PubMed

    Burnett, Don S

    2006-12-15

    Cometary particles returned by the Stardust Discovery Mission are primarily silicate materials of solar system origin. Some of the grains were formed at high temperatures close to the Sun, but then transported far out to the Kuiper belt region of the solar system before being incorporated in the comet.

  1. Chemical diversity in the comet population

    NASA Astrophysics Data System (ADS)

    Biver, Nicolas

    2015-08-01

    For the last 3 decades, infrared and microwave techniques have enabled the detection of up to 25 different parent molecules in the coma of comets. Several molecules have been detected in over 40 different comets. A large diversity of composition is seen in the sample, comprising comets of various dynamical origin. Abundances relative to water for the molecules can vary by a factor 3 to more than 10. The taxonomic study of a sample of comets in which the abundance of several molecules (e.g., HCN, CH3OH, CO, CH4, C2H6, H2S, H2CO, CH3CN, cs,...) has been measured does not show any clear grouping. Except for fragments of a common parent comet, every comet observed shows a different composition. The absence of any clear correlation between the volatile content of the comets and their dynamical origin (Kuiper Belt versus Oort Cloud) suggest that there is no clear dychotomy between two origins for the comets. Their diveristy in composition may also suggest that radial and temporal mixing in the early protoplanetary nebula may have played an important role.

  2. Active bodies in the near-Earth region: The tenuous boundary between comets and asteroids

    NASA Astrophysics Data System (ADS)

    Fernández, Julio A.; Sosa, Andrea

    2016-01-01

    We analyze the dynamics and activity observed in bodies approaching the Earth (perihelion distances q < 1.3 au) in short-period orbits (P < 20 yr), which essentially are near-Earth Jupiter Family Comets (NEJFCs) and near-Earth asteroids (NEAs). In the general definition, comets are ``active'', i.e. they show some coma, while asteroids are ``inactive'', i.e. they only show a bare nucleus. Besides their activity, NEJFCs are distinguished from NEAs by their dynamical evolution: NEJFCs move on unstable orbits subject to frequent close encounters with Jupiter, whereas NEA orbits are much more stable and tend to avoid close encounters with Jupiter. However, some JFCs are found to move on stable, asteroidal-type orbits, so the question arises if these objects are asteroids that have become active, perhaps upon approach to the Sun. In this sense they may be regarded as the counterparts of the main-belt comets (Hsieh & Jewitt 2006). On the other hand, some seemingly inert NEAs move on unstable, comet-type orbits, so the question about what is a comet and what is an asteroid has become increasingly complex.

  3. Ocean-like water in the Jupiter-family comet 103P/Hartley 2.

    PubMed

    Hartogh, Paul; Lis, Dariusz C; Bockelée-Morvan, Dominique; de Val-Borro, Miguel; Biver, Nicolas; Küppers, Michael; Emprechtinger, Martin; Bergin, Edwin A; Crovisier, Jacques; Rengel, Miriam; Moreno, Raphael; Szutowicz, Slawomira; Blake, Geoffrey A

    2011-10-05

    For decades, the source of Earth's volatiles, especially water with a deuterium-to-hydrogen ratio (D/H) of (1.558 ± 0.001) × 10(-4), has been a subject of debate. The similarity of Earth's bulk composition to that of meteorites known as enstatite chondrites suggests a dry proto-Earth with subsequent delivery of volatiles by local accretion or impacts of asteroids or comets. Previous measurements in six comets from the Oort cloud yielded a mean D/H ratio of (2.96 ± 0.25) × 10(-4). The D/H value in carbonaceous chondrites, (1.4 ± 0.1) × 10(-4), together with dynamical simulations, led to models in which asteroids were the main source of Earth's water, with ≤10 per cent being delivered by comets. Here we report that the D/H ratio in the Jupiter-family comet 103P/Hartley 2, which originated in the Kuiper belt, is (1.61 ± 0.24) × 10(-4). This result substantially expands the reservoir of Earth ocean-like water to include some comets, and is consistent with the emerging picture of a complex dynamical evolution of the early Solar System.

  4. Both size-frequency distribution and sub-populations of the main-belt asteroid population are consistent with YORP-induced rotational fission

    NASA Astrophysics Data System (ADS)

    Jacobson, S.; Scheeres, D.; Rossi, A.; Marzari, F.; Davis, D.

    2014-07-01

    From the results of a comprehensive asteroid-population-evolution model, we conclude that the YORP-induced rotational-fission hypothesis has strong repercussions for the small size end of the main-belt asteroid size-frequency distribution and is consistent with observed asteroid-population statistics and with the observed sub-populations of binary asteroids, asteroid pairs and contact binaries. The foundation of this model is the asteroid-rotation model of Marzari et al. (2011) and Rossi et al. (2009), which incorporates both the YORP effect and collisional evolution. This work adds to that model the rotational fission hypothesis (i.e. when the rotation rate exceeds a critical value, erosion and binary formation occur; Scheeres 2007) and binary-asteroid evolution (Jacobson & Scheeres, 2011). The YORP-effect timescale for large asteroids with diameters D > ˜ 6 km is longer than the collision timescale in the main belt, thus the frequency of large asteroids is determined by a collisional equilibrium (e.g. Bottke 2005), but for small asteroids with diameters D < ˜ 6 km, the asteroid-population evolution model confirms that YORP-induced rotational fission destroys small asteroids more frequently than collisions. Therefore, the frequency of these small asteroids is determined by an equilibrium between the creation of new asteroids out of the impact debris of larger asteroids and the destruction of these asteroids by YORP-induced rotational fission. By introducing a new source of destruction that varies strongly with size, YORP-induced rotational fission alters the slope of the size-frequency distribution. Using the outputs of the asteroid-population evolution model and a 1-D collision evolution model, we can generate this new size-frequency distribution and it matches the change in slope observed by the SKADS survey (Gladman 2009). This agreement is achieved with both an accretional power-law or a truncated ''Asteroids were Born Big'' size-frequency distribution

  5. Spectral diversity and photometric behavior of main-belt and near-Earth vestoids and (4) Vesta: A study in preparation for the Dawn encounter

    NASA Astrophysics Data System (ADS)

    Hicks, Michael D.; Buratti, Bonnie J.; Lawrence, Kenneth J.; Hillier, John; Li, Jian-Yang; Reddy, Vishnu; Schröder, Stefan; Nathues, Andreas; Hoffmann, Martin; le Corre, Lucille; Duffard, Rene; Zhao, Hai-Bin; Raymond, Carol; Russell, Christopher; Roatsch, Thomas; Jaumann, Ralf; Rhoades, Heath; Mayes, Deronda; Barajas, Tzitlaly; Truong, Thien-Tin; Foster, James; McAuley, Amanda

    2014-06-01

    In anticipation of the Dawn Mission to 4 Vesta, we conducted a ground-based campaign of Bessel BVRI filter photometry of five V-type near-Earth asteroids over a wide range of solar phase angles. We also obtained medium-resolution optical spectroscopy (0.38 μm < λ < 0.92 μm; R ˜ 500) of sixteen near-Earth and main-belt V-type asteroids in order to investigate their spectral diversity and to draw connections between spacecraft data of Vesta and V-type asteroids. Our disk-integrated photometry extended the excursion in solar phase angle beyond the maximum of 24° available from Earth for Vesta to 87°, which is more typical of the geometry during the Dawn approach and mapping phases. The majority of our broad-band observations were obtained at the JPL 0.6-m Table Mountain Observatory but multiple nights were also contributed by the Calar Alto 1.2-m and 2.2-m telescopes, as well as by the Purple Mountain 1-m Schmidt. Our results include a determination of rotation periods for 4 asteroids, identification of a binary candidate and four new V-type asteroids, including a confirmation of two main-belt V-type asteroids beyond the Jupiter 1:3 resonance (Cruikshank, D.P., Tholen, D.J., Bell, J.F., Hartmann, W.K., Brown, R.H. [1991]. Icarus 89, 1-13; Lazzaro, D. et al. [2000]. Science 288, 2033-2035; Roig, F., Gil-Hutton, R. [2006]. Icarus 183(2), 411-419; Moskovitz, N.A., Jedicke, R., Gaidos, E., Willman, M., Nesvorný, D., Fevig, R., Ivezić, Ž. [2008]. Icarus 198, 77-90). This latter finding supports the hypothesis that some vestoids may be crustal fragments of a disrupted basaltic parent body compositionally similar to 4 Vesta. We also obtained rotationally resolved medium resolution spectra of Vesta during the Dawn orbit insertion phase, which will be valuable for calibration and comparison of spacecraft data. Modeling of a composite V-type asteroid phase curve yielded a generic photometric model for V asteroids. We also find that a significant amount of the spectral

  6. The Volatile Fraction of Comets as Quantified at Infrared Wavelengths - An Emerging Taxonomy and Implications for Natal Heritage

    NASA Technical Reports Server (NTRS)

    Mumma, M. J.; DiSanti, M. A.; Bonev, B. P.; Villanueva, G. L.; Magee-Sauer, K.; Gibb, E. L.; Paganini, L.; Radeva, Y. L.; Charnley, S. B.

    2012-01-01

    It is relatively easy to identify the reservoir from which a given comet was ejected. But dynamical models demonstrate that the main cometary reservoirs (Kuiper Belt, Oort Cloud) each contain icy bodies that formed in a range of environments in the protoplanetary disk, and the Oort Cloud may even contain bodies that formed in disks of sibling stars in the Sun s birth cluster. The cometary nucleus contains clues to the formative region(s) of its individual components. The composition of ices and rocky grains reflect a range of processes experienced by material while on the journey from the natal interstellar cloud core to the cometary nucleus. For that reason, emphasis is placed on classifying comets according to their native ices and dust (rather than orbital dynamics). Mumma & Charnley [1] reviewed the current status of taxonomies for comets and relation to their natal heritage.

  7. Small Comet Abundance and Solar System Location

    NASA Astrophysics Data System (ADS)

    Phillips, C. B.; Moore, J.; Zahnle, K.

    2001-12-01

    We present geological, historical, and observational evidence which implies that the proportion of small comets is related to where in the solar system the population is counted. A detailed count of craters in the 1-5 km size range on Jupiter's moon Europa yields a slope of -1.45 for the cumulative size-frequency crater distribution. This is strongly depleted in small objects relative to the far outer solar system. We compare the Europan distribution to crater counts on Neptune's moon Triton and extrapolated observational evidence of Kuiper Belt Objects. We find that small comets appear to be rarer at Triton than in the Kuiper Belt, and that small comets are five times rarer at Europa than they appear to be at Triton. We have extended our study into the inner solar system by considering the discovery histories of long and short period comets. We find that, while large comets have been discovered at ever-increasing rates over the last few centuries, small comets have not paralleled this increase. In one example, the known number of small Jupiter-family comets in Earth-crossing orbits has not changed significantly in the two and a half centuries since comet detection has been intensely pursued. In another example, we focus on the sungrazing comets as found by the SOHO satellite and otherwise. Many of the sungrazers are undoubtedly small comets. But 94 of the 95 known sungrazers follow the same orbit - i.e., they are fragments of one great comet disrupted by close passage to the Sun long ago. Thus SOHO could see unique small comets, if they were present, and so the number of unique small objects in the inner solar system is few to none. Small comets are therefore found relatively frequently in the outer solar system, but their numbers decrease by the orbit of Jupiter, and they are very rare in the inner solar system. One explanation for this decrease is the preferential sublimation and coupled sublimation-enhancing disaggregation of small icy bodies as they approach

  8. Caroline Lucretia Herschel -- Comet Huntress

    NASA Astrophysics Data System (ADS)

    Hughes, D. W.

    1999-04-01

    Caroline Herschel (1750-1848) was an active astronomer at a time when discovering comets, and calculating their orbits, was one of the main astronomical activities. She discovered eight comets and held the ladies' world record in this field until April 1987 when she was toppled from the podium by Carolyn S. Shoemaker. This paper places the Herschel cometary discoveries into the context of the contemporary cometary astronomy.

  9. Comet LINEAR Splits Further

    NASA Astrophysics Data System (ADS)

    2001-05-01

    made by Emmanuel Jehin, Andreas Jaunsen, Hermann Boehnhardt, Mario Kiekebusch, Hernan Nunez, Rodrigo Amestica, Christian Herrera, Francisco Delgado, Julio Navarrete (ESO VLT, Chile) and Richard West (ESO Garching, Germany). Technical information about the photos PR Photos 18a-b/01 are based on a 1-min exposure on May 16, 2001 at 23:10 hrs UT through an R-filtre with the VLT Test Camera at the Cassegrain focus (under the main mirror) of the 8.2-m VLT YEPUN (UT4) telescope on Paranal. Although the comet was low in the western sky, the atmospheric conditions were good and the seeing was excellent, 0.6 arcsec. The telescope was set to follow the motion of the comet in the sky. The fields shown measure 17 x 18 arcsec 2 and 27 x 21 arcsec 2 , respectively; 1 pixel = 0.0455 arcsec. North is up and East is left.

  10. Comet formation

    NASA Astrophysics Data System (ADS)

    Blum, J.

    2014-07-01

    There has been vast progress in our understanding of planetesimal formation over the past decades, owing to a number of laboratory experiments as well as to refined models of dust and ice agglomeration in protoplanetary disks. Coagulation rapidly forms cm-sized ''pebbles'' by direct sticking in collisions at low velocities (Güttler et al. 2010; Zsom et al. 2010). For the further growth, two model approaches are currently being discussed: (1) Local concentration of pebbles in nebular instabilities until gravitational instability occurs (Johansen et al. 2007). (2) A competition between fragmentation and mass transfer in collisions among the dusty bodies, in which a few ''lucky winners'' make it to planetesimal sizes (Windmark et al. 2012a,b; Garaud et al. 2013). Predictions of the physical properties of the resulting bodies in both models allow a distinction of the two formation scenarios of planetesimals. In particular, the tensile strength (i.e, the inner cohesion) of the planetesimals differ widely between the two models (Skorov & Blum 2012; Blum et al. 2014). While model (1) predicts tensile strengths on the order of ˜ 1 Pa, model (2) results in rather compactified dusty bodies with tensile strengths in the kPa regime. If comets are km-sized survivors of the planetesimal-formation era, they should in principle hold the secret of their formation process. Water ice is the prime volatile responsible for the activity of comets. Thermophysical models of the heat and mass transport close to the comet-nucleus surface predict water-ice sublimation temperatures that relate to maximum sublimation pressures well below the kPa regime predicted for formation scenario (2). Model (1), however, is in agreement with the observed dust and gas activity of comets. Thus, a formation scenario for cometesimals involving gravitational instability is favored (Blum et al. 2014).

  11. Belt-driven conveyor belts

    SciTech Connect

    Not Available

    1984-01-01

    An intermediate belt drive system offers a number of advantages over conventional systems, including lower power requirements and the ability to use lower quality, cheaper, conveyor belts. The advantages of a correctly designed belt conveyor with end pulley drives are included.

  12. Optical Studies of Active Comets

    NASA Technical Reports Server (NTRS)

    Jewitt, David

    1998-01-01

    This grant was to support optical studies of comets close enough to the sun to be outgassing. The main focus of the observations was drawn to the two extraordinarily bright comets Hyakutake and Hale-Bopp, but other active comets were also studied in detail during the period of funding. Major findings (all fully published) under this grant include: (1) Combined optical and submillimeter observations of the comet/Centaur P/Schwassmann-Wachmann 1 were used to study the nature of mass loss from this object. The submillimeter observations show directly that the optically prominent dust coma is ejected by the sublimation of carbon monoxide. Simultaneous optical-submillimeter observations allowed us to test earlier determinations of the dust mass loss rate. (2) We modelled the rotation of cometary nuclei using time-resolved images of dust jets as the primary constraint. (3) We obtained broad-band optical images of several comets for which we subsequently attempted submillimeter observations, in order to test and update the cometary ephemerides. (4) Broad-band continuum images of a set of weakly active comets and, apparently, inactive asteroids were obtained in BVRI using the University of Hawaii 2.2-m telescope. These images were taken in support of a program to test the paradigm that many near-Earth asteroids might be dead or dormant comets. We measured coma vs. nucleus colors in active comets (finding that coma particle scattering is different from, and cannot be simply related to, nucleus color). We obtained spectroscopic observations of weakly active comets and other small bodies using the HIRES spectrograph on the Keck 10-m telescope. These observation place sensitive limits to outgassing from these bodies, aided by the high (40,000) spectral resolution of HIRES.

  13. Rosetta following a living comet

    NASA Astrophysics Data System (ADS)

    Accomazzo, Andrea; Ferri, Paolo; Lodiot, Sylvain; Pellon-Bailon, Jose-Luis; Hubault, Armelle; Porta, Roberto; Urbanek, Jakub; Kay, Ritchie; Eiblmaier, Matthias; Francisco, Tiago

    2016-09-01

    The International Rosetta Mission was launched on 2nd March 2004 on its 10 year journey to rendezvous with comet 67P Churyumov-Gerasimenko. Rosetta performed comet orbit insertion on the 6th of August 2014, after which it characterised the nucleus and orbited it at altitudes as low as a few kilometres. In November 2014 Rosetta delivered the lander Philae to perform the first soft landing ever on the surface of a comet. The critical landing operations have been conducted with remarkable accuracy and will constitute one of the most important achievements in the history of spaceflight. After this critical operation, Rosetta began the escort phase of the comet in its journey in the Solar System heading to the perihelion, reached in August 2015. Throughout this period, the comet environment kept changing with increasing gas and dust emissions. A first phase of bound orbits was followed by a sequence of complex flyby segments which allowed the scientific instruments to perform in depth investigation of the comet environment and nucleus. The unpredictable nature of the comet activity forced the mission control team to implement unplanned changes to the flight plan prepared for this mission phase and to plan the whole mission in a more dynamic way than originally conceived. This paper describes the details of the landing operations and of the main comet escort phase. It also includes the mission status as achieved after perihelion and the findings about the evolution of the comet and its environment from a mission operations point of view. The lessons learned from this unique and complex operations phase and the plans for the next mission phases, which include a mission extension into 2016, are also described.

  14. Color Systematics of Comets and Related Bodies

    NASA Astrophysics Data System (ADS)

    Jewitt, David

    2015-12-01

    Most comets are volatile-rich bodies that have recently entered the inner solar system following long-term storage in the Kuiper belt and the Oort cloud reservoirs. These reservoirs feed several distinct, short-lived "small body" populations. Here, we present new measurements of the optical colors of cometary and comet-related bodies including long-period (Oort cloud) comets, Damocloids (probable inactive nuclei of long-period comets) and Centaurs (recent escapees from the Kuiper belt and precursors to the Jupiter family comets). We combine the new measurements with published data on short-period comets, Jovian Trojans and Kuiper belt objects to examine the color systematics of the comet-related populations. We find that the mean optical colors of the dust in short-period and long-period comets are identical within the uncertainties of measurement, as are the colors of the dust and of the underlying nuclei. These populations show no evidence for scattering by optically small particles or for compositional gradients, even at the largest distances from the Sun, and no evidence for ultrared matter. Consistent with earlier work, ultrared surfaces are common in the Kuiper belt and on the Centaurs, but not in other small body populations, suggesting that this material is hidden or destroyed upon entry to the inner solar system. The onset of activity in the Centaurs and the disappearance of the ultrared matter in this population begin at about the same perihelion distance (˜10 AU), suggesting that the two are related. Blanketing of primordial surface materials by the fallback of sub-orbital ejecta, for which we calculate a very short timescale, is the likely mechanism. The same process should operate on any mass-losing body, explaining the absence of ultrared surface material in the entire comet population. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the

  15. Chemical diversity in the comet population

    NASA Astrophysics Data System (ADS)

    Biver, Nicolas; Bockelée-Morvan, Dominique

    2016-10-01

    For the last 3 decades, infrared and microwave techniques have enabled the detection of up to 27 parent molecules in the coma of comets. Several molecules have been detected in over 40 different comets. A large diversity of composition is seen in the sample, comprising comets of various dynamical origins. Abundances relative to water for the molecules can vary by a factor 3 to more than 10. The taxonomic study of a sample of comets in which the abundance of several molecules (e.g., HCN, CH3OH, CO, CH4, C2H6, H2S, H2CO, CH3CN, CS, . . .) has been measured does not show any clear grouping. Except for fragments of a common parent comet, every observed comet shows a different composition. The absence of any clear correlation between the volatile content of the comets and their dynamical origin (Kuiper Belt versus Oort Cloud) is consistent with a common origin for these two populations. Their diversity in composition may also suggest that radial and temporal mixing in the early proto-planetary nebula may have played an important role.

  16. Vega: Two Belts and the Possibility of Planets

    NASA Image and Video Library

    2013-01-08

    In this diagram, the Vega system, which was already known to have a cooler outer belt of comets orange, is compared to our solar system with its asteroid and Kuiper belts. The ring of warm, rocky debris was detected using NASA Spitzer Space Telescope,

  17. The empty primordial asteroid belt.

    PubMed

    Raymond, Sean N; Izidoro, Andre

    2017-09-01

    The asteroid belt contains less than a thousandth of Earth's mass and is radially segregated, with S-types dominating the inner belt and C-types the outer belt. It is generally assumed that the belt formed with far more mass and was later strongly depleted. We show that the present-day asteroid belt is consistent with having formed empty, without any planetesimals between Mars and Jupiter's present-day orbits. This is consistent with models in which drifting dust is concentrated into an isolated annulus of terrestrial planetesimals. Gravitational scattering during terrestrial planet formation causes radial spreading, transporting planetesimals from inside 1 to 1.5 astronomical units out to the belt. Several times the total current mass in S-types is implanted, with a preference for the inner main belt. C-types are implanted from the outside, as the giant planets' gas accretion destabilizes nearby planetesimals and injects a fraction into the asteroid belt, preferentially in the outer main belt. These implantation mechanisms are simple by-products of terrestrial and giant planet formation. The asteroid belt may thus represent a repository for planetary leftovers that accreted across the solar system but not in the belt itself.

  18. The empty primordial asteroid belt

    PubMed Central

    Raymond, Sean N.; Izidoro, Andre

    2017-01-01

    The asteroid belt contains less than a thousandth of Earth’s mass and is radially segregated, with S-types dominating the inner belt and C-types the outer belt. It is generally assumed that the belt formed with far more mass and was later strongly depleted. We show that the present-day asteroid belt is consistent with having formed empty, without any planetesimals between Mars and Jupiter’s present-day orbits. This is consistent with models in which drifting dust is concentrated into an isolated annulus of terrestrial planetesimals. Gravitational scattering during terrestrial planet formation causes radial spreading, transporting planetesimals from inside 1 to 1.5 astronomical units out to the belt. Several times the total current mass in S-types is implanted, with a preference for the inner main belt. C-types are implanted from the outside, as the giant planets’ gas accretion destabilizes nearby planetesimals and injects a fraction into the asteroid belt, preferentially in the outer main belt. These implantation mechanisms are simple by-products of terrestrial and giant planet formation. The asteroid belt may thus represent a repository for planetary leftovers that accreted across the solar system but not in the belt itself. PMID:28924609

  19. CINE: Comet INfrared Excitation

    NASA Astrophysics Data System (ADS)

    de Val-Borro, Miguel; Cordiner, Martin A.; Milam, Stefanie N.; Charnley, Steven B.

    2017-08-01

    CINE calculates infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. One of the main mechanisms for molecular excitation in comets is the fluorescence by the solar radiation followed by radiative decay to the ground vibrational state. This command-line tool calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Fluorescence coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

  20. New Research by CCD Scanning for Comets and Asteroids

    NASA Technical Reports Server (NTRS)

    Gehrels, Tom; McMillan, Robert S.

    1997-01-01

    The purpose of Spacewatch is to explore the various populations of small objects within the solar system. Spacewatch provides data for studies of comets and asteroids, finds potential targets for space missions, and provides information on the environmental problem of possible impacts. Moving objects are discovered by scanning the sky with charge-coupled devices (CCDs) on the 0.9-meter Spacewatch Telescope of the University of Arizona on Kitt Peak. Each Spacewatch scan consists of three drift scan passes over an area of sky using a CCD filtered to a bandpass of 0.5-1.0 microns (approximately V+R+I with peak sensitivity at 0.7 micron). The effective exposure time for each pass is 143 seconds multiplied by the secant of the declination. We have been finding some 30,000 new asteroids per year and applying their statistics to the study of the collisional history of the solar system. As of the end of the observing run of Nov. 1997, Spacewatch had found a total of 153 Near-Earth Asteroids (NEAs) and 8 new comets since the project began in the 1980s, and had recovered one lost comet. The total number of NEAs found by Spacewatch big enough to be hazardous if they were to impact the Earth is 36. Spacewatch is also efficient in recovery of known comets and has detected and reported positions for more than 137,000 asteroids, mostly new ones in the main belt, including more than 16,000 asteroids designated by the Minor Planet Center (MPC).

  1. New Research by CCD Scanning for Comets and Asteroids

    NASA Technical Reports Server (NTRS)

    Gehrels, Tom

    1997-01-01

    Spacewatch was begun in 1980; its purpose is to explore the various populations of small objects within the solar system. Spacewatch provides data for studies of comets and asteroids, finds potential targets for space missions, and provides information on the environmental problem of possible impacts. Moving objects are discovered by scanning the sky with charge-coupled devices (CCDS) on the 0.9-meter Spacewatch Telescope of the University of Arizona on Kitt Peak. Each Spacewatch scan consists of three drift scan passes over an area of sky using a CCD filtered to a bandpass of 0.5-1.0 pm (approximately V+R+I with peak sensitivity at 0.7 pm). The effective exposure time for each pass is 143 seconds multiplied by the secant of the declination. The area covered by each scan is 32 arcminutes in declination by about 28 minutes of time in right ascension. The image scale is 1.05 arcseconds per pixel. Three passes take about 1.5 hours to complete and show motions of individual objects over a one hour time baseline. The limiting magnitude is about 21.5 in single scans. CCD scanning was developed by Spacewatch in the early 1980s, with improvements still being made - particularly by bringing a new 1.8-m Spacewatch Telescope on line. In the meantime, we have been finding some 30,000 new asteroids per year and applying their statistics to the study of the collisional history of the solar system. Spacewatch had found a total of 150 Near-Earth Asteroids (NEAS) and 8 new comets, and had recovered one lost comet (P/Spitaler in 1993). Spacewatch is also efficient in recovery of known comets and has detected and reported positions for more than 137,000 asteroids, mostly new ones in the main belt, including more than 10,882 asteroids designated by the Minor Planet Center (MPC).

  2. Helium and Neon in Comets

    NASA Technical Reports Server (NTRS)

    Jewitt, David

    1996-01-01

    Two comets were observed with EUVE in late 1994. Both comet Mueller and comet Borrelly are short-period comets having well established orbital elements and accurate ephemerides. Spectra of 40 ksec were taken of each. No evidence for emission lines from either Helium or Neon was detected. We calculated limits on the production rates of these atoms (relative to solar) assuming a standard isotropic outflow model, with a gas streaming speed of 1 km/s. The 3-sigma (99.7% confidence) limits (1/100,000 for He, 0.8 for Ne) are based on a conservative estimate of the noise in the EUVE spectra. They are also weakly dependent on the precise pointing and tracking of the EUVE field of view relative to the comet during the integrations. These limits are consistent with ice formation temperatures T greater than or equal to 30 K, as judged from the gas trapping experiments of Bar-Nun. For comparison, the solar abundances of these elements are He/O = 110, Ne/O = 1/16. Neither limit was as constraining as we had initially hoped, mainly because comets Mueller and Borrelly were intrinsically less active than anticipated.

  3. CCD photometry of distant comets. III. Ensemble properties of Jupiter-family comets

    NASA Astrophysics Data System (ADS)

    Lowry, S. C.; Fitzsimmons, A.; Collander-Brown, S.

    2003-01-01

    We describe the results of a ground-based observational ``snapshot'' study of Jupiter-family comets in the heliocentric range 2.29 AU <= Rh <= 5.72 AU. Results are presented based on observations from the 1m JKT on the island of La Palma. A total of 25 comets were targeted with 15 being positively detected. Broad-band VRI photometry was performed to determine dimensions, colour indices, and dust production rates in terms of the ``Afrho '' formalism. The results for selected comets are compared with previous investigations. Ensemble properties of the Jupiter-family population have been investigated by combining the results presented here with those of Lowry et al. (\\cite{Lowry1999}), and Lowry & Fitzsimmons (\\cite{Lowry2001}). We find that the cumulative size distribution of the Jupiter-family comets can be described by a power law of the form; Sigma (> r)~ r-1.6 +/- 0.1. This size distribution is considerably shallower than that found for the observed Edgeworth-Kuiper belt objects, which may reflect either an intrinsic difference at small km-sizes in the belt, or the various processes affecting the nuclei of comets as their orbits evolve from the Edgeworth-Kuiper belt to the inner Solar system. Also, there would appear to be no correlation between nuclear absolute magnitude and perihelion distance. Finally, for the sample of active comets, there is a distinct correlation between absolute R band magnitude and perihelion distance, which can be explained by either a discovery bias towards brighter comets or in terms of ``rubble'' mantle formation.

  4. Comet rendezvous mission study

    NASA Technical Reports Server (NTRS)

    Friedlander, A. L.; Wells, W. C.

    1971-01-01

    Four periodic comets with perihelia between 1980 and 1986 (Encke, d'Arrest, Kipff, and Halley) are used as candidates for the comet rendezvous mission study. All these comet apparitions are especially favorable for rendezvous missions, because of early earth-based comet recovery, good opportunities to view their activity from earth, and reasonable launch vehicle and trajectory requirements for nominal payloads.

  5. Hubble Witnesses Comet Crash

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Quick Time Movie for PIA02122 Hubble Witnesses Comet Crash

    [figure removed for brevity, see original site] Figure 1: Hubble Witnesses Comet Crash

    These pictures of comet Tempel 1 were taken by NASA's Hubble Space Telescope. They show the comet before and after it ran over NASA's Deep Impact probe.

  6. Comet Bradfield 1979 X - The gassiest comet

    NASA Technical Reports Server (NTRS)

    Ahearn, M. F.; Birch, P. V.; Millis, R. L.

    1981-01-01

    The Comet Bradfield 1979 X provided the most recent opportunity to obtain quantitative photometric data on a comet. Although the comet was not unusually luminous, its very close approach to earth made it possible to observe it from the time of discovery at a heliocentric distance of just over 0.5 AU until it was beyond 1.5 AU from the Sun. The observations conducted are discussed along with aspects of data reduction. It was found that the OH production of comets can be experimentally studied on the basis of a routine procedure. The Comet Bradfield 1979 X was one of the gassiest comets ever observed, comparable to Comet P/Encke. The production rates of all molecular species were found to decline sharply with heliocentric distance.

  7. HUBBLE DETECTION OF COMET NUCLEUS AT FRINGE OF SOLAR SYSTEM

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is sample data from NASA's Hubble Space Telescope that illustrates the detection of comets in the Kuiper Belt, a region of space beyond the orbit of the planet Neptune. This pair of images, taken with the Wide Field Planetary Camera 2 (WFPC2), shows one of the candidate Kuiper Belt objects found with Hubble. Believed to be an icy comet nucleus several miles across, the object is so distant and faint that Hubble's search is the equivalent of finding the proverbial needle-in-haystack. Each photo is a 5-hour exposure of a piece of sky carefully selected such that it is nearly devoid of background stars and galaxies that could mask the elusive comet. The left image, taken on August 22, 1994, shows the candidate comet object (inside circle) embedded in the background. The right picture, take of the same region one hour forty-five minutes later shows the object has apparently moved in the predicted direction and rate of motion for a kuiper belt member. The dotted line on the images is a possible orbit that this Kuiper belt comet is following. A star (lower right corner) and a galaxy (upper right corner) provide a static background reference. In addition, other objects in the picture have not moved during this time, indicating they are outside our solar system. Through this search technique astronomers have identified 29 candidate comet nuclei belonging to an estimated population of 200 million particles orbiting the edge of our solar system. The Kupier Belt was theorized 40 years ago, and its larger members detected several years ago. However, Hubble has found the underlying population of normal comet-sized bodies. Credit: A. Cochran (University of Texas) and NASA

  8. HUBBLE DETECTION OF COMET NUCLEUS AT FRINGE OF SOLAR SYSTEM

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is sample data from NASA's Hubble Space Telescope that illustrates the detection of comets in the Kuiper Belt, a region of space beyond the orbit of the planet Neptune. This pair of images, taken with the Wide Field Planetary Camera 2 (WFPC2), shows one of the candidate Kuiper Belt objects found with Hubble. Believed to be an icy comet nucleus several miles across, the object is so distant and faint that Hubble's search is the equivalent of finding the proverbial needle-in-haystack. Each photo is a 5-hour exposure of a piece of sky carefully selected such that it is nearly devoid of background stars and galaxies that could mask the elusive comet. The left image, taken on August 22, 1994, shows the candidate comet object (inside circle) embedded in the background. The right picture, take of the same region one hour forty-five minutes later shows the object has apparently moved in the predicted direction and rate of motion for a kuiper belt member. The dotted line on the images is a possible orbit that this Kuiper belt comet is following. A star (lower right corner) and a galaxy (upper right corner) provide a static background reference. In addition, other objects in the picture have not moved during this time, indicating they are outside our solar system. Through this search technique astronomers have identified 29 candidate comet nuclei belonging to an estimated population of 200 million particles orbiting the edge of our solar system. The Kupier Belt was theorized 40 years ago, and its larger members detected several years ago. However, Hubble has found the underlying population of normal comet-sized bodies. Credit: A. Cochran (University of Texas) and NASA

  9. Activity in distant comets

    NASA Technical Reports Server (NTRS)

    Luu, Jane X.

    1992-01-01

    Activity in distant comets remains a mystery in the sense that we still have no complete theory to explain the various types of activity exhibited by different comets at large distances. This paper explores the factors that should play a role in determining activity in a distant comet, especially in the cases of comet P/Tempel 2, comet Schwassmann-Wachmann 1, and 2060 Chiron.

  10. ESA Unveils Its New Comet Chaser.

    NASA Astrophysics Data System (ADS)

    1999-07-01

    October 2007 before heading away from the Sun towards Comet Wirtanen. As it bounces around the Solar System, Rosetta will also make two excursions into the main asteroid belt, where it will obtain the first close-up images and information on two contrasting objects, 4979 Otawara and 140 Siwa. Scientists believe Otawara is less than 20 km across, whereas Siwa is probably 110 km in diameter, much larger than any asteroid which has so far been visited by spacecraft. Rosetta will fly to within 1,000 km of Otawara in July 2006, followed by a similar rendezvous with Siwa two years later. However, the most difficult phase of the mission will be the final rendezvous with the fast-moving comet (the foreseen date for the rendezvous manoeuvre is 27 November 2011, close approach is set for 20 May 2012 and orbit insertion around the nucleus is set for 28 May 2012). Thus, after a 5.3 billion km space odyssey, Rosetta will make first contact with Wirtanen about 675 million km from the Sun. At this distance, sunlight is 20 times weaker than on Earth, and the comet's nucleus will still be frozen and inactive. Once the navigation team are able to determine the comet's exact location from images returned by the spacecraft camera, a series of braking manoeuvres will allow Rosetta to match speed and direction with its target. After about seven months of edging closer, Rosetta will eventually close to within 2 km of Wirtanen's frozen nucleus. From its close orbit above the tiny nucleus, Rosetta will be able to send back the most detailed images and information ever obtained of a comet. When a suitable landing site has been chosen, about a month after global mapping starts, the orbiter will release a 100 kg lander onto the comet's solid surface. Touchdown must be quite slow - less than one metre per second - to allow for the almost negligible gravitational pull of the tiny nucleus. In order to ensure that the lander does not bounce and disappear into space, an anchoring harpoon will be fired

  11. Presence and control of evaporite top seals on occurrence and distribution of hydrocarbon traps: main fairway, Central Overthrust belt, Wyoming and Utah

    SciTech Connect

    McIntyre, J.F.

    1988-02-01

    In the Central Overthrust belt fairway, there are 18 known productive formations ranging from Cambrian to Cretaceous in age. Four units - the Ordovician Big Horn formation, Mississippian Mission Canyon formation, Jurassic Nugget formation, and Jurassic Twin Creek Formation - account for 99% of a reported 1.4 billion bbl of oil estimated recoverable reserves discovered to date. A critical factor necessary for significant hydrocarbon accumulations is the presence of effective evaporite seals above these reservoirs. Major accumulations exist in anticlines associated with Paleozoic or Jurassic cutoffs in the hanging wall of the Absaroka thrust with recognized source rocks occurring in the Cretaceous footwall section. Vertical migration is required to source the overlying reservoirs. Migration pathways are via hanging wall cutoffs of these reservoirs or through fractures in the cores of the structures. Hanging wall reservoirs either lacking top seals or having top seals disrupted by extensive fracturing due to folding or faulting, permit vertical migration into higher, more effectively sealed reservoirs. In the Overthrust producing fairway, anhydrites of the Mission Canyon formation and Gypsum Spring Member of the Twin Creek formation as well as the Jurassic Preuss salt are the three effective seal units. Analysis of Overthrust belt traps suggests that the presence and ductile nature of these evaporite seals are important controlling factors for the significant hydrocarbon accumulations in this highly deformed terrain.

  12. The Low Albedo of Comets

    NASA Astrophysics Data System (ADS)

    Buratti, B. J.; Choukroun, M.; Bauer, J. M.

    2016-12-01

    Comets are among the handful of objects with very low albedos, in the 0.02-0.06 range. Dark material is common in the outer Solar System, but analysis of the spectra and albedo of this material by spacecraft including Cassini and New Horizons shows that it is diverse, covering a range of compositions. Some is neutral-colored in the visible, such as that found on Phoebe, while some is very red, such as that on the surfaces of D-type asteroids or the low-albedo side of Iapetus. The different types of low-albedo material may reflect both compositional diversity, including contamination by volatiles or darkening agents, and divergent alteration histories. The key question is whether a particular sub-type of low albedo material is pristine - an unprocessed accumulation of interstellar dust - or an end product of polymerization and photolysis into ever more complex materials. Comets have albedos similar to the leading hemisphere of Iapetus, the surface of Titan, and the lowest-albedo C-type and D-type asteroids. Observations by the WISE and NEOWISE cameras show that comets have consistently low albedos (1). The first quantitative measurement of low-albedo material in the Kuiper Belt, from which comets such as Jupiter Family Comets including 67P/Churyumov-Gerasimenko come, shows that even this material is not as dark as that found on comets (2). Results from both Stardust (3) and more recently Rosetta (4, 5) show that cometary surfaces contain prebiotic molecules, including the amino acid glycine. Other very low albedo objects have also been connected to complex organic molecules: on Iapetus, PAHs have been detected (6), and Titan's surface is believed to be covered with hydrocarbons produced in its haze layer (7). The presence of organic molecules, including complex ones, could be the unique characteristic of the very darkest material. The delivery of pre-biotic material from comets to the young Earth could represent a key link in the origins of terrestrial life. (1

  13. Infrared Kuiper Belt Constraints

    SciTech Connect

    Teplitz, V.L.; Stern, S.A.; Anderson, J.D.; Rosenbaum, D.; Scalise, R.J.; Wentzler, P.

    1999-05-01

    We compute the temperature and IR signal of particles of radius {ital a} and albedo {alpha} at heliocentric distance {ital R}, taking into account the emissivity effect, and give an interpolating formula for the result. We compare with analyses of {ital COBE} DIRBE data by others (including recent detection of the cosmic IR background) for various values of heliocentric distance {ital R}, particle radius {ital a}, and particle albedo {alpha}. We then apply these results to a recently developed picture of the Kuiper belt as a two-sector disk with a nearby, low-density sector (40{lt}R{lt}50{endash}90 AU) and a more distant sector with a higher density. We consider the case in which passage through a molecular cloud essentially cleans the solar system of dust. We apply a simple model of dust production by comet collisions and removal by the Poynting-Robertson effect to find limits on total and dust masses in the near and far sectors as a function of time since such a passage. Finally, we compare Kuiper belt IR spectra for various parameter values. Results of this work include: (1) numerical limits on Kuiper belt dust as a function of ({ital R}, {ital a}, {alpha}) on the basis of four alternative sets of constraints, including those following from recent discovery of the cosmic IR background by Hauser et al.; (2) application to the two-sector Kuiper belt model, finding mass limits and spectrum shape for different values of relevant parameters including dependence on time elapsed since last passage through a molecular cloud cleared the outer solar system of dust; and (3) potential use of spectral information to determine time since last passage of the Sun through a giant molecular cloud. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}

  14. Rosetta - a comet ride to solve planetary mysteries

    NASA Astrophysics Data System (ADS)

    2003-01-01

    be kept in hibernation during most of its 8-year trek towards Wirtanen. What makes Rosetta's cruise so long? To reach Comet Wirtanen, the spacecraft needs to go out in deep space as far from the Sun as Jupiter is. No launcher could possibly get Rosetta there directly. ESA's spacecraft will gather speed from gravitational ‘kicks’ provided by three planetary fly-bys: one of Mars in 2005 and two of Earth in 2005 and 2007. During the trip, Rosetta will also visit two asteroids, Otawara (in 2006) and Siwa (in 2008). During these encounters, scientists will switch on Rosetta's instruments for calibration and scientific studies. Long trips in deep space include many hazards, such as extreme changes in temperature. Rosetta will leave the benign environment of near-Earth space to the dark, frigid regions beyond the asteroid belt. To manage these thermal loads, experts have done very tough pre-launch tests to study Rosetta's endurance. For example, they have heated its external surfaces to more than 150°C, then quickly cooled it to -180°C in the next test. The spacecraft will be fully reactivated prior to the comet rendezvous manoeuvre in 2011. Then, Rosetta will orbit the comet - an object only 1.2 km wide - while it cruises through the inner Solar System at 135 000 kilometres per hour. At that time of the rendezvous - around 675 million km from the Sun - Wirtanen will hardly show any surface activity. It means that the carachteristic coma (the comet’s ‘atmosphere’) and the tail will not be formed yet, because of the large distance from the Sun. The comet's tail is in fact made of dust grains and frozen gases from the comet's surface that vapourise because of the Sun's heat. During 6-month, Rosetta will extensively map the comet surface, prior to selecting a landing site. In July 2012, the lander will self-eject from the spacecraft from a height of just one kilometre. Touchdown will take place at walking speed - less than 1 metre per second. Immediately after

  15. Physical and dynamical properties of a quasi-Hilda comet , 212P/2000YN30

    NASA Astrophysics Data System (ADS)

    Cheng, Y.-C.; Ip, W.-H.

    2012-05-01

    We detected an outburst event on comet 212P in the 3:2 MMR belt of Jupiter for only 3 months in 2009. It has a typical color trend as common Jupiter-family Comets. From our clone particle orbital simulation, the half-lifetime is about 0.2 Myrs.

  16. Lightcurves and rotational periods of comet-sized Jovian Trojan asteroids

    NASA Astrophysics Data System (ADS)

    French, L.; Stephens, R.; Coley, D.; Wasserman, L.

    2014-07-01

    The Jovian Trojans are among the most enigmatic objects in the Solar System. They have been studied less than main-belt asteroids because of their low albedos and greater distance from the Sun. Several lines of evidence support a common origin for the Jovian Trojan asteroids and cometary nuclei. Their spectra and low albedos bear a strong resemblance to those of comets. The Nice Model predicts that the Trojans may well be objects that originated with today's Kuiper Belt Objects which predicts that today's Trojans were trapped in their current locations at Jupiter's L4 and L5 points after Saturn and Jupiter passed through a 2:1 resonance. We are surveying Trojan rotation properties to test the Nice Model hypothesis. One approach is a comparison of rotation properties of similar-sized Trojans and comets. We present new lightcurve information for several Trojans ≲ 30 km in diameter, more than doubling the number of objects in this size range for which some rotation information is known. The minimum densities for objects with complete lightcurves are estimated and are found to be comparable to those measured for cometary nuclei. Observations were obtained using the Cerro Tololo (CTIO) Blanco 4-m telescope, the CTIO 0.9-m telescope, and 0.4-m and 0.35-m telescopes at the Center for Solar System Studies (CS3) from 2011 August to 2014 May. The lower limit of densities of the small Trojans in our study are comparable to the densities for the two Trojans which have been directly measured, and those of similar sized comets. These results suggest these Trojans have an icy composition with significant amount of internal space; they are consistent with a comet-like composition for these bodies.

  17. High Resolution 3D Radar Imaging of Comet Interiors

    NASA Astrophysics Data System (ADS)

    Asphaug, E. I.; Gim, Y.; Belton, M.; Brophy, J.; Weissman, P. R.; Heggy, E.

    2012-12-01

    Knowing the interiors of comets and other primitive bodies is fundamental to our understanding of how planets formed. We have developed a Discovery-class mission formulation, Comet Radar Explorer (CORE), based on the use of previously flown planetary radar sounding techniques, with the goal of obtaining high resolution 3D images of the interior of a small primitive body. We focus on the Jupiter-Family Comets (JFCs) as these are among the most primitive bodies reachable by spacecraft. Scattered in from far beyond Neptune, they are ultimate targets of a cryogenic sample return mission according to the Decadal Survey. Other suitable targets include primitive NEOs, Main Belt Comets, and Jupiter Trojans. The approach is optimal for small icy bodies ~3-20 km diameter with spin periods faster than about 12 hours, since (a) navigation is relatively easy, (b) radar penetration is global for decameter wavelengths, and (c) repeated overlapping ground tracks are obtained. The science mission can be as short as ~1 month for a fast-rotating JFC. Bodies smaller than ~1 km can be globally imaged, but the navigation solutions are less accurate and the relative resolution is coarse. Larger comets are more interesting, but radar signal is unlikely to be reflected from depths greater than ~10 km. So, JFCs are excellent targets for a variety of reasons. We furthermore focus on the use of Solar Electric Propulsion (SEP) to rendezvous shortly after the comet's perihelion. This approach leaves us with ample power for science operations under dormant conditions beyond ~2-3 AU. This leads to a natural mission approach of distant observation, followed by closer inspection, terminated by a dedicated radar mapping orbit. Radar reflections are obtained from a polar orbit about the icy nucleus, which spins underneath. Echoes are obtained from a sounder operating at dual frequencies 5 and 15 MHz, with 1 and 10 MHz bandwidths respectively. The dense network of echoes is used to obtain global 3D

  18. Rosetta Comet Spreads its Jets

    NASA Image and Video Library

    2014-10-24

    This image was taken by the Optical, Spectroscopic, and Infrared Remote Imaging System, Rosetta main onboard scientific imaging system, on Sept. 10, 2014. Jets of cometary activity can be seen along almost the entire body of the comet. http://photojournal.jpl.nasa.gov/catalog/PIA18886

  19. Formation and evolution of the trans-Neptunian belt and dust

    NASA Astrophysics Data System (ADS)

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

    Trans-Neptunian objects (TNOs) with diameter greater than 100 km currently moving in not too eccentric orbits could be formed directly by the contraction of large rarefied condensations. Along with the gravitational influence of planets, gravitational interactions of TNOs played a certain role in their orbital evolution as well. More than 20% of Earth-crossing objects could have come from the trans-Neptunian belt. TNOs and Centaurs (invisible comets mainly beyond Jupiter) could produce an important contribution to the dust content of the interplanetary dust cloud.

  20. Comet Odyssey: Comet Surface Sample Return

    NASA Astrophysics Data System (ADS)

    Weissman, Paul R.; Bradley, J.; Smythe, W. D.; Brophy, J. R.; Lisano, M. E.; Syvertson, M. L.; Cangahuala, L. A.; Liu, J.; Carlisle, G. L.

    2010-10-01

    Comet Odyssey is a proposed New Frontiers mission that would return the first samples from the surface of a cometary nucleus. Stardust demonstrated the tremendous power of analysis of returned samples in terrestrial laboratories versus what can be accomplished in situ with robotic missions. But Stardust collected only 1 milligram of coma dust, and the 6.1 km/s flyby speed heated samples up to 2000 K. Comet Odyssey would collect two independent 800 cc samples directly from the surface in a far more benign manner, preserving the primitive composition. Given a minimum surface density of 0.2 g/cm3, this would return two 160 g surface samples to Earth. Comet Odyssey employs solar-electric propulsion to rendezvous with the target comet. After 180 days of reconnaissance and site selection, the spacecraft performs a "touch-and-go” maneuver with surface contact lasting 3 seconds. A brush-wheel sampler on a remote arm collects up to 800 cc of sample. A duplicate second arm and sampler collects the second sample. The samples are placed in a return capsule and maintained at colder than -70 C during the return flight and at colder than -30 C during re-entry and for up to six hours after landing. The entire capsule is then refrigerated and transported to the Astromaterials Curatorial Facility at NASA/JSC for initial inspection and sample analysis by the Comet Odyssey team. Comet Odyssey's planned target was comet 9P/Tempel 1, with launch in December 2017 and comet arrival in June 2022. After a stay of 300 days at the comet, the spacecraft departs and arrives at Earth in May 2027. Comet Odyssey is a forerunner to a flagship Cryogenic Comet Sample Return mission that would return samples from deep below the nucleus surface, including volatile ices. This work was supported by internal funds from the Jet Propulsion Laboratory.

  1. Comet Surface Sampling Technologies

    NASA Astrophysics Data System (ADS)

    Zacny, K.; Chu, P.; Paulsen, G.; Indyk, S.

    2014-06-01

    The goal of the Comet Surface Sample Return (CSSR) is to acquire and return to Earth a ≥500 cc) sample. Honeybee developed several sampling technologies including a standalone CSSR Probe (CSSRP) and Pyramid Comet Sampler (PyCoS).

  2. Bye, Bye Comet

    NASA Image and Video Library

    SOHO watched as a fairly bright comet dove towards the Sun in a white streak and was not seen again after its close encounter (May 10-11, 2011). The comet, probably part of the Kreutz family of com...

  3. Flight of the Comet

    NASA Image and Video Library

    This video clip was compiled from images taken by NASA's EPOXI mission spacecraft during its flyby of comet Hartley 2 on Nov. 4, 2010. During the encounter, the spacecraft and comet whisked past ea...

  4. Flight of the Comet

    NASA Image and Video Library

    2010-11-05

    Image taken by NASA EPOXI mission spacecraft during its flyby of comet Hartley 2 on Nov. 4, 2010. The spacecraft came within about 700 kilometers 435 miles of the comet nucleus at the time of closest approach.

  5. Nongravitational forces on comets

    NASA Technical Reports Server (NTRS)

    Marsden, B. G.

    1976-01-01

    Methods are presented and discussed for determining the effects of nongravitational forces on the orbits of comets. These methods are applied to short-period and long-period comets. Results are briefly described.

  6. CometQ: An automated tool for the detection and quantification of DNA damage using comet assay image analysis.

    PubMed

    Ganapathy, Sreelatha; Muraleedharan, Aparna; Sathidevi, Puthumangalathu Savithri; Chand, Parkash; Rajkumar, Ravi Philip

    2016-09-01

    DNA damage analysis plays an important role in determining the approaches for treatment and prevention of various diseases like cancer, schizophrenia and other heritable diseases. Comet assay is a sensitive and versatile method for DNA damage analysis. The main objective of this work is to implement a fully automated tool for the detection and quantification of DNA damage by analysing comet assay images. The comet assay image analysis consists of four stages: (1) classifier (2) comet segmentation (3) comet partitioning and (4) comet quantification. Main features of the proposed software are the design and development of four comet segmentation methods, and the automatic routing of the input comet assay image to the most suitable one among these methods depending on the type of the image (silver stained or fluorescent stained) as well as the level of DNA damage (heavily damaged or lightly/moderately damaged). A classifier stage, based on support vector machine (SVM) is designed and implemented at the front end, to categorise the input image into one of the above four groups to ensure proper routing. Comet segmentation is followed by comet partitioning which is implemented using a novel technique coined as modified fuzzy clustering. Comet parameters are calculated in the comet quantification stage and are saved in an excel file. Our dataset consists of 600 silver stained images obtained from 40 Schizophrenia patients with different levels of severity, admitted to a tertiary hospital in South India and 56 fluorescent stained images obtained from different internet sources. The performance of "CometQ", the proposed standalone application for automated analysis of comet assay images, is evaluated by a clinical expert and is also compared with that of a most recent and related software-OpenComet. CometQ gave 90.26% positive predictive value (PPV) and 93.34% sensitivity which are much higher than those of OpenComet, especially in the case of silver stained images. The

  7. A Million Comet Pieces

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] A Million Comet Pieces (poster version)

    This infrared image from NASA's Spitzer Space Telescope shows the broken Comet 73P/Schwassman-Wachmann 3 skimming along a trail of debris left during its multiple trips around the sun. The flame-like objects are the comet's fragments and their tails, while the dusty comet trail is the line bridging the fragments.

    Comet 73P /Schwassman-Wachmann 3 began to splinter apart in 1995 during one of its voyages around the sweltering sun. Since then, the comet has continued to disintegrate into dozens of fragments, at least 36 of which can be seen here. Astronomers believe the icy comet cracked due the thermal stress from the sun.

    The Spitzer image provides the best look yet at the trail of debris left in the comet's wake after its 1995 breakup. The observatory's infrared eyes were able to see the dusty comet bits and pieces, which are warmed by sunlight and glow at infrared wavelengths. This comet debris ranges in size from pebbles to large boulders. When Earth passes near this rocky trail every year, the comet rubble burns up in our atmosphere, lighting up the sky in meteor showers. In 2022, Earth is expected to cross close to the comet's trail, producing a noticeable meteor shower.

    Astronomers are studying the Spitzer image for clues to the comet's composition and how it fell apart. Like NASA's Deep Impact experiment, in which a probe smashed into comet Tempel 1, the cracked Comet 73P/Schwassman-Wachmann 3 provides a perfect laboratory for studying the pristine interior of a comet.

    This image was taken from May 4 to May 6 by Spitzer's multi-band imaging photometer, using its 24-micron wavelength channel.

  8. Radiation belts of jupiter.

    PubMed

    Stansberry, K G; White, R S

    1973-12-07

    Predictions of Jupiter's electron and proton radiation belts are based mainly on decimeter observations of 1966 and 1968. Extensive calculations modeling radial diffusion of particles inward from the solar wind and electron synchrotron radiation are used to relate the predictions and observations.

  9. The comets of 1999

    NASA Astrophysics Data System (ADS)

    Shanklin, J.

    2009-12-01

    This report is the tenth in the annual series which gives for each comet: the discovery details, orbital data and general information, magnitude parameters and BAA Comet Section observations. Further details of the analysis techniques used in this report are given in an earlier paper. Ephemerides for the comets predicted to return during the year can be found in the BAA or ICQ Handbooks.

  10. The comets of 2000

    NASA Astrophysics Data System (ADS)

    Shanklin, J. D.

    2010-08-01

    This report is the eleventh in the annual series which gives for each comet: the discovery details, orbital data and general information, magnitude parameters and BAA Comet Section observations. Further details of the analysis techniques used in this report are given in an earlier paper. Ephemerides for the comets predicted to return during the year can be found in the BAA or ICQ Handbooks.

  11. Newton and comets

    NASA Astrophysics Data System (ADS)

    Bork, Alfred

    1987-12-01

    The publication of Isaac Newton's ``notions about motion'' 300 years ago was a major moment in the history of science. In the period just before 1687 Newton's correspondence was much concerned with comets. In this period two bright comets were seen. These comets appear to have been a major stimulation to Newton's work on mechanics.

  12. Is (1) Ceres a Small Planet or a Large Comet?

    NASA Astrophysics Data System (ADS)

    Küppers, M.; O'Rourke, L.; Bockelée-Morvan, D.; Zakharov, V.; Lee, S.; Von Allmen, P.; Carry, B.; Teyssier, D.; Marston, A.; Müller, T.; Crovisier, J.; Barucci, M. A.; Moreno, R.

    2014-12-01

    The snowline conventionally divides Solar System objects into dry bodies, ranging out to the main asteroid belt, and icy bodies beyond the belt. Recently, the detection of dust emission from "main-belt comets" and of hydration features and possible water ice absorption on some main-belt asteroids together with theories of migration of small bodies in the solar system cast some doubts on the classical picture. Ceres, contributing about 30 % of the mass of the asteroid belt, is thought to be differentiated into an icy core and a silicate mantle and hydrated minerals were found on infrared spectra of its surface. A marginal detection of OH, a photodissociation product of water was reported in 1991, but questioned by later, more sensitive observations.. Observations of Ceres with the Heterodyne Instrument for the Far Infrared (HIFI) on the Herschel Space Observatory in the context of the MACH 11 guaranteed time program and with a follow up DDT program detected water vapour from Ceres on 3 occasions in 2012 and 2013. The production rate of water on Ceres is a few times 1026 s-1. The signal from the water vapour from Ceres was found to be linearly polarized during some of the observations, with the absorption being stronger in the horizontal branch. The measured line area ratio of up to 2.5 between H and V polarizations is so far unexplained. The water signal varies on time scales of hours. Those variations are interpreted as localized sources on Ceres surface rotating into and out of the hemisphere visible by Herschel. The time variability is consistent with those sources being dark features known from ground-based adaptive optics observations. The water vapour on Ceres may be either produced by near surface ice heated by sunlight (cometary activity) or by cryovolcanoes or geysers getting their energy from Ceres' interior. In the first case the production rate is expected to peak around perihelion, while for volcanic the time variations are expected to be more

  13. Dust particles from comets and asteroids collected at the Earth's orbit: Parent-daughter relationships

    NASA Technical Reports Server (NTRS)

    Jackson, A. A.; Zook, H. A.

    1991-01-01

    The relative contributions of comets and asteroids to the reservoir of dust in the interplanetary medium is not well known. There are direct observations of dust released from comets and there is evidence to associate the IRAS dust bands with possible collisions of Asteroids in the main belt. It is believed that one may combine lab analysis of the physics and chemistry of captured particles with orbital data in order to identify comet and asteroid parent bodies. It is possible to use the collected orbits of the dust to connect with its source in two ways. One is to consider the long time orbit evolution of the dust under Poynting-Robertson drag. The other is to look at the prompt orbit change of dust from comets onto trajectories that intersect the earth's orbit. In order to characterize the orbits of dust particles evolved over a long period of time, a study of its orbital evolution was undertaken. Various parameters associated with these dust orbits as they cross the Earth's orbit were considered in order to see if one may discriminate between particles evolved from comets and asteroids. The method was to calculate by a numerical procedure the orbits of dust particles after they left their parent bodies. It appears that as the particles pass the Earth's orbit, asteroidal grains and cometary grains can be differentiated on the basis of their measured orbital eccentricities even after much planetary perturbation. Broad parent daughter associations can be made on this basis from measurement of their trajectories intercepted in earth orbit.

  14. Abstracts for the International Conference on Asteroids, Comets, Meteors 1991

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Topics addressed include: chemical abundances; asteroidal belt evolution; sources of meteors and meteorites; cometary spectroscopy; gas diffusion; mathematical models; cometary nuclei; cratering records; imaging techniques; cometary composition; asteroid classification; radio telescopes and spectroscopy; magnetic fields; cosmogony; IUE observations; orbital distribution of asteroids, comets, and meteors; solar wind effects; computerized simulation; infrared remote sensing; optical properties; and orbital evolution.

  15. Disintegration of comet nuclei

    NASA Astrophysics Data System (ADS)

    Ksanfomality, Leonid V.

    2012-02-01

    The breaking up of comets into separate pieces, each with its own tail, was seen many times by astronomers of the past. The phenomenon was in sharp contrast to the idea of the eternal and unchangeable celestial firmament and was commonly believed to be an omen of impending disaster, especially for comets with tails stretching across half the sky. It is only now that we have efficient enough space exploration tools to see comet nuclei and even - in the particular case of small comet Hartley-2 in 2010 - to watch their disintegration stage. There are also other suspected candidates for disintegration in the vast family of comet nuclei and other Solar System bodies.

  16. Reality of comet nucleus.

    NASA Technical Reports Server (NTRS)

    Lyttleton, R. A.

    1972-01-01

    The prime problem of a comet mission must be to settle whether the cometary nucleus has an actual tangible material existence, or whether it arises from some optical effect present only at times within comets. The absence of any large particles in a comet seems to be demonstrated by certain meteor showers. A feature that would seem to indicate that a comet consists primarily of a swarm of particles is that the coma in general contracts as the comet approaches the sun, roughly in proportion within the distance, and then expands again as it recedes.

  17. The origin of comets

    NASA Astrophysics Data System (ADS)

    Bailey, M. E.; Clube, S. V. M.; Napier, W. M.

    Theories of the nature and origin of comets are discussed in a historical review covering the period from ancient times to the present. Consideration is given to the ancient controversy as to the atmospheric or celestial nature of comets, Renaissance theories of comet orbits, superstitions regarding the effects of comets, Kant's (1755) theory of solar-system origin, the nineteenth-century discovery of the relationship between comets and meteor showers, and the continuing solar-system/interstellar debate. Oort's (1950) model of a comet swarm surrounding the solar system is examined in detail; arguments advanced to explain the formation of comets within this model are summarized; and the question of cometary catastrophism is addressed.

  18. Chemical diversity of organic volatiles among comets: An emerging taxonomy and implications for processes in the proto-planetary disk

    NASA Astrophysics Data System (ADS)

    Mumma, Michael J.

    2008-10-01

    As messengers from the early Solar System, comets contain key information from the time of planet formation and even earlier some may contain material formed in our natal interstellar cloud. Along with water, the cometary nucleus contains ices of natural gases (CH4, C2H6), alcohols (CH3OH), acids (HCOOH), embalming fluid (H2CO), and even anti-freeze (ethylene glycol). Comets today contain some ices that vaporize at temperatures near absolute zero (CO, CH4), demonstrating that their compositions remain largely unchanged after 4.5 billion years. By comparing their chemical diversity, several distinct cometary classes have been identified but their specific relation to chemical gradients in the proto-planetary disk remains murky. How does the compositional diversity of comets relate to nebular processes such as chemical processing, radial migration, and dynamical scattering? No current reservoir holds a unique class, but their fractional abundance can test emerging dynamical models for origins of the scattered Kuiper disk, the Oort cloud, and the (proposed) main-belt comets. I will provide a simplified overview emphasizing what we are learning, current issues, and their relevance to the subject of this Symposium.

  19. Dynamical evolution of comet pairs

    NASA Astrophysics Data System (ADS)

    Sosa, Andrea; Fernández, Julio A.

    2016-10-01

    Some Jupiter family comets in near-Earth orbits (thereafter NEJFCs) show a remarkable similarity in their present orbits, like for instance 169P/NEAT and P/2003 T12 (SOHO), or 252P/LINEAR and P/2016 BA14 (PANSTARRS). By means of numerical integrations we studied the dynamical evolution of these objects. In particular, for each pair of presumably related objects, we are interested in assessing the stability of the orbital parameters for several thousand years, and to find a minimum of their relative spatial distance, coincident with a low value of their relative velocity. For those cases for which we find a well defined minimum of their relative orbital separation, we are trying to reproduce the actual orbit of the hypothetical fragment by modeling a fragmentation of the parent body. Some model parameters are the relative ejection velocity (a few m/s), the orbital point at which the fragmentation could have happened (e.g. perihelion), and the elapsed time since fragmentation. In addition, some possible fragmentation mechanisms, like thermal stress, rotational instability, or collisions, could be explored. According to Fernández J.A and Sosa A. 2015 (Planetary and Space Science 118,pp.14-24), some NEJFCs might come from the outer asteroid belt, and then they would have a more consolidated structure and a higher mineral content than that of comets coming from the trans-Neptunian belt or the Oort cloud. Therefore, such objects would have a much longer physical lifetime in the near-Earth region, and could become potential candidates to produce visible meteor showers (as for example 169P/NEAT which has been identified as the parent body of the alpha-Capricornid meteoroid stream, according to Jenniskens, P., Vaubaillon, J., 2010 (Astron. J. 139), and Kasuga, T., Balam, D.D., Wiegert, P.A., 2010 (Astron. J. 139).

  20. The Mineralogy of Comet Wild 2

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael

    2007-01-01

    The nature of cometary solids is of fundamental importance to our understanding of the early solar nebula and protoplanetary history. Samples of Comet Wild 2, provided by the Stardust Mission, have now been examined in terrestrial labs for two years, and are very surprising! Here we describe mainly the critical phases olivine, pyroxene and Fe-Ni sulfides in Wild 2 grains, as a guide to the general mineralogy of the returned comet samples.

  1. THE CANADA-FRANCE ECLIPTIC PLANE SURVEY-L3 DATA RELEASE: THE ORBITAL STRUCTURE OF THE KUIPER BELT

    SciTech Connect

    Kavelaars, J. J.; Jones, R. L.; Murray, I.; Gladman, B. J.; Petit, J.-M.; Van Laerhoven, C.; Parker, Joel Wm.; Bieryla, A.; Nicholson, P.; Margot, J. L.; Rousselot, P.; Mousis, O.; Scholl, H.; Marsden, B.; Benavidez, P.; Campo Bagatin, A.; Doressoundiram, A.; Veillet, C.

    2009-06-15

    We report the orbital distribution of the trans-Neptunian comets discovered during the first discovery year of the Canada-France Ecliptic Plane Survey (CFEPS). CFEPS is a Kuiper Belt object survey based on observations acquired by the Very Wide component of the Canada-France-Hawaii Telescope Legacy Survey (LS-VW). The first year's detections consist of 73 Kuiper Belt objects, 55 of which have now been tracked for three years or more, providing precise orbits. Although this sample size is small compared to the world-wide inventory, because we have an absolutely calibrated and extremely well-characterized survey (with known pointing history) we are able to de-bias our observed population and make unbiased statements about the intrinsic orbital distribution of the Kuiper Belt. By applying the (publically available) CFEPS Survey Simulator to models of the true orbital distribution and comparing the resulting simulated detections to the actual detections made by the survey, we are able to rule out several hypothesized Kuiper Belt object orbit distributions. We find that the main classical belt's so-called 'cold' component is confined in semimajor axis (a) and eccentricity (e) compared to the more extended 'hot' component; the cold component is confined to lower e and does not stretch all the way out to the 2:1 resonance but rather depletes quickly beyond a = 45 AU. For the cold main classical belt population we find a robust population estimate of N(H{sub g} < 10) = 50 {+-} 5 x 10{sup 3} and find that the hot component of the main classical belt represents {approx}60% of the total population. The inner classical belt (sunward of the 3:2 mean-motion resonance) has a population of roughly 2000 trans-Neptunian objects with absolute magnitudes H{sub g} < 10, and may not share the inclination distribution of the main classical belt. We also find that the plutino population lacks a cold low-inclination component, and so, the population is somewhat larger than recent estimates

  2. Physical processes in comets

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.; Huebner, W. F.

    1976-01-01

    The paper discusses physical processes in comets which involve solar and nuclear radial forces that affect the motions of gases and icy grains, gas-phase chemistry very close to the nuclei of large comets near the sun, sublimation of icy grains, dissociation of parent molecules into radicals and of radicals into atoms, and ionization by sunlight and collisions. The composition and dimensions of nuclei are examined along with variations in intrinsic brightness, the nature of volatiles, gas production rates in the coma, characteristics of icy grains in the coma, and the structure of streamers, ion tails, and dust tails. The structure of the coma is described in detail on the basis of spectroscopic observations of several comets. The origin of comets is briefly reviewed together with the relation of comets to earth, the interplanetary complex, and the interstellar medium. Desirable future observations are noted, especially by space missions to comets.

  3. Ammonia abundances in comets

    NASA Astrophysics Data System (ADS)

    Wyckoff, S.; Tegler, S.; Engel, L.

    The emission band strengths of the NH2 bands of Comets Halley, Hartley-Good, Thiele, and Borrelly were measured to determine the NH2 column densities for the comets. Production rates obtained using the Haser and vectorial models are in agreement within the observational errors, suggesting that a simple two-step decay model may be used to approximate the NH2 distribution in a comet's coma. Ammonia-to-water abundance ratios from 0.01 to 0.4 percent were found for the four comets. The ratio in Comet Halley is found to be Q(NH3)/Q(H2O) = 0.002 + or - 0.001. No significant difference in the ammonia abundance was found before or after perihelion in Comet Halley.

  4. Ultraviolet observations of comets

    NASA Technical Reports Server (NTRS)

    Code, A. D.; Houck, T. E.; Lillie, C. F.

    1972-01-01

    The first observations of a comet in the vacuum ultraviolet were obtained on January 14, 1970, when OAO-2 recorded the spectrum of the bright comet Tago-Sato-Kosaka (1969g). The observations revealed, among other things, the predicted extensive hydrogen Lyman alpha halo. OAO-2 continued to collect spectrophotometric measurements of this comet throughout January of that year; a photograph of the nucleus in Lyman alpha revealed finer scale structures. In February of 1970, the bright comet Bennet (1969i) became favorable for space observations. On the basis of the OAO discovery, OGO-V made several measurements of comet Bennet with low spatial resolution photometers. Comet Enke was detected by OGO in January of 1971 at a large heliocentric distance from its Lyman alpha emission.

  5. I Spy a Comet!

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image shows comet Tempel 1 as seen through the clear filter of the medium resolution imager camera on Deep Impact. It was taken on June 25, 2005, when the spacecraft was 8,007,845.1 kilometers (4,976,075 miles) away from the comet. Ten images were combined to create this picture, and a logarithmic stretch was applied to enhance the coma of the comet.

  6. Comet Dead Ahead

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image shows comet Tempel 1 as seen through the clear filter of the medium resolution imager camera on Deep Impact. It was taken on June 26, 2005, when the spacecraft was 7,118,499.4 kilometers (4,423,435 miles) away from the comet. Eight images were combined to create this picture, and a logarithmic stretch was applied to enhance the coma of the comet.

  7. Rendezvous with Comet Kopff

    NASA Technical Reports Server (NTRS)

    Miller, Sylvia; Lisman, Sima

    1989-01-01

    Plans for the Comet Rendezvous Asteroid Flyby (CRAF) mission are discussed. The CRAF spacecraft and mission configurations are illustrated and the scientific studies planned for the mission are listed. The scientific benefits of the study of comets and asteroids are reviewed and the characteristics of Comet Kopff are outlined. In addition, the structure, propulsion, attitude and articulation control, radio frequency and antenna, power and pyro, command, and data storage subsystems are described.

  8. First Comet Encounter

    NASA Image and Video Library

    2010-09-09

    Dr. Michael A'Hearn, Principal Investigator, EPOXI Comet Encounter Mission, speaks during a symposium commemorating a quarter-century of comet discoveries, Friday, Sept. 10, 2010, in the Knight studio at the Newseum in Washington. The International Sun-Earth Explorer-3 (ISEE-3) spacecraft flew past the comet Giacobini-Zinner on Sept. 11, 1985 which established a foundation of discoveries that continue today. Photo Credit: (NASA/Paul E. Alers)

  9. Comet Dead Ahead

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image shows comet Tempel 1 as seen through the clear filter of the medium resolution imager camera on Deep Impact. It was taken on June 26, 2005, when the spacecraft was 7,118,499.4 kilometers (4,423,435 miles) away from the comet. Eight images were combined to create this picture, and a logarithmic stretch was applied to enhance the coma of the comet.

  10. Searching for Extreme Kuiper Belt Objects and Inner Oort Cloud Objects

    NASA Astrophysics Data System (ADS)

    Sheppard, Scott S.; Trujillo, Chad; Tholen, Dave

    2015-11-01

    Since late 2012 we have been performing the largest and deepest survey for distant solar system objects. In the nearly one thousand square degrees we have covered so far we have discovered the object with the most distant perihelion known (2012 VP113), several extreme Kuiper Belt objects with moderate perihelia and large eccentricities, one of the top ten intrinsically brightest Trans-Neptunian objects, an ultra-wide Kuiper Belt binary, one of the most distant known active comets and two active asteroids in the main belt of asteroids. The Kuiper Belt population has an outer edge at about 50 AU. Sedna and our recent discovery, 2012 VP113, are the only known objects with perihelia significantly beyond this edge at about 80 AU. These inner Oort cloud objects obtained their orbits when the solar system was vastly different from now. Thus the dynamical and physical properties of objects in this region offer key constraints on the formation and evolution of our solar system. We will discuss the most recent results of our survey.

  11. COMETARY VOLATILES AND THE ORIGIN OF COMETS

    SciTech Connect

    A'Hearn, Michael F.; Feaga, Lori M.; Sunshine, Jessica M.; Besse, Sebastien; Bodewits, Dennis; Farnham, Tony L.; Kelley, Michael S.; Keller, H. Uwe; Kawakita, Hideyo; Hampton, Donald L.; Kissel, Jochen; Klaasen, Kenneth P.; Yeomans, Donald K.; Meech, Karen J.; Schultz, Peter H.; Thomas, Peter C.; Veverka, Joseph; Groussin, Olivier; Lisse, Carey M.; and others

    2012-10-10

    We describe recent results on the CO/CO{sub 2}/H{sub 2}O composition of comets together with a survey of older literature (primarily for CO/H{sub 2}O) and compare these with models of the protoplanetary disk. Even with the currently small sample, there is a wide dispersion in abundance ratios and little if any systematic difference between Jupiter-family comets (JFCs) and long-period and Halley-type comets (LPCs and HTCs). We argue that the cometary observations require reactions on grain surfaces to convert CO to CO{sub 2} and also require formation of all types of comets in largely, but not entirely, overlapping regions, probably between the CO and CO{sub 2} snow lines. Any difference in the regions of formation is in the opposite direction from the classical picture with the JFCs having formed closer to the Sun than the LPCs. In the classical picture, the LPCs formed in the region of the giant planets and the JFCs formed in the Kuiper Belt. However, these data suggest, consistent with suggestions on dynamical grounds, that the JFCs and LPCs formed in largely overlapping regions where the giant planets are today and with JFCs on average forming slightly closer to the Sun than did the LPCs. Presumably at least the JFCs passed through the scattered disk on their way to their present dynamical family.

  12. Special Report: Chemistry of Comets.

    ERIC Educational Resources Information Center

    A'Hearn, Michael F.

    1984-01-01

    Discusses the chemistry of comets. How comets provide clues to the birth of the solar system, photolytic reactions on comets involving water, chemical modeling, nuclear chemistry, and research findings are among the areas considered. (JN)

  13. Special Report: Chemistry of Comets.

    ERIC Educational Resources Information Center

    A'Hearn, Michael F.

    1984-01-01

    Discusses the chemistry of comets. How comets provide clues to the birth of the solar system, photolytic reactions on comets involving water, chemical modeling, nuclear chemistry, and research findings are among the areas considered. (JN)

  14. Stochasticity of comet P/Slaughter-Burnham

    NASA Technical Reports Server (NTRS)

    Benest, Daniel; Gonczi, R.

    1992-01-01

    Three comets are now known to be at or near the 1/1 resonance with Jupiter: P/Slaughter-Burnham, P/Boethin and the newly discovered P/Ge-Wang. Although details of the individual orbits differ, the three comets have very similar dynamical behavior: their orbits show many transitions between the different types of resonant motion (satellite libration, anti-satellite libration, and circulating motion). The stochastic character of such cometary orbits, mainly due to encounters with Jupiter is investigated using Lyapunov Characteristic Indicators. For each comet of the group, we study the influences on the stochasticity of initial eccentricity, inclination, longitude of node, and l-l(sub J) (mean longitude of comet minus mean longitude of Jupiter). We present here our first results for P/Slaughter-Burnham.

  15. Physical and dynamical properties of the anomalous comet 249P/LINEAR

    NASA Astrophysics Data System (ADS)

    Fernández, Julio A.; Licandro, Javier; Moreno, Fernando; Sosa, Andrea; Cabrera-Lavers, Antonio; de León, Julia; Birtwhistle, Peter

    2017-10-01

    class of near-Earth JFC whose source region is not the distant trans-neptunian population, but much closer in the asteroid belt. Therefore, 249P/LINEAR may be a near-Earth counterpart of the so-called main-belt comets or active asteroids.

  16. Systematic conveyor belt cleaning

    SciTech Connect

    Rappen, A.

    1984-01-01

    The currently available conveyor belt cleaning devices are enumerated. Recent investigations have confirmed the belt scraping devices based on intermittent linear contact by means of individually adjustable and spring-loaded scraper blades, usually of metallic construction as the most advanced type of belt cleaner. The system also allows application on reversing belts. Criteria are presented for assessing the performance of a belt cleaner.

  17. Studying comets with NEOWISE

    NASA Astrophysics Data System (ADS)

    Stevenson, R.; Bauer, J.; Kramer, E.; Fernández, Y.; Mainzer, A.; Grav, T.; Masiero, J.

    2014-07-01

    The Wide-Field Infrared Survey Explorer (WISE) mission detected more than 150 comets during its all-sky survey between January 2010 and February 2011. The comets were imaged at 4 infrared wavelengths (3.4, 4.6, 12, and 22 microns). The large sample of both long-period and Jupiter-family comets observed at a range of heliocentric distances allows for systematic comparison of the properties of both dynamical families. Nucleus diameters and albedos, dust comae temperatures, CO and CO_{2} emission rates, and dust tail and trail morphologies are some of the properties studied with the WISE data. This work is being continued by the reactivated NEOWISE mission [1]. In 2013, the WISE spacecraft was brought out of hibernation to resume discovering, tracking, and characterizing small bodies in the Solar System by imaging the sky at solar elongations of ˜90° at wavelengths of 3.4 and 4.6 microns. Since NEOWISE resumed its all-sky survey on December 23, 2013, 10 comets have been observed, including one previously-unknown long-period comet -- C/2014 C3 (NEOWISE). Of particular interest are the NEOWISE observations of comet C/2013 A1 (Siding Spring), which will have a close encounter with Mars in October 2014. NEOWISE observed this comet in January 2014 and will observe it twice more before the comet's close approach to Mars. NEOWISE will continue to operate until early 2017, greatly enhancing our understanding of cometary properties as studied in the infrared.

  18. Asteroids, Comets, Meteors 1991

    NASA Technical Reports Server (NTRS)

    Harris, Alan W. (Editor); Bowell, Edward (Editor)

    1992-01-01

    Papers from the conference are presented and cover the following topics with respect to asteroids, comets, and/or meteors: interplanetary dust, cometary atmospheres, atmospheric composition, comet tails, astronomical photometry, chemical composition, meteoroid showers, cometary nuclei, orbital resonance, orbital mechanics, emission spectra, radio astronomy, astronomical spectroscopy, photodissociation, micrometeoroids, cosmochemistry, and interstellar chemistry.

  19. Changing Speed of Comets

    ERIC Educational Resources Information Center

    Follows, Mike

    2003-01-01

    It is shown that highly elliptical orbits, such as those of comets, can be explained well in terms of energy rather than forces. The principle of conservation of energy allows a comet's velocity to be calculated at aphelion and perihelion. An example asks students to calculate whether they can run fast enough to escape from a small asteroid.…

  20. Kitt Peak Observes Comet

    NASA Image and Video Library

    2005-05-16

    he Kitt Peak National Observatory 2.1-meter telescope observed comet Tempel 1 on April 11, 2005, when the comet was near its closest approach to the Earth. A pinkish dust jet is visible to the southwest, with the broader neutral gas coma surrounding it.

  1. Changing Speed of Comets

    ERIC Educational Resources Information Center

    Follows, Mike

    2003-01-01

    It is shown that highly elliptical orbits, such as those of comets, can be explained well in terms of energy rather than forces. The principle of conservation of energy allows a comet's velocity to be calculated at aphelion and perihelion. An example asks students to calculate whether they can run fast enough to escape from a small asteroid.…

  2. Comet Borrelly Varied Landscape

    NASA Image and Video Library

    2001-11-03

    Sunlight illuminates the bowling-pin shaped nucleus from directly below comet Borrelly as seen by NASA Deep Space 1. At this distance, many features become vivid on the surface of the nucleus, including a jagged line between day and night on the comet.

  3. Taking a Comet Temperature

    NASA Image and Video Library

    2015-10-01

    Image of the southern polar regions of comet 67P/Churyumov-Gerasimenko taken by Rosetta Optical, Spectroscopic, and Infrared Remote Imaging System OSIRIS on September 29, 2014, when the comet was still experiencing the long southern winter. http://photojournal.jpl.nasa.gov/catalog/PIA19969

  4. Meteoroid streams and comet disintegration

    NASA Astrophysics Data System (ADS)

    Guliyev, A.

    2016-01-01

    The results of the statistical analysis of the dynamic parameters of 114 comets that have undergone nuclear splitting are presented in the article. The list of the objects contains: comets that have split in the period of the observation; data of twin-comets; lost comets with designation D; comets with large-scale structure in the coma. We will describe these comets as "splitted". Some aspects of the following hypothesis are studied: disintegration of comet nuclei happens as the result of their collision with meteoroid streams. For the verification of this hypothesis, the position of splitted comet orbits relatively to 125 meteor streams from Kronk's list is analyzed. It was found that the total number of comet orbit nodes located close to the meteor stream planes (for the distances up to 0.1 AU) is N = 1041. It is shown that if these comets are replaced by randomly selected different comets, N will be reduced by a factor of approximately three.

  5. The evolution of comet orbits

    NASA Technical Reports Server (NTRS)

    Everhart, E.

    1976-01-01

    The origin of comets and the evolution of their orbits are discussed. Factors considered include: the law of survival of comets against ejection on hyperbolic orbits; short-period comets are not created by single close encounters of near-parabolic comets with Jupiter; observable long-period comets do not evolve into observable short-period comets; unobservable long-period comets with perihelia near Jupiter can evolve into observable short-period comets; long-period comets cannot have been formed or created within the planetary region of the solar system (excluding the effects of stellar perturbations); it is possible that some of the short-period comets could have been formed inside the orbit of Neptune; circularly-restricted three-body problem, and its associated Jacobi integral, are not valid approximations to use in studying origin and evolution of comets.

  6. Comet Scientists Honor Colleagues

    NASA Image and Video Library

    2015-09-29

    Scientists from the European Space Agency Rosetta team have honored two late team members by naming comet features after them. The comet is 67P/Churyumov-Gerasimenko, where the mission successfully landed a probe. One of the features is shown here in these Rosetta images, with the picture on the right being a close-up view. The "C. Alexander Gate" is found on the comet's smaller lobe, and is dedicated to Claudia Alexander, the U.S. project scientist from NASA's Jet Propulsion Laboratory, Pasadena, California, who passed away in July of this year. Image credit left: ESA's comet viewer http://sci.esa.int/comet-viewer. http://photojournal.jpl.nasa.gov/catalog/PIA19838

  7. The chemistry of comets

    NASA Technical Reports Server (NTRS)

    Delsemme, A. H.

    1988-01-01

    Comets appear to represent a population of rather homogeneous objects. In particular, the original size distribution peaks at a mean diameter of the order of 10 km. Cometary dust grains appear to be made of clusters of extremely fine particles (0.1-1.0 micron) sintered by heat at a variable degree during their perihelion passages. The brightness laws of comets appear to be derived only by the sublimation of water ice or at least of gas hydrates of the clathrate type. Pristine nuclei are likely to be radially undifferentiated; only their crustal surface must be outgassed and sintered by the heat of perihelion passages. Comet Halley is confirmed to be in the same general class as the bright comets of the 1970s. With an organic fraction of 33 percent in the cometary dust, the carbon of Comet Halley is close to cosmic abundances.

  8. Observations of ammonia in comets with Herschel

    NASA Astrophysics Data System (ADS)

    Biver, N.; Bockelée-Morvan, D.; Hartogh, P.; Crovisier, J.; de Val-Borro, M.; Kidger, M.; Küppers, M.; Lis, D.; Moreno, R.; Szutowicz, S.; HssO Team

    2014-07-01

    Ammonia is the most abundant nitrogen bearing species in comets. However, it has been scarcely observed in comets due to the weakness of the lines observable from the ground at infrared and centimetre wavelengths. Nevertheless, its main photodissociation product NH_2 has been observed in several comets in the visible. The fundamental rotational J_{K}=(1_0-0_0) transition of NH_3 at 572.5 GHz has been observed in comets since 2004, with the Odin satellite (Biver et al. 2007). In the frame of the Herschel guaranteed time key program ''HssO'' (Hartogh et al. 2009), ammonia was detected with the HIFI instrument in comets 10P/Tempel 2 (Biver et al. 2012), 45P/Honda- Mrkos-Pajdusakova, 103P/Hartley 2, and C/2009 P1 (Garradd). The hyperfine structure of the line is resolved. We have built a complete excitation model to interpret these observations, including the radial distribution in comet 103P. The derived abundances relative to water are on the order of 0.5 %, similar to the values inferred from visible observations of NH_2.

  9. Submillimeter Continuum Observations of Comets

    NASA Technical Reports Server (NTRS)

    Jewitt, David

    1998-01-01

    The aim of this proposal was to study the submillimeter continuum emission from comets. The study was based mainly on the exploitation of the world's leading submillimeter telescope, the JCMT (James Clerk Maxwell Telescope) on Mauna Kea. Submillimeter wavelengths provide a unique view of cometary physics for one main reason. The cometary size distribution is such that the scattering cross-section is dominated by small dust grains, while the mass is dominated by the largest particles. Submillimeter continuum radiation samples cometary particles much larger than those sampled by more common observations at shorter (optical and infrared) wavelengths and therefore provides a nearly direct measure of the cometary dust mass.

  10. Realm of the comets

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.

    1987-01-01

    Studies of Jovian perturbations of the orbits of long-period comets led to the concept of the Oort cloud of 180 billion comets at 50,000-150,000 AU from the sun. Several comets are induced to move toward the sun every million years by the passage of a star at a distance of a few light years. The location of the cloud has since been revised to 20,000-100,000 AU, and comets are now accepted as remnant material fron the proto-solar system epoch. The galactic disk and random, close-passing stars may also cause rare, large perturbations in the orbits of the cloud comets, sending large numbers of comets through the inner solar system. The resulting cometary storm is a candidate cause for the wholesale extinction of dinosaurs in the Cretaceous-Terniary transition due to large number of planetesimals, or one large comet, striking the earth, in a short period of time. The IRAS instruments have detected similar clouds of material around other stars.

  11. Realm of the comets

    SciTech Connect

    Weissman, P.R.

    1987-03-01

    Studies of Jovian perturbations of the orbits of long-period comets led to the concept of the Oort cloud of 180 billion comets at 50,000-150,000 AU from the sun. Several comets are induced to move toward the sun every million years by the passage of a star at a distance of a few light years. The location of the cloud has since been revised to 20,000-100,000 AU, and comets are now accepted as remnant material fron the proto-solar system epoch. The galactic disk and random, close-passing stars may also cause rare, large perturbations in the orbits of the cloud comets, sending large numbers of comets through the inner solar system. The resulting cometary storm is a candidate cause for the wholesale extinction of dinosaurs in the Cretaceous-Terniary transition due to large number of planetesimals, or one large comet, striking the earth, in a short period of time. The IRAS instruments have detected similar clouds of material around other stars.

  12. The end states of long-period comets and the origin of Halley-type comets

    NASA Astrophysics Data System (ADS)

    Fernández, Julio A.; Gallardo, Tabaré; Young, Juan D.

    2016-09-01

    We analyse a sample of 73 old long-period comets (LPCs) (orbital periods 200 < P < 1000 yr) with perihelion distances q < 2.5 au, discovered in the period 1850-2014. We cloned the observed comets and also added fictitious LPCs with perihelia in the Jupiter's zone. We consider both a purely dynamical evolution and a physico-dynamical one with different physical lifetimes. We can fit the computed energy distribution of comets with q < 1.3 au to the observed one only within the energy range 0.01 < x < 0.04 au-1 (or periods 125 < P < 1000 yr), where the `energy' is taken as the inverse of the semimajor axis a, namely x ≡ 1/a. The best results are obtained for physical lifetimes of about 200-300 revolutions (for a comet with a standard q = 1 au). We find that neither a purely dynamical evolution, nor a physico-dynamical one can reproduce the long tail of larger binding energies (x ≳ 0.04 au-1) that correspond to most Halley-type comets (HTCs) and Jupiter-family comets. We conclude that most HTCs are not the end states of the evolution of LPCs, but come from a different source, a flattened one that we identify with the Centaurs that are scattered to the inner planetary region from the trans-Neptunian belt. These results also show that the boundary between LPCs and HTCs should be located at an energy x ˜ 0.04 au-1 (P ˜ 125 yr), rather than the conventional classical boundary at P = 200 yr.

  13. Comet Bursting Through Relaxation

    NASA Astrophysics Data System (ADS)

    Jacobson, Seth A.; Scheeres, D. J.

    2012-10-01

    Comets may be excited and occupy non-principal axis (complex) rotation states for a large fraction of their lifetimes. Many comet nuclei have been identified or are suspected to occupy non-principal axis (complex) rotation [Belton 2005, etc.] as well as have evolving rotation rates [Belton 2011, etc.]. Comet orbits drive these rotation states through cycles of excitation due to surface jets and relaxation due to time variable internal stresses that dissipate energy in the anelastic comet interior. Furthermore, relaxation from complex rotation can increase the loads along the symmetry axis of prolate comets. These loads stretch the body along the symmetry axis and may be the cause of the characteristic ``bowling pin’’ shape and eventually may lead to failure. This is an alternative model for comet bursting. Each cycle deposits only a small amount of energy and stress along the axis, but this process is repeated every orbit during which jets are activated. Our model for the evolution of comet nuclei includes torques due to a number of discrete jets located on the surface based on Neishtadt et al. [2002]. The model also includes internal dissipation using an approach developed by Sharma et al. [2005] and Vokrouhlicky et al. [2009]. These equations are averaged over the instantaneous spin state and the heliocentric orbit so the long-term evolution of the comet can be determined. We determine that even after the inclusion of internal dissipation there still exist non-principal axis equilibrium states for certain jet geometries. For ranges of dissipation factors and jet geometries, prolate comets are found to occupy states that have time variable internal loads over long time periods. These periodic loadings along the symmetry axis may lead to ``necking’’ as the body extends along the axis to release the stress and eventually disruption.

  14. Laterally bendable belt conveyor

    DOEpatents

    Peterson, William J.

    1985-01-01

    An endless, laterally flexible and bendable belt conveyor particularly adapted for coal mining applications in facilitating the transport of the extracted coal up- or downslope and around corners in a continuous manner is disclosed. The conveying means includes a flat rubber belt reinforced along the middle portion thereof along which the major portion of the belt tension is directed so as to cause rotation of the tubular shaped belt when trammed around lateral turns thus preventing excessive belt bulging distortion between adjacent belt supports which would inhibit belt transport. Pretension induced into the fabric reinforced flat rubber belt by conventional belt take-up means supports the load conveyed when the belt conveyor is making lateral turns. The carrying and return portions of the belt are supported and formed into a tubular shape by a plurality of shapers positioned along its length. Each shaper is supported from above by a monorail and includes clusters of idler rollers which support the belt. Additional cluster rollers in each shaper permit the belt supporting roller clusters to rotate in response to the belt's operating tension imposed upon the cluster rollers by induced lateral belt friction forces. The freely rotating roller clusters thus permit the belt to twist on lateral curves without damage to itself while precluding escape of the conveyed material by effectively enclosing it in the tube-shaped, inner belt transport length.

  15. Laterally bendable belt conveyor

    SciTech Connect

    Peterson, W.J.

    1985-07-02

    An endless, laterally flexible and bendable belt conveyor particularly adapted for coal mining applications in facilitating the transport of the extracted coal up- or downslope and around corners in a continuous manner is disclosed. The conveying means includes a flat rubber belt reinforced along the middle portion thereof along which the major portion of the belt tension is directed so as to cause rotation of the tubular shaped belt when trammed around lateral turns thus preventing excessive belt bulging distortion between adjacent belt supports which would inhibit belt transport. Pretension induced into the fabric reinforced flat rubber belt by conventional belt take-up means supports the load conveyed when the belt conveyor is making laterial turns. The carrying and return portions of the belt are supported and formed into a tubular shape by a plurality of shapers positioned along its length. Each shaper is supported from above by a monorail and includes clusters of idler rolles which support the belt. Additional cluster rollers in each shaper permit the belt supporting roller clusters to rotate in response to the belt's operating tension imposed upon the cluster rollers by induced lateral belt friction forces. The freely rotating roller clusters thus permit the belt to twist on lateral curves without damage to itself while precluding escape of the conveyed material by effectively enclosing it in the tube-shaped, inner belt transport length.

  16. Laterally bendable belt conveyor

    SciTech Connect

    Peterson, W.J.

    1982-09-24

    An endless, laterally flexible and bendable belt conveyor particularly adapted for coal mining applications in facilitating the transport of the extracted coal up- or downslope and around corners in a continuous manner is disclosed. The conveying means includes a flat rubber belt reinforced along the middle portion thereof along which the major portion of the belt tension is directed so as to cause rotation of the tubular shaped belt when trammed around lateral turns thus preventing excessive belt bulging distortion between adjacent belt supports which would inhibit belt transport. Pretension induced into the fabric reinforced flat rubber belt by conventional belt take-up means supports the load conveyed when the belt conveyor is making lateral turns. The carrying and return portions of the belt are supported and formed into a tubular shape by a plurality of shapers positioned along its length. Each shaper is supported from above by a monorail and includes clusters of idler rollers which support the belt. Additional cluster rollers in each shaper permit the belt supporting roller clusters to rotate in response to the belt's operating tension imposed upon the cluster rollers by induced lateral belt friction forces. The freely rotating roller clusters thus permit the belt to twist on lateral curves without damage to itself while precluding escape of the conveyed material by effectively enclosing it in the tube-shaped, inner belt transport length.

  17. Thermal conductivity of comets

    NASA Technical Reports Server (NTRS)

    Kumar, G. N.; Vachon, R. I.; Khader, M. S.

    1975-01-01

    The thermal conductivity of two comet models is calculated. Both models assume the comets to be heterogeneous in composition. One model considers the comet to have a nucleus of water-ice mixed with basaltic and meteoritic material in the form of dust and agglomerated particles surrounded by a layer of water-frost. The second model assumes the frost and water-ice layers have sublimated, leaving a porous structure to some depth composed of solid basaltic and meteoritic material with residual gases. K values are calculated as a function of depth, density, temperature and porosity.

  18. A Comet's Missing Light

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-05-01

    On 28 November 2013, comet C/2012 S1 better known as comet ISON should have passed within two solar radii of the Suns surface as it reached perihelion in its orbit. But instead of shining in extreme ultraviolet (EUV) wavelengths as it grazed the solar surface, the comet was never detected by EUV instruments. What happened to comet ISON?Missing EmissionWhen a sungrazing comet passes through the solar corona, it leaves behind a trail of molecules evaporated from its surface. Some of these molecules emit EUV light, which can be detected by instruments on telescopes like the space-based Solar Dynamics Observatory (SDO).Comet ISON, a comet that arrived from deep space and was predicted to graze the Suns corona in November 2013, was expected to cause EUV emission during its close passage. But analysis of the data from multiple telescopes that tracked ISON in EUV including SDO reveals no sign of it at perihelion.In a recent study, Paul Bryans and DeanPesnell, scientists from NCARs High Altitude Observatory and NASA Goddard Space Flight Center, try to determine why ISON didnt display this expected emission.Comparing ISON and LovejoyIn December 2011, another comet dipped into the Suns corona: comet Lovejoy. This image, showingthe orbit Lovejoy took around the Sun, is a composite of SDO images of the pre- and post-perihelion phases of the orbit. Click for a closer look! The dashed part of the curve represents where Lovejoy passed out of view behind the Sun. [Bryans Pesnell 2016]This is not the first time weve watched a sungrazing comet with EUV-detecting telescopes: Comet Lovejoy passed similarly close to the Sun in December 2011. But when Lovejoy grazed the solar corona, it emitted brightly in EUV. So why didnt ISON? Bryans and Pesnell argue that there are two possibilities:the coronal conditions experienced by the two comets were not similar, orthe two comets themselves were not similar.To establish which factor is the most relevant, the authors first demonstrate that both

  19. The Comet With a Broken Heart

    NASA Astrophysics Data System (ADS)

    2006-04-01

    On the night of April 23 to 24, ESO's Very Large Telescope observed fragment B of the comet Schwassmann-Wachmann 3 that had split a few days earlier. To their great surprise, the ESO astronomers discovered that the piece just ejected by fragment B was splitting again! Five other mini-comets are also visible on the image. The comet seems thus doomed to disintegrate but the question remains in how much time. Comet 73P/Schwassmann-Wachmann 3 (SW 3) is a body with a very tormented past. This comet revolves around the Sun in about 5.4 years, in a very elongated orbit that brings it from inwards of the Earth's orbit to the neighbourhood of giant planet Jupiter. In 1995, when it was coming 'close' to the Earth, it underwent a dramatic and completely unexpected, thousand-fold brightening. Observations in 1996, with ESO's New Technology Telescope and 3.6-m telescope, at La Silla, showed that this was due to the fact that the comet had split into three distinct pieces. Later, in December 1996, two more fragments were discovered. At the last comeback, in 2001, of these five fragments only three were still seen, the fragments C (the largest one), B and E. No new fragmentations happened during this approach, apparently. ESO PR Photo 15a/06 ESO PR Photo 15a/06 Fragment B of Comet SW-3 Things were different this time, when the comet moved again towards its closest approach to the Sun - and to the Earth. Early in March, seven fragments were observed, the brightest (fragment C) being of magnitude 12, i.e. 250 fainter than what the unaided can see, while fragment B was 10 times fainter still. In the course of March, 6 new fragments were seen. Early in April, fragment B went into outburst, brightening by a factor 10 and on 7 April, six new fragments were discovered, confirming the high degree of fragmentation of the comet. On 12 April, fragment B was as bright as the main fragment C, with a magnitude around 9 (16 times fainter than what a keen observer can see with unaided eyes

  20. Jets on Comet Borrelly

    NASA Image and Video Library

    2001-11-03

    This very long exposure was taken by NASA Deep Space 1 to show detailed structures in the faint parts of comet Borrelly inner coma. As a result, the nucleus has been greatly over-exposed and its shape appears distorted.

  1. Bright Comet ISON

    NASA Image and Video Library

    2017-09-27

    Comet ISON shines brightly in this image taken on the morning of 19 Nov. 2013. This is a 10-second exposure taken with the Marshall Space Flight Center 20" telescope in New Mexico. The camera there is black and white, but the smaller field of view allows for a better "zoom in" on the comet's coma, which is essentially the head of the comet. Credit: NASA/MSFC/MEO/Cameron McCarty -------- More details on Comet ISON: Comet ISON began its trip from the Oort cloud region of our solar system and is now travelling toward the sun. The comet will reach its closest approach to the sun on Thanksgiving Day -- 28 Nov 2013 -- skimming just 730,000 miles above the sun's surface. If it comes around the sun without breaking up, the comet will be visible in the Northern Hemisphere with the naked eye, and from what we see now, ISON is predicted to be a particularly bright and beautiful comet. Catalogued as C/2012 S1, Comet ISON was first spotted 585 million miles away in September 2012. This is ISON's very first trip around the sun, which means it is still made of pristine matter from the earliest days of the solar system’s formation, its top layers never having been lost by a trip near the sun. Comet ISON is, like all comets, a dirty snowball made up of dust and frozen gases like water, ammonia, methane and carbon dioxide -- some of the fundamental building blocks that scientists believe led to the formation of the planets 4.5 billion years ago. NASA has been using a vast fleet of spacecraft, instruments, and space- and Earth-based telescope, in order to learn more about this time capsule from when the solar system first formed. The journey along the way for such a sun-grazing comet can be dangerous. A giant ejection of solar material from the sun could rip its tail off. Before it reaches Mars -- at some 230 million miles away from the sun -- the radiation of the sun begins to boil its water, the first step toward breaking apart. And, if it survives all this, the intense radiation

  2. Slice of Comet Dust

    NASA Image and Video Library

    2006-02-21

    This image illustrates one of several ways scientists have begun extracting comet particles from NASAa Stardust spacecraft collector. First, a particle and its track are cut out of the collector material, called aerogel.

  3. Space missions to comets

    NASA Technical Reports Server (NTRS)

    Neugebauer, M. (Editor); Yeomans, D. K. (Editor); Brandt, J. C. (Editor); Hobbs, R. W. (Editor)

    1979-01-01

    The broad impact of a cometary mission is assessed with particular emphasis on scientific interest in a fly-by mission to Halley's comet and a rendezvous with Tempel 2. Scientific results, speculations, and future plans are discussed.

  4. N_2(+) in Comets?

    NASA Astrophysics Data System (ADS)

    Cochran, A. L.; Barker, E. S.; Cochran, W. D.

    1999-09-01

    Comets delivered some of the volatiles that we see today in the atmospheres of the terrestrial planets, but it is not certain how important a source of volatiles the comets represent. In order to ascertain the relative importance of comets as a source of volatiles, it is necessary to understand the volatile abundances of comets. Owen and Bar-Nun (Icarus 116, 215, 1995) have pointed out that nitrogen is an important guide to the volatile abundances of comets because it is trapped and released by amorphous ice in a manner which is similar to argon. Since nitrogen is cosmically abundant and can exist in a variety of molecules with varying amounts of volatility, it can be compared with several reservoirs of ices in astronomical sources. However, measuring the N_2 content of cometary comae is extremely difficult because the available transitions are few, and the Earth's atmosphere contains significant quantities of N_2. In the past, the (0,0) transition of N_2(+) has been reported in the spectra of comets. This transition occurs at approximately 3900 Angstroms. However, care must be taken when observing this transition because N_2(+) is excited in the atmosphere of the Earth, especially near dusk and dawn when comets are often observed. Thus, accurate measurement of N_2(+) in cometary spectra requires both good spatial and spectral resolution to separate the features from that of the Earth. We obtained high S/N spectra of Hale-Bopp at R=200,000 and at several distances into the tail in order to place hard limits on the N_2(+) in the coma of this comet. In addition, we obtained excellent observations of comet de Vico, both of the optocenter and the tail. There is no clear detection of N_2(+) in either of these comets. We report on our observations and on the limits we can place on N_2(+) in these comets and compare them with previous observations. This work was supported by NASA Grant NAG5 4208.

  5. COMET KOHAUTEK - ART CONCEPTS

    NASA Image and Video Library

    1973-11-27

    S73-37273 (24 Dec. 1973) --- An artist's concept illustrating the trajectory of the newly-discovered Comet Kohoutek in relation to the sun and to Earth and the plane of Earth's orbit. The picture show's the position of Kohoutek on Christmas Eve, 1973. The Skylab space station in Earth orbit will provide a favorable location from which to observe the passing of the comet. Photo credit: NASA

  6. Comet composition and Lab

    NASA Astrophysics Data System (ADS)

    Bockelée-Morvan, Dominique; Biver, Nicolas

    2016-10-01

    Comet composition and properties provide information on chemical and physical processes that occurred in the early Solar system, 4.6 Gyr ago. The study of comets and of star-forming regions both help for a better understanding of the formation of planetary systems. A review of our present knowledge of cometary composition is presented. We also discuss laboratory studies that would be helpful for data analysis.

  7. Comets: Search and Discovery

    NASA Astrophysics Data System (ADS)

    Shanklin, J.; Murdin, P.

    2003-04-01

    Comet discovery in the traditional sense by an amateur astronomer may be a thing of the past. The development of increasing numbers of professional all-sky survey programs, many specifically designed to spot moving or changing objects, means that the future prospects for visual discovery of a comet by an amateur astronomer are bleak. In the near future the professional programs are likely to cover...

  8. First Comet Encounter

    NASA Image and Video Library

    2010-09-09

    Dr. Anita Cochran, Assistant Director, McDonald Observatory at the University of Texas-Austin, speaks during a symposium commemorating a quarter-century of comet discoveries, Friday, Sept. 10, 2010, in the Knight studio at the Newseum in Washington. The International Sun-Earth Explorer-3 (ISEE-3) spacecraft flew past the comet Giacobini-Zinner on Sept. 11, 1985 which established a foundation of discoveries that continue today. Photo Credit: (NASA/Paul E. Alers)

  9. First Comet Encounter

    NASA Image and Video Library

    2010-09-09

    Dr. James L. Green, Director of Planetary Science at NASA, speaks during a symposium commemorating a quarter-century of comet discoveries, Friday, Sept. 10, 2010, in the Knight studio at the Newseum in Washington. The International Sun-Earth Explorer-3 (ISEE-3) spacecraft flew past the comet Giacobini-Zinner on Sept. 11, 1985 which established a foundation of discoveries that continue today. Photo Credit: (NASA/Paul E. Alers)

  10. First Comet Encounter

    NASA Image and Video Library

    2010-09-09

    Kjell Stakkestad, President and CEO of KinetX Inc., speaks during a symposium commemorating a quarter-century of comet discoveries, Friday, Sept. 10, 2010, in the Knight studio at the Newseum in Washington. The International Sun-Earth Explorer-3 (ISEE-3) spacecraft flew past the comet Giacobini-Zinner on Sept. 11, 1985 which established a foundation of discoveries that continue today. Photo Credit: (NASA/Paul E. Alers)

  11. Rosetta Comet Marches On

    NASA Image and Video Library

    2015-06-19

    This image, taken by ESA Rosetta navigation camera, was taken from a distance of about 53 miles 86 kilometers from the center of Comet 67P/Churyumov-Gerasimenko on March 14, 2015. The image has a resolution of 24 feet (7 meters) per pixel and is cropped and processed to bring out the details of the comet's activity. http://photojournal.jpl.nasa.gov/catalog/PIA19687

  12. Carbon in comet dust

    NASA Technical Reports Server (NTRS)

    Brownlee, D. E.

    1990-01-01

    The association of Halley particle results with data from existing meteoritic materials that can be analyzed in the laboratory is discussed. Comet samples must exist in present collections of meteoritic materials and the Halley results provide clues for identifying them. Although it is not presently possible to positively identify cometary meteorites or cometary interplanetary dust (IDP) samples, it is possible to determine which materials are similar to Halley dust and which ones are distinctly unlike Halley. The properties of these existing Halley-compatible samples provide insight into the possible properties of cometary material. Positive identification of meteoritic comet samples or direct samples returned from a comet nucleus would of course revolutionize our ability to study carbonaceous matter in comets. Modern analytical techniques are very powerful and it is possible to perform elemental, chemical, mineralogical and even limited isotopic analysis on micron-size particles. There is an important synergism between the laboratory studies of collected samples and astronomical data from comets and interstellar grains. To fully interpret results there must be convincing methods for associating a particular class or classes of meteoritic material with comets. Ultimately this will be done by direct comet sample return such as the Rosetta mission under development by ESA. At the present time the only links that can be made involve comparison with sample properties and measurable properties of comets. Unfortunately there is at present no known unique property of cometary dust that allows its absolute identification in the laboratory. The results from Halley encounters and observation do provide much new information on cometary grains. The Halley grain compositions, density, size distribution and scattering properties all provide a basis for future investigations. Other Halley properties such as the presence of polyoxymethylene and the 3.4um emission feature could

  13. Comet Stepping Stones

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image from NASA's Spitzer Space Telescope shows three of the many fragments making up Comet 73P /Schwassman-Wachmann 3. The infrared picture also provides the best look yet at the crumbling comet's trail of debris, seen here as a bridge connecting the larger fragments.

    The comet circles around our sun every 5.4 years. In 1995, it splintered apart into four pieces, labeled A through D, with C being the biggest. Since then, the comet has continued to fracture into dozens of additional pieces. This image is centered about midway between fragments C and B; fragment G can be seen in the upper right corner.

    The comet's trail is made of dust, pebbles and rocks left in the comet's wake during its numerous journeys around the sun. Such debris can become the stuff of spectacular meteor showers on Earth.

    This image was taken on April 1, 2006, by Spitzer's multi-band imaging photometer using the 24-micron wavelength channel.

  14. Comet Stepping Stones

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image from NASA's Spitzer Space Telescope shows three of the many fragments making up Comet 73P /Schwassman-Wachmann 3. The infrared picture also provides the best look yet at the crumbling comet's trail of debris, seen here as a bridge connecting the larger fragments.

    The comet circles around our sun every 5.4 years. In 1995, it splintered apart into four pieces, labeled A through D, with C being the biggest. Since then, the comet has continued to fracture into dozens of additional pieces. This image is centered about midway between fragments C and B; fragment G can be seen in the upper right corner.

    The comet's trail is made of dust, pebbles and rocks left in the comet's wake during its numerous journeys around the sun. Such debris can become the stuff of spectacular meteor showers on Earth.

    This image was taken on April 1, 2006, by Spitzer's multi-band imaging photometer using the 24-micron wavelength channel.

  15. Short-Period Comets: Primordial Bodies or Collisional Fragments?

    PubMed

    Farinella; Davis

    1996-08-16

    Modeling results show that collisions among Edgeworth-Kuiper Belt Objects (EKOs), a vast swarm of small bodies orbiting beyond Neptune, have been a major process affecting this population and its progeny, the short-period comets. Most EKOs larger than about 100 kilometers in diameter survive over the age of the solar system, but at smaller sizes collisional breakup is frequent, producing a cascade of fragments having a power law size-frequency distribution. Collisions are also a plausible mechanism for injecting EKOs 1 to 10 kilometers in diameter into dynamical resonances, where they can be transported into the inner solar system to become short-period comets. The fragmental nature of these comets may explain their physical properties, such as shape, color, and strength.

  16. The gravitational sculpting of the Kuiper belt

    NASA Astrophysics Data System (ADS)

    Levison, H. F.; Duncan, M. J.

    1993-03-01

    Results are presented of numerical integrations over billion year time scales of the orbital evolution of more than one thousand test particles on initially low-inclination, low-eccentricity orbits within the proposed Kuiper belt beyond Neptune. Particles which eventually crossed Neptune's orbit often showed long periods (up to several billion years) of relatively low-eccentricity oscillations punctuated by a very rapid jump to Neptune-crossing eccentricity. This flux may be the ultimate source of present-day short-period comets. It is found here that there exists a correlation between Liapunov and crossing times in the Kuiper belt. None of the particles in the study with Liapunov time scales greater than about 1 Myr actually became a Neptune-crosser in 4 Gyr. An intricate structure to the region between 35 and 45 AU is found at the end of the billion year simulation. Implications for the origins of short-period comets and the detectability of objects currently in the Kuiper belt are discussed.

  17. Belt attachment and system

    DOEpatents

    Schneider, Abraham D.; Davidson, Erick M.

    2016-02-02

    Disclosed herein is a belt assembly including a flexible belt with an improved belt attachment. The belt attachment includes two crossbars spaced along the length of the belt. The crossbars retain bearings that allow predetermined movement in six degrees of freedom. The crossbars are connected by a rigid body that attaches to the bearings. Implements that are attached to the rigid body are simply supported but restrained in pitching rotation.

  18. Comets: Data, problems, and objectives

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1977-01-01

    A highly abridged review of new relevant results from the observations of Comet Kohoutek is followed by an outline summary of our basic knowledge concerning comets, both subjects being confined to data related to the nature and origin of comets rather than the phenomena (for example, plasma phenomena are omitted). The discussion then centers on two likely places of cometary origin in the developing solar system, the proto-Uranus-Neptune region versus the much more distant fragmented interstellar cloud region, now frequented by comets of the Opik-Oort cloud. The Comet Kohoutek results add new insights, particularly with regard to the parent molecules and the nature of meteoric solids in comets, to restrict the range of the physical circumstances of comet formation. A few fundamental and outstanding questions are asked, and a plea made for unmanned missions to comets and asteroids in order to provide definitive answers as to the nature and origin of comets, asteroids, and the solar system generally.

  19. Comet ISON Enhanced

    NASA Image and Video Library

    2017-09-27

    Taken on 19 Nov. 2013, this image shows a composite "stacked" image of comet ISON. These five stacked images of 10 seconds each were taken with the 20" Marshall Space Flight Center telescope in New Mexico. This technique allows the comet's sweeping tail to emerge with more detail. Credit: NASA/MSFC/MEO/Cameron McCarty -------- More details on Comet ISON: Comet ISON began its trip from the Oort cloud region of our solar system and is now travelling toward the sun. The comet will reach its closest approach to the sun on Thanksgiving Day -- 28 Nov 2013 -- skimming just 730,000 miles above the sun's surface. If it comes around the sun without breaking up, the comet will be visible in the Northern Hemisphere with the naked eye, and from what we see now, ISON is predicted to be a particularly bright and beautiful comet. Catalogued as C/2012 S1, Comet ISON was first spotted 585 million miles away in September 2012. This is ISON's very first trip around the sun, which means it is still made of pristine matter from the earliest days of the solar system’s formation, its top layers never having been lost by a trip near the sun. Comet ISON is, like all comets, a dirty snowball made up of dust and frozen gases like water, ammonia, methane and carbon dioxide -- some of the fundamental building blocks that scientists believe led to the formation of the planets 4.5 billion years ago. NASA has been using a vast fleet of spacecraft, instruments, and space- and Earth-based telescope, in order to learn more about this time capsule from when the solar system first formed. The journey along the way for such a sun-grazing comet can be dangerous. A giant ejection of solar material from the sun could rip its tail off. Before it reaches Mars -- at some 230 million miles away from the sun -- the radiation of the sun begins to boil its water, the first step toward breaking apart. And, if it survives all this, the intense radiation and pressure as it flies near the surface of the sun could

  20. What's Causing the Activity on Comet 67P?

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-09-01

    self-heating between parts of the surface in contact.Plot of the modeled temperature of two typical surfaces on the comet: one from the neck region (solid line) and one from the head region (dashed line). Unlike the head, the neck displays drastic drops in temperature as a result of shadowing. [Al-Lagoa et al. 2015]Using this model, the authors find that the temperatures behaved as they predicted: the shadows falling on the comets neck causes this region to experience very rapid temperature changes relative to the rest of the body. The authors also found a definite correlation between the regions of most rapid temperature variations and the regions of the comet that show signs of activity in Rosetta images. This provides strong evidence that thermal cracking is indeed taking place in the shadowed regions of the neck, gradually eroding away the surface.Should this model prove correct, its a step toward understanding the evolution of comets like 67P. In addition, the results from this study imply that thermal cracking might happen faster than previously estimated in shadowed regions of other atmosphereless bodies, both near Earth and in the asteroid belt.CitationV. Al-Lagoa et al 2015 ApJ 810 L22. doi:10.1088/2041-8205/810/2/L22

  1. Comparing CN Features in Two Comets: 1P/Halley and 103P/Hartley 2

    NASA Astrophysics Data System (ADS)

    Samarasinha, Nalin H.; Lejoly, Cassandra; Barrera, Jose; Mueller, Beatrice; Schleicher, David

    2015-11-01

    Comets 1P/Halley and 103P/Hartley 2 show distinct CN features in their respecive comae. Both comets are non-principal-axis rotators. 1P/Halley is the proto-type for Halley-type comets with the Oort Cloud as its possible source region, whereas 103P/Hartley 2 is a Jupiter-Family comet that possibly originated from the Kuiper Belt. Both comets were spacecraft targets and studied widely from both space and from the ground.We will discuss the properties of CN features, and in particular the behavior of the derived outflow velocities based on the CN features present in the groundbased coma images of these two comets. The corresponding heliocentric distances for CN images of comet 1P/Halley range from approximately 0.8 AU to 2.0 AU (during its post-perihelion leg of the 1986 apparition). For CN images of comet 103P/Hartley 2, the corresponding heliocentric distances range from 1.31 AU through the perihelion (at 1.06 AU) to 1.25 AU (during its 2010 apparition).Ultimately, these results will be used to understand the rotational states and the activity behaviors of these two comets.

  2. Collisions with meteoroids as one of possible mechanisms of formation of hyperbolic orbits for comets

    NASA Astrophysics Data System (ADS)

    Guliyev, Ayyub; Nabiyev, Shaig

    2016-07-01

    Based on some characteristics of comets having osculating hyperbolic orbits (hereinafter hyperbolic comets) following working hypothesis is proposed: one of the reasons for the increase of the parameter e of comets could be their collision with large meteoroids from meteor streams, asteroids and Kuiper belts, etc. To test this hypothesis motion areas of 128 meteor showers from the Kronks catalogue are analyzed. The purpose of the analysis is to check the excess of nodes of hyperbolic comets in these zones. To solve the task, we suggest the following algorithm of calculations. Number (N) of orbital nodes of hyperbolic comets according to the distances 0.001, 0.005, 0.01, 0.05 i 0.1 a.u. from each stream is calculated. For the determination of the exceed' measure of N the special algorithm is developed. It allows to find the expected value and dispersion for these comet nodes. Comparative analysis of the parameter N in 63 cases displays its excess. It means one of possibility reasons of formation of the e excess is comets collision with meteoroids in the streams. Asteroid and Kuiper belts as potential sources of vast number of sporadic meteoroids are tested similarity. Results of the analysis are satisfactory for the working hypothesis.

  3. Comets in Australian Aboriginal Astronomy

    NASA Astrophysics Data System (ADS)

    Hamacher, Duane W.; Norris, Ray P.

    2011-03-01

    We present 25 accounts of comets from 40 Australian Aboriginal communities, citing both supernatural perceptions of comets and historical accounts of historically bright comets. Historical and ethnographic descriptions include the Great Comets of 1843, 1861, 1901, 1910, and 1927. We describe the perceptions of comets in Aboriginal societies and show that they are typically associated with fear, death, omens, malevolent spirits, and evil magic, consistent with many cultures around the world. We also provide a list of words for comets in 16 different Aboriginal languages.

  4. Comets and the Stardust Mission

    SciTech Connect

    LLNL - University of California Television

    2008-05-16

    The occasional appearance of comets has awed humans throughout history. But how much do we really know about comets? Did a comet kill the dinosaurs? And, what can comets tell us about our own ancient history? With comet dust from NASA's Stardust mission, scientists like Hope Ishii, a Research Scientist at Lawrence Livermore National Laboratory, are beginning to answer these questions. She and high school teacher Tom Shefler look at how comets formed, their role in the Earth's history and the clues about what happened over 4 billion years ago. Series: Science on Saturday [5/2008] [Science] [Show ID: 14492

  5. Comets and the Stardust Mission

    ScienceCinema

    LLNL - University of California Television

    2016-07-12

    The occasional appearance of comets has awed humans throughout history. But how much do we really know about comets? Did a comet kill the dinosaurs? And, what can comets tell us about our own ancient history? With comet dust from NASA's Stardust mission, scientists like Hope Ishii, a Research Scientist at Lawrence Livermore National Laboratory, are beginning to answer these questions. She and high school teacher Tom Shefler look at how comets formed, their role in the Earth's history and the clues about what happened over 4 billion years ago. Series: Science on Saturday [5/2008] [Science] [Show ID: 14492

  6. The study of comets, part 1. [conference on photometry and spectrum analysis of Kohoutek comet and comet tails

    NASA Technical Reports Server (NTRS)

    Donn, B. (Editor); Mumma, M. J. (Editor); Jackson, W. M. (Editor); Ahearn, M. (Editor); Harrington, R. (Editor)

    1976-01-01

    Papers are presented dealing with observations of comets. Topic discussed include: photometry, polarimetry, and astrometry of comets; detection of water and molecular transitions in comets; ion motions in comet tails; determination of comet brightness and luminosity; and evolution of cometary orbits. Emphasis is placed on analysis of observations of comet Kohoutek.

  7. The comet assay: a heavenly method!

    PubMed

    Collins, Andrew R

    2015-01-01

    The contributions to this special issue of Mutagenesis have been selected to cover the main research areas served by the comet assay, namely genotoxicology, environmental toxicology, human biomonitoring and fundamental investigations into mechanisms of DNA damage and repair. Innovative methods are described, technical issues are explored, and guidelines are given for venturing into relatively new or unexploited areas of research. The popularity of the comet assay in a historical context is illustrated by a bibliometric survey. © The Author 2014. Published by Oxford University Press on behalf of the UK Environmental Mutagen Society. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  8. Study of some comets through imaging polarimetry

    NASA Astrophysics Data System (ADS)

    Roy Choudhury, S.; Hadamcik, E.; Sen, A. K.

    2015-12-01

    Comets C/2007 N3 (Lulin), C/2011 L4 (PANSTARRS) and 290P/Jager were observed at phase angles <40○; between 2009 and 2014; with the 0.8 m Telescope at Haute-Provence Observatory (OHP) in France. The observations were polarimetric and mainly carried out in the red and near infra-red wavelength domains to reduce gaseous contaminations. The overall shape of the coma of comet Lulin is about circular without evident jet structure. The coma of comet C/2011 L4 is enlarged in the antisolar direction. Jets in a fan-like structure have been noticed between position angles 135°-245° in the treated intensity images. A correlated higher polarization region is noted on the corresponding polarization map. The shape of the coma of 290P/Jager is slightly elongated in the antisolar direction. Deeper negative polarization is found in the inner coma. The whole coma polarization values of these three comets correspond to the synthetic phase curve for comets at similar phase angles and wavelength.

  9. The Chemical Composition of an Extrasolar Kuiper-Belt-Object

    NASA Astrophysics Data System (ADS)

    Xu, S.; Zuckerman, B.; Dufour, P.; Young, E. D.; Klein, B.; Jura, M.

    2017-02-01

    The Kuiper Belt of our solar system is a source of short-period comets that may have delivered water and other volatiles to Earth and the other terrestrial planets. However, the distribution of water and other volatiles in extrasolar planetary systems is largely unknown. We report the discovery of an accretion of a Kuiper-Belt-Object analog onto the atmosphere of the white dwarf WD 1425+540. The heavy elements C, N, O, Mg, Si, S, Ca, Fe, and Ni are detected, with nitrogen observed for the first time in extrasolar planetary debris. The nitrogen mass fraction is ∼2%, comparable to that in comet Halley and higher than in any other known solar system object. The lower limit to the accreted mass is ∼1022 g, which is about one hundred thousand times the typical mass of a short-period comet. In addition, WD 1425+540 has a wide binary companion, which could facilitate perturbing a Kuiper-Belt-Object analog into the white dwarf’s tidal radius. This finding shows that analogs to objects in our Kuiper Belt exist around other stars and could be responsible for the delivery of volatiles to terrestrial planets beyond the solar system. Part of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among Caltech, the University of California and NASA. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  10. Sampling the stuff of a comet

    NASA Astrophysics Data System (ADS)

    Knacke, R.

    1987-03-01

    The composition of the clouds around Comet Halley during its perihelion passage was examined using intercept spacecraft, IUE, ICE and Pioneer Venus spacecraft, and ground-based instruments. Spectral data showed that the dust emitted in jets was mainly carbon, hydrogen, oxygen and nitrogen (CHON), with additives of Fe, Si, and Mg. The C abundance is similar to that in the sun and in the galactic stellar abundances, which supports the model of comets as proto-stellar nebula material. The nucleus was observed to shed 16 tons of water per second, a rate which at times may have doubled. Noticeably absent from the spectra were CH4 lines, an absence common in interstellar clouds. The possibilities that the comet contains a large deuterium-hydrogen ratio and carbonaceous material are discussed.

  11. Sampling the stuff of a comet

    SciTech Connect

    Knacke, R.

    1987-03-01

    The composition of the clouds around Comet Halley during its perihelion passage was examined using intercept spacecraft, IUE, ICE and Pioneer Venus spacecraft, and ground-based instruments. Spectral data showed that the dust emitted in jets was mainly carbon, hydrogen, oxygen and nitrogen (CHON), with additives of Fe, Si, and Mg. The C abundance is similar to that in the sun and in the galactic stellar abundances, which supports the model of comets as proto-stellar nebula material. The nucleus was observed to shed 16 tons of water per second, a rate which at times may have doubled. Noticeably absent from the spectra were CH/sub 4/ lines, an absence common in interstellar clouds. The possibilities that the comet contains a large deuterium-hydrogen ratio and carbonaceous material are discussed.

  12. A mantle conveyor belt beneath the Tethyan collisional belt

    NASA Astrophysics Data System (ADS)

    Becker, T. W.; Faccenna, C.

    2011-12-01

    Collisional belts are generated by the arrival of continental lithosphere into a subduction zone, leading to stacking of crustal slices during indentation. The Tethyan suture from the Bitlis to the Himalayas is a prime example where the Arabian and Indian plates collided with Eurasia during the Cenozoic, generating the highest mountain belts on Earth (Argand, 1924). While the kinematics of this process are well established, its dynamics are more uncertain. India and Arabia intriguingly keep advancing in spite of large collisional resisting forces. We perform global mantle circulation computations to test the role of deep mantle flow as a driving force for the kinematics of the Tethyan collisional belt, evaluating different boundary conditions and mantle density distributions as inferred from seismic tomography or slab models. Our results show that mantle drag exerted on the base of the lithosphere by a large-scale upwelling is likely the main cause for the ongoing indentation of the Indian and Arabian plates into Eurasia.

  13. To explore a comet - The Comet Rendezvous Asteroid Flyby mission at Comet Kopff

    NASA Technical Reports Server (NTRS)

    Cheng, Jeannie T.; Ionasescu, Rodica; Kakuda, Roy Y.; Sweetser, Theodore H.

    1990-01-01

    The Comet Rendezvous Asteroid Flyby (CRAF) mission has the primary goal of determining the composition and physical characteristics of a comet. To achieve this goal, a spacecraft will rendezvous with Comet Kopff and spend 2.5 years near the comet to study it with a variety of instruments. A penetrator will also be released by the spacecraft and propel itself into the nucleus of the comet for direct measurements. This paper presents a typical scenario for orbiting the comet, which provides for meeting all major scientific objectives.

  14. The Rosetta Mission to Comet 67P/ Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Buratti, Bonnie J.

    2017-06-01

    As remnant bodies left over from the formation of the Solar System, comets offer clues to the physical conditions and architecture of the protosolar nebula. The Rosetta spacecraft, which included an orbiter and a lander that were built and managed by the European Space Agency with NASA contributing four instruments and scientific expertise, was the first mission to orbit and study a comet through a perihelion passage. The targeted Jupiter-family comet 67P/ Churyumov-Gerasimenko, is seemingly two distinct planetesimals stuck together. The comet has not melted or been processed substantially, except for its outer layers, which consist of reaccreted dust and a crust of heated, devolatized, and annealed refractory materials and organics. The exceptionally low density (0.53 gm/cc) of 67P/ implies it is a rubble pile. The comet also appears to contain a hierarchy of building blocks: smaller spherically shaped meter-sized bodies can be seen in its interior, and even smaller cm-sized pebbles were imaged by the camera as the spacecraft made a soft crash landing on the comet’s surface on 30 September 2016. The unexpected discovery of molecular oxygen, nitrogen, and hydrogen imply that 67P/ was formed under cold conditions not exceeding 30K. The discovery of many organic compounds, including the amino acid glycine, lends support to the idea that comets, which originate in the Kuiper Belt and the Oort Cloud, brought the building blocks of life to Earth. More laboratory data on organic compounds would help to identify additional organic compounds on the comet. The differences between cometary and terrestrial D/H ratios suggest that comets are not the primary source of terrestrial water, although data on more comets is needed to confirm this result.Besides being primordial objects offering a window into the formation of solar systems, comets are astrophysical laboratories, ejecting dust and charged particles into the plasma comprising the solar wind. Several unusual phenomena

  15. Unidentified ions in comets

    NASA Technical Reports Server (NTRS)

    Engel, Lisa

    1990-01-01

    Optical spectra were taken of comets Halley, West, and Brorsen-Metcalf in the wavelength region 3200 to 6400 A. These spectra were offset approximately 10(exp -5) to 10(exp -6) km tailward from the nucleus so that the features detected were all ions with the exception of a very small residual C2 emission at 5165 A. The full labeled tail spectrum of comet Halley is given. While most of the features detected are attributable to CO(+), H2O(+), CO2(+), CH(+), and OH(+), there are three moderately strong bands in the spectra of comets Halley and Brorsen-Metcalf which remain unidentified. These features were not detected in comet West. All three spectra in the 4800 to 5400 A region are presented, Brorsen-Metcalf is the gassiest of the three. The central wavelengths of the unidentified features are 4930, 5300, and 6000 A. In an effort to identify the ions responsible for these features as well as to confirm previous identifications, laboratory spectra of ions were compared with the comet spectra. H2O(+) and CO(+) are known to have extensive emission in the 4800 to 6200 A region. Therefore, the possibility that these unidentified features are due to H2O(+) and CO(+) was investigated. A search for the following bands was conducted: H2O(+) (11-0), H2O(+) (12-0), H2O(+) (13-1), CO(+) (1-1), and CO(+) (0-0). CO(+) (1-1) and CO(+) (0-0) were previously identified and are present in all the spectra examined. The H2O(+) (11-0) band was identified. Comparison of the H2O(+) (11-0) synthetic spectrum with comet Brorsen-Metcalf data is presented. The relative fluxes of the blended H2O(+) lines in the synthetic spectrum match those of the cometary data. After eliminating H2O(+) and CO(+) as significant contributors to the stronger unidentified features, spectra of ions which are not yet identified in the optical region of comets were compared to the data. These ions are NH(+), CS(+), and C2(+). None of these ions appears to be a significant contributor to the optical spectra of these

  16. Unidentified ions in comets

    NASA Technical Reports Server (NTRS)

    Engel, Lisa

    1990-01-01

    Optical spectra were taken of comets Halley, West, and Brorsen-Metcalf in the wavelength region 3200 to 6400 A. These spectra were offset approximately 10(exp -5) to 10(exp -6) km tailward from the nucleus so that the features detected were all ions with the exception of a very small residual C2 emission at 5165 A. The full labeled tail spectrum of comet Halley is given. While most of the features detected are attributable to CO(+), H2O(+), CO2(+), CH(+), and OH(+), there are three moderately strong bands in the spectra of comets Halley and Brorsen-Metcalf which remain unidentified. These features were not detected in comet West. All three spectra in the 4800 to 5400 A region are presented, Brorsen-Metcalf is the gassiest of the three. The central wavelengths of the unidentified features are 4930, 5300, and 6000 A. In an effort to identify the ions responsible for these features as well as to confirm previous identifications, laboratory spectra of ions were compared with the comet spectra. H2O(+) and CO(+) are known to have extensive emission in the 4800 to 6200 A region. Therefore, the possibility that these unidentified features are due to H2O(+) and CO(+) was investigated. A search for the following bands was conducted: H2O(+) (11-0), H2O(+) (12-0), H2O(+) (13-1), CO(+) (1-1), and CO(+) (0-0). CO(+) (1-1) and CO(+) (0-0) were previously identified and are present in all the spectra examined. The H2O(+) (11-0) band was identified. Comparison of the H2O(+) (11-0) synthetic spectrum with comet Brorsen-Metcalf data is presented. The relative fluxes of the blended H2O(+) lines in the synthetic spectrum match those of the cometary data. After eliminating H2O(+) and CO(+) as significant contributors to the stronger unidentified features, spectra of ions which are not yet identified in the optical region of comets were compared to the data. These ions are NH(+), CS(+), and C2(+). None of these ions appears to be a significant contributor to the optical spectra of these

  17. Frequency and intensity of comet showers from the Oort cloud

    SciTech Connect

    Heisler, J.; Alcock, C.; Tremaine, S.

    1987-05-01

    The nature of new comets and the frequency and intensity of comet showers are presently studied by means of a simulation in which an ensemble of one million comets is perturbed at random times by the Bahcall-Soneira (1980) Galaxy model's population of main sequence stars and white dwarfs. The time-integrated flux is dominated by the showers for comets whose semimajor axes are less than about 30,000 AU. The inclusion of tidal effects increases the loss rate of comets with semimajor axes between 10,000 and 20,000 AU by a factor of about 4, so that the Galactic tide, rather than individual stellar perturbations, is the dominant Oort cloud evolution-driving mechanism. 44 references.

  18. Dust bands in the asteroid belt

    NASA Technical Reports Server (NTRS)

    Sykes, Mark V.; Greenberg, Richard; Dermott, Stanley F.; Nicholson, Philip D.; Burns, Joseph A.

    1989-01-01

    This paper describes the original IRAS observations leading to the discovery of the three dust bands in the asteroid belt and the analysis of data. Special attention is given to an analytical model of the dust band torus and to theories concerning the origin of the dust bands, with special attention given to the collisional equilibrium (asteroid family), the nonequilibrium (random collision), and the comet hypotheses of dust-band origin. It is noted that neither the equilibrium nor nonequilibrium models, as currently formulated, present a complete picture of the IRAS dust-band observations.

  19. Constraining the cometary flux through the asteroid belt during the late heavy bombardment

    NASA Astrophysics Data System (ADS)

    Brož, M.; Morbidelli, A.; Bottke, W. F.; Rozehnal, J.; Vokrouhlický, D.; Nesvorný, D.

    2013-03-01

    In the Nice model, the late heavy bombardment (LHB) is related to an orbital instability of giant planets which causes a fast dynamical dispersion of a trans-Neptunian cometary disk. We study effects produced by these hypothetical cometary projectiles on main belt asteroids. In particular, we want to check whether the observed collisional families provide a lower or an upper limit for the cometary flux during the LHB. We present an updated list of observed asteroid families as identified in the space of synthetic proper elements by the hierarchical clustering method, colour data, albedo data and dynamical considerations and we estimate their physical parameters. We selected 12 families which may be related to the LHB according to their dynamical ages. We then used collisional models and N-body orbital simulations to gain insight into the long-term dynamical evolution of synthetic LHB families over 4 Gyr. We account for the mutual collisions between comets, main belt asteroids, and family members, the physical disruptions of comets, the Yarkovsky/YORP drift in semimajor axis, chaotic diffusion in eccentricity/inclination, or possible perturbations by the giant-planet migration. Assuming a "standard" size-frequency distribution of primordial comets, we predict the number of families with parent-body sizes DPB ≥ 200 km - created during the LHB and subsequent ≃4 Gyr of collisional evolution - which seems consistent with observations. However, more than 100 asteroid families with DPB ≥ 100 km should be created at the same time which are not observed. This discrepancy can be nevertheless explained by the following processes: i) asteroid families are efficiently destroyed by comminution (via collisional cascade), ii) disruptions of comets below some critical perihelion distance (q ≲ 1.5 AU) are common. Given the freedom in the cometary-disruption law, we cannot provide stringent limits on the cometary flux, but we can conclude that the observed distribution of

  20. Hubble View of Comet ISON

    NASA Image and Video Library

    This time-lapse sequence of images from the Hubble Space Telescope shows comet ISON as it appeared on May 8, 2013. At the time the images were taken, the comet was 403 million miles from the Earth,...

  1. Spacecraft Images Comet Target Jets

    NASA Image and Video Library

    2010-11-04

    NASA Deep Impact spacecraft High- and Medium-Resolution Imagers HRI and MRI captured multiple jets emanating from comet Hartley 2 turning on and off while the spacecraft is 8 million kilometers 5 million miles away from the comet.

  2. The nature of comet nuclei

    NASA Technical Reports Server (NTRS)

    Sykes, Mark V.; Walker, Russell G.

    1992-01-01

    The icy-conglomerate model of comet nuclei has dominated all others since its introduction. It provided a basis for understanding the non-gravitational motions of comets which had perplexed dynamicists up to that time, and provided a focus for understanding cometary composition and origin. The image of comets as dirty snowballs was quickly adopted. Comet nuclei including their trail mass loss rates and refractory to volatile mass ratios are described.

  3. Infrared observations of comets

    NASA Technical Reports Server (NTRS)

    Hanner, Martha S.

    1991-01-01

    Selected comets are observed in the near infrared (1 to 2.2 micron) and thermal infrared (3.5 to 20 micron) with the NASA Infrared Telescope Facility (IRTF) and other telescopes as appropriate, in order to characterize the physical properties of the dust grains; their composition, size distribution, emissivity, and albedo. Systematic variations in these properties among comets are looked for, in order to understand the heterogeneity of comet nuclei. Spectrophotometry of the 10 micron silicate emission feature is particularly emphasized. The rate of dust production from the nucleus and its temporal variability are also determined. Knowledge of the dust environment is essential to S/C design and mission planning for NASA's CRAF mission.

  4. IRAS observations of comets

    NASA Technical Reports Server (NTRS)

    Walker, R. G.; Matson, D. L.; Veeder, G. J.

    1986-01-01

    The moderate spatial resolution and high sensitivity of the Infrared Astronomical Satellite (IRAS), which surveyed the celestial sphere during 1983 at wavelengths of 12, 25, 60, and 100 microns, were particularly well suited to detecting extended thermal emission from cometary dust. Sources with infrared color temperatures characteristic of solar system bodies, and at the ephemerides position of known comets were selected for analysis by the IRAS Asteroid Data Analysis System (ADAS). The data base is now available for use by researchers. This paper describes the development of the data base, details its entries, and presents a statistical analysis of its contents. The IRAS survey contains multiple observations of many periodic comets. A brief description and analysis is given of the observed infrared and derived physical properties for several comets of special interest.

  5. Astrobiology of Comets

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Wickramasinghe, Nalin C.; Wallis, Max K.; Sheldon, Robert B.

    2004-01-01

    We review the current state of knowledge concerning microbial extremophiles and comets and the potential significance of comets to Astrobiology. We model the thermal history of a cometary body, regarded as an assemblage of boulders, dust, ices and organics, as it approaches a perihelion distance of - IAU. The transfer of incident energy from sunlight into the interior leads to the melting of near surface ices, some under stable porous crust, providing possible habitats for a wide range of microorganisms. We provide data concerning new evidence for indigenous microfossils in CI meteorites, which may be the remains of extinct cometary cores. We discuss the dominant microbial communities of polar sea-ice, Antarctic ice sheet, and cryoconite environments as possible analogs for microbial ecosystems that may grow in sub-crustal pools or in ice/water films in comets.

  6. Planetary perturbations for Oort cloud comets: II. Implications for the origin of observable comets

    NASA Astrophysics Data System (ADS)

    Fouchard, M.; Rickman, H.; Froeschlé, Ch.; Valsecchi, G. B.

    2014-03-01

    We present Monte Carlo simulations of the dynamical history of the Oort cloud, where in addition to the main external perturbers (Galactic tides and stellar encounters) we include, as done in a companion paper (Fouchard, M., Rickman, H., Froeschlé, Ch., Valsecchi, G.B. [2013b]. Icarus, in press), the planetary perturbations experienced each time the comets penetrate to within 50 AU of the Sun. Each simulation involves an initial sample of four million comets and extends over a maximum of 5 Gyr. For better understanding of the outcomes, we supplement the full dynamical model by others, where one or more of the effects are left out. We concentrate on the production of observable comets, reaching for the first time a perihelion within 5 AU of the Sun. We distinguish between four categories, depending on whether the comet jumps across, or creeps through, the Jupiter-Saturn barrier (perihelion distances between 5 and 15 AU), and whether the orbit leading to the observable perihelion is preceded by a major planetary perturbation or not. For reasons explained in the paper, we call the strongly perturbed comets "Kaib-Quinn comets". We thus derive a synthetic picture of the Oort spike, from which we draw two main conclusions regarding the full dynamical model. One is that 2/3 of the observable comets are injected with the aid of a planetary perturbation at the previous perihelion passage, and about half of the observable comets are of the Kaib-Quinn type. The other is that the creepers dominate over the jumpers. Due to this fact, the spike peaks at only 31 000 AU, and the majority of new comets have semi-major axes less than this value. The creepers show a clear preference for retrograde orbits as a consequence of the need to avoid untimely, planetary ejection before becoming observable. Thus, the new comets should have a 60/40 preference for retrograde against prograde orbits in apparent conflict with observations. However, both these and other results depend on our model

  7. Discovering the Nature of Comets.

    ERIC Educational Resources Information Center

    Whipple, Fred L.

    1986-01-01

    "The Mystery of Comets" by Dr. Fred Whipple provides an introduction to the modern picture of comets and his personal reminiscences of how his model of comets came to be. An adaptation of several sections of the book is presented. (JN)

  8. Look--It's a Comet!

    ERIC Educational Resources Information Center

    Berglund, Kay

    1997-01-01

    Describes a classroom lesson on comets that uses modeling and guided imagery to spark students' curiosity. Comet models are built using chunks of rock salt, polystyrene balls, and tinsel. Abstract ideas are made more concrete with a guided imagery story called Comet Ride! Includes an introduction to the use of parallax to measure the distance of…

  9. Term Projects on Interstellar Comets

    ERIC Educational Resources Information Center

    Mack, John E.

    1975-01-01

    Presents two calculations of the probability of detection of an interstellar comet, under the hypothesis that such comets would escape from comet clouds similar to that believed to surround the sun. Proposes three problems, each of which would be a reasonable term project for a motivated undergraduate. (Author/MLH)

  10. Discovering the Nature of Comets.

    ERIC Educational Resources Information Center

    Whipple, Fred L.

    1986-01-01

    "The Mystery of Comets" by Dr. Fred Whipple provides an introduction to the modern picture of comets and his personal reminiscences of how his model of comets came to be. An adaptation of several sections of the book is presented. (JN)

  11. Look--It's a Comet!

    ERIC Educational Resources Information Center

    Berglund, Kay

    1997-01-01

    Describes a classroom lesson on comets that uses modeling and guided imagery to spark students' curiosity. Comet models are built using chunks of rock salt, polystyrene balls, and tinsel. Abstract ideas are made more concrete with a guided imagery story called Comet Ride! Includes an introduction to the use of parallax to measure the distance of…

  12. Term Projects on Interstellar Comets

    ERIC Educational Resources Information Center

    Mack, John E.

    1975-01-01

    Presents two calculations of the probability of detection of an interstellar comet, under the hypothesis that such comets would escape from comet clouds similar to that believed to surround the sun. Proposes three problems, each of which would be a reasonable term project for a motivated undergraduate. (Author/MLH)

  13. Comets, meteorites and atmospheres

    NASA Technical Reports Server (NTRS)

    Owen, T.; Bar-Nun, A.

    1996-01-01

    The relatively low value of Xe/Kr in the atmospheres of Earth and Mars seems to rule out meteorites as the major carriers of noble gases to the inner planets. Laboratory experiments on the trapping of gases in ice forming at low temperatures suggest that comets may be a better choice. It is then possible to develop a model for the origin of inner planet atmospheres based on volatiles delivered by comets added to volatiles originally trapped in planetary rocks. The model will be tested by results from the Galileo Entry Probe.

  14. First Comet Encounter

    NASA Image and Video Library

    2010-09-09

    Members of the audience look on as Dr. James L. Green, Director of Planetary Science at NASA, right, speaks with Dr. Robert Farquar, an executive for space exploration at KinetX Inc., during a symposium commemorating a quarter-century of comet discoveries, Friday, Sept. 10, 2010, in the Knight studio at the Newseum in Washington. The International Sun-Earth Explorer-3 (ISEE-3) spacecraft flew past the comet Giacobini-Zinner on Sept. 11, 1985 which established a foundation of discoveries that continue today. Photo Credit: (NASA/Paul E. Alers)

  15. First Comet Encounter

    NASA Image and Video Library

    2010-09-09

    Dr. James L. Green, Director of Planetary Science at NASA, right, speaks with Dr. Robert Farquar, an executive for space exploration at KinetX Inc., during a symposium commemorating a quarter-century of comet discoveries, Friday, Sept. 10, 2010, in the Knight studio at the Newseum in Washington. The International Sun-Earth Explorer-3 (ISEE-3) spacecraft flew past the comet Giacobini-Zinner on Sept. 11, 1985 which established a foundation of discoveries that continue today. Photo Credit: (NASA/Paul E. Alers)

  16. Taking a Comet Temperature

    NASA Image and Video Library

    2015-10-01

    Subsurface temperature maps of 67P/Churyumov-Gerasimenko, showing the southern hemisphere of the comet. The maps are based on observations obtained with ESA MIRO instrument. The maps are based on observations obtained with the Microwave Instrument for the Rosetta Obiter (MIRO) at millimeter (left) and sub-millimeter (right) wavelengths between September and October 2014. The MIRO data are projected on a digital shape model of the comet. A temperature bar (in degrees Kelvin), is to the right. http://photojournal.jpl.nasa.gov/catalog/PIA19970

  17. Synaptic ribbon. Conveyor belt or safety belt?

    PubMed

    Parsons, T D; Sterling, P

    2003-02-06

    The synaptic ribbon in neurons that release transmitter via graded potentials has been considered as a conveyor belt that actively moves vesicles toward their release sites. But evidence has accumulated to the contrary, and it now seems plausible that the ribbon serves instead as a safety belt to tether vesicles stably in mutual contact and thus facilitate multivesicular release by compound exocytosis.

  18. Migration of comets to near-Earth orbits

    NASA Astrophysics Data System (ADS)

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

    2002-09-01

    The orbital evolution of ~5000 Jupiter-crossing objects rbital evolution of ~5000 Jupiter-crossing objects (JCOs) with initial periods <10 yr under the gravitational influence of the planets (except Mercury and Pluto) was integrated using the Bulirsh-Stoer method. The simulations showed that most of the collisions of former JCOs with the terrestrial planets are due to a small ( ~0.1-1%) portion of objects that moved for several Myrs in orbits with aphelion distances Q<4.7 AU. Some had typical asteroidal and NEO orbits and could have Q<3 AU for millions of years. Usually ~0.1% of JCOs reached semi-major axes a<2 AU for >=0.5 Myr, and some moved in such orbits for more than 5 Myr. In our runs one former JCO had Aten-type orbits for >3 Myr, and the probability of its collision with the Earth was greater than that of all other simulated former JCOs. This object also moved for about 10 Myr (before its collision with Venus) in inner-Earth orbits (with Q<0.983AU) and its probability of collision with Venus was even greater than the total probability of collisions of all the other simulated JCOs with Earth. On average, one of 300 JCOs collided with the Sun, and an object spent 0.13 Myr in Jupiter-crossing orbits, and for 1/3 of this time it had a period <20 yr. The above results were obtained using the method of Bulirsh and Stoer, but the evolution of 3100 orbits was also investigated with a symplectic method. For a symplectic method, simulated former JCOs spent more time in orbits with a<2 AU. Results of the orbital evolution of JCOs show that many Earth-crossing objects can move in highly eccentric (e>0.6) orbits and, probably, most of the 1-km objects in such orbits have not yet been discovered. Results of the orbital evolution of trans-Neptunian objects and JCOs showed that a considerable portion of NEOs could have come from the trans-Neptunian belt (so they can be extinct comets). In principle, this belt can provide most of the Earth-crossing objects (especially

  19. Stardust (Comet) Samples and the Meteorite Record

    NASA Astrophysics Data System (ADS)

    Weisberg, M.; Connolly, H.; Zolensky, M.; Bland, P.; Bradley, J.; Braerley, A.; Bridges, J.; Brownlee, D.; Butterworth, A.; Dai, Z.; Ebel, D.; Genge, M.; Gounelle, M.; Graham, G.; Grossman, J.; Grossman, L.; Harvey, R.; Ishii, H.; Kearsley, A.; Keller, L.; Krot, A.; Langenhorst, F.; Lanzirotti, A.; Leroux, H.; Matrajt, G.; Messenger, K.; Mikouchi, T.; Nakamura, T.; Ohsumi, K.; Okudaira, K.; Perronnet, M.; Simon, S.; Stephan, T.; Stroud, R.; Taheri, M.; Tomeoka, K.; Toppani, A.; Tsou, P.; Tsuchiyama, A.; Velbel, M.; Weber, I.; Westphal, A.; Yano, H.; Zega, T.

    2006-12-01

    Perhaps the most intriguing aspect of the material collected by Stardust from `comet Wild 2 is the preponderance of high temperature and reduced crystalline phases, which are characteristic of chondrites thought to derive from the main Asteroid Belt (2-4 AU) [1]. Here we compare the mineralogy of Stardust samples to that of chondrite groups. Results: Investigation by the Preliminary Examination Team (PET) of particles from Wild 2 shows a mineral assemblage typical of chondrites, with olivine, pyroxene, FeNi-metal and sulfide as common components. Olivine and low-Ca pyroxene have a range of mg# (Fa0.5-41 and Fs0-48, respectively), which indicates that the material is unequilibrated, similar to types 2 and 3 chondrites. Some forsterite with <1 wt% FeO has up to 6.4 wt% MnO and 1.4 wt% Cr2O3. Other silicates observed are Ti-bearing aluminus diopside and rare melilite, typical of some calcium, aluminum-rich inclusions (CAIs) in carbonaceous (C) chondrites. Additionally, FeNi- metal and sulfides including pentlandite [(FeNi)9S8)] and Fe-Ni-Cu and Fe-Zn sulfide, phases observed in C and enstatite (E) chondrites, are present in some particles. V-bearing osbornite (TiN), a phase also observed in some C and E chondrites, occurs associated with unidentified Zr-rich phase(s). Discussion: The observations by the PET are based on work done in a short period of time on a limited number of particles less than several microns in size, and, hence, conclusions based on these data are tentative. Many C chondrite groups have the wide range of ferromagnesian silicate compositions found in the Stardust samples. However, the range of olivine and pyroxene compositions, occurrence of Mn-, Cr-rich olivine, metal and pentlandite are features most consistent with CR and CH chondrites, though a CM-like lithology cannot be ruled out. Mn-, Cr- rich forsterite is found in the matrix and in amoeboid olivine aggregates in CR chondrites [2, 3]; Osbornite-bearing CAIs have been identified in the ALH

  20. A volatility index for comets

    NASA Technical Reports Server (NTRS)

    Whipple, Fred L.

    1992-01-01

    The variations in total brightness of a comet when it is most active, near perihelion, are presently used as the bases of a volatility index (VI) for short-period (SP) and long-period (LP) comets. Volatility does not correlate with period among the LP comets, and thereby shows no 'aging' effect; similarly, the VI measurements are the same for SP and for LP comets and exhibit no correlation with (1) absolute magnitude near perihelion, (2) orbital inclination, or (3) activity index measuring the intrinsic brightness change from great solar distances to the maximum near perihelion. Active comets are shown to be basically alike irrespective of their orbits or 'ages'.

  1. Infrared observations of faint comets

    NASA Technical Reports Server (NTRS)

    Campins, H.; Gradie, J.; Lebofsky, M.; Rieke, G.

    1981-01-01

    Infrared observations of the periodic comets Encke, Stephan-Oterma and Chernykh indicate that the dusty component in this class of comets is not radically different from the dusty component found in nonperiodic comets. The differences in the infrared behavior among these three comets suggest that a range of behaviors rather than a single behavior typifies the cometary activity. The range in albedo (0.02 to 0.10) of the dust calculated for the periodic comets is similar to the range in albedos seen among the asteroids.

  2. Infrared Spectroscopy of the Dust in Comets and Relationships to Interstellar Dust

    NASA Technical Reports Server (NTRS)

    Hanner, Martha S.

    2003-01-01

    Infrared spectroscopy of the dust in comets reveals a complex mix of silicate materials, including both crystalline and non-crystalline components of both olivine (forsterite) and pyroxene composition. These various components do not necessarily share a common origin. Since comets formed in cold regions of the solar nebula, pre-solar grains in the nebula could have been accreted into comets with little alteration. Some of the cometary silicates may be of circumstellar (formed in circumstellar outflows of evolved stars) or interstellar (formed in dense region of the interstellar medium) origin. Spectral similarities to both circumstellar and interstellar silicates are seen in comet spectra. the short-period Kuiper Belt comets) show weak or no spectral features. The lack of features is generally explained as a particle size effect: the small silicate grains are embedded in larger, optically thick particles. However, compositional differences cannot be ruled out. For example, no unambiguous signature of forsterite has yet been seen in the spectrum of a short-period comet. Thus, the Stardust sample from short-period comet P/Wild 2 will be extremely valuable. Not only grain by grain composition and isotopic ratios but also grain morphology, irradiation history, and evidence of organic refractory mantles are important for understanding their origin. The relative abundance and distinguishing characteristics of the various crystalline and non-crystalline silicate components needs to be established. While some comets, such as Hale-Bopp, display a rich infrared spectrum, others (particularly

  3. Compositional homogeneity in the fragmented comet 73P/Schwassmann-Wachmann 3.

    PubMed

    Dello Russo, N; Vervack, R J; Weaver, H A; Biver, N; Bockelée-Morvan, D; Crovisier, J; Lisse, C M

    2007-07-12

    The remarkable compositional diversity of volatile ices within comets can plausibly be attributed to several factors, including differences in the chemical, thermal and radiation environments in comet-forming regions, chemical evolution during their long storage in reservoirs far from the Sun, and thermal processing by the Sun after removal from these reservoirs. To determine the relevance of these factors, measurements of the chemistry as a function of depth in cometary nuclei are critical. Fragmenting comets expose formerly buried material, but observational constraints have in the past limited the ability to assess the importance of formative conditions and the effects of evolutionary processes on measured composition. Here we report the chemical composition of two distinct fragments of 73P/Schwassmann-Wachmann 3. The fragments are remarkably similar in composition, in marked contrast to the chemical diversity within the overall comet population and contrary to the expectation that short-period comets should show strong compositional variation with depth in the nucleus owing to evolutionary processing from numerous close passages to the Sun. Comet 73P/Schwassmann-Wachmann 3 is also depleted in the most volatile ices compared to other comets, suggesting that the depleted carbon-chain chemistry seen in some comets from the Kuiper belt reservoir is primordial and not evolutionary.

  4. SLH Timing Belt Powertrain

    SciTech Connect

    Schneider, Abe

    2014-04-09

    The main goal of this proposal was to develop and test a novel powertrain solution for the SLH hydroEngine, a low-cost, efficient low-head hydropower technology. Nearly two-thirds of U.S. renewable electricity is produced by hydropower (EIA 2010). According to the U.S. Department of Energy; this amount could be increased by 50% with small hydropower plants, often using already-existing dams (Hall 2004). There are more than 80,000 existing dams, and of these, less than 4% generate power (Blankinship 2009). In addition, there are over 800 irrigation districts in the U.S., many with multiple, non-power, low-head drops. These existing, non-power dams and irrigation drops could be retrofitted to produce distributed, baseload, renewable energy with appropriate technology. The problem is that most existing dams are low-head, or less than 30 feet in height (Ragon 2009). Only about 2% of the available low-head hydropower resource in the U.S. has been developed, leaving more than 70 GW of annual mean potential low-head capacity untapped (Hall 2004). Natel Energy, Inc. is developing a low-head hydropower turbine that operates efficiently at heads less than 6 meters and is cost-effective for deployment across multiple low-head structures. Because of the unique racetrack-like path taken by the prime-movers in the SLH, a flexible powertrain is required. Historically, the only viable technological solution was roller chain. Despite the having the ability to easily attach blades, roller chain is characterized by significant drawbacks, including high cost, wear, and vibration from chordal action. Advanced carbon- fiber-reinforced timing belts have been recently developed which, coupled with a novel belt attachment system developed by Natel Energy, result in a large reduction in moving parts, reduced mass and cost, and elimination of chordal action for increased fatigue life. The work done in this project affirmatively addressed each of the following 3 major uncertainties concerning

  5. Imaging studies of comets

    NASA Technical Reports Server (NTRS)

    Niedner, Malcolm B., Jr.; Klinglesmith, Daniel A., III; Westpfahl, David J.

    1991-01-01

    The Joint Observatory for Cometary Research's (JOCR) historical mission has been to provide understanding of large-scale interactions between bright comets and solar wind using wide-angle (Schmidt) imagery and spacecraft data; in this pursuit the JOCR has excelled. The 16 inch Newtonian/Cassegrain telescope was upgraded to permit filtered, narrow-field charge coupled device (CCD) imaging of both bright and faint comets. Thus, the goal of obtaining narrow-band imagery of the near-nuclear region of bright comets was added to JOCR's original mission with emphasis on ionization processes and total gas production. A 300 mm lens/CCD system exists with 3 degree field of view (FOV) which uses comet filters; this system bridges the gap between the wide-field (8 x 10 deg) Schmidt plates and the several-arcmin. field of the 16 inch telescope. JOCR is located under dark skies on South Baldy Mountain (el. 10,600 ft.) near Socorro, NM, and is one of the last truly dark sites in the continental U.S.

  6. Comets in Indian Scriptures

    NASA Astrophysics Data System (ADS)

    Das Gupta, P.

    2016-01-01

    The Indo-Aryans of ancient India observed stars and constellations for ascertaining auspicious times in order to conduct sacrificial rites ordained by the Vedas. Naturally, they would have sighted comets and referred to them in the Vedic texts. In Rigveda (circa 1700-1500 BC) and Atharvaveda (circa 1150 BC), there are references to dhumaketus and ketus, which stand for comets in Sanskrit. Rigveda speaks of a fig tree whose aerial roots spread out in the sky (Parpola 2010). Had this imagery been inspired by the resemblance of a comet's tail with long and linear roots of a banyan tree (ficus benghalensis)? Varahamihira (AD 550) and Ballal Sena (circa AD 1100-1200) described a large number of comets recorded by ancient seers, such as Parashara, Vriddha Garga, Narada, and Garga, to name a few. In this article, we propose that an episode in Mahabharata in which a radiant king, Nahusha, who rules the heavens and later turns into a serpent after he kicked the seer Agastya (also the star Canopus), is a mythological retelling of a cometary event.

  7. Finding Comet Halley.

    ERIC Educational Resources Information Center

    Glenn, William H.

    1985-01-01

    Provides background information and references on Comet Halley (which will be observable by telescope in October 1985 and reach its most brilliant appearance in March and April of 1986). Suggestions for equipment and maps of its path through the sky are included. (DH)

  8. DRBE comet trails

    SciTech Connect

    Arendt, Richard G.

    2014-12-01

    Re-examination of the Cosmic Background Explorer Diffuse Infrared Background Experiment (DIRBE) data reveals the thermal emission of several comet dust trails. The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported. The known trails of 2P/Encke and 73P/Schwassmann–Wachmann 3 are also seen. The dust trails have 12 and 25 μm surface brightnesses of <0.1 and <0.15 MJy sr{sup −1}, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals 1 additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

  9. DIRBE Comet Trails

    NASA Astrophysics Data System (ADS)

    Arendt, Richard G.

    2014-12-01

    Re-examination of the Cosmic Background Explorer Diffuse Infrared Background Experiment (DIRBE) data reveals the thermal emission of several comet dust trails. The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported. The known trails of 2P/Encke and 73P/Schwassmann-Wachmann 3 are also seen. The dust trails have 12 and 25 μm surface brightnesses of \\lt 0.1 and \\lt 0.15 MJy sr-1, respectively, which is \\lt 1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals 1 additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

  10. Comets and life

    NASA Technical Reports Server (NTRS)

    Oro, J.; Berry, J. M.

    1987-01-01

    Some of the chemical species which have been detected in comets include H2O, HCN, CH3CN, CO, CO2, NH3, CS, C2 and C3. All of these have also been detected in the interstellar medium, indicating a probable relationship between interstellar dust and gas clouds and comets. Laboratory experiments carried out with different mixtures of these molecules give rise to the formation of the biochemical compounds which are necessary for life, such as amino acids, purines, pyrimidines, monosaccharides, etc. However, in spite of suggestions to the contrary, the presence of life in comets is unlikely. On the other hand, the capture of cometary matter by the primitive earth is considered essential for the development of life on this planet. The amount of cometary carbon-containing matter captured by the earth, as calcualted by different authors, is several times larger than the total amount of organic matter present in the biosphere (10 to the 18th g). The major classes of reactions which were probably involved in the formation of key biochemical compounds are discussed. The tentative conclusions are that: (1) comets played a predominant role in the emergence of life on earth, and (2) they are the cosmic connection with extraterrestrial life.

  11. DIRBE Comet Trails

    NASA Technical Reports Server (NTRS)

    Arendt, Richard G.

    2015-01-01

    Re-examination of the COBE DIRBE data reveals the thermal emission of several comet dust trails.The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported.The known trails of 2P/Encke, and 73P/Schwassmann-Wachmann 3 are also seen. The dust trails have 12 and 25 microns surface brightnesses of <0.1 and <0.15 MJy/sr, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals one additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

  12. Halley's Comet: A Bibliography.

    ERIC Educational Resources Information Center

    Freitag, Ruth S., Comp.

    Included in this bibliography are over 3,200 references to publications on Halley's Comet, its history, orbital motion, and physical characteristics, meteor streams associated with it, preparations for space missions to study it in 1986, and popular reaction to its appearances. Also cited are a few papers that, although they devote little…

  13. Rendezvous with a comet

    NASA Astrophysics Data System (ADS)

    Taylor, Matt

    2014-10-01

    After making a successful rendezvous with Comet 67P/Churyumov-Gerasimenko earlier this year, Europe's Rosetta craft is now riding alongside this celestial body and next month is set to land a probe on its surface. Matt Taylor describes the excitement of this unique project and the scientific insights that it hopes to achieve.

  14. Mars Comet Encounter Briefing

    NASA Image and Video Library

    2014-10-09

    Dwayne Brown, NASA public affairs officer, moderates a media briefing where panelists outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. Photo Credit: (NASA/Joel Kowsky)

  15. Halley's Comet: A Bibliography.

    ERIC Educational Resources Information Center

    Freitag, Ruth S., Comp.

    Included in this bibliography are over 3,200 references to publications on Halley's Comet, its history, orbital motion, and physical characteristics, meteor streams associated with it, preparations for space missions to study it in 1986, and popular reaction to its appearances. Also cited are a few papers that, although they devote little…

  16. Comet radar explorer

    NASA Astrophysics Data System (ADS)

    Farnham, Tony; Asphaug, Erik; Barucci, Antonella; Belton, Mike; Bockelee-Morvan, Dominique; Brownlee, Donald; Capria, Maria Teresa; Carter, Lynn; Chesley, Steve; Farnham, Tony; Gaskell, Robert; Gim, Young; Heggy, Essam; Herique, Alain; Klaasen, Ken; Kofman, Wlodek; Kreslavsky, Misha; Lisse, Casey; Orosei, Roberto; Plaut, Jeff; Scheeres, Dan

    The Comet Radar Explorer (CORE) is designed to perform a comprehensive and detailed exploration of the interior, surface, and inner coma structures of a scientifically impor-tant Jupiter family comet. These structures will be used to investigate the origins of cometary nuclei, their physical and geological evolution, and the mechanisms driving their spectacular activity. CORE is a high heritage spacecraft, injected by solar electric propulsion into orbit around a comet. It is capable of coherent deep radar imaging at decameter wavelengths, high resolution stereo color imaging, and near-IR imaging spectroscopy. Its primary objective is to obtain a high-resolution map of the interior structure of a comet nucleus at a resolution of ¿100 elements across the diameter. This structure shall be related to the surface geology and morphology, and to the structural details of the coma proximal to the nucleus. This is an ideal complement to the science from recent comet missions, providing insight into how comets work. Knowing the structure of the interior of a comet-what's inside-and how cometary activity works, is required before we can understand the requirements for a cryogenic sample return mission. But more than that, CORE is fundamental to understanding the origin of comets and their evolution in time. The mission is made feasible at low cost by the use of now-standard MARSIS-SHARAD reflec-tion radar imaging hardware and data processing, together with proven flight heritage of solar electric propulsion. Radar flight heritage has been demonstrated by the MARSIS radar on Mars Express (Picardi et al., Science 2005; Plaut et al., Science 2007), the SHARAD radar onboard the Mars Reconnaissance Orbiter (Seu et al., JGR 2007), and the LRS radar onboard Kaguya (Ono et al, EPS 2007). These instruments have discovered detailed subsurface structure to depths of several kilometers in a variety of terrains on Mars and the Moon. A reflection radar deployed in orbit about a comet

  17. Finding Comet Halley.

    ERIC Educational Resources Information Center

    Glenn, William H.

    1985-01-01

    Provides background information and references on Comet Halley (which will be observable by telescope in October 1985 and reach its most brilliant appearance in March and April of 1986). Suggestions for equipment and maps of its path through the sky are included. (DH)

  18. Comet from 40 Meters

    NASA Image and Video Library

    2014-11-13

    This image was taken by the Philae lander of the European Space Agency Rosetta mission when it was about 130 feet 40 meters above the surface of comet 67P/Churyumov-Gerasimenko during descent to the surface on Nov. 12, 2014.

  19. Ammonia abundances in four comets

    NASA Astrophysics Data System (ADS)

    Wyckoff, S.; Tegler, S. C.; Engel, L.

    1991-02-01

    NH2 emission band strengths were measured in four comets and the NH2 column densities were determined in order to measure the ammonia content of the comets. The mean ammonia/water abundance ratio derived for the four comets is found to be 0.13 + or - 0.06 percent, with no significant variation among the comets. The uniformity of this abundance attests to a remarkable degree of chemical homogeneity over large scales in the comet-forming region of the primordial solar nebula, and contrasts with the CO abundance variations found previously in comets. The N2 and NH3 abundances indicate a condensation temperature in the range 20-160 K, consistent with virtually all comet formation hypotheses.

  20. Ammonia abundances in four comets

    NASA Technical Reports Server (NTRS)

    Wickoff, Susan; Tegler, Stephen C.; Engel, Lisa

    1991-01-01

    NH2 emission band strengths were measured in four comets and the NH2 column densities were determined in order to measure the ammonia content of the comets. The mean ammonia/water abundance ratio derived for the four comets is found to be 0.13 + or - 0.06 percent, with no significant variation among the comets. The uniformity of this abundance attests to a remarkable degree of chemical homogeneity over large scales in the comet-forming region of the primordial solar nebula, and contrasts with the CO abundance variations found previously in comets. The N2 and NH3 abundances indicate a condensation temperature in the range 20-160 K, consistent with virtually all comet formation hypotheses.

  1. A Search of Reactivated Comets

    NASA Astrophysics Data System (ADS)

    Ye, Quan-Zhi

    2017-05-01

    Dormant or near-dormant short-period comets can unexpectedly regain the ability to eject dust. In many known cases, the resurrection is short-lived and lasts less than one orbit. However, it is possible that some resurrected comets can remain active in later perihelion passages. We search the archival images of various facilities to look for these “reactivated” comets. We identify two candidates, 297P/Beshore and 332P/Ikeya-Murakami, both of which were found to be inactive or weakly active in the previous orbit before their discovery. We derive a reactivation rate of ˜ 0.007 {{comet}}-1 {{orbit}}-1, which implies that typical short-period comets only become temporarily dormant a few times or less. Smaller comets are prone to rotational instability and may undergo temporary dormancy more frequently. Next generation high-cadence surveys may find more reactivation events of these comets.

  2. Disappearance and disintegration of comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1984-01-01

    The present investigation has the objective to provide a summary of the existing evidence on the disappearance of comets and to draw conclusions regarding the physical processes involved in the disappearance. Information concerning the classification of evidence and the causes of apparent disappearance of comets is presented in a table. Attention is given to the dissipating comets, the headless sungrazing comet 1887 I, and the physical behavior of the dissipating comets and the related phenomena. It is found that all comets confined to the planetary region of the solar system decay on astronomically short time scales. However, only some of them appear to perish catastrophically. Some of the observed phenomena could be successfully interpreted. But little insight has been obtained into the character of the processes which the dissipating comets experience.

  3. Dynamical studies of the Kuiper belt and the Centaurs

    NASA Astrophysics Data System (ADS)

    Volk, Kathryn Margaret

    The Kuiper belt is a population of small bodies located outside Neptune's orbit. The observed Kuiper belt objects (KBOs) can be divided into several subclasses based on their dynamical structure. I construct models for these subclasses and use numerical integrations to investigate their long-term evolution. I use these models to quantify the connection between the Kuiper belt and the Centaurs (objects whose orbits cross the orbits of the giant planets) and the short-period comets in the inner solar system. I discuss how these connections could be used to determine the physical properties of KBOs and what future observations could conclusively link the comets and Centaurs to specific Kuiper belt subclasses. The Kuiper belt's structure is determined by a combination of long-term evolution and its formation history. The large eccentricities and inclinations of some KBOs and the prevalence of KBOs in mean motion resonances with Neptune are evidence that much of the Kuiper belt's structure originated during the solar system's epoch of giant planet migration; planet migration can sculpt the Kuiper belt's scattered disk, capture objects into mean motion resonances, and dynamically excite KBOs. Different models for planet migration predict different formation locations for the subclasses of the Kuiper belt, which might result in different size distributions and compositions between the subclasses; the high-inclination portion of the classical Kuiper belt is hypothesized to have formed closer to the Sun than the low-inclination classical Kuiper belt. I use my model of the classical Kuiper belt to show that these two populations remain largely dynamically separate over long timescales, so primordial physical differences could be maintained until the present day. The current Kuiper belt is much less massive than the total mass required to form its largest members. It must have undergone a mass depletion event, which is likely related to planet migration. The Haumea

  4. Temperatures within comet nuclei.

    PubMed

    Squyres, S W; McKay, C P; Reynolds, R T

    1985-12-10

    We have performed a theoretical study of temperatures beneath the surface of a comet's nucleus. We solve the one-dimensional heat conduction equation for the outer portion of the comet. The upper boundary condition of the model is given by energy balance at the surface of the nucleus, including conduction of heat inward, radiation, insolation as modified by the coma, and sublimation. Our coma model assumes single scattering and includes attenuation of direct sunlight by dust grains, scattering of light onto the nucleus, and infrared radiation by dust grains. The lower boundary condition is zero net heat flux around an orbit. The thermal conductivity expression for the nucleus includes direct conduction at grain boundaries, radiative conduction, and Knudsen flow vapor diffusion. The thermal diffusivity of the nucleus and the resultant temperature profiles are shown to be strongly dependent on the physical properties of the material, including porosity, pore size, and compaction. The temperature profiles and the equilibrium temperature deep within the comet also depend on the functional relationship between thermal conductivity and temperature; the highest deep equilibrium temperatures are found for models where the thermal conductivity increases strongly with increasing temperature. The dependence of temperatures on the albedo and thermal emissivity of the nucleus is also calculated, as well as the variation of temperature with latitude for a variety of pole orientations. The effect of a dust mantle on subsurface temperatures is also investigated. All calculations are presented for short-period comets with orbits that make them accessible for exploration by spacecraft rendezvous. In situ measurements of the thermal profile in the upper meter of a comet nucleus can substantially constrain the thermal diffusivity of the material, which in turn can provide significant information about the physical properties of the nucleus.

  5. Unveiling the formation and evolution of comets

    NASA Astrophysics Data System (ADS)

    Lasue, J.; Levasseur-Regourd, A. C.; Botet, R.; Coradini, A.; Desanctis, M. C.; Kofman, W.

    2007-08-01

    energy of the cometesimals and their probable re-accretion after collision events in the Kuiper Belt can be used to interpret the typical layered structure observed for comet 9P/Tempel 1 [10] and evaluate the tensile strengths inside the nucleus. Thermal evolution models of comet nuclei explain the current comet observations with the presence of primordial volatiles [11]. A quasi-3D approach (for non-spherically shaped comet nuclei) is used to interpret the current activity of comets in terms of initial characteristics, and to predict shape and internal stratification evolution of the nucleus. Tensile strength indications and activity predictions from such simulations will provide vital clues for the international Rosetta mission landing on the nucleus of comet 67P/Churyumov-Gerasimenko. During the Rosetta rendezvous, the CONSERT experiment will investigate the deep interior of the nucleus from measurements of the propagation delay of long wavelength radio waves [12]. The analysis and 3D reconstruction of the waves passing through the nucleus will put constraints on the materials constituting the comet and the inhomogeneities within the nucleus. While it is now established that nuclei have low densities and are significantly fragile, it will then be possible to better constrain their formation process and their evolution. [1] A'Hearn et al., Science 310, 258 (2005) [2] Samarasinha, Icarus 154, 540 (2001) [3] Trigo-Rodriguez and Llorca, Mon. Not. R. Astron. Soc. 372, 655 (2006) [4] A'Hearn and Combi, Icarus 187, 1 (2007) [5] Hanner and Bradley, In: Comets II, Festou, Keller, Weaver (eds), pp 555 (2004) [6] Brownlee et al., Science 314, 1711 (2006) [7] Lasue and Levasseur-Regourd, J. Quant. Spectros. Radiat. Transfer 100, 220-236 (2006) [8]Levasseur-Regourd et al., (2007), Planet Space Sci., doi:10.1016/j.pss.2006.11.014 in press. [9] Hörz et al., Science 314, 1716 (2006) [10] Belton et al., Icarus 187, 332 (2007) [11] DeSanctis et al., Astron. Astrophys. 444, 605 (2005

  6. Discovery of the candidate Kuiper belt object 1992 QB1

    NASA Technical Reports Server (NTRS)

    Jewitt, David; Luu, Jane

    1993-01-01

    The discovery of a new faint object in the outer solar system, 1992 QB1, moving beyond the orbit of Neptune is reported. It is suggested that the 1992 QB1 may represent the first detection of a member of the Kuiper belt (Edgworth, 1949; Kuiper, 1951), the hypothesized population of objects beyond Neptune and a possible source of the short-period comets, as suggested by Whipple (1964), Fernandez (1980), and Duncan et al. (1988).

  7. Comets, Asteroids, and the Origin of the Biosphere

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2006-01-01

    During the past few decades, the role of comets in the delivery of water, organics, and prebiotic chemicals to the Biosphere of Earth during the Hadean (4.5-3.8 Ga) period of heavy bombardment has become more widely accepted. However comets are still largely regarded as frigid, pristine bodies of protosolar nebula material that are entirely devoid of liquid water and consequently unsuitable for life in any form. Complex organic compounds have been observed comets and on the water rich asteroid 1998 KY26, which has color and radar reflectivity similar to the carbonaceous meteorites. Near infrared observations have indicated the presence of crystalline water ice and ammonia hydrate on the large Kuiper Belt object (50000) Quaoar with resurfacing that may indicate cryovolcanic outgassing and the Cassini spacecraft has detected water-ice geysers on Saturn s moon Enceladus. Spacecraft observations of the chemical compositions and characteristics of the nuclei of several comets (Halley, Borrelly, Wild 2, and Tempel 1) have now firmly established that comets contain a suite of complex organic chemicals; water is the predominant volatile; and that extremely high temperatures (approx.350-400 K) can be reached on the surface of the very black (albedo-0.03) nuclei when the comets are with 1.5 AU from the Sun. Impact craters and pinnacles observed on comet Wild 2 suggest a thick crust and episodic outbursts and jets observed on the nuclei of several comets are interpreted as indications that localized regimes of liquid water and water vapor can periodically exist beneath the crust of some comets. The Deep Impact observations indicate that the temperature on the nucleus of of comet Tempel 1 at 1.5 AU varied from 330K on the sunlit side to a minimum of 280+/-8 K. It is interesting that even the coldest region of the comet surface was slightly above the ice/liquid water phase transition temperature. These results suggest that pools and films of liquid water can exist in a wide

  8. Theories of comets to the age of Laplace

    NASA Astrophysics Data System (ADS)

    Heidarzadeh, Tofigh

    Although the development of ideas about cometary motion has been investigated in several projects, a comprehensive and detailed survey of physical theories of comets has not been conducted. The available works either illustrate relatively short periods in the history of physical cometology or portray a landscape view without adequate details. The present study is an attempt to depict the details of the major physical theories of comets from Aristotle to the age of Laplace. The basic question from which this project originated was simple: how did natural philosophers and astronomers define the nature and place of a new category of celestial objects--the comets--after Brahe's estimation of cometary distances? However, a study starting merely from Brahe without covering classical and medieval thought about comets would be incomplete. Thus, based on the fundamental physical characteristics attributed to comets, the history of cometology may be divided into three periods: from Aristotle to Brahe, in which comets were assumed to be meteorological phenomena; from Brahe to Newton, when comets were admitted as celestial bodies but with unknown trajectories; and from Newton to Laplace, in which they were treated as members of the solar system having more or less the same properties of the planets. By estimating the mass of comets in the 1800s, Laplace diverted cometology into a different direction wherein they were considered among the smallest bodies in the solar system and deprived of the most important properties that had been used to explain their physical constitution during the previous two millennia. Ideas about the astrological aspects of comets are not considered in this study. Also, topics concerning the motion of comets are explained to the extent that is helpful in illustrating their physical properties. The main objective is to demonstrate the foundations of physical theories of comets, and the interaction between observational and mathematical astronomy, and

  9. The role of collisional compaction in primitive asteroids and comets

    NASA Astrophysics Data System (ADS)

    Trigo-Rodríguez, J. M.; Blum, J.

    2008-09-01

    During the early stages of solar system formation the consolidation of asteroids and comets took place. We have just learnt from recent space missions that some of these minor bodies have been preserved in a pristine way in several regions of our Solar System. From our experience on primitive meteorites we know that these bodies should contain valuable clues on the origin of the Solar System. Studies of the physical, chemical, and isotopic properties of the components of these minor bodies will provide important clues on their origin. We expect very different collisional histories undergone by these bodies depending on their particular formation, migration, and storage regions [1]. In Fig. 1 appears a schematic representation of the protoplanetary disk in the region of consolidation of the terrestrial planets about 4565 million years ago. Bodies located in the outer part of the main belt would have incorporated significant amounts of ice in their volume, but their migration to and residence times in other regions would have defined their physico-chemical properties. Recent laboratory studies and observational data compiled from comets, meteorites and meteoroids [2] suggest that the porosity of these bodies should have decreased with time depending on the degree of collisions, aqueous alteration and heating. For typical stony targets, the tensile strength and gravity are the main properties that are defining the formation of impact craters and subsequently the degree of impact metamorphism and mineralogy of the shocked materials. However, little is known about the influence of porosity on the impact process although the crushing of pore space is an efficient mechanism for absorbing shock waves, also increasing the postshock temperatures [2]. In this context, a Near-Earth Object (NEO) sample return mission called Marco Polo is being studied within the Cosmic Vision programme. Such kind of mission would be returning to the Earth unaltered material from a NEO, just

  10. 67P, Singing Comet

    NASA Astrophysics Data System (ADS)

    Smirnova, Ekaterina

    2017-04-01

    I would like to propose to present a short science-art-music collaboration film called "67P, Singing Comet" (5:27 min). If time of the session will allow, prior to the film I would like to make a slide show introduction to this project, highlighting the inspiration - the mission Rosetta by the European Space Agency (ESA) - and the artistic collaboration that took place in creating this piece. 
 Inspired by the ESA Rosetta mission to the comet 67P, Ekaterina Smirnova (artist and project director, New York), Lee Mottram (clarinetist, Wales), Takuto Fukuda (composer, Japan) and Brian Hekker (video editor, New York) collaborated to create a unique atmospheric piece.
 Water and the origins of life throughout the Universe (specifically the Earth) is an element of the mission and the focus of Ekaterina's artistic vision. Ekaterina literally and figuratively paints a sensory assemblage using a combination of synthetic and natural elements to shape this artistic creation. To paint her watercolor works she is using a replica of the water found on the comet and implementing her own heartbeat into the music to create a recognizable inward sound of life.
 The Electro-Acoustic composition by Takuto Fukuda features an electronically manipulated performance by clarinetist Lee Mottram. The piece ceremoniously begins with reverberant bursts of low-register atonal bells transporting the listener to their ethereal inner origins of body and mind. The imagination takes the experience to an unknown destination as it gains speed gliding through the visual and audible textures of space and time. 
The comet's water similarly reacts with an ebb and flow thawing ice to potentially give life a chance as it is thrust along an orbit around the Sun. Near then far from the heat the comet forms frozen particles from vapors as it reaches it's furthest stretches creating an aerodynamic tail of icicles that slowly dissipate in a cycle that repeats itself until the comet's ultimate collision

  11. Rivet-fastener belt splices reduce conveyor downtime

    SciTech Connect

    Not Available

    1982-11-01

    At Sahara Coal Co's No. 21 Mine in Illinois some 18 miles of conveyor belting are in underground use bringing coal from the faces to a main haulage conveyor which transports the coal to the surface. The belt material is nylon carcass with rubber cover. Because of relatively low roof clearance, thinner belt than is typically used underground is employed, since a 500 ft roll of thicker belting would be unable to negotiate low-clearance entries. This thinner belt material could not be spliced using conventional fasteners, but solid-plate rivetted splicing has been found to be satisfactory.

  12. P31comet, a member of the synaptonemal complex, participates in meiotic DSB formation in rice.

    PubMed

    Ji, Jianhui; Tang, Ding; Shen, Yi; Xue, Zhihui; Wang, Hongjun; Shi, Wenqing; Zhang, Chao; Du, Guijie; Li, Yafei; Cheng, Zhukuan

    2016-09-20

    The human mitotic arrest-deficient 2 (Mad2) binding protein p31(comet) participates in the spindle checkpoint and coordinates cell cycle events in mitosis although its function in meiosis remains unknown in all organisms. Here, we reveal P31(comet) as a synaptonemal complex (SC) protein in rice (Oryza sativa L.). In p31(comet), homologous pairing and synapsis are eliminated, leading to the homologous nondisjunction and complete sterility. The failure in loading of histone H2AX phosphorylation (γH2AX) in p31(comet), together with the suppressed chromosome fragmentation in rice completion of meiotic recombination 1 (com1) p31(comet) and radiation sensitive 51c (rad51c) p31(comet) double mutants, indicates that P31(comet) plays an essential role in double-strand break (DSB) formation. Interestingly, the dynamic colocalization pattern between P31(comet) and ZEP1 (a transverse filament protein of SC) by immunostaining, as well as the interaction between P31(comet) and CENTRAL REGION COMPONENT 1 (CRC1) in yeast two-hybrid assays, suggests possible involvement of P31(comet) in SC installation. Together, these data indicate that P31(comet) plays a key role in DSB formation and SC installation, mainly through its cooperation with CRC1.

  13. P31comet, a member of the synaptonemal complex, participates in meiotic DSB formation in rice

    PubMed Central

    Ji, Jianhui; Tang, Ding; Shen, Yi; Xue, Zhihui; Wang, Hongjun; Shi, Wenqing; Zhang, Chao; Du, Guijie; Li, Yafei; Cheng, Zhukuan

    2016-01-01

    The human mitotic arrest-deficient 2 (Mad2) binding protein p31comet participates in the spindle checkpoint and coordinates cell cycle events in mitosis although its function in meiosis remains unknown in all organisms. Here, we reveal P31comet as a synaptonemal complex (SC) protein in rice (Oryza sativa L.). In p31comet, homologous pairing and synapsis are eliminated, leading to the homologous nondisjunction and complete sterility. The failure in loading of histone H2AX phosphorylation (γH2AX) in p31comet, together with the suppressed chromosome fragmentation in rice completion of meiotic recombination 1 (com1) p31comet and radiation sensitive 51c (rad51c) p31comet double mutants, indicates that P31comet plays an essential role in double-strand break (DSB) formation. Interestingly, the dynamic colocalization pattern between P31comet and ZEP1 (a transverse filament protein of SC) by immunostaining, as well as the interaction between P31comet and CENTRAL REGION COMPONENT 1 (CRC1) in yeast two-hybrid assays, suggests possible involvement of P31comet in SC installation. Together, these data indicate that P31comet plays a key role in DSB formation and SC installation, mainly through its cooperation with CRC1. PMID:27601671

  14. Numerical simulations of comets - Predictions for Comet Giacobini-Zinner

    NASA Technical Reports Server (NTRS)

    Fedder, J. A.; Lyon, J. G.; Giuliani, J. L., Jr.

    1986-01-01

    Simulations of Comet Giacobini-Zinner's interaction with solar wind are described and results are presented. The simulations are carried out via the numerical solution of the ideal MHD equations as an initial value problem in a uniform solar wind. The calculations are performed on a Cartesian mesh centered at the comet. Results reveal that the first significant modifications of the solar wind along the ISEE/ICE trajectory will occur 100,000 km from the solar wind comet axis.

  15. ISO spectroscopic observations of short-period comets

    NASA Astrophysics Data System (ADS)

    Crovisier, J.; Encrenaz, Th.; Lellouch, E.; Bockelée-Morvan, D.; Altieri, B.; Leech, K.; Salama, A.; Griffin, M. J.; de Graauw, Th.; van Dishoeck, E. F.; Knacke, R.; Brooke, T. Y.

    1999-03-01

    Two Infrared Space Observatory programmes (guaranteed time and open time) were devoted to high-resolution spectroscopic observations of short-period comets. 22P/Kopff was observed on October-December 1996 with SWS and LWS. Due to the weakness of the object, only the ν3 ro-vibrational lines of water were detected, with SWS. Comet 103P/Hartley 2 was observed close to its perihelion (at 1.04 AU from Sun and 0.82 AU from Earth) on January 1998 with SWS, LWS and CAM. The bands of H2O and CO2 at 2.7 and 4.3 μm are detected, with [CO2]/[H2O] = 10 %. The 2.7 μm band of H2O is observed with a high signal-to-noise ratio with SWS, which permits to evaluate the rotational temperature of water to 16-20 K and its ortho-to-para ratio to ~ 2.7, corresponding to a spin temperature of ~ 35 K. The 5-17 μm spectrum of comet Hartley 2 observed with CAM-CVF shows the 9-12 μm signature of silicates. Silicate emission around 10 μm is present at a level of about 20 % of the continuum, with a peak at 11.3 μm indicative of crystalline silicates. This is the first time crystalline silicates are found in a short-period comet. The ISO observations of the Jupiter-family comet P/Hartley 2, presumably originating from the Edgeworth-Kuiper belt, are compared to those of comet Hale-Bopp which came from the Oort cloud.

  16. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1977-01-01

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

  17. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1976-01-01

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

  18. Carbon isotopes in comets

    NASA Technical Reports Server (NTRS)

    Wehinger, Peter A.

    1990-01-01

    The progress is reported of high resolution spectra of selected bright comets with the aim of determining the carbon isotope abundance ratio, C-12/C-13. The ratio was determined for various Solar System objects (in the atmospheres of the giant planets, meteorites, the Earth, and the solar photosphere), where the C-12/C-13 = 89/1. In the interstellar medium, optical and radio observations give a range of C-12/C-13 = 43-67/1 depending on the observing techniques used and the specific interstellar cloud observed. The echelle spectra is presented of the CN(0,0) violet system in three comets: P/Brorsen-Metcalf, C/Okazaki-Levy-Rudenko, and C/Austin. P/Brorsen-Metcalf has a period of 70 y (prograde) compared with P/Halley which is 76 y (retrograde). The similar periods made P/Brorsen-Metcalf of special interest for comparison with P/Halley.

  19. Diatoms in comets

    NASA Technical Reports Server (NTRS)

    Hoover, R.; Hoyle, F.; Wallis, M. K.; Wickramasinghe, N. C.

    1986-01-01

    The fossil record of the microscopic algae classified as diatoms suggests they were injected to earth at the Cretaceous boundary. Not only could diatoms remain viable in the cometary environment, but also many species might replicate in illuminated surface layers or early interior layers of cometary ice. Presumably they reached the solar system on an interstellar comet as an already-evolved assemblage of organisms. Diatoms might cause color changes to comet nuclei while their outgassing decays and revives around highly elliptical orbits. Just as for interstellar absorption, high-resolution IR observations are capable of distinguishing whether the 10-micron feature arises from siliceous diatom material or mineral silicates. The 10-30-micron band and the UV 220-nm region can also provide evidence of biological material.

  20. The composition of comets

    NASA Technical Reports Server (NTRS)

    Jessberger, E. K.; Kissel, J.; Rahe, J.

    1989-01-01

    The present discussion of recent studies concerning cometary composition gives attention to the results obtained by in situ measurements of Comet Halley's dust composition by Vega 1's impact mass spectrometer, which discovered a mineral fraction that appears to be CI chondritic, as well as an organic fraction consisting of highly unsaturated hydrocarbons. The mineral fraction of comets appears to form a core that is embedded in essentially organic material; the spectroscopic invisibility of carbon is due to its presence in the cometary dust. The mass of most dust particles is found to be in the 10 to the -12th to 10 to the -14th g range. A considerable fraction of the dust grains serves as an extended source of gas in the inner coma.