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Sample records for main belt comets

  1. Puzzling Snowballs: Main Belt Comets

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Meech, Karen

    2015-03-01

    Main belt comets (MBCs) are a class of newly discovered objects that exhibit comet-like appearances and yet are dynamically indistinguishable from ordinary main belt asteroids. The measured size and albedo of MBCs are similar to those of classical comets. At present, six MBCs have been discovered, namely 133P/Elst-Pizarro, 176P/LINEAR, 238P/Read, P/2008 R1, P/La Sagra and P/2006 VW139. The total number of active MBCs is estimated to be at the level of a few hundreds (Hsieh & Jewitt, 2006). Several explanations for the activity of MBCs have been suggested. These include impact ejection, sublimation and rotational instability. However, since renewed activity has been observed in 133P and 238P at successive perihelion passages, the most likely explanation may be a thermally-driven process - e.g sublimation of exposed surface ice. Although the proximity of MBCs to the Sun (r ~ 3 AU) makes the survival of surface ice improbable, thermal models have shown that water ice is thermally stable under a regolith layer a few meters thick. The study of MBCs has recently been complicated by the discoveries of two asteroid collisional events (P/2010 A2 (LINEAR) and (596) Scheila) in 2010, where comet-like dust coma/tail have been attributed to recent impacts. If MBCs are indeed icy, they represent the closest and the third established reservoir of comets (after the Oort cloud and the Kuiper belt). As such, they may have been an important source of water for the Earth's oceans. I will review the current state of MBC studies, present the latest observational results and discuss possible mechanisms that could produce the observed activity. I will also talk about current and future space missions that are dedicated or closely related to MBC studies.

  2. 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. PMID:16556801

  3. 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.

  4. 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.

  5. 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.

  6. Main-belt comets: sublimation-driven activity in the asteroid belt

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.

    2016-01-01

    Our knowledge of main-belt comets (MBCs), which exhibit comet-like activity likely due to the sublimation of volatile ices, yet orbit in the main asteroid belt, has increased greatly since the discovery of the first known MBC, 133P/Elst-Pizarro, in 1996, and their recognition as a new class of solar system objects after the discovery of two more MBCs in 2005. I review work that has been done over the last 10 years to improve our understanding of these enigmatic objects, including the development of systematic discovery methods and diagnostics for distinguishing MBCs from disrupted asteroids (which exhibit comet-like activity due to physical disruptions such as impacts or rotational destabilization). I also discuss efforts to understand the dynamical and thermal properties of these objects.

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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.

  16. The reactivation of main-belt Comet 324P/La Sagra (P/2010 R2)

    NASA Astrophysics Data System (ADS)

    Hsieh, H. H.; Sheppard, S. S.

    2015-11-01

    We present observations using the Baade Magellan and Canada-France-Hawaii telescopes showing that main-belt comet 324P/La Sagra, formerly known as P/2010 R2, has become active again for the first time since originally observed to be active in 2010-2011. The object appears point-source-like in 2015 March and April as it approached perihelion (true anomaly of ν ˜ 300°), but was ˜1 mag brighter than expected if inactive, suggesting the presence of unresolved dust emission. Activity was confirmed by observations of a cometary dust tail in 2015 May and June. We find an apparent net dust production rate of {dot{M}_d}≲ 0.1 kg s-1 during these observations. 324P is now the fourth main-belt comet confirmed to be recurrently active, a strong indication that its activity is driven by sublimation. It now has the largest confirmed active range of all likely main-belt comets, and also the most distant confirmed inbound activation point at R ˜ 2.8 au. Further observations during the current active period will allow direct comparisons of activity strength with 324P's 2010 activity.

  17. The Reactivation of Main-Belt Comet 324P/La Sagra (P/2010 R2)

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.; Sheppard, Scott

    2015-11-01

    We present observations using the Baade Magellan and Canada-France-Hawaii telescopes showing that main-belt comet 324P/La Sagra, formerly known as P/2010 R2, has become active again for the first time since originally observed to be active in 2010-2011. The object appears point-source-like in March and April 2015 as it approached perihelion (true anomaly of ν~300 deg), but was ~1 mag brighter than expected if inactive, suggesting the presence of unresolved dust emission. Activity was confirmed by observations of a cometary dust tail in May and June 2015. We find an apparent net dust production rate of <0.1 kg/s during these observations. 324P is now the fourth main-belt comet confirmed to be recurrently active, a strong indication that its activity is driven by sublimation. It now has the largest confirmed active range of all likely main-belt comets, and also the most distant confirmed inbound activation point at R~2.8 AU. Further observations during the current active period will allow direct comparisons of activity strength with 324P’s 2010 activity.

  18. Rotation Analyses of Main-belt Comet P/2006 VW139

    NASA Astrophysics Data System (ADS)

    Kaluna, Heather; Meech, K.; Hsieh, H. H.

    2013-10-01

    Originally, the term main-belt comet (MBC) was coined to describe any asteroid within the main-belt that had a comet-like dust tail or coma as a result of sublimating ice [1]. Another term, disrupted asteroid, was introduced to further distinguish main-belt asteroids whose activity appears to be the result of processes other than sublimation [2]. The origin of activity in MBCs is not definitively known, but Jewitt [3] described a suite of possible mechanisms that could result in the comet-like activity observed on these asteroids. A true main-belt comet would be active as a result of ice sublimation driven dust ejection [2] and although no direct evidence of gas has been observed on these asteroids, recurrent activity is observed on several of these objects and is a strong indicator that sublimation is the driving force for activity [4]. Other potential mechanisms include rotational instability and impact ejection. We are interested in determining the rotation period of the recently discovered MBC P/2006 VW139 [2] to assess the possibility of rotational instability as a mechanism for activity in this MBC. We will present rotation period analyses of data collected in 2011 from the University of Hawai’i 2.2m, Lowell Perkins 1.8m, Himalayan Chandra 2.0m, Faulkes 2.0m and in 2012 from the University of Hawai’i 2.2m and Gemini North 8.1 meter telescopes. Due to the sparseness of the 2011 data as well as the effects of coma contamination, we are comparing the rotation periods derived from the 2011 to that of our 2012 data. Aside from attempting to clarify the true nature of the activity in MBCs, determining the nucleus properties of the known MBCs is also necessary to determine what distinguishes them from other non-active asteroids [2]. [1] Hsieh, H. H., & Jewitt, D. 2006, Science, 312, 561 [2] Hsieh, H. H., et al. 2012, ApJ, 748, L15 [3] Jewitt, D. 2012, AJ, 143, 66 [4] Hsieh, H. H., Yang, B., and Haghighipour, N. 2012, ApJ, 744, 9

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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).

  4. 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.

  5. 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.

  6. Limits on the size and orbit distribution of main belt comets

    NASA Astrophysics Data System (ADS)

    Sonnett, Sarah; Kleyna, Jan; Jedicke, Robert; Masiero, Joseph

    2011-10-01

    The first of a new class of objects now known as main belt comets (MBCs) or "activated asteroids" was identified in 1996. The seven known members of this class have orbital characteristics of main belt asteroids yet exhibit dust ejection like comets. In order to constrain their physical and orbital properties we searched the Thousand Asteroid Light Curve Survey (TALCS; Masiero, J.R., Jedicke, R., Durech, J., Gwyn, S., Denneau, L., Larsen, J. [2009]. Icarus 204, 145-171) for additional candidates using two diagnostics: tail and coma detection. This was the most sensitive MBC survey effort to date, extending the search from MBCs with H ˜ 18 ( D ˜ 1 km) to MBCs as small as H ˜ 21 ( D ˜ 150 m). We fit each of the 924 objects detected by TALCS to a PSF model incorporating both a coma and nuclear component to measure the fractional contribution of the coma to the total surface brightness. We determined the significance of the coma detection using the same algorithm on a sample of null detections of comparable magnitude and rate of motion. We did not identify any MBC candidates with this technique to a sensitivity limit on the order of cometary mass loss rate of about 0.1 kg/s. Our tail detection algorithm relied on identifying statistically significant flux in a segmented annulus around the candidate object. We show that the technique can detect tail activity throughout the asteroid belt to the level of the currently known MBCs. Although we did not identify any MBC candidates with this technique, we find a statistically significant detection of faint activity in the entire ensemble of TALCS asteroids. This suggests that many main belt asteroids are active at very low levels. Our null detection of MBCs allows us to set 90% upper confidence limits on the number distribution of MBCs as a function of absolute magnitude, semi-major axis, eccentricity, and inclination. There are ≲400,000 MBCs in the main belt brighter than HV = 21 (˜150-m in diameter) and the MBC

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. Hubble Investigation of the First Known, Multi-Fragment Main Belt Comet: P/2013 R3

    NASA Astrophysics Data System (ADS)

    Jewitt, David

    2013-10-01

    Comet-like object P/2013 R3, announced on 2013 Sept 27, is the latest of the newly discovered class of active asteroids {equivalently main-belt comets, MBCs}. Observations with the Keck 10-m telescope on Oct 01 and 02 reveal that P/2013 R3 is a multiple object, with three co-moving components resolved at 1.0 arcsec resolution. Multiplicity has never before been seen in the MBCs and offers the opportunity to study internal dynamics in detail. We request five orbits of DD time to explore P/2013 R3 at resolutions and sensitivities only possible with Hubble, to search for fainter fragments and to determine the dynamics of the components. P/2013 R3 is a leading candidate for a body breaking up under rotational stresses {presumably induced by YORP radiation forces}, and Hubble data will test this hypothesis by pin-pointing the dates of ejection of the fragments, their speeds, and their directions. Our Hubble MBC program has been remarkably successful in probing the activation triggers for this new class of objects, and our proposed program on P/2013 R3 will provide the first opportunity to track fragments associated with the activation event.

  12. 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.

  13. 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).

  14. 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.

  15. Hubble Space Telescope Investigation of Main-belt Comet 133P/Elst-Pizarro

    NASA Astrophysics Data System (ADS)

    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 HV = 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-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.

  16. Physical Properties of Main-Belt Comet P/2005 U1 (Read)

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

    The main-belt comets occupy dynamically asteroidal orbits in the main asteroid belt. Here we present physical observations of the second-known member of this population, P/2005 U1 (Read), which showed vigorous cometary activity from 2005 October 24 to 2005 December 27. Monte Carlo numerical simulations of P/Read's dust emission indicate that the coma and tail are optically dominated by dust particles larger than 10 μm in size with terminal ejection velocities of 0.2-3 m s-1. We estimate P/Read's mass-loss rate during this period to be approximately 0.2 kg s-1, roughly an order of magnitude larger than that calculated for 133P/Elst-Pizarro. We also find that emission likely began at least 2 months prior to P/Read's discovery, though we note this is a lower limit and that earlier start times are possible. Optical colors measured for P/Read while it was active are approximately solar (B - V = 0.63 ± 0.05, V - R = 0.37 ± 0.04, R - I = 0.39 ± 0.04) but are likely to be dominated by coma particles. Observations of P/Read in 2007 when it appears largely inactive show an extremely small nucleus with an absolute magnitude of HR ~ 20.1 ± 0.4, corresponding to an effective radius of re ~ 0.3 km. P/Read's activity is consistent with sublimation-driven dust emission and inconsistent with dust emission due to an impact, though the unusual strength of the 2005 outburst suggests the possibility that it could have been due to the sublimation of a freshly exposed reservoir of volatile material. 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. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Additionally, some data were obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in

  17. 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

  18. 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° <~

  19. 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.

  20. Lightcurve-based search for main-belt comets with the PTF survey

    NASA Astrophysics Data System (ADS)

    Waszczak, A.; Ofek, E.; Kulkarni, S.

    2014-07-01

    Cometary activity in main-belt asteroids remains poorly-understood but has profound implications for our understanding of solar system formation (e.g., Hsieh & Jewit 2006, Science 312). Two methods to detect activity are (1) morphological, i.e., measuring extendedness on a per-observation basis, and (2) photometric, i.e., measuring intrinsic brightness variation over time. Waszczak et al. (2013, MNRAS 433) described initial results on method (1); we now present progress on method (2). We extracted 7.2 million observations of 395,000 asteroids from 5 years (2009--2014) of Palomar Transient Factory (PTF) survey data (Law et al. 2009, PASP 121; Rau et al. 2009, PASP 121). Of these, we fit 2.2 million observations of 63,000 asteroids to a lightcurve model incorporating rotation with 2nd-order Fourier coefficients and the IAU phase-function parameter G. Each fit includes ≥15 observations within a single opposition and filter (92 % r-band, 8 % g-band; multiple fits exist for 4,900 objects seen in multiple oppositions and/or both filters). As a sample, the RMS scatter and reduced χ^2 of our lightcurves are a factor of two smaller than those produced by the fiducial model used by JPL's HORIZONS and the MPC (i.e., no rotational correction and a fixed G=0.15). We describe a statistical search for cometary contributions in the residuals of these lightcurves.

  1. 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

  2. Determination of an upper limit for the water outgassing rate of main-belt comet P/2012 T1 (PANSTARRS)

    NASA Astrophysics Data System (ADS)

    O'Rourke, Laurence; Snodgrass, Colin; de Val-Borro, Miguel; Biver, Nicolas; Bockelée-Morvan, Dominique; Hsieh, Henry; Teyssier, David; Fernandez, Yan; Küppers, Michael; Micheli, Marco; Hartogh, Paul

    2015-04-01

    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 (Wainscoat et al. 2012). 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 H2O 110--101 ground state rotational line at 557 GHz from P/2012 T1 (PANSTARRS) with the Heterodyne Instrument for the Far Infrared (HIFI; de Graauw et al. 2010) on board the Herschel Space Observatory (Pilbratt et al, 2010) on 2013 January 16, when the object was at a heliocentric distance of 2.504 AU and a distance from Herschel of 2.059 AU. Perihelion was in early 2012 September at a heliocentric distance of 2.411 AU. To analyse the data we used a molecular excitation model equivalent to that utilized to analyze both Herschel and ground-based cometary observations (Hartogh et al. 2010, 2011; de Val-Borro et al. 2010, 2012a, 2012b). While no H2O line emission was detected in our observations, we were able to derive sensitive 3sigma upper limits for the water production rate and column density of

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. From Kuiper Belt to Comet: The Shapes of the Nuclei

    NASA Astrophysics Data System (ADS)

    Jewitt, D.; Sheppard, S.; Fernandez, Y.

    2003-05-01

    It is widely believed that escaped objects from the Kuiper Belt are the source of both the Centaurs and the nuclei of the Jupiter Family Comets (JFCs). If the JFC nuclei are produced by collisional breakup of parent objects in the Kuiper Belt, then it is reasonable to expect that their shape distribution should be consistent with those of fragments produced in disintegrative laboratory experiments, or with the small main-belt asteroids (which are produced collisionally). We test this idea using a sample of eleven well-observed cometary nuclei. Our main result is that the nuclei are, on average, much more elongated than either the collisionally produced small main-belt asteroids or the fragments created in laboratory impact experiments. Several interpretations of this systematic shape difference are possible (including the obvious one that the JFC nuclei are not, after all, produced collisionally in the Kuiper Belt). Our preferred explanation, however, is that the asphericities of the nuclei have been modified by one or more processes of mass loss. An implication of this interpretation is that the JFC nuclei in our sample are highly evolved, having lost a major part of their original mass. In turn, this implies that the angular momenta of the nuclei are also non-primordial: the JFC nuclei are highly physically evolved objects. We will discuss the evidence supporting these conclusions. This work has been recently published in Astronomical Journal, 125, 3366-3377 (2003).

  10. 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.

  11. Secular light curves of comets, II: 133P/Elst Pizarro, an asteroidal belt comet

    NASA Astrophysics Data System (ADS)

    Ferrín, Ignacio

    2006-12-01

    is possible, or (b) the existence of a sharp polar active region pointing to the Sun at time = LAG, that may take the form of a polar ice cap, a polar fissure or even a polar crater. The diameter of this zone is calculated at ˜1.8 km. (7) A new time-age is defined and it its found that T-AGE = 80 cy for 133P, a moderately old comet. (8) We propose that the object has its origin in the main belt of asteroids, thus being an asteroid-comet hybrid transition object, an asteroidal belt comet (ABC), proven by its large density. (9) Concerning the final evolutionary state of this object, to be a truly extinct comet the radius must be less than the thermal wave depth, which at 1 AU is ˜250 m (at the perihelion distance of 133P the thermal wave penetrates only ˜130 m). Comets with radius larger than this value cannot become extinct but dormant. Thus we conclude that 133P cannot evolve into a truly extinct comet because it has too large a diameter. Instead it is shown to be entering a dormant phase. (10) We predict the existence of truly extinct comets in the main belt of asteroids (MBA) beginning at absolute magnitude ˜21.5 (diameter smaller than ˜190 m). (11) The object demonstrates that a comet may have an outburst of ˜2.3 mag, and not show any detectable coma. (12) Departure from a photometric R law is a more sensitive method (by a factor of 10) to detect activity than star profile fitting or spectroscopy. (13) Sufficient evidence is presented to conclude that 133P is the first member of a new class of objects, an old asteroidal belt comet, ABC, entering a dormant phase.

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

    PubMed

    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. PMID:15637267

  13. Debiasing the Main-Belt Asteroid Population

    NASA Astrophysics Data System (ADS)

    Spahr, Timothy Bruce

    1998-12-01

    We present here two general techniques to remove observational selection effects from asteroid surveys. When applied to two specific asteroid surveys, these methods have allowed the first computation of the debiased distribution of asteroidal orbital elements and sizes for the first time. The first survey was conducted in 1960. Advances in computing have allowed the data to be re-analyzed using an existing computer program and given a much more rigorous statistical treatment. The survey was confined to the near-ecliptic at opposition, therefore its usefulness is limited with regard to highly inclined orbits. To compensate for this limitation, we conducted our own survey aimed specifically at high-inclination objects. Since these orbits are, in general, distributed differently than lower-inclination orbits, removing observational selection effects required creating a statistical technique using Monte-Carlo type simulations. The results of this work show no evidence for differing slopes of the size-frequency distribution throughout the asteroid belt, from the highly inclined Hungaria-type asteroids in the inner edge of the belt (1.8-2.0 AU), to the outer belt (3-3.5 AU). The slopes of the absolute-magnitude frequency distributions, being less than 0.5, show that the asteroidal size distribution is somewhat shallower than what would be predicted assuming the asteroids to be a collisionally evolved population of bodies with size-independent impact strengths. Also determined are rough numbers of asteroids in the main dynamical families of Eos, Maria, Themis, and Koronis, which comprise a significant fraction of the total number of objects in the main belt. This work has also resulted in the discovery of a new asteroid dynamical family, and possibly two new asteroid groups.

  14. The evolution of water in carbonaceous main belt asteroids

    NASA Astrophysics Data System (ADS)

    Kaluna, Heather Maria

    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

  15. 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.

  16. 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

  17. Dynamic picture of the main asteroid belt

    NASA Astrophysics Data System (ADS)

    Michtchenko, T. A.; Lazzaro, D.; Carvano, J. M.; Mothé-Diniz, T.

    2011-10-01

    Using the Spectral Analysis Method introduced by Michtchenko et al. (2002), we construct a dynamic portrait of the main asteroid belt. For this task, we use information extracted from the distribution of test particles (which were initially placed on a perfectly rectangular grid of initial conditions) after 4.2 Myr of gravitational interactions with the Sun and five planets, from Mars to Neptune. We illustrate in detail the asteroidal behavior on the dynamical, averaged and frequency maps. On the maps, we superpose information on the proper elements and proper frequencies of real objects, extracted from the data base, Ast- DyS (http://hamilton.dm.unipi.it/astdys), constructed by Milani and Knežević (2003). A comparison of the maps with the distribution of real objects allows us to detect dynamical mechanisms acting in the domain under study. These mechanisms are related to meanmotion and secular resonances. We note that the twoand three-body mean-motion resonances and the secular resonances (strong linear and weaker non-linear) play an important role in the diffusive transportation of the objects and the formation of the clumps which could be misidentified as asteroid families. The longlasting action of the resonances, overlaid with the Yarkovsky effect, may explain many observed features of the density, size and taxonomic distributions of the asteroids.

  18. 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)

  19. 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.

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

    PubMed

    Alan Stern, S

    2003-08-01

    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. PMID:12904784

  1. The Fossilized Size Distribution of the Main Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Bottke, W. F.; Durda, D.; Nesvorny, D.; Jedicke, R.; Morbidelli, A.

    2004-05-01

    The main asteroid belt evolved into its current state via two processes: dynamical depletion and collisional evolution. During the planet formation epoch, the primordial main belt (PMB) contained several Earth masses of material, enough to allow the asteroids to accrete on relatively short timescales (e.g., Weidenschilling 1977). The present-day main belt, however, only contains 5e-4 Earth masses of material (Petit et al. 2002). To explain this mass loss, we suggest the PMB evolved in the following manner: Planetesimals and planetary embryos accreted (and differentiated) in the PMB during the first few Myr of the solar system. Gravitational perturbations from these embryos dynamically stirred the main belt, enough to initiate fragmentation. When Jupiter reached its full size, some 10 Myr after the solar system's birth, its perturbations, together with those of the embryos, dynamically depleted the main belt region of > 99% of its bodies. Much of this material was sent to high (e,i) orbits, where it continued to pummel the surviving main belt bodies at high impact velocities for more than 100 Myr. While some differentiated bodies in the PMB were disrupted, most were instead scattered; only small fragments from this population remain. This period of comminution and dynamical evolution in the PMB created, among other things, the main belt's wavy size-frequency distribution, such that it can be considered a "fossil" from this violent early epoch. From this time forward, however, relatively little collisional evolution has taken place in the main belt, consistent with the surprising paucity of prominent asteroid families. We will show that the constraints provided by asteroid families and the shape of the main belt size distribution are essential to obtaining a unique solution from our model's initial conditions. We also use our model results to solve for the asteroid disruption scaling law Q*D, a critical function needed in all planet formation codes that include

  2. 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.

  3. Lightcurve Analysis of Ten Main-belt Asteroids

    NASA Astrophysics Data System (ADS)

    Fauerbach, Michael; Marks, Scott A.; Lucas, Michael P.

    2008-06-01

    We report lightcurve periods for ten main-belt asteroids observed at the Evelyn L. Egan Observatory: 26 Proserpina, 78 Diana, 242 Kriemhild, 287 Nephthys, 348 May, 368 Haidea, 446 Aeternitas, 872 Holda, 905 Universitas, and 1013 Tombecka.

  4. 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.

  5. 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.

  6. 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.

  7. A possible collision involving the large main-belt asteroid (596) Schiela

    NASA Astrophysics Data System (ADS)

    Miles, R.

    2011-02-01

    On 2010 December 11.5, Steve Larson of the Lunar and Planetary Laboratory, University of Arizona, observing with the 0.68m f/1.8 Schmidt telescope of the Catalina Sky Survey, found that the minor planet (596) Scheila appeared to be exhibiting comet-like behaviour. This unique phenomenon is thought to be the result of a high-speed collision between Scheila (diameter ~113km) and a much smaller object, possibly some 10-100 metres across, orbiting in the outer regions of the Main Belt. The discovery was reported in Central Bureau Electronic Telegram no.2583 issued by the IAU on December 12.

  8. The Fossilized Size Distribution of the Main Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Bottke, W. F.; Durda, D.; Nesvorny, D.; Jedicke, R.; Morbidelli, A.

    2003-05-01

    At present, we do not understand how the main asteroid belt evolved into its current state. During the planet formation epoch, the primordial main belt (PMB) contained several Earth masses of material, enough to allow the asteroids to accrete on relatively short timescales (e.g., Weidenschilling 1977). The present-day main belt, however, only contains 5e-4 Earth masses of material (Petit et al. 2002). Constraints on this evolution come from (i) the observed fragments of differentiated asteroids, (ii) meteorites collected from numerous differentiated parent bodies, (iii) the presence of ˜ 10 prominent asteroid families, (iv) the "wavy" size-frequency distribution of the main belt, which has been shown to be a by-product of substantial collisional evolution (e.g., Durda et al. 1997), and (v) the still-intact crust of (4) Vesta. To explain the contradictions in the above constraints, we suggest the PMB evolved in this fashion: Planetesimals and planetary embryos accreted (and differentiated) in the PMB during the first few Myr of the solar system. Gravitational perturbations from these embryos dynamically stirred the main belt, enough to initiate fragmentation. When Jupiter reached its full size, some 10 Myr after the solar system's birth, its perturbations, together with those of the embryos, dynamically depleted the main belt region of ˜ 99% of its bodies. Much of this material was sent to high (e,i) orbits, where it continued to pummel the surviving main belt bodies at high impact velocities for more than 100 Myr. While some differentiated bodies in the PMB were disrupted, most were instead scattered; only small fragments from this population remain. This period of comminution and dynamical evolution in the PMB created, among other things, the main belt's wavy size distribution, such that it can be considered a "fossil" from this violent early epoch. From this time forward, however, relatively little collisional evolution has taken place in the main belt

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. COMETS!

    NASA Astrophysics Data System (ADS)

    Eicher, David J.; Levy, David H.

    2013-11-01

    Foreword David H. Levy; Preface; Acknowledgments; 1. Strange lights in the sky; 2. Great comets of the past; 3. What are comets?; 4. Comets of the modern era; 5. Comets in human culture; 6. Where comets live; 7. The expanding science of comets; 8. Observing comets; 9. Imaging comets; Glossary; Bibliography; Index.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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. PMID:19242470

  20. 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.

  1. Are Main-belt Asteroids a Sufficient Source for the Earth-Approachers?

    NASA Astrophysics Data System (ADS)

    Rabinowitz, D. L.; Wetherill, G. W.

    1995-09-01

    Until recently, only the orbit distribution of large Earth-approaching asteroids (diameter, d~1km) was known. Meteor orbits were known only from their atmospheric trajectories, and only for objects with d<1m. These were explained by previous theoretical models [1, 2] as the fragments of main-belt asteroids, perturbed by orbital resonances and planetary encounters to Earth-crossing orbits. Another calculation [3] showed that short-period comets, perturbed by encounters with Jupiter and the terrestrial planets, could supply a significant fraction of the Earth-crossing population. Now the Spacewatch Telescope at the University of Arizona has extended the observed sizes of the Earth approachers down to d~5m. The data reveal a size distribution that increases in slope with decreasing size, coincident with an increased fraction of low-eccentricity orbits [4]. The colors of the small Earth approachers also show significant deviations compared with the colors of larger Earth approachers and main-belt asteroids [5]. These observations are not predicted by previous models that assume a source in the main belt, and they may indicate the admixture of inactive, cometary fragments, and/or impact ejecta from a local source, such as the Moon, Mars, or Earth. Before looking to comets and impact ejecta, however, more work is required to rule out the main belt as a viable source. We have developed a new Monte Carlo program based on Opik theory to model both the size and orbit distributions of the Earth approachers, assuming they originate as collisional fragments of main-belt asteroids and continue to fragment by colliding with other main-belt asteroids, as they evolve to Earth-crossing. Using computational methods developed for earlier calculations [1, 2, 6], this model accounts for the dynamical effects of both the nu6 secular resonance and the 3:1 mean motion resonance with Jupiter. This model also takes into account a map of collision probability as a function of orbital elements

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Comets.

    NASA Astrophysics Data System (ADS)

    Merlin, J. C.

    Contents: 1. Introduction. 2. Comet observation now and in the past. 3. The observation of known comets. 4. Drawing comets. 5. Estimating the total magnitude. 6. Photoelectric photometry of comets. 7. Cometary photography. 8. Searching for comets. 9. Mathematical techniques. 10. IAU Telegram code.

  8. 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

  9. 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.

  10. 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.

  11. The distribution of mantle material among main-belt asteroids

    NASA Astrophysics Data System (ADS)

    DeMeo, Francesca E.; Carry, Benoit; Binzel, Richard P.; Moskovitz, Nicholas; Polishook, David; Burt, Brian J.

    2014-06-01

    We expect there to have been many bodies in the Main Asteroid Belt (MB) sufficiently heated at the time of solar system formation to allow their interiors to differentiate into an iron core and silicate-rich crust and mantle. Evidence for early solar system differentiation includes the diversity of iron meteorites that imply the existence of over 60 distinct parent bodies (Mittlefehldt et al. 2006). Searches have been performed to identify silicate-rich basaltic crust material (spectral V-type asteroids) in the outer MB have been successful (e.g., Roig et al. 2006, Masi et al. 2008, Moskovitz et al. 2008, Solontoi et al. 2012). The olivine-rich mantles of differentiated asteroids should have produced substantially greater volumes (and therefore substantially greater numbers) of remnant asteroids compared with basaltic and iron samples. Yet olivine-rich asteroids (A-types) are one of the rarest asteroid types (Bus & Binzel 2002, DeMeo et al. 2009). An alternative way to search for differentiated bodies that have been heavily or completely disrupted is to identify these spectral A-type asteroids, characterized by a very wide and deep 1 micron absorption indicative of large amounts (> 80%) of olivine. Burbine et al. (1996) proposed that these asteroids are only found among the largest because most were “battered to bits” due to collisions, so smaller A-types were below our detection limit. Using the Sloan Digital Sky Survey Moving Object Catalog to select A-type asteroid candidates, we have conducted a near-infrared spectral survey of asteroids over 12 nights in the near-infrared in an effort to determine the distribution and abundance of crustal and mantle material across the Main Asteroid Belt (MB). From three decades of asteroid spectral observations only ~10 A-type asteroids have been discovered. In our survey we have detected >20 A-type asteroids thus far throughout the belt, tripling the number of known A-types. We present these spectra and their

  12. Orbital Distribution of Main-belt S-type Asteroids

    NASA Astrophysics Data System (ADS)

    Bus, S. J.; Binzel, R. P.; Volquardsen, E. L.; Berghuis, J. L.

    2004-11-01

    We present preliminary results from an ongoing near-infrared spectroscopic survey of silicate-rich asteroids. The goals of this survey are to sample the full range of silicate mineralogies present in the main belt for asteroids with diameters larger than 5 km, and to map the distributions of these mineralogies as functions of orbital elements. Results from this work will help place constraints on conditions in the inner solar system during proto-planetary formation, and on the degree of heating/differentiation that occurred in the asteroid belt. The largest class of silicate-rich asteroids is the S-types. Members of this class have spectra containing diagnostic absorption bands centered near 1- and 2-microns. Variations in these bands are indicative of a wide range in pyroxene/olivine compositions (i.e. Gaffey et al. 1993, Icarus 106, 573). Our study of the S-type asteroids combines visible-wavelength spectra from the SMASSII survey (Bus and Binzel 2002, Icarus 158, 106) with high S/N near-IR (0.8 - 2.5 micron) spectra that are being obtained with SpeX (Rayner et al. 2003, PASP 115, 362) at the NASA Infrared Telescope Facility. The analysis presented here uses both band-parameter measurements (Cloutis et al. 1986, JGR 91, 11641) and principal component analysis (PCA) to group the S-type asteroids into sub-classes based on their spectral properties and inferred compositions. Based on our present sample of over 150 asteroids, we examine the distributions of these groupings as functions of orbital semi-major axis, eccentricity and inclination. Our goal is to determine the amount of spectral variation present among members of several dynamical families, and to look for larger-scale trends in olivine/pyroxene composition with heliocentric distance that may provide clues about heating across the early asteroid belt. This work was supported by NSF grant AST-0307688.

  13. A recent disruption of the main-belt asteroid P/2010 A2.

    PubMed

    Jewitt, David; Weaver, Harold; Agarwal, Jessica; Mutchler, Max; Drahus, Michal

    2010-10-14

    Most inner main-belt asteroids are primitive rock and metal bodies in orbit about the Sun between Mars and Jupiter. Disruption, through high-velocity collisions or rotational spin-up, is believed to be the primary mechanism for the production and destruction of small asteroids and a contributor to dust in the Sun's zodiacal cloud, while analogous collisions around other stars feed dust to their debris disks. Unfortunately, direct evidence about the mechanism or rate of disruption is lacking, owing to the rarity of the events. Here we report observations of P/2010 A2, a previously unknown inner-belt asteroid with a peculiar, comet-like morphology. The data reveal a nucleus of diameter approximately 120 metres with an associated tail of millimetre-sized dust particles. We conclude that it is most probably the remnant of a recent asteroidal disruption in February/March 2009, evolving slowly under the action of solar radiation pressure, in agreement with independent work. PMID:20944743

  14. 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.

  15. On the oldest asteroid families in the main belt

    NASA Astrophysics Data System (ADS)

    Carruba, Valerio; Nesvorný, David; Aljbaae, Safwan; Domingos, Rita C.

    2015-11-01

    Asteroid families are group of minor bodies produced by collisions. Once the parent body is disrupted by a collision and fragments are launched into space, their orbits evolve because of several gravitational and non-gravitational effects, such as diffusion in mean-motion resonances, Yarkovsky and YORP effects, collisional evolution etc. The subsequent dynamical evolution of asteroid family members may cause some of the original fragments to travel beyond the recognizable limits of the asteroid family. Eventually, the whole family will dynamically disperse and no longer be recognizable. Dynamical erosion of asteroid families has been the subject of a few recent studies, mostly focused on smaller asteroid groups.A natural question that may arise concerns the timescales 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, when resonant dynamics, Yarkovsky and stochastic YORP effects, and past changes in the solar luminosity are considered. None of the studied families is estimated to be older than 3.0 Gyr. Results of our numerical simulations show that some of the members of the largest families studied could have survived since 4.2 Gyr, but with a significant depletion in the number of the smallest (D < 5 km) family members.

  16. 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

    2012-10-01

    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. PMID:23038467

  17. Refining the Orbits of Known Main-Belt Binary Asteroids

    NASA Astrophysics Data System (ADS)

    Marchis, Franck; Berthier, Jerome; Descamps, Pascal; Hestroffer, Daniel

    2006-02-01

    We propose to use the high angular resolution provided by NIRI/ALTAIR to follow-up the orbits of binary main-belt systems already discovered (121 Hermione, 130 Elektra, 379 Huenna, 762 Pulcova, 1509 Esclangona) to improve their orbital elements. Determination of the precise orbital elements of the secondary can be done by multiple observations spanning large periods of time (on several years). Our group developed two independent visual methods to separate the geometrical orbit determination from the dynamical one including secular variations of the orbital plane and the pericenter. Without any assumptions, they led to the determination of the main orbital elements (a, P, e, i) of binary systems (see Marchis et al., 2004, 2005bcd). Additional observations will allow to detect unambiguously the precession of their orbit and constrain the distribution of mass in their interior (density, mass, porosity) giving direct insights on their formation processes. The recent discovery of two moonlets orbiting 87 Sylvia (Marchis et al.,2005e) indicates that multiple systems exist and should be discovered with large AO campaign.

  18. 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.

  19. 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. PMID:16421563

  20. 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

  1. 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.

  2. Characteristics of Known Triple Asteroid Systems in the Main Belt

    NASA Astrophysics Data System (ADS)

    Marchis, Franck; Berthier, J.; Burns, K. J.; Descamps, P.; Durech, J.; Emery, J. P.; Enriquez, J. E.; Lainey, V.; Reiss, A. E.; Vachier, F.

    2010-10-01

    Since the discovery of "Sylvia Remus II” [1], around the binary asteroid (87) Sylvia [2] using the VLT/NACO instrument, the number of known triple systems increased significantly. Using the same instrument, a second moonlet was discovered around the binary (45) Eugenia [3] in 2007 [4]. Using an improved W.M. Keck II AO system, [5] announced the discovery of two 3 & 5-km moons orbiting the M-type asteroid (216) Kleopatra and more recently, [6] revealed the presence of two tiny 4-km moons around the C-type (93) Minerva. 3749 Balam is a different triple asteroid system whose existence was suggested by combining lightcurves and AO observations [7]. The properties of these triple systems have been derived individually and published recently [1, 8,9,10]. We will review and contrast their characteristics, including the orbital parameters of the satellite orbits, the size and shape of the primary and the satellites, their taxonomic classes, their bulk densities, and their ages. The goal of this study is to uncover clues concerning the formation and evolution of these mini-planetary systems. The National Science Foundation supported this research under award number AAG-0807468. 1. Marchis et al. Nature 2005 2. Brown et al., IAU 7588, 2001 3. Merline et al. Nature 401, 1999 4. Marchis et al. IAU 1073, 2007 5. Marchis et al. IAU 8980, 2008 6. Marchis et al., IAU 9069, 2009 7. Marchis et al., IAU 8928, 2008 8. Marchis et al., A Dynamical Solution of the Triple Asteroid System (45) Eugenia , Icarus in press, 2010 9. Descamps et al, Triplicity and Physical Characteristics of Asteroid 216 Kleopatra Icarus, in revision, 2010 10. Marchis et al., Triplicity and Physical Characteristics of the main-belt Asteroid (93) Minerva, Icarus submitted 2010

  3. Size Distribution of Main-Belt Asteroids with High Inclination

    NASA Astrophysics Data System (ADS)

    Terai, Tsuyoshi; Itoh, Yoichi

    2011-04-01

    We investigated the size distribution of high-inclination main-belt asteroids (MBAs) so as to explore asteroid collisional evolution under hypervelocity collisions of around 10 km s-1. We performed a wide-field survey for high-inclination sub-km MBAs using the 8.2-m Subaru Telescope with the Subaru Prime Focus Camera (Suprime-Cam). Suprime-Cam archival data were also used. A total of 616 MBA candidates were detected in an area of 9.0 deg² with a limiting magnitude of 24.0 mag in the SDSS r filter. Most of the candidate diameters were estimated to be smaller than 1 km. We found a scarcity of sub-km MBAs with high inclination. Cumulative size distributions (CSDs) were constructed using Subaru data and published asteroid catalogs. The power-law indexes of the CSDs were 2.17±0.02 for low-inclination (<15°) MBAs and 2.02±0.03 for high-inclination (>15°) MBAs in the 0.7-50 km diameter range. The high-inclination MBAs had a shallower CSD. We also found that the CSD of S-like MBAs had a small slope with high inclination, whereas the slope did not vary with the inclination in the C-like group. The most probable cause of the shallow CSD of the high-inclination S-like MBAs is the large power-law index in the diameter-impact strength curve in hypervelocity collisions. The collisional evolution of MBAs may have advanced with oligopolistic survival during the dynamical excitation phase in the final stage of planet formation.

  4. Mid-Infrared Spectroscopy of 11 Main-Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Takahashi, Jun; Itoh, Yoichi; Takahashi, Shigeru

    2011-06-01

    We present mid-infrared (8-13μm) spectra of 11 main-belt asteroids: 1 Ceres, 3 Juno, 7 Iris, 11 Parthenope, 20 Massalia, 24 Themis, 41 Daphne, 42 Isis, 44 Nysa, 67 Asia, and 88 Thisbe. This paper makes the first report on the mid-infrared spectrum for 5 asteroids. Our observation was conducted with Michelle on UKIRT. The modified Standard Thermal Model (STM) has provided a slightly better fit to the observed spectra than the model without any modification. For 1 Ceres, we detected an emission feature that surpasses the thermal continuum by 6.2±1.1%. For the other 10 asteroids, no feature has been detected above their observational errors. However, their S/N ratios are sufficient to only detect 6% emission excess. As the causes of the observed spectral distinction, we examine possible (1) chemical and (2) physical differences on the surfaces of the asteroids: (1) 1 Ceres has silicates with a lower degree of polymerization than do the other asteroids; (2a) the dominant grain size on 1 Ceres is nearer to 200μm, and probably smaller than that on the other asteroids; (2b) In addition, 1 Ceres has very small (<5μm) grains on its surface, while the other asteroids have grains that are moderately small, but larger than on 1 Ceres. In either case, the observed spectral distinctiveness of 1 Ceres, the largest asteroid, suggests that the properties of an asteroid surface may be correlated with the asteroid size.

  5. Main-Belt Source Regions for Potentially Hazardous Near-Earth Asteroids and Sample Return Targets

    NASA Astrophysics Data System (ADS)

    Binzel, Richard P.; DeMeo, F. E.; Burt, B. J.; Polishook, D.; Burbine, T. H.; Moskovitz, N.; Bus, S. J.; Tokunaga, A.; Birlan, M.

    2015-11-01

    Spectroscopic and taxonomic information is now available for more than 1000 near-Earth objects (NEOs), thanks in large measure to the NASA IRTF long-term NEO spectral reconnaissance program we call the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) [1]. This sample comprises about 10% of the total NEO population, including Potentially Hazardous Asteroids (PHAs), and finds that all defined main-belt asteroid classes are also present within the near-Earth population. Using this largest available NEO dataset and dynamic source region models (such as [2]) we will present new results on the provenance of PHAs, source regions for each of the asteroid taxonomic classes, and pinpoint sources for major meteorite classes such as H, L, and LL ordinary chondrites. In finding these correlations, we find that source region signatures for B-, C-, and Cg-type NEOs include Jupiter family comets, further adding interest to the sampling of these classes by impending missions [3, 4]. This work is supported by the National Science Foundation Grant 0907766 and NASA Grant NNX10AG27G.[1] Tokunaga, A. et al. (2006) BAAS 38, 59.07. [2] Bottke, W.F. et al. (2002), Icarus 156, 399. [3] Lauretta, D. S. et al. (2015), MAPS 50, 834. [4] Abe, M. et al. (2012) 39th COSPAR, Abstract H0.2-7-12.

  6. 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.

  7. Discovery and Characteristics of the Rapidly Rotating Active Asteroid (62412) 2000 SY178 in the Main Belt

    NASA Astrophysics Data System (ADS)

    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-3.

  8. 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}.

  9. 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

  10. 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.

  11. 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

  12. Comets

    NASA Video Gallery

    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. 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

  14. Dynamical delivery of volatiles to the outer main belt

    NASA Astrophysics Data System (ADS)

    Grazier, Kevin R.; Castillo-Rogez, Julie C.; Sharp, Philip W.

    2014-04-01

    We quantify the relative contribution of volatiles supplied from outer Solar System planetesimal reservoirs to large wet asteroids during the first few My after the beginning of the Solar System. To that end, we simulate the fate of planetesimals originating within different regions of the Solar System - and thus characterized by different chemical inventories - using a highly accurate integrator tuned to handle close planet/planetesimal encounters. The fraction of icy planetesimals crossing the Asteroid Belt was relatively significant, and our simulations show that planetesimals originating from the Jupiter/Saturn region were orders of magnitude more abundant than those stemming from the Uranus and Neptune regions when the planets were just embryos. As the planets reached their full masses the Jupiter/Saturn and Saturn/Uranus regions contributed similar fractions of planetesimals for any material remaining in these reservoirs late in the stage of planetary formation, This implies that large asteroids like Ceres accreted very little material enriched in low-eutectic volatiles (e.g., methanol, nitrogen and methane ices, etc.) and clathrate hydrates expected to condense at the very low temperatures predicted for beyond Saturn’s orbit in current early solar nebula models. Further, a large fraction of the content in organics of Ceres and neighboring ice-rich objects originates from the outer Solar System.

  15. Two new basaltic objects in the Outer Main Belt

    NASA Astrophysics Data System (ADS)

    Duffard, R.; Roig, F.; Gil-Hutton, R.; Moskovitz, N. A.

    2007-08-01

    The existence of basalt on the surface of asteroids provides information about their thermal history that is likely related to their formation and collisional evolution. Basaltic materials on the surface of an asteroid are indicators of past partial melting, a phenomenon that occurs due to the complicated interplay of heating and cooling processes within the interior of rocky bodies. Until recently, most of the known basaltic asteroids, taxonomically classified as V-type, were members of the Vesta dynamical family. Currently, several V-type asteroids are know to reside outside the Vesta family (e.g. [3][8]), and several NEAs with basaltic mineralogical surface composition have been recognized (e.g. [5] [1][6]). The asteroid (1459) Magnya, a basaltic object in the outer asteroid belt [10], is sufficiently distant from the Vesta family so that its probability of origin from this family is very low [11]. [12] presented the possibility of searching yet unknown V-type asteroids using photometric data from the Sloan Digital Sky Survey (SDSS). A sub-product of this survey is the Moving Objects Catalog (MOC), which in its third release provides five band photometry for 43424 asteroids [7][9]. [12] introduced a systematic method to identify possible candidate V-type asteroids from the SDSS-MOC, applying the Principal Components Analysis to the data. They found 263 V-type candidates that are not members of the Vesta dynamical family. The most interesting result is the presence of 8 V-type candidates in the middle/outer asteroid belt, i.e. with a > 2.5 AU: (7472), (10537), (21238), (40521), (44496), (55613), (66905) and (105041). These asteroids are quite isolated in proper elements space and do not belong to any of the major dynamical families. They are not close in proper elements space to (1459) Magnya either. In a recent study, [2] analyzed the spectra of (21238) in the near infrared (NIR) and confirmed its basaltic nature. In this work we present low resolution spectra

  16. Two new basaltic objects in the Outer Main Belt

    NASA Astrophysics Data System (ADS)

    Duffard, R.; Roig, F.; Gil-Hutton, R.; Moskovitz, N. A.

    2007-08-01

    The existence of basalt on the surface of asteroids provides information about their thermal history that is likely related to their formation and collisional evolution. Basaltic materials on the surface of an asteroid are indicators of past partial melting, a phenomenon that occurs due to the complicated interplay of heating and cooling processes within the interior of rocky bodies. Until recently, most of the known basaltic asteroids, taxonomically classified as V-type, were members of the Vesta dynamical family. Currently, several V-type asteroids are know to reside outside the Vesta family (e.g. [3][8]), and several NEAs with basaltic mineralogical surface composition have been recognized (e.g. [5] [1][6]). The asteroid (1459) Magnya, a basaltic object in the outer asteroid belt [10], is sufficiently distant from the Vesta family so that its probability of origin from this family is very low [11]. [12] presented the possibility of searching yet unknown V-type asteroids using photometric data from the Sloan Digital Sky Survey (SDSS). A sub-product of this survey is the Moving Objects Catalog (MOC), which in its third release provides five band photometry for 43424 asteroids [7][9]. [12] introduced a systematic method to identify possible candidate V-type asteroids from the SDSS-MOC, applying the Principal Components Analysis to the data. They found 263 V-type candidates that are not members of the Vesta dynamical family. The most interesting result is the presence of 8 V-type candidates in the middle/outer asteroid belt, i.e. with a > 2.5 AU: (7472), (10537), (21238), (40521), (44496), (55613), (66905) and (105041). These asteroids are quite isolated in proper elements space and do not belong to any of the major dynamical families. They are not close in proper elements space to (1459) Magnya either. In a recent study, [2] analyzed the spectra of (21238) in the near infrared (NIR) and confirmed its basaltic nature. In this work we present low resolution spectra

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. Thermophysical modeling of main-belt asteroids from WISE data

    NASA Astrophysics Data System (ADS)

    Hanuš, J.; Delbó, M.; Durech, J.; Alí-Lagoa, V.

    2014-07-01

    We determine asteroid physical parameters such as size, surface roughness, albedo, and thermal inertia by applying the implementation of the thermophysical model (TPM) of Lagerros (1996; 1997; 1998) to the thermal data obtained by the NASA WISE satellite. We present thermophysical parameters for ˜150 asteroids, which gives us so far the largest sample of asteroids with determined values of thermal inertia. On several individual cases, we discuss the reliability of our determinations and limitations of the TPM method we use. As initial shapes, we adopt convex shape models from the DAMIT database (Durech et al., 2010) and present new determinations based on combined dense and sparse-in-time disk-integrated photometry and the lightcurve inversion method (Kaasalainen & Torppa 2001; Kaasalainen et al., 2001). We use thermal data from the WISE filters W3 and W4, as well as the data observed by the IRAS satellite. However, due to the intriguing accuracy of the fluxes and larger amount of measurements, the WISE data are significantly more important and dominate the modeling. The WISE data are processed the same way as in Alí-Lagoa et al. (2014) for asteroid (341 843) 2008 EV_5. We show the main results of the study of derived thermophysical parameters within the whole population of MBAs and within several asteroid families with the main focus on the thermal inertia. The thermal inertia increases with decreasing size (as previously shown by Delbó et al., 2007), but a large range of thermal inertia values is observed within the similar size ranges between D˜10-100 km. Surprisingly, we derived very low (<10 J m^{-2} s^{-1/2} K^{-1}) thermal inertias for many asteroids (˜20) with various sizes. The range of thermal inertia values is large even within a few asteroid families.

  2. The Statistical Asteroid Model. I. The Main-Belt Population for Diameters Greater than 1 Kilometer

    NASA Astrophysics Data System (ADS)

    Tedesco, Edward F.; Cellino, Alberto; Zappalá, Vincenzo

    2005-06-01

    We describe the creation of a model of the main asteroid belt whose purpose is to describe the main-belt asteroid size frequency distribution and simulate the number of main-belt asteroids and their fluxes at visual through mid-infrared (~0.3-70 μm) wavelengths in any area of sky for an arbitrary date. This model is based on a population of ~1.9×106 asteroids obtained from the complete known asteroid sample, plus extrapolation of the size-frequency distributions of 15 asteroid dynamical families and three background populations, to a diameter limit of 1 km. The model is compared with data and other models, example applications are given, planned refinements and extensions to the model are presented, and some implications of the resulting size frequency distribution are discussed.

  3. Dynamical Evolution of Main-Belt Meteoroids: Numerical Simulations Incorporating Planetary Perturbations and Yarkovsky Drag

    NASA Astrophysics Data System (ADS)

    Burns, J. A.; Bottke, W. F.; Rubincam, D. P.

    2000-05-01

    Using an RMVS N-body integrator, we track meteoroid orbital histories, including planetary perturbations plus the Yarkovsky (radiation-recoil) effect (seasonal and diurnal variants, producing orbital collapse or growth, depending on meteoroid properties and spin); collisions stochastically alter spin rates and directions. Considering two drift rates, we follow -- for tens of Myr -- one hundred bodies started from the positions of each of ten asteroids (e.g., Vesta, Hebe, Maria, Flora, Hestia) scattered across the inner main belt. This region contains the powerful Jovian 3:1 mean-motion resonance and the ν 6 secular resonance, as well as numerous weaker three-body (Jupiter, Saturn, meteoroid) and Martian mean-motion resonances. Once modest eccentricities are achieved, orbits can pass near Mars, which significantly affects them. Dynamical evolution in the main belt can be quite complex. Depending on the speed and direction of orbital evolution as well as the particular resonance, particles may i) be captured, increasing e and/or i while a stays constant; or ii) jump across, kicking e, i and a, but bypassing potential ``escape hatches'' from the main belt. Chaos ensues once resonances overlap. Following convoluted trajectories, which vary with initial conditions and collisional histories, most meteoroids reach Earth-crossing orbits via the 3:1 or ν 6 resonance after tens of Myr in the main belt. These timescales correspond well to the measured cosmic-ray-exposure ages of chondrites and achondrites. Meteorite source are, however, less clear; since Yarkovsky drift allows access to a dense forest of resonant sites, nearly any body in the main belt can add to the cumulate meteoroid flux. Ejecta from small parent bodies will dominate the meteoroid flux if the main- belt size-distribution at sub-km sizes is in collisional equilibrium, while big parent bodies dominate if observed population trends for km-sized bodies persist to smaller radii.

  4. Fomalhaut's Main Belt Structure and the Eccentric Orbit of Fomalhaut b

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    We present a significant update to the observations and understanding of the planetary system sur- rounding the nearby, 440 Myr old, A3V star Fomalhaut. Our latest HST/STIS high-contrast optical images confirm that the low-mass object Fomalhaut b has a hightly eccentric orbit (e˜0.8). Its periapse is near 30 AU and in the sky-plane projection Fomalhaut b will begin crossing the main belt (a˜140 AU) two decades in the future. An MCMC analysis of the astrometry indicates apsidal alignment between Fomalhaut b and the belt, but the mutual inclination is not necessarily coplanar. We find that only 12 per cent of Fomalhaut b's ascending and descending nodes would physically encounter the belt. The non-detections of Fomalhaut b at infrared wavelengths suggest that its mass is less than a Jupiter mass, and its optical luminosity may be due to a circumplanetary dust ring or an irregular satellite cloud. We suggest that Fomalhaut b's minimum mass is a few times that of the dwarf planet Ceres in order for the circumplanetary cloud to survive shearing during periapse passage. In addition, we give observational evidence that the main belt may have an azimuthal dust depletion approximately 50 AU wide. Taken together, the eccentric orbit of Fomalhaut b and the main belt struc- ture indicate that other, yet-to-be-detected planet-mass objects may dynamically influence the system.

  5. 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.

  6. Progress on the Size Frequency Distribution of Small Main-belt Asteroids

    NASA Astrophysics Data System (ADS)

    Burt, Brian; Trilling, D. E.; Hines, D. C.; Stapelfeldt, K. R.; Rebull, L. M.; Fuentes, C. I.; Hulsebus, A.

    2012-10-01

    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 obtained Spitzer 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 and the presence of size distribution variations with inclination and radial distance in the belt. We acknowledge and thank funding from PMDAP through NASA.

  7. 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.

  8. Outer Main Belt Asteroids: Identification and Distribution of Four Spectral Groups

    NASA Astrophysics Data System (ADS)

    Takir, D.; Emery, J. P.; McSween, H. Y.

    2011-03-01

    VNIR spectra of outer main belt asteroids have revealed an interesting trend spanning the 2.5 < a < 4.6 AU region. Four spectral groups were identified: the Ceres-like group, the sharp OH group, the rounded H2O group, and the featureless group.

  9. 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.

  10. 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.

  11. 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

  12. A Survey of the Dynamics of Main-Belt Asteroids. I

    NASA Astrophysics Data System (ADS)

    Dvorak, R.; Muller, P.; Kallrath, J.

    1993-07-01

    We present a survey of the dynamical structure of the main asteroid belt between Mars and Jupiter. The results are displayed as 3-dimensional plots showing the dynamical evolution of fictitious asteroids with initial semimajor axes ranging from 0.3 to 0.8 (in units of the semimajor axis of Jupiter's orbit) which includes all the existing main belt asteroids. The initial eccentricity of these bodies was fixed between 0.0 and 0.25 which is in the most interesting range. We chose a mesh with a grid width in initial semimajor axis Δa = 0.002 and Δe = 0.025 in initial eccentricity. The orbits of about 3500 fictitious asteroids (2750 are shown in the graphs) were integrated numerically over 104 Jupiter periods corresponding to approximately 105 years. We take the standard deviations σ of the semimajor axis α, eccentricity e and inclination i, as parameters characterizing the orbital perturbations due to Jupiter. These σ(α), σ(e), σ(i) are plotted as functions of the initial conditions α and e. All the main perturbations associated with the mean motion resonance are well reproduced. These results are compared to existing numerical ones and also to recently derived analytical developments. Furthermore, our results do not only reproduce the actual distribution of the main belt asteroids with respect to the semimajor axis, but also reveal some "new" resonances which are manifested through larger deviations of the three elements mentioned.

  13. 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.

  14. Dawn : a mission in developement for exploration of main belt asteroids Vesta and Ceres

    NASA Technical Reports Server (NTRS)

    Rayman, Marc D.; Fraschetti, Thomas C.; Russell, Christopher T.; Raymond, Carol A.

    2004-01-01

    Dawn is in development for a 2006 launch on a mission to explore main belt asteroids in order to yield insights into important questions about the formation and evolution of the solar system. Its objective is to acquire detailed data from orbit around two complementary bodies, Vesta and Ceres, the two most massive asteroids. The project relies on extensive heritage from other deep-space and Earth-orbiting missions, thus permitting the ambitious objectives to be accomplished with an affordable budget.

  15. High Latitude Dust Bands in the Main Asteroid Belt: Fingerprints of Recent Breakup Events

    NASA Astrophysics Data System (ADS)

    Bottke, William; Durda, Daniel; Jayaraman, Sumita; Lien, David; Nesvorny, David; Reach, William; Stansberry, John; Sykes, Mark; Walker, Russell

    2005-06-01

    The present population of main belt asteroids is largely the result of many past collisions. Ideally, the fragments produced by each impact event could help us understand the collisional processes that shaped the planets during early epochs. Most known asteroid fragment families, however, are very old and thus have undergone significant collisional and dynamical evolution since their formation. This evolution masks the properties of the original collisions. To overcome this problem, our team has used numerical methods and a large database of asteroid orbits to identify several families produced by recent disruption events (<< few tens of My). Not only have these young families undergone little collisional and dynamical evolution, but several of them appear to be the source of dust bands observed by IRAS (e.g., the Karin and Veritas families, both which are < 10 My old; Nesvorny et al. 2002; 2003). Here we propose to use Spitzer observations to investigate the structure of high latitude dust bands in the main asteroid belt. Our results indicate that 2 faint dust bands identified by IRAS, the J/K band at proper inclination i = 12 deg and the M/N band at i = 15 deg, were produced by break up events associated with asteroids (4652) Iannini and (1521) Seinajoki, respectively. Numerical integration work by our team suggests the former family is < 5 My old, making it the youngest family yet discovered in the main belt. Taking advantage of the increased sensitivity of Spitzer over IRAS, we will determine the dust production rate and size distribution in the high latitude bands, relate them to the Zodiacal Cloud, and use this data to constrain main belt collisional processes.

  16. Radar Observations of Near-Earth and Main-Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Benner, L. A. M.; Busch, M. W.; Giorgini, J. D.; Taylor, P. A.; Margot, J.-L.

    Radar is a very powerful technique for characterizing near-Earth and main-belt asteroids and for improving their orbits. This results from radar's ability to spatially resolve objects that often cannot be resolved at comparable resolutions by other groundbased techniques. Radar has revealed binary and contact binary objects, at least two triple systems, non-principal-axis rotators, objects whose radar reflectivity and circular polarization ratio have longitudinal variation, irregularly shaped near-Earth asteroids, objects with metallic compositions, objects with rubble-pile structures, and detailed radar images of main-belt asteroids that reveal complicated surfaces and substantial topographic relief. This chapter concentrates on the most significant advances in the field since publication of the radar chapter by Ostro et al. (2002) in Asteroids III. Detailed descriptions of asteroid radar observing techniques and terminology have appeared in Ostro (1993) and Ostro et al. (2002) (Asteroids III), so we refer readers to those papers for background information. This chapter emphasizes the first ground-truth tests of asteroid shape models by spacecraft encounters, population trends among near-Earth and main-belt asteroids, results for selected objects, new observing techniques, improved capabilities at radar telescopes, and improvements in three-dimensional shape modeling. We conclude with a discussion of future prospects.

  17. 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).

  18. 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.

  19. 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.

  20. 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.

  1. 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}.

  2. 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.

  3. 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.

  4. CHARACTERIZATION OF ACTIVE MAIN BELT OBJECT P/2012 F5 (GIBBS): A POSSIBLE IMPACTED ASTEROID

    SciTech Connect

    Stevenson, R.; Kramer, E. A.; Bauer, J. M.; Masiero, J. R.; Mainzer, A. K.

    2012-11-10

    In this work, we characterize the recently discovered active main belt object P/2012 F5 (Gibbs), which was discovered with a dust trail >7' in length in the outer main belt, 7 months prior to aphelion. We use optical imaging obtained on UT 2012 March 27 to analyze the central condensation and the long trail. We find B-band and R-band apparent magnitudes of 20.96 {+-} 0.04 mag and 19.93 {+-} 0.02 mag, respectively, which give an upper limit on the radius of the nucleus of 2.1 km. The geometric scattering cross-section of material in the trail was {approx}4 Multiplication-Sign 10{sup 8} m{sup 2}, corresponding to a mass of {approx}5 Multiplication-Sign 10{sup 7} kg. Analysis of infrared images taken by the Wide-field Infrared Survey Explorer in 2010 September reveals that the object was below the detection limit, suggesting that it was less active than it was during 2012, or possibly inactive, just six months after it passed through perihelion. We set a 1{sigma} upper limit on its radius during this time of 2.9 km. P/2012 F5 (Gibbs) is dynamically stable in the outer main belt on timescales of {approx}1 Gyr, pointing toward an asteroidal origin. We find that the morphology of the ejected dust is consistent with it being produced by a single event that occurred on UT 2011 July 7 {+-} 20 days, possibly as the result of a collision with a small impactor.

  5. Observational constraints on the catastrophic disruption rate of main-belt asteroids

    NASA Astrophysics Data System (ADS)

    Denneau, L., Jr.; Jedicke, R.; Fitzsimmons, A.; Pan-Starrs 1 Science Collaboration (Ps1SC)

    2014-07-01

    We have calculated 90 % confidence limits on the steady-state rate of impact-generated catastrophic disruptions (CD) of main-belt asteroids in terms of the absolute magnitude at which one CD occurs per year (H_0^{CL}) as a function of the post-disruption increase in brightness (Δ m) and subsequent brightness decay rate (τ). The confidence limits were calculated using the brightest unknown main-belt asteroid (V=18.5) detected with the PanSTARRS1 telescope. We measured the system's CD detection efficiency over a 453-day interval using the PanSTARRS moving object processing system (MOPS) and a simple model for the CD event's photometric behavior in a small aperture centered on the CD event. We then calculated the H^{CL}_0 contours in the ranges from 0.5 mag < Δ m < 20 mag and 0.001 mag d^{-1} < τ < 10 mag d^{-1} encompassing measured values from known cratering and disruption events and our model's predictions. Our simplistic CD model suggests that Δ m ˜ 20 mag and 0.01 mag d^{-1} < τ < 0.1 mag d^{-1} which would imply that H_0 > 28 -- strongly inconsistent with the H_0 = 23.26±0.02 predicted by Bottke et al. (2005). However, if we assume that H_0 = 23.26, our results suggest that 11.0 mag < Δ m < 12.4 mag which is entirely inconsistent with our simplistic impact-generated CD model. We think the solution to the discrepancy is that about 99.9% of main-belt catastrophic disruptions in the size range to which this study was sensitive (˜ 100 m) are rotation-generated and not impact-generated. We estimate that current and upcoming asteroid surveys may discover up to about 10 CDs/year brighter than V = 18.5.

  6. 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.

  7. Outer Main Belt asteroids: Identification and distribution of four 3-μm spectral groups

    NASA Astrophysics Data System (ADS)

    Takir, Driss; Emery, Joshua P.

    2012-06-01

    This paper examines the distribution and the abundance of hydrated minerals (any mineral that contains H2O or OH) on outer Main Belt asteroids spanning the 2.5 < a < 4.0 AU region. The hypothesis we are testing is whether planetesimals that accreted closer to the Sun experienced a higher degree of aqueous alteration. We would expect then to see a gradual decline of the abundance of hydrated minerals among the outer Main Belt asteroids with increasing heliocentric distance (2.5 < a < 4.0 AU). We measured spectra (0.8-2.5 μm and 1.9-4.1 μm) of 28 outer Main Belt asteroids using the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF). We identified four groups on the basis of the shape and the band center of the 3-μm feature. The first group, which we call "sharp", exhibits a sharp 3-μm feature, attributed to hydrated minerals (phyllosilicates). Most asteroids in this group are located in the 2.5 < a < 3.3 AU region. The second group, which we call "Ceres-like", consists of 10 Hygiea and 324 Bamberga. Like Asteroid Ceres, these asteroids exhibit a 3-μm feature with a band center of 3.05 ± 0.01 μm that is superimposed on a broader absorption feature from ˜2.8 to 3.7 μm. The third group, which we call "Europa-like", includes 52 Europa, 31 Euphrosyne, and 451 Patientia. Objects in this group exhibit a 3-μm feature with a band center of 3.15 ± 0.01 μm. Both the Ceres-like and Europa-like groups are concentrated in the 2.5 < a < 3.3 AU region. The fourth group, which we call "rounded", is concentrated in the 3.4 < a < 4.0 AU region. Asteroids in this group are characterized by a rounded 3-μm feature, attributed to H2O ice. A similar rounded 3-μm feature was also identified in 24 Themis and 65 Cybele. Unlike the sharp group, the rounded group did not experience aqueous alteration. Of the asteroids observed in this study, 140 Siwa, a P-type, is the only one that does not exhibit a 3-μm feature. These results are important to constrain the

  8. 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

  9. 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

  10. 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

  11. Main-belt Asteroids in the K2 Engineering Field of View

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

  12. 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.

  13. 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

  14. 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

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

    PubMed

    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

  16. 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

  17. Mutual Orbits, Bulk Densities, Formation and Evolution of Multiple Visualized Main-Belt Asteroids

    NASA Astrophysics Data System (ADS)

    Marchis, Franck; Descamps, P.; Berthier, J.; Hestroffer, D.; Vachier, F.; Baek, M.

    2007-10-01

    The advent of high angular resolution imaging, provided by high angular resolution instruments such as Adaptive Optics (AO) or Hubble Space Telescope, permitted the visual discovery of more than fifty multiple asteroid systems over the last twelve years, including two triple main-belt asteroid systems, 45 Eugenia and 87 Sylvia, discovered by our team. Over the past few years, we have focused our attention on the multiple systems located in the main-belt. We initiated an intensive campaign of observations in 2003 that combines the AO high-resolution capabilities of various 8m-10m class telescopes (UT4 of the Very Large Telescope, W.M. Keck-II and Gemini-North) in order to resolve them and study their characteristics (orbits, mass, density, and shape). We recently published a complete analysis of the orbit, size and shape of 90 Antiope, which is a similar-sized doublet system (Descamps et al., Icarus, 2007). We performed the same analysis on the asteroids with small (a few km) satellite, and published a complete analysis of 12 binary systems (Marchis et al., Nature, 2005; Icarus, submitted, 2007ab). Our work revealed a large diversity in their mutual orbits, suggesting a different origin and evolution. Their bulk density is quite variable depending on their taxonomic classes, and in the most case, they have a significant macro-porosity (>30%) that suggests a rubble-pile interior. We will also present a synthesis of these multiple asteroid system properties, including additional studies in progress (lightcurve of mutual events) and future ideas (comparative spectroscopy), which will help to get insights on the formation process of these systems. This work was supported by the National Science Foundation Science and Technology Center for Adaptive Optics (No. AST-9876783) and by the National Aeronautics and Space Administration issue through the Science Mission Directorate Research and Analysis Programs number NNG05GF09G.

  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. 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).

  20. 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).

  1. 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.

  2. 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,...

  3. 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,...

  4. 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,...

  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,...

  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,...

  7. Asteroid proper elements and the dynamical structure of the asteroid main belt

    NASA Astrophysics Data System (ADS)

    Milani, A.; Knezevic, Z.

    1994-02-01

    We have computed proper elements for 12,573 asteroids, including all the ones with orbits accurate enough to be useful for family identification. This was done with an upgraded version of our iterative analytical algorithm, resulting in significantly improved accuracy for most asteroids in the low to moderate inclination and eccentricity region of the main belt (typical instability in the proper e and sin I being less than or = 0.0015 over 5 Myr). This stability has been verified by numerical integrations (within a realistic model) of 35 test cases. In a small percentage of cases, the accuracy of the proper elements computation was degraded by the effects of some resonance, either in mean motion or secular. We have been able to list the resonances responsible for this degradation in almost all the cases, in such a way that these are properly flagged with a 'resonance code.' This list of resonances, including nine high-degree secular resonances not known before our work, provides a detailed map of the dynamical structure of the asteroid main belt. We investigate the long-term dynamics of some of these secular resonances and find both very large amplitude oscillations of the eccentricity and irregular behavior for asteroids affected by one or more resonances. We show the geometry of these resonances in the proper elements space and their relationship with the asteroid distribution and with the most prominent families. In the second part of the paper, we give a detailed description of the improvements of this version of the proper elements theory with respect to the previously published ones. (A. Milani and Z. Knezevic, 1990, 1992). We discuss the success of some of these improvements in cases which were previously of degraded accuracy, and we also comment on the failure of some attempted improvements. We conjecture that our theory is very close to the fundamental limitations to the accuracy of any analytical theory, which result from the fact that there is an

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

    NASA Astrophysics Data System (ADS)

    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 ( 1/4×R) 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 determine a unique

  9. 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.

  10. 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

  11. 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

  12. 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

  13. On the current distribution of main belt objects: Constraints for evolutionary models

    NASA Astrophysics Data System (ADS)

    Michtchenko, T. A.; Lazzaro, D.; Carvano, J. M.

    2016-04-01

    Context. It is widely accepted that the current distribution of material in the main asteroidal belt (MB) is a product of the evolutionary history of the solar system during its whole lifetime of ~4.5 billions of years and is, consequently, a major witness of the diverse stages of this evolution. Aims: The purpose of this paper is twofold: first, we study the principal aspects of the distribution of the asteroids in proper element space, mass, and, physical composition for a complete picture of the current MB. Second, we analyze if and how these current distributions can be explained by the long-lasting dynamical effects of the planets on this region of the solar system. Methods: We studied the distribution in the proper element space for the sample that consists of about 350 000 objects whose proper orbital elements are available from the database AstDyS. We studied the distribution in size and physical composition using the most recent and large available datasets. We constructed the dynamical portrait of the MB in form of the dynamical and averaged maps via the spectral analysis method. Results: The main properties of the current distributions of MB objects are identified. A comparison of the distributions of real objects with dynamical maps allows us to detect principal mechanisms of the diffusive transportation of the objects. These mechanisms are related to mean-motion resonances (MMRs) and secular resonances (SRs), overlaying with the slow dissipative Yarkovsky/Yorp drift. Conclusions: We identify the most relevant distributions of the material in the MB and show that many of the current features of the MB can be explained by the interplay of diverse dynamical mechanisms due to the planetary perturbations over 4 Gyr with nongravitational effects, without the need of 'catastrophic' events or 'ad hoc' migration mechanisms during the early stages of the solar system. In this sense, the obtained distributions can provide relevant constraints for modeling the

  14. Spitzer/IRS Observations Of Multiple Main-Belt And Binary Near-Earth Asteroids

    NASA Astrophysics Data System (ADS)

    Enriquez, J. Emilio; Marchis, F.; Emery, J. P.; Im, S.

    2010-10-01

    Since the discovery of Ida's companion in 1993, 195 companions of asteroids have been discovered. To understand the formation process of these interesting bodies, their physical properties such as their bulk density, size, shape, and surface roughness need to be determined. During the Spitzer Cycle-4, we obtained IRS thermal emission spectra (5-42 um) of 23 known binary systems. The majority of asteroids are from the main-belt (16), while the rest are NEOs (7). After extracting the thermal spectra, we used a modified Standard Thermal Model (STM) to calculate their equivalent diameter (from 0.8 km to 237 km), their albedo (from 0.04 for C-type to 0.394 for a V-type) and their beaming factor related to the surface roughness and thermal inertia. We derive their emissivity spectra, which is useful to detect silicate features. Combining these measurements with 3D-models of these multiple asteroid systems obtained by lightcurve inversion, we should be able to derive an accurate estimate of their bulk-density and contrast them with their taxonomic classes. Preliminary studies by Marchis et al. (2008)1, suggested a relationship between bulk density and the taxonomic class of asteroids, which varies from 0.9 g/cc for C-complex to 2.4 g/cc for S-complex asteroids. The National Science Foundation supported this research under award number AAG-0807468. It was conducted with the Spitzer space telescope, which is operated by JPL under a contract with NASA. 1 Marchis et al. , 2008, "Mid-infrared Spectra of Binary Asteroids With Spitzer/IRS", 40th DPS Meeting, Bulletin of the American Astronomical Society, 40, 508

  15. 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

  16. 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.

  17. 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

  18. Main Stages of Geodynamic Evolution of the Caucasian Segment of the Alpine-Mediterranean Belt

    NASA Astrophysics Data System (ADS)

    Gamkrelidze, Irakli; Shengelia, David; Maisadze, Ferando; Tsutsunava, Tamara; Chichinadze, Giorgi

    2013-04-01

    Within the oceanic area of Tethys, with a typical oceanic crust, in geological past relatively small continental or subcontinental plates (terranes) were situated. The Greater Caucasian, Black Sea - Central Transcaucasian, Baiburt - Sevanian and Iran - Afghanian accretionary terranes, which in geological past represented island arcs or microcontinents, are identified in the Caucasian segment of the Alpine-Mediterranean belt. They are separated by ophiolite sutures (relics of small or large oceanic basins) of different age. During the Late Precambrian, Paleozoic and Early Mesozoic these terranes underwent horizontal displacement in different directions and ultimately they joined the Eurasian continent. New LA-ICP-MS U-Pb zircon dating along with available geologic, petrologic and geochemical investigations, allow to trace with confidence the main stages of regional metamorphism, granite formation and, consequently, pre-Alpine continental crust making within the Caucasus. At the pre-Grenville stage (1200 Ma and more) between the Baltica and Gondvana ancient continents, on the oceanic crust of Prototethys accumulation mainly of terrigenous sediments and of basic volcanites took place. At the Grenville stage (1000-800 Ma) subcontinental or primitive continental crust (gneiss-migmatite complex and synmetamorphic grenitoids of sodium series) were formed in suprasubduction conditions by both sides of Proto-Paleotethys and along the northern peripheries of comparatively small oceanic basins of the Arkhiz and Southern Slope of the Greater Caucasus. At the Baikalian stage (650-550 Ma) plagiogneissic complex has been cut by Precambrian gabbroids and intruded by large bodies of quartz-diorites. The next, Late Baikalian stage (540-500 Ma) is determined by the intrusion of Cambrian basites and Late Baikalian granitoids and by manifestation of intensive suprasubduction regional metamorphism. Late Baikalian tectogenesis is accompanied by contraction of the small oceanic basin of

  19. 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.

  20. 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.

  1. Photometric geodesy of main-belt asteroids. IV - An updated analysis of lightcurves for poles, periods, and shapes

    NASA Technical Reports Server (NTRS)

    Drummond, J. D.; Weidenschilling, S. J.; Chapman, C. R.; Davis, D. R.

    1991-01-01

    The Drummond et al. (1988) analysis of main-belt asteroids is presently extended, using three independent methods to derive poles, periods, phase functions, and triaxial ellipsoid shapes from lightcurve maxima and minima. This group of 26 asteroids is also reinvestigated with a view to the distributions of triaxial shapes and obliquity distributions. Poles weakly tend to avoid asteroid orbital planes; a rough-smooth dichotomization appears to be justified by the persistence of two solar phase angle-amplitude relations. Seven of the objects may be Jacobi ellipsoids if axial ratios are slightly exaggerated by a systematic effect of the analytical method employed.

  2. 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.

  3. Non-destructive collisions and the evolution of the orbits of binary asteroid systems in the Main Belt

    NASA Astrophysics Data System (ADS)

    Dell'Oro, A.; Cellino, A.; Paolicchi, P.

    2012-09-01

    The effect of collisions on the stability of binary asteroids is discussed. The following mechanisms are taken into account: (1) complete disruption of one of the members of the system and (2) increase of linear momentum imparted by non-disruptive collisions. The latter effect is found to progressively increase the orbital energy of the systems up to the limit of binary gravitational instability. We focus on the case of binary asteroids belonging to the Main Belt. We show that the probability that a binary system 'evaporates' before collisional disruption of one of the two members is not negligible. As a consequence, the expected lifetime of a binary system can decrease significantly. Binary 'evaporation' causes the two former members to continue to exist as independent asteroids forming a so-called asteroid pair. The efficiency of this mechanism critically depends on the properties of the binary system and on the collisional environment. Several different scenarios have been taken into account concerning the size distribution of possible projectiles in the asteroid Main Belt, while the estimate of the fragmentation threshold in energetic impacts is based on the work of Benz & Asphaug. We estimate the expected average lifetime of a binary system as a function of different parameters including the size of the primary, the size ratio of the members and the orbital properties of the system. Moreover, the expected lifetimes of binary asteroids which are known today have been computed as a function of different possible collisional environments.

  4. Nine Galileo Views in Exaggerated 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 in exaggerated color to bring out subtle color contrasts caused by small variations in composition and surface microtexture of the asteroid's soil. In natural color Ida appears gray with slight overtones of red or brown. 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'). Note in particular the color differences associated with the rims and floors of certain impact craters, which may have excavated to layers of slightly differing composition or may have ingested material from impactors of different compositions. 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). 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

  5. 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.

  6. 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

  7. The Near-IR Spectrocopy of Two M-Class Main Belt Asteroids, 418 Alemannia and 504 Cora

    NASA Astrophysics Data System (ADS)

    Reynolds, Chalbeth; Hardersen, P. S.; Gaffey, M. J.

    2007-10-01

    418 Alemannia and 504 Cora are two M-class main belt asteroids (Tholen, 1984, 1989) that were observed as part of a comprehensive NIR spectral survey of the main-belt M-class population. Previous studies of M-class asteroids show that while some are spectrally featureless, most exhibit weak 1- and/or 2-micron absorption features that suggest the presence of mafic silicate or oxides minerals such as pyroxene(s), olivine, or spinels. The presence of NiFe metal is often inferred in addition to silicate minerals. Potential meteorite analogs include pallasites, mesosiderites and CO/CV chondrites, although many M-asteroids do not have clear meteorite analogs. Hardersen et al. (2005, 2006, 2007) has discovered significant spectral, mineralogic, and geologic diversity among 28 of the 40 M-class asteroids studied thus far. NIR spectroscopic observations of 418 Alemannia and 504 Cora were collected using the NASA Infrared Telescope Facility / SpeX on Mauna Kea, Hawai'I from January 22-24, 2007 UT. NIR spectra of 418 Alemannia display a weak 0.9 micron absorption feature superimposed on an overall reddish spectrum. The average NIR spectrum of 504 Cora exhibits weak 0.9- and 1.9-micron absorption features, suggestive of the presence of surficial pyroxene. A thorough spectral, mineralogic, and dynamical analysis of these asteroids will be presented along with suggestions of any potential meteorite analog. This research is generously supported by NASA Planetary Astronomy Grant NNG05GH01G.

  8. 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)

  9. Thermal Intertias of Main-Belt Asteroids from Wise Thermal Infrared Data

    NASA Astrophysics Data System (ADS)

    Hanus, Josef; Delbo', Marco; Durech, Josef; Alí-Lagoa, Victor

    2014-11-01

    By means of a modified thermophysical model (TPM) that takes into account asteroid shape and pole uncertainties, we analyze the thermal infrared data acquired by the NASA's Wide-field Infrared Survey Explorer (WISE) of about 300 asteroids with derived convex shape models. We adopt convex shape models from the DAMIT database (Durech et al., 2010, A&A 513, A46) and present new determinations based on optical disk-integrated photometry and the lightcurve inversion method (Kaasalainen & Torppa, 2001, Icarus 153, 37). This work more than double the number of asteroids with determined thermophysical properties. We also discuss cases in which shape uncertainties prevent the determination of reliable thermophysical properties. This is per-se a novel result, as the effect of shape has been often neglected in thermophysical modeling of asteroids.We also present the main results of the statistical study of derived thermophysical parameters within the whole population of MBAs and within few asteroid families. The thermal inertia increases with decreasing size, but a large range of thermal inertia values is observed within the similar size ranges between 10-100 km. Surprisingly, we derive low (<20J m^{-2} s^{-1/2} K^{-1}) thermal inertia values for several asteroids with sizes D>10 km, indicating a very fine and mature regolith on these small bodies. The work of JH and MD was carried under the contract 11-BS56-008 (SHOCKS) of the French Agence National de la Recherche (ANR), and JD has been supported by the grant GACR P209/10/0537 of the Czech Science Foundation.

  10. Craters on comets

    NASA Astrophysics Data System (ADS)

    Vincent, Jean-Baptiste; Oklay, Nilda; Marchi, Simone; Höfner, Sebastian; Sierks, Holger

    2015-03-01

    This paper reviews the observations of crater-like features on cometary nuclei. We compare potential crater sizes and morphologies, and we discuss the probability of impacts between small asteroids in the Main Belt and a comet crossing this region of the Solar System. Finally, we investigate the fate of the impactor and its chances of survival on the nucleus. We find that comets do undergo impacts although the rapid evolution of the surface erases most of the features and make craters difficult to detect. In the case of a collision between a rocky body and a highly porous cometary nucleus, two specific crater morphologies can be formed: a central pit surrounded by a shallow depression, or a pit, deeper than typical craters observed on rocky surfaces. After the impact, it is likely that a significant fraction of the projectile will remain in the crater. During its two years long escort of comet 67P/Churyumov-Gerasimenko, ESA's mission Rosetta should be able to detect specific silicates signatures at the bottom of craters or crater-like features, as evidence of this contamination. For large craters, structural changes in the impacted region, in particular compaction of material, will affect the local activity. The increase of tensile strength can extinct the activity by preventing the gas from lifting up dust grains. On the other hand, material compaction can help the heat flux to travel deeper in the nucleus, potentially reaching unexposed pockets of volatiles, and therefore increasing the activity. Ground truth data from Rosetta will help us infer the relative importance of those two effects.

  11. ESA's Comet Orbiter Rosetta and Lander Philae

    NASA Astrophysics Data System (ADS)

    McKenna-Lawlor, S.; Schwehm, G.; Schulz, R.; Ulamec, S.

    2014-05-01

    Rosetta is the first mission designed to orbit, and deploy a Lander onto the surface of, a comet, 67P/Churyumov-Gerasimenko (67P/C-G). After an active Cruise Phase, which included three swingbys at the Earth, one at Mars and two flybys at Main Belt asteroids, the spacecraft is scheduled to orbit the comet nucleus and, after careful reconnaissance, deliver to the surface, while still at a distance of about 3 AU from the Sun, its Lander (Philae). The Lander payload, which comprises ten onboard experiments, will investigate the physical properties of the cometary surface/subsurface, measuring in particular their chemical, mineralogical and isotopic compositions. The lifetime of the Lander will depend on the prevailing cometary environment. The spacecraft will meanwhile continue to orbit and map the comet as it advances along its trajectory toward the Sun, utilizing eleven payload experiments to investigate how the comet becomes gradually more active and how its interactions with the solar wind develop. Post-perihelion Rosetta will continue to orbit, and make observations of the gradually declining comet environment out to a distance of ˜ 2 AU.

  12. Comet nucleus and asteroid sample return missions

    NASA Astrophysics Data System (ADS)

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

    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.

  13. 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.

  14. Space weathering of near-Earth and main belt silicate-rich asteroids: observations and ion irradiation experiments

    NASA Astrophysics Data System (ADS)

    Marchi, S.; Brunetto, R.; Magrin, S.; Lazzarin, M.; Gandolfi, D.

    2005-12-01

    In this paper we report the results of a comparison between ion irradiation experiments (N^+, Ar^+, Ar++) on silicates, a large spectral data set of silicate-rich (S-type) asteroids, and ordinary chondrite meteorites (OCs). Ion irradiation experiments - conducted on Fe-poor olivine, Fe-poor orthopyroxene, bulk silicate-rich rocks and one OC - have been monitored by means of reflectance spectroscopy (0.3-2.5 μm). All these experiments produce reddening and darkening of reflectance spectra. The observational data consist of a set of visible and near-infrared (0.4-2.4 μm) spectra of S-type asteroids, that belong to main belt (MBAs) and near-Earth (NEOs) populations. By analyzing the spectra of OCs, MBAs, and NEOs, we find a similar mineralogy between most asteroids and meteorites, but different distributions of spectral slopes. We interpret these findings in the frame of space weathering induced by solar wind ion irradiation.

  15. 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.

  16. About origin of comet 55P

    NASA Astrophysics Data System (ADS)

    Guliyev, R. A.

    2014-12-01

    55P is a periodic comet with an orbital period of 33 years. It fits the classical definition of a Halley-type comet. The comet is the parent body of the Leonid meteor shower. Orbital simulation of the comet's 55P/Tempel-Tuttle orbit for 5000 years before its discovery by a variety of integrators is provided in this work. In particular the idea of capturing the comet 55P by Uranus from the field of long-period comets during the integration period is checked. The hypothesis about its capture from the Kuiper belt for the study period is checked also. Both ideas have not been confirmed.

  17. 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. PMID:26990270

  18. Collisional Evolution of Edgeworth-Kuiper Belt Objects

    NASA Astrophysics Data System (ADS)

    Davis, D. R.; Farinella, P.

    1997-01-01

    The Edgeworth-Kuiper Belt contains a population of objects ≈10 3times that of the main asteroid belt, spread over a volume ≈10 3larger and with relative speeds ≈10 times lower. As for the asteroids, the size distribution of Edgeworth-Kuiper Belt objects has been modified by mutual impacts over Solar System history. We have modeled this collisional evolution process using a numerical code developed originally to study asteroid collisional evolution but modified to reflect collision rates in the Edgeworth-Kuiper Belt. Our numerical simulations show that collisional evolution is substantial in the inner part of the Edgeworth-Kuiper Belt, but its intensity decreases with increasing distance from the Sun. In the inner belt, objects with diameters D> 50-100 km are not depleted by disruptive collisions; hence they reflect the original (formative) population (many of them, however, may have been converted into "rubble piles"). On the other hand, smaller objects are mostly multigenerational fragments, although the original population must have contained a significant number of bodies down to at least a few tens of kilometers in size in order to initiate a collisional cascade. About 10 fragments, 1-10 km in size, are produced per year in the inner Edgeworth-Kuiper Belt, with a few percent of them inserted into chaotic resonant orbits. This is in rough agreement with the required influx rate of Jupiter-family comets. Both collisions and dynamical instabilities associated with resonances are processes that can inject comets into the "escape hatches," but our results indicate that most comets coming from the Edgeworth-Kuiper Belt would be fragments from larger parent bodies, rather than primitive planetesimals. However, this does not apply to Chiron-sized ( D> 100 km) objects, which must be primordial and delivered to the outer Solar System by either dynamical processes or nondisruptive collisions.

  19. 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

  20. 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

  1. 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

  2. Quaternary slip-rates of the Kazerun and the Main Recent Faults: active strike-slip partitioning in the Zagros fold-and-thrust belt

    NASA Astrophysics Data System (ADS)

    Authemayou, Christine; Bellier, Olivier; Chardon, Dominique; Benedetti, Lucilla; Malekzade, Zaman; Claude, Christelle; Angeletti, Bernard; Shabanian, Esmaeil; Abbassi, Mohammad Reza

    2009-07-01

    The aim of this work is to constrain the Late Quaternary activity of two major dextral strike-slip faults of the Zagros fold-and-thrust belt of Southern Iran, within the framework of right-oblique convergence between Arabia and Eurasia. The NW-trending Main Recent fault marks the rear of the belt along two thirds of its length. Its southeastern tip connects to the northern termination of the N-trending Kazerun Fault, which affects the entire width of the belt. Horizontal slip rates have been estimated on these two faults over the last 140 ka from lateral offsets of streams and fans and in situ cosmogenic 36Cl exposure dating of cobbles sampled on the surface of these geomorphic features. Compared to GPS data, the obtained minimum slip rate of 3.5-12.5 mm yr-1 on the Main Recent Fault implies strike-slip partitioning of the convergence along this fault. Minimum slip rate of the Kazerun Fault is 2.5-4 mm yr-1 for its northern strand, 1.5-3.5 mm yr-1 for its central segment and is negligible for its southern segment. These results are consistent with southward distribution of the slip from along the Main Recent Fault to the longitudinal thrusts and folds of the fold-and-thrust belt through the Kazerun Fault, with a decrease of slip from the southeastern tip of the Main Recent Fault towards the southern termination of the Kazerun Fault. The Kazerun and associated faults form the horsetail termination of the Main Recent fault and may be seen as the propagating southeastern front of the fault system that accommodates indentation of Eurasia by Arabia.

  3. Dust evolution from comets and asteroids: Their velocities at Earth orbit intersection

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    In this study on the evolution of dust particles from comets and asteroids, the effects of accurate many-body planetary motion on the gravitational perturbations of the dust grains are computed. In a computer simulation, dust grains of radius 10, 30, and 100 micron were released at perihelion passage from each of 36 different celestial bodies: 16 main asteroids, 15 short period comets with perihelion greater than 1 AU, and 5 short period comets with perihelion less than 1 AU. It is found that when dust grains evolve to intersection with the earth's orbit, they nearly always retain orbital characteristics indicative of their origins. Grains from main belt asteroids differ significantly in orbital characteristics, especially orbital eccentricity, from grains that evolve from comets.

  4. 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

  5. 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

  6. 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.

  7. From asteroids to comets: Gas and dust production of the small-bodies in the solar system

    NASA Astrophysics Data System (ADS)

    Gilbert, Alyssa M.

    -levet technique, while over 11,000 objects were visually inspected. This is the largest search for main-belt comets (MBCs) of any kind to date, which also examined the general main-belt population. One unknown object was found to show cometary activity. Upper limits were derived for the expected number of weakly and strongly active MBCs in the main-belt. Key words. Comets, asteroids, transition objects, main-belt comets, activated asteroids, solar system, cometary activity, physical evolution, orbit, Jupiter Tisserand parameter, optical spectra, optical observations, emission lines, gas production rate, dust production rate, Elginfield telescope, Dominion Astrophysical Observatory, Cerro-Tololo Inter-American Observatory, Canada-France-Hawaii Telescope, Legacy Survey, spectrograph, CCD camera.

  8. 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.

  9. Physical observations of comets: Their composition, origin and evolution

    NASA Technical Reports Server (NTRS)

    Cochran, Anita L.; Barker, Edwin S.; Cochran, William D.

    1991-01-01

    The composition, origins, and evolution of comets were studied. The composition was studied using spectroscopic observations of primarily brighter comets at moderate and high resolution for the distribution of certain gases in the coma. The origins was addressed through an imaging search for the Kuiper belt of comets. The evolution was addressed by searching for a link between comets and asteroids using an imaging approach to search for an OH coma.

  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. 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

  12. 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.

  13. 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 ).

  14. Craters on comets

    NASA Astrophysics Data System (ADS)

    Vincent, J.; Oklay, N.; Marchi, S.; Höfner, S.; Sierks, H.

    2014-07-01

    This paper reviews the observations of crater-like features on cometary nuclei. ''Pits'' have been observed on almost all cometary nuclei but their origin is not fully understood [1,2,3,4]. It is currently assumed that they are created mainly by the cometary activity with a pocket of volatiles erupting under a dust crust, leaving a hole behind. There are, however, other features which cannot be explained in this way and are interpreted alternatively as remnants of impact craters. This work focusses on the second type of pit features: impact craters. We present an in-depth review of what has been observed previously and conclude that two main types of crater morphologies can be observed: ''pit-halo'' and ''sharp pit''. We extend this review by a series of analysis of impact craters on cometary nuclei through different approaches [5]: (1) Probability of impact: We discuss the chances that a Jupiter Family Comet like 9P/Tempel 1 or the target of Rosetta 67P/Churyumov-Gerasimenko can experience an impact, taking into account the most recent work on the size distribution of small objects in the asteroid Main Belt [6]. (2) Crater morphology from scaling laws: We present the status of scaling laws for impact craters on cometary nuclei [7] and discuss their strengths and limitations when modeling what happens when a rocky projectile hits a very porous material. (3) Numerical experiments: We extend the work on scaling laws by a series of hydrocode impact simulations, using the iSALE shock physics code [8,9,10] for varying surface porosity and impactor velocity (see Figure). (4) Surface processes and evolution: We discuss finally the fate of the projectile and the effects of the impact-induced surface compaction on the activity of the nucleus. To summarize, we find that comets do undergo impacts although the rapid evolution of the surface erases most of the features and make craters difficult to detect. In the case of a collision between a rocky body and a highly porous

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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)

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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. PMID:11961547

  7. 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.

  8. 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; Corre, Lucille Le; 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

  9. Herschel celestial calibration sources. Four large main-belt asteroids as prime flux calibrators for the far-IR/sub-mm range

    NASA Astrophysics Data System (ADS)

    Müller, Thomas; Balog, Zoltán; Nielbock, Markus; Lim, Tanya; Teyssier, David; Olberg, Michael; Klaas, Ulrich; Linz, Hendrik; Altieri, Bruno; Pearson, Chris; Bendo, George; Vilenius, Esa

    2014-07-01

    Celestial standards play a major role in observational astrophysics. They are needed to characterise the performance of instruments and are paramount for photometric calibration. During the Herschel Calibration Asteroid Preparatory Programme approximately 50 asteroids have been established as far-IR/sub-mm/mm calibrators for Herschel. The selected asteroids fill the flux gap between the sub-mm/mm calibrators Mars, Uranus and Neptune, and the mid-IR bright calibration stars. All three Herschel instruments observed asteroids for various calibration purposes, including pointing tests, absolute flux calibration, relative spectral response function, observing mode validation, and cross-calibration aspects. Here we present newly established models for the four large and well characterized main-belt asteroids (1) Ceres, (2) Pallas, (4) Vesta, and (21) Lutetia which can be considered as new prime flux calibrators. The relevant object-specific properties (size, shape, spin-properties, albedo, thermal properties) are well established. The seasonal (distance to Sun, distance to observer, phase angle, aspect angle) and daily variations (rotation) are included in a new thermophysical model setup for these targets. The thermophysical model predictions agree within 5 % with the available (and independently calibrated) Herschel measurements. The four objects cover the flux regime from just below 1,000 Jy (Ceres at mid-IR N-/Q-band) down to fluxes below 0.1 Jy (Lutetia at the longest wavelengths). Based on the comparison with PACS, SPIRE and HIFI measurements and pre-Herschel experience, the validity of these new prime calibrators ranges from mid-infrared to about 700 μm, connecting nicely the absolute stellar reference system in the mid-IR with the planet-based calibration at sub-mm/mm wavelengths.

  10. 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. PMID:17170288

  11. 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

    2011-10-13

    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. PMID:21976024

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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).

  19. Search for Dormant Comets in Near-Earth Space

    NASA Astrophysics Data System (ADS)

    Kim, Yoonyoung

    2013-06-01

    It is considered that comets have been injected into near-Earth space from outer region (e.g. Kuiper-belt region), providing rich volatile and organic compounds to the earth. Some comets are still active while most of them are dormant with no detectable tails and comae. Here we propose to make a multi-band photometric observation of near-Earth objects (NEOs) with comet-like orbits. We select our targets out of infrared asteroidal catalogs based on AKARI and WISE observations. With a combination of taxonomic types by Subaru observation and albedos by AKARI or WISE, we aim to dig out dormant comet candidates among NEOs. Our results will provide valuable information to figure out the dynamical evolution and fate of comets. We would like to emphasize that this is the first taxonomic survey of dormant comets to utilize the infrared data archive with AKARI and WISE.

  20. Comets and the KAO

    NASA Technical Reports Server (NTRS)

    Lynch, David K.; Larson, Harold P.

    1995-01-01

    Seven comets have been observed from the Kuiper Airborne Observatory (KAO) in its twenty year history. Of these, comets p/Halley (1986 3) and Comet Wilson (1987 7) produced significant scientific results. Comet Halley was a bright and highly predictable comet that allowed a well-planned and coordinated observing program. Comet Wilson, on the other hand, was a dynamically new comet discovered only a few months before perihelion. In this paper we review the scientific discoveries made by the airborne program and the KAO on these comets, including the discovery of water, new structure in the silicate emission band, and a number of as yet unexplained spectral features.

  1. Comments on comet shapes and aggregation processes

    NASA Technical Reports Server (NTRS)

    Hartmann, William K.

    1989-01-01

    An important question for a comet mission is whether comet nuclei preserve information clarifying aggregation processes of planetary matter. New observational evidence shows that Trojan asteroids, as a group, display a higher fraction of highly-elongated objects than the belt. More recently evidence has accumulated that comet nuclei, as a group, also display highly-elongated shapes at macro-scale. This evidence comes from the several comets whose nuclear lightcurves or shapes have been well studied. Trojans and comet nuclei share other properties. Both groups have extremely low albedos and reddish-to neutral-black colors typical of asteroids of spectral class D, P, and C. Both groups may have had relatively low collision frequencies. An important problem to resolve with spacecraft imaging is whether these elongated shapes are primordial, or due to evolution of the objects. Two hypotheses that might be tested by a combination of global-scale and close-up imaging from various directions are: (1) The irregular shapes are primordial and related to the fact that these bodies have had lower collision frequencies than belt asteroids; or (2) The irregular shapes may be due to volatile loss.

  2. 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).

  3. 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).

  4. Mission options for the first SEPS application. [rendezvous with near earth asteroids and comets

    NASA Technical Reports Server (NTRS)

    Yen, C.-W. L.

    1981-01-01

    Missions to comets and asteroids are primary candidates for Solar Electric Propulsion System (SEPS) applications. NASA estimates that the first SEPS mission might be launched as early as 1988. This paper presents mission opportunities available for launches between 1988 and early 1991 and discusses the performance capabilities of the current SEPS. Use of a Shuttle Two-Stage IUS and/or a Shuttle Wide Tank Centaur launch vehicle is assumed in the performance assessment. The list of possible first SEPS missions consists of nine missions to comets of primary interest and examples of multiple asteroid rendezvous missions. Both an earth crossing asteroid and a main belt asteroid are considered as first possible targets in the multiple asteroid rendezvous examples. Mission opportunity and performance maps for Eros and Anteros are presented which provide exact performance data and optimal launch and arrival dates for any launch year.

  5. Life cycle of a comet magnetosphere

    NASA Astrophysics Data System (ADS)

    Nilsson, Hans; Stenberg Wieser, Gabriella; Behar, Etienne

    2016-04-01

    Rosetta has followed comet 67P from low activity at more than 3 AU heliocentric distance to high activity at perihelion and then out again. We study the evolution of the dynamic ion environment using the RPC-ICA ion spectrometer. Initially the solar wind permeated the near comet environment. The solar wind was deflected due to mass loading, but not much slowed down. In mid to late April 2015 the solar wind started to disappear from the observation region. This was associated with the solar wind deflection reaching 90°, indicating that the solar wind free region formed due to severe mass loading and associated solar wind deflection. A comet magnetosphere had formed. Accelerated water ions, moving mainly in the anti-sunward direction kept being observed also after the solar wind disappeared from the location of Rosetta. We report how the accelerated water ion environment changed as Rosetta was located relatively deeper in the comet magnetosphere as comet activity increased. Shortly after perihelion, Rosetta made an excursion to 1500 km cometocentric distance, the only data providing a spatial context to the observations made inside the comet magnetosphere once it formed.. We discuss the data from the excursion and what we learn about the scale size of the comet magnetosphere as well as the energy transfer from the solar wind to the comet environment inside the comet magnetosphere. As comet 67P is now moving away from the sun, beginning in late December 2015 the solar wind has started to permeate the comet environment again. We compare this with the early data when comet 67P was approaching the sun, and discuss whether we see any asymmetries between a growing and waning comet magnetosphere.

  6. 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.

  7. 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.

  8. Comet Samples Returned by Stardust, Insight into the Origin of Comets and Crystalline Silicates in Disks

    NASA Astrophysics Data System (ADS)

    Brownlee, D. E.; Joswiak, D.; Matrajt, G.; Tsou, P.

    2009-12-01

    The comet samples returned by the NASA Stardust mission contain abundant crystalline silicates that are very similar to inner solar materials found in primitive asteroidal meteorites. Isotopic compositions indicate that the bulk of the silicates from comet Wild 2 formed in the solar nebula and that the pre-solar content is less than in primitive meteorites. It appears that the bulk of the coarse-grained components of this Jupiter Family Comet formed in the inner regions of the solar nebula and were transported to the edge of the solar system where Kuiper Belt comets accreted. The data is consistent with substantial large-scale radial transport of micron to millimeter grains in the solar nebula. The isotopic, elemental and mineralogical compositions of the majority of Wild 2 silicates as well as the textural relationship between phases do not appear to be compatible with origin by 1000 K annealing of pre-solar grains.

  9. 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}

  10. Comet Bennett 1970 II.

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.; Miller, F. D.

    1973-01-01

    The model for dust comets, formulated by Finson and Probstein, which had previously been tested only on Comet Arend-Roland 1957 III, has been successfully applied to three calibrated photographic plates of Comet Bennett. The size distribution, emission rate, and initial velocities of dust particles emitted from the comet's nucleus are given.