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Sample records for comet nucleus samples

  1. Comet nucleus sample return mission

    NASA Technical Reports Server (NTRS)

    1983-01-01

    A comet nucleus sample return mission in terms of its relevant science objectives, candidate mission concepts, key design/technology requirements, and programmatic issues is discussed. The primary objective was to collect a sample of undisturbed comet material from beneath the surface of an active comet and to preserve its chemical and, if possible, its physical integrity and return it to Earth in a minimally altered state. The secondary objectives are to: (1) characterize the comet to a level consistent with a rendezvous mission; (2) monitor the comet dynamics through perihelion and aphelion with a long lived lander; and (3) determine the subsurface properties of the nucleus in an area local to the sampled core. A set of candidate comets is discussed. The hazards which the spacecraft would encounter in the vicinity of the comet are also discussed. The encounter strategy, the sampling hardware, the thermal control of the pristine comet material during the return to Earth, and the flight performance of various spacecraft systems and the cost estimates of such a mission are presented.

  2. 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.

  3. Comet nucleus and asteroid sample return missions

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  4. Comet nucleus and asteroid sample return missions

    NASA Astrophysics Data System (ADS)

    1992-06-01

    Three Advanced Design Projects have been completed this academic year at Penn State. At the beginning of the fall semester the students were organized into eight groups and given their choice of either a comet nucleus or an asteroid sample return mission. Once a mission had been chosen, the students developed conceptual designs. These were evaluated at the end of the fall semester and combined into three separate mission plans, including a comet nucleus same return (CNSR), a single asteroid sample return (SASR), and a multiple asteroid sample return (MASR). To facilitate the work required for each mission, the class was reorganized in the spring semester by combining groups to form three mission teams. An integration team consisting of two members from each group was formed for each mission so that communication and information exchange would be easier among the groups. The types of projects designed by the students evolved from numerous discussions with Penn State faculty and mission planners at the Johnson Space Center Human/Robotic Spacecraft Office. Robotic sample return missions are widely considered valuable precursors to manned missions in that they can provide details about a site's environment and scientific value. For example, a sample return from an asteroid might reveal valuable resources that, once mined, could be utilized for propulsion. These missions are also more adaptable when considering the risk to humans visiting unknown and potentially dangerous locations, such as a comet nucleus.

  5. Comet nucleus and asteroid sample return missions

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Three Advanced Design Projects have been completed this academic year at Penn State. At the beginning of the fall semester the students were organized into eight groups and given their choice of either a comet nucleus or an asteroid sample return mission. Once a mission had been chosen, the students developed conceptual designs. These were evaluated at the end of the fall semester and combined into three separate mission plans, including a comet nucleus same return (CNSR), a single asteroid sample return (SASR), and a multiple asteroid sample return (MASR). To facilitate the work required for each mission, the class was reorganized in the spring semester by combining groups to form three mission teams. An integration team consisting of two members from each group was formed for each mission so that communication and information exchange would be easier among the groups. The types of projects designed by the students evolved from numerous discussions with Penn State faculty and mission planners at the Johnson Space Center Human/Robotic Spacecraft Office. Robotic sample return missions are widely considered valuable precursors to manned missions in that they can provide details about a site's environment and scientific value. For example, a sample return from an asteroid might reveal valuable resources that, once mined, could be utilized for propulsion. These missions are also more adaptable when considering the risk to humans visiting unknown and potentially dangerous locations, such as a comet nucleus.

  6. Isotopic microanalysis of returned comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Zinner, Ernst

    1989-01-01

    If isotopic measurements of interplanetary dust particles (IDPs) and primitive meteorites can serve as a guide to the isotopic analysis of returned comet nucleus material, an essential requirement will be the capability for microanalysis. The reason is that in both types of extraterrestrial samples large isotopic heterogeneities on a small spatial scale have become apparent once it was possible to measure isotopes in small samples. In the discovery of large isotopic anomalies the ion microprobe has played a significant role because of its high spatial resolution for isotopic ratio measurements. The largest isotopic anomalies in C, N, O, Mg, Si, Ca and Ti found to date were measured by ion microprobe mass spectrometry. The most striking examples are D/H measurements in IDPs and isotopic measurements of C, N and Si in SiC from the CM chondrites Murray and Murchison.

  7. Analysis of Returned Comet Nucleus Samples

    NASA Astrophysics Data System (ADS)

    Chang, Sherwood

    1997-12-01

    This volume contains abstracts that have been accepted by the Program Committee for presentation at the Workshop on Analysis of Returned Comet Nucleus Samples, held in Milpitas, California, January 16-18, 1989. Conveners are Sherwood Chang (NASA Ames Research Center) and Larry Nyquist (NASA Johnson Space Center). Program Committee members are Thomas Ahrens (ex-officio; California Institute of Technology), Lou Allamandola (NASA Ames Research Center), David Blake (NASA Ames Research Center), Donald Brownlee (University of Washington, Seattle), Theodore E. Bunch (NASA Ames Research Center), Humberto Campins (Planetary Science Institute), Jeff Cuzzi (NASA Ames Research Center), Eberhard Griin (Max-Plank-Institut fiir Kemphysik), Martha Hanner (Jet Propulsion Laboratory), Alan Harris (Jet Propulsion Laboratory), John Kerrid-e (University of Califomia, Los Angeles), Yves Langevin (University of Paris), Gerhard Schwehm (ESTEC), and Paul Weissman (Jet Propulsion Laboratory). Logistics and administrative support for the workshop were provided by the Lunar and Planetary Institute Projects Office.

  8. Analysis of Returned Comet Nucleus Samples

    NASA Technical Reports Server (NTRS)

    Chang, Sherwood (Compiler)

    1997-01-01

    This volume contains abstracts that have been accepted by the Program Committee for presentation at the Workshop on Analysis of Returned Comet Nucleus Samples, held in Milpitas, California, January 16-18, 1989. Conveners are Sherwood Chang (NASA Ames Research Center) and Larry Nyquist (NASA Johnson Space Center). Program Committee members are Thomas Ahrens (ex-officio; California Institute of Technology), Lou Allamandola (NASA Ames Research Center), David Blake (NASA Ames Research Center), Donald Brownlee (University of Washington, Seattle), Theodore E. Bunch (NASA Ames Research Center), Humberto Campins (Planetary Science Institute), Jeff Cuzzi (NASA Ames Research Center), Eberhard Griin (Max-Plank-Institut fiir Kemphysik), Martha Hanner (Jet Propulsion Laboratory), Alan Harris (Jet Propulsion Laboratory), John Kerrid-e (University of Califomia, Los Angeles), Yves Langevin (University of Paris), Gerhard Schwehm (ESTEC), and Paul Weissman (Jet Propulsion Laboratory). Logistics and administrative support for the workshop were provided by the Lunar and Planetary Institute Projects Office.

  9. Analytical study of comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Albee, A. L.

    1989-01-01

    Analytical procedures for studying and handling frozen (130 K) core samples of comet nuclei are discussed. These methods include neutron activation analysis, x ray fluorescent analysis and high resolution mass spectroscopy.

  10. Triple F - A Comet Nucleus Sample Return Mission

    NASA Technical Reports Server (NTRS)

    Kueppers, Michael; Keller, H. U.; Kuehrt, E.; A'Hearn, M. F.; Altwegg, K.; Bertrand, R.; Busemann, H.; Capria, M. T.; Colangeli, L.; Davidsson, B.; Ehrenfreund, P.; Knollenberg, J.; Mottola, S.; Weiss, P.; Zolensky, M.; Akim, E.; Basilevsky, A.; Galimov, E.; Gerasimov, M.; Korablev, O.; Charnley, S.; Nittler, L. R.; Sandford, S.; Weissman, P.

    2008-01-01

    The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA's Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three sample cores of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-andgo sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.

  11. Triple F - A Comet Nucleus Sample Return Mission

    NASA Technical Reports Server (NTRS)

    Kueppers, Michael; Keller, Horst Uwe; Kuhrt, Ekkehard; A'Hearn, Michael; Altwegg, Kathrin; Betrand, Regis; Busemann, Henner; Capria, Maria Teresa; Colangeli, Luigi

    2008-01-01

    The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA s Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three samples of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-and-go sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.

  12. Triple F—a comet nucleus sample return mission

    NASA Astrophysics Data System (ADS)

    Küppers, Michael; Keller, H. U.; Kührt, E.; A'Hearn, M. F.; Altwegg, K.; Bertrand, R.; Busemann, H.; Capria, M. T.; Colangeli, L.; Davidsson, B.; Ehrenfreund, P.; Knollenberg, J.; Mottola, S.; Rathke, A.; Weiss, P.; Zolensky, M.; Akim, E.; Basilevsky, A.; Galimov, E.; Gerasimov, M.; Korablev, O.; Lomakin, I.; Marov, M.; Martynov, M.; Nazarov, M.; Zakharov, A.; Zelenyi, L.; Aronica, A.; Ball, A. J.; Barbieri, C.; Bar-Nun, A.; Benkhoff, J.; Biele, J.; Biver, N.; Blum, J.; Bockelée-Morvan, D.; Botta, O.; Bredehöft, J.-H.; Capaccioni, F.; Charnley, S.; Cloutis, E.; Cottin, H.; Cremonese, G.; Crovisier, J.; Crowther, S. A.; Epifani, E. M.; Esposito, F.; Ferrari, A. C.; Ferri, F.; Fulle, M.; Gilmour, J.; Goesmann, F.; Gortsas, N.; Green, S. F.; Groussin, O.; Grün, E.; Gutiérrez, P. J.; Hartogh, P.; Henkel, T.; Hilchenbach, M.; Ho, T.-M.; Horneck, G.; Hviid, S. F.; Ip, W.-H.; Jäckel, A.; Jessberger, E.; Kallenbach, R.; Kargl, G.; Kömle, N. I.; Korth, A.; Kossacki, K.; Krause, C.; Krüger, H.; Li, Z.-Y.; Licandro, J.; Lopez-Moreno, J. J.; Lowry, S. C.; Lyon, I.; Magni, G.; Mall, U.; Mann, I.; Markiewicz, W.; Martins, Z.; Maurette, M.; Meierhenrich, U.; Mennella, V.; Ng, T. C.; Nittler, L. R.; Palumbo, P.; Pätzold, M.; Prialnik, D.; Rengel, M.; Rickman, H.; Rodriguez, J.; Roll, R.; Rost, D.; Rotundi, A.; Sandford, S.; Schönbächler, M.; Sierks, H.; Srama, R.; Stroud, R. M.; Szutowicz, S.; Tornow, C.; Ulamec, S.; Wallis, M.; Waniak, W.; Weissman, P.; Wieler, R.; Wurz, P.; Yung, K. L.; Zarnecki, J. C.

    2009-03-01

    The Triple F ( Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA’s Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three sample cores of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-and-go sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.

  13. Workshop on Analysis of Returned Comet Nucleus Samples

    NASA Technical Reports Server (NTRS)

    1989-01-01

    This volume contains abstracts that were accepted by the Program Committee for presentation at the workshop on the analysis of returned comet nucleus samples held in Milpitas, California, January 16 to 18, 1989. The abstracts deal with the nature of cometary ices, cryogenic handling and sampling equipment, origin and composition of samples, and spectroscopic, thermal and chemical processing methods of cometary nuclei. Laboratory simulation experimental results on dust samples are reported. Some results obtained from Halley's comet are also included. Microanalytic techniques for examining trace elements of cometary particles, synchrotron x ray fluorescence and instrument neutron activation analysis (INAA), are presented.

  14. Analysis of organic compounds in returned comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Cronin, J. R.

    1989-01-01

    Techniques for analysis of organic compounds in returned comet nucleus samples are described. Interstellar, chondritic and transitional organic components are discussed. Appropriate sampling procedures will be essential to the success of these analyses. It will be necessary to return samples that represent all the various regimes found in the nucleus, e.g., a complete core, volatile components (deep interior), and crustal components (surface minerals, rocks, processed organics such as macromolecular carbon and polymers). Furthermore, sampling, storage, return, and distribution of samples must be done under conditions that preclude contamination of the samples by terrestrial matter.

  15. Electron Spin Resonance (ESR) Studies of Returned Comet Nucleus Samples

    NASA Technical Reports Server (NTRS)

    Tsay, Fun-Dow; Kim, Soon Sam; Liang, Ranty H.

    1997-01-01

    Electron Spin Resonance (ESR) studies have been carried out on organic and inorganic free radicals generated by gamma-ray and/or UV-irradiation and trapped in ice matrices. It is suggested that the concentration of these free radicals together with their thermal stability can be used as an accurate built-in geothermometer and radiation probe for returned comet nucleus sample studies. ESR studies have also been carried out on paramagnetic (Mn(2+), Ti(3+), and Fe(3+)) and ferromagnetic (ferric oxide and metallic iron) centers known to be present in terrestrial and extraterrestrial samples. The presence or absence of these magnetic centers coupled with their characteristic ESR lineshape can be used to investigate the shock effects, quenching/cooling rate and oxidation-reduction conditions in the formation and subsequent evolution of returned comet nucleus samples.

  16. Solar Sail Application to Comet Nucleus Sample Return

    NASA Technical Reports Server (NTRS)

    Taylor, Travis S.; Moton, Tryshanda T.; Robinson, Don; Anding, R. Charles; Matloff, Gregory L.; Garbe, Gregory; Montgomery, Edward

    2003-01-01

    Many comets have perihelions at distances within 1.0 Astronomical Unit (AU) from the sun. These comets typically are inclined out of the ecliptic. We propose that a solar sail spacecraft could be used to increase the inclination of the orbit to match that of these 1.0 AU comets. The solar sail spacecraft would match the orbit velocity for a short period of time, which would be long enough for a container to be injected into the comet's nucleus. The container would be extended from a long durable tether so that the solar sail would not be required to enter into the potentially degrading environment of the comet s atmosphere. Once the container has been filled with sample material, the tether is retracted. The solar sail would then lower its inclination and fly back to Earth for the sample return. In this paper, we describe the selection of cometary targets, the mission design, and the solar sailcraft design suitable for sail-comet rendezvous as well as possible rendezvous scenarios.

  17. Electron Spin Resonance (ESR) studies of returned comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Tsay, Fun-Dow; Kim, Soon Sam; Liang, Ranty H.

    1989-01-01

    The most important objective of the Comet Nucleus Sample Returm Mission is to return samples which could reflect formation conditions and evolutionary processes in the early solar nebula. It is expected that the returned samples will consist of fine-grained silicate materials mixed with ices composed of simple molecules such as H2O, NH3, CH4 as well as organics and/or more complex compounds. Because of the exposure to ionizing radiation from cosmic-ray, gamma-ray, and solar wind protons at low temperature, free radicals are expected to be formed and trapped in the solid ice matrices. The kind of trapped radical species together with their concentration and thermal stability can be used as a dosimeter as well as a geothermometer to determine thermal and radiation histories as well as outgassing and other possible alternation effects since the nucleus material was formed. Since free radicals that are known to contain unpaired electrons are all paramagnetic in nature, they can be readily detected and characterized in their native form by the Electron Spin Resonance (ESR) method. In fact, ESR has been shown to be a non-destructive, highly sensitive tool for the detection and characterization of paramagnetic, ferromagnetic, and radiation damage centers in terrestrial and extraterrestrial geological samples. The potential use of ESR as an effective method in the study of returned comet nucleus samples, in particular, in the analysis of fine-grained solid state icy samples is discussed.

  18. Mechanical and SEM analysis of artificial comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Thiel, K.; Kochan, H.; Roessler, K.; Gruen, E.; Schwehm, G.; Hellmann, H.; Hsiung, P.; Koelzer, G.

    1989-01-01

    Since 1987 experiments dealing with comet nucleus phenomena have been carried out in the DFVLR space simulation chambers. The main objective of these experiments is a better understanding of thermal behavior, surface phenomena and especially the gas dust interaction. As a function of different sample compositions and exposure to solar irradiation (xenon-bulbs) crusts of different hardness and thickness were measured. The measuring device consists of a motor driven pressure foot (5 mm diameter), which is pressed into the sample. The applied compressive force is electronically monitored. The microstructure of the crust and dust residuals is investigated by scanning electron microscopy (SEM) techniques. Stress-depth profiles of an unirradiated and an irradiated model comet are given.

  19. Mineralogy and Petrology of COMET WILD2 Nucleus Samples

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael; Bland, Phil; Bradley, John; Brearley, Adrian; Brennan, Sean; Bridges, John; Brownlee, Donald; Butterworth, Anna; Dai, Zurong; Ebel, Denton

    2006-01-01

    The sample return capsule of the Stardust spacecraft will be recovered in northern Utah on January 15, 2006, and under nominal conditions it will be delivered to the new Stardust Curation Laboratory at the Johnson Space Center two days later. Within the first week we plan to begin the harvesting of aerogel cells, and the comet nucleus samples they contain for detailed analysis. By the time of the LPSC meeting we will have been analyzing selected removed grains for more than one month. This presentation will present the first results from the mineralogical and petrological analyses that will have been performed.

  20. Workshop on Analysis of Returned Comet Nucleus Samples

    NASA Astrophysics Data System (ADS)

    Chang, Sherwood

    This volume contains abstracts that have been accepted by the Program Committee for presentation at the Workshop on Analysis of Returned Comet Nucleus Samples, held in Milpitas, California, January 16-18, 1989. Conveners are Sherwood Chang (NASA Ames Research Center) and Larry Nyquist (NASA Johnson Space Center). Program Committee members are Thomas Ahrens (ex-officio; California Institute of Technology), Lou Allamandola (NASA Ames Research Center), David Blake (NASA Ames Research Center), Donald Brownlee (University of Washington, Seattle), Theodore E. Bunch (NASA Ames Research Center), Humberto Campins (Planetary Science Institute), Jeff Cuzzi (NASA Ames Research Center), Eberhard Griin (Max-Plank-Institut fiir Kemphysik), Martha Hanner (Jet Propulsion Laboratory), Alan Harris (Jet Propulsion Laboratory), John Kerrid-e (University of Califomia, Los Angeles), Yves Langevin (University of Paris), Gerhard Schwehm (ESTEC), and Paul Weissman (Jet Propulsion Laboratory). Logistics and administrative support for the workshop were provided by the Lunar and Planetary Institute Projects Office.

  1. Concepts for the curation, primary examination, and allocation of comet nucleus samples by a comet sample receiving laboratory

    NASA Astrophysics Data System (ADS)

    Stoffler, D.

    1991-04-01

    The Comet Nucleus Sample Return Mission Rosetta, a cornerstone mission of ESA jointly planned with NASA, requires the implementation of a highly sophisticated curatorial facility for the returned samples. A concept for the instrumentation and the mode of operation of a Comet Sample Receiving Laboratory (CSRL) is proposed. The main elements of the facility are (1) cryogenic evacuated cabinets with robotic manipulators; (2) devices for sample dissection, aliquotization, phase separation, and thin section preparation; and (3) instrumentation for nondestructive chemical and physical analyses and facilities for destructive mineralogical, textural, and (micro)chemical analyses. It is recommended that a very detailed primary sample examination and analysis be performed on a small representative fraction of the samples at the P-T-conditions of the parent comet nucleus before sample aliquots are released to principle investigators. The CSRL should be staffed with top rank personnel and supervised by an international peer review panel which may also be responsible for the selection of investigators and the allocation of samples.

  2. Mineralogy and Petrology of Comet Wild 2 Nucleus Samples

    SciTech Connect

    Zolensky, M E; Zega, T J; Yano, H; Wirick, S; Westphal, A J; Weisberg, M K; Weber, I; Warren, J L; Velbel, M A; Tsuchiyama, A; Tsou, P; Toppani, A; Tomioka, N; Tomeoka, K; Teslich, N; Taheri, M; Susini, J; Stroud, R; Stephan, T; Stadermann, F J; Snead, C J; Simon, S B; Siminovici, A; See, T H; Robert, F; Rietmeijer, F M; Rao, W; Perronnet, M C; Papanastassiou, D A; Okudaira, K; Ohsumi, K; Ohnishi, I; Nakanura-Messenger, K; Nakamura, T; Mostefaoui, S; Mikouchi, T; Meibom, A; Matrajt, G; Marcus, M A; Leroux, H; Lemelle, L; Le, L; Lanzirotti, A; Langenhorst, F; Krot, A N; Keller, L P; Kearsley, A T; Joswiak, D; Jacob, D; Ishii, H; Harvey, R; Hagiya, K; Grossman, L; Graham, G A; Gounelle, M; Gillet, P; Genge, M J; Flynn, G; Ferrior, T; Fallon, S; Ebel, D S; Dai, Z R; Cordier, P; Chi, M; Butterworth, A L; Brownlee, D E; Bridges, J C; Brennan, S; Brearley, A; Bradley, J P; Bleuet, P; Bland, P A; Bastien, R

    2006-10-11

    The bulk of the Wild 2 samples appear to be weakly-constructed mixtures of nanometerscale grains with occasional much larger (>1{micro}m) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in Wild 2 require a wide range of formation conditions, probably reflecting different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and absence of hydrous phases indicate that Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require large-scale radial transport in the early protoplanetary disk. The nature of cometary solids is of fundamental importance to our understanding of the early solar nebula and protoplanetary history. Until now we have had to study comets from afar using spectroscopy, or settle for analyses of interplanetary dust particles (IDPs) of uncertain provenance. We report here mineralogical and petrographic analyses of particles derived directly from Comet Wild 2. All of the Wild 2 particles we have thus far examined have been modified in various ways by the capture process. All particles that may have been loose aggregates, ''traveling sand piles'', disaggregated into individual components with the larger, denser components penetrating more deeply into the aerogel. Individual grains experienced a wide range of heating effects that range from excellent preservation to melting (Fig. 1); such behavior was expected (1, 2 ,3). What is remarkable is the extreme variability of these modifications and the fact that severely modified and unmodified materials can be found within a micrometer of each other, requiring tremendous local temperature gradients. Fortunately, we have an internal gauge of impact collection heating. Fe-Ni sulfides are ubiquitous in the Wild 2 samples, are very sensitive indicators of

  3. A comet nucleus sample return mission using solar electric earth gravity assist

    NASA Astrophysics Data System (ADS)

    Kawaguchi, J.

    The paper presents the Comet Nucleus Sample and Return (CNSR) Mission strategy using electric propulsion. The mission objective is very clear and may provide clues to the understanding of the origin of the solar system and of life. The target comet here is an extinct comet, to which a concrete and promising sample collection scenario was constructed. The essence of this paper lies in the use of its novel energy accumulation ring located around the Earth trajectory that gains the angular momentum that results in the high speed Earth swing-by after one or one and a half year quasi-synchronous flight. The spacecraft returns back to the Earth at a specific period regardless of how large the relative excess velocity is gained. This is the essence of the scheme. While the targets accessed via the scheme shown are limited, this strategy enables even a NASA DISCOVERY class, small spacecraft to perform the valuable CNSR mission. The plan is found feasible, and the launch window is open in 2005 and the spacecraft can return the sample back to the Earth in only eight years. Another window in 2009-2010 is also provided. A concrete proposal is shown for the comet Wilson-Harrington (W.H.) here. The ISAS of Japan opens the window to the international organizations for collaboration in this mission.

  4. Hummingbird Comet Nucleus Analysis Mission

    NASA Technical Reports Server (NTRS)

    Kojiro, Daniel; Carle, Glenn C.; Lasher, Larry E.

    2000-01-01

    Hummingbird is a highly focused scientific mission, proposed to NASA s Discovery Program, designed to address the highest priority questions in cometary science-that of the chemical composition of the cometary nucleus. After rendezvous with the comet, Hummingbird would first methodically image and map the comet, then collect and analyze dust, ice and gases from the cometary atmosphere to enrich characterization of the comet and support landing site selection. Then, like its namesake, Hummingbird would carefully descend to a pre-selected surface site obtaining a high-resolution image, gather a surface material sample, acquire surface temperature and then immediately return to orbit for detailed chemical and elemental analyses followed by a high resolution post-sampling image of the site. Hummingbird s analytical laboratory contains instrumentation for a comprehensive molecular and elemental analysis of the cometary nucleus as well as an innovative surface sample acquisition device.

  5. Thermal histories of the samples of two KOSI comet nucleus simulation experiments

    NASA Technical Reports Server (NTRS)

    Spohn, T.; Benkhoff, J.; Klinger, J.; Gruen, E.; Kochan, H.

    1989-01-01

    Temperatures recorded during two KOSI comet nucleus simulation experiments strongly suggest that heat transport by vapor flow into the interior of the sample is very important. Two comet nucleus simulation experiments have been done by the KOSI team in a big space simulator. The thermal evolution of the sample during insolation and the results of simplified thermal evolution calculations are discussed. The observed thermal histories cannot be explained by a simple model with heat transferred by heat conduction at a constant conductivity, so a coupled heat and mass transfer problem was considered. The porous ice matrix was assumed to have a constant thermal conductivity and to be in thermal equilibrium with vapor in the pores, the internal pressure being the vapor pressure. The vapor was modelled as an ideal gas because, at the temperatures relevant to the problem, the mean free path length of the vapor molecules is large in comparison with the pore dimensions. The heat capacity at constant volume per unit mass of the two phase mixture was also assumed constant. The vapor was allowed to flow and transfer heat in response to an internal pressure gradient.

  6. Comet Odyssey: Comet Surface Sample Return

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  7. Mineralogy and petrology of comet 81P/wild 2 nucleus samples

    USGS Publications Warehouse

    Zolensky, M.E.; Zega, T.J.; Yano, H.; Wirick, S.; Westphal, A.J.; Weisberg, M.K.; Weber, I.; Warren, J.L.; Velbel, M.A.; Tsuchiyama, A.; Tsou, P.; Toppani, A.; Tomioka, N.; Tomeoka, K.; Teslich, N.; Taheri, M.; Susini, J.; Stroud, R.; Stephan, T.; Stadermann, F.J.; Snead, C.J.; Simon, S.B.; Simionovici, A.; See, T.H.; Robert, F.; Rietmeijer, F.J.M.; Rao, W.; Perronnet, M.C.; Papanastassiou, D.A.; Okudaira, K.; Ohsumi, K.; Ohnishi, I.; Nakamura-Messenger, K.; Nakamura, T.; Mostefaoui, S.; Mikouchi, T.; Meibom, A.; Matrajt, G.; Marcus, M.A.; Leroux, H.; Lemelle, L.; Le, L.; Lanzirotti, A.; Langenhorst, F.; Krot, A.N.; Keller, L.P.; Kearsley, A.T.; Joswiak, D.; Jacob, D.; Ishii, H.; Harvey, R.; Hagiya, K.; Grossman, L.; Grossman, J.H.; Graham, G.A.; Gounalle, M.; Gillet, P.; Genge, M.J.; Flynn, G.; Ferroir, T.; Fallon, S.; Ebel, D.S.; Dai, Z.R.; Cordier, P.; Clark, B.; Chi, M.; Butterworth, A.L.; Brownlee, D.E.; Bridges, J.C.; Brennan, S.; Brearley, A.; Bradley, J.P.; Bleuet, P.; Bland, P.A.; Bastien, R.

    2006-01-01

    The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.

  8. Supporting online materials for mineralogy and petrology of Comet81P/Wild 2 nucleus samples

    SciTech Connect

    Zolensky, Michael E.; Zega, Thomas J.; Yano, Hajime; Wirick, Sue; Westphal, Andrew J.; Weisberg, Mike K.; Weber, Iris; Warren, Jack L.; Velbel, Michael A.; Tsuchiyama, Akira; Tsou, Peter; Toppani, Alice; Tomioka, Naotaka; Tomeoka, Kazushige; Teslich, Nick; Taheri, Mitra; Susini, Jean; Stroud, Rhonda; Stephan, Thomas; Stadermann, Frank J.; Snead, Christopher J.; Simon, Steven B.; Simionovici, Alexandre; See,Thomas H.; Robert Francois; Rietmeijer, Frans J.M.; Rao, William; Perronnet, Murielle C.; Papanastassiou, Dimitri A.; Okudaira, Kyoko; Ohsumi, Kazumasa; Ohnishi, Ichiro; Nakamura-Messenger, Keilo; Nakamura,Tomoki; Mostefaoui, Smail; Mikouchi, Takashi; Meibom, Anders; Matrajt,Graciela; Marcus, Matthew A.; Leroux, Hugues; Lemelle, Laurence; Antonio,Loan Le; Lanzirotti, Antonio; Langenhorst, Falko; Krot, Alexander N.; Keller, Lindsay P.; Kearsley, Anton T.; Joswiak, Davis; Jacob, Damien; Ishii, Hope; Harvey, Ralph; Hagiya, Kenji; Grossman, Lawrence; Grossman,Jeffrey N.; Graham, Giles A.; Gounelle, Matthieu; Gillet, Philippe; Genge, Matthew J.; Flynn, George; Ferroir, Tristan; Fallow, Stewart; Ebel, Denton S.; Dai, Zu Rong; Cordier, Patrick; Clark, Benton; Chi,Miaofang; Butterworth, Anna L.; Brownlee, Donald E.; Bridges, John C.; Brennan, Sean; Brearley, Adrian; Bradley, John P.; Bleuet, Pierre; Bland,Phil A.; Bastien, Ron

    2006-01-01

    The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.

  9. Measurements of long-lived cosmogenic nuclides in returned comet nucleus samples

    NASA Technical Reports Server (NTRS)

    Nishiizumi, K.; Kohl, C. P.; Arnold, J. R.

    1989-01-01

    Measurements of long lived cosmic ray produced radionuclides have given much information on the histories and rates of surface evolution for meteorites, the Moon and the Earth. These nuclides can be equally useful in studying cometary histories and post nebular processing of cometary surfaces. The concentration of these nuclides depends on the orbit of the comet (cosmic ray intensity changes with distance from the sun), the depth of the sampling site in the comet surface, and the rate of continuous evolution of the surface (erosion rate of surface materials). If the orbital parameters and the sampling depth are known, production rates of cosmogenic nuclides can be fairly accurately calculated by theoretical models normalized to measurement on lunar surface materials and meteoritic samples. Due to the continuous evaporation of surface materials, it is expected that the long lived radioactivities will be undersaturated. Accurate measurements of the degree of undersaturation in nuclides of different half-lives allows for the determination of the rate of surface material loss over the last few million years.

  10. The Mineralogy of Comet Wild-2 Nucleus Samples - What We Think We Know And What We Do Not Know

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.

    2007-01-01

    The sample return capsule of the Stardust spacecraft was successfully recovered in northern Utah on January 15, 2006, and its cargo of coma grains from Comet Wild-2 has now been the subject of intense investigation by approximately 200 scientists scattered across five continents. We can now perform mineralogical and petrographic analyses of particles derived directly from the Jupiter-family Comet Wild-2

  11. Nucleus model for periodic Comet Tempel 2

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    1991-01-01

    Observational data obtained primarily during 1988 are analyzed and synthesized to develop a comprehensive physical model for the nucleus of Periodic Comet Tempel 2, one of the best studied members of Jupiter's family of short-period comets. It is confirmed that a previous investigation provided reliable information on the comet's spin-axis orientation, which implies and obliquity of 54 degrees of the orbit plane to the equatorial plane and which appears to have varied little - if at all - with time. This conclusion is critical for fitting a triaxial ellipsoid to approximate the figure of the nucleus.

  12. The bare nucleus of comet Neujmin 1

    NASA Technical Reports Server (NTRS)

    Campins, Humberto; A'Hearn, Michael F.; Mcfadden, Lucy-Ann

    1987-01-01

    Simultaneous visible and infrared observations of comet P/Neujmin 1 1984c are presented which show that the comet has a large (mean radius 10 km), dark (geometric albedo 2-3 percent) nucleus with a surface which is mostly inert material but which still shows a low level of gaseous activity. This is the first physical evidence that cometary nuclei can leave behind an inert body after the coma activity ceases. No asteroid or asteroid class has been found to match the reflectance and albedo of this comet except possibly some D asteroids.

  13. Nucleus of Comet P/Arend-Rigaux

    SciTech Connect

    Brooke, T.Y.; Knacke, R.F.

    1986-07-01

    Photometry data at 1-20 microns taken of Comet P/Arend-Rigaux are reported. The observations were carried out to test the possibility of observing the nuclei of low activity, nearly extinct comets at visible and IR wavelengths. The data were collected in February 1985 using the NASA 3 m IR telescope on Mauna Kea. The comet was at 1.67 AU heliocentric distance at the time. Attempts were made to detect rotation of the core on the bases of variations in the J, H and K light curves. The images obtained were those of a rotating nucleus with a radius of 4.0-6.2 km surrounded by a faint coma. The comet had a geometric albedo of 0.01-0.03 and a near-IR red slope that exhibited no evidence of the presence of ice. 32 references.

  14. A Model of Comet Nucleus Rotation

    NASA Astrophysics Data System (ADS)

    Keller, H. U.; Jorda, L.; Rickman, H.; Thomas, N.

    2000-10-01

    Modelling cometary rotation is of particular interest for the preparation of space missions to comets. For example, the mapping phase during the ROSETTA mission must be planned keeping in mind that, unlike most asteroids, the rotational state of most short-period comets might be complex (excited). The modelling of cometary nucleus rotation can also provide us with important parameters that are needed to interpret coma structures or to build time-dependent thermal models of the nucleus. We combine a general three-dimensional model for the nucleus shape, surface properties, and insolation with a simplified thermal model to calculate the local time-dependent activity and consequently the non-gravitational forces acting on the nucleus. The torque of this force is then used to numerically solve the forced Euler equations for a homogeneously outgassing irregularly-shaped cometary nucleus. We will discuss the results of our model for comets 46P/Wirtanen, the target of the ROSETTA mission, and 19P/Borrelly, the target of DEEP-SPACE 1 and derive some generalized inferences.

  15. Nucleus of Comet IRAS-Araki-Alcock (1983 VII)

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1988-01-01

    Optical, radar, infrared, UV, and microwave-continuum observations of Comet IRAS-Araki-Alcok were obtained in May 1983, the week of the comet's close approach to earth. The comet has a nucleus dimension and a rotation period which are similar to those of Comet Halley, but a different morphological signature (a persisting sunward fan-shaped coma). Time variations are noted in the projected nucleus cross section. Results suggest significant limb-darkening effects in the relevant domains of radio waves, and that the comet's interior must be extremely cold. It is found that the thermal-infrared fluxes from the inner coma of the comet are dominated by the nucleus.

  16. Comet Borrelly Nucleus Found to the Side

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Deep Space 1 flew by comet Borrelly on September 22, 2001 and took these measurements with its plasma instruments between 90,000 kilometers (56,000 miles) and 2,000 kilometers (1,200 miles) away. These data show that the flow of ions around the comet's rocky, icy nucleus (the center of the deep V-shaped feature) is not centered on the comet's nucleus as scientists expected before the Borrelly flyby. Ions in the turbulent flow are heated to about 1 million Kelvin (2 million degrees Fahrenheit) causing the bands of ions to appear broad and jagged compared to the solar wind.

    Deep Space 1 completed its primary mission testing ion propulsion and 11 other advanced, high-risk technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to undertake this chancy but exciting, and ultimately successful, encounter with the comet. More information can be found on the Deep Space 1 home page at http://nmp.jpl.nasa.gov/ds1/ .

    Deep Space 1 was launched in October 1998 as part of NASA's New Millennium Program, which is managed by JPL for NASA's Office of Space Science, Washington, D.C. The California Institute of Technology manages JPL for NASA.

  17. Comet nucleus impact probe feasibility study

    NASA Technical Reports Server (NTRS)

    Castro, A. J.

    1980-01-01

    A top level listing of the comet nucleus impact probe (CNIP) feasibility experiments requirements are presented. A conceptual configuration which shows that the feasibility of engineering the experiment is possible and describes the candidate hardware is discussed. The design studies required in order to design the operating experiment are outlined. An overview of a program plan used to estimate a rough order of magnitude cost for the CNIP experiment is given.

  18. The observation of comets by the "COMET"!! - Disintegrated nucleus of comet LINEAR (C/1999 S4)

    NASA Astrophysics Data System (ADS)

    Fukushima, Hideo

    2001-03-01

    We, COMET (Comet Observation Mitaka Eager Team), are operating a 50-cm reflector not only for social education open to the public, but also for wide purpose such as students' observation practice and our own researches. The availability of occupying telescope time makes us possible to carry out long-term monitoring observations of comets, which resulted in great contribution to the cometary science. In this article, a present stutus of our monitoring observation is introduced, together with a short documentary story of comet LINEAR (C/1999 S4), of which nucleus was disintegrated against high expectation of being a naked-eye object.

  19. SOCCER: Comet Coma Sample Return Mission

    NASA Technical Reports Server (NTRS)

    Albee, A. L.; Uesugi, K. T.; Tsou, Peter

    1994-01-01

    Comets, being considered the most primitive bodies in the solar system, command the highest priority among solar system objects for studying solar nebula evolution and the evolution of life through biogenic elements and compounds. Sample Of Comet Coma Earth Return (SOCCER), a joint effort between NASA and the Institute of Space and Astronautical Science (ISAS) in Japan, has two primary science objectives: (1) the imaging of the comet nucleus and (2) the return to Earth of samples of volatile species and intact dust. This effort makes use of the unique strengths and capabilities of both countries in realizing this important quest for the return of samples from a comet. This paper presents an overview of SOCCER's science payloads, engineering flight system, and its mission operations.

  20. The primordial nucleus of Comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Davidsson, Bjorn; Sierks, Holger; Guettler, Carsten; Marzari, Francesco; Pajola, Maurizio; Rickman, Hans; A'Hearn, Michael; Auger, Anne-Therese; El-Maarry, Mohamed; Fornasier, Sonia; Gutierrez, Pedro; Keller, Horst Uwe; Massironi, Matteo; Snodgrass, Colin; Vincent, Jean-Baptiste; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Barucci, Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Cremonese, Gabriele; Da Deppo, Vania; Debei, Stefano; De Cecco, Mariolino; Feller, Clement; Fulle, Marco; Groussin, Olivier; Hviid, Stubbe; Hoefner, Sebastian; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Joerg; Kovacs, Gabor; Kramm, Joerg-Rainer; Kuehrt, Ekkehard; Kueppers, Michael; La Forgia, Fiorangela; Lara, Luisa; Lazzarin, Monica; Lopez Moreno, Jose; Moissl-Fraund, Richard; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Thomas, Nicolas; Tubiana, Cecilia

    2015-11-01

    Observations of Comet 67P/Churyumov-Gerasimenko by Rosetta show that the nucleus is bi-lobed, extensively layered, has a low bulk density, a high dust-to-ice mass ratio (implying high porosity), and weak strength except for a thin sintered surface layer. The comet is rich in supervolatiles (CO, CO2, N2), may contain amorphous water ice, and displays little to no signs of aqueous alteration. Lack of phyllosilicates in Stardust samples from Comet 81P/Wild 2 provides further support that comet nuclei did not contain liquid water.These properties differ from those expected for 50-200 km diameter bodies in the primordial disk. We find that thermal processing due to Al-26, combined with collisional compaction, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles, containing little to no amorphous water ice, and that have experienced extensive aqueous alteration. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. We therefore conclude that observed comet nuclei are primordial rubble piles, and not collisional rubble piles.We propose a concurrent comet and TNO formation scenario that is consistent with these observations. We argue that TNOs form due to streaming instabilities at sizes of about 50-400 km and that about 350 of these grow slowly in a low-mass primordial disk to the size of Triton, causing little viscous stirring during growth. We propose a dynamically cold primordial disk, that prevents medium-sized TNOs from breaking into collisional rubble piles, and allows for the survival of primordial rubble-pile comets. We argue that comets form by hierarchical agglomeration out of material that remains after TNO formation. This slow growth is necessary to avoid thermal processing by Al-26, and to allow comet nuclei to incorporate 3 Myr old material from the inner Solar System, found in

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

    NASA Technical Reports Server (NTRS)

    2002-01-01

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

  2. 3200 Phaethon, Asteroid or Comet Nucleus?

    NASA Astrophysics Data System (ADS)

    Boice, Daniel C.; Benkhoff, Johannes

    2015-08-01

    Physico-chemical modeling is central to understand the important physical processes in small solar system bodies. We have developed a computer simulation, SUISEI, that includes the physico-chemical processes relevant to comets within a global modeling framework. Our goals are to gain valuable insights into the intrinsic properties of cometary nuclei so we can better understand observations and in situ measurements. SUISEI includes a 3-D model of gas and heat transport in porous sub-surface layers in the interior of the nucleus.We present results on the application of SUISEI to the near-Sun object, Phaethon. Discovered in 1983 and classified as an asteroid, it has recently exhibited an active dust coma. Phaethon has long been associated as the source of the Geminids meteor shower so the dust activity provides a clear link to the meteor shower. The observed dust activity would traditionally lead to Phaethon being also classified as a comet (e.g., 2060-95P/Chiron, 133P/Elst-Pizarro). This is unusual since the orbit of Phaethon has a perihelion of 0.14 AU, resulting in surface temperatures of more than 1025K, much too hot for water ice or other volatiles to exist near the surface and drive the activity. This situation and others such as the “Active Asteroids” necessitates a revision of how we understand and classify these small asteroid-comet transition objects.We conclude the following for Phaethon:1. It is likely to contain relatively pristine volatiles in its interior despite repeated near perihelion passages of 0.14 AU during its history in its present orbit,2. Steady water gas fluxes at perihelion and throughout its orbit are insufficient to entrain the currently observed dust production,3. Thermal gradients into the surface as well as those caused by diurnal rotation are consistent with the mechanism of dust release due to thermal fracture,4. The initial large gas release during the first perihelion passage may be sufficient to produce enough dust to explain

  3. Comet coma sample return instrument

    NASA Technical Reports Server (NTRS)

    Albee, A. L.; Brownlee, Don E.; Burnett, Donald S.; Tsou, Peter; Uesugi, K. T.

    1994-01-01

    The sample collection technology and instrument concept for the Sample of Comet Coma Earth Return Mission (SOCCER) are described. The scientific goals of this Flyby Sample Return are to return to coma dust and volatile samples from a known comet source, which will permit accurate elemental and isotopic measurements for thousands of individual solid particles and volatiles, detailed analysis of the dust structure, morphology, and mineralogy of the intact samples, and identification of the biogenic elements or compounds in the solid and volatile samples. Having these intact samples, morphologic, petrographic, and phase structural features can be determined. Information on dust particle size, shape, and density can be ascertained by analyzing penetration holes and tracks in the capture medium. Time and spatial data of dust capture will provide understanding of the flux dynamics of the coma and the jets. Additional information will include the identification of cosmic ray tracks in the cometary grains, which can provide a particle's process history and perhaps even the age of the comet. The measurements will be made with the same equipment used for studying micrometeorites for decades past; hence, the results can be directly compared without extrapolation or modification. The data will provide a powerful and direct technique for comparing the cometary samples with all known types of meteorites and interplanetary dust. This sample collection system will provide the first sample return from a specifically identified primitive body and will allow, for the first time, a direct method of matching meteoritic materials captured on Earth with known parent bodies.

  4. Comet sample acquisition for ROSETTA lander mission

    NASA Astrophysics Data System (ADS)

    Marchesi, M.; Campaci, R.; Magnani, P.; Mugnuolo, R.; Nista, A.; Olivier, A.; Re, E.

    2001-09-01

    ROSETTA/Lander is being developed with a combined effort of European countries, coordinated by German institutes. The commitment for such a challenging probe will provide a unique opportunity for in-situ analysis of a comet nucleus. The payload for coring, sampling and investigations of comet materials is called SD2 (Sampling Drilling and Distribution). The paper presents the drill/sampler tool and the sample transfer trough modeling, design and testing phases. Expected drilling parameters are then compared with experimental data; limited torque consumption and axial thrust on the tool constraint the operation and determine the success of tests. Qualification campaign involved the structural part and related vibration test, the auger/bit parts and drilling test, and the coring mechanism with related sampling test. Mechanical check of specimen volume is also reported, with emphasis on the measurement procedure and on the mechanical unit. The drill tool and all parts of the transfer chain were tested in the hypothetical comet environment, charcterized by frozen material at extreme low temperature and high vacuum (-160°C, 10-3 Pa).

  5. Figure Caption for pair of images of 'Comet Nucleus Q

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Figure Caption for pair of images of 'Comet Nucleus Q'. 21Jul94 Last Look at the Q-nuclei First image - March 30, 1994. Two Q-nuclei and a split nucleus, P. Second image - July 20, 1994. at T - 10 hours. Both nuclei still show no sign of further fragmentation, although the coma near each is being stretched out along the direction of motion. Both images were taken with the WFPC2 Planetary Camera using a red filter. Credit: H. A. Weaver and T. E. Smith

  6. Study of Comet Nucleus Gamma-Ray Spectrometer Penetration System

    NASA Technical Reports Server (NTRS)

    Adams, G. L.; Amundsen, R. J.; Beardsley, R. W.; Cash, R. H.; Clark, B. C.; Knight, T. C. D.; Martin, J. P.; Monti, P.; Outteridge, D. A.; Plaster, W. D.

    1986-01-01

    A penetrator system has been suggested as an approach for making in situ measurements of the composition and physical properties of the nucleus of a comet. This study has examined in detail the feasibility of implementing the penetrator concept. The penetrator system and mission designs have been developed and iterated in sufficient detail to provide a high level of confidence that the concept can be implemented within the constraints of the Mariner Mark 2 spacecraft.

  7. Sampling the stuff of a comet

    SciTech Connect

    Knacke, R.

    1987-03-01

    The composition of the clouds around Comet Halley during its perihelion passage was examined using intercept spacecraft, IUE, ICE and Pioneer Venus spacecraft, and ground-based instruments. Spectral data showed that the dust emitted in jets was mainly carbon, hydrogen, oxygen and nitrogen (CHON), with additives of Fe, Si, and Mg. The C abundance is similar to that in the sun and in the galactic stellar abundances, which supports the model of comets as proto-stellar nebula material. The nucleus was observed to shed 16 tons of water per second, a rate which at times may have doubled. Noticeably absent from the spectra were CH/sub 4/ lines, an absence common in interstellar clouds. The possibilities that the comet contains a large deuterium-hydrogen ratio and carbonaceous material are discussed.

  8. Calculated dynamical evolution of the nucleus of comet Hartley 2

    NASA Astrophysics Data System (ADS)

    Ksanfomality, Leonid

    2013-04-01

    The nucleus of comet Hartley 2 has a relatively regular dumbbell shape with unequal heads. The narrow part of elongated shape contains a relatively smooth region whose covering material is highly different in its shallow structure compared to other parts of this celestial body. The surface of crudely spherical parts of the nucleus is different from the surface of the "neck", which implies a hypothesis that the shape of the nucleus of Hartley 2 is indicative of destruction of this celestial body occurring in our days. The nucleus rotates around its axis passing through the center of mass, and centrifugal forces arise. This process is hindered by gravitation between parts of the nucleus and gradual slowing of rotation due to body lengthening because of the increase in the moment of inertia (proportional to R2) and due to friction losses in the neck material. We posed the task to determine centrifugal and gravitational forces in the neck (and, respectively, the strains of stretching and compression), the moment of inertia of the body and supply of its rotational energy E, the volume of the nucleus and its average density, and the position of the barycenter and center of rotation. It can be assumed that these forces cause slow but progressive lengthening of the neck which should eventually result in fragmentation of the nucleus. Centrifugal forces can be found as a result of summation of forces produced by parts of the body. According to the calculation model, the total stretching forces in the section passing through the narrowest cut of the neck are 1.21E6 N. The corresponding compression forces in the section passing through the narrow section are 1.04E6 N. The comparison of these values indicates a paradoxical result: stretching strains dominate in the neck, while compressions are dominant in the section passing through the common center of mass. The excess of stretching strains in the neck is 11%. The inference is as follows: the right part of the neck and the

  9. Low encounter speed comet COMA sample return missions

    NASA Technical Reports Server (NTRS)

    Tsou, P.; Yen, C. W.; Albee, A. L.

    1994-01-01

    Comets, being considered the most primitive bodies in the solar system, command the highest priority among solar-system objects for studying solar nebula evolution and the evolution of life through biogenic elements and compounds. The study of comets, and more especially, of material from them, provides an understanding of the physical, chemical, and mineralogical processes operative in the formation and earliest development of the solar systems. These return samples will provide valuable information on comets and serve as a rosetta stone for the analytical studies conducted on interplanetary dust particles over the past two decades, and will provide much needed extraterrestrial samples for the planetary materials community since the Apollo program. Lander sample return missions require rather complex spacecraft, intricate operations, and costly propulsion systems. By contrast, it is possible to take a highly simplified approach for sample capture and return in the case of a comet. In the past, we have considered Earth free-return trajectory to the comet, in which passive collectors intercept dust and volatiles from the cometary coma. However, standard short period cometary free-return trajectories results in the comet to the spacecraft encounter speeds in the range of 10 km/s. At these speeds the kinetic energy of the capture process can render significant modification of dust structure, change of solid phase as well as the lost of volatiles components. This paper presents a class of new missions with trajectories with significant reduction of encounter speeds by incorporating gravity assists and deep space maneuvering. Low encounter speed cometary flyby sample return will enable a marked increase in the value of the return science. Acquiring thousands of samples from a known comet and thousands of images of a comet nucleus would be space firsts. Applying new approach in flight mechanics to generate a new class of low encounter speed cometary sample return

  10. The primordial nucleus of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Davidsson, B. J. R.; Sierks, H.; Güttler, C.; Marzari, F.; Pajola, M.; Rickman, H.; A'Hearn, M. F.; Auger, A.-T.; El-Maarry, M. R.; Fornasier, S.; Gutiérrez, P. J.; Keller, H. U.; Massironi, M.; Snodgrass, C.; Vincent, J.-B.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; De Cecco, M.; Feller, C.; Fulle, M.; Groussin, O.; Hviid, S. F.; Höfner, S.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Moissl-Fraund, R.; Mottola, S.; Naletto, G.; Oklay, N.; Thomas, N.; Tubiana, C.

    2016-07-01

    Context. We investigate the formation and evolution of comet nuclei and other trans-Neptunian objects (TNOs) in the solar nebula and primordial disk prior to the giant planet orbit instability foreseen by the Nice model. Aims: Our goal is to determine whether most observed comet nuclei are primordial rubble-pile survivors that formed in the solar nebula and young primordial disk or collisional rubble piles formed later in the aftermath of catastrophic disruptions of larger parent bodies. We also propose a concurrent comet and TNO formation scenario that is consistent with observations. Methods: We used observations of comet 67P/Churyumov-Gerasimenko by the ESA Rosetta spacecraft, particularly by the OSIRIS camera system, combined with data from the NASA Stardust sample-return mission to comet 81P/Wild 2 and from meteoritics; we also used existing observations from ground or from spacecraft of irregular satellites of the giant planets, Centaurs, and TNOs. We performed modeling of thermophysics, hydrostatics, orbit evolution, and collision physics. Results: We find that thermal processing due to short-lived radionuclides, combined with collisional processing during accretion in the primordial disk, creates a population of medium-sized bodies that are comparably dense, compacted, strong, heavily depleted in supervolatiles like CO and CO2; they contain little to no amorphous water ice, and have experienced extensive metasomatism and aqueous alteration due to liquid water. Irregular satellites Phoebe and Himalia are potential representatives of this population. Collisional rubble piles inherit these properties from their parents. Contrarily, comet nuclei have low density, high porosity, weak strength, are rich in supervolatiles, may contain amorphous water ice, and do not display convincing evidence of in situ metasomatism or aqueous alteration. We outline a comet formation scenario that starts in the solar nebula and ends in the primordial disk, that reproduces these

  11. The rate of formation of clusters on the surface of the comet's nucleus

    NASA Astrophysics Data System (ADS)

    Shoyokubov, Shoayub

    2016-07-01

    The paper describes the positive and negative clusters ions formation rate on the surface of comet nucleus under the influence of corpuscular solar wind particles taking into account the experimentally calculated coefficients of secondary ion emission.

  12. Collisions between the nucleus of Comet Halley and dust from its own meteoroid stream

    NASA Astrophysics Data System (ADS)

    Williams, I. P.; Hughes, D. W.; McBride, N.; Wu, Z.

    1993-01-01

    As Comet Halley orbits the Sun it continuously ploughs through its own meteoroid stream. We show that the collision velocity between the stream meteoroids and the surface of the cometary nucleus is far from negligible, the mean value being about 4.0 km/s. Half of the collisions occur when the comet is close to perihelion. The total amount of its own dust hit by Comet Halley per orbit is around 17 g, and this damages a mere 8 x 10 exp -8 percent of the surface of the nucleus.

  13. Comet coma sample return via Giotto II

    NASA Technical Reports Server (NTRS)

    Tsou, P.; Brownlee, D. E.; Albee, A. L.

    1985-01-01

    A comet coma sample return is possible with a low-cost flyby mission. Collecting coma materials and returning them to earth can be accomplished in a free-return trajectory. Intact capture of coma dust, preserving the cometary dust mineralogy, is possible at low encounter speeds. Samples from a known cometary source can then be compared with the wealth of information on meteorites and interplanetary dust. Sample return via Giotto II is a unique, low-cost NASA/ESA cooperative opportunity. With ESA providing the Giotto spacecraft and payload and NASA the sample return capability, first-class science can be accomplished at a very low cost for both NASA and ESA. This paper focuses on the sample return aspects, including sample return objectives, sample collection techniques, experimental work to verify collection concepts, and some of the characteristics of the cometary targets for sample return.

  14. Optical image of a cometary nucleus: 1980 flyby of Comet Encke

    NASA Technical Reports Server (NTRS)

    Wells, W. C.; Benson, R. S.; Anderson, A. D.; Gal, G.

    1974-01-01

    The feasibility was investigated of obtaining optical images of a cometary nucleus via a flyby of Comet Encke. A physical model of the dust cloud surrounding the nucleus was developed by using available physical data and theoretical knowledge of cometary physics. Using this model and a Mie scattering code, calculations were made of the absolute surface brightness of the dust in the line of sight of the on-board camera and the relative surface brightness of the dust compared to the nucleus. The brightness was calculated as a function of heliocentric distance and for different phase angles (sun-comet-spacecraft angle).

  15. Characterization of the NASA EPOXI Mission Target Comet Nucleus 103P/Hartley 2

    NASA Astrophysics Data System (ADS)

    Lisse, Carey; A'Hearn, Michael; Farnham, Tony; Fernandez, Yanga; Groussin, Olivier; Meech, Karen; Reach, William

    2008-03-01

    In July 2007 NASA selected the EPOXI mission for flight operations. This mission utilizes the Deep Impact flyby spacecraft, which survived encounter with comet 9P/Tempel (T1) unscathed after returning, in conjunction with Spitzer, a wealth of data on the primordial makeup of comets. EPOXI will rendezvous with comet 103P/Hartley2 (H2) and obtain comparable remote imaging observations of the nucleus surface. However, little is known about its nucleus, not its size, rotation rate, or albedo. Mission success depends critically on the ability of the EPOXI spacecraft to navigate to the comet and make accurate, non-saturated measurements. Despite robust targeting algorithms, large uncertainties in size, shape, albedo, and rotational state significantly degrade the probability that the spacecraft will view a sunlit portion of the surface. We propose here to use Spitzer's MIPS 24 um imaging camera to characterize the nucleus of comet 103P/Hartley2. Observing the comet at 5 different epochs will allow easy detection of the moving object vs. background stellar sources, as well as providing a gross measure of the rotational variability. The derived science will add directly to the JFC nucleus survey of Fernandez et al (PID 30908), and the comet trail survey of Reach et al (PID 3119). Our proposal calls for characterization of H2 during the 11 Aug - 20 Sep 3008 observability window, the only one available during Cycle 5, when the comet will be 5.4 AU from the Sun and 5.0 AU from Spitzer, well outside the ice line and thus inactive. The characterization involves fixed- single mode, dithered MIPS maps of the region immediately surrounding the comet, performed 5 times to verify the motion of the target. The total telescope time requested is 2.64 hours.

  16. Comprehensive model for the nucleus of Periodic Comet Tempel 2 and its activity

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    1991-01-01

    A comprehensive synergistic physical model for the nucleus of Periodic Comet Tempel 2 was developed on the basis of observations carried out in 1988. The model includes the best possible estimates of the comet's bulk properties (including the dimensions and the approximate shape), information on its state of rotation, and the characterization of its activity. The model is shown to be consistent with all lines of evidence that are currently available, including relevant information from earlier apparitions.

  17. 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.

  18. 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.

  19. Comet C/2011 J2 (LINEAR) nucleus splitting: Dynamical and structural analysis

    NASA Astrophysics Data System (ADS)

    Manzini, Federico; Oldani, Virginio; Hirabayashi, Masatoshi; Behrend, Raoul; Crippa, Roberto; Ochner, Paolo; Pina, José Pablo Navarro; Haver, Roberto; Baransky, Alexander; Bryssinck, Eric; Dan, Andras; De Queiroz, Josè; Frappa, Eric; Lavayssiere, Maylis

    2016-07-01

    After the discovery of the breakup event of comet C/2011 J2 in August 2014, we followed the primary body and the main fragment B for about 120 days in the context of a wide international collaboration. From the analysis of all published magnitude estimates we calculated the comet's absolute magnitude H=10.4, and its photometric index n=1.7. We also calculated a water production of only 110 kg/s at the perihelion. These values are typical of a low-activity, long-period or new comet. Analysis of the motion of fragment B over the observation period showed that the first breakout event likely occurred between 12 July and 30 July 2014. Nucleus B remained persistently visible throughout the 4-month observation period. The projected separation velocity of nucleus B from the parent body was 4.22 m/s at the time of the breakup and 12.7 m/s at the end of the observation period, suggesting that nucleus B was subjected to a constant deceleration a = 6.87 • 10-7 m / s2 . The spin period of the main nucleus was estimated as 4.56 h±0.05 h by photometric analysis. The structural analysis of the comet showed a cohesive strength of the nucleus greater than ~0.9 kPa; assuming a bulk density of 500 kg/m3, with a rotation period of 4.56 h the cometary nucleus might have failed structurally, especially if the body was elongated. These results suggest that the nucleus of comet C/2011 J2 has an elongated shape, with a ratio of the semi-minor axis to the semi-major axis β < 0.675 ; the semi-major axis of the pristine nucleus could be larger than 8 km. From this study, we propose that rotational disruption, possibly combined with sublimation pressure, was a reasonable explanation for the breakup event in comet C/2011 J2.

  20. Rotation states of the nucleus of Comet Halley compatible with spacecraft images

    NASA Astrophysics Data System (ADS)

    Abergel, A.; Bertaux, J. L.

    1990-07-01

    The positions of the nucleus of Comet Halley have been interpreted, for the observations conducted by the flybys of Vegas 1 and 2 and Giotto, with a pure rotation motion and a period of about 54 hours. Comparisons with ground-based estimates of either the angular momentum or the instantaneous rotation axis of the nucleus indicate that the observed rotation axis during the three spacecraft encounters was moving; on this basis it is suggested that the rotation rate of the nucleus cannot be simple, for all that it may not be far from a pure rotation.

  1. MRO HiRISE Observations of the Nucleus of Comet C/2013 A1 (Siding Spring)

    NASA Astrophysics Data System (ADS)

    McEwen, A. S.; Delamere, W. A.; Heyd, R.; Mattson, S.; Tamppari, L.; Zurek, R. W.; Schaller, C.; Block, K.; Polit, A. T.; Milkovich, S. M.; Hansen, C. J.; Thomas, N.; Cremonese, G.

    2014-12-01

    Comet C/2013 A1 (Siding Spring) will pass Mars at a distance of 131,000 ± 3,000 km on Oct 19, 2014. Mars Reconnaissance Orbiter (MRO) will observe the comet on multiple orbits within 2.5 days before and after closest approach. The HiRISE telescope has a 50 cm aperture and an instantaneous field of view of one micro-radian per pixel, so the best image will have a scale near 131 m/pixel. If imaging is successful (i.e., not too smeared) and if the nucleus is larger than ~200 m diameter, this will provide the first resolved images of the nucleus of a long-period comet. Previous resolved images cover the nuclei of short-period comets, whose surfaces have been processed by many close passes by the sun. The encounter velocity is 56 km/s, so the best observations of the nucleus are only possible a few hours near closest approach, as seen from portions of 3 MRO orbits. A total of 20 HiRISE observations are planned for these 3 orbits, with exposure times varying from 0.13 to 2.5 s to cover a range of potential brightness. The HiRISE CCDs are operated at much higher temperatures, 20-30C, than those used for astronomical observations, so the maximum exposure time is limited by dark current signal. HiRISE objectives are to measure the shape and dimensions of the nucleus, determine its albedo (currently unknown for long-period comets), measure the rotation period and axis, and observe the inner coma for bright jets or outbursts. The phase angles range from 90 to 107 degrees, which will make imaging the nucleus challenging. The fast relative motions and changing geometries of the comet and MRO also make it challenging to acquire unsmeared images, since the image must pass directly down the 128 lines used for time-delay integration (TDI). Although the comet's trajectory is probably well known (as nongravitational effects have not been detected), the exact timing is uncertain. Small timing errors could result in the image passing down the TDI rows at an angle, producing smeared

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

    SciTech Connect

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

    2012-10-10

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

  3. Non-destructive analyses of cometary nucleus samples using synchrotron radiation

    SciTech Connect

    Flynn, G.J.; Sutton, S.R.; Rivers, M.L.

    1989-01-01

    Trace element abundances and abundance patterns in meteorites have proven to be diagnostic indicators of nebular and parent body fractionations, formation temperature, thermal metamorphism and, co-genesis. If comets are more primitive samples of the solar nebula than the meteorites, then trace element abundances in the returned comet nucleus samples should be better indicators of primitive solar nebula conditions than those of meteorites. Comet nucleus samples are likely to consist of a mixture of ices and mineral grains. To provide a complete picture of the elemental distributions, trace element abundance data on the bulk material, as well as separated mineral grains and ices, will be required. This paper discusses the present and future analytical capabilities. 22 refs., 2 figs.

  4. A homogeneous nucleus for comet 67P/Churyumov-Gerasimenko from its gravity field

    NASA Astrophysics Data System (ADS)

    Pätzold, M.; Andert, T.; Hahn, M.; Asmar, S. W.; Barriot, J.-P.; Bird, M. K.; Häusler, B.; Peter, K.; Tellmann, S.; Grün, E.; Weissman, P. R.; Sierks, H.; Jorda, L.; Gaskell, R.; Preusker, F.; Scholten, F.

    2016-02-01

    Cometary nuclei consist mostly of dust and water ice. Previous observations have found nuclei to be low-density and highly porous bodies, but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov-Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kilometres. The gravitational point mass is GM = 666.2 ± 0.2 cubic metres per second squared, giving a mass M = (9,982 ± 3) × 109 kilograms. Together with the current estimate of the volume of the nucleus, the average bulk density of the nucleus is 533 ± 6 kilograms per cubic metre. The nucleus appears to be a low-density, highly porous (72-74 per cent) dusty body, similar to that of comet 9P/Tempel 1. The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material.

  5. A homogeneous nucleus for comet 67P/Churyumov-Gerasimenko from its gravity field.

    PubMed

    Pätzold, M; Andert, T; Hahn, M; Asmar, S W; Barriot, J-P; Bird, M K; Häusler, B; Peter, K; Tellmann, S; Grün, E; Weissman, P R; Sierks, H; Jorda, L; Gaskell, R; Preusker, F; Scholten, F

    2016-02-01

    Cometary nuclei consist mostly of dust and water ice. Previous observations have found nuclei to be low-density and highly porous bodies, but have only moderately constrained the range of allowed densities because of the measurement uncertainties. Here we report the precise mass, bulk density, porosity and internal structure of the nucleus of comet 67P/Churyumov-Gerasimenko on the basis of its gravity field. The mass and gravity field are derived from measured spacecraft velocity perturbations at fly-by distances between 10 and 100 kilometres. The gravitational point mass is GM = 666.2 ± 0.2 cubic metres per second squared, giving a mass M = (9,982 ± 3) × 10(9) kilograms. Together with the current estimate of the volume of the nucleus, the average bulk density of the nucleus is 533 ± 6 kilograms per cubic metre. The nucleus appears to be a low-density, highly porous (72-74 per cent) dusty body, similar to that of comet 9P/Tempel 1. The most likely composition mix has approximately four times more dust than ice by mass and two times more dust than ice by volume. We conclude that the interior of the nucleus is homogeneous and constant in density on a global scale without large voids. The high porosity seems to be an inherent property of the nucleus material. PMID:26842054

  6. Deep Space 1 photometry of the nucleus of Comet 19P/Borrelly

    NASA Astrophysics Data System (ADS)

    Buratti, B. J.; Hicks, M. D.; Soderblom, L. A.; Britt, D.; Oberst, J.; Hillier, J. K.

    2004-01-01

    The NASA-JPL Deep Space 1 Mission (DS1) encountered the short-period Jupiter-family Comet 19P/Borrelly on September 22, 2001, about 8 days after perihelion. DS1's payload contained a remote-sensing package called MICAS (Miniature Integrated Camera Spectrometer) that included a 1024 square CCD and a near IR spectrometer with ˜12 nm resolution. Prior to its closest approach of 2171 km, the remote-sensing package on the spacecraft obtained 25 CCD images of the comet and 45 near-IR spectra (L. Soderblom et al., 2002, Science 296, 1087-1091). These images provided the first close-up view of a comet's nucleus sufficiently unobscured to perform quantitative photometric studies. At closest approach, corresponding to a resolution of 47 meters per pixel, the intensity of the coma was less than 1% of that of the nucleus. An unprecedented range of high solar phase angles (52-89 degrees), viewing geometries that are in general attainable only when a comet is active, enabled the first quantitative and disk resolved modeling of surface photometric physical parameters, including the single particle phase function and macroscopic roughness. The disk-integrated geometric albedo of Borrelly's nucleus is 0.029±0.006, comparable to the dark hemisphere of Iapetus, the lowest albedo C-type asteroids, and the uranian rings. The Bond albedo, 0.009±0.002, is lower than that of any Solar System object measured. Such a low value may enhance the heating of the nucleus and sublimation of volatiles, which in turn causes the albedo to decrease even further. A map of normal reflectance of Borrelly shows variations far greater than those seen on asteroids. The two main terrain types, smooth and mottled, exhibit mean normal reflectances of 0.03 and 0.022. The physical photometric parameters of Borrelly's nucleus are typical of other small dark bodies, particularly asteroids, except preliminary modeling results indicate its regolith may be substantially fluffier. The nucleus exhibits significant

  7. The nonmagnetic nucleus of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Auster, Hans-Ulrich; Apathy, Istvan; Berghofer, Gerhard; Fornacon, Karl-Heinz; Remizov, Anatoli; Carr, Chris; Güttler, Carsten; Haerendel, Gerhard; Heinisch, Philip; Hercik, David; Hilchenbach, Martin; Kührt, Ekkehard; Magnes, Werner; Motschmann, Uwe; Richter, Ingo; Russell, Christopher T.; Przyklenk, Anita; Schwingenschuh, Konrad; Sierks, Holger; Glassmeier, Karl-Heinz

    2015-07-01

    Knowledge of the magnetization of planetary bodies constrains their origin and evolution, as well as the conditions in the solar nebular at that time. On the basis of magnetic field measurements during the descent and subsequent multiple touchdown of the Rosetta lander Philae on the comet 67P/Churyumov-Gerasimenko (67P), we show that no global magnetic field was detected within the limitations of analysis. The Rosetta Magnetometer and Plasma Monitor (ROMAP) suite of sensors measured an upper magnetic field magnitude of less than 2 nanotesla at the cometary surface at multiple locations, with the upper specific magnetic moment being <3.1 × 10-5 ampere-square meters per kilogram for meter-size homogeneous magnetized boulders. The maximum dipole moment of 67P is 1.6 × 108 ampere-square meters. We conclude that on the meter scale, magnetic alignment in the preplanetary nebula is of minor importance.

  8. COSAC prepares for sampling and in situ analysis of cometary matter from comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Goesmann, F.; Raulin, F.; Bredehöft, J. H.; Cabane, M.; Ehrenfreund, P.; MacDermott, A. J.; McKenna-Lawlor, S.; Meierhenrich, U. J.; Muñoz Caro, G. M.; Szopa, C.; Sternberg, R.; Roll, R.; Thiemann, W. H.-P.; Ulamec, S.

    2014-11-01

    The comet rendezvous mission Rosetta will be the first mission to encounter and land on a comet nucleus. After a 10-year journey Rosetta is set for rendezvous with Comet 67P/Churyumov-Gerasimenko. The mission goal is: to study the origin of comets; the relationship between cometary and interstellar material and its implications for the origin of the solar system. The Rosetta spacecraft with an overall mass of about 3000 kg was launched in March 2004 and brought into cometary orbit towards comet 67P/Churyumov-Gerasimenko with 4 gravity assist maneuvers. On its way Rosetta passed and observed two asteroids, (2867) Šteins in 2008 and (21) Lutetia in 2010, respectively. In June 2011 Rosetta entered into hibernation and woke up - as planned - on January 20, 2014. In November 2014 Rosetta's Philae lander and 10 science instruments will be deployed onto the surface of comet 67P/Churyumov-Gerasimenko. This will be followed by the first ever in situ investigation of a comet nucleus. Onboard Philae is the COmetary SAmpling and Composition experiment (COSAC), one of two evolved gas analysers that will investigate organic compounds within the material of the nucleus. Data from the COSAC instrument are expected to provide important insights into the early history of our solar system and contribute to our knowledge of small bodies that may have seeded the early Earth through impacts. In this paper we review recent developments in cometary science, including data on target comet 67P/Churyumov-Gerasimenko. We report on laboratory measurements and the calibration of the COSAC instrument as well as the preparation for operations on the nucleus of comet 67P/Churyumov-Gerasimenko.

  9. Velocity of Ejection of Meteor Particle from the Nucleus of Comets

    NASA Astrophysics Data System (ADS)

    Safarov, Abduljalol; Ibadinov, Khursand

    2016-07-01

    The time and velocity of dust particles of anomalous tail of comets was determine. Velocity ejection of dust particles from the nuclei of comets C/1851 U1, C/1877 G1, C/1921 E1, C/1925 V1, C/1962 C1, C/1969 T1, C/1975 V2, 2P/1924 and 26P/1927 F1 reaching up to 0.4 km/s can be attributed to the removal of large dust particles from the surface of the icy nucleus of comet sublimating molecules. In comets C/1823 Y1, C/1844 Y1, C/1882 R1, C/1883 D1, C/1888 R1, C/1892 E1, D/1894 F1, C/1910 A1, C/1921 E1, C/1922 U1, C/1930 D1, C/1930 O1, C/1931 P1, C/1932 M1, C/1935 A1, C/1954 O1, C/1961 O1, C/1963 A1, C/1968 H1, C/1973 E1, C/1980 P1, C/1984 N2, C/1987 P1, C/1995 O1, C/1999 H1, C/1999 T2, C/1999 S4, C/2002 T7, C/2004 F4, C/2004 Q2, 6P/1950, 7P/1869 G1, 7P/1933, 10P/1930, 19P/1918, 34P/1938 J1, 35P/1939, 67P/1982, 73P/1930 J1, 96P/1986 J1 and 109P/1862 O1 ejection velocity (up to a few km/s) of the particles of anomalous tail from the nuclei significantly exceed the thermal velocity of the molecules sublimating ice nuclei. Such velocity may be explained by the removal of particles from the surface of the nucleus after the collision of the comet nucleus with meteoroids

  10. Trace element abundance determinations by Synchrotron X Ray Fluorescence (SXRF) on returned comet nucleus mineral grains

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Sutton, S. R.

    1989-01-01

    Trace element analyses were performed on bulk cosmic dust particles by Proton Induced X Ray Emission (PIXE) and Synchrotron X Ray Fluorescence (SXRF). When present at or near chondritic abundances the trace elements K, Ti, Cr, Mn, Cu, Zn, Ga, Ge, Se, and Br are presently detectable by SXRF in particles of 20 micron diameter. Improvements to the SXRF analysis facility at the National Synchrotron Light Source presently underway should increase the range of detectable elements and permit the analysis of smaller samples. In addition the Advanced Photon Source will be commissioned at Argonne National Laboratory in 1995. This 7 to 8 GeV positron storage ring, specifically designed for high-energy undulator and wiggler insertion devices, will be an ideal source for an x ray microprobe with one micron spatial resolution and better than 100 ppb elemental sensitivity for most elements. Thus trace element analysis of individual micron-sized grains should be possible by the time of the comet nucleus sample return mission.

  11. Redistribution of particles across the nucleus of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Thomas, N.; Davidsson, B.; El-Maarry, M. R.; Fornasier, S.; Giacomini, L.; Gracia-Berná, A. G.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kührt, E.; La Forgia, F.; Lai, I. L.; Liao, Y.; Marschall, R.; Massironi, M.; Mottola, S.; Pajola, M.; Poch, O.; Pommerol, A.; Preusker, F.; Scholten, F.; Su, C. C.; Wu, J. S.; Vincent, J.-B.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Debei, S.; de Cecco, M.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Kramm, J.-R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Michalik, H.; Naletto, G.; Agarwal, J.; Güttler, C.; Oklay, N.; Tubiana, C.

    2015-11-01

    Context. We present an investigation of the surface properties of areas on the nucleus of comet 67P/Churyumov-Gerasimenko. Aims: We aim to show that transport of material from one part of the cometary nucleus to another is a significant mechanism that influences the appearance of the nucleus and the surface thermal properties. Methods: We used data from the OSIRIS imaging system onboard the Rosetta spacecraft to identify surface features on the nucleus that can be produced by various transport mechanisms. We used simple calculations based on previous works to establish the plausibility of dust transport from one part of the nucleus to another. Results: We show by observation and modeling that "airfall" as a consequence of non-escaping large particles emitted from the neck region of the nucleus is a plausible explanation for the smooth thin deposits in the northern hemisphere of the nucleus. The consequences are also discussed. We also present observations of aeolian ripples and ventifacts. We show by numerical modeling that a type of saltation is plausible even under the rarified gas densities seen at the surface of the nucleus. However, interparticle cohesive forces present difficulties for this model, and an alternative mechanism for the initiation of reptation and creep may result from the airfall mechanism. The requirements on gas density and other parameters of this alternative make it a more attractive explanation for the observations. The uncertainties and implications are discussed.

  12. 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.

  13. The nucleus of comet 67P through the eyes of the OSIRIS cameras

    NASA Astrophysics Data System (ADS)

    Guettler, Carsten; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; OSIRIS Team; Capaccioni, Fabrizio; Filacchione, Gianrico; Ciarniello, Mauro; Erard, Stephane; Rinaldi, Giovanna; Tosi, Federico

    2015-11-01

    The Rosetta spacecraft is studying comet 67P/Churyumov-Gerasimenko from a close distance since August 2014. Onboard the spacecraft, the two scientific cameras, the OSIRIS narrow- and the wide-angle camera, are observing the cometary nucleus, its activity, as well as the dust and gas environment.This overview paper will cover OSIRIS science from the early arrival and mapping phase, the PHILAE landing, and the escort phase including the two close fly-bys. With a first characterization of global physical parameters of the nucleus, the OSIRIS cameras also provided the data to reconstruct a 3D shape model of the comet and a division into morphologic sub-units. From observations of near-surface activity, jet-like features can be projected onto the surface and active sources can be correlated with surface features like cliffs, pits, or flat planes. The increase of activity during and after perihelion in August 2015 showed several outbursts, which were seen as strong, collimated jets originating from the southern hemisphere.A comparison of results between different Rosetta instruments will give further inside into the physics of the comet's nucleus and its coma. The OSIRIS and VIRTIS instruments are particularly well suited to support and complement each other. With an overlap in spectral range, one instrument can provide the best spatial resolution while the other is strong in the spectral resolution. A summary on collaborative efforts will be given.

  14. Challenges of deflecting an asteroid or comet nucleus with a nuclear burst

    SciTech Connect

    Bradley, Paul A; Plesko, Cathy S; Clement, Ryan R. C.; Conlon, Le Ann M; Weaver, Robert P; Guzik, Joyce A; Pritchett - Sheets, Lori A; Huebner, Walter F

    2009-01-01

    There are many natural disasters that humanity has to deal with over time. These include earthquakes, tsunamis, hurricanes, floods, asteroid strikes, and so on. Some of these disasters occur slowly enough that some advance warning is possible for affected areas. In this case, the response is to evacuate the affected area and deal wilh the damage later. The Katrina and Rita hurricane evacuations on the U.S. Gulf Coasl in 2005 demonstrated the chaos that can result from such a response. In contrast with other natural disasters, it is likely that an asteroid or comet nucleus on a collision course with Earth will be detected with enough warning time to possibly deflect it away. Thanks to Near-Earth Object (NED) surveys, people are working towards a goal of cataloging at least 90% of all near-Earth objects with diameters larger than {approx} 140 meters in the next fifteen years. The important question then, is how to mitigate the threat from an asteroid or comet nucleus found to be on a collision course with Earth. In this paper. we briefly review some possible deflection methods, describe their good and bad points, and then embark on a more detailed description of using nuclear munitions in a standoff mode to deflect the asteroid or comet nucleus before it can hit Earth.

  15. The Resolved Nucleus and Coma of Comet Siding Spring from MRO Observations

    NASA Astrophysics Data System (ADS)

    Farnham, Tony L.; Delamere, W. Alan; Kelley, Michael S. P.; Heyd, Rodney; Li, Jian-Yang

    2015-11-01

    Comet Siding Spring (C/2013 A1) is a dynamically new comet discovered on January 4, 2013. On October 19, 2014, just 6 days pefore perihelion, Siding Spring made an historic close approach (C/A) to Mars, closing to a distance of only 140,500 km. We used the HiRISE camera on the Mars Reconaissance Orbiter to observe the comet from October 17-20 (C/A-60 hr to C/A+15 hrs) obtaining 122 images, primarily in broadband filters centered near 500 (BG) and 700 (RED) nm, with another filter near 900 (IR) nm added near close approach. The HiRISE pixel scale in these observations is as small as 138 m/pix, essentially making this event a fortuitous natural flyby of a dynamically new comet.Enhancement of the closest approach images using both an unsharp mask and a coma fitting and subtraction routine, reveals a sharply-defined crescent that changes its appearance as the viewing geometry varies during the comet's passage. The crescent is likely the illuminated limb of the nucleus, making this the first occasion on which the nucleus of a dynamically new comet has been resolved. Preliminary analyses indicate that the nucleus is elongated (prolate ellipsoid) with a length on the order of a kilometer.Photometric measurements of the coma in a constant 48-km radius aperture show brightness variations in the RED filter sequence, with a periodicity of 8.1 hr. Because this is a measure of dust production, the single-peaked lightcurve represents the rotation period of the nucleus. During the observations, one primary fan feature is seen in the coma. The lightcurve variations, with amplitude of ~40% (60-140%) of the average brightness in the 48 km aperture, correlate to the feature visibility, indicating that the jet that produces it is the primary source of activity. The shape and direction of the fan suggests that the source is near a pole, producing a cone of dust around the spin axis. We anticipate that the long time baseline and wide range of viewpoints covered in the MRO images will be

  16. Exposed water ice on the nucleus of comet 67P/Churyumov-Gerasimenko.

    PubMed

    Filacchione, G; De Sanctis, M C; Capaccioni, F; Raponi, A; Tosi, F; Ciarniello, M; Cerroni, P; Piccioni, G; Capria, M T; Palomba, E; Bellucci, G; Erard, S; Bockelee-Morvan, D; Leyrat, C; Arnold, G; Barucci, M A; Fulchignoni, M; Schmitt, B; Quirico, E; Jaumann, R; Stephan, K; Longobardo, A; Mennella, V; Migliorini, A; Ammannito, E; Benkhoff, J; Bibring, J P; Blanco, A; Blecka, M I; Carlson, R; Carsenty, U; Colangeli, L; Combes, M; Combi, M; Crovisier, J; Drossart, P; Encrenaz, T; Federico, C; Fink, U; Fonti, S; Ip, W H; Irwin, P; Kuehrt, E; Langevin, Y; Magni, G; McCord, T; Moroz, L; Mottola, S; Orofino, V; Schade, U; Taylor, F; Tiphene, D; Tozzi, G P; Beck, P; Biver, N; Bonal, L; Combe, J-Ph; Despan, D; Flamini, E; Formisano, M; Fornasier, S; Frigeri, A; Grassi, D; Gudipati, M S; Kappel, D; Mancarella, F; Markus, K; Merlin, F; Orosei, R; Rinaldi, G; Cartacci, M; Cicchetti, A; Giuppi, S; Hello, Y; Henry, F; Jacquinod, S; Reess, J M; Noschese, R; Politi, R; Peter, G

    2016-01-21

    Although water vapour is the main species observed in the coma of comet 67P/Churyumov-Gerasimenko and water is the major constituent of cometary nuclei, limited evidence for exposed water-ice regions on the surface of the nucleus has been found so far. The absence of large regions of exposed water ice seems a common finding on the surfaces of many of the comets observed so far. The nucleus of 67P/Churyumov-Gerasimenko appears to be fairly uniformly coated with dark, dehydrated, refractory and organic-rich material. Here we report the identification at infrared wavelengths of water ice on two debris falls in the Imhotep region of the nucleus. The ice has been exposed on the walls of elevated structures and at the base of the walls. A quantitative derivation of the abundance of ice in these regions indicates the presence of millimetre-sized pure water-ice grains, considerably larger than in all previous observations. Although micrometre-sized water-ice grains are the usual result of vapour recondensation in ice-free layers, the occurrence of millimetre-sized grains of pure ice as observed in the Imhotep debris falls is best explained by grain growth by vapour diffusion in ice-rich layers, or by sintering. As a consequence of these processes, the nucleus can develop an extended and complex coating in which the outer dehydrated crust is superimposed on layers enriched in water ice. The stratigraphy observed on 67P/Churyumov-Gerasimenko is therefore the result of evolutionary processes affecting the uppermost metres of the nucleus and does not necessarily require a global layering to have occurred at the time of the comet's formation. PMID:26760209

  17. Crystallization, sublimation, and gas release in the interior of a porous comet nucleus

    NASA Technical Reports Server (NTRS)

    Prialnik, Dina

    1992-01-01

    A numerical code is developed for evolutionary calculations of the thermal structure and composition of a porous comet nucleus made of water ice, in amorphous or crystalline form, other volatiles, dust, and gases trapped in amorphous ice. Bulk evaporation, crystallization, gas release, and free (Knudsen) flow of gases through the pores are taken into account. The numerical scheme yields exact conservation laws for mass and energy. The code is used to study the effect of bulk evaporation of ice in the interior of a comet nucleus during crystallization. It is found that evaporation controls the temperature distribution; the vapor prevents cooling of the crystallized layer of ice, by recondensation and release of latent heat. Thus high temperatures are maintained below the surface of the nucleus and down to depths of tens or hundreds of meters, even at large heliocentric distances, as long as crystallization goes on. Gas trapped in the ice and released during the phase transition flows both toward the interior and toward the surface and out of the nucleus. The progress of crystallization is largely determined by the contribution of gas fluxes to heat transfer.

  18. 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.

  19. HUBBLE SPACE TELESCOPE OBSERVATIONS OF THE NUCLEUS OF COMET C/2012 S1 (ISON)

    SciTech Connect

    Lamy, Philippe L.; Toth, Imre; Weaver, Harold A.

    2014-10-10

    We report on the analysis of several sequences of broadband visible images of comet C/2012 S1 (ISON) taken with the Wide Field Camera 3 of the Hubble Space Telescope on 2013 April 10, May 8, October 9, and November 1 in an attempt to detect and characterize its nucleus. Whereas the overwhelming coma precluded the detection of the nucleus in the first two sequences, the contrast was sufficient in early October to unambiguously retrieve the signal from the nucleus. Two images taken within a few minutes led to similar V magnitudes for the nucleus of 21.97 and 22.0 with a 1σ uncertainty of 0.065. Assuming a standard value for the geometric albedo (0.04) and a linear phase function with a coefficient of 0.04 mag deg{sup –1}, these V values imply that the nucleus radius is 0.68 ± 0.02 km. Although this result does depend on these two assumptions, we argue that the radius most likely lies in the range 0.6-0.9 km. This result is consistent with the constraints derived from the water production rates reported by Combi et al. The last sequence of images in 2013 November revealed temporal variation of the innermost coma. If attributed to a single rotating jet, this coma brightness variation suggests the rotational period of the nucleus may be close to ∼10.4 hr.

  20. The nucleus of Comet Borrelly: A study of morphology and surface brightness

    USGS Publications Warehouse

    Oberst, J.; Howington-Kraus, E.; Kirk, R.; Soderblom, L.; Buratti, B.; Hicks, M.; Nelson, R.; Britt, D.

    2004-01-01

    Stereo images obtained during the DS1 flyby were analyzed to derive a topographic model for the nucleus of Comet 19P/Borrelly for morphologic and photometric studies. The elongated nucleus has an overall concave shape, resembling a peanut, with the lower end tilted towards the camera. The bimodal character of surface-slopes and curvatures support the idea that the nucleus is a gravitational aggregate, consisting of two fragments in contact. Our photometric modeling suggests that topographic shading effects on Borrelly's surface are very minor (<10%) at the given resolution of the terrain model. Instead, albedo effects are thought to dominate Borrelly's large variations in surface brightness. With 90% of the visible surface having single scattering albedos between 0.008 and 0.024, Borrelly is confirmed to be among the darkest of the known Solar System objects. Photometrically corrected images emphasize that the nucleus has distinct, contiguous terrains covered with either bright or dark, smooth or mottled materials. Also, mapping of the changes in surface brightness with phase angle suggests that terrain roughness at subpixel scale is not uniform over the nucleus. High surface roughness is noted in particular near the transition between the upper and lower end of the nucleus, as well as near the presumed source region of Borrelly's main jets. Borrelly's surface is complex and characterized by distinct types of materials that have different compositional and/or physical properties. ?? 2003 Elsevier Inc. All rights reserved.

  1. Physical Characteristics of Asteroid-like Comet Nucleus C/2001 OG108 (LONEOS)

    NASA Technical Reports Server (NTRS)

    Abell, P. A.; Fernandez, Y. R.; Pravec, P.; French, L. M.; Farnham, T. L.; Gaffey, M. J.; Hardersen, P. S.; Kusnirak, P.; Sarounova, L.; Sheppard, S. S.

    2003-01-01

    For many years several investigators have suggested that some portion of the near-Earth asteroid population may actually be extinct cometary nuclei. Evidence used to support these hypotheses was based on: observations of asteroid orbits and associated meteor showers (e.g. 3200 Phaethon and the Geminid meteor shower); low activity of short period comet nuclei, which implied nonvolatile surface crusts (e.g. Neujmin 1, Arend-Rigaux); and detections of transient cometary activity in some near-Earth asteroids (e.g. 4015 Wilson-Harrington). Recent investigations have suggested that approximately 5-10% of the near- Earth asteroid population may be extinct comets. However if members of the near-Earth asteroid population are extinct cometary nuclei, then there should be some objects within this population that are near their final stages of evolution and so should demonstrate only low levels of activity. The recent detections of coma from near-Earth object 2001 OG108 have renewed interest in this possible comet-asteroid connection. This paper presents the first high quality ground-based near-infrared reflectance spectrum of a comet nucleus combined with detailed lightcurve and albedo measurements.

  2. Two independent and primitive envelopes of the bilobate nucleus of comet 67P

    NASA Astrophysics Data System (ADS)

    Massironi, Matteo; Simioni, Emanuele; Marzari, Francesco; Cremonese, Gabriele; Giacomini, Lorenza; Pajola, Maurizio; Jorda, Laurent; Naletto, Giampiero; Lowry, Stephen; El-Maarry, Mohamed Ramy; Preusker, Frank; Scholten, Frank; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; A'Hearn, Michael F.; Agarwal, Jessica; Auger, Anne-Thérèse; Barucci, M. Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis; Capanna, Claire; da Deppo, Vania; Davidsson, Björn; Debei, Stefano; de Cecco, Mariolino; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Groussin, Olivier; Gutiérrez, Pedro J.; Güttler, Carsten; Hviid, Stubbe F.; Ip, Wing-Huen; Knollenberg, Jörg; Kovacs, Gabor; Kramm, Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M.; Lazzarin, Monica; Lin, Zhong-Yi; Lopez Moreno, Josè J.; Magrin, Sara; Michalik, Harald; Mottola, Stefano; Oklay, Nilda; Pommerol, Antoine; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste

    2015-10-01

    The factors shaping cometary nuclei are still largely unknown, but could be the result of concurrent effects of evolutionary and primordial processes. The peculiar bilobed shape of comet 67P/Churyumov-Gerasimenko may be the result of the fusion of two objects that were once separate or the result of a localized excavation by outgassing at the interface between the two lobes. Here we report that the comet's major lobe is enveloped by a nearly continuous set of strata, up to 650 metres thick, which are independent of an analogous stratified envelope on the minor lobe. Gravity vectors computed for the two lobes separately are closer to perpendicular to the strata than those calculated for the entire nucleus and adjacent to the neck separating the two lobes. Therefore comet 67P/Churyumov-Gerasimenko is an accreted body of two distinct objects with `onion-like' stratification, which formed before they merged. We conclude that gentle, low-velocity collisions occurred between two fully formed kilometre-sized cometesimals in the early stages of the Solar System. The notable structural similarities between the two lobes of comet 67P/Churyumov-Gerasimenko indicate that the early-forming cometesimals experienced similar primordial stratified accretion, even though they formed independently.

  3. Two independent and primitive envelopes of the bilobate nucleus of comet 67P.

    PubMed

    Massironi, Matteo; Simioni, Emanuele; Marzari, Francesco; Cremonese, Gabriele; Giacomini, Lorenza; Pajola, Maurizio; Jorda, Laurent; Naletto, Giampiero; Lowry, Stephen; El-Maarry, Mohamed Ramy; Preusker, Frank; Scholten, Frank; Sierks, Holger; Barbieri, Cesare; Lamy, Philippe; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; A'Hearn, Michael F; Agarwal, Jessica; Auger, Anne-Thérèse; Barucci, M Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis; Capanna, Claire; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Groussin, Olivier; Gutiérrez, Pedro J; Güttler, Carsten; Hviid, Stubbe F; Ip, Wing-Huen; Knollenberg, Jörg; Kovacs, Gabor; Kramm, Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M; Lazzarin, Monica; Lin, Zhong-Yi; Lopez Moreno, Josè J; Magrin, Sara; Michalik, Harald; Mottola, Stefano; Oklay, Nilda; Pommerol, Antoine; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste

    2015-10-15

    The factors shaping cometary nuclei are still largely unknown, but could be the result of concurrent effects of evolutionary and primordial processes. The peculiar bilobed shape of comet 67P/Churyumov-Gerasimenko may be the result of the fusion of two objects that were once separate or the result of a localized excavation by outgassing at the interface between the two lobes. Here we report that the comet's major lobe is enveloped by a nearly continuous set of strata, up to 650 metres thick, which are independent of an analogous stratified envelope on the minor lobe. Gravity vectors computed for the two lobes separately are closer to perpendicular to the strata than those calculated for the entire nucleus and adjacent to the neck separating the two lobes. Therefore comet 67P/Churyumov-Gerasimenko is an accreted body of two distinct objects with 'onion-like' stratification, which formed before they merged. We conclude that gentle, low-velocity collisions occurred between two fully formed kilometre-sized cometesimals in the early stages of the Solar System. The notable structural similarities between the two lobes of comet 67P/Churyumov-Gerasimenko indicate that the early-forming cometesimals experienced similar primordial stratified accretion, even though they formed independently. PMID:26416730

  4. The asteroid-comet continuum from laboratory and space analyses of comet samples and micrometeorites

    NASA Astrophysics Data System (ADS)

    Engrand, Cecile; Duprat, Jean; Bardin, Noemie; Dartois, Emmanuel; Leroux, Hugues; Quirico, Eric; Benzerara, Karim; Rémusat, Laurent; Dobrică, Elena; Delauche, Lucie; Bradley, John; Ishii, Hope; Hilchenbach, Martin; COSIMA Team

    2015-08-01

    Comets are probably the best archives of the nascent solar system, 4.5 Gyr ago, and their compositions reveal crucial clues on the structure and dynamics of the early protoplanetary disk. Anhydrous minerals (olivine and pyroxene) have been identified in cometary dust for a few decades. Surprisingly, samples from comet Wild2 returned by the Stardust mission in 2006 also contain high temperature mineral assemblages like chondrules and refractory inclusions, which are typical components of primitive meteorites (carbonaceous chondrites - CCs). A few Stardust samples have also preserved some organic matter of comet Wild 2 that share some similarities with CCs. Interplanetary dust falling on Earth originate from comets and asteroids in proportions to be further constrained. These cosmic dust particles mostly show similarities with CCs, which in turn only represent a few percent of meteorites recovered on Earth. At least two (rare) families of cosmic dust particles have shown strong evidences for a cometary origin: the chondritic porous interplanetary dust particles (CP-IDPs) collected in the terrestrial stratosphere by NASA, and the ultracarbonaceous Antarctic Micrometeorites (UCAMMs) collected from polar snow and ice by French and Japanese teams. The Rosetta mission currently carries dust analyzers capable of measuring dust flux, sizes, physical properties and compositions of dust particles from the Jupiter family comet 67P/Churyumov-Gerasimenko (COSIMA, GIADA, MIDAS), as well as gas analyzers (ROSINA, PTOLEMY, COSAC). A growing number of evidences highlights the existence of a continuum between asteroids and comets, already in the early history of the solar system. We will present the implications of the analyses of samples in the laboratory and in space to a better understanding of the early protoplanetary disk.

  5. Photometry of dust grains of comet 67P and connection with nucleus regions

    NASA Astrophysics Data System (ADS)

    Cremonese, G.; Simioni, E.; Ragazzoni, R.; Bertini, I.; La Forgia, F.; Pajola, M.; Oklay, N.; Fornasier, S.; Lazzarin, M.; Lucchetti, A.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; A'Hearn, M. F.; Agarwal, J.; Barucci, M. A.; Bertaux, J.-L.; Da Deppo, V.; Davidsson, B.; De Cecco, M.; Debei, S.; Fulle, M.; Groussin, O.; Güttler, C.; Gutierrez, P. J.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kramm, J.-R.; Kueppers, M.; Kürt, E.; Lara, L. M.; Magrin, S.; Lopez Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Preusker, F.; Scholten, F.; Thomas, N.; Tubiana, C.; Vincent, J.-B.

    2016-04-01

    Aims: Multiple pairs of high-resolution images of the dust coma of comet 67P/Churyumov-Gerasimenko have been collected by OSIRIS onboard Rosetta allowing extraction and analysis of dust grain tracks. Methods: We developed a quasi automatic method to recognize and to extract dust tracks in the Osiris images providing size, FWHM and photometric data. The dust tracks characterized by a low signal-to-noise ratio were checked manually. We performed the photometric analysis of 70 dust grain tracks observed on two different Narrow Angle Camera images in the two filters F24 and F28, centered at λ = 480.7 nm and at λ = 743.7 nm, respectively, deriving the color and the reddening of each one. We then extracted several images of the nucleus observed with the same filters and with the same phase angle to be compared with the dust grain reddening. Results: Most of the dust grain reddening is very similar to the nucleus values, confirming they come from the surface or subsurface layer. The histogram of the dust grain reddening has a secondary peak at negative values and shows some grains with values higher than the nucleus, suggesting a different composition from the surface grains. One hypothesis comes from the negative values point at the presence of hydrated minerals in the comet.

  6. 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).

  7. Peculiar Near-nucleus Outgassing of Comet 17P/Holmes during its 2007 Outburst

    NASA Astrophysics Data System (ADS)

    Qi, Chunhua; Hogerheijde, Michiel R.; Jewitt, David; Gurwell, Mark A.; Wilner, David J.

    2015-01-01

    We present high angular resolution Submillimeter Array observations of the outbursting Jupiter family comet 17P/Holmes on 2007 October 26-29, achieving a spatial resolution of 2.''5, or ~3000 km at the comet distance. The observations resulted in detections of the rotational lines CO 3-2, HCN 4-3, H13CN 4-3, CS 7-6, H2CO 31, 2-21, 1, H2S 22, 0-21, 1, and multiple CH3OH lines, along with the associated dust continuum at 221 and 349 GHz. The continuum has a spectral index of 2.7 ± 0.3, slightly steeper than blackbody emission from large dust particles. From the imaging data, we identify two components in the molecular emission. One component is characterized by a relatively broad line width (~1 km s-1 FWHM) exhibiting a symmetric outgassing pattern with respect to the nucleus position. The second component has a narrower line width (<0.5 km s-1 FWHM) with the line center redshifted by 0.1-0.2 km s-1 (cometocentric frame), and shows a velocity shift across the nucleus position with the position angle gradually changing from 66° to 30° within the four days of observations. We determine distinctly different CO/HCN ratios for each of the components. For the broad-line component we find CO/HCN < 7, while in the narrow-line component, CO/HCN = 40 ± 5. We hypothesize that the narrow-line component originates from the ice grain halo found in near-nucleus photometry, believed to be created by sublimating recently released ice grains around the nucleus during the outburst. In this interpretation, the high CO/HCN ratio of this component reflects the more pristine volatile composition of nucleus material released in the outburst.

  8. Exposed water ice on the nucleus of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Filacchione, G.; de Sanctis, M. C.; Capaccioni, F.; Raponi, A.; Tosi, F.; Ciarniello, M.; Cerroni, P.; Piccioni, G.; Capria, M. T.; Palomba, E.; Bellucci, G.; Erard, S.; Bockelee-Morvan, D.; Leyrat, C.; Arnold, G.; Barucci, M. A.; Fulchignoni, M.; Schmitt, B.; Quirico, E.; Jaumann, R.; Stephan, K.; Longobardo, A.; Mennella, V.; Migliorini, A.; Ammannito, E.; Benkhoff, J.; Bibring, J. P.; Blanco, A.; Blecka, M. I.; Carlson, R.; Carsenty, U.; Colangeli, L.; Combes, M.; Combi, M.; Crovisier, J.; Drossart, P.; Encrenaz, T.; Federico, C.; Fink, U.; Fonti, S.; Ip, W. H.; Irwin, P.; Kuehrt, E.; Langevin, Y.; Magni, G.; McCord, T.; Moroz, L.; Mottola, S.; Orofino, V.; Schade, U.; Taylor, F.; Tiphene, D.; Tozzi, G. P.; Beck, P.; Biver, N.; Bonal, L.; Combe, J.-Ph.; Despan, D.; Flamini, E.; Formisano, M.; Fornasier, S.; Frigeri, A.; Grassi, D.; Gudipati, M. S.; Kappel, D.; Mancarella, F.; Markus, K.; Merlin, F.; Orosei, R.; Rinaldi, G.; Cartacci, M.; Cicchetti, A.; Giuppi, S.; Hello, Y.; Henry, F.; Jacquinod, S.; Reess, J. M.; Noschese, R.; Politi, R.; Peter, G.

    2016-01-01

    Although water vapour is the main species observed in the coma of comet 67P/Churyumov-Gerasimenko and water is the major constituent of cometary nuclei, limited evidence for exposed water-ice regions on the surface of the nucleus has been found so far. The absence of large regions of exposed water ice seems a common finding on the surfaces of many of the comets observed so far. The nucleus of 67P/Churyumov-Gerasimenko appears to be fairly uniformly coated with dark, dehydrated, refractory and organic-rich material. Here we report the identification at infrared wavelengths of water ice on two debris falls in the Imhotep region of the nucleus. The ice has been exposed on the walls of elevated structures and at the base of the walls. A quantitative derivation of the abundance of ice in these regions indicates the presence of millimetre-sized pure water-ice grains, considerably larger than in all previous observations. Although micrometre-sized water-ice grains are the usual result of vapour recondensation in ice-free layers, the occurrence of millimetre-sized grains of pure ice as observed in the Imhotep debris falls is best explained by grain growth by vapour diffusion in ice-rich layers, or by sintering. As a consequence of these processes, the nucleus can develop an extended and complex coating in which the outer dehydrated crust is superimposed on layers enriched in water ice. The stratigraphy observed on 67P/Churyumov-Gerasimenko is therefore the result of evolutionary processes affecting the uppermost metres of the nucleus and does not necessarily require a global layering to have occurred at the time of the comet’s formation.

  9. Comet 19P/Borrelly in Three Dimensions: Coma and Nucleus

    NASA Astrophysics Data System (ADS)

    Soderblom, L. A.

    2002-12-01

    On September 22, 2001 the ion propulsion-powered NASA-JPL Deep Space 1 (DS1) spacecraft passed 2171 km from the nucleus of 19P/Borrelly with a relative velocity of 16.5 km/sec. The advanced technology Miniature Integrated Camera and Spectrometer (MICAS) aboard DS1, collected 25 high resolution images of the coma, jets and nucleus of the Jupiter-family short-period comet. These images were acquired at over a wide range of phase angles allowing detailed characterization of the surface topography of the nucleus, the three-dimensional characteristics of the coma, and the relationships between the two. The very low albedo, elongate nucleus exhibits large albedo variations and complex geology. Observations starting a few days before and extending up to encounter show a prominent jet emanating roughly normal to long axis of nucleus from a broad central depression into a direction about 35 degrees from the sun line (RA: 223 degrees and DEC: -15 degrees). Both fan-like and highly collimated jets are observed in the near-nucleus coma. The collimated jets have cylindrical cores (about 0.5 km x 5 km in dimension) and bubble-shaped bright bases; two are traceable to darker circular patches on the nucleus. The main jet is evidently co-aligned with the rotation axis. This places the sub-solar point only 30 degrees from the pole and, therefore, the pole is in constant sunlight around perihelion. Such an orientation for the pole would also represent a stable rotation of the nucleus around its short axis.

  10. A Portrait of the Nucleus of Comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Lamy, Philippe L.; Toth, Imre; Davidsson, Björn J. R.; Groussin, Olivier; Gutiérrez, Pedro; Jorda, Laurent; Kaasalainen, Mikko; Lowry, Stephen C.

    2007-02-01

    In 2003, comet 67P/Churyumov Gerasimenko was selected as the new target of the Rosetta mission as the most suitable alternative to the original target, comet 46P/Wirtanen, on the basis of orbital considerations even though very little was known about the physical properties of its nucleus. In a matter of a few years and based on highly focused observational campaigns as well as thorough theoretical investigations, a detailed portrait of this nucleus has been established that will serve as a baseline for planning the Rosetta operations and observations. In this review article, we present a novel method to determine the size and shape of a cometary nucleus: several visible light curves were inverted to produce a size scale free three dimensional shape, the size scaling being imposed by a thermal light curve. The procedure converges to two solutions which are only marginally different. The nucleus of comet 67P/Churyumov Gerasimenko emerges as an irregular body with an effective radius (that of the sphere having the same volume) = 1.72 km and moderate axial ratios a/b = 1.26 and a/c = 1.5 to 1.6. The overall dimensions measured along the principal axis for the two solutions are 4.49 4.75 km, 3.54 3.77 km and 2.94 2.92 km. The nucleus is found to be in principal axis rotation with a period = 12.4 12.7 h. Merging all observational constraints allow us to specify two regions for the direction of the rotational axis of the nucleus: RA = 220°+50° -30° and Dec = -70° ± 10° (retrograde rotation) or RA = 40°+50° -30° and Dec = +70°± 10° (prograde), the better convergence of the various determinations presently favoring the first solution. The phase function, although constrained by only two data points, exhibits a strong opposition effect rather similar to that of comet 9P/Tempel 1. The definition of the disk integrated albedo of an irregular body having a strong opposition effect raises problems, and the various alternatives led to a R-band geometric albedo in the

  11. The Nucleus of Comet 9P-Tempel 1: Shape and Geology from Two Flybys

    NASA Technical Reports Server (NTRS)

    Thomas, P.; A'Hearn, M.; Belton, M. J. S.; Brownlee, D.; Carcich, B.; Hermalyn, B.; Klaasen, K.; Sackett, S.; Schultz, P. H.; Veverka, J.; Bhaskaran, S.; Bodewits, D.; Chesley, S.; Clark, B.; Farnham, T.; Groussin, O.; Harris, J.; Kissel, J.; Li, J.-Y; Meech, K.; Melosh, J.; Quick, A.; Richardson, J.; Sunshine, J.; Wellnitz, D.

    2012-01-01

    The nucleus of comet Tempel 1 has been investigated at close range during two spacecraft missions separated by one comet orbit of the Sun, 5 1/2 years. The combined imaging covers 70% of the surface of this object which has a mean radius of 2.83 +/- 0.1 km. The surface can be divided into two terrain types: rough, pitted terrain and smoother regions of varying local topography. The rough surface has round depressions from resolution limits (10 m/pixel) up to 1 km across, spanning forms from crisp steep-walled pits, to subtle albedo rings, to topographic rings, with all ranges of morphologic gradation. Three gravitationally low regions of the comet have smoother terrain, parts of which appear to be deposits from minimally modified flows, with other parts likely to be heavily eroded portions of multiple layer piles. Changes observed between the two missions are primarily due to backwasting of scarps bounding one of these probable flow deposits. This style of erosion is also suggested by remnant mesa forms in other areas of smoother terrain. The two distinct terrains suggest either an evolutionary change in processes, topographically- controlled processes, or a continuing interaction of erosion and deposition.

  12. The nucleus of Comet 9P/Tempel 1: Shape and geology from two flybys

    NASA Astrophysics Data System (ADS)

    Thomas, P.; A'Hearn, M.; Belton, M. J. S.; Brownlee, D.; Carcich, B.; Hermalyn, B.; Klaasen, K.; Sackett, S.; Schultz, P. H.; Veverka, J.; Bhaskaran, S.; Bodewits, D.; Chesley, S.; Clark, B.; Farnham, T.; Groussin, O.; Harris, A.; Kissel, J.; Li, J.-Y.; Meech, K.; Melosh, J.; Quick, A.; Richardson, J.; Sunshine, J.; Wellnitz, D.

    2013-02-01

    The nucleus of comet Tempel 1 has been investigated at close range during two spacecraft missions separated by one comet orbit of the Sun, 5½ years. The combined imaging covers ˜70% of the surface of this object which has a mean radius of 2.83 ± 0.1 km. The surface can be divided into two terrain types: rough, pitted terrain and smoother regions of varying local topography. The rough surface has round depressions from resolution limits (˜10 m/pixel) up to ˜1 km across, spanning forms from crisp steep-walled pits, to subtle albedo rings, to topographic rings, with all ranges of morphologic gradation. Three gravitationally low regions of the comet have smoother terrain, parts of which appear to be deposits from minimally modified flows, with other parts likely to be heavily eroded portions of multiple layer piles. Changes observed between the two missions are primarily due to backwasting of scarps bounding one of these probable flow deposits. This style of erosion is also suggested by remnant mesa forms in other areas of smoother terrain. The two distinct terrains suggest either an evolutionary change in processes, topographically-controlled processes, or a continuing interaction of erosion and deposition.

  13. Trajectory analysis for the nucleus and dust of comet C/2013 A1 (Siding Spring)

    SciTech Connect

    Farnocchia, Davide; Chesley, Steven R.; Chodas, Paul W.; Tricarico, Pasquale; Kelley, Michael S. P.; Farnham, Tony L.

    2014-08-01

    Comet C/2013 A1 (Siding Spring) will experience a high velocity encounter with Mars on 2014 October 19 at a distance of 135,000 km ± 5000 km from the planet center. We present a comprehensive analysis of the trajectory of both the comet nucleus and the dust tail. The nucleus of C/2013 A1 cannot impact on Mars even in the case of unexpectedly large nongravitational perturbations. Furthermore, we compute the required ejection velocities for the dust grains of the tail to reach Mars as a function of particle radius and density and heliocentric distance of the ejection. A comparison between our results and the most current modeling of the ejection velocities suggests that impacts are possible only for millimeter to centimeter size particles released more than 13 AU from the Sun. However, this level of cometary activity that far from the Sun is considered extremely unlikely. The arrival time of these particles spans a 20-minute time interval centered at 2014 October 19 at 20:09 TDB, i.e., around the time that Mars crosses the orbital plane of C/2013 A1. Ejection velocities larger than currently estimated by a factor >2 would allow impacts for smaller particles ejected as close as 3 AU from the Sun. These particles would reach Mars from 19:13 TDB to 20:40 TDB.

  14. An Overview of the Comet Nucleus TOUR Discovery Mission and a Description of Neutral Gas and Ion Measurements Planned

    NASA Technical Reports Server (NTRS)

    Mahaffy, Paul; Veverka, Joe; Niemann, Hasso; Harpold, Dan; Chiu, Mary; Reynolds, Edward; Owen, Toby; Kasprzak, Wayne; Patrick, Ed; Raaen, Eric

    2001-01-01

    The CONTOUR (Comet Nucleus TOUR) Mission led by its Principal Investigator Professor Joseph Veverka of Cornell is presently under development at the Johns Hopkins Applied Physics Laboratory for launch in July of 2002 with a flyby of Comet Encke scheduled for November 3, 2003 at a solar distance of 1.07 au. A robust Whipple dust shield is designed to allow a close nucleus approach distance (less than 150 km). The 2nd nominal CONTOUR target is Comet Schwassmann-Wachmann 3, although the spacecraft can alternately be directed to a new comet if such an interesting target is discovered. CONTOUR contains 4 instruments: an imaging spectrometer (CRISP) developed at APL that will obtain both high resolution nucleus images through 8 filters and IR spectra (800 to 2550 nm) of the nucleus, a narrow field of view forward imager (CFI) to locate the target days before the encounter, a dust composition time of flight mass spectrometer (CIDA) provided by Dr. J. Kissel and von Hoemer & Sulger, GmbH, and a mass spectrometer (NGIMS) provided by Goddard Space Flight Center to measure neutral gas and ambient ions. Laboratory calibration of the NGIMS has now been completed. NGIMS also includes an in-flight calibration system that we plan to exercise before and after each comet encounter. We will provide an overview of the CONTOUR Mission and discuss more specifically the NGIMS measurement goals for this mission.

  15. Seasonal Evolution on the Nucleus of Comet C/2013 A1 (Siding Spring)

    NASA Astrophysics Data System (ADS)

    Li, Jian-Yang; Samarasinha, Nalin H.; Kelley, Michael S. P.; Farnham, Tony L.; Bodewits, Dennis; Lisse, Carey M.; Mutchler, Max J.; A'Hearn, Michael F.; Delamere, W. Alan

    2016-02-01

    We observed Comet C/Siding Spring using the Hubble Space Telescope (HST) during its close approach to Mars. The high spatial resolution images obtained through the F689M, F775W, and F845M filters reveal the characteristics of the dust coma. The dust production rate of C/Siding Spring, quantified by Afρ, is 590 ± 30, 640 ± 30, and 670 ± 30 cm in a 420 km radius aperture at a 38° solar phase angle through the three filters, respectively, consistent with other observations at a similar time and geometry, and with model predictions based on earlier measurements. The dust expansion velocity is ˜150-250 m s-1 for micron-sized dust grains, similar to the speeds found for other comets. The coma has a color slope of (5.5 ± 1.5)%/100 nm between 689 and 845 nm, similar to previous HST measurements at comparable aperture sizes, consistent with the lack of color dependence on heliocentric distance for almost all previously observed active comets. The rotational period of the nucleus of C/Siding Spring is determined from the periodic brightness variation in the coma to be 8.00 ± 0.08 hr, with no excited rotational state detected. The dust coma shows a broad and diffuse fan-shaped feature in the sunward direction, with no temporal morphological variation observed. The projected orientation of the dust feature, combined with the previous analysis of the coma morphology and other characteristics, suggests secular activity evolution of the comet in its inner solar system passage as one previously observed active region turns off whereas new regions exposed to sunlight due to seasonal illumination change.

  16. PECULIAR NEAR-NUCLEUS OUTGASSING OF COMET 17P/HOLMES DURING ITS 2007 OUTBURST

    SciTech Connect

    Qi, Chunhua; Gurwell, Mark A.; Wilner, David J.; Hogerheijde, Michiel R.; Jewitt, David

    2015-01-20

    We present high angular resolution Submillimeter Array observations of the outbursting Jupiter family comet 17P/Holmes on 2007 October 26-29, achieving a spatial resolution of 2.''5, or ∼3000 km at the comet distance. The observations resulted in detections of the rotational lines CO 3-2, HCN 4-3, H{sup 13}CN 4-3, CS 7-6, H{sub 2}CO 3{sub 1,} {sub 2}-2{sub 1,} {sub 1}, H{sub 2}S 2{sub 2,} {sub 0}-2{sub 1,} {sub 1}, and multiple CH{sub 3}OH lines, along with the associated dust continuum at 221 and 349 GHz. The continuum has a spectral index of 2.7 ± 0.3, slightly steeper than blackbody emission from large dust particles. From the imaging data, we identify two components in the molecular emission. One component is characterized by a relatively broad line width (∼1 km s{sup –1} FWHM) exhibiting a symmetric outgassing pattern with respect to the nucleus position. The second component has a narrower line width (<0.5 km s{sup –1} FWHM) with the line center redshifted by 0.1-0.2 km s{sup –1} (cometocentric frame), and shows a velocity shift across the nucleus position with the position angle gradually changing from 66° to 30° within the four days of observations. We determine distinctly different CO/HCN ratios for each of the components. For the broad-line component we find CO/HCN < 7, while in the narrow-line component, CO/HCN = 40 ± 5. We hypothesize that the narrow-line component originates from the ice grain halo found in near-nucleus photometry, believed to be created by sublimating recently released ice grains around the nucleus during the outburst. In this interpretation, the high CO/HCN ratio of this component reflects the more pristine volatile composition of nucleus material released in the outburst.

  17. I. T. - R. O. C. K. S. Comet Nuclei Sample Return Mission

    NASA Astrophysics Data System (ADS)

    Dalcher, N.

    2009-04-01

    Ices, organics and minerals recording the chemical evolution of the outer regions of the early solar nebula are the main constituents of comets. Because comets maintain the nearly pristine nature of the cloud where they formed, the analyses of their composition, structure, thermodynamics and isotope ratios will increase our understanding of the processes that occurred in the early phases of the solar system as well as the Interstellar Medium (ISM) Cloud that predated the formation of the solar nebula [1]. While the deep impact mission aimed at determining the internal structure of comet Temple1's nuclei [e.g. 3], the stardust mission sample return has dramatically increased our understanding of comets. Its first implications indicated that some of the comet material originated in the inner solar system and was later transported outward beyond the freezing line [4]. A wide range of organic compounds identified within different grains of the aerogel collectors has demonstrated the heterogeneity in their assemblages [5]. This suggests either many histories associated with these material or possibly analytical constraints imposed by capture heating of Wild2 material in silica aerogel. The current mission ROSETTA, will further expand our knowledge about comets considerably through rigorous in situ analyses of a Jupiter Family Comet (JFC). As the next generation of comet research post ROSETTA, we present the comet nuclei sample return mission IT - ROCKS (International Team - Return Of Comet's Key Samples) to return several minimally altered samples from various locations of comet 88P/Howell, a typical JFC. The mission scenario includes remote sensing of the comet's nucleus with onboard instruments similar to the ROSETTA instruments [6, 7, 8] (VIS, IR, Thermal IR, X-Ray, Radar) and gas/dust composition measurements including a plasma science package. Additionally two microprobes [9] will further investigate the physical properties of the comet's surface. Retrieving of the

  18. EVIDENCE FOR FRESH FROST LAYER ON THE BARE NUCLEUS OF COMET HALE-BOPP AT 32 AU DISTANCE

    SciTech Connect

    Szabo, Gyula M.; Kiss, Laszlo L.; Pal, Andras; Kiss, Csaba; Sarneczky, Krisztian; Juhasz, Attila; Hogerheijde, Michiel R.

    2012-12-10

    Here, we report that the activity of comet Hale-Bopp ceased between late 2007 and 2009 March, at about 28 AU distance from the Sun. At that time, the comet resided at a distance from the Sun that exceeded the freeze-out distance of regular comets by an order of magnitude. A Herschel Space Observatory PACS scan was taken in mid-2010, in the already inactive state of the nucleus. The albedo has been found to be surprisingly large (8.1% {+-} 0.9%), which exceeds the value known for any other comets. With re-reduction of archive Hubble Space Telescope images from 1995 and 1996, we confirm that the pre-perihelion albedo resembled that of an ordinary comet and was smaller by a factor of two than the post-activity albedo. Our further observations with the Very Large Telescope also confirmed that the albedo increased significantly by the end of the activity. We explain these observations by proposing gravitational redeposition of icy grains toward the end of the activity. This is plausible for such a massive body in a cold environment, where gas velocity is lowered to the range of the escape velocity. These observations also show that giant comets are not just the upscaled versions of the comets we know but can be affected by processes that are yet to be fully identified.

  19. Seasonal effects on the nucleus of comet 67P revealed by Rosetta/VIRTIS

    NASA Astrophysics Data System (ADS)

    Tosi, Federico; Capaccioni, Fabrizio; Filacchione, Gianrico; Erard, Stéphane; Rouseeau, Batiste; Combe, Jean-Philippe; Capria, Maria Teresa; Leyrat, Cédric; Longobardo, Andrea; Bockelée-Morvan, Dominique; Kappel, David; Arnold, Gabriele; Fonti, Sergio; Mancarella, Francesca; Kuehrt, Ekkehard; Mottola, Stefano

    2016-04-01

    We describe thermal effects on the nucleus of comet 67P. Due to the overall low thermal inertia of the nucleus surface, the surface temperature is essentially dominated by the instantaneous value of the solar incidence angle and the heliocentric distance. However, for each location, the smallest achievable value of insolation angle depends on the season and topography. Given the substantial obliquity of comet 67P, seasons are such that the northern hemisphere is mainly illuminated at aphelion while the southern hemisphere receives most insolation soon after perihelion. In addition, the heliocentric distance strongly affects the surface temperature, all other parameters being equal. This is a larger effect in comets than in asteroids, due to the wide range of heliocentric distance values spanned by comets. When Rosetta started its global mapping observation campaign, in early August 2014, hyperspectral images acquired by the VIRTIS imaging spectrometer onboard the Rosetta Orbiter covered only the northern regions of the cometary surface, and the equatorial belt became gradually unveiled, while the southern region has been revealed from 2015 onwards. In parallel, the comet's heliocentric distance has been decreasing from ˜3.6 AU down to 1.24 AU, the distance at which the perihelion passage occurred on 13 August 2015. By relating surface temperatures as measured by VIRTIS to three variables: solar incidence angle, true local solar time and heliocentric distance, we aim to separate the relative contributions due to season and to the heliocentric distance. To do this, we use both VIRTIS-M data (namely data from the mapping spectrometer covering the 1-5 μm range, available up to April 2015, i.e. before the failure of the IR cryocooler) and VIRTIS-H data (namely data from the high-resolution point spectrometer covering the 2-5 μm range), and we focus in particular on three regions: one in the northern hemisphere, one in the equatorial region and one in the southern

  20. On the search for trajectories for a cometary nucleus sample return mission

    NASA Technical Reports Server (NTRS)

    Schobert, D.; Igenbergs, E.; Loeb, H.; Stuhlinger, E.

    1986-01-01

    The steps in the procedure for the generation of single trajectories for a comet nucleus sample return mission described by Stuhlinger et al. (1985) are discussed. The following assumptions are made for such a mission: (1) the spacecraft is equipped with an ion propulsion system supplied by solar cells, and (2) the comet has a low inclination and a period of about six years. The calculation of a specific trajectory incorporates the following main parameters: (1) the spacecraft mass at the beginning of the mission and the hyperbolic excess velocity, (2) the mass as a function of the injection energy, and (3) the available thrust level. The limitation of a supply of solar electric power to the region within 3 AU of the sun and the placement of permanent in-situ experiments at the comet are discussed. It is concluded that single trajectories for a nucleus sample return mission can be generated. A further step would be an integration of single solutions into classes of trajectories.

  1. Rosetta/OSIRIS: Nucleus morphology and activity of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Sierks, Holger

    2015-08-01

    Introduction: The Rosetta mission of the European Space Agency arrived on August 6, 2014, at the target comet 67P/Churyumov-Gerasimenko after 10 years of cruise. OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is the scientific imaging system onboard Rosetta. It comprises a Narrow Angle Camera (NAC) for broad-band nucleus surface and dust studies and a Wide Angle Camera (WAC) for the wide field coma investigations.OSIRIS images the nucleus and the coma of comet 67P/C-G from the arrival throughout early mapping phase, PHILAE landing, and escort phase with close fly-by beginning of the year 2015.The team paper presents the surface morphology and activity of the nucleus as seen in gas, dust, and local jets and the larger scale coma studied by OSIRIS.Acknowledgements: OSIRIS was built by a consortium led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany, in collaboration with CISAS, University of Padova, Italy, the Laboratoire d'Astrophysique de Marseille, France, the Instituto de Astrofísica de Andalucia, CSIC, Granada, Spain, the Scientific Support Office of the European Space Agency, Noordwijk, The Netherlands, the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain, the Universidad Politéchnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut für Datentechnik und Kommunikationsnetze der Technischen Universität Braunschweig, Germany.Additional Information: The OSIRIS team is H. Sierks, C. Barbieri, P. Lamy, R. Rodrigo, D. Koschny, H. Rickman, J. Agarwal, M. A'Hearn, I. Bertini, F. Angrilli, M. A. Barucci, J. L. Bertaux, G. Cremonese, V. Da Deppo, B. Davidsson, S. Debei, M. De Cecco, S. Fornasier, M. Fulle, O. Groussin, C. Güttler, P. Gutierrez, S. Hviid, W. Ip, L. Jorda, H. U. Keller, J. Knollenberg, R. Kramm, E. Kührt, M. Küppers, L. Lara, M. Lazzarin, J. J. Lopez, S. Lowry, S. Marchi, F. Marzari, H. Michalik, S. Mottola, G. Naletto, N. Oklay, L

  2. Millimeter and Submillimeter Observations of Comet 67P's Nucleus, Gas, and Dust with the Rosetta/MIRO Instrument

    NASA Astrophysics Data System (ADS)

    Hofstadter, Mark

    2016-04-01

    The Microwave Instrument for the Rosetta Orbiter (MIRO) has been making measurements of comet 67P/C-G since June 2014, when the comet was 3.92 AU from the Sun and Rosetta was approximately 400,000 km from the nucleus. Those first observations were spatially unresolved measurements of the 556 GHz water line, used to infer the abundance and velocity of water vapor in the coma (Gulkis et al. 2015, Science 347). In the almost two years since that time, as the spacecraft has moved closer to the nucleus and the comet has become more active (perihelion at 1.2 AU from the Sun occurred in August 2015), MIRO's submillimeter spectrometer (working at frequencies near 550 GHz, or wavelengths near 0.5 mm) has been used to determine the velocity, abundance, and spatial distribution of H216O, H217O, H218O, CH3OH, NH3, and CO in the coma as a function of time (e.g. water is discussed by Biver et al. 2015 and Lee et al. 2015, Astron. and Astrophys. 583). In addition to its submillimeter spectrometer, MIRO has two broad band continuum channels operating at wavelengths near 0.5 and 1.6 millimeter. These channels are designed to probe the nucleus ˜1 millimeter to 10 cm below the surface. Data have been used to infer properties such as thermal inertia, porosity, and ice content as functions of location, depth, and time (e.g. Schloerb et al. 2015 and Choukroun et al. 2015, Astron. and Astrophys. 583). These channels have also been used to map the distribution of relatively large dust grains (radius > ˜1 mm) in the inner coma of the comet, with the potential to constrain models of dust acceleration, cooling, and fragmentation. This talk will review the latest results from MIRO's measurements of the nucleus, coma, and dust, and discuss some of the processes that couple these components of the comet.

  3. 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...

  4. The STARDUST Discovery Mission: Data from the Encounter with Comet Wild 2 and the Expected Sample Return

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.

    2004-01-01

    On January 2,2004, the STARDUST spacecraft made the closest ever flyby (236 km) of the nucleus of a comet - Comet Wild 2. During the fly by the spacecraft collected samples of dust from the coma of the comet. These samples will be returned to Earth on January 15,2006. After a brief preliminary examination to establish the nature of the returned samples, they will be made available to the general scientific community for study. In addition to its aerogel dust collector, the STARDUST spacecraft was also equipped with instruments that made in situ measurements of the comet during the flyby. These included several dust impact monitors, a mass spectrometer, and a camera. The spacecraft's communication system was also used to place dynamical constraints on the mass of the nucleus and the number of impacts the spacecraft had with large particles. The data taken by these instruments indicate that the spacecraft successfully captured coma samples. These instruments, particularly the camera, also demonstrated that Wild 2 is unlike any other object in the Solar System previously visited by a spacecraft. During my talk I will discuss the scientific goals of the STARDUST mission and provide an overview of its design and flight to date. I will then end with a description of the exciting data returned by the spacecraft during the recent encounter with Wild 2 and discuss what these data tell us about the nature of comets. It will probably come as no surprise that the encounter data raise as many (or more) new questions as they answer old ones.

  5. Development of Sample Handling and Analytical Expertise For the Stardust Comet Sample Return

    SciTech Connect

    Bradley, J; Bajt, S; Brennan, S; Graham, G; Grant, P; Hutcheon, I; Ishii, H; Pianetta, P; Toppani, A; Westphal, A

    2006-02-09

    NASA's Stardust mission returned to Earth in January 2006 with ''fresh'' cometary particles from a young Jupiter family comet. The cometary particles were sampled during the spacecraft flyby of comet 81P/Wild-2 in January 2004, when they impacted low-density silica aerogel tiles and aluminum foils on the sample tray assembly at approximately 6.1 km/s. This LDRD project has developed extraction and sample recovery methodologies to maximize the scientific information that can be obtained from the analysis of natural and man-made nano-materials of relevance to the LLNL programs.

  6. Estimating the strength of the nucleus material of comet 67P Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Basilevsky, A. T.; Krasil'nikov, S. S.; Shiryaev, A. A.; Mall, U.; Keller, H. U.; Skorov, Yu. V.; Mottola, S.; Hviid, S. F.

    2016-07-01

    Consideration is given to the estimates for the strength of the consolidated material forming the bulk of the nucleus of comet 67P Churyumov-Gerasimenko and those for the strength of the surface material overlying the consolidated material at the sites of the first and last contact of the Philae lander with the nucleus. The strength of the consolidated material was estimated by analyzing the terrain characteristics of the steep cliffs, where the material is exposed on the surface. Based on these estimates, the tensile strength of the material is in the range from 1.5 to 100 Pa; the shear strength, from ˜13 to ⩾30 Pa; and the compressive strength, from 30 to 150 Pa, possibly up to 1.5 kPa. These are very low strength values. Given the dependence of the measurement results on the size of the measured object, they are similar to those of fresh dry snow at -10°C. The (compressive) strength of the surface material at the site of the first touchdown of Philae on the nucleus is estimated from the measurements of the dynamics of the surface impact by the spacecraft's legs and the geometry of the impact pits as 1-3 kPa. For comparison with the measurement results for ice-containing materials in terrestrial laboratories, it needs to be taken into account that the rate of deformation by Philae's legs is four orders of magnitude higher than that in typical terrestrial measurements, leading to a possible overestimation of the strength by roughly an order of magnitude. There was an attemp to put one of the MUPUS sensors into the surface material at the site of the last contact of Philae with the nucleus. Noticeable penetration of the tester probe was not achieved that led to estimation of the minimum compressive strength of the material to be ⩾4 MPa4 This fairly high strength appears to indicate the presence of highly porous ice with grains "frozen" at contacts.

  7. Global Shape and Topography of the Nucleus of Comet 67P/C-G from ROSETTA/OSIRIS Images

    NASA Astrophysics Data System (ADS)

    Jorda, L.; Gaskell, R.; Hviid, S.; Capanna, C.; Groussin, O.; Gutierrez, P.; Lamy, P.; Scholten, F.; Preusker, F.; Kaasalainen, M.; Keller, H. U.; Knollenberg, J.; Kührt, E.; Mottola, S.; Sierks, H.; Snodgrass, C.; Thomas, N.; Toth, I.; Vincent, J.-B.

    2014-04-01

    The ROSETTA spacecraft will approach the nucleus of comet P/Churyumov-Gerasimenko in early August 2014 after a successful wake-up on January 20, 2014. The OSIRIS instrument is a set of two cameras aboard ROSETTA: the Narrow Angle Camera and the Wide Angle Camera which have fields-of-view of 2.2° and about 12° respectively. Both cameras are equipped with a 2K by 2K CCD detector. The two cameras have been successfully re-commissioned at the end of March 2014. Observations during the approach and first bound orbits in July-August 2014 will allow to map the surface of the nucleus with OSIRIS at a scale as small as 1 m/pixel. The images will be used to reconstruct the 3D global topography of the nucleus at high-resolution with a combination of two advanced reconstruction techniques: stereophotogrammetry and stereophotoclinometry. The reconstructed global shape will be used to determine the bulk density of the nucleus with an accuracy of a few percent and to localize and quantitatively characterize the main topographic features at its surface. It will also allow us to identify the different types of terrains present at the surface of the nucleus. We will describe and discuss the bulk properties of the nucleus (bulk shape, density and moments of inertia) against those of other comets observed from the ground or by previous space probes. We will also identify the main topographic features from a combined analysis of images and global digital terrain models and compare them with those identified at the surface of comets P/Borrelly, P/Wild 2 and P/Tempel 1 by previous space probes. Finally, we will propose a preliminary interpretation for the processes involved in their formation.

  8. Earth's 2006 Encounter with Comet 73P/Schwassmann-Wachmann: Products of Nucleus Fragmentation Seen in Closeup

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    2007-01-01

    The large numbers of nucleus fragments observed are a spectacular illustration of the process of cascading fragmentation in progress, a concept introduced to interpret the properties of the Kreutz system of sungrazers and comet D/1993 F2. The objective is to describe the fragmentation sequence and hierarchy of comet 73P, the nature of the fragmentation process and observed events, and the expected future evolution of this comet. The orbital arc populated by the fragments refers to an interval of 3.74 days in the perihelion time. This result suggests that they all could be products (but not necessarily first-generation fragments) of two 1995 events, in early September (involving an enormous outburst) and at the beginning of November. The interval of perihelion times is equivalent to a range of about 2.5 m/s in separation velocity or 0.00012 the Sun's attraction in nongravitational deceleration. Their combined effect suggests minor orbital momentum changes acquired during fragmentation and decelerations compatible with survival over two revolutions about the Sun. Fragment B is a likely first-generation product of one of the 1995 events. From the behavior of the primary fragment C, 73P is not a dying comet, even though fragment B and others were episodically breaking up into many pieces. Each episode began with the sudden appearance of a starlike nucleus condensation and a rapidly expanding outburst, followed by a development of jets, and a gradual tailward extension of the fading condensation, until the discrete masses embedded in it could be resolved. In April-May, this debris traveled first to the southwest, but models show their eventual motion toward the projected orbit. Fainter fragments were imaged over limited time, apparently because of their erratic activity (interspersed with periods of dormancy) rather than improptu disintegration. A dust trail joining the fragments and reminiscent of comet 141P/Machholz suggests that cascading fragmentation exerts itself

  9. Constraints on the nucleus of comet C/2012 S1 (ISON) from the Hubble Space Telescope observations

    NASA Astrophysics Data System (ADS)

    Lamy, P.; Toth, I.; Li, J.; Weaver, H.

    2014-07-01

    Comet C/2012 S1 (ISON) was both a dynamically new comet, visiting the inner solar system for the first time since being scattered and deeply frozen in the Oort Cloud, and a sungrazing comet. This unique combination made it an attractive target for the Hubble Space Telescope. It was observed on 10 April 2013 when the comet was 4.15 au from the Sun, 4.24 au from the Earth, and at a phase angle of 13.7°, henceforth well before C/ISON crossed the ''snow line'' (2.5--3 au), avoiding strong activity driven by water-ice sublimation and, thus, potentially increasing the chance of detecting its nucleus. The observations were performed over three separate orbits spanning a time interval of 18 hours using the Wide Field Camera 3 (WFC3) UVIS detector to image C/ISON through two broadband filters, the ''wide-V'' F606W and ''blue'' F438W filters (Li at al. 2013). The twelve images obtained with the F606W filter were analyzed using our well-proven technique of fitting a parametric model of the expected surface brightness to the observed images (e.g., Lamy et al. 2006). The model consists of an unresolved point source and a coma specified by a power law, both convolved with the point spread function of the telescope. The nucleus is basically undetected, which imposes an upper limit of its radius of ˜0.3 km. However, the analysis is complicated by the so-called ''breathing'' of the WFC3 camera, an uncontrolled slight defocus which distorts the PSF. We investigated this question in detail and considered various cases of defocus. We will report on this effort and the resulting robust upper limit which we can put on the size of the nucleus of C/ISON.

  10. Fireball on 6 July 2002 over the Mediterranean Sea is a fragment of the comet's nucleus

    NASA Astrophysics Data System (ADS)

    Churyumov, Klim; Kruchinenko, Vitaly G.; Churyumova, Tetyana; Mozgova, Alyona

    2015-03-01

    Today has been known for a considerable number of cases, the explosion of large meteoroids in Earth's atmosphere. This is confirmed by the data of registrations of fireballs by devices and the results of measurements in the atmosphere of bright light flashes by photodiodes Corporation ``Sandia Laboratories", which were installed on geostationary satellites of the United States, and also by data of measurements of acoustic-gravitational waves from the thermal explosions of meteoroids [ReVelle D.O. Historical detection of atmospheric impacts by large bolides using acoustic-gravity waves, Near-Earth Objects, Ed. Remo J. Annals of the New York Academy of Sciences 882, 284-302, 1997]. The work [Brown P., Spalding R.E., ReVelle D.O. et al. The flux of small near-Earth objects colliding with the Earth, Nature 420, 314-316, 2002.] shows the results of processing the observations of flashes of large meteoroids in Earth's atmosphere, obtained with the help of geostationary satellites of the United States. Over 8.5 years (from February 1994 to September 2002) 300 such events were registered. On July 6, 2002 r over the Mediterranean Sea a bright fireball was registered. The energy of the meteoroid explosion that caused the phenomenon of the car, was 26 kilotons of TNT [Brown et al., 2002]. We believe that this energy refers to the height of the full bracking of the meteoroid. At a speed of 20.3 km/s adopted by the authors, body mass at this height is 5 × 108 g, and when entering the Earth's atmosphere, it was about 7 × 108 g. Based on the obtained values of the mass, we conclude that the exploded meteoroid, causing a phenomenon of the fireball was a fragment of the comet nucleus. In processing the density of the body were taken 1 g/cm 3 and the initial velocity (~30 km/s).

  11. The activity and size of the nucleus of comet Hale-Bopp (C/1995 O1) [see comment].

    PubMed

    Weaver, H A; Feldman, P D; A'Hearn, M F; Arpigny, C; Brandt, J C; Festou, M C; Haken, M; McPhate, J B; Stern, S A; Tozzi, G P

    1997-03-28

    Analysis of Hubble Space Telescope (HST) images of comet Hale-Bopp (C/1995 O1) suggests that the effective diameter of the nucleus is between 27 to 42 kilometers, which is at least three times larger than that of comet P/Halley. The International Ultraviolet Explorer and HST spectra showed emissions from OH (a tracer of H2O) and CS (a tracer of CS2) starting in April 1996, and from the CO Cameron system (which primarily traces CO2) starting in June 1996. The variation of the H2O production rate with heliocentric distance was consistent with sublimation of an icy body near its subsolar point. The heliocentric variation in the production rates of CS2 and dust was different from that of H2O, which implies that H2O sublimation did not control the CS2 or dust production during these observations. PMID:9072959

  12. Study of sampling systems for comets and Mars

    NASA Technical Reports Server (NTRS)

    Amundsen, R. J.; Clark, B. C.

    1987-01-01

    Several aspects of the techniques that can be applied to acquisition and preservation of samples from Mars and a cometary nucleus were examined. Scientific approaches to sampling, grounded in proven engineering methods are the key to achieving the maximum science value from the sample return mission. If development of these approaches for collecting and preserving does not preceed mission definition, it is likely that only suboptimal techniques will be available because of the constraints of formal schedule timelines and the normal pressure to select only the most conservative and least sophisticated approaches when development has lagged the mission milestones. With a reasonable investment now, before the final mission definition, the sampling approach can become highly developed, ready for implementation, and mature enough to help set the requirements for the mission hardware and its performance.

  13. Modeling and Simulation of a Tethered Harpoon for Comet Sampling

    NASA Technical Reports Server (NTRS)

    Quadrelli, Marco B.

    2014-01-01

    This paper describes the development of a dynamic model and simulation results of a tethered harpoon for comet sampling. This model and simulation was done in order to carry out an initial sensitivity analysis for key design parameters of the tethered system. The harpoon would contain a canister which would collect a sample of soil from a cometary surface. Both a spring ejected canister and a tethered canister are considered. To arrive in close proximity of the spacecraft at the end of its trajectory so it could be captured, the free-flying canister would need to be ejected at the right time and with the proper impulse, while the tethered canister must be recovered by properly retrieving the tether at a rate that would avoid an excessive amplitude of oscillatory behavior during the retrieval. The paper describes the model of the tether dynamics and harpoon penetration physics. The simulations indicate that, without the tether, the canister would still reach the spacecraft for collection, that the tether retrieval of the canister would be achievable with reasonable fuel consumption, and that the canister amplitude upon retrieval would be insensitive to variations in vertical velocity dispersion.

  14. Deep Space 1 photometry of the nucleus of Comet P/19 Borrelly

    NASA Technical Reports Server (NTRS)

    Buratti, B. J.; Britt, D.; Oberst, J.; Soderblom, L. A.; Hillier, J. K.; Hicks, M. D.

    2002-01-01

    The NASA-JPL Deep Space 1 Mission (DS1) encountered the short-period Jupiter-family comet 19/P Borrelly on September 22, 2001, about 8 days after perihelion. DS1's payload contained a remote-sensing package that included a 1024 square CCD and a near IR spectrometer with 12nm resolution. Prior to its closest approach, the remote-sensing package on the spacecraft obtained 25 CCD images of the comet and 45 near-IR spectra.

  15. Parametric Dielectric Model Of Comet 67p/churyumov-gerasimenko: Implications On Sounding Cometary Nucleus Using Radar Tomography

    NASA Astrophysics Data System (ADS)

    Kataria, Tiffany; Heggy, E.; Clifford, S. M.; Lasue, J.; Kofman, W.

    2008-09-01

    The Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) onboard the ROSETTA mission will probe the nucleus of comet 67P/Churyumov-Gerasimenko in 2014. The variations in signal attenuations to be observed in the 90 MHz-radar tomographies is expected to depend mainly on the three-dimensional variations of the dielectrical properties of the cometary material as a function of porosity, temperature, and mineralogical composition. To explore the parametric space associated with the variations of these parameters and their impacts on the observed dielectrical properties inverted from the CONSERT data, we use the current state of knowledge from the observations made by Tempel-1 and Hayabusa to develop parametric dielectric models of possible internal structures of 67P/C-G. The first model reflects the layered-pile structure proposed by Belton et al. (2007), and the second reflects the rubble-pile model proposed by Weissman et al. (1986). The relative complex dielectric permittivities assigned to each dielectric model are based on laboratory measurements of chondrite dust/water ice mixtures, and are varied as a function of dust fraction, porosity and temperature. For the layered pile model, where porosity is assumed constant at the level of 70% and temperature 20m below the surface is 40 K, the dielectric constant varies mainly as a function of dust fraction, ranging between 4.386-i0.0121 in the pure surface dust mantle to 2.081-i0.000182 in one of the inner ice-rich layers. The modeled dielectric permittivities are consistent with the expected deep penetration of the CONSERT wave through the nucleus. Preliminary results suggest that the changes in the physical properties of the nucleus induce substantial variation in the dielectric properties of cometary material that can be identified in the radar tomography.

  16. Global and Spatially Resolved Photometric Properties of the Nucleus of Comet 67P/C-G from OSIRIS Images

    NASA Astrophysics Data System (ADS)

    Lamy, P.

    2014-04-01

    Following the successful wake-up of the ROSETTA spacecraft on 20 January 2014, the OSIRIS imaging system was fully re-commissioned at the end of March 2014 confirming its initial excellent performances. The OSIRIS instrument includes two cameras: the Narrow Angle Camera (NAC) and the Wide Angle Camera (WAC) with respective fieldsofview of 2.2° and 12°, both equipped with 2K by 2K CCD detectors and dual filter wheels. The NAC filters allow a spectral coverage of 270 to 990 nm tailored to the investigation of the mineralogical composition of the nucleus of comet P/Churyumov- Gerasimenko whereas those of the WAC (245-632 nm) aim at characterizing its coma [1]. The NAC has already secured a set of four complete light curves of the nucleus of 67P/C-G between 3 March and 24 April 2014 with a primary purpose of characterizing its rotational state. A preliminary spin period of 12.4 hours has been obtained, similar to its very first determination from a light curve obtained in 2003 with the Hubble space telescope [2]. The NAC and WAC will be recalibrated in the forthcoming weeks using the same stellar calibrators VEGA and the solar analog 16 Cyg B as for past inflight calibration campaigns in support of the flybys of asteroids Steins and Lutetia. This will allow comparing the pre- and post-hibernation performances of the cameras and correct the quantum efficiency response of the two CCD and the throughput for all channels (i.e., filters) if required. The accurate photometric analysis of the images requires utmost care due to several instrumental problems, the most severe and complex to handle being the presence of optical ghosts which result from multiple reflections on the two filters inserted in the optical beam and on the thick window which protects the CCD detector from cosmic ray impacts. These ghosts prominently appear as either slightly defocused images offset from the primary images or large round or elliptical halos. We will first present results on the global

  17. VIRTIS-Rosetta observations of the nucleus of 67P/Churyumov-Gerasimenko during the Comet Characterisation phase (July-August 2014)

    NASA Astrophysics Data System (ADS)

    Capaccioni, Fabrizio; Filacchione, Gianrico; Erard, Stephane; Arnold, Gabriele; Capria, Maria Teresa; De Sanctis, Maria Cristina; Bockelee-Morvan, Dominique; Tosi, Federico; Leyrat, Cedric; Tozzi, Gian Paolo; Drossart, Pierre; Ciarniello, Mauro; Raponi, Andrea; Piccioni, Giuseppe; Formisano, Michelangelo; Schmitt, Bernard; Migliorini, Alessandra; Longobardo, Andrea; Palomba, Ernesto; Kuehrt, Ekkehard; Flamini, Enrico

    2014-11-01

    The paper will describe the major results obtained during the comet nucleus characterization phase, July-August 2014, of the Rosetta Mission by the instrument VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer), the dual channel spectrometer onboard Rosetta. The nucleus observations in this phase were performed in a wide range of illumination conditions and with spatial sampling varying from the initial 500m down to 20m. VIRTIS covers the spectral range from 0.25 to 5micron with a mapping channel (VIRTIS-M) and the range 2-5micron with a High Spectral Resolution channel (VIRTIS-H). Both channels have been used to generate maps correlated to various properties (temperature, albedo, composition) of the illuminated areas. Special emphasis was placed on mapping those surface regions considered reachable areas for the Philae Lander descent, and to those area in the “neck” of the nucleus which from the very early Osiris observations did show hints of surface outgassing activity. Authors acknowledge the support from national funding agencies, ASI, DLR and CNES.

  18. Suprathermal electrons near the nucleus of comet 67P/Churyumov-Gerasimenko at 3 AU: Model comparisons with Rosetta data

    NASA Astrophysics Data System (ADS)

    Madanian, H.; Cravens, T. E.; Rahmati, A.; Goldstein, R.; Burch, J.; Eriksson, A. I.; Edberg, N. J. T.; Henri, P.; Mandt, K.; Clark, G.; Rubin, M.; Broiles, T.; Reedy, N. L.

    2016-06-01

    Observations of the coma near the nucleus of comet 67P/Churyumov-Gerasimenko (67P) made by the IES (Ion and Electron Sensor) instrument onboard the Rosetta Orbiter during late 2014 showed that electron fluxes greatly exceeded solar wind electron fluxes. The IES is part of the Rosetta Plasma Consortium. This paper reports on electron energy spectra measured by IES near the nucleus as well as approximate densities and average energies for the suprathermal electrons when the comet was at a heliocentric distance of about 3 AU. Comparisons are made with electron densities measured by other instruments. The high electron densities observed (e.g., ne ≈ 10-100 cm-3) must be associated with the cometary ion density enhancement created mainly by the photoionization of cometary gas by solar radiation; there are other processes that also contribute. Quasineutrality requires that the electron and ion densities be the same, and under certain conditions an ambipolar electric field is required to achieve quasi-neutrality. We present the results of a test particle model of cometary ion pickup by the solar wind and a two-stream electron transport code and use these results to interpret the IES data. We also estimate the effects on the electron spectrum of a compression of the electron fluid parcel. The electrons detected by IES can have energies as high as about 100-200 eV near the comet on some occasions, in which case the hot electrons can significantly enhance ionization rates of neutrals via impact ionization.

  19. Shape, Density, and Geology of the Nucleus of Comet 103P/Hartley 2

    NASA Technical Reports Server (NTRS)

    Thomas, P.C.; A'hearn, Michael F.; Veverka, Joseph; Belton, Michael J. S.; Kissel, Jochen; Belton, Michael J. S.; Klaasen, Kenneth P.; McFadden, Lucy A.; Melosh, H. Jay; Schultz, Peter H.; Besse, Sebastien; Carcich, Brian T.; Farnham, Tony L.; Groussin, Olivier; Hermalyn, Brendan; Li, Jian-Yang; Lindler, Don J.; Lisse, Carey M.; Meech, Karen; Richardson, James E.

    2013-01-01

    Data from the Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) mission show Comet 103P/Hartley 2 is a bi-lobed, elongated, nearly axially symmetric comet 2.33 km in length. Surface features are primarily small mounds <40 m across, irregularly-shaped smooth areas on the two lobes, and a smooth but variegated region forming a “waist” between the two lobes. Assuming parts of the comet body approach the shape of an equipotential surface, the mean density of Hartley 2 is modeled to be 200–400 kg /cubic m.. Such a mean density suggests mass loss per orbit of >1%. The shape may be the evolutionary product of insolation, sublimation, and temporary deposition of materials controlled by the object’s complex rotation.

  20. Ion trap mass spectrometry on a comet nucleus: the Ptolemy instrument and the Rosetta space mission.

    PubMed

    Todd, John F J; Barber, Simeon J; Wright, Ian P; Morgan, Geraint H; Morse, Andrew D; Sheridan, Simon; Leese, Mark R; Maynard, Jon; Evans, Suzanne T; Pillinger, Colin T; Drummond, Duncan L; Heys, Samantha C; Huq, S Ejaz; Kent, Barry J; Sawyer, Eric C; Whalley, Martin S; Waltham, Nicholas R

    2007-01-01

    In May 2014, the Rosetta spacecraft is scheduled to rendezvous with the comet Churyumov-Gerasimenko ('67P'). One of the instruments on board the 'Lander' which will descend on to the surface of the comet is a miniaturised GC/MS system that incorporates an ion trap mass spectrometer, specially developed for isotope ratio analysis. This article describes the development and optimisation of the ion trap for this unique application, and presents a summary of the range of pre-programmed experiments that will contribute to the characterisation of the solid and volatile cometary materials. PMID:17154436

  1. Curation and Analysis of Samples from Comet Wild-2 Returned by NASA's Stardust Mission

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, Keiko; Walker, Robert M.

    2015-01-01

    The NASA Stardust mission returned the first direct samples of a cometary coma from comet 81P/Wild-2 in 2006. Intact capture of samples encountered at 6 km/s was enabled by the use of aerogel, an ultralow dense silica polymer. Approximately 1000 particles were captured, with micron and submicron materials distributed along mm scale length tracks. This sample collection method and the fine scale of the samples posed new challenges to the curation and cosmochemistry communities. Sample curation involved extensive, detailed photo-documentation and delicate micro-surgery to remove particles without loss from the aerogel tracks. This work had to be performed in highly clean facility to minimize the potential of contamination. JSC Curation provided samples ranging from entire tracks to micrometer-sized particles to external investigators. From the analysis perspective, distinguishing cometary materials from aerogel and identifying the potential alteration from the capture process were essential. Here, transmission electron microscopy (TEM) proved to be the key technique that would make this possible. Based on TEM work by ourselves and others, a variety of surprising findings were reported, such as the observation of high temperature phases resembling those found in meteorites, rarely intact presolar grains and scarce organic grains and submicrometer silicates. An important lesson from this experience is that curation and analysis teams must work closely together to understand the requirements and challenges of each task. The Stardust Mission also has laid important foundation to future sample returns including OSIRIS-REx and Hayabusa II and future cometary nucleus sample return missions.

  2. VIRTIS/Rosetta Observes Comet 67P/Churyumov-Gerasimenko: Nucleus and Coma Derived Composition and Physical Properties.

    NASA Astrophysics Data System (ADS)

    Capaccioni, F.; Filacchione, G.; Erard, S.; Arnold, G.; De Sanctis, M. C.; Bockelée-Morvan, D.; Leyrat, C.; Tosi, F.; Ciarniello, M.; Raponi, A.; Migliorini, A.; Quirico, E.; Rinaldi, G.; Schmitt, B.; Carlson, R. W.; Combi, M. R.; Fink, U.; Tozzi, G. P.; Palomba, E.; Longobardo, A.; Formisano, M.; Debout, V.; Drossart, P.; Piccioni, G.; Fougere, N.

    2015-12-01

    The paper will describe the major results obtained throughout the nominal mission by the instrument VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer), the dual channel spectrometer onboard Rosetta, on the surface composition and thermal properties of the nucleus of comet 67P/Churyumov-Gerasimenko and on the 2D distribution of H2O and CO2 in the coma. VIRTIS is a dual channel spectrometer; VIRTIS-M (M for Mapper) is a hyper spectral imager covering a wide spectral range from 0.25 through 5μm. VIRTIS-M uses a slit and a scan mirror to generate images with spatial resolution of 250 μrad over a FOV of 3.7°. The second channel is VIRTIS-H (H for High-resolution), a point spectrometer with high spectral resolution (λ/Δλ=3000 @3μm) in the range 2-5 μm. The nucleus observations have been performed in a wide range of conditions with best spatial resolution of 2.5m. The surface temperature has been determined since the first distant observations when the nucleus filled one single VIRTIS-M pixel and continuously monitored since. Maximum temperature determined until April 2015 are as high as 300K at the subsolar point. Modeling of the thermophysical properties allowed to derive the thermal inertia of the crust. The VIRTIS composition analysis has showed evidence of carbon-bearing compounds on the nucleus of the comet 67P/Churyumov-Gerasimenko. The very low reflectance of the nucleus (normal albedo of 0.060 ± 0.003 at 0.55 μm), the spectral slopes in VIS and IR ranges (5-25 and 1.5-5 % kÅ-1) and the broad absorption feature in the 2.9-3.6 μm range present across the entire illuminated surface, are compatible with a surface crust made of a complex mixture of dark disordered poly-aromatic compounds, opaque minerals and several chemical species containing: -COOH, CH2 / CH3, -OH (in Alcohols) and possibly NH4+. Both channels are contributing to the determination of the spatial distribution of H2O and CO2 in the coma; their abundances as a function of altitude

  3. The Nucleus and Coma of Comet 67P/C-G at Millimeter and Submillimeter Wavelengths as seen by MIRO

    NASA Astrophysics Data System (ADS)

    Hofstadter, M. D.; Gulkis, S.; Allen, M.; Von Allmen, P.; Beaudin, G.; Biver, N.; Bockelée-Morvan, D.; Choukroun, M.; Crovisier, J.; Encrenaz, P.; Encrenaz, T.; Frerking, M. A.; Hartogh, P.; Ip, W. H.; Janssen, M. A.; Jarchow, C.; Keihm, S. J.; Lee, S.; Lellouch, E.; Leyrat, C.; Rezac, L.; Schloerb, F. P.; Spilker, T. R.

    2015-12-01

    The Microwave Instrument on the Rosetta Orbiter (MIRO) makes submillimeter- and millimeter-wavelength observations of Comet 67P/Churyumov-Gerasimenko. Broadband continuum measurements at wavelengths of 0.5 and 1.6 mm probe the thermal and dielectric properties of the nucleus subsurface. High-resolution spectroscopic measurements of 8 molecular lines in the submillimeter (H2O, H217O, H218O, CO, NH3, and three lines of CH3OH) constrain the abundance, velocity, and temperature of gases in the coma. These measurements allow MIRO to study the nucleus and coma as a coupled system. Using its two continuum channels, MIRO has mapped the thermal properties of the nucleus subsurface (depths from millimeters to tens of centimeters), and generally finds its properties to be consistent with very porous, dusty material. We see temperature variations due to diurnal and seasonal changes in insolation, and also see evidence for subsurface ice in some regions. This talk will provide an update on our observations of variations over time, variations with temperature, and variations in composition. We also will report on our attempts to detect the continuum thermal emission of dust in the coma. MIRO's spectroscopic observations have shown the abundance and velocity of gas as it comes off the nucleus to vary with time and location. The regions MIRO sees as particularly active are generally consistent with activity reported by other instruments. Moving away from the nucleus, MIRO is sensitive to the three-dimensional structure of the coma. We will present an update on our understanding of that structure, which is influenced by the shape of the nucleus, nucleus rotation, and processes acting within and on the coma. Our ultimate goal is to develop a coupled model of the nucleus and coma, tracing the processes by which solar heating of the surface drives sublimation of subsurface ice and generation of dust, and how gases and dust evolve in the coma. Part of this work was conducted at the Jet

  4. Studying comets with NEOWISE

    NASA Astrophysics Data System (ADS)

    Stevenson, R.; Bauer, J.; Kramer, E.; Fernández, Y.; Mainzer, A.; Grav, T.; Masiero, J.

    2014-07-01

    The Wide-Field Infrared Survey Explorer (WISE) mission detected more than 150 comets during its all-sky survey between January 2010 and February 2011. The comets were imaged at 4 infrared wavelengths (3.4, 4.6, 12, and 22 microns). The large sample of both long-period and Jupiter-family comets observed at a range of heliocentric distances allows for systematic comparison of the properties of both dynamical families. Nucleus diameters and albedos, dust comae temperatures, CO and CO_{2} emission rates, and dust tail and trail morphologies are some of the properties studied with the WISE data. This work is being continued by the reactivated NEOWISE mission [1]. In 2013, the WISE spacecraft was brought out of hibernation to resume discovering, tracking, and characterizing small bodies in the Solar System by imaging the sky at solar elongations of ˜90° at wavelengths of 3.4 and 4.6 microns. Since NEOWISE resumed its all-sky survey on December 23, 2013, 10 comets have been observed, including one previously-unknown long-period comet -- C/2014 C3 (NEOWISE). Of particular interest are the NEOWISE observations of comet C/2013 A1 (Siding Spring), which will have a close encounter with Mars in October 2014. NEOWISE observed this comet in January 2014 and will observe it twice more before the comet's close approach to Mars. NEOWISE will continue to operate until early 2017, greatly enhancing our understanding of cometary properties as studied in the infrared.

  5. Spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from the OSIRIS instrument onboard the ROSETTA spacecraft

    NASA Astrophysics Data System (ADS)

    Fornasier, S.; Hasselmann, P. H.; Barucci, M. A.; Feller, C.; Besse, S.; Leyrat, C.; Lara, L.; Gutierrez, P. J.; Oklay, N.; Tubiana, C.; Scholten, F.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; A'Hearn, M. F.; Bertaux, J.-L.; Bertini, I.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Fulle, M.; Groussin, O.; Güttler, C.; Hviid, S. F.; Ip, W.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, R.; Kührt, E.; Küppers, M.; La Forgia, F.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Matz, K.-D.; Michalik, H.; Moreno, F.; Mottola, S.; Naletto, G.; Pajola, M.; Pommerol, A.; Preusker, F.; Shi, X.; Snodgrass, C.; Thomas, N.; Vincent, J.-B.

    2015-11-01

    Context. The Rosetta mission of the European Space Agency has been orbiting the comet 67P/Churyumov-Gerasimenko (67P) since August 2014 and is now in its escort phase. A large complement of scientific experiments designed to complete the most detailed study of a comet ever attempted are onboard Rosetta. Aims: We present results for the photometric and spectrophotometric properties of the nucleus of 67P derived from the OSIRIS imaging system, which consists of a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC). The observations presented here were performed during July and the beginning of August 2014, during the approach phase, when OSIRIS was mapping the surface of the comet with several filters at different phase angles (1.3°-54°). The resolution reached up to 2.1 m/px. Methods: The OSIRIS images were processed with the OSIRIS standard pipeline, then converted into I/F radiance factors and corrected for the illumination conditions at each pixel using the Lommel-Seeliger disk law. Color cubes of the surface were produced by stacking registered and illumination-corrected images. Furthermore, photometric analysis was performed both on disk-averaged photometry in several filters and on disk-resolved images acquired with the NAC orange filter, centered at 649 nm, using Hapke modeling. Results: The disk-averaged phase function of the nucleus of 67P shows a strong opposition surge with a G parameter value of -0.13 ± 0.01 in the HG system formalism and an absolute magnitude Hv(1,1,0) = 15.74 ± 0.02 mag. The integrated spectrophotometry in 20 filters covering the 250-1000 nm wavelength range shows a red spectral behavior, without clear absorption bands except for a potential absorption centered at ~290 nm that is possibly due to SO2 ice. The nucleus shows strong phase reddening, with disk-averaged spectral slopes increasing from 11%/(100 nm) to 16%/(100 nm) in the 1.3°-54° phase angle range. The geometric albedo of the comet is 6.5 ± 0.2% at 649 nm, with

  6. The gas distribution of comet Halley and its relation to the nucleus rotation

    NASA Technical Reports Server (NTRS)

    Cochran, Anita L.; Trout, Anthony P.

    1994-01-01

    We used a set of spatially resolved spectra of comet Halley to explore whether the gas distribution profile could be inverted to yield information on the rotation of the comet. The data were obtained both pre- and post-perihelion. The pre-perihelion data showed reasonable symmetry and so were used to define the lifetimes against photodissociation of the various molecules. These lifetimes were then used to define the lifetimes against photodissociation of the various molecules. These lifetimes were then used along with a nonsteady-state vectorial model to fit the post-perihelion gas distribution profiles. The resulting molecular lightcurves are compared with the photometric lightcurves of Schlicher et al. (1990) to show that the rotational information is encoded in the observed gas distribution within the coma. The molecular lightcurves can differentiate between the preferred Schlicher et al. average period and the period they find for the same time interval as the spectra.

  7. Dynamic Acquisition and Retrieval Tool (DART) for Comet Sample Return : Session: 2.06.Robotic Mobility and Sample Acquisition Systems

    NASA Technical Reports Server (NTRS)

    Badescu, Mircea; Bonitz, Robert; Kulczycki, Erick; Aisen, Norman; Dandino, Charles M.; Cantrell, Brett S.; Gallagher, William; Shevin, Jesse; Ganino, Anthony; Haddad, Nicolas; Walkemeyer, Phillip; Backes, Paul; Shiraishi, Lori

    2013-01-01

    The 2011 Decadal Survey for planetary science released by the National Research Council of the National Academies identified Comet Surface Sample Return (CSSR) as one of five high priority potential New Frontiers-class missions in the next decade. The main objectives of the research described in this publication are: develop a concept for an end-to-end system for collecting and storing a comet sample to be returned to Earth; design, fabricate and test a prototype Dynamic Acquisition and Retrieval Tool (DART) capable of collecting 500 cc sample in a canister and eject the canister with a predetermined speed; identify a set of simulants with physical properties at room temperature that suitably match the physical properties of the comet surface as it would be sampled. We propose the use of a dart that would be launched from the spacecraft to impact and penetrate the comet surface. After collecting the sample, the sample canister would be ejected at a speed greater than the comet's escape velocity and captured by the spacecraft, packaged into a return capsule and returned to Earth. The dart would be composed of an inner tube or sample canister, an outer tube, a decelerator, a means of capturing and retaining the sample, and a mechanism to eject the canister with the sample for later rendezvous with the spacecraft. One of the significant unknowns is the physical properties of the comet surface. Based on new findings from the recent Deep Impact comet encounter mission, we have limited our search of solutions for sampling materials to materials with 10 to 100 kPa shear strength in loose or consolidated form. As the possible range of values for the comet surface temperature is also significantly different than room temperature and testing at conditions other than the room temperature can become resource intensive, we sought sample simulants with physical properties at room temperature similar to the expected physical properties of the comet surface material. The chosen

  8. Carbon in comet dust

    NASA Technical Reports Server (NTRS)

    Brownlee, D. E.

    1990-01-01

    The association of Halley particle results with data from existing meteoritic materials that can be analyzed in the laboratory is discussed. Comet samples must exist in present collections of meteoritic materials and the Halley results provide clues for identifying them. Although it is not presently possible to positively identify cometary meteorites or cometary interplanetary dust (IDP) samples, it is possible to determine which materials are similar to Halley dust and which ones are distinctly unlike Halley. The properties of these existing Halley-compatible samples provide insight into the possible properties of cometary material. Positive identification of meteoritic comet samples or direct samples returned from a comet nucleus would of course revolutionize our ability to study carbonaceous matter in comets. Modern analytical techniques are very powerful and it is possible to perform elemental, chemical, mineralogical and even limited isotopic analysis on micron-size particles. There is an important synergism between the laboratory studies of collected samples and astronomical data from comets and interstellar grains. To fully interpret results there must be convincing methods for associating a particular class or classes of meteoritic material with comets. Ultimately this will be done by direct comet sample return such as the Rosetta mission under development by ESA. At the present time the only links that can be made involve comparison with sample properties and measurable properties of comets. Unfortunately there is at present no known unique property of cometary dust that allows its absolute identification in the laboratory. The results from Halley encounters and observation do provide much new information on cometary grains. The Halley grain compositions, density, size distribution and scattering properties all provide a basis for future investigations. Other Halley properties such as the presence of polyoxymethylene and the 3.4um emission feature could

  9. Cometary science. On the nucleus structure and activity of comet 67P/Churyumov-Gerasimenko.

    PubMed

    Sierks, Holger; Barbieri, Cesare; Lamy, Philippe L; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica; A'Hearn, Michael F; Angrilli, Francesco; Auger, Anne-Therese; Barucci, M Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis; Capanna, Claire; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Giacomini, Lorenza; Groussin, Olivier; Gutierrez-Marques, Pablo; Gutiérrez, Pedro J; Güttler, Carsten; Hoekzema, Nick; Hviid, Stubbe F; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kovacs, Gabor; Kramm, J Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M; Lazzarin, Monica; Leyrat, Cédric; Lopez Moreno, Josè J; Magrin, Sara; Marchi, Simone; Marzari, Francesco; Massironi, Matteo; Michalik, Harald; Moissl, Richard; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Pajola, Maurizio; Pertile, Marco; Preusker, Frank; Sabau, Lola; Scholten, Frank; Snodgrass, Colin; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste; Wenzel, Klaus-Peter; Zaccariotto, Mirco; Pätzold, Martin

    2015-01-23

    Images from the OSIRIS scientific imaging system onboard Rosetta show that the nucleus of 67P/Churyumov-Gerasimenko consists of two lobes connected by a short neck. The nucleus has a bulk density less than half that of water. Activity at a distance from the Sun of >3 astronomical units is predominantly from the neck, where jets have been seen consistently. The nucleus rotates about the principal axis of momentum. The surface morphology suggests that the removal of larger volumes of material, possibly via explosive release of subsurface pressure or via creation of overhangs by sublimation, may be a major mass loss process. The shape raises the question of whether the two lobes represent a contact binary formed 4.5 billion years ago, or a single body where a gap has evolved via mass loss. PMID:25613897

  10. On the nucleus structure and activity of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Sierks, Holger; Barbieri, Cesare; Lamy, Philippe L.; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; Agarwal, Jessica; A'Hearn, Michael F.; Angrilli, Francesco; Auger, Anne-Therese; Barucci, M. Antonella; Bertaux, Jean-Loup; Bertini, Ivano; Besse, Sebastien; Bodewits, Dennis; Capanna, Claire; Cremonese, Gabriele; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Ferri, Francesca; Fornasier, Sonia; Fulle, Marco; Gaskell, Robert; Giacomini, Lorenza; Groussin, Olivier; Gutierrez-Marques, Pablo; Gutiérrez, Pedro J.; Güttler, Carsten; Hoekzema, Nick; Hviid, Stubbe F.; Ip, Wing-Huen; Jorda, Laurent; Knollenberg, Jörg; Kovacs, Gabor; Kramm, J. Rainer; Kührt, Ekkehard; Küppers, Michael; La Forgia, Fiorangela; Lara, Luisa M.; Lazzarin, Monica; Leyrat, Cédric; Lopez Moreno, Josè J.; Magrin, Sara; Marchi, Simone; Marzari, Francesco; Massironi, Matteo; Michalik, Harald; Moissl, Richard; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Pajola, Maurizio; Pertile, Marco; Preusker, Frank; Sabau, Lola; Scholten, Frank; Snodgrass, Colin; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste; Wenzel, Klaus-Peter; Zaccariotto, Mirco; Pätzold, Martin

    2015-01-01

    Images from the OSIRIS scientific imaging system onboard Rosetta show that the nucleus of 67P/Churyumov-Gerasimenko consists of two lobes connected by a short neck. The nucleus has a bulk density less than half that of water. Activity at a distance from the Sun of >3 astronomical units is predominantly from the neck, where jets have been seen consistently. The nucleus rotates about the principal axis of momentum. The surface morphology suggests that the removal of larger volumes of material, possibly via explosive release of subsurface pressure or via creation of overhangs by sublimation, may be a major mass loss process. The shape raises the question of whether the two lobes represent a contact binary formed 4.5 billion years ago, or a single body where a gap has evolved via mass loss.

  11. Gravitational slopes, geomorphology, and material strengths of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations

    NASA Astrophysics Data System (ADS)

    Groussin, O.; Jorda, L.; Auger, A.-T.; Kührt, E.; Gaskell, R.; Capanna, C.; Scholten, F.; Preusker, F.; Lamy, P.; Hviid, S.; Knollenberg, J.; Keller, U.; Huettig, C.; Sierks, H.; Barbieri, C.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Agarwal, J.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Gutiérrez, P. J.; Güttler, C.; Ip, W.-H.; Kramm, J.-R.; Küppers, M.; Lazzarin, M.; Lara, L. M.; Lopez Moreno, J. J.; Marchi, S.; Marzari, F.; Massironi, M.; Michalik, H.; Naletto, G.; Oklay, N.; Pommerol, A.; Pajola, M.; Thomas, N.; Toth, I.; Tubiana, C.; Vincent, J.-B.

    2015-11-01

    Aims: We study the link between gravitational slopes and the surface morphology on the nucleus of comet 67P/Churyumov-Gerasimenko and provide constraints on the mechanical properties of the cometary material (tensile, shear, and compressive strengths). Methods: We computed the gravitational slopes for five regions on the nucleus that are representative of the different morphologies observed on the surface (Imhotep, Ash, Seth, Hathor, and Agilkia), using two shape models computed from OSIRIS images by the stereo-photoclinometry (SPC) and stereo-photogrammetry (SPG) techniques. We estimated the tensile, shear, and compressive strengths using different surface morphologies (overhangs, collapsed structures, boulders, cliffs, and Philae's footprint) and mechanical considerations. Results: The different regions show a similar general pattern in terms of the relation between gravitational slopes and terrain morphology: i) low-slope terrains (0-20°) are covered by a fine material and contain a few large (>10 m) and isolated boulders; ii) intermediate-slope terrains (20-45°) are mainly fallen consolidated materials and debris fields, with numerous intermediate-size boulders from <1 m to 10 m for the majority of them; and iii) high-slope terrains (45-90°) are cliffs that expose a consolidated material and do not show boulders or fine materials. The best range for the tensile strength of overhangs is 3-15 Pa (upper limit of 150 Pa), 4-30 Pa for the shear strength of fine surface materials and boulders, and 30-150 Pa for the compressive strength of overhangs (upper limit of 1500 Pa). The strength-to-gravity ratio is similar for 67P and weak rocks on Earth. As a result of the low compressive strength, the interior of the nucleus may have been compressed sufficiently to initiate diagenesis, which could have contributed to the formation of layers. Our value for the tensile strength is comparable to that of dust aggregates formed by gravitational instability and tends to favor

  12. 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.

  13. Analysis of the Touch-And-Go Surface Sampling Concept for Comet Sample Return Missions

    NASA Technical Reports Server (NTRS)

    Mandic, Milan; Acikmese, Behcet; Bayard, David S.; Blackmore, Lars

    2012-01-01

    This paper studies the Touch-and-Go (TAG) concept for enabling a spacecraft to take a sample from the surface of a small primitive body, such as an asteroid or comet. The idea behind the TAG concept is to let the spacecraft descend to the surface, make contact with the surface for several seconds, and then ascend to a safe location. Sampling would be accomplished by an end-effector that is active during the few seconds of surface contact. The TAG event is one of the most critical events in a primitive body sample-return mission. The purpose of this study is to evaluate the dynamic behavior of a representative spacecraft during the TAG event, i.e., immediately prior, during, and after surface contact of the sampler. The study evaluates the sample-collection performance of the proposed sampling end-effector, in this case a brushwheel sampler, while acquiring material from the surface during the contact. A main result of the study is a guidance and control (G&C) validation of the overall TAG concept, in addition to specific contributions to demonstrating the effectiveness of using nonlinear clutch mechanisms in the sampling arm joints, and increasing the length of the sampling arms to improve robustness.

  14. Infrared Spectroscopy of Comet Wild-2 Samples Returned by the Stardust Mission.

    NASA Astrophysics Data System (ADS)

    Keller, L.; Bajt, S.; Borg, J.; Brucato, J.; Colangeli, L.; D'Hendecourt, L.; Djouadi, Z.; Flynn, G.; Grossemy, F.; Matrajt, G.; Mennella, V.; Palumbo, M.; Rotundi, A.; Wooden, D.

    2006-12-01

    Comets are widely believed to be repositories of the building blocks of the solar system that include both presolar and early nebular matter. The nature of these organic and inorganic materials in comets is inferred through the analysis and interpretation of features in their infrared (IR) spectra, especially the mid- and far-IR parts of the spectrum where organic materials and minerals have diagnostic bands. With bonafide samples of a specific comet now returned by the Stardust mission, their detailed analysis provides a direct test of current hypotheses regarding the chemical and mineralogical composition of comets based largely on astronomical measurements, comet encounter missions and laboratory analyses of cometary IDPs. Indigenous organic matter from Comet Wild-2 was collected by the Stardust mission and survived capture. It is associated with discrete particles and as finely disseminated material within impact cavities in the aerogel collection medium. Fourier transform infrared (FTIR) measurements of extracted particles and in situ measurements from individual impact tracks show absorption features in the C-H stretching region that are consistent with long chain aliphatic hydrocarbons. Extracted terminal particles and some of the particles from the base of the impact cavity also show sharp features in mid- and far-IR spectra consistent with crystalline silicates, including enstatite, olivine and diopside. Amorphous silicates are also a major component of comet Wild-2 samples. Indeed, despite complications due to overlap with the aerogel Si-O feature, the majority of Wild-2 particles analyzed to date with IR spectroscopy are dominated by amorphous silicates, although the thermal effects of the particle collection are still being assessed. No FTIR evidence for hydrated silicates or carbonates has been observed to date in any of the extracted particles. The presence of the crystalline silicates in the Wild-2 samples indicates that it is not an assemblage of

  15. Editorial of the special issue - "Rosetta and Philae at comet 67P/Churyumov-Gerasimenko"

    NASA Astrophysics Data System (ADS)

    Ulamec, Stephan; Taylor, Matthew G. G. T.

    2016-08-01

    Giotto, the first european/ESA - interplanetary space probe had not flown by Halley's comet, yet, when the first plans for the next mission to investigate a comet were being made. back in 1984, Rosetta became part of ESAs horizon 2000 programme, originally envisioned as a comet nucleus sample return mission.

  16. Hot OH and CN: Evidence for organic molecules close to the nucleus of comet Halley

    NASA Astrophysics Data System (ADS)

    Clairemidi, J.; Moreels, G.

    1989-12-01

    During the encounter session of Vega 2 with comet Halley on 6 Mar. 1986, advantage was taken of the approach motion and of the resulting zoom effect to assemble the monochromatic charts produced by a three channel spectrometer in composite images at selected wavelengths. Two jets are clearly apparent in most of the monochromatic images. The OH and CN emission originating from the jets exhibit a pronounced peculiarity. The bands located at 309 and 388 nm show an excess of emission at 305 and 383 nm. The proposed mechanism, specific to the jets, is the photodissociation of one or several organic molecules of the type A-OH or B-CN which would release hot OH and CN when submitted to the solar UV flux. These organic molecules would be a component of the envelope of the CHON submicronic grains dragged by the gaseous jets. They provide an additional argument in favor of the similarity between cometary and interstellar matter.

  17. Twentieth century light curves and the nucleus of comet P/Tempel 2

    NASA Technical Reports Server (NTRS)

    Rickman, Hans; Festou, Michel C.; Tancredi, Gonzalo; Kamel, L.

    1992-01-01

    Observations of P/Tempel 2 from 1899 to 1988 corresponding to 13 apparitions are analyzed in order to estimate the perihelion asymmetry of the gas production curve for different periods of its evolution. Using the correlation found by Festou et al. (1990) between the perihelion asymmetries and the delay in perihelion passage due to the action of nongravitational forces, we estimate the mass of the comet to be M approximately equals 1.6 plus or minus 0.5 x 10(exp 14) kg. Assuming a volume of 500 cu km, based on nuclear observations, a density of 0.3 plus or minus 0.1 g/cu cm is obtained.

  18. COMETARY SCIENCE. The nonmagnetic nucleus of comet 67P/Churyumov-Gerasimenko.

    PubMed

    Auster, Hans-Ulrich; Apathy, Istvan; Berghofer, Gerhard; Fornacon, Karl-Heinz; Remizov, Anatoli; Carr, Chris; Güttler, Carsten; Haerendel, Gerhard; Heinisch, Philip; Hercik, David; Hilchenbach, Martin; Kührt, Ekkehard; Magnes, Werner; Motschmann, Uwe; Richter, Ingo; Russell, Christopher T; Przyklenk, Anita; Schwingenschuh, Konrad; Sierks, Holger; Glassmeier, Karl-Heinz

    2015-07-31

    Knowledge of the magnetization of planetary bodies constrains their origin and evolution, as well as the conditions in the solar nebular at that time. On the basis of magnetic field measurements during the descent and subsequent multiple touchdown of the Rosetta lander Philae on the comet 67P/Churyumov-Gerasimenko (67P), we show that no global magnetic field was detected within the limitations of analysis. The Rosetta Magnetometer and Plasma Monitor (ROMAP) suite of sensors measured an upper magnetic field magnitude of less than 2 nanotesla at the cometary surface at multiple locations, with the upper specific magnetic moment being <3.1 × 10(-5) ampere-square meters per kilogram for meter-size homogeneous magnetized boulders. The maximum dipole moment of 67P is 1.6 × 10(8) ampere-square meters. We conclude that on the meter scale, magnetic alignment in the preplanetary nebula is of minor importance. PMID:25873744

  19. The 67P/Churyumov-Gerasimenko comet: colors, albedo variations and inhomogeneity of the nucleus from the ROSETTA/OSIRIS images

    NASA Astrophysics Data System (ADS)

    Fornasier, S.; Leyrat, C.; Barucci, M. A.; Hasselmann, P. H.; Thomas, N.; Kueppers, M.; Sierks, H.; Oklay, N.; Snodgrass, C.; Tubiana, C.; Vincent, J. B.; Jorda, L.; Keller, H. U.; Hviik, S.; Magrin, S.; Massironi, M.; Besse, S.; Pajola, M.

    2014-04-01

    Rosetta is the cornerstone mission of the European Space Agency devoted to the study of the minor bodies. Launched on 2 March 2004, Rosetta has as primary target the comet 67P/Churyumov-Gerasimenko, a short period comet of the Jupiter's family. On its journey to the comet, after three Earth and one Mars gravity assist manoeuvres, Rosetta flew by two selected asteroids, 2867 Steins, in September 2008, and 21 Lutetia in July 2010. In June 2011, Rosetta was placed in hibernation for 31 months to save its power resources, and it was successfully reactivated on January 2014, before the rendez-vous maneuver to the comet at 4 AU from the Sun. The spacecraft will orbit and perform long-term exploration of the cometary nucleus and coma, including its innermost part, for more than 1 year and a half, following the comet up to its perihelion at 1.37 AU and shortly after it. A large complement of scientific experiments designed to complete the most detailed study of a comet ever attempted are on board Rosetta, including imaging cameras, spectrometers, dust analysers, radio science experiment, and the Philae lander that will land on the nucleus in November 2014. In this work we will present the results on the 67P nucleus physical-chemical properties derived from the OSIRIS images acquired during the comet approach phase and the first bound orbits in July-August 2014. OSIRIS is constituted of aWide Angle Camera (WAC) and a Narrow Angle Camera (NAC) [1]. The NAC camera will obtain high resolution images with different filters in the near UV-near IR range. Those filters are optimised for the mineralogical studies of the nucleus. The WAC camera has a wide field of view (12×12 degrees) and narrow band filters devoted to the study of the gaseous species of the coma. In the July-August 2014 timeframe, OSIRIS will map the entire surface of the comet with several filters in the 250-1000 nm range, at different phase angles (5- 50 degrees), and with a resolution up to 1 m/px with the NAC

  20. GIADA: shining a light on the monitoring of the comet dust production from the nucleus of 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Della Corte, V.; Rotundi, A.; Fulle, M.; Gruen, E.; Weissman, P.; Sordini, R.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Accolla, M.; Zakharov, V.; Mazzotta Epifani, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Colangeli, L.; Palumbo, P.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Green, S. F.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. M.; Rietmeijer, F. J. M.; Rodrigo, R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jeronimo, J. M.; Leese, M. R.; Lopez-Jimenez, A. C.; Altobelli, N.

    2015-11-01

    Context. During the period between 15 September 2014 and 4 February 2015, the Rosetta spacecraft accomplished the circular orbit phase around the nucleus of comet 67P/Churyumov-Gerasimenko (67P). The Grain Impact Analyzer and Dust Accumulator (GIADA) onboard Rosetta monitored the 67P coma dust environment for the entire period. Aims: We aim to describe the dust spatial distribution in the coma of comet 67P by means of in situ measurements. We determine dynamical and physical properties of cometary dust particles to support the study of the production process and dust environment modification. Methods: We analyzed GIADA data with respect to the observation geometry and heliocentric distance to describe the coma dust spatial distribution of 67P, to monitor its activity, and to retrieve information on active areas present on its nucleus. We combined GIADA detection information with calibration activity to distinguish different types of particles that populate the coma of 67P: compact particles and fluffy porous aggregates. By means of particle dynamical parameters measured by GIADA, we studied the dust acceleration region. Results: GIADA was able to distinguish different types of particles populating the coma of 67P: compact particles and fluffy porous aggregates. Most of the compact particle detections occurred at latitudes and longitudes where the spacecraft was in view of the comet's neck region of the nucleus, the so-called Hapi region. This resulted in an oscillation of the compact particle abundance with respect to the spacecraft position and a global increase as the comet moved from 3.36 to 2.43 AU heliocentric distance. The speed of these particles, having masses from 10-10 to 10-7 kg, ranged from 0.3 to 12.2 m s-1. The variation of particle mass and speed distribution with respect to the distance from the nucleus gave indications of the dust acceleration region. The influence of solar radiation pressure on micron and submicron particles was studied. The

  1. Physical Properties of the Nucleus of Comet 28P/Neujmin 1

    NASA Astrophysics Data System (ADS)

    Mueller, B. E. A.; Heinrichs, A. M.; Samarasinha, N. H.

    2002-09-01

    Comet 28P/Neujmin 1 was observed in April 2002 for 4 consecutive nights at the CTIO 1.5m telescope in the broadband V, R, and I filters. The rotational lightcurve observations in R yield a preliminary rotation period of 12.7+/- 0.1 hours, in excellent agreement with determinations from Delahodde et al. (2001) and Jewitt and Meech (1988). Our observations in R cover 80% of the rotational phase for a double peaked lightcurve. The peak to peak variation in the lightcurve is 0.56 mag, giving a lower limit of the nuclear axial ratio a/b of 1.7. Our V and I observations partially cover a rotational phase and show no evidence of a variation in the V-R or R-I colors. Colors and an effective radius will also be determined. Our lightcurve analysis will be put into context with all previous data. For this purpose we will apply model simulations and will present the results at the meeting. This work was supported by a grant from the NASA Planetary Astronomy Program. AMH acknowledges funds from the NSF Research Experience for Undergraduates (REU) Program. References: Delahodde, Meech, Hainaut, & Dotto 1981. A&A 376, 672 Jewitt & Meech 1988. Ap.J. 328, 974

  2. Measurements of the near-nucleus coma of comet 67P/Churyumov-Gerasimenko with the Alice far-ultraviolet spectrograph on Rosetta

    NASA Astrophysics Data System (ADS)

    Feldman, Paul D.; A'Hearn, Michael F.; Bertaux, Jean-Loup; Feaga, Lori M.; Parker, Joel Wm.; Schindhelm, Eric; Steffl, Andrew J.; Stern, S. Alan; Weaver, Harold A.; Sierks, Holger; Vincent, Jean-Baptiste

    2015-11-01

    Aims: The Alice far-ultraviolet spectrograph onboard Rosetta is designed to observe emissions from various atomic and molecular species from within the coma of comet 67P/ Churyumov-Gerasimenko and to determine their spatial distribution and evolution with time and heliocentric distance. Methods: Following orbit insertion in August 2014, Alice made observations of the inner coma above the limbs of the nucleus of the comet from cometocentric distances varying between 10 and 80 km. Depending on the position and orientation of the slit relative to the nucleus, emissions of atomic hydrogen and oxygen were initially detected. These emissions are spatially localized close to the nucleus and spatially variable with a strong enhancement above the comet's neck at northern latitudes. Weaker emission from atomic carbon and CO were subsequently detected. Results: Analysis of the relative line intensities suggests photoelectron impact dissociation of H2O vapor as the source of the observed H i and O i emissions. The electrons are produced by photoionization of H2O. The observed C i emissions are also attributed to electron impact dissociation, of CO2, and their relative brightness to H i reflects the variation of CO2 to H2O column abundance in the coma.

  3. Motion of Dust Structures in the Circumnuclear Region of Comet Hale-Bopp and Rotation of the Cometary Nucleus

    NASA Astrophysics Data System (ADS)

    Churyumov, K. I.; Evtushevskii, A. M.; Kravtsov, F. I.

    2001-01-01

    The motion of dust structures in the circumnuclear region of comet Hale-Bopp is studied. About 270 envelope images were obtained with the AZT-8 reflector (D = 0.7 m, F = 28 m) and the Filin-3 image intensifier. We carried out our observations at the observational station of the Astronomical Observatory of Shevchenko Kiev State University in the village of Lesniki (near Kiev). The recording from the image-intensifier screen was made on Foto-100 film during 23 nights from March 24 to May 10, 1997. The circumnuclear region was imaged both in white light (without filters) and with IHW CO^+ (λ_ef = 426 nm), C_3 (λ_ef = 496 nm), C_2 (λ_ef = 514 nm), and RC (red continuum, λ_ef = 684 nm) narrow-band interference filters. Based on our measurements of the radial expansion of dust structures, we determined the velocities, 0.61-1.99 km s^-1 accelerations, from -18.3 × 10^-3 to 4.0 × 10^-3 m s^-2 and rotation period of the cometary nucleus, 111.41^h +/- 0.05^h.

  4. Non-destructive trace element microanalysis of as-received cometary nucleus samples using synchrotron x ray fluorescence

    NASA Technical Reports Server (NTRS)

    Sutton, S. R.

    1989-01-01

    The Synchrotron X ray Fluorescence (SXRF) microprobe at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, will be an excellent instrument for non-destructive trace element analyses of cometary nucleus samples. Trace element analyses of as-received cometary nucleus material will also be possible with this technique. Bulk analysis of relatively volatile elements will be important in establishing comet formation conditions. However, as demonstrated for meteorites, microanalyses of individual phases in their petrographic context are crucial in defining the histories of particular components in unequilibrated specimens. Perhaps most informative in comparing cometary material with meteorites will be the halogens and trace metals. In-situ, high spatial resolution microanalyses will be essential in establishing host phases for these elements and identifying terrestrial (collection/processing) overprints. The present SXRF microprobe is a simple, yet powerful, instrument in which specimens are excited with filtered, continuum synchrotron radiation from a bending magnet on a 2.5 GeV electron storage ring. A refrigerated cell will be constructed to permit analyses at low temperatures. The cell will consist essentially of an air tight housing with a cold stage. Kapton windows will be used to allow the incident synchrotron beam to enter the cell and fluorescent x rays to exit it. The cell will be either under vacuum or continuous purge by ultrapure helium during analyses. Several other improvements of the NSLS microprobe will be made prior to the cometary nucleus sample return mission that will greatly enhance the sensitivity of the technique.

  5. Discrete sources of cryovolcanism on the nucleus of Comet 29P/Schwassmann-Wachmann and their origin

    NASA Astrophysics Data System (ADS)

    Miles, Richard

    2016-07-01

    Evidence for long-lived sources of cryovolcanism on the nucleus of the Comet 29P/Schwassmann-Wachmann has been found from a study of its times of outburst (t0) and the morphological development of inner coma structures. Analysis of data from the Minor Planet Center observations archive spanning 2002-2014 and other observations have yielded 64 outburst times of mainly well-observed events with a median timing uncertainty of 0.40 d. Outbursts comprise largely (i) isolated explosive events; or (ii) multiple outbursts occurring typically within 5-15 d of each other. On rare occasions, a form of continuous or gradually increasing activity is manifest, appearing to be the result of a series of mini-outbursts. Quasi-periodicity in t0 is manifested as an excess of outbursts every 52-60 d, along with a paucity of events every ∼30 d and ∼90 d. Seasonal changes in activity are evident from the temporal analysis of the outburst data. An unambiguous periodicity of 57.6 ± 0.4 d has been found in the times of 26 outbursts during 2010-2014, with all active sources at that time localised within a longitude span of ∼135-150°. Cluster analysis of t0 data for 2002-2010 and 2010-2014, and HST imaging from 1996 confirm and refine the apparent periodicity, indicating that outbursts appear to be grouped in longitude centred on at least 6 circumferential locations. Sources of activity generally persist for at least 10-20 yr, and some appear discrete in nature, able to re-outburst after a single day-night cycle. Given that outbursts are triggered by solar heating, the analysis yields a value for the mean solar day of 57.71 ± 0.06 d, equivalent to a sidereal rotation period of 57.09 ± 0.06 d, assuming the more probable prograde direction of spin. A novel outburst mechanism is outlined in which some cometary ices, principally solid CH4, confined under pressure (>12 kPa) beneath a stabilisation crust, begin to melt and absorb supervolatile gases, mainly CO and N2. These gases

  6. Aerobraking strategies for the sample of comet coma earth return mission

    NASA Technical Reports Server (NTRS)

    Abe, Takashi; Kawaguchi, Jun'ichiro; Uesugi, Kuninori; Yen, Chen-Wan L.

    1990-01-01

    The results of a study to the validate the applicability of the aerobraking concept to the SOCCER (sample of comet coma earth return) mission using a six-DOF computer simulation of the aerobraking process are presented. The SOCCER spacecraft and the aerobraking scenario and power supply problem are briefly described. Results are presented for the spin effect, payload exposure problem, and sun angle effect.

  7. Searching for Amino Acids in Meteorites and Comet Samples

    NASA Technical Reports Server (NTRS)

    Cook, Jamie Elsila

    2010-01-01

    Chemistry plays an important role in the interdisciplinary field of astrobiology, which strives to understand the origin, distribution, and evolution of life throughout the universe. Chemical techniques are used to search for and characterize the basic ingredients for life, from the elements through simple molecules and up to the more complex compounds that may serve as the ingredients for life. The Astrobiology Analytical Laboratory at NASA Goddard uses state-of-the-art laboratory analytical instrumentation in unconventional ways to examine extraterrestrial materials and tackle some of the big questions in astrobiology. This talk will discuss some of the instrumentation and techniques used for these unique samples, as well as some of our most interesting results. The talk will present two areas of particular interest in our laboratory: (1) the search for chiral excesses in meteoritic amino acids, which may help to explain the origin of homochirality in life on Earth; and (2) the detection of amino acids and amines in material returned by NASA's Stardust mission, which rendevouzed with a cornet and brought back cometary particles to the Earth.

  8. The Preliminary Examination of Organics in the Returned Stardust Samples from Comet Wild 2

    NASA Technical Reports Server (NTRS)

    Sandford, S. A.; Aleon, J.; Alexander, C.; Butterworth, A.; Clemett, S. J.; Cody, G.; Cooper, G.; Dworkin, J. P.; Flynn, G. J.; Gilles, M. K.

    2006-01-01

    The primary objective of STARDUST is to collect coma samples from comet 8lP/Wild 2. These samples were collected by impact onto aerogel tiles on Jan 2, 2004 when the spacecraft flew through the comet's coma at a relative velocity of about 6.1 km/sec. Measurements of dust impacts on the front of the spacecraft suggest that the aerogel particle collector was impacted by 2800 +/- 500 particles larger than 15 micron in diameter. Following recovery of the Sample Return Capsule (SRC) on Jan 15, 2006, the aerogel collector trays will be removed in a clean room at JSC. After documentation of the collection, selected aerogel tiles will be removed and aerogel and cometary samples will be extracted for study. A number of different extraction techniques will be used, each optimized for the analytical technique that is to be used. The STARDUST Mission will carry out a 6 month preliminary examination (PE) of a small portion of the returned samples. The examination of the samples will be made by a number of subteams that will concentrate on specific aspects of the samples. One of these is the Organics PE Team (see the author list above for team members). These team members will use a number of analytical techniques to produce a preliminary characterization of the abundance and nature of the organics (if any) in the returned samples.

  9. 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.

  10. Organics in the samples returned from comet 81P/Wild 2 by the Stardust Spacecraft

    NASA Astrophysics Data System (ADS)

    Sandford, Scott A.

    2008-10-01

    The Stardust Mission collected samples from Comet 81P/Wild 2 on 2 Jan 2004 and returned these samples to Earth on 15 Jan 2006. After recovery, a six month preliminary examination was done on a portion of the samples. Studies of the organics in the samples were made by the Organics Preliminary Examination Team (PET) - a worldwide group of over 55 scientists. This paper provides a brief overview of the findings of the Organics PET. Organics in the samples were studied using a multitude of analytical techniques including spatial determination of C and heteroatom elemental abundances (STXM), functional group identification (micro-FTIR/Raman, C,N,O-XANES), and specific molecular identification of certain classes of organics (HPLC-LIF, L2MS, TOF-SIMS). Analyses were also made of spacecraft components and environmental samples collected near the recovered returned capsule to assess contamination issues. The distribution of organics (abundance, functionality, and relative elemental abundances of C,N,O) is heterogeneous both within and between particles. They are an unequilibrated reservoir that experienced little parent body processing after incorporation into the comet. Some organics look like those seen in IDPs (and to a lesser extent, meteorites), while new aromatic-poor and highly labile organics, not seen in meteoritic materials, are also present. The organics are O,N-rich compared to meteoritic organics. Some of the organics have an interstellar heritage, as evidenced by D and 15N enrichments.

  11. Properties of the Nucleus, Dust Coma, and Gas Coma of Comet 29P/Schwassmann-Wachmann 1 As Observed By WISE/NEOWISE

    NASA Astrophysics Data System (ADS)

    Fernandez, Yanga R.; Bauer, J. M.; Lisse, C. M.; Grav, T.; Mainzer, A. K.; Masiero, J. R.; Walker, R. G.; Meech, K. J.

    2012-10-01

    We present our analysis of mid-infrared imaging of comet 29P/Schwassmann-Wachmann 1 by the Wide-field Infrared Survey Explorer (WISE) [1,2]. The comet was observed on May 3-4, 2010 - not in strong outburst - with imaging at 3.4, 4.6, 12, and 22 microns (a.k.a. bands W1, W2, W3, and W4). W1 and W2 were sensitive to the reflected-sunlight continuum and W3 and W4 to thermal emission. The comet's coma was seen in all bands, with a point-source clearly embedded in W1, W3, and W4 imaging. A coma-fitting technique [3,4] let us photometrically extract this point-source from the images, thereby letting us measure the nucleus's size, W1-band geometric albedo, and infrared beaming. The dust coma was most clearly seen at bands W1, W3, and W4, letting us estimate the dust production rate, extract spatially-resolved information about the dust albedo and color temperature, and constrain the grain composition and size distribution. W2 imaging shows a coma whose radial surface-brightness profile and photometry suggest we are seeing a gas component, specifically emission from CO and/or CO2, i.e. high-abundance species with emission lines within the bandpass. This lets us estimate 29P’s gas production rate and dust-to-gas ratio independently from earlier methods. We present a comparison of our dust, gas, and nucleus results to those from earlier studies of this comet. References: [1] E. L. Wright et al. 2010, AJ, 140, 1868. [2] A. K. Mainzer et al. 2011, ApJ, 731, 53. [3] C. M. Lisse et al. 1999, Icarus, 140, 189. [4] P. L. Lamy et al. 2004, in Comets II, pp. 223-264. Acknowledgements: This publication makes use of data products from (1) WISE, which is a joint project of UCLA and JPL/Caltech, funded by NASA; and (2) NEOWISE, which is a project of JPL/Caltech, funded by the Planetary Science Division of NASA.

  12. Evolution of the ultraviolet coma of comet Austin (1982g.)

    NASA Technical Reports Server (NTRS)

    Feldman, P. D.; Ahearn, M. F.; Schleicher, D. G.; Festou, M. C.; Wallis, M. K.; Burton, W. M.; Hughes, D. W.; Keller, H. U.; Benvenuti, P.

    1984-01-01

    Ultraviolet spectra of comet Austin (1982) obtained in July 1982 at heliocentric distances ranging from 1.10 to 0.81 AU preperihelion with the IUE reveal that the comet is very similar in chemical composition and appearance to comet Bradfield (1979X). In addition, the derived H2O production rate is found to vary with heliocentric distance as r to the -3.6, similar to the r to the -3.7 behavior found for comet Bradfield. It is pointed out, however, that the limited sample rate precludes the observation of the short-term variations which could be produced by a rotating nonuniform cometary nucleus.

  13. Short-wavelength infrared (1.3-2.6 μm) observations of the nucleus of Comet 19P/Borrelly

    USGS Publications Warehouse

    Soderblom, L.A.; Britt, D.T.; Brown, R.H.; Buratti, B.J.; Kirk, R.L.; Owen, T.C.; Yelle, R.V.

    2004-01-01

    During the last two minutes before closest approach of Deep Space 1 to Comet 19P/Borrelly, a long exposure was made with the short-wavelength infrared (SWIR) imaging spectrometer. The observation yielded 46 spectra covering 1.3–2.6 μm; the footprint of each spectrum was ∼160 m × width of the nucleus. Borrelly's highly variegated and extremely dark 8-km-long nucleus exhibits a strong red slope in its short-wavelength infrared reflection spectrum. This slope is equivalent to J–K and H–K colors of ∼0.82 and ∼0.43, respectively. Between 2.3–2.6 μm thermal emission is clearly detectable in most of the spectra. These data show the nucleus surface to be hot and dry; no trace of H2O ice was detected. The surface temperature ranged continuously across the nucleus from ⩽300 K near the terminator to a maximum of ∼340 K, the expected sub-solar equilibrium temperature for a slowly rotating body. A single absorption band at ∼2.39 μm is quite evident in all of the spectra and resembles features seen in nitrogen-bearing organic molecules that are reasonable candidates for compositional components of cometary nuclei. However as of yet the source of this band is unknown.

  14. Adaptation of G-TAG Software for Validating Touch-and-Go Comet Surface Sampling Design Methodology

    NASA Technical Reports Server (NTRS)

    Mandic, Milan; Acikmese, Behcet; Blackmore, Lars

    2011-01-01

    The G-TAG software tool was developed under the R&TD on Integrated Autonomous Guidance, Navigation, and Control for Comet Sample Return, and represents a novel, multi-body dynamics simulation software tool for studying TAG sampling. The G-TAG multi-body simulation tool provides a simulation environment in which a Touch-and-Go (TAG) sampling event can be extensively tested. TAG sampling requires the spacecraft to descend to the surface, contact the surface with a sampling collection device, and then to ascend to a safe altitude. The TAG event lasts only a few seconds but is mission-critical with potentially high risk. Consequently, there is a need for the TAG event to be well characterized and studied by simulation and analysis in order for the proposal teams to converge on a reliable spacecraft design. This adaptation of the G-TAG tool was developed to support the Comet Odyssey proposal effort, and is specifically focused to address comet sample return missions. In this application, the spacecraft descends to and samples from the surface of a comet. Performance of the spacecraft during TAG is assessed based on survivability and sample collection performance. For the adaptation of the G-TAG simulation tool to comet scenarios, models are developed that accurately describe the properties of the spacecraft, approach trajectories, and descent velocities, as well as the models of the external forces and torques acting on the spacecraft. The adapted models of the spacecraft, descent profiles, and external sampling forces/torques were more sophisticated and customized for comets than those available in the basic G-TAG simulation tool. Scenarios implemented include the study of variations in requirements, spacecraft design (size, locations, etc. of the spacecraft components), and the environment (surface properties, slope, disturbances, etc.). The simulations, along with their visual representations using G-View, contributed to the Comet Odyssey New Frontiers proposal

  15. Comet C/2011 W3 (Lovejoy): Orbit Determination, Outbursts, Disintegration of Nucleus, Dust-tail Morphology, and Relationship to New Cluster of Bright Sungrazers

    NASA Astrophysics Data System (ADS)

    Sekanina, Zdenek; Chodas, Paul W.

    2012-10-01

    We describe the physical and orbital properties of C/2011 W3. After surviving perihelion passage, the comet was observed to undergo major physical changes. The permanent loss of the nuclear condensation and the formation of a narrow spine tail were observed first at Malargue, Argentina, on December 20 and then systematically at Siding Spring, Australia. The process of disintegration culminated with a terminal fragmentation event on December 17.6 UT. The postperihelion dust tail, observed for ~3 months, was the product of activity over <2 days. The nucleus' breakup and crumbling were probably caused by thermal stress due to the penetration of the intense heat pulse deep into the nucleus' interior after perihelion. The same mechanism may be responsible for cascading fragmentation of sungrazers at large heliocentric distances. The delayed response to the hostile environment in the solar corona is at odds with the rubble-pile model, since the residual mass of the nucleus, estimated at ~1012 g (equivalent to a sphere 150-200 m across) just before the terminal event, still possessed nontrivial cohesive strength. The high production rates of atomic oxygen, observed shortly after perihelion, are compatible with a subkilometer-sized nucleus. The spine tail—the product of the terminal fragmentation—was a synchronic feature, whose brightest part contained submillimeter-sized dust grains, released at velocities of up to 30 m s-1. The loss of the nuclear condensation prevented an accurate orbital-period determination by traditional techniques. Since the missing nucleus must have been located on the synchrone, whose orientation and sunward tip have been measured, we compute the astrometric positions of this missing nucleus as the coordinates of the points of intersection of the spine tail's axis with the lines of forced orbital-period variation, derived from the orbital solutions based on high-quality preperihelion astrometry from the ground. The resulting orbit gives 698

  16. COMET C/2011 W3 (LOVEJOY): ORBIT DETERMINATION, OUTBURSTS, DISINTEGRATION OF NUCLEUS, DUST-TAIL MORPHOLOGY, AND RELATIONSHIP TO NEW CLUSTER OF BRIGHT SUNGRAZERS

    SciTech Connect

    Sekanina, Zdenek; Chodas, Paul W. E-mail: Paul.W.Chodas@jpl.nasa.gov

    2012-10-01

    We describe the physical and orbital properties of C/2011 W3. After surviving perihelion passage, the comet was observed to undergo major physical changes. The permanent loss of the nuclear condensation and the formation of a narrow spine tail were observed first at Malargue, Argentina, on December 20 and then systematically at Siding Spring, Australia. The process of disintegration culminated with a terminal fragmentation event on December 17.6 UT. The postperihelion dust tail, observed for {approx}3 months, was the product of activity over <2 days. The nucleus' breakup and crumbling were probably caused by thermal stress due to the penetration of the intense heat pulse deep into the nucleus' interior after perihelion. The same mechanism may be responsible for cascading fragmentation of sungrazers at large heliocentric distances. The delayed response to the hostile environment in the solar corona is at odds with the rubble-pile model, since the residual mass of the nucleus, estimated at {approx}10{sup 12} g (equivalent to a sphere 150-200 m across) just before the terminal event, still possessed nontrivial cohesive strength. The high production rates of atomic oxygen, observed shortly after perihelion, are compatible with a subkilometer-sized nucleus. The spine tail-the product of the terminal fragmentation-was a synchronic feature, whose brightest part contained submillimeter-sized dust grains, released at velocities of up to 30 m s{sup -1}. The loss of the nuclear condensation prevented an accurate orbital-period determination by traditional techniques. Since the missing nucleus must have been located on the synchrone, whose orientation and sunward tip have been measured, we compute the astrometric positions of this missing nucleus as the coordinates of the points of intersection of the spine tail's axis with the lines of forced orbital-period variation, derived from the orbital solutions based on high-quality preperihelion astrometry from the ground. The

  17. Subaru/COMICS Mid-Infrared Observation of the Near-Nucleus Region of Comet 17P/Holmes at the Early Phase of an Outburst

    NASA Astrophysics Data System (ADS)

    Watanabe, Jun-Ichi; Honda, Mitsuhiko; Ishiguro, Masateru; Ootsubo, Takafumi; Sarugaku, Yuki; Kadono, Toshihiko; Sakon, Itsuki; Fuse, Tetsuharu; Takato, Naruhisa; Furusho, Reiko

    2009-08-01

    Mid-infrared 8--25μm imaging and spectroscopic observations of the comet 17P/Holmes in the early phase of its outburst in brightness were performed on 2007 October 25--28UT using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the 8.2-m Subaru Telescope. We detected an isolated dust cloud that moved toward the south-west direction from the nucleus. The 11.2μm peak of a crystalline silicate feature onto a broad amorphous silicate feature was also detected both in the central condensation of the nucleus and an isolated dust cloud. The color temperature of the isolated dust cloud was estimated to be ˜200K, which is slightly higher than the black-body temperature. Our analysis of the motion indicates that the isolated cloud moved anti-sunward. We propose several possibilities for the motion of the cloud: fluffy dust particles in the isolated cloud started to depart from the nucleus due to radiation pressure almost as soon as the main outburst occurred, or dust particles moved by some other anti-sunward forces, such as a rocket effect and photophoresis when the surrounding dust coma became optically thin. The origin and the nature of the isolated dust cloud are discussed in this paper.

  18. Morphology of the nucleus of Comet 67P/Churyumov--Gerasimenko from stereo and high spatial resolution OSIRIS-NAC images

    NASA Astrophysics Data System (ADS)

    Lamy, P. L.; Groussin, O.; Romeuf, D.; Auger, A. T.; Jorda, L.; Capanna, C.; Faury, G.

    2015-12-01

    The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA's Rosetta spacecraft has acquired images of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko at scales down to 0.2 m/pixel. We employ a variety of techniques to characterize its morphology. Digital terrain modeling (DTM), indispensable for quantitative morphological analysis is performed using stereophotoclinometry (SPC). Depending upon the observational coverage, the resolution of the DTMs exceeds 1 m in the most favorable cases. The ultimate stereographic analysis is performed by exploiting pairs of images able to produce anaglyphs whose spatial resolution surpasses that of the DTMs. Digital image filtering and contrast enhancement techniques are applied on the original images as appropriate. We first concentrate on the dust covered terrains possibly resulting from airfall deposits, on the quasi circular depressions or basins possibly connected to collapses of the underground terrain, and on large scarps that suggest extensive mass disruption. We pay special attention to lithologies that may give clues to the subsurface structure of the nucleus. Our ultimate goal is to understand the processes at work on the nucleus, directly or indirectly connected to its activity as there appears to a variety of processes far beyond what was classically considered in the past, for instance airfall deposits, surface dust transport, mass wasting, and insolation weathering.

  19. Morphology of the nucleus of Comet 67P/Churyumov-Gerasimenko from stereo and high spatial resolution OSIRIS-NAC images

    NASA Astrophysics Data System (ADS)

    Lamy, Philippe; Groussin, Olivier; Romeuf, David; Thomas, Nicolas; Auger, Anne-Thérèse; Jorda, Laurent; Gaskell, Robert; Capanna, Claire; Llebaria, Antoine

    2015-04-01

    The Narrow Angle Camera (NAC) of the OSIRIS imaging system aboard ESA's Rosetta spacecraft has acquired images of the surface of the nucleus of comet 67P/Churyumov-Gerasimenko at scales down to 0.2 m/pixel. We employ a variety of techniques to characterize its morphology. Digital terrain modeling (DTM), indispensable for quantitative morphological analysis is performed using stereophotoclinometry (SPC). Depending upon the observational coverage, the resolution of the DTMs exceed 1 m in the most favorable cases. The ultimate stereographic analysis is performed by exploiting pairs of images able to produce anaglyphs whose spatial resolution surpasses that of the DTMs. Digital image filtering and contrast enhancement techniques are applied on the original images as appropriate. We first concentrate on the dust covered terrains possibly resulting from airfall deposits, on the quasi-circular depressions or basins possibly connected to collapses of the underground terrain, and on large scarps that suggest extensive mass disruption. We pay special attention to lithologies that may give clues to the subsurface structure of the nucleus. Our ultimate goal is to understand the processes at work on the nucleus, directly or indirectly connected to its activity as there appears to a variety of processes far beyond what was classicaly considered in the past, for instance airfall deposits, surface dust transport, mass wasting, and insolation weathering.

  20. Modeling the nucleus and jets of comet 81P/Wild 2 based on the Stardust encounter data

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek; Brownlee, Donald E.; Economou, Thanasis E.; Tuzzolino, Anthony J.; Green, Simon F.

    2004-01-01

    We interpret the nucleus properties and jet activity from the Stardust spacecraft imaging and the onboard dust monitoring system data. Triangulation of 20 jets shows that 2 emanate from the nucleus dark side and 16 emanate from sources that are on slopes where the Sun's elevation is greater than predicted from the fitted triaxial ellipsoid. Seven sources, including five in the Mayo depression, coincide with relatively bright surface spots. Fitting the imaged jets, the spikelike temporal distribution of dust impacts indicates that the spacecraft crossed thin, densely populated sheets of particulate ejecta extending from small sources on the rotating nucleus, consistent with an emission cone model.

  1. The Light Curve Of The Dust Cloud Ejected By The Collision Between The Deep Impact Projectile And The Nucleus Of Comet 9P/Tempel 1

    NASA Astrophysics Data System (ADS)

    Kueppers, Michael; Rengel, M.; Keller, H. U.; Gutiérrez, P. J.; Hviid, S. F.

    2007-10-01

    When Deep Impact fired its projectile into the nucleus of comet 9P/Tempel 1, a cloud made of dust and icy grains was ejected from the impact crater. The dust was subsequently accelerated by gas drag. About a week after the impact event, the dust cloud had dispersed due to its expansion and the force exerted by solar radiation pressure. The light curve of the dust cloud contains information about its formation and evolution: The time scale of production of impact created material can be derived from the time scale of the brightness increase. The velocity distribution of the cloud is indicative of acceleration processes in the inner coma of the comet. Finally, the abundance of large dust particles created by the impact can be estimated from the brightness of the cloud several days after the impact when small particles have been pushed away by radiation pressure. Here we analyze data obtained by the Narrow Angle Camera (NAC) of OSIRIS onboard the ESA spacecraft Rosetta to derive the velocity distribution of the dust cloud from an inversion of its light curve. OSIRIS observed comet Tempel 1 near-continuously for more than two weeks around the impact. A model of the expansion of the ejecta is compared to the light curve seen by the NAC. We derive a broad velocity distribution of the dust particles, which peaks at around 225 m/s, in good agreement with published estimates. The velocities suggest that the impact ejecta were quickly accelerated by gas in the cometary coma. We will discuss implications of our results for the evolution of the dust cloud during the first hours after the impact and provide estimates of the released dust mass. OSIRIS is funded by the agencies ASI, CNES, DLR, the Spanish Space Program (Ministerio de Educación y Ciencia), SNSB, and ESA.

  2. Detection of changes of the surface morphology of the nucleus of comet 67P/Churyumov-Gerasimenko - Implications for the erosion

    NASA Astrophysics Data System (ADS)

    Lamy, Philippe; Groussin, Olivier; El-Maarry, M. R.; Faury, Guillaume; Auger, Anne-Thérèse

    2016-07-01

    Search for morphological changes at the surface of the nucleus of comet 67P/Churyumov-Gerasimenko (67/P C-G) since its perihelion passage in August 2015 has been a major objective of the OSIRIS team in order to understand the erosion processes. At time of writing, the changes detected so far at a distance of 48 km (that is a pixel scale of 90 cm for the OSIRIS Narrow Angle Camera) are subtle even in regions which were the most exposed to solar illumination around perihelion time: Imhotep, Khonsu and Khepry. In this presentation, we will concentrate on the Khepry region where several changes of different kinds have been positively detected: disappearance of several bright spots, localized receding of a large part (roughly 40 x 130 m) of the surface by approximately 12 m (that could result from either erosion or localized collapse), and appearance of several new boulders. As the Rosetta-comet distance will keep decreasing, we hope to report further changes at the COSPAR conference. We will finally confront quantitative estimates of the putative eroded mass with independent evidences coming from in-situ as well as remote-sensing observations carried over several past apparitions.

  3. Bright ice spots on the nucleus of comet 67P/Churyumov-Gerasimenko as observed by Rosetta OSIRIS and VIRTIS instruments

    NASA Astrophysics Data System (ADS)

    Barucci, Maria Antonietta; Fulchignoni, Marcello; Pommerol, Antoine; Erard, Stéphane; Oklay, Nilda; Tosi, Federico; Capaccioni, Fabrizio; Sierks, Holger; Filacchione, Gianrico; Bockelee-Morvan, Dominique; Guettler, Carsten; Fornasier, Sonia; Raponi, Andrea; Deshapriya, J. D. P.; Feller, Clement; Ciarniello, Mauro; Leyrat, Cedric

    2016-07-01

    Since the Rosetta mission arrived at the comet 67P/Churyumov-Gerasimenko (67/P C-G) on August 2014, the comet nucleus has been mapped by both OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System), and VIRTIS (Visible Infrared Thermal Imaging Spectrometer) acquiring a huge quantity of surface's images and spectra, producing the most detailed maps at the highest spatial resolution of a cometary nucleus. The OSIRIS imaging system (NAC & WAC) has a set of filters at different wavelengths from the ultraviolet (269 nm) to the near-infrared (989 nm). The OSIRIS imaging system has been the first instrument with the capability to map a comet surface at a high resolution reaching a maximum resolution of 11cm/px during the closest fly-by on February 14, 2015 at a distance of about 6 km from the nucleus surface while the VIRTIS spectro-imager (with two channels M and H) operates from 0.25 to 5m with medium and high spectral resolution. The spectral analysis on global scale from the VIRTIS data indicates that the nucleus presents different terrains covered by a very dark and dehydrated organic-rich material [1]. OSIRIS images indicate a morphologically complex and dark surface with a variety of terrain types and several intricate features [2]. The surface shows albedo variation and from the spectrophotometric analysis a large heterogeneity on the surface properties [3, 4, 5]. Limited evidences of exposed H2O ice have been found on the surface of 67/P C-G up to now [6, 7, 8], even though ices are considered to be a major constituent of cometary nuclei. The aim of this work is, taking advantage of the high resolution of the OSIRIS images, i) to detect the bright spots at all dimensions by albedo and spectral slope analyses, ii) to select those spots which could be resolved by VIRTIS and iii ) to deeply analyse the corresponding spectra. The OSIRIS analysis has been carried out on the colours and spectrophotometry of the whole 67/P C-G nucleus from images acquired

  4. Distribution of water around the nucleus of comet 67P/Churyumov-Gerasimenko at 3.4 AU from the Sun as seen by the MIRO instrument on Rosetta

    NASA Astrophysics Data System (ADS)

    Biver, N.; Hofstadter, M.; Gulkis, S.; Bockelée-Morvan, D.; Choukroun, M.; Lellouch, E.; Schloerb, F. P.; Rezac, L.; Ip, W. H.; Jarchow, C.; Hartogh, P.; Lee, S.; von Allmen, P.; Crovisier, J.; Leyrat, C.; Encrenaz, P.

    2015-11-01

    The Microwave Instrument on the Rosetta Orbiter (MIRO) has been observing the coma of comet 67P/Churyumov-Gerasimenko almost continuously since June 2014 at wavelengths near 0.53 mm. We present here a map of the water column density in the inner coma (within 3 km from nucleus center) when the comet was at 3.4 AU from the Sun. Based on the analysis of the HO and HO (110-101) lines, we find that the column density can vary by two orders of magnitude in this region. The highest column density is observed in a narrow region on the dayside, close to the neck and north pole rotation axis of the nucleus, while the lowest column density is seen against the nightside of the nucleus where outgassing seems to be very low. We estimate that the outgassing pattern can be represented by a Gaussian distribution in a solid angle with FWHM ≈ 80°.

  5. LCOGT Network observations of spacecraft target comets

    NASA Astrophysics Data System (ADS)

    Lister, Tim; Knight, Matthew M.; Snodgrass, Colin; Samarasinha, Nalin H.

    2015-01-01

    Las Cumbres Observatory Global Telescope (LCOGT) network currently has 12 telescopes at 6 locations in the northern and southern hemispheres with expansion plans for more. This network is versatile and can respond rapidly to target of opportunity events and also perform long term monitoring of slowly changing astronomical phenomena.We have been using the LCOGT Network to perform photometric monitoring of comet 67P/Churyumov-Gerasimenko to support the ESA Rosetta comet mission and of C/2013 A1 (Siding Spring) as part of the ground-based observation teams for these important comets. This broadband photometry will allow a vital link between the detailed in-situ measurements made by the spacecraft and the global properties of the coma, at a time when the comet is only visible for short periods from single sites. The science we can extract includes the rotational state of the nucleus, characterization of the nucleus' activity, gas and dust properties in the coma (e.g., outflow velocities), chemical origin of gas species in the coma, and temporal behavior of the coma structure when the comet is close to the sun. Comet Siding Spring is a dynamically new comet on its first approach to the Sun that will pass close to Mars, so we can directly sample the composition of an original unaltered remnant of the protoplanetary disc. We will also be making use of specialized comet filters available at LCOGT's 2-m Faulkes Telescope North (FTN) to obtain a unique data set on comet C/2013 A1 (Siding Spring), as part of a large worldwide campaign. As one of only two robotic telescope equipped with cometary narrowband filters in the Northern hemisphere and having the largest aperture plus a high quality site, FTN can provide critical regular monitoring that cannot be achieved by any other single facility in the campaign.

  6. Application of Solar Electric Propulsion to a Comet Surface Sample Return Mission

    NASA Technical Reports Server (NTRS)

    Cupples, Mike; Coverstone, Victoria; Woo, Byoungsam

    2004-01-01

    Current NSTAR (planned for the Discovery Mission: Dawn) and NASA's Evolutionary Xenon Thruster based propulsion systems were compared for a comet surface sample return mission to Tempe1 1. Mission and systems analyses were conducted over a range of array power for each propulsion system with an array of 12 kW EOL at 1 AU chosen for a baseline. Engine configurations investigated for NSTAR included 4 operational engines with 1 spare and 5 operational engines with 1 spare. The NEXT configuration investigated included 2 operational engines plus 1 spare, with performance estimated for high thrust and high Isp throttling modes. Figures of merit for this comparison include Solar Electric Propulsion dry mass, average engine throughput, and net non-propulsion payload returned to Earth flyby.

  7. THE NUCLEUS OF COMET 10P/TEMPEL 2 IN 2013 AND CONSEQUENCES REGARDING ITS ROTATIONAL STATE: EARLY SCIENCE FROM THE DISCOVERY CHANNEL TELESCOPE

    SciTech Connect

    Schleicher, David G.; Knight, Matthew M.; Levine, Stephen E.

    2013-11-01

    We present new lightcurve measurements of Comet 10P/Tempel 2 carried out with Lowell Observatory's Discovery Channel Telescope in early 2013 when the comet was at aphelion. These data represent some of the first science obtained with this new 4.3 m facility. With Tempel 2 having been observed to exhibit a small but ongoing spin-down in its rotation period for over two decades, our primary goals at this time were two-fold. First, to determine its current rotation period and compare it to that measured shortly after its most recent perihelion passage in 2010, and second, to disentangle the spin-down from synodic effects due to the solar day and Earth's orbital motion and to determine the sense of rotation, i.e., prograde or retrograde. At our midpoint of 2013 February 24, the observed synodic period is 8.948 ± 0.001 hr, exactly matching the predicted prograde rotation solution based on 2010 results, and yields a sidereal period of the identical value due to the solar and Earth synodic components just canceling out during the interval of the 2013 observations. The retrograde solution is ruled out because the associated sidereal periods in 2010 and 2013 are quite different even though we know that extremely little outgassing, needed to produce torques, occurred in this interval. With a definitive sense of rotation, the specific amounts of spin-down to the sidereal period could be assessed. The nominal values imply that the rate of spin-down has decreased over time, consistent with the secular drop in water production since 1988. Our data also exhibited an unexpectedly small lightcurve amplitude which appears to be associated with viewing from a large, negative sub-Earth latitude, and a lightcurve shape deviating from a simple sinusoid implying a highly irregularly shaped nucleus.

  8. Comet composition and density analyzer

    NASA Technical Reports Server (NTRS)

    Clark, B. C.

    1982-01-01

    Distinctions between cometary material and other extraterrestrial materials (meteorite suites and stratospherically-captured cosmic dust) are addressed. The technique of X-ray fluorescence (XRF) for analysis of elemental composition is involved. Concomitant with these investigations, the problem of collecting representative samples of comet dust (for rendezvous missions) was solved, and several related techniques such as mineralogic analysis (X-ray diffraction), direct analysis of the nucleus without docking (electron macroprobe), dust flux rate measurement, and test sample preparation were evaluated. An explicit experiment concept based upon X-ray fluorescence analysis of biased and unbiased sample collections was scoped and proposed for a future rendezvous mission with a short-period comet.

  9. Autonomous Onboard Science Data Analysis for Comet Missions

    NASA Technical Reports Server (NTRS)

    Thompson, David R.; Tran, Daniel Q.; McLaren, David; Chien, Steve A.; Bergman, Larry; Castano, Rebecca; Doyle, Richard; Estlin, Tara; Lenda, Matthew

    2012-01-01

    Coming years will bring several comet rendezvous missions. The Rosetta spacecraft arrives at Comet 67P/Churyumov-Gerasimenko in 2014. Subsequent rendezvous might include a mission such as the proposed Comet Hopper with multiple surface landings, as well as Comet Nucleus Sample Return (CNSR) and Coma Rendezvous and Sample Return (CRSR). These encounters will begin to shed light on a population that, despite several previous flybys, remains mysterious and poorly understood. Scientists still have little direct knowledge of interactions between the nucleus and coma, their variation across different comets or their evolution over time. Activity may change on short timescales so it is challenging to characterize with scripted data acquisition. Here we investigate automatic onboard image analysis that could act faster than round-trip light time to capture unexpected outbursts and plume activity. We describe one edge-based method for detect comet nuclei and plumes, and test the approach on an existing catalog of comet images. Finally, we quantify benefits to specific measurement objectives by simulating a basic plume monitoring campaign.

  10. Ultraviolet observations of comets

    NASA Technical Reports Server (NTRS)

    Code, A. D.; Houck, T. E.; Lillie, C. F.

    1972-01-01

    The first observations of a comet in the vacuum ultraviolet were obtained on January 14, 1970, when OAO-2 recorded the spectrum of the bright comet Tago-Sato-Kosaka (1969g). The observations revealed, among other things, the predicted extensive hydrogen Lyman alpha halo. OAO-2 continued to collect spectrophotometric measurements of this comet throughout January of that year; a photograph of the nucleus in Lyman alpha revealed finer scale structures. In February of 1970, the bright comet Bennet (1969i) became favorable for space observations. On the basis of the OAO discovery, OGO-V made several measurements of comet Bennet with low spatial resolution photometers. Comet Enke was detected by OGO in January of 1971 at a large heliocentric distance from its Lyman alpha emission.

  11. The impact of lymphocyte isolation on induced DNA damage in human blood samples measured by the comet assay.

    PubMed

    Bausinger, Julia; Speit, Günter

    2016-09-01

    The comet assay is frequently used in human biomonitoring for the detection of exposure to genotoxic agents. Peripheral blood samples are most frequently used and tested either as whole blood or after isolation of lymphocytes (i.e. peripheral blood mononuclear cells, PBMC). To investigate a potential impact of lymphocyte isolation on induced DNA damage in human blood samples, we exposed blood ex vivo to mutagens with different modes of genotoxic action. The comet assay was performed either directly with whole blood at the end of the exposure period or with lymphocytes isolated directly after exposure. In addition to the recommended standard protocol for lymphocyte isolation, a shortened protocol was established to optimise the isolation procedure. The results indicate that the effects of induced DNA strand breaks and alkali-labile sites induced by ionising radiation and alkylants, respectively, are significantly reduced in isolated lymphocytes. In contrast, oxidative DNA base damage (induced by potassium bromate) and stable bulky adducts (induced by benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide; BPDE) seem to be less affected. Our findings suggest that in vivo-induced DNA damage might also be reduced in isolated lymphocytes in comparison with the whole blood depending of the types of DNA damage induced. Because only small genotoxic effects can generally be expected in human biomonitoring studies with the comet assay after occupational and environmental exposure to genotoxic agents, any loss might be relevant and should be avoided. The possibility of such effects and their potential impact on variability of comet assay results in human biomonitoring should be considered when performing or evaluating such kind of studies. PMID:27154923

  12. Carbon XANES Data from Six Aerogel Picokeystones Cut from the Top and Bottom Sides of the Stardust Comet Sample Tray

    NASA Technical Reports Server (NTRS)

    Wirick, S.; Flynn, G. J.; Frank, D.; Sandford, S. A.; Zolensky, M. E.; Tsou, P.; Peltzer, C.; Jacobsen, C.

    2009-01-01

    Great care and a large effort was made to minimize the amount of organic matter contained within the flight aerogel used to collect Comet 81P/Wild 2 samples. Even so, by the very nature of the production process and silica aerogel s affinity for volatile organics keeping silica aerogel free from organics is a monumental task. Silica aerogel from three production batches was flown on the Stardust sample return mission. All 3 types had layered densities varying from 5mg/ml to 50 mg/ml where the densest aerogel was farthest away from the collection area. A 2 step gelation process was used to make the flight aerogel and organics used in this process were tetraethylorthosilicate, ethanol and acetonitrile. Both ammonium hydroxide and nitric acid were also used in the aerogel production process. The flight aerogel was baked at JPL at 300 C for 72 hours, most of the baking was done at atmosphere but twice a day the oven was pumped to 10 torr for hour [1]. After the aerogel was baked it was stored in a nitrogen purged cabinet until flight time. One aerogel cell was located in the SRC away from any sample collection area as a witness to possible contamination from out gassing of the space craft, re-entry gases and any other organic encounter. This aerogel was aerogel used in the interstellar collection sample tray and is the least dense of the 3 batches of aerogel flown. Organics found in the witness tile include organics containing Si-CH3 bonds, amines and PAHS. Besides organic contamination, hot spots of calcium were reported in the flight aerogel. Carbonates have been detected in comet 81P/Wild2 samples . During preflight analyses, no technique was used to analyze for carbonates in aerogel. To determine if the carbonates found in 81P/Wild2 samples were from the comet, it is necessary to analyze the flight aerogel for carbonate as well as for organics.

  13. Thermal evolution of Comet P/Tempel 1 - Representing the group of targets for the CRAF and CNSR missions

    NASA Technical Reports Server (NTRS)

    Bar-Nun, Akiva; Heifet, Eyal; Prialnik, Dina

    1989-01-01

    A numerical definition of the thermal evolution of spherically symmetric models of the nucleus in the orbit of Comet P/Tempel-1 is presently used to ascertain the properties of the outer layers of comets under consideration for the future Comet Rendezvous and Asteroid Flyby and the Comet Nucleus Sample Return missions. Evolutionary sequences are computed for different values of density, dust/ice mass ratio, and the dust fraction not lost with ice sublimation. It is found that inner and outer surface temperatures of the dust mantle are comparatively insensitive to parameter changes, and that the total thickness of the crystalline ice layer between the dust mantle and the amorphous ice core will make it difficult for the comet-mission probes to sample pristine ice.

  14. 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).

  15. Application of solar electric propulsion to comet and asteroid rendezvous and docking /CARD/ missions with sample return.

    NASA Technical Reports Server (NTRS)

    Odom, P. R.; Cikanek, H. A.; Allen, L. C.

    1972-01-01

    Summary of a feasibility study of CARD mission/system concepts for comet Encke and asteroid Eros missions in the late 1970s. A common planetary vehicle employing a modular SEP (solar electric propulsion) system and a direct rendezvous/docking mode with a staged science/sampling module appears feasible based on 1973 technology. The SEP system utilizes 3.5-kW, 3500-sec Isp mercury ion thrusters and rollout solar arrays sized at 36 (Encke) and 13 (Eros) kW based on the Titan III family launch vehicles. Science payloads, sampling concepts, and supporting spacecraft subsystems are defined. Problem areas are identified, and programmatic considerations are discussed.

  16. Gas release in comet nuclei

    NASA Technical Reports Server (NTRS)

    Prialnik, Dina; Bar-Nun, Akiva

    1990-01-01

    Processes taking place during the evolution of a comet nucleus are examined, taking into account the release of gas on crystallization and the gas flow through the porous nucleus. In particular, the stresses caused by the gas pressure, the contribution of gas flow to the heat transfer, and the rate of gas emission by the comet along its orbit were determined using a model of spherically symmetric comet nucleus made of porous amorphous ice, with 10 percent CO gas trapped in it. Several values of density and pore size are considered, and for each combination of parameters, the model is evolved for 20-30 revolutions in Comet P/Halley's orbit. It is shown that a model of 0.2 g/cu cm density reproduces well many of the light-curve and activity characteristics of Comet P/Halley.

  17. Collecting Comet Samples by ER-2 Aircraft: Cosmic Dust Collection During the Draconid Meteor Shower in October 2012

    NASA Technical Reports Server (NTRS)

    Bastien, Ron; Burkett, P. J.; Rodriquez, M.; Frank, D.; Gonzalez, C.; Robinson, G.-A.; Zolensky, M.; Brown, P.; Campbell-Brown, M.; Broce, S.; Kapitzke, M.; Moes, T.; Steel, D.; Williams, T.; Gearheart, D.

    2014-01-01

    Many tons of dust grains, including samples of asteroids and comets, fall from space into the Earth's atmosphere each day. NASA periodically collects some of these particles from the Earth's stratosphere using sticky collectors mounted on NASA's high-flying aircraft. Sometimes, especially when the Earth experiences a known meteor shower, a special opportunity is presented to associate cosmic dust particles with a known source. NASA JSC's Cosmic Dust Collection Program has made special attempts to collect dust from particular meteor showers and asteroid families when flights can be planned well in advance. However, it has rarely been possible to make collections on very short notice. In 2012, the Draconid meteor shower presented that opportunity. The Draconid meteor shower, originating from Comet 21P/Giacobini-Zinner, has produced both outbursts and storms several times during the last century, but the 2012 event was not predicted to be much of a show. Because of these predictions, the Cosmic Dust team had not targeted a stratospheric collection effort for the Draconids, despite the fact that they have one of the slowest atmospheric entry velocities (23 km/s) of any comet shower, and thus offer significant possibilities of successful dust capture. However, radar measurements obtained by the Canadian Meteor Orbit Radar during the 2012 Draconids shower indicated a meteor storm did occur October 8 with a peak at 16:38 (+/-5 min) UTC for a total duration of approximately 2 hours.

  18. Characterizing water/rock interaction in simulated comet nuclei via calorimetry: Tool for in-situ science, laboratory analysis, and sample preservation

    NASA Technical Reports Server (NTRS)

    Allton, Judith H.; Gooding, James L.

    1991-01-01

    Although results from the Giotto and Vega spacecraft flybys of comet P/Halley indicate a complex chemistry for both the ices and dust in the nucleus, carbonaceous chondrite meteorites are still regarded as useful analogs for the rocky components. Carbonaceous chondrites mixed with water enable simulation of water/rock interactions which may occur in cometary nuclei. Three general types of interactions can be expected between water and minerals at sub-freezing temperatures: heterogeneous nucleation of ice by insoluble minerals; adsorption of water vapor by hygroscopic phases; and freezing and melting point depression of liquid water sustained by soluble minerals. Two series of experiments were performed in a differential scanning calorimeter (DSC) with homogenized powders of the following whole-rock meteorites and comparison samples: Allende (CV3), Murchison (CM2), Orgueil (CI), Holbrook (L6), and Pasamonte (eucrite) meteorites as well as on peridotite (PCC-1, USGS), saponite (Sap-Ca-1, CMS), montmorillonite (STx-1, CMS), and serpentine (Franciscan Formation, California). Results are briefly discussed.

  19. Comet Halley and nongravitational forces

    NASA Technical Reports Server (NTRS)

    Yeomans, D. K.

    1977-01-01

    The motion of comet Halley is investigated over the 1607-1911 interval. The required nongravitational-force model was found to be most consistent with a rocket-type thrust from the vaporization of water ice in the comet's nucleus. The nongravitational effects are time-independent over the investigated interval.

  20. Observations of Periodic Comet 2P/Encke: Physical Properties of the Nucleus and First Visual-Wavelength Detection of Its Dust Trail

    NASA Technical Reports Server (NTRS)

    Lowry, Stephen C.; Weissman, Paul R.; Sykes, Mark V.; Reach, William T.

    2003-01-01

    We are conducting an observational program designed to determine the overall distributions of size, shape, rotation period, and surface characteristics of cometary nuclei. Here, we present results from a study of the Jupiter- family comet 2P/Encke based on observations from Steward Observatory's 2.3m Bok Telescope at Kitt Peak. This comet has been observed extensively in the past and was one of the primary flyby targets of the recently failed CONTOUR mission.

  1. Elemental Compositions of Comet 81P/Wild 2 Samples Collected by Stardust

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Bleuet, P.; Borg, J.; Bradley, J.; Brenker, F.; Brennan, S.; Bridges, J.; Brownlee, D. E.; Bullock, E.; Clark, B. C.; Papanastassiou, D. A.; Schwandt, C. S.; See, T. H.; Taylor, S.; Tsou, P.

    2006-01-01

    We measured the chemical compositions of material from 23 particles in aerogel and residue in 7 craters in aluminum foil, collected during passage of the Stardust spacecraft through the coma of Comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size-scale analyzed, 180 nanograms. The mean chemical composition of this Wild 2 material agrees with the CI meteorite composition for the refractory elements Mg, Si, Cr, Fe, and Ni to 35%, and for Ca and Mn to 50%. The data suggest the moderately volatile elements Cu, Zn, and Ga may be enriched in this Wild 2 material.

  2. The gas production rate of periodic comet d'Arrest

    NASA Technical Reports Server (NTRS)

    Festou, Michel C.; Feldman, Paul D.; Ahearn, Michael F.

    1992-01-01

    Comet P/d'Arrest is a potential target for a rendezvous mission to a short period comet. Its light curve is rather peculiar, the comet being active only after perihelion passage. One apparition out of two is easy to observe from the ground. The 1995 apparition of the comet will offer a unique opportunity to characterize the outgassing properties of its nucleus.

  3. EPOXI at Comet Hartley 2

    NASA Technical Reports Server (NTRS)

    A'Hearn, Michael F.; Belton, Michael J. S.; Delamere, W. Alan; Feaga, Lori M.; Hampton, Donald; Kissel, Jochen; Klaasen, Kenneth P.; McFadden, Jessica M.; Meech, Karen J.; Melosh, H. Jay; Schultz, Peter H.; Sunshine, Jessica M.; Thomas, Peter C.; Veverka, Joseph; Wellnitz, Dennis D.; Yeomans, Donald K.; Besse, Sebastien; Bodewits, Dennis; Bowling, Timothy J.; Carcish, Brian T.; Collins, Steven M.; Farnham, Tony F.; Groussin, Oliver; Hermalyn, Brendan; Kelley, Michael S.

    2011-01-01

    Understanding how comets work, i,e., what drives their activity, is crucial to using comets to study the early solar system. EPOXI flew past comet 103P/Hartley 2, one with an unusually small but very active nucleus. taking both images and spectra. Unlike large, relatively inactive nuclei, this nncleus is outgassing primarily due to CO2, which drags chnnks of ice out of the nnclens. It also shows significant differences in the relative abundance of volatiles from various parts of the nucleus.

  4. Elemental Compositions of Comet 81P/Wild 2 Samples Collected by Stardust

    SciTech Connect

    Flynn,G.; Bleuet, P.; Borg, J.; Bradley, J.; Brenker, F.; Brennan, S.; Bridges, J.; Brownlee, D.; Bullock, E.; et al.

    2006-01-01

    We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed ({approx}180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.

  5. Elemental composition of Comet 81P/Wild2 samples collected byStardust

    SciTech Connect

    Flynn, G.J.; Bleuet, P.; Borg, J.; Bradley, J.P.; Brenker, F.E.; Brennan, S.; Bridges, J.; Brownlee, D.E.; Bullock, E.S.; Burghammer,Manfred; Clark, B.C.; Dai, Zu Rong; Daghlian, C.P.; Djouadi, Z.; Fakra,S; Ferroir, T.; Floss, C.; Franchi, I.A.; Gainsforth, Z.; Gallien, J.P.; Gillet, P.; Grant, P.G.; Graham, G.A.; Green, S.F.; Grossemy, F.; Heck,P.R.; Herzog, G.F.; Hoppe, P.; Horz, F.; Huth, J.; Ignatyev, K.; Ishii,H.A.; Janssens, K.; Joswiak, D.; Kearsley, A.T.; Khodja, H.; Lanzirotti,A.; Leitner, J.; Lemelle, L.; Leroux, H.; Luening, K.; MacPherson, G.J.; Marhas, K.K.; Marcus, M.A.; Matrajt, G.; Nakamura, T.; Nakamura-Messenger, K.; Nakano, T.; Newville, M.; Papanastassiou, D.A.; Pianette, P.; Rao, William; Riekel, C.; Rietmeijer, F.J.M.; Rost, D.; Schwandt, C.S.; See, T.H.; Sheffield-Parker, J.; Simionovici, A.; Sitnitsky, Ilona; Snead, C.J.; Stadermann, F.J.; Stephan, T.; Stroud,R.M.; Susini, J.; Suzuki, Y.; Sutton, S.R.; Taylor, S.; Teslich, N.; Troadec, D.; Tsou, P.; Tsuchiyama, A.; Uesugi, K.; Vekemans, B.; Vicenzi,E.P.; Vincze, L.; Westphal, A.J.; Wozniakiewicz, P.; Zinner, E.; Zolensky, M.E.

    2006-01-01

    We measured the elemental compositions of material from 23 particles in aerogel and from residue in seven craters in aluminum foil that was collected during passage of the Stardust spacecraft through the coma of comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size scale analyzed ({approx}180 ng). The mean elemental composition of this Wild 2 material is consistent with the CI meteorite composition, which is thought to represent the bulk composition of the solar system, for the elements Mg, Si, Mn, Fe, and Ni to 35%, and for Ca and Ti to 60%. The elements Cu, Zn, and Ga appear enriched in this Wild 2 material, which suggests that the CI meteorites may not represent the solar system composition for these moderately volatile minor elements.

  6. Physical aging in comets

    NASA Technical Reports Server (NTRS)

    Meech, Karen J.

    1991-01-01

    The question of physical aging in cometary nuclei is addressed in order to elucidate the relationship between the past conditions in the protosolar nebula and the present state of the cometary nucleus, and to understand the processes that will physically and chemically alter the nucleus as a function of time. Attention is given to some of the processes that might be responsible for causing aging in comets, namely, radiation damage in the upper layers of the nucleus during the long residences in the Oort cloud, processing from heating and collisions within the Oort cloud, loss of highly volatile species from the nucleus on the first passage through the inner solar system, buildup of a dusty mantle, which can eventually prohibit further sublimation, and a change in the porosity, and hence the thermal properties, of the nucleus. Recent observations suggest that there are distinct differences between 'fresh' Oort cloud comets and thermally processed periodic comets with respect to intrinsic brightness and rate of change of activity as a function of distance.

  7. Piece of a Comet

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image shows a comet particle collected by the Stardust spacecraft. The particle is made up of the silicate mineral forsterite, also known as peridot in its gem form. It is surrounded by a thin rim of melted aerogel, the substance used to collect the comet dust samples. The particle is about 2 micrometers across.

  8. HUBBLE SEES MINI-COMET FRAGMENTS FROM COMET LINEAR

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [lower right] In one stunning Hubble picture the fate of the mysteriously vanished solid nucleus of Comet LINEAR has been settled. The Hubble picture shows that the comet nucleus has been reduced to a shower of glowing 'mini-comets' resembling the fiery fragments from an exploding aerial firework. This is the first time astronomers have ever gotten a close-up look at what may be the smallest building blocks of cometary nuclei, the icy solid pieces called 'cometesimals', which are thought to be less than 100 feet across. The farthest fragment to the left, which is now very faint, may be the remains of the parent nucleus that fragmented into the cluster of smaller pieces to the right. The comet broke apart around July 26, when it made its closest approach to the Sun. The picture was taken with Hubble's Wide Field Planetary Camera 2 on August 5, 2000, when the comet was at a distance of 64 million miles (102 million kilometers) from Earth. Credit: NASA, Harold Weaver (the Johns Hopkins University), and the HST Comet LINEAR Investigation Team [upper left] A ground-based telescopic view (2.2-meter telescope) of Comet LINEAR taken on August 5, at nearly the same time as the Hubble observations. The comet appears as a diffuse elongated cloud of debris without any visible nucleus. Based on these images, some astronomers had concluded that the ices in the nucleus had completely vaporized, leaving behind a loose swarm of dust. Hubble's resolution was needed to pinpoint the remaining nuclei (inset box shows HST field of view as shown in lower right). Credit: University of Hawaii

  9. Stardust Curation at Johnson Space Center: Photo Documentation and Sample Processing of Submicron Dust Samples from Comet Wild 2 for Meteoritics Science Community

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, K.; Zolensky, M. E.; Bastien, R.; See, T. H.; Warren, J. L.; Bevill, T. J.; Cardenas, F.; Vidonic, L. F.; Horz, F.; McNamara, K. M.; Allen, C. C.; Westphal, A. J.; Snead, C.; Ishii, H. A.; Brownlee, D.

    2007-01-01

    Dust particles released from comet 81P/Wild-2 were captured in silica aerogel on-board the STARDUST spacecraft and successfully returned to the Earth on January 15, 2006. STARDUST recovered thousands of particles ranging in size from 1 to 100 micrometers. The analysis of these samples is complicated by the small total mass collected ( < 1mg), its entrainment in the aerogel collection medium, and the fact that the cometary dust is comprised of submicrometer minerals and carbonaceous material. During the six month Preliminary Examination period, 75 tracks were extracted from the aerogel cells , but only 25 cometary residues were comprehensively studied by an international consortium of 180 scientists who investigated their mineralogy/petrology, organic/inorganic chemistry, optical properties and isotopic compositions. These detailed studies were made possible by sophisticated sample preparation methods developed for the STARDUST mission and by recent major advances in the sensitivity and spatial resolution of analytical instruments.

  10. The TRAPPIST comet survey

    NASA Astrophysics Data System (ADS)

    Jehin, E.; Opitom, C.; Manfroid, J.; Hutsemékers, D.; Gillon, M.

    2014-07-01

    distribution of several species among which OH, NH, CN, C2 and C3 as well as ions like CO+. The dust production rates (Afrho) and color of the dust are determined through four dust continuum bands (UC, BC, GC, RC). Such regular measurements are rare because of the lack of observing time on larger telescopes. Yet they are very valuable as they show how the gas production rate of each species evolves with respect to the distance to the Sun. Those observations allow to determine the composition of the comets and the chemical class to which they belong (rich or poor in carbon for instance [3]), possibly revealing the origin of those classes but also if there are some changes of the abundance ratios along the orbit (evolutionary effects). Indeed with half a dozen of comets observed each year --- and as long as possible along their orbit --- this program will provide a good statistical sample after a few years. We will present the results of this monitoring after three years of operations. Thanks to the way the telescope is operated, follow-up of split comets and of special outburst events is possible right after an alert is given and can bring important information on the nature of comets. In addition to providing the productions rates of the different species through a proper photometric calibration, image analysis can reveal coma features (jets, fans, tails), that can lead to the detection of active regions and measure the rotation period of the nucleus. The monitoring is also useful to assess the gas and dust activity of a given comet in order to prepare more detailed observations with larger telescopes. Such data can be obtained at any time under request. Finally a dozen of faint comets (V < 20) are monitored once a week through B, V, Rc, Ic filters and magnitudes and positions are sent to the MPC.

  11. Metallic atoms and ions in comets: Comet Halley 1986 3

    NASA Technical Reports Server (NTRS)

    Ibadov, S.

    1992-01-01

    The origin of metallic atoms and ions in the cometary comae is investigated theoretically. Two effects are revealed in the comas of bright comets: (1) the Na anomalous type effect is possible within the gas-dust jets of comet P/Halley 1986 3 due to cooling cometary dust by cryogenic gas flow from the nucleus; and (2) the production of ions of refractory elements (Fe(+), Si(+), etc.) at large heliocentric distances is possible in the comas of the Halley type dusty comets due to high-velocity impacts between cometary and zodiacal dust particles. Spectral observations of comets with high sensitivity and spatial resolution are important for studying both comets and interplanetary dust.

  12. Anatomy of a Busted Comet

    NASA Technical Reports Server (NTRS)

    2008-01-01

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

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

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

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

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

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

  13. CO2 Orbital Trends in Comets

    NASA Astrophysics Data System (ADS)

    Kelley, Michael; Feaga, Lori; Bodewits, Dennis; McKay, Adam; Snodgrass, Colin; Wooden, Diane

    2014-12-01

    Spacecraft missions to comets return a treasure trove of details of their targets, e.g., the Rosetta mission to comet 67P/Churyumov-Gerasimenko, the Deep Impact experiment at comet 9P/Tempel 1, or even the flyby of C/2013 A1 (Siding Spring) at Mars. Yet, missions are rare, the diversity of comets is large, few comets are easily accessible, and comet flybys essentially return snapshots of their target nuclei. Thus, telescopic observations are necessary to place the mission data within the context of each comet's long-term behavior, and to further connect mission results to the comet population as a whole. We propose a large Cycle 11 project to study the long-term activity of past and potential future mission targets, and select bright Oort cloud comets to infer comet nucleus properties, which would otherwise require flyby missions. In the classical comet model, cometary mass loss is driven by the sublimation of water ice. However, recent discoveries suggest that the more volatile CO and CO2 ices are the likely drivers of some comet active regions. Surprisingly, CO2 drove most of the activity of comet Hartley 2 at only 1 AU from the Sun where vigorous water ice sublimation would be expected to dominate. Currently, little is known about the role of CO2 in comet activity because telluric absorptions prohibit monitoring from the ground. In our Cycle 11 project, we will study the CO2 activity of our targets through IRAC photometry. In conjunction with prior observations of CO2 and CO, as well as future data sets (JWST) and ongoing Earth-based projects led by members of our team, we will investigate both long-term activity trends in our target comets, with a particular goal to ascertain the connections between each comet's coma and nucleus.

  14. 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.

  15. 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.

  16. A Comet's Missing Light

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-05-01

    comets experienced very similar radiation fields as they passed perihelion. They also show that the properties of the Suns corona experienced by each comet like its density and magnetic field topology were roughly the same.Bryans and Pesnell argue that, as both comets appear to have encountered similar solar conditions, the most likely explanation for ISONs lack of detectable EUV emission is that it didnt deposit as much material in its orbit as Lovejoy did. They show that this would happen if ISONs nucleus were four times smaller in radius than Lovejoys, spanning a mere 5070 meters in comparison to Lovejoys 200300 meters.This conclusion is consistent with white-light observations of ISON that suggest that, though it might have started out significantly larger than Lovejoy, ISON underwent dramatic mass loss as it approached the Sun. By the time it arrived at perihelion, it was likely no longer large enough to create a strong EUV signal resulting in the non-detection of this elusive comet with SDO and other telescopes.CitationPaul Bryans and W. Dean Pesnell 2016 ApJ 822 77. doi:10.3847/0004-637X/822/2/77

  17. DISSECTING PHOTOMETRIC REDSHIFT FOR ACTIVE GALACTIC NUCLEUS USING XMM- AND CHANDRA-COSMOS SAMPLES

    SciTech Connect

    Salvato, M.; Hasinger, G.; Ilbert, O.; Rau, A.; Brusa, M.; Bongiorno, A.; Civano, F.; Elvis, M.; Zamorani, G.; Vignali, C.; Comastri, A.; Bardelli, S.; Bolzonella, M.; Cappelluti, N.; Aussel, H.; Le Floc'h, E.; Mainieri, V.; Capak, P.; Caputi, K.; and others

    2011-12-01

    In this paper, we release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the Cosmic Evolution Survey (COSMOS) field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redshifts comparable to the highest quality results presently available for normal galaxies. We demonstrate that morphologically extended, faint X-ray sources without optical variability are more accurately described by a library of normal galaxies (corrected for emission lines) than by active galactic nucleus (AGN) dominated templates, even if these sources have AGN-like X-ray luminosities. Preselecting the library on the bases of the source properties allowed us to reach an accuracy {sigma}{sub {Delta}z/(1+z{sub s{sub p{sub e{sub c)}}}}}{approx}0.015 with a fraction of outliers of 5.8% for the entire Chandra-COSMOS sample. In addition, we release revised photometric redshifts for the 1735 optical counterparts of the XMM-detected sources over the entire 2 deg{sup 2} of COSMOS. For 248 sources, our updated photometric redshift differs from the previous release by {Delta}z > 0.2. These changes are predominantly due to the inclusion of newly available deep H-band photometry (H{sub AB} = 24 mag). We illustrate once again the importance of a spectroscopic training sample and how an assumption about the nature of a source together, with the number and the depth of the available bands, influences the accuracy of the photometric redshifts determined for AGN. These considerations should be kept in mind when defining the observational strategies of upcoming large surveys targeting AGNs, such as eROSITA at X-ray energies and the Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe in the radio band.

  18. Comets - Chemistry and chemical evolution

    NASA Technical Reports Server (NTRS)

    Donn, B.

    1982-01-01

    Research on the chemical composition and conditions in comets and their possible role in the origin of life on earth is surveyed. The inorganic and organic compounds and ions indicated in the ultraviolet and visible spectra of comets are noted, and evidence for the existence of at least a small proportion of complex organic molecules in comets is presented. It is then pointed out that while cometary material could have reached the earth and provided volatile elements from which biochemical compounds could have formed, it is unlikely that a cometary nucleus could have withstood the temperatures and pressures necessary to sustain an environment in which life could have originated.

  19. Maverick Comet Splits during Dramatic Outburst

    NASA Astrophysics Data System (ADS)

    1996-01-01

    this process is almost always accompanied by a significant brightening. For instance, the nucleus of comet Shoemaker-Levy 9 broke up into at least 21 individual pieces when it passed very close to Jupiter on July 8, 1992; this was the reason that it became bright enough to be detected some eight months later. In the case of SW-3, the opening of rifts and the subsequent splitting took place far from any planet and must in some way have been caused by increased solar heating. Nevertheless, it is not yet known exactly which physical and chemical processes are involved. It will now be interesting to continue the observations of the individual nuclei as long as possible. From accurate positional measurements, it may later become possible to perform a backwards extrapolation and determine the exact conditions of the splitting process (time, involved forces) and thereby cast more light on the physical aspects of this event. SW-3: Still a Possible Rosetta Target? The break-up of a solar system object is a dramatic and relatively rare event. We are here directly witnessing the ageing of a comet, perhaps even the prelude to its death. Earlier measurements indicate that the diameter of SW-3's nucleus is smaller than about 3 kilometres, but since we do not know the size of the pieces that broke off (this may be indicated by how long they will remain active), nor their number (we may only see the largest), we cannot yet determine with any certainty the remaining lifetime of the main nucleus. At the first glance, this seems to indicate that SW-3 must be removed from the list of potential targets for the Rosetta mission - we cannot risk that it no longer exists when the space probe arrives ! On the other hand, due to the break-up there is now a lot of ``fresh'' cometary material on the surface of the nucleus and around it, i.e. matter that has remained unchanged since the beginning of the solar system, some 4,500 million years ago. The possibility to gain direct access to a sample of

  20. 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.

  1. Laboratory Studies of Cometary Materials - Continuity Between Asteroid and Comet

    NASA Technical Reports Server (NTRS)

    Messenger, Scott; Walker, Robert M.

    2015-01-01

    Laboratory analysis of cometary samples have been enabled by collection of cometary dust in the stratosphere by high altitude aircraft and by the direct sampling of the comet Wild-2 coma by the NASA Stardust spacecraft. Cometary materials are composed of a complex assemblage of highly primitive, unprocessed interstellar and primordial solar system materials as well as a variety of high temperature phases that must have condensed in the inner regions of the protoplanetary disk. These findings support and contradict conclusions of comet properties based solely on astronomical observations. These sample return missions have instead shown that there is a continuity of properties between comets and asteroids, where both types of materials show evidence for primitive and processed materials. Furthermore, these findings underscore the importance and value of direct sample return. There will be great value in comparing the findings of the Stardust cometary coma sample return mission with those of future asteroid surface sample returns OSIRIS-REx and Hayabusa II as well as future comet nucleus sample returns.

  2. Rotation period of comet Donati

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1978-01-01

    Consideration is given to the rotation period of comet Donati (1858 VI) whose haloes were approximate parabolic envelopes having foci near the apparent nucleus and vertices toward the sun forward from the tail axis. The regularity and sharpness of the halves suggest that they represent the repetitive ejection of material from an active area which is exposed to solar radiation as the cometary nucleus rotates. Bobrovnikov's results (1954) are used to evaluate the linear expansion velocity of such haloes. This calculation is applied to the comet and a linear correction is used to assess the results.

  3. Infrared observations of comets

    NASA Astrophysics Data System (ADS)

    Hobbs, R. W.

    1981-10-01

    Infrared observation are important for deducing a great deal about properties of the cometary dust surrounding the cometary nucleus. All observations in the infrared are limited to long period comets. Three features of the spectrum which seem to be present in nearly all of the comets observed are discussed. First, there is a peak in the spectrum in the near infrared and visible wavelength, which can be attributed to scattered sunlight. This feature, as expected, gets fainter as a comet recedes from the sun. The second dominant feature in the spectrum is a broad peak in the infrared which is attributed to the thermal emission of the dust in the coma. This part of the spectrum also gets dimmer as the comet gets further from the sun but, at the same time the peak of the spectrum shifts to longer wavelengths, indicating that the dust from which this radiation arises is cooling as the comets recedes. The other feature in the spectrum which is noted is the emission feature at about 10 microns attributed to emission from metallic silicates. T.M.

  4. Bow Shocks at Comets

    NASA Astrophysics Data System (ADS)

    Coates, Andrew J.

    2009-11-01

    Comets provide a wonderful laboratory to study the interaction of a fast flowing plasma, the solar wind, with neutral gas from the comet. On ionization, the more massive newly-born cometary ions are assimilated into the solar wind flow, eventually causing its deceleration via this `mass loading'. One of the effects of this is the cometary bow shock. The exploration of comet Halley by an armada of spacecraft in 1986, as well as the in-situ exploration of comets Giacobini-Zinner (1985), Grigg-Skjellerup (1992) and Borrelly (2001), has revealed important results on the behavior of these weak shocks and showed that mass loading plays a key role. In 2014, the Rosetta mission will provide the first observations of the formation of the cometary bow shock as a comet, Churyumov-Gerasimenko, nears the Sun. Rosetta will also provide the first measurements of the collision-dominated near-nucleus region. Here, we briefly review what we know about cometary bow shocks, and we examine the prospects for Rosetta.

  5. CO2 Orbital Trends in Comets

    NASA Astrophysics Data System (ADS)

    Kelley, Michael; Bodewits, Dennis; Feaga, Lori; Knight, Matthew; McKay, Adam; Snodgrass, Colin; Wooden, Diane

    2016-08-01

    Carbon dioxide is a primary volatile in comet nuclei, and potentially a major contributor to comet activity (i.e., the process of mass loss). However, CO2 cannot be observed directly from the ground, and past surveys of this molecule in comets were limited to space-borne snapshot observations. This situation limits our understanding of the behavior of CO2 in comets, and its role in driving comet mass loss. To address this deficiency, we were awarded a Cy11 Spitzer program designed to quantify the production rate of CO2 on >month-long timescales for 21 comets. We request an additional 269~hr in Cy13 to complete the Spitzer portion of our survey, and to add three more comets (46P/Wirtanen and 2 Target of Opportunity Oort cloud comets). Our survey is designed to probe the orbital trends of CO2 production in the comet population. We aim to: 1) examine the role of CO2 in the persistent post-perihelion activity observed in Jupiter-family comets; 2) measure the seasonal variations of CO2/H2O as a proxy for nucleus heterogeneity, when possible; 3) search for orbital trends sensitive to cumulative insolation as a proxy for nucleus layering; and 4) examine how Oort cloud comets evolve by comparing dynamically new and old targets. The final data set will allow us to investigate the effects of heating on the evolution of comets, if nucleus structures can be inferred through activity, and set the stage for JWST investigations into comet activity and composition.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  7. 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.

  8. 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.

  9. ESA Unveils Its New Comet Chaser.

    NASA Astrophysics Data System (ADS)

    1999-07-01

    into the surface immediately on impact. By this time, the warmth of the Sun will probably have begun to vapourise parts of the nucleus, initiating some form of surface outgassing. For a period of about a month, data from the lander's eight experiments will be relayed to Earth via the orbiter. They will send back unique information on the nature and composition of the nucleus. Samples for chemical analysis will be taken of the organic crust and ices to a depth of at least 20 cm. Other instruments will measure characteristics such as near-surface strength, density, texture, porosity and thermal properties. Meanwhile, as Comet Wirtanen approaches the Sun, the Rosetta orbiter will fly alongside it, mapping its surface and studying changes in its activity. As its icy nucleus evaporates, 12 experiments on the orbiter will map its surface and study the dust and gas particles it ejects. For the first time, scientists will be able to monitor at close quarters the dramatic changes which take place as a comet plunges sunwards at a speed of 46,000 kph. The stream of data will include a mass of new information about the comet's changes in behaviour as it approaches the Sun, including: * variations in the temperature of the nucleus, * changing intensity and location of gas and dust jets on the nucleus, * the amount of gas and dust emitted from the nucleus, * the size, composition and impact velocity of dust particles, * the nature of the comet's interaction with the charged particles of the solar wind. By mission's end in July 2013, Rosetta will have spent almost two years chasing the comet for millions of kilometres through space. It will also have returned a treasure trove of data, which will enable us to learn more about how the planets formed and where we came from. Why Rosetta? Space exploration is all about discovering the unknown. Just as, 200 years ago, the discovery of the Rosetta Stone eventually enabled Champollion to unravel the mysteries of ancient Egyptian

  10. Submillimeter Studies of Comets

    NASA Technical Reports Server (NTRS)

    Jewitt, David; Morgan, Thomas (Technical Monitor)

    2002-01-01

    This proposal supported observations of comets at submillimeter wavelengths. The prime science objectives were to use rotational transitions in molecules to measure the compositions and outgassing rates of the comets. The second science objectives focussed on the use of the submillimeter continuum radiation to provide a measure of the solid particle content and production rate in the comets. Both quantities provide fundamental constraints on the nature of these primitive bodies. The gas and dust measurements provide context for NASA's on-going and future studies of comets using in-situ spacecraft. Submillimeter continuum data, in particular, samples the largest particles in the cometary dust grain size distribution. These particles contain the bulk of the mass and present potential hazards to spacecraft when inside the dust coma.

  11. Dissecting Photometric Redshift for Active Galactic Nucleus Using XMM- and Chandra-COSMOS Samples

    NASA Astrophysics Data System (ADS)

    Salvato, M.; Ilbert, O.; Hasinger, G.; Rau, A.; Civano, F.; Zamorani, G.; Brusa, M.; Elvis, M.; Vignali, C.; Aussel, H.; Comastri, A.; Fiore, F.; Le Floc'h, E.; Mainieri, V.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Capak, P.; Caputi, K.; Cappelluti, N.; Carollo, C. M.; Contini, T.; Garilli, B.; Iovino, A.; Fotopoulou, S.; Fruscione, A.; Gilli, R.; Halliday, C.; Kneib, J.-P.; Kakazu, Y.; Kartaltepe, J. S.; Koekemoer, A. M.; Kovac, K.; Ideue, Y.; Ikeda, H.; Impey, C. D.; Le Fevre, O.; Lamareille, F.; Lanzuisi, G.; Le Borgne, J.-F.; Le Brun, V.; Lilly, S.; Maier, C.; Manohar, S.; Masters, D.; McCracken, H.; Messias, H.; Mignoli, M.; Mobasher, B.; Nagao, T.; Pello, R.; Puccetti, S.; Perez-Montero, E.; Renzini, A.; Sargent, M.; Sanders, D. B.; Scodeggio, M.; Scoville, N.; Shopbell, P.; Silvermann, J.; Taniguchi, Y.; Tasca, L.; Tresse, L.; Trump, J. R.; Zucca, E.

    2011-12-01

    In this paper, we release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the Cosmic Evolution Survey (COSMOS) field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redshifts comparable to the highest quality results presently available for normal galaxies. We demonstrate that morphologically extended, faint X-ray sources without optical variability are more accurately described by a library of normal galaxies (corrected for emission lines) than by active galactic nucleus (AGN) dominated templates, even if these sources have AGN-like X-ray luminosities. Preselecting the library on the bases of the source properties allowed us to reach an accuracy \\sigma _{\\Delta z/(1+z_{spec})}\\sim 0.015 with a fraction of outliers of 5.8% for the entire Chandra-COSMOS sample. In addition, we release revised photometric redshifts for the 1735 optical counterparts of the XMM-detected sources over the entire 2 deg2 of COSMOS. For 248 sources, our updated photometric redshift differs from the previous release by Δz > 0.2. These changes are predominantly due to the inclusion of newly available deep H-band photometry (H AB = 24 mag). We illustrate once again the importance of a spectroscopic training sample and how an assumption about the nature of a source together, with the number and the depth of the available bands, influences the accuracy of the photometric redshifts determined for AGN. These considerations should be kept in mind when defining the observational strategies of upcoming large surveys targeting AGNs, such as eROSITA at X-ray energies and the Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe in the radio band. Based on observations by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under

  12. Observations performed by the SESAME/Permittivity Probe during the descent and after the landing of Philae upon the nucleus of Comet Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Schmidt, Walter; Le Gall, Alice; Hamelin, Michel; Caujolle-Bert, Sylvain; Lethuillier, Anthony; Ciarletti, Valerie; Grard, Réjean

    2015-04-01

    The Permittivity Probe (PP), a component of the SESAME instrument on board Rosetta's Lander Philae, was operated prior to the separation of Philae from Rosetta, during the descent and at the location of the final landing site. The working principle of PP consists in measuring, with a receiving dipole, the voltage induced in the medium by a current of known phase and amplitude injected by a transmitting antenna. The primary objective of PP is to analyse the electrical properties of the comet surface material down to a depth of about 2 m, and to record their variations with temperature, solar illumination and heliocentric distance. These observations are particularly sensitive to the concentration of water ice at the landing site. The second objective of the instrument is to monitor the spectrum of the electromagnetic and electrostatic waves generated by the interaction between the comet and the solar wind at frequencies of up to 20 kHz. The measurements performed during the descent were mainly devoted to the calibration of the instrument in its nominal configuration, with deployed landing gear and away from the Rosetta spacecraft influence, in an environment of known permittivity, either a vacuum or a plasma whose density and temperature would have been derived from the LAP and MIP data. This approach is unfortunately invalidated owing to the fact the PP receiver was most of the time saturated by the operation of the CONSERT radar during the descent, an interference which seemed to have been minimized during in-flight interference tests, but which was significantly stronger after separation of Philae from Rosetta. Nevertheless, it was possible to recover some information about the instrument's transmitter and receiver performances then used during the analysis of the data measured on the cometary surface. Undisturbed measurements were fortunately performed at the landing site, under various solar illuminations, using the three feet of Philae as transmitting and

  13. 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)

  14. Jets on comet Borrelly

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This very long exposure was taken by NASA's Deep Space 1 to show detailed structures in the faint parts of comet Borrelly's inner coma. As a result, the nucleus has been greatly over-exposed and its shape appears distorted. The main jet extends to the lower right about 30 degrees off the Sun-line. Faint structures in the coma stretch from the nucleus in all directions. The surface of Borrelly is composed of a mixture of dust and water ice, and as the comet approaches the Sun the ice sublimes. Dust carried outward by expanding gas makes the jets visible.

    Deep Space 1 completed its primary mission testing ion propulsion and 11 other advanced, high-risk technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to undertake this chancy but exciting, and ultimately successful, encounter with the comet. More information can be found on the Deep Space 1 home page at http://nmp.jpl.nasa.gov/ds1/ .

    Deep Space 1 was launched in October 1998 as part of NASA's New Millennium Program, which is managed by JPL for NASA's Office of Space Science, Washington, D.C. The California Institute of Technology manages JPL for NASA.

  15. Comet Borrelly's Varied Landscape

    NASA Technical Reports Server (NTRS)

    2001-01-01

    In this Deep Space 1 image of comet Borrelly, sunlight illuminates the bowling-pin shaped nucleus from directly below. At this distance, many features are become vivid on the surface of the nucleus, including a jagged line between day and night on the comet, rugged terrain on both ends with dark patches, and smooth, brighter terrain near the center. The smallest discernable features are about 110 meters (120 yards) across.

    Deep Space 1 completed its primary mission testing ion propulsion and 11 other advanced, high-risk technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to undertake this chancy but exciting, and ultimately successful, encounter with the comet. More information can be found on the Deep Space 1 home page at http://nmp.jpl.nasa.gov/ds1/ .

    Deep Space 1 was launched in October 1998 as part of NASA's New Millennium Program, which is managed by JPL for NASA's Office of Space Science, Washington, D.C. The California Institute of Technology manages JPL for NASA.

  16. 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.

  17. Comet Tempel 2: Orbit, ephemerides and error analysis

    NASA Technical Reports Server (NTRS)

    Yeomans, D. K.

    1978-01-01

    The dynamical behavior of comet Tempel 2 is investigated and the comet is found to be very well behaved and easily predictable. The nongravitational forces affecting the motion of this comet are the smallest of any comet that is affected by nongravitational forces. The sign and time history of these nongravitational forces imply (1) a direct rotation of the comet's nucleus and (2) the comet's ability to outgas has not changed substantially over its entire observational history. The well behaved dynamical motion of the comet, the well observed past apparitions, the small nongravitational forces and the excellent 1988 ground based observing conditions all contribute to relatively small position and velocity errors in 1988 -- the year of a proposed rendezvous space mission to this comet. To assist in planned ground based and earth orbital observations of this comet, ephemerides are given for the 1978-79, 1983-84 and 1988 apparitions.

  18. In-situ chemical and isotopic analysis of a comet by Ptolemy

    NASA Astrophysics Data System (ADS)

    Morse, A. D.; Barber, S. J.; Leese, M. R.; Morgan, G. H.; Sheridan, S.; Wright, I. P.; Zarnecki, J. C.; Pillinger, C. T.

    2003-04-01

    Ptolemy is a Gas Chromatograph - Mass Spectrometer, one of the instruments on board the Rosetta Lander, intended to land on comet Wirtanen. Ptolemy is designed to measure the composition and isotope ratios of gases released from comet samples during pyrolysis or combustion. The total mass of the instrument is 4.6 kg and it fits into a space of 33 x 25 x 11 cm. Following touchdown on the comet nucleus, comet samples are obtained by the SD2 instrument, which drills a core sample and loads it into one of 26 ovens on a carousel. One of the ovens already contains a molecular sieve absorbent so that the comet "atmosphere" can also be sampled. The sample is then heated by the oven and the gases released are transferred to the Ptolemy instrument. Within Ptolemy, the raw sample gases can be chemically processed to convert them into molecules suitable for isotopic analysis. The processed sample mixture gas is injected into one of three GC columns to separate it into its constituent components before analysis by the mass spectrometer. An ion trap mass spectrometer has been used as this gives considerable reduction of mass, power and volume, compared to standard magnetic sector mass spectrometers normally used for isotopic analysis. Laboratory experiments have shown that an ion trap is capable of measuring carbon and nitrogen isotope ratios to a precision of +/- 20 per mil or better. We will present data from the Flight instrument plus results of ongoing characterisation studies using the identical Qualification Model.

  19. The 2009 Apparition of methuselah comet 107P/Wilson-Harrington: A case of comet rejuvenation?

    NASA Astrophysics Data System (ADS)

    Ferrín, Ignacio; Hamanowa, Hiromi; Hamanowa, Hiroko; Hernández, Jesús; Sira, Eloy; Sánchez, Albert; Zhao, Haibin; Miles, Richard

    2012-09-01

    detectors than on 1949. This is good evidence to conclude that this object is very near extinction and belongs to the graveyard of comets. In a Remaining Revolutions vs. Water-Budget Age plot, we have identified the region of the graveyard, and 107P is a member of this group. (8) Using the amplitude of the secular light curve (ASEC) vs. Diameter (DEFFE) diagram (Fig. 15), we show that 107P is the most evolved object in the current data base of comets. In the classification scheme of Ferrín (PSS, 58, 365-391, 2010), 107P is a methuselah comet (WB-AGE=7800>100 comet years), medium size (1.4nucleus, fast rotating (PROT=6.093 h<7 h), belonging to the graveyard of comets (the region with ASEC<1 mag in Fig. 15 or 1.000 cycomet is temporarily being rejuvenated due to a trend of apparitions with decreasing perihelion distances. (9) Since the general flow of the sample is down and to the left in the ASEC vs. DEFFE diagram, and since this flow has been going on for centuries, and since dwarf comets evolve much more rapidly than large comets, the existence of a significant population of dormant and extinct comets located in the lower left region of the diagram is predicted. This is the graveyard. Three comets have been identified as members of the graveyard, 107P, 133P and D/1891W1 Blanpain.

  20. Radar observations of Comet Halley

    NASA Technical Reports Server (NTRS)

    Campbell, D. B.; Harmon, J. K.; Shapiro, I. I.

    1989-01-01

    Five nights of Arecibo radar observations of Comet Halley are reported which reveal a feature in the overall average spectrum which, though weak, seems consistent with being an echo from the comet. The large radar cross section and large bandwidth of the feature suggest that the echo is predominantly from large grains which have been ejected from the nucleus. Extrapolation of the dust particle size distribution to large grain sizes gives a sufficient number of grains to account for the echo. The lack of a detectable echo from the nucleus, combined with estimates of its size and rotation rate from spacecraft encounters and other data, indicate that the nucleus has a surface of relatively high porosity.

  1. Detecting active comets with SDSS

    SciTech Connect

    Solontoi, Michael; Ivezic, Zeljko; West, Andrew A.; Claire, Mark; Juric, Mario; Becker, Andrew; Jones, Lynne; Hall, Patrick B.; Kent, Steve; Lupton, Robert H.; Quinn, Tom; /Washington U., Seattle, Astron. Dept. /Princeton U. Observ.

    2010-12-01

    Using a sample of serendipitously discovered active comets in the Sloan Digital Sky Survey (SDSS), we develop well-controlled selection criteria for greatly increasing the efficiency of comet identification in the SDSS catalogs. After follow-up visual inspection of images to reject remaining false positives, the total sample of SDSS comets presented here contains 19 objects, roughly one comet per 10 million other SDSS objects. The good understanding of selection effects allows a study of the population statistics, and we estimate the apparent magnitude distribution to r {approx} 18, the ecliptic latitude distribution, and the comet distribution in SDSS color space. The most surprising results are the extremely narrow range of colors for comets in our sample (e.g. root-mean-square scatter of only {approx}0.06 mag for the g-r color), and the similarity of comet colors to those of jovian Trojans. We discuss the relevance of our results for upcoming deep multi-epoch optical surveys such as the Dark Energy Survey, Pan-STARRS, and the Large Synoptic Survey Telescope (LSST), and estimate that LSST may produce a sample of about 10,000 comets over its 10-year lifetime.

  2. 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.

  3. 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.

  4. ISO's analysis of Comet Hale-Bopp

    NASA Astrophysics Data System (ADS)

    1997-03-01

    The European Space Agency's Infrared Space Observatory ISO inspected Comet Hall-Bopp during the spring and autumn of 1996. The need to keep ISO's telescope extremely cold restricts the spacecraft's pointing in relation to the Sun and the Earth and it ruled out observations at other times. The analyses of the 1996 observations are not yet complete, but already they give new insight into the nature of comets. Comet Hale-Bopp is believed to be a large comet with a nucleus up to 40 kilometres wide. It was discovered in July 1995 by two American astronomers working independently, Alan Hale and Thomas Bopp. At that time, the comet was a billion kilometres away from the Sun, but 200 times brighter than Halley's Comet was, when at a comparable distance. Comet Hale-Bopp will make its closest approach to the Earth on 22 March, and its closest approach to the Sun (perihelion) on 1 April 1997. Some scientific results from ISO The discovery of Comet Hale-Bopp occurred before ISO's launch in November 1995. When first observed by ISO in March and April 1996, the comet was still 700 million kilometres from the Sun, and almost as far from the Earth and ISO. With its privileged view of infrared wavebands inaccessible from the Earth's surface, ISO's photometer ISOPHOT discovered that carbon dioxide was an important constituent of the comet's emissions of vapour.ISOPHOT measured the temperature of the dust cloud around Comet Hale-Bopp. In March 1996, when the comet was still more than 700 million kilometres from the Sun, the dust cloud was at minus 120 degrees C. When ISOPHOT made similar observations in October 1996, the comet was 420 million kilometres from the Sun, and the dust cloud had warmed to about minus 50 degrees C. Intensive observations of Comet Hale-Bopp were also made by ISO's Short-Wave Spectrometer SWS, the Long-Wave Spectrometer LWS, and the ISOPHOT spectrometer PHOT-S. Results are due for publication at the end of March. They will give details about the composition

  5. Photographic observations of comets at Lowell Observatory. [Halley's comet

    NASA Technical Reports Server (NTRS)

    Giclas, H. L.

    1981-01-01

    Observations of Halley's comet at Lowell Observatory cover a period from November 10, 1909 to May 17, 1911: 334 direct photographs were taken, 118 objective prism spectra, and 32 slit spectrograms of the nucleus, many of them including 5 arc minutes of the surrounding coma. Just one morning's observations are illustrated as an example of utilizing every possible resource available at the Observatory at the time. Observational improvements developed since then are described and some suggestions for the coming return of Halley's comet are made.

  6. Vaporization in Comets; outbursts from Comet Schwassmann-Wachmann 1

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    Revised estimates are presented which show that the total mass and kinetic energy in a typical Comet P/Schassmann-Wachmann 1 outburst are lower than previously estimated, and that this mass is comparable to the mass of gas vaporized, as inferred from recent observations of CO(+) in this comet. The storage of energy suggested by many authors is therefore not neccessary. A simple equilibrium vaporization of CO2 or CO which is suddenly exposed, on a nucleus that is otherwise primarily composed of H2O, is proposed. Under these conditions, calculations of the variation of vaporization with rotational phase indicate that the mechanism can quantitatively produce outbursts of the size observed.

  7. Active processes in cometary nucleus and new meteoroid swarms

    NASA Astrophysics Data System (ADS)

    Ibadinov, Kh. I.; Buriev, A. M.; Safarov, A. G.; Rahmonov, A. A.

    2015-07-01

    Based on the catalogs of comets capable of nucleus splitting and comets with abnormal tail 30 short-Jupiter-family comets were identified, which are capable of producing meteoroid swarms that do not intersect the Earth's orbit, but are of interest for drafting of space missions and studying the distribution of meteoroid streams.

  8. Comet Halley - The orbital motion

    NASA Technical Reports Server (NTRS)

    Yeomans, D. K.

    1977-01-01

    The orbital motion of Comet Halley is investigated over the interval from A.D. 837 to 2061. Using the observations from 1607 through 1911, least-squares differential orbit corrections were successfully computed using the existing model for the nongravitational forces. The nongravitational-force model was found to be consistent with the outgassing-rocket effect of a water-ice cometary nucleus and, prior to the 1910 return, these forces are time-independent for nearly a millennium. For the 1986 return, viewing conditions are outlined for the comet and the related Orionid and Eta Aquarid meteor showers.

  9. An inside look at Halley's comet

    NASA Astrophysics Data System (ADS)

    Beatty, J. K.

    1986-05-01

    The 1985-1986 emergence of Halley's comet, the first since the advent of the space age, was explored by a variety of spacecraft. The Vega 1, launched by the USSR together with the Eastern-block alliance, passed 5523 miles from the comet's nucleus at 7:20:06 Universal time. It indicated that the comet was about 300 miles closer to the sun than had been predicted. The Japanese spacecraft, Suisei, was created to map the distribution of neutral hydrogen atoms outside Halley's visible coma. Its pictures indicated that the comet's output of water varied between 25 and 60 tons per second. Five days after the Vega 2's passage through the comet, the Giotto (sponsored by the European Space Agency) probe appeared. Giotto's close approach took place 3.1 minutes after midnight UT on March 14th; the craft had passed 376 miles from its target. Giotto's data indicated that the nucleus was bigger than expected, and that the comet was composed primarily of water, CO2 and N2. The Vegas and Giotto found that as the solar wind approaches Halley, it slows gradually and the solar magnetic lines embedded in the wind begin to pile up. Pick-up ions, from the comet's halo of neutral hydrogen, were found in this solar wind. Sensors on the Vega spacecraft found a variety of plasma waves propagating inside the bow wave. In order to synthesize all the results, a conference on the exploration of Halley's comet will be held this October.

  10. Assessment and control of organic and other contaminants associated with the Stardust sample return from comet 81P/Wild 2

    NASA Astrophysics Data System (ADS)

    Sandford, Scott A.; Bajt, Saša; Clemett, Simon J.; Cody, George D.; Cooper, George; Degregorio, Bradley T.; de Vera, Vanessa; Dworkin, Jason P.; Elsila, Jamie E.; Flynn, George J.; Glavin, Daniel P.; Lanzirotti, Antonio; Limero, Thomas; Martin, Mildred P.; Snead, Christopher J.; Spencer, Maegan K.; Stephan, Thomas; Westphal, Andrew; Wirick, Sue; Zare, Richard N.; Zolensky, Michael E.

    2010-03-01

    Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si-CH3 groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust.

  11. Assessment and Control of Organic and other Contaminants Associated with the Stardust Sample Return from Comet 81P/Wild 2

    SciTech Connect

    Sandford, S.; Bajt, S; Clemett, S; Cody, G; Cooper, G; Degregorio, B; de Vera, V; Dworkin, J; Flynn, G; et al.

    2010-01-01

    Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si-CH{sub 3} groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust.

  12. Assessment and Control of Organic and Other Contaminants Associated with the Stardust Sample Return from Comet 81P/Wild 2

    SciTech Connect

    Sanford, S.; Bajt, S; Clemett, S; Cody, G; Cooper, G; Degregorio, B; DeVera, V; Dworkin, J; Elsila, J; et al.

    2010-01-01

    Numerous potential sources of organic contaminants could have greatly complicated the interpretation of the organic portions of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft. Measures were taken to control and assess potential organic (and other) contaminants during the design, construction, and flight of the spacecraft, and during and after recovery of the sample return capsule. Studies of controls and the returned samples suggest that many of these potential sources did not contribute any significant material to the collectors. In particular, contamination from soils at the recovery site and materials associated with the ablation of the heatshield do not appear to be significant problems. The largest source of concern is associated with the C present in the original aerogel. The relative abundance of this carbon can vary between aerogel tiles and even within individual tiles. This C was fortunately not distributed among a complex mixture of organics, but was instead largely present in a few simple forms (mostly as Si-CH{sub 3} groups). In most cases, the signature of returned cometary organics can be readily distinguished from contaminants through their different compositions, nonterrestrial isotopic ratios, and/or association with other cometary materials. However, some conversion of the carbon indigenous to the flight aerogel appears to have happened during particle impact, and some open issues remain regarding how this C may be processed into new forms during the hypervelocity impact collection of the comet dust.

  13. Aggregate dust particles at comet 67P/Churyumov–Gerasimenko

    NASA Astrophysics Data System (ADS)

    Bentley, Mark S.; Schmied, Roland; Mannel, Thurid; Torkar, Klaus; Jeszenszky, Harald; Romstedt, Jens; Levasseur-Regourd, Anny-Chantal; Weber, Iris; Jessberger, Elmar K.; Ehrenfreund, Pascale; Koeberl, Christian; Havnes, Ove

    2016-09-01

    Comets are thought to preserve almost pristine dust particles, thus providing a unique sample of the properties of the early solar nebula. The microscopic properties of this dust played a key part in particle aggregation during the formation of the Solar System. Cometary dust was previously considered to comprise irregular, fluffy agglomerates on the basis of interpretations of remote observations in the visible and infrared and the study of chondritic porous interplanetary dust particles that were thought, but not proved, to originate in comets. Although the dust returned by an earlier mission has provided detailed mineralogy of particles from comet 81P/Wild, the fine-grained aggregate component was strongly modified during collection. Here we report in situ measurements of dust particles at comet 67P/Churyumov–Gerasimenko. The particles are aggregates of smaller, elongated grains, with structures at distinct sizes indicating hierarchical aggregation. Topographic images of selected dust particles with sizes of one micrometre to a few tens of micrometres show a variety of morphologies, including compact single grains and large porous aggregate particles, similar to chondritic porous interplanetary dust particles. The measured grain elongations are similar to the value inferred for interstellar dust and support the idea that such grains could represent a fraction of the building blocks of comets. In the subsequent growth phase, hierarchical agglomeration could be a dominant process and would produce aggregates that stick more easily at higher masses and velocities than homogeneous dust particles. The presence of hierarchical dust aggregates in the near-surface of the nucleus of comet 67P also provides a mechanism for lowering the tensile strength of the dust layer and aiding dust release.

  14. Aggregate dust particles at comet 67P/Churyumov-Gerasimenko.

    PubMed

    Bentley, Mark S; Schmied, Roland; Mannel, Thurid; Torkar, Klaus; Jeszenszky, Harald; Romstedt, Jens; Levasseur-Regourd, Anny-Chantal; Weber, Iris; Jessberger, Elmar K; Ehrenfreund, Pascale; Koeberl, Christian; Havnes, Ove

    2016-01-01

    Comets are thought to preserve almost pristine dust particles, thus providing a unique sample of the properties of the early solar nebula. The microscopic properties of this dust played a key part in particle aggregation during the formation of the Solar System. Cometary dust was previously considered to comprise irregular, fluffy agglomerates on the basis of interpretations of remote observations in the visible and infrared and the study of chondritic porous interplanetary dust particles that were thought, but not proved, to originate in comets. Although the dust returned by an earlier mission has provided detailed mineralogy of particles from comet 81P/Wild, the fine-grained aggregate component was strongly modified during collection. Here we report in situ measurements of dust particles at comet 67P/Churyumov-Gerasimenko. The particles are aggregates of smaller, elongated grains, with structures at distinct sizes indicating hierarchical aggregation. Topographic images of selected dust particles with sizes of one micrometre to a few tens of micrometres show a variety of morphologies, including compact single grains and large porous aggregate particles, similar to chondritic porous interplanetary dust particles. The measured grain elongations are similar to the value inferred for interstellar dust and support the idea that such grains could represent a fraction of the building blocks of comets. In the subsequent growth phase, hierarchical agglomeration could be a dominant process and would produce aggregates that stick more easily at higher masses and velocities than homogeneous dust particles. The presence of hierarchical dust aggregates in the near-surface of the nucleus of comet 67P also provides a mechanism for lowering the tensile strength of the dust layer and aiding dust release. PMID:27582221

  15. High Resolution 3D Radar Imaging of Comet Interiors

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  16. Physical processes in comets

    NASA Technical Reports Server (NTRS)

    Newburn, Ray L., Jr.

    1991-01-01

    Post-Halley comets are known to be irregular objects with most nucleus activity very localized and with the dust coma capable of fragmentation and apparently being a source of gas. Older, 1-D strategies which assume steady isotropic outflow of material can give poor time-and-space averaged results, at best. With 2-D data, images through interference filters, it is hoped that: dust structures can be seen that give evidence of the proper geometry for data reduction; gradients along the axes of symmetry and evidence of fragmentation can be studied; and that evidence for gas abundance gradients associated with the dust can be found. High quality data from brighter comets can then be used to suggest improved data reduction procedures for fainter ones. To obtain such data, large image-quality interference filters were procured for use with a charge coupled device (CCD) camera at Lick Observatory, where the scale of the 1 m Nickel reflector is ideal for brighter comets. Whenever possible, data is taken simultaneously with other telescopes and equipment, especially spectroscopy at the Lick 3 m or infrared photometry at the Infrared Telescope Facility (IRTF) on Mauna Kea.

  17. Dynamic sublimation pressure and the catastrophic breakup of Comet ISON

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan K.; Johnson, Brandon C.; Bowling, Timothy; Jay Melosh, H.; Minton, David; Lisse, Carey M.; Battams, Karl

    2015-09-01

    Previously proposed mechanisms have difficulty explaining the disruption of Comet C/2012 S1 (ISON) as it approached the Sun. We describe a novel cometary disruption mechanism whereby comet nuclei fragment and disperse through dynamic sublimation pressure, which induces differential stresses within the interior of the nucleus. When these differential stresses exceed its material strength, the nucleus breaks into fragments. We model the sublimation process thermodynamically and propose that it is responsible for the disruption of Comet ISON. We estimate the bulk unconfined crushing strength of Comet ISON's nucleus and the resulting fragments to be 0.5 Pa and 1-9 Pa, respectively, assuming typical Jupiter Family Comet (JFC) albedos. However, if Comet ISON has an albedo similar to Pluto, this strength estimate drops to 0.2 Pa for the intact nucleus and 0.6-4 Pa for its fragments. Regardless of assumed albedo, these are similar to previous strength estimates of JFCs. This suggests that, if Comet ISON is representative of dynamically new comets, then low bulk strength is a primordial property of some comet nuclei, and not due to thermal processing during migration into the Jupiter Family.

  18. Coordinated analysis of Comet 81P/Wild-2 dust samples: Nanoscale measurements of its organic/ inorganic chemical and isotopic composition and optical properties

    NASA Astrophysics Data System (ADS)

    Messenger, K. N.; Messenger, S. R.; Clemett, S. J.; Keller, L. P. Class='hr'>; Zolensky, M. E.

    2006-12-01

    Dust particles released from comet 81P/Wild-2 were captured in silica aerogel on-board the STARDUST spacecraft and successfully returned to the Earth on January 15, 2006. This is the first sample of extraterrestrial materials returned from beyond the moon. STARDUST recovered thousands of particles ranging in size from 1 to 100 micrometers. The analysis of these samples is complicated by the small total mass collected (< 1 mg), its entrainment in the aerogel collection medium, and the fact that the cometary dust is comprised of submicrometer minerals and carbonaceous material. During the six month preliminary examination period, 75 tracks were extracted from the aerogel cells and 25 cometary grains were fully studied by an international collaboration among 150 scientists who investigated their mineralogy/petrology, organic/inorganic chemistry, optical properties and isotopic compositions. This scientific consortium was made possible by sophisticated sample preparation methods developed for the STARDUST mission and by recent major advances in the sensitivity and spatial resolution of analytical instruments. Coordinated and replicate analyses of the samples were made possible by subdividing individual particles into 50 nm-thick sections by ultramicrotomy, providing up to 100 sections from a 20 um particle. We present results of a coordinated study of comet Wild 2 dust samples in which individual particles were analyzed by FTIR microspectroscopy, field emission scanning-transmission electron microscopy (STEM), and isotopic measurements with a NanoSIMS 50L ion microprobe. The STEM is equipped with a thin window energy- dispersive X-ray (EDX) spectrometer that was used to acquire spectrum images that contained a high count- rate EDX spectrum in each pixel, enabling the determination of the nm-scale spatial distribution of quantitative element abundances. These samples were later analyzed by the JSC NanoSIMS 50L ion microprobe, which acquired 100 nm spatial resolution C

  19. A comet engulfs Mars: MAVEN observations of comet Siding Spring's influence on the Martian magnetosphere

    NASA Astrophysics Data System (ADS)

    Espley, Jared R.; DiBraccio, Gina A.; Connerney, John E. P.; Brain, David; Gruesbeck, Jacob; Soobiah, Yasir; Halekas, Jasper; Combi, Michael; Luhmann, Janet; Ma, Yingjuan; Jia, Yingdong; Jakosky, Bruce

    2015-11-01

    The nucleus of comet C/2013 A1 (Siding Spring) passed within 141,000 km of Mars on 19 October 2014. Thus, the cometary coma and the plasma it produces washed over Mars for several hours producing significant effects in the Martian magnetosphere and upper atmosphere. We present observations from Mars Atmosphere and Volatile EvolutioN's (MAVEN's) particles and field's instruments that show the Martian magnetosphere was severely distorted during the comet's passage. We note four specific major effects: (1) a variable induced magnetospheric boundary, (2) a strong rotation of the magnetic field as the comet approached, (3) severely distorted and disordered ionospheric magnetic fields during the comet's closest approach, and (4) unusually strong magnetosheath turbulence lasting hours after the comet left. We argue that the comet produced effects comparable to that of a large solar storm (in terms of incident energy) and that our results are therefore important for future studies of atmospheric escape, MAVEN's primary science objective.

  20. A Comet Engulfs Mars: MAVEN Observations of Comet Siding Spring's Influence on the Martian Magnetosphere

    NASA Technical Reports Server (NTRS)

    Espley, Jared R.; Dibraccio, Gina A.; Connerney, John E. P.; Brain, David; Gruesbeck, Jacob; Soobiah, Yasir; Halekas, Jasper S.; Combi, Michael; Luhmann, Janet; Ma, Yingjuan

    2015-01-01

    The nucleus of comet C/2013 A1 (Siding Spring) passed within 141,000?km of Mars on 19 October 2014. Thus, the cometary coma and the plasma it produces washed over Mars for several hours producing significant effects in the Martian magnetosphere and upper atmosphere. We present observations from Mars Atmosphere and Volatile EvolutioN's (MAVEN's) particles and field's instruments that show the Martian magnetosphere was severely distorted during the comet's passage. We note four specific major effects: (1) a variable induced magnetospheric boundary, (2) a strong rotation of the magnetic field as the comet approached, (3) severely distorted and disordered ionospheric magnetic fields during the comet's closest approach, and (4) unusually strong magnetosheath turbulence lasting hours after the comet left. We argue that the comet produced effects comparable to that of a large solar storm (in terms of incident energy) and that our results are therefore important for future studies of atmospheric escape, MAVEN's primary science objective.

  1. The Comet Halley archive: Summary volume

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek (Editor); Fry, Lori (Editor)

    1991-01-01

    The contents are as follows: The Organizational History of the International Halley Watch; Operations of the International Halley Watch from a Lead Center Perspective; The Steering Group; Astrometry Network; Infrared Studies Network; Large-Scale Phenomena Network; Meteor Studies Network; Near-Nucleus Studies Network; Photometry and Polarimetry Network; Radio Science Network; Spectroscopy and Spectrophotometry Network; Amateur Observation Network; Use of the CD-ROM Archive; The 1986 Passage of Comet Halley; and Recent Observations of Comet Halley.

  2. Spectrophotometry of faint comets: The asteroid approach

    NASA Technical Reports Server (NTRS)

    Degewij, J.

    1981-01-01

    Observing programs at optical (0.35-0.8 micron) and near-infrared (1.1-2.4 micron) wavelengths, directed at the acquisition of reflection spectra of faint and distant comets, are described. The ultimate goal is to obtain spectrophotometric measurements of comets for which a significant part of the light is expected to be reflected by the solid surface of the nucleus.

  3. Thermal modeling of Halley's comet

    USGS Publications Warehouse

    Weissman, P.R.; Kieffer, H.H.

    1984-01-01

    The comet thermal model of Weissman and Kieffer is used to calculate gas production rates and other parameters for the 1986 perihelion passage of Halley's Comet. Gas production estimates are very close to revised pre-perihelion estimates by Newburn based on 1910 observations of Halley; the increase in observed gas production post-perihelion may be explained by a variety of factors. The energy contribution from multiply scattered sunlight and thermal emission by coma dust increases the total energy reaching the Halley nucleus at perihelion by a factor of 2.4. The high obliquity of the Halley nucleus found by Sekanina and Larson may help to explain the asymmetry in Halley's gas production rates around perihelion. ?? 1984.

  4. Interstellar and cometary ices: Molecular emission from comet Hale-Bopp

    NASA Technical Reports Server (NTRS)

    Irvine, W. M.; DeVries, C. H.; Dickens, J. E.; Lovell, A. J.; Schloerb, F. P.; Senay, M.; Jewitt, D.; Matthews, H. E.

    1997-01-01

    Observations of rotational translations of neutral molecules, radicals and ions in the comet Hale-Bopp are reported on. Sample spectra and maps of the emission for the J = 1 to 0 transition of HCN, the J = 2 to 1 transition of CS and the J = 1 to 0 transition of HCO+ are presented. While the emission from HCN is typically centered on the position of the nucleus and is symmetric, the emission from HCO+ exhibits multiple peaks, together with evidence for acceleration away from the nucleus.

  5. The C-12/C-13 abundance ratio in Comet Halley

    SciTech Connect

    Wyckoff, S.; Lindholm, E.; Wehinger, P.A.; Peterson, B.A.; Zucconi, J.M.

    1989-04-01

    The individual (C-13)N rotational lines in Comet Halley are resolved using high-resolution spectra of the CN B2Sigma(+)-X2Sigma(+) (0,0) band. The observe C-12/C-13 abundance ratio excludes a site of origin for the comet near Uranus and Neptune and suggests a condensation environment quite distinct from other solar system bodies. Two theories are presented for the origin of Comet Halley. One theory suggest that the comet originated 4.5 Gyr ago in an inner Oort cloud at a heliocentric distance greater than 100 AU where chemical fractionation led to the C-13 enrichment in the CN parent molecule prior to condensation of the comet nucleus. According to the other, more plausible theory, the comet nucleus condensed relatively recently from the interstellar medium which has become enriches in C-13 and was subsequently gravitationally captured by the solar system. 107 refs.

  6. Comparative CO/CO2 Production in NEOWISE-Observed Comets

    NASA Astrophysics Data System (ADS)

    Bauer, James M.; Stevenson, Rachel; Kramer, Emily; Grav, Tommy; Mainzer, A.; Masiero, Joseph; Cutri, Roc; Dailey, John; Sonnett, Sarah; Nugent, Carolyn; Meech, Karen; Walker, Russ; Lisse, Carey; Waszczak, Adam; Lucas, Andrew; Blair, Nathan; Wright, Edward

    2014-11-01

    NEOWISE [1,2] is the NASA Planetary Division-funded mission that utilizes data from the Wide-Field Infrared Survey Explorer (WISE) spacecraft to detect and characterize moving objects. NEOWISE has provided a large statistical sampling of comets in various states of activity, containing a variety of types of comets. This data set provides a unique opportunity to discern the trends in their observable properties and compare the ensemble properties between comet types, and may allow us to discern subtypes. The WISE spacecraft has discovered 22 new cometary bodies and observed over 160 comets, yielding the largest sample of comets yet observed at thermal-IR wavelengths. This collection offers a diverse range of comet behavior including highly active and inactive bodies from both long period comet (LPC) and short period comet (SPC) populations. We have conducted analyses of the physical properties of the NEOWISE-observed comets. In particular, our analysis constrains the quantity and nature of the ejected coma dust for large particles, and provides estimates of the nucleus sizes and albedos, as well as the production rates and extent of the CO/CO2 gas species. WISE is sensitive to CO and CO2 emission lines that fall within the 4.6 micron band pass (W2), at 4.3 and 4.7 microns, respectively. The quantity of dust present is found from the signal in the three other bands, centered at 3.4, 12, & 22 microns, and the dust signal in W2 is deduced, such that excess signal in W2 can be identified. We find detectable signal excess in nearby comets ~1AU distance from the Sun, as well as those as distant as 4.5AU, and approximately a third of both LPCs and SPCs show 4.6 micron infrared excess in our data. We will discuss in depth the production rates for the CO/CO2 gas species derived from the entire sample of comets. Acknowledgements: This work was supported by NEOWISE, which is a project of JPL/CalTech, funded by the Planetary Science Division of NASAReferences: [1] Mainzer, A

  7. Comet Siding Spring at Mars: Using MRO to Interpret HST Imaging of Comets

    NASA Astrophysics Data System (ADS)

    Li, Jian-Yang

    2014-10-01

    Comet C/Siding Spring is a dynamically new (DN) comet, and will approach Mars to within 135,000 km on October 19, 2014. This encounter presents the first ever opportunity for us to observe a DN comet from close distances. The planned observations from the Mars Reconnaissance Orbiter (MRO) can potentially resolve the nucleus to 140 m/pix, and trace the dust and gas activity to their sources on the nucleus. This "natural flyby" will allow us to directly compare a DN comet with previous comet flyby mission targets (all highly evolved comets), and generalize those mission results to more comets. We propose to observe C/Siding Spring with seven HST orbits during its Mars encounter. These observations will take advantage of this rare opportunity to study the evolution of C/Siding Spring, use the MRO observations to help us interpret HST observations of comets in general, and put the MRO observations into a broader context. We plan to image the dust coma with filters F689M and F845M, and the cyanogen coma with filter FQ387N. Comparisons with previous HST observations when the comet was far from the Sun, combined with MRO observations, will allow us to study the evolution of the coma of C/Siding Spring, and tie it to the sources on the nucleus. Putting MRO and HST observations together, we can reconstruct the 3-D structure in the inner coma, and study the possible chemical heterogeneity on the nucleus. HST is needed because of the unfavorable observing conditions from the ground, the specific timing of our observations, and its high resolution and high sensitivity. This proposal is part of a coordinated observing campaign of C/Siding Spring both from the ground and from space.

  8. Halley's comet - Its size and decay rate

    NASA Astrophysics Data System (ADS)

    Wallis, M. K.; Wickramasinghe, N. C.

    1985-09-01

    The outgassing rates inferred from the 1910 apparition and the brightness decay over the previous two millenia are compatible with the minimum nuclear brightness currently observed if the comet nucleus is small, 1.8 - 2.7 km radius with an albedo of 0.1 - 0.2. Outgassing is faster than from a bare nucleus of dirty H2O-ice, which is attributed either to a hot microdust coma or to an organic polymer composition. Halley's comet will decay away within another 45 - 65 apparitions.

  9. Comets: chemistry and chemical evolution.

    PubMed

    Donn, B

    1982-01-01

    Lasting commitment to cosmic chemistry and an awareness of the fascinating role of comets in that study was a consequence of an association with Harold Urey early in my astronomical career. Urey's influence on cometary research spread as colleagues with whom I was associated, in turn, developed their own programs in cometary chemistry. One phase of the Chicago research shows that Whipple's icy nucleus would be below about 250 K. This property, combined with their small internal pressure, means cometary interiors remain essentially unchanged during their lifetime. Observations of cometary spectra indicate that they are rich in simple organic species. Experiments on comet-like ice mixture suggests that the extensive array of interstellar molecules also may be found in comets. The capture of cometary debris by the earth or the impact of comets would have been an early source of biochemically significant molecules. Recent hypotheses on radiogenic heating and melting of water ice in the central zone of nuclei do not seem consistent with recent observations or ideas of structure. Thus comets are not a likely place for life to develop. PMID:7097774

  10. Lessons learnt from Comets Tempel and Wild: Implications for the Rosetta Lander

    NASA Astrophysics Data System (ADS)

    Ulamec, S.; Biele, J.; Bohnhardt, H.; Espinasse, S.; Gaudon, P.; Goesmann, F.; Knollenberg, J.; Kuhrt, E.; Richter, L.; Roll, R.

    "Rosetta" is a Cornerstone Mission of the previous Horizon 2000 ESA Programme. Its goal is to rendezvous with comet 67/P Churyumov-Gerasimenko after a 10 years cruise and to study both its nucleus and coma through an orbiting spacecraft and a landed platform. The latter, named "Philae", has been designed to land softly on the comet nucleus and is equipped with 10 scientific instruments to perform in-situ studies of the cometary material. Philae has been provided by an international consortium with participation of Germany (lead), France, Italy, UK, Finland, Ireland, Hungary and Austria. Philae will perform scientific investigations to get a first in-situ analysis of primordial material from the early solar system directly on a cometary nucleus, as well as study its structure and physical properties. Rosetta has successfully been launched on March 2nd, 2004 from Kourou in French Guyane. Since then two missions to comets, Deep Impact to comet Tempel 1 (July 2005) and the return of samples from comet Wild 2 by Stardust (January 2006), have improved our understanding of these bodies considerably. The paper will discuss, in how far this partly revised image of the nature of comets could influence the mission of Philae. Due to the different scenario of Rosetta, compared to flyby and impact missions, certain parallels, however, are difficult to be drawn. The surface properties of the nucleus are important for safe landing and anchoring. The instruments performance is partly depending on the sample material. The delivery of the Lander to the surface of the comet is foreseen in November 2014 at a distance of about 3 Astronomical Units (AU) to the sun. This will take place after a phase of close investigation of Churyumov-Gerasimenko by the Rosetta Orbiter instruments. After landing first science operations sequence of about 120 hours is planned, when several instruments and sub-systems can be operated simultaneously. In the following long term operations phase, relying on

  11. Comet explorer spacecraft design project

    NASA Technical Reports Server (NTRS)

    1987-01-01

    The small, chemically primitive objects of the solar system, comets and asteroids, are one of the most important frontiers remaining for future planetary exploration. So stated the Solar System Exploration Committee of the NASA Advisory Council in its 1986 report 'Planetary Exploration Through the Year 2000.' The Halley's comet flyby missions completed last spring raised more questions than were answered about the nature of comets. The next mission to a comet must be able to explore some of these questions. In the late 1990's, a spacecraft might be built to explore the hazardous area surrounding a comet nucleus. Rigorous pointing requirements for remote sensing instruments will place a considerable burden on their attendant control systems. To meet these requirements we have pursued the initial design and analysis of a multi-bodied comet explorer spacecraft. Sized so as to be built on-orbit after the space station is operational, the spacecraft is comprised of Orbit Replaceable Unit (ORU) subsystems, packaged into two major components: a three-axis controlled instrument platform and a spinning, detached comet dust shield. Such a configuration decouples the dynamics of dust impaction from the stringent pointing out requirements of the imaging experiments. At the same time, it offers an abundance of simple analysis problems that may be carried out by undergraduates. These problems include the following: Selection of subsystem components, sizing trade studies, investigation of three-axis and simple spin dynamics, design of simple control systems, orbit determination, and intercept trajectory generation. Additionally, such topics as proposal writing project management, human interfacing, and costing have been covered. A new approach to design teaching has been taken, whereby students will 'learn by teaching.' They are asked to decompose trade options into a set of 'if-then' rules, which then 'instruct' the Mechanically Intelligent Designer (MIND) expert design system

  12. Polarimetry of comets

    NASA Astrophysics Data System (ADS)

    Hines, D.

    2014-07-01

    Linear polarimetry is a powerful diagnostic tool that can provide information that may not be available from total intensity alone. While total-intensity imaging in two band-passes yields a color and places some constraints on the gross dust properties in a comet, there remain significant difficulties in interpreting such color information, and especially determining the detailed structure, composition, shape/size, or orientation of the dust particles. By adding polarimetry observations (even in a single band-pass) these properties can be highly constrained, improving significantly the characterization of cometary dust particles (e.g., [1,2]). The polarization of light scattered by cometary dust depends on the angle through which the light is scattered, often parameterized using the Sun-Target-Observer (STO) angle, or phase angle α, which is related to the physical scattering angle via α = 180 - scattering angle. Maximum polarization occurs at α ˜ 90--100 degrees with the plane of the scattered-light dominant electric vector (plane of polarization) perpendicular to the STO scattering plane. However, for α ≲ 20 degrees, the plane of polarization often can be in the STO plane, a phenomenon referred to as ''negative polarization''. While aperture polarimetry can yield the globally averaged properties of dust particles, imaging polarimetry provides even more diagnostic power by enabling different populations of particles, in structures such as jets, to be identified and characterized. Ground-based imaging polarimetry of comets obtained at various phase angles usually show different polarization levels throughout the coma, indicating an inhomogeneous distribution of dust particles [3--6]. While much of the coma is often positively (or slightly negatively) polarized, the innermost region, called the circum-nucleus halo, can have a large negative polarization (˜ -6 percent) at small phase angles (α ˜ 10--15 degrees). This implies that particles in the circum-nucleus

  13. Comet and Asteroid Missions in NASA's New Millennium Program

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.

    2000-01-01

    NASA's New Millennium Program (NMP) is designed to develop, test, and flight validate new, advanced technologies for planetary and Earth exploration missions, using a series of low cost spacecraft. Two of NMP's current missions include encounters with comets and asteroids. The Deep Space 1 mission was launched on October 24, 1998 and will fly by asteroid 1992 KD on July 29, 1999, and possibly Comet Wilson-Harrington and/or Comet Borrelly in 2001. The Space Technology 4/Champollion mission will be launched in April, 2003 and will rendezvous with, orbit and land on periodic Comet Tempel 1 in 2006. ST-4/Champollion is a joint project with CNES, the French space agency. The DS-1 mission is going well since launch and has already validated several major technologies, including solar electric propulsion (SEP), solar concentrator arrays, a small deep space transponder, and autonomous navigation. The spacecraft carries two scientific instruments: MICAS, a combined visible camera and UV and IR spectrometers, and PEPE, an ion and electron spectrometer. Testing of the science instruments is ongoing. Following the asteroid encounter in July, 1999, DS-1 will go on to encounters with one or both comets if NASA approves funding for an extended mission. The ST-4/Champollion mission will use an advanced, multi-engine SEP system to effect a rendezvous with Comet P/Tempel 1 in February, 2006, after a flight time of 2.8 years. After orbiting the comet for several months in order to map its surface and determine its gravity field, ST-4/Chainpollion will descend to the comet's surface and will anchor itself with a 3-meter long harpoon. Scientific experiments include narrow and wide angle cameras for orbital mapping, panoramic and near-field cameras for landing site mapping, a gas chromatograph/mass spectrometer, a combined microscope and infrared spectrometer, and physical properties probes. Cometary samples will be obtained from depths up to 1.4 meters. The spacecraft is solar powered

  14. Overview of the Results of the Organics PET Study of the Cometary Samples from Comet Wild 2 by the Stardust Mission

    NASA Technical Reports Server (NTRS)

    Sandford, S. A.; Aleon, J.; Alexander, C. M. O'D.; Araki, T.; Bajt, S.; Baratta, G. A.; Borg, J.; Bradley J. P.; Brownlee, D. E.; Brucato, J. R.; Burchell, M. J.; Busemann, H.; Butterworth, A.; Clemett, S. J.; Cody, G.; Colangeli, L.; Cooper, G.

    2007-01-01

    STARDUST is the first mission designed to bring samples back to Earth from a known comet. The captured samples were successfully returned to Earth on 15 Jan 2006, after which they were subjected to a preliminary examination by a number of teams of scientists from around the world. This abstract describes the efforts of the Organics Preliminary Examination Team (PET). More detailed discussions of specific analyses of the samples can be found in other papers presented at this meeting by individual members of the Organics PET (see the author list above for team members). The studied Wild 2 gas and dust samples were collected by impact onto aerogel tiles and Al foils when the spacecraft flew through the coma of 81P/Wild 2 on 2 Jan 2004 at a relative velocity of approx.6.1 kilometers per second. After recovery of the Sample Return Capsule (SRC) on 15 Jan 2006, the aerogel collector trays were removed in a clean room at JSC. After documentation of the collection, selected aerogel tiles and aluminum foils were removed and aerogel and cometary samples extracted for study.

  15. The Composition of Comets

    NASA Astrophysics Data System (ADS)

    Cochran, Anita L.; Levasseur-Regourd, Anny-Chantal; Cordiner, Martin; Hadamcik, Edith; Lasue, Jérémie; Gicquel, Adeline; Schleicher, David G.; Charnley, Steven B.; Mumma, Michael J.; Paganini, Lucas; Bockelée-Morvan, Dominique; Biver, Nicolas; Kuan, Yi-Jehng

    2015-12-01

    This paper is the result of the International Cometary Workshop, held in Toulouse, France in April 2014, where the participants came together to assess our knowledge of comets prior to the ESA Rosetta Mission. In this paper, we look at the composition of the gas and dust from the comae of comets. With the gas, we cover the various taxonomic studies that have broken comets into groups and compare what is seen at all wavelengths. We also discuss what has been learned from mass spectrometers during flybys. A few caveats for our interpretation are discussed. With dust, much of our information comes from flybys. They include in situ analyses as well as samples returned to Earth for laboratory measurements. Remote sensing IR observations and polarimetry are also discussed. For both gas and dust, we discuss what instruments the Rosetta spacecraft and Philae lander will bring to bear to improve our understanding of comet 67P/Churyumov-Gerasimenko as "ground-truth" for our previous comprehensive studies. Finally, we summarize some of the initial Rosetta Mission findings.

  16. Episodic Aging and End States of Comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    2008-01-01

    It is known that comets are aging very rapidly on cosmic scales, because they rapidly shed mass. The processes involved are (i) normal activity - sublimation of ices and expulsion of dust from discrete emission sources on and/or below the surface of a comet's nucleus, and (ii) nuclear fragmentation. Both modes are episodic in nature, the latter includes major steps in the comet's life cycle. The role and history of dynamical techniques used are described and results on mass losses due to sublimation and dust expulsion are reviewed. Studies of split comets, Holmes-like exploding comets, and cataclysmically fragmenting comets show that masses of 10 to 100 million tons are involved in the fragmentation process. This and other information is used to investigate the nature of comets' episodic aging. Based on recent advances in understanding the surface morphology of cometary nuclei by close-up imaging, a possible mechanism for large-scale fragmentation events is proposed and shown to be consistent with evidence available from observations. Strongly flattened pancake-like shapes appear to be required for comet fragments by conceptual constraints. Possible end states are briefly examined.

  17. Gas release in comet nuclei.

    PubMed

    Prialnik, D; Bar-Nun, A

    1990-11-01

    The evolution of a comet nucleus is investigated, taking into account the crystallization process by which the gas trapped in the ice is released to flow through the porous ice matrix. The equations of conservation of the energy and of the masses of ice and gas are solved throughout the nucleus, to obtain the evolution of the temperature, gas pressure and density profiles. A spherical nucleus composed of cold, porous amorphous ice, with 10% of CO trapped in it, serves as initial model. Several values of density (porosity) and pore size are considered. For each combination of parameters the model is evolved for 20-30 revolutions in comet P/Halley's orbit. Two aspects of the release of gas upon crystallization are analyzed and discussed: (a) the resulting continuous outward flux with high peaks at the time of crystallization, which is a cyclic process in the low-density models and sporadic in the high-density ones; (b) the internal pressures obtained down to depths of a few tens to approximately 200 m (depending on parameters), that are found to exceed the compressional strength of cometary ice. As a result, both cracking and explosions of the overlying ice layer and ejection of gas and ice/dust grains are expected to follow crystallization. They should appear as outbursts or sudden brightening of the comet. The model of 0.2 g cm-3 density is found to reproduce quite well many of the light-curve and activity characteristics of comet P/Halley. PMID:11538699

  18. On observing comets for nuclear rotation

    NASA Astrophysics Data System (ADS)

    Whipple, F. L.

    1981-10-01

    The prevalent non-gravitational motions among comets demonstrate that the sublimination does not reach a maximum at the instant of maximum insolation on the nucleus. The occurrence of halos or "parabolic" envelopes in the comae of some comets and of jets, rays, fans, streamers and similar phenomena very near the nucleus in the brightest comets demonstrates that the sublimation process is not uniform over the nuclei. In other words, the nuclei of many comets contain relatively small active regions which provide much or most of the sublimation when these areas are turned toward the Sun. The period of rotation can be determind by measurement of the diameters of the halos or of the latus recta of the "parabolic" envelopes, if the expansion velocities are averaged from observations as a function of solar distance. Experience from analyses of some 80 well observed comets shows that the nuclei are "spotted" for more than a third of all comets, regardless of the "age" as measured by the original inverse semimajor axis including correction for planetary perturbations.

  19. On observing comets for nuclear rotation

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1981-01-01

    The prevalent non-gravitational motions among comets demonstrate that the sublimination does not reach a maximum at the instant of maximum insolation on the nucleus. The occurrence of halos or "parabolic" envelopes in the comae of some comets and of jets, rays, fans, streamers and similar phenomena very near the nucleus in the brightest comets demonstrates that the sublimation process is not uniform over the nuclei. In other words, the nuclei of many comets contain relatively small active regions which provide much or most of the sublimation when these areas are turned toward the Sun. The period of rotation can be determind by measurement of the diameters of the halos or of the latus recta of the "parabolic" envelopes, if the expansion velocities are averaged from observations as a function of solar distance. Experience from analyses of some 80 well observed comets shows that the nuclei are "spotted" for more than a third of all comets, regardless of the "age" as measured by the original inverse semimajor axis including correction for planetary perturbations.

  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. Studying Jupiter-Family Comets and Long Period Comets Detected by WISE/NEOWISE

    NASA Astrophysics Data System (ADS)

    Kramer, E. A.; Fernandez, Y.; Bauer, J. M.; Mainzer, A.; Walker, R. G.; Grav, T.; Masiero, J.; Lisse, C.; Meech, K. J.; Cutri, R. M.; McMillan, R. S.; Tholen, D. J.; Wright, E.

    2011-10-01

    The WISE mission surveyed the sky in four infrared wavelength bands from Jan. 2010 to Feb. 2011. By covering the entire sky, WISE serendipitously observed a large number of active comets. We will present preliminary results from the analysis of several Jupiter-family comets and long period comets (listed in Table 1). The analysis will characterize various properties of each body, including dust production rate, grain properties, nucleus size estimates, albedo constraints, and constraints of the CO/CO2 gas emission. Several of these objects were also observed as part of the Spitzer SEPPCoN program, allowing comparisons to be made between these two studies.

  2. When comets get old: A synthesis of comet and meteor observations of the low activity comet 209P/LINEAR

    NASA Astrophysics Data System (ADS)

    Ye, Quan-Zhi; Hui, Man-To; Brown, Peter G.; Campbell-Brown, Margaret D.; Pokorný, Petr; Wiegert, Paul A.; Gao, Xing

    2016-01-01

    It is speculated that some weakly active comets may be transitional objects between active and dormant comets. These objects are at a unique stage of the evolution of cometary nuclei, as they are still identifiable as active comets, in contrast to inactive comets that are observationally indistinguishable from low albedo asteroids. In this paper, we present a synthesis of comet and meteor observations of Jupiter-family Comet 209P/LINEAR, one of the most weakly active comets recorded to-date. Images taken by the Xingming 0.35-m telescope and the Gemini Flamingo-2 camera are modeled by a Monte Carlo dust model, which yields a low dust ejection speed (1/10 of that of moderately active comets), dominance of large dust grains, and a low dust production of 0.4kgs-1 at 19 d after the 2014 perihelion passage. We also find a reddish nucleus of 209P/LINEAR that is similar to D-type asteroids and most Trojan asteroids. Meteor observations with the Canadian Meteor Orbit Radar (CMOR), coupled with meteoroid stream modeling, suggest a low dust production of the parent over the past few hundred orbits, although there are hints of a some temporary increase in activity in the 18th century. Dynamical simulations indicate 209P/LINEAR may have resided in a stable near-Earth orbit for ∼104 yr, which is significantly longer than typical JFCs. All these lines of evidence imply that 209P/LINEAR as an aging comet quietly exhausting its remaining near surface volatiles. We also compare 209P/LINEAR to other low activity comets, where evidence for a diversity of the origin of low activity is seen.

  3. Space observations of comets during solar flares: A possible explanation for comet brightness outbursts

    NASA Astrophysics Data System (ADS)

    Ibadov, S.

    2012-02-01

    Problems connected with mechanisms for comet brightness outbursts as well as for gamma-ray bursts remain open. Meantime, calculations show that irradiation of a certain class of comet nuclei, having high specific electric resistance, by intense fluxes of energetic protons and positively charged ions with kinetic energies more than 1 MeV/nucleon, ejected from the Sun during strong solar flares, can produce a macroscopic high-voltage electric double layer with positive charge in the subsurface zone of the nucleus, during irradiation times of the order of 10-100 h at heliocentric distances around 1-10 AU. The maximum electric energy accumulated in such layer will be restricted by the electric discharge potential of the layer material. For comet nuclei with typical radii of the order of 1-10 km the accumulated energy of such natural electric capacitor is comparable to the energy of large comet outbursts that are estimated on the basis of ground based optical observations. The impulse gamma and X-ray radiation together with optical burst from the comet nucleus during solar flares, anticipated due to high-voltage electric discharge, may serve as an indicator of realization of the processes above considered. Multi-wavelength observations of comets and pseudo-asteroids of cometary origin, having brightness correlation with solar activity, using ground based optical telescopes as well as space gamma and X-ray observatories, during strong solar flares, are very interesting for the physics of comets as well as for high energy astrophysics.

  4. Comet Borrelly Slows Solar Wind

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Over 1300 energy spectra taken on September 22, 2001 from the ion and electron instruments on NASA's Deep Space 1 span a region of 1,400,000 kilometers (870,000 miles) centered on the closest approach to the nucleus of comet Borrelly. A very strong interaction occurs between the solar wind (horizontal red bands to left and right in figure) and the comet's surrounding cloud of dust and gas, the coma. Near Deep Space 1's closest approach to the nucleus, the solar wind picked up charged water molecules from the coma (upper green band near the center), slowing the wind sharply and creating the V-shaped energy structure at the center.

    Deep Space 1 completed its primary mission testing ion propulsion and 11 other advanced, high-risk technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to undertake this chancy but exciting, and ultimately successful, encounter with the comet. More information can be found on the Deep Space 1 home page at http://nmp.jpl.nasa.gov/ds1/ .

    Deep Space 1 was launched in October 1998 as part of NASA's New Millennium Program, which is managed by JPL for NASA's Office of Space Science, Washington, D.C. The California Institute of Technology manages JPL for NASA.

  5. Water Ice in Comets: A Comparative Study

    NASA Astrophysics Data System (ADS)

    Protopapa, Silvia; Sunshine, J.; Feaga, L. M.; Kelley, M. S.; A'Hearn, M. F.; Farnham, T.; DIXI Team

    2013-06-01

    Processes involving the sublimation of volatiles dominate cometary activity and drive the release of ancient material from within the nucleus into the coma. As comets are kept cold for most of their history, they contain the least processed primordial materials that accumulated into the giant planets. In addition, comets may have delivered their ices and organics to the primitive Earth. The Deep Impact eXtended Investigation (DIXI) to comet Hartley 2 revealed a highly active comet with bright icy-rich jets. We present a detailed characterization of the composition and texture of the ices and refractories in the inner-most coma of Hartley 2, closer than a few kilometers from the surface. This analysis is conducted using laboratory measurements of optical constants of cometary analog materials. We also discuss the implications of these findings on the accretion process that led to the formation of cometary nuclei and therefore of planets. The physical makeup of the ice grains in comet Hartley 2 is compared with that of water ice in the interior, surface, and coma of other comets (e.g., 9P/Tempel 1, C/2002 T7 (LINEAR), 17P/Holmes). Through this comparative study, we investigate how ice is redistributed from the interior to the surface and ultimately into the coma of comets.

  6. Spanish Monitoring of Comets: Making Sense of Amateur Photometric Data

    NASA Astrophysics Data System (ADS)

    Kidger, Mark R.

    2002-03-01

    Amateur astronomers have always represented an important observing group in cometary astronomy. Much of our knowledge of cometary light curves has come from amateur data, initially in the form of total visual magnitude estimates and now increasingly in the form of CCD observations. The increasingly widespread use by amateur astronomers of CCD cameras of excellent sensitivity and good cosmetic quality has revolutionised astrometry, allowing far more intensive astrometric monitoring of comets to be carried out down to magnitude 18 and fainter, with a corresponding enormous increase in the quality of calculated orbits. Although amateur CCD photometry is extensively available in the Internet, its use has been less widespread. The reason is the lack of standardisation in the way that this data is taken that leads to amateur CCD light curves having enormous dispersion. All amateur CCD photometry is aperture photometry, but it is seen that neither does it represent well the equivalent of m1 (total visual magnitude), even with a large aperture, nor is it close to the definition of m2 (the nucleus magnitude). The problem is examined using data from the Spanish Comet Observers Group archives to show that by careful standardisation of data acquisition amateur CCD data can produce high quality, well-sampled and physically meaningful light curves. Examples are presented of the results for recent comets including 19P/Borrelly, 51P/Harrington, C/2001 TU80 (LINEAR-NEAT), C/2000 WM1 (LINEAR) & C/2001 A2 (LINEAR).

  7. Comet rendezvous mission study

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

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

  8. From interstellar dust to comets

    NASA Technical Reports Server (NTRS)

    Greenberg, J. M.

    1989-01-01

    The bulk and microstructure of comet nuclei are derived from the morphological structure and chemical composition of submicron sized interstellar dust grains which have undergone cold aggregation in the pre-solar nebula. The evolutionary picture of dust which is emerging is a cyclic one in which the particles, before being destroyed or going into solar system bodies, find themselves during their 5 billion year lifetime alternately in diffuse clouds and in molecular clouds. A small silicate core captured within a molecular cloud accretes various ices and gradually builds up an inner mantle of organic refractory material which has been produced by photoprocessing of the volatile ices. Clumps of grains form, and then clumps of clumps, and so on, until finally we reach the size of the comet nucleus.

  9. Rationalization of Comet Halley's periods

    NASA Astrophysics Data System (ADS)

    Belton, M. J. S.

    1990-07-01

    The sense of long axis orientation of Comet Halley during the Vega 1 encounter must be reversed from that deduced by Sagdeev et al. (1986) in order to harmonize the comet nucleus' Vega/Giotto-observed orientations with periodicities extracted from time-series brightness data. It is also demonstrated that Vega/Giotto observations can be satisfied by either a 2.2- or 3.7-day long-axis free precession period. A novel Fourier algorithm is used to reanalyze five independent data sets; strong evidence is adduced for periods harmonically related to a 7.4-day period. The preferred candidate models for Halley's nuclear rotation are characterized by a long-axis precession period of 3.7 days.

  10. Navigation of the EPOXI Spacecraft to Comet Hartley 2

    NASA Technical Reports Server (NTRS)

    Bhaskaran, Shyam; Abrahamson, Matt; Chesley, Steven; Chung, Min-Kun; Halsell, Allen; Haw, Robert; Helfrich, Cliff; Jefferson, David; Kennedy, Brian; McElrath, Tim; Owen, William; Rush, Brian; Smith, Jonathon; Wang, Tseng-Chan; Yen, Chen-Wan

    2011-01-01

    On November 4, 2010, the EPOXI spacecraft flew by the comet Hartley 2, marking the fourth time that a NASA spacecraft successfully captured high resolution images of a cometary nucleus. EPOXI is the extended mission of the Deep Impact mission, which delivered an impactor on comet Tempel-1 on July 4, 2005. EPOXI officially started in September 2007 and eventually took over 3 years of flight time and had 3 Earth gravity assists to achieve the proper encounter conditions. In the process, the mission was redesigned to accommodate a new comet as the target and changes in the trajectory to achieve better imaging conditions at encounter. Challenges in navigation of the spacecraft included precision targeting of several Earth flybys and the comet encounter, uncertainties in determining the ephemeris of the comet relative to the spacecraft, and the high accuracy trajectory knowledge needed to image the comet during the encounter. This paper presents an overview of the navigation process used for the mission.

  11. Astrometry, morphology, and polarimetry of Comet Donati in 1858

    NASA Astrophysics Data System (ADS)

    Pettersen, Bjørn Ragnvald

    2015-03-01

    We present unpublished observations of Comet Donati 1858 V recently recovered in an old storage facility at the University Observatory in Oslo. Carefully-made drawings reveal temporal changes in the appearance of this comet. Fine structures in the tail were noted, some of which were short lived. Envelopes in the comet's head, apparently due to outgassing from the nucleus, were monitored over several days. Astrometric positions of the comet's head derived by various combinations of telescopes and micrometers reveal a standard deviation of ± 6". Visual polarimetry of the coma and tail revealed polarized light and determined that the polarization plane contained the comet and the Sun. Thus the polarized light from the comet was reflected sunlight. The observations are discussed in relation to contemporary publications.

  12. Comet Halley, parameter study I

    SciTech Connect

    Huebner, W.F.; Fikani, M.M.

    1982-06-01

    To aid in defining a mission to comet P/Halley, its inner coma is simulated by a computer program that models time-dependent chemical reactions in a radially and isentropically expanding gas, taking into account attenuation of solar ultraviolet radiation in the subsolar direction. Column density predictions are based on intelligently selected combinations of poorly known values for nucleus parameters that include size, visual albedo, and infrared emissivity. Only one chemical composition and a minor modification of it are considered here; the dust-to-gas ratio in this model is zero. Although the somewhat optimistically volatile composition chosen here favors a smaller nucleus, a mean nuclear radius of only 0.5 km is unlikely. No significant increase of molecular column density is predicted by this model as a spacecraft approaches, once it is less than a few 10/sup 4/ km from the nucleus. Predictions are made for various heliocentric distances of interest for comet missions and for ground observations.

  13. Activity in distant comets

    NASA Technical Reports Server (NTRS)

    Luu, Jane X.

    1992-01-01

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

  14. Dynamical and Physical Models of Ecliptic Comets

    NASA Astrophysics Data System (ADS)

    Dones, L.; Boyce, D. C.; Levison, H. F.; Duncan, M. J.

    2005-08-01

    In most simulations of the dynamical evolution of the cometary reservoirs, a comet is removed from the computer only if it is thrown from the Solar System or strikes the Sun or a planet. However, ejection or collision is probably not the fate of most active comets. Some, like 3D/Biela, disintegrate for no apparent reason, and others, such as the Sun-grazers, 16P/Brooks 2, and D/1993 F2 Shoemaker-Levy 9, are pulled apart by the Sun or a planet. Still others, like 107P/Wilson Harrington and D/1819 W1 Blanpain, are lost and then rediscovered as asteroids. Historically, amateurs discovered most comets. However, robotic surveys now dominate the discovery of comets (http://www.comethunter.de/). These surveys include large numbers of comets observed in a standard way, so the process of discovery is amenable to modeling. Understanding the selection effects for discovery of comets is a key problem in constructing models of cometary origin. To address this issue, we are starting new orbital integrations that will provide the best model to date of the population of ecliptic comets as a function of location in the Solar System and the size of the cometary nucleus, which we expect will vary with location. The integrations include the gravitational effects of the terrestrial and giant planets and, in some cases, nongravitational jetting forces. We will incorporate simple parameterizations for mantling and mass loss based upon detailed physical models. This approach will enable us to estimate the fraction of comets in different states (active, extinct, dormant, or disintegrated) and to track how the cometary size distribution changes as a function of distance from the Sun. We will compare the results of these simulations with bias-corrected models of the orbital and absolute magnitude distributions of Jupiter-family comets and Centaurs.

  15. The Deep Space 4/Champollion Comet Rendezvous and Lander Technology Demonstration Mission

    NASA Technical Reports Server (NTRS)

    Smythe, William D.; Weissman, Paul R.; Muirhead, Brian K.; Tan-Wang, Grace H.; Sabahi, Dara; Grimes, James M.

    2000-01-01

    The Deep Space 4/Champollion mission is designed to test and validate technologies for landing on and anchoring to small bodies, and sample collection and transfer, in preparation for future sample return missions from comets, asteroids, and satellites. in addition, DS-4 will test technologies for advanced, multi-engine solar electric propulsion (SEP) systems, inflatable-rigidizable solar arrays, autonomous navigation and precision guidance for landing, autonomous hazard detection and avoidance, and advanced integrated avionics and packaging concepts. Deep Space-4/Champollion consists of two spacecraft: an orbiter/carrier vehicle which includes the multi-engine SEP stage, and a lander, called Champollion, which will descend to the surface of the 46P/Tempel 1 cometary nucleus. The spacecraft will launch in April, 2003 and land on the comet in September, 2006 Deep Space 4/Champollion is a joint project between NASA and CNES, the French space agency.

  16. ISO's analysis of Comet Hale-Bopp

    NASA Astrophysics Data System (ADS)

    1997-03-01

    The European Space Agency's Infrared Space Observatory ISO inspected Comet Hall-Bopp during the spring and autumn of 1996. The need to keep ISO's telescope extremely cold restricts the spacecraft's pointing in relation to the Sun and the Earth and it ruled out observations at other times. The analyses of the 1996 observations are not yet complete, but already they give new insight into the nature of comets. Comet Hale-Bopp is believed to be a large comet with a nucleus up to 40 kilometres wide. It was discovered in July 1995 by two American astronomers working independently, Alan Hale and Thomas Bopp. At that time, the comet was a billion kilometres away from the Sun, but 200 times brighter than Halley's Comet was, when at a comparable distance. Comet Hale-Bopp will make its closest approach to the Earth on 22 March, and its closest approach to the Sun (perihelion) on 1 April 1997. Some scientific results from ISO The discovery of Comet Hale-Bopp occurred before ISO's launch in November 1995. When first observed by ISO in March and April 1996, the comet was still 700 million kilometres from the Sun, and almost as far from the Earth and ISO. With its privileged view of infrared wavebands inaccessible from the Earth's surface, ISO's photometer ISOPHOT discovered that carbon dioxide was an important constituent of the comet's emissions of vapour.ISOPHOT measured the temperature of the dust cloud around Comet Hale-Bopp. In March 1996, when the comet was still more than 700 million kilometres from the Sun, the dust cloud was at minus 120 degrees C. When ISOPHOT made similar observations in October 1996, the comet was 420 million kilometres from the Sun, and the dust cloud had warmed to about minus 50 degrees C. Intensive observations of Comet Hale-Bopp were also made by ISO's Short-Wave Spectrometer SWS, the Long-Wave Spectrometer LWS, and the ISOPHOT spectrometer PHOT-S. Results are due for publication at the end of March. They will give details about the composition

  17. Comet P/Encke's nongravitational force

    NASA Technical Reports Server (NTRS)

    A'Hearn, Michael F.; Schleicher, David G.

    1988-01-01

    A nearly direct measurement of the nongravitational force on a cometary nucleus is presented. IUE spectra of comet P/Encke show significant Greenstein effects even when centered on the nucleus. These imply net heliocentric components of outflow of 1.6 and 0.3 km/s for the OH radicals before and after perihelion near r = 0.8 AU. This implies a large asymmetry in the radial nongravitational acceleration (A1) about perihelion, which must be taken into account in order to derive the mass of the nucleus. The asymmetry is consistent with Sekanina's (1988) latest model for the Encke nucleus, but the measurements suggest an outflow velocity near 2 km/s, significantly greater than generally accepted values. A tentative value for the mass of the Encke nucleus is proposed, although improved modeling of the nongravitational acceleration is required to obtain a definitive value.

  18. Rosetta - a comet ride to solve planetary mysteries

    NASA Astrophysics Data System (ADS)

    2003-01-01

    kilometres of Halley). It sent back wonderful pictures and data that showed that comets contain complex organic molecules. These kinds of compounds are rich in carbon, hydrogen, oxygen, and nitrogen. Intriguingly, these are the elements which make up nucleic acids and amino acids, which are essential ingredients for life as we know it. Giotto continued its successful journey and flew by Comet Grigg-Skjellerup in 1992 within about 200 km distance. Now scientists will be eagerly waiting to be able to answer some of the new intriguing questions that arose from analysing the exciting results from Giotto. Other past missions that have flown by a comet were: NASA’s ICE mission in 1985, the two Russian VEGA spacecraft and the two Japanese spacecraft Suisei and Sakigake that were part of the armada that visited comet Halley in 1986; NASA’s Deep Space 1 flew-by comet Borelly in 2001 and NASA’s Stardust will fly-by comet Wild 2 in early 2004 and will return samples of the comet’s coma in 2006. Unfortunately NASA’s Contour launched in Summer 2002 failed when it was inserted onto its interplanetary trajectory. In 2004 we will see the launch of Deep Impact, a spacecraft that will shoot a massive block of copper into a comet nucleus.

  19. Solar-wind velocity measurements from near-Sun comets C/2011 W3 (Lovejoy), C/2011 L4 (Pan-STARRS), and C/2012 S1 (ISON)

    NASA Astrophysics Data System (ADS)

    Ramanjooloo, Y.; Jones, G. H.; Coates, A.; Owens, M. J.; Battams, K.

    2014-07-01

    Since the mid-20th century, comets' plasma (type I) tails have been studied as natural probes of the solar wind [1]. Comets have induced magnetotails, formed through the draping of the heliospheric magnetic field by the velocity shear in the mass-loaded solar wind. These can be easily observed remotely as the comets' plasma tails, which generally point away from the Sun. Local solar-wind conditions directly influence the morphology and dynamics of a comet's plasma tail. During ideal observing geometries, the orientation and structure of the plasma tail can reveal large-scale and small-scale variations in the local solar-wind structure. These variations can be manifested as tail condensations, kinks, and disconnection events. Over 50 % of observed catalogued comets are sungrazing comets [2], fragments of three different parent comets. Since 2011, two bright new comets, C/2011 W3 [3] (from hereon comet Lovejoy) and C/2012 S1 [4] (hereon comet ISON) have experienced extreme solar-wind conditions and insolation of their nucleus during their perihelion passages, approaching to within 8.3×10^5 km (1.19 solar radii) and 1.9×10^6 km (2.79 solar radii) of the solar centre. They each displayed a prominent plasma tail, proving to be exceptions amongst the observed group of sungrazing comets. These bright sungrazers provide unprecedented access to study the solar wind in the heretofore unprobed innermost region of the solar corona. The closest spacecraft in-situ sampling of the solar wind by the Helios probes reached 0.29 au. For this study, we define a sungrazing comet as one with its perihelion within the solar Roche limit (3.70 solar radii). We also extend this study to include C/2011 L4 [5] (comet Pan-STARRS), a comet with a much further perihelion distance of 0.302 au. The technique employed in this study was first established by analysing geocentric amateur observations of comets C/2001 Q4 (NEAT) and C/2004 Q2 (Machholz) [7]. These amateur images, obtained with modern

  20. Landslides and impacts on comets.

    NASA Astrophysics Data System (ADS)

    Czechowski, Leszek

    2016-07-01

    The recent landing of Philae on the comet 67P/Czuriumow-Gierasimienko indicates that elastic properties of comet's nuclei could be similar to elastic properties of dry snow, namely Young modulus is assumed to be 106 - 108 Pa. We considered a simple model of two spheres (with radius 1400 m each) connected by cylinder (with radius of 200 m and length of 200 m). Density is 470 kg m-3. This shape corresponds approximately to shape of some comets. A few vibration modes are possible. In present research we consider 3 modes: bending, lengthening-shortening along axis of symmetry, and torsion. Let assume that comets are hit by small meteoroid of the mass of 1 kg and velocity 20 km s-1. The maximum values of acceleration of the surface resulting from this impact are given in Table 1. Note that these values are higher than acceleration of the gravity of the comet. Consequently, these vibrations could be an important factor of surface evolution, e.g. they could trigger landslides. It could be alternative mechanism to that presented in [4] (i.e. fluidization). Acknowledgement: The research is partly supported by Polish National Science Centre (decision 2014/15/B/ST 10/02117) References [1] T. Spohn, J. Knollenberg, A. J. Ball, M. Ba-naszkiewicz, J. Benkhoff, M. Grott, J. Gry-gorczuk, C. Hüttig, A. Hagermann, G. Kargl, E. Kaufmann, N. Kömle, E. Kührt, K. J. Kossacki, W. Marczewski, I. Pelivan, R. Schrödter, K. Seiferlin. (2015) Thermal and mechanical properties of the near-surface layers of comet 67P/Churyumov- Gera-simenko Science 31 July 2015: Vol. 349 no. 6247 DOI: 10.1126/science.aab0464 [2] Reuter B. (2013) On how to measure snow mechanical properties relevant to slab avalanche release. International Snow Science Workshop Grenoble - Chamonix Mont-Blanc - 2013 007 [3] Ball A.J. (1997) Ph. D. Thesis: Measuring Physical Properties at the Surface of a Comet Nu-cleus, Univ.of Kent U.K. [4] Belton M. J.S., Melosh J. (2009). Fluidization and multiphase transport of

  1. Comet missions and what can still be done from ground

    NASA Astrophysics Data System (ADS)

    Schulz, Rita

    2015-11-01

    Much of the knowledge on comet nuclei that has become available since the 1P/Halley encounters in 1986, is based on space missions. The nucleus shape and some surface parameters (topography, morphology, thermal, optical behaviour, composition) can directly be determined through remote-sensing measurements at close encounters. At present, 8 comets have been visited. The information that became available from these missions is discussed in view to its relevance for understanding solar system formation. Emphasis is put on comets 81P/Wild-2, 9P/Tempel, 103/Hartley-3 and 67P/Churyumov-Gerasimenko. Furthermore, options and prospects are discussed on how to benefit more effectively from spacecraft data. If the knowledge coming from spacecraft data is properly transferred to other comets, it will provide new means to distinguish whether differences between comets, observed in the coma, reflect differences of the nucleus or are related to different environmental conditions of the comets at the time of observation. This in turn has important implications to the question of how and where comets were formed in the early solar system. Some unknowns can only be addressed if data exist of a statistically relevant number of comets, hence may remain open for a rather long time. Options will be discussed on how to approach these questions in the future.

  2. Parametric Dielectric Model of Comet Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Heggy, E.; Palmer, E. M.; Kofman, W. W.; Clifford, S. M.; Righter, K.; Herique, A.

    2012-12-01

    In 2014, the European Space Agency's Rosetta mission is scheduled to rendezvous with Comet 67P/Churyumov-Gerasimenko (Comet 67P). Rosetta's CONSERT experiment aims to explore the cometary nucleus' geophysical properties using radar tomography. The expected scientific return and inversion algorithms are mainly dependent on our understanding of the dielectric properties of the comet nucleus and how they vary with the spatial distribution of geophysical parameters. Using observations of comets 9P/Tempel 1 and 81P/Wild 2 in combination with dielectric laboratory measurements of temperature, porosity, and dust-to-ice mass ratio dependencies for cometary analog material, we have constructed two hypothetical three-dimensional parametric dielectric models of Comet 67P's nucleus to assess different dielectric scenarios of the inner structure. Our models suggest that dust-to-ice mass ratios and porosity variations generate the most significant measurable dielectric contrast inside the comet nucleus, making it possible to explore the structural and compositional hypotheses of cometary nuclei. Surface dielectric variations, resulting from temperature changes induced by solar illumination of the comet's faces, have also been modeled and suggest that the real part of the dielectric constant varies from 1.9 to 3.0, hence changing the surface radar reflectivity. For CONSERT, this variation could be significant at low incidence angles, when the signal propagates through a length of dust mantle comparable to the wavelength. The overall modeled dielectric permittivity spatial and temporal variations are therefore consistent with the expected deep penetration of CONSERT's transmitted wave through the nucleus. It is also clear that changes in the physical properties of the nucleus induce sufficient variation in the dielectric properties of cometary material to allow their inversion from radar tomography.

  3. 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

  4. Cosmic dust and the comet connection

    NASA Astrophysics Data System (ADS)

    Knacke, R.

    1984-09-01

    Spacecraft flybys, direct collection at earth, and new instrumentation for earth-based telescopes may soon make it possible to interpret the physical and chemical properties of fine cometary dust particles. Spectral studies have shown that a comet's diffuse curved tail reveals a solar spectrum probably due to sunlight reflected by particles approximately one micron in size. Model studies have shown that a distant comet may be a solid mixture of ices and granular rocky material without a tail. As the comet approaches the sun, longer infrared wavelengths reflect falling dust temperatures, and only silicates seem to emit strongly. The dust may be mainly made up of Si with Mg and Fe, and O. The rest of the nucleus may be composed of H2O, CO2, CO and perhaps CH4 and NH3. Interplanetary dust collected by the Helios spacecraft reveals a low density, fragile structure, and chemical analysis of bright meteors shows a similarity to carbonaceous chondrites. Because of interstellar dust resembling in some aspects the silicate structure of comets, and because these particles are found in regions of recent star formation, the question is raised whether comets containing this dust could be forming at such locations. Missions to Halley's comet in 1986 by ESA's Giotto spacecraft, and the Soviet Union's Vega spacecraft are outlined.

  5. Space observations of comets during solar flares

    NASA Astrophysics Data System (ADS)

    Ibadov, Subhon; Ibodov, Firuz S.

    Problems connected with mechanisms for comet outbursts as well as for gamma-ray bursts remain open. Meantime, calculations show that an irradiation of a certain class of cometary nuclei, having high specific electric resistance, by intense fluxes of energetic protons and posi-tively charged ions with kinetic energies more than 1 MeV/nucleon, ejected from the Sun during strong solar flares, can produce a macroscopic high-voltage electric double layer with positive charge in the subsurface region of the nucleus, during irradiation time of the order of 10-100 hours at heliocentric distances around 1-10 AU. The maximum electric energy accumulated in such layer will be restricted by discharge potential of the layer material. For the comet nuclei with the typical radius of the order of 1-10 km the accumulated energy of such natural electric capacitor is comparable to the energy of large comet outbursts that are estimated on the basis of ground-based optical observations of comets. The impulse X-ray radiation anticipated from the high-voltage electric discharge of the capacitor may serve as an indicator of realization of the processes above considered. Therefore, space observations of comets and pseudo-asteroids of cometary origin, having brightness correlation with solar activity, using space X-ray obser-vatories during strong solar flares are very interesting for the physics of comets as well as for high energy astrophysics.

  6. 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.

  7. Comet or Asteroid?

    NASA Astrophysics Data System (ADS)

    1997-11-01

    , Institute of Planetary Exploration) soon thereafter obtained seven unfiltered CCD images on three consecutive nights with the 60-cm `Bochum telescope' at La Silla, Uri Carsenty found a tail extending 15 arcseconds in the WSE direction from the point source, cf. ESO Press Photo 31b/97. The (red) magnitude was about 19, or 150,000 times fainter than what is visible to the naked eye. More observations were obtained at La Silla during the following nights, confirming the persistent presence of this tail. NTT observations confirm the cometary nature of P/1997 T3 ESO Press Photo 31c/97 ESO Press Photo 31c/97 [JPG, 52k] Caption: Deep NTT image of P/1997 T3. This image covers a field of 105 x 60 arcsec and is a composite of several CCD exposures. It was taken with the ESO New Technology Telescope (NTT) and the EMMI multi-mode instrument by ESO astronomers Hermann Boehnhardt and Olivier Hainaut on different days between 21 and 25 October 1997. By computer processing, the images of P/1997 T3 are aligned to the same pixel position and co-added in order to increase the visibility of the comet. Due to the motion of the comet, multiple images of several galaxies and stars appear in this photo. At the time of the observations, the comet was about 3.34 AU from Earth and about 4.30 AU from the Sun. A larger version [JPG, 384k] is also available. In late October 1997, further images of the new object and its tail were taken with the ESO 3.5-m New Technology Telescope (NTT) at La Silla, cf. ESO Press Photo 31c/97. On these, the narrow tail was seen to be at least 90 arcsec long and pointing roughly in the Sun direction . The steady appearance and the sunward orientation of the tail indicates that it consists of dust. Moreover, a preliminary image analysis shows the presence of a weak and very condensed coma of dust grains around the nucleus. Interestingly, a series of images through several broadband filters with a total of almost 30 min exposure time did not show any trace of a normal, anti

  8. Ground-based photometry of comets in the spectral interval 3000 to 3500 angstrom

    NASA Technical Reports Server (NTRS)

    Willis, R. L.; Ahearn, M. F.

    1981-01-01

    Abundances and production rates of CN, C3, and C2 for fifteen comets were determined and the variation of these parameters with helicentric distance for two comets were monitored. While these measurements provide much information about the similarities and differences among comets, only a small fraction of the total material in any of the comets observed was sampled.

  9. New Insights of Comets from the EPOXI Mission

    NASA Astrophysics Data System (ADS)

    Meech, Karen J.; A'Hearn, M. F.

    2013-01-01

    Comet missions are changing the paradigm for understanding comet activity, composition, and the formation of planetesimals in the protoplanetary disk. Each encounter has shown the diversity of surface morphologies and new insights into comet chemistry, formation scenarios, activity mechanisms and geology. Prior to the comet 103P/Hartley 2 EPOXI encounter, the prevailing view was that H 2O-ice sublimation controlled most comet activity. Differences in the amounts of minor parent/daughter photodissociation species are attributed to differences in formation location, temperature and disk chemistry. However, reconstructing the protoplanetary disk dynamics and chemistry consistent with observations hasn’t yet been achieved. The EPOXI mission flew past the nucleus of comet 103P/Hartley 2 on 11/4/2010. This small nucleus was known to be exceptionally active prior to the encounter, by virtue of a very large water production rate relative to its surface area. EPOXI provided stunning images of a small nucleus with strong chemical heterogeneity and a swarm of large icy chunks driven from the nucleus by CO2 jets. The EPOXI ground-based campaign provided a long-term baseline of observations of the pre-perihelion brightening of the comet which also showed that comet Hartley 2’s perihelion activity was dominated by sub-surface CO2 outgassing. The nucleus morphology was different from that of other nuclei visited by spacecraft; some rough topographic regions showed visible surface ice. Because the Earth’s atmosphere is opaque at the wavelengths for CO2 emission, there is only a little information about CO2 abundance in comets (primarily from space missions), yet CO, CO2 and H2O are likely key tracers of the chemistry in the protoplanetary disk. EPOXI has shown the crucial role that CO2 plays in comet activity. Further, CO2 abundance does not appear to be correlated with other parent volatiles, nor with dynamical classes suggesting that we need to revise our understanding of

  10. Comets. [and solar system evolution

    NASA Technical Reports Server (NTRS)

    Neugebauer, M.

    1986-01-01

    The nature, history, and evolution of comets are considered. Cometary ions, formed by photoionization and other processes, are forced into a highly structured ion tail by the interaction with the solar wind. The importance of comets to solar-system studies lies in the possibilities that they are well-preserved samples of either the interstellar cloud which collapsed to form the solar system or the planetesimals from which the outer planets accumulated, and that they provided either the prebiotic complex molecules from which life evolved or some volatiles necessary for the evolution of these molecules.

  11. ROTATION OF COMET 103P/HARTLEY 2 FROM STRUCTURES IN THE COMA

    SciTech Connect

    Samarasinha, Nalin H.; Mueller, Beatrice E. A.; A'Hearn, Michael F.; Farnham, Tony L.; Gersch, Alan

    2011-06-10

    The CN coma structure of the NASA EPOXI mission target, comet 103P/Hartley 2, was observed during 20 nights from 2010 September to December. These CN images probe the rotational state of the comet's nucleus and provide a ground-based observational context to complement the EPOXI observations. A dynamically excited cometary nucleus with a changing rotational rate is observed, a characteristic not seen in any comet in the past. The lack of rotational damping during the four-month observing interval places constraints on the interior structure of the nucleus.

  12. Bye, Bye Comet

    NASA Video Gallery

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

  13. Flight of the Comet

    NASA Video Gallery

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

  14. Comet Shoemaker-Levy 9: An Active Comet

    NASA Technical Reports Server (NTRS)

    Rettig, Terrence W.; Hahn, Joseph M.

    1997-01-01

    The important elements of the debate over the activity versus dormancy of comet Shoemaker Levy 9 (S-L 9) are reviewed. It is argued that the circularity of the isophotes in the inner comae of S-L 9 as well as the spatial dependencies of the comae brightness profiles are indicators of sustained dust production by S-L 9. It is also shown that the westward tail orientations, which were formerly interpreted as a sign of the comet's dormancy, are not a good indicator of either activity or dormancy. Rather, the tail orientations simply place constraints on the dust production rate for grains smaller than approx. equals 5(micron). All the available evidence points to S-L 9 as having been an active, dust-producing comet. Synthetic images of an active comet are fitted to Hubble Space Telescope images of the S-L 9 fragment K, and its grain size and outflow velocity distributions are extracted. These findings show that the appearance of the dust coma was dominated by large grains having radii between approx. equals 30 (micron) and approx. equals 3 mm, produced at a rate of M approx. equals 22 kg/ s, and ejected at outflow velocities of approx. equals 0.5 m/ s. Only upper limits on the production rates of smaller grains are obtained. The nucleus of fragment K was not observed directly but its size is restricted to lie within a rather narrow interval 0.4 less than or equal to Rf less than or equal to 1.2 km.

  15. Rosetta—one comet rendezvous and two asteroid fly-bys

    NASA Astrophysics Data System (ADS)

    Schulz, R.

    2009-08-01

    One of the two planetary cornerstone missions of the European Space Agency is the Rosetta mission to comet 67P/Churyumov-Gerasimenko. Rosetta is a rendezvous mission with a comet nucleus, which combines an Orbiter with a Lander. It will monitor the evolution of the comet nucleus and the coma as a function of increasing and decreasing solar flux input along the comet’s pre- and post-perihelion orbit. Different instrumentations will be used in parallel, from multi-wavelength spectrometry to in-situ measurements of coma and nucleus composition and physical properties. Rosetta will go in orbit around the nucleus of its target comet 67P/Churyumov-Gerasimenko, when it is still far from the Sun and accompany the comet along its way to perihelion and beyond. In addition the Rosetta Lander Philae will land on the nucleus surface, before the comet is too active to permit such a landing (i.e. at around r = 3 AU) and examine the surface and subsurface composition of the comet nucleus as well as its physical properties.

  16. Fabry-Perot observations of comet Kohoutek

    NASA Technical Reports Server (NTRS)

    Roesler, F. L.; Scherb, F.; Huppler, D.; Reynolds, R. J.; Trauger, J.

    1975-01-01

    Observations of H alpha, H20(+), and emission lines from comet Kohoutek were made. Analyses of H alpha line profiles and line intensities indicate that the mean outflow velocity of the hydrogen atoms was 7.8 + or - 0.2 km s(-1) and that the hydrogen atom production rate varied for comet-sun distances between 1 AU and 0.4 AU. The identification of an H20(+) emission feature in certain H alpha scans indicates that the H20(+) ions were moving in a tailward direction with a velocity of 20 to 40 km s(-1) with respect to the comet nucleus. An upper limit of 1 part in 100 was found for the D/H ratio in the cometary atomic hydrogen cloud.

  17. There is no 'cometopause' at comet Halley

    NASA Astrophysics Data System (ADS)

    Reme, H.; Mazelle, C.; D'Uston, C.; Korth, A.; Lin, R. P.; Chaizy, P.

    1994-02-01

    Immediately after the flybys at comet Halley by a fleet of spacecraft in 1986, Gringauz et al. (1986a) reported the detection by the Vega-2 spacecraft of a chemical and sharp plasma boundary, which they named the 'cometopause,' at a distance of about 1.6 x 105 km from the nucleus. Gringauz and Verigin (1991) presented the 'cometopause' as a permanent feature of the solar wind - Halley type comet interaction at about 1 UA from the Sun. This permanent boundary presumably separates an upstream region dominated by the solar wind from the downstream region where heavy cometary ions dominate. We present here the analysis of the results of the Giotto positive ion cluster composition analyzer - Reme plasma analyzer (PICCA-RPA2) ion mass spectrometer and electron electrostatic analyzer - Reme plasma analyzer (EESA-RPA1) electron spectrometer data, which clearly show that there is no such boundary at comet Halley.

  18. The HNC/HCN ratio in comets.

    PubMed

    Irvine, W M; Dickens, J E; Lovell, A J; Schloerb, F P; Senay, M; Bergin, E A; Jewitt, D; Matthews, H E

    1997-01-01

    The abundance ratio of the isomers HCN and HNC has been investigated in comet Hale-Bopp (C/1995 O1) through observations of the J = 4-3 rotational transitions of both species for heliocentric distances 0.93 < r < 3 AU, both pre- and post-perihelion. After correcting for the optical depth of the stronger HCN line, we find that the column density ratio of HNC/HCN in our telescope beam increases significantly as the comet approaches the Sun. We compare this behavior to that predicted from an ion-molecule chemical model and conclude that the HNC is produced in significant measure by chemical processes in the coma; i.e., for comet Hale-Bopp, HNC is not a parent molecule sublimating from the nucleus. PMID:11543322

  19. 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.

  20. ICE observations of Comet Giacobini-Zinner

    NASA Astrophysics Data System (ADS)

    Cowley, S. W. H.

    1987-09-01

    An overview is given of data collected by the International Cometary Explorer (ICE) spacecraft on its encounter (passing through the tail at 7800 km from the nucleus) with Comet Giacobini-Zinner on September 15, 1985. The trajectory of the ICE relative to the comet structures and the instrument package are described and consideration is given to thermal-plasma, magnetic-field, plasma-wave, and energetic-ion observations. A sharp boundary was crossed on both inbound and outbound parts of the trajectory, with a width (10,000 km) equal to the energetic-heavy-ion Larmor radius; this boundary is tentatively attributed to a weak shock in the subsolar mass-loaded region upstream from the comet. Unexpectedly high degrees of field and plasma turbulence and broadband wave activity were observed in the encounter.

  1. The HNC/HCN ratio in comets

    NASA Technical Reports Server (NTRS)

    Irvine, W. M.; Dickens, J. E.; Lovell, A. J.; Schloerb, F. P.; Senay, M.; Bergin, E. A.; Jewitt, D.; Matthews, H. E.; Ferris, J. P. (Principal Investigator)

    1997-01-01

    The abundance ratio of the isomers HCN and HNC has been investigated in comet Hale-Bopp (C/1995 O1) through observations of the J = 4-3 rotational transitions of both species for heliocentric distances 0.93 < r < 3 AU, both pre- and post-perihelion. After correcting for the optical depth of the stronger HCN line, we find that the column density ratio of HNC/HCN in our telescope beam increases significantly as the comet approaches the Sun. We compare this behavior to that predicted from an ion-molecule chemical model and conclude that the HNC is produced in significant measure by chemical processes in the coma; i.e., for comet Hale-Bopp, HNC is not a parent molecule sublimating from the nucleus.

  2. Laboratory simulations of comet surfaces

    NASA Technical Reports Server (NTRS)

    Stephens, John R.; Gustafson, Bo A. S.

    1988-01-01

    The geometric albedos of frozen mixtures consisting of colloidal silica and carbon black mixed with water have been measured over the wavelength range of 400 to 800 nm to compare with recent observations of Comet Halley. Data were obtained as a function of sample temperature, scattering angle, and wavelength as the frozen samples warmed to 0 C in vacuum. Scattering from water ice, flat black paint, and Kodak white reflectance paint were also measured. Lab simulations show that the change in albedo of the samples show that sublimation of the water from the sample surface can have a major effect on the albedo of a particle/ice sample in the visible. Such processing may have a marked effect on the visible albedo of comet surfaces as well.

  3. Following Sungrazing Comets Exploration of a Mission Concept

    NASA Astrophysics Data System (ADS)

    Shutts, Adam Ryan

    This thesis presents a space mission concept that consists of a spacecraft following a sungrazing comet along its orbit while consistently remaining within the shadow of the object. By locating the spacecraft within the shadow of the comet at the comet-Sun L2 equilibrium point, the spacecraft can be shielded from the immense radiation of the Sun. This concept provides a new vantage point to observe comet/Sun interactions while investigating the effects of comet outgassing, exploring the physical consequences of close perihelion passage, and probing the composition of the Sun's corona. A rigorous search is performed to select a sample comet to design a mission about. The Elliptic Hill Three Body Problem dynamical model is introduced to model the interactions of the spacecraft, comet, and Sun and the L2 libration point location is calculated. Environmental modeling is conducted to estimate the size of the comet's shadow and the thermal conditions the comet and spacecraft will encounter. The consequences of this analysis introduce the possibility of a two-stage mission design due to extreme fluctuations in the thermal environment. A linear controller is derived to station-keep the spacecraft at the comet-Sun L2 point. The feasibility of moving the spacecraft closer to the comet is examined and inverse dynamics theory is applied to create various transfers that bring the spacecraft closer to the comet's surface for improved image and data collection.

  4. From the interstellar medium to planetary atmospheres via comets

    NASA Astrophysics Data System (ADS)

    Owen, Tobias C.; Bar-Nun, Akiva

    Laboratory experiments on the trapping of gases by ice forming at low temperatures implicate comets as major carries of the heavy noble gases to the inner planets. Recent work on deuterium in Comet Hale-Bopp provides good evidence that comets contain some unmodified interstellar material. However, if the sample of three comets analyzed so far is typical, the Earth's oceans cannot have been produced by comets alone. The highly fractionated neon in the Earth's atmosphere also indicates the importance of non-icy carriers of volatiles, as do the noble gas abundances in meteorites from Mars.

  5. The Mineralogy of Comet Wild 2

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael

    2007-01-01

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

  6. Organic Molecules in Comet C/2012 F6 (Lemmon)

    NASA Astrophysics Data System (ADS)

    Chuang, Y.-L.; Kuan, Y.-J.; Cordiner, M. A.; Charnley, S. B.

    2015-12-01

    Results obtained from ALMA observations of Comet C/2012 F6 (Lemmon) are presented. The 265-GHz continuum peak is uncovered to be offset spatially from spectral peaks, probably due to contamination from dust-tail emission. An isovelocity pattern typical to a rotating solid-body plane is apparent in the moment-1 HCN map. HNCO, cyclopropenylidene and vinyl cyanide are tentatively detected. The spatial distribution of HNCO appears to be localized and inhomogeneous in the cometary nucleus if HNCO is a primary species. Methanol gas is not only concentrated on the cometary nucleus but also extended to the north. c-C3H2 is likely associated with the cometary nucleus and C2H3CN, with the dust tail. The mighty ALMA certainly turns every ordinary comet into a Hale-Bopp, the brightest comet of the 20th century.

  7. Imaging polarimetry of Comet C/2012 L2 (LINEAR)

    NASA Astrophysics Data System (ADS)

    Deb Roy, P.; Das, H. S.; Medhi, Biman J.

    2015-01-01

    We present the polarimetric results and analysis of Comet C/2012 L2 (LINEAR) observed at 31°.1 phase angle before perihelion passage. The observations of the comet were carried out using ARIES Imaging Polarimeter (AIMPOL) mounted on the 1.04-m Sampurnanand telescope of ARIES, Nainital, India on 11 and 12 March, 2013 using R photometric band (λ = 630 nm, Δλ = 120 nm) . The extended coma of the comet (∼65000 km) shows a significant variation in the intensity as well as polarization profile in all considered directions which suggest that the dust particles originate from the active areas of the nucleus. The elongation of the coma is prominent along the Sun-comet position angle. The polarization of Comet C/2012 L2 (LINEAR) do not show steep radial dependence on the aperture size during both the nights of observation. A jet extended in the antisolar direction is well observed in both intensity and polarization map.

  8. Lyman-alpha observations of Comet West /1975n/

    NASA Technical Reports Server (NTRS)

    Opal, C. B.; Carruthers, G. R.

    1977-01-01

    The rate of hydrogen production of Comet West is studied through rocket observation of solar Lyman-alpha radiation resonantly scattered by the escaping hydrogen atoms. Two sets of Lyman-alpha exposure sequences are used to obtain computer-smoothed brightness contour (isophote) maps covering a density range of 100:1. A simple radial outflow model is applied to the contour maps to determine the rate of hydrogen production (3.2 by 10 to the 30th power atoms/sec.) Discrepancies between the observed shape of the outer isophotes and predicted models may be explained by optical depth effects, or by the presence of small pieces of the comet's nucleus distributed along the orbit. Hydrogen, carbon, and oxygen production for Comet West and Comet Kohoutek are compared; differences may be accounted for by variations in the composition or evolution of the two comets.

  9. Photographic Observations of Comet Bennett, 1970II

    NASA Technical Reports Server (NTRS)

    Larson, S. M.; Minton, R. B.

    1972-01-01

    Direct photography of Comet Bennett with a range of focal lengths shows structure in the coma and strong Type 1 and Type 2 tails. The Type 1 tail shows motion in 15 minutes. The inner coma contains spiral-shaped jets of a type observed visually on occasion in the past but not photographed before. The spiral shape is apparently due to the rotation of the nucleus. On the assumption that the outward velocity of the jets is 0.6 km/sec, as estimated by Delsemme, a rotation period of 1.4 to 1.5 days is derived for the nucleus. The rotation is direct (in the sense of the comet's orbital motion).

  10. Photographic observations of Comet Bennett, 1970II.

    NASA Technical Reports Server (NTRS)

    Larson, S. M.; Minton, R. B.

    1972-01-01

    Direct photography of Comet Bennett with a range of focal lengths shows structure in the coma and strong Type I and Type II tails. The Type I tail shows motion in 15 minutes. The inner coma contains spiral-shaped jets of a type observed visually on occasion in the past but not photographed before. The spiral shape is apparently due to the rotation of the nucleus. On the assumption that the outward velocity of the jets is 0.6 km/sec, as estimated by Delsemme, a rotation period of 1.4-1.5 days is derived for the nucleus. The rotation is direct (i.e., in the sense of the comet's orbital motion).

  11. Methane in Oort cloud comets

    NASA Astrophysics Data System (ADS)

    Gibb, E. L.; Mumma, M. J.; Dello Russo, N.; DiSanti, M. A.; Magee-Sauer, K.

    2003-10-01

    We detected CH 4 in eight Oort cloud comets using high-dispersion ( λ/Δ λ˜2×10 4) infrared spectra acquired with CSHELL at NASA's IRTF and NIRSPEC at the W.M. Keck Observatory. The observed comets were C/1995 O1 (Hale-Bopp), C/1996 B2 (Hyakutake), C/1999 H1 (Lee), C/1999 T1 (McNaught-Hartley), C/1999 S4 (LINEAR), C/2000 WM 1 (LINEAR), C/2001 A2 (LINEAR), and 153/P Ikeya-Zhang (C/2002 C1). We detected the R0 and R1 lines of the ν3 vibrational band of CH 4 near 3.3 μm in each comet, with the exception of McNaught-Hartley where only the R0 line was measured. In order to obtain production rates, a fluorescence model has been developed for this band of CH 4. We report g-factors for the R0 and R1 transitions at several rotational temperatures typically found in comet comae and relevant to our observations. Using g-factors appropriate to Trot as determined from HCN, CO and/or H 2O and C 2H 6, CH 4 production rates and mixing ratios are presented. Abundances of CH 4/H 2O are compared among our existing sample of comets, in the context of establishing their place of origin. In addition, CH 4 is compared to native CO, another hypervolatile species, and no correlation is found among the comets observed.

  12. The neutral coma of comets: A review

    NASA Technical Reports Server (NTRS)

    Delsemme, A. H.

    1976-01-01

    The hypothesis that water snow controls the vaporization of the nucleus of some comets seems verified from the general order of magnitude of the size of their nucleus and of their nuclear albedo; the largest observed production rates are H and OH which both seem to originate from the photodissociation of H2O, as also confirmed by the scale length of the invisible parent molecule producing OH. However, comet Encke is not uniformly covered by water snow, as it produces only one tenth of the expected vaporization. Early results on comet Kohoutek suggest that the conclusions could be slightly different for some of the new comets in Oort's sense. If the far ultraviolet observations confirm the early assessments of the production rates of C, O and H, then at least another major constituent competing with water has not yet been detected. Such a major constituent is suggested by the ratios C/O = 0.24 and H/O = 2.5.

  13. Comet C/2011 J2 (LINEAR): Photometry and stellar transit

    NASA Astrophysics Data System (ADS)

    Ivanova, Oleksandra; Borysenko, Serhii; Zubko, Evgenij; Krišandová, Zuzana Seman; Svoreň, Ján; Baransky, Aleksandr; Gabdeev, Maksim

    2016-03-01

    We present results of two-year photometric monitoring of Comet C/2011 J2 (LINEAR) that spans the time period from February 2013 through December 2014, before and after perihelion passage. The observations were conducted with broadband R filter. Analysis of observations of Comet C/2011 J2 (LINEAR) allows estimating the nucleus radius as function of geometric albedo and phase-darkening coefficient. Furthermore, our observations showed split of the comet. Fragment (B) additional to the primary C/2011 J2 nucleus was unambiguously detected; relative velocity is estimated to be ~0.17 ″/day. We derive the Afρ parameter and estimate the dust production rate in Comet C/2011 J2 (LINEAR) over the entire run of observations. We found a noticeable increase in Afρ parameter between September 18, 2014 and November 5, 2014, epoch when the nucleus presumably got split. On September 28, 2014, we observed a transit of the 16-magnitude star (USNO-A2 1275-18299027) near nucleus of the Comet C/2011 J2 (LINEAR). We retrieve the optical depth of the coma τ=0.034±0.1. The filling factor f that corresponds to such optical depth is in good quantitative agreement with the value that can be derived from the Afρ parameter under reasonable assumption on geometric albedo of cometary dust.

  14. Comet C/2011 J2 (LINEAR): Photometry and Stellar transit

    NASA Astrophysics Data System (ADS)

    Ivanova, Oleksandra; Baransky, Alexandr; Gabdeev, Maksim; Borysenko, Serhii; Zubko, Evgenij; Seman Krišandová, Zuzana; Svoreň, Jan

    2016-07-01

    We present results of two-year photometric monitoring of Comet C/2011 J2 (LINEAR) that spans the time period from February 2013 through December 2014, before and after perihelion passage. The observations were conducted with broadband R filter. Analysis of observations of Comet C/2011 J2 (LINEAR) allows estimating the nucleus radius as function of geometric albedo and phase-darkening coefficient. Furthermore, our observations showed split of the comet. Fragment (B) additional to the primary C/2011 J2 nucleus was unambiguously detected; relative velocity is estimated to be ˜~ 0.17 arcsec/day. We derive the Afρ parameter and estimate the dust production rate in Comet C/2011 J2 (LINEAR) over the entire run of observations. We found a noticeable increase in Afρ parameter between September 18, 2014 and November 5, 2014, epoch when the nucleus presumably got split. On September 28, 2014, we observed a transit of the 16-magnitude star (USNO-A2 1275-18299027) near nucleus of the Comet C/2011 J2 (LINEAR). We retrieve the optical depth of the coma τ = 0.034 ±± 0.1. The filling factor f that corresponds to such optical depth is in good quantitative agreement with the value that can be derived from the Afρ parameter under reasonable assumption on geometric albedo of cometary dust.

  15. Comet Donati (C/1858 L1)

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    A long-period comet discovered by Giovanni Donati in June 1858. It reached its greatest magnitude of -1 shortly before perihelion (0.58 AU) on 20 September, and was closest to Earth (0.5 AU) on 9 October. Its appearance was impressive, with a prominent curved dust tail stretching an estimated 60°, and two thin gas tails. Concentric, sharply defined shells of material ahead of the nucleus suggest...

  16. The origin of comets

    NASA Astrophysics Data System (ADS)

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

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

  17. 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.

  18. Early close image of comet Borrelly

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The solid nucleus of comet Borrelly is barely resolved in this image, enhanced to reveal the highly collimated dust extending towards the bottom left corner of the picture. The jet is attributed to dust carried outward by gas expanding outwards into a cone about 20 degrees across. The surface of Borrelly is composed of a mixture of dust and water ice, and as the comet approaches the Sun the water ice sublimes. The gases produced inside the comet by the Sun's heating race away from the surface into the vacuum of space, carrying the dust away with them. The jet was also seen in images acquired around 9 hours earlier. This suggests that the emission is coming from close to the rotation axis at the comet's constantly illuminated pole. The Sun is at the bottom of the image.

    Deep Space 1 completed its primary mission testing ion propulsion and 11 other advanced, high-risk technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to undertake this chancy but exciting, and ultimately successful, encounter with the comet. More information can be found on the Deep Space 1 home page at http://nmp.jpl.nasa.gov/ds1/ .

    Deep Space 1 was launched in October 1998 as part of NASA's New Millennium Program, which is managed by JPL for NASA's Office of Space Science, Washington, D.C. The California Institute of Technology manages JPL for NASA.

  19. WISE Observations of Rendezvous Mission Candidate Comets

    NASA Astrophysics Data System (ADS)

    Lisse, Carey M.; Bauer, J. M.; Fernandez, Y. R.; Mainzer, A. K.; Walker, R. G.; Meech, K. J.; Grav, T.; Weissman, P. R.; Kramer, E.; Stevenson, R.

    2012-10-01

    In 1992, Osip et al. wrote: "Several comet flyby and/or rendezvous missions are currently being planned, for which supporting groundbased data from previous apparitions should prove useful. Here, we discuss groundbased narrowband photometry obtained over the last 15 years for nine candidate comets, five of which have been observed on multiple apparitions -- we derive limits on the size of each cometary nucleus. In order to facilitate spacecraft mission planning, we also present molecular abundance ratios, note variations in cometary activity as a function of orbital position and between apparitions, and note the overall degree of dustiness. A detailed analysis of the characteristics of these nine viable mission candidates will provide necessary information for prioritizing targets for any future missions." In this work, we update Osip et al.'s 1992 work using recent photometric infrared observations of the best candidate comet spacecraft targets observed by WISE and other (IRAS, MSX, ISO, Spitzer) infrared space telescopes. The comets studied include 2P/Encke, 9P/Tempel 1, 10P Tempe1 2, 19P/Borrelly, 22P/Kopff, 67P/Churyumov-Gerasimenko, 81P/Wild, 103P/Hartley 2, 107P/Wilson-Harrington. We present imagery, photometry, and temporal trend data, and derived estimates of the dust mass, spatial distribution, albedo/emissivity, and PSD for each comet.

  20. A CCD portrait of Comet P/Tempel 2

    SciTech Connect

    Jewitt, D.; Luu, J.; MIT, Cambridge, MA )

    1989-06-01

    The development of activity in Comet P/Tempel 2 is studied from aphelion (R = 4 AU) to perihelion (R = 1.4 AU) using extensive time-series CCD photometry and CCD spectra. The comet undergoes a profound morphological change at R of about 2-2.5 AU, from a bare nucleus at larger distances to an active comet supporting a coma of gas and dust. Cyclic photometric variations with the period T = 8.95 + or - 0.01 hr. are present at all R, and are attributed to the rotation of the nucleus at this period. The nucleus is prolate (axes a:b:c = 1.9:1:1), a property shared with other nuclei studied using CCD photometry. Novel results include a limit on the bulk density of the nucleus, rho above 300 kg/cu m, and a 20-A-resolution CCD spectrum of the nucleus. Spatially and temporally resolved photometry is used to study the effects of nucleus rotation on the coma. The coma does not share the dramatic photometric variations shown by the nucleus. It possesses a steep surface-brightness distribution, which is attributable to progressive destruction of the coma grains with increasing space exposure. 41 refs.

  1. Isotope measurements of a comet by the Ptolemy instrument on Rosetta

    NASA Astrophysics Data System (ADS)

    Franchi, Ian; Morse, Andrew; Andrews, Dan; Sheridan, Simon; Barber, Simeon; Leese, Mark; Morgan, Geraint; Wright, Ian; Pillinger, Colin

    Remote observations of comets (spacecraft fly-bys and telescopes) reveal a vast reservoir of volatile organic species, along with the water ice, other volatiles and silicate dust fractions that make up these very primitive bodies. Understanding the nature of cometary materials, in order to unravel their origin and history, is particularly challenging. Remote observation is only possible for the coma, the constituents of which are likely fractionated and modified compared to the primordial material within the comet. A number of opportunities exist for very detailed study of cometary material with ground-based laboratory instrumentation. How-ever, dissipation of energy during capture (e.g. NASA Stardust samples) or atmospheric entry (stratospheric interplanetary dust particles) has the potential to extensively modify, or even obliterate, detailed information about the nature and origin of the more volatile, biologically important organic species present. Collecting and returning pristine material from the surface of a comet remains very challenging and therefore direct study of the volatile portions can only readily be performed on the comet itself by remote instruments. The ESA Rosetta mission, that will make long-term measurements of a comet as it approaches the sun from 3.5 AU to 1.4 AU over a period of at least six months, includes the Philae lander as well as the orbiter spacecraft. Ptolemy, on board Philae, is a GC-MS instrument designed for the analysis of cometary volatiles, organic materials and silicates. The objectives of Ptolemy are to provide a complete description of the nature and distribution of light elements (H, C, N and O) present in the nucleus of the comet, as well as determining their stable isotopic compositions. Ptolemy also aims to provide ground-truth measurements of those volatiles that are subsequently detected further out from the nucleus in the coma. Samples from the surface and sub-surface, collected by the lander drilling system (SD2

  2. High-Resolution Infrared Spectroscopic Measurements of Comet 2PlEncke: Unusual Organic Composition and Low Rotational Temperatures

    NASA Technical Reports Server (NTRS)

    Radeva, Yana L.; Mumma, Michael J.; Villanueva, Geronimo L.; Bonev, Boncho P.; DiSanti, Michael A.; A'Hearn, Michael F.; Dello Russo, Neil

    2013-01-01

    We present high-resolution infrared spectroscopic measurements of the ecliptic comet 2P/Encke, observed on 4-6 Nov. 2003 during its close approach to the Earth, using the Near Infrared Echelle Spectrograph on the Keck II telescope. We present flux-calibrated spectra, production rates, and mixing ratios for H2O, CH3OH, HCN, H2CO, C2H2, C2H6, CH4 and CO. Comet 2P/Encke is a dynamical end-member among comets because of its short period of 3.3 years. Relative to "organics-normal" comets, we determined that 2PlEncke is depleted in HCN, H2CO, C2H2, C2H6, CH4 and CO, but it is enriched in CH3OH. We compared mixing ratios of these organic species measured on separate dates, and we see no evidence of macroscopic chemical heterogeneity in the nucleus of 2P/Encke, however, this conclusion is limited by sparse temporal sampling. The depleted abundances of most measured species suggest that 2P/Encke may have formed closer to the young Sun, before its insertion to the Kuiper belt, compared with "organics-normal" comets - as was previously suggested for other depleted comets (e.g. C/1999 S4 (LINEAR)). We measured very low rotational temperatures of 20 - 30 K for H2O, CH3OH and HCN in the near nucleus region of 2P/Encke, which correlate with one of the lowest cometary gas production rates (approx. 2.6 x 10(exp 27) molecules/s) measured thus far in the infrared. This suggests that we are seeing the effects of more efficient radiative cooling, insufficient collisional excitation, and/or inefficient heating by fast H-atoms (and icy grains) in the observed region of the coma. Its extremely short orbital period, very low gas production rate, and classification as an ecliptic comet, make 2PlEncke an important addition to our growing database, and contribute significantly to the establishment of a chemical taxonomy of comets.

  3. Cometary nucleus and active regions

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1984-01-01

    On the basis of the icy conglomerate model of cometary nuclei, various observations demonstrate the spotted nature of many or most nuclei, i.e., regions of unusual activity, either high or low. Rotation periods, spin axes and even precession of the axes are determined. The observational evidence for variations in activity over the surfaces of cometary nuclei are listed and discussed. On June 11 the comet IRAS-ARAKI-ALCOCK approached the Earth to a distance of 0.031 AU, the nearest since C/Lexell, 1770 I, providing a unique opportunity for near-nucleus observations. Preliminary analysis of these images establishes the spin axis of the nucleus, with an oblioquity to the orbit plane of approximately 50 deg, and a lag angle of sublimation approximately 35 deg from the solar meridian on the nucleus. Asymmetries of the inner coma suggests a crazy-quilt distribution of ices with differing volatility over the surface of the nucleus. The observations of Comet P/Homes 1892 III, exhibiting two 8-10 magnitude bursts, are carefully analyzed. The grazing encounter produced, besides the first great burst, an active area on the nucleus, which was rotating retrograde with a period of 16.3hr and inclination nearly 180 deg. After the first burst the total magnitude fell less than two magnitudes from November 7 to November 30 (barely naked eye) while the nuclear region remained diffuse or complex, rarely if ever showing a stellar appearance. The fading was much more rapid after the second burst. The grazing encounter distributed a volume of large chunks in the neighborhood of the nucleus, maintaining activity for weeks.

  4. Hydrogen cyanide polymers, comets and the origin of life.

    PubMed

    Matthews, Clifford N; Minard, Robert D

    2006-01-01

    Hydrogen cyanide polymers--heterogeneous solids ranging in colour from yellow to orange to brown to black--could be major components of the dark matter observed on many bodies of the outer solar system including asteroids, moons, planets and, especially, comets. The presence on cometary nuclei of frozen volatiles such as methane, ammonia and water subjected to high energy sources makes them attractive sites for the ready formation and condensed-phase polymerization of hydrogen cyanide. This could account for the dark crust observed on Comet Halley in 1986 by the Vega and Giotto missions. Dust emanating from its nucleus would arise partly from HCN polymers as suggested by the Giotto detection of free hydrogen cyanide, CN radicals, solid particles consisting only of H, C and N, or only of H, C, N, O, and nitrogen-containing organic compounds. Further evidence for cometary HCN polymers could be expected from in situ analysis of the ejected material from Comet Tempel 1 after collision with the impactor probe from the two-stage Deep Impact mission on July 4, 2005. Even more revealing will be actual samples of dust collected from the coma of Comet Wild 2 by the Stardust mission, due to return to Earth in January 2006 for analyses which we have predicted will detect these polymers and related compounds. In situ results have already shown that nitriles and polymers of hydrogen cyanide are probable components of the cometary dust that struck the Cometary and Interstellar Dust Analyzer of the Stardust spacecraft as it approached Comet Wild 2 on January 2, 2004. Preliminary evidence (January 2005) obtained by the Huygens probe of the ongoing Cassini-Huygens mission to Saturn and its satellites indicates the presence of nitrogen-containing organic compounds in the refractory organic cores of the aerosols that give rise to the orange haze high in the atmosphere of Titan, Saturn's largest moon. Our continuing investigations suggest that HCN polymers are basically of two types

  5. Stardust: Catching a Comet and Bringing it Home

    NASA Technical Reports Server (NTRS)

    Brownlee, Donald E.

    2007-01-01

    The NASA STARDUST mission collected thousands of particles from Comet Wild 2 that are now being studied by two hundred scientists around the world. The spacecraft captured the samples during a close flyby of the comet in 2004 and returned them to Earth with a dramatic entry into the atmosphere early in 2006. The precious cargo of comet dust is being studied to determine new information about the origin of the Sun and planets. The comet formed at the edge of the solar system, beyond the orbit of Neptune, and is a sample of the material from which the solar system was formed. One of the most dramatic early findings from the mission was that a comet that formed in the coldest place in the solar system contained minerals that formed in the hottest place in the solar system. The comet samples are telling stories of fire and ice and they providing fascinating and unexpected information about our origins.

  6. WILL COMET ISON (C/2012 S1) SURVIVE PERIHELION?

    SciTech Connect

    Knight, Matthew M.; Walsh, Kevin J.

    2013-10-10

    On 2013 November 28 Comet ISON (C/2012 S1) will pass by the Sun with a perihelion distance of 2.7 solar radii. Understanding the possible outcomes for the comet's response to such a close passage by the Sun is important for planning observational campaigns and for inferring ISON's physical properties. We present new numerical simulations and interpret them in context with the historical track record of comet disruptions and of sungrazing comet behavior. Historical data suggest that sizes below ∼200 m are susceptible to destruction by sublimation driven mass loss, while we find that for ISON's perihelion distance, densities lower than 0.1 g cm{sup –3} are required to tidally disrupt a retrograde or non-spinning body. Such low densities are substantially below the range of the best-determined comet nucleus densities, though dynamically new comets such as ISON have few measurements of physical properties. Disruption may occur for prograde rotation at densities up to 0.7 g cm{sup –3}, with the chances of disruption increasing for lower density, faster prograde rotation, and increasing elongation of the nucleus. Given current constraints on ISON's nucleus properties and the typically determined values for these properties among all comets, we find tidal disruption to be unlikely unless other factors (e.g., spin-up via torquing) affect ISON substantially. Whether or not disruption occurs, the largest remnant must be big enough to survive subsequent mass loss due to sublimation in order for ISON to remain a viable comet well after perihelion.

  7. Linear and circular polarimetry of recent comets: Observational results for eight comets

    NASA Astrophysics Data System (ADS)

    Rosenbush, V.; Ivanova, A.; Kiselev, N.; Afanasiev, V.; Kolesnikov, S.; Shakhovskoy, D.

    2014-07-01

    We present the results of polarimetric observations for a number of recent comets carried out at the 6-m telescope of the Special Astrophysical Observatory (Russia) and the 2.6-m telescope of the Crimean Astrophysical Observatory (Ukraine) during 2011--2013. Comets 103P/Hartley 2, C/2009 P1 (Garradd), C/2011 L4 (PANSTARRS), C/2012 S1 (ISON), C/2013 R1 (Lovejoy), 29P/Schwassmann-Wachmann 1, C/2010 S1 (LINEAR), and C/2011 R1 (McNaught) were observed at different distances from the Sun (0.9--6.3 au) and at different phase angles (6.2--83.5 deg). The results obtained are compared with the phase-angle dependencies of linear polarization typical for the high-polarization and low-polarization comets. The linear polarization of comet S1 (LINEAR) and Schwassmann-Wachmann 1 are the first ever measured at the heliocentric distances larger than 6 au. The maps of circular polarization over the coma and its variations with the distance from the nucleus of comets P1 (Garradd), L4 (PANSTARRS), R1 (McNaught), and Schwassmann-Wachmann 1 are obtained. In all cases, left-handed circular polarization is detected and its value is within the range from -0.04 % up to -0.3 %. Detection of left-handed circular polarization in these comets has confirmed our previous conclusion that circular polarization of comets is predominantly left-handed. We will discuss the possible reasons for the diversity and similarity of linear and circular polarization in comets.

  8. Outbursts and cavities in comets

    NASA Astrophysics Data System (ADS)

    Ipatov, Sergei

    Based on analysis of the images made during the first 13 minutes after the collision of the impact module of the Deep Impact (DI) spacecraft with Comet 9P/Tempel 1, Ipatov & A'Hearn [1] studied time variations of ejection of material after this impact. They showed that, besides the normal ejection, at time t_{e} after the DI collision between 8 s and 60 s there was a considerable additional ejection (a triggered outburst) of small (micron size) particles. It increased the mean velocities of observed small ejected particles (compared with the normal ejection). The outburst could be caused by excavation of a large cavity with dust and gas under pressure. The largest cavity excavated after the collision could be relatively deep because a considerable excess ejection lasted during about 50 s. Schultz et al. [2] concluded that the diameter d_{tc} of the DI transient crater was about 200 m. Some authors support smaller values of d_{tc}. The depth of the DI crater at t_{e}=8 s was estimated in [3] to be about 6 m for d_{tc}=200 m and 4 m for d_{tc}=100 m. The distance between the pre-impact surface of Comet 9P/Tempel 1 and the upper border of the largest excavated cavity equal to about 4-6 m, and sizes of particles inside the cavities of a few microns are in good agreement with the results obtained by Kossacki & Szutowicz [4]. In their models of the explosion of Comet 17P/Holmes, the initial sublimation front of the CO ice was located at a depth of 4 m, 10 m, or 20 m, and calculations were finished when the CO pressure exceeded the threshold value 10 kPa. It was shown that the pressure of CO vapor can rise to this value only when the nucleus is composed of very fine grains, a few microns in radius. The porous structure of comets provides enough space for sublimation. The projection of the velocity of the leading edge of the DI cloud (onto the plane perpendicular to the line of sight) was about 100-200 m/s and is typical for outburst particles ejected from comets

  9. EXTINCTION IN THE COMA OF COMET 17P/HOLMES

    SciTech Connect

    Lacerda, Pedro; Jewitt, David

    2012-11-20

    On 2007 October 29, the outbursting comet 17P/Holmes passed within 0.''79 of a background star. We recorded the event using optical, narrowband photometry and detect a 3%-4% dip in stellar brightness bracketing the time of closest approach to the comet nucleus. The detected dimming implies an optical depth {tau} Almost-Equal-To 0.04 at 1.''5 from the nucleus and an optical depth toward the nucleus center {tau}{sub n} < 13.3. At the time of our observations, the coma was optically thick only within {rho} {approx}< 0.''01 from the nucleus. By combining the measured extinction and the scattered light from the coma, we estimate a dust red albedo p{sub d} = 0.006 {+-} 0.002 at {alpha} = 16 Degree-Sign phase angle. Our measurements place the most stringent constraints on the extinction optical depth of any cometary coma.

  10. Physical processes in comets

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.; Huebner, W. F.

    1976-01-01

    The paper discusses physical processes in comets which involve solar and nuclear radial forces that affect the motions of gases and icy grains, gas-phase chemistry very close to the nuclei of large comets near the sun, sublimation of icy grains, dissociation of parent molecules into radicals and of radicals into atoms, and ionization by sunlight and collisions. The composition and dimensions of nuclei are examined along with variations in intrinsic brightness, the nature of volatiles, gas production rates in the coma, characteristics of icy grains in the coma, and the structure of streamers, ion tails, and dust tails. The structure of the coma is described in detail on the basis of spectroscopic observations of several comets. The origin of comets is briefly reviewed together with the relation of comets to earth, the interplanetary complex, and the interstellar medium. Desirable future observations are noted, especially by space missions to comets.

  11. Comet Dead Ahead

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image shows comet Tempel 1 as seen through the clear filter of the medium resolution imager camera on Deep Impact. It was taken on June 26, 2005, when the spacecraft was 7,118,499.4 kilometers (4,423,435 miles) away from the comet. Eight images were combined to create this picture, and a logarithmic stretch was applied to enhance the coma of the comet.

  12. I Spy a Comet!

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image shows comet Tempel 1 as seen through the clear filter of the medium resolution imager camera on Deep Impact. It was taken on June 25, 2005, when the spacecraft was 8,007,845.1 kilometers (4,976,075 miles) away from the comet. Ten images were combined to create this picture, and a logarithmic stretch was applied to enhance the coma of the comet.

  13. Special Report: Chemistry of Comets.

    ERIC Educational Resources Information Center

    A'Hearn, Michael F.

    1984-01-01

    Discusses the chemistry of comets. How comets provide clues to the birth of the solar system, photolytic reactions on comets involving water, chemical modeling, nuclear chemistry, and research findings are among the areas considered. (JN)

  14. Outbursts from cavities in comets

    NASA Astrophysics Data System (ADS)

    Ipatov, S.

    2014-07-01

    few minutes when they moved from R=1 to 10 km. The largest cavity excavated after the collision could be relatively deep because a considerable excess ejection lasted during about 50 s. According to Schultz et al. [2], the diameter d_{tc} of the DI transient crater was about 200 m, but some authors support smaller values of d_{tc}. I estimated [3] the depth of the DI crater at t_{e}=8 s to be about 6 m for d_{tc}=200 m and 4 m for d_{tc}=100 m. The cavity could be located not exactly below the center of the crater (i.e., at a little smaller depth of the crater), but the gas and dust could begin to eject via cracks. The distance between the pre-impact surface of Comet 9P/Tempel 1 and the upper border of the largest excavated cavity of about 4-6 m, and sizes of particles inside the cavities of a few microns are in good agreement with the results obtained by Kossacki and Szutowicz [4]. These authors concluded that the rapid sublimation of the CO ice in a cavity could lead to a rise of gas pressure above the tensile strength of the nucleus. In their models of the explosion of Comet 17P/Holmes, the pressure of CO vapor can rise to the threshold value of 10 kPa only when the nucleus is composed of very fine grains, a few microns in radius. The porous structure of comets provides enough space for sublimation. The projection of the velocity of the leading edge of the DI cloud (onto the plane perpendicular to the line of sight) was about 100-200 m/s and is typical for outburst particles ejected from comets (references to the papers devoted to natural outbursts can be found in [5]). The similarity of velocities of particles ejected at triggered and natural outbursts shows that these outbursts could be caused by similar internal processes in comets. It is possible that cavities with dust and gas under pressure can be located a few meters below the surfaces of comets. After some time, gas under pressure can make its way from a cavity to the surface of a comet, and the gas formed

  15. Comet Dust After Deep Impact

    NASA Technical Reports Server (NTRS)

    Wooden, Diane H.; Harker, David E.; Woodward, Charles E.

    2006-01-01

    a more diverse mineralogy. The lower spatial resolution, high sensitivity Spitzer IRS data reveal resonances of refractory minerals (those seen by GEMINI+Michelle plus ortho-pyroxene)) as well resonances that can be attributed to phillosilicates (layer lattice silicates such as Montmorillonite) (Lisse et al. 2006). Pre- and post-impact, micron to submicron grains were deciphered to be present in the coma by the modeling the high spatial resolution images to account for nucleus plus inner coma fluxes (Wooden et al. 2005, 2006; Harker et al. 2005, 2006a). Note also that crystalline silicates were released from the interior of 73P-B/SW-3 as it disintegrated (Harker et al. 2006b). From the Deep Impact and the disintegration of 73P-B, we are led to ask the questians: Why is the mineralogy of the dust released from a volatile-rich pocket beneath the surface different from the dust that is released from the nominally active areas? Could the most volatile pockets be exhausted quickly? Why would crystalline silicates be associated with more volatile materials? Perhaps the structure of the comet is so inhomogeneous, e.g., the layered pile mode2 of the nucleus (Belton et al. 2006), that a reservoir of crystalline silicate and submicron grains just happens to not be released by the nominally active areas of comet 9P? Perhaps comets lose matter through their mantles from below their surfaces, thus preserving ancient topographic structures and radiation damaged silicates and carbon? We will discuss and ponder different scenarios. We will discuss future directions for coordinated observations of JF comets.

  16. Assessment by Ames test and comet assay of toxicity potential of polymer used to develop field-capable rapid-detection device to analyze environmental samples

    NASA Astrophysics Data System (ADS)

    Hebert, Amanda; Bishop, Michelle; Bhattacharyya, Dhiman; Gleason, Karen; Torosian, Stephen

    2015-08-01

    There is need for devices that decrease detection time of food-borne pathogens from days to real-time. In this study, a rapid-detection device is being developed and assessed for potential cytotoxicity. The device is comprised of melt-spun polypropylene coupons coated via oxidative chemical vapor deposition (oCVD) with 3,4-Ethylenedioxythiophene (EDOT), for conductivity and 3-Thiopheneethanol (3TE), allowing antibody attachment. The Ames test and comet assay have been used in this study to examine the toxicity potentials of EDOT, 3TE, and polymerized EDOT-co-3TE. For this study, Salmonella typhimurium strain TA1535 was used to assess the mutagenic potential of EDOT, 3TE and the copolymer. The average mutagenic potential of EDOT, 3TE and copolymer was calculated to be 0.86, 0.56, and 0.92, respectively. For mutagenic potential, on a scale from 0 to 1, close to 1 indicates low potential for toxicity, whereas a value of 0 indicates a high potential for toxicity. The comet assay is a single-cell gel electrophoresis technique that is widely used for this purpose. This assay measures toxicity based on the area or intensity of the comet-like shape that DNA fragments produce when DNA damage has occurred. Three cell lines were assessed; FRhK-4, BHK-21, and Vero cells. After averaging the results of all three strains, the tail intensity of the copolymer was 8.8 % and tail moment was 3.0, and is most similar to the untreated control, with average tail intensity of 5.7 % and tail moment of 1.7. The assays conducted in this study provide evidence that the copolymer is non-toxic to humans.

  17. Hydrogen cyanide polymers on comets

    NASA Astrophysics Data System (ADS)

    Matthews, C. N.; Ludicky, R.

    1992-11-01

    The original presence on cometary nuclei of frozen volatiles such as methane, ammonia and water makes them ideal sites for the formation and condensed-phase polymerization of hydrogen cyanide. We propose that the non-volatile black crust of comet Halley consists largely of such polymers. Dust emanating from Halley's nucleus, contributing to the coma and tail, would also arise partly from these solids. Indeed, secondary species such as CN have been widely detected, as well as HCN itself and particles consisting only of H, C and N. Our continuing investigations suggest that the yellow-orange-brown-black polymers are of two types: ladder structures with conjugated -C--N- bonds, and polyamidines readily converted by water to polypeptides. These easily formed macromolecules could be major components of the dark matter observed on the giant planets Jupiter and Saturn, as well as on outer solar system bodies such as asteroids, moons and other comets. Implications for prebiotic chemistry are profound. Primitive Earth may have been covered by HCN polymers either through cometary bombardment or by terrestrial happenings of the kind that brought about the black crust of Halley. The resulting proteinaceous matrix could have promoted the molecular interactions leading to the emergence of life.

  18. Properties of simulated comet mantle

    NASA Technical Reports Server (NTRS)

    Fanale, F. P.; Saunders, S.; Banerdt, B.; Stephens, J.; Laue, E.; Sutton, S.

    1984-01-01

    The properties of freeze-dried dilute dispersions of dust in water ice are of considerable interest in studies of comet nucleus mantles. The formation of a rind residue produced by the sublimation of water ice containing various amounts of fine clay particles may be an important process. A simulation of the development of the dry dust rind on the surface of comets is presented. This rind is the result of preferential ice sublimation. The development and disruption of this rind and its subsequent levitation by water vapor flow is studied. The most interesting rind simulant is produced by dispersing 0.1 micron particles of montmorillonite in water in concentrations of 10%, 1%, and 0.1%. These dispersions are then sprayed into liquid nitrogen in the form of 100 micron droplets. The frozen droplets are then freeze-dried in a vacuum which prevents the ice temperature from rising above -30 C. Sublimation of the nitrogen and the water produced dry rinds. The most striking result was the development of large cohesive matrices of individual clay particles, and in some cases a continuous cohesive crust. Scanning electron microscope (SEM) observations reveal that the material formed by freeze-drying the 0.1% dispersion does not retain the original spherical shape of the sprayed 100 micron droplets; instead it consists of a continuous filamentary network, as shown in the SEM stereo micrographs.

  19. The mass disruption of Jupiter Family comets

    NASA Astrophysics Data System (ADS)

    Belton, Michael J. S.

    2015-01-01

    I show that the size-distribution of small scattered-disk trans-neptunian objects when derived from the observed size-distribution of Jupiter Family comets (JFCs) and other observational constraints implies that a large percentage (94-97%) of newly arrived active comets within a range of 0.2-15.4 km effective radius must physically disrupt, i.e., macroscopically disintegrate, within their median dynamical lifetime. Additional observational constraints include the numbers of dormant and active nuclei in the near-Earth object (NEO) population and the slope of their size distributions. I show that the cumulative power-law slope (-2.86 to -3.15) of the scattered-disk TNO hot population between 0.2 and 15.4 km effective radius is only weakly dependent on the size-dependence of the otherwise unknown disruption mechanism. Evidently, as JFC nuclei from the scattered disk evolve into the inner Solar System only a fraction achieve dormancy while the vast majority of small nuclei (e.g., primarily those with effective radius <2 km) break-up. The percentage disruption rate appears to be comparable with that of the dynamically distinct Oort cloud and Halley type comets (Levison, H.F., Morbidelli, A., Dones, L., Jedicke, R., Wiegert, P.A., Bottke Jr., W.F. [2002]. Science 296, 2212-2215) suggesting that all types of comet nuclei may have similar structural characteristics even though they may have different source regions and thermal histories. The typical disruption rate for a 1 km radius active nucleus is ∼5 × 10-5 disruptions/year and the dormancy rate is typically 3 times less. We also estimate that average fragmentation rates range from 0.01 to 0.04 events/year/comet, somewhat above the lower limit of 0.01 events/year/comet observed by Chen and Jewitt (Chen, J., Jewitt, D.C. [1994]. Icarus 108, 265-271).

  20. Dust emission of Comet Halley at large heliocentric distances

    NASA Technical Reports Server (NTRS)

    Gruen, E.; Schwehm, G.; Massonne, L.; Fertig, J.; Graser, U.

    1985-01-01

    Comet Halley is currently approaching the inner solar system. Four spacecrafts (NASA's spacecraft, two Russian Vega probes and the Japanese MS-T5 spacecraft) have already been launched to encounter the comet in March 1986. Two additional Halley probes (the European Giotto spacecraft and another Japanese Planet-A probe) will be launched in mid-85 to join the armada. Observations of dust emissions from Halley's Comet are discussed. The evaporation of cometary ices causes the emission of particulates from the nucleus. These observations will be used to determine the fly-by strategy of the Giotto spacecraft by taking into account the distribution of dust in the vicinity of the nucleus and the associated hazard for the space mission.

  1. Colors of active regions on comet 67P

    NASA Astrophysics Data System (ADS)

    Oklay, N.; Vincent, J.-B.; Sierks, H.; Besse, S.; Fornasier, S.; Barucci, M. A.; Lara, L.; Scholten, F.; Preusker, F.; Lazzarin, M.; Pajola, M.; La Forgia, F.

    2015-10-01

    The OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) scientific imager (Keller et al. 2007) is successfully delivering images of comet 67P/Churyumov-Gerasimenko from its both wide angle camera (WAC) and narrow angle camera (NAC) since ESA's spacecraft Rosetta's arrival to the comet. Both cameras are equipped with filters covering the wavelength range of about 200 nm to 1000 nm. The comet nucleus is mapped with different combination of the filters in resolutions up to 15 cm/px. Besides the determination of the surface morphology in great details (Thomas et al. 2015), such high resolution images provided us a mean to unambiguously link some activity in the coma to a series of pits on the nucleus surface (Vincent et al. 2015).

  2. A search for frosts in Comet Bowell /1980b/

    NASA Technical Reports Server (NTRS)

    Campins, H.; Lebofsky, L. A.; Rieke, G. H.; Lebofsky, M. J.

    1982-01-01

    Infrared observations of Comet Bowell represent the first search for frost signatures in a comet beyond 2 AU from the sun. Broad- and narrowband photometry has been obtained as well as CVF spectrophotometry of this comet and there is no evidence for absorption features in the spectral area between 1.25 and 2.3 microns. Models of the coma have been generated which constrain the volatile content of the grains an; are in agreement with the observed albedo. The darkness of the coma particles at large heliocentric distances indicates a low albedo nucleus as well. Brightness variations during the observing period seem to indicate an active nucleus at 4.5 AU from the sun.

  3. Observation of Comet C/2013 US (Catalina) in Tajikistan

    NASA Astrophysics Data System (ADS)

    Buriev, Anvardzhon

    2016-07-01

    Kh. I. Ibadinov, A.M. Buriev Institute of Astrophysics of the Academy of Sciences of Tajikistan E-mail: ibadinov@mail.ru, anvar10@mail.ru The position, magnitude in BVRI filters and diameter of the nucleus of comet C/ 2013 US 10 (CANALINA) on the basis of CCD observations with AZT-8 telescope Hissar Astronomical observatory in 2016 were founded.

  4. Temporal Variation of Chemical Composition of Comet C/2007 N3 (lulin) Observed in the Near-infrared Wavelength Region

    NASA Astrophysics Data System (ADS)

    Kobayashi, Hitomi; Kawakita, H.; Dello Russo, N.; Vervack, R. J.; Weaver, H. A.; Biver, N.; Bockelee-Morvan, D.; Crovisier, J.

    2009-09-01

    Oort Cloud comet C/2007 N3 (Lulin) approached the Sun in February 2009. Its maximum brightness was about 4th magnitude in V-band. The high productivity of Lulin provided the opportunity to measure chemical composition and monitor the overall volatile productivity of the comet over time. High dispersion near-infrared spectroscopic observations of C/2007 N3 (Lulin) were carried out in August 2008 and January through March 2009 by three different telescopes/instruments atop Mauna Kea, Hawaii: Subaru/IRCS, Keck II/NIRSPEC and IRTF/CSHELL. The spectral resolving powers are 10,000 for IRCS and 25,000 for both NIRSPEC and CSHELL. We present the composition of organic volatiles and the rotational and nuclear spin temperature of water in Lulin. We sampled H2O, OH, HCN, C2H2, NH3, CH4, C2H6, CO, CH3OH, and H2CO in our observations. The temporal coverage of our observations allowed a search for chemical heterogeneity within the nucleus of Lulin, and we discuss the absolute and relative production rates of these species with time and compare the chemistry of Lulin to other comets. The nuclear spin temperature of H2O will also be compared to derived values from other comets.

  5. Meteoroid streams and comet disintegration

    NASA Astrophysics Data System (ADS)

    Guliyev, A.

    2016-01-01

    The results of the statistical analysis of the dynamic parameters of 114 comets that have undergone nuclear splitting are presented in the article. The list of the objects contains: comets that have split in the period of the observation; data of twin-comets; lost comets with designation D; comets with large-scale structure in the coma. We will describe these comets as "splitted". Some aspects of the following hypothesis are studied: disintegration of comet nuclei happens as the result of their collision with meteoroid streams. For the verification of this hypothesis, the position of splitted comet orbits relatively to 125 meteor streams from Kronk's list is analyzed. It was found that the total number of comet orbit nodes located close to the meteor stream planes (for the distances up to 0.1 AU) is N = 1041. It is shown that if these comets are replaced by randomly selected different comets, N will be reduced by a factor of approximately three.

  6. The evolution of comet orbits

    NASA Technical Reports Server (NTRS)

    Everhart, E.

    1976-01-01

    The origin of comets and the evolution of their orbits are discussed. Factors considered include: the law of survival of comets against ejection on hyperbolic orbits; short-period comets are not created by single close encounters of near-parabolic comets with Jupiter; observable long-period comets do not evolve into observable short-period comets; unobservable long-period comets with perihelia near Jupiter can evolve into observable short-period comets; long-period comets cannot have been formed or created within the planetary region of the solar system (excluding the effects of stellar perturbations); it is possible that some of the short-period comets could have been formed inside the orbit of Neptune; circularly-restricted three-body problem, and its associated Jacobi integral, are not valid approximations to use in studying origin and evolution of comets.

  7. Changing Speed of Comets

    ERIC Educational Resources Information Center

    Follows, Mike

    2003-01-01

    It is shown that highly elliptical orbits, such as those of comets, can be explained well in terms of energy rather than forces. The principle of conservation of energy allows a comet's velocity to be calculated at aphelion and perihelion. An example asks students to calculate whether they can run fast enough to escape from a small asteroid.…

  8. Comet Ge-Wang

    NASA Astrophysics Data System (ADS)

    Ge, Yong-liang; Wang, Qi; Han, Tao

    1990-03-01

    Comet Ge-Wang (1988o) was discovered by GE Yong-liang and WANG Qi at Xinglong Station of Beijing Observatory on 1988 November 4. We collected 13 observations of this comet in China and abroad and calculated its orbit. It passed the perihelion on 1988 May 23. Ephemerides up to 1991 April are given.

  9. Comet Ge-Wang

    NASA Astrophysics Data System (ADS)

    Ge, Yong-Liang; Wang, Qi; Han, Tao

    1989-03-01

    Comet Ge-Wang (1988o) was discovered by GE Yong-liang and WANG Qi at Xinglong Station of Beijing Observatory on November 4, 1988. Thirteen observations of this comet were collected in China and abroad and calculated its orbit. It passed the perihelion on May 23, 1988. Ephemerides up to April 1991 are given.

  10. Asteroids, Comets, Meteors 1991

    NASA Technical Reports Server (NTRS)

    Harris, Alan W. (Editor); Bowell, Edward (Editor)

    1992-01-01

    Papers from the conference are presented and cover the following topics with respect to asteroids, comets, and/or meteors: interplanetary dust, cometary atmospheres, atmospheric composition, comet tails, astronomical photometry, chemical composition, meteoroid showers, cometary nuclei, orbital resonance, orbital mechanics, emission spectra, radio astronomy, astronomical spectroscopy, photodissociation, micrometeoroids, cosmochemistry, and interstellar chemistry.

  11. Unveiling the formation and evolution of comets

    NASA Astrophysics Data System (ADS)

    Lasue, J.; Levasseur-Regourd, A. C.; Botet, R.; Coradini, A.; Desanctis, M. C.; Kofman, W.

    2007-08-01

    energy of the cometesimals and their probable re-accretion after collision events in the Kuiper Belt can be used to interpret the typical layered structure observed for comet 9P/Tempel 1 [10] and evaluate the tensile strengths inside the nucleus. Thermal evolution models of comet nuclei explain the current comet observations with the presence of primordial volatiles [11]. A quasi-3D approach (for non-spherically shaped comet nuclei) is used to interpret the current activity of comets in terms of initial characteristics, and to predict shape and internal stratification evolution of the nucleus. Tensile strength indications and activity predictions from such simulations will provide vital clues for the international Rosetta mission landing on the nucleus of comet 67P/Churyumov-Gerasimenko. During the Rosetta rendezvous, the CONSERT experiment will investigate the deep interior of the nucleus from measurements of the propagation delay of long wavelength radio waves [12]. The analysis and 3D reconstruction of the waves passing through the nucleus will put constraints on the materials constituting the comet and the inhomogeneities within the nucleus. While it is now established that nuclei have low densities and are significantly fragile, it will then be possible to better constrain their formation process and their evolution. [1] A'Hearn et al., Science 310, 258 (2005) [2] Samarasinha, Icarus 154, 540 (2001) [3] Trigo-Rodriguez and Llorca, Mon. Not. R. Astron. Soc. 372, 655 (2006) [4] A'Hearn and Combi, Icarus 187, 1 (2007) [5] Hanner and Bradley, In: Comets II, Festou, Keller, Weaver (eds), pp 555 (2004) [6] Brownlee et al., Science 314, 1711 (2006) [7] Lasue and Levasseur-Regourd, J. Quant. Spectros. Radiat. Transfer 100, 220-236 (2006) [8]Levasseur-Regourd et al., (2007), Planet Space Sci., doi:10.1016/j.pss.2006.11.014 in press. [9] Hörz et al., Science 314, 1716 (2006) [10] Belton et al., Icarus 187, 332 (2007) [11] DeSanctis et al., Astron. Astrophys. 444, 605 (2005

  12. Physical Mechanism of Comet Outbursts: The Movie

    NASA Astrophysics Data System (ADS)

    Hartmann, William K.

    2014-11-01

    During experiments conducted in 1976 at the NASA Ames Research Center’s Vertical Gun Facility (VGF), the author studied low velocity impacts into simulated regolith powders and gravels, in order to examine physics of low-velocity collisions during early solar system planetesimal formation. In one “accidental” experiment, the bucket of powder remained gas-charged during evacuation of the VGF vacuum chamber. The impactor, moving at 5.5 m/s, disturbed the surface, initiating eruptions of dust-charged gas, shooting in jets from multiple vents at speeds up to about 3 m/s, with sporadic venting until 17 seconds after the impact. This experiment was described in [1], which concluded that it simulated comet eruption phenomena. In this hypothesis, a comet nucleus develops a lag deposit of regolith in at least some regions. At a certain distance from the sun, the thermal wave penetrates to an ice-rich depth, causing sublimation. Gas rises into the regolith, collects in pore spaces, and creates a gas-charged powder, as in our experiment. Any surface disturbance, such as a meteoroid, may initiate a temporary eruption, or eventually the gas pressure becomes sufficient to blow off the overburden. Our observed ejection speed would be sufficient to launch dust off of a kilometer-scale comet nucleus.Film (100 frames/s) of the event was obtained, but was partially torn up in a projector. It has recently been reconstituted (Centric Photo Labs, Tucson) and dramatically illustrates various cometary phenomena. Parabolic curtains of erupted material resemble curtains of material photographed from earth in real comet comas, “falling back” under solar wind forces. In retrospect, the mechanism photographed here helps explain:*sporadic eruptions in Comet P/Schwassmann-Wachmann 1 (near-circular orbit at ~6 A.U., where repeated recharge may occur).*sporadic eruptions on “asteroid” 2060 Chiron (which stays beyond 8.5 A.U.). *the thicker dust curtain (and longer eruption?) than

  13. 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

  14. Outburst of Comet Halley at 14.3 AU

    NASA Technical Reports Server (NTRS)

    Meech, Karen J.

    1991-01-01

    Observations of comet Halley on February 15, 1991 showed that the comet had undergone a tremendous outburst in brightness sometime before the past month. At the time of the observation, the comet was at a heliocentric distance, R of 14.3 AU, and the expected nuclear magnitude was near 25.4 in the m sub R bandpass. The comet was observed to have an extensive dust coma, extending at least 300,000 km in diameter towards a position angle of 135 degrees. The anti-solar direction was at a position angle of 27 degrees. The brightness of the comet within a 5 arcsec aperture was approximately 20.2, and the total brightness of the nucleus and coma is estimated near 17. An effective exposure of 4.75 hours shows that the coma is well defined with a brightness enhancement at the outer edge. The last observations of the comet were obtained during April 1990 with the Cerro Tololo 4m telescope when the comet was at a distance, R of 12.75 AU. At that time the comet had reached its expected nuclear brightness of 24.9 and there was no evidence of activity. This new episode of activity in the comet is most likely caused by sublimation of a more volatile species than water, for example CO or CO2, which had built up sufficient pressure beneath the dust mantle to initiate an outburst. Continued monitoring of the comet is planned to observe the evolution of the dust coma. Measurements of the expansion velocity may suggest which volatile was responsible for the activity.

  15. Comets: Role and importance to exobiology

    NASA Technical Reports Server (NTRS)

    Delsemme, Armand H.

    1992-01-01

    The transfer of organic compounds from interstellar space to the outskirts of a protoplanetary disk, their accretion into cometary objects, and the transport of the latter into the inner solar system by orbital diffusion throw a new light on the central problem of exobiology. It suggests the existence of a cosmic mechanism, working everywhere, that can supply prebiotic compounds to ubiquitous rocky planets, in search of the proper environment to start life in many places in the Universe. Under the heading of chemistry of the cometary nucleus, the following topics are covered: radial homogeneity of the nucleus; the dust-to-ice ratio; nature of the dust grains; origin of the dust in comets; nature of the volatile fraction; the CO distribution in comet Halley; dust contribution to the volatile fraction; elemental balance sheet of comet Halley; quantitative molecular analysis of the volatile fraction; and isotopic ratios. Under the heading of exogenous origin of carbon on terrestrial planets the following topics are covered: evidence for a high-temperature phase; from planetesimals to planets; a veneer of volatile and organic material; and cometary contribution.

  16. Variability in Comet P/Swift-Tuttle

    NASA Technical Reports Server (NTRS)

    Schulz, Rita; Mcfadden, Lucy A.; Chamberlin, Alan B.; A'Hearn, Michael F.; Schleicher, David G.

    1994-01-01

    Spatial profiles of the coma of Comet P/Swift-Tuttle perpendicular to the projected Sun-comet line were obtained for the emission bands of CN, C2, and C3 as well as for two continuum bands from spectrophotometric observations taken from Oct. 5 to 8, 1992. The intensities were converted into emissivities per sq km in the cases of the continua and into column densities for the emission band profiles. Spatial and temporal variabilities have been found in all five investigated components, which are consistent with the rotational period of the nucleus determined from the observations of the comet during its last perihelion passage in 1862. The emission band profiles were fitted with the vectorial model and the production rates of CN, C2, and C3 were determined. One half of the profiles was fitted adequately under steady state conditions for the production rate in a first approximation, whereas the other half showed prominent bumps, which could only be explained by introducing a time-dependent production rate. Further investigations showed evidence for the presence of gaseous as well as dust jets in the coma, which indicated the presence of at least two active areas on the surface of the nucleus. The projected radial expansion velocities of two different features were determined to be (430 +/- 100) and (460 +/- 100) m/sec, respectively.

  17. A mission design for the Halley comet rendezvous using Ion Drive

    NASA Technical Reports Server (NTRS)

    Boain, R. J.

    1977-01-01

    The Ion Drive propulsion system, a derivative of the old Solar Electric Propulsion (SEP) technology is considered adequate to perform all mission objectives of a proposed Halley's comet rendezvous (scheduled for launch in 1982) except one: control of thermal energy from the concentrating solar arrays. This problem can be solved, however, by adding a separable tail probe to the baseline system. The system consists of an Ion Propulsion Module (IPM) and a Mission Module (MM). Scientific objectives include a determination of the structure of the comet nucleus, an evaluation of nucleus evolution, an assay of the comet's atmosphere and ionosphere, and a study of the interaction between the comet and the interplanetary medium. Attention is given to the navigation parameters necessary for heliocentric transfer and post-rendezvous circumnavigation of the comet.

  18. Observations of formaldehyde in Comet Machholtz (1988j)

    NASA Technical Reports Server (NTRS)

    Snyder, Lewis E.; Palmer, Patrick; De Pater, Imke

    1990-01-01

    Comet Machholtz's 1(11)-1(10) formaldehyde emission was detected with the VLA in September, 1988 at 6-cm wavelength; the small blueshift of -0.76 + or - 0.40 km/sec noted by these observations is consistent with an anisotropic outgassing of the cometary nucleus in the solar direction. The derived formaldehyde production rate for Comet Halley, which exhibits a similar emission line blueshift, was 1.5 x 10 to the 28th mol/sec, while for Comet Machholtz the production rate is about an order of magnitude higher, at 2 x 10 to the 29th mol/sec. The fading of Comet Machholtz after these observations is ascribed to its breakup.

  19. The chemistry of comets

    NASA Technical Reports Server (NTRS)

    Delsemme, A. H.

    1988-01-01

    Comets appear to represent a population of rather homogeneous objects. In particular, the original size distribution peaks at a mean diameter of the order of 10 km. Cometary dust grains appear to be made of clusters of extremely fine particles (0.1-1.0 micron) sintered by heat at a variable degree during their perihelion passages. The brightness laws of comets appear to be derived only by the sublimation of water ice or at least of gas hydrates of the clathrate type. Pristine nuclei are likely to be radially undifferentiated; only their crustal surface must be outgassed and sintered by the heat of perihelion passages. Comet Halley is confirmed to be in the same general class as the bright comets of the 1970s. With an organic fraction of 33 percent in the cometary dust, the carbon of Comet Halley is close to cosmic abundances.

  20. Analysis and Interpretation of Comet Measurements from SMEI

    NASA Astrophysics Data System (ADS)

    Buffington, A.; Bisi, M. M.; Clover, J. M.; Hick, P. P.; Jackson, B. V.

    2007-12-01

    The Solar Mass Ejection Imager (SMEI) has observed several comets and traced their plasma tails as far as 108 km from their nucleus. A time sequence of SMEI orbital sky maps displays considerable tail motion and disruption for several of these comets. Tracking these motions versus time, when combined with ephemeris information about their distance from the Earth allows a determination of solar wind speeds and their variation with the location of the comet. In the case of comets C/2001 Q4 (NEAT) and C/2002 T7 (LINEAR), which passed within about 0.3 AU of Earth in April and May of 2004, the SMEI observations show that speeds during disruptions are typically 50 to 100 km s-1 less than speeds before and after. Time durations of the disturbances vary between 3 and 8 hours, and correspond to distances traversed by the comets of ~106 km (0.007 AU). We compare these observations with interplanetary scintillation (IPS) three-dimensional tomographic reconstructions and find no evidence that the comet-tail features are due to large-scale density or velocity structures. We also compare these with near-by spacecraft measurements such as the Advanced Composition Explorer (ACE), and find a similar result. This suggests that the comet-tail disruptions are caused by small-scale changes in the solar wind acting over distances that are short compared with 1 AU.

  1. A Comet Engulfs Mars: MAVEN observations of Comet Siding Spring’s Effects on the Martian Magnetosphere

    NASA Astrophysics Data System (ADS)

    Espley, Jared R.; DiBraccio, Gina A.; Connerney, Jack; Brain, David; Gruesbeck, Jacob; Soobiah, Yasir; Halekas, Jasper; Combi, Michael; Luhmann, Janet; Ma, Yingjuan; Jia, Yingdong; Jakosky, Bruce

    2015-11-01

    The nucleus of Comet C/2013 A1 (Siding Spring) passed within 135,000 km of Mars on Oct. 19, 2014. Thus the cometary coma and the plasma it produces washed over Mars for several hours producing significant effects in the martian magnetosphere and upper atmosphere. We present observations from MAVEN’s particles and fields instruments that show the martian magnetosphere was severely distorted during the comet’s passage. We note four specific major effects: 1) a variable induced magnetospheric boundary, 2) a strong rotation of the magnetic field as the comet approached, 3) severely distorted and disordered ionospheric fields during the comet’s closest approach, and 4) unusually strong magnetosheath turbulence lasting hours after the comet left. We argue that the comet had effects comparable to a large solar storm (in terms of incident energy) and so was a fascinating opportunity to explore atmospheric escape, MAVEN’s primary science objective.

  2. Comet 81P/wild 2 under a microscope

    USGS Publications Warehouse

    Brownlee, D.; Tsou, P.; Aleon, J.; O'D, Alexander, C. M.; Araki, T.; Bajt, S.; Baratta, G.A.; Bastien, R.; Bland, P.; Bleuet, P.; Borg, J.; Bradley, J.P.; Brearley, A.; Brenker, F.; Brennan, S.; Bridges, J.C.; Browning, N.D.; Brucato, J.R.; Bullock, E.; Burchell, M.J.; Busemann, H.; Butterworth, A.; Chaussidon, M.; Cheuvront, A.; Chi, M.; Cintala, M.J.; Clark, B. C.; Clemett, S.J.; Cody, G.; Colangeli, L.; Cooper, G.; Cordier, P.; Daghlian, C.; Dai, Z.; D'Hendecourt, L.; Djouadi, Z.; Dominguez, G.; Duxbury, T.; Dworkin, J.P.; Ebel, D.S.; Economou, T.E.; Fakra, S.; Fairey, S.A.J.; Fallon, S.; Ferrini, G.; Ferroir, T.; Fleckenstein, H.; Floss, C.; Flynn, G.; Franchi, I.A.; Fries, M.; Gainsforth, Z.; Gallien, J.-P.; Genge, M.; Gilles, M.K.; Gillet, P.; Gilmour, J.; Glavin, D.P.; Gounelle, M.; Grady, M.M.; Graham, G.A.; Grant, P.G.; Green, S.F.; Grossemy, F.; Grossman, L.; Grossman, J.N.; Guan, Y.; Hagiya, K.; Harvey, R.; Heck, P.; Herzog, G.F.; Hoppe, P.; Horz, F.; Huth, J.; Hutcheon, I.D.; Ignatyev, K.; Ishii, H.; Ito, M.; Jacob, D.; Jacobsen, C.; Jacobsen, S.; Jones, S.; Joswiak, D.; Jurewicz, A.; Kearsley, A.T.; Keller, L.P.; Khodja, H.; Kilcoyne, A.L.D.; Kissel, J.; Krot, A.; Langenhorst, F.; Lanzirotti, A.; Le, L.; Leshin, L.A.; Leitner, J.; Lemelle, L.; Leroux, H.; Liu, M.-C.; Luening, K.; Lyon, I.; MacPherson, G.; Marcus, M.A.; Marhas, K.; Marty, B.; Matrajt, G.; McKeegan, K.; Meibom, A.; Mennella, V.; Messenger, K.; Messenger, S.; Mikouchi, T.; Mostefaoui, S.; Nakamura, T.; Nakano, T.; Newville, M.; Nittler, L.R.; Ohnishi, I.; Ohsumi, K.; Okudaira, K.; Papanastassiou, D.A.; Palma, R.; Palumbo, M.E.; Pepin, R.O.; Perkins, D.; Perronnet, M.; Pianetta, P.; Rao, W.; Rietmeijer, F.J.M.; Robert, F.; Rost, D.; Rotundi, A.; Ryan, R.; Sandford, S.A.; Schwandt, C.S.; See, T.H.; Schlutter, D.; Sheffield-Parker, J.; Simionovici, A.; Simon, S.; Sitnitsky, I.; Snead, C.J.; Spencer, M.K.; Stadermann, F.J.; Steele, A.; Stephan, T.

    2006-01-01

    The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales.

  3. Comet 81P/Wild 2 under a microscope.

    PubMed

    Brownlee, Don; Tsou, Peter; Aléon, Jérôme; Alexander, Conel M O'd; Araki, Tohru; Bajt, Sasa; Baratta, Giuseppe A; Bastien, Ron; Bland, Phil; Bleuet, Pierre; Borg, Janet; Bradley, John P; Brearley, Adrian; Brenker, F; Brennan, Sean; Bridges, John C; Browning, Nigel D; Brucato, John R; Bullock, E; Burchell, Mark J; Busemann, Henner; Butterworth, Anna; Chaussidon, Marc; Cheuvront, Allan; Chi, Miaofang; Cintala, Mark J; Clark, B C; Clemett, Simon J; Cody, George; Colangeli, Luigi; Cooper, George; Cordier, Patrick; Daghlian, C; Dai, Zurong; D'Hendecourt, Louis; Djouadi, Zahia; Dominguez, Gerardo; Duxbury, Tom; Dworkin, Jason P; Ebel, Denton S; Economou, Thanasis E; Fakra, Sirine; Fairey, Sam A J; Fallon, Stewart; Ferrini, Gianluca; Ferroir, T; Fleckenstein, Holger; Floss, Christine; Flynn, George; Franchi, Ian A; Fries, Marc; Gainsforth, Z; Gallien, J-P; Genge, Matt; Gilles, Mary K; Gillet, Philipe; Gilmour, Jamie; Glavin, Daniel P; Gounelle, Matthieu; Grady, Monica M; Graham, Giles A; Grant, P G; Green, Simon F; Grossemy, Faustine; Grossman, Lawrence; Grossman, Jeffrey N; Guan, Yunbin; Hagiya, Kenji; Harvey, Ralph; Heck, Philipp; Herzog, Gregory F; Hoppe, Peter; Hörz, Friedrich; Huth, Joachim; Hutcheon, Ian D; Ignatyev, Konstantin; Ishii, Hope; Ito, Motoo; Jacob, Damien; Jacobsen, Chris; Jacobsen, Stein; Jones, Steven; Joswiak, David; Jurewicz, Amy; Kearsley, Anton T; Keller, Lindsay P; Khodja, H; Kilcoyne, A L David; Kissel, Jochen; Krot, Alexander; Langenhorst, Falko; Lanzirotti, Antonio; Le, Loan; Leshin, Laurie A; Leitner, J; Lemelle, L; Leroux, Hugues; Liu, Ming-Chang; Luening, K; Lyon, Ian; Macpherson, Glen; Marcus, Matthew A; Marhas, Kuljeet; Marty, Bernard; Matrajt, Graciela; McKeegan, Kevin; Meibom, Anders; Mennella, Vito; Messenger, Keiko; Messenger, Scott; Mikouchi, Takashi; Mostefaoui, Smail; Nakamura, Tomoki; Nakano, T; Newville, M; Nittler, Larry R; Ohnishi, Ichiro; Ohsumi, Kazumasa; Okudaira, Kyoko; Papanastassiou, Dimitri A; Palma, Russ; Palumbo, Maria E; Pepin, Robert O; Perkins, David; Perronnet, Murielle; Pianetta, P; Rao, William; Rietmeijer, Frans J M; Robert, François; Rost, D; Rotundi, Alessandra; Ryan, Robert; Sandford, Scott A; Schwandt, Craig S; See, Thomas H; Schlutter, Dennis; Sheffield-Parker, J; Simionovici, Alexandre; Simon, Steven; Sitnitsky, I; Snead, Christopher J; Spencer, Maegan K; Stadermann, Frank J; Steele, Andrew; Stephan, Thomas; Stroud, Rhonda; Susini, Jean; Sutton, S R; Suzuki, Y; Taheri, Mitra; Taylor, Susan; Teslich, Nick; Tomeoka, Kazu; Tomioka, Naotaka; Toppani, Alice; Trigo-Rodríguez, Josep M; Troadec, David; Tsuchiyama, Akira; Tuzzolino, Anthony J; Tyliszczak, Tolek; Uesugi, K; Velbel, Michael; Vellenga, Joe; Vicenzi, E; Vincze, L; Warren, Jack; Weber, Iris; Weisberg, Mike; Westphal, Andrew J; Wirick, Sue; Wooden, Diane; Wopenka, Brigitte; Wozniakiewicz, Penelope; Wright, Ian; Yabuta, Hikaru; Yano, Hajime; Young, Edward D; Zare, Richard N; Zega, Thomas; Ziegler, Karen; Zimmerman, Laurent; Zinner, Ernst; Zolensky, Michael

    2006-12-15

    The Stardust spacecraft collected thousands of particles from comet 81P/Wild 2 and returned them to Earth for laboratory study. The preliminary examination of these samples shows that the nonvolatile portion of the comet is an unequilibrated assortment of materials that have both presolar and solar system origin. The comet contains an abundance of silicate grains that are much larger than predictions of interstellar grain models, and many of these are high-temperature minerals that appear to have formed in the inner regions of the solar nebula. Their presence in a comet proves that the formation of the solar system included mixing on the grandest scales. PMID:17170289

  4. Comet assay to sense neutron 'fingerprint'.

    PubMed

    Gajendiran, N; Tanaka, K; Kamada, N

    2000-09-18

    The suitability of comet assay to identify DNA damage induced by neutrons of varying energy was tested. For this purpose, monoenergetic neutrons from Hiroshima University Radiobiological Research Accelerator (HIRRAC) were used to induce DNA damage in irradiated human peripheral blood lymphocytes. The level of damage was computed as tail moment for different doses (0.125-1 Gy) and compared with the effects resulting from irradiation with (60)Co gamma. The neutron-irradiated cells exhibited longer comet tails consisting of tiny pieces of broken DNA in contrast to the streaking tails generated by (60)Co gamma. The peak biological effectiveness occurred at 0.37 and 0.57 MeV; a further increase or decrease in neutron energy led to a reduced RBE value. The RBE values, as measured by the comet assay, were 6.3, 5.4, 4.7, 4.3, 2.6, and 1.7 for 0.37, 0.57, 0.79, 0.186, 1, and 2.3 MeV neutrons. The lower RBE value obtained by the comet assay when compared to that for other biological end points is discussed. This study reports the usefulness of the alkaline comet assay for identifying DNA damage induced by neutrons of the same radiation weighting factor. The comet assay is a potential tool for use in neutron therapy, as well as a method for the rapid screening of samples from individuals accidentally exposed to radiation. PMID:11024477

  5. Energetic ions at Comet Grigg-Skjellerup measured from the Giotto spacecraft

    NASA Astrophysics Data System (ADS)

    McKenna-Lawlor, S. M. P.; Daly, P. W.; Kirsch, E.; O'Sullivan, D.; Thompson, A.; Wenzel, K.-P.; Afonin, V.

    1993-05-01

    The detection is reported by the EPONA instrument on Giotto of charged energetic particles deep within the inner coma of Comet Grigg-Skjellerup. Well-defined periodic intensity variation recorded in the particle fluxes suggest that the ions close to the nucleus were strongly coupled to the ambient magnetic field. The present data indicate that Giotto flew on the nightside of the nucleus.

  6. TRAPPIST monitoring of comet C/2012 F6 (Lemmon)

    NASA Astrophysics Data System (ADS)

    Opitom, C.; Jehin, E.; Manfroid, J.; Hutsemékers, D.; Gillon, M.; Magain, P.

    2015-02-01

    We report the results of the long-term narrowband photometry and imaging monitoring of comet C/2012 F6 (Lemmon) with the robotic TRAPPIST telescope (La Silla Observatory). Observations covered 52 nights pre- and post-perihelion between December 11, 2012, and June 11, 2013 (perihelion: 24 March, 2013). We followed the evolution of the OH, NH, CN, C3, and C2 production rates computed with the Haser model as well as the evolution of the A(θ)fρ parameter as a proxy for the dust production. All five gas species display similar slopes for the heliocentric dependence. An asymmetry about perihelion is observed, the rate of brightening being steeper than the rate of fading. The chemical composition of the comet's coma changes slightly along the orbit: the relative abundance of C2 to CN increases with the heliocentric distance (r) below -1.4 au and decreases with r beyond 1.4 au while the C3-to-CN ratio is constant during our observations. The behavior of the dust is different from that of the gas, the slope of the heliocentric dependence becoming steeper in early February, correlated to a change in the visual lightcurve slope. However, the dust color does not vary during the observations. The application of several enhancement techniques on the images revealed structures in the CN, C3, and C2 images. These features imply the existence of one or several active zone(s) on the comet nucleus. The shape of the structures is similar in these three filters and changes from a roughly hourglass shape in December and January to a corkscrew shape in February and March. The structures in the continuum filters (sampling the dust) are not correlated to those observed for the gas. During several full nights in February, we observed changes in the CN and C2 structures that repeated periodically because of the nucleus rotation, our derived rotational period being of 9.52 ± 0.05 h. Full Tables 2, 4, 6 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130

  7. Infrared imaging of comets

    NASA Technical Reports Server (NTRS)

    Telesco, Charles M.

    1988-01-01

    Thermal infrared imaging of comets provides fundamental information about the distribution of dust in their comae and tails. The imaging program at NASA Marshall Space Flight Center (MSFC) uses a unique 20-pixel bolometer array that was developed to image comets at 8 to 30 micrometer. These images provide the basis for: (1) characterizing the composition and size distribution of particles, (2) determining the mass-loss rates from cometary nuclei, and (3) describing the dynamics of the interaction between the dust and the solar radiation. Since the array became operational in 1985, researchers have produced a unique series of IR images of comets Giacobini-Zinner (GZ), Halley, and Wilson. That of GZ was the first groundbased thermal image ever made of a comet and was used to construct, with visible observations, an albedo map. Those data and dynamical analyses showed that GZ contained a population of large (approximately 300 micrometer), fluffy dust grains that formed a distinict inner tail. The accumulating body of images of various comets has also provided a basis for fruitfully intercomparing comet properties. Researchers also took advantage of the unique capabilities of the camera to resolve the inner, possible protoplanetary, disk of the star Beta Pictoris, while not a comet research program, that study is a fruitful additional application of the array to solar system astronomy.

  8. Realm of the comets

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.

    1987-01-01

    Studies of Jovian perturbations of the orbits of long-period comets led to the concept of the Oort cloud of 180 billion comets at 50,000-150,000 AU from the sun. Several comets are induced to move toward the sun every million years by the passage of a star at a distance of a few light years. The location of the cloud has since been revised to 20,000-100,000 AU, and comets are now accepted as remnant material fron the proto-solar system epoch. The galactic disk and random, close-passing stars may also cause rare, large perturbations in the orbits of the cloud comets, sending large numbers of comets through the inner solar system. The resulting cometary storm is a candidate cause for the wholesale extinction of dinosaurs in the Cretaceous-Terniary transition due to large number of planetesimals, or one large comet, striking the earth, in a short period of time. The IRAS instruments have detected similar clouds of material around other stars.

  9. Realm of the comets

    SciTech Connect

    Weissman, P.R.

    1987-03-01

    Studies of Jovian perturbations of the orbits of long-period comets led to the concept of the Oort cloud of 180 billion comets at 50,000-150,000 AU from the sun. Several comets are induced to move toward the sun every million years by the passage of a star at a distance of a few light years. The location of the cloud has since been revised to 20,000-100,000 AU, and comets are now accepted as remnant material fron the proto-solar system epoch. The galactic disk and random, close-passing stars may also cause rare, large perturbations in the orbits of the cloud comets, sending large numbers of comets through the inner solar system. The resulting cometary storm is a candidate cause for the wholesale extinction of dinosaurs in the Cretaceous-Terniary transition due to large number of planetesimals, or one large comet, striking the earth, in a short period of time. The IRAS instruments have detected similar clouds of material around other stars.

  10. Comet Bursting Through Relaxation

    NASA Astrophysics Data System (ADS)

    Jacobson, Seth A.; Scheeres, D. J.

    2012-10-01

    Comets may be excited and occupy non-principal axis (complex) rotation states for a large fraction of their lifetimes. Many comet nuclei have been identified or are suspected to occupy non-principal axis (complex) rotation [Belton 2005, etc.] as well as have evolving rotation rates [Belton 2011, etc.]. Comet orbits drive these rotation states through cycles of excitation due to surface jets and relaxation due to time variable internal stresses that dissipate energy in the anelastic comet interior. Furthermore, relaxation from complex rotation can increase the loads along the symmetry axis of prolate comets. These loads stretch the body along the symmetry axis and may be the cause of the characteristic ``bowling pin’’ shape and eventually may lead to failure. This is an alternative model for comet bursting. Each cycle deposits only a small amount of energy and stress along the axis, but this process is repeated every orbit during which jets are activated. Our model for the evolution of comet nuclei includes torques due to a number of discrete jets located on the surface based on Neishtadt et al. [2002]. The model also includes internal dissipation using an approach developed by Sharma et al. [2005] and Vokrouhlicky et al. [2009]. These equations are averaged over the instantaneous spin state and the heliocentric orbit so the long-term evolution of the comet can be determined. We determine that even after the inclusion of internal dissipation there still exist non-principal axis equilibrium states for certain jet geometries. For ranges of dissipation factors and jet geometries, prolate comets are found to occupy states that have time variable internal loads over long time periods. These periodic loadings along the symmetry axis may lead to ``necking’’ as the body extends along the axis to release the stress and eventually disruption.

  11. Submillimeter Continuum Observations of Comets

    NASA Technical Reports Server (NTRS)

    Jewitt, David

    1998-01-01

    The aim of this proposal was to study the submillimeter continuum emission from comets. The study was based mainly on the exploitation of the world's leading submillimeter telescope, the JCMT (James Clerk Maxwell Telescope) on Mauna Kea. Submillimeter wavelengths provide a unique view of cometary physics for one main reason. The cometary size distribution is such that the scattering cross-section is dominated by small dust grains, while the mass is dominated by the largest particles. Submillimeter continuum radiation samples cometary particles much larger than those sampled by more common observations at shorter (optical and infrared) wavelengths and therefore provides a nearly direct measure of the cometary dust mass.

  12. Amino Acids from a Comet

    NASA Technical Reports Server (NTRS)

    Cook, Jamie Elisla

    2009-01-01

    NASA's Stardust spacecraft returned samples from comet 81P/Wild 2 to Earth in January 2006. Examinations of the organic compounds in cometary samples can reveal information about the prebiotic organic inventory present on the early Earth and within the early Solar System, which may have contributed to the origin of life. Preliminary studies of Stardust material revealed the presence of a suite of organic compounds including several amines and amino acids, but the origin of these compounds (cometary- vs. terrestrial contamination) could not be identified. We have recently measured the carbon isotopic ratios of these amino acids to determine their origin, leading to the first detection of a coetary amino acid.

  13. Comet Science Working Group report on the Halley Intercept Mission

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The Halley Intercept Mission is described and the scientific benefits expected from the program are defined. One characteristic of the mission is the optical navigation and resulting accurate delivery of the spacecraft to a desired point near the nucleus. This accuracy of delivery has two important implications: (1) high probability that the mass spectrometers and other in situ measurement devices will reach the cometary ionosphere and the zone of parent molecules next to the nucleus; (2) high probability that sunlit, high resolution images of Halley's nucleus will be obtained under proper lighting conditions. In addition an observatory phase is included during which high quality images of the tail and coma structure will be obtained at progressively higher spatial resolutions as the spacecraft approaches the comet. Complete measurements of the comet/solar wind interaction can be made around the time of encounter. Specific recommendations are made concerning project implementation and spacecraft requirements.

  14. CME impact on comet 67P

    NASA Astrophysics Data System (ADS)

    Edberg, Niklas J. T.; Andrews, David J.; Burch, Jim L.; Carr, Christopher M.; Cupido, Emanuele; Eriksson, Anders I.; Glassmeier, Karl-Heinz; Goldstein, Ray; Henri, Pierre; Koenders, Christoph; Mandt, Kathy; Nilsson, Hans; Odelstad, Elias; Stenberg Wieser, Gabriella; Vigren, Erik

    2016-04-01

    We present observations from the Rosetta Plasma Consortium (RPC) of an impact of a coronal mass ejection (CMEs) on comet 67P. The CME impacted during a dayside excursion in early October 2015 when Rosetta slowly moved from a distance of ~300 km to 1500 km from the comet nucleus. Although this was still deep down in the cometary coma, the CME impact caused a significant disturbance to the plasma environment. As the CME impacted, the magnetic field strength increased to reach a maximum of 250 nT, which is the highest magnetic field strength ever observed at 67P. Lots of magnetic field oscillations and increased fluxes of energized (~100 eV) electrons and ions were observed concurrently, and the ionospheric low-energy plasma density increased by roughly one order of magnitude. An interesting phenomenon that could occur during a CME impact is a so-called tail disconnection event, when magnetic reconnection, either on the dayside of the comet or in the tail, causes a large fraction of the tail to be disconnected from the comet. Rosetta, being relatively close to the nucleus, can at best directly observe signatures of dayside reconnection when draped interplanetary magnetic fields of different polarities convects through the plasma environment and reconnects at the location of Rosetta. Rosetta cannot directly observe any tail-side disconnection event due to the orbit constraints. However, signatures of such events might resemble substorm effects in the terrestrial ionosphere with increased wave activity, increased ionization, energization of electrons and possibly ions. We discuss the RPC measurements during the October CME in this context and try to determine if a tail disconnection event could have occurred at this time.

  15. Systems for COMET

    NASA Technical Reports Server (NTRS)

    Andrews, Harry

    1991-01-01

    The Centers for Commercial Development of Space (CCDS) have become the nation's primary focus for stimulating private sector investment in space. In establishing the COMmercial Experiment Transporter (COMET) program, the CCDS's have taken a major step toward the full scale commercial development of space. The COMET program will enable the CCDS community to turn the goal of commercial space into reality, and in the process, establish U.S. leadership in the global market for space systems and services. Some details are presented on the systems that make up the COMET missions, specifically as they describe the accommodation for potential users and mission parameters.

  16. The loss and depth of CO2 ice in comet nuclei

    NASA Technical Reports Server (NTRS)

    Fanale, F. P.; Salvail, J. R.

    1987-01-01

    An analytical model was developed to simulate the material differentiation of a cometary nucleus composed of water ice, putative unclathrated CO2 ice and silicate dust in specified proportions. Selective sublimation of any free CO2 ice present in a comet would produce a surface layer of water ice and dust overlying the original CO2 rich material. This surface layer reduces the temperature of buried CO2 ice and restricts the outflow of gaseous CO2. On each orbit, water sublimation at smaller heliocentric distances temporarily reduces the thickness of the water ice and dust layer and liberates dust. The model includes the effects of nucleus rotation, arbitrary orientation of the rotation axis, latitude, heat conduction into the deep interior of the nucleus and restriction of CO2 gas outflow by the water ice and dust layer. The effects of the permeability of the surface water ice layer, the nucleus rotation rate, and the latitude were investigated. Comparison of these and similar results with observations could yield information regarding the permeability and chemical composition of cometary material and suggest sampling strategies to minimize fractionation effects.

  17. Sample Return from the Stardust Mission

    NASA Technical Reports Server (NTRS)

    2006-01-01

    On January 2,2004, the STARDUST spacecraft made a close flyby (236 km) of the nucleus of a comet - Comet Wild 2. During the flyby the spacecraft collected samples of dust from the coma of the comet. These samples were successfully returned to Earth on January 15,2006. After a six month preliminary examination to establish the nature of the returned samples, they will be made available to the general scientific community for study. STARDUST is one of the missions carried out under NASA's Discovery Mission Program. During my talk I will present a brief overview of the scientific goals of the STARDUST mission and describe the mission's design and flight. I will also discuss the reentry and recovery of the Stardust Sample Return Capsule (SRC) in Utah, with an emphasis on those aspects of the recovery important for minimizing the degree of contamination (particularly organic contamination) of the samples. Finally, I will discuss some of the results coming out of the preliminary examination of the returned samples, with an emphasis on the nature of organic materials found in the samples.

  18. First International Conference on Comet Hale-Bopp. Proceedings. Conference, Puerto de la Cruz, Tenerife (Spain), 2 - 5 Feb 1998.

    NASA Astrophysics Data System (ADS)

    A'Hearn, M. F.; Boehnhardt, H.; Kidger, M.; West, R. M.

    The following topics were dealt with: comet Hale-Bopp (1995 O1), comet nucleus properties, nuclear rotation and size, satellite claim, radio and submillimetre observations, coma morphology, chemical composition studies, tail studies, X-ray emission, dust shells, IR spectra, polarization observations, solar wind interaction.

  19. Shape Effect in Aggregation and Thermal Evolution of Comet Nuclei

    NASA Astrophysics Data System (ADS)

    Lasue, Jeremie; Coradini, A.; Levasseur-Regourd, A. C.; Botet, R.; De Sanctis, M. C.; Capria, M. T.; Magni, G.; Turrini, D.

    2007-10-01

    Comet nuclei are considered as the most pristine bodies of the Solar System. Their study consequently sheds an important light on the processes occurring during the initial stages of the solar system formation. Simulations have been developed in our teams to describe new aspects of comet formation and evolution. Particle aggregation simulations taking into account age-related cohesive energy of cometesimals during accretions in the Kuiper belt can be used to interpret the layered structure and surface features observed for comet 9P/Tempel 1 [1] and quantify the tensile strengths of these objects. Thermal evolution models of comet nuclei have been rather successful in explaining global aspects of comet observations [2]. A new quasi-3D approach for non-spherically shaped comet nuclei has been developed to analyse the effect of the irregular shapes (non-spherical shapes, mountain-like and crater-like features) of comet nuclei on their thermal evolution, on the local crust formation and the onset of their activity. Our simulations suggest that depressions on the surface play a role in the internal stratification of the nucleus and can disappear in a comet's lifetime [3]. New simulations specifically designed for the orbital history and irregular shape of 67P/Churyumov-Gerasimenko will be presented. These tensile strength indications and activity predictions will provide vital clues for the international Rosetta mission rendezvous that will provide further constraints on the formation and evolution processes of comets. [1] Belton et al., Icarus 187, 332 (2007) [2] DeSanctis et al., Astron. Astrophys. 444, 605 (2005) [3] Lasue et al., in preparation This research has been funded by the French Space Agency (CNES)

  20. Abundant Solar Nebula Solids in Comets

    NASA Technical Reports Server (NTRS)

    Messenger, S.; Keller, L. P.; Nakamura-Messenger, K.; Nguyen, A. N.; Clemett, S.

    2016-01-01

    Comets have been proposed to consist of unprocessed interstellar materials together with a variable amount of thermally annealed interstellar grains. Recent studies of cometary solids in the laboratory have shown that comets instead consist of a wide range of materials from across the protoplanetary disk, in addition to a minor complement of interstellar materials. These advances were made possible by the return of direct samples of comet 81P/Wild 2 coma dust by the NASA Stardust mission and recent advances in microscale analytical techniques. Isotopic studies of 'cometary' chondritic porous interplanetary dust particles (CP-IDPs) and comet 81P/Wild 2 Stardust samples show that preserved interstellar materials are more abundant in comets than in any class of meteorite. Identified interstellar materials include sub-micron-sized presolar silicates, oxides, and SiC dust grains and some fraction of the organic material that binds the samples together. Presolar grain abundances reach 1 weight percentage in the most stardust-rich CP-IDPs, 50 times greater than in meteorites. Yet, order of magnitude variations in presolar grain abundances among CP-IDPs suggest cometary solids experienced significant variations in the degree of processing in the solar nebula. Comets contain a surprisingly high abundance of nebular solids formed or altered at high temperatures. Comet 81P/Wild 2 samples include 10-40 micron-sized, refractory Ca- Al-rich inclusion (CAI)-, chondrule-, and ameboid olivine aggregate (AOA)-like materials. The O isotopic compositions of these refractory materials are remarkably similar to their meteoritic counterparts, ranging from 5 percent enrichments in (sup 16) O to near-terrestrial values. Comet 81P/Wild 2 and CP-IDPs also contain abundant Mg-Fe crystalline and amorphous silicates whose O isotopic compositions are also consistent with Solar System origins. Unlike meteorites, that are dominated by locally-produced materials, comets appear to be composed of

  1. Dust tail striae: Lessons from recent comets

    NASA Astrophysics Data System (ADS)

    Jones, G.; Battams, K.

    2014-07-01

    Striae are features rarely observed in cometary dust tails. These are near-linear structures that, unlike synchronic bands, are not aligned with the nucleus position, and have only been clearly observed in a few high-production-rate comets, including C/1957 P1 (Mrkos), C/1962 C1 (Seki-Lines), C/1975 V1 (West), and C/1996 O1 (Hale-Bopp). The formation of striae is difficult to explain, but several scenarios for their creation have been proposed [1]. These include that of Sekanina & Farrell [2], who proposed that striae are the result of a two-step fragmentation process, where parent particles are released from the nucleus which, after a delay, all fragment over a very short period of time. The fragmentation products then separate according to their β parameter, i.e., the degree to which the particles are influenced by radiation pressure force compared to gravitational force, to form the linear structures we observe as striae. Although there are issues with identifying a process through which many particles will collectively delay their break-up and then fragment within a short period, this scenario does fit many observations well [3]. Other proposed scenarios are more complex, including the formation of striae through a continuous cascade of fragmentation to ever smaller particle sizes [4]. As these formation scenarios result in different distributions of dust-particle sizes within individual striae, the processes occurring may therefore be identifiable if these distributions can be inferred. If the fragmentation processes taking place can be identified, then, in turn, more could be learnt about the structure of the original dust grains that go on to form these sometimes beautiful tail structures. Here, we present the analysis of striae in several comets observed from space by the SOHO LASCO coronagraph [5] and SECCHI heliospheric imagers aboard the twin STEREO spacecraft [6]. The comets studied are C/2002 V1 (NEAT) in January 2002, C/2006 P1 (McNaught) during its

  2. Infrared Imaging, Spectroscopic, and Photometric Studies of Comets

    NASA Technical Reports Server (NTRS)

    Gehrz, Robert D.

    1997-01-01

    We have continued our program of infrared (IR) photometric, imaging, spectroscopic, and polarimetric temporal observations of comets to study the properties of comet dust and comet nuclei. During the first two years we digitized our IR data base on P/Halley and other recent comets to facilitate further analysis and comparison with other data bases, and found compelling evidence for the emission of a burst of small grains from P/Halley's nucleus at perihelion. We reported imaging and photometric observations of Comets Austin 1990 V and Swift-Tuttle 1992. The Swift-Tuttle 1992t observations included IR photometry, several 7-14 micron long-slit spectra of the coma and a time-sequence of more than 150 10 micron broadband images of the coma. An analysis of near-IR images of the inner coma of P/Halley obtained on three consecutive nights in 1986 March showed sunwardjets. We completed our analysis of IR imaging spectrosco-photometric data on comets. We also obtained observations of Comets Hyakutake 1996 B2 and Hale/Bopp 1995 01. We obtained infrared imaging, photometric, spectroscopic and polarimetric temporal observations of bright comets using a network of five telescopes, with emphasis on simultaneous observations of comets at many wavelengths with different instruments. Our program offers several unique advantages: 1) rapid observational response to new comets with dedicated infrared telescopes; 2) observations within a few degrees of the sun when comets are near perihelion and 3) access to advanced infrared array imagers and spectrometers. In particular, reduction, analysis, publication and archiving of our Jupiter/sl-9 and Comet Hyakutake infrared data received special emphasis. Instrumentation development included installation of the latest version of the innovative FORTH telescope control and a data acquisition system that enables us to control three telescopes remotely by telephone from anywhere in the world for comet observations in broad daylight. We have

  3. RADAR OBSERVATIONS OF COMET 103P/HARTLEY 2

    SciTech Connect

    Harmon, John K.; Nolan, Michael C.; Howell, Ellen S.; Taylor, Patrick A.; Giorgini, Jon D.

    2011-06-10

    Comets rarely come close enough to be studied intensively with Earth-based radar. The most recent such occurrence was when Comet 103P/Hartley 2 passed within 0.12 AU in late 2010 October, less than two weeks before the EPOXI flyby. This offered a unique opportunity to improve pre-encounter trajectory knowledge and obtain complementary physical data for a spacecraft-targeted comet. 103P/Hartley 2 is only the fourth comet nucleus to be imaged with radar and already the second to be identified as an elongated, bilobate object based on its delay-Doppler signature. The images show the dominant spin mode to be a rotation about the short axis with a period of 18.2 hr. The nucleus has a low radar albedo consistent with a surface density of 0.5-1.0 g cm{sup -3}. A separate echo component was detected from large (>cm) grains ejected anisotropically with velocities of several to tens of meters per second. Radar shows that, in terms of large-grain production, 103P/Hartley 2 is an unusually active comet for its size.

  4. Space missions to comets

    NASA Technical Reports Server (NTRS)

    Neugebauer, M. (Editor); Yeomans, D. K. (Editor); Brandt, J. C. (Editor); Hobbs, R. W. (Editor)

    1979-01-01

    The broad impact of a cometary mission is assessed with particular emphasis on scientific interest in a fly-by mission to Halley's comet and a rendezvous with Tempel 2. Scientific results, speculations, and future plans are discussed.

  5. Comet: A VOEvent broker

    NASA Astrophysics Data System (ADS)

    Swinbank, J.

    2014-11-01

    The VOEvent standard provides a means of describing transient celestial events in a machine-readable format. This is an essential step towards analysing and, where appropriate, responding to the large volumes of transients which will be detected by future large scale surveys. The VOEvent Transport Protocol (VTP) defines a system by which VOEvents may be disseminated to the community. We describe the design and implementation of Comet, a freely available, open source implementation of VTP. We use Comet as a base to explore the performance characteristics of the VTP system, in particular with reference to meeting the requirements of future survey projects. We describe how, with the aid of simple extensions to VTP, Comet can help users filter high-volume streams of VOEvents to extract only those which are of relevance to particular science cases. Based on these tests and on the experience of developing Comet, we derive a number of recommendations for future refinements of the VTP standard.

  6. Hubble Sees Material Ejected From Comet Hale-Bopp

    NASA Technical Reports Server (NTRS)

    1995-01-01

    These NASA Hubble Space Telescope pictures of comet Hale-Bopp show a remarkable 'pinwheel' pattern and a blob of free-flying debris near the nucleus. The bright clump of light along the spiral (above the nucleus, which is near the center of the frame) may be a piece of the comet's icy crust that was ejected into space by a combination of ice evaporation and the comet's rotation, and which then disintegrated into a bright cloud of particles.

    Although the 'blob' is about 3.5 times fainter than the brightest portion at the nucleus, the lump appears brighter because it covers a larger area. The debris follows a spiral pattern outward because the solid nucleus is rotating like a lawn sprinkler, completing a single rotation about once per week.

    Ground-based observations conducted over the past two months have documented at least two separate episodes of jet and pinwheel formation and fading. By coincidence, the first Hubble images of Hale-Bopp, taken on September 26, 1995, immediately followed one of these outbursts and allow researchers to examine it at unprecedented detail. For the first time they see a clear separation between the nucleus and some of the debris being shed. By putting together information from the Hubble images and those taken during the recent outburst using the 82 cm telescope of the Teide Observatory (Tenerife, Canary Islands, Spain), astronomers find that the debris is moving away from the nucleus at a speed (projected on the sky) of about 68 miles per hour (109 kilometers per hour).

    The Hubble observations will be used to determine if Hale-Bopp is really a giant comet or rather a more moderate-sized object whose current activity is driven by outgassing from a very volatile ice which will 'burn out' over the next year. Comet Hale-Bopp was discovered on July 23, 1995 by amateur astronomers Alan Hale and Thomas Bopp. Though this comet is still well outside the orbit of Jupiter (almost 600 million miles, or one billion kilometers from Earth

  7. The recent dynamical history of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Maquet, L.

    2015-07-01

    This paper presents the past evolution of the orbital elements of comet 67P/Churyumov-Gerasimenko, target of the Rosetta spacecraft. The gravitational orbit of the comet is affected by the sublimation of ice from the nucleus that triggers non-gravitational forces. The comet also experienced several close encounters with Jupiter, especially notable were those in 1959 and 1923 (less than 1 AU). These perturbations cause the chaoticity of the comet orbit at short time scale. The goal of this paper is to have a precise idea of the comet's recent dynamical history. This is done by studying the mean trends of the orbital elements of the comet and also by characterising its chaotic motion with the fast Lyapunov indicator. To compute these mean trends, two sets (considering or not the non-gravitational forces) of 1000 clone orbits of the comet were considered. This paper shows that the last close encounter with Jupiter on February 4, 1959, drastically modified the orbital elements of the comet (especially the perihelion distance: from more than 2.7 AU before the encounter to 1.3 AU after the encounter). The motion of the comet is also shown to be chaotic before the close encounter with Jupiter on October 2, 1923. The mean trends of the orbital elements of the comet are also presented in this paper (for two time scales: 270 years in the past and 10 000 years in the past).

  8. Physical Properties of Cometary Nucleus Candidates

    NASA Technical Reports Server (NTRS)

    Jewitt, David; Hillman, John (Technical Monitor)

    2003-01-01

    In this proposal we aim to study the physical properties of the Centaurs and the dead comets, these being the precursors to, and the remnants from, the active cometary nuclei. The nuclei themselves are very difficult to study, because of the contaminating effects of near-nucleus coma. Systematic investigation of the nuclei both before they enter the zone of strong sublimation and after they have depleted their near-surface volatiles should neatly bracket the properties of these objects, revealing evolutionary effects.

  9. In-situ investigations of the ionosphere of comet 67P

    NASA Astrophysics Data System (ADS)

    Eriksson, A. I.; Edberg, N. J. T.; Odelstad, E.; Vigren, E.; Engelhardt, I.; Henri, P.; Lebreton, J.-P.; Galand, M.; Carr, C. M.; Koenders, C.; Nilsson, H.; Broiles, T.; Rubin, M.

    2015-10-01

    Since arrival of Rosetta at its target comet 67P/Churyumov-Gerasimenko in August 2014, the plasma environment has been dominated by ionized gas emanating from the comet nucleus rather than by solar wind plasma. This was evident early on from the strong modulation seen with Rosetta's position in a reference frame fixed to the rotating nucleus, with higher plasma densities observed when the spacecraft is above the neck region and when the comet exposes maximum area to the sun. In this respect, Rosetta is inside the comet ionosphere, providing excellent in situ investigation opportunities for the instruments of the Rosetta Plasma Consortium (RPC). In contrast to the often modelled scenario for a very active comet, the Langmuir probe instrument (RPC-LAP) finds electron temperatures mainly in the range of tens of thousand kelvin around this less active comet. This can be attributed to the lower density of neutral gas, meaning little cooling of recently produced electrons. A side effect of this is that the spacecraft charges negatively when within about 100 km from the nucleus. Interesting in itself, this also may point to similar charging for dust grains in the coma, with implications for the detection of the smallest particles and possibly for processes like electrostatic fragmentation. The inner coma also proves to be very dynamic, with large variations not only with latitude and longitude in a comet frame, but also with the solar wind and various wave phenomena.

  10. Comet Hyakutake to Approach the Earth in Late March 1996

    NASA Astrophysics Data System (ADS)

    1996-03-01

    Astronomers Prepare for a Rare Event In the early morning of January 31, 1996, Japanese amateur astronomer Yuji Hyakutake made his second comet discovery within five weeks. He found the new comet near the border between the southern constellations of Hydra (The Water-Snake) and Libra (The Scales), amazingly just three degrees from the position where he detected another comet on December 26, 1995. After two weeks of hectic activity among amateur and professional astronomers all over the world, much interesting information has now been gathered about the new comet which has been designated C/1996 B2 (Hyakutake) . In particular, it has been found to move in a near-parabolic orbit that will bring it unusually close to the Earth next month. It is then expected to become bright enough to be seen with the unaided eye and to remain so during several weeks thereafter. Preparations are now made to observe the celestial visitor with a large number of telescopes, on the ground and in space. This event offers a rare opportunity to study the immediate surroundings of a cometary nucleus in detail and the specialists intend to make the most of it. Discovery and orbit Yuji Hyakutake, of profession photoengraver and a well-known amateur astronomer, announced his new discovery without delay, and within 24 hours, it had been sighted by several other observers in Japan and Australia. Experienced comet-watchers described its appearance as `diffuse with central condensation and of magnitude 11-12', i.e. a little more than 100 times fainter than what can be seen with the unaided eye. This brightness is not unusual for a comet discovered by an amateur, although it would probably have been missed, had it been just a little fainter. In the present case, the decisive factors for Hyakutake's success were undoubtedly his very powerful equipment (25 x 150 binoculars) and the advantageous combination of the comet's southern position in the sky and his location in Kagoshima, the southernmost

  11. Comet Stepping Stones

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image from NASA's Spitzer Space Telescope shows three of the many fragments making up Comet 73P /Schwassman-Wachmann 3. The infrared picture also provides the best look yet at the crumbling comet's trail of debris, seen here as a bridge connecting the larger fragments.

    The comet circles around our sun every 5.4 years. In 1995, it splintered apart into four pieces, labeled A through D, with C being the biggest. Since then, the comet has continued to fracture into dozens of additional pieces. This image is centered about midway between fragments C and B; fragment G can be seen in the upper right corner.

    The comet's trail is made of dust, pebbles and rocks left in the comet's wake during its numerous journeys around the sun. Such debris can become the stuff of spectacular meteor showers on Earth.

    This image was taken on April 1, 2006, by Spitzer's multi-band imaging photometer using the 24-micron wavelength channel.

  12. Autonomous Navigation Performance During The Hartley 2 Comet Flyby

    NASA Technical Reports Server (NTRS)

    Abrahamson, Matthew J; Kennedy, Brian A.; Bhaskaran, Shyam

    2012-01-01

    On November 4, 2010, the EPOXI spacecraft performed a 700-km flyby of the comet Hartley 2 as follow-on to the successful 2005 Deep Impact prime mission. EPOXI, an extended mission for the Deep Impact Flyby spacecraft, returned a wealth of visual and infrared data from Hartley 2, marking the fifth time that high-resolution images of a cometary nucleus have been captured by a spacecraft. The highest resolution science return, captured at closest approach to the comet nucleus, was enabled by use of an onboard autonomous navigation system called AutoNav. AutoNav estimates the comet-relative spacecraft trajectory using optical measurements from the Medium Resolution Imager (MRI) and provides this relative position information to the Attitude Determination and Control System (ADCS) for maintaining instrument pointing on the comet. For the EPOXI mission, AutoNav was tasked to enable continuous tracking of a smaller, more active Hartley 2, as compared to Tempel 1, through the full encounter while traveling at a higher velocity. To meet the mission goal of capturing the comet in all MRI science images, position knowledge accuracies of +/- 3.5 km (3-?) cross track and +/- 0.3 seconds (3-?) time of flight were required. A flight-code-in-the-loop Monte Carlo simulation assessed AutoNav's statistical performance under the Hartley 2 flyby dynamics and determined optimal configuration. The AutoNav performance at Hartley 2 was successful, capturing the comet in all of the MRI images. The maximum residual between observed and predicted comet locations was 20 MRI pixels, primarily influenced by the center of brightness offset from the center of mass in the observations and attitude knowledge errors. This paper discusses the Monte Carlo-based analysis that led to the final AutoNav configuration and a comparison of the predicted performance with the flyby performance.

  13. The submillimeter radio continuum of Comet P/Brorsen-Metcalf

    SciTech Connect

    Jewitt, D.; Luu, J. MIT, Cambridge, MA )

    1990-12-01

    Observations of Comet P/Brorsen-Metcalf in the submillimeter radio continuum are presented. The observations were taken using the James Clerk Maxwell Telescope on Mauna Kea, and include the first truly submillimeter detection of a comet, and the first submillimeter continuum spectrum. The submillimeter radiation is attributed to thermal emission from a transient population of large grains with a total mass of (1-10) x 10 to the 9th kg. The large grains may be produced by catastrophic failure of part of the refractory mantle on the surface of the cometary nucleus. Models of the submillimeter continuum are discussed. 49 refs.

  14. Hco+ in the Coma of Comet Hale-Bopp

    NASA Astrophysics Data System (ADS)

    Lovell, A. J.; Schloerb, F. P.; Bergin, E. A.; Dickens, J. E.; De Vries, C. H.; Senay, M. C.; Irvine, W. M.

    1997-05-01

    Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO^+ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO^+ emission require a low abundance of HCO^+ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (T_e). To set constraints on the formation of HCO^+ in the coma, as well as the location and magnitude of the transition to higher T_e, the data are compared with the results of ion-molecule chemistry models.

  15. HCO+ in the coma of comet Hale-Bopp.

    PubMed

    Lovell, A J; Schloerb, F P; Bergin, E A; Dickens, J E; Devries, C H; Senay, M C; Irvine, W M

    Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO+ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO+ emission require a low abundance of HCO+ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (Te). To set constraints on the formation of HCO+ in the coma, as well as the location and magnitude of the transition to higher Te, the data are compared with the results of ion-molecule chemistry models. PMID:11543348

  16. HCO+ in the coma of comet Hale-Bopp

    NASA Technical Reports Server (NTRS)

    Lovell, A. J.; Schloerb, F. P.; Bergin, E. A.; Dickens, J. E.; Devries, C. H.; Senay, M. C.; Irvine, W. M.; Ferris, J. P. (Principal Investigator)

    1997-01-01

    Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO+ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO+ emission require a low abundance of HCO+ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (Te). To set constraints on the formation of HCO+ in the coma, as well as the location and magnitude of the transition to higher Te, the data are compared with the results of ion-molecule chemistry models.

  17. First High-Resolution Infrared Spectroscopic Measurements of Comet 2P/Encke: Unusual Organic Composition and Low Rotational Temperatures

    NASA Astrophysics Data System (ADS)

    Radeva, Yana L.; Mumma, M. J.; Villanueva, G. L.; Bonev, B. P.; DiSanti, M. A.; A'Hearn, M. F.; Dello Russo, N.

    2012-10-01

    We present the first high-resolution infrared spectra of the ecliptic comet 2P/Encke, acquired on UT 4 - 6 Nov. 2003, with the Near Infrared Echelle Spectrograph (NIRSPEC) on the Keck II telescope. 2P/Encke is a dynamical end-member among comets. Its very short period of 3.3 years (with perihelion at 0.34 AU and aphelion at 4.09 AU) exposes the nucleus to unusually high insolation throughout its orbit, raising the prospect that native ices may have experienced significant fractionation over time. Here, we present flux-calibrated spectra, production rates, and mixing ratios for H2O, CH3OH, HCN, H2CO, C2H2, C2H6, CH4 and CO, and compare the abundance ratios with the “organics-normal” population. We also extracted very low rotational temperatures (20 - 30 K) for H2O, HCN, and CH3OH in the near-nucleus coma, which correlate with one of the lowest cometary gas production rates ( 1027 molecules s-1) measured thus far in the infrared. We determined that 2P/Encke is enriched in CH3OH, but depleted in C2H6, C2H2, HCN, CH4, H2CO and CO. We compared mixing ratios of these organic species measured on separate dates, and found no evidence of macroscopic chemical heterogeneity in this cometary nucleus, however, we are limited by sparse temporal sampling of our observations. The depleted abundances of most measured species but retention of the high temperature volatiles (H2O, CH3OH) are consistent with fractionation of 2P/Encke’s native ices by thermal processing while in its current orbit. 2P/Encke is unique in terms of its short period, unusual organic composition, low rotational temperatures and low production rates. The discovery of its unusual organic composition is an important contribution to the emerging chemical taxonomy of comets.

  18. Comets and the Stardust Mission

    SciTech Connect

    LLNL - University of California Television

    2008-05-16

    The occasional appearance of comets has awed humans throughout history. But how much do we really know about comets? Did a comet kill the dinosaurs? And, what can comets tell us about our own ancient history? With comet dust from NASA's Stardust mission, scientists like Hope Ishii, a Research Scientist at Lawrence Livermore National Laboratory, are beginning to answer these questions. She and high school teacher Tom Shefler look at how comets formed, their role in the Earth's history and the clues about what happened over 4 billion years ago. Series: Science on Saturday [5/2008] [Science] [Show ID: 14492

  19. Comets and the Stardust Mission

    ScienceCinema

    LLNL - University of California Television

    2009-09-01

    The occasional appearance of comets has awed humans throughout history. But how much do we really know about comets? Did a comet kill the dinosaurs? And, what can comets tell us about our own ancient history? With comet dust from NASA's Stardust mission, scientists like Hope Ishii, a Research Scientist at Lawrence Livermore National Laboratory, are beginning to answer these questions. She and high school teacher Tom Shefler look at how comets formed, their role in the Earth's history and the clues about what happened over 4 billion years ago. Series: Science on Saturday [5/2008] [Science] [Show ID: 14492

  20. Comets in Australian Aboriginal Astronomy

    NASA Astrophysics Data System (ADS)

    Hamacher, Duane W.; Norris, Ray P.

    2011-03-01

    We present 25 accounts of comets from 40 Australian Aboriginal communities, citing both supernatural perceptions of comets and historical accounts of historically bright comets. Historical and ethnographic descriptions include the Great Comets of 1843, 1861, 1901, 1910, and 1927. We describe the perceptions of comets in Aboriginal societies and show that they are typically associated with fear, death, omens, malevolent spirits, and evil magic, consistent with many cultures around the world. We also provide a list of words for comets in 16 different Aboriginal languages.

  1. The study of comets, part 1. [conference on photometry and spectrum analysis of Kohoutek comet and comet tails

    NASA Technical Reports Server (NTRS)

    Donn, B. (Editor); Mumma, M. J. (Editor); Jackson, W. M. (Editor); Ahearn, M. (Editor); Harrington, R. (Editor)

    1976-01-01

    Papers are presented dealing with observations of comets. Topic discussed include: photometry, polarimetry, and astrometry of comets; detection of water and molecular transitions in comets; ion motions in comet tails; determination of comet brightness and luminosity; and evolution of cometary orbits. Emphasis is placed on analysis of observations of comet Kohoutek.

  2. Spectroscopic Evidence for Interstellar Ice in Comet Hyakutake

    NASA Technical Reports Server (NTRS)

    Irvine, W. M.; Bockelee-Morvan, D.; Lis, D. C.; Matthews, H. E.; Biver, N.; Crovisier, J.; Davies, J. K.; Dent, W. R. F.; Gautier, D.; Godfrey, P. D.; Keene, J.; Lovell, A. J.; Owen, T. C.; Phillips, T. G.; Rauer, H.; Schloerb, F. P.; Senay, M.; Young, K.

    1996-01-01

    Volatile compounds in comets are the most pristine materials surviving from the time of formation of the Solar System, and thus potentially provide information about conditions that prevailed in the primitive solar material. Moreover, comets may have supplied a substantial fraction of the volatiles on the terrestrial planets, perhaps including organic compounds that played a role in the origin of life on Earth. Here we report the detection of hydrogen isocyanide (HNC) in comet Hyakutake. The abundance of HNC relative to hydrogen cyanide (HCN) is very similar to that observed in quiescent interstellar molecular clouds, and quite different from the equilibrium ratio expected in the outermost solar nebula, where comets are thought to form. Such a departure from equilibrium has long been considered a hallmark of gas-phase chemical processing in the interstellar medium, suggesting that interstellar gases have been incorporated into the comet's nucleus, perhaps as ices frozen onto interstellar grains. If this interpretation is correct, our results should provide constraints on the temperature of the solar nebula, and the subsequent chemical processes that occurred in the region where comets formed.

  3. Spectroscopic evidence for interstellar ices in comet Hyakutake.

    PubMed

    Irvine, W M; Bockelee-Morvan, D; Lis, D C; Matthews, H E; Biver, N; Crovisier, J; Davies, J K; Dent, W R; Gautier, D; Godfrey, P D; Keene, J; Lovell, A J; Owen, T C; Phillips, T G; Rauer, H; Schloerb, F P; Senay, M; Young, K

    1996-10-01

    Volatile compounds in comets are the most pristine materials surviving from the time of formation of the Solar System, and thus potentially provide information about conditions that prevailed in the primitive solar nebula. Moreover, comets may have supplied a substantial fraction of the volatiles on the terrestrial planets, perhaps including organic compounds that played a role in the origin of life on Earth. Here we report the detection of hydrogen isocyanide (HNC) in comet Hyakutake. The abundance of HNC relative to hydrogen cyanide (HCN) is very similar to that observed in quiescent interstellar molecular clouds, and quite different from the equilibrium ratio expected in the outermost solar nebula, where comets are thought to form. Such a departure from equilibrium has long been considered a hallmark of gas-phase chemical processing in the interstellar medium, suggesting that interstellar gases have been incorporated into the comet's nucleus, perhaps as ices frozen onto interstellar grains. If this interpretation is correct, our results should provide constraints on the temperature of the solar nebula, and the subsequent chemical processes that occurred in the region where comets formed. PMID:8837771

  4. Comets as collisional fragments of a primordial planetesimal disk

    NASA Astrophysics Data System (ADS)

    Morbidelli, A.; Rickman, H.

    2015-11-01

    Context. The Rosetta mission and its exquisite measurements have revived the debate on whether comets are pristine planetesimals or collisionally evolved objects. Aims: We investigate the collisional evolution experienced by the precursors of current comet nuclei during the early stages of the solar system in the context of the so-called Nice model. Methods: We considered two environments for the collisional evolution: (1) the transplanetary planetesimal disk, from the time of gas removal until the disk was dispersed by the migration of the ice giants; and (2) the dispersing disk during the time that the scattered disk was formed. We performed simulations using different methods in the two cases to determine the number of destructive collisions typically experienced by a comet nucleus of 2 km radius. Results: In the widely accepted scenario, where the dispersal of the planetesimal disk occurred at the time of the Late Heavy Bombardment about 4 Gy ago, comet-sized planetesimals have a very low probability of surviving destructive collisions in the disk. On the extreme assumption that the disk was dispersed directly upon gas removal, a significant fraction of the planetesimals might have remained intact. However, these survivors would still bear the marks of many nondestructive impacts. Conclusions: The Nice model of solar system evolution predicts that typical km-sized comet nuclei are predominantly fragments resulting from collisions experienced by larger parent bodies. An important goal for future research is to investigate whether the observed properties of comet nuclei are compatible with such a collisional origin.

  5. Ensemble Properties of Comets in the Sloan Digital Sky Survey

    SciTech Connect

    Solontoi, Michael; Ivezic, Zeljko; Juric, Mario; Becker, Andrew C.; Jones, Lynne; West, Andrew A.; Kent, Steve; Lupton, Robert H.; Claire, Mark; Knapp, Gillian R.; Quinn, Tom; /Washington U., Seattle, Astron. Dept. /Princeton U. Observ.

    2012-02-01

    We present the ensemble properties of 31 comets (27 resolved and 4 unresolved) observed by the Sloan Digital Sky Survey (SDSS). This sample of comets represents about 1 comet per 10 million SDSS photometric objects. Five-band (u, g, r, i, z) photometry is used to determine the comets colors, sizes, surface brightness profiles, and rates of dust production in terms of the Afp formalism. We find that the cumulative luminosity function for the Jupiter Family Comets in our sample is well fit by a power law of the form N(comets. The resolved comets show an extremely narrow distribution of colors (0.57 {+-} 0.05 in g - r for example), which are statistically indistinguishable from that of the Jupiter Trojans. Further, there is no evidence of correlation between color and physical, dynamical, or observational parameters for the observed comets.

  6. 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.

  7. The 10 micron spectral structure in comets

    NASA Technical Reports Server (NTRS)

    Lynch, David K.; Russell, Ray W.; Campins, Humberto

    1989-01-01

    The 10 micron spectra of comets Halley (1982i), Wilson (1986l), Kohoutek (1973f) and Bradfield (1987s) are presented and compared. The silicate emission profiles of Halley and Bradfield are seen to be remarkably similar in that both contain a sharp break in the spectrum at 11.3 microns. Comet Bradfield does not show the same double peak structure seen in olivine and reported in Comet Halley be Campins and Ryan (1988) and Bregman, et al. (1987). The authors interpret the 11.3 micron signature as being due to olivine-type dust grains with at least some degree of crystallinity. Olivine alone is not enough to reproduce the shape of the 10 micron structure. However, in view of the authors' past success in fitting interstellar dust features with the emissivity profile obtained from amorphous grains produced by laser-vaporizing olivine, this is a very appealing identification. They note that there are significant variations in olivine spectra due to compositional differences, grain size distribution and related grain temperature variations to make the olivine identification tentative. They further tentatively identify the 9.8 micron feature in Halley as being due to either amorphorous olivine or a phyllosilicate (layer lattice). Neither the spectra of Halley, Kohoutek, nor Bradfield exhibited the 12.2 micron feature seen in Comet Wilson, which may prove diagnostic of the composition or thermal history differences between these comets. IR spectra of various mineral samples are discussed in terms of their match to cometary spectra.

  8. Laboratory Simulations: The Primordial Comet Mantle

    NASA Technical Reports Server (NTRS)

    Johnson, R. E.

    1997-01-01

    Laboratory data are needed to understand the formation of organics in cometary and precometary materials and for deciding on the fate of the volatiles. Appropriate experiments were described in the talk at Milipitas. Because of its importance for the comet sample return mission, I discuss here the relevance of this data for predicting the thickness, nature, and ability to survive of the cosmic-ray produced primordial comet mantle ('crust'). That part of the mantle which becomes predominantly refractory is approx. 30 gm/sq cm thick. The tensile strength of this outer mantle is such that it might survive the comet's entrance into the inner solar system. In addition, important modifications to the ices occur to depths approx. 300 gm/cu cm. Based on this it is expected that a deep probe is needed to obtain minimally altered material.

  9. Comets after Hyakutake and Hale-Bopp

    NASA Technical Reports Server (NTRS)

    Mumma, Michael J.

    1999-01-01

    Being icy, cometary nuclei are the most easily modified bodies in the solar system - even modest heating is sufficient to induce significant weight loss. This sublimative loss and longterm storage far from the sun protect the nucleus against internal warming and ensure that cometary nuclei today contain the least processed material remaining from the early nebula - or perhaps from the natal cloud. The chemical compositions of ices, low temperature-refractory organics, and refractory minerals (and their physical states) provide sensitive probes of the origin and history of this material. The fortunate appearance of Hyakutake and Hale-Bopp has provided a wealth of information on these Oort cloud comets, obtained with a wide range of astronomical approaches. I will review certain key results for these comets, such as chemical abundances, isotopic abundance ratios, nuclear spin statistics, and nuclear vs extended production of "parent volatiles", and will illustrate how these test the origins of cometary material. A comparison with 1P/Halley--a third comet from the giant planet nebular region--will be discussed in the context of heterogeneity among these bodies.

  10. Hubble View of Comet ISON

    NASA Video Gallery

    This time-lapse sequence of images from the Hubble Space Telescope shows comet ISON as it appeared on May 8, 2013. At the time the images were taken, the comet was 403 million miles from the Earth,...

  11. EPOXI: Comet 103p/Hartley 2 Observations from a Worldwide Campaign

    NASA Technical Reports Server (NTRS)

    Meech, K. J.; Hearn, M. F. A.; Bauer, J. M.; Bonev, B. P.; Charnley, S. B.; DiSanti, M. A.; Gersch, A.; Immler, S. M.; Kaluna, H. M.; Keane, J. V.; Kelley, M. S.; Kleyna, J.; Landsman, W. B.; Milam, S. N.; Mumma, M. J.; Pittichova, J.; Riesen, T. E.; Sarid, G.; Sonnett, S.; Villanueva, G. L.; Wiessman, P. R.; Wooden, D. H.; Yanamandra-Fischer, P. A.; Yeomans, D. K.; Zenn, T.

    2011-01-01

    Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales. at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P (Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was approximately 16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO2-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production.

  12. Photometric behavior of comet Hale-Bopp (C/1995 O1) before perihelion.

    PubMed

    Schleicher, D G; Lederer, S M; Millis, R L; Farnham, T L

    1997-03-28

    Narrowband photometric observations of comet Hale-Bopp (C/1995 O1) between 25 July 1995 and 15 February 1997 indicated gas and dust production rates of 20 and 100 times greater, respectively, than observed at the same heliocentric distances for comet P/Halley in 1985. Hale-Bopp produced dust at a rate greater than has been observed for any other comet at any distance since at least 1977. On the basis of the observed production rate of the hydroxyl molecule, the calculated minimum effective diameter of Hale-Bopp's nucleus is 17 kilometers, but the actual diameter of the nucleus is likely to be at least two to three times larger. The chemical composition of Hale-Bopp is consistent with that of other long-period comets originating from the Oort Cloud. PMID:9072963

  13. Close encounters and collisions of comets with the earth

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.; Yeomans, D. K.

    1984-01-01

    A computer search for earth-approaching comets among those listed in Marsden's (1983) updated orbit catalog has identified 36 cases at which minimum separation distance was less than 2500 earth radii. A strong representation of short period comets in the sample is noted, and the constant rate of the close approaching comets in the last 300 years is interpreted to suggest the lack of long-period comets intrinsically fainter than an absolute magnitude of about 11. A comet-earth collision rate derived from the statistics of these close encounters implies an average period of 33-64 million years between any two events. This rate is comparable with the frequency of geologically recent global catastrophes which appear to be associated with extraterrestrial object impacts, such as the Cretaceous-Tertiary extinction 65 million years ago and the late Eocene event 34 million years ago.

  14. The nature of comet nuclei

    NASA Technical Reports Server (NTRS)

    Sykes, Mark V.; Walker, Russell G.

    1992-01-01

    The icy-conglomerate model of comet nuclei has dominated all others since its introduction. It provided a basis for understanding the non-gravitational motions of comets which had perplexed dynamicists up to that time, and provided a focus for understanding cometary composition and origin. The image of comets as dirty snowballs was quickly adopted. Comet nuclei including their trail mass loss rates and refractory to volatile mass ratios are described.

  15. Comet: Multifunction VOEvent broker

    NASA Astrophysics Data System (ADS)

    Swinbank, John

    2014-04-01

    Comet is a Python implementation of the VOEvent Transport Protocol (VTP). VOEvent is the IVOA system for describing transient celestial events. Details of transients detected by many projects, including Fermi, Swift, and the Catalina Sky Survey, are currently made available as VOEvents, which is also the standard alert format by future facilities such as LSST and SKA. The core of Comet is a multifunction VOEvent broker, capable of receiving events either by subscribing to one or more remote brokers or by direct connection from authors; it can then both process those events locally and forward them to its own subscribers. In addition, Comet provides a tool for publishing VOEvents to the global VOEvent backbone.

  16. Astrobiology of Comets

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Wickramasinghe, Nalin C.; Wallis, Max K.; Sheldon, Robert B.

    2004-01-01

    We review the current state of knowledge concerning microbial extremophiles and comets and the potential significance of comets to Astrobiology. We model the thermal history of a cometary body, regarded as an assemblage of boulders, dust, ices and organics, as it approaches a perihelion distance of - IAU. The transfer of incident energy from sunlight into the interior leads to the melting of near surface ices, some under stable porous crust, providing possible habitats for a wide range of microorganisms. We provide data concerning new evidence for indigenous microfossils in CI meteorites, which may be the remains of extinct cometary cores. We discuss the dominant microbial communities of polar sea-ice, Antarctic ice sheet, and cryoconite environments as possible analogs for microbial ecosystems that may grow in sub-crustal pools or in ice/water films in comets.

  17. Planetary perturbations and the origins of short-period comets

    NASA Astrophysics Data System (ADS)

    Quinn, T.; Tremaine, S.; Duncan, M.

    1990-06-01

    To investigate the dynamical plausibility of possible sources for the short-period comets, a representative sample of comet orbits in the field of the sun and the giant planets was integrated, with the aim to determine whether the distribution of orbits from a proposed source that reach observable perihelia (q less than 2.5 AU) matches the observed distribution of short-period orbits. It is found that the majority of the short-period comets, those with orbital period P less than 20 yr (the 'Jupiter family'), cannot arise from isotropic orbits with perihelia near Jupiter's orbit, because the resulting observable comet orbits have the wrong distribution in period, inclination, and argument of perihelion. The simulations also show that Jupiter-family comets cannot arise from isotropic orbits with perihelia in the Uranus-Neptune region. On the other hand, a source of low-inclination Neptune-crossing orbits yields a distribution of observable Jupiter-family comets that is consistent with the data in all respects. These results imply that the Jupiter-family comets arise from a disk source in the outer solar system rather than from the Oort comet cloud.

  18. Planetary perturbations and the origins of short-period comets

    SciTech Connect

    Quinn, T.; Tremaine, S.; Duncan, M. Queen's Univ., Kingston )

    1990-06-01

    To investigate the dynamical plausibility of possible sources for the short-period comets, a representative sample of comet orbits in the field of the sun and the giant planets was integrated, with the aim to determine whether the distribution of orbits from a proposed source that reach observable perihelia (q less than 2.5 AU) matches the observed distribution of short-period orbits. It is found that the majority of the short-period comets, those with orbital period P less than 20 yr (the Jupiter family), cannot arise from isotropic orbits with perihelia near Jupiter's orbit, because the resulting observable comet orbits have the wrong distribution in period, inclination, and argument of perihelion. The simulations also show that Jupiter-family comets cannot arise from isotropic orbits with perihelia in the Uranus-Neptune region. On the other hand, a source of low-inclination Neptune-crossing orbits yields a distribution of observable Jupiter-family comets that is consistent with the data in all respects. These results imply that the Jupiter-family comets arise from a disk source in the outer solar system rather than from the Oort comet cloud. 30 refs.

  19. Hubble Images of Comet Hale-Bopp

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This is a series of Hubble Space Telescope observations of the region around the nucleus of Hale-Bopp, taken on eight different dates since September 1995. They chronicle changes in the evolution of the nucleus as it moves ever closer to, and is warmed by, the sun.

    The first picture in the sequence, seen at upper left shows a strong dust outburst on the comet that occurred when it was beyond the orbit of Jupiter. Images in the Fall of 1996 show multiple jets that are presumably connected to the activation of multiple vents on the surface of the nucleus.

    In these false color images, taken with the Wide Field and Planetary Camera 2, the faintest regions are black, the brightest regions are white, and intermediate intensities are represented by different levels of red. All images are processed at the same spatial scale of 280 miles per pixel (470 kilometers), so the solid nucleus, no larger than 25 miles across, is far below Hubble's resolution.

    The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

    This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

  20. Discovering the Nature of Comets.

    ERIC Educational Resources Information Center

    Whipple, Fred L.

    1986-01-01

    "The Mystery of Comets" by Dr. Fred Whipple provides an introduction to the modern picture of comets and his personal reminiscences of how his model of comets came to be. An adaptation of several sections of the book is presented. (JN)

  1. Term Projects on Interstellar Comets

    ERIC Educational Resources Information Center

    Mack, John E.

    1975-01-01

    Presents two calculations of the probability of detection of an interstellar comet, under the hypothesis that such comets would escape from comet clouds similar to that believed to surround the sun. Proposes three problems, each of which would be a reasonable term project for a motivated undergraduate. (Author/MLH)

  2. Look--It's a Comet!

    ERIC Educational Resources Information Center

    Berglund, Kay

    1997-01-01

    Describes a classroom lesson on comets that uses modeling and guided imagery to spark students' curiosity. Comet models are built using chunks of rock salt, polystyrene balls, and tinsel. Abstract ideas are made more concrete with a guided imagery story called Comet Ride! Includes an introduction to the use of parallax to measure the distance of…

  3. A model of extended sources in comets: Polyoxymethylene as a progenitor of formaldehyde in comet Halley

    NASA Astrophysics Data System (ADS)

    Benilan, Y.; Cottin, H.; Fray, N.; Gazeau, M.-C.; Raulin, F.

    2001-11-01

    Measurements performed with the NMS mass spectrometer on board Giotto, show that the formaldehyde density profile, as a function of the distance to nucleus of comet Halley, cannot be explained by a direct release of formaldehyde from the nucleus. Thus, there is an extended source of formaldehyde in comet Halley. Such an extended source of formaldehyde has also been detected in comets Hyakutake and Hale-Bopp. Polyoxymethylene (POM) has been often pushed forward to interpret H2CO extended source but until very recently important quantitative data were missing to allow a discerning analysis of this hypothesis. Formaldehyde production rate from POM on solid grains is a function of several unknown parameters: the matrix in which POM is imbedded, the geometry of the grains, the chemical structure of the polymer, its photodegradation rate and its temperature. We have obtained experimental data concerning the photo and thermal degradation of POM and modeled the contribution of solid POM present on particles to the gaseous phase. First results were presented in (Cottin et al., 2001) for a single size population of grains, and temperature as free parameter. We have now extended our model to a more realistic grain population, based on actual measurements in Halley coma, for which velocity and temperature of each grain are a function of its size and composition. We have calculated the best fits to Giotto measurements and derived the amount of POM required to account H2CO observation. The results show that the presence of solid POM on grains can provide a realistic explanation of the formaldehyde extended source observed in several comets. Even if the model still needs to be improved, for example to include different grains geometry, it can already be used to test other polymers like poly-HCN against known extended sources such as CN, C2 or C3, as soon as laboratory measurements are available. Cottin, H., Gazeau, M.C., Bénilan, Y. & Raulin, F. 2001, ApJ, 556, 417

  4. Sun-plunging Comets and Cometary Flares

    NASA Astrophysics Data System (ADS)

    Brown, J. C.; Carlson, R. W.

    2012-12-01

    During 2011, NASA's Solar Dynamics Observatory (SDO) made the first ever direct observations of sun-grazing comet destruction in the inner solar atmosphere. On July 6, the nucleus material of Comet C/2011 N3 (SOHO) (perihelion distance q~1.14R_sun) was observed to vaporize, decelerate and radiate, with total nucleus destruction over a path length ~ R_sun through the lower corona (density n ~ 10^8/cm^3). On Dec. 16, the much more massive Comet C/2011 W3 (Lovejoy), with similar q~1.17 R_sun), was seen vaporizing until it vanished behind the solar limb then re-emerging in a much diminished state. A range of current work on these data is being presented by others in this AGU session. These two 'sun-skimming' comets had q in the low corona. There, mass loss is dominated by insolation-driven sublimation, so the physics of their destruction is largely similar to those with q>> R_sun. However, Brown et al. (Astron. Astrophys. 535, A71, 2011) showed that mass loss and destruction is completely different for 'sun-plunging' comets with qn*= 2.5x10^11/cm^3, increasing exponentially with depth on scale height H~100-500 km). Consequently sun-plunger mass loss and destruction is dominated by ablation and by ram-pressure-driven explosion. The very large cometary kinetic energy (2x10^27 erg x (M/10^12) for mass M g) and its highly localized deposition in time (<10 s) and space (<6000 km ~ 10") should produce signatures somewhat like solar magnetic flares. Such 'cometary flare' events should offer wholly new ways to probe properties both of comets (e.g. element abundances) and of the low solar atmosphere (e.g magnetic fields). Super-flares produced by very large sun-plungers could have serious terrestrial consequences. We will present and discuss results of our current work on sun-plunging comets and explosive cometary flares, including

  5. Activity of Comet Hale-Bopp (1995 01) Beyond 6 AU From the Sun

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1996-01-01

    The physical evolution of comet Hale-Bopp is investigated along the preperihelic arc of its orbit at heliocentric distances larger than 6 AU. The comet's considerable intrinsic brightness and activity are explained by the existence of a relatively larg area on its nucleus surface that is a resevoir of both carbon monoxide and dust particulates. Three recuring dust emission events observed in August-October 1995 are studied in some detail.

  6. Discovery of cometary kilometric radiations and plasma waves at Comet Halley

    NASA Astrophysics Data System (ADS)

    Oya, H.; Morioka, A.; Miyake, W.; Smith, E. J.; Tsurutani, B. T.

    1986-05-01

    The plasma-wave probe carried by the spacecraft Sakigake discovered discrete spectra of emissions from comet Halley in the frequency range 30 - 195 kHz. The observed cometary kilometric radiation appears to come from moving shocks in the coma region which are possibly associated with temporal variations of the solar wind. Waves due to plasma instabilities associated with the pick-up of cometary ions by the solar wind were observed within a region almost 107km from the comet nucleus.

  7. STARDUST and HAYABUSA: Sample Return Missions to Small Bodies in the Solar System

    NASA Technical Reports Server (NTRS)

    Sandford, S. A.

    2005-01-01

    There are currently two active spacecraft missions designed to return samples to Earth from small bodies in our Solar System. STARDUST will return samples from the comet Wild 2, and HAYABUSA will return samples from the asteroid Itokawa. On January 3,2004, the STARDUST spacecraft made the closest ever flyby (236 km) of the nucleus of a comet - Comet Wild 2. During the flyby the spacecraft collected samples of dust from the coma of the comet. These samples will be returned to Earth on January 15,2006. After a brief preliminary examination to establish the nature of the returned samples, they will be made available to the general scientific community for study. The HAYABUSA spacecraft arrived at the Near Earth Asteroid Itokawa in September 2005 and is currently involved in taking remote sensing data from the asteroid. Several practice landings have been made and a sample collection landing will be made soon. The collected sample will be returned to Earth in June 2007. During my talk I will discuss the scientific goals of the STARDUST and HAYABUSA missions and provide an overview of their designs and flights to date. I will also show some of the exciting data returned by these spacecraft during their encounters with their target objects.

  8. Vaporization of comet nuclei - Light curves and life times

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    The effects of vaporization from the nucleus of a comet are examined and it is shown that a latitude dependence of vaporization can explain the asymmetries in cometary light curves. An attempt is made to explain the observed variation in molecular production rates with heliocentric distance when employing CO2 and clathrate hydrate ice as cometary nuclei substances. The energy balance equation and the vapor pressure equations of water and CO2 are used in calculating the vaporization from a surface. Calculations were carried out from both dry-ice and water-ice nuclei, using a variety of different effective visual albedos, but primarily for a thermal infrared of 0 (emission). Attention is given to cometary lifetimes and light curves and it was determined that the asymmetry in light curves occurs (occasionally) as a 'seasonal' effect due to a variation in the angle between the comet's rotation axis and the sun-comet line.

  9. An analysis of the coma of comet Bennett 1970 II

    NASA Technical Reports Server (NTRS)

    Oppenheimer, M.

    1978-01-01

    Brightness profiles for emission features of H2O(+) in comet Bennett 1970 II are analyzed, taking into account the role of chemical reactions in the coma. By comparing the rates of transport processes derived from the brightness profile with known chemical rate constants, upper limits on the abundances and production rates of H2O, CH4, NH3, and other possible coma constituents are found. The derived upper limit on the H2O production rate inside 10 to the 4th power km is less than the observed OH production rate averaged over the coma of this comet. It is concluded that the brightness profiles of H2O(+) and OH in comet Bennett 1970 II which are presently available are inconsistent with production of OH primarily by photodissociation of H2O molecules sublimating from the nucleus. The existence of an extended source of H2O is not ruled out.

  10. Study of a comet rendezvous mission, volume 1

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The feasibility, scientific objectives, modes of exploration and implementation alternatives of a rendezvous mission to Encke's comet in 1984 are considered. Principal emphasis is placed on developing the scientific rationale for such a mission, based on available knowledge and best estimates of this comet's physical characteristics, including current theories of its origin, evolution and composition. Studied are mission profile alternatives, performance tradeoffs, preferred exploration strategy, and a spacecraft design concept capable of performing this mission. The study showed that the major scientific objectives can be met by a Titan IIID/Centaur-launched 17.5 kw solar electric propulsion spacecraft which carries 60 kg of scientific instruments and is capable of extensive maneuvering within the comet envelope to explore the coma, tail and nucleus.

  11. Does Comet WILD-2 contain Gems?

    NASA Technical Reports Server (NTRS)

    Chi, M.; Ishii, H.; Dai, Z. R.; Toppani, A.; Joswiak, D. J.; Leroux, H.; Zolensky, M.; Keller, L. P.; Browning, N. D.

    2007-01-01

    It is expected that Comet Wild-2 dust should resemble anhydrous carbon-rich, chondritic porous (CP) interplanetary dust particles (IDPs) collected in the stratosphere because some CP IDPs are suspected to be from comets. The rarity of carbonaceous grains and presolar silicates, as well as the presence of high-temperature inner solar nebula minerals in the Wild-2 sample (e.g. osbornite and melilite), appear incompatible with most CP IDPs. However, it is premature to draw firm conclusions about the mineralogy of comet Wild-2 because only approx. 1% of the sample has been examined. The most abundant silicates in CP IDPs are GEMS (glass with embedded metal and sulfides). Nonsolar O isotopic compositions confirm that at least some GEMS in IDPs are presolar amorphous silicates. The presence or absence of GEMS in the Wild-2 sample is important because it addresses, (a) the relationship between CP IDPs and comets, and (b) the hypothesis that other GEMS in IDPs formed in the solar nebula. Here we show that most of the GEMSlike materials so far identified in Stardust aerogel were likely impact generated during collection. At the nanometer scale, they are compositionally and crystallographically distinct from GEMS in IDPs.

  12. Using comet light-curve asymmetries to predict comet returns

    NASA Astrophysics Data System (ADS)

    Festou, M.; Rickman, H.; Kamel, L.

    1990-05-01

    The gravitational attractions of the sun and planets do not account completely for the orbital motions of short-period comets. To clarify the roles of the radial and transverse components of the nongravitational force on such comets, observational data on gas production rates from the comets are used here as a diagnostic of the force. The shapes of the production curves, based mostly on visual light curves, correlate very well with the nongravitational delays or advances of a number of comets. This correlation is used here to predict a substantial advance of the recent perihelion passage of comet P/Brorsen-Metcalf, as verified by observations.

  13. Carbonaceous Components in the Comet Halley Dust

    NASA Technical Reports Server (NTRS)

    Fomenkova, M. N.; Chang, S.; Mukhin, L. M.

    1994-01-01

    Cometary grains containing large amounts of carbon and/or organic matter (CHON) were discovered by in situ measurements of comet Halley dust composition during VEGA and GIOTTO flyby missions. In this paper, we report the classification of these cometary, grains by means of cluster analysis, discuss the resulting compositional groups, and compare them with substances observed or hypothesized in meteorites, interplanetary dust particles, and the interstellar medium. Grains dominated by carbon and/or organic matter (CHON grains) represent approx. 22% of the total population of measured cometary dust particles. They, usually contain a minor abundance of rock-forming elements as well. Grains having organic material are relatively more abundant in the vicinity of the nucleus than in the outer regions of the coma, which suggests decomposition of the organics in the coma environment. The majority of comet Halley organic particles are multicomponent mixtures of carbon phases and organic compounds. Possibly, the cometary CHON grains may be related to kerogen material of an interstellar origin in carbonaceous meteorites. Pure carbon grains, hydrocarbons and polymers of cyanopolyynes, and multi-carbon monoxides are present in cometary dust as compositionally simple and distinctive components among a variety of others. There is no clear evidence of significant presence of pure formaldehyde or HCN polymers in Halley dust particles. The diversity of types of cometary organic compounds is consistent with the inter-stellar dust model of comets and probably reflects differences in composition of precursor dust. Preservation of this heterogeneity among submicron particles suggest the gentle formation of cometary, nucleus by aggregation of interstellar dust in the protosolar nebula without complete mixing or chemical homogenization at the submicron level.

  14. Comets, meteorites and atmospheres

    NASA Technical Reports Server (NTRS)

    Owen, T.; Bar-Nun, A.

    1996-01-01

    The relatively low value of Xe/Kr in the atmospheres of Earth and Mars seems to rule out meteorites as the major carriers of noble gases to the inner planets. Laboratory experiments on the trapping of gases in ice forming at low temperatures suggest that comets may be a better choice. It is then possible to develop a model for the origin of inner planet atmospheres based on volatiles delivered by comets added to volatiles originally trapped in planetary rocks. The model will be tested by results from the Galileo Entry Probe.

  15. Chemical and physical properties of comets in the Lowell database: Results from 35 years of narrow-band photometry

    NASA Astrophysics Data System (ADS)

    Schleicher, D.; Bair, A.

    2014-07-01

    As remnants from the epoch of early solar-system formation, comet nuclei are less processed than any other class of objects currently available for detailed study. Consequently, differences in the chemical composition among comets can indicate either differences in protoplanetary material and primordial conditions in our solar system or subsequent evolutionary effects. By gathering chemical and physical data on a large sample of comets and correlating these with dynamical properties, we can perform statistical analyses to determine the actual cause of a specific difference in properties. We have recently completed a new uniform reduction and set of analyses of the Lowell comet database, which includes 35 years of narrowband photometry of 167 comets. To minimize uncertainties due to too few data points or other systematics, a restricted subset of the database was created for chemical compositional studies, and mean abundance ratios were computed for each of these 101 comets. We used a variety of taxonomic techniques to identify seven compositional classes and to determine the membership of each class. Several classes are simply sub-groups of the original carbon-chain depleted class as defined by A'Hearn et al. (1995); all evidence continues to indicate that carbon-chain depletion reflects the primordial composition at the time and location of cometary accretion and is not associated with evolution. Among the other new classes is one containing five comets that are depleted in ammonia but are not depleted in carbon-chain molecules, but it is unclear if this compositional class is primordial or not. Other, non-compositional analyses were performed, using appropriate sub-sets of the entire database for each investigation. These included active areas, active fractions, and the behavior of the dust-to-gas ratio. Regarding the dust-to-gas ratio, we observed trends with respect to both perihelion distance and to age, implying an evolution of the surface of the nucleus

  16. The internal density distribution of comet 67P/C-G based on 3D models

    NASA Astrophysics Data System (ADS)

    Jorda, Laurent; Hviid, Stubbe; Capanna, Claire; Gaskell, Robert; Gutierrez, Pedro; Preusker, Frank; Rodionov, Sergey; Scholten, Frank

    2016-04-01

    The OSIRIS camera aboard the Rosetta spacecraft observed the nucleus of comet 67P/C-G from the mapping phase in summer 2014 until now. The images have allowed the reconstruction in three-dimension of nucleus surface with stereophotogrammetry (Preusker et al., Astron. Astrophys.) and stereophotoclinometry (Jorda et al., submitted to Icarus) techniques. We use the reconstructed models to constrain the internal density distribution based on: (i) the measurement of the offset between the center of mass and center of figure of the object, and (ii) the assumption that flat areas observed at the surface of the comet correspond to iso-gravity surfaces. The results of our analysis will be presented, and the consequences for the internal structure and formation of the nucleus of comet 67P/C-G will be discussed.

  17. Encounter of the Ulysses Spacecraft with the Ion Tail of Comet McNaught

    NASA Technical Reports Server (NTRS)

    Neugebauer, M.; Gloeckler, G.; Gosling, J. T.; Rees, A.; Skoug, R.; Goldstein, B. E.; Armstrong, T. P.; Combi, M. R.; Makinen, T.; McComas, D. J.; VonSteiger, R.; Zurbuchen, T. H.; Smith, E. J.; Geiss, J.; Lanzerotti, L. J.

    2007-01-01

    Comet McNaught was the brightest comet observed from Earth in the last 40 years. For a period of five days in early 2007 February, four instruments on the Ulysses spacecraft directly measured cometary ions and key properties of the interaction of the comet's ion tail with the high-speed solar wind from the polar regions of the Sun. Because of the record-breaking duration of the encounter, the data are unusually comprehensive. O3(+) ions were detected for the first time in a comet tail, coexisting with singly charged molecular ions with masses in the range 28-35 amu. The presence of magnetic turbulence and of ions with energies up to approximately 200 keV indicate that at a distance of approximately 1.6 AU from the comet nucleus, the ion tail McNaught had not yet reached equilibrium with the surrounding solar wind.

  18. Geomorphological Mapping on the Southern Hemisphere of Comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Lee, Jui-Chi; Massironi, Matteo; Giacomini, Lorenza; Ip, Wing-Huen; El-Maarry, Mohamed R.

    2016-04-01

    Since its rendezvous with comet 67P/Churyumov-Gerasimenko on the sixth of August, 2014, the Rosetta spacecraft has carried out close-up observations of the nucleus and coma of this Jupiter family comet. The OSIRIS, the Scientific Imaging Camera System onboard the Rosetta spacecraft, which consists of a narrow-angle and wide-angle camera (NAC and WAC), has made detailed investigations of the physical properties and surface morphology of the comet. From May 2015, the southern hemisphere of the comet became visible and the adaptical resolution was high enough for us to do a detailed analysis of the surface. Previous work shows that the fine particle deposits are the most extensive geomorphological unit in the northern hemisphere. On the contrary, southern hemisphere is dominated by rocky-like stratified terrain. The southern hemisphere of the nucleus surface reveals quite different morphologies from the northern hemisphere. This could be linked to the different insolation condition between northern and southern hemisphere. As a result, surface geological processes could operate with a diverse intensity on the different sides of the comet nucleus. In this work, we provide the geomorphological maps of the southern hemisphere with linear features and geological units identified. The geomorphological maps described in this study allow us to understand the processes and the origin of the comet.

  19. Sample Returns Missions in the Coming Decade

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Mitcheltree, Robert A.; Cheatwood, F. McNeil

    2000-01-01

    In the coming decade, several missions will attempt to return samples to Earth from varying parts of the solar system. These samples will provide invaluable insight into the conditions present during the early formation of the solar system, and possibly give clues to how life began on Earth. A description of five sample return missions is presented (Stardust, Genesis, Muses-C. Mars Sample Return, and Comet Nucleus Sample Return). An overview of each sample return mission is given, concentrating particularly on the technical challenges posed during the Earth entry, descent, and landing phase of the missions. Each mission faces unique challenges in the design of an Earth entry capsule. The design of the entry capsule must address the aerodynamic, heating, deceleration, landing, and recovery requirements for the safe return of samples to Earth.

  20. Gas Arcs in Comet Hyakutake: Revisited

    NASA Astrophysics Data System (ADS)

    Combi, M. R.; Harris, W. M.; Kabin, K.

    2000-10-01

    The recent break-up of the nucleus of Comet LINEAR S4 demonstrates that fragmentation is an important cometary process and that it is not a rare phenomenon. Comet Hyakutake (1996 B2) underwent an outburst of gas production on March 21, 1996. Subsequent to the outburst, fragments, or condensations as they have been called, were observed moving tailward from the position of the nucleus. Arc-shaped structures were seen in images of gas species (OH, CN and C2) providing clear evidence of production of gas from cometary nucleus debris also tailward of the nucleus. We have already (Harris et al. 1997, Science 277, 676) described observations taken with the WIYN telescope consisting of a 6-hour time sequence of images on March 26, 1996 of CN and dust continuum and a single OH image showing that the arc, and by inference it's source, was generally moving tailward with the visible condensations. The entire OH arc was reproduced using a kinetic Direct Simulation Monte Carlo (DSMC) calculation for water and all its photodissociation products. DSMC is suited to this physical environment that is in transition from fluid conditions in the inner coma to free-expansion in the outer coma. Our model asuming a string of fragments within the apex of the arc (i.e., the intersection of the arc and the tailward sun-comet line) reproduced the arc. Here we present a more extensive parameter study of the arc using DSMC and a solution of the standard perfect-fluid Euler equations. We find that a secondary source just behind the apex of the arc can reproduce the OH arc, but the location of the source must be much closer to the apex than indicated by solutions of the Navier-Stokes equations (NSE) (Rodionov et al. 1998, Icarus 136, 232). We find that we must use unrealistically large collision cross sections to reproduce the NSE results, and that the NSE results are not substantially different from a simpler Euler equation approach. This work has been supported by NASA Planetary Atmospheres

  1. The Three Sources of Gas in the Comae of Comets

    NASA Technical Reports Server (NTRS)

    Huebner, W. F.

    1995-01-01

    Surface water ice on a comet nucleus is the major source of coma gas. Dust, entrained by coma gas, fragments and vaporizes, forming a second, distributed source of coma gas constituents. Ice species more volatile than water ice below the surface of the nucleus are a third source of coma gas. Vapors from these ices, produced by heat penetrating into the nucleus, diffuse through pores outward into the coma. The second and third sources provide minor, but sometimes easily detectible, gaseous species in the coma. We present mixing ratios of observed minor coma constituents relative to water vapor as a function of heliocentric and cometocentric distances and compare these ratios with model predictions, assuming the sources of the minor species are either coma dust or volatile ices in the nucleus.

  2. Sublimation rates of carbon monoxide and carbon dioxide from comets at large heliocentric distances

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    1992-01-01

    Using a simple model for outgassing from a small flat surface area, the sublimation rates of carbon monoxide and carbon dioxide, two species more volatile than water ice that are known to be present in comets, are calculated for a suddenly activated discrete source on the rotating nucleus. The instantaneous sublimation rate depends upon the comet's heliocentric distance and the Sun's zenith angle at the location of the source. The values are derived for the constants of CO and CO2 in an expression that yields the local rotation-averaged sublimation rate as a function of the comet's spin parameters and the source's cometocentric latitude.

  3. A CO2-rich coma model applied to the neutral coma of Comet West

    NASA Technical Reports Server (NTRS)

    Mitchell, G. F.; Swift, M. B.; Huntress, W. T.

    1982-01-01

    Models of the cometary coma in which the dominant volatile is CO2 have been constructed for a range of heliocentric distances. Model coma abundances of C2, C3, and CN are compared with the abundances observed in Comet West and are found to be in good agreement. Furthermore, the variation with heliocentric distance of C2, C3, and CN model abundances agree well with the observed variation in Comet West. The present work lends detailed support to a previous suggestion that a substance more volatile than water, such as CO2, controls the evaporation of the nucleus of Comet West. The implications for cometary formation are briefly discussed.

  4. Spatial distribution of low energy plasma at comet 67P from Rosetta RPC-LAP measurements

    NASA Astrophysics Data System (ADS)

    Edberg, Niklas J. T.; Eriksson, Anders I.; Odelstad, Elias; Vigren, Erik; Henri, Pierre; Lebreton, Jean-Pierre; Mandt, Kathleen; Nilsson, Hans; Carr, Chris; Cupido, Emanuele; Vallat, Claire; Altwegg, Kathrin

    2015-04-01

    We present in situ measurements of the low energy plasma environment around comet 67P from the two Langmuir probes (LAP) on the Rosetta spacecraft, which form part of the Rosetta plasma consortium (RPC). RPC-LAP has operated almost continuously as Rosetta has orbited the comet at close distance (10-30 km) at low velocity (about 1 m/s) since August 2014. Using the RPC-LAP measurements we have produced global maps of the low energy plasma in the vicinity of 67P. Initial estimates indicate that the plasma density has reached values of several 100 cm^-3 and that the electron temperature has typically been in the range 5-10 eV, when the comet was beyond 2.5 AU from the sun. Photoionisation is the dominating process for producing the plasma around the comet while charge-exchange and impact ionisation may also contribute. The plasma environment has been found to be strongly coupled to the local neutral gas density, which in turn is coupled to which area on the comet is facing the sun. The northern summer neck-area of the comet outgasses more than other areas and above this region are the highest densities observed. In the southern winter and above the two main lobes of the comet body, the plasma density is lower. The plasma density is hence not determined by the solar wind, but by the outgassing from the comet. The 12.4-hour rotation period of the comet together with the varying latitude of the slow-moving Rosetta provide strong modulation of the RPC-LAP measurements. Besides orbiting the comet, Rosetta will also perform flybys of the comet in early 2015 when Rosetta will move to distances of several hundred kilometres from the nucleus. These flybys provide a cut-through view of the near-comet plasma environment, which will possibly give some insight to the solar-wind interaction with the cometary coma.

  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. Lingering Grains of Truth around Comet 17P/Holmes

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    Comet 17P/Holmes underwent a massive outburst in 2007 October, brightening by a factor of almost a million in under 48 hr. We used infrared images taken by the Wide-Field Infrared Survey Explorer mission to characterize the comet as it appeared at a heliocentric distance of 5.1 AU almost 3 yr after the outburst. The comet appeared to be active with a coma and dust trail along the orbital plane. We constrained the diameter, albedo, and beaming parameter of the nucleus to 4.135 ± 0.610 km, 0.03 ± 0.01, and 1.03 ± 0.21, respectively. The properties of the nucleus are consistent with those of other Jupiter family comets. The best-fit temperature of the coma was 134 ± 11 K, slightly higher than the blackbody temperature at that heliocentric distance. Using Finson-Probstein modeling, we found that the morphology of the trail was consistent with ejection during the 2007 outburst and was made up of dust grains between 250 μm and a few cm in radius. The trail mass was ~1.2-5.3 × 1010 kg.

  7. Lingering grains of truth around comet 17P/HOLMES

    SciTech Connect

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

    2014-06-01

    Comet 17P/Holmes underwent a massive outburst in 2007 October, brightening by a factor of almost a million in under 48 hr. We used infrared images taken by the Wide-Field Infrared Survey Explorer mission to characterize the comet as it appeared at a heliocentric distance of 5.1 AU almost 3 yr after the outburst. The comet appeared to be active with a coma and dust trail along the orbital plane. We constrained the diameter, albedo, and beaming parameter of the nucleus to 4.135 ± 0.610 km, 0.03 ± 0.01, and 1.03 ± 0.21, respectively. The properties of the nucleus are consistent with those of other Jupiter family comets. The best-fit temperature of the coma was 134 ± 11 K, slightly higher than the blackbody temperature at that heliocentric distance. Using Finson-Probstein modeling, we found that the morphology of the trail was consistent with ejection during the 2007 outburst and was made up of dust grains between 250 μm and a few cm in radius. The trail mass was ∼1.2-5.3 × 10{sup 10} kg.

  8. Rosetta Lander - Philae on Comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Biele, J.; Ulamec, S.; Cozzoni, B.; Fantinati, C.; Gaudon, P.; Geurts, K.; Jurado, E.; Küchemann, O.; Lommatsch, V.; Finke, F.; Maibaum, M.; Moussi-Soffys, A.; Salatti, M.

    2015-10-01

    Rosetta is a Cornerstone Mission of the ESA Horizon 2000 programme. In August 2014 it reached comet 67P/Churyumov-Gerasimenko after a 10 year cruise. Both its nucleus and coma have been studied with its orbiter payload of eleven PI instruments, allowing the selection of a landing site for Philae. The landing on the comet nucleus successfully took place on November 12th 2014. Philae touched the comet surface seven hours after ejection from the orbiter. After several bounces it came to rest and continued to send scientific data to Earth. All ten instruments of its payload have been operated at least once. Due to the fact that the Lander could not be anchored, the originally planned first scientific sequence had to be modified. Philae went into hibernation on November 15th, after its primary battery ran out of energy. Re-activation of the Lander is expected in spring/summer 2015 (before the conference) when CG is closer to the sun and the solar generator of Philae will provide more power. The presentation will give an overview of the activities of Philae on the comet, including a status report on the re-activation after hibernation. Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI with additional contributions from Hungary, UK, Finland, Ireland and Austria.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  10. The Stardust Discovery Mission - Returning Unique Samples of Early Solar System Organics

    NASA Technical Reports Server (NTRS)

    Sandford, Scott

    2006-01-01

    On January 2,2004, the STARDUST spacecraft made the closest ever flyby (236 km) of the nucleus of a comet - Comet Wild 2. During the flyby the spacecraft collected samples of dust from the coma of the comet. These samples were successfully returned to Earth on January 15,2006. After a six-month preliminary examination to establish the nature of the returned samples, they will be made available to the general scientific community for study. During my talk I will discuss the scientific goals of the STARDUST mission and provide a brief overview of the mission's design and flight. I will also discuss the recovery of the Stardust Sample Return Capsule (SRC), with an emphasis on those aspects of the recovery important for minimizing the degree of contamination (particularly organic contamination) of the samples. Finally, the first samples are only just now being distributed for preliminary examination, but I hope to be able to talk about some of the preliminary findings from the returned comet samples.

  11. CHEMICAL COMPOSITION OF COMET C/2007 N3 (LULIN): ANOTHER ''ATYPICAL'' COMET

    SciTech Connect

    Gibb, Erika L.; Sudholt, Emily; Bonev, Boncho P.; Villanueva, Geronimo; Radeva, Yana; DiSanti, Michael A.; Mumma, Michael J.

    2012-05-10

    We measured the volatile chemical composition of comet C/2007 N3 (Lulin) on three dates from 2009 January 30 to February 1 using NIRSPEC, the high-resolution ({lambda}/{Delta}{lambda} Almost-Equal-To 25,000), long-slit echelle spectrograph at Keck 2. We sampled nine primary (parent) volatile species (H{sub 2}O, C{sub 2}H{sub 6}, CH{sub 3}OH, H{sub 2}CO, CH{sub 4}, HCN, C{sub 2}H{sub 2}, NH{sub 3}, CO) and two product species (OH* and NH{sub 2}). We also report upper limits for HDO and CH{sub 3}D. C/2007 N3 (Lulin) displayed an unusual composition when compared to other comets. Based on comets measured to date, CH{sub 4} and C{sub 2}H{sub 6} exhibited 'normal' abundances relative to water, CO and HCN were only moderately depleted, C{sub 2}H{sub 2} and H{sub 2}CO were more severely depleted, and CH{sub 3}OH was significantly enriched. Comet C/2007 N3 (Lulin) is another important and unusual addition to the growing population of comets with measured parent volatile compositions, illustrating that these studies have not yet reached the level where new observations simply add another sample to a population with well-established statistics.

  12. Comet P/Holmes, 1892III - A case of duplicity?

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1984-01-01

    An analysis of observations of comet P/Holmes 1892III's two 8-10 mag bursts indicates that these phenomena are consistent with the grazing encounter of a small satellite with the nucleus on November 4.6, 1892, and the final encounter on January 16.3, 1893. While after the first burst the total magnitude fell less than 2 mag from November 7 to 30, the fading was much more rapid after the second burst. It is suggested that the grazing encounter distributed a volume of large chunks in the neighborhood of the nucleus, maintaining activity for weeks.

  13. Hubble Space Telescope View of Comet C/Siding Spring during its Close Encounter with Mars

    NASA Astrophysics Data System (ADS)

    Li, J. Y.; Samarasinha, N. H.; Kelley, M. S. P.; Farnham, T. L.; Bodewits, D.; A'Hearn, M. F.; Lisse, C. M.; Delamere, W. A.; Mutchler, M. J.

    2014-12-01

    Comet C/2013 A1 (Siding Spring) is a dynamically new comet whose physical and chemical status should be the least evolved since the formation of cometesimals during the planetary system formation processes. Its close encounter with Mars on October 19, 2014 at a distance of 131,000 km allows for imaging its nucleus and inner coma by MRO/HiRISE at 140 m/pix resolution. Such an encounter offers us the opportunity to do cometary flyby science for a dynamically new comet for the first time ever. Those observations have the potential to advance our understanding of comets in ways similar to previous flyby missions to periodic comets. An extensive observing campaign from many ground- and space-based platforms is supporting the "flyby" observations from Mars spacecraft. We will monitor the comet with Hubble Space Telescope for >24 hrs total observing time around the encounter, to obtain images of the inner coma at ~46 km/pix at the comet. These observations will allow us to perform detailed studies of the morphology of the dust and gas coma of C/Siding Spring, and to connect the observations performed from various platforms at various spatial resolutions and over a long time baseline. The ultimate goal is to correlate large-scale coma behaviors to the nucleus as resolved by MRO/HiRISE. We will report the HST observations and the preliminary results.

  14. Mass spectra of heavy ions near comet Halley

    NASA Technical Reports Server (NTRS)

    Korth, A.; Richter, A. K.; Loidl, A.; Anderson, K. A.; Carlson, C. W.

    1986-01-01

    The heavy-ion analyzer, RPA2-PICCA, aboard the Giotto spacecraft, detected the first cometary ions at a distance of about 1.05 million km from the nucleus of comet Halley. In the inner coma the major ions identified are associated with the H2O, CO and CO2 groups. Ions of larger atomic mass unit are also present, corresponding possibly to various hydrocarbons, heavy metals of the iron-group or to sulphur compounds.

  15. DRBE comet trails

    SciTech Connect

    Arendt, Richard G.

    2014-12-01

    Re-examination of the Cosmic Background Explorer Diffuse Infrared Background Experiment (DIRBE) data reveals the thermal emission of several comet dust trails. The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported. The known trails of 2P/Encke and 73P/Schwassmann–Wachmann 3 are also seen. The dust trails have 12 and 25 μm surface brightnesses of <0.1 and <0.15 MJy sr{sup −1}, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals 1 additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

  16. Comets in Indian Scriptures

    NASA Astrophysics Data System (ADS)

    Das Gupta, P.

    2016-01-01

    The Indo-Aryans of ancient India observed stars and constellations for ascertaining auspicious times in order to conduct sacrificial rites ordained by the Vedas. Naturally, they would have sighted comets and referred to them in the Vedic texts. In Rigveda (circa 1700-1500 BC) and Atharvaveda (circa 1150 BC), there are references to dhumaketus and ketus, which stand for comets in Sanskrit. Rigveda speaks of a fig tree whose aerial roots spread out in the sky (Parpola 2010). Had this imagery been inspired by the resemblance of a comet's tail with long and linear roots of a banyan tree (ficus benghalensis)? Varahamihira (AD 550) and Ballal Sena (circa AD 1100-1200) described a large number of comets recorded by ancient seers, such as Parashara, Vriddha Garga, Narada, and Garga, to name a few. In this article, we propose that an episode in Mahabharata in which a radiant king, Nahusha, who rules the heavens and later turns into a serpent after he kicked the seer Agastya (also the star Canopus), is a mythological retelling of a cometary event.

  17. Finding Comet Halley.

    ERIC Educational Resources Information Center

    Glenn, William H.

    1985-01-01

    Provides background information and references on Comet Halley (which will be observable by telescope in October 1985 and reach its most brilliant appearance in March and April of 1986). Suggestions for equipment and maps of its path through the sky are included. (DH)

  18. DIRBE Comet Trails

    NASA Astrophysics Data System (ADS)

    Arendt, Richard G.

    2014-12-01

    Re-examination of the Cosmic Background Explorer Diffuse Infrared Background Experiment (DIRBE) data reveals the thermal emission of several comet dust trails. The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported. The known trails of 2P/Encke and 73P/Schwassmann-Wachmann 3 are also seen. The dust trails have 12 and 25 μm surface brightnesses of \\lt 0.1 and \\lt 0.15 MJy sr-1, respectively, which is \\lt 1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals 1 additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

  19. Halley's Comet: A Bibliography.

    ERIC Educational Resources Information Center

    Freitag, Ruth S., Comp.

    Included in this bibliography are over 3,200 references to publications on Halley's Comet, its history, orbital motion, and physical characteristics, meteor streams associated with it, preparations for space missions to study it in 1986, and popular reaction to its appearances. Also cited are a few papers that, although they devote little…

  20. Comets and life

    NASA Technical Reports Server (NTRS)

    Oro, J.; Berry, J. M.

    1987-01-01

    Some of the chemical species which have been detected in comets include H2O, HCN, CH3CN, CO, CO2, NH3, CS, C2 and C3. All of these have also been detected in the interstellar medium, indicating a probable relationship between interstellar dust and gas clouds and comets. Laboratory experiments carried out with different mixtures of these molecules give rise to the formation of the biochemical compounds which are necessary for life, such as amino acids, purines, pyrimidines, monosaccharides, etc. However, in spite of suggestions to the contrary, the presence of life in comets is unlikely. On the other hand, the capture of cometary matter by the primitive earth is considered essential for the development of life on this planet. The amount of cometary carbon-containing matter captured by the earth, as calcualted by different authors, is several times larger than the total amount of organic matter present in the biosphere (10 to the 18th g). The major classes of reactions which were probably involved in the formation of key biochemical compounds are discussed. The tentative conclusions are that: (1) comets played a predominant role in the emergence of life on earth, and (2) they are the cosmic connection with extraterrestrial life.

  1. Slice of Comet Dust

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image illustrates one of several ways scientists have begun extracting comet particles from the Stardust spacecraft's collector. First, a particle and its track are cut out of the collector material, called aerogel, in a wedge-shaped slice called a keystone. A specialized silicon pickle fork is then used to remove the keystone from the remaining aerogel for further analysis.

  2. DIRBE Comet Trails

    NASA Technical Reports Server (NTRS)

    Arendt, Richard G.

    2015-01-01

    Re-examination of the COBE DIRBE data reveals the thermal emission of several comet dust trails.The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported.The known trails of 2P/Encke, and 73P/Schwassmann-Wachmann 3 are also seen. The dust trails have 12 and 25 microns surface brightnesses of <0.1 and <0.15 MJy/sr, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals one additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

  3. Disappearance and disintegration of comets

    NASA Astrophysics Data System (ADS)

    Sekanina, Z.

    1984-04-01

    The present investigation has the objective to provide a summary of the existing evidence on the disappearance of comets and to draw conclusions regarding the physical processes involved in the disappearance. Information concerning the classification of evidence and the causes of apparent disappearance of comets is presented in a table. Attention is given to the dissipating comets, the headless sungrazing comet 1887 I, and the physical behavior of the dissipating comets and the related phenomena. It is found that all comets confined to the planetary region of the solar system decay on astronomically short time scales. However, only some of them appear to perish catastrophically. Some of the observed phenomena could be successfully interpreted. But little insight has been obtained into the character of the processes which the dissipating comets experience.

  4. Detection of Irradiation Treatment of Foods Using DNA `Comet Assay'

    NASA Astrophysics Data System (ADS)

    Khan, Hasan M.; Delincée, Henry

    1998-06-01

    Microgel electrophoresis of single cells (DNA comet assay) has been investigated to detect irradiation treatment of some food samples. These samples of fresh and frozen rainbow trout, red lentil, gram and sliced almonds were irradiated to 1 or 2 kGy using 10 MeV electron beam from a linear accelerator. Rainbow trout samples yielded good results with samples irradiated to 1 or 2 kGy showing fragmentation of DNA and, therefore, longer comets with no intact cells. Unirradiated samples showed shorter comets with a significant number of intact cells. For rainbow trout stored in a freezer for 11 days the irradiated samples can still be discerned by electrophoresis from unirradiated samples, however, the unirradiated trouts also showed some longer comets besides some intact cells. Radiation treatment of red lentils can also be detected by this method, i.e. no intact cells in 1 or 2 kGy irradiated samples and shorter comets and some intact cells in unirradiated samples. However, the results for gram and sliced almond samples were not satisfactory since some intact DNA cells were observed in irradiated samples as well. Probably, incomplete lysis has led to these deviating results.

  5. Infrared observations of oxidized carbon in comet C/2002 t7 (LINEAR)

    NASA Astrophysics Data System (ADS)

    Anderson, William Michael, Jr.

    2010-11-01

    Cometary nuclei are generally recognized as the most primitive remnants of the early Solar System. Their physical and chemical attributes allow a glimpse into the conditions under which icy bodies formed. Parent volatiles in comets are now routinely studied, and a significant diversity in composition among the comets sampled to date has been demonstrated. This forms the foundation of an emerging cometary taxonomy based on chemical composition. In spring 2004, comet C/2002 T7 (LINEAR) was observed using the facility echelle spectrometer (CSHELL) at the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. CSHELL offers seeing-limited spatial resolution and sufficiently high spectral resolving power (R = lambda/Deltalambda ˜ 2.5 x 10 4) to permit line-by-line intensities to be measured along its 30 arc-second slit. Its small pixels favor measurement of molecules released from ices housed in cometary nuclei ("native" ices) over those released from spatially extended sources in the coma. Emission lines from multiple molecular species were targeted in the 3 to 5 mum wavelength region. The observations revealed an extremely rich volatile chemistry in C/2002 T7. I present the chemical composition of oxidized carbon in C/2002 T7 (LINEAR). Carbon monoxide (CO), formaldehyde (H2CO), and methyl alcohol (CH 3OH) were detected simultaneously or nearly simultaneously with H 2O on multiple UT dates spanning 2004 May 3-9 (heliocentric distance Rh = 0.66 -- 0.71 AU) and May 30 - June 2 (R h = 0.99 -- 1.03 AU). I will discuss native production rates, rotational temperatures, and mixing ratios (abundances relative to H2O) for oxidized carbon. My results illustrate that C/2002 T7 (LINEAR) is enriched in CH3OH, while CO is borderline depleted compared to other Oort cloud comets that have been measured. I tested for chemical heterogeneity in C/2002 T7 (LINEAR), both diurnal, presumably associated with rotation of the nucleus, and serial (i.e., over a range in Rh). However, no evidence

  6. ESA Unveils Its New Comet Chaser.

    NASA Astrophysics Data System (ADS)

    1999-07-01

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

  7. Scientific returns from a program of space missions to comets

    NASA Technical Reports Server (NTRS)

    Delsemme, A. H.

    1979-01-01

    A program of cometary missions is proposed. The nature and size of interstellar dust, its origin and evolution; identification of new interstellar molecules; clarification of interstellar chemistry; accretion of grains into protosolar cometesimals; role of a T Tauri wind in the dissipation of the protosolar nebula; record of isotopic anomalies, better preserved in comets than in meteorites; cosmogenic and radiogenic dating of comets; cosmochronology and mineralogy of meteorites, as compared with that of cometary samples; origin of the earth's biosphere, and the origin of life are topics discussed in relation to comet exploration.

  8. On the origin of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Marchi, Simone; Rickman, Hans; Barbieri, Cesare; Naletto, Giampiero; Sierks, Holger

    2015-08-01

    One of the main aims of the ESA Rosetta mission is to unravel the origin of the solar system by exploring comet 67P/Churyumov-Gerasimenko (hereinafter 67P).We discuss here data from the OSIRIS scientific cameras as basic constraints, focusing our attention to the overall bi-lobate shape and the presence of key geological features, such as layers and fractures. In particular, the presence of thick layering and wide spread fracturing is used to infer large-scale structural properties of the nucleus, which may bear implications for its assemblage. Furthermore, we assess the origin and evolution of comet 67P in relation to that of comets in general and in the framework of the "Nice" model for the evolution of the solar system.We argue that the two lobes of 67P are derived from two distinct objects that form a contact binary. The lobes are separate bodies, though sufficiently similar to have formed in the same environment. By an estimate of the collisional rate of comet nuclei in the trans-planetary disk that appears to have been the repository of all comets observed today, we estimate the probability of survival for 67P during the early epochs of the solar system. We find that comets of similar size as 67P are likely collisionally evolved objects, although survival can be achieved under certain circumstances.A collisional origin of the contact binary is suggested, and the low bulk density of the aggregate and abundance of volatile species show that a gentle merger must have occurred. For this, we narrow down two main scenarios: the primordial accretion of planetesimals, and the re-accretion of fragments after an energetic impact onto a larger parent body. We also discuss to what extent the primordial signatures exhibited by 67P (and possibly other comet nuclei as well) are more consistent with the accretion of primordial objects or collisional fragments.

  9. Millimeter and submillimeter observations of comet 67P/C-G with the MIRO instrument

    NASA Astrophysics Data System (ADS)

    Hofstadter, M. D.; Gulkis, S.

    2015-10-01

    The Microwave Instrument on the Rosetta Orbiter (MIRO) [3] makes submillimeter- and millimeterwavelength observations of the nucleus and coma of the target comet of the Rosetta mission (Comet 67P/Churyumov-Gerasimenko). By making broadband continuum measurements at two wavelengths (approximately 0.5 and 1.6 mm), MIRO probes the thermal and dielectric properties of the nucleus subsurface. High-resolution spectroscopic measurements of 8 molecular lines in the submillimeter (H2O, H2 17O, H2 18O, CO, NH3, and three lines of CH3OH) constrain the abundance, velocity, and temperature of gases in the coma. These measurements allow MIRO to study the nucleus and coma as a coupled system. Upon arrival at the comet (August 2014) measurements by MIRO [4] and other instruments quickly determined that the upper ~10 cm of the nucleus generally have thermal properties consistent with very porous, dusty material, but that there is ice within the upper few cm at least in some regions. It was also found that gas emission from the nucleus varies with location and time. More recently, we have begun to study in detail the time and spatial variability of the nucleus [2, 6] and coma [1, 5]. This presentation will provide an overview of the MIRO instrument, our data sets, and provide a high-level discussion of what we are learning about the upper meter of the nucleus' surface and the distribution and transport of water.

  10. Understanding the nucleus of 67P/C-G through laboratory experiments

    NASA Astrophysics Data System (ADS)

    Laufer, Diana; Ba-Nun, Akiva

    2015-04-01

    On August the 6th, 2014 the Rosetta spacecraft arrived at Comet 67P/Churyumov-Gerasimenko and on November the 12th, the Philae probe landed, sending the most detailed close-up pictures, with a few meters resolution, of the surface of the comet. We will present an explanation of the observed surface features on the comet nucleus, as derived from our laboratory experimental results, such as craters, boulders, active areas and smooth terrains, due to ice sublimation and evolution of gases from the interior of the nucleus. A large flux of ice grains was observed to emanate from the central part "the neck" of the nucleus. Our experiments demonstrated that a huge flux of ice grains is ejected together with gas jets from the ice. As the comet approaches the Sun, gases emerge from pockets up to the ice surface quiescently and also accumulate in larger cavities which explode to release gas jets together with a huge amount of micron size ice grains, forming craters and smooth surfaces. Also comparing our experimental results on the density, thermal conductivity and mechanical strength with the in situ results of comet 67P C-G, as done with comet Temple 1 in the Deep Impact mission, will be used for better understanding of the internal properties of the nucleus. The experimental results on gas trapping in the ice and its release upon warming up will be presented and compared with Rosetta's findings. Authors acknowledge the funding from the Israeli Ministry of Science, Technology and Space.

  11. Observing campaigns for two unique comets: C/2012 S1 ISON and C/2013 A1 Siding Spring

    NASA Astrophysics Data System (ADS)

    Knight, Matthew

    During 2013-2014, comets C/2012 S1 (ISON) and C/2013 A1 (Siding Spring) have been the subjects of international observing campaigns due to their unique and fortuitous orbits. Dynamically new comet ISON was discovered in 2012 September and was destroyed during its perihelion passage at a sungrazing distance of 0.0124 AU (just 1.7 solar radii above the Sun’s photosphere) on 2013 November 28. It was of high scientific interest as the first known dynamically new sungrazing comet, became very bright near perihelion when it was extensively observed by telescopes on SOHO and STEREO, and had favorable observing circumstances for spacecraft at both Mars and Mercury. As a result, comet ISON was studied intensively by observers around the world and by more than ten spacecraft, making it one of the best-observed comets in history. Comet Siding Spring is a dynamically new comet discovered in 2013 January that passes 0.0009 AU (~135,000 km) from Mars on 2014 October 19. This is approximately 16 times smaller than the closest known approach by a comet to Earth and should bring Mars and its fleet of orbiting spacecraft within the comet’s coma. This incredibly close approach may allow the nucleus to be resolved by spacecraft at Mars, a feat only previously accomplished by a handful of missions to short period comets, and never for a dynamically new or long period comet. Observations are ongoing by ground- and space-based observatories in order to characterize both the comet itself and the hazard it may pose to the Martian spacecraft fleet. As members of NASA’s Comet ISON Observing Campaign team, we have been involved in encouraging and facilitating observations of comet ISON and are serving a similar role for comet Siding Spring. We will review the successes of these campaigns and highlight major results and ongoing work.

  12. Surface Contact Model for Comets and Asteroids

    NASA Technical Reports Server (NTRS)

    Blackmore, Lars James C.; Trease, Brian P.; Acikmese, Behcet; Mandic, Milan; Carson, John M.

    2011-01-01

    A contact force model was developed for use in touch and go (TAG) surface sampling simulations on small celestial bodies such as comets and asteroids. In TAG scenarios, a spacecraft descending toward the surface of a small body comes into contact with the surface for a short duration of time, collects material samples with a sampler device, and then ascends to leave the surface. The surface contact required 6-DOF (degrees of freedom) dynamics models due to coupling of the attitude and translation dynamics during the contact. The model described here is for contact scenarios that utilize a rotating brush wheel sampler (BWS) to collect surface material. The model includes stiffness and damping of the surface material during BWS vertical motion, lateral friction from the BWS dragging across the surface, and lateral shear from the rotating BWS scooping the surface material. This model is useful for any mission to asteroids or comets that incorporates surface sampling operations.

  13. Development of Sampling Techniques For Planetary Surfaces

    NASA Astrophysics Data System (ADS)

    Coste, P.; Eiden, M.; Gromov, V.; Ilykorpi, T.; Kochan, H.; Re, E.; Richter, L.

    During the last 15 years, the European Space Agency has initiated the development of a number of sampling techniques for planetary surfaces, in the frame of its basic Technology and Research Programme (TRP). Sampling may be performed by means of drilling, coring, milling, grain scooping or picking, and penetration. The items addressed in particular are: the Sample Acquisition System (SAS) for the late Comet Nucleus Sample and Return mission; the Small Sample Acquisition and Distribution Tool (SSA/DT): the Mole and the Sampling Mole (SM). Some of these devices have found a direct application within an ESA planetary mission, as expected; in other cases, their concept was used and modified to fulfill updated requirements. Sampling or soil probing capabilities are included to various extents in these current or near-future ESA missions: the Huygens Probe (on NASA's CASSINI spacecraft), on its way to Titan surface; the RoLand Lander (on ROSETTA s/c), onto Comet Wirtanen; the Beagle2 Lander (carried by MARS EXPRESS s/c) sampling the Martian surface and sub- surface. Future sampling missions to Mercury, the Moon and to asteroids are being studied. Even more challenging missions to Venus are considered.

  14. On the relationship between gas and dust in 15 comets: an application to Comet 103P/Hartley 2 target of the NASA EPOXI mission of opportunity

    NASA Astrophysics Data System (ADS)

    Sanzovo, G. C.; Sanzovo, D. Trevisan; de Almeida, A. A.

    After the success of Deep Impact mission to hit the nucleus of Comet 9P/Tempel 1 with an impactor, the concerns are turned now to the possible reutilization of this dormant flyby spacecraft in the study of another comet, for only about 10% of the cost of the original mission. Comet 103P/Hartley 2 on UT 2010 October 11 is the most attractive target in terms of available fuel at rendezvous and arrival time at the comet. In addition, the comet has a low inclination so that major orbital plane changes in the spacecraft trajectory are unnecessary. In an effort to provide information concerning the planning of this new NASA EPOXI space mission of opportunity, we use in this work, visual magnitudes measurements available from International Comet Quarterly (ICQ) to obtain, applying the Semi-Empirical Method of Visual Magnitudes - SEMVM (de Almeida, Singh, & Huebner 1997), the water production rates (in molecules/s) related to its perihelion passage of 1997. When associated to the water vaporization theory of Delsemme (1982), these rates allowed the acquisition of the minimum dimension for the effective nuclear radius of the comet. The water production rates were then converted into gas production rates (in g/s) so that, with the help of the strong correlation between gas and dust found for 12 periodic comets and 3 non-period comets (Trevisan Sanzovo 2006), we obtained the dust loss rates (in g/s), its behavior with the heliocentric distance and the dust-to-gas ratios in this physically attractive rendezvous target-comet to Deep Impact spacecraft at a closest approach of 700 km.

  15. Fission and reconfiguration of bilobate comets as revealed by 67P/Churyumov-Gerasimenko.

    PubMed

    Hirabayashi, Masatoshi; Scheeres, Daniel J; Chesley, Steven R; Marchi, Simone; McMahon, Jay W; Steckloff, Jordan; Mottola, Stefano; Naidu, Shantanu P; Bowling, Timothy

    2016-06-16

    The solid, central part of a comet--its nucleus--is subject to destructive processes, which cause nuclei to split at a rate of about 0.01 per year per comet. These destructive events are due to a range of possible thermophysical effects; however, the geophysical expressions of these effects are unknown. Separately, over two-thirds of comet nuclei that have been imaged at high resolution show bilobate shapes, including the nucleus of comet 67P/Churyumov-Gerasimenko (67P), visited by the Rosetta spacecraft. Analysis of the Rosetta observations suggests that 67P's components were brought together at low speed after their separate formation. Here, we study the structure and dynamics of 67P's nucleus. We find that sublimation torques have caused the nucleus to spin up in the past to form the large cracks observed on its neck. However, the chaotic evolution of its spin state has so far forestalled its splitting, although it should eventually reach a rapid enough spin rate to do so. Once this occurs, the separated components will be unable to escape each other; they will orbit each other for a time, ultimately undergoing a low-speed merger that will result in a new bilobate configuration. The components of four other imaged bilobate nuclei have volume ratios that are consistent with a similar reconfiguration cycle, pointing to such cycles as a fundamental process in the evolution of short-period comet nuclei. It has been shown that comets were not strong contributors to the so-called late heavy bombardment about 4 billion years ago. The reconfiguration process suggested here would preferentially decimate comet nuclei during migration to the inner solar system, perhaps explaining this lack of a substantial cometary flux. PMID:27281196

  16. Comet 46P/Wirtanen: Evolution of the Subsurface Layer

    NASA Astrophysics Data System (ADS)

    Kossacki, Konrad J.; Szutowicz, S. Ławomira; Leliwa-Kopystyński, Jacek

    1999-11-01

    Cometary nuclei are composed mostly of water ice and mineral grains. When a comet passes near the Sun, volatiles sublimate. This process leads to the formation of a dust layer covering the nucleus. Various other metamorphic processes are also predicted to modify the subsurface layer of the nucleus. Consequently, it should become stratified and more cohesive than initially. At present, because of preparations for the Rosetta mission to Comet 46P/Wirtanen, it is especially important to understand the processes responsible for the evolution of a cometary nucleus. This can be of key importance to a successful landing on the nucleus and further interpretation of the results of the mission. This work is intended primarily to estimate how quickly the process of grain sintering can modify the outer part of the nucleus. Other effects, such as crystallization of water ice, are, however, also taken into account. The simulation is performed for the period 1944 to 2016 taking into account the orbit of the comet perturbed by planets and by nongravitational effects. The numerical procedure used to simulate the evolution of the material texture and temperature distribution below the dust layer is based on the self-consistent model of the thermal and structural evolution of an initially homogeneous ice-dust mixture. The original model is, however, significantly extended. The present analysis includes the possible presence of amorphous water ice and other, nonwater volatiles. They are assumed to be initially trapped in amorphous water ice. It was found that a cohesive layer from about 1 m to about 10 m thick can be formed, depending on the size of the ice grains and the properties of the dust mantle.

  17. Comet 46P/Wirtanen: evolution of the subsurface layer

    NASA Astrophysics Data System (ADS)

    Kossacki, K. J.; Szutowicz, S.; Leliwa-Kopystynski, J.

    1998-09-01

    The cometary nuclei are composed mostly of water ice and mineral grains. Volatiles sublimate however when a comet passes near the Sun, leading to the formation of a dust layer covering the nucleus. Various other metamorphic processes are also predicted to modify the subsurface layer of the nucleus. Consequently, it should become stratified and more cohesive than initially. At present, due to the preparation of the mission Rosetta to the comet 46P/Wirtanen it is especially important to understand the processes responsible for the evolution of a cometary nucleus. This can be of key importance for the successful landing on the nucleus and further interpretation of the results of the mission. This work is mostly intended to estimate how quickly the process of grain sintering could modify the outer part of nucleus. The other effects, like crystallization of water ice are however also taken into account. The simulation is performed for the time period from 1948 to 2016. The orbit of the comet is calculated according to the forced precession model. The evolution of the material texture and temperature distribution below the dust layer is simulated according to the selfconsistent model of the thermal and structural evolution of an initially homogeneous ice--dust mixture. The present analysis includes the presence of amorphous water ice and other, non-water volatiles. They are assumed initially trapped in amorphous water ice. It is found, that the cohesive layer from about one meter up to about ten meters thick can be formed, depending on the size of ice grains and the properties of the dust mantle.

  18. Morphology of comet Churyumov-Gerasimenko in its 1969--1970 apparition

    NASA Astrophysics Data System (ADS)

    Churyumov, K.; Mozgova, A.; Kleshchonok, V.

    2014-07-01

    The short-period comet Churyumov-Gerasimenko or 67P was discovered by the Kyiv astronomers Klim Churyumov and Svitlana Gerasimenko on October 22, 1969, on the basis of five photographic plates exposed with the help of the 50-cm Maksutov reflector of the Alma-Ata Astrophysical Institute on 9, 11, and 21 Sept. 1969. The first 5 precise positions of the comet were sent to Dr. Brian Marsden, who showed it was a new comet. The comet had an apparent magnitude of 13 and a faint tail about 1 arcmin in length at the position angle 280°. Over the entire period of our observations from Sept. 9, 1969 to March 1, 1970, the comet had a narrow, straight tail, probably of type I. Its length ranged from 1' to 11'. On November 16, the comet had a fan-like tail. Some characteristics related to the structure of the comet are determined and discussed: d, the diameter of the coma; P, the position angle of the tail; and, s, the length of the tail. The tail axis deviated from the prolonged radius vector by up to the average angle ˜ 6°, during Nov. 17 -- Dec. 11, 1969, and by up to the average angle ˜ 21° during Dec. 16, 1969 -- March 1, 1970. This fact tells probably about the decrease of the speed of the solar wind and the decrease of the interaction between the solar wind and the plasma tail of the comet. Rosetta, a European space vehicle was launched on March 2, 2004 from Kourou to visit the icy nucleus of the short-period comet Churyumov-Gerasimenko . On Jan. 20, 2014, after 10 years of flight and 31-month sleep, Rosetta was woken up successfully and will now approach the icy nucleus of comet Churyumov-Gerasimenko and pass into orbit around the cometary nucleus. In Nov. 2014, the Philae probe will be sent from Rosetta to the nucleus of comet 67P to study relict matter from the era of Solar System formation.

  19. The volatile composition of comets as inferred from gas production

    NASA Astrophysics Data System (ADS)

    McKay, Adam Joseph

    Comets are small (1-10 km in radius) icy objects that orbit the Sun on highly eccentric orbits. The composition of comets has been relatively unalterred since their formation 4.5 billion years ago due to their small size and their cold storage in the Kuiper Belt and Oort Cloud. This makes comets "fossils" that can be studied in order to understand the physical conditions and composition of our Solar System during its infancy. Specifically, studying the volatile (ice) composition of comets can place constraints on molecule formation during the planetary formation stage and volatile transport to the inner Solar System. However, for most comets we must infer the volatile composition of the nucleus from gas present in the coma. The composition of the coma is alterred by physical and chemical processes, so the composition of the coma does not exactly reflect that of the nucleus. In this thesis we present analysis of observations of comets 103P/Hartley and C/2009 P1 Garradd in an effort to understand the physical and chemical processes operating in cometary comae. We obtained optical and NIR spectra in an effort to understand the gas production of comets Hartley and Garradd. We employed the ARCES instrument mounted on the ARC 3.5-meter telescope at Apache Point Observatory in Sunspot, NM to acquire optical spectra, while we used the CSHELL instrument mounted on NASA IRTF on Mauna Kea in Hawaii to acquire NIR spectra. We started our analysis with studies of atomic oxygen using the optical spectra and of CO and H2O using the NIR spectra. Specifically, the 5577 A, 6300, and 6300 A lines can potentially used as a proxy for CO2 in comets, which is very imporant because CO2 cannot be observed from the ground directly. Our analysis of the oxygen lines in several comets confirms that analysis of the oxygen line intensities can be employed to obtain quantitative measurements of CO2 in comets, though the accuracy of this method still needs to be firmly established. We also

  20. Early evolution of comet 67P studied with the RPC-LAP onboard Rosetta

    NASA Astrophysics Data System (ADS)

    Miloch, Wojciech; Edberg, Niklas J. T.; Eriksson, Anders I.; Yang, Lei; Paulsson, Joakim J. P.; Wedlund, Cyril Simon; Odelstad, Elias

    2016-07-01

    The Rosetta mission provides the in-situ measurements of a comet that are closest to a comet's aphelion ever made. The Rosetta Plasma Consortium (RPC) is a set of five instruments on board the spacecraft that specialise in the measurements of the plasma environment of comet 67P. One of the instruments is RPC-LAP, which consists of two Langmuir Probes and can measure the density, temperature, and flow speed of the plasma in the vicinity of the comet. At the early stage of the Rosetta mission, when the spacecraft is far from the nucleus of comet 67P, the ion part of the current-voltage characteristics of RPC-LAP1 is dominated by the photoemission current which surpasses the currents from the dilute solar wind plasma. As Rosetta starts orbiting around the nucleus in September 2014, LAP1 picks up signatures of local plasma density enhancements corresponding to variations of water-group ions observed in the vicinity of the comet. With the help of current-voltage characteristics and the spacecraft potential, we identify and characterise in space and time the entering of this coma-dominated plasma. In particular we determine the transition for entering the ion dominated region characterised by the 6-hour variations in the local plasma density due to the comet rotation. This transition manifests as a steep gradient in the density with respect to the distance to the comet nucleus. We discuss these RPC-LAP results together with the corresponding measurements by other instruments to provide a comprehensive picture of the transition.

  1. COMETARY VOLATILES AND THE ORIGIN OF COMETS

    SciTech Connect

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

    2012-10-10

    We describe recent results on the CO/CO{sub 2}/H{sub 2}O composition of comets together with a survey of older literature (primarily for CO/H{sub 2}O) and compare these with models of the protoplanetary disk. Even with the currently small sample, there is a wide dispersion in abundance ratios and little if any systematic difference between Jupiter-family comets (JFCs) and long-period and Halley-type comets (LPCs and HTCs). We argue that the cometary observations require reactions on grain surfaces to convert CO to CO{sub 2} and also require formation of all types of comets in largely, but not entirely, overlapping regions, probably between the CO and CO{sub 2} snow lines. Any difference in the regions of formation is in the opposite direction from the classical picture with the JFCs having formed closer to the Sun than the LPCs. In the classical picture, the LPCs formed in the region of the giant planets and the JFCs formed in the Kuiper Belt. However, these data suggest, consistent with suggestions on dynamical grounds, that the JFCs and LPCs formed in largely overlapping regions where the giant planets are today and with JFCs on average forming slightly closer to the Sun than did the LPCs. Presumably at least the JFCs passed through the scattered disk on their way to their present dynamical family.

  2. Comet Tempel 1 Went Back to Sleep

    NASA Astrophysics Data System (ADS)

    2005-07-01

    after the impact, the morphology of Comet Tempel 1 had changed, with the appearance of a new plume-like structure, produced by matter being ejected with a speed of about 700 to 1000 km/h (see ESO PR Photo 23/05). This structure, however, diffused away in the following days, being more and more diluted and less visible, the comet taking again the appearance it had before the impact. Further images obtained with, among others, the adaptive optics NACO instrument on the Very Large Telescope, showed the same jets that were visible prior to impact, demonstrating that the comet activity survived widely unaffected by the spacecraft crash. The study of the gas in Comet Tempel 1 (see "Looking for Molecules"), made with UVES on Kueyen (UT2 of the VLT), reveals a small flux increase the first night following the impact. At that time, more than 17 hours after the impact, the ejected matter was fading away but still measurable thanks to the large light collecting power of the VLT. The data accumulated during 10 nights around the impact have provided the astronomers with the best ever time series of optical spectra of a Jupiter Family comet, with a total of more than 40 hours of exposure time. This unique data set has already allowed the astronomers to characterize the normal gas activity of the comet and also to detect, to their own surprise, an active region. This active region is not related to the impact as it was also detected in data collected in June. It shows up about every 41 hours, the rotation period of the comet nucleus determined by the Deep Impact spacecraft. Exciting measurements of the detailed chemical composition (such as the isotopic ratios) of the material released by the impact as well as the one coming from that source will be performed by the astronomers in the next weeks and months. Further spectropolarimetric observations with FORS1 have confirmed the surface of the comet to be rather evolved - as expected - but more importantly, that the dust is not coming

  3. Comparison of the spectral peculiarities of the selected Jupiter-family and Oort Cloud comets

    NASA Astrophysics Data System (ADS)

    Ponomarenko, V.; Churyumov, K.; Kleshchonok, V.

    2014-07-01

    The results of the observations and study of the middle-resolution optical spectra (λ/ Δλ≈1500 and λ/ Δλ≈15000) of comets are presented. The investigated objects are separated into two types: the Jupiter-family comets (81P/Wild 2, 103P/Hartley 2) and the comets of the Oort cloud (C/2007 N3 (Lulin), C/2009 K5 (McNaught) and C/2009 P1 (Garradd)). The spectra were obtained with the echelle spectrograph and with the slit spectrograph installed on the 2-m Zeiss reflector of the High-mountain astronomical station of Institute of Astronomy of Russian Academy of Sciences and Main Astronomical Observatory of National Academy of Sciences of Ukraine at Terskol in 2009--2011. The comparative analysis of the spectral peculiarities of the two types of selected comets is presented. The energy distributions in the spectra for the near-nucleus regions of comets are built and a detailed identification of the spectral emission lines in the spectra is made. The physical parameters of the neutral comas of the comets (velocities of gas expansion, lifetimes of molecules C_2, C_3, and CN, and other parameters) are calculated using the Shulman's and Haser's models. The luminescent cometary continuum level (nonsolar origin) in the spectra of comets is detected. The parameters of the luminescent continuum are obtained. The substances that are luminophors are proposed. The peculiarities of the luminescent continuum of these comets are discussed.

  4. Compositional homogeneity in the fragmented comet 73P/Schwassmann-Wachmann 3.

    PubMed

    Dello Russo, N; Vervack, R J; Weaver, H A; Biver, N; Bockelée-Morvan, D; Crovisier, J; Lisse, C M

    2007-07-12

    The remarkable compositional diversity of volatile ices within comets can plausibly be attributed to several factors, including differences in the chemical, thermal and radiation environments in comet-forming regions, chemical evolution during their long storage in reservoirs far from the Sun, and thermal processing by the Sun after removal from these reservoirs. To determine the relevance of these factors, measurements of the chemistry as a function of depth in cometary nuclei are critical. Fragmenting comets expose formerly buried material, but observational constraints have in the past limited the ability to assess the importance of formative conditions and the effects of evolutionary processes on measured composition. Here we report the chemical composition of two distinct fragments of 73P/Schwassmann-Wachmann 3. The fragments are remarkably similar in composition, in marked contrast to the chemical diversity within the overall comet population and contrary to the expectation that short-period comets should show strong compositional variation with depth in the nucleus owing to evolutionary processing from numerous close passages to the Sun. Comet 73P/Schwassmann-Wachmann 3 is also depleted in the most volatile ices compared to other comets, suggesting that the depleted carbon-chain chemistry seen in some comets from the Kuiper belt reservoir is primordial and not evolutionary. PMID:17625560

  5. Comments on the Rotational State and Non-Gravitational Forces of Comet 46/WIRTANEN. Revised

    NASA Technical Reports Server (NTRS)

    Samarasinha, Nalin H.; Mueller, Beatrice E. A.; Belton, Michael J. S.

    1995-01-01

    We apply our experience of modeling the rotational state and non-gravitational forces of comet 1 P/Halley and other comets to comet 46P/Wirtanen. While the paucity of physical data on 46P/Wirtanen makes this process somewhat speculative, this comet's place as target for the important Rosetta mission gives significance to such a study. Our arguments are based on the summary of observational data provided by Jorda and Rickman (1995) and a comparative study of the behavior of other periodic comets. We find 46P/Wirtanen to have a level of surface activity relative to its mass that is dynamically more akin to that found in comet 1 P/Halley than in a typical periodic comet. We show through an illustrative numerical example that this apparent fact should likely lead to an excited spin state for this comet and that significant changes in the spin period could occur in a single pass through perihelion. We argue that the available observations are not sufficient to substantiate the claim of Jorda and Rickman (1995) that the nucleus is undergoing retrograde rotation and it is possible that the rotation is either prograde as well as retrograde. The substantial requirements that must be placed on any future observing program necessary to determine the precise rotational state are outlined. We advocate an extended (approx. two month) southern hemisphere observing campaign to determine the nuclear rotational state in 1996 if possible before activity turns on.

  6. The combined SOHO-STEREO dataset: Simultaneous observations of comets from multiple vantage points

    NASA Astrophysics Data System (ADS)

    Knight, M.; Begun, J.; Kelley, M.; Battams, K.; A'Hearn, M.

    2014-07-01

    The set of comets observed by Solar and Heliospheric Observatory (SOHO) and Solar-TErrestrial RElations Observatory (STEREO) provides a large (>2500 comets) and unique database for studying cometary properties. Sungrazing comets are discovered in SOHO or STEREO images on average every few days, with individual comets typically observable for up to a few days. We compiled photometry of more than 20 comets observed simultaneously by the same telescope and filter on both STEREO spacecraft to construct the first dust scattering phase function ever directly computed from simultaneous observations of the same object from two vantage points, thus removing uncertainty caused by changing heliocentric distance between observations. The collective dust scattering phase function spans phase angles from 28--153 deg and agrees reasonably well with the theoretical curve from [1]. However, individual comets deviate from the predicted curve by varying amounts during their apparition. This may suggest that the dust properties of individual comets change on the timescale of hours due to the dramatically different heliocentric distance or that the number of dust grains in the coma is changing due to nucleus activity, rotation, and/or erosion. We have also begun a study of the dust tails of selected well-observed comets in our database. This project utilizes the 3-D aspects of the combined SOHO and STEREO dataset to constrain the dust properties and time of release better than is possible with observations from a single location. We will present ongoing results of these investigations and place them into the wider context of sungrazing comet studies, notably by comparison with SOHO and STEREO observations of comet C/2012 S1 ISON [2], the most extensively observed sungrazing comet in history.

  7. Comets, Asteroids, and the Origin of the Biosphere

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.

    2006-01-01

    During the past few decades, the role of comets in the delivery of water, organics, and prebiotic chemicals to the Biosphere of Earth during the Hadean (4.5-3.8 Ga) period of heavy bombardment has become more widely accepted. However comets are still largely regarded as frigid, pristine bodies of protosolar nebula material that are entirely devoid of liquid water and consequently unsuitable for life in any form. Complex organic compounds have been observed comets and on the water rich asteroid 1998 KY26, which has color and radar reflectivity similar to the carbonaceous meteorites. Near infrared observations have indicated the presence of crystalline water ice and ammonia hydrate on the large Kuiper Belt object (50000) Quaoar with resurfacing that may indicate cryovolcanic outgassing and the Cassini spacecraft has detected water-ice geysers on Saturn s moon Enceladus. Spacecraft observations of the chemical compositions and characteristics of the nuclei of several comets (Halley, Borrelly, Wild 2, and Tempel 1) have now firmly established that comets contain a suite of complex organic chemicals; water is the predominant volatile; and that extremely high temperatures (approx.350-400 K) can be reached on the surface of the very black (albedo-0.03) nuclei when the comets are with 1.5 AU from the Sun. Impact craters and pinnacles observed on comet Wild 2 suggest a thick crust and episodic outbursts and jets observed on the nuclei of several comets are interpreted as indications that localized regimes of liquid water and water vapor can periodically exist beneath the crust of some comets. The Deep Impact observations indicate that the temperature on the nucleus of of comet Tempel 1 at 1.5 AU varied from 330K on the sunlit side to a minimum of 280+/-8 K. It is interesting that even the coldest region of the comet surface was slightly above the ice/liquid water phase transition temperature. These results suggest that pools and films of liquid water can exist in a wide

  8. Post-perihelion brightening of Halley's Comet: A case of nuclear summer

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.

    1986-01-01

    Increased brightness and gas production rates for Halley's comet after perihelion are explained as a result of seasonal effects on an obliquely rotating nucleus. The highly eccentric cometary orbit causes a rapid change in solar declination as the comet rounds perihelion, resulting in drastic changes in the insolation reaching the Northern and Southern Hemispheres of the nucleus. The rapid heating of the Northern Hemisphere post-perihelion likely results in substantial cracking of the non-volatile surface crust due to thermal stresses, exposing areas of fresh volatile ices. The orientation of the triaxial ellipsoid nucleus may also play a role in exposing more surface area to continuous sunlight and sublimation after perihelion. Post-perihelion brightening models based on heat flow and storage in sub-surface layers of the nucleus pre-perihelion are likely not viable because of the low thermal conductivities of porous, low density cometary surface materials.

  9. The composition of comets

    NASA Technical Reports Server (NTRS)

    Jessberger, E. K.; Kissel, J.; Rahe, J.

    1989-01-01

    The present discussion of recent studies concerning cometary composition gives attention to the results obtained by in situ measurements of Comet Halley's dust composition by Vega 1's impact mass spectrometer, which discovered a mineral fraction that appears to be CI chondritic, as well as an organic fraction consisting of highly unsaturated hydrocarbons. The mineral fraction of comets appears to form a core that is embedded in essentially organic material; the spectroscopic invisibility of carbon is due to its presence in the cometary dust. The mass of most dust particles is found to be in the 10 to the -12th to 10 to the -14th g range. A considerable fraction of the dust grains serves as an extended source of gas in the inner coma.

  10. Diatoms in comets

    NASA Technical Reports Server (NTRS)

    Hoover, R.; Hoyle, F.; Wallis, M. K.; Wickramasinghe, N. C.

    1986-01-01

    The fossil record of the microscopic algae classified as diatoms suggests they were injected to earth at the Cretaceous boundary. Not only could diatoms remain viable in the cometary environment, but also many species might replicate in illuminated surface layers or early interior layers of cometary ice. Presumably they reached the solar system on an interstellar comet as an already-evolved assemblage of organisms. Diatoms might cause color changes to comet nuclei while their outgassing decays and revives around highly elliptical orbits. Just as for interstellar absorption, high-resolution IR observations are capable of distinguishing whether the 10-micron feature arises from siliceous diatom material or mineral silicates. The 10-30-micron band and the UV 220-nm region can also provide evidence of biological material.

  11. Physical properties of asteroids in comet-like orbits in the infrared asteroidal survey catalogs

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Ishiguro, M.; Usui, F.

    2014-07-01

    Dormant comet and Infrared Asteroidal Survey Catalogs. Comet nucleus is a solid body consisting of dark refractory material and ice. Cometary volatiles sublimate from subsurface layer by solar heating, leaving behind large dust grains on the surface. Eventually, the appearance could turn into asteroidal rather than cometary. It is, therefore, expected that there would be ''dormant comets'' in the list of known asteroids. Over past decade, several ground-based studies have been performed to dig out such dormant comets. One common approach is applying a combination of optical and dynamical properties learned from active comet nucleus to the list of known asteroids. Typical comet nucleus has (i) Tisserand parameter with respect to Jupiter, T_{J}<3, (ii) low geometric albedo, p_{v}<0.1 and (iii) reddish or neutral spectra, similar to P, D, C-type asteroids. Following past ground-based surveys, infrared space missions gave us an opportunity to work on further study of dormant comets. To the present, three infrared asteroidal catalogs taken with IRAS[1], AKARI[2] and WISE[3] are available, providing information of sizes and albedos which are useful to study the physical properties of dormant comets as well as asteroids. Usui et al. (2014) merged three infrared asteroidal catalogs with valid sizes and albedos into single catalog, what they called I-A-W[4]. We applied a huge dataset of asteroids in I-A-W to investigate the physical properties of asteroids in comet-like orbits (ACOs, whose orbits satisfy Q>4.5 au and T_{J}<3). Here we present a study of ACOs in infrared asteroidal catalogs taken with AKARI, IRAS and WISE. In this presentation, we aim to introduce albedo and size properties of ACOs in infrared asteroidal survey catalogs, in combination with orbital and spectral properties from literature. Results and Implications. We summarize our finding and implication as followings: - are 123 ACOs (Q>4.5 au and T_J<3) in I-A-W catalog after rejection of objects with large

  12. Several Jets and a Crater on Comet Borrelly

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This image, taken by Deep Space 1 on September 22, 2001, has been enhanced to reveal dust being ejected from the nucleus of comet Borrelly. As a result, the nucleus, which is about eight kilometers (about five miles) long, is bright white in the image. The main dust jet is directed towards the bottom left of the frame, around 35 degrees away from the comet-Sun line. The jet emerges as actually comprised of at least three smaller features. This active region as a whole is at least three kilometers (less than two miles) long.

    Another, smaller, jet feature is seen on the tip of the nucleus on the lower right-hand limb. Dust also seems to be ejected from there into the night-side hemisphere, probably from the dayside hemisphere. The expansion of the gas and dust mixture into the vacuum of space has swept some material around the body of the nucleus so that it appears above the night-side hemisphere. The night-side of the nucleus could not be seen, of course.

    The line between day and night on the comet is towards the upper right. This representation shows a faint ring of brightness separated from the terminator by a dark, unlit area. It is possible that this is a crater rim, seen in grazing illumination, which is just about to cross into darkness as the comet rotates. The direction to the Sun is directly downwards.

    Deep Space 1 completed its primary mission testing ion propulsion and 11 other advanced, high-risk technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to undertake this chancy but exciting, and ultimately successful, encounter with the comet. More information can be found on the Deep Space 1 home page at http://nmp.jpl.nasa.gov/ds1/ .

    Deep Space 1 was launched in October 1998 as part of NASA's New Millennium Program, which is managed by JPL for NASA's Office of Space Science, Washington, D.C. The California Institute of Technology manages JPL for NASA.

  13. The Molecular Composition of Comet C/2007 W1 (Boattini): Evidence of a Peculiar Outgassing and a Rich Chemistry

    NASA Technical Reports Server (NTRS)

    Villanueva, G. L.; Mumma, M. J.; DiSanti, M. A.; Bonev, B. P.; Gibb, E. L.; Magee-Sauer, K.; Blake, G. A.; Salyk, C.

    2011-01-01

    We measured the chemical composition of Comet C/2007 W1 (Boattini) using the long-slit echelle grating spectrograph at Keck-2 (NIRSPEC) on 2008 July 9 and 10. We sampled 11 volatile species (H2O, OH*, C2H6, CH3OH, H2CO, CH4, HCN, C2H2, NH3, NH2, and CO), and retrieved three important cosmogonic indicators: the ortho-para ratios of H2O and CH4, and an upper-limit for the D/H ratio in water. The abundance ratios of almost all trace volatiles (relative to water) are among the highest ever observed in a comet. The comet also revealed a complex outgassing pattern, with some volatiles (the polar species H2O and CH3OH) presenting very asymmetric spatial profiles (extended in the anti-sunward hemisphere), while others (e.g., C2H6 and HCN) showed particularly symmetric profiles. We present emission profiles measured along the Sun-comet line for all observed volatiles, and discuss different production scenarios needed to explain them. We interpret the emission profiles in terms of release from two distinct moieties of ice, the first being clumps of mixed ice and dust released from the nucleus into the sunward hemisphere. The second moiety considered is very small grains of nearly pure polar ice (water and methanol, without dark material or apolar volatiles). Such grains would sublimate only very slowly, and could be swept into the anti-sunward hemisphere by radiation pressure and solar-actuated non-gravitational jet forces, thus providing an extended source in the anti-sunward hemisphere.

  14. IUE observations of faint comets

    NASA Astrophysics Data System (ADS)

    Weaver, H. A.; Feldman, P. D.; Festou, M.; A'Hearn, M. F.; Keller, H. U.

    1981-09-01

    Ultraviolet spectra of seven comets taken with the same instrument are given. The comets P/Encke (1980), P/Tuttle (1980 h), P/Stephan-Oterma (1980 g