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Sample records for comet nucleus samples

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Current trajectory options for a comet nucleus sample return mission

    NASA Astrophysics Data System (ADS)

    Sauer, Carl G., Jr.

    1992-08-01

    A summary of the current trajectory options available for the ESA comet nucleus sample return mission, Rosetta, is presented. These options include direct trajectories, delta-V-EGA trajectories using a Titan IV/Centaur launch vehicle with upgraded solid rocket motors, a trajectory involving a gravity assist of the earth (VEGA) prior to comet rendezvous, and one involving an additional gravity assist of the earth (VEEGA). Other propulsion options proposed and discussed are solar electric propulsion/ballistic trajectory modes and nuclear electric propulsion trajectory modes. Tables of performance data for each of these trajectory options are given.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Reality of comet nucleus.

    NASA Technical Reports Server (NTRS)

    Lyttleton, R. A.

    1972-01-01

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

  18. Aerocapture guidance and navigation for the Rosetta Comet Nucleus Sample Return Mission

    NASA Astrophysics Data System (ADS)

    Serrano-Martinez, J. B.; Hechler, M.

    The aerocapture/reentry phase of the Comet Nucleus Sample Return Mission Rosetta when returning from the Comet back to earth is discussed. The guidance and navigation process for a guided atmospheric entry to ground from an entry velocity of over 15 km/s has been simulated and the feasibility of such an entry at an entry angle of -10.5 deg, using an Apollo shape vehicle and guidance methods similar to those used for Apollo and the Shuttle Orbiter, has been demonstrated. Landing precision of less than 10 km at accelerations below 20 g can be reached. Critical areas of system design like the center of gravity location of the entry vehicle are addressed.

  19. 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.

  20. Comet Odyssey: Comet Surface Sample Return

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  1. 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.

  2. 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.

  3. 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.

  4. Retrieving samples from comet nuclei

    NASA Astrophysics Data System (ADS)

    Stuhlinger, Ernst; Bassner, Helmut; Fechtig, Hugo; Igenbergs, Eduard; Kuczera, Heribert; Loeb, Horst; Schobert, Detlef

    1987-09-01

    A comet nucleus sampling scenario is proposed. Material samples for analysis in earth-based laboratories should be collected continuously to a depth of 3 m below the surface, and at a solar distance of at least 2.5 AU where the comet surface is inactive. The spacecraft is propelled by chemical and electric thrusters. While hovering above the comet nucleus at an altitude of 500 to 1000 m, the spacecraft will dispatch a rotating drill on a tether. The drill pipe will be driven into the nucleus by a rocket-powered reaction wheel. The inner pipe of the drill, when filled with cometary material, will be withdrawn by the tether, stored on the spacecraft, and transported back to Earth.

  5. 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

  6. Dynamical evolution of comet nucleus rotation

    NASA Astrophysics Data System (ADS)

    Scheeres, D. J.; Sidorenko, V. V.; Neishtadt, A. I.; Vasiliev, A. A.

    2001-11-01

    The rotational dynamics of outgassing cometary nuclei are investigated analytically using dynamical systems theory. We develop a general theory for the averaged evolution of a comet nucleus rotation state assuming that the nucleus is a spheroid (either prolate or oblate) and that the outgassing torques are a function of solar insolation and heliocentric distance. The resulting solutions are a function of the comet outgassing properties, its heliocentric orbit, and the assumed distribution of active regions on its surface. We find that the long-term evolution of the comet nucleus rotation is a strong function of the distribution of active regions over its surface. Specifically, we find that a comet nucleus with a uniformly active surface will tend towards a rotation state with a nutation angle of ~ 55 degrees and an angular momentum perpendicular to the sun-perihelion direction. Conversely, a comet nucleus with an isolated active region will tend towards a zero nutation angle with its symmetry axis and angular momentum aligned parallel to the sun-perihelion direction. For active surface regions between these extremes we find 4 qualitatively different dynamical outcomes. In all cases, the theory predicts that the comet nucleus angular momentum will have a secular increase, a phenomenon that could contribute to nucleus splitting of active comets. These results can be used to discriminate between competing theories of comet outgassing based on a nucelus' rotation state. They also allow for a range of plausible a priori constraints to be placed on a comet's rotation state to aid in the interpretation of its outgassing structure. This work was supported by the NASA JURRISS program under Grant NAG5-8715. AIN, AAV and VVS acknowledge support from Russian Foundation for Basic research via Grants 00-01-00538 and 00-01-0174 respectively. DJS acknowledges support from the PG&G program via Grant NAG5-9017.

  7. 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.

  8. Odyssey Comet Nucleus Orbiter: The Next Step in Cometary Exploration

    NASA Technical Reports Server (NTRS)

    Weissman, P. R.; Nilsen, E. N.; Smythe, W. D.; Marriott, J.; Reinert, R.

    2001-01-01

    Cometary nuclei are the most primitive bodies in the solar system, containing a cosmo-chemical record of the primordial solar nebula. Flyby missions to comets, such as those that encountered Comet Halley in 1986, provide a glimpse at this record. However, to study a cometary nucleus in detail requires a rendezvous mission, i.e., a nucleus orbiter. Only an orbiter provides the ability to map the entire nucleus surface at high resolution, to study the complex chemistry in the cometary coma and its variation with time, and to determine the mass and bulk density of the nucleus, key parameters in understanding how small bodies first formed in the solar nebula. A nucleus orbiter also provides the opportunity to sense the nucleus surface in preparation for more ambitious landing and sample return missions in the future. Additional information is contained in the original extended abstract.

  9. 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.

  10. Dynamical evolution of comet nucleus rotation

    NASA Astrophysics Data System (ADS)

    Scheeres, D. J.; Sidorenko, V. V.; Neishtadt, A. I.; Vasiliev, A. A.

    2002-09-01

    The rotational dynamics of outgassing cometary nuclei are investigated analytically. We develop a general theory for the evolution of a comet nucleus' rotation state using averaging theory and assuming that the outgassing torques are a function of solar insolation and heliocentric distance. The resulting solutions are a function of the nucleus inertia ellipsoid, its outgassing properties, its heliocentric orbit, and the assumed distribution of active regions on its surface. We find that the long-term evolution of the comet nucleus rotation is a strong function of the distribution of active regions over its surface. In particular, we find that nuclei with nearly axisymmetric inertia ellipsoids and a uniformly active surface will tend towards a rotation state that has a nutation angle of ~ 55 degrees and its angular momentum perpendicular to the sun-perihelion direction. If such a comet nucleus has only one isolated active region, it will tend towards a zero nutation angle with its approximate symmetry axis and rotational angular momentum aligned parallel to the sun-perihelion direction. In the general case for an inertia ellipsoid that is not close to being axisymmetric we find a much richer set of possible steady-state solutions that are stable, ranging from rotation about the maximum moment of the inertia axis, to SAM and LAM non-principal axis rotation states. The resulting stable rotation states are a strong function of outgassing activity distribution, which we show using a simplified model of the comet Halley nucleus. Also, we demonstrate that comet Borrely observations are consistent with a stable rotation state. Our results can be used to discriminate between competing theories of comet outgassing based on a nucelus' rotation state. They also allow for a range of plausible a priori constraints to be placed on a comet's rotation state to aid in the interpretation of its outgassing structure. This work was supported by the NASA JURRISS program under Grant NAG5

  11. Nucleus morphology of Comet Halley

    NASA Technical Reports Server (NTRS)

    Reitsema, H. J.; Delamere, W. A.; Huebner, W. F.; Keller, H. U.; Schmidt, W. K. H.; Wilhelm, K.; Schmidt, H. U.; Whipple, Fred L.

    1986-01-01

    Images obtained by the Halley multicolor camera were used to determine the projected size and shape of the nucleus. The location of the terminator and numerous surface features were determined. There is good correlation between the brightest surface features and the dust jets; however, many bright features are seen which are not associated with jets. Most of the observed features are circular and appear to be related to surface elevation. The angularity of the terminator gives an indication of the three-dimensional structure of the face which was observed.

  12. 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.

  13. Dust activity of Comet Halley's nucleus

    NASA Technical Reports Server (NTRS)

    Keller, H. U.; Delamere, W. A.; Huebner, W. F.; Reitsema, H.; Schmidt, H. U.; Schmidt, W. K. H.; Whipple, Fred L.; Wilhelm, K.

    1986-01-01

    Images obtained by the Halley multicolor camera using the clear filter with a pass band from 300 to 1000 nm were used to study dust activity in the comet nucleus. Comparisons with ground based observations confirm that dust production towards the Sun increases in activity relative to the southern background source while the Giotto spacecraft was approaching. This is in agreement with the assumption that the sunward activity becomes stronger when the source rotates towards the Sun. Estimated dust column density is 90 billion/sqm, with optical thickness less than or = 0.3. Surface reflectivity is less than 1%, indicating a very rough surface with large fractions of shadowed areas.

  14. 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

  15. Surface Photometric Variation of Comet Borrelly's Nucleus

    NASA Astrophysics Data System (ADS)

    Li, J.; A'Hearn, M. F.; McFadden, L. A.

    2004-11-01

    Comet Borrelly was visited by Deep Space 1 in Sept. 2001 (Soderblom et al. 2004) The images of comet Borrelly's nucleus show large brightness variation over the surface even after the effect of shape is taken into account (Oberst et al. 2004, Kirk et al. 2004). It is not yet known whether this variation is caused by albedo variation (Oberst et al. 2004, Buratti et al. 2004) or the variation of other physical properties such as surface roughness (Kirk et al. 2004) or solar phase function. In our analysis, the disk-resolved images from the DS1 spacecraft (Soderblom et al. 2004) were used, coupled with the shape model of Borrelly's nucleus developed from stereo imaging (Oberst et al. 2004, Kirk et al. 2004), to fit the bidirectional reflectance as a function of local illumination and viewing geometry for individual terrains as defined by Britt et al. (2004). Results show that the surface reflectance variation is, contrary to previous interpretations, most likely due to the combination of albedo variation (a factor of 1.5) and the variation of the asymmetry factor (g) of the single-particle phase function. We find the roughness parameter (theta_bar) is <25o over the surface. The surface on Borrelly's nucleus can be highly back-scattering (g <= -0.7) for mottled terrain, and close to isotropic scattering (g -0.15) for smooth terrain, with single scattering albedo ranging from 0.05 to 0.07. This work is supported by NASA grant NNG04GA92G.

  16. 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

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

    SciTech Connect

    Sekanina, Z.

    1988-06-01

    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. 63 references.

  18. Near-nucleus photometry of comets using archived NEAT data

    NASA Astrophysics Data System (ADS)

    Hicks, Michael D.; Bambery, Raymond J.; Lawrence, Kenneth J.; Kollipara, Priya

    2007-06-01

    Though optimized to discover and track fast moving Near-Earth Objects (NEOs), the Near-Earth Asteroid Tracking (NEAT) survey dataset can be mined to obtain information on the comet population observed serendipitously during the asteroid survey. We have completed analysis of over 400 CCD images of comets obtained during the autonomous operations of two 1.2-m telescopes: the first on the summit of Haleakala on the Hawaiian island of Maui and the second on Palomar Mountain in southern California. Photometric calibrations of each frame were derived using background catalog stars and the near-nucleus comet photometry measured. We measured dust production and normalized magnitudes for the coma and nucleus in order to explore cometary activity and comet size-frequency distributions. Our data over an approximately two-year time frame (2001 August-2003 February) include 52 comets: 12 periodic, 19 numbered, and 21 non-periodic, obtained over a wide range of viewing geometries and helio/geocentric distances. Nuclear magnitudes were estimated for a subset of comets observed. We found that for low-activity comets ( Afρ<100 cm) our model gave reasonable estimates for nuclear size and magnitude. The slope of the cumulative luminosity function of our sample of low-activity comets was 0.33 ± 0.04, consistent with the slope we measured for the Jupiter-family cometary nuclei collected by Fernández et al. [Fernández, J.A., Tancredi, G., Rickman, H., Licandro, J., 1999. Astron. Astrophys. 392, 327-340] of 0.38 ± 0.02. Our slopes of the cumulative size distribution α=1.50±0.08 agree well with the slopes measured by Whitman et al. [Whitman, K., Morbidelli, A., Jedicke, R., 2006. Icarus 183, 101-114], Meech et al. [Meech, K.J., Hainaut, O.R., Marsden, B.G., 2004. Icarus 170, 463-491], Lowry et al. [Lowry, S.C., Fitzsimmons, A., Collander-Brown, S., 2003. Astron. Astrophys. 397, 329-343], and Weissman and Lowry [Weissman, P.R., Lowry, S.C., 2003. Lunar Planet. Sci. 34. Abstract 34].

  19. 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

  20. 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.

  1. Comet coma sample return instrument

    NASA Astrophysics Data System (ADS)

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

    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.

  2. Hubble Imaging of the Nucleus of Comet ISON

    NASA Astrophysics Data System (ADS)

    Lamy, Philippe

    2013-10-01

    Comet C/2012 S1 {ISON} is both a new "nearly isotropic" and a sungrazing comet with anoutstanding apparition in cycle 21, passing within 0.42 AU of the Earth.We propose a 12-orbit Hubble postperihelion investigation of this comet that will provide a detailed view of its nucleus originating from the Oort cloud and of the possible consequences of its very close approach to the Sun at a perihelion distance of 0.012471 AU such as fragmentation.We will determine the size, shape, rotational period, and color {UBVRI} ofthe nucleus of C/2012 S1 or of its fragment should disruption occurs. This passage of a new "nearly isotropic" comet very close tothe Earth offers a rare opportunity to investigate this population ofobjects, and we expect many other observatories to attempt detecting itsnucleus in the mid-infrared, millimetric and centimetric domains.Combining the Hubble results with those from other observatories shouldyield a comprehensive picture of this NIC that can be compared to thedetailed data collected on ecliptic comets {ECs} during the past 3decades. The differences and similarities between NICs and ECs shouldyield valuable insights into the origin and evolution of comets.

  3. Did Struve observe the nucleus of Halley's comet in 1835?

    NASA Astrophysics Data System (ADS)

    Wittmann, Axel D.

    During its apparition in 1835 Halley's comet reached its minimum distance from the earth (0.187 au) on 13 October in the constellation of Ursa Major. Telescopic visual observations were made, e.g., by F.W. Bessel at Königsberg and by F.G.W. Struve at Dorpat (Tartu). In particular a drawing made by Struve on 8 October of what he calls the `nucleus' and describes as a small, slightly yellowish glowing piece of coal of elongated shape bears such a striking resemblance to the images of Halley's nucleus obtained in 1986 by the Giotto spacecraft that it merits further examination: Could Struve, who had been using a 24.4 cm refractor at 254-fold magnification, possibly have observed the real nucleus? Closer examination shows that neither Struve's maximum possible resolution (0.13 arc seconds or 23 km at the comet), nor his measured size of the nucleus (160 x 400 km), nor his verbal description of the nucleus (as a bright object) support this idea: It rather seems that the term `nucleus' was used at the time for the brightest, innermost part of the coma. It is concluded that, nevertheless, Struve quite correctly envisaged the structure of the innermost coma, and to a considerable degree of accuracy anticipated the correct shape and structure of the nucleus (elongated, 1:2) and its localized sources of outstreaming gas.

  4. 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

  5. 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.

  6. Sampling the stuff of a comet

    NASA Astrophysics Data System (ADS)

    Knacke, R.

    1987-03-01

    The composition of the clouds around Comet Halley during its perihelion passage was examined using intercept spacecraft, IUE, ICE and Pioneer Venus spacecraft, and ground-based instruments. Spectral data showed that the dust emitted in jets was mainly carbon, hydrogen, oxygen and nitrogen (CHON), with additives of Fe, Si, and Mg. The C abundance is similar to that in the sun and in the galactic stellar abundances, which supports the model of comets as proto-stellar nebula material. The nucleus was observed to shed 16 tons of water per second, a rate which at times may have doubled. Noticeably absent from the spectra were CH4 lines, an absence common in interstellar clouds. The possibilities that the comet contains a large deuterium-hydrogen ratio and carbonaceous material are discussed.

  7. Autonomous nucleus tracking for comet/asteroid encounters: the Stardust example.

    NASA Astrophysics Data System (ADS)

    Bhaskaran, S.; Riedel, J. E.; Synnott, S. P.

    Stardust is a mission to fly by comet Wild-2 in early 2004 and return samples of the coma to Earth. During its 120 - 150 km flyby of the comet nucleus, a secondary science goal is to obtain images of the nucleus using the onboard navigation camera. Due to the 40 minute round-trip light time, ground processing of navigation data to update pointing information to maintain the nucleus in the camera field-of-view is impractical. Thus, a simple, reliable, and fast algorithm was developed to close the navigation loop onboard during encounter. The algorithm uses images of the nucleus during approach to update target relative state information. This involves centroiding on the image to obtain nucleus center-of-figure data and then processing the data through a Kalman filter to update the spacecraft, position and attitude. Monte Carlo simulations were then performed to test the algorithm. These simulations incorporated errors in spacecraft initial position and in attitude knowledge to provide a "truth" model which the filter must recover from. The results of the simulations proved that the algorithm was successful in maintaining the nucleus in the camera field-of-view assuming nominal values for the error sources. Even with worst case errors, the algorithm performed successfully in over 90% of the cases.

  8. 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

  9. 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

  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. Comets

    NASA Astrophysics Data System (ADS)

    Brownlee, D. E.

    2003-12-01

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

  12. Visible and infrared study of comet 2P/Encke's nucleus during its 2013 apparition

    NASA Astrophysics Data System (ADS)

    Fernandez, Y.; Mueller, B.; Samarasinha, N.; Woodney, L.; Abell, P.

    2014-07-01

    The 2013 apparition of comet 2P/Encke provided an opportunity to study the comet while it was relatively close to the Earth. The comet passed 0.48 au from the Earth on October 17, the closest such passage since 2003 and until 2030. We initiated a visible and infrared observational campaign for the apparition with the goal of further characterizing the physical, thermal, and rotational properties of the P/Encke nucleus. While thermal-emission data on the nucleus have been obtained in the past (e.g. [1--4]), observations in 2013 timed to coincide with an equator-on view afforded us the chance to have a rarely-seen vantage point of the nucleus. Low-resolution spectra over wavelengths from 0.7 to 2.5 μ m were obtained over four nights (UT Sept. 26, 28, 30, Oct. 1) that span all of the nucleus rotational longitudes. The spectra were acquired at the NASA Infrared Telescope Facility (IRTF) using its SpeX instrument, and they sample reflected sunlight at the short wavelengths and Wien-side thermal emission at the long wavelengths. We will present results on thermal inertia and albedo from a preliminary analysis of these data. We have shown through observations over the past 13 years that the rotation period of P/Encke's nucleus changes by about 4 minutes per orbit [5,6]. Furthermore, the typical lightcurve has the normal two-humped shape but with humps that have vastly different amplitudes (e.g., [7]). Thus, the equator-on view gave us the chance to further investigate P/Encke's rotation state and shape. We obtained visible-wavelength photometry of the nucleus in the R band at NASA/IRTF with the MORIS instrument on the aforementioned dates, at the NOAO Kitt Peak 2.1-meter telescope over UT Sept. 11, 12, 13, and 14, and at the CSUSB Murrillo Family Observatory 0.5-meter telescope over several dates in Sept. and Oct. [8]. The MORIS data in particular gave us the rotational context and absolute flux calibration for the spectra. We will present new, preliminary constraints on

  13. The Asymmetric Coma of Comets. I. Asymmetric Outgassing from the Nucleus of Comet 2P/Encke

    NASA Astrophysics Data System (ADS)

    Festou, M. C.; Barale, O.

    2000-06-01

    Very little is known about how outgassing regions are distributed over the nucleus of comets. In periodic comets, active regions are believed to be few and of small extent. Since periodic comets are notorious for their lack of (small) solid particles that efficiently scatter sunlight, we try to find traces of the existence of production sites by examining the morphology of the gas coma. We use a new coma model in which results from hydrodynamics calculations describing the inner coma are used as limit conditions for a collisionless description of the outer coma. The production pattern of the parent species mainly depends on the extent and location of the production region(s) and on the rotational state of the nucleus. Analyzing 1980 observations of comet 2P/Encke, we find that free emission from a single, small, active region located near the subsolar point of a nonrotating nucleus is excluded. But such an active region on a rotating nucleus produces well the observed coma morphology. Our data then allow us to determine the orientation of the comet spin axis and the cometocentric latitude of the source. Emission from a few small production regions spread over the sunward part of a nonrotating nucleus or emission at a very low rate from a larger subsolar area could also fit the data. Although we do not find a unique solution to our problem, the excellent quality of our fits indicates that our approach, if used with enough care, can provide a new tool to investigate the properties of comet nuclei when the coma is far from spherically symmetric and, ultimately, to study the effects of the nongravitational force that is acting on comet nuclei.

  14. Systematic random sampling of the comet assay.

    PubMed

    McArt, Darragh G; Wasson, Gillian R; McKerr, George; Saetzler, Kurt; Reed, Matt; Howard, C Vyvyan

    2009-07-01

    The comet assay is a technique used to quantify DNA damage and repair at a cellular level. In the assay, cells are embedded in agarose and the cellular content is stripped away leaving only the DNA trapped in an agarose cavity which can then be electrophoresed. The damaged DNA can enter the agarose and migrate while the undamaged DNA cannot and is retained. DNA damage is measured as the proportion of the migratory 'tail' DNA compared to the total DNA in the cell. The fundamental basis of these arbitrary values is obtained in the comet acquisition phase using fluorescence microscopy with a stoichiometric stain in tandem with image analysis software. Current methods deployed in such an acquisition are expected to be both objectively and randomly obtained. In this paper we examine the 'randomness' of the acquisition phase and suggest an alternative method that offers both objective and unbiased comet selection. In order to achieve this, we have adopted a survey sampling approach widely used in stereology, which offers a method of systematic random sampling (SRS). This is desirable as it offers an impartial and reproducible method of comet analysis that can be used both manually or automated. By making use of an unbiased sampling frame and using microscope verniers, we are able to increase the precision of estimates of DNA damage. Results obtained from a multiple-user pooled variation experiment showed that the SRS technique attained a lower variability than that of the traditional approach. The analysis of a single user with repetition experiment showed greater individual variances while not being detrimental to overall averages. This would suggest that the SRS method offers a better reflection of DNA damage for a given slide and also offers better user reproducibility.

  15. 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.

  16. Visible and Infrared Study of Comet 2P/Encke's Nucleus During Its 2013 Apparition

    NASA Astrophysics Data System (ADS)

    Fernandez, Yanga R.; Mueller, Beatrice E.; Samarasinha, Nalin H.; Woodney, Laura M.; Abell, Paul A.

    2014-11-01

    The 2013 apparition of comet 2P/Encke provided an opportunity to study the comet while it was relatively close to Earth (0.48 AU on October 17, the closest pass until 2030). We initiated a multiwavelength observing campaign for September and October with the goal of further characterizing the physical, thermal, and rotational properties of 2P's nucleus. Spectral observations were timed to coincide with an equator-on view of the nucleus, a rarely-seen vantage point compared to previous data (e.g. [1,2,3,4]). The spectra span both Wien-side thermal emission and reflected sunlight, covering 0.7 to 2.5 μm, and sample all of the nucleus's rotational longitudes. They were obtained using the SpeX instrument at the NASA Infrared Telescope Facility (IRTF). We will present results on thermal inertia and albedo from a preliminary analysis of these data. Visible observations over the past 13 years have shown that the rotation period of 2P's nucleus increases by ~4 minutes per orbit [5,6], and that the light curve has a two-humped shape but that the humps have quite different amplitudes (e.g. [7]). Thus the equator-on view gave us the chance to further investigate 2P's rotation state and shape. We used the CSUSB Murillo Family Observatory 0.5-meter telescope [8], the NOAO Kitt Peak 2.1-meter telescope, and the MORIS instrument at NASA/IRTF to obtain R-band, time-series photometry of the nucleus. We will present new, preliminary constraints on the secular changes in the nucleus's spin state and on the nucleus's shape based on these new data. We thank the allocation committees of the IRTF and NOAO telescopes for granting the time used for this project. References: [1] Y. R. Fernandez et al. 2000, Icarus 147, 145. [2] M. S. Kelley et al. 2006, ApJ 651, 1256. [3] Y. R. Fernandez et al. 2008, 40th Meeting of the DPS, #16.24. [4] P. Abell et al. 2009, 41st Meeting of the DPS, #20.02. [5] B. E. A. Mueller et al. 2008, 40th Meeting of the DPS, #16.25. [6] N. H. Samarasinha and B. E. A

  17. 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.

  18. 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.

  19. Comets

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  20. Formation of the dumbbell-like nucleus of a comet by sublimation

    NASA Astrophysics Data System (ADS)

    Vavilov, Dmitrii; Medvedev, Yurii; Zatitskiy, Pavel

    2016-10-01

    The nucleus of the comet 67P/Churyumov-Gerasimenko is an elongated body with a deep groove around the middle. There are also other comets that look like dumbbells (e.g. 103P/Hartley 2, 19P/Borrelly, 1P/Halley). Two most probable interpretations are discussed in the scientific society. The first hypothesis explains the creation of such an object as sticking of two cometesimals during the process of formation. The second one suggests that the sublimation process can change the nucleus shape and make a groove in the middle.In this work we consider the second hypothesis. It was assumed that the spin axis of the nucleus is perpendicular to the plane of the cometary orbit and that initially the nucleus shape is a sphere. Thus, the problem is represented as a differential equation, which describes the change of the cometary nucleus. We solved this equation analytically. It was shown that initially a convex cometary nucleus (e.g. a sphere), consisting of homogeneous material, can not be transformed into a dumbbell-like body by the influence of sublimation. However, assuming that the density in the centre of the nucleus is less than on the surface, a groove can arise on the equator of the cometary nucleus as a result of sublimation.

  1. Radiometric observations of the nucleus of Comet Halley

    NASA Technical Reports Server (NTRS)

    Delamere, W. A.; Reitsema, H. J.; Huebner, W. F.; Schmidt, H. U.; Keller, H. U.; Schmidt, W. K. H.; Wilhelm, K.; Whipple, Fred L.

    1986-01-01

    Images obtained by the Halley multicolor camera (HMC) were used to determine the surface brightness of the nucleus. Radiometric values of jet-free areas of the surface are presented and a range of possible surface brightness values are derived. These direct measures are compared with brightnesses derived from the size of the nucleus, as determined from HMC images, and ground-based observations obtained before the onset of coma activity.

  2. Spitzer Space Telescope Observations of the Nucleus of Comet 103P/Hartley 2

    NASA Astrophysics Data System (ADS)

    Lisse, C. M.; Fernandez, Y. R.; Reach, W. T.; Bauer, J. M.; A’Hearn, M. F.; Farnham, T. L.; Groussin, O.; Belton, M. J.; Meech, K. J.; Snodgrass, C. D.

    2009-09-01

    We have used the Spitzer Space Telescope InfraRed Spectrograph (IRS) 22-μm peakup array to observe thermal emission from the nucleus and trail of comet 103P/Hartley 2, the target of NASA’s Deep Impact Extended Investigation (DIXI). The comet was observed on UT 2008 August 12 and 13, while 5.5 AU from the Sun. We obtained two 200 frame sets of photometric imaging over a 2.7 hr period. To within the errors of the measurement, we find no detection of any temporal variation between the two images. The comet showed extended emission beyond a point source in the form of a faint trail directed along the comet’s antivelocity vector. After modeling and removing the trail emission, a NEATM model for the nuclear emission with beaming parameter of 0.95 ± 0.20 indicates a small effective radius for the nucleus of 0.57 ± 0.08 km and low geometric albedo 0.028 ± 0.009 (1σ). With this nucleus size and a water production rate of 3 × 1028 molecules s-1 at perihelion, we estimate that ∼100% of the surface area is actively emitting volatile material at perihelion. Reports of emission activity out to ∼5 AU support our finding of a highly active nuclear surface. Compared to Deep Impact’s first target, comet 9P/Tempel 1, Hartley 2’s nucleus is one-fifth as wide (and about one-hundredth the mass) while producing a similar amount of outgassing at perihelion with about 13 times the active surface fraction. Unlike Tempel 1, comet Hartley 2 should be highly susceptible to jet driven spin-up torques, and so could be rotating at a much higher frequency. Since the amplitude of nongravitational forces are surprisingly similar for both comets, close to the ensemble average for ecliptic comets, we conclude that comet Hartley 2 must have a much more isotropic pattern of time-averaged outgassing from its nuclear surface. Barring a catastrophic breakup or major fragmentation event, the comet should be able to survive up to another 100 apparitions (∼700 yr) at its current rate of

  3. A three-dimensional model of the nucleus of Comet Halley

    NASA Technical Reports Server (NTRS)

    Wilhelm, K.; Cosmovici, C. B.; Delamere, W. A.; Huebner, W. F.; Keller, H. U.; Reitsema, H.; Schmidt, H. U.; Whipple, Fred L.

    1986-01-01

    The nucleus of comet Halley was observed by the Halley Multicolor Camera (HMC) during the last minutes of the flyby sequence before reaching the point of closest approach. The phase angle change during the observational period was less than 17 deg, so HMC data can only define a two-dimensional contour of the nucleus at a certain time. The overall geometry during the HMC observations is outlined and the findings are related to information available from other sources at different times. The nucleus of the comet is described as a triaxial ellipsoid with major axes of 16, 10, and 9 km. The rotation axis is directed towards delta 1950 = -(40 + or - 5) deg and alpha 1950 = (50 + or - 10) deg. The rotation with a period of P = (54 + or - 1) is in a prograde sense with respect to the orbital motion.

  4. 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.

  5. The Nucleus of 10 Short-Period Comets

    NASA Astrophysics Data System (ADS)

    Lamy, P. L.; Toth, I.; Weaver, H. A.; Delahodde, C. E.; Jorda, L.; A'Hearn, M. F.

    2001-11-01

    We report on the successful detection and extensive characterization of the nuclei of 10 short-period comets with the Hubble Space Telescope: 47P/Ashbrook-Jackson, 61P/Shajn-Schaldach, 70P/Kojima, 74P/Smirnova-Chernikh, 76P/West-Kohoutek-Ikemura, 82P/Gehrels 3, 86P/Wild 3, 87P/Bus, 110P/Hartley 3, 147P/Kushida-Muramatsu. The observations were performed with the Planetary Camera of WFPC2 during cycle 9, between July 2000 and June 2001. Each comet was observed eight times over a time span of about 12 hours through different filters, up to three (V, R, I) for the brightest ones. The sizes were determined assuming a geometric albedo of 0.04 for the R band and a phase law of 0.04 mag/deg. We confirm our past findings that cometary nuclei are generally extremely small; the radius of 147P/Kushida-Muramatsu was only 0.13 km. We also present the results for the colors and the lightcurves of the nuclei and discuss the implications for their shape and rotational state. This work was supported by grants from the Universite de Provence, from C.N.E.S., C.N.R.S. (France), from the Hungarian Academy of Science and from NASA through grant HST-GO-08699.01-A from the STScI.

  6. Discovery of very fine dust near the nucleus of Comet Halley

    NASA Astrophysics Data System (ADS)

    Sagdeev, R. Z.; Evlanov, E. N.; Zubkov, B. V.; Prilutski, O. F.; Fomenkova, M. N.

    1990-08-01

    The analysis of spectra obtained with the PUMA mass analyzers on Vega 1 and 2 indicates that a large number of unidentified peaks may be connected with impacts of very fine dust particles in the mass range from 10 to the -17th to 10 to the -20th g. The mass flow of the tiny dust particles can be large as several percent of the total mass flow of dust from Comet Halley. The discovery of very fine dust particles in the Halley dust envelope is consistent with the view of the comet's nucleus as an aggregate of interstellar dust in which tiny particles are present.

  7. Data set generation and inversion simulation of radio waves propagating through a two-dimensional comet nucleus (CONSERT experiment)

    NASA Astrophysics Data System (ADS)

    Benna, M.; Piot, A.; Barriot, J.-P.; Kofman, W.

    2002-11-01

    To prepare the Comet Nucleus Sounding Experiment using Radio wave Transmission during the Rosetta mission, we study the electromagnetic wave propagation through a comet nucleus model and tomographic inversion in a two-dimensional setting. For the propagation, the Ray Tracing Method (RTM) is validated with respect to the Pseudo-Spectral Time Domain (PSTD) method. For the inverse problem, a Tikhonov-like inverse RTM method based on weak permittivity assumptions is used, with synthetic data derived from the PSTD algorithm. Reconstruction results show that the Consert data will permit a reliable tomography of the comet nucleus. Surface data will enhance the quality of the imaging.

  8. 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.

  9. 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

    2016-02-04

    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.

  10. 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.

  11. 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

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

    NASA Astrophysics Data System (ADS)

    Engrand, Cécile; Duprat, Jean; Bardin, Noémie; Dartois, Emmanuel; Leroux, Hugues; Quirico, Eric; Benzerara, Karim; Remusat, Laurent; Dobrică, Elena; Delauche, Lucie; Bradley, John; Ishii, Hope; Hilchenbach, Martin

    2016-10-01

    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. Analyses of dust particles from the Jupiter family comet 67P/Churyumov-Gerasimenko by the dust analyzers on Rosetta orbiter (COSIMA, GIADA, MIDAS) suggest a relationship to interplanetary dust/micrometeorites. A growing number of evidences highlights the existence of a continuum between asteroids and comets, already in the early history of the solar system.

  13. 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.

  14. High-resolution imaging studies of the near-nucleus regions of comets

    NASA Astrophysics Data System (ADS)

    Goldberg, B. A.; Slavin, J. A.; Halliday, I.; McIntosh, B. A.; Aikman, G. C. L.; Cook, A. F.

    1986-12-01

    High-resolution, calibrated images of the near-nucleus regions of Halley, Giacobini-Zinner (for ICE encounter) and additional comets displaying widely differing levels of activity were acquired with a CCD sensor at the Cassegrain focus of the 3.6 m Canada-France-Hawaii Telescope (CFHT). The International Halley Watch designated interference filters were used. Successful correlation of ICE magnetic field data with the optical images obtained with the CFHT on the night of encounter (11 Sept. 1985) primarily through the H2O(+) and neighboring continuum passbands and with 300 km spatial resolution provokes reinterpretation of the observed structure of cometary ion tails. The observations of Halley, limited by bad weather, were made at significant periods of the apparition: the first, in December 1984 with the comet at 5.3 AU during the period of the onset of activity; and the last, in November 1985 with the comet near opposition. The December observations show evidence of residual activity. The 18 November data show a highly-condensed inner coma with an extreme falloff in brightness from the region of the nucleus. These data provide the basis for characterizing the gas and dust environment in the immediate vicinity of the active nucleus.

  15. Challenges of Deflecting an Asteroid or Comet Nucleus with a Nuclear Burst

    NASA Astrophysics Data System (ADS)

    Bradley, P. A.; Plesko, C. S.; Clement, R. R. C.; Conlon, L. M.; Weaver, R. P.; Guzik, J. A.; Pritchett-Sheats, L. A.; Huebner, W. F.

    2010-01-01

    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 with the damage later. The Katrina and Rita hurricane evacuations on the U.S. Gulf Coast 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 (NEO) surveys, people are working towards a goal of cataloging at least 90% of all near-Earth objects with diameters larger than ~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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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).

  6. 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.

  7. The nucleus of Comet 67P/Churyumov-Gerasimenko. A new shape model and thermophysical analysis

    NASA Astrophysics Data System (ADS)

    Lowry, S.; Duddy, S. R.; Rozitis, B.; Green, S. F.; Fitzsimmons, A.; Snodgrass, C.; Hsieh, H. H.; Hainaut, O.

    2012-12-01

    Context. Comet 67P/Churyumov-Gerasimenko is the target of the European Space Agency Rosetta spacecraft rendez-vous mission. Detailed physical characteristation of the comet before arrival is important for mission planning as well as providing a test bed for ground-based observing and data-analysis methods. Aims: To conduct a long-term observational programme to characterize the physical properties of the nucleus of the comet, via ground-based optical photometry, and to combine our new data with all available nucleus data from the literature. Methods: We applied aperture photometry techniques on our imaging data and combined the extracted rotational lightcurves with data from the literature. Optical lightcurve inversion techniques were applied to constrain the spin state of the nucleus and its broad shape. We performed a detailed surface thermal analysis with the shape model and optical photometry by incorporating both into the new Advanced Thermophysical Model (ATPM), along with all available Spitzer 8-24 μm thermal-IR flux measurements from the literature. Results: A convex triangular-facet shape model was determined with axial ratios b/a = 1.239 and c/a = 0.819. These values can vary by as much as 7% in each axis and still result in a statistically significant fit to the observational data. Our best spin state solution has Psid = 12.76137 ± 0.00006 h, and a rotational pole orientated at Ecliptic coordinates λ = 78°(±10°), β = + 58°(±10°). The nucleus phase darkening behaviour was measured and best characterized using the IAU HG system. Best fit parameters are: G = 0.11 ± 0.12 and HR(1,1,0) = 15.31 ± 0.07. Our shape model combined with the ATPM can satisfactorily reconcile all optical and thermal-IR data, with the fit to the Spitzer 24 μm data taken in February 2004 being exceptionally good. We derive a range of mutually-consistent physical parameters for each thermal-IR data set, including effective radius, geometric albedo, surface thermal inertia

  8. The Nucleus of Comet 22P/Kopff and Its Inner Coma

    NASA Astrophysics Data System (ADS)

    Lamy, P. L.; Toth, I.; Jorda, L.; Groussin, O.; A'Hearn, M. F.; Weaver, H. A.

    2002-04-01

    We report the detection of the nucleus of Comet 22P/Kopff with the Planetary Camera of the Hubble Space Telescope (HST) and with the Infrared Camera of the Infrared Space Observatory (ISOCAM). The HST observations were performed on 18 July 1996, 16 days after its perihelion passage of 2 July 1996, when it was at Rh=1.59 AU from the Sun and Δ=0.57 AU from the Earth. A sequence of images taken with four broad-band filters was repeated eight times over a 12-h time interval. The ISOCAM observations were performed on 15 October 1996, 106 days after the perihelion passage, when the comet was at Rh=1.89 AU from the Sun and Δ=1.32 AU from the Earth. Seven images were obtained with a broad-band filter centered at 11.5 μm. In both instances, the spatial resolution was appropriate to separate the signal of the nucleus from that of the coma. We determine the Johnson-Kron-Cousins BVRI magnitudes of the nucleus. The visible lightcurves constrain neither the rotation period nor the ratio of semiaxes. We favor the solution of a rather spherical nucleus, although the situation of a pole-on view of an irregular body cannot be excluded. The systematic decreasing trend of the lightcurves could suggest a period of several days. Combining the visible and infrared observations, we find that an ice-dust mixed model is ruled out, while the standard thermal model leads to a nuclear radius of Rn=1.67±0.18 km of albedo pv=0.042±0.006. The red color of the nucleus is characterized by a nearly constant gradient of S'=14±5% per kÅ from 400 to 800 nm. We estimate a fractional active area of 0.35 which places 22P/Kopff in the class of highly active short-period comets. At Rh=1.59 AU, the dust coma is characterized by a red color with a reflectivity gradient S'=17±3% per kÅ, compatible with that of the nucleus, and Afρ=545 cm, yielding a dust production rate of Qd=130 kg sec -1.

  9. 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.

  10. 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.

  11. 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.

  12. Hubble Space Telescope observations of the nucleus of Comet 9P/Tempel 1

    NASA Astrophysics Data System (ADS)

    Lamy, P. L.; Toth, I.; A'Hearn, M. F.; Weaver, H. A.; Weissman, P. R.

    The nucleus of Comet 9P/Tempel 1, the target of the Deep Impact mission, was detected during Hubble Space Telescope observations taken with the wide-field planetary camera 2 (WFPC2) on 31 December 1997 when the comet's solar phase angle was 3.°8, its heliocentric distance was 4.48 AU, and its geocentric distance was 3.53 AU. Sixteen images were taken through the F675W filter, and all of them revealed a point-like source without any detectable coma. From these images, we derived the R magnitude of the nucleus in the Johnson Kron Cousins photometric system for the entire 11.5-h time span of the observations. Assuming a prolate spheroid whose spin axis lies close to the plane of the sky, the partial lightcurve indicates semi-axes a-3.9 km and b-2.8 km (assuming a geometric albedo of 0.04 for the R band and a phase coefficient of 0.04 mag deg-1) and a rotational period in the range of ˜25-33 h. The upper limit of the parameter Afρ, which characterizes the dust production rate, is 1 cm. We also derive a fractional active area at 1.78 AU of ˜4%.

  13. The Nucleus of Comet 67P/Churyumov-Gerasimenko: Lots of Surprises

    NASA Astrophysics Data System (ADS)

    Weissman, Paul R.; Rosetta Science Working Team

    2016-10-01

    ESA's Rosetta mission has made many new and unexpected discoveries since its arrival at comet 67P/Churyumov-Gerasimenko in August 2014. The first of these was the unusual shape of the cometary nucleus. Although bilobate nuclei had been seen before, the extreme concavities on 67P were unexpected. Evidence gathered during the mission suggests that two independent bodies came together to form 67P, rather than the nucleus being a single body that was sculpted by sublimation and/or other processes. Although not a surprise, early observations showed that the nucleus rotation period had decreased by ~22 minutes since the previous aphelion passage. A similar rotation period decrease was seen post-perihelion during the encounter. These changes likely arise from asymmetric jetting forces from the irregular nucleus. Initially, Rosetta's instruments found little evidence for water ice on the surface; the presence of surface water ice increased substantially as the nucleus approached perihelion. The nucleus bulk density, 533 ± 6 kg/m3, was measured with Radio Science and OSIRIS imaging of the nucleus volume. This confirmed previous estimates based on indirect methods that the bulk density of cometary nuclei was on the order of 500-600 kg/m3 and on measurement of the density of 9P/Tempel 1's nucleus by Deep Impact. Nucleus topography proved to be highly varied, from smooth dust-covered plains to shallow circular basins, to the very rough terrain where the Philae lander came to rest. Evidence of thermal cracking is everywhere. The discovery of cylindrical pits on the surface, typically 100-200m in diameter with similar depths was a major surprise and has been interpreted as sinkholes. "Goose-bump" terrain consisting of apparently random piles of boulders 2-3 m in diameter was another unexpected discovery. Apparent layering with scales of meters to many tens of meters was seen but there was little or no evidence for impact features. Radar tomography of the interior of the "head

  14. Rotation and color properties of the nucleus of Comet 2P/Encke

    NASA Astrophysics Data System (ADS)

    Lowry, Stephen C.; Weissman, Paul R.

    2007-05-01

    We present results from CCD observations of Comet 2P/Encke acquired at Steward Observatory's 2.3 m Bok Telescope on Kitt Peak. The observations were carried out in October 2002 when the comet was near aphelion. Rotational lightcurves in B-, V-, and R-filters were acquired over two nights of observations, and analysed to study the physical and color properties of the nucleus. The average apparent R-filter magnitude across both nights corresponds to a mean effective radius of 3.95±0.06 km, and this value is similar to that found for the V- and B-filters. Taking the observed brightness range, we obtain a/b⩾1.44±0.06 for the semi-axial ratio of Encke's nucleus. Applying the axial ratio to the R-filter photometry gives nucleus semi-axes of [3.60±0.09]×[5.20±0.13] km, using the empirically-derived albedo and phase coefficient. No coma or tail was seen despite deep imaging of the comet, and flux limits from potential unresolved coma do not exceed a few percent of the total measured flux, for standard coma models. This is consistent with many other published data sets taken when the comet was near aphelion. Our data includes the first detailed time series multi-color measurements of a cometary nucleus, and significant color variations were seen on October 3, though not repeated on October 4. The average color indices across both nights are: (V-R)=0.39±0.06 and (B-V)=0.73±0.06 ( R¯=19.76±0.03). We analysed the R-filter time-series photometry using the method of Harris et al. [Harris, A.W., Young, J.W., Bowell, E., Martin, L.J., Millis, R.L., Poutanen, M., Scaltriti, F., Zappala, V., Schober, H.J., Debehogne, H., Zeigler, K.W., 1989. Icarus 77, 171-186] to constrain the rotation period of the comet's nucleus, and find that a period of ˜11.45 h will satisfy the data, however the errors bars are large. We have successfully linked our data with the September 2002 data from Fernández et al. [Fernández, Y.R., Lowry, S.C., Weissman, P.R., Mueller, B.E.A., Samarasinha

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

    NASA Astrophysics Data System (ADS)

    Hsieh, Henry H.

    2014-11-01

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

  16. Visual Colors of the Nucleus of Periodic Comet 2P/Encke

    NASA Astrophysics Data System (ADS)

    Lowry, S. C.; Weissman, P. R.

    2003-05-01

    Comet 2P/Encke has been observed extensively in the past and was one of the planned flyby targets of the recently failed CONTOUR mission [1]. We present results for comet Encke based on observations with Steward Observatory's 2.3-m Bok telescope at Kitt Peak and Palomar Observatory's 1.5-m telescope. Our observations consist of time-series BVR photometry obtained under photometric conditions in October 2002, when the comet was at an inbound heliocentric distance of 3.93 AU. From these data we obtain the nucleus color indices and search for signs of color variation with rotation, which may provide evidence of nucleus surface inhomogeniety. We also provide an update of our analysis of observations obtained in September 2002, which include time-series R filter photometry of Encke when it was at a heliocentric distance of 3.97 AU. From these data we have derived an estimate of the rotation period and limits on the nuclear size and shape. The September rotational lightcurve is highly asymmetric - a feature also observed by Meech et al. and Fernandez et al. [2,3] - with a periodicity of 11.03 hours. We also discuss our previously reported visual wavelength detection of comet Encke's dust trail [4]. The Encke dust trail had only been detected at IR wavelengths [5,6]. This visual detection was achieved by co-adding four nights of continuous R filter observations from the September 2002 run. Combining photometric measurements at visual and IR wavelengths will allow us to constrain the physical properties of the dust particles within the trail. This work was supported in part by the NASA Planetary Astronomy program, and was performed jointly at the Jet Propulsion Laboratory and Queen's University Belfast. [1] Bell, J.F., and 18 colleagues. 2000. M&PS 35, A23. [2] Meech, K.J., Y. Fernandez, and J. Pittichova. 2001. BAAS 33, 1075 (abstract). [3] Fernandez, Y.R., S.C. Lowry, P.R. Weissman, and K.J. Meech. 2002. BAAS 34, 887 (abstract). [4] Lowry, S.C., P.R. Weissman, M.V. Sykes

  17. 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.

  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. Infrared spectrophotometry of Comet IRAS-Araki-Alcock (1983d) - A bare nucleus revealed?

    NASA Technical Reports Server (NTRS)

    Hanner, M. S.; Aitken, D. K.; Knacke, R.; Mccorkle, S.; Roche, P. F.; Tokunaga, A. T.

    1985-01-01

    Spectra of the central core and surrounding coma of Comet IRAS-Araki-Alcock (1983d) were obtained at 8-13 microns on May 11 and 2-4 microns on May 12, 1983. Spatially resolved measurements at 10 microns with a 4-arcsec beam showed that the central core was more than 100 times brighter than the inner coma only 8 arcsec away; for radially outflowing dust, the brightness ratio would be a factor of 8. The observations of the central core are consistent with direct detection of a nucleus having a radius of approximately 5 km. The temperature of the sunlit hemisphere was greater than 300 K. Spectra of the core are featureless, while spectra of the coma suggest weak silicate emission. The spectra show no evidence for icy grains. The dust production rate on May 11.4 was about 100,000 g/sec, assuming that the gas flux from the dust-producing areas on the nucleus was about 0.00001 g/sq cm per sec.

  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. 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.

  3. 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.

  4. 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...

  5. Impact penetrometry on a comet nucleus - interpretation of laboratory data using penetration models

    NASA Astrophysics Data System (ADS)

    Kömle, Norbert I.; Ball, Andrew J.; Kargl, Günter; Keller, Thomas; Macher, Wolfgang; Thiel, Markus; Stöcker, Jakob; Rohe, Christian

    2001-05-01

    The first - and possibly deepest - in situ science measurements on the 46P/Wirtanen nucleus will be made by two sensors of the Rosetta Lander's MUPUS experiment. A piezoelectric shock accelerometer (ANC-M) and a resistance temperature sensor (ANC-T) will be mounted in the Lander's harpoon anchor. This will be shot into the surface at about 60 m s -1 on touchdown, reaching a final depth of between a few centimetres and about 2.5 m, depending on the hardness of the ground and the maximum available cable length. Early indications of the strength of the surface material and any distinct layers should prove valuable to subsequent depth-sensitive investigations, including the MUPUS thermal probe, seismic sounding experiments, the sampling drill and composition analyses of the extracted material. Interpretation of the ANC-M data will help to constrain models of the formation and evolution of the material found at the landing site and document the mechanical and structural context of nearby sampled material. We report on the results of recent test shots performed with a prototype anchor into several porous materials: two types of glass foam, H 2O ice and CO 2 ice. With the help of data from direct shear tests and quasi-static penetration tests, we interpret the processed deceleration data using a cavity-expansion penetration model. Layers of distinctly different strengths can be detected and located, and the deceleration profiles are in reasonable agreement with the profiles obtained by quasi-static tests. The anchor projectile's long sharp tip tends to smear out the boundaries, however. In applying the penetration model we found that the coefficient of sliding friction and the target's volumetric strain have a much stronger influence on the deceleration profile than the initial target density and angle of internal friction. Very small values of volumetric strain (corresponding to high 'drag coefficient') were required to fit deceleration profiles to the measured data for

  6. 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.

  7. 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.

  8. 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.

  9. Rosetta and Comet Composition of Volatile and Refractories in the Nucleus of 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Calmonte, Ursina; Alice Team; Stern, Alan; CONSTERT Team; Kofman, Wlodek; COSIMA Team; Hilchenbach, Martin; GIADA Team; Rotundi, Alessandra; MIDAS Team; Bentley, Mark; MIRO Team; Hofstadter, Mark; OSIRIS Team; Sierks, Holger; ROSINA Team; Altwegg, Kathrin; RPC Team; Nilsson, Hans; Burch, James; Eriksson, Anders; Heinz-Glassmeier, Karl; Henri, Pierre; Carr, Christopher; RSI Team; Paetzold, Martin; VIRTIS Team; Capaccioni, Fabrizio; Lander Team; Boehnhardt, Hermann; Bibring, Jean-Pierre; IDS Team; Gruen, Eberhard; Fulchignoni, Marcello; Weissman, Paul; Project Scientist Team; Taylor, Matt; Buratti, Bonnie; Altobelli, Nicolas; Choukroun, Mathieu; Ground-Based Observations Team; Snodgrass, Colin

    2016-10-01

    The Rosetta mission has been taking measurements of its target comet 67P/Churyumov-Gerasimenko since early 2014 and will complete operations at the end of September 2016.The mission Science Management Plan, in 1994, laid out the five prime goals and themes of the mission.1) To study the global characterisation of the nucleus, the determination of the dynamics properties, surface morphology and composition of the comet.2) Examination of the Chemical, Mineralogical and isotopic compositions of volatiles and refractories in a cometary nucleus.3) Physical interrelation of volatiles and refractories in a cometary nucleus4) Study of the development of cometary activity and the process in the surface layer of the nucleus and in the inner coma5) The origins of comets, the relationship between cometary and interstellar material and the implications for the origin of the Solar System.To cover all aspects of the Rosetta mission in this dedicated session, this abstracts is one of 5, and focuses on theme 2:In this contribution we will focus on the highlights of the volatile and refractory inventory, the compositional evolution during orbit, and the major constraints from this to the Solar System formation. In particular we will detail the evolution of the volatile composition along the comet's orbit around the Sun ranging from beyond 3 AU to the perihelion at a heliocentric distance of 1.24 AU and back to 3.6 AU and discussion new parent molecules in the cometary volatile inventory that give new insights into the Solar System formation.

  10. 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

  11. 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.

  12. Hubble Space Telescope observations of the nucleus and inner coma of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Lamy, P. L.; Toth, I.; Weaver, H. A.; Jorda, L.; Kaasalainen, M.; Gutiérrez, P. J.

    2006-11-01

    Context: .Following the postponement of the launch of the Rosetta spacecraft scheduled in January 2003, comet 67P/Churyumov-Gerasimenko emerged as the most suitable new target. However a critical issue was the size, that is, the mass of its nucleus, as the surface module Philae was designed to land on a nucleus with a radius no larger than approximately 1.5 km. Aims: . It was therefore crucial to the success of the mission to achieve a timely characterization of the nucleus of 67P/C-G so as to take any proper action on the design needed before the new launch. Methods: . We used the Wide Field Planetary Camera 2 (WFPC2) of the Hubble Space Telescope (HST) whose superior spatial resolution enabled us to accurately separate the signal of the nucleus from that of the coma. The observations were performed on 12 and 13 March 2003, when the comet was 2.50 AU from the Sun, 1.52 AU from the Earth, and at a phase angle of 4.8°. Results: . The nucleus of comet 67P/Churyumov-Gerasimenko was easily detected, and we measured its V and R magnitudes in the Johnson-Kron-Cousins photometric system. Assuming that the nucleus is spherical, with a geometric albedo of 0.04 and a phase coefficient of 0.04 mag/deg for the R band, we derived a radius of 1.98±0.02 km. The spheroidal solution has semiaxes a = 2.41 km and b = c = 1.55 km and a rotational period of 12.41±0.41 h. We inverted the light curve and solved it for a full three-dimensional nucleus having an overall size of 4.56×3.81×3.44 km viewed at an aspect angle of ˜80° (i.e., near equatorial view) at the time of our observations. When combined with other constraints, the direction of the pole is found at either RA = 40°+70°-20° and Dec = +70±10° (prograde rotation) or RA = 250±30° and Dec = -70±10° (retrograde rotation). The color of the nucleus is moderately red with (V-R)=0.52±0.05. From an analysis of the dust coma, we derived Afρ = 40.2±0.3 cm, a dust production rate Qd ˜ 4 kg s-1, and we characterized its

  13. 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).

  14. 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.

  15. 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.

  16. Decimetre-scaled spectrophotometric properties of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    We present the results of the photometric and spectrophotometric properties of the 67P/Churyumov-Gerasimenko nucleus derived with the OSIRIS instrument during the closest fly-by over the comet, which took place on 14 th February 2015 at a distance of {\\~} 6 km from the surface. Several images covering the 0{\\deg}-33{\\deg} phase angle range were acquired, and the spatial resolution achieved was 11 cm/pxl. The flown-by region is located on the big lobe of the comet, near the borders of the Ash, Apis and Imhotep regions. Our analysis shows that this region features local heterogeneities at the decimetre scale. We observed difference of reflectance up to 40{\\%} between bright spots and sombre regions, and spectral slope variations up to 50{\\%}. The spectral reddening effect observed globally on the comet surface by Fornasier et al. (2015) is also observed locally on this region, but with a less steep behaviour. We note that numerous metre-sized boulders, which exhibit a smaller opposition effect, also appear spectrally redder than their surroundings. In this region, we found no evidence linking observed bright spots to exposed water-ice-rich material. We fitted our dataset using the Hapke 2008 photometric model. The region overflown is globally as dark as the whole nucleus (geometric albedo of 6.8{\\%}) and it has a high porosity value in the uppermost-layers (86{\\%}). These results of the photometric analysis at a decimetre scale indicate that the photometric properties of the flown-by region are similar to those previously found for the whole nucleus.

  17. 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.

  18. Preliminary solution for the shape and rotational state of the nucleus of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Lamy, P.; Jorda, L.; Kaasalainen, M.; Hviid, S.; Faury, G.; Toth, I.; Groussin, O.

    2014-07-01

    In preparation of ESA's ROSETTA mission to comet 67P/Churyumov-Gerasimenko, solutions for the shape and rotational state of its nucleus have been published based on observation with the Hubble and Spitzer space telescopes as well as ground-based observations (Lamy et al. 2006, 2007, 2008; Lowry et al. 2012). Following the wake-up of the Rosetta spacecraft in January 2014 and the successful commissioning of the OSIRIS camera system in March, a first lightcurve of the inactive nucleus has been obtained on 23 March 2014 with the OSIRIS Narrow Angle Camera (NAC). Further lightcurves will be acquired in the forthcoming months. We will present an updated solution for the shape and rotational state based on these data sets as of end of June 2014 combined with past Hubble and Spitzer space telescopes as well as ground-based observations using the technique of lightcurve inversion.

  19. 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

  20. Comet 67P Nucleus Water Ice Distribution and Evolution Inferred from Inner Coma Structure Seen by Rosetta/MIRO

    NASA Astrophysics Data System (ADS)

    Lee, Seungwon; von Allmen, Paul; MIRO Team

    2016-10-01

    The spatial structure and temporal evolution of the inner coma of Comet 67P have been observed by Microwave Instrument on Rosetta Orbiter (MIRO) since the Rosetta Orbiter has rendezvoused with Comet 67P in August 2014. Among the several cometary gas emission lines that the MIRO spectrometer is tuned to, the water isotopologue H218O line is optically thin and is used to probe the inner coma structure as the MIRO beam scans the space near the comet nucleus. The water line area/strength shows clearly that the day side of coma has a lot more gas than the night side of coma and the summer hemisphere side of coma has a lot more gas than the winter hemisphere side of coma. These diurnal and seasonal dependencies strongly suggest that the water gas in the coma is from the sublimation of ice in the nucleus, where its rate greatly depends on the thermal condition of surface and near-surface governed by the sun illumination condition. In addition to the sun illumination condition, the water ice distribution on 67P nucleus affects the inner coma structure. We model the inner coma structures with various ice distributions and compare them with the observation. The comparison undoubtedly shows that the ice is not uniformly distributed on 67P nucleus. The observation favors the model with the ice distributed only in polar caps in both poles. The observation also shows the evidence of temporal evolution of the ice distribution. The southern polar ice cap was less active a few months before the perihelion (August 2015), became more active near the perihelion, and became less active a few months after the perihelion. Note that the ice cap activity change due to the temperature-dependent sublimation rate change is already taken into account, and does not explain the temporal variation of the inner coma structure. This result indicates that there was a change of ice distribution (polar cap size) or ice location near the surface (how deep the dust layer covers the ice).

  1. 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.

  2. Seasonal exposure of carbon dioxide ice on the nucleus of comet 67P/Churyumov-Gerasimenko.

    PubMed

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

    2016-12-23

    Carbon dioxide (CO2) is one of the most abundant species in cometary nuclei, but because of its high volatility, CO2 ice is generally only found beneath the surface. We report the infrared spectroscopic identification of a CO2 ice-rich surface area located in the Anhur region of comet 67P/Churyumov-Gerasimenko. Spectral modeling shows that about 0.1% of the 80- by 60-meter area is CO2 ice. This exposed ice was observed a short time after the comet exited local winter; following the increased illumination, the CO2 ice completely disappeared over about 3 weeks. We estimate the mass of the sublimated CO2 ice and the depth of the eroded surface layer. We interpret the presence of CO2 ice as the result of the extreme seasonal changes induced by the rotation and orbit of the comet.

  3. Seasonal exposure of carbon dioxide ice on the nucleus of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Carbon dioxide (CO2) is one of the most abundant species in cometary nuclei, but because of its high volatility, CO2 ice is generally only found beneath the surface. We report the infrared spectroscopic identification of a CO2 ice-rich surface area located in the Anhur region of comet 67P/Churyumov-Gerasimenko. Spectral modeling shows that about 0.1% of the 80- by 60-meter area is CO2 ice. This exposed ice was observed a short time after the comet exited local winter; following the increased illumination, the CO2 ice completely disappeared over about 3 weeks. We estimate the mass of the sublimated CO2 ice and the depth of the eroded surface layer. We interpret the presence of CO2 ice as the result of the extreme seasonal changes induced by the rotation and orbit of the comet.

  4. 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.

  5. 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.

  6. Water and Carbon Dioxide Ices-Rich Areas on Comet 67P/CG Nucleus Surface

    NASA Astrophysics Data System (ADS)

    Filacchione, G.; Capaccioni, F.; Raponi, A.; De Sanctis, M. C.; Ciarniello, M.; Barucci, M. A.; Tosi, F.; Migliorini, A.; Capria, M. T.; Erard, S.; Bockelée-Morvan, D.; Leyrat, C.; Arnold, G.; Kappel, D.; McCord, T. B.

    2017-01-01

    fields ice grains [3]; 3) different combinations of water ice and dark terrain in intimate mixing with small grains (tens of microns) or in areal mixing with large grains (mm- sized) are seen on the eight bright areas discussed in [4]; 4) the CO2 ice in the Anhur region appears grouped in areal patches made of 50 μm sized grains [5]. While the spectroscopic identification of water and carbon dioxide ices is made by means of diagnostic infrared absorption features, their presence cause significant effects also at visible wavelengths, including the increase of the albedo and the reduction of the spectral slope which results in a more blue color [9,10]. In summary, thermodynamic conditions prevailing on the 67P/CG nucleus surface allow the presence of only H2O and CO2 ices. Similar properties are probably common among other Jupiter family comets.

  7. 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

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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.

  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. Model Of Comet Dust Consistent With Ground Based Observations And Studies Of Stardust Returned Samples

    NASA Astrophysics Data System (ADS)

    Kolokolova, Ludmilla; Kimura, H.

    2007-10-01

    Recently a significant progress has been achieved in theoretical interpretation of the remote-sensing studies of comet dust. The most successful model was the one that presented comet dust as large aggregates of submicron particles. This model could qualitatively explain spectral and angular change in comet dust brightness, polarization, and thermal emission and was also consistent with the composition of the comet dust obtained in-situ for comet Halley. The tracks in Stardust aerogel confirmed presence of large aggregates in the dust of comet Wild-2 and, thus, supported the theoretical model. However, among the Stardust samples, compact particles of silicate composition were also found. In this paper we present a model of comet dust that is consistent with the Stardust findings, i.e. presents a mixture of aggregates and compact particles. A power-law size distribution was selected with the power equal to -3 that is between the power obtained by Stardust DFMI measurements and the power obtained from the study of the tracks in the aerogel (Hoertz et al., Science, 314, 1716, 2006). Aggregates in our model were simulated as Ballistic Cluster-Cluster Aggregates and compact particles were simulated as a polydisperse mixture of silicate spheroids with some distribution of the aspect ratio. The computations were based on the T-matrix codes by Mishchenko et al. This model could provide much better fit to the photometric and polarimetric observational data than the model which considered only aggregates. The model reproduces the correct shape of the polarization curve, including negative polarization reaching the value -2% and positive polarization with the maximum value less than 35%, red polarimetric color, red color of comet dust, albedo of the dust equal to 4%, and the ratio of silicates to carbonaceous materials in the dust equal to 0.5 that is in accordance with the elemental abundances of Halley's dust.

  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. 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.

  17. 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.

  18. 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

  19. 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

  20. Coma morphology and dust-emission pattern of periodic Comet Halley. II - Nucleus spin vector and modeling of major dust features in 1910

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.; Larson, S. M.

    1984-01-01

    The continuous ejection of dust from discrete emission sources on the rotating nucleus of the Comet Halley is modelled in order to explain the evolution of spiral jets which unwind from the nucleus condensation into envelopes or halos in the comet head. The model is applied to digitally processed images of three features of the comet taken from Mount Wilson plates during the 1910 fly-by. The model permits a determination of the motion and spin vector for each emission source, its cometocentric coordinates, and a function relating particle ejection velocity to the solar radiation pressure exerted on the ejecta. It is found that the obliquity of the comet orbit's plane to its equatorial plane is 45 deg, the axis of rotation period of 17.3 days. The derived function of particle ejection velocity to the solar radiation pressure implied no contribution from grains larger than 10 microns in radius. High dust loading of gas flows from the June 1910 emission sources is indicated. It is estimated that because of the favorable approach geometry of the Gioto spacecraft during its 1986 flyby, the likelihood of encountering dense jets of dust is small.

  1. Infrared Spectroscopy of Comet 81P/Wild 2 Samples Returned by Stardust

    NASA Astrophysics Data System (ADS)

    Keller, Lindsay P.; Bajt, Saša; Baratta, Giuseppe A.; Borg, Janet; Bradley, John P.; Brownlee, Don E.; Busemann, Henner; Brucato, John R.; Burchell, Mark; Colangeli, Luigi; D'Hendecourt, Louis; Djouadi, Zahia; Ferrini, Gianluca; Flynn, George; Franchi, Ian A.; Fries, Marc; Grady, Monica M.; Graham, Giles A.; Grossemy, Faustine; Kearsley, Anton; Matrajt, Graciela; Nakamura-Messenger, Keiko; Mennella, Vito; Nittler, Larry; Palumbo, Maria E.; Stadermann, Frank J.; Tsou, Peter; Rotundi, Alessandra; Sandford, Scott A.; Snead, Christopher; Steele, Andrew; Wooden, Diane; Zolensky, Mike

    2006-12-01

    Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust.

  2. Infrared Spectrocopy of Comet 81P/Wild 2 Samples Returned by Stardust

    SciTech Connect

    Keller,L.; Bajt, S.; Baratta, G.; Borg, J.; Bradley, J.; Brownlee, D.; Busemann, H.; Brucato, J.; Burchell, M.; et al.

    2006-01-01

    Infrared spectra of material captured from comet 81P/Wild 2 by the Stardust spacecraft reveal indigenous aliphatic hydrocarbons similar to those in interplanetary dust particles thought to be derived from comets, but with longer chain lengths than those observed in the diffuse interstellar medium. Similarly, the Stardust samples contain abundant amorphous silicates in addition to crystalline silicates such as olivine and pyroxene. The presence of crystalline silicates in Wild 2 is consistent with mixing of solar system and interstellar matter. No hydrous silicates or carbonate minerals were detected, which suggests a lack of aqueous processing of Wild 2 dust.

  3. Clues to cometary circular polarization from studying the magnetic field in the vicinity of the nucleus of comet 67P/Churyumov–Gerasimenko

    NASA Astrophysics Data System (ADS)

    Kolokolova, Ludmilla; Koenders, Christoph; Goetz, Charlotte; Rosenbush, Vera; Kiselev, Nikolai; Hoang, Thiem; Lazarian, Alexander

    2016-11-01

    Circular polarization in cometary continuum bands has been observed for more than 30 years. Recently, imaging data on circular polarization have been obtained for more than 10 comets using the 6-m Big Telescope Alt-azimuthal (BTA) telescope (Russia). However, despite the accumulation of significant amounts of data, the mechanisms that form circular polarization in the cometary environment are still a mystery. Regular mechanisms, such as multiple scattering in an optically thick medium or the domination of particles or materials of a specific mirror asymmetry (including homochirality), could not explain the observations. Particle alignment was considered the most feasible mechanism; however, the cause of the particle alignment was not clear. The most reasonable mechanism, alignment in a magnetic field, was considered doubtful, as comets do not have their own magnetic field and, according to the in situ results for comet Halley, the solar magnetic field could not penetrate deeply into the coma. However, new theoretical studies of cometary coma interaction with the solar magnetic field and, especially, Rosetta observations of the diamagnetic cavity of comet 67P/Churyumov-Gerasimenko showed that the solar wind magnetic field can penetrate as close to the nucleus as several dozen kilometres. This allows us to suggest alignment in the solar magnetic field as a reason for the observed circular polarization. Based on the data obtained for comet 67P, we estimate the time necessary for the alignment of cometary particles in the solar magnetic field. The estimates obtained are consistent with the observations of cometary circular polarization.

  4. Measuring the Permittivity of the Nucleus of a Comet: the PP-SESAME Experiment on Board the Philae/ROSETTA Lander

    NASA Astrophysics Data System (ADS)

    Lethuillier, A.; Le Gall, A. A.; Hamelin, M.; Ciarletti, V.; Caujolle-Bert, S.; Schmidt, W.; Grard, R.; Seidensticker, K. J.; Fischer, H. H.

    2015-12-01

    The Permittivity Probe (SESAME-PP) on-board the Philae Lander of the ROSETTA mission was designed to constrain the complex permittivity of the first 2 m of the nucleus of comet 67P/Churyumov-Gerasimenko and to monitor its variations with time. Doing so, it is meant to provide a unique insight into the composition of the comet, and in particular, into its water content. PP-SESAME acquired data on November 13, 2015, both during Philae descent to the comet and at the surface of the nucleus. The PP-SESAME instrument is derived from the quadrupole array technique. A sinusoidal electrical current is sent into the ground through a transmitting dipole, and the induced electrical voltage on a receiving dipole is measured. The complex permittivity of the material is inferred from the mutual impedance derived from the measurements. In practice, the influence of both the electronic circuit of the instrument and the conducting elements in its close environment must be accounted for in order to best estimate both the dielectric constant and electrical conductivity of the ground. For that purpose, we have developed a method called the "capacity-influence matrix method". A replica of the instrument was recently built in LATMOS (France) in order to validate this method. In this paper, we will present the tests conducted with the replica in a controlled environment and their comparison to numerical simulations. We will also show simulations relevant to the PP-SESAME experiment on the nucleus of comet 67P/Churyumov-Gerasimenko. These simulations were run for realistic scenarios of the Philae's attitude and environment at its final landing site. We discuss their implications in terms of surface electrical and compositional properties.

  5. Geologic analysis of the Rosetta NavCam, Osiris and ROLIS images of the comet 67P/Churyumov-Gerasimenko nucleus

    NASA Astrophysics Data System (ADS)

    Basilevsky, A. T.; Mall, U.; Keller, H. U.; Skorov, Yu. V.; Hviid, S. F.; Mottola, S.; Krasilnikov, S. S.; Dabrowski, B.

    2017-03-01

    This paper is based on geologic analysis of the surface morphology of nucleus of the Jupiter family comet 67P. This comet was visited by the ESA mission Rosetta, which escorted the comet since May 2014 till the end of September 2016 and studied it by 11 instruments of the mission orbiter and 10 instruments of the lander. The nucleus is 4 km in diameter, has a bilobate shape with the smaller (Head) and larger (Body) lobes, and the narrow neck between them. For the analysis, primarily images taken by the Rosetta Navigation camera (NavCam) were used and then complemented by selected images from the ROLIS and OSIRIS cameras. Two major types of the nucleus material are distinguished by us and other researchers: 1) the consolidated nucleus material and 2) the loose material, a kind of cometary regolith, covering the nucleus consolidated material. On the surface of the consolidated material rather long (up to hundreds meters) straight lineaments are distinguishable. They probably correspond to fractures and in some cases to strata. Their presence suggests that the consolidated material is rather compact and lacks voids larger than tens of meters across. Surfaces of consolidated nucleus material typically show knobby appearance at the scales from tens of meters and meters to centimeters and millimeters. This suggests that this material is grainy, consisting of more and less resistant (to surface weathering) ;particles; on the scale of the visible knobs. The geometric analysis of steep slopes based on the nucleus shape model allowed us to estimate a tensile, shear and compressive strength of the consolidated material. It was shown that the 67P consolidated nucleus material is very fragile, and taking into account the scale effect one can conclude that it is as fragile as fresh fallen snow and maybe even more fragile. In addition, estimates of the compressive strength of the surface material were considered at the sites of the first and the last contacts of the Philae lander

  6. 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.

  7. Entry Dispersion Analysis for the Stardust Comet Sample Return Capsule

    NASA Technical Reports Server (NTRS)

    Desai, Prasun N.; Mitcheltree, Robert A.; Cheatwood, F. McNeil

    1997-01-01

    Stardust will be the first mission to return samples from beyond the Earth-Moon system. The sample return capsule, which is passively controlled during the fastest Earth entry ever, will land by parachute in Utah. The present study analyzes the entry, descent, and landing of the returning sample capsule. The effects of two aerodynamic instabilities are revealed (one in the high altitude free molecular regime and the other in the transonic/subsonic flow regime). These instabilities could lead to unacceptably large excursions in the angle-of-attack near peak heating and main parachute deployment, respectively. To reduce the excursions resulting from the high altitude instability, the entry spin rate of the capsule is increased. To stabilize the excursions from the transonic/subsonic instability, a drogue chute with deployment triggered by an accelerometer and timer is added prior to main parachute deployment. A Monte Carlo dispersion analysis of the modified entry (from which the impact of off-nominal conditions during the entry is ascertained) shows that the capsule attitude excursions near peak heating and drogue chute deployment are within Stardust program limits. Additionally, the size of the resulting 3-sigma landing ellipse is 83.5 km in downrange by 29.2 km in crossrange, which is within the Utah Test and Training Range boundaries.

  8. 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.

  9. 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.

  10. 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

  11. The prediction of the gas environment of the PHILAE probe during its 2014 descent to the nucleus of the comet 67P

    NASA Astrophysics Data System (ADS)

    Crifo, J.-F.; Zakharov, V. V.; Rodionov, A. V.; Lukyanov, G. A.

    2016-11-01

    One of the objectives of the ESA "ROSETTA" mission to the comet 67P was to insert, in August 2014, an orbiter probe around the so-called nucleus of the comet, and to deposit the "PHILAE" lander at the surface of the nucleus in November 2014. The selection of the landing site and the definition of the release point and initial descent velocity vector were made in the period August to October 2014 on the basis of simulations of the descent trajectory. This requested an assessment of the gravitational and aerodynamic forces on PHILAE. We here describe the so-called RZC model developed to predict the gas environment of 67P in November 2014 and compute the aerodynamic force. We first outline the unusual diffculties resulting from (1) the complexity of the nucleus surface on all scales, (2) the absence of direct measurements of the gas flux at the surface itself, (3) the time-dependence of the gas production induced by the fast nucleus rotation, (4) the need to perform the whole program within less than three months. Then we outline the physical approach adopted to overcome these diffculties, and describe the RZC model which included three differing tools: (1) a set of gasdynamic/gaskinetic codes to compute the vacuum outflow of a rarefied gas mixture from a highly aspherical rotating solid source; (2) an heuristic approach to deal with the solid/gas initial boundary conditions, and (3) an iterative procedure to derive the gas production parameters on the nucleus surface from the observational data acquired from the orbiter probe. The satisfactory operation of the RZC code in the weeks preceding the November 2014 PHILAE descent is shown, and the forecasted aerodynamic force during the PHILAE descent is compared to the gravitational force.

  12. 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.

  13. 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.

  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. 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.

  16. 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.

  17. Studying the nucleus of comet 9P/Tempel 1 using the structure of the Deep Impact ejecta cloud at the early stages of its development

    NASA Astrophysics Data System (ADS)

    Kolokolova, Ludmilla; Nagdimunov, Lev; A'Hearn, Michael; King, Ashley; Wolff, Michael

    2016-11-01

    The paper presents an attempt to extract information about the comet 9P/Tempel 1 nucleus from the characteristics of the ejecta cloud produced by the impactor of the Deep Impact mission. For this purpose we use two techniques. We first study the shadow cast on the nucleus surface by the ejecta cloud and investigate how areas of different brightness are related to the varying optical thickness or albedo of the ejecta cloud. The shadow was seen during the first 2.0 s after the impact (afterward it became obscured by the ejecta cloud). We have found that all brightness variations in the shadow are the result of the surface inhomogeneities, indicating that during first 2.0 s the ejecta cloud was homogeneous within the MRI spatial resolution. Our second technique is to study the obscuration of the nucleus limb by the ejecta. This study covers the period 0.76-68.8 s after impact and is based on comparison of the ejecta cloud brightness on the limb and just beyond the limb. At this stage we do see inhomogeneities in the ejecta cloud that relate to the albedo and optical thickness variations in the ejected dust. Specifically, we have found two distinct bands of low optical thickness and one band of a high optical thickness. Based on crater formation ideas we estimate the depth of excavation of the ejected material for the found inhomogeneities and, thus, define a potential layering structure for the comet nucleus, Our estimates suggest that the low-optical thickness material was excavated from a depth of 15-18 and 30-32 m in the case the porous nucleus material and 37-46 and 87-93 m in the case of a non-porous nucleus material, and a layer of high optical thickness originated from the depth 9-11 m for porous material or 20-23 m for non-porous material. Based on the crater diameter estimates, we expect that the real depth of the layers is between these two cases. The rest of the ejecta do not show any signs of layering but have significant azimuthal inhomogeneity with

  18. Near-nucleus H2O(+) structures in comets Brorsen-Metcalf, Okazaki-Levy-Rudenko, and Austin

    NASA Technical Reports Server (NTRS)

    Larson, Stephen M.

    1990-01-01

    Comets P/Brorsen-Metcalf, Okazaki-Levy-Rudenko, and Austin were all observed to have well developed H2O+ structure close to the nuclei that showed changes on a time scale of only a few minutes. Some preliminary data on the observed ion morphology and their evolution is presented.

  19. 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

  20. 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

  1. 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.

  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. Detection of exposed H2O ice on the nucleus of comet 67P/Churyumov-Gerasimenko. as observed by Rosetta OSIRIS and VIRTIS instruments

    NASA Astrophysics Data System (ADS)

    Barucci, M. A.; Filacchione, G.; Fornasier, S.; Raponi, A.; Deshapriya, J. D. P.; Tosi, F.; Feller, C.; Ciarniello, M.; Sierks, H.; Capaccioni, F.; Pommerol, A.; Massironi, M.; Oklay, N.; Merlin, F.; Vincent, J.-B.; Fulchignoni, M.; Guilbert-Lepoutre, A.; Perna, D.; Capria, M. T.; Hasselmann, P. H.; Rousseau, B.; Barbieri, C.; Bockelée-Morvan, D.; Lamy, P. L.; De Sanctis, C.; Rodrigo, R.; Erard, S.; Koschny, D.; Leyrat, C.; Rickman, H.; Drossart, P.; Keller, H. U.; A'Hearn, M. F.; Arnold, G.; Bertaux, J.-L.; Bertini, I.; Cerroni, P.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; El-Maarry, M. R.; Fonti, S.; Fulle, M.; Groussin, O.; Güttler, C.; Hviid, S. F.; Ip, W.; Jorda, L.; Kappel, D.; Knollenberg, J.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Mancarella, F.; Marzari, F.; Mottola, S.; Naletto, G.; Pajola, M.; Palomba, E.; Quirico, E.; Schmitt, B.; Thomas, N.; Tubiana, C.

    2016-11-01

    Context. Since the orbital insertion of the Rosetta spacecraft, comet 67P/Churyumov-Gerasimenko (67P) has been mapped by OSIRIS camera and VIRTIS spectro-imager, producing a huge quantity of images and spectra of the comet's nucleus. Aims: The aim of this work is to search for the presence of H2O on the nucleus which, in general, appears very dark and rich in dehydrated organic material. After selecting images of the bright spots which could be good candidates to search for H2O ice, taken at high resolution by OSIRIS, we check for spectral cubes of the selected coordinates to identify these spots observed by VIRTIS. Methods: The selected OSIRIS images were processed with the OSIRIS standard pipeline and corrected for the illumination conditions for each pixel using the Lommel-Seeliger disk law. The spots with higher I/F were selected and then analysed spectrophotometrically and compared with the surrounding area. We selected 13 spots as good targets to be analysed by VIRTIS to search for the 2 μm absorption band of water ice in the VIRTIS spectral cubes. Results: Out of the 13 selected bright spots, eight of them present positive H2O ice detection on the VIRTIS data. A spectral analysis was performed and the approximate temperature of each spot was computed. The H2O ice content was confirmed by modeling the spectra with mixing (areal and intimate) of H2O ice and dark terrain, using Hapke's radiative transfer modeling. We also present a detailed analysis of the detected spots.

  4. 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.

  5. 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

  6. Analysis of R-band observations of an outburst of Comet 29P/Schwassmann-Wachmann 1 to place constraints on the nucleus' rotation state

    NASA Astrophysics Data System (ADS)

    Schambeau, Charles A.; Fernández, Yanga R.; Samarasinha, Nalin H.; Mueller, Beatrice E. A.; Woodney, Laura M.

    2017-03-01

    We present analysis of five nights of R-band observations of Comet 29P/Schwassmann-Wachmann 1 (SW1) taken on September 2008 which show the comet undergoing an outburst. Coma morphology shows a projected asymmetric shell of material expanding radially and four linear features on the northern side of the coma at position angles 37°, 78°, 300°, and 353°. Using the measured projected radial outflow velocity of 0.11 ±0.02 km/s for the shell material, we calculate an outburst time of UT 2008-09-21.03 ±0.95 days. By tracking the inner and outer extent of the northern linear features, we found that the features are fully contained within the expanding shell of material. This suggested both shell and linear features originated during the same event and activity originating from different regions on the nuclear surface are not necessary to generate both types of morphological structure observed. A 3-D Monte Carlo coma model was used to model the outburst. Morphological features present in the observations were modeled allowing constraints to be placed on the spin state of SW1's nucleus. The evolution of morphological features allows constraints on the rotation period P assuming an outburst duration Δt and the spin period constraints are expressed in terms of their ratio P/Δt. Since the spin-pole orientation could not be constrained, four spin-pole orientations were chosen for modeling the coma. Spin-period constraints for each assumed pole orientation are discussed. Overall, modeling suggested either a spin period on the order of days, a spin-pole orientation nearly along the sub-Earth direction, or a combination of both. To place an independent constraint on the outburst duration, radial surface-brightness profiles of the observations were compared with profiles from synthetic models, giving an upper-limit of Δt ≤ 1.5 days. Longer outbursts resulted in a higher number of dust grains in close proximity to the nucleus during the observations and a profile slope too

  7. 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°.

  8. 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.

  9. Gas chromatography for space exploration : application to the in situ analysis of Titan's atmosphere, comets nucleus and martian soil

    NASA Astrophysics Data System (ADS)

    Sternberg, R.; Szopa, C.; Buch, A.; Mettetal, F.; Coscia, D.; Coll, P.; Cabane, M.; Rodier, C.; Vidal-Madjar, C.; Raulin, F.

    Gas chromatography is one of the most powerful technique for the in situ chemical investigation of extraterrestrial environments Its successful use in past planetary missions to Mars 1976-78 and Venus 1978-85 made it the main method selected for the in situ molecular characterization of the Titan s atmosphere comets and the Martian soil Indeed gas chromatography fully meet the severe constraints required in space instrumentation such as small weight and size low power consumption high mechanical strength and resistance to deep space conditions vacuum cosmic rays This paper presents the gas chromatographic subsystems which have been developed at LISA and SA respectively for the Huygens probe of the Cassini-Huygens mission to Titan 1 the Philae probe of the Rosetta mission to a comet 2 and the future landing probe of the MSL 2009 mission to Mars 3 The coupling of these GC subsystems with pyrolysis and chemical derivatization techniques allows the chemical analysis of a wide range of molecules including non-volatiles complex organics such as aminoacides and nucleobases the search of wich is of particular interest for exobiology The analytical capabilities of these subsystems with a particular emphasis of their exobiological aspects and implications are described 1 G Israel C Szopa F Raulin M Cabane P Coll R Sternberg et al Nature vol438 796-799 2005 2 C Szopa R Sternberg F Raulin and H Rosenbauer PSS 863-877 2003 3 Cabane M P Coll C Szopa G Isra e l F Raulin

  10. Comet radar explorer

    NASA Astrophysics Data System (ADS)

    Farnham, Tony; Asphaug, Erik; Barucci, Antonella; Belton, Mike; Bockelee-Morvan, Dominique; Brownlee, Donald; Capria, Maria Teresa; Carter, Lynn; Chesley, Steve; Farnham, Tony; Gaskell, Robert; Gim, Young; Heggy, Essam; Herique, Alain; Klaasen, Ken; Kofman, Wlodek; Kreslavsky, Misha; Lisse, Casey; Orosei, Roberto; Plaut, Jeff; Scheeres, Dan

    The Comet Radar Explorer (CORE) is designed to perform a comprehensive and detailed exploration of the interior, surface, and inner coma structures of a scientifically impor-tant Jupiter family comet. These structures will be used to investigate the origins of cometary nuclei, their physical and geological evolution, and the mechanisms driving their spectacular activity. CORE is a high heritage spacecraft, injected by solar electric propulsion into orbit around a comet. It is capable of coherent deep radar imaging at decameter wavelengths, high resolution stereo color imaging, and near-IR imaging spectroscopy. Its primary objective is to obtain a high-resolution map of the interior structure of a comet nucleus at a resolution of ¿100 elements across the diameter. This structure shall be related to the surface geology and morphology, and to the structural details of the coma proximal to the nucleus. This is an ideal complement to the science from recent comet missions, providing insight into how comets work. Knowing the structure of the interior of a comet-what's inside-and how cometary activity works, is required before we can understand the requirements for a cryogenic sample return mission. But more than that, CORE is fundamental to understanding the origin of comets and their evolution in time. The mission is made feasible at low cost by the use of now-standard MARSIS-SHARAD reflec-tion radar imaging hardware and data processing, together with proven flight heritage of solar electric propulsion. Radar flight heritage has been demonstrated by the MARSIS radar on Mars Express (Picardi et al., Science 2005; Plaut et al., Science 2007), the SHARAD radar onboard the Mars Reconnaissance Orbiter (Seu et al., JGR 2007), and the LRS radar onboard Kaguya (Ono et al, EPS 2007). These instruments have discovered detailed subsurface structure to depths of several kilometers in a variety of terrains on Mars and the Moon. A reflection radar deployed in orbit about a comet

  11. Water and carbon dioxide sources on comet 67P nucleus as measured from the VIRTIS-H instrument aboard Rosetta

    NASA Astrophysics Data System (ADS)

    Bockelee-Morvan, D.; . Debout, V.; Erard, S.; Leyrat, C.; Capaccioni, F.; Filacchione, G.; Drossart, P.; Fougere, N.; Combi, M.; Arnold, G.; Biver, N.; Crovisier, J.; Encrenaz, T.; Schmitt, B.; Virtis Team

    2015-10-01

    Using the high spectral-resolution channel of the Visible InfraRed Thermal Imaging Spectrometer (VIRTIS-H) onboard Rosetta, we observed the n3 vibrational bands of H2O and CO2 at 2.67 and 4.27 μm in comet 67P/Churyumov-Gerasimenko [1]. Observations were undertaken in limb viewing geometry with various line-of-sight (LOS) orientations in the body-fixed frame. A geometry tool is used to characterize the position of the LOS with respect to geomorphologic regions [6] and the illumination properties of these regions. We will present the heliocentric evolution, diurnal variations and distribution of H2O and CO2 production. Inhomogeneities in the CO2/H2O relative production rates will be discussed

  12. 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.

  13. 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.

  14. 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.

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Sandford, S. A.; Aléon, 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.; D'Hendecourt, L.; Djouadi, Z.; Dworkin, J. P.; Ferrini, G.; Fleckenstein, H.; Flynn, G. F.; Franchi, I. A.; Fries, M.; Gilles, M. K.; Glavin, D. P.; Gounelle, M.; Grossemy, F.; Jacobsen, C.; Keller, L. P.; Kilcoyne, A. L. D.; Leitner, J.; Matrajt, G.; Meibom, A.; Mennella, V.; Mostefaoui, S.; Nittler, L. R.; Palumbo, M. E.; Papanastassiou, D. A.; Robert, F.; Rotundi, A.; Snead, C. J.; Spencer, M. K.; Steele, A.; Stephan, T.; Tsou, P.; Tyliszczak, T.; Westphal, A. J.; Wirick, S.; Wopenka,, B.; Yabuta, H.; Zare, R. N.; Zolensky, M. E.

    2007-03-01

    This presenation will provide an overview of the efforts and results produced by the Organics Preliminary Examination Team during their studies of the samples returned from comet Wild 2 by the Stardust spacecraft.

  17. 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).

  18. 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.

  19. Temperatures within comet nuclei.

    PubMed

    Squyres, S W; McKay, C P; Reynolds, R T

    1985-12-10

    We have performed a theoretical study of temperatures beneath the surface of a comet's nucleus. We solve the one-dimensional heat conduction equation for the outer portion of the comet. The upper boundary condition of the model is given by energy balance at the surface of the nucleus, including conduction of heat inward, radiation, insolation as modified by the coma, and sublimation. Our coma model assumes single scattering and includes attenuation of direct sunlight by dust grains, scattering of light onto the nucleus, and infrared radiation by dust grains. The lower boundary condition is zero net heat flux around an orbit. The thermal conductivity expression for the nucleus includes direct conduction at grain boundaries, radiative conduction, and Knudsen flow vapor diffusion. The thermal diffusivity of the nucleus and the resultant temperature profiles are shown to be strongly dependent on the physical properties of the material, including porosity, pore size, and compaction. The temperature profiles and the equilibrium temperature deep within the comet also depend on the functional relationship between thermal conductivity and temperature; the highest deep equilibrium temperatures are found for models where the thermal conductivity increases strongly with increasing temperature. The dependence of temperatures on the albedo and thermal emissivity of the nucleus is also calculated, as well as the variation of temperature with latitude for a variety of pole orientations. The effect of a dust mantle on subsurface temperatures is also investigated. All calculations are presented for short-period comets with orbits that make them accessible for exploration by spacecraft rendezvous. In situ measurements of the thermal profile in the upper meter of a comet nucleus can substantially constrain the thermal diffusivity of the material, which in turn can provide significant information about the physical properties of the nucleus.

  20. Dust environment and dynamical history of a sample of short-period comets . II. 81P/Wild 2 and 103P/Hartley 2

    NASA Astrophysics Data System (ADS)

    Pozuelos, F. J.; Moreno, F.; Aceituno, F.; Casanova, V.; Sota, A.; López-Moreno, J. J.; Castellano, J.; Reina, E.; Climent, A.; Fernández, A.; San Segundo, A.; Häusler, B.; González, C.; Rodriguez, D.; Bryssinck, E.; Cortés, E.; Rodriguez, F. A.; Baldris, F.; García, F.; Gómez, F.; Limón, F.; Tifner, F.; Muler, G.; Almendros, I.; de los Reyes, J. A.; Henríquez, J. A.; Moreno, J. A.; Báez, J.; Bel, J.; Camarasa, J.; Curto, J.; Hernández, J. F.; González, J. J.; Martín, J. J.; Salto, J. L.; Lopesino, J.; Bosch, J. M.; Ruiz, J. M.; Vidal, J. R.; Ruiz, J.; Sánchez, J.; Temprano, J.; Aymamí, J. M.; Lahuerta, L.; Montoro, L.; Campas, M.; García, M. A.; Canales, O.; Benavides, R.; Dymock, R.; García, R.; Ligustri, R.; Naves, R.; Lahuerta, S.; Pastor, S.

    2014-11-01

    Aims: This paper is a continuation of the first paper in this series, where we presented an extended study of the dust environment of a sample of short-period comets and their dynamical history. On this occasion, we focus on comets 81P/Wild 2 and 103P/Hartley 2, which are of special interest as targets of the spacecraft missions Stardust and EPOXI. Methods: As in the previous study, we used two sets of observational data: a set of images, acquired at Sierra Nevada and Lulin observatories, and the Afρ data as a function of the heliocentric distance provided by the amateur astronomical association Cometas-Obs. The dust environment of comets (dust loss rate, ejection velocities, and size distribution of the particles) was derived from our Monte Carlo dust tail code. To determine their dynamical history we used the numerical integrator Mercury 6.2 to ascertain the time spent by these objects in the Jupiter family Comet region. Results: From the dust analysis, we conclude that both 81P/Wild 2 and 103P/Hartley 2 are dusty comets, with an annual dust production rate of 2.8 × 109 kg yr-1 and (0.4-1.5) × 109 kg yr-1, respectively. From the dynamical analysis, we determined their time spent in the Jupiter family Comet region as ~40 yr in the case of 81P/Wild 2 and ~1000 yr for comet 103P/Hartley 2. These results imply that 81P/Wild 2 is the youngest and the most active comet of the eleven short-period comets studied so far, which tends to favor the correlation between the time spent in JFCs region and the comet activity previously discussed.

  1. 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.

  2. 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.

  3. 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.

  4. Comets. [IUE

    NASA Technical Reports Server (NTRS)

    Ahearn, Michael F.

    1988-01-01

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

  5. 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.

  6. Candidate Sample Acquisition System for the Rosetta Mission

    NASA Astrophysics Data System (ADS)

    Magnani, P. G.; Gerli, C.; Colombina, G.; Vielmo, P.

    1997-12-01

    The Comet Nucleus Sample Return (CNSR) Mission, is a cornerstone of ESA scientific program. While Giotto, Vega I and II provided the first picture of a comet nucleus, a much improved understanding of the nucleus and processes on it will result from in situ measurements and Earth based analysis of the material samples collected on the nucleus surface. The CNSR baseline mission foresees the landing and anchoring of a spacecraft on the comet nucleus surface, and the collection of the following three types of samples by means of a dedicated "Sample Acquisition System" (SAS): (1) a core sample gathered from surface down to a maximum depth of 3 meters to be cut in 0,5 m. long sections for storage; (2) a volatile material sample, to be gathered at the bottom of the core sample hole; and (3) a surface material sample, gathered from one or more locations on the surface. These samples will have to be placed in a storage canister in the capsule (to be returned on Earth) and preserved therein at a temperature not higher than 160 k. If on board sensing instrumentation identified comet nucleus features not allowing a safe landing, a back-up system based on a 'harpoon" sampler, would be launched from the spacecraft hovering the comet, and recovered via a tether line; degraded sample quality would be accepted in this case (no surface and volatile samples and limited core sampling depth).

  7. 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.

  8. 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.

  9. 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.

  10. The dynamical history of comet Halley

    NASA Technical Reports Server (NTRS)

    Yeomans, D. K.

    1985-01-01

    The history of the attempts to predict the motion of comet Halley is outlined and the importance of the so-called nongravitational forces acting upon this comet is emphasized. Recent orbital work of the International Halley Watch Astrometry Network is reviewed. Comet Halley's transverse nongravitational parameter is positive and nearly constant with time suggesting that the comet is in direct rotation without precession of the spin pole. The nongravitational effects are consistent with the vaporization of water ice from the comet's nucleus and long term integrations suggest that the comet has been in its present orbit for at least 16,000 years and probably much longer.

  11. Sulfides and oxides in comets

    NASA Technical Reports Server (NTRS)

    Rietmeijer, Frans J. M.

    1988-01-01

    Metal abundances associated with Sun-grazing P/comet Ikeya-Seki 1965f, the mineralogy of chrondritic interplanetary dust particles and cosmochemical affinities of Co, V, Cr, and Ni in extraterrestrial materials and probable vaporization data for nonsilicate minerals are used to evaluate the putative dearth of nonsilicates in short-period comets. It is concluded that sulfides and oxides are common, albeit minor, constituents of these comets. Sulfides and oxides can form in situ during perihelion passage in the nucleus of active short-period comets by sulfidation of Mg, Fe-silicates.

  12. 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.

  13. 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

  14. A Creaking and Cracking Comet

    NASA Astrophysics Data System (ADS)

    Faurschou Hviid, Stubbe; Hüttig, Christian; Groussin, Olivier; Mottola, Stefano; Keller, Horst Uwe; OSIRIS Team

    2016-10-01

    Since the middle of 2014 the OSIRIS cameras on the ESA Rosetta mission have been monitoring the evolution of the comet 67P/Churyumov-Gerasimenko as it passed through perihelion. During the perihelion passage several change events have been observed on the nucleus surface. For example existing large scale cracks have expanded and new large scale cracks have been created. Also several large scale "wave pattern" like change events have been observed in the Imhotep and Hapi regions. These are events not directly correlated with any normal visible cometary activity. One interpretation is that these are events likely caused by "seismic" activity. The seismic activity is created by the self-gravity stress of the non-spherical comet nucleus and stress created by the non-gravitational forces acting on the comet. The non-gravitational forces are changing the rotation period of the comet (~20min/perihelion passage) which induces a changing mechanical stress pattern through the perihelion passage. Also the diurnal cycle with its changing activity pattern is causing a periodic wobble in the stress pattern that can act as a trigger for a comet quake. The stress pattern has been modeled using a finite element model that includes self-gravity, the comet spin and the non-gravitational forces based on a cometary activity model. This paper will discuss what can be learned about the comet nucleus structure and about the cometary material properties from these events and from the FEM model.

  15. 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.

  16. Comet LINEAR Splits Further

    NASA Astrophysics Data System (ADS)

    2001-05-01

    Third Nucleus Observed with the VLT Summary New images from the VLT show that one of the two nuclei of Comet LINEAR (C/2001 A2), now about 100 million km from the Earth, has just split into at least two pieces . The three fragments are now moving through space in nearly parallel orbits while they slowly drift apart. This comet will pass through its perihelion (nearest point to the Sun) on May 25, 2001, at a distance of about 116 million kilometres. It has brightened considerably due to the splitting of its "dirty snowball" nucleus and can now be seen with the unaided eye by observers in the southern hemisphere as a faint object in the southern constellation of Lepus (The Hare). PR Photo 18a/01 : Three nuclei of Comet LINEAR . PR Photo 18b/01 : The break-up of Comet LINEAR (false-colour). Comet LINEAR splits and brightens ESO PR Photo 18a/01 ESO PR Photo 18a/01 [Preview - JPEG: 400 x 438 pix - 55k] [Normal - JPEG: 800 x 875 pix - 136k] ESO PR Photo 18b/01 ESO PR Photo 18b/01 [Preview - JPEG: 367 x 400 pix - 112k] [Normal - JPEG: 734 x 800 pix - 272k] Caption : ESO PR Photo 18a/01 shows the three nuclei of Comet LINEAR (C/2001 A2). It is a reproduction of a 1-min exposure in red light, obtained in the early evening of May 16, 2001, with the 8.2-m VLT YEPUN (UT4) telescope at Paranal. ESO PR Photo 18b/01 shows the same image, but in a false-colour rendering for more clarity. The cometary fragment "B" (right) has split into "B1" and "B2" (separation about 1 arcsec, or 500 km) while fragment "A" (upper left) is considerably fainter. Technical information about these photos is available below. Comet LINEAR was discovered on January 3, 2001, and designated by the International Astronomical Union (IAU) as C/2001 A2 (see IAU Circular 7564 [1]). Six weeks ago, it was suddenly observed to brighten (IAUC 7605 [1]). Amateurs all over the world saw the comparatively faint comet reaching naked-eye magnitude and soon thereafter, observations with professional telescopes indicated

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Infrared observations of comets

    NASA Technical Reports Server (NTRS)

    Hanner, Martha S.

    1991-01-01

    Selected comets are observed in the near infrared (1 to 2.2 micron) and thermal infrared (3.5 to 20 micron) with the NASA Infrared Telescope Facility (IRTF) and other telescopes as appropriate, in order to characterize the physical properties of the dust grains; their composition, size distribution, emissivity, and albedo. Systematic variations in these properties among comets are looked for, in order to understand the heterogeneity of comet nuclei. Spectrophotometry of the 10 micron silicate emission feature is particularly emphasized. The rate of dust production from the nucleus and its temporal variability are also determined. Knowledge of the dust environment is essential to S/C design and mission planning for NASA's CRAF mission.

  3. 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.

  4. 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

  5. The physics of comets

    NASA Technical Reports Server (NTRS)

    Mendis, D. A.; Houpis, H. L. F.; Marconi, M. L.

    1985-01-01

    This volume of the 'Fundamentals of Cosmic Physics' is concerned with the physics of comets. Aspects regarding the nucleus are discussed, taking into account observations, radius and albedo, mass, rotation, splitting and disruption, the temperature and sublimation of the cometary nucleus, the chemical composition, the electrostatic charging of the cometary nucleus, and the structure and evolution of the cometary nucleus. Other topics explored are related to the atmosphere and its interaction with the solar wind, the plasma tail, and the dust tail. Attention is given to excitation mechanisms, atmospheric abundances and production rates, chemical models of the inner coma, collisional processes and the multifluid approach, radiative transfer, the ionization processes, models of the inner layer, the outer coma, acceleration mechanisms in the plasma tail, the structure of the plasma tail, the cometary magnetosphere, dust grain orbits, gas-dust interaction in the inner coma, and the nature of the cometary dust.

  6. 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.

  7. Surface albedo of cometary nucleus

    NASA Astrophysics Data System (ADS)

    Mukai, T.; Mukai, S.

    A variation of the albedo on the illuminated disk of a comet nucleus is estimated, taking into account the multiple reflection of incident light due to small scale roughness. The dependences of the average albedo over the illuminated disk on the degree of roughness and on the complex refractive index of the surface materials are examined. The variation estimates are compared with measurements of the nucleus albedo of Comet Halley (Reitsema et al., 1987).

  8. 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

  9. 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.

  10. 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.

  11. Prompt Gamma Activation Analysis (PGAA): Technique of choice for nondestructive bulk analysis of returned comet samples

    NASA Technical Reports Server (NTRS)

    Lindstrom, David J.; Lindstrom, Richard M.

    1989-01-01

    Prompt gamma activation analysis (PGAA) is a well-developed analytical technique. The technique involves irradiation of samples in an external neutron beam from a nuclear reactor, with simultaneous counting of gamma rays produced in the sample by neutron capture. Capture of neutrons leads to excited nuclei which decay immediately with the emission of energetic gamma rays to the ground state. PGAA has several advantages over other techniques for the analysis of cometary materials: (1) It is nondestructive; (2) It can be used to determine abundances of a wide variety of elements, including most major and minor elements (Na, Mg, Al, Si, P, K, Ca, Ti, Cr, Mn, Fe, Co, Ni), volatiles (H, C, N, F, Cl, S), and some trace elements (those with high neutron capture cross sections, including B, Cd, Nd, Sm, and Gd); and (3) It is a true bulk analysis technique. Recent developments should improve the technique's sensitivity and accuracy considerably.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Fine-Gained CAIs in Comet Samples: Moderate Refractory Character and Comparison to Small Refractory Inclusions in Chondrites

    NASA Technical Reports Server (NTRS)

    Joswiak, D. J.; Brownlee, D. E.; Nguyen, A. N.; Messenger, S

    2017-01-01

    Examination of >200 comet Wild 2 particles collected by the Stardust (SD) mission shows that the CAI abundance of comet Wild 2's rocky material is near 1% and that nearly 50% of all bulbous tracks will contain at least one recognizable CAI fragment. A similar abundance to Wild 2 is found in a giant cluster IDP thought to be of cometary origin. The properties of these CAIs and their comparison with meteoritic CAIs provide important clues on the role of CAIs in the early Solar System (SS) and how they were transported to the edge of the solar nebula where Kuiper Belt comets formed. Previously, only two CAIs in comet Wild 2 had been identified and studied in detail. Here we present 2 new Wild 2 CAIs and 2 from a giant cluster cometary IDP, describe their mineralogical characteristics and show that they are most analogous to nodules in spinel-rich, fine-grained inclusions (FGIs) observed in CV3 and other chondrites. Additionally, we present new O isotope measurements from one CAI from comet Wild 2 and show that its oxygen isotopic composition is similar to some FGIs. This is only the second CAI from Wild 2 in which O isotopes have been measured.

  17. Distant Comets Photometry and Dust Modeling

    NASA Astrophysics Data System (ADS)

    Pittichova, Jana; Meech, K. J.; Bar-Nun, A.; Notesco, G.

    2008-09-01

    Several comets have been observed to develop coma on their in-bound leg at heliocentric distances from 5.84 to 11.49 AU. We will present the observational evidence for their activity and propose an explanation based on experiments carried out on amorphous, gas-laden ice samples that are 0.1 to 100 microns thick and formed by flowing water vapor and CO onto a cold surface. The considerable gas emission occurs when the amorphous ice anneals before 135K, where it transforms into a crystalline structure. This activity was found experimentally to be associated with gas release during annealing of the gas-laden amorphous ice. We observed and measured optical CCD photometry for two short-period and five long-period, dynamically new comets, that have enter the inner solar system directly from the Oort cloud for the first time. All of these comets have been observed pre-perihelion. Observations were done with the University of Hawaii 2.2-m telescope on Mauna Kea with the Tektronix 2x2K CCD camera through the Kron-Cousins B, V, R, I filter system. In order to observationally distinguish the physical causes of activity, not only is it important to observe comets at large heliocentric distances, but also those that are dynamically new and on the in-bound leg of their orbits at distances beyond where the amorphous to crystalline ice phase transition can occur. This research includes observations of the level of nucleus activity as a function of distance. We also would like to present Finson-Probstein (FP) dust modeling investigation on select comets. From the FP dust modeling of a cometary tail we can determine three basic parameters: the dust production rate, the particle distribution, and the emission velocity of the grains.

  18. Stardust Encounters Comet 81P/Wild 2

    NASA Technical Reports Server (NTRS)

    Tsou, P.; Brownlee, D. E.; Anderson, J. D.; Bhaskaran, S.; Cheuvront, A. R.; Clark, B. C.; Duxbury, T.; Economou, T.; Green, S. F.; Hanner, M. S.; Horz, F.; Kissel, J.; McDonnell, J. A. M.; Newburn, R. L.; Ryan, R. E.; Sandford, S. A.; Sekanina, Z.; Tuzzolino, A. J.; Vellinga, J. M.; Zolensky, M. E.

    2004-01-01

    Stardust successfully encountered comet 81P/Wild 2 on 2 January 2004 at a distance of 236.4 +/- 1 km. All encounter investigations acquired valuable new and surprising findings. The time-of-flight spectrometer registered 29 spectra during flyby and measured the first negative ion mass spectra of cometary particles. The dust detectors recorded particles over a broad mass range, 10(exp -11) to 10(exp -4) g. Unexpectedly, the dust distribution along Stardust's flight path was far from uniform, but instead occurred in short 'bursts', suggesting in-flight breakup of fragments ejected from the nucleus. High-resolution, stunning images of the Wild 2 surface show a diverse and complex variety of landforms not seen from comets 1P/Halley and 19P/Borrelly or icy satellites of the outer solar system. Longer-exposure images reveal large numbers of jets projected nearly around the entire perimeter of the nucleus, many of which appear to be highly collimated. A triaxial ellipsoidal fit of the Wild 2 nucleus images yields the principal nucleus radii of 1.65 X 2.00 X2.75 km (+/- 0.05 km). The orientations and source locations on the nucleus surface of 20 highly collimated and partially overlapping jets have been traced. There is every indication that the expected samples were successfully collected from the Wild 2 coma and are poised for a return to Earth on 15 January 2006.

  19. From the Vega mission to comet Halley to the Rosetta mission to comet 67/P Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Zelenyi, L. M.; Ksanfomality, L. V.

    2016-12-01

    The data acquired by the Vega and Giotto spacecraft, while investigating comet 1P/Halley in 1986, are compared to the results of the first phase of exploration of the nucleus of comet 67P/Churyumov-Gerasimenko performed with the Rosetta and Philae modules. The course of the Rosetta mission activity and the status of the modules after the Philae probe landing on the comet's nucleus are overviewed. Since some elements of the touchdown equipment failed, a number of in-situ experiments on the comet's nucleus were not carried out.

  20. Unidentified ions in comets

    NASA Technical Reports Server (NTRS)

    Engel, Lisa

    1990-01-01

    Optical spectra were taken of comets Halley, West, and Brorsen-Metcalf in the wavelength region 3200 to 6400 A. These spectra were offset approximately 10(exp -5) to 10(exp -6) km tailward from the nucleus so that the features detected were all ions with the exception of a very small residual C2 emission at 5165 A. The full labeled tail spectrum of comet Halley is given. While most of the features detected are attributable to CO(+), H2O(+), CO2(+), CH(+), and OH(+), there are three moderately strong bands in the spectra of comets Halley and Brorsen-Metcalf which remain unidentified. These features were not detected in comet West. All three spectra in the 4800 to 5400 A region are presented, Brorsen-Metcalf is the gassiest of the three. The central wavelengths of the unidentified features are 4930, 5300, and 6000 A. In an effort to identify the ions responsible for these features as well as to confirm previous identifications, laboratory spectra of ions were compared with the comet spectra. H2O(+) and CO(+) are known to have extensive emission in the 4800 to 6200 A region. Therefore, the possibility that these unidentified features are due to H2O(+) and CO(+) was investigated. A search for the following bands was conducted: H2O(+) (11-0), H2O(+) (12-0), H2O(+) (13-1), CO(+) (1-1), and CO(+) (0-0). CO(+) (1-1) and CO(+) (0-0) were previously identified and are present in all the spectra examined. The H2O(+) (11-0) band was identified. Comparison of the H2O(+) (11-0) synthetic spectrum with comet Brorsen-Metcalf data is presented. The relative fluxes of the blended H2O(+) lines in the synthetic spectrum match those of the cometary data. After eliminating H2O(+) and CO(+) as significant contributors to the stronger unidentified features, spectra of ions which are not yet identified in the optical region of comets were compared to the data. These ions are NH(+), CS(+), and C2(+). None of these ions appears to be a significant contributor to the optical spectra of these

  1. 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

  2. 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)

  3. Gas phase chemistry in comets

    NASA Technical Reports Server (NTRS)

    Oppenheimer, M.

    1976-01-01

    The significance of gas phase reactions in determining the nuclear structure of comets is discussed. The sublimation of parent molecules such as H2O, CH4, CO2, and NH3 from the surface of the nucleus and their subsequent photodissociation and ionization in forming observed cometary molecular species are elaborated.

  4. A close look at Halley's comet

    SciTech Connect

    Balsiger, H.; Fechtig, H.; Geiss, J.

    1988-09-01

    Halley's comet is not only the most famous and historically the most important of comets, but also one of the best-suited to space probe encounters. Halley's comet has an orbit that is sufficiently well known for a probe to be directed close enough to the nucleus to obtain good data. Moreover, the strong emission of gas and dust from the comet suggests that it retains much of its original icy and dusty components. In other words, the comet probably consists of pristine material, and so it reflects the conditions prevailing when the solar system was born. This paper is based primarily on the results obtained by the Giotto space probe. The Giotto mission made particularly significant contributions in determining the composition of the neutral and ionized gases in the coma. Undoubtedly the highlight of the Giotto voyage was the close approach of the spacecraft to the nucleus itself. Now the missions to Halley's comet have confirmed the essential features of the accepted model of cometary nuclei: the dirty snowball model. The dimensions of the nucleus have been estimated to be roughly 16-by-eight-by-eight kilometers. The surface area of the nucleus is approximately four times larger than had been thought. A further surprise is that the jets appear to be emitted from a relatively small fraction of the comet's total surface. 7 figs.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  6. 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

  7. 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

  8. Comets at radio wavelengths

    NASA Astrophysics Data System (ADS)

    Crovisier, Jacques; Bockelée-Morvan, Dominique; Colom, Pierre; Biver, Nicolas

    2016-11-01

    Comets are considered as the most primitive objects in the Solar System. Their composition provides information on the composition of the primitive solar nebula, 4.6 Gyr ago. The radio domain is a privileged tool to study the composition of cometary ices. Observations of the OH radical at 18 cm wavelength allow us to measure the water production rate. A wealth of molecules (and some of their isotopologues) coming from the sublimation of ices in the nucleus have been identified by observations in the millimetre and submillimetre domains. We present an historical review on radio observations of comets, focusing on the results from our group, and including recent observations with the Nançay radio telescope, the IRAM antennas, the Odin satellite, the Herschel space observatory, ALMA, and the MIRO instrument aboard the Rosetta space probe.

  9. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1977-01-01

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

  10. Dust evolution from comets

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1976-01-01

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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Sketching Comets

    NASA Astrophysics Data System (ADS)

    Perez, Jeremy

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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. Comet Schwassmann-Wachmann I

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    NASA's new Spitzer Space Telescope has captured an image of an unusual comet that experiences frequent outbursts, which produce abrupt changes in brightness. Periodic comet Schwassmann-Wachmann I (P/SW-1) has a nearly circular orbit just outside that of Jupiter, with an orbital period of 14.9 years. It is thought that the outbursts arise from the build-up of internal gas pressure as the heat of the Sun slowly evaporates frozen carbon dioxide and carbon monoxide beneath the blackened crust of the comet nucleus. When the internal pressure exceeds the strength of the overlying crust, a rupture occurs, and a burst of gas and dust fragments is ejected into space at speeds of 450 miles per hour (200 meters per second).

    This 24-micron image of P/SW-1 was obtained with the multiband imaging photometer for Spitzer. The image shows thermal infrared emission from the dusty coma and tail of the comet. The nucleus of the comet is about 18 miles (30 kilometers) in diameter and is too small to be resolved by Spitzer. The micron-sized dust grains in the coma and tail stream out away from the Sun. The dust and gas comprising the comet's nucleus is part of the same primordial materials from which the Sun and planets were formed billions of years ago. The complex carbon-rich molecules they contain may have provided some of the raw materials from which life originated on Earth.

    Schwassmann-Wachmann 1 is thought to be a member of a relatively new class of objects called 'Centaurs,' of which 45 objects are known. These are small icy bodies with orbits between those of Jupiter and Neptune. Astronomers believe that Centaurs are recent escapees from the Kuiper Belt, a zone of small bodies orbiting in a cloud at the distant reaches of the solar system.

    Two asteroids, 1996 GM36 (left) and 5238 Naozane (right) were serendipitously captured in the comet image. Because they are closer to us than the comet and have faster orbital

  1. 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.

  2. 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.

  3. 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.

  4. 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

    2016-09-01

    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.

  5. 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

  6. 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.

  7. Interception of comet Hyakutake's ion tail at a distance of 500 million kilometres

    PubMed

    Gloeckler; Geiss; Schwadron; Fisk; Zurbuchen; Ipavich; von Steiger R; Balsiger; Wilken

    2000-04-06

    Remote sensing observations and the direct sampling of material from a few comets have established the characteristic composition of cometary gas. This gas is ionized by solar ultraviolet radiation and the solar wind to form 'pick-up' ions, ions in a low ionization state that retain the same compositional signatures as the original gas. The pick-up ions are carried outward by the solar wind, and they could in principle be detected far from the coma (Sampling of pick-up ions has also been used to study interplanetary dust, Venus' tail and the interstellar medium.) Here we report the serendipitous detection of cometary pick-up ions, most probably associated with the tail of comet Hyakutake, at a distance of 3.4 AU from the nucleus. Previous observations have provided a wealth of physical and chemical information about a small sample of comets, but this detection suggests that remote sampling of comet compositions, and the discovery of otherwise invisible comets, may be possible.

  8. 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.

  9. 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.

  10. Catastrophic Disruption of Comet ISON

    NASA Astrophysics Data System (ADS)

    Keane, Jacqueline V.; Milam, Stefanie N.; Coulson, Iain M.; Kleyna, Jan T.; Sekanina, Zdenek; Kracht, Rainer; Riesen, Timm-Emmanuel; Meech, Karen J.; Charnley, Steven B.

    2016-11-01

    We report submillimeter 450 and 850 μm dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31-0.08 au prior to perihelion on 2013 November 28 (r h = 0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60″ (>105 km) in the anti-solar direction. Deconvolution of the November 28.04 850 μm image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing ˜5.2 × 1010 kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the comet's residual nucleus.

  11. Catastrophic Disruption of Comet ISON

    NASA Technical Reports Server (NTRS)

    Keane, Jacqueline V.; Milam, Stefanie N.; Coulson, Iain M.; Kleyna, Jan T.; Sekanina, Zdenek; Kracht, Rainer; Riesen, Timm-Emmanuel; Meech, Karen J.; Charnley, Steven B.

    2016-01-01

    We report submillimeter 450 and 850 microns dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31-0.08 au prior to perihelion on 2013 November 28 (rh?=?0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60? (greater than 10(exp 5) km in the anti-solar direction. Deconvolution of the November 28.04 850 microns image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing approximately 5.2?×?10(exp 10) kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the comet's residual nucleus.

  12. 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.

  13. 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.

  14. Featured Image: A Comet's Coma

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-11-01

    This series of images (click for the full view!) features the nucleus of comet 67P/Churymov-Gerasimenko. The images were taken with the Wide Angle Camera of RosettasOSIRIS instrument asRosetta orbited comet 67P. Each column represents a different narrow-band filter that allows us to examine the emission of a specific fragment species, and the images progress in time from January 2015 (top) to June 2015 (bottom). In a recent study, Dennis Bodewits (University of Maryland) and collaborators used these images to analyze the comets inner coma, the cloud of gas and dust produced around the nucleus as ices sublime. OSIRISs images allowed the team to explore how the 67Ps inner coma changed over time as the comet approached the Sun marking the first time weve been able to study such an environment at this level of detail. To read more about what Bodewits and collaborators learned, you can check out their paper below!CitationD. Bodewits et al 2016 AJ 152 130. doi:10.3847/0004-6256/152/5/130

  15. 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.

  16. 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

  17. The splitting of Comet Halley 1986

    NASA Astrophysics Data System (ADS)

    Chen, Dao-Han; Zheng, Jia-Quing; Liu, Zong-Li; Yan, Lin-Shan; Lui, Lin-Zhong; Zhou, Xing-Hai; Wu, Zhi-Xian; Gilmore, A. C.

    1987-09-01

    Nine photographs taken on 25 Mar., 1986 show that the nucleus of Comet Halley split into 2 widely separated nuclei. The separated projected distance on the plane of the sky is 5000 km. The principal nucleus and the secondary nucleus exhibit their own comas. The prominant jet ejected from the companion curves up to a height of several thousand kilometers and the secondary nucleus must fade out of sight within only a few days. In combination with the results of photoelectric observations it seems that this event of splitting coincides with an outburst. Photographs were digitized, and the image enhancement is described.

  18. 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

  19. 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.

  20. 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

  1. 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.

  2. Three predictions: Comet 67P/Churyumov-Gerasimenko, comet C/2012 K1 PANSTARRS, and comet C/2013 V5 Oukaimeden

    NASA Astrophysics Data System (ADS)

    Ferrín, Ignacio

    2014-09-01

    We make the following predictions: (1) The secular light curve (SLC) of comet 67P/Churyumov-Gerasimenko exhibits a photometric anomaly in magnitude that is present in 1982, 1996, 2002 and 2009. Thus it must be real. We interpret this anomaly as a topographic feature on the surface of the nucleus that may be a field of debris, a region made only of dust or an area of solid stones but in any case it is depleted in volatiles. We predict that images taken by spacecraft Rosetta will show a region morphologically different to the rest of the nucleus, at the pole pointing to the Sun near perihelion. (2) Comet C/2012 K1 PANSTARRS exhibits the same Slope Discontinuity Event (SDE)+magnitude dip after the event than other comets listed in Table 1 most of which disintegrated. This group includes comet C/2012 S1 ISON. Thus, it is reasonable to expect that this comet may disintegrate too. The probability of disintegration of this comet is 27%. (3) Comet C/2013 V5 Oukaimeden exhibits the same SDE+standstill signature exhibited by other comets in Table 1. We predict that there is a 93% probability that this comet will disintegrate. (4) Another purpose of this work is to present evidence to conclude that the SLCs have predictive power.

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

    NASA Astrophysics Data System (ADS)

    Ye (叶泉志), Quan-Zhi; Hui (许文韬), Man-To; Brown, Peter G.; Campbell-Brown, Margaret D.; Pokorný, Petr; Wiegert, Paul A.; Gao (高兴), 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.

  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. The comet disintegration and meteor streams

    NASA Astrophysics Data System (ADS)

    Guliyev, A. S.; Poladova, U. J.

    2015-03-01

    Possibility of disintegration of proto-comet nucleus of sungraser comets in three zones of Solar System predicted by one of authors is considered. Testing of parameters of 118 split comets confirms the basic idea. Results of the statistical analysis of comet outbursts gave us additional argument in favor of this assumption. Almost twenty years have passed since, as a result of the search for host phases of isotopically unusual noble gases, the first discovery in 1987 of surviving pre-solar minerals (diamond and silicon carbide) in primitive meteorites. These were followed by others (graphite, refractory oxides, silicon nitride, and finally silicates) in the years since. Pre-solar grains occur in even higher abundance than in meteorites in interplanetary dust particles (IDPs). The result is a kind of `new astronomy' based on the study of pre-solar condensates with all the methods available in modern analytical laboratories.

  6. Thermal modeling of comet Kopff: Implications for the CRAF mission

    NASA Technical Reports Server (NTRS)

    Weissman, Paul; Clause, Celia

    1991-01-01

    A thermal model of periodic comet Kopff was developed to aid in planning for the Comet Rendezvous Asteroid Flyby mission. The model is based on the comet nucleus model, which estimates the surface temperature distribution and sublimation rates on a rotating icy sphere in heliocentric orbit. The model results are compared with the observed gas production rates from Kopff in 1983. It is found that approximately 15 percent of the sunlit nucleus surface is active, a relatively high fraction for a typical short-period comet. This suggests that the actual nucleus radius may be larger than the model value. The slope of the observed gas production curve with heliocentric distance is steeper than that predicted by the thermal model. This may indicate the existence of a more complex process than direct sublimation of surface ices, such as gas diffusion through a nonvolatile insulating crust.

  7. 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).

  8. 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.

  9. 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.

  10. Simulations of directed energy comet deflection

    NASA Astrophysics Data System (ADS)

    Zhang, Qicheng; Lubin, Philip M.; Hughes, Gary B.

    2016-09-01

    Earth-crossing asteroids and comets pose a long-term hazard to life and property on Earth. Schemes to mitigate the impact threat have been studied extensively but tend to focus on asteroid diversion while neglecting the possibility of a comet threat. Such schemes often demand physically intercepting the target by spacecraft, a task feasible only for targets identified decades in advance in a restricted range of orbits. A threatening comet is unlikely to satisfy these criteria and so necessitates a fundamentally different approach for diversion. Comets are naturally perturbed from purely gravitational trajectories through solar heating of their surfaces which activates sublimation-driven jets. Artificial heating of a comet, such as by a high-powered laser array in Earth orbit, may supplement natural heating by the Sun to purposefully manipulate its path to avoid an impact. The effectiveness of any particular laser array for a given comet depends on the comet's heating response which varies dramatically depending on factors including nucleus size, orbit and dynamical history. These factors are incorporated into a numerical orbital model using established models of nongravitational perturbations to evaluate the effectiveness and feasibility of using high-powered laser arrays in Earth orbit or on the ground to deflect a variety of comets. Simulation results suggest that orbital arrays of 500m and 10GW operating for 10 min=d over 1 yr may be adequate for mitigating impacts by comets up to 500m in diameter. Continuously operating ground-based arrays of 100m and 10GW may be similarly effective when appropriately located.

  11. Hubble Probes Inner Region of Comet Hyakutake

    NASA Technical Reports Server (NTRS)

    1996-01-01

    These are NASA Hubble Space Telescope images of comet Hyakutake (designated C/1996 B2), taken at 8:30 P.M., EST on Monday, March 25 when the comet passed at a distance of only 9.3 million miles from Earth.

    Unlike most of the published images of Hyakutake, these Hubble images focus on a very small region near the heart of the comet, the icy, solid nucleus. The Hubble images provide an exceptionally clear view of the near-nucleus region of comet Hyakutake.

    The images were taken through a red filter with the Wide Field Planetary Camera 2 (in WF mode). The sunward and tailward directions are at approximately the 4 o'clock and 11 o'clock positions, respectively. Celestial North and East are at approximately the 5:30 and 2:30 positions, respectively.

    FULL-FIELD VIEW (Left) This image is 2070 miles across (3340 km) and shows that most of the dust is being produced on the sunward-facing hemisphere of the comet. Also at upper left are three small pieces which have broken off the comet and are forming there own tails.

    Icy regions on the nucleus are activated as they rotate into sunlight, ejecting large amounts of dust in the jets that are faintly visible in this image. Sunlight striking this dust eventually turns it around and 'blows' it into the tailward hemisphere. What might be another jet is emanating from the nightside of the nucleus, but this direction might be misleading due to the angle of the jet relative to our line-of-site.

    CLOSE-UP OF NUCLEUS (Bottom Right) This expanded view of the near-nucleus region is only 470 miles (760 km) across. The nucleus is near the center of the frame, but the brightest area is probably the tip of the strongest dust jet rather than the nucleus itself. Presumably, the nucleus surface lies just below this bright jet. Further analysis may allow scientists to disentangle the nucleus from its atmosphere (coma), presently its difficult to estimate the nucleus' size.

    CLOSE-UP OF COMET FRAGMENTS (Top Right) This image shows

  12. 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.

  13. Evidence for geologic processes on comets

    NASA Astrophysics Data System (ADS)

    Sunshine, Jessica M.; Thomas, Nicolas; El-Maarry, Mohamed Ramy; Farnham, Tony L.

    2016-11-01

    Spacecraft missions have resolved the nuclei of six periodic comets and revealed a set of geologically intriguing and active small bodies. The shapes of these cometary nuclei are dominantly bilobate reflecting their formation from smaller cometesimals. Cometary surfaces include a diverse set of morphologies formed from a variety of mechanisms. Sublimation of ices, driven by the variable insolation over the time since each nucleus was perturbed into the inner Solar System, is a major process on comets and is likely responsible for quasi-circular depressions and ubiquitous layering. Sublimation from near-vertical walls is also seen to lead to undercutting and mass wasting. Fracturing has only been resolved on one comet but likely exists on all comets. There is also evidence for mass redistribution, where material lifted off the nucleus by subliming gases is deposited onto other surfaces. It is surprising that such sedimentary processes are significant in the microgravity environment of comets. There are many enigmatic features on cometary surfaces including tall spires, kilometer-scale flows, and various forms of depressions and pits. Furthermore, even after accounting for the differences in resolution and coverage, significant diversity in landforms among cometary surfaces clearly exists. Yet why certain landforms occur on some comets and not on others remains poorly understood. The exploration and understanding of geologic processes on comets is only beginning. These fascinating bodies will continue to provide a unique laboratory for examining common geologic processes under the uncommon conditions of very high porosity, very low strength, small particle sizes, and near-zero gravity.

  14. 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

  15. 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

  16. OpenComet: an automated tool for comet assay image analysis.

    PubMed

    Gyori, Benjamin M; Venkatachalam, Gireedhar; Thiagarajan, P S; Hsu, David; Clement, Marie-Veronique

    2014-01-01

    Reactive species such as free radicals are constantly generated in vivo and DNA is the most important target of oxidative stress. Oxidative DNA damage is used as a predictive biomarker to monitor the risk of development of many diseases. The comet assay is widely used for measuring oxidative DNA damage at a single cell level. The analysis of comet assay output images, however, poses considerable challenges. Commercial software is costly and restrictive, while free software generally requires laborious manual tagging of cells. This paper presents OpenComet, an open-source software tool providing automated analysis of comet assay images. It uses a novel and robust method for finding comets based on geometric shape attributes and segmenting the comet heads through image intensity profile analysis. Due to automation, OpenComet is more accurate, less prone to human bias, and faster than manual analysis. A live analysis functionality also allows users to analyze images captured directly from a microscope. We have validated OpenComet on both alkaline and neutral comet assay images as well as sample images from existing software packages. Our results show that OpenComet achieves high accuracy with significantly reduced analysis time.

  17. 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.

  18. Formation of Explosive Comet in Proto-planetary Nebula

    NASA Astrophysics Data System (ADS)

    Gladysheva, O.

    2013-09-01

    The question about the formation of the comet's nucleus is examined, taking into account the peculiarities of the destruction of the Tunguska cosmic body. According to the suggested model, the comet's nucleus consists from ample quantity of organic coverings, one covering inserts into another covering, similar to Russian set of nesting dolls. The space between neighbouring coverings is filled by different size lumps and grains down to micron size. Comets were formed in the inner region of the solar system in the early stages of the evolution of the proto-planetary cloud. Proto-comets began to accumulate their mass on the periphery of protoplanetary nebula (far from the ecliptic), where the temperature decreases to <100 K. Then, under the influence of gravitation, comets many times crossed the plane of the ecliptic, performing relaxation oscillations. Coverings on comet surfaces formed during every crossing by the comet of the ecliptic area, where the temperature was high. During their oscillations, most comets were thrown out of the inner regions of the solar system by planetary perturbations in the Öpik-Oort cloud.

  19. 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

  20. 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.

  1. Chemical diversity in the comet population

    NASA Astrophysics Data System (ADS)

    Biver, Nicolas

    2015-08-01

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

  2. Numerical simulation of comet nuclei. I - Water-ice comets

    NASA Technical Reports Server (NTRS)

    Herman, G.; Podolak, M.

    1985-01-01

    A one-dimensional numerical model of pure water-ice cometary nuclei is presented, and the influence of the nuclear interior as a heat reservoir on the behavior of the nuclear surface is examined. It is shown that a number of effects, including the thermal inertia due to heat stored in the core and the release of latent heat, which goes entirely into heating the adjacent layers or into sublimation on passing through a phase transition from amorphous to crystalline ice, can help to explain such characteristics as the asymmetrical lightcurve of Comet Halley. Results are given for the cases of Comet Schwassmann-Wachmann 1 and Comet Encke. Consideration is also given to the insulating effect of an evolving dust mantle. The role of this mantle in determining the surface temperature of the ice core is studied as a function of the mass fraction of the dust in the ice-dust mixture and the thermal conductivity of the nucleus. The loose-lattice model of Mendis and Brin (1977) indicates that both high dust to ice ratios and high-core conductivities inhibit mantle blowoff.

  3. Asteroids and Comets Outreach Compilation

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Contents include various different animations in the area of Asteroids and Comets. Titles of the short animated clips are: STARDUST Mission; Asteroid Castallia Impact Simulation; Castallia, Toutatis and the Earth; Simulation Asteroid Encounter with Earth; Nanorover Technology Task; Near Earth Asteroid Tracking; Champollian Anchor Tests; Early Views of Comets; Exploration of Small Bodies; Ulysses Resource Material from ESA; Ulysses Cometary Plasma Tail Animation; and various discussions on the Hale-Bopp Comet. Animation of the following are seen: the Stardust aerogel collector grid collecting cometary dust particles, comet and interstellar dust analyzer, Wiper-shield and dust flux monitor, a navigation camera, and the return of the sample to Earth; a comparison of the rotation of the Earth to the Castallia and Tautatis Asteroids; an animated land on Tautatis and the view of the motion of the sky from its surface; an Asteroid collision with the Earth; the USAF Station in Hawaii; close-up views of asteroids; automatic drilling of the Moon; exploding Cosmic Particles; and the dropping off of the plasma tail of a comet as it travels near the sun.

  4. 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.

  5. 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

  6. Nongravitational forces on comets

    NASA Technical Reports Server (NTRS)

    Marsden, B. G.

    1976-01-01

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

  7. 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...

  8. 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...

  9. 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.

  10. A Million Comet Pieces

    NASA Technical Reports Server (NTRS)

    2006-01-01

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

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

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

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

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

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

  11. THE NEOWISE-DISCOVERED COMET POPULATION AND THE CO + CO{sub 2} PRODUCTION RATES

    SciTech Connect

    Bauer, James M.; Stevenson, Rachel; Kramer, Emily; Mainzer, A. K.; Masiero, Joseph R.; Weissman, Paul R.; Nugent, Carrie R.; Sonnett, Sarah; Grav, Tommy; Fernández, Yan R.; Cutri, Roc M.; Dailey, John W.; Masci, Frank J.; Blair, Nathan; Lucas, Andrew; Meech, Karen J.; Walker, Russel; Lisse, C. M.; McMillan, Robert S.; Wright, Edward L.; Collaboration: WISE and NEOWISE Teams

    2015-12-01

    The 163 comets observed during the WISE/NEOWISE prime mission represent the largest infrared survey to date of comets, providing constraints on dust, nucleus size, and CO + CO{sub 2} production. We present detailed analyses of the WISE/NEOWISE comet discoveries, and discuss observations of the active comets showing 4.6 μm band excess. We find a possible relation between dust and CO + CO{sub 2} production, as well as possible differences in the sizes of long and short period comet nuclei.

  12. 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.

  13. The comets of 1999

    NASA Astrophysics Data System (ADS)

    Shanklin, J.

    2009-12-01

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

  14. The comets of 2000

    NASA Astrophysics Data System (ADS)

    Shanklin, J. D.

    2010-08-01

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

  15. Newton and comets

    NASA Astrophysics Data System (ADS)

    Bork, Alfred

    1987-12-01

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

  16. 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.

  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

    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.

  19. 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.

  20. Mid-infrared spectra of comet nuclei

    NASA Astrophysics Data System (ADS)

    Kelley, Michael S. P.; Woodward, Charles E.; Gehrz, Robert D.; Reach, William T.; Harker, David E.

    2017-03-01

    Comet nuclei and D-type asteroids have several similarities at optical and near-IR wavelengths, including near-featureless red reflectance spectra, and low albedos. Mineral identifications based on these characteristics are fraught with degeneracies, although some general trends can be identified. In contrast, spectral emissivity features in the mid-infrared provide important compositional information that might not otherwise be achievable. Jovian Trojan D-type asteroids have emissivity features strikingly similar to comet comae, suggesting that they have the same compositions and that the surfaces of the Trojans are highly porous. However, a direct comparison between a comet and asteroid surface has not been possible due to the paucity of spectra of comet nuclei at mid-infrared wavelengths. We present 5-35 μm thermal emission spectra of comets 10P/Tempel 2, and 49P/Arend-Rigaux observed with the Infrared Spectrograph on the Spitzer Space Telescope. Our analysis reveals no evidence for a coma or tail at the time of observation, suggesting the spectra are dominated by the comet nucleus. We fit each spectrum with the near-Earth asteroid thermal model (NEATM) and find sizes in agreement with previous values. However, the NEATM beaming parameters of the nuclei, 0.74-0.83, are systematically lower than the Jupiter-family comet population mean of 1.03 ± 0.11, derived from 16- and 22-μm photometry. We suggest this may be either an artifact of the spectral reduction, or the consequence of an emissivity low near 16 μm. When the spectra are normalized by the NEATM model, a weak 10-μm silicate plateau is evident, with a shape similar to those seen in mid-infrared spectra of D-type asteroids. A silicate plateau is also evident in previously published Spitzer spectra of the nucleus of comet 9P/Tempel 1. We compare, in detail, these comet nucleus emission features to those seen in spectra of the Jovian Trojan D-types (624) Hektor, (911) Agamemnon, and (1172) Aneas, as well

  1. 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.

  2. The Mariner Mark II Comet Rendezvous/Asteroid Flyby Mission

    NASA Technical Reports Server (NTRS)

    Stetson, D. S.; Lundy, S. A.; Yen, C. L.

    1984-01-01

    The Comet Rendezvous/Asteroid Flyby will be the first mission in the Mariner Mark II program. The July 1990 launch will result in a fast flyby of the asteroid Tanete in May 1991 and a rendezvous with comet Kopff in February 1994, 879 days before comet perihelion. The spacecraft will return detailed data on the comet nucleus and its environment for nearly 1000 days. Several important comet characteristics will not be precisely known until the spacecraft performs its first measurements, which means that operations strategies must be adaptable to a range of conditions. In addition, the operation of a spacecraft in a dusty environment near a low-mass body imposes unique constraints on trajectory and orbit design.

  3. Disintegration of comet nuclei

    NASA Astrophysics Data System (ADS)

    Ksanfomality, Leonid V.

    2012-02-01

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

  4. 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.

  5. Detailed abundances of a large sample of giant stars in M 54 and in the Sagittarius nucleus

    NASA Astrophysics Data System (ADS)

    Carretta, E.; Bragaglia, A.; Gratton, R. G.; Lucatello, S.; Bellazzini, M.; Catanzaro, G.; Leone, F.; Momany, Y.; Piotto, G.; D'Orazi, V.

    2010-09-01

    Homogeneous abundances of light elements, α-elements, and Fe-group elements from high-resolution FLAMES spectra are presented for 76 red giant stars in NGC 6715 (M 54), a massive globular cluster (GC) lying in the nucleus of the Sagittarius dwarf galaxy. We also derived detailed abundances for 27 red giants belonging to the Sgr nucleus. Our abundances measure the intrinsic metallicity dispersion (~0.19 dex, rms scatter) of M 54, with the bulk of stars peaking at [Fe/H] ~ -1.6 and a long tail extending to higher metallicities, similar to ω Cen. The spread in these probable nuclear star clusters exceeds those of most GCs: these massive clusters are located in a region intermediate between normal GCs and dwarf galaxies. The GC M 54 exibits a Na-O anticorrelation, a typical signature of GCs, which is instead absent for the Sgr nucleus. The light elements (Mg, Al, Si) participating in the high temperature Mg-Al cycle show that the entire pattern of (anti)correlations produced by proton-capture reactions in H-burning is clearly different between the most metal-rich and most metal-poor components in the two most massive GCs in the Galaxy, confirming early results based on the Na-O anticorrelation. As in ω Cen, stars affected by most extreme processing, i.e. showing the signature of more massive polluters, are those of the metal-rich component. These observations can be understood if the burst of star formation giving birth to the metal-rich component was delayed by as much as 10-30 Myr with respect to the metal-poor one. The evolution of these massive GCs can be easily reconciled in the general scenario for the formation of GCs sketched previously by ourselves, taking into account that ω Cen may have already incorporated the surrounding nucleus of its progenitor and lost the remainder of the hosting galaxy while the two are still observable as distinct components in M 54 and the surrounding field. Based on observations collected at ESO telescopes under programme 081.D

  6. Detection of CN emission in Comet P/Halley

    NASA Technical Reports Server (NTRS)

    Wyckoff, S.; Wehinger, P. A.; Belton, M. J. S.

    1986-01-01

    The first detection of the CN 3883 A band in emission in Comet P/Halley (1982) in February 1985 is reported. The detection technique, which is described, used blind offsets from secondary reference stars to the comet's predicted position, and involved plotting the comet's track on an enlargement of an appropriate section of the Palomar Sky Survey E plates. The strong solar continuum in the resulting cometary spectrum demonstrates the dominance of the dust reflection spectrum and the reflection from the nucleus. The 3883 A feature is identified with the v = 0 band sequence of the blue system of CN; no other significant features were identified in the spectrum.

  7. On the composition of the dust component of comet nuclei

    NASA Astrophysics Data System (ADS)

    Iavnel', A. A.

    1988-11-01

    This paper considers the composition of the dust component of comet nuclei, with special attention given to Vega mass-spectrometry data on the Comet Halley nucleus and neutron-activation analysis data on magnetite spherules found at the Tungusk site. A comparison of these data with those on the carbonaceous chondrites of the Ornans (CO) and the Ivuna (CI) types and on the particles from the Draconid meteoritic shower suggest that Comet Halley, whose dust-particle composition corresponded to that of the CI type except for a higher content of volatiles, was formed at a greater distance from the sun than the asteroids.

  8. Small-size dust particles near Halley's Comet

    NASA Astrophysics Data System (ADS)

    Sagdeev, R. Z.; Evlanov, E. N.; Fomenkova, M. N.; Prilutskii, O. F.; Zubkov, B. V.

    Dust-impact PUMA mass-analyzers aboard the spacecrafts VEGA-1 and VEGA-2 allow to conduct the first direct measurements of mass-spectra of comet Halley's dust envelope particles with masses higher than 10 to the -17th g. The analysis of spectra measured by the PUMA instruments showed that unindentified peaks in this spectra could be associated with very small particles. Detection of small-size particles in the dust envelope of comet Halley agrees with the idea that the comet's nucleus is an interstellar dust aggregate which contains very small particles.

  9. Ion composition and dynamics at comet Halley

    NASA Technical Reports Server (NTRS)

    Balsiger, H.; Altwegg, K.; Buehler, F.; Geiss, J.; Ghielmetti, A. G.; Goldstein, B. E.; Goldstein, R.; Huntress, W. T.

    1986-01-01

    The Giotto space probe's ion mass spectrometer has obtained data on the composition and velocity distributions of cometary ions at distances of between 7.5 million and 1300 km from the comet Halley nucleus. Solar wind He(2+) was found throughout the coma, as close as 5000 km, with the He(+) produced by charge exchange being within about 200,000 km. A pile-up of heavy cometary ions was found at about 10,000 km from the nucleus. Inside the contact surface, which was found at about 4600 km, ion temperatures as low as about 340 K and outflow velocities of about 1 km/sec were found.

  10. Discovery of Accelerating Plasmoids in the Tail of Comet Encke

    NASA Astrophysics Data System (ADS)

    Kellett, B.; Bingham, R.; Davies, J. A.; Bewsher, D.; Harrison, R. A.; Davis, C. J.; Eyles, C. J.; Crothers, S. R.

    2007-12-01

    Comet 2P/Encke was the second comet to have its return correctly predicted (in 1819). Encke is a Jupiter-family comet with a period of 3.30 years and a perihelion distance of 0.338 AU. The interaction between cometary plasma and the solar wind plasma provides the potential for remote monitoring of the solar wind. In this regard comet Encke is potentially a very useful probe of the solar wind because of its very short orbital period and therefore large number of close approaches to the Sun. However, for this reason it is likely to have exhausted most of its reserves of ice and therefore possess a less dense plasma tail. The comet could therefore respond faster and more dynamically to solar wind variations than the tail of a more active or higher gas production comet. The Heliospheric Imager (HI) of STEREO-A (HI-1A), observed comet 2P/Encke during April, 2007. The comet was predicted to have reached perihelion on April 19th 0 UT. This paper will only consider the observations obtained by HI-1A on April 25th to 27th, 2007. At this time the comet was around 0.63 AU from Earth and 0.39 AU from the Sun. The comet was seen to exhibit a distinct "flick" of its plasma tail on April 26th and a series of "whiplash" events. However, the most interest phenomena seen was a whole series of "plasmoids" that were observed to break off from the brighter part of the tail near the nucleus and accelerate along the tail for 4-5 million kilometres down-wind of the nucleus.

  11. The comet Halley diamagnetic cavity boundary

    NASA Technical Reports Server (NTRS)

    Cravens, T. E.; Lindgren, C. J.; Puhl, P.

    1995-01-01

    The magnetometer onboard the Giotto spacecraft observed a diamagnetic cavity surrounding the nucleus of comet Halley. A narrow transition layer with enhanced plasma density is formed at this shock-like boundary as a flux of cometary ions flowing into it from within the cavity is removed by electron-ion recombination. We examine the structure of this layer using both a two-dimensional magnetohydrodynamical model and a one- dimensional hybrid code.

  12. Constraints from Comets

    NASA Technical Reports Server (NTRS)

    Wooden, Diane H.

    2006-01-01

    Crystalline silicates identified in the laboratory examinations of cometary interplanetary dust particles, in Stardust particles, and in the IR spectra of comets and protoplanetary disks typically have high Mg and low Fe contents. In contrast, the amorphous silicates in IDPs and comets are predominantly Fe-rich. Mg-rich crystalline silicates are hypothesized to form by heating of amorphous silicates at temperatures above 1000 K. Annealing does not change the stoichiometry, i.e., the chemistry of the grains. Therefore, annealing is not expected to change an Fe-bearing amorphous silicate into a Mg-rich crystal. We discuss this challenge to the annealing scenario, review the condensation scenarios, and discuss the possibility that Fe reduction, a process thought to contribute in chondrule-formation, is the missing link between Fe-rich amorphous silicates and Mg rich crystalline silicates. We discuss the time scales for these processes in terms of time dependent 2D models of disks (by Gail & collaborators) and in terms of shocks. We mention the Stardust sample return results on Mg-rich crystalline silicates.

  13. Chemical diversity in the comet population

    NASA Astrophysics Data System (ADS)

    Biver, Nicolas; Bockelée-Morvan, Dominique

    2016-10-01

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

  14. Acellular comet assay: a tool for assessing variables influencing the alkaline comet assay.

    PubMed

    Kennedy, Erin K; McNamee, James P; Prud'homme Lalonde, Louise; Jones, Trevor; Wilkinson, Diana

    2012-01-01

    In this study, an acellular modification to the alkaline comet assay to further evaluate key variables within the assay that may influence the outcome of genotoxicity studies is described. This acellular comet assay can detect differences of 0.2 Gy of (60)Co gamma-ray radiation between 0 and 1 Gy and differences of 1 Gy between 0 and 8 Gy; thus, this assay is applicable for a wide range of DNA damage levels. It is also shown that DNA damage from different radiation energies was not significantly different from (60)Co gamma-ray. This assay displayed a statistical increase in DNA damage due to uncontrolled exposure to natural light; however, the slope of the dose-response curve for light-exposed samples was similar to that for samples protected from light. A comparison of the alkaline comet assay with the acellular comet assay allowed for the intrinsic repair capacity of the alkaline comet assay to be quantified.

  15. 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

  16. WISE/NEOWISE Comets: Nucleii and CO/CO2 Emission

    NASA Astrophysics Data System (ADS)

    Bauer, James M.; Stevenson, R.; Kramer, E. A.; Mainzer, A. K.; Grav, T.; Masiero, J. R.; Fernandez, Y. R.; Lisse, C. M.; Meech, K. J.; Weissman, P. R.; Cutri, R.; Dailey, J. W.; Tholen, D. J.; Walker, R. G.; Lucas, A.; Gautier, T. N., IV; Wright, E. L.; WISE Team

    2012-10-01

    The Wide-field Infrared Survey Explorer (WISE) mission conducted a survey of the entire sky from January 2010 through January 2011, ending operations on February 1, 2011[1]. The spacecraft imaged over 150 comets, each simultaneously in four bands, at thermal (12 and 22 μm) and mid-IR (3.5 and 4.6 μm) wavelengths. These observations provide a unique opportunity to measure many of the otherwise inaccessible properties of a large sample of comets. Long period comets (LPCs) comprise roughly a third of the sample, along with Jupiter-family and Halley-type comets (JFCs & HTC). This ensemble provides meaningful statistics on comet population sub-types regarding nucleus sizes and albedos, dust characteristics, dust mass loss rates, and emission of gas species. We present here an overview of the ensemble's nucleus size and 3.5 μm albedo distributions for a subset of the LPCs, HTCs, and JFCs. We also provide CO/CO2 gas emission based on 4.6 μm flux excess [2,3,4]. Related works [5,6] provide comparative analyses of dust properties in the active bodies across different comet populations. References: [1] Mainzer, A.K., et al. (2011) ApJ, 731, 53. [2] Bauer, J.M. et al. (2011) ApJ, 738, 171. [3] Bauer, J.M. et al. (2012) ApJ, 747, 39. [4] Bauer, J.M. et al. (2012) ApJ, submitted. [5] Kramer et al. (2012) AAS DPS meeting. [6] Stevenson et al. (2012) AAS DPS meeting. Acknowledgements: This publication makes use of data products from WISE, which is a joint project of UCLA, and JPL/Caltech, funded by NASA, as well as data obtained at the Palomar Observatory’s 200-inch (Caltech) and the SOAR 4m (NOAO). This work was primarily supported by NEOWISE, which is a project of JPL/Caltech, funded by the Planetary Science Division of NASA.

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

    NASA Astrophysics Data System (ADS)

    Matthews, Clifford N.; Minard, Robert D.

    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

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. Ammonia abundances in comets

    NASA Astrophysics Data System (ADS)

    Wyckoff, S.; Tegler, S.; Engel, L.

    The emission band strengths of the NH2 bands of Comets Halley, Hartley-Good, Thiele, and Borrelly were measured to determine the NH2 column densities for the comets. Production rates obtained using the Haser and vectorial models are in agreement within the observational errors, suggesting that a simple two-step decay model may be used to approximate the NH2 distribution in a comet's coma. Ammonia-to-water abundance ratios from 0.01 to 0.4 percent were found for the four comets. The ratio in Comet Halley is found to be Q(NH3)/Q(H2O) = 0.002 + or - 0.001. No significant difference in the ammonia abundance was found before or after perihelion in Comet Halley.

  3. Comet Mineralogy as Inferred from Infrared Spectra of Comets

    NASA Technical Reports Server (NTRS)

    Wooden, Diane H.

    2006-01-01

    For most comets, infrared (IR) spectroscopy (remote sensing) is the method through which we diagnose the mineralogy and size distribution of dust in their comae. The shape and contrast of the IR spectral features depend on the particle size: optically active minerals (absorbing of visible and near-IR solar photons) and submicron solid grains or highly porous (> 90% vacuum) grains primarily contribute to the shapes of the observed resonances. Comet mineralogies typically are determined by fitting thermal emission models of ensembles of discrete mineral grains to observed IR spectral energy distributions. The absorptivities (Q-abs) and scattering efficiencies (Q-scat) of the discrete mineral grains are computed using Mie scattering, Maxwell-Garnet mixing, Discrete Dipole Approximation, and Multi-Layered Sphere codes. These techniques when applied to crystalline minerals, specifically olivine (Mg_x, Fe_1-x)2 Si04, x>0.9, require the use of ellipsoidal shaped particles with elongated axial ratios or hollow spheres to produce the shapes of the resonances observed both from comet comae and laboratory samples. The wavelength positions of the distinct resonances from submicron-radii crystalline silicates, as well as their thermal equilibrium temperatures, constrain the crystalline olivine to have a relatively high Mg-content (x>0.9, or Fo>90). Only resonances computed for submicron Mg-rich crystalline olivine and crystalline orthopyroxene match the observed IR spectral features. However, this has led to the interpretation that micron-radii and larger crystals are absent from comet comae. Furthermore, the mass fraction of silicate crystals is dependent upon whether just the submicron portion of the size distribution is being compared or the submicron crystals compare to the aggregates of porous amorphous silicates that are computationally tractable as porous spheres. We will discuss the Deep Impact results as examples of these challenges to interpreting mid-IR spectra of

  4. Extrasolar comets: The origin of dust in exozodiacal disks?

    NASA Astrophysics Data System (ADS)

    Marboeuf, U.; Bonsor, A.; Augereau, J.-C.

    2016-11-01

    Comets have been invoked in numerous studies as a potentially important source of dust and gas around stars, but none has studied the thermo-physical evolution, out-gassing rate, and dust ejection of these objects in such stellar systems. In this paper we investigate the thermo-physical evolution of comets in exo-planetary systems in order to provide valuable theoretical data required to interpret observations of gas and dust. We use a quasi-3D model of cometary nucleus to study the thermo-physical evolution of comets evolving around a single star from 0.1 to 50 AU, whose homogeneous luminosity varies from 0.1 to 70L⊙. This paper provides thermal evolution, physical alteration, mass ejection, lifetimes, and the rate of dust and water gas mass productions for comets as a function of the distance to the star and stellar luminosity. Results show significant physical changes to comets at high stellar luminosities. The mass loss per revolution and the lifetime of comets depend on their initial size, orbital parameters and follow a power law with stellar luminosity. The models are presented in such a manner that they can be readily applied to any planetary system. By considering the examples of the Solar System, Vega and HD 69830, we show that dust grains released from sublimating comets have the potential to create the observed (exo)zodiacal emission. We show that observations can be reproduced by 1 to 2 massive comets or by a large number of comets whose orbits approach close to the star. Our conclusions depend on the stellar luminosity and the uncertain lifetime of the dust grains. We find, as in previous studies, that exozodiacal dust disks can only survive if replenished by a population of typically sized comets renewed from a large and cold reservoir of cometary bodies beyond the water ice line. These comets could reach the inner regions of the planetary system following scattering by a (giant) planet.

  5. 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.

  6. Comet Dead Ahead

    NASA Technical Reports Server (NTRS)

    2005-01-01

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

  7. 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)

  8. 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.

  9. Summer fireworks on comet 67P

    NASA Astrophysics Data System (ADS)

    Vincent, J.-B.; A'Hearn, M. F.; Lin, Z.-Y.; El-Maarry, M. R.; Pajola, M.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Fornasier, S.; Fulle, M.; Gicquel, A.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann, M.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Massironi, M.; Mottola, S.; Naletto, G.; Oklay, N.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.

    2016-11-01

    During its two years mission around comet 67P/Churyumov-Gerasimenko, ESA's Rosetta spacecraft had the unique opportunity to follow closely a comet in the most active part of its orbit. Many studies have presented the typical features associated to the activity of the nucleus, such as localized dust and gas jets. Here we report on series of more energetic transient events observed during the three months surrounding the comet's perihelion passage in August 2015. We detected and characterized 34 outbursts with the Rosetta cameras, one every 2.4 nucleus rotation. We identified 3 main dust plume morphologies associated to these events: a narrow jet, a broad fan, and more complex plumes featuring both previous types together. These plumes are comparable in scale and temporal variation to what has been observed on other comets. We present a map of the outbursts source locations, and discuss the associated topography. We find that the spatial distribution sources on the nucleus correlates well with morphological region boundaries, especially in areas marked by steep scarps or cliffs. Outbursts occur either in the early morning or shortly after the local noon, indicating two potential processes: Morning outbursts may be triggered by thermal stresses linked to the rapid change of temperature, afternoon events are most likely related to the diurnal or seasonal heat wave reaching volatiles buried under the first surface layer. In addition, we propose that some events can be the result of a completely different mechanism, in which most of the dust is released upon the collapse of a cliff.

  10. 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.

  11. CO in Distantly Active Comets

    NASA Astrophysics Data System (ADS)

    Womack, M.; Sarid, G.; Wierzchos, K.

    2017-03-01

    The activity of most comets near the Sun is dominated by the sublimation of frozen water, the most abundant ice in comets. Some comets, however, are active well beyond the water-ice sublimation limit of ∼3 au. Three bodies dominate the observational record and modeling efforts for distantly active comets: the long-period comet C/1995 O1 (Hale-Bopp), and the short-period comets (with Centaur orbits) 29P/Schwassmann-Wachmann 1 and 2060 Chiron. We summarize what is known about these three objects with an emphasis on their gaseous comae. We calculate their CN/CO and CO2/CO production rate ratios from the literature and discuss implications, such as HCN and CO2 outgassing are not significant contributors to their comae. Using our own data we derive CO production rates, Q(CO), for all three objects to examine whether there is a correlation between gas production and different orbital histories and/or size. The CO measurements of Hale-Bopp (4–11 AU) and 29P are consistent with a nominal production rate of Q(CO) = 3.5 × 1029 r‑2 superimposed with sporadic outbursts. The similarity of Hale-Bopp CO production rates for pre- and post-perihelion suggests that thermal inertia was not very important and therefore most of the activity is at or near the surface of the comet. We further examine the applicability of existing models in explaining the systematic behavior of our small sample. We find that orbital history does not appear to play a significant role in explaining 29P’s CO production rates. 29P outproduces Hale-Bopp at the same heliocentric distance, even though it has been subjected to much more solar heating. Previous modeling work on such objects predicts that 29P should have been devolatilized over a fresher comet like Hale-Bopp. This may point to 29P having a different orbital history than current models predict, with its current orbit acquired more recently. On the other hand, Chiron’s CO measurements are consistent with it being significantly depleted

  12. Asteroids and Comets — Did the Diversify of Nebular Solids Decline with Distance from the Sun?

    NASA Astrophysics Data System (ADS)

    Brownlee, D. E.; Joswiak, D. J.

    2015-07-01

    The Mn contents of ferrous olivine grains in a cluster IDP of probable cometary origin match what is seen in comet Wild 2 olivines. This finding is consistent with suggestions that most comets contain similar averaged samplings of nebular solids.

  13. 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).

  14. 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.…

  15. 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.

  16. Searching for evidence for different activity drivers in long- and short-period comets from the WISE/NEOWISE data set

    NASA Astrophysics Data System (ADS)

    Kramer, E.; Fernandez, Y.; Bauer, J.; Stevenson, R.; Mainzer, A.; Grav, T.; Masiero, J.; Walker, R.; Lisse, C.; WISE Team

    2014-07-01

    Introduction: The Wide-field Infrared Survey Explorer (WISE) mission surveyed the sky in four infrared wavelength bands (3.4, 4.6, 12 and 22 μ m) between January 2010 and February 2011 [1,2]. During the mission, WISE serendipitously observed over 150 comets, including 21 newly discovered objects. About half of the comets observed by WISE displayed a significant dust tail in the 12 and 22 μ m (thermal emission) bands. The Figure below shows a sampling of six comets in the 22 μ m band, showing the range of activity levels and dust morphology present in the data. Since the observed objects are a mix of both long-period (LP) and short-period (SP) comets, differences in activity can be used to better understand the thermal processing that each of these populations has undergone. Approach: For the comets that displayed a significant dust tail, we have estimated the sizes and ages of the particles using dynamical models based on the Finson-Probstein method [3,4]. The main parameter in these models is the ratio of solar radiation pressure to solar gravity, called β. We have then compared these models to the data using a novel tail-fitting method that allows the best-fit model to be chosen analytically rather than subjectively. For comets that were observed multiple times by WISE, the particle properties were estimated separately, and then compared. Results: The ages of the dust tails seen vary in age from a few months to several years, with the average for both SP and LP comets being between 1--2 years. While many of the dust tails are comprised of grains emitted near perihelion, several comets exhibit tails that depart from this trend significantly. For both the SP and LP comets, the median β value was about 0.01, suggesting that the tail particles are on the order of tens of microns in size. Our preliminary analysis suggests that while the sizes and ages of the particles that comprise the dust tails of LP and SP comets are similar, the heliocentric distance at which

  17. 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.

  18. 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.

  19. The Rosetta mission: Clues on the origin of comet nuclei

    NASA Astrophysics Data System (ADS)

    Davidsson, Bjorn; Stern, S. Alan; Kofman, Wlodek; Hilchenbach, Martin; rotundi, alessandra; Bentley, Mark; Hofstadter, Mark; Sierks, Holger; Altwegg, Kathrin; Nilsson, Hans; Burch, James L.; Eriksson, Anders I.; Glassmeier, Karl-Heinz; Henri, Pierre; Carr, Christopher M.; Pätzold, Martin; Capaccioni, Fabrizio; Boehnhardt, Hermann; Bibring, Jean-Pierre; Fulle, Marco; Fulchignoni, Marcello; Gruen, Eberhard; Weissman, Paul R.; Taylor, Matt; Buratti, Bonnie J.; Choukroun, Mathieu; Altobelli, Nicolas; Snodgrass, Colin; Rosetta Science Working Team

    2016-10-01

    The Rosetta mission has been taking measurements of its target Comet 67P/Churyumov-Gerasimenko sinceearly 2014 and will complete operations at the end of September 2016. The mission Science Management Plan,in 1994, laid out the the prime goals and themes of the mission. These five themes were:1) To study the global characterization of the Nucleus, the determination of the dynamics properties ,surface morphology and composition of the comet.2) Examination of the Chemical, Mineralogical and isotopic compositions of volatiles and refractoriesin a cometary nucleus.3) Physical interrelation of volatile and refractories in a cometary nucleus4) Study the development of cometary activity and the process in the surface layer of thenucleus and in the inner coma5) The origins of comets, the relationship between cometary and interstellar material and theimplications for the origin of the solar system,To cover all aspects of the Rosetta mission in this special Show case session, this abstracts isone of 5, with this particular presentation focusing on theme 5.Several scenarios for comet nucleus formation have been proposed, such as hierarchical agglomeration,or gravitational collapse of pebble swarms created either by turbulent eddies or by streaming instabilities.In addition, the question of survival of such primordial nuclei versus severe collisional processinghas been debated. The pros and cons of these hypotheses are discussed in the light of Rosetta's discoveries.

  20. 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.

  1. 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

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Constraints on Comet 332P/Ikeya-Murakami

    NASA Astrophysics Data System (ADS)

    Hui, Man-To; Ye, Quan-Zhi; Wiegert, Paul

    2017-01-01

    Encke-type comet 332P/Ikeya-Murakami is experiencing cascading fragmentation events during its 2016 apparition. It is likely the first splitting Encke-type comet ever observed. A nongravitational solution to the astrometry reveals a statistical detection of the radial and transverse nongravitational parameters, {A}1=(1.54+/- 0.39)× {10}-8 au day‑2 and {A}2=(7.19+/- 1.92)× {10}-9 au day‑2, respectively, which implies a nucleus erosion rate of (9.1+/- 1.7)‰ per orbital revolution. The mass-loss rate likely has to be supported by a much larger fraction of an active surface area than known cases of short-period comets; it may be relevant to the ongoing fragmentation. We failed to detect any serendipitous pre-discovery observations of the comet in archival data from major sky surveys, whereby we infer that 332P used to be largely inactive, and is perhaps among the few short-period comets that have been reactivated from weakly active or dormant states. We therefore constrain an upper limit to the nucleus size as 2.0 ± 0.2 km in radius. A search for small bodies in similar orbits to that of 332P reveals comet P/2010 B2 (WISE) to be the best candidate. From an empirical generalized Jupiter-family (Encke-type included) comet population model, we estimate the likelihood of a chance alignment of the 332P–P/2010 B2 pair to be 1 in 33, a small number indicative of a genetic linkage between the two comets on a statistical basis. The pair possibly originated from a common progenitor, which underwent a disintegration event well before the twentieth century.

  10. Comet 81P/wild 2 under a microscope

    USGS Publications Warehouse

    Brownlee, D.; Tsou, P.; Aleon, J.; O'D, Alexander; 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.

  11. Comet 81P/Wild 2 Under a Microscope

    NASA Astrophysics Data System (ADS)

    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

    2006-12-01

    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.

  12. 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.

  13. 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.

  14. Outburst and nuclear breakup of Comet Halley - 1910

    NASA Technical Reports Server (NTRS)

    Wood, H. J.; Albrecht, R.

    1981-01-01

    Computer processing of five plates of Comet Halley taken during the 1910 apparition shows that on May 24 strong asymmetric (with respect to the tail axis) fountain-like parabolic plumes had developed on the sunward side of the nucleus. Visual observations showed that after an initial fading while passing in front of the sun, the brightness increased to about magnitude 1. On the plates taken May 31, the nucleus is clearly divided into at least three parts of nearly equal brightness. However, the last plate on June 3 shows a symmetrical coma with a small stellar-like nucleus.

  15. 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.

  16. 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

  17. Beyond 3 AU from the Sun: "Hypervolatiles" in Distant Comets

    NASA Astrophysics Data System (ADS)

    Bonev, Boncho P.; Villanueva, Geronimo Luis; Mumma, Michael J.; DiSanti, Michael A.; Paganini, Lucas; Boehnhardt, Hermann; Lippi, Manuela; Gibb, Erika L.; Bockelee-Morvan, Dominique; de Val-Borro, Miguel; Kawakita, Hideyo; Altwegg, Kathrin

    2016-10-01

    Our understanding of inner coma composition in comets has long been biased towards heliocentric distances (Rh) smaller than 2-3 AU. However, observations far from the Sun are also of high value for better understanding the nucleus structure and outgassing of volatiles. Substantial and very important evidence for the activity of distant comets has been accumulated from photometry and analyses of light curves, but direct detections of primary (parent) volatiles are still rare. For example, comet C/2006 W3 (Christensen) remained outside 3.1 AU throughout its apparition, yet it presented the best opportunity since Hale-Bopp (1997) for detailed spectroscopic studies in a distant comet. C/2006 W3 was observed from several space- and ground-based facilities using both infrared and radio techniques. CO, CH4, and C2H6 were measured via infrared spectroscopy at ESO-VLT at Rh = 3.25 AU. Production rates were found to exceed those measured for each of these species in most other comets, despite those comets being observed much closer to the Sun. With its relatively high CO/CO2 ratio, C/2006 W3 also appears as an outlier in the AKARI comet survey of 18 comets. The detections of H2O (Herschel Space Observatory) and CO (ESO-VLT) allow for constraining the coma abundance ratio H2O/CO at Rh = 5 AU.We will compare the C2H6/CH4/CO ratios in C/2006 W3 with those in other comets spanning a large range in Rh: from D/2012 S1 ISON (~0.7 AU) to 29P/Schwassmann-Wachmann 1 (~ 6.3 AU). Notably in situ measurements by the Rosetta mission were performed in the coma of 67P/Churyumov-Gerasimenko, at a very similar heliocentric distance to C/2006 W3 (3.15 AU). While comparisons of column-integrated remote sensing measurements and abundances from in-situ mass spectrometry (as performed by the ROSINA instrument) are not straightforward, both types of measurement are of high value for constraining models of nucleus outgassing beyond 3 AU from the Sun, where the inferred nucleus structure and

  18. The Comet Radar Explorer Mission

    NASA Astrophysics Data System (ADS)

    Asphaug, Erik; Belton, Mike; Bockelee-Morvan, Dominique; Chesley, Steve; Delbo, Marco; Farnham, Tony; Gim, Yonggyu; Grimm, Robert; Herique, Alain; Kofman, Wlodek; Oberst, Juergen; Orosei, Roberto; Piqueux, Sylvain; Plaut, Jeff; Robinson, Mark; Sava, Paul; Heggy, Essam; Kurth, William; Scheeres, Dan; Denevi, Brett; Turtle, Elizabeth; Weissman, Paul

    2014-11-01

    Missions to cometary nuclei have revealed major geological surprises: (1) Global scale layers - do these persist through to the interior? Are they a record of primary accretion? (2) Smooth regions - are they landslides originating on the surface? Are they cryovolcanic? (3) Pits - are they impact craters or sublimation pits, or rooted in the interior? Unambiguous answers to these and other questions can be obtained by high definition 3D radar reflection imaging (RRI) of internal structure. RRI can answer many of the great unknowns in planetary science: How do primitive bodies accrete? Are cometary nuclei mostly ice? What drives their spectacular activity and evolution? The Comet Radar Explorer (CORE) mission will image the detailed internal structure of the nucleus of 10P/Tempel 2. This ~16 x 8 x 7 km Jupiter Family Comet (JFC), or its parent body, originated in the outer planets region possibly millions of years before planet formation. CORE arrives post-perihelion and observes the comet’s waning activity from safe distance. Once the nucleus is largely dormant, the spacecraft enters a ~20-km dedicated Radar Mapping Orbit (RMO). The exacting design of the RRI experiment and the precise navigation of RMO will achieve a highly focused 3D radar reflection image of internal structure, to tens of meters resolution, and tomographic images of velocity and attenuation to hundreds of meters resolution, tied to the gravity model and shape. Visible imagers will produce maps of the surface morphology, albedo, color, texture, and photometric response, and images for navigation and shape determination. The cameras will also monitor the structure and dynamics of the coma, and its dusty jets, allowing their correlation in 3D with deep interior structures and surface features. Repeated global high-resolution thermal images will probe the near-surface layers heated by the Sun. Derived maps of thermal inertia will be correlated with the radar boundary response, and photometry and

  19. 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.

  20. 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.

  1. Surface photometry of comet P/Encke

    NASA Technical Reports Server (NTRS)

    Djorgovski, S.; Spinrad, H.

    1985-01-01

    A scheme to clean cometary digital images from offending background-star trails, and this technique has been applied to a pair of deep Kitt Peak 4-m plates of comet P/Encke, taken in October 1980. Simultaneous and subsequent digital spectra have been obtained at Lick Observatory. The non-polluted coma images show a strong asymmetric sunward-oriented fan/jet, and an extended and rounder (mostly gaseous) main coma, out to approximately 100,000 km radius. The stellar-trail point-spread function has a narrow width (sigma approximately 0.6 arcsec), so that spatial resolution better than approximately 300 km is achieved at the comet. The photometric gradient near the nucleus is very steep, strongly suggesting an icy-grain component which evaporates quickly (at radii equal to or less than 500 km) in the sunlight. Further from the nucleus, the profile becomes shallower, bluer, and more gas dominated. The effect of solar radiation pressure on C2, CN, and other molecules is probably responsible for the rounding of the outer, fainter isophotes. The source of the molecules is likely to be larger than the nucleus itself, and a substantial fraction may originate in the jet. The technique described here may also be applicable in surface photometry of galaxies, in cases where the heavy image pollution by foreground stars is present.

  2. Surface photometry of comet P/Encke

    NASA Astrophysics Data System (ADS)

    Djorgovski, S.; Spinrad, H.

    1985-05-01

    A scheme to clean cometary digital images from offending background-star trails, and this technique has been applied to a pair of deep Kitt Peak 4-m plates of comet P/Encke, taken in October 1980. Simultaneous and subsequent digital spectra have been obtained at Lick Observatory. The non-polluted coma images show a strong asymmetric sunward-oriented fan/jet, and an extended and rounder (mostly gaseous) main coma, out to approximately 100,000 km radius. The stellar-trail point-spread function has a narrow width (sigma approximately 0.6 arcsec), so that spatial resolution better than approximately 300 km is achieved at the comet. The photometric gradient near the nucleus is very steep, strongly suggesting an icy-grain component which evaporates quickly (at radii equal to or less than 500 km) in the sunlight. Further from the nucleus, the profile becomes shallower, bluer, and more gas dominated. The effect of solar radiation pressure on C2, CN, and other molecules is probably responsible for the rounding of the outer, fainter isophotes. The source of the molecules is likely to be larger than the nucleus itself, and a substantial fraction may originate in the jet. The technique described here may also be applicable in surface photometry of galaxies, in cases where the heavy image pollution by foreground stars is present.

  3. 67P/Churyumov Gerasimenko nucleus model: Portrayal of the Rosetta target

    NASA Astrophysics Data System (ADS)

    De Sanctis, M. C.; Capria, M. T.; Coradini, A.

    2006-01-01

    Rosetta is a cornerstone ESA mission dedicated to the detailed study of a comet nucleus before and after the onset of activity. Comet 67P/Churyumov-Gerasimenko is the new Rosetta target. At the moment, little is known about this comet, but the successful design of the ROSETTA mission requires some preliminary knowledge of the comet's physical parameters. In fact, surface and interior temperature, day-night variations, onset of activity, percentage of active surface, intensity of different gas and dust fluxes are needed to select safe orbits around the comet and to optimize the scientific return. These quantities cannot be determined only through ground-based observations, so predictive models of the thermal evolution and differentiation of a cometary nucleus are necessary. We have developed a comet nucleus thermal evolution model that helps in the estimations of the above quantities. The ideal nucleus is an initially homogeneous and porous sphere, composed by a mixture of different ices and dust particles. The results have been computed with a numerical code solving simultaneously the heat conduction and gas diffusion equations through an idealized spherical comet nucleus. We show the results obtained applying this model to a comet nucleus with the characteristics of Churyumov-Gerasimenko. The results indicate that the peculiar dynamical history has a strong effect on the comet with the formation of a dust mantle before the 1959 close encounter. After that event, the perihelion distance was reduced and the comet was probably "reactivated". In our model, we see a slight increase of the activity passage after passage. We found a good agreement between the model results and the few data available.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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

  9. Comets: Search and Discovery

    NASA Astrophysics Data System (ADS)

    Shanklin, J.; Murdin, P.

    2003-04-01

    Comet discovery in the traditional sense by an amateur astronomer may be a thing of the past. The development of increasing numbers of professional all-sky survey programs, many specifically designed to spot moving or changing objects, means that the future prospects for visual discovery of a comet by an amateur astronomer are bleak. In the near future the professional programs are likely to cover...

  10. Comet composition and Lab

    NASA Astrophysics Data System (ADS)

    Bockelée-Morvan, Dominique; Biver, Nicolas

    2016-10-01

    Comet composition and properties provide information on chemical and physical processes that occurred in the early Solar system, 4.6 Gyr ago. The study of comets and of star-forming regions both help for a better understanding of the formation of planetary systems. A review of our present knowledge of cometary composition is presented. We also discuss laboratory studies that would be helpful for data analysis.

  11. Physics of comets

    NASA Astrophysics Data System (ADS)

    Krishna Swamy, K. S.

    1. General introduction. 1.1. Historical perspective. 1.2. Discovery. 1.3. Appearance. 1.4. Statistics. 1.5. Importance. 1.6. Brightness. 1.7. Main characteristics. 1.8. Spacecraft encounters with comets. 1.9. An overall view -- 2. Dynamics. 2.1. Orbital elements. 2.2. Orbit in space -- 3. Physical aspects. 3.1. Black body radiation. 3.2. Perfect gas law. 3.3. Dissociative equilibrium. 3.4. Doppler shift. 3.5. Spectroscopy. 3.6. Isotopic effect. 3.7. Franck-Condon factors. 3.8. Intensity of emitted lines. 3.9. Boltzmann distribution. 3.10. [symbol]-doubling. 3.11. Photochemistry of water. 3.12. Silicate. 3.13. Annealing. 3.14. Carbon. 3.15. Solar radiation. 3.16. Solar wind -- 4. Spectra. 4.1. Main characteristics. 4.2. Forbidden transitions. 4.3. Line-to-continuum ratio -- 5. Spectra of coma. 5.1. Fluorescence process. 5.2. Excitation temperature. 5.3. Abundances of heavy elements. 5.4. Isotopic abundances. 5.5. Summary -- 6. Gas production rates in coma. 6.1. Theoretical models. 6.2. Results. 6.3. Analysis of hydrogen observations. 6.4. Related studies. 6.5. Parent molecules. 6.6. Chemical diversity. 6.7. Summary -- 7. Dust tails. 7.1. Dynamics. 7.2. Anti-tail. 7.3. Dust trails. 7.4. Sodium gas tails. 7.5. Dust features -- 8. Light scattering theory. 8.1. Mie scattering theory. 8.2. Approximate expressions. 8.3. Computation of cross sections. 8.4. Results. 8.5. Particles of other types. 8.6. Optical constants -- 9. The nature of dust particles. 9.1. Visible continuum. 9.2. Polarization. 9.3. Grain sizes. 9.4. Infrared measurements. 9.5. Spectral feature. 9.6. Properties derived from direct measurements. 9.7. Radiation pressure effects. 9.8. Summary -- 10. Ion tails. 10.1. Evidence for the solar wind. 10.2. Dynamical aberration. 10.3. Theoretical considerations. 10.4. Instabilities and waves. 10.5. Acceleration of cometary ions. 10.6. Large scale structures. 10.7. X-rays. 10.8. Summary -- 11. Nucleus. 11.1. Morphology. 11.2. Theory of vapourization. 11

  12. 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.

  13. General Comet Traits and Comparison of their Dynamical History

    NASA Astrophysics Data System (ADS)

    Choukroun, Mathieu; A'Hearn, Michael F.; Vincent, Jean-Baptiste; Bockelee-Morvan, Dominique; Buratti, Bonnie J.; Crovisier, Jacques; Gulkis, Samuel; Von Allmen, Paul; Weissman, Paul R.

    2016-10-01

    Six comets have been visited by spacecrafts to date (1P/Halley, 19P/Borelly, 81P/Wild 2, 9P/Tempel 1, 103P/Hartley 2, and 67P/Churyumov-Gerasimenko). Very diverse nucleus morphologies are observed, within asingle comet and between them: pits, layered regions, scarps, smooth regions. The relative abundances and extent of these morphologies vary largely between comets. On 81P, pits and layered terrains are particularly abundant, while smooth regions are much less abundant. Conversely, on 9P and 19P, pits are notably less abundant, while smooth areas are abundant and more of greater extent. An evolutionary sequence of comet morphologies has been proposed previously, with the formation of pitted and layered terrains with large topography by early activity, and as activity proceeds, materials are mobilized and eventually form smoother, erosional regions. Observations of 67P seem to place it in between 81P and 9P/19P in this evolutionary sequence. Here we compare nucleus morphologies, outgassing rates, and dynamical history of these comets, in an attempt to test this evolutionary sequence, and to assess whether other properties may also be related to their dynamical history.This work has been conducted in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Government sponsorship acknowledged.

  14. Comet Stepping Stones

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This image from NASA's Spitzer Space Telescope shows three of the many fragments making up Comet 73P /Schwassman-Wachmann 3. The infrared picture also provides the best look yet at the crumbling comet's trail of debris, seen here as a bridge connecting the larger fragments.

    The comet circles around our sun every 5.4 years. In 1995, it splintered apart into four pieces, labeled A through D, with C being the biggest. Since then, the comet has continued to fracture into dozens of additional pieces. This image is centered about midway between fragments C and B; fragment G can be seen in the upper right corner.

    The comet's trail is made of dust, pebbles and rocks left in the comet's wake during its numerous journeys around the sun. Such debris can become the stuff of spectacular meteor showers on Earth.

    This image was taken on April 1, 2006, by Spitzer's multi-band imaging photometer using the 24-micron wavelength channel.

  15. THE PLASMA ENVIRONMENT IN COMETS OVER A WIDE RANGE OF HELIOCENTRIC DISTANCES: APPLICATION TO COMET C/2006 P1 (MCNAUGHT)

    SciTech Connect

    Shou, Y.; Combi, M.; Gombosi, T.; Toth, G.; Jia, Y.-D.; Rubin, M.

    2015-08-20

    On 2007 January 12, comet C/2006 P1 (McNaught) passed its perihelion at 0.17 AU. Abundant remote observations offer plenty of information on the neutral composition and neutral velocities within 1 million kilometers of the comet nucleus. In early February, the Ulysses spacecraft made an in situ measurement of the ion composition, plasma velocity, and magnetic field when passing through the distant ion tail and the ambient solar wind. The measurement by Ulysses was made when the comet was at around 0.8 AU. With the constraints provided by remote and in situ observations, we simulated the plasma environment of Comet C/2006 P1 (McNaught) using a multi-species comet MHD model over a wide range of heliocentric distances from 0.17 to 1.75 AU. The solar wind interaction of the comet at various locations is characterized and typical subsolar standoff distances of the bow shock and contact surface are presented and compared to analytic solutions. We find the variation in the bow shock standoff distances at different heliocentric distances is smaller than the contact surface. In addition, we modified the multi-species model for the case when the comet was at 0.7 AU and achieved comparable water group ion abundances, proton densities, plasma velocities, and plasma temperatures to the Ulysses/SWICS and SWOOPS observations. We discuss the dominating chemical reactions throughout the comet-solar wind interaction region and demonstrate the link between the ion composition near the comet and in the distant tail as measured by Ulysses.

  16. Comets: Data, problems, and objectives

    NASA Technical Reports Server (NTRS)

    Whipple, F. L.

    1977-01-01

    A highly abridged review of new relevant results from the observations of Comet Kohoutek is followed by an outline summary of our basic knowledge concerning comets, both subjects being confined to data related to the nature and origin of comets rather than the phenomena (for example, plasma phenomena are omitted). The discussion then centers on two likely places of cometary origin in the developing solar system, the proto-Uranus-Neptune region versus the much more distant fragmented interstellar cloud region, now frequented by comets of the Opik-Oort cloud. The Comet Kohoutek results add new insights, particularly with regard to the parent molecules and the nature of meteoric solids in comets, to restrict the range of the physical circumstances of comet formation. A few fundamental and outstanding questions are asked, and a plea made for unmanned missions to comets and asteroids in order to provide definitive answers as to the nature and origin of comets, asteroids, and the solar system generally.

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  19. 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.

  20. Decay of COSAC and Ptolemy mass spectra at comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Krüger, Harald; Goesmann, Fred; Giri, Chaitanya; Wright, Ian; Morse, Andrew; Bredehöft, Jan Hendrik; Ulamec, Stephan; Cozzoni, Barbara; Ehrenfreund, Pascale; Gautier, Thomas; McKenna-Lawlor, Susan; Raulin, Francois; Steininger, Harald; Szopa, Cyril

    2017-03-01

    Context. The Rosetta lander Philae successfully landed on the nucleus of comet 67P/Churyumov-Gerasimenko on 12 November 2014. Philae is equipped with two gas analysers: The Cometary Sampling and Composition experiment (COSAC) and the gas chromatograph and mass spectrometer Ptolemy. Aims: COSAC is designed for in situ analysis of organic molecules on 67P while Ptolemy is optimised to measure ratios of stable isotopes. Methods: On 12 to 14 November 2014, both instruments measured the organic composition of the comet nucleus material through seven measurements in sniffing mode during Philae's hopping and at its final landing site Abydos. We compare the temporal evolution of intensities of several ion species identified by both mass spectrometers. For COSAC, this is the first analysis of the temporal behaviour of the measured ion species. Results: All ion species showed the highest intensities in the first spectra measured by both instruments approximately 20 to 30 min after Philae's first touchdown at Agilkia, and a decay during the six consecutive measurements at Abydos. Both instruments measured an almost identical decay of the water peak (m/z 18), and CO (m/z 28) behaved similarly. In the COSAC measurements, the peak at m/z 44 decays much slower than all the other ion species, including the water peak. In particular, the m/z 44 peak decays much slower in the COSAC measurements than in the Ptolemy data. This supports our earlier interpretation that COSAC analysed, for the first time, a regolith sample from a cometary nucleus in situ, while Ptolemy measured cometary gas from the ambient coma. The m/z 44 peak measured by COSAC was likely dominated by organic species, whereas the peak measured by Ptolemy was interpreted to be mostly due to CO2. Ion species heavier than m/z 30 tend to decay somewhat slower in the COSAC measurements than in the Ptolemy data, which may be related to differences in the exhaust designs between both instruments.

  1. 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.

  2. 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.

  3. Spectrophotometric observations of comet P/Giacobini-Zinner

    NASA Technical Reports Server (NTRS)

    Konno, I.; Wyckoff, S.; Wehinger, P. A.

    1989-01-01

    Spectroscopic observations of the Giacobini-Zinner comet were performed on March 20, June 20 and 21, September 11, and October 19, 1985. The September observations were performed at perihelion, exactly at the time of the International Cometary Explorer (ICE) encounter with the comet. The March and June observations were obtained with an intensified image dissector scanner (IIDS) on the 2.1-meter Kitt Peak telescope and the September and the October observations were obtained with a charge-coupled device (CCD) on the 4-meter Kitt Peak telescope. The nucleus spectra from these observations are presented.

  4. 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.

  5. Comets and the Stardust Mission

    ScienceCinema

    LLNL - University of California Television

    2016-07-12

    The occasional appearance of comets has awed humans throughout history. But how much do we really know about comets? Did a comet kill the dinosaurs? And, what can comets tell us about our own ancient history? With comet dust from NASA's Stardust mission, scientists like Hope Ishii, a Research Scientist at Lawrence Livermore National Laboratory, are beginning to answer these questions. She and high school teacher Tom Shefler look at how comets formed, their role in the Earth's history and the clues about what happened over 4 billion years ago. Series: Science on Saturday [5/2008] [Science] [Show ID: 14492

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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

    1996-10-03

    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.

  11. 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.

  12. 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.

  13. Constraining the bulk Dust to Ice Ratio and Compressive Strength for Comet Churyumov Gerasimenko Using CONSERT Radar Observations

    NASA Astrophysics Data System (ADS)

    Heggy, E.; Shafie, A.; Herique, A.; Lasue, J.; Kofman, W. W.; Levasseur-Regourd, A. C.

    2015-12-01

    Using CONSERT most recent Bistatic observations in the Post-Philae landing phase we estimate the variability in the subsurface Dust to Ice ratios for comet Churyumov Gerasimenko under different dielectric hypotheses inverted from the 90 MHz radar observations and constrained by both the COSIMA and the Radio science experiments. In particular we constrain the comet dust type and ratios to the ice mass in the nucleus body. Additionally we estimat the subsurface density and porosity from CONSERT dielectric inversion and compare it to the values estimated for the upper crust from the Philae landing dynamics. Our preliminary results suggest that the comet dielectric properties are consistent with carbonated chondrites dust and water crystalline ice mixtures with very low dust concentration in the comet deep subsurface. Additionally we develop an empirical model that correlates the surface and subsurface compressive strengths to the dielectric properties. The compressive strength of both the surface and the subsurface are explored using this model using the dielectric properties inverted from the CONSERT observations. Our preliminary results suggest that the average surface compressive strength at 67P surface range from 2 kPa to 1 MPa, for a mean surface temperature of -70° C. We also analyzed the OSIRIS images of the Philae lander first impact footprints which are suggested to be ~15 cm deep into the upper regolith and hence suggesting a low surface compressive strength close to 2 kPa. The comet subsurface compressive strength of subsurface is estimated to be < 1kPa. We will discuss the implications of our results for understanding cometary formation and future sampling experiments.

  14. 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.

  15. 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.

  16. 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.

  17. 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,...

  18. Photometry of the comet 2060 Chiron

    NASA Technical Reports Server (NTRS)

    Buratti, Bonnie J.; Marcialis, Robert L.; Dunbar, R. Scott

    1991-01-01

    The comet 2060 Chiron has proven to be an interesting and enigmatic object. Situated between the orbits of Saturn and Uranus, it was originally classified as the most distant asteroid. It began to show cometary behavior in 1987 by increasing a full magnitude in brightness and developing a coma; there is evidence also for similar earlier outbursts. A thorough study of Chiron is important for two reasons: (1) it is a transition object defining the relationship between comets, asteroids, and meteorites; and (2) a full description of its changes in brightness - particularly on time scale of hours - will provide an empirical foundation for understanding the physical mechanisms (including outgassing, sublimation of volatiles, and even significant mass ejections) driving the evolution of comets. Short term outbursts were observed in early 1989, and a rapid decrease in brightness of Chiron's coma was observed in 1990 in the V and R filters. Also, a rotational lightcurve was detected of the nucleus with an amplitude only 1/4 that observed in its quiescent state: this fact indicates the increased importance of the optically thin coma to the observed brightness.

  19. 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.

  20. 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.

  1. IRAS observations of comets

    NASA Technical Reports Server (NTRS)

    Walker, R. G.; Matson, D. L.; Veeder, G. J.

    1986-01-01

    The moderate spatial resolution and high sensitivity of the Infrared Astronomical Satellite (IRAS), which surveyed the celestial sphere during 1983 at wavelengths of 12, 25, 60, and 100 microns, were particularly well suited to detecting extended thermal emission from cometary dust. Sources with infrared color temperatures characteristic of solar system bodies, and at the ephemerides position of known comets were selected for analysis by the IRAS Asteroid Data Analysis System (ADAS). The data base is now available for use by researchers. This paper describes the development of the data base, details its entries, and presents a statistical analysis of its contents. The IRAS survey contains multiple observations of many periodic comets. A brief description and analysis is given of the observed infrared and derived physical properties for several comets of special interest.

  2. 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.

  3. 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.

  4. 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.

  5. Effects of the law for nongravitational forces on the precession model of comet Encke

    NASA Astrophysics Data System (ADS)

    Sekanina, Z.

    1986-02-01

    The precession model for P/Encke formulated by Whipple and Sekanina (1979) is re-examined in the light of the recent measurements of the OH and H production rates, which according to A'Hearn et al. (1985) indicate that the comet's visual light curve cannot be employed to approximate the variations with time in the nongravitational force that is being exerted on the nucleus by the comet's outgassing. The optimized precession solution derived here with the use of the A'Hearn et al. production law is shown to require unacceptably small nucleus dimensions and to offer an inferior fit to observed variations in the orientation of the comet's preperihelion fan-shaped coma. It is concluded that the Whipple-Sekanina model remains the best available precession solution for this comet.

  6. 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…

  7. 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)

  8. 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)

  9. 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/

  10. 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.

  11. Are Comet Outbursts the Result of Avalanches?

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan; Melosh, H. Jay

    2016-10-01

    Recently, Rosetta became the first spacecraft to make high-resolution observations of a comet outburst (a rapid, ephemeral increase in dust production) emerging from the surface of a comet nucleus. These outbursts occurred near perihelion, lasted only a few minutes, and produced a highly collimated outburst plume without any corresponding increase in H2O or CO2 gas production (See abstract by Rinaldi et al.). These observations cannot be explained by proposed driving outburst mechanisms (such as crystallization of amorphous ice, cryovolcanic gas exsolution, or explosive outgasing of subsurface chambers), all of which are driven by gas, and would therefore lead to an increase in the gas production.We propose instead that the observed outbursts on Comet 67P/Churyumov-Gerasimenko (hereafter 67P) are the result of cometary avalanches. The surface of 67P contains many cliffs and scarps, with dusty surface layers blanketing the shallower slopes above and below these steep surfaces. The Rosetta spacecraft returned clear evidence of mass wasting, which form icy talus fields that are the source of much of 67P's cometary activity. Additionally, Rosetta observed morphological changes over time in the shallower, dusty surface layers above these steep slopes, which suggest that avalanches periodically release dusty materials onto these active talus fields.Here we present the results of a numerical simulation of dusty material avalanching into an active area (active talus field). These simulations show that such avalanches will generate a transient, highly collimated outburst plume that closely matches the observed morphology of the outbursts emanating from the surface of 67P. This mechanism predicts that cometary outbursting should not be directly associated with any increase in gas production, consistent with observations. Additionally, we show that regions of the nucleus that have sourced outburst plumes contain steep surfaces (above the angle of repose), which is required

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Comet giacobini-zinner: plasma description.

    PubMed

    Bame, S J; Anderson, R C; Asbridge, J R; Baker, D N; Feldman, W C; Fuselier, S A; Gosling, J T; McComas, D J; Thomsen, M F; Young, D T; Zwickl, R D

    1986-04-18

    A strong interaction between the solar wind and comet Giacobini-Zinner was observed oh 11 September 1985 with the Los Alamos plasma electron experiment on the International Cometary Explorer (ICE) spacecraft. As ICE approached an intercept point 7800 kilometers behind the nucleus from the south and receded to the north, upstream phenomena due to the comet were observed. Periods of enhanced electron heat flux from the comet as well as almost continuous electron density fluctuations were measured. These effects are related to the strong electron heating observed in the cometary interaction region and to cometary ion pickup by the solar wind, respectively. No evidence for a conventional bow shock was found as ICE entered and exited the regions of strongest interaction of the solar wind with the cometary environment. The outer extent of this strong interaction zone was a transition region in which the solar wind plasma was heated, compressed, and slowed. Inside the inner boundary of the transition region was a sheath that enclosed a cold intermediate coma. In the transition region and sheath, small-scale enhancements in density were observed. These density spikes may be due to an instability associated with cometary ion pickup or to the passage of ICE through cometary ray structures. In the center of the cold intermediate coma a narrow, high-density core of plasma, presumably the developing plasma tail was found. In some ways this tail can be compared to the plasma sheet in Earth's magnetotail and to the current sheet in the tail at Venus. This type of configuration is expected in the double-lobe magnetic topology detected at the comet, possibly caused by the theoretically expected draping of the interplanetary magnetic field around its ionosphere.

  19. The next three decades of the comet assay: a report of the 11th International Comet Assay Workshop.

    PubMed

    Koppen, Gudrun; Azqueta, Amaya; Pourrut, Bertrand; Brunborg, Gunnar; Collins, Andrew R; Langie, Sabine A S

    2017-03-04

    The International Comet Assay Workshops are a series of scientific conferences dealing with practical and theoretical aspects of the Comet Assay (single-cell gel electrophoresis)-a simple method for detecting DNA strand breaks. The first paper describing such an assay was published over 30 years ago in 1984 by Swedish researchers O. Ostling and K. J. Johanson. Appropriately, the theme for the 2015 meeting was looking to the future: 'The Next 3 Decades of the Comet Assay'. The programme included 25 oral and 43 poster presentations depicting the latest advances in technical developments as well as applications of the comet assay in genotoxicity testing (in vitro and in vivo) and biomonitoring of both humans and the environment. Open discussion sessions based on questions from the participants allowed exchange of practical details on current comet assay protocols. This report summarises technical issues of high importance which were discussed during the sessions. We provide information on ways to improve the assay performance, by testing for cytotoxicity, by using reference samples to reduce or allow for inter-experimental variation, and by standardising quantification of the damage, including replicates and scoring enough comets to ensure statistical validity. After 30 years of experimentation with the comet assay, we are in a position to control the important experimental parameters and make the comet assay a truly reliable method with a wealth of possible applications.

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

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.; Neugebauer, Marcia

    1991-01-01

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

  1. 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.

  2. Optical Detection of Anomalous Nitrogen in Comets

    NASA Astrophysics Data System (ADS)

    2003-12-01

    exceedingly difficult to procure the high-quality, high-resolution spectra needed to show the very faint emissions of the rare species. So far, they were only possible when a very bright comet happened to pass by, perhaps once a decade, thereby significantly limiting such studies. And there has always been some doubt whether the brightest comets are also truly representative of this class of objects. Observations of fainter, more typical comets had to await the advent of powerful instruments and telescopes. First UVES spectrum of a comet ESO PR Photo 28a/03 ESO PR Photo 28a/03 [Preview - JPEG: 495 x 400 pix - 183k [Normal - JPEG: 990 x 800 pix - 450k] ESO PR Photo 28b/03 ESO PR Photo 28b/03 [Preview - JPEG: 502 x 400 pix - 115k [Normal - JPEG: 1004 x 800 pix - 290K] Captions : PR Photo 28a/03 displays an image of Comet LINEAR (C/2000 WM1) with the UVES slit viewer image. The colour composite in the large frame (sky field: 16 x 16 arcmin 2 ) was obtained by Gordon Garradd (Loomberah, NSW, Australia). [Image Copyright (c) 2002 Gordon Garradd (loomberah@ozemail.com.au]. The UVES slit viewer photo (small frame; 40 x 40 arcsec 2 ) is a false-colour image taken in the (red) R-band with UVES+KUEYEN on March 22, 2002; it shows the position of the narrow spectrograph slit (0.45 arcsec wide and 8 arcsec long) crossing the inner coma and through which the comet's light was captured to produce the high-resolution spectra. The slit has been offset from the center of light to reduce contamination from solar light reflected off dust particles in the comet's coma - there is most dust near the nucleus. PR Photo 28b/03 shows a small part of the UVES spectrum with an emission band (ultraviolet light at wavelength 390 nm) from CN molecules [3] in the comet's atmosphere. The emission lines are produced by absorption of the solar light by these molecules, followed by re-emission of lines of specific wavelengths. This physical process is known as "resonance-fluorescence" - it is the same process

  3. A continuing controversy: Has the cometary nucleus been resolved?

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1976-01-01

    Evidence is presented for classifying cometary nuclei into two basic types, described by core mantle and coreless models. Mass loss related nongravitational effects in a comet's motion as a function of time are included in considering gradual evaporation of an icy envelope surrounding the meteoric matrix in the core of the nucleus.

  4. 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.

  5. Rendezvous with a comet

    NASA Astrophysics Data System (ADS)

    Taylor, Matt

    2014-10-01

    After making a successful rendezvous with Comet 67P/Churyumov-Gerasimenko earlier this year, Europe's Rosetta craft is now riding alongside this celestial body and next month is set to land a probe on its surface. Matt Taylor describes the excitement of this unique project and the scientific insights that it hopes to achieve.

  6. 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…

  7. 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.

  8. DRBE comet trails

    SciTech Connect

    Arendt, Richard G.

    2014-12-01

    Re-examination of the Cosmic Background Explorer Diffuse Infrared Background Experiment (DIRBE) data reveals the thermal emission of several comet dust trails. The dust trails of 1P/Halley, 169P/NEAT, and 3200 Phaethon have not been previously reported. The known trails of 2P/Encke and 73P/Schwassmann–Wachmann 3 are also seen. The dust trails have 12 and 25 μm surface brightnesses of <0.1 and <0.15 MJy sr{sup −1}, respectively, which is <1% of the zodiacal light intensity. The trails are very difficult to see in any single daily image of the sky, but are evident as rapidly moving linear features in movies of the DIRBE data. Some trails are clearest when crossing through the orbital plane of the parent comet, but others are best seen at high ecliptic latitudes as the Earth passes over or under the dust trail. All these comets have known associations with meteor showers. This re-examination also reveals 1 additional comet and 13 additional asteroids that had not previously been recognized in the DIRBE data.

  9. Imaging studies of comets

    NASA Technical Reports Server (NTRS)

    Niedner, Malcolm B., Jr.; Klinglesmith, Daniel A., III; Westpfahl, David J.

    1991-01-01

    The Joint Observatory for Cometary Research's (JOCR) historical mission has been to provide understanding of large-scale interactions between bright comets and solar wind using wide-angle (Schmidt) imagery and spacecraft data; in this pursuit the JOCR has excelled. The 16 inch Newtonian/Cassegrain telescope was upgraded to permit filtered, narrow-field charge coupled device (CCD) imaging of both bright and faint comets. Thus, the goal of obtaining narrow-band imagery of the near-nuclear region of bright comets was added to JOCR's original mission with emphasis on ionization processes and total gas production. A 300 mm lens/CCD system exists with 3 degree field of view (FOV) which uses comet filters; this system bridges the gap between the wide-field (8 x 10 deg) Schmidt plates and the several-arcmin. field of the 16 inch telescope. JOCR is located under dark skies on South Baldy Mountain (el. 10,600 ft.) near Socorro, NM, and is one of the last truly dark sites in the continental U.S.

  10. 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)

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Understanding the Effects of Collisional Evolution and Spacecraft Impact Experiments on Comets and Asteroids

    NASA Technical Reports Server (NTRS)

    Lederer, S.M.; Jensen, E.A.; Fane, M.; Smith, D.C.; Holmes, J.; Keller, L.P.; Lindsay, S.S.; Wooden, D.H.; Whizin, A.; Cintala, M.J.; Zolensky, M.E.

    2017-01-01

    Comets and asteroids have endured impacts from other solar system bodies that result in outcomes ranging from catastrophic collisions to regolith evolution due to micrometeorid bombardment of the surface ices and refactory components. Experiments designed to better understand these relics of solar system formation have been conducted on Earth in a laboratory setting, as well as in space through, e.g., the Deep Impact Mission to Comet Tempel 1. Deep Impact fired a high-speed impactor into the roughly 6 km nucleus of the comet. The ejecta plume generated by the impact was studied by both spacecraft instrumentation and groundbased telescopes.

  17. Scenarios for distributed sources of formaldehyde in the atmosphere of comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Cottin, H.; Hadraoui, K.; Bardyn, A.; Le Roy, L.; Fray, N.; Briois, C.; Thirkell, L.; Merouane, S.; Hornung, K.; Langevin, Y.; Hilchenbach, M.

    2015-10-01

    The polymer of formaldehyde ((H2CO)n - polyoxymethylene - POM) has been tentatively detected in comet 1P/Halley by mass spectrometry with PICCA instrument onboard the Giotto spacecraft [1]. Although its detection has been questioned [2], this polymer could be the origin of distributed formaldehyde observed in the atmosphere of comet Halley and others [3]. We will present modelling results of the photo and thermal degradation of POM on grains in the environment of comet 67P/Churyumov-Gerasimenko, and discuss the extent to which distributed formaldehyde could be detected with Rosetta spacecraft observations in case POM is actually part of the nucleus component.

  18. 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.

  19. 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.

  20. Ephemeris data and error analysis in support of a Comet Encke intercept mission

    NASA Technical Reports Server (NTRS)

    Yeomans, D. K.

    1974-01-01

    Utilizing an orbit determination based upon 65 observations over the 1961 - 1973 interval, ephemeris data were generated for the 1976-77, 1980-81 and 1983-84 apparitions of short period comet Encke. For the 1980-81 apparition, results from a statistical error analysis are outlined. All ephemeris and error analysis computations include the effects of planetary perturbations as well as the nongravitational accelerations introduced by the outgassing cometary nucleus. In 1980, excellent observing conditions and a close approach of comet Encke to the earth permit relatively small uncertainties in the cometary position errors and provide an excellent opportunity for a close flyby of a physically interesting comet.

  1. Gas-to-Dust Ratio of Two Comets: Implication for Inhomogeneity of Cometary Nuclei?

    NASA Astrophysics Data System (ADS)

    Kawakita, Hideyo; Furusho, Reiko; Fujii, Mitsugu; Watanabe, Jun-Ichi

    1997-10-01

    We performed spectroscopic observations of Comet Tabur (C/1996Q1) from 1996 September 14 to October 16, on 9 nights. The gas-to-dust ratio was determined for C/Tabur, and compared with that of Comet Liller (C/1988A1), whose orbital elements are quite similar to those of C/Tabur. The gas-to-dust mass ratio obtained for C/Tabur is one order larger than C/Liller. Because this similarity of the orbits indicates a splitting of these comets in the past, the obtained difference in the gas-to-dust mass ratio should be due to an inhomogeneity of the cometary nucleus.

  2. Ammonia abundances in four comets

    NASA Astrophysics Data System (ADS)

    Wyckoff, S.; Tegler, S. C.; Engel, L.

    1991-02-01

    NH2 emission band strengths were measured in four comets and the NH2 column densities were determined in order to measure the ammonia content of the comets. The mean ammonia/water abundance ratio derived for the four comets is found to be 0.13 + or - 0.06 percent, with no significant variation among the comets. The uniformity of this abundance attests to a remarkable degree of chemical homogeneity over large scales in the comet-forming region of the primordial solar nebula, and contrasts with the CO abundance variations found previously in comets. The N2 and NH3 abundances indicate a condensation temperature in the range 20-160 K, consistent with virtually all comet formation hypotheses.

  3. 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.

  4. The Rotation State of Comet 103P/Hartley 2

    NASA Astrophysics Data System (ADS)

    Farnham, Tony; Knight, Matthew M.; Schleicher, David G.

    2016-10-01

    On November 4, 2010, the Deep Impact (DI) spacecraft made its closest approach to comet 103P/Hartley 2, passing only 694 km from the nucleus. Observations of the coma produced a lightcurve that shows the nucleus is in a state of non-principal axis rotation that evolves with time, while other observations revealed a nucleus that has concentrated collimated jets driven by CO2 emission (A'Hearn et al., 2011), large variability in the production of H2O and CO2 (Besse et al. 2016), and ice patches on the surface (Sunshine et al. 2011). To properly interpret the significance of these phenomena, it is necessary to understand the rotation of the nucleus, so that its thermal history can be derived and properly modeled, while at the same time, it is likely that the comet's high activity levels play an important role in the nucleus dynamics.An analysis of the lightcurve by Belton et al (2013) described the comet's rotation state, with two periodicities (primary of 18 h, secondary of 28 or 55 h) that change with time. Although their solution describes the periodicities observed around closest approach, it is insufficient to reproduce the changes in coma morphology with time. We are performing an analysis of the structures in the coma (Farnham 2009), using Monte Carlo routines to model the outflowing dust produced by active sources on the nucleus, to derive a comprehensive solution for the nucleus' rotation.We are also obtaining new observations of Hartley 2 in June/July 2016 (r~3.2 AU) to measure the nucleus' primary component period before the comet becomes highly active. This will provide an end-state measure of the rotation from the 2010 apparition, as well as a starting value for the current apparition, to allow its continuing evolution to be monitored. We will present an update on the status and preliminary results of these analyses.This work is funded by NASA Grant NNX12AQ64G.A'Hearn, M.F., et al. (2011) Science 332, 1396-1400Belton M.J.S., et al. (2013) Icarus 222, 595

  5. Planetary perturbations for Oort cloud comets: II. Implications for the origin of observable comets

    NASA Astrophysics Data System (ADS)

    Fouchard, M.; Rickman, H.; Froeschlé, Ch.; Valsecchi, G. B.

    2014-03-01

    We present Monte Carlo simulations of the dynamical history of the Oort cloud, where in addition to the main external perturbers (Galactic tides and stellar encounters) we include, as done in a companion paper (Fouchard, M., Rickman, H., Froeschlé, Ch., Valsecchi, G.B. [2013b]. Icarus, in press), the planetary perturbations experienced each time the comets penetrate to within 50 AU of the Sun. Each simulation involves an initial sample of four million comets and extends over a maximum of 5 Gyr. For better understanding of the outcomes, we supplement the full dynamical model by others, where one or more of the effects are left out. We concentrate on the production of observable comets, reaching for the first time a perihelion within 5 AU of the Sun. We distinguish between four categories, depending on whether the comet jumps across, or creeps through, the Jupiter-Saturn barrier (perihelion distances between 5 and 15 AU), and whether the orbit leading to the observable perihelion is preceded by a major planetary perturbation or not. For reasons explained in the paper, we call the strongly perturbed comets "Kaib-Quinn comets". We thus derive a synthetic picture of the Oort spike, from which we draw two main conclusions regarding the full dynamical model. One is that 2/3 of the observable comets are injected with the aid of a planetary perturbation at the previous perihelion passage, and about half of the observable comets are of the Kaib-Quinn type. The other is that the creepers dominate over the jumpers. Due to this fact, the spike peaks at only 31 000 AU, and the majority of new comets have semi-major axes less than this value. The creepers show a clear preference for retrograde orbits as a consequence of the need to avoid untimely, planetary ejection before becoming observable. Thus, the new comets should have a 60/40 preference for retrograde against prograde orbits in apparent conflict with observations. However, both these and other results depend on our model

  6. 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.

  7. Comet Halley - The gas composition derived from space missions

    NASA Astrophysics Data System (ADS)

    Encrenaz, T.

    1987-09-01

    Important results have been obtained by the Vega and Giotto missions concerning Comet Halley's gas composition. Water vapor and CO2 have been identified with respective production rates of about 10 to the 30th/s and 10 to the 28th/s. In addition, there is evidence for the presence of hydrocarbons and/or carbonaceous material in large amounts in the immediate vicinity of the nucleus.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2003-01-01

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

  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. 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

  12. The excited spin state of Comet 2P/Encke

    NASA Astrophysics Data System (ADS)

    Belton, Michael J. S.; Samarasinha, Nalin H.; Fernández, Yan R.; Meech, Karen J.

    2005-05-01

    Ways to rationalize the different periods (e.g., 15.08 h, Luu and Jewitt, 1990, Icarus 86, 69-81; 11.01 h, Fernández et al., 2004, Icarus, in this issue; Lowry et al., 2003, Lunar Planet. Sci. XXXIV, Abstract 2056) seen in near aphelion R-band light curves of Comet 2P/Encke are explored. We show that the comet is usually active at aphelion and it's observed light curves contain signal from both the nucleus and an unresolved coma. The coma contribution to the observed brightness is generally found to dominate with the nucleus providing from 28 to 87% of the total brightness. The amplitude of the observed variations cannot be explained by the nucleus alone and are due to coma activity. We show that some seven periodicities exist in the observed light curves at various times and that this is likely the result of an active nucleus spinning in an excited spin state. The changing periodicities are probably due to changes in the relative strengths of the active areas. We work out possible excited states based on experience with model light curves and by using an analogy to light curve observations of Comet 1P/Halley for which the spin state has been separately determined from spacecraft observations. There is a possibility of a fully relaxed principal axis spin state (0.538 d -1; P=44.6 h) but, because it provides a poorer fit to the observed periodicities than the best fit excited state together with the absence of a peak near 1.08 d -1 ( 2f) in the frequency spectrum of the Fernández et al. (2000, Icarus 147, 145-160) thermal IR lightcurve, we consider it unlikely. Both SAM and LAM excited states are allowed by the underlying periodicities and additional information is needed to choose between these. Our choice of a low excitation SAM state, i.e., one in which the instantaneous spin axis nutates around the total angular momentum vector in a motion that is characterized by limited angular oscillations around the long axis, is based on Sekanina's (1988, Astron J. 95

  13. Navigation capability for an ion drive rendezvous with Halley's Comet

    NASA Technical Reports Server (NTRS)

    Thornton, C. L.; Jacobson, R. A.

    1977-01-01

    An analysis has been conducted in connection with plans for a study of Halley's Comet during its 1986 apparition. The use of low-thrust vehicles, utilizing an ion drive system, is being considered for a comet rendezvous mission. A preliminary trajectory for the Halley rendezvous mission calls for launch on June 20, 1982, followed by rendezvous on December 21, 1985. The navigation analysis described focuses on the terminal approach to Halley, the 60-day period preceding rendezvous. Navigation analysis assumptions are examined, taking into account navigation error sources, radio tracking, onboard optical data, earth-based comet observations, and orbit determination and guidance strategies. The preliminary mission design considers a rendezvous at approximately 56,000 km from the comet nucleus (6,000 km outside the dust envelope). Navigation performance is measured in terms of comet-relative position and velocity errors at encounter. Variations to the baseline navigation study provide illustrations concerning the close link between delivery accuracy and stochastic thrust errors.

  14. Constraints on Comet 332P/Ikeya-Murakami

    NASA Astrophysics Data System (ADS)

    Hui, Man-To; Ye, Quan-Zhi

    2016-10-01

    Encke-type comet 332P/Ikeya-Murakami is experiencing a series of cascading fragmentation events during its 2016 apparition. It is likely the first splitting Encke-type comet ever being observed. A nongravitational solution to the available astrometry including high quality observations from the Canada-France-Hawaii Telescope by Kleyna et al. (private communication) reveals a statistical detection of the radial and transverse nongravitational parameters, A1 = (1.54 ± 0.39) × 10-8 AU day-2, and A2 = (7.19 ± 1.92) × 10-9 AU day-2, respectively, based upon which we calculated the erosion rate of the comet, which is large and hence is likely related to the ongoing fragmentation events. We have constrained the nucleus size from our archival search for serendipitously pre-discovery observations of the comet from major sky surveys. Our study also suggests a potential generic relationship between comet P/2010 B2 (WISE) and 332P. Detailed information will be presented.

  15. CCD observations of distant comets from Palomar and Steward Observatories

    NASA Astrophysics Data System (ADS)

    Lowry, Stephen C.; Weissman, Paul R.

    2003-08-01

    We are conducting a ground-based observational study of distant cometary nuclei with the aim of increasing the current database of physical parameters of individual objects, and to estimate the overall distributions of size, rotation period, axial ratio, and color indices. Additionally, we are obtaining CCD spectroscopy and photometry of established and potential targets of current and future spacecraft missions. The results presented here are derived from CCD imaging obtained using the 2.3-m Bok telescope of Steward Observatory (Arizona), obtained in May 2001, and the 5-m Hale telescope at Palomar Observatory (California), obtained in May 2000 and March 2001. Comets observed include 4P/Faye, 6P/d'Arrest, 22P/Kopff, 36P/Whipple, 50P/Arend, 78P/Gehrels 2, 92P/Sanguin, 107P/Wilson-Harrington, and 128P/Shoemaker-Holt 1-A. Of the nine comets observed, only Comets 4P/Faye and 50P/Arend displayed visible coma activity. We have performed either single R filter or multi-filter ( BVRI) measurements on these comets, from which we obtain radius and broadband color estimates as well as Afρ values for the active comets. For selected objects we have performed time-series R filter imaging from which we have derived the rotation period and lower limits on the nuclear axial ratio and density. The radius results obtained are included in the cometary nucleus size distribution estimate by Weissman and Lowry (2003).

  16. 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.

  17. ESO observations of the Nucleus of Rosetta Target 67P/C-G

    NASA Astrophysics Data System (ADS)

    Lowry, S. C.; Duddy, S.; Fitzsimmons, A.; Snodgrass, C.; Hsieh, H.; Hainaut, O.

    2011-10-01

    Rosetta is ESA's new comet orbiter mission, launched in March 2004 and currently en route to Jupiter-family comet 67P/Churyumov-Gerasimenko. The probe will rendezvous with the comet in 2014 and remain in orbit around the nucleus for on-going detailed physical and compositional analysis. Pre-encounter observations of the target are important for characterization of the heliocentric light-curve behaviour and the physical properties of the nucleus, information that is critical for mission planning. The nucleus was first characterized using HST observations in 2003 (Lamy et al. 2006) and observed directly in May 2005 by ground based telescopes (Lowry et al. 2006) when it was at 5.6 AU from the Sun. An extensive database of nucleus observations have since been acquired, not only from large ground-based telescopes like the ESO VLT (Tubiana et al. 2008 & 2011), but also from Spitzer (Kelley et al. 2006 & 2009; Lamy et al. 2008).

  18. 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.

  19. Recommendations for safety testing with the in vivo comet assay.

    PubMed

    Vasquez, Marie Z

    2012-08-30

    While the in vivo comet assay increases its role in regulatory safety testing, deliberations about the interpretation of comet data continue. Concerns can arise regarding comet assay publications with limited data from non-blind testing of positive control compounds and using protocols (e.g. dose concentrations, sample times, and tissues) known to give an expected effect. There may be a tendency towards bias when the validation or interpretation of comet assay data is based on results generated by widely accepted but non-validated assays. The greatest advantages of the comet assay are its sensitivity and its ability to detect genotoxicity in tissues and at sample times that could not previously be evaluated. Guidelines for its use and interpretation in safety testing should take these factors into account. Guidelines should be derived from objective review of data generated by blind testing of unknown compounds dosed at non-toxic concentrations and evaluated in a true safety-testing environment, where the experimental design and conclusions must be defensible. However, positive in vivo comet findings with such compounds are rarely submitted to regulatory agencies and this data is typically unavailable for publication due to its proprietary nature. To enhance the development of guidelines for safety testing with the comet assay, and with the permission of several sponsors, this paper presents and discusses relevant data from multiple GLP comet studies conducted blind, with unknown pharmaceuticals and consumer products. Based on these data and the lessons we have learned through the course of conducting these studies, I suggest significant adjustments to the current conventions, and I provide recommendations for interpreting in vivo comet assay results in situations where risk must be evaluated in the absence of carcinogenicity or clinical data.

  20. 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.

  1. An infrared search for HDO in comets

    NASA Astrophysics Data System (ADS)

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

    2002-11-01

    We searched for HDO emission in our infrared database of six Oort Cloud comets (C/2002 C1 (Ikeya-Zhang), C/2001 A2 (LINEAR), C/2000 WM1 (LINEAR), C/1999 H1 (Lee), C/1999 S4 (LINEAR), and C/1999 T1 (McNaught-Hartley)). Spectral lines of the ν1 fundamental vibrational band of HDO were sampled using high resolution infrared spectra acquired with both CSHELL at NASA's IRTF and NIRSPEC at the W.M. Keck Observatory. Of these comets, the recent apparition of the bright Comet Ikeya-Zhang, with its high gas production rate and good geocentric Doppler shift, provided an exceptional opportunity to search for minor constituents such as HDO. We report tentative detections of HDO in three Oort Cloud comets with upper limits determined for the remaining three. These data, combined with future observations, will be used to test models of nebular chemistry and delivery of water and organics to the early Earth.

  2. 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.

  3. 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

  4. Carbon isotopes in comets

    NASA Technical Reports Server (NTRS)

    Wehinger, Peter A.

    1990-01-01

    The progress is reported of high resolution spectra of selected bright comets with the aim of determining the carbon isotope abundance ratio, C-12/C-13. The ratio was determined for various Solar System objects (in the atmospheres of the giant planets, meteorites, the Earth, and the solar photosphere), where the C-12/C-13 = 89/1. In the interstellar medium, optical and radio observations give a range of C-12/C-13 = 43-67/1 depending on the observing techniques used and the specific interstellar cloud observed. The echelle spectra is presented of the CN(0,0) violet system in three comets: P/Brorsen-Metcalf, C/Okazaki-Levy-Rudenko, and C/Austin. P/Brorsen-Metcalf has a period of 70 y (prograde) compared with P/Halley which is 76 y (retrograde). The similar periods made P/Brorsen-Metcalf of special interest for comparison with P/Halley.

  5. 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.

  6. The First Detailed IR Observations of a Sungrazing Comet: C/2011 W3 Lovejoy

    NASA Astrophysics Data System (ADS)

    Knight, Matthew; Fernandez, Yanga; Lisse, Carey; Osip, David

    2012-01-01

    We propose to observe the newly discovered comet C/2011 W3 Lovejoy in February 2012 at 3.6 and 4.5 microns. Lovejoy is a member of the Kreutz group of sungrazing comets and is the first sungrazing comet known to have survived perihelion during the era of modern observations (since 1970). The size of its nucleus is currently unconstrained but is critical for understanding Lovejoy's place in the Kreutz group hierarchy (either as one of the 1600+ known "pygmy" fragments or one of a handful of major fragments of the parent body, which created the rest). Spitzer observations of the nucleus's thermal emission, when combined with planned optical observations (we have an approved HST DDT proposal and plan to obtain concurrent observations from Las Campanas Observatory), would let us definitively measure the size of a Kreutz nucleus for the first time, thereby giving us confidence in estimating sizes of other Kreutz fragments from visible data alone. The observations would also let us constrain the Kreutz nucleus's thermal properties and compare them to other comets that do not suffer such extreme heating. Kreutz comets are known to fragment frequently, and we expect to be sensitive down to fragments ~40 m in radius at 4.5 microns. The imaging of the dust, combined with other visible-wavelength imaging, will let us constrain dust grain sizes (via dynamical [Finson-Probstein] modeling) and grain albedos (vi a photometry). We would also be able to measure the dust production rate and thus constrain fragment lifetimes. These Spitzer observations would be the first infrared observations of a sungrazing comet since Comet Ikeya-Seki in 1965, and the first in the modern infrared era with sensitive, space-based detectors.

  7. Characterization of Comet 252P/LINEAR during its 2016 Earth Encounter

    NASA Astrophysics Data System (ADS)

    Li, Jian-Yang; Samarasinha, Nalin H.; Kelley, Michael S.; Farnocchia, Davide; Mutchler, Maximilian J.

    2016-10-01

    Comet 252P/LINEAR had a close encounter to Earth at 14 lunar distances in March 2016, representing one of the closest encounters of known comets in history and a good opportunity to measure its nucleus size and to resolve its inner coma. Observations from previous apparitions suggested a small nucleus of about or less than 1 km, and very weak activity for this comet. The similarity between the orbits of 252P and P/2016 BA16 suggests that they might be a pair of fragments from one common parent comet. We imaged 252P with the Hubble Space Telescope Wide Field Camera 3 through r'- and V-band filters over ~45 min on March 14 and over ~8 hours on April 4, 2016 at pixel scales down to 1.4 km/pix. The dust coma shows a strong enhancement in the sunward direction within about 1".5 (about 100 km at the comet) for both epochs. Image enhancement with 1/rho normalization shows that the sunward feature moves about the nucleus for ~60 deg in the second epoch, consistent with a ~7.35-hr period. The r'-band partial lightcurve measured in the April 4 images in a 0".2-radius aperture shows variability of about 0.14 mag or larger. This partial lightcurve is not consistent with the 7.35-hr period, but is consistent with a periodicity of ~5.5 hr or its multiples. The r'-band mean value of Afrho is 13 cm for March 14 and 46 cm for April 4 in a 0".2-radius aperture. We will also measure the nucleus size of this comet, and discuss its implications about the evolutionary state of the comet.

  8. 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.

  9. 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.

  10. Comet LINEAR C/1999 S4 - an absolutely well-behaved comet before breakup

    NASA Astrophysics Data System (ADS)

    Peschke, S. B.; Lisse, C. M.; Fernandez, Y. R.; Ressler, M.; Stickel, M.; Kaminski, C.; Golish, B.

    2000-10-01

    We present results from infrared imaging of comet LINEAR C/1999 S4 on June 17 - 19, 2000 (pre-breakup), using the near-IR camera NSFCAM and the mid-IR camera MIRLIN at the 3m NASA/IRTF. Images and multi-wavelength spectroscopy were obtained in the zJHK'L'MNQ bands, and were used to create a 1.0 - 25 μ m SED of the comet's dust and nucleus. The coma's contribution at each wavelength was modeled using spatial fitting (Fernandez 1999, PhD thesis; Lisse et al. 1999, Icarus 140, 189). The resulting comatic and nuclear SEDs were then modeled using modified Mie theory (Lisse et al. 1998, ApJ 496, 971) and the standard nuclear thermal models (Lebofsky and Spencer 1989, Asteroids II, 128), respectively. We report the resulting dust PSD, mass loss rate, and albedo, as well as the nuclear radius, and we compare these results to those obtained by others from optical data both before and after the comet's breakup in late July 2000.

  11. 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