Physical Processing of Cometary Nuclei

NASA Technical Reports Server (NTRS)

Weissman, Paul R.; Stern, S. Alan

1997-01-01

Cometary nuclei preserve a cosmo-chemical record of conditions and processes in the primordial solar nebula, and possibly even the interstellar medium. However, that record is not perfectly preserved over the age of the solar system due to a variety of physical processes which act to modify cometary surfaces and interiors. Possible structural and/or internal processes include: collisional accretion, disruption, and reassembly during formation; internal heating by long and short-lived radionuclides; amorphous to crystalline phase transitions, and thermal stresses. Identified surface modification processes include: irradiation by galactic cosmic rays, solar protons, UV photons, and the Sun's T Tauri stage mass outflow; heating by passing stars and nearby supernovae; gardening by debris impacts; the accretion of interstellar dust and gas and accompanying erosion by hypervelocity dust impacts and sputtering; and solar heating with accompanying crust formation. These modification processes must be taken into account in both the planning and the interpretation of the results of a Comet Nucleus Sample Return Mission. Sampling of nuclei should be done at as great a depth below the surface crust as technically feasible, and at vents or fissures leading to exposed volatiles at depth. Samples of the expected cometary crust and near-surface layers also need to be returned for analysis to achieve a better understanding of the effects of these physical processes. We stress that comets are still likely less modified dm any other solar system bodies, but the degree of modification can vary greatly from one comet to the next.

Correlated Microanalysis of Cometary Organic Grains Returned by Stardust

NASA Technical Reports Server (NTRS)

DeGregorio, B. T.; Stroud, R. M.; Nittler, L. R.; Cody, G. D,; Kilcoyne, A. L. D.

2011-01-01

Preliminary examination (PE) of samples returned from Comet 81P/Wild 2 by the NASA Stardust mission revealed a wide variety of carbonaceous samples [e.g. 1]. Carbonaceous matter is present as inclusions, rinds, and films in polyminerallic terminal particles [2-4], as carbon-rich particles along track walls [2, 5, 6], and as organic matter in aerogel around tracks [7, 8]. The organic chemistry of these samples ranges from purely aliphatic hydrocarbons to highly-aromatic material, often modified by various organic functional groups [2, 4, 5, 9-11]. Difficulty arises when interpreting the genesis of these carbonaceous samples, since contaminants could be introduced from the spacecraft [12], aerogel [1, 8], or during sample preparation. In addition, hypervelocity capture into aerogel may have heated cometary material in excess of 1000 C, which could have significantly altered the structure and chemistry of carbonaceous matter. Fortunately, much of this contamination or alteration can be identified through correlated microanalysis with transmission electron microscopy (TEM), scanning-transmission X-ray microscopy (STXM), and nanoscale secondary ion mass spectroscopy (SIMS).

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.

The oxygen isotopic composition (18O/16O) in the dust of comet 67P/Churyumov-Gerasimenko measured by COSIMA on-board Rosetta

NASA Astrophysics Data System (ADS)

Paquette, J. A.; Engrand, C.; Hilchenbach, M.; Fray, N.; Stenzel, O. J.; Silen, J.; Rynö, J.; Kissel, J.

2018-07-01

The oxygen isotopic ratio 18O/16O has been measured in cometary gas for a wide variety of comets, but the only measurements in cometary dust were performed by the Stardust cometary sample return mission. Most such measurements find a value of the ratio that is consistent with Vienna Standard Mean Ocean Water (VSMOW) within errors. In this work we present the result of a measurement, using the COSIMA (the COmetary Secondary Ion Mass Analyser) instrument on the Rosetta orbiter, of the oxygen isotopic ratio in dust from Comet 67P/Churyumov-Gerasimenko. Measuring the 18O/16O ratio with COSIMA is challenging for a number of reasons, but it is possible with a reasonable degree of precision. We find a result of 2.00 × 10-3 ± 1.2 × 10-4, which is consistent within errors with VSMOW.

Non-destructive sampling of a comet

NASA Astrophysics Data System (ADS)

Jessberger, H. L.; Kotthaus, M.

1991-04-01

Various conditions which must be met for the development of a nondestructive sampling and acquisition system are outlined and the development of a new robotic sampling system suited for use on a cometary surface is briefly discussed. The Rosetta mission of ESA will take samples of a comet nucleus and return both core and volatile samples to earth. Various considerations which must be taken into account for such a project are examined including the identification of design parameters for sample quality; the identification of the most probable site conditions; the development of a sample acquisition system with respect to these conditions; the production of model materials and model conditions; and the investigation of the relevant material properties. An adequate sampling system should also be designed and built, including various tools, and the system should be tested under simulated cometary conditions.

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.

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.;

Ultra-Fast Laser Desorption/Laser Ionization Mass Spectrometry for the Organic Analysis of Stardust Sample Return

NASA Technical Reports Server (NTRS)

Clemett, Simon J.; McKay, David S.

2005-01-01

The STARDUST sample return capsule is anticipated to provide 500-1000 cometary particles 15 m in size. These were collected during the 340 km flyby of Comet P/Wild-2 and impacted the aerogel collection medium at a relative velocity of approx. 6.1 /kms. Hypervelocity impact studies suggest that some fraction of the original organic inventory of collected particles ought to remain intact, although there is likely to be a significant amount of devolatilization and disassociation of the lower mass organic fraction.

Vega-Giotto flyby missions and cometary cosmogony

NASA Technical Reports Server (NTRS)

Lang, Bruno

1989-01-01

The most important implication of the Vega/Giotto flyby missions to Halley's Comet for cometary cosmogony is the opportunity to absorb the results of the in-situ measurements as made onboard the spacecrafts. Unfortunately the exploration of ejecta form the nucleus was unable to provide an unambiguous definition of the chemical-mineralogical nature of the nucleus: it failed to provide information comparable to that which was expected from a sample return mission. However, the obtained results are significant enough to affect and redirect cosmogonical thinking. Accordingly, the understanding of the cometary-matter dichotomy is modified as deduced from the distiction of water-dominated volitiles and silicate-based non-volitiles. Organic carbon compounds emerge as a major constituent of cometary nuclei. Presently, it is likely that the revision of Whipple's classic concept of the icy conglomerate cannot be avoided. Affected by the Vega/Giotto flyby missions to Hally's Comet, cometary cosmogony seems to enter a new conceptual period. The results of the in-situ measurements (mass spectrometric, UV spectroscopic, and IR spectroscopic) appear to be of basic importance. A chemical explanation is employed to explain the occurrence inside the nuclei of the variety of species, as inferred from the mass spectrometric data, to predict the results of the processes possibly involved. A cosmochemical factor is postulated to operate behind the observed cometary phenomena. The chemistry of the interstellar medium, covering the circumstellar and interstellar dust, advances cometary cosmogony.

Cometary Dust

NASA Astrophysics Data System (ADS)

Levasseur-Regourd, Anny-Chantal; Agarwal, Jessica; Cottin, Hervé; Engrand, Cécile; Flynn, George; Fulle, Marco; Gombosi, Tamas; Langevin, Yves; Lasue, Jérémie; Mannel, Thurid; Merouane, Sihane; Poch, Olivier; Thomas, Nicolas; Westphal, Andrew

2018-04-01

This review presents our understanding of cometary dust at the end of 2017. For decades, insight about the dust ejected by nuclei of comets had stemmed from remote observations from Earth or Earth's orbit, and from flybys, including the samples of dust returned to Earth for laboratory studies by the Stardust return capsule. The long-duration Rosetta mission has recently provided a huge and unique amount of data, obtained using numerous instruments, including innovative dust instruments, over a wide range of distances from the Sun and from the nucleus. The diverse approaches available to study dust in comets, together with the related theoretical and experimental studies, provide evidence of the composition and physical properties of dust particles, e.g., the presence of a large fraction of carbon in macromolecules, and of aggregates on a wide range of scales. The results have opened vivid discussions on the variety of dust-release processes and on the diversity of dust properties in comets, as well as on the formation of cometary dust, and on its presence in the near-Earth interplanetary medium. These discussions stress the significance of future explorations as a way to decipher the formation and evolution of our Solar System.

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.

The Oxygen Isotopic Composition (18O/16O) in the Dust of Comet 67P/Churyumov-Gerasimenko Measured by COSIMA On-board Rosetta

NASA Astrophysics Data System (ADS)

Paquette, J. A.; Engrand, C.; Hilchenbach, M.; Fray, N.; Stenzel, O. J.; Silen, J.; Rynö, J.; Kissel, J.

2018-03-01

The oxygen isotopic ratio 18O/16O has been measured in cometary gas for a wide variety of comets, but the only measurements in cometary dust were performed by the Stardust cometary sample return mission. Most such measurements find a value of the ratio that is consistent with Vienna Standard Mean Ocean Water (VSMOW) within errors. In this work we present the result of a measurement, using the COSIMA instrument on the Rosetta orbiter, of the oxygen isotopic ratio in dust from Comet 67P/Churyumov-Gerasimenko. Measuring the 18O/16O ratio with COSIMA is challenging for a number of reasons, but it is possible with a reasonable degree of precision. We find a result of 2.00 × 10-3 ± 1.2 × 10-4 which is consistent within errors with VSMOW.

Handling and analysis of ices in cryostats and glove boxes in view of cometary samples

NASA Technical Reports Server (NTRS)

Roessler, K.; Eich, G.; Heyl, M.; Kochan, H.; Oehler, A.; Patnaik, A.; Schlosser, W.; Schulz, R.

1989-01-01

Comet nucleus sample return mission and other return missions from planets and satellites need equipment for handling and analysis of icy samples at low temperatures under vacuum or protective gas. Two methods are reported which were developed for analysis of small icy samples and which are modified for larger samples in cometary matter simulation experiments (KOSI). A conventional optical cryostat system was modified to allow for transport of samples at 5 K, ion beam irradiation, and measurement in an off-line optical spectrophotometer. The new system consists of a removable window plug containing nozzles for condensation of water and volatiles onto a cold finger. This plug can be removed in a vacuum system, changed against another plug (e.g., with other windows (IR, VIS, VUV) or other nozzles). While open, the samples can be treated under vacuum with cooling by manipulators (cut, removal, sample taking, irradiation with light, photons, or ions). After bringing the plug back, the samples can be moved to another site of analysis. For handling the 30 cm diameter mineral-ice samples from the KOSI experiments an 80x80x80 cm glove box made out of plexiglass was used. The samples were kept in a liquid nitrogen bath, which was filled from the outside. A stream a dry N2 and evaporating gas from the bath purified the glove box from impurity gases and, in particular, H2O, which otherwise would condense onto the samples.

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.

Penetrator Coring Apparatus for Cometary Surfaces

NASA Technical Reports Server (NTRS)

Braun, David F.; Heinrich, Michael; Ai, Huirong Anita; Ahrens, Thomas J.

2004-01-01

Touch and go impact coring is an attractive technique for sampling cometary nuclei and asteroidal surface on account of the uncertain strength properties and low surface gravities of these objects. Initial coring experiments in low temperature (approx. 153K polycrystalline ice) and porous rock demonstrate that simultaneous with impact coring, measurements of both the penetration strength and constraints on the frictional properties of surface materials can be obtained upon core penetration and core sample extraction. The method of sampling an asteroid, to be deployed, on the now launched MUSES-C mission, employs a small gun device that fires into the asteroid and the resulted impact ejecta is collected for return to Earth. This technique is well suited for initial sampling in a very low gravity environment and deployment depends little on asteroid surface mechanical properties. Since both asteroids and comets are believed to have altered surface properties a simple sampling apparatus that preserves stratigraphic information, such as impact coring is an attractive alternate to impact ejecta collection.

Insights into the nature of cometary organic matter from terrestrial analogues

NASA Astrophysics Data System (ADS)

Court, Richard W.; Sephton, Mark A.

2012-04-01

The nature of cometary organic matter is of great interest to investigations involving the formation and distribution of organic matter relevant to the origin of life. We have used pyrolysis-Fourier transform infrared (FTIR) spectroscopy to investigate the chemical effects of the irradiation of naturally occurring bitumens, and to relate their products of pyrolysis to their parent assemblages. The information acquired has then been applied to the complex organic matter present in cometary nuclei and comae. Amalgamating the FTIR data presented here with data from published studies enables the inference of other comprehensive trends within hydrocarbon mixtures as they are progressively irradiated in a cometary environment, namely the polymerization of lower molecular weight compounds; an increased abundance of polycyclic aromatic hydrocarbon structures; enrichment in 13C; reduction in atomic H/C ratio; elevation of atomic O/C ratio and increase in the temperature required for thermal degradation. The dark carbonaceous surface of a cometary nucleus will display extreme levels of these features, relative to the nucleus interior, while material in the coma will reflect the degree of irradiation experienced by its source location in the nucleus. Cometary comae with high methane/water ratios indicate a nucleus enriched in methane, favouring the formation of complex organic matter via radiation-induced polymerization of simple precursors. In contrast, production of complex organic matter is hindered in a nucleus possessing a low methane/water ration, with the complex organic matter that does form possessing more oxygen-containing species, such as alcohol, carbonyl and carboxylic acid functional groups, resulting from reactions with hydroxyl radicals formed by the radiolysis of the more abundant water. These insights into the properties of complex cometary organic matter should be of particular interest to both remote observation and space missions involving in situ analyses and sample return of cometary materials.

The Importance of Meteorite Collections to Sample Return Missions: Past, Present, and Future Considerations

NASA Technical Reports Server (NTRS)

Welzenbach, L. C.; McCoy, T. J.; Glavin, D. P.; Dworkin, J. P.; Abell, P. A.

2012-01-01

While much of the scientific community s current attention is drawn to sample return missions, it is the existing meteorite and cosmic dust collections that both provide the paradigms to be tested by these missions and the context for interpreting the results. Recent sample returns from the Stardust and Hayabusa missions provided us with new materials and insights about our Solar System history and processes. As an example, Stardust sampled CAIs among the population of cometary grains, requiring extensive and unexpected radial mixing in the early solar nebula. This finding would not have been possible, however, without extensive studies of meteoritic CAIs that established their high-temperature, inner Solar System formation. Samples returned by Stardust also revealed the first evidence of a cometary amino acid, a discovery that would not have been possible with current in situ flight instrument technology. The Hayabusa mission provided the final evidence linking ordinary chondrites and S asteroids, a hypothesis that developed from centuries of collection and laboratory and ground-based telescopic studies. In addition to these scientific findings, studies of existing meteorite collections have defined and refined the analytical techniques essential to studying returned samples. As an example, the fortuitous fall of the Allende CV3 and Murchison CM2 chondrites within months before the return of Apollo samples allowed testing of new state-of-the-art analytical facilities. The results of those studies not only prepared us to better study lunar materials, but unanticipated discoveries changed many of our concepts about the earliest history and processes of the solar nebula. This synergy between existing collections and future space exploration is certainly not limited to sample return missions. Laboratory studies confirmed the existence of meteorites from Mars and raised the provocative possibility of preservation of ancient microbial life. The laboratory studies in turn led to a new wave of Mars exploration that ultimately could lead to sample return focused on evidence for past or present life. This partnership between collections and missions will be increasingly important in the coming decades as we discover new questions to be addressed and identify targets for for both robotic and human exploration . Nowhere is this more true than in the ultimate search for the abiotic and biotic processes that produced life. Existing collections also provide the essential materials for developing and testing new analytical schemes to detect the rare markers of life and distinguish them from abiotic processes. Large collections of meteorites and the new types being identified within these collections, which come to us at a fraction of the cost of a sample return mission, will continue to shape the objectives of future missions and provide new ways of interpreting returned samples.

Stardust in STARDUST - the C, N, and O Isotopic Compositions of Wild 2 Cometary Matter in Al Foil Impacts

NASA Technical Reports Server (NTRS)

Stadermann, Frank J.; Hoppe, Peter; Floss, Christine; Heck, Philipp R.; Hoerz, Friedrich; Huth, Joachim; Kearsley, Anton T.; Leitner, Jan; Marhas, Kuljeet K.; McKeegan, Kevin D.;

Stardust in STARDUST - the C, N, and O Isotopic Compositions of Wild 2 Cometary Matter in Al foil Impacts

NASA Technical Reports Server (NTRS)

Stadermann, Frank J.; Hoppe, Peter; Floss, Christine; Hoerz, Friedrich; Huth, Joachim; Kearsley, Anton T.; Leitner, Jan; Marhas, Kuljeet K.; McKeegan, Kevin D.; Stephan, Thomas;

The Stardust: A Successful Encounter with the Remarkable Comet Wild 2

NASA Technical Reports Server (NTRS)

Brownlee, D. E.; Anderson, J. D.; Atkins, K.; Bhaskaran, S.; Cheuvront, A. R.; Clark, B. C.; Duxbury, T. C.; Economou, T.; Hanner, M. S.; Hoerz, F.

2004-01-01

On January 2, 2004 the Stardust spacecraft completed a close flyby of comet Wild2 (P81). Flying at a relative speed of 6.1 km/s within 237km of the 5 km nucleus, the spacecraft took 72 close-in images, measured the flux of impacting particles and did in-situ compositional analysis of freshly released dust with a time-of-flight mass spectrometer. The primary goal of the mission is to collect >500 particles >15 m diameter and return them to Earth on January 15, 2006. The cometary particles ranging in size from a micron to approx.100 microns were collected in low density silica aerogel. After returning over a hundred 2x4x3 cm aerogel collection cells will be processed at the curatorial facility at the NASA Johnson Space Center and 5 to 100 micron size extracted cometary particles will be distributed to analysts by a system that will be based on the allocation procedures for cosmic dust, Antarctic meteorites and lunar samples.

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.;

Focused Ion Beam Recovery of Hypervelocity Impact Residue in Experimental Craters on Metallic Foils

NASA Technical Reports Server (NTRS)

Graham, G. A.; Teslich, N.; Dai, Z. R.; Bradley, J. P.; Kearsley, A. T.; Horz, F.

2006-01-01

The Stardust sample return capsule will return to Earth in January 2006 with primitive debris collected from Comet 81P/Wild-2 during the fly-by encounter in 2004. In addition to the cometary particles embedded in low-density silica aerogel, there will be microcraters preserved in the Al foils (1100 series; 100 micrometers thick) that are wrapped around the sample tray assembly. Soda lime spheres (approximately 49 m in diameter) have been accelerated with a light-gas-gun into flight-grade Al foils at 6.35 km s(sup -1) to simulate the potential capture of cometary debris. The preserved crater penetrations have been analyzed using scanning electron microscopy (SEM) and x-ray energy dispersive spectroscopy (EDX) to locate and characterize remnants of the projectile material remaining within the craters. In addition, ion beam induced secondary electron imaging has proven particularly useful in identifying areas within the craters that contain residue material. Finally, high-precision focused ion beam (FIB) milling has been used to isolate and then extract an individual melt residue droplet from the interior wall of an impact penetration. This enabled further detailed elemental characterization, free from the background contamination of the Al foil substrate. The ability to recover pure melt residues using FIB will significantly extend the interpretations of the residue chemistry preserved in the Al foils returned by Stardust.

Space Art "Stardust"

NASA Image and Video Library

2008-01-08

Artist Paul Henry Ramirez captured symbolically the Stardust mission in this peice titled "Stardust". The Stardust mission in January of 2006 completed a seven-year, 2.8 billion mile journey to fly by a comet and return samples to Earth. The material is a first sample of pristine cometary material which will increase human understanding of interstellar dust. Stardust, 2007. Acrylic Micaceous Iron Oxide, Aluminum and crystal, hologram glitter Mylar 20" round canvas. Copyrighted: For more information contact Curator, NASA Art Program.

STARDUST: An Incredulous Dream to Incredible Return

NASA Technical Reports Server (NTRS)

Tsou, Peter

2006-01-01

This viewgraph presentation reviews the Stardust mission. The goal of the mission was to return to Earth a very small part of a comet for study. The success of the mission gave us a small part of a comet to use for research into questions such as the cometary origin of water and life on earth and the formation of the solar system. The slides review the challenges, the strategy, the laboratory experiments, the instrument development, the characteristics of Aerogel, the Stardust trajectory, pictures of the samples and a listing of the firsts that were accomplished during the Stardust project.

ESA confirms ROSETTA and FIRST in its long-term science programme

NASA Astrophysics Data System (ADS)

1993-11-01

ROSETTA was originally conceived as a comet-nucleus sample-return mission that should have brought back cometary material to Earth to be able to study it with the most advanced laboratory analysis techniques available. The original mission could not be implemented as it was too ambitious and too complex. Therefore in 1992 the concept had to be revised. The mission was reconsidered as being performed by ESA alone on the basis of European technology and the Ariane 5 launch capability. However, the opportunity for other agencies to join and augment the scientific return was left open, and international partners have already indicated to ESA their interest to join. The new baseline mission is a rendezvous with a comet and at least one (most probably two) flybys of asteroids. After gravity-assist manoeuvres at the Earth and Mars or Venus to acquire the necessary energy to reach the comet at its aphelion (the part of the orbit farthest from the Sun), the spacecraft will stay with the comet along its trajectory into the inner solar system through perihelion (the orbital point nearest to the Sun) to study the material that constitutes the comet, and the cometary processes that evolve with the decreasing distance from the Sun. A Surface Science Station will be deployed onto the comets' nucleus surface to provide the means for in-situ studies of the nucleus. The mission retains as far as possible the objectives of the original comet-nucleus sample-return mission and concentrates on the in-situ investigations of cometary matter and the structure of the nucleus. "As we cannot bring the cometary material into our terrestrial laboratories, we will take our laboratories to the comet" said Dr. Roger Bonnet, ESA Director of Science. Potential target comets are Schwassmann- Wachmann 3, Wirtanen, Finlay and Brooks 2 for a launch in the time interval 2002-2004. "Both teams for ROSETTA and FIRST" added Dr. Bonnet, "defined excellent missions with exciting prospects for the science to be achieved. For programmatic reasons ROSETTA will be implemented as Cornerstone 3, following Cluster and SOHO and XMM". "However", he continued, "the work on FIRST will proceed at a very high level to further develop the critical technologies, like for instance the 3 m telescope mirror, the coolers and the detectors. The major elements of the Horizon 2000 science programme are now under way and we will start the process to define the 'post-Horizon 2000' programme".

Submillimeter Measurements of Photolysis Products in Interstellar Ice Analogs: A New Experimental Technique

NASA Technical Reports Server (NTRS)

Milam, Stefanie N.; Weaver, Susanna Widicus

2012-01-01

Over 150 molecular species have been confirmed in space, primarily by their rotational spectra at millimeter/submillimeter wavelengths, which yield an unambiguous identification. Many of the known interstellar organic molecules cannot be explained by gas-phase chemistry. It is now presumed that they are produced by surface reactions of the simple ices and/or grains observed and released into the gas phase by sublimation, sputtering, etc. Additionally, the chemical complexity found in meteorites and samples returned from comets far surpasses that of the remote detections for the interstellar medium (ISM), comets, and planetary atmospheres. Laboratory simulations of interstellar/cometary ices have found, from the analysis of the remnant residue of the warmed laboratory sample, that such molecules are readily formed; however, it has yet to be determined if they are formed during the warm phase or within the ice during processing. Most analysis of the ice during processing reveals molecular changes, though the exact quantities and species formed are highly uncertain with current techniques due to overwhelming features of simple ices. Remote sensing with high resolution spectroscopy is currently the only method to detect trace species in the ISM and the primary method for comets and icy bodies in the Solar System due to limitations of sample return. We have recently designed an experiment to simulate interstellar/cometary/planetary ices and detect trace species employing the same techniques used for remote observations. Preliminary results will be presented.

Laboratory investigations

NASA Technical Reports Server (NTRS)

Russell, Ray W.

1988-01-01

Laboratory studies related to cometary grains and the nuclei of comets can be broken down into three areas which relate to understanding the spectral properties, the formation mechanisms, and the evolution of grains and nuclei: (1) Spectral studies to be used in the interpretation of cometary spectra; (2) Sample preparation experiments which may shed light on the physical nature and history of cometary grains and nuclei by exploring the effects on grain emissivities resulting from the ways in which the samples are created; and (3) Grain processing experiments which should provide insight on the interaction of cometary grains with the environment in the immediate vicinity of the cometary nucleus as the comet travels from the Oort cloud through perihelion, and perhaps even suggestions regarding the relationship between interstellar grains and cometary matter. A summary is presented with a different view of lab experiments than is found in the literature, concentrating on measurement techniques and sample preparations especially relevant to cometary dust.

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.

Cosmogenic nuclides in cometary materials: Implications for rate of mass loss and exposure history

NASA Astrophysics Data System (ADS)

Herzog, G. F.; Englert, P. A. J.; Reedy, R. C.

As planned, the Rosetta mission will return to earth with a 10-kg core and a 1-kg surface sample from a comet. The selection of a comet with low current activity will maximize the chance of obtaining material altered as little as possible. Current temperature and level of activity, however, may not reliably indicate previous values. Fortunately, from measurements of the cosmogenic nuclide contents of cometary material, one may estimate a rate of mass loss in the past and perhaps learn something about the exposure history of the comet. Perhaps the simplest way to estimate the rate of mass loss is to compare the total inventories of several long-lived cosmogenic radionuclides with the values expected on the basis of model calculations. Although model calculations have become steadily more reliable, application to bodies with the composition of comets will require some extension beyond the normal range of use. In particular, the influence of light elements on the secondary particle cascade will need study, in part through laboratory irradiations of volatile-rich materials. In the analysis of cometary data, it would be valuable to test calculations against measurements of short-lived isotopes.

Non-Random Spatial Distribution of Impacts in the Stardust Cometary Collector

NASA Technical Reports Server (NTRS)

Westphal, Andrew J.; Bastien, Ronald K.; Borg, Janet; Bridges, John; Brownlee, Donald E.; Burchell, Mark J.; Cheng, Andrew F.; Clark, Benton C.; Djouadi, Zahia; Floss, Christine

2007-01-01

In January 2004, the Stardust spacecraft flew through the coma of comet P81/Wild2 at a relative speed of 6.1 km/sec. Cometary dust was collected at in a 0.1 sq m collector consisting of aerogel tiles and aluminum foils. Two years later, the samples successfully returned to earth and were recovered. We report the discovery that impacts in the Stardust cometary collector are not distributed randomly in the collecting media, but appear to be clustered on scales smaller than approx.10 cm. We also report the discovery of at least two populations of oblique tracks. We evaluated several hypotheses that could explain the observations. No hypothesis was consistent with all the observations, but the preponderance of evidence points toward at least one impact on the central Whipple shield of the spacecraft as the origin of both clustering and low-angle oblique tracks. High-angle oblique tracks unambiguously originate from a noncometary impact on the spacecraft bus just forward of the collector. Here we summarize the observations, and review the evidence for and against three scenarios that we have considered for explaining the impact clustering found on the Stardust aerogel and foil collectors.

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.

Cometary Coma Chemical Composition (C4) Mission

NASA Technical Reports Server (NTRS)

Carle, Glenn C.; Clark, Benton C.; Knocke, Philip C.; OHara, Bonnie J.; Adams, Larry; Niemann, Hasso B.; Alexander, Merle; Veverka, Joseph; Goldstein, Raymond; Huebner, Walter;

Electron Beam Analysis of Micrometeoroids Captured in Aerogel as Stardust Analogues

NASA Technical Reports Server (NTRS)

Graham, G. A.; Sheffield-Parker, J.; Bradley, P.; Kearsley, A. T.; Dai, Z. R.; Mayo, S. C.; Teslich, N.; Snead, C.; Westphal, A. J.; Ishii, H.

2005-01-01

In January 2004, NASA s Stardust spacecraft passed through the tail of Comet 81P/Wild-2. The on-board dust flux monitor instrument indicated that numerous micro- and nano-meter sized cometary dust particles were captured by the dedicated silica aerogel capture cell. The collected cometary particles will be returned to Earth in January 2006. Current Stardust analogues are: (i) Light-gas-gun accelerated individual mineral grains and carbonaceous meteoritic material in aerogels at the Stardust encounter velocity ca.approximately 6 kilometers per second. (ii) Aerogels exposed in low-Earth orbit (LEO) containing preserved cosmic dust grains. Studies of these impacts offer insight into the potential state of the captured cometary dust by Stardust and the suitability of various analytical techniques. A number of papers have discussed the application of sophisticated synchrotron analytical techniques to analyze Stardust particles. Yet much of the understanding gained on the composition and mineralogy of interplanetary dust particles (IDPs) has come from electron microscopy studies. Here we discuss the application of scanning electron microscopy (SEM) for Stardust during the preliminary phase of post-return investigations.

Japanese Exploration to Solar System Small Bodies: Rewriting a Planetary Formation Theory with Astromaterial Connection (Invited)

NASA Astrophysics Data System (ADS)

Yano, H.

2013-12-01

Three decades ago, Japan's deep space exploration started with Sakigake and Suisei, twin flyby probes to P/Halley. Since then, the Solar System small bodies have been one of focused destinations to the Japanese solar system studies even today. Only one year after the Halley armada launch, the very first meeting was held for an asteroid sample return mission at ISAS, which after 25 years, materialized as the successful Earth return of Hayabusa , an engineering verification mission for sample return from surfaces of an NEO for the first time in the history. Launched in 2003 and returned in 2010, Hayabusa became the first to visit a sub-km, rubble-pile potentially hazardous asteroid in near Earth space. Its returned samples solved S-type asteroid - ordinary chondrite paradox by proving space weathering evidences in sub-micron scale. Between the Halley missions and Hayabusa, SOCCER concept by M-V rocket was jointly studied between ISAS and NASA; yet it was not realized due to insufficient delta-V for intact capture by decelerating flyby/encounter velocity to a cometary coma. The SOCCER later became reality as Stardust, NASA Discovery mission for cometary coma dust sample return in1999-2006. Japan has collected the second largest collection of the Antarctic meteorites and micrometeorites of the world and asteromaterial scientists are eager to collaborate with space missions. Also Japan enjoyed a long history of collaborations between professional astronomers and high-end amateur observers in the area of observational studies of asteroids, comets and meteors. Having these academic foundations, Japan has an emphasis on programmatic approach to sample returns of Solar System small bodies in future prospects. The immediate follow-on to Hayabusa is Hayabusa-2 mission to sample return with an artificial impactor from 1999 JU3, a C-type NEO in 2014-2020. Following successful demonstration of deep space solar sail technique by IKAROS in 2010-2013, the solar power sail is a deep space probe with hybrid propulsion of solar photon sail and ion engine system that will enable Japan to reach out deep interplanetary space beyond the main asteroid belt. Since 2002, Japanese scientists and engineers have been investigating the solar power sail mission to Jupiter Trojans and interdisciplinary cruising science, such as infrared observation of zodiacal light due to cosmic dust, which at the same time hit a large cross section of the solar sail membrane dust detector, concentrating inside the main asteroid belt. Now the mission design has extended from cruising and fly-by only to rendezvous and sample return options from Jupiter Trojan asteroids. Major scientific goal of Jupiter Trojan exploration is to constrain its origin between two competing hypothesis such as remnants of building blocks the Jovian system as the classic model and the second generation captured EKBOs as the planetary migration models, in which several theories are in deep discussion. Also important is to better understand mixing process of material and structure of the early Solar System just beyond snow line. The current plan involves its launch and both solar photon and IES accelerations combined with Earth and Jupiter gravity assists in 2020's, detailed rendezvous investigation of a few 10-km sized D-type asteroid among Jupiter Trojans in early 2030's and an optional sample return of its surface materials to the Earth in late 2030's.

Opportunities for ballistic missions to Halley's comet

NASA Technical Reports Server (NTRS)

Farquhar, R. W.; Wooden, W. H., II

1977-01-01

Alternative strategies for ballistic missions to Halley's comet in 1985-86 are described. A large scientific return would be acquired from a ballistic Halley intercept in spite of the high flyby speeds that are associated with this mission mode. The possibility of retargeting the cometary spacecraft to additional comets after the Halley intercept also exists. Two cometary spacecraft of identical design would be used to carry out four separate cometary encounters over a 3 year period. One spacecraft would intercept Halley's comet before its perihelion passage in December 1985 and then go on to comet Borrelly with an encounter in January 1988. The other spacecraft would be targeted for a postperihelion Halley intercept in March 1986 before proceeding toward an encounter with comet Tempel 2 in September 1988.

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.

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.

Electron Microscopy Studies of Comet Wild-2 Particulate Residue Preserved in the Stardust Metallic Foil Craters

NASA Astrophysics Data System (ADS)

Graham, G. A.; Kearsley, A. T.; Dai, Z.; Leroux, H.; Teslich, N. E.; Stroud, R.; Borg, J.; Bradley, J. P.; Horz, F. P.; Zolensky, M.

2006-12-01

The study of comets is fundamental to the understanding of early solar system processes. Much of the current knowledge of cometary compositions comes from `fly-by' missions or remote sensing studies but not, until now, from the laboratory analyses of samples. The Stardust spacecraft (NASA's 4th Discovery mission) was launched in 1999 and in January 2004 had a successful fly-by close to the nucleus of comet Wild 2. During the encounter, the collector tray assembly containing the principle particle capture technology of low- density silica aerogel was deployed. In addition, the metallic foils (1100 series Aluminum) wrapped around the collector frame also picked up material from the 6.1 km/s cometary particle collisions. Since the retrieval of the sample return capsule in January 2006, and as part of the preliminary examination, a selected number of foils have been scanned using SEM-EDX to locate cometary dust derived impact craters. Craters ranging from 100 nanometers to several hundreds of micrometers in diameter, containing both monomineralic and polymineralic projectile melts, have been identified, measured and analyzed. Focused ion beam microscopy techniques have been used to take cross-section slices of either individual craters or specific residue fragments, and thin them to electron transparency. TEM-EDX analysis of these slices shows that crystalline grains are occasionally preserved, despite the high shock pressures and temperatures that caused most of the particle to melt. Observations from the crater residues make a useful addition to studies of the composition and mineralogy of the cometary particulates preserved within the impact tracks in the silica aerogel. This work was in part performed under the auspices of the U.S. Department of Energy, National Nuclear Security Administration by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Aerodynamics of Stardust Sample Return Capsule

NASA Technical Reports Server (NTRS)

Mitcheltree, R. A.; Wilmoth, R. G.; Cheatwood, F. M.; Brauckmann, G. J.; Greene, F. A.

1997-01-01

Successful return of interstellar dust and cometary material by the Stardust Sample Return Capsule requires an accurate description of the Earth entry vehicle's aerodynamics. This description must span the hypersonic-rarefied, hypersonic-continuum, supersonic, transonic, and subsonic flow regimes. Data from numerous sources are compiled to accomplish this objective. These include Direct Simulation Monte Carlo analyses, thermochemical nonequilibrium computational fluid dynamics, transonic computational fluid dynamics, existing wind tunnel data, and new wind tunnel data. Four observations are highlighted: 1) a static instability is revealed in the free-molecular and early transitional-flow regime due to aft location of the vehicle s center-of-gravity, 2) the aerodynamics across the hypersonic regime are compared with the Newtonian flow approximation and a correlation between the accuracy of the Newtonian flow assumption and the sonic line position is noted, 3) the primary effect of shape change due to ablation is shown to be a reduction in drag, and 4) a subsonic dynamic instability is revealed which will necessitate either a change in the vehicle s center-of-gravity location or the use of a stabilizing drogue parachute.

Volatiles (H, C, N, O, noble gases) in comets as tracers of early solar system events (Invited)

NASA Astrophysics Data System (ADS)

Marty, B.

2013-12-01

Volatiles (H, C, N, O, noble gases) present the largest variations in their relative abundances and, importantly, in their isotopic ratios, among solar system elements. The original composition of the protosolar nebula has been investigated through the measurements of primitive meteorites and of in-situ (e.g. Galileo probe analysis of the Jupiter's atmosphere) and sample-return (Genesis, recovery and analysis of solar wind) missions. The protosolar gas was poor in deuterium, in 15N and in 17,18O. Variations among solar system reservoir reach several hundreds of percents for the D/H and 15N/14N ratios. These variations are possibly : (i) due to interactions between XUV photons of the proto-Sun and the-dust, (ii) result from low temperature ion-molecule reactions, or (iii) constitute an heritage on interstellar volatiles trapped in dust (e.g., organics). Likewise, noble gases are elementally and isotopically (1% per amu for xenon) fractionated with respect to the composition of the solar wind (our best proxy for the protosolar nebula composition). Cometary matter directly measured on coma, or in Stardust material, or in IDPs, seems to present among the largest heterogeneities in their stable isotope compositions but knowledge on their precise compositions of the different phases and species is partial and mosty lacking. Among the several important issues requiring a better knowledge of cometary volatiles are the origin(s) of volatile elements on Earth and Moon, on Mars and on Venus, understanding large scale circulation of matter between hot and frozen zones, and the possibility of interstellar heritage for organics. Critical measurements to be made by the next cometary missions include the value of the D/H ratio in water ice, in NH3 and organics. Nitrogen is particularly interesting as cometary HCN and CN are rich in 15N, but an isotoppe mass balance will require to measure the main host species (N2 ?). Noble gases are excellent tracers of physical processes, including the delivery of volatile elements onto planets and atmospheric escape processes, but their cometary inventory is almost not known. The only noble gas (helium and neon) measurement in cometary matter from Stardust suggests that they may be genetically linked to organic matter found in primitive meteorites rather than to the proto-solar gas. Trapping of noble gases in comets is an important issue not only for the physical conditions of cometary formation and evolution, but also for better understanding the possible contribution of cometary matter to Earth and Moon.

Cometary Dust: The Diversity of Primitive Matter

NASA Technical Reports Server (NTRS)

Wooden, D. H.; Ishiiii, H. A.; Zolensky, M. E.

2017-01-01

The connections between comet dust and primitive chondrites from asteroids has strengthened considerably over the past decade. Understanding the importance of the connections between Stardust samples and chondrites requires geochemistry lingo as well as a perspective of other cometary dust samples besides Stardust. We present the principal findings of an extensive review prepared for by us for the June 2016 "Cometary Science After Rosetta" meeting at The Royal Society, London.

The International Cometary Explorer (ICE)wallsheet teacher's guide

NASA Technical Reports Server (NTRS)

Maran, S. P. (Editor)

1985-01-01

On September 11, 1985, the veteran NASA spacecraft ISEE-3 which has been renamed the International Cometary Explorer (ICE) will make the first visit of a spacecraft to a comet. A teachers' guide to the NASA wallsheet on the ICE and its mission is presented. This circumstance of course results from the current interest in the return of Halley's Comet. This teacher's guide will be helpful in understanding scientists strong interest in sending the ICE spacecraft to investigate the tail of a much less famous object Comet Giacobin-Zinner.

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 materials that were formed across a wide swath of the early protoplanetary disk.

Systematic Examination of Stardust Bulbous Track Wall Materials

NASA Technical Reports Server (NTRS)

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

2013-01-01

Analyses of Comet Wild-2 samples returned by NASA's Stardust spacecraft have focused primarily on terminal particles (TPs) or well-preserved fine-grained materials along the track walls [1,2]. However much of the collected material was melted and mixed intimately with the aerogel by the hypervelocity impact [3,4]. We are performing systematic examinations of entire Stardust tracks to establish the mineralogy and origins of all comet Wild 2 components [7,8]. This report focuses on coordinated analyses of indigenous crystalline and amorphous/melt cometary materials along the aerogel track walls, their interaction with aerogel during collection and comparisons with their TPs.

Final Reports of the Stardust ISPE: Seven Probable Interstellar Dust Particles

NASA Technical Reports Server (NTRS)

Allen, Carlton; Sans Tresseras, Juan-Angel; Westphal, Andrew J.; Stroud, Rhonda M.; Bechtel, Hans A.; Brenker, Frank E.; Butterworth, Anna L.; Flynn, George J.; Frank, David R.; Gainsforth, Zack;

Evolution of carbonaceous chondrite parent bodies: Insights into cometary nuclei

NASA Technical Reports Server (NTRS)

Mcsween, Harry Y., Jr.

1989-01-01

It is thought that cometary samples will comprise the most primitive materials that are able to be sampled. Although parent body alteration of such samples would not necessarily detract from scientists' interest in them, the possibility exists that modification processes may have affected cometary nuclei. Inferences about the kinds of modifications that might be encountered can be drawn from data on the evolution of carbonaceous chondrite parent bodies. Observations suggest that, of all the classes of chondrites, these meteorites are most applicable to the study of comets. If the proportion of possible internal heat sources such as Al-26 in cometary materials are similar to those in chondrites, and if the time scale of comet accretion was fast enough to permit incorporation of live radionuclides, comets might have had early thermal histories somewhat like those of carbonaceous chondrite parent bodies.

Detection of cometary amines in samples returned by Stardust

NASA Astrophysics Data System (ADS)

Glavin, D. P.; Dworkin, J. P.; Sandford, S. A.

2008-02-01

The abundances of amino acids and amines, as well as their enantiomeric compositions, were measured in samples of Stardust comet-exposed aerogel and foil using liquid chromatography with UV fluorescence detection and time of flight mass spectrometry (LC-FD/ToF-MS). A suite of amino acids and amines including glycine, L-alanine, β-alanine (BALA), γ-amino-n-butyric acid (GABA), ɛ-amino-n-caproic acid (EACA), ethanolamine (MEA), methylamine (MA), and ethylamine (EA) were identified in acid-hydrolyzed, hot-water extracts of these Stardust materials above background levels. With the exception of MA and EA, all other primary amines detected in cometexposed aerogel fragments C2054,4 and C2086,1 were also present in the flight aerogel witness tile that was not exposed to the comet, indicating that most amines are terrestrial in origin. The enhanced relative abundances of MA and EA in comet-exposed aerogel compared to controls, coupled with MA to EA ratios (C2054,4: 1.0 ± 0.2; C2086,1: 1.8 ± 0.2) that are distinct from preflight aerogels (E243-13C and E243-13F: 7 ± 3), suggest that these volatile amines were captured from comet Wild 2. MA and EA were present predominantly in an acid-hydrolyzable bound form in the aerogel, rather than as free primary amines, which is consistent with laboratory analyses of cometary ice analog materials. It is possible that Wild 2 MA and EA were formed on energetically processed icy grains containing ammonia and approximately equal abundances of methane and ethane. The presence of cometary amines in Stardust material supports the hypothesis that comets were an important source of prebiotic organic carbon and nitrogen on the early Earth.

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.

The measurement of trace elements in interplanetary dust and cometary particles by ultra-high sensitivity INAA

NASA Technical Reports Server (NTRS)

Zolensky, M. E.; Lindstrom, David J.; Lindstrom, Richard M.; Lindstrom, M. M.

1989-01-01

Today the major elemental composition of interplanetary dust particles (IDPs) is routinely determined in many laboratories. These and mineralogical studies have revealed the presence of at least two major types of IDPs, chondritic and refractory. Preliminary results of a successful attempt to determine abundances of a large suite of trace elements from both chondritic and refractory IDPs are reported. The analytical procedure can be used in the grain-by-grain analysis of returned cometary samples. Chondritic and refractory IDPs are characterized by standard scanning electron microscopy and energy dispersive x ray spectroscopy (SEM-EDX) techniques. With this system, detection limits for many elements are well below picogram levels, and some approach femtogram levels. This technique is non-destructive, although some sample handling is required, so particles can be analyzed by other techniques after instrument neutron activation analysis (INAA) is completed. Data is presently being reduced from the analyses of 7 IDPs. These are U2015E10, U2015F1, W7029-A2, W7029-A3, W7013A8, LACl (all chondritic) and 705 (refractory). So far, 17 different major and trace elements were detected and measured in these particles, including rare earths and some very volatile elements (Br and Zn).

Opportunities for ballistic missions to Halley's comet

NASA Technical Reports Server (NTRS)

Farquhar, R. W.; Wooden, W. H., II

1977-01-01

Alternative strategies for ballistic missions to Halley's comet in 1985-86 are described. It is shown that a large science return would be acquired from a ballistic Halley intercept in spite of the high flyby speeds of almost 60 km/sec that are associated with this mission mode. The possibility of retargeting the cometary spacecraft to additional comets after the Halley intercept also exists. In one scenario two cometary spacecraft of identical design would be used to carry out four separate cometary encounters over a three-year period. One spacecraft would intercept Halley before its perihelion passage in December 1985 and then go on to comet Borrelly witn an encounter in January 1988. The other spacecraft would be targeted for a post-perihelion Halley intercept in March 1986 before proceeding towards an encounter with comet Tempel-2 in September 1988. The flyby speeds for the Borrelly and Tempel-2 intercepts are 21 and 13 km/sec, respectively.

The nature of cometary materials

NASA Technical Reports Server (NTRS)

Stephens, James

1989-01-01

Because cometary surfaces are likely to be far colder and of a different composition than planetary surfaces, there are some new considerations that must be examined in regards to placing instrumented packages or sample return devices on their surfaces. The qualitative analysis of the problem of attaching hardware to a comet and not being ejected back into space can be divided into two parts. The first problem is to pierce the mantle and obtain access to the icy core. Drilling through the mantle requires that the drilling forces be reacted. Reacting such forces probably requires attachment to the icy core below. Therefore, some kinetic impact piercing device is likely to be required as the first act of attachment. The second problem for a piercing device to overcome is the force produced by the impact kinetic energy that tries to eject the piercing device back into space. The mantle and icy core can absorb some of the impact kinetic energy in the form of fracture formation and friction energy. The energy that is not absorbed in these two ways is stored by the core as elastic deformation of the mantle and icy core. It is concluded that because the cometary materials are almost certainly brittle and the icy core is likely to be self lubricating, the elastic rebound and gas pressure expulsion forces must be counteracted by forces greater than those that may be provided by a piercing device or its capture devices (barbs).

Formation and processing of organics in the early solar system.

PubMed

Kerridge, J F

1999-01-01

Until pristine samples can be returned from cometary nuclei, primitive meteorites represent our best source of information about organic chemistry in the early solar system. However, this material has been affected by secondary processing on asteroidal parent bodies which probably did not affect the material now present in cometary nuclei. Production of meteoritic organic matter apparently involved the following sequence of events: Molecule formation by a variety of reaction pathways in dense interstellar clouds; Condensation of those molecules onto refractory interstellar grains; Irradiation of organic-rich interstellar-grain mantles producing a range of molecular fragments and free radicals; Inclusion of those interstellar grains into the protosolar nebula with probable heating of at least some grain mantles during passage through the shock wave bounding the solar accretion disc; Agglomeration of residual interstellar grains and locally produced nebular condensates into asteroid-sized planetesimals; Heating of planetesimals by decay of extinct radionuclides; Melting of ice to produce liquid water within asteroidal bodies; Reaction of interstellar molecules, fragments and radicals with each other and with the aqueous environment, possibly catalysed by mineral grains; Loss of water and other volatiles to space yielding a partially hydrated lithology containing a complex suite of organic molecules; Heating of some of this organic matter to generate a kerogen-like complex; Mixing of heated and unheated material to yield the meteoritic material now observed. Properties of meteoritic organic matter believed to be consistent with this scenario include: Systematic decrease of abundance with increasing C number in homologous series of characterisable molecules; Complete structural diversity within homologous series; Predominance of branched-chain isomers; Considerable isotopic variability among characterisable molecules and within kerogen-like material; Substantial deuterium enrichment in all organic fractions; Some fractions significantly enriched in nitrogen-15; Modest excesses of L-enantiomers in some racemisation-resistant molecules but no general enantiomeric preference. Despite much speculation about the possible role of Fischer-Tropsch catalytic hydrogenation of CO in production of organic molecules in the solar nebula, no convincing evidence for such material has been found in meteorites. A similarity between some meteoritic organics and those produced by Miller-Urey discharge synthesis may reflect involvement of common intermediates rather than the operation of electric discharges in the early solar system. Meteoritic organic matter constitutes a useful, but not exact, guide to what we shall find with in situ analytical and sample-return missions to cometary nuclei.

Laboratory analyses of micron-sized solid grains: Experimental techniques and recent results

NASA Technical Reports Server (NTRS)

Colangeli, L.; Bussoletti, E.; Blanco, A.; Borghesi, A.; Fonti, S.; Orofino, V.; Schwehm, G.

1989-01-01

Morphological and spectrophotometric investigations have been extensively applied in the past years to various kinds of micron and/or submicron-sized grains formed by materials which are candidate to be present in space. The samples are produced in the laboratory and then characterized in their physio-chemical properties. Some of the most recent results obtained on various kinds of carbonaceous materials are reported. Main attention is devoted to spectroscopic results in the VUV and IR wavelength ranges, where many of the analyzed samples show typical fingerprints which can be identified also in astrophysical and cometary materials. The laboratory methodologies used so far are also critically discussed in order to point out capabilities and present limitations, in the view of possible application to returned comet samples. Suggestions are given to develop new techniques which should overcome some of the problems faced in the manipulation and analysis of micron solid samples.

Lunar and Planetary Science XXXV: Asteroids, Meteors, Comets

NASA Technical Reports Server (NTRS)

2004-01-01

Reports included:Long Term Stability of Mars Trojans; Horseshoe Asteroids and Quasi-satellites in Earth-like Orbits; Effect of Roughness on Visible Reflectance Spectra of Planetary Surface; SUBARU Spectroscopy of Asteroid (832) Karin; Determining Time Scale of Space Weathering; Change of Asteroid Reflectance Spectra by Space Weathering: Pulse Laser Irradiation on Meteorite Samples; Reflectance Spectra of CM2 Chondrite Mighei Irradiated with Pulsed Laser and Implications for Low-Albedo Asteroids and Martian Moons; Meteorite Porosities and Densities: A Review of Trends in the Data; Small Craters in the Inner Solar System: Primaries or Secondaries or Both?; Generation of an Ordinary-Chondrite Regolith by Repetitive Impact; Asteroid Modal Mineralogy Using Hapke Mixing Models: Validation with HED Meteorites; Particle Size Effect in X-Ray Fluorescence at a Large Phase Angle: Importance on Elemental Analysis of Asteroid Eros (433); An Investigation into Solar Wind Depletion of Sulfur in Troilite; Photometric Behaviour Dependent on Solar Phase Angle and Physical Characteristics of Binary Near-Earth-Asteroid (65803) 1996 GT; Spectroscopic Observations of Asteroid 4 Vesta from 1.9 to 3.5 micron: Evidence of Hydrated and/or Hydroxylated Minerals; Multi-Wavelength Observations of Asteroid 2100 Ra-Shalom: Visible, Infrared, and Thermal Spectroscopy Results; New Peculiarities of Cometary Outburst Activity; Preliminary Shape Modeling for the Asteroid (25143) Itokawa, AMICA of Hayabusa Mission; Scientific Capability of MINERVA Rover in Hayabusa Asteroid Mission; Characteristics and Current Status of Near Infrared Spectrometer for Hayabusa Mission; Sampling Strategy and Curation Plan of Hayabusa Asteroid Sample Return Mission; Visible/Near-Infrared Spectral Properties of MUSES C Target Asteroid 25143 Itokawa; Calibration of the NEAR XRS Solar Monitor; Modeling Mosaic Degradation of X-Ray Measurements of 433 Eros by NEAR-Shoemaker; Scattered Light Remediation and Recalibration of near Sheomaker s NIS Global Dataaset at 433 Eros; Evaluation of Preparation and Measuring Techniques for Interplanetary Dust Particles for the MIDAS Experiment on Rosetta; Chiron: a Proposed Remote Sensing Prompt Gamma Ray Activation Analysis Instrument for a Nuclear Powered Prometheus Mission;From Present Surveying to Future Prospecting of the Asteroid Belt; Asteroid Physical Properties Probe Microgravity Testing of a Surface Sampling System for Sample Return from Small Solar System Bodies;and Penetrator Coring Apparatus for Cometary Surfaces.

Description and Analysis of Core Samples: The Lunar Experience

NASA Technical Reports Server (NTRS)

McKay, David S.; Allton, Judith H.

1997-01-01

Although no samples yet have been returned from a comet, extensive experience from sampling another solar system body, the Moon, does exist. While, in overall structure, composition, and physical properties the Moon bears little resemblance to what is expected for a comet, sampling the Moon has provided some basic lessons in how to do things which may be equally applicable to cometary samples. In particular, an extensive series of core samples has been taken on the Moon, and coring is the best way to sample a comet in three dimensions. Data from cores taken at 24 Apollo collection stations and 3 Luna sites have been used to provide insight into the evolution of the lunar regolith. It is now well understood that this regolith is very complex and reflects gardening (stirring of grains by micrometeorites), erosion (from impacts and solar wind sputtering), maturation (exposure on the bare lunar surface to solar winds ions and micrometeorite impacts) and comminution of coarse grains into finer grains, blanket deposition of coarse-grained layers, and other processes. All of these processes have been documented in cores. While a cometary regolith should not be expected to parallel in detail the lunar regolith, it is possible that the upper part of a cometary regolith may include textural, mineralogical, and chemical features which reflect the original accretion of the comet, including a form of gardening. Differences in relative velocities and gravitational attraction no doubt made this accretionary gardening qualitatively much different than the lunar version. Furthermore, at least some comets, depending on their orbits, have been subjected to impacts of the uppermost surface by small projectiles at some time in their history. Consequently, a more recent post-accretional gardening may have occurred. Finally, for comets which approach the sun, large scale erosion may have occurred driven by gas loss. The uppermost material of these comets may reflect some of the features of this erosional process, such as crust formation, and variations with depth might be expected. Overall, the upper few meters of a comet may be as complex in their own way as the upper few meters of the lunar regolith have proven to be, and by analogy, detailed studies of core samples containing this depth information will be needed to understand these processes and the details of the accretional history and the subsequent alteration history of comets.

From C/Mrkos to P/Halley: 30 years of cometary spectroscopy

NASA Technical Reports Server (NTRS)

Arpigny, C.; Dossin, F.; Woszczyk, A.; Donn, B.; Rahe, J.; Wyckoff, Susan

1991-01-01

An Atlas of Cometary Spectra was compiled, as a sequel to the well-known Atlas published by Swings and Haser in 1956. The new atlas comprises some 400 reproductions of cometary spectra secured in the world's largest observatories during the three decades or so from the passage of comet Mrkos 1957 V, for which the very first high-dispersion spectrum was obtained, to the return of Halley's comet. The illustrations refer to 40 different comet apparitions; they are grouped into a set of 186 loose 11 x 14 in. plates, while the texts, comments, and relevant data are given in a separate booklet. The main purpose of this atlas is to show in detail the tremendous progress which was achieved in cometary spectroscopy during the period covered, essentially thanks to the use of high-resolution coude spectrographs and large telescopes, the considerable extension of the observed wavelength range, and the advent of electronic detectors. It is divided into two parts. Part 1, which contains about two-thirds of the selected material, presents photographic spectra, while electronically recorded spectra covering the vacuum ultraviolet, through the optical, infrared, and radio regions appear in Part 2.

Comparison of the Organic Composition of Cometary Samples with Residues Formed from the UV Irradiation of Astrophysical Ice Analogs

NASA Technical Reports Server (NTRS)

Milam, S. N.; Nuevo, M.; Sandford, S. A.; Cody, G. D.; Kilcoyne, A. L. D.; Stroud, R. M.; DeGregorio, B. T.

2010-01-01

The NASA Stardust mission successfully collected material from Comet 81P/Wild 2 [1], including authentic cometary grains [2]. X-ray absorption near-edge structure (XANES) spectroscopy analysis of these samples indicates the presence of oxygen-rich and nitrogen-rich organic materials, which contain a broad variety of functional groups (carbonyls, C=C bonds, aliphatic chains, amines, arnides, etc.) [3]. One component of these organics appears to contain very little aromatic carbon and bears some similarity to the organic residues produced by the irradiation of ices of interstellar/cometary composition, Stardust samples were also recently shown to contain glycine, the smallest biological amino acid [4]. Organic residues produced froth the UV irradiation of astrophysical ice analogs are already known to contain a large suite of organic molecules including amino acids [5-7], amphiphilic compounds (fatty acids) [8], and other complex species. This work presents a comparison between XANES spectra measured from organic residues formed in the laboratory with similar data of cometary samples collected by the Stardust mission

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.

Electron beam analysis of particulate cometary material

NASA Technical Reports Server (NTRS)

Bradley, John

1989-01-01

Electron microscopy will be useful for characterization of inorganic dust grains in returned comet nucleus samples. The choice of instrument(s) will depend primarily on the nature of the samples, but ultimately a variety of electron-beam methods could be employed. Scanning and analytical (transmission) electron microscopy are the logical choise for morphological, mineralogical, and bulk chemical analyses of dust grains removed from ices. It may also be possible to examine unmelted ice/dust mixtures using an environmental scanning electron microscope equipped with a cryo-transfer unit and a cold stage. Electron microscopic observations of comet nuclei might include: (1) porosities of dust grains; (2) morphologies and microstructures of individual mineral grains; (3) relative abundances of olivine, pyroxene, and glass; and (4) the presence of phases that might have resulted from aqueous alteration (layer silicates, carbonates, sulfates).

Characterization of Three Carbon- and Nitrogen-Rich Particles from Comet 81P/WILD

NASA Technical Reports Server (NTRS)

Gallien, J.-P.; Khodja, H.; Herzog, G. F.; Taylor, S.; Koepsell, E.; Daghlian, C. P.; Flynn, G. J.; Sitnitsky, I.; Lanzirotti, A.; Sutton, S. R.;

Coordinated Microanalyses of Seven Particles of Probable Interstellar Origin from the Stardust Mission

NASA Technical Reports Server (NTRS)

Westphal, Andrew J.; Stroud, Rhonda M.; Bechtel, Hans A.; Brenker, Frank E.; Butterworth, Anna L.; Flynn, George J.; Frank, David R.; Gainsforth, Zack; Hillier, Jon K.; Postberg, Frank;

Research and Development on In-Situ Measurement Sensors for Micro-Meteoroid and Small Space Debris at JAXA

NASA Astrophysics Data System (ADS)

Kitazawa, Y.; Matsumoto, H.; Okudaira, O.; Kimoto, Y.; Hanada, T.; Faure, P.; Akahoshi, Y.; Hattori, M.; Karaki, A.; Sakurai, A.; Funakoshi, K.; Yasaka, T.

2013-08-01

The Japan Aerospace Exploration Agency (JAXA) has been conducting R&D into in-situ sensors for measuring micro-meteoroid and small-sized debris (MMSD) since the 1980s. Research into active sensors started with the meteoroid observation experiment conducted using the HITEN (MUSES-A) satellite that ISAS/JAXA launched in 1990. The main purpose behind the start of passive collector research was SOCCER, a late-80s Japan-US mission that was designed to capture cometary dust and then return to the Earth. Although this mission was cancelled, the research outcomes were employed in a JAXA mission for the return of MMSD samples using calibrated aerogel and involving the space shuttle and the International Space Station. Many other important activities have been undertaken as well, and the knowledge they have generated has contributed to JAXA's development of a new type of active dust sensor. This paper reports on the R&D conducted at JAXA into in-situ MMSD measurement sensors.

Photometric study of cometary analogs in the LOSSy laboratory at the University of Bern

NASA Astrophysics Data System (ADS)

Pommerol, A.; Thomas, N.; Jost, B.; Poch, O.

2014-07-01

We have set up the LOSSy laboratory (Laboratory for Outflow Studies of Sublimating Materials) to study the spectro-photometric properties of various analogs of planetary-object surfaces, with a special emphasis on icy samples and their evolution under simulated space conditions. This laboratory is currently equipped with two facilities: the PHIRE-2 radio-goniometer, designed to measure the bidirectional visible reflectance of samples under a wide range of geometries and the SCITEAS simulation chamber, designed to follow the evolution of icy samples subliming under low temperature and low pressure conditions by means of VIS-NIR hyperspectral imaging. We will report on the characterization of cometary analogs using both facilities. We produce these analogs by mixing in various proportions fine-grained ice, mineral and organic matter. Various preparation protocols have been defined to produce different textures of sample. Using the PHIRE-2 radio-goniometer, we are building a catalog of bidirectional reflectance data for various cometary analogs, varying by steps the different parameters susceptible to affect the reflectance phase function. In particular, we have recently upgraded the instrument to be able to characterize in detail the opposition effect by allowing measurements of the reflectance at very low phase angle. This laboratory dataset is intended to be used for the analysis of the data acquired by the OSIRIS imager onboard Rosetta. Using the SCITEAS simulation chamber, we have followed for 30 hours the evolution of a cometary analog placed under secondary vacuum (<10^{-6} mbar) and maintained at low temperature (170-200 K) for more than 30 hours. We analyzed the temporal evolution of the morphology and the photometry of the surface of the sample to identify which processes affect the surfaces of cometary nuclei during sublimation and how they affect their visible and near-infrared surface properties.

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.

Ultrasonic Micro-Blades for the Rapid Extraction of Impact Tracks from Aerogel

NASA Technical Reports Server (NTRS)

Ishii, H. A.; Graham, G. A.; Kearsley, A. T.; Grant, P. G.; Snead, C. J.; Bradley, J. P.

2005-01-01

The science return of NASA's Stardust Mission with its valuable cargo of cometary debris hinges on the ability to efficiently extract particles from silica aerogel collectors. The current method for extracting cosmic dust impact tracks is a mature procedure involving sequential perforation of the aerogel with glass needles on computer controlled micromanipulators. This method is highly successful at removing well-defined aerogel fragments of reasonable optical clarity while causing minimal damage to the surrounding aerogel collector tile. Such a system will be adopted by the JSC Astromaterials Curation Facility in anticipation of Stardust s arrival in early 2006. In addition to Stardust, aerogel is a possible collector for future sample return missions and is used for capture of hypervelocity ejecta in high power laser experiments of interest to LLNL. Researchers will be eager to obtain Stardust samples for study as quickly as possible, and rapid extraction tools requiring little construction, training, or investment would be an attractive asset. To this end, we have experimented with micro-blades for the Stardust impact track extraction process. Our ultimate goal is a rapid extraction system in a clean electron beam environment, such as an SEM or dual-beam FIB, for in situ sample preparation, mounting and analysis.

Stardust Hypervelocity Entry Observing Campaign Support

NASA Technical Reports Server (NTRS)

Kontinos, Dean A.; Jordan, David E.; Jenniskens, Peter

2009-01-01

In the early morning of January 15, 2006, the Stardust Sample Return Capsule (SRC) successfully delivered its precious cargo of cometary particles to the awaiting recovery team at the Utah Test and Training Range (UTTR). As the SRC entered at 12.8 km/s, the fastest manmade object to traverse the atmosphere, a team of researchers imaged the event aboard the NASA DC-8 airborne observatory. At SRC entry, the airplane was at an altitude of 11.9 km positioned within 6.4 km of the prescribed, preferred target view location. The incoming SRC was first acquired approximately 18 seconds (s) after atmospheric interface and tracked for approximately 60 s, an observation period that is roughly centered in time around predicted peak heating.

Chondrulelike objects in short-period comet 81P/Wild 2.

PubMed

Nakamura, Tomoki; Noguchi, Takaaki; Tsuchiyama, Akira; Ushikubo, Takayuki; Kita, Noriko T; Valley, John W; Zolensky, Michael E; Kakazu, Yuki; Sakamoto, Kanako; Mashio, Etsuko; Uesugi, Kentaro; Nakano, Tsukasa

2008-09-19

The Stardust spacecraft returned cometary samples that contain crystalline material, but the origin of the material is not yet well understood. We found four crystalline particles from comet 81P/Wild 2 that were apparently formed by flash-melting at a high temperature and are texturally, mineralogically, and compositionally similar to chondrules. Chondrules are submillimeter particles that dominate chondrites and are believed to have formed in the inner solar nebula. The comet particles show oxygen isotope compositions similar to chondrules in carbonaceous chondrites that compose the middle-to-outer asteroid belt. The presence of the chondrulelike objects in the comet suggests that chondrules have been transported out to the cold outer solar nebula and spread widely over the early solar system.

International Space Station (ISS) External Television (TV) Camera Shutdown Investigation

NASA Technical Reports Server (NTRS)

Kichak, Robert; Young, Eric; Pandipati, Chetty; Cooke, Robert

2009-01-01

In the early morning of January 15, 2006, the Stardust Sample Return Capsule (SRC) successfully delivered its precious cargo of cometary particles to the awaiting recovery team at the Utah Test and Training Range (UTTR). As the SRC entered at 12.8 km/s, the fastest manmade object to traverse the atmosphere, a team of researchers imaged the event aboard the NASA DC-8 airborne observatory. At SRC entry, the airplane was at an altitude of 11.9 km positioned within 6.4 km of the prescribed, preferred target view location. The incoming SRC was first acquired approximately 18 seconds (s) after atmospheric interface and tracked for approximately 60 s, an observation period that is roughly centered in time around predicted peak heating.

Locating Stardust-like Particles in Aerogel Using X-Ray Techniques

NASA Technical Reports Server (NTRS)

Jurewicz, A. J. G.; Jones, S. M.; Tsapin, A.; Mih, D. T.; Connolly, H. C., Jr.; Graham, G. A.

2003-01-01

Silica aerogel is the material that the spacecraft STARDUST is using to collect interstellar and cometary silicates. Anticipating the return of the samples to earth in January of 2006, MANY individual investigators and, especially, the investigators in NASA's SRLIDAP program are studying means of both in situ analysis of particles, as well as particle extraction. To help individual PI's with extraction of particles from aerogel in their own laboratories, we are exploring the use of standard laboratory x-ray equipment and commercial techniques for precisely locating specific particles in aerogel. We approached the evaluation of commercial x-ray techniques as follows. First, we determined the most appropriate detector for use with aerogel and particulates. Then, we compared and contrasted techniques useful for university laboratories.

Comet Halley - The orbital motion

NASA Technical Reports Server (NTRS)

Yeomans, D. K.

1977-01-01

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

Origin and Evolution of Organic Matter Preserved in Stardust Cometary Aerogel Tracks

NASA Technical Reports Server (NTRS)

McKay, D.S.; Clemett, S.J.; Nakamura-Messenger, K.

2009-01-01

The STARDUST spacecraft captured dust samples from Comet 81P/Wild 2 at a relative velocity of 6.1 km/s in a low density silica aerogel and returned them to the Earth. One of the main of the scientific goals established for the mission was to determine whether comets contained complex organic materials and, contingently, the nature and abundance of this material. [1] Although contamination concerns due to carbonaceous impurities intrinsic to the flight aerogel remain, it is generally accepted that at least a fraction of the captured dust particles contain an indigenous organic component. [2] However, understanding the nature and abundance of this material is complicated by nature of the collection process. The rapid dissipation of particle s kinetic energy during its impact and deceleration cause both the particle and surrounding aerogel to experience an intense thermal pulse of upwards of 2000K for a period up to several hundred nanoseconds [3]. During this period thermal alteration and or destruction of organic species present in the impacting particle are likely to occur. We have used the technique of ultrafast two-step laser mass spectrometry (ultra L2MS) [4] to investigate how the nature and distribution of aromatic and conjugated organic species varies between and within aerogel cometary tracks and their associated terminal particles.

Comet Halley Returns. A Teacher's Guide, 1985-1986.

ERIC Educational Resources Information Center

Chapman, Robert D.; Bondurant, R. Lynn, Jr.

This booklet was designed as an aid for elementary and secondary school teachers. It is divided into two distinct parts. Part I is a brief tutorial which introduces some of the most important concepts about comets. Areas addressed include: the historical importance of Comet Halley; how comets are found and names; cometary orbits; what Comet Halley…

Constraints on the formation age of cometary material from the NASA Stardust mission.

PubMed

Matzel, J E P; Ishii, H A; Joswiak, D; Hutcheon, I D; Bradley, J P; Brownlee, D; Weber, P K; Teslich, N; Matrajt, G; McKeegan, K D; MacPherson, G J

2010-04-23

We measured the 26Al-26Mg isotope systematics of a approximately 5-micrometer refractory particle, Coki, returned from comet 81P/Wild 2 in order to relate the time scales of formation of cometary inclusions to their meteoritic counterparts. The data show no evidence of radiogenic 26Mg and define an upper limit to the abundance of 26Al at the time of particle formation: 26Al/27Al < 1 x 10(-5). The absence of 26Al indicates that Coki formed >1.7 million years after the oldest solids in the solar system, calcium- and aluminum-rich inclusions (CAIs). The data suggest that high-temperature inner solar system material formed, was subsequently transferred to the Kuiper Belt, and was incorporated into comets several million years after CAI formation.

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.

Nebular and Interstellar Materials in a Giant Cluster IDP of Probable Cometary Origin

NASA Technical Reports Server (NTRS)

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

2015-01-01

Comets contain a complex mixture of materials with presolar and Solar System origins. Chondritic porous interplanetary dust particles (CP-IDPs) are associated with comets by their fragile nature, unequilibrated anhydrous mineralogy and high abundances of circumstellar grains and isotopically anomalous organic materials. Comet 81P/Wild 2 samples returned by the Stardust spacecraft contain presolar materials as well as refractory 16O-rich Ca-Al-rich inclusion- (CAI), chondrule-, and AOA-like materials. We are conducting coordinated chemical, mineralogical, and isotopic studies of a giant cluster CP-IDP (U2-20-GCA) to determine the proportions of inner Solar System and interstellar materials. We previously found that this IDP contains abundant presolar silicates (approx. 1,800 ppm) and 15N-rich hotspots [6].

Interstellar and Solar Nebula Materials in Cometary Dust

NASA Technical Reports Server (NTRS)

Messenger, Scott; Nakamura-Messenger, Keiko; Keller, Lindsay; Nguyen, Ann; Clemett, Simon

2017-01-01

Laboratory studies of cometary dust collected in the stratosphere and returned from comet 81P/Wild 2 by the Stardust spacecraft have revealed ancient interstellar grains and molecular cloud organic matter that record a range of astrophysical processes and the first steps of planetary formation. Presolar materials are rarer meteorites owing to high temperature processing in the solar nebula and hydrothermal alteration on their asteroidal parent bodies. The greater preservation of presolar materials in comets is attributed to their low accretion temperatures and limited planetary processing. Yet, comets also contain a large complement of high temperature materials from the inner Solar System. Owing to the limited and biased sampling of comets to date, the proportions of interstellar and Solar System materials within them remains highly uncertain. Interstellar materials are identified by coordinated isotopic, mineralogical, and chemical measurements at the scale of individual grains. Chondritic porous interplanetary dust particles (CP IDPs) that likely derive from comets are made up of 0.1 - 10 micron-sized silicates, Fe-Ni-sulfides, oxides, and other phases bound by organic material. As much as 1% of the silicates are interstellar grains that have exotic isotopic compositions imparted by nucleosynthetic processes in their parent stars. Crystalline silicates in CP IDPs dominantly have normal isotopic compositions and probably formed in the Solar System. 81P samples include isotopically normal refractory minerals that resemble Ca-Al rich inclusions and chondrules common in meteorites. The origins of sub-micron amorphous silicates in IDPs are not certain, but at least a few % of them are interstellar grains. The remainder have isotopic compositions consistent with Solar System origins and elemental compositions that are inconsistent with interstellar grain properties, thus favoring formation in the solar nebula [4]. The organic component in comets and primitive meteorites has large enrichments in D/H and N-15/N-14 relative to terrestrial materials. These isotopic signatures are probably due to low temperature chemical processes in cold molecular clouds or the outermost reaches of the protoplanetary disk. The greatest isotopic anomalies are found in sub-micron organic nanoglobules that show chemical signatures of interstellar chemistry. The observation that cometary dust is mostly composed of isotopically normal minerals within isotopically anomalous organic matter is difficult to reconcile with the formation models of each component. The mineral component likely formed in high temperature processes in the inner Solar System, while the organic fraction shows isotopic and chemical signatures of formation near 10 K. Studying more primitive remnants of the Solar System starting materials would help in resolving this paradox. Comets formed across a vast expanse of the outer disk under differing thermal and collisional regimes, and some are likely to be better preserved than others. Finding truly pristine aggregates of presolar materials may require return of a pristine sample of comet nucleus material.

Dust in Cometary Comae: Present Understanding of the Structure and Composition of Dust Particles

NASA Technical Reports Server (NTRS)

Levasseur-Regourd, A. C.; Zolensky, M.; Lasue, J.

2007-01-01

In situ probing of a very few cometary comae has shown that dust particles present a low albedo and a low density, and that they consist of both rocky material and refractory organics. Remote observations of solar light scattered by cometary dust provide information on the properties of dust particles in the coma of a larger set of comets. The observations of the linear polarization in the coma indicate that the dust particles are irregular, with a size greater (on the average) than about one micron. Besides, they suggest, through numerical and experimental simulations, that both compact grains and fluffy aggregates (with a power law of the size distribution in the -2.6 to -3 range), and both rather transparent silicates and absorbing organics are present in the coma. Recent analysis of the cometary dust samples collected by the Stardust mission provide a unique ground truth and confirm, for comet 81P/Wild 2, the results from remote sensing observations. Future space missions to comets should, in the next decade, lead to a more precise characterization of the structure and composition of cometary dust particles.

MIRO Computational Model

NASA Technical Reports Server (NTRS)

Broderick, Daniel

2010-01-01

A computational model calculates the excitation of water rotational levels and emission-line spectra in a cometary coma with applications for the Micro-wave Instrument for Rosetta Orbiter (MIRO). MIRO is a millimeter-submillimeter spectrometer that will be used to study the nature of cometary nuclei, the physical processes of outgassing, and the formation of the head region of a comet (coma). The computational model is a means to interpret the data measured by MIRO. The model is based on the accelerated Monte Carlo method, which performs a random angular, spatial, and frequency sampling of the radiation field to calculate the local average intensity of the field. With the model, the water rotational level populations in the cometary coma and the line profiles for the emission from the water molecules as a function of cometary parameters (such as outgassing rate, gas temperature, and gas and electron density) and observation parameters (such as distance to the comet and beam width) are calculated.

The Inner Coma Physical Environments of Ecliptic Comets 45P/Honda-Mrkos-Pajdusakova, 2P/Encke, and 41P/Tuttle-Giacobini-Kresak Revealed Through Long-Slit Spectroscopy at NASA IRTF

NASA Astrophysics Data System (ADS)

Bonev, Boncho P.; DiSanti, Michael A.; Roth, Nathan; Dello Russo, Neil; Vervack, Ronald J.; Gibb, Erika L.; Villanueva, Geronimo Luis; Combi, Michael R.; Fougere, Nicolas; Kawakita, Hideyo; McKay, Adam J.; Saki, Mohammad; Cordiner, Martin; Protopapa, Silvia; de Val-Borro, Miguel

2017-10-01

Understanding the physical processes in the inner regions of cometary atmospheres is vital for interpretation of molecular cometary emission at all wavelengths. Furthermore, because ecliptic comets are continuously evaluated as space mission targets, understanding their coma environments is a central theme in both enhancing the science return of past missions (EPOXI, Rosetta) and in selecting future mission targets. With this motivation, we report long-slit high-resolution observations of H2O emission in the comae of three ecliptic comets observed in early 2017: 45P/Honda-Mrkos-Pajdusakova, 2P/Encke, and 41P/Tuttle-Giacobini-Kresak. Using the new crossed-dispersed spectrograph iSHELL at NASA IRTF, we detected a suite of water rovibrational emission lines from these comets and measured the spatial distributions of H2O rotational temperatures and molecular column densities. Both parameters are highly diagnostic of the physical environment in cometary comae, the competition between cooling and heating processes in these environments, and the presence (or lack thereof) of extended coma sources of gas-phase H2O. Comets 2P and 45P allowed a rare glimpse into coma physics at small (< 0.6 AU) heliocentric distances, where photochemical heating is particularly important, but direct H2O observations have been sparse. Our results add to the small sample of spatial-spectral measurements of this type. They will be discussed in the context of coma physics models along with prospects for investigations during the upcoming favorable apparitions of ecliptic comets 21P/Giacobini-Zinner and 46P/Wirtanen. We gratefully acknowledge support from the NASA Solar System Workings, Planetary Atmospheres, Earth and Space Science Fellowship, Solar System Observations, Emerging Worlds, and Astrobiology Programs, and NSF Solar and Planetary Research Grants. We are grateful to the entire IRTF staff for their help with these challenging observations, most of which were done during daytime.

Ground truth of (sub-)micrometre cometary dust - Results of MIDAS onboard Rosetta

NASA Astrophysics Data System (ADS)

Mannel, Thurid; Bentley, Mark; Schmied, Roland; Torkar, Klaus; Jeszenszky, Harald; Romsted, Jens; Levasseur-Regourd, A.; Weber, Iris; Jessberger, Elmar K.; Ehrenfreund, Pascale; Köberl, Christian; Havnes, Ove

2016-10-01

The investigation of comet 67P by Rosetta has allowed the comprehensive characterisation of pristine cometary dust particles ejected from the nucleus. Flying alongside the comet at distances as small as a few kilometres, and with a relative velocity of only centimetres per second, the Rosetta payload sampled almost unaltered dust. A key instrument to study this dust was MIDAS (the Micro-Imaging Dust Analysis System), a dedicated atomic force microscope that scanned the surfaces of hundreds of (sub-)micrometre sized particles in 3D with resolutions down to nanometres. This offers the unique opportunity to explore the morphology of smallest cometary dust and expand our current knowledge about cometary material.Here we give an overview of dust collected and analysed by MIDAS and highlight its most important features. These include the ubiquitous agglomerate nature of the dust, which is found at all size scales from the largest (>10 µm) through to the smallest (<1 µm) dust particles. The sub-units show characteristic sizes and shapes that are compared with model predictions for interstellar dust.Our findings constrain key parameters of the evolution of the early Solar System. We will discuss which dust growth model is favoured by the observed morphology and how the results restrict cometary formation. Finally, dust particles detected by MIDAS resemble primitive interplanetary dust which is a strong argument for a common cometary origin.

COSIMA-Rosetta calibration for in situ characterization of 67P/Churyumov-Gerasimenko cometary inorganic compounds

NASA Astrophysics Data System (ADS)

Krüger, Harald; Stephan, Thomas; Engrand, Cécile; Briois, Christelle; Siljeström, Sandra; Merouane, Sihane; Baklouti, Donia; Fischer, Henning; Fray, Nicolas; Hornung, Klaus; Lehto, Harry; Orthous-Daunay, Francois-Régis; Rynö, Jouni; Schulz, Rita; Silén, Johan; Thirkell, Laurent; Trieloff, Mario; Hilchenbach, Martin

2015-11-01

COmetary Secondary Ion Mass Analyzer (COSIMA) is a time-of-flight secondary ion mass spectrometry (TOF-SIMS) instrument on board the Rosetta space mission. COSIMA has been designed to measure the composition of cometary dust particles. It has a mass resolution m/Δm of 1400 at mass 100 u, thus enabling the discrimination of inorganic mass peaks from organic ones in the mass spectra. We have evaluated the identification capabilities of the reference model of COSIMA for inorganic compounds using a suite of terrestrial minerals that are relevant for cometary science. Ground calibration demonstrated that the performances of the flight model were similar to that of the reference model. The list of minerals used in this study was chosen based on the mineralogy of meteorites, interplanetary dust particles and Stardust samples. It contains anhydrous and hydrous ferromagnesian silicates, refractory silicates and oxides (present in meteoritic Ca-Al-rich inclusions), carbonates, and Fe-Ni sulfides. From the analyses of these minerals, we have calculated relative sensitivity factors for a suite of major and minor elements in order to provide a basis for element quantification for the possible identification of major mineral classes present in the cometary particles.

GIADA: extended calibration activities before the comet encounter

NASA Astrophysics Data System (ADS)

Accolla, Mario; Sordini, Roberto; Della Corte, Vincenzo; Ferrari, Marco; Rotundi, Alessandra

2014-05-01

The Grain Impact Analyzer and Dust Accumulator - GIADA - is one of the payloads on-board Rosetta Orbiter. Its three detection sub-systems are able to measure the speed, the momentum, the mass, the optical cross section of single cometary grains and the dust flux ejected by the periodic comet 67P Churyumov-Gerasimenko. During the Hibernation phase of the Rosetta mission, we have performed a dedicated extended calibration activity on the GIADA Proto Flight Model (accommodated in a clean room in our laboratory) involving two of three sub-systems constituting GIADA, i.e. the Grain Detection System (GDS) and the Impact Sensor (IS). Our aim is to carry out a new set of response curves for these two subsystems and to correlate them with the calibration curves obtained in 2002 for the GIADA payload onboard the Rosetta spacecraft, in order to improve the interpretation of the forthcoming scientific data. For the extended calibration we have dropped or shot into GIADA PFM a statistically relevant number of grains (i.e. about 1 hundred), acting as cometary dust analogues. We have studied the response of the GDS and IS as a function of grain composition, size and velocity. Different terrestrial materials were selected as cometary analogues according to the more recent knowledge gained through the analyses of Interplanetary Dust Particles and cometary samples returned from comet 81P/Wild 2 (Stardust mission). Therefore, for each material, we have produced grains with sizes ranging from 20-500 μm in diameter, that were characterized by FESEM and micro IR spectroscopy. Therefore, the grains were shot into GIADA PFM with speed ranging between 1 and 100 ms-1. Indeed, according to the estimation reported in Fink & Rubin (2012), this range is representative of the dust particle velocity expected at the comet scenario and lies within the GIADA velocity sensitivity (i.e. 1-100 ms-1 for GDSand 1-300 ms-1for GDS+IS 1-300 ms-1). The response curves obtained using the data collected during the GIADA PFM extended calibration will be linked to the on-ground calibration data collected during the instrument qualification campaign (performed both on Flight and Spare Models, in 2002). The final aim is to rescale the Extended Calibration data obtained with the GIADA PFM to GIADA presently onboard the Rosetta spacecraft. In this work we present the experimental procedures and the setup used for the calibration activities, particularly focusing on the new response curves of GDS and IS sub-systems obtained for the different cometary dust analogues. These curves will be critical for the future interpretation of scientific data. Fink, U. & Rubin, M. (2012), The calculation of Afρ and mass loss rate for comets, Icarus, Volume 221, issue 2, p. 721-734

Groundbased cometary studies

NASA Technical Reports Server (NTRS)

Schleicher, David G.

1991-01-01

The physical properties of comets were studied by applying a wide variety of observational techniques. Emphasis is on simultaneous or coordinated observations in different spectral regions (e.g., visible and thermal IR or visible and far UV) or with different instrumentation (imaging, spectroscopy, and photometry). The aim was to: (1) measure the basic properties of cometary nuclei by studying comets whose comae are so anemic that the signal from the nucleus can be extracted; (2) investigate the group characteristics of comets by narrowband photometry applied uniformly to a large sample of comets; (3) understand the detailed physics and chemistry occurring in cometary comae through wide-field charge coupled device (CCD) imaging using narrow filters and through long-slit CCD spectroscopy; and (4) investigate the rotational states of comets through time-resolution photometry.

TOF-SIMS Analysis of Crater Residues from Wild 2 Cometary on Stardust Aluminum Foil

NASA Technical Reports Server (NTRS)

Leutner, Jan; Stephan, Thomas; Kearsley, T.; Horz, Friedrich; Flynn, George J.; Sandford, Scott A.

2006-01-01

Impact residues of cometary particles on aluminum foils from the Stardust mission were investigated with TOF-SIMS for their elemental and organic composition. The residual matter from comet 81P/Wild 2 shows a wide compositional range, from nearly monomineralic grains to polymict aggregates. Despite the comparably small analyzed sample volume, the average element composition of the investigated residues is similar to bulk CI chondritic values. Analysis of organic components in impact residues is complicated, due to fragmentation and alteration of the compounds during the impact process and by the presence of contaminants on the aluminum foils. Nevertheless, polycyclic aromatic hydrocarbons (PAHs) that are unambiguously associated with the impact residues were observed, and thus are most likely of cometary origin.

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.

Lunar and Planetary Science XXXV: Special Session: Oxygen in the Solar System, I

NASA Technical Reports Server (NTRS)

2004-01-01

The Special Session: Oxygen in the Solar System, I, included the following reports:Oxygen in the Solar System: Origins of Isotopic and Redox Complexity; The Origin of Oxygen Isotope Variations in the Early Solar System; Solar and Solar-Wind Oxygen Isotopes and the Genesis Mission; Solar 18O/17O and the Setting for Solar Birth; Oxygen Isotopes in Early Solar System Materials: A Perspective Based on Microbeam Analyses of Chondrules from CV Carbonaceous Chondrites; Insight into Primordial Solar System Oxygen Reservoirs from Returned Cometary Samples; Tracing Meteorites to Their Sources Through Asteroid Spectroscopy; Redox Conditions Among the Terrestrial Planets; Redox Complexity in Martian Meteorites: Implications for Oxygen in the Terrestrial Planets; Implications of Sulfur Isotopes for the Evolution of Atmospheric Oxygen; Oxygen in the Outer Solar System; and On the Oxidation States of the Galilean Satellites: Implications for Internal Structures.

Aerogel Track Morphology: Measurement, Three Dimensional Reconstruction and Particle Location using Confocal Laser Scanning Microscopy

NASA Technical Reports Server (NTRS)

Kearsley, A. T.; Ball, A. D.; Wozniakiewicz, P. A.; Graham, G. A.; Burchell, M. J.; Cole, M. J.; Horz, F.; See, T. H.

2007-01-01

The Stardust spacecraft returned the first undoubted samples of cometary dust, with many grains embedded in the silica aerogel collector . Although many tracks contain one or more large terminal particles of a wide range of mineral compositions , there is also abundant material along the track walls. To help interpret the full particle size, structure and mass, both experimental simulation of impact by shots and numerical modeling of the impact process have been attempted. However, all approaches require accurate and precise measurement of impact track size parameters such as length, width and volume of specific portions. To make such measurements is not easy, especially if extensive aerogel fracturing and discoloration has occurred. In this paper we describe the application and limitations of laser confocal imagery for determination of aerogel track parameters, and for the location of particle remains.

Hyperspectral Analyses of Wild 2 Grains Using Synchrotron Radiation

NASA Astrophysics Data System (ADS)

Simionovici, A. S.; Lemelle, L.; Ferroir, T.; Gillet, P.; Borg, J.; Grossemy, F.; Djouadi, Z.; Bleuet, P.; Susini, J.

2006-12-01

This work is part of the Preliminary Examination Team (PET) on Bulk Chemistry investigation of Wild 2 cometary grains brought back to Earth by the NASA Stardust mission [1]. X-rays are among the least destructive yet sensitive micro-probes, capable of analysing minute samples embedded in low density collectors, so methods based on Synchrotron Radiation had access to Stardust samples in priority. The main goal of the PET was to produce a preliminary characterization of the abundance and nature of the elements present in the returned samples [2]. In this phase it was paramount to analyze the grains in-situ, in the aerogel foam of the collectors to record the total mass fragments and avoid extraction risks. We have performed measurements on beamlines ID22/ID21 of the ESRF synchrotron in Grenoble, France, devoted to high/low energy microspectroscopy and recorded results on a collection of 6 keystones. Terminal particles as well as fragmentation tracks in the aerogel were mapped out with micron resolution, recording total mass composition for elements of Z>15 by means of X-ray fluorescence [3], as well as structural information by X-ray diffraction. This allowed the direct identification of the mineralogy of some of the grains. Finally, we recorded the evolution of the charge states of S and Fe as a function of the position in the track by means of micro-Xanes measurements. All these analyses were combined to produce a description of the Wild 2 cometary grains [4], as well as a history of their formation and of the thermal interactions during their slowing down in the aerogel collectors. [1] Brownlee, D. E. et al., LPSC XXXVII, abstract nr. 2286, 2006. [2] G. J. Flynn et al., LPSC XXXVII, abstract nr. 1217, 2006. [3] A. Simionovici, P. Chevallier, Chap. 7, Handbook of Practical X-Ray Fluorescence Analysis, 66-83, Springer, 2006. [4] G. J. Flynn et al., Science, (submitted), 2006.

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), are heated in an oven and can be injected into one of three gas chromatography columns (GC) for analysis by the mass spectrometer. Accurate isotopic analysis is achieved by chemical processing before and/or after the GC columns and by direct comparison with reference materials of known isotopic composition. Recent operations of the Ptolemy mass spectrometer during recent spacecraft checkouts have shown that the Ptolemy instrument is operational and should be capable of meeting its science aims.

Analysis of Cometary Dust Impact Residues in the Aluminum Foil Craters of Stardust

NASA Technical Reports Server (NTRS)

Graham, G. A.; Kearsley, A. T.; Vicenzi, E. P.; Teslich, N.; Dai, Z. R.; Rost, D.; Horz, F.; Bradley, J. P.

2007-01-01

In January 2006, the sample return capsule from NASA s Stardust spacecraft successfully returned to Earth after its seven year mission to comet Wild-2. While the principal capture medium for comet dust was low-density graded silica aerogel, the 1100 series aluminum foil (approximately 100 m thick) which wrapped around the T6064 aluminum frame of the sample tray assembly (STA) contains micro-craters that constitute an additional repository for Wild-2 dust. Previous studies of similar craters on spacecraft surfaces, e.g. the Long Duration Exposure Facility (LDEF), have shown that impactor material can be preserved for elemental and mineralogical characterization, although the quantity of impact residue in Stardust craters far exceeds previous missions. The degree of shock-induced alteration experienced by the Wild-2 particles impacting on foil will generally be greater than for those captured in the low-density aerogel. However, even some of the residues found in LDEF craters showed not only survival of crystalline silicates but even their solar flare tracks, which are extremely fragile structures and anneal at around 600 C. Laboratory hypervelocity experiments, using analogues of Wild-2 particles accelerated into flight-grade foils under conditions close to those of the actual encounter, showed retention of abundant projectile residues at the Stardust encounter velocity of 6.1 km/s. During the preliminary examination (PE) of the returned foils, using optical and electron microscopy studies, a diverse range in size and morphologies of micro-craters was identified. In this abstract we consider the state of residue preservation in a diverse range of craters with respect to their elemental composition and inferred mineralogy of the original projectiles.

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: ladder structures with conjugated -C=N- bonds and polyamidines readily converted by water to polypeptides. Thermochemolysis GC-MS studies show that cleavage products of the polymer include alpha-amino acids, nitrogen heterocycles such as purines and pyrimidines, and provide evidence for peptide linkages. Hydrogen cyanide polymers are a plausible link between cosmochemistry and the origin of informational macromolecules. Implications for prebiotic chemistry are profound. Following persistent bolide bombardment, primitive Earth may have been covered by water and carbonaceous compounds, particularly HCN polymers which would have supplied essential components for establishing protein/nucleic acid life.

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.

Microanalysis of Hypervelocity Impact Residues of Possible Interstellar Origin

NASA Technical Reports Server (NTRS)

Stroud, Rhonda M.; Achilles, Cheri; Allen, Carlton; Anasari, Asna; Bajt, Sasa; Bassim, Nabil; Bastien, Ron S.; Bechtel, H. A.; Borg, Janet; Brenker, Frank E.;

Presolar Materials in a Giant Cluster IDP of Probable Cometary Origin

NASA Technical Reports Server (NTRS)

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

2015-01-01

Chondritic porous interplanetary dust particles (CP-IDPs) have been linked to comets by their fragile structure, primitive mineralogy, dynamics, and abundant interstellar materials. But differences have emerged between 'cometary' CP-IDPs and comet 81P/Wild 2 Stardust Mission samples. Particles resembling Ca-Al-rich inclusions (CAIs), chondrules, and amoeboid olivine aggregates (AOAs) in Wild 2 samples are rare in CP-IDPs. Unlike IDPs, presolar materials are scarce in Wild 2 samples. These differences may be due to selection effects, such as destruction of fine grained (presolar) components during the 6 km/s aerogel impact collection of Wild 2 samples. Large refractory grains observed in Wild 2 samples are also unlikely to be found in most (less than 30 micrometers) IDPs. Presolar materials provide a measure of primitive-ness of meteorites and IDPs. Organic matter in IDPs and chondrites shows H and N isotopic anomalies attributed to low-T interstellar or protosolar disk chemistry, where the largest anomalies occur in the most primitive samples. Presolar silicates are abundant in meteorites with low levels of aqueous alteration (Acfer 094 approximately 200 ppm) and scarce in altered chondrites (e.g. Semarkona approximately 20 ppm). Presolar silicates in minimally altered CP-IDPs range from approximately 400 ppm to 15,000 ppm, possibly reflecting variable levels of destruction in the solar nebula or statistical variations due to small sample sizes. Here we present preliminary isotopic and mineralogical studies of a very large CP-IDP. The goals of this study are to more accurately determine the abundances of presolar components of CP-IDP material for comparison with comet Wild 2 samples and meteorites. The large mass of this IDP presents a unique opportunity to accurately determine the abundance of pre-solar grains in a likely cometary sample.

Nanoscale infrared spectroscopy as a non-destructive probe of extraterrestrial samples.

PubMed

Dominguez, Gerardo; Mcleod, A S; Gainsforth, Zack; Kelly, P; Bechtel, Hans A; Keilmann, Fritz; Westphal, Andrew; Thiemens, Mark; Basov, D N

2014-12-09

Advances in the spatial resolution of modern analytical techniques have tremendously augmented the scientific insight gained from the analysis of natural samples. Yet, while techniques for the elemental and structural characterization of samples have achieved sub-nanometre spatial resolution, infrared spectral mapping of geochemical samples at vibrational 'fingerprint' wavelengths has remained restricted to spatial scales >10 μm. Nevertheless, infrared spectroscopy remains an invaluable contactless probe of chemical structure, details of which offer clues to the formation history of minerals. Here we report on the successful implementation of infrared near-field imaging, spectroscopy and analysis techniques capable of sub-micron scale mineral identification within natural samples, including a chondrule from the Murchison meteorite and a cometary dust grain (Iris) from NASA's Stardust mission. Complementary to scanning electron microscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy probes, this work evidences a similarity between chondritic and cometary materials, and inaugurates a new era of infrared nano-spectroscopy applied to small and invaluable extraterrestrial samples.

Comet 81p/Wild 2: The Updated Stardust Coma Dust Fluence Measurement for Smaller (Sub 10-Micrometre) Particles

NASA Technical Reports Server (NTRS)

Price, M. C.; Kearsley, A. T.; Burchell, M. J.; Horz, Friedrich; Cole, M. J.

2009-01-01

Micrometre and smaller scale dust within cometary comae can be observed by telescopic remote sensing spectroscopy [1] and the particle size and abundance can be measured by in situ spacecraft impact detectors [2]. Initial interpretation of the samples returned from comet 81P/Wild 2 by the Stardust spacecraft [3] appears to show that very fine dust contributes not only a small fraction of the solid mass, but is also relatively sparse [4], with a low negative power function describing grain size distribution, contrasting with an apparent abundance indicated by the on-board Dust Flux Monitor Instrument (DFMI) [5] operational during the encounter. For particles above 10 m diameter there is good correspondence between results from the DFMI and the particle size inferred from experimental calibration [6] of measured aerogel track and aluminium foil crater dimensions (as seen in Figure 4 of [4]). However, divergence between data-sets becomes apparent at smaller sizes, especially submicrometre, where the returned sample data are based upon location and measurement of tiny craters found by electron microscopy of Al foils. Here effects of detection efficiency tail-off at each search magnification can be seen in the down-scale flattening of each scale component, but are reliably compensated by sensible extrapolation between segments. There is also no evidence of malfunction in the operation of DFMI during passage through the coma (S. Green, personal comm.), so can the two data sets be reconciled?

Analysis and interpretation of CCD data on P/Halley and physical parameters and activity status of cometary nuclei at large heliocentric distance

NASA Technical Reports Server (NTRS)

Belton, Michael J. S.; Mueller, Beatrice

1991-01-01

The scientific objectives were as follows: (1) to construct a well sampled photometric time series of comet Halley extending to large heliocentric distances both post and pre-perihelion passage and derive a precise ephemeris for the nuclear spin so that the physical and chemical characteristics of individual regions of activity on the nucleus can be determined; and (2) to extend the techniques in the study of Comet Halley to the study of other cometary nuclei and to obtain new observational data.

Creating cometary models using ancient Chinese data

NASA Astrophysics Data System (ADS)

Yeomans, D. K.

For more than two millennia, Chinese court astronomers maintained a rather comprehensive record of cometary sightings. Owing to the significance of comets as portents for the reigning emperor, early sky watchers from China (as well as their counterparts from Korea and Japan) carefully noted each cometary apparition for the purpose of astrological predictions. The dates and corresponding celestial locations and motions were usually recorded and in some cases, the colors, coma sizes, and tail lengths were also noted. These ancient observations represent the only source of information available for modeling the long-term behavior of periodic comets. For comets Halley and Swift-Tuttle, Chinese records have been identified as far back as 240 B.C. and 69 B.C. respectively and these data have been used to define their long-term motions. As a result, heliocentric and geocentric distances for each Chinese sighting of these two comets can be computed and estimates can be made for each comet's intrinsic brightness at various observed returns. Although the earliest identified apparition of comet Tempel-Tuttle is A.D. 1366, the associated Leonid meteor showers were noted back to at least A.D. 902. The Leonid meteor stream is young in the sense that outstanding meteor displays occur only near the time of the parent comet's perihelion passages. The ancient Chinese records of the Leonid meteor showers and storms have been used to map the particle distribution around the parent comet and this information was used to guide predictions for the 1998-1999 Leonid meteor showers.

Cometary Evolution: Clues on Physical Properties from Chondritic Interplanetary Dust Particles

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.; Mackinnon, Ian D. R.

1989-01-01

The degree of diversity or similarity detected in comets depends primarily on the lifetimes of the individual cometary nuclei at the time of analysis. It is inherent in our understanding of cometary orbital dynamics and the seminal model of comet origins by Oort that cometary evolution is the natural order of events in our Solar System. Thus, predictions of cometary behaviour in terms of bulk physical, mineralogical or chemical parameters should contain an appreciation of temporal variation(s). Previously, Rietmeijer and Mackinnon developed mineralogical bases for the chemical evolution of cometary nuclei primarily with regard to the predominantly silicate fraction of comet nuclei. We suggested that alteration of solids in cometary nuclei should be expected and that indications of likely reactants and products can be derived from judicious comparison with terrestrial diagenetic environments which include hydrocryogenic and low-temperature aqueous alterations. In a further development of this concept, Rietmeijer provides indirect evidence for the formation of sulfides and oxides in comet nuclei. Furthermore, Rietmeijer noted that timescales for hydrocryogenic and low-temperature reactions involving liquid water are probably adequate for relatively mature comets, e.g. P/comet Halley. In this paper, we will address the evolution of comet nuclei physical parameters such as solid particle grain size, porosity and density. In natural environments, chemical evolution (e.g. mineral reactions) is often accompanied by changes in physical properties. These concurrent changes are well-documented in the terrestrial geological literature, especially in studies of sediment diagenesis and we suggest that similar basic principles apply within the upper few meters of active comet nuclei. The database for prediction of comet nuclei physical parameters is, in principle, the same as used for the proposition of chemical evolution. We use detailed mineralogical studies of chondritic interplanetary dust particles (IDPS) as a guide to the likely constitution of mature comets traversing the inner Solar System. While there is, as yet, no direct proof that a specific sub-group or type of chondritic IDP is derived from a specific comet, it is clear that these particles are extraterrestrial in origin and that a certain portion of the interplanetary flux received by the Earth is cometary in origin. Two chondritic porous (CP) MPs, sample numbers W7010A2 and W7029Cl, from the Johnson Space Center Cosmic Dust Collection have been selected for this study of putative cometary physical parameters. This particular type of particle is considered a likely candidate for a cometary origin on the basis of mineralogy, bulk composition and morphology. While many IDPs have been subjected to intensive study over the past decade, we can develop a physical parameter model on only these two CP IDPs because few others have been studied in sufficient detail.

Cometary Evolution: Clues on Physical Properties from Chondritic Interplanetary Dust Particles

NASA Technical Reports Server (NTRS)

Reitmeijer, Frans J. M.; Mackinnon, Ian D. R.

1997-01-01

The degree of diversity or similarity detected in comets depends primarily on the lifetimes of the individual cometary nuclei at the time of analysis. It is inherent in our understanding of cometary orbital dynamics and the seminal model of comet origins that cometary evolution is the natural order of events in our Solar System. Thus, predictions of cometary behaviour in terms of bulk physical, mineralogical or chemical parameters should contain an appreciation of temporal variation(s). Previously, Rietmeijer and Mackinnon [1987] developed mineralogical bases for the chemical evolution of cometary nuclei primarily with regard to the predominantly silicate fraction of comet nuclei. We suggested that alteration of solids in cometary nuclei should be expected and that indications of likely reactants and products can be derived from judicious comparison with terrestrial diagenetic environments which include hydrocryogenic and low-temperature aqueous alterations. In a further development of this concept, Rietmeijer [1988] provides indirect evidence for the formation of sulfides and oxides in comet nuclei. Furthermore, Rietmeijer [1988] noted that timescales for hydrocryogenic and low-temperature reactions involving liquid water are probably adequate for relatively mature comets, e.g. P/comet Halley. In this paper, we will address the evolution of comet nuclei physical parameters such as solid particle grain size, porosity and density. In natural environments, chemical evolution (e.g. mineral reactions) is often accompanied by changes in physical properties. These concurrent changes are well-documented in the terrestrial geological literature, especially in studies of sediment diagenesis and we suggest that similar basic principles apply within the upper few meters of active comet nuclei. The database for prediction of comet nuclei physical parameters is, in principle, the same as used for the proposition of chemical evolution. We use detailed mineralogical studies of chondritic interplanetary dust particles (IDPS) as a guide to the likely constitution of mature comets traversing the inner Solar System. While there is, as yet, no direct proof that a specific sub-group or type of chondritic IDP is derived from a specific comet, it is clear that these particles are extraterrestrial in origin and that a certain portion of the interplanetary flux received by the Earth is cometary in origin. Two chondritic porous (CP) IDPS, sample numbers W701OA2 and W7029CI, from the Johnson Space Center Cosmic Dust Collection have been selected for this study of putative cometary physical parameters. This particular type of particle is considered a likely candidate for a cometary origin on the basis of mineralogy, bulk composition and morphology. While many IDPs have been subjected to intensive study over the past decade, we can develop a physical parameter model on only these two CP IDPs because few others have been studied in sufficient detail.

Terrestrial analysis of the organic component of comet dust.

PubMed

Sandford, Scott A

2008-01-01

The nature of cometary organics is of great interest, both because these materials are thought to represent a reservoir of the original carbon-containing materials from which everything else in our solar system was made and because these materials may have played key roles in the origin of life on Earth. Because these organic materials are the products of a series of universal chemical processes expected to operate in the interstellar media and star-formation regions of all galaxies, the nature of cometary organics also provides information on the composition of organics in other planetary systems and, by extension, provides insights into the possible abundance of life elsewhere in the universe. Our current understanding of cometary organics represents a synthesis of information from telescopic and spacecraft observations of individual comets, the study of meteoritic materials, laboratory simulations, and, now, the study of samples collected directly from a comet, Comet P81/Wild 2.

The survivability of phyllosilicates and carbonates impacting Stardust Al foils: Facilitating the search for cometary water

DOE PAGES

Wozniakiewicz, Penelope J.; Ishii, Hope A.; Kearsley, Anton T.; ...

2015-11-05

Comet 81P/Wild 2 samples returned by NASA's Stardust mission provide an unequalled opportunity to study the contents of, and hence conditions and processes operating on, comets. They can potentially validate contentious interpretations of cometary infrared spectra and in situ mass spectrometry data: specifically the identification of phyllosilicates and carbonates. However, Wild 2 dust was collected via impact into capture media at ~6 km s -1, leading to uncertainty as to whether these minerals were captured intact, and, if subjected to alteration, whether they remain recognizable. Here, we simulated Stardust Al foil capture conditions using a two-stage light-gas gun, and directlymore » compared transmission electron microscope analyses of pre- and postimpact samples to investigate survivability of lizardite and cronstedtite (phyllosilicates) and calcite (carbonate). We find the phyllosilicates do not survive impact as intact crystalline materials but as moderately to highly vesiculated amorphous residues lining resultant impact craters, whose bulk cation to Si ratios remain close to that of the impacting grain. Closer inspection reveals variation in these elements on a submicron scale, where impact-induced melting accompanied by reducing conditions (due to the production of oxygen scavenging molten Al from the target foils) has resulted in the production of native silicon and Fe- and Fe-Si-rich phases. In contrast, large areas of crystalline calcite are preserved within the calcite residue, with smaller regions of vesiculated, Al-bearing calcic glass. Unambiguous identification of calcite impactors on Stardust Al foil is therefore possible, while phyllosilicate impactors may be inferred from vesiculated residues with appropriate bulk cation to Si ratios. Finally, we demonstrate that the characteristic textures and elemental distributions identifying phyllosilicates and carbonates by transmission electron microscopy can also be observed by state-of-the-art scanning electron microscopy providing rapid, nondestructive initial mineral identifications in Stardust residues.« less

Proceedings of the Shuttle-based Cometary Science Workshop: a Forum for the Presentation and Discussion of Possible Shuttle-based Experiments and Observations of Comets and Cometary-like Materials

NASA Technical Reports Server (NTRS)

Gary, G. A. (Editor); Clifton, K. S. (Editor)

1976-01-01

The prospects of cometary research from the space shuttle are examined. Topics include: the shuttle as research environment; on-board experiments at zero-gravity and release of gas and dust to simulate cometary phenomena; and cometary observations from space.

Laboratory studies of cometary ice analogues

NASA Astrophysics Data System (ADS)

Schmitt, B.; Espinasse, S.; Grim, R. J. A.; Greenberg, J. M.; Klinger, J.

1989-12-01

Laboratory studies were performed in order to simulate the physico-chemical processes that are likely to occur in the near surface layers of short and intermediate period comets. Pure H2O ice as well as CO:H2O, CO2:H2O, CH4:H2O, CO:CO2:H2O, and NH3:H2O ice mixtures were studied in the temperature range between 10 and 180 K. The evolution of the composition of ice mixtures, the crystallization of H2O ice as well as the formation and decompostion of clathrate hydrate by different processes were studied as a function of temperature and time. Using the results together with numerical modeling, predictions are made about the survival of amorphous ice, CO, CO2, CH4, and NH3 in the near surface layers of short period comets. The likeliness of finding clathrate and molecular hydrates is discussed. It is proposed that the analytical methods developed here could be fruitfully adapted to the analysis of returned comet samples.

Stardust Imaging of Comet Wild 2: First Look

NASA Technical Reports Server (NTRS)

Newburn, R.; Acton, C.; Bhaskaran, S.; Brownlee, D.; Cheuvront, A.; Duxbury, T.; Hanner, M.; Semenov, B.; Sandford, S.; Tsou, P.

2004-01-01

On 2 January 2004 during its historic flight to return cometary dust samples to earth, the STARDUST spacecraft flew within the coma of comet Wild 2 and also took 72 images where the surface was resolved during the flyby. A combination of long and short exposures was used to observe the jets and the surface. Comet Surface: The images revealed a planetary body, one not having a significant atmosphere, quite different from any other such body seen from other spacecraft. Surface depressions, potentially a combination of craters and vents, were not bowl-shaped but typically had steep walls and flattened floors. One depression considered to be a vent, the source of a jet, had a depth to diameter ratio of approx.0.4, with near vertical walls. Jets: At least 10 to possibly 20 jets were active during the flyby. Some were traced back to the surface where they seem to originate from the near vertical walls of depressions (vents) that were facing the sun, having the highest solar insolation.

Microstructural Study of Micron-Sized Craters Simulating Stardust Impacts in Aluminum 1100 Targets

NASA Technical Reports Server (NTRS)

Leroux, Hugues; Borg, Janet; Troadec, David; Djouadi, Zahia; Horz, Friedrich

2006-01-01

Various microscopic techniques were used to characterize experimental micro- craters in aluminium foils to prepare for the comprehensive analysis of the cometary and interstellar particle impacts in aluminium foils to be returned by the Stardust mission. First, SEM (Scanning Electron Microscopy) and EDS (Energy Dispersive X-ray Spectroscopy) were used to study the morphology of the impact craters and the bulk composition of the residues left by soda-lime glass impactors. A more detailed structural and compositional study of impactor remnants was then performed using TEM (Transmission Electron Microscopy), EDS, and electron diffraction methods. The TEM samples were prepared by Focused Ion Beam (FIB) methods. This technique proved to be especially valuable in studying impact crater residues and impact crater morphology. Finally, we also showed that InfraRed microscopy (IR) can be a quick and reliable tool for such investigations. The combination of all of these tools enables a complete microscopic characterization of the craters.

Similarities Between Cometary, Meteoritic, and Laboratory Analog Dust: Hints from the Attribution of the 10-micrometer Band

NASA Astrophysics Data System (ADS)

Colangeli, L.; Mennella, V.; Bussoletti, E.; Merluzzi, P.; Rotundi, A.; Palumbo, P.; di Marino, C.

1993-07-01

It is well known that the infrared emission of many comets is characterized by a broad feature at 10 micrometers, that has been attributed to a Si-O stretching resonance in amorphous and/or hydrated silicate grains. In the case of comets Halley [1,2], Bradfield [3] and Levy [4] two spectral components have been observed: the wide peak centered at 9.8 micrometers and a sharp feature at 11.3 micrometers. This last band has been interpreted with crystalline olivine silicatic grains [1,2,5]. However, recently, it has been pointed out [6] that the laboratory data frequently used in the fits refer to grains embedded in a matrix, which should produce a significant shift of the peak position, according to Mie computations. We have performed laboratory experiments on various silicatic samples with the perspective of determining their optical properties, to study experimentally the influence of matrix effects, and to use the final spectra to perform comparisons with observations. The samples are four terrestrial materials, olivine forsterite, jadeite pyroxene, andesite feldspar and impactite glass, and two meteoritic samples, chondrite (Zacatecas, Mexico) and pallasite (Atacama, Chile). Fine powders of the bulk materials were obtained by grinding calibrated mass amounts of the various samples in an agata mill. The morphological characterization of the samples was performed by means of S.E.M. (scanning electron microscopy) technique. EDX analysis was also performed to determine elemental composition. IR transmission spectra were obtained by using a double beam spectrophotometer that covers the spectral range 2.5-50 micrometers. The standard pellet technique was used by embedding dust samples in KBr or CsI matrices. For comparison, measurements were also performed by depositing small amounts of dust onto KBr windows. In this last case, dust-matrix interaction should be practically absent as grains are simply sitting onto the matrix. The data obtained from the spectroscopic analysis have allowed us to evidence the following main results. Matrix effects do not appear as relevant as suggested by computations performed by the Mie theory. In particular, the peak shift observed for crystalline olivine is from 11.3 micrometers in CsI (n(sub)o = 1.7) to 11.2 micrometers in vacuum (n(sun)o = 1.0). On the other hand, jadeite and andesite grains present main peaks around 10 micrometers, in contrast to cometary spectra. We can, therefore, conclude that crystalline olivine grains are good candidates to simulate the cometary 11.3 micrometer sharp feature, even when matrix effects are accounted for. The impactite sample presents a main broad band around 9.2 micrometers, due to its mainly amorphous composition. This band could resemble the broad 10 micron cometary band; however, its profile is rather broader than that observed for cometary dust. Concerning the meteoritic samples, both chondrite and pallasite show a well defined main peak at 11.3-11.4 micrometers, comparable to cometary spectra. Again, chondrite band profile is too broad. On the contrary, pallasite appears to be a good candidate to reproduce observations. This result appears reasonable if one considers that the sample is formed by small olivine crystals embedded in a iron matrix. In conclusion, the comparison between the spectra of olivine-rich meteoritic grains and cometary dust could suggest either a common origin of the two classes of materials or, at least, a similarity in the processes experienced by them during past evolution. This result appears very relevant because it could imply that the systematic study in the laboratory of meteoritic materials can provide information about the past history of comets. Acknowledgements: This work was partly supported by ASI, CNR, and MURST 40% and 60%. References: [1] Bregman J. D. et al. (1987) Astron. Astrophys., 187, 616. [2] Campins H. and Ryan E. V. (1989) Ap. J., 341, 1059. [3] Hanner M. S. et al. (1990) Ap. J., 348, 312. [4] Lynch D. K. et al. (1990) 22nd annual meeting of the division for planetary sciences, Charlottesville, Virginia. [5] Sandford S. A. and Walker R. M. (1985) Ap. J., 291, 838. [6] Orofino V. et al. (1993) Astron. Astrophys., submitted.

PHYS: Division of Physical Chemistry 258 - Properties and Origins of Cometary and Asteroidal Organic Matter Delivered to the Early Earth

NASA Technical Reports Server (NTRS)

Messenger, Scott; Nguyen, Ann

2017-01-01

Comets and asteroids may have contributed much of the Earth's water and organic matter. The Earth accretes approximately 4x10(exp 7) Kg of dust and meteorites from these sources every year. The least altered meteorites contain complex assemblages of organic compounds and abundant hydrated minerals. These carbonaceous chondrite meteorites probably derive from asteroids that underwent hydrothermal processing within the first few million years after their accretion. Meteorite organics show isotopic and chemical signatures of low-T ion-molecule and grain-surface chemistry and photolysis of icy grains that occurred in cold molecular clouds and the outer protoplanetary disk. These signatures have been overprinted by aqueously mediated chemistry in asteroid parent bodies, forming amino acids and other prebiotic molecules. Comets are much richer in organic matter but it is less well characterized. Comet dust collected in the stratosphere shows larger H and N isotopic anomalies than most meteorites, suggesting better preservation of primordial organics. Rosetta studies of comet 67P coma dust find complex organic matter that may be related to the macromolecular material that dominates the organic inventory of primitive meteorites. The exogenous organic material accreting on Earth throughout its history is made up of thousands of molecular species formed in diverse processes ranging from circumstellar outflows to chemistry at near absolute zero in dark cloud cores and the formative environment within minor planets. NASA and JAXA are currently flying sample return missions to primitive, potentially organic-rich asteroids. The OSIRIS-REx and Hayabusa2 missions will map their target asteroids, Bennu and Ryugu, in detail and return regolith samples to Earth. Laboratory analyses of these pristine asteroid samples will provide unprecedented views of asteroidal organic matter relatively free of terrestrial contamination within well determined geological context. Studies of extraterrestrial materials and returned samples are essential to understand the origins of Solar System organic material and the roles of comets and asteroids to providing the starting materials for the emergence of life.

The Origin, Composition and History of Comets from Spectroscopic Studies

NASA Technical Reports Server (NTRS)

Allamandola, L. J.

1997-01-01

A wealth of information essential to understanding the composition and physical structure of cometary ice and hence gain deep insight into the comet's origin and history, can be gleaned by carrying out a full range of spectroscopic studies on the returned sample. These studies ought to be among the first performed as they are generally non-destructive and will provide a broad data bank which will be crucial in planning subsequent analysis. Examples of the spectroscopic techniques along with relative sensitivities and transitions probed, are discussed. Different kind of "spectroscopy" is summarized, with emphasis placed on the kind of information each provides. Infrared spectroscopy should be the premier method of analysis as the mid-IR absorption spectrum of a substance contains more global information about the identity and structure of that material than any other property. In fact, the greatest strides in our understanding of the composition of interstellar ices (thought by many to be the primordial material from which comets have formed) have been taken during the past ten years or so because this was when high quality infrared spectra of the interstellar medium (ISM) first became available. The interpretation of the infrared spectra of mixtures, such as expected in comets, is often (not always) ambiguous. Consequently, a full range of other non-destructive, complementary spectroscopic measurements are required to fully characterize the material, to probe for substances for which the IR is not well suited and to lay the groundwork for future analysis. Given the likelihood that the icy component (including some of the organic and mineral phases) of the returned sample will be exceedingly complex, these techniques must be intensely developed over the next decade and then made ready to apply flawlessly to what will certainly be one of the most precious, and most challenging, samples ever analyzed.

The Nature of Punctuational Crises and the Spenglerian Model of Civilization

NASA Astrophysics Data System (ADS)

Clube, S. V. M.

Mankind's essentially untroubled state of mind in the presence of comets during the last two centuries has been fortified by the overall relative brevity of cometary apparitions and the calculated infrequency of cometary encounters with planets. During the course of the Space Age, however, the fact of cometary splitting has also become increasingly secure and there is growing appreciation of the fact that mankind's state of mind can never be altogether relaxed. Indeed a watershed in the modern perception of cometary facts has evidently been reached with the most recent and devastating example of cometary splitting, that of the fragmentation of Comet P/Shoemaker-Levy 9 and its subsequent bombardment of planet Jupiter. Thus there is a recognized tendency now amongst comets, especially those in short-period orbits, due to the occasionally excessive effects of solar irradiation, planetary tides and small body impacts, which gives rise to individual swarms of cometary debris, and it is the resulting repeated penetration of such dispersed swarms by our planet which apparently increases the danger to mankind from time to time. The danger comprises global coolings, atmospheric pollution and super-Tunguska events, the cometary debris being responsible for both high-level dust insertions and low-level multimegaton explosions in the Earth's atmosphere along with a generally enhanced fireball flux. Historically, the presence of such danger was drawn to mankind's attention by the observed bombardments over several decades due to "blazing stars threatening the world with famine, plague and war; to princes death; to kingdoms many curses; to all estates many losses; to herdsmen rot; to ploughmen hapless seasons; to sailors storms; to cities civil treasons." The sense of cosmic destiny aroused by these bombardments evidently involved degrees of fatalism and public anxiety which were deplored by both ecclesiastical authorities and secular administrations with the result that acknowledged dispensers of prognosis and mitigation who endorsed the adverse implications of 'blazing stars' (astrologers, soothsayers etc.) were commonly impugned and censured. Nowadays, of course, we are able to recognise that the Earth's environment is not only one of essentially uniformitarian calm, as formerly assumed, but one that is also interrupted by 'punctuational crises', each crisis being the sequence of events which arises due to the fragmentation of an individual comet whose orbit intersects the Earth's. That even modest crises can arouse apprehension is known through the circumstances of the nineteenth century break-up of Comet Biela. Indeed it seems that these crises are rather frequently characterized by relatively violent (paradigm shifting) transmutations of human society such as were originally proposed by Spengler and Toynbee more than sixty years ago on the basis of historical analysis alone. It would appear, then, that the historical fear of comets which has been with us since the foundation of civilization, far from being the reflection of an astrological perception of the cosmos which was deranged and therefore abandoned, has a perfectly rational basis in occasional cometary fragmentation events. Such events recur and evidently have quite serious implications for society and government today. Thus when cosmic danger returns and there is growing awareness of the fact, we find that society is capable of becoming uncontrollably convulsed as 'enlightenment' spreads. A revival of millenarian expectations under these circumstances, for example, is not so much an underlying consequence but a deviant manifestation of the violent turmoil into which society falls, often to revolutionary effect.

Progress of Cometary Science in the Past 100 Years

NASA Technical Reports Server (NTRS)

Sekanina, Zdenek

1999-01-01

Enormous strides made by cometary science during the 20th century defy any meaningful comparison of its state 100 years ago and now. The great majority of the subfields enjoying much attention nowadays did not exist in the year 1900. Dramatic developments, especially in the past 30-50 years, have equally affected observational and theoretical studies of comets. The profound diversification of observing techniques has been documented by the ever widening limits on the electromagnetic spectrum covered. While the time around 1900 marked an early period of slow and painful experimentation with photographic methods in cometary studies, observations of comets from the x-ray region to the radio waves have by now become routine. Many of the new techniques, and all those involved with the wavelengths shorter than about 300 nm, were made possible by another major breakthrough of this century - observing from space. Experiments on dedicated Earth-orbiting satellites as well as several deep-space probes have provided fascinating new information on the nature and makeup of comets. In broader terms, much of the progress has been achieved thanks to fundamental discoveries and major advances in electronics, whose applications resulted in qualitatively new instruments (e.g. radiotelescopes) and sensors or detectors (e.g. CCD arrays). The most universal effect on the entire cometary science, from observing to data handling to quantitative interpretations, has been, as in any other branch of science, due to the introduction of electronic computers, with their processing capabilities not only unheard of, but literally unimaginable, in the age of classical desk calculators. As if all this should not be enough, the today's generations of comet scientists have, in addition, been blessed with nature's highly appreciated cooperation. Indeed, in the span of a dozen years, between 1985 and 1997, we were privileged to witness four remarkable cometary events: (i) a return of Halley's celebrated comet; (ii) the impact of an extensively fragmented comet Shoemaker-Levy 9 into Jupiter - a once-in-a-millenium episode; (iii) a closeup, appearance of a small but very active Earth-approaching comet Hyakutake; and (iv) an unforgettable celestial show of comet Hale-Bopp, one of the brightest and the most massive comets ever observed. We have been - and for many years to come will be - harvesting scientifically lucrative findings based on the flood of data accumulated during observational campaigns organized for these and other recent objects. Our understanding of cometary phenomena will continue to grow as observing techniques are further being improved and as more sophisticated theories are being developed. Recent accomplishments achieved in the rapidly expanding field of comets are certain to stimulate the members of this astronomical community in their quest for new discoveries in the 21st century!

Returning Samples from Enceladus

NASA Astrophysics Data System (ADS)

Tsou, P.; Kanik, I.; Brownlee, D.; McKay, C.; Anbar, A.; Glavin, D.; Yano, H.

2012-12-01

From the first half century of space exploration, we have obtained samples only from the Moon, comet Wild 2, the Solar Wind and the asteroid Itokawa. The in-depth analyses of these samples in terrestrial laboratories have yielded profound knowledge that could not have been obtained without the returned samples. While obtaining samples from Solar System bodies is crucial science, it is rarely done due to cost and complexity. Cassini's discovery of geysers on Enceladus and organic materials, indicate that there is an exceptional opportunity and science rational to do a low-cost flyby sample return mission, similar to what was done by the Stardust. The earliest low cost possible flight opportunity is the next Discovery Mission [Tsou et al 2012]. Enceladus Plume Discovery - While Voyager provided evidence for young surfaces on Enceladus, the existence of Enceladus plumes was discovered by Cassini. Enceladus and comets are the only known solar system bodies that have jets enabling sample collection without landing or surface contact. Cassini in situ Findings -Cassini's made many discoveries at Saturn, including the break up of large organics in the plumes of Enceladus. Four prime criteria for habitability are liquid water, a heat source, organics and nitrogen [McKay et al. 2008, Waite et al. 2009, Postberg et al. 2011]. Out of all the NASA designated habitability targets, Enceladus is the single body that presents evidence for all four criteria. Significant advancement in the exploration of the biological potential of Enceladus can be made on returned samples in terrestrial laboratories where the full power of state-of-the-art laboratory instrumentation and procedures can be used. Without serious limits on power, mass or even cost, terrestrial laboratories provide the ultimate in analytical capability, adaptability, reproducibility and reliability. What Questions can Samples Address? - Samples collected from the Enceladus plume will enable a thorough and replicated search for chemical biosignatures to understand the habitability potential of the subsurface ocean of Enceladus [Glavin et al. 2011]. By assessing the chiral excess among different amino acids, identifying chains of amino acids, isolate distinct sequences of these chains and the same for nucleic acids, we can formulate a new set of hypotheses to address some of the key science questions required for investigating the stage of extraterrestrial life at Enceladus beyond the four factors of habitability. Criticality of Analyses - For extraterrestrial organic matter analyses such as chirality and compound-specific isotopes, the repeatable robustness of laboratory measurements is a necessity. These analyses require a series of chemical extraction and derivatization steps prior to analysis that is adapted to the sample and procedures results-driven. The Stardust mission is an excellent example of the challenges in the analysis of organics. Confirmation of the cometary origin of the amino acid glycine from comet Wild 2 was obtained 3 years after the samples were returned to Earth. This long period of laboratory development allowed several modifications to the extraction protocol, multiple analytical techniques and instrumentations. Reference: Tsou et al., Astrobiology, in press 2012. McKay et al. Astrobiology 2008. Waite et al. Nature V 460 I 7254, 2009. Postberg et al. EPSC 642P 2011. Glavin et al., LPSC, #5002, 2011.

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

NASA Astrophysics Data System (ADS)

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

2015-11-01

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

Numerical Simulations of Lightcurves of Non-principal Axis Rotators

NASA Astrophysics Data System (ADS)

Mueller, Beatrice E. A.; Samarasinha, N. H.

2012-10-01

Theory predicts that most short-period comets should be in non-principal axis (NPA) rotational states (Jewitt 1997) due to torques caused by outgassing from the nuclei. However the fraction that is currently observed to be in such a state is small (less than 15%; Samarasinha et al 2004, and references therein). This suggests that NPA states naturally occurring as a consequence of cometary jetting are more rapidly damped because comets are structurally far weaker than has been assumed. However, there is a serious question whether this discrepancy is real or an artifact of interpreting lightcurve observations. We will present initial results of our numerical simulation of the observational manifestation of lightcurves over the range of possible NPA rotation states and determine the effects of observing geometry, signal-to-noise, and sampling. References: Jewitt, D. 1997. Cometary Rotation: An Overview. Earth, Moon, and Planets 79, 35-53. Samarasinha, N.H., B.E.A. Mueller, M.J.S. Belton,L. Jorda 2004. Rotation of Cometary Nuclei. In Comets II, pp. 281-299.

The forest and the trees. [comments on comet nuclei, cometary origin, and correlations among cometary data

NASA Technical Reports Server (NTRS)

Whipple, Fred L.

1991-01-01

Comments on the nature of cometary nuclei, some problems regarding cometary origin, and some correlations among cometary data are presented. Comparisons with an earlier report on cometary nuclei are noted, and most of the earlier advances in concept are substantiated. The mean density of the Halley nucleus may have been underestimated, while the nature of the rotation remains uncertain. The dust/gas ratio apparently needs to be increased by as much as two times, perhaps to unity or higher. CHON grains appear to be important sources of gas. Evidence is presented to support the thesis that aging among long-period comets increases statistically as the periods decrease. Data on the orientation of cometary axes with respect to the Galaxy and the properties of clusters defined by these axes are presented.

Measurements in Vacuum of the Complex Permittivity of Planetary Regolith Analog Materials in Support of the OSIRIS-REx Mission

NASA Astrophysics Data System (ADS)

Boivin, A.; Hickson, D. C.; Cunje, A.; Tsai, C. A.; Ghent, R. R.; Daly, M. G.

2017-12-01

In preparation for the OSIRIS-REx sample return mission, ground based radar data have been used to help characterize the carbonaceous asteroid (101955) Bennu as well as to produce a 3-D shape model. Radar data have also been used to derive the near-surface bulk density of the asteroid, a key engineering factor for sample acquisition and return. The relationship between radar albedo and bulk density of the nearsurface depends on the relative permittivity of the material, in this case regolith. The relative permittivity is complex such that ɛ r = ɛ r' + i ɛ r'', where ɛ r' is the dielectric constant and ɛ r'' is the loss factor. Laboratory permittivity measurements have been made in the past on a myriad of samples including Earth materials, lunar Apollo and analog samples, Mars soil analog samples, some meteorites, and cometary analog samples in support of the Rosetta mission. These measurements have been made in different frequency bands and in various conditions; however, no measurements to date have systematically explored the effect of changes in mineralogy on the complex permittivity, and particularly the loss tangent (tanδ , the ratio of ɛ r'' to ɛ r'). The loss tangent controls the absorption of the signal by the material. Continuing our investigation of the effects of mineralogy on these properties, we will present for the first time results of complex permittivity measurements of the UCF/DSI-CI-2 CI asteroid regolith simulant produced by Deep Space Industries Inc. The simulant is mineralogically similar to the CI meteorite Orgueil. CI meteorites are the most spectrally similar meteorites to (101955) Bennu. Since the simulant has been provided to us un-mixed, several sub-samples will be created containing different amounts of carbon, thus allowing us to systematically investigate the effects of carbon content on the permittivity. In order to remove moisture from our samples, powders are baked at 250°C for 48hrs prior to being loaded into a coaxial transmission line and measured under vacuum. Measurements are made using a sweep of frequencies from 300 KHz to 8.5 GHz.

Mission strategy for cometary exploration in the 1980's

NASA Technical Reports Server (NTRS)

Farquhar, R. W.

1976-01-01

A specific plan for a sequence of cometary intercept missions in the 1980's is reported. Each mission is described in detail and the supporting role of ground based cometary observations is included. Only three launches are required in the proposed mission sequence for six cometary encounters with comets Encke, Giacobini-Zinner, Borrelly and Halley. Cometary ephemerics errors are reduced to very small values because of a favorable earth-comet orbital geometry for Encke 1980, and excellent earth based sighting conditions exist for the entire 1985 mission set.

Could life have evolved in cometary nuclei

NASA Technical Reports Server (NTRS)

Bar-Nun, A.; Lazcano-Araujo, A.; Oro, J.

1981-01-01

The suggestion by Hoyle and Wickramasinghe (1978) that life might have originated in cometary nuclei rather than directly on the earth is discussed. Factors in the cometary environment including the conditions at perihelion passage leading to the ablation of cometary ices, ice temperatures, the absence of an atmosphere and discrete liquid and solid surfaces, weak cometary structure incapable of supporting a liquid core, and radiation are presented as arguments against biopoesis in comets. It is concluded that although the contribution of cometary and meteoritic matter was significant in shaping the earth environment, the view that life on earth originally arose in comets is untenable, and the proposition that the process of interplanetary infection still occurs is unlikely in view of the high specificity of host-parasite relationships.

Are cometary nuclei primordial rubble piles?

NASA Technical Reports Server (NTRS)

Weissman, P. R.

1986-01-01

Whipple's icy conglomerate model for the cometary nucleus has had considerable sucess in explaining a variety of cometary phenomena such as gas production rates and nongravitational forces. However, as discussed here, both observational evidence and theoretical considerations suggest that the cometary nucleus may not be a well-consolidated single body, but may instead be a loosely bound agglomeration of smaller fragments, weakly bonded and subject to occasional or even frequent disruptive events. The proposed model is analogous to the 'rubble pile' model suggested for the larger main-belt asteroids, although the larger cometary fragments are expected to be primordial condensations rather than collisionally derived debris as in the asteroid case. The concept of cometary nuclei as primordial rubble piles is proposed as a modification of the basic Whipple model, not as a replacement for it.

SEM-EDS Analyses of Small Craters in Stardust Aluminum Foils: Implications for the Wild-2 Dust Distribution

NASA Technical Reports Server (NTRS)

Borg, J.; Horz, F.; Bridges, J. C.; Burchell, M. J.; Djouadi, Z.; Floss, C.; Graham, G. A.; Green, S. F.; Heck, P. R.; Hoppe, P.;

Stardust: An overview of the craters in aluminium foils (calibration, classification and particle size distribution)

NASA Astrophysics Data System (ADS)

Burchell, M. J.; Kearsley, A. T.; Wozniakiewicz, P. J.; Hörz, F.; Borg, J.; Graham, G. A.; Leroux, H.; Bridges, J. C.; Bland, P. A.; Bradley, J. P.; Dai, Z. R.; Teslich, N.; See, T.; Warren, J.; Bastien, R.; Hoppe, P.; Heck, P. R.; Huth, J.; Stadermann, F. J.; Floss, C.; Marhas, K.; Stephan, T.; Leitner, J.; Green, S. F.

2007-08-01

The NASA Stardust mission (1) to comet 81P/Wild-2 returned to Earth in January 2006 carrying a cargo of dust captured intact in aerogel and as residue rich craters in aluminium foils (2). Although the aerogel (and its content of dust grains) has gathered most attention, the foils have also been subject to extensive analysis. Many groups contributed to the dimensional characterization of representative populations of foilcraters in the Preliminary Examination and combined with a laboratory calibration this yielded a particle size distribution of the dust encountered during the fly by of the comet (3). The calibration experiments will be described in this paper in detail. They involved using the two stage light gas gun at the University of Kent (4) to impact Stardust grade aluminium foils (from the same batch as used on Stardust) with projectiles at 6.1 km/s (the cometary encounter speed). A variety of projectiles were used to simulate possible cometary dust grain composition, morphology and structure. Prior to the return of Stardust, glass beads were used to provide the initial calibration (5) which was used to obtain the size distribution reported in (3). A range of projectiles of differing density were then used (6) to determine the sensitivity of the results to impactor density (also allowed for in (5)). Subsequently this work has been significantly extended (7) to allow for a greater range of projectile densities and strengths. The work has now been extended further to allow for aggregate impactors which have a high individual grain density, but a low overall bulk density. In addition, the results have been extended down in impactor size from the previous lower limit of 10 microns to 1.5 micron impactor diameter. The application of these new calibration results to the measurement of the cometary dust size distribution will be discussed. It will be shown that the changes are within the range originally presented in (3). The results will be compared to the dust size distribution obtained from the tracks in the aerogel and the combined results contrasted to those obtained with active impact detectors in real time during the cometary encounter (8, 9). At small dust grain sizes (a few microns and below) a significant discrepancy is seen which is still unexplained. References (1) Brownlee D.E. et al., J. Geophys. Res. 108, E10, 8111, 2003. (2) Brownlee D.E. et al., Science 314, 1711 - 1716, 2006. (3) Hörz F. et al., Science 314, 1716 - 1719, 2006. (4) Burchell M.J. et al., Meas. Sci. Technol. 10, 41 - 50, 1999. (5) Kearsley A.T. et al., MAPS 41, 167 - 180, 2006. (6) Kearsley A.T. et al., MAPS 42, 191 - 210, 2007. (7) Kearsley A.T. et al., MAPS submitted, 2007. (8) Tuzzolino A.J. et al., Science 304, 1776 - 1780. (9) Green, S.F. et al., J. Geophys. Res. 109, E12S04, 2004.

Electromagnetic instabilities in solar wind interaction with dusty cometary plasmas

NASA Technical Reports Server (NTRS)

Verheest, Frank; Meuris, Peter

1995-01-01

Dusty plasmas contain charged dust grains which are much more massive than protons, carry high negative charges due to preferential capture of electrons, and do not have a fixed charge. Fluctuations in the grain charges due to liberation or capture of additional electrons and protons translate as mass and momentum losses or gains for these species, which can render linear modes unstable. On the other hand, many authors have addressed the pickup of ions of cometary origin by the solar wind, which for the parallel part is due to relative streaming between cometary and solar wind ions which excites low-frequency electromagnetic turbulence. In the present work we look again at those instabilities by including effects due to the presence of charged dust in the cometary environments. We have investigated several frequency regimes: nonresonant below the cometary watergroup gyrofrequency, nonresonant below the cometary charged dust gyrofrequency (new and interesting but highly unlikely!) and resonant with the cometary watergroup ions. For most parameter ranges either the existing instabilities are enhanced, showing that the presence of charged dust facilitates the cometary ion pickup by the solar wind, or new instabilities have been shown to exist. Similar conclusions might be relevant for other kinds of astrophysical and heliospheric plasmas containing charged dust, as in planetary rings.

Structure and density of cometary nuclei

NASA Astrophysics Data System (ADS)

Weissman, Paul R.; Lowry, Stephen C.

2008-09-01

Understanding the nature of the cometary nucleus remains one of the major problems in solar system science. Whipple’s (1950) icy conglomerate model has been very successful at explaining a range of cometary phenomena, including the source of cometary activity and the nongravitational orbital motion of the nuclei. However, the internal structure of the nuclei is still largely unknown. We review herein the evidence for cometary nuclei as fluffy aggregates or primordial rubble piles, as first proposed by Donn et al. (1985) and Weissman (1986). These models assume that cometary nuclei are weakly bonded aggregations of smaller, icy- onglomerate planetesimals, possibly held together only by self-gravity. Evidence for this model comes from studies of the accretion and subsequent evolution of material in the solar nebula, from observations of disrupted comets, and in particular comet Shoemaker-Levy 9, from measurements of the ensemble rotational properties of observed cometary nuclei, and from recent spacecraft missions to comets. Although the evidence for rubble pile nuclei is growing, the eventual answer to this question will likely not come until we can place a spacecraft in orbit around a cometary nucleus and study it in detail over many months to years. ESA’s Rosetta mission, now en route to comet 67P/Churyumov- Gerasimenko, will provide that opportunity.

Sizing Up the Comets: The NEOWISE Mission Survey of Cometary Nucleii

NASA Astrophysics Data System (ADS)

Bauer, James M.; Grav, Tommy; Mainzer, A. K.; Kramer, Emily; Stevenson, Rachel A.; Fernández, Yanga R.; Masiero, Joseph R.; Nugent, Carolyn R.; Cutri, Roc M.; Sonnett, Sarah; Masci, Frank J.; Meech, Karen J.; Walker, Russel; Lisse, Carey M.; Weissman, Paul R.; Dailey, John W.; Blair, Nathan; Lucas, Andrew; McMillan, Robert S.; Wright, Edward L.

2015-11-01

The NEOWISE mission has provided the largest cometary survey in the infrared. The NEOWISE mission was originally an augmentation to detect solar system objects, and specifically Near Earth Objects, using the Wide-Field Infrared Survey Explorer (WISE) spacecraft. Funded by NASA's Planetary Division through the Near-Earth Object Observation program, NEOWISE detected moving objects throughout the WISE mission[1-2], after which the spacecraft was placed in a state of hybernation. After 32 months, the re-christened NEOWISE spacecraft was returned to a zenith-pointing orbit. On December 23, 2013, the reactivated survey began[3].While NEOWISE's primary purpose was the detection of NEOs, a total of 163 comets have been identified in the prime survey (January 7, 2010 - Febraury 1, 2011), and over 75 have been observed during the NEOWISE reactivate mission to date. These observations have been made at multiple epochs, often when the comets were at large heliocentric distances or exhibited little or no activity. Preliminary analysis of the 25 NEOWISE-discovered comets has indicated possible differences between the size distributions of long-period comets (LPCs) and short-period comets (SPCs) in their raw (not de-biased) samples[4]. On average the observed LPCs were larger than the SPCs. We will discuss the results of the analysis of the larger sample of more than 65 nucleii extracted from the prime mission data, as well as the reactivated mission sample.This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration, as well as data products from NEOWISE, which is a project of JPL/Caltech, funded by the Planetary Science Division of NASA. RS, SS, and EK were supported by the NASA Postdoctoral Program.[1] Cutri et al. 2013 (http://wise2.ipac.caltech.edu/docs/release/allsky/expsup/index.html)[2] Mainzer et al. 2011. ApJ 731, 53.[3] Mainzer et al. 2014. ApJ 792, 30.[4] Bauer, J. M. et al. 2015.The NEOWISE-Discovered Comet Population and the CO+CO2 production rates. ApJ. Submitted.

The application of simple mass spectrometers to planetary sub-surface sampling using penetrators

NASA Astrophysics Data System (ADS)

Sheridan, Simon; Morse, Andrew; Bardwell, Max; Barber, Simeon; Wright, Ian

2010-05-01

Ptolemy is an ion trap based gas-chromatograph isotope ratio mass spectrometer which is on-board the Rosetta Lander [Wright et al., 2006; Todd et al., 2007]. The instrument uses the principles of MODULUS (Methods of Determining and Understanding Light Elements From Unequivocal Stable Isotope Compositions [Pillinger and Wright, 1993], to enable results obtained in space to be interpreted directly in the context of terrestrial analyses of meteorites and returned samples. MODULUS typically involves use of a complex sample processing system to purify and separate individual species from a complex starting sample, allowing analysis by a relatively simple, low resolution, but stable and precise mass spectrometer instrumentation. A number of exciting future mission opportunities are arising where it is unlikely that it will be feasible to incorporate the full MODULUS-style sample processing system. Of particular interest are missions that offer the opportunity to gain access to surface and sub-surface material through the deployment of mass spectrometers from either high-speed penetrator platforms [Smith et al., 2009] or from sub-surface penetrating mole devices deployed by soft landers [Richter et al., 2003]. We will present work aimed at overcoming the resolution restrictions of ion trap mass spectrometers. It is anticipated that this will enable MODULUS style science return from relatively simple instrumentation which is compatible with the future miniaturised sampling platforms currently under consideration for Mars, asteroids, comets and planetary moons. References: Wright I. P., Barber S. J., Morgan G. H., Morse A. D., Sheridan S., Andrews D. J., Maynard J., Yau D., Evans S. T., Leese M. R., Zarnecki J. C., Kent B. J., Waltham N. R., Whalley M. S., Heys S., Drummond D. L., Edeson R. L., Sawyer E. C., Turner R. F., and Pillinger C. T. (2006). Ptolemy - an instrument to measure stable isotopic ratios of key volatiles on a cometary nucleus. Space Science Reviews, 128 (1-4), 363-387. Todd, J.F.J., Barber, S.J., Wright, I.P., Morgan, G.H., Morse, A.D., Sheridan, S., Leese, M.R., Maynard, J., Evans, S.T., Pillinger, C.T. et al. (2007). Ion trap mass spectrometry on a comet nucleus: the Ptolemy instrument and the Rosetta space mission. J. Mass Spectrom. 42,1-10. Pillinger C. T., and Wright I. P. (1993). MODULUS - Methods Of Determining and Understanding Light elements from Unequivocal Stable isotope composition. A type 2 proposal submitted to the RoLand Cometary Lander of the ESA International Rosetta Mission for the provision of Ptolemy - an evolved gas analyser. Richter L., Coste P., Grzesik A., Magnani P., Nadalini R., Neuhaus D., Re E., Romstedt J., Sims M. and Sohl F. (2005). Instrumented Moles for Planetary Subsurface Regolith Studies. Geophysical Research Abstracts, Vol. 7, 08659 A. Smith A.,. Crawford I. A., Gowen R. A., Ball A. J., Barber S. J., Church P., Coates A. J., Gao Y., Griffiths A. D., Hagermann A.,•Joy K. H., Phipps A., Pike W. T., Scott R., Sheridan S., Sweeting M., Talboys D.,•Tong V.,•Wells N.,• Biele J., Chela-Flores J.,•Dabrowski B., Flannagan J., Grande M., Grygorczuk J., Kargl G.,. Khavroshkin O. B.,•Klingelhoefer G., Knapmeyer M.,• Marczewski W., McKenna-Lawlor S.,•Richter L., Rothery D. A., Seweryn K., Ulamec S., Wawrzaszek R., Wieczorek M., Wright I. P. and Sims M. (2009). LunarEX - a proposal to cosmic vision. Exp Astron 23:711-740: DOI 10.1007/s10686-008-9109-6

The cometary and asteroidal origins of meteors

NASA Technical Reports Server (NTRS)

Kresak, L.

1973-01-01

A quantitative examination of the gravitational and nongravitational changes of orbits shows that for larger interplanetary bodies the perturbations by Jupiter strongly predominate over all other effects, which include perturbations by other planets, splitting of comet nuclei and jet effects of cometary ejections. The structure of meteor streams, indicates that the mutual compensation of the changes in individual elements entering the Jacobian integral, which is characteristic for the comets, does not work among the meteoroids. It appears that additional forces of a different kind must exert appreciable influence on the motion of interplanetary particles of meteoroid size. Nevertheless, the distribution of the Jacobian constant in various samples of meteor orbits furnishes some information on the type of their parent bodies and on the relative contribution of individual sources.

The structure of mass-loading shocks. [interaction of solar wind with cometary coma or local interstellar medium using two-fluid model

NASA Technical Reports Server (NTRS)

Zank, G. P.; Khabibrakhmanov, I. KH.; Story, T.

1993-01-01

A new two-fluid model which describes mass loading in the solar wind (e.g., the interaction of the solar wind with a cometary coma or the local interstellar medium) is presented. The self-consistent back-reaction of the mass-loaded ions is included through their effective scattering in low-frequency MHD turbulence and the invocation of a diffusive approximation. Such an approximation has the advantage of introducing self-consistent dissipation coefficients into the governing equations, thereby facilitating the investigation of the internal structure of shocks in mass-loading environments. To illustrate the utility of the new model, we consider the structure of cometary shocks in the hypersonic one-dimensional limit, finding that the incoming solar wind is slowed by both mass loading and the development of a large cometary ion pressure gradient. The shock is broadened and smoothed by the cometary ions with a thickness of the order of the cometary ion diffusion scale.

Space Weathering Impact on Solar System Surfaces and Planetary Mission Science

NASA Technical Reports Server (NTRS)

Cooper, John F.

2011-01-01

We often look "through a glass, darkly" at solar system bodies with tenuous atmospheres and direct surface exposure to the local space environment. Space weathering exposure acts via universal space-surface interaction processes to produce a thin patina of outer material covering, potentially obscuring endogenic surface materials of greatest interest for understanding origins and interior evolution. Examples of obscuring exogenic layers are radiation crusts on cometary nuclei and iogenic components of sulfate hydrate deposits on the trailing hemisphere of Europa. Weathering processes include plasma ion implantation into surfaces, sputtering by charged particles and solar ultraviolet photons, photolytic chemistry driven by UV irradiation, and radiolytic chemistry evolving from products of charged particle irradiation. Regolith structure from impacts, and underlying deeper structures from internal evolution, affects efficacy of certain surface interactions, e.g. sputtering as affected by porosity and surface irradiation dosage as partly attenuated by local topographic shielding. These processes should be regarded for mission science planning as potentially enabling, e.g. since direct surface sputtering, and resultant surface-bound exospheres, can provide in-situ samples of surface composition to ion and neutral mass spectrometers on orbital spacecraft. Sample return for highest sensitivity compOSitional and structural analyses at Earth will usually be precluded by limited range of surface sampling, long times for return, and high cost. Targeted advancements in instrument technology would be more cost efficient for local remote and in-situ sample analysis. More realistic laboratory simulations, e.g. for bulk samples, are needed to interpret mission science observations of weathered surfaces. Space environment effects on mission spacecraft and science operations must also be specified and mitigated from the hourly to monthly changes in space weather and from longer term (e.g., solar cycle) evolution of space climate. Capable instrumentation on planetary missions can and should be planned to contribute to knowledge of interplanetary space environments. Evolving data system technologies such as virtual observatories should be explored for more interdisciplinary application to the science of planetary surface, atmospheric, magnetospheric, and interplanetary interactions.

The Philae lander mission and science overview.

PubMed

Boehnhardt, Hermann; Bibring, Jean-Pierre; Apathy, Istvan; Auster, Hans Ulrich; Ercoli Finzi, Amalia; Goesmann, Fred; Klingelhöfer, Göstar; Knapmeyer, Martin; Kofman, Wlodek; Krüger, Harald; Mottola, Stefano; Schmidt, Walter; Seidensticker, Klaus; Spohn, Tilman; Wright, Ian

2017-07-13

The Philae lander accomplished the first soft landing and the first scientific experiments of a human-made spacecraft on the surface of a comet. Planned, expected and unexpected activities and events happened during the descent, the touch-downs, the hopping across and the stay and operations on the surface. The key results were obtained during 12-14 November 2014, at 3 AU from the Sun, during the 63 h long period of the descent and of the first science sequence on the surface. Thereafter, Philae went into hibernation, waking up again in late April 2015 with subsequent communication periods with Earth (via the orbiter), too short to enable new scientific activities. The science return of the mission comes from eight of the 10 instruments on-board and focuses on morphological, thermal, mechanical and electrical properties of the surface as well as on the surface composition. It allows a first characterization of the local environment of the touch-down and landing sites. Unique conclusions on the organics in the cometary material, the nucleus interior, the comet formation and evolution became available through measurements of the Philae lander in the context of the Rosetta mission.This article is part of the themed issue 'Cometary science after Rosetta'. © 2017 The Author(s).

Modeling Cometary Coma with a Three Dimensional, Anisotropic Multiple Scattering Distributed Processing Code

NASA Technical Reports Server (NTRS)

Luchini, Chris B.

1997-01-01

Development of camera and instrument simulations for space exploration requires the development of scientifically accurate models of the objects to be studied. Several planned cometary missions have prompted the development of a three dimensional, multi-spectral, anisotropic multiple scattering model of cometary coma.

Cometary kilometric radio waves and plasma waves correlated with ion pick-up effect at Comet Halley

NASA Technical Reports Server (NTRS)

Oya, H.; Morioka, A.; Miyake, W.; Smith, E. J.; Tsurutani, B. T.

1985-01-01

Bow-shock movements at Comet Halley are inferred from the discrete spectra of the cometary kilometric radiation (30-195 kHz); the observed emissions can be interpreted as being generated and propagating from the moving shock. The shock motion is possibly associated with the time variation of the solar wind and cometary outgassing. It is concluded that these plasma wave phenomena are manifestations of ion pick-up processes, which occur even in a remote region 7 million to 10 million km from the cometary nucleus.

Cometary dust: the diversity of primitive refractory grains

PubMed Central

Ishii, H. A.

2017-01-01

Comet dust is primitive and shows significant diversity. Our knowledge of the properties of primitive cometary particles has expanded significantly through microscale investigations of cosmic dust samples (anhydrous interplanetary dust particles (IDPs), chondritic porous (CP) IDPs and UltraCarbonaceous Antarctic micrometeorites, Stardust and Rosetta), as well as through remote sensing (Spitzer IR spectroscopy). Comet dust are aggregate particles of materials unequilibrated at submicrometre scales. We discuss the properties and processes experienced by primitive matter in comets. Primitive particles exhibit a diverse range of: structure and typology; distribution of constituents; concentration and form of carbonaceous and refractory organic matter; Mg- and Fe-contents of the silicate minerals; sulfides; existence/abundance of type II chondrule fragments; high-temperature calcium–aluminium inclusions and ameboid-olivine aggregates; and rarely occurring Mg-carbonates and magnetite, whose explanation requires aqueous alteration on parent bodies. The properties of refractory materials imply there were disc processes that resulted in different comets having particular selections of primitive materials. The diversity of primitive particles has implications for the diversity of materials in the protoplanetary disc present at the time and in the region where the comets formed. This article is part of the themed issue ‘Cometary science after Rosetta’. PMID:28554979

Cometary jets in interaction with the solar wind: a hybrid simulation study

NASA Astrophysics Data System (ADS)

Wiehle, Stefan; Motschmann, Uwe; Gortsas, Nikolaos; Mueller, Joachim; Kriegel, Hendrik; Koenders, Christoph; Glassmeier, Karl-Heinz

The effect of a cometary jet on the solar wind interaction is studied using comet 67P/Churyumov-Gerasimenko as case study. This comet is the target of the Rosetta-mission which will arrive in 2014. Observations suggest that cometary outgassing is confined to only a few percent of the cometary surface; thus, the measurement of jets is expected. Most former comet simulations did not attend to this fact and used an isotropic outgassing scheme or simplified outgassing patterns. Here, a single sun-facing jet is set to be the only source of cometary gas produc-tion. Using an analytic profile, this outgassing jet was implemented in a hybrid simulation code which treats protons and cometary heavy ions as particles and electrons as massless fluid. In a simulation series, the geometric parameters of the jet were varied to study the effect of different opening angles while the integrated outgassing rate remained constant. It was shown that the resulting solar wind interaction is highly dependent on the geometry of the jet. The plasma-structures like the solar wind pile-up found in the situation with isotropic outgassing are moved more and more sunward as the opening angle of the jet decreases. Furthermore, the cometary ion tail shows some kind of splitting which is not known from isotropic models.

Progress in our understanding of cometary dust tails

NASA Technical Reports Server (NTRS)

Sekanina, Z.

1976-01-01

Various analytical techniques are employed to analyze observations on the character, composition, and size distribution of solid particles in cometary dust tails. Emphasized is the mechanical theory that includes solar gravitational attraction and solar radiation pressure to explain dust particle motions in cometary tails, as well as interactions between dust and plasma.

Cometary exploration in the shuttle era

NASA Technical Reports Server (NTRS)

Farquhar, R. W.; Wooden, W. H., II

1978-01-01

A comprehensive program plan for cometary exploration in the 1980-2000 time frame is proposed. Plans for ground-based observations, a Spacelab cometary observatory, and the Space Telescope are included in the observational program. The cometary mission sequence begins with a dual-spacecraft flyby of Halley's comet. The nominal mission strategy calls for a simultaneous launch of two spacecraft towards an intercept with Halley in March 1986. After the Halley encounter, the spacecraft are retargeted: one to intercept comet Borrelly in January 1988 and the other to intercept comet Tempel-2 in September 1988. The additional cometary intercepts are accomplished by utilizing a novel Earth-swingby technique. The next mission in the cometary program plan, a rendezvous with Encke's comet, is scheduled for launch in early 1990. It is planned to rendezvous with Encke in September 1992 at a heliocentric distance of 4 AU. Following this near-aphelion rendezvous, the spacecraft will remain with with Encke through the next two perihelion passages in February 1994 and May 1997. The rendezvous mission will be terminated about seven months after the second perihelion passage.

Cometary Plasma Probed by Rosetta

NASA Astrophysics Data System (ADS)

Galand, Marina; Vigren, Erik; Raghuram, Susarla; Schwartz, Steve; Eriksson, Anders; Edberg, Niklas; Lebreton, Jean-Pierre; Henri, Pierre; Burch, Jim; Fuselier, Stephen; Haessig, Myrtha; Mandt, Kathy; Altwegg, Kathrin; Tzou, Chia-You

2015-04-01

In Fall 2014, comet 67P/Churyumov-Gerasimenko, the main target of the Rosetta mission, was at 3 AU from the Sun. Its outgassing rate was only of the order of 5×1025 s-1 based on Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) / Cometary Pressure Sensor (COPS). Despite such a thin coma, a plasma of cometary origin has been detected by Rosetta Plasma Consortium (RPC) sensors and ROSINA/ Double Focusing Mass Spectrometer (DFMS). Close to the comet they have revealed the presence of a cometary ionosphere, with a hot electron population, consistent with the deposition of Extreme UltraViolet (EUV) solar radiation. We will present a comparison between RPC sensors and an energy deposition model in terms of suprathermal electron intensities [RPC/ Ion and Electron Sensor (IES)] and electron temperature and density [RPC/ LAngmuir Probe (LAP) and RPC/ Mutual Impedance Probe (MIP)]. We will also compare ion composition among the main species, between our ionospheric model and ROSINA/DFMS. We will discuss effects of the space environment on the cometary plasma. Finally, we will highlight any evolution in the cometary plasma as the comet is getting closer to perihelion.

Models for Cometary Comae Containing Negative Ions

NASA Technical Reports Server (NTRS)

Cordiner, M. A.; Charnley, S. B.

2012-01-01

The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions O(-), OH(-), C(-), CH(-) and CN(-) have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu [I]. Organic molecular anions such as C4H(-) and C6H(-) are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been fully explored. We present details of our new models for the chemistry of cometary comae that include atomic and molecular anions. We calculate the impact of these anions on the charge balance and examine their importance for cometary coma chemistry.

Isotopic compositions of cometary matter returned by Stardust.

PubMed

McKeegan, Kevin D; Aléon, Jerome; Bradley, John; Brownlee, Donald; Busemann, Henner; Butterworth, Anna; Chaussidon, Marc; Fallon, Stewart; Floss, Christine; Gilmour, Jamie; Gounelle, Matthieu; Graham, Giles; Guan, Yunbin; Heck, Philipp R; Hoppe, Peter; Hutcheon, Ian D; Huth, Joachim; Ishii, Hope; Ito, Motoo; Jacobsen, Stein B; Kearsley, Anton; Leshin, Laurie A; Liu, Ming-Chang; Lyon, Ian; Marhas, Kuljeet; Marty, Bernard; Matrajt, Graciela; Meibom, Anders; Messenger, Scott; Mostefaoui, Smail; Mukhopadhyay, Sujoy; Nakamura-Messenger, Keiko; Nittler, Larry; Palma, Russ; Pepin, Robert O; Papanastassiou, Dimitri A; Robert, François; Schlutter, Dennis; Snead, Christopher J; Stadermann, Frank J; Stroud, Rhonda; Tsou, Peter; Westphal, Andrew; Young, Edward D; Ziegler, Karen; Zimmermann, Laurent; Zinner, Ernst

2006-12-15

Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single (17)O-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is (16)O-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion.

Cometary pick-up ions observed near Giacobini-Zinner

NASA Technical Reports Server (NTRS)

Gloeckler, G.; Hovestadt, D.; Ipavich, F. M.; Scholer, M.; Klecker, B.

1986-01-01

The number and energy density of cometary water-group ions observed near Comet Giacobini-Zinner are derived using the rest-frame distribution functions. The data reveal that density profiles of inbound and outbound passes and their shape correlate with pick-up ion production model predictions. The lose rate and production rate of water-group cometary molecules calculated from predicted and measured density profiles are 2 x 10 to the -6th/sec and 2.6 x 10 to the 28th/sec respectively. The shapes of the distribution functions are examined to study the solar wind/cometary ions interaction process.

Cometary pick-up ions observed near Giacobini-Zinner

NASA Astrophysics Data System (ADS)

Gloeckler, G.; Hovestadt, D.; Ipavich, F. M.; Scholer, M.; Klecker, B.; Galvin, A. B.

1986-03-01

The number and energy density of cometary water-group ions observed near Comet Giacobini-Zinner are derived using the rest-frame distribution functions. The data reveal that density profiles of inbound and outbound passes and their shape correlate with pick-up ion production model predictions. The lose rate and production rate of water-group cometary molecules calculated from predicted and measured density profiles are 2 x 10 to the -6th/sec and 2.6 x 10 to the 28th/sec respectively. The shapes of the distribution functions are examined to study the solar wind/cometary ions interaction process.

Roadmap of next generation minor body explorations in Japan

NASA Astrophysics Data System (ADS)

Yano, H.

As of the early 2004, more than 250,000 minor bodies in the solar system have been detected. Among them, several thousands of asteroids are determined orbital elements well and even multi-band spectroscopic observation from ground enables us to classify taxonomy of them in statistically valid numbers. On the other hand, there have been several 10,000s of meteorite and cosmic dust samples already collected in the terrestrial environment. Thus, asteroid studies in statistical manners are practically conducted by ground observation and meteoritic analyses. It is a unique contribution of planetary exploration to provide the ground truth which bridges between abundant database of the ground observation and that of the meteoritic analyses, by bringing samples back to the Earth from a particular asteroid investigated in-situ. In May 2003, JAXA/ISAS successfully launched the Hayabusa (MUSES-C) spacecraft as the first kind of such minor body exploration, which will bring surface samples of an S-type NEO back to the Earth in mid 2007. Many of Japanese planetary scientists hope to advance such sample return strategies as their new expertise in the post-Hayabusa era. Now the ISAS new minor body exploration working group is about to start. Mission candidates include multiple sample returns from known spectra asteroids, in order to complete the asteroid taxonomy-meteoritic connection issue as early as possible (next 10-20 years) with possible international collaborations. One of such ideas is the multiple rendezvous sample return mission to known spectra NEOs of both primitive types (i.e., C, P/D) and differentiated types (e.g., V, M). Another is fly-by investigation and sample collection of multiple asteroids that belong to a single main-belt family. It will provide direct information of the interior as well as collisional history of their parent body, a refractory planetesimal disrupted by mutual collisions in the early stage of the Solar System evolution. One scenario targets the Koronis family including the Ida-Gaspra system, the only family asteroid visited by spacecraft in the past, and its dust band. Another aims the Nysa-Polana Family, which has several spectral types. Also what ISAS is planning is the solar powered sail mission which will make fly-by observations of main belt asteroids as well as Jovian Trojan asteroids, most of which are D-type asteroids with the absence of water absorption lines. Understanding generic connections among the Trojans, short-period cometary nucleus and the outermost D-type asteroids in the main belt may be a clue of how to distinguish between asteroids and comets, depending upon where they originated with respect to heliocentric distance in the early solar system.

Shapes of cometary isophotes with Maxwellian distribution of initial velocities for neutral molecules

NASA Astrophysics Data System (ADS)

Žáček, P.; Wolf, M.

2017-10-01

This paper contains necessary modification of Bessel's equations for the axial cometary syndyne. This correction provides the accurate values of molecular acceleration in a cometary tail and precise values of decay constants for radiating molecules and their lifetimes. In consequence the hypothesis of the predissociation of molecules seems to be useless.

The Amazing Apparition of 73P/Schwassmann-Wachmann 3 in 2006

NASA Astrophysics Data System (ADS)

Weaver, Harold A.

2006-09-01

Most comets may meet their ultimate demise as a result of catastrophic fragmentation events, and that process was prominently displayed during the 2006 apparition of comet 73P/Schwassmann-Wachmann 3 (73P/SW3). This Jupiter-family comet with an orbital period of 5.4 yr was discovered when it passed within 0.06 AU of the Earth during the spring of 1930. However, it was subsequently lost until 1979 when it arrived at perihelion about 5 weeks later than predicted, probably owing to a close approach to Jupiter in 1965. Several remarkable outbursts in dust and gas activity were observed during the 1995 apparition, and four separate fragments were clearly detected and followed for several months. The solar elongation angle was unfavorably small, and the geocentric distance rather large, throughout the 2000-2001 apparition, and only two fragments were definitely detected then. Thus, it was with considerable uncertainty that cometary researchers approached the 2006 apparition, when the geometry would be nearly as favorable as for the discovery apparition with the comet passing within 0.08 AU during May 2006. Owing to the extremely fragile nature of cometary nuclei in general, and the previously recorded breakup of 73P/SW3, there was no guarantee that any fragment would return this year. To the delight of professional and amateur astronomers alike, the 2006 apparition of 73P/SW3 was nothing short of spectacular, as over 60 new fragments were detected and monitored during the late-winter and spring. Ground-based and space-based observatories, large and small, intensively monitored 73P/SW3 to document the disintegration of its nuclei and to measure the composition of its larger fragments. This paper will review the scientific results obtained during the 2006 apparition of 73P/SW3 and reflect on what the disintegration of this comet reveals about the nature of cometary nuclei.

Three Dimensional Explicit Model for Cometary Tail Ions Interactions with Solar Wind

NASA Astrophysics Data System (ADS)

Al Bermani, M. J. F.; Alhamed, S. A.; Khalaf, S. Z.; Ali, H. Sh.; Selman, A. A.

2009-06-01

The different interactions between cometary tail and solar wind ions are studied in the present paper based on three-dimensional Lax explicit method. The model used in this research is based on the continuity equations describing the cometary tail-solar wind interactions. Three dimensional system was considered in this paper. Simulation of the physical system was achieved using computer code written using Matlab 7.0. The parameters studied here assumed Halley comet type and include the particle density rho, the particles velocity v, the magnetic field strength B, dynamic pressure p and internal energy E. The results of the present research showed that the interaction near the cometary nucleus is mainly affected by the new ions added to the plasma of the solar wind, which increases the average molecular weight and result in many unique characteristics of the cometary tail. These characteristics were explained in the presence of the IMF.

Anions in Cometary Comae

NASA Technical Reports Server (NTRS)

Charnley, Steven B.

2011-01-01

The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions 0-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydro dynamical model of Rodgers & Charnley (2002), we investigate the role of large carbon-chain anions in cometary coma chemistry. We calculate the effects of these anions on coma thermodynamics, charge balance and examine their impact on molecule formation.

Astrophysics with Extraterrestrial Materials

NASA Astrophysics Data System (ADS)

Nittler, Larry R.; Ciesla, Fred

2016-09-01

Extraterrestrial materials, including meteorites, interplanetary dust, and spacecraft-returned asteroidal and cometary samples, provide a record of the starting materials and early evolution of the Solar System. We review how laboratory analyses of these materials provide unique information, complementary to astronomical observations, about a wide variety of stellar, interstellar and protoplanetary processes. Presolar stardust grains retain the isotopic compositions of their stellar sources, mainly asymptotic giant branch stars and Type II supernovae. They serve as direct probes of nucleosynthetic and dust formation processes in stars, galactic chemical evolution, and interstellar dust processing. Extinct radioactivities suggest that the Sun's birth environment was decoupled from average galactic nucleosynthesis for some tens to hundreds of Myr but was enriched in short-lived isotopes from massive stellar winds or explosions shortly before or during formation of the Solar System. Radiometric dating of meteorite components tells us about the timing and duration over which solar nebula solids were assembled into the building blocks of the planets. Components of the most primitive meteoritical materials provide further detailed constraints on the formation, processing, and transport of material and associated timescales in the Sun's protoplanetary disk as well as in other forming planetary systems.

Comparison of the oxidation state of Fe in comet 81P/Wild 2 and chondritic-porous interplanetary dust particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogliore, Ryan C.; Butterworth, Anna L.; Fakra, Sirine C.

2010-07-16

The fragile structure of chondritic-porous interplanetary dust particles (CP-IDPs) and their minimal parent-body alteration have led researchers to believe these particles originate in comets rather than asteroids where aqueous and thermal alterations have occurred. The solar elemental abundances and atmospheric entry speed of CP-IDPs also suggest a cometary origin. With the return of the Stardust samples from Jupiter-family comet 81P/Wild 2, this hypothesis can be tested. We have measured the Fe oxidation state of 15 CP-IDPs and 194 Stardust fragments using a synchrotron-based x-ray microprobe. We analyzed {approx}300 ng of Wild 2 material - three orders of magnitude more materialmore » than other analyses comparing Wild 2 and CP-IDPs. The Fe oxidation state of these two samples of material are > 2{sigma} different: the CP-IDPs are more oxidized than the Wild 2 grains. We conclude that comet Wild 2 contains material that formed at a lower oxygen fugacity than the parent-body, or parent bodies, of CP-IDPs. If all Jupiter-family comets are similar, they do not appear to be consistent with the origin of CP-IDPs. However, comets that formed from a different mix of nebular material and are more oxidized than Wild 2 could be the source of CP-IDPs.« less

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

NASA Technical Reports Server (NTRS)

1991-01-01

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

Review of investigations performed in the USSR on close approaches of comets to Jupiter and the evolution of cometary orbits

NASA Technical Reports Server (NTRS)

Kazimirchak-Polonskaya, E. I.

1976-01-01

Methods are reviewed for calculating the evolution of cometary orbits with emphasis on the orbital changes that take place when comets pass within the spheres of action of giant planets. Topics discussed include: differences and difficulties in methods used for the calculation of large perturbations by Jupiter; the construction of numerical theories of motion covering the whole period of observations of each comet, allowing for planetary perturbations and the effects of nongravitational forces; and investigations of the evolution of cometary orbits over the 400 year interval 1660-2060. The classical theory of cometary capture is briefly discussed.

The Size Distribution of Jupiter-Family Cometary Nuclei

NASA Technical Reports Server (NTRS)

Weissman, Paul R.; Lowry, Stephen C.

2003-01-01

Introduction: We are continuing our program to determine the size distribution of cometary nuclei. We have compiled a catalog of 105 measurements of 57 cometary nuclei, drawn from the general literature, from our own program of CCD photometry of distant cometary nuclei (Lowry and Weissman), and from unpublished observations by colleagues. We model the cumulative size distribution of the nuclei as a power law. Previous determinations of the size distribution slope do not agree. Fernandez et al. found a slope of alpha = 2.65+/-0.25 whereas Lowry et al. and Weissman and Lowry each found a slope of alpha = 1.60+/-0.10.

Infrared molecular emissions from comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.; Mumma, M. J.

1983-01-01

The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued.

P/2006 HR30 (Siding Spring): A Low-activity Comet in Near-Earth Space

NASA Technical Reports Server (NTRS)

Hicks, Michael D.; Bauer, James M.

2007-01-01

The low cometary activity of P/2006 HR30 (Siding Spring) allowed a unique opportunity to study the nucleus of a periodic comet while near perihelion. P/2006 HR30 was originally targeted as a potential extinct comet, and we measured spectral reflectance and dust production using long-slit CCD spectroscopy and wide-field imaging obtained at the Palomar Mountain 200 inch telescope on 2006 August 3 and 4. The dust production Afp = 19.7 +/- 0.4 cm and mass-loss rate Q(dust) 4.1 +/- 0.1 kg/sec of the comet were approximately 2 orders of magnitude dust less than 1P/Halley at similar heliocentric distance. The VRI colors derived from the spectral reflectance were compared to Kuiper Belt objects, Centaurs, and other cometary nuclei. We found that the spectrum of P/2006 HR30 was consistent with other comets. However, the outer solar system bodies have a color distribution statistically distinct from cometary nuclei. It is our conjecture that cometary activity, most likely the reaccretion of ejected cometary dust, tends to moderate and mute the visible colors of the surface of cometary nuclei.

Cometary coma chemical composition (C4) mission. [Abstract only

NASA Technical Reports Server (NTRS)

Carle, G. C.; Clark, B. C.; Niemann, H. B.; Alexander, M.; Knocke, P. C.; O'Hara, B. J.

1994-01-01

Cometary missions are of enormous fundamental importance for many different space science disciplines, including exobiology. Comets are presumed relics of the earliest, most primitive material in the solar nebula and are related to the planetesimals. They undoubtedly provided a general enrichment of volatiles to the inner solar system (contributing to atmospheres and oceans) and may have been key to the origin of life. A Discovery class, comet rendezvous mission, the Cometary Coma Chemical Composition (C4) Mission, was selected for further study by NASA earlier this year. The C4 Mission is a highly focused and usefully-limited subset of the Cometary Rendezvous Asteroid Flyby (CRAF) Mission, concentrating exclusively on measurements which will lead to an understanding of the chemical composition and make-up of the cometary nucleus. The scientific goals of the Cometary Coma Chemical Composition (C4) Mission are to rendezvous with a short-period comet and (1) to determine the elemental, chemical, and isotopic composition of the nucleus and (2) to characterize the chemical and isotopic nature of its atmosphere. Further, it is a goal to obtain preliminary data on the development of the coma (dust and gas composition) as a function of time and orbital position.

Geochemical evidences for two chondritic-like cometary or asteroidal impacts before and at the K/T boundary

NASA Technical Reports Server (NTRS)

Liu, Y.-G.; Schmitt, R. A.

1993-01-01

A number of geological and palaeontological evidences support multiple impacts of cometary showers within a short time (approximately 1-3 Ma) and their connection with mass extinctions. Observations include clustered crater ages, stratigraphic horizons of impact ejecta closely spaced in time, and evidence for stepwise mass extinctions spanning intervals of 1-3 Ma. For the K/T boundary, three candidates, Popigai, Manson, and Yucatan, have been proposed as impact craters. Two distinct strata at the K/T boundary in western North America have been interpreted as evidence for two sequential impacts. If multiple impacts occurred within a time span of about 1 Ma then multiple Ir enrichments should be observed. DSDP Hole 577B on the Shatsky Plateau in the northern Pacific at K/T time is the first site. Samples contain approximately greater than 97 percent CaCO3, which exhibit clear chemical signals associated with asteroidal/cometary impact. Ir, Fe, and Cr data are presented. From the Th-normalized data, two satellite peaks below the major peak at 78 cm and 81 cm of 577B-1-4 are clearly shown. The major Ir peak (K/T boundary) is at 72 cm. Fe and Cr, from C1-like impactor ejecta fallout, also show two peaks at the same positions. For hole 738C on the southern Kerguelen Plateau, Ir values reach a peak concentration of 18 ppb in the clay layer at 96.0-96.2 cm in section 20R-5, and gradually tail off. In the sample 115 cm above the boundary, Ir concentrations have still not reached background levels. From the Ir peak downward to the lowermost sample analyzed at 102 cm, the Ir concentration is still as high as 1.7 ppb. From the Th-normalized data, we observe a small Ir/Th peak at 100-101 cm. Though this peak is within the error margin, the trend is clear. Fe and Cr exhibit the same pattern. The third case is Hole 690C on the Queen Maud Ridge. Again, the Ir/Th plot indicates the strong possibility of satellite peaks at approximately 52 cm. The main peak is at 39-40 cm. For the Stevns Klint K/T boundary layers, the stratification of trace elements appears threefold with peak concentrations in sublayers A1, A3, and B2 for different element groups, including Ir. C1 ratios for many siderophile elements found in combined layers III and IV, corresponding to layers A, B, C, and D, strongly support the impact hypothesis. Also, multiple Ir anomalies in the K/T section at Lattengebirge, Bavarian Alps are reported. Recent works on Ni-rich spinels and Ir at the K/T boundaries clearly establish cometary/asteroidal impacts at the K/T boundary. Lastly, cometary showers can explain the enhanced Ir contents over approximately a 1 Ma interval in Gubbio shales.

Tidal Effects on the Oort Cloud Comets and Dynamics of the Sun in the Spiral Arms of the Galaxy

NASA Astrophysics Data System (ADS)

De Biasi, Alice

2014-01-01

The Solar System presents a complex dynamical structure and is not isolated from the Galaxy. In particular the comet reservoir of our planetary system, the Oort cloud, is extremely sensitive to the the galactic environment due to its peripheral collocation inside the Solar System. In this framework, the growing evidences about a possible migration of the Sun open new research scenarios relative to the effects that such kind of migration might induce on the cometary motion. Following several previous studied, we identified the spiral arm structure as the main perturbation that is able to produce an efficient solar migration through the disk. Widening the classical model for the spiral arms, provided by Lin& Shu to a 3D formalism, we verified the compatibility between the presence of the spiral perturbation and a significant solar motion for an inner Galactic position to the current one, in agreement with the constrains in position, velocity and metallicity due to the present conditions of our star. The main perturbers of the Oort cloud, the close stellar passages and the tidal field of the Galaxy, might be both affected by the variation of Galactic environment that the solar migration entails. Despite that, in order to isolate the effects to the two different perturbators, we decided to focus our attention only on the Galactic tide. The perturbation due to the spiral structure was included in the study on the cometary motion, introducing the solar migration and adding the direct presence of the non-axisymmetric component in the Galactic potential of the tidal field. The results show a significant influence of the spiral arm in particular on cometary objects belonged to the outer shell of the Oort cloud, for which provides an injection rate three times bigger than the integration performed without the spiral arms. The introduction of the spiral perturbation seems to bolster the planar component of the tide, indeed it produces the most significant variation of the perihelion distance for moderate inclination orbits with respect to the plane. The peak for the cometary injections has been registered between 6 and 7 kpc. If this evidence will be confirmed by more realistic cometary sample, it might involve a redefinition of the habitability edges in the Galaxy (GHZ). In particular regions not precluded to the formation of life, may compromise the development of the life with a high cometary impact risk

Recent researches into solid bodies and magnetic fields in the solar system; Proceedings of the Topical Meeting and Symposium, Ottawa, Canada, May 16-June 2, 1982

NASA Technical Reports Server (NTRS)

Vette, J. I. (Editor); Runcorn, S. K. (Editor); Gruen, E. (Editor); Mcdonnell, J. A. M.

1982-01-01

Topics discussed include the magnetic history of the early solar system, impact processes in solid bodies (e.g., meteoroids and asteroids), and topics related to cometary missions. The section devoted to cometary missions lays particular stress on missions to Comet Halley; attention is given to such aspects of these missions as the investigation of hypervelocity impact on the Giotto Halley mission dust shield, the detection of energetic cometary and solar particles by the EPONA instrument on the Giotto mission, the dust hazard near Comet Halley in regard to the Vega project, and cometary ephemerides for spacecraft flyby missions.

Infrared molecular emissions from comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.; Mumma, M. J.

1984-01-01

The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued. Previously announced in STAR as N83-30344

Physics of Intact Capture of Cometary Coma Dust Samples

NASA Astrophysics Data System (ADS)

Anderson, William

2011-06-01

In 1986, Tom Ahrens and I developed a simple model for hypervelocity capture in low density foams, aimed in particular at the suggestion that such techniques could be used to capture dust during flyby of an active comet nucleus. While the model was never published in printed form, it became known to many in the cometary dust sampling community. More sophisticated models have been developed since, but our original model still retains superiority for some applications and elucidates the physics of the capture process in a more intuitive way than the more recent models. The model makes use of the small value of the Hugoniot intercept typical of highly distended media to invoke analytic expressions with functional forms common to fluid dynamics. The model successfully describes the deceleration and ablation of a particle that is large enough to see the foam as a low density continuum. I will present that model, updated with improved calculations of the temperature in the shocked foam, and show its continued utility in elucidating the phenomena of hypervelocity penetration of low-density foams.

Asteroid-comet continuum objects in the solar system.

PubMed

Hsieh, Henry H

2017-07-13

In this review presented at the Royal Society meeting, 'Cometary science after Rosetta', I present an overview of studies of small solar system objects that exhibit properties of both asteroids and comets (with a focus on so-called active asteroids). Sometimes referred to as 'transition objects', these bodies are perhaps more appropriately described as 'continuum objects', to reflect the notion that rather than necessarily representing actual transitional evolutionary states between asteroids and comets, they simply belong to the general population of small solar system bodies that happen to exhibit a continuous range of observational, physical and dynamical properties. Continuum objects are intriguing because they possess many of the properties that make classical comets interesting to study (e.g. relatively primitive compositions, ejection of surface and subsurface material into space where it can be more easily studied, and orbital properties that allow us to sample material from distant parts of the solar system that would otherwise be inaccessible), while allowing us to study regions of the solar system that are not sampled by classical comets.This article is part of the themed issue 'Cometary science after Rosetta'. © 2017 The Author(s).

'Peeling a comet': Layering of comet analogues

NASA Astrophysics Data System (ADS)

Kaufmann, E.; Hagermann, A.

2017-09-01

Using a simple comet analogue we investigate the influence of subsurface solar light absorption by dust. We found that a sample initially consisting of loose water ice grains and carbon particles becomes significantly harder after being irradiated with artificial sunlight for several hours. Further a drastic change of the sample surface could be observed. These results suggests that models should treat the nucleus surface as an interactive transitional zone to better represent cometary processes.

The mini-CIDEX GC/IMS: Analysis of cometary ice and dust

NASA Technical Reports Server (NTRS)

Kojiro, Daniel R.; Carle, Glenn C.; Humphry, Donald E.; Shao, Maxine; Takeuchi, Nori

1995-01-01

Comets are recognized as among the most scientifically important objects in the solar system. They are presumed relics of the early primitive material in the solar nebula and are believed to have provided a general enrichment of volatiles to the inner solar system. The Cometary Coma Chemical Composition (C4) Mission, a proposed Discovery-Class Mission, will analyze materials released into the coma, providing information leading to the understanding of the chemical composition and make-up of the cometary nucleus. As one of two scientific instruments in the C4 spacecraft, an advanced and streamlined version of the Cometary Ice and Dust Experiment (CIDEX), a mini-CIDEX, will employ an X-Ray Fluorescence (XRF) spectrometer to determine bulk elemental composition of cometary dust grains and a Gas Chromatograph/Ion Mobility Spectrometer (GC/IMS) for determination of the molecular composition of dust and ices following stepwise pyrolysis and combustion. A description of the mini-CIDEX IMS will be provided as well as data from analyses conducted using the mini-CIDEX breadboard instrument.

Survey for Ortho-to-Para Abundance Ratios (OPRs) of NH2 in Comets: Revisit to the Meaning of OPRs of Cometary Volatiles

NASA Astrophysics Data System (ADS)

Kawakita, Hideyo; Shinnaka, Yoshiharu; Jehin, Emmanuel; Decock, Alice; Hutsemekers, Damien; Manfroid, Jean

2016-10-01

Since molecules having identical protons can be classified into nuclear-spin isomers (e.g., ortho-H2O and para-H2O for water) and their inter-conversions by radiative and non-destructive collisional processes are believed to be very slow, the ortho-to-para abundance ratios (OPRs) of cometary volatiles such as H2O, NH3 and CH4 in coma have been considered as primordial characters of cometary molecules [1]. Those ratios are usually interpreted as nuclear-spin temperatures although the real meaning of OPRs is in strong debate. Recent progress in laboratory studies about nuclear-spin conversion in gas- and solid-phases [2,3] revealed short-time nuclear-spin conversions for water, and we have to reconsider the interpretation for observed OPRs of cometary volatiles. We have already performed the survey for OPRs of NH2 in more than 20 comets by large aperture telescopes with high-resolution spectrographs (UVES/VLT, HDS/Subaru, etc.) in the optical wavelength region [4]. The observed OPRs of ammonia estimated from OPRs of NH2, cluster around ~1.1 (cf. 1.0 as a high-temperature limit), indicative of ~30 K as nuclear-spin temperatures. We present our latest results for OPRs of cometary NH2 and discuss about the real meaning of OPRs of cometary ammonia, in relation to OPRs of water in cometary coma. Chemical processes in the inner coma may play an important role to achieve un-equilibrated OPRs of cometary volatiles in coma.This work was financially supported by MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018 (No. S1411028) (HK) and by Graint-in-Aid for JSPS Fellows, 15J10864 (YS).References:[1] Mumma & Charnley, 2011, Annu. Rev. Astro. Astrophys. 49, 471.[2] Hama & Watanabe, 2013, Chem. Rev. 113, 8783.[3] Hama et al., 2008, Science 351, 6268.[4] Shinnaka et al., 2011, ApJ 729, 81.

Three dimensional Particle-in-Cell (PIC) simulations of the 67P environment

NASA Astrophysics Data System (ADS)

Divin, Andrey; Deca, Jan; Henri, Pierre; Horanyi, Mihaly; Markidis, Stefano; Lapenta, Giovanni; Olshevsky, Vyacheslav; Eriksson, Anders

2017-04-01

ESA's Rosetta orbiter spacecraft escorted comet 67P/Churyumov-Gerasimenko for two years, carrying 21 scientific instruments. Five of those were dedicated to plasma measurements. The mission revealed for the first time, and in unprecedented detail, the fascinating evolution of a comet and its interaction with our Sun as it races along its 6.45yr elliptical orbit around the Sun. Using a self-consistent 3-D fully kinetic electromagnetic particle-in-cell approach, we focus on the global cometary environment and, in particular, on the collisionless electron-kinetic interaction. We include cometary ions and electrons produced by the ionization of the outgassing cometary atmosphere in addition to the solar wind ion and electron plasma flow. We approximate mass-loading of the cold cometary ion and electron populations using a 1/r relation with distance to the comet with a total neutral production rate of Q = 1026 s-1. Our simulation results disentangle for the first time the kinetic ion and electron dynamics of the solar wind interaction with a weakly outgassing comet. The simulated global structure of the solar wind-comet interaction confirms the results reported in hybrid simulations of the induced cometary magnetosphere. Moreover, we show that cometary and solar wind electrons neutralize the solar wind protons and cometary ions, respectively, in the region of influence around the comet, representing to first order a four-fluid behavior. The electron energy distribution close to the comet is shown to be a mix of cometary and solar wind electrons that appear as, respectively, a thermal and a suprathermal components. Analyzing ion and electron energy distribution functions, and comparing with plasma measurements from ESA's Rosetta mission to comet 67P/Churyumov-Gerasimenko, we conclude that a detailed kinetic treatment of the electron dynamics is critical to fully capture the complex physics of mass-loading plasmas.

"CHON" particles: The interstellar component of cometary dust

NASA Technical Reports Server (NTRS)

Lien, David J.

1998-01-01

Interstellar dust is characterized by strong absorption in the ultraviolet and the mid-IR. Current models of interstellar dust are based on three chemically distinct components: a form of carbon (usually graphite), a silicate, and a blend of polycyclic aromatic hydrocarbons or other carbonaceous material. Previous work using effective medium theories to understand the optical properties of cometary dust suggested that an amalgam of materials could reproduce the observed interstellar and cometary dust features. Recently, Lawler and Brownlee (1992) re-analyzed the PIA and PUMA-1 data sets from the Giotto flyby of P/Halley and discovered that the so-called "CHON" particles were actually composed of a blend of carbon-bearing and silicon-bearing materials. Based on effective medium theories, the absorption spectrum of such a material would display the spectral features of each of the components - strong UV absorption from the carbonaceous component and strong absorption in the IR from the silicate component. To test this idea, vapor-deposited samples were created using two different deposition techniques: sputtering with an argon RF magnetron and deposition from an argon plasma torch. Two different compositions were tested: a blend of graphite and silica in a 7:1 ratio and an amalgam of materials whose approximate composition matches the "CHON"-silicate abundances for the uncompressed PIA data set of Lawler and Brownlee: graphite, iron oxide, magnesium oxide, ammonium sulfate, calcium carbonate, and silica in mass ratios of 6:4.3:4:2.2:1:9. The samples were finely ground and pressed into 2" diameter disks using a 40 ton press. In all, four different experiments were performed: one with each of the compositions (C:SiO and "CHON") in both the RF magnetron and the plasma torch chambers. The RF magnetron created a uniform dark thin film on the substrate surface, and the plasma torch created a coating of small (<100 micron) diameter grey particles. The spectra of all four samples show a strong, broad absorption feature at around 220 nm as well as a strong but narrower absorption peak near 10 microns. The RF magnetron sputtered samples showed some sub-structure in the UV, and the peak of the absorption was shifted toward longer wavelengths. The UV absorption in the plasma torch deposited samples have no sub-structure, and the peak absorption is very near 220 nm. Strong absorption near 9 microns is seen in the spectra from both sample preparation techniques, and is consistent with the IR spectra of some terrestrial silicates. Other features, particularly at 6.2 and 8.6 microns, are seen in the interstellar medium. A strong feature near 2 microns is due to absorbed water in the sample. Based on the results of these experiments, there is evidence that a material with a composition similar to that detected in "CHON" particles in the coma of P/Halley have a spectral signature which reproduces the main absorption features of interstellar dust. This suggests that the "CHON" particles could be the interstellar component of cometary dust.

The Diversity of Carbon in Cometary Refractory Dust Particles

NASA Technical Reports Server (NTRS)

Wooden, D. H.

2018-01-01

When comparing the dark icy surfaces of outer solar system small bodies and the composition of carbonaceous chondrites derived from dark asteroids we find a significant discrepancy in the assessed amounts of elemental carbon: up to 80% amorphous carbon is used to model the dark surfaces of Kuiper Belt Objects and Centaurs whereas at most 5% of elemental carbon is found in carbonaceous chondrites. If we presume that regimes of comet nuclei formation are analogous to disk regimes where other outer solar system ice-rich bodies formed then we can turn to comet dust to gain insights into the diversity in the concentration and forms of carbon available in the outer disk. Comet dust offers important insights into the diversity in the amounts and forms of carbon that were incorporated into aggregate dust particles in the colder parts of the protoplanetary disk out of which comet nuclei accreted. Comet nuclei are amongst the most primitive bodies because they have remained cold and unequilibrated. Comet dust particles reveal the presence of forms of elemental carbon and of soluble and insoluble organic matter, and in a great diversity of concentrations from very little, e.g., Stardust samples of comet 81P/Wild 2, to 80% by volume for Ultra Carbonaceous Antarctic Micro Meteorites (UCAMMs). Cometary outbursts and/or jet activity also demonstrate variations in the concentration of carbon in the grains at different grain sizes within a single comet. We review the diversity of carbon-bearing dust grains in cometary samples, flyby measurements and deduced from remote-sensing to enrich the discussion about the diversity of carbonaceous matter available in the outer ice-rich disk at the time of comet nuclei formation.

The 8-13 micron spectra of comets and the composition of silicate grains

NASA Technical Reports Server (NTRS)

Hanner, Martha S.; Lynch, David K.; Russell, Ray W.

1994-01-01

We have analyzed the existing spectra of seven comets which show an emission feature at 7.8-13 micrometers. Most have been converted to a common calibration, taking into account the SiO feature in late-type standard stars. The spectra are compared with spectra of the Trapezium, interplanetary dust particles (IDPs), laboratory mineral samples, and small particle emission models. The emission spectra show a variety of shapes; there is no unique 'cometary silicate'. A peak at 11.20-11.25 micrometers, indicative of small crystalline olivine particles, is seen in only three comets of this sample, P/Halley, Bradfield 1987 XXIX, and Levy 1990 XX. The widths of the emission features range from 2.6 to 4.1 micrometers (FWHM). To explain the differing widths and the broad 9.8 micrometers maximum, glassy silicate particles, including both pyroxene and olivine compositions, are the most plausible candidates. Calculations of emission models confirm that small grains of glassy silicate well mixed with carbonaceous material are plausible cometary constituents. No single class of chondritic aggregate IDPs exhibits spectra closely matching the comet spectra. A mixture of IDP spectra, particularly the glass-rich aggregates, approximately matches the spectra of comets P/Halley, Levy, and Bradfield 1987 XXIX. Yet, if comets are simply a mix of IDP types, it is puzzling that the classes of IDPs are so distinct. None of the comet spectra match the spectrum of the Trapezium. Thus, the mineralogy of the cometary silicates is not the same as that of the interstellar medium. The presence of a component of crystalline silicates in comets may be evidence of mixing between high- and low-temperature regions in the solar nebula.

The Search for Interstellar Sulfide Grains

NASA Technical Reports Server (NTRS)

Keller, Lindsay P.; Messenger, Scott

2010-01-01

The lifecycle of sulfur in the galaxy is poorly understood. Fe-sulfide grains are abundant in early solar system materials (e.g. meteorites and comets) and S is highly depleted from the gas phase in cold, dense molecular cloud environments. In stark contrast, sulfur is essentially undepleted from the gas phase in the diffuse interstellar medium, indicating that little sulfur is incorporated into solid grains in this environment. It is widely believed that sulfur is not a component of interstellar dust grains. This is a rather puzzling observation unless Fe-sulfides are not produced in significant quantities in stellar outflows, or their lifetime in the ISM is very short due to rapid destruction. Fe sulfide grains are ubiquitous in cometary samples where they are the dominant host of sulfur. The Fe-sulfides (primarily pyrrhotite; Fe(1-x)S) are common, both as discrete 0.5-10 micron-sized grains and as fine (5-10 nm) nanophase inclusions within amorphous silicate grains. Cometary dust particles contain high abundances of well-preserved presolar silicates and organic matter and we have suggested that they should contain presolar sulfides as well. This hypothesis is supported by the observation of abundant Fe-sulfides grains in dust around pre- and post-main sequence stars inferred from astronomical spectra showing a broad 23 micron IR feature due to FeS. Fe-sulfide grains also occur as inclusions in bona fide circumstellar amorphous silicate grains and as inclusions within deuterium-rich organic matter in cometary dust samples. Our irradiation experiments show that FeS is far more resistant to radiation damage than silicates. Consequently, we expect that Fe sulfide stardust should be as abundant as silicate stardust in solar system materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Floss, Christine; Stadermann, Frank J.; Ong, W. J.

We carried out hypervelocity impact experiments in order to test the possibility that presolar grains are preferentially destroyed during impact of the comet 81P/Wild 2 samples into the Stardust Al foil collectors. Powdered samples of the ungrouped carbonaceous chondrite Acfer 094 were shot at 6 km s{sup -1} into Stardust flight spare Al foil. Craters from the Acfer 094 test shots, as well as ones from the actual Stardust cometary foils, were analyzed by NanoSIMS ion imaging to search for presolar grains. We found two O-rich presolar grains and two presolar SiC grains in the Acfer 94 test shots, withmore » measured abundances in the foils of 4 and 5 ppm, respectively, significantly lower than the amount of presolar grains actually present in this meteorite. Based on known abundances of these phases in Acfer 094, we estimate a loss of over 90% of the O-rich presolar grains; the fraction of SiC lost is lower, reflecting its higher resistance to destruction. In the Stardust cometary foils, we identified four O-rich presolar grains in 5000 {mu}m{sup 2} of crater residue. Including a presolar silicate grain found by Leitner et al., the overall measured abundance of O-rich presolar grains in Wild 2 is {approx}35 ppm. No presolar SiC has been found in the foil searches, although one was identified in the aerogel samples. Based on the known abundances of presolar silicates and oxides in Acfer 094, we can calculate the pre-impact abundances of these grains in the Stardust samples. Our calculations indicate initial abundances of 600-830 ppm for O-rich presolar grains. Assuming a typical diameter of {approx}300 nm for SiC suggests a presolar SiC abundance of {approx}45 ppm. Analyses of the Stardust samples indicated early on that recognizable presolar components were not particularly abundant, an observation that was contrary to expectations that the cometary material would, like interplanetary dust particles, be dominated by primitive materials from the early solar system (including abundant presolar grains), which had remained essentially unaltered over solar system history in the cold environment of the Kuiper Belt. Our work shows that comet Wild 2, in fact, does contain more presolar grains than measurements on the Stardust samples suggest, with abundances similar to those observed in primitive IDPs.« less

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.

Chemical and Hydrodynamical Models of Cometary Comae

NASA Technical Reports Server (NTRS)

Charnley, Steven

2012-01-01

Multi-fluid modelling of the outflowing gases which sublimate from cometary nuclei as they approach the Sun is necessary for understanding the important physical and chemical processes occurring in this complex plasma. Coma chemistry models can be employed to interpret observational data and to ultimately determine chemical composition and structure of the nuclear ices and dust. We describe a combined chemical and hydrodynamical model [1] in which differential equations for the chemical abundances and the energy balance are solved as a function of distance from the cometary nucleus. The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of 1P/Halley. The anions O(-), OH(-), C(-), CH(-) and CN(-) have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu [2]. Organic molecular anions such as C4H(-) and C6H(-) are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been fully explored. We present details of new models for the chemistry of cometary comae that include atomic and molecular anions and calculate the impact of these anions on the coma physics and chemistry af the coma.

ACE-SWICS In Situ Plasma Composition of Fragmented Comet 73P/Schwassmann-Wachmann 3

NASA Astrophysics Data System (ADS)

Gilbert, J. A.; Lepri, S. T.; Rubin, M.; Zurbuchen, T.

2013-12-01

The interiors of comets contain some of the most pristine material in the solar system. Comet 73P/Schwassmann-Wachmann 3, discovered in 1930 with a double nucleus, is a Jupiter-family comet with a 5.34-year period. This comet split into 5 fragments in 1995 and disintegrated into nearly 70 pieces in 2006. In May and June of 2006, recently ionized cometary particles originating from some of these fragments were collected with the ACE-SWICS sensor. Due to a combination of the close proximity of the fragments passing between ACE-SWICS and the Sun, and the instrument characteristics, unique measurements regarding the charge state composition and the elemental abundances of both cometary and heliospheric plasma were made during this time. The cometary material released from some of these fragments can be identified by the concentrations of water-group pick-up ions having a mass-per-charge of 16-18 amu/e. With a focus on Helium, Carbon, and water-group ions, we present an analysis of the cometary plasma. Charge state ratios of C+/O+ fall below 0.1 during detection of comet fragment plasma, and there is a clear increase in He+ during fragment crossings. The C/O ratio and He charge states are used to provide constraints on the activity of the cometary fragments and also the spatial distribution of the extended and ionized cometary tail.

Formation environment of cometary nuclei in the primordial solar nebula

NASA Astrophysics Data System (ADS)

Yamamoto, T.

1985-01-01

The formation environment of comets in the primordial solar nebula is investigated from the point of view of the chemical composition of the ices of cometary nuclei. A sublimation sequence for various species of possible constituents of the nuclear ice, which would have condensed on the grain surface in the parent interstellar cloud was obtained by calculating the temperature of grains in the solar nebula. On this basis, an allowed range of the nebular temperature in the formation region of cometary nuclei is obtained from a condition for retention of the ices of the nuclear composition. Combining this result with models of the solar nebula, the region for the formation of cometary nuclei in the solar nebula is discussed. It is shown that cometary nuclei formed at least beyond the region between the formation regions of Saturn and Uranus. Finally, an upper limit is estimated for the grain temperature in the region of comet formation at an earlier stage of the solar nebula. The grain temperature is shown to be less than 60 K at this stage.

VizieR Online Data Catalog: 18-cm OH lines in comets (Crovisier+, 2002)

NASA Astrophysics Data System (ADS)

Crovisier, J.; Colom, P.; Gerard, E.; Bockelee-Morvan, D.; Bourgois, G.

2002-10-01

Since the apparition of comet Kohoutek 1973 XII, the 18-cm lines of the OH radical have been systematically observed in a number of comets with the Nancay radio telescope. Between 1973 and 1999, 52 comets have been successfully detected. This allowed an evaluation of the cometary water production rates and their evolution with time, as well as a study of several physical processes such as the excitation mechanisms of the OH radio lines, the expansion of cometary atmospheres, their anisotropy in relation to non-gravitational forces, and the Zeeman effect in relation to the cometary magnetic field. Part of these observations and their analysis have already been published. The bulk of the results are now organized in a data base. The present paper is a general presentation of the Nancay cometary data base and a more specific description of the observations of 53 cometary apparitions between 1982 and 1999. Comets observed before 1982 are only partly incorporated in the data base. Observations of comets since 2000 have benefited from a major upgrade of the telescope; they will be presented in forthcoming publications. (5 data files).

Non-destructive hyperspectral imaging of quarantined Mars Returned Samples

NASA Astrophysics Data System (ADS)

Simionovici, Alexandre; Viso, Michel; Beck, Pierre; Lemelle, Laurence; Westphal, Andrew; Vincze, Laszlo; Schoonjans, Tom; Fihman, Francois; Chazalnoel, Pascale; Ferroir, Tristan; Solé, Vicente Armando; Tucoulou, R.

Introduction: In preparation for the upcoming International Mars Sample Return mission (MSR), returning samples containing potential biohazards, we have implemented a hyperspec-tral method of in-situ analysis of grains performed in BSL4 quarantine conditions, by combining several non-destructive imaging diagnostics. This allows sample transportation on optimized experimental setups, while monitoring the sample quarantine conditions. Our hyperspectral methodology was tested during analyses of meteorites [1-2] and cometary and interstellar grains from the recent NASA Stardust mission [3-6]. Synchrotron Radiation protocols: X-ray analysis methods are widely accepted as the least destructive probes of fragile, unique samples. Diffraction, X-ray fluorescence and ab-sorption micro/nano-spectroscopies were performed on chondritic test samples using focused monochromatic beams at the ESRF synchrotron in Grenoble, France. 2D maps of grain com-position down to ppm concentrations and polycrystalline structure have simultaneously been acquired, followed by X-ray absorption performed on elements of Z 26. Ideally, absorption micro-tomography can later be performed in full-beam mode to record the 3D morphology of the grain followed by fluorescence-tomography in focus-beam mode which complements this picture with a 3D elemental image of the grain. Lab-based protocols: Raman and IR-based spectroscopies have been performed in reflection mode for mineralogical imaging of the grains in the laboratory using commercial microscopes. The spatial resolution varied in the 1-10 m range. Laser limited penetration of opaque samples permits only 2D imaging of the few nanometer-thick outer layers of the grains. Mineralogical maps are now routinely acquired using Raman spectroscopy at sub-micron scales through the 3 container walls of the Martian sample holder, followed by IR few-micrometer spot measurements recording C-based and potential aqueous alteration distributions. Sample Holder: A miniaturized sample-holder [7] has been designed and built to allow direct analyses of a set of extraterrestrial grains confined in a sealed triple container and remotely po-sitioned in front of the X-ray or laser beams of the various setups. The grains are held in several thin walls (10 m) ultrapure silica capillaries which are sufficiently resistant for manual/remote-controlled micro-manipulation but semitransparent for the characteristic X-rays, Raman and IR radiations. Miniaturized pressure/temperature sensors located in each container periodically monitor the integrity of the ensemble, ensuring BSL4 condi-tions. References: [1] B. Golosio, A. Simionovici, A. Somogyi, L. Lemelle, M. Chukalina, A. Brunetti, Jrnl. of App. Phys. 94, 145-157, 2003 [2] L. Lemelle, A. Simionovici, R. Truche, Ch. Rau, M. Chukalina, Ph. Gillet, Am. Min. 87 , 547-553, 2004 [3] Michael E. Zolensky et al., Science 314, 1735-1739, 2006 [4] G. J. Flynn et al., Science 314, 1731-1735, 2006 [5] Pierre Bleuet, Alexandre Simionovici, Laurence Lemelle, Tristan Ferroir, Peter Cloetens, Rémi Tu-coulou, Jean Susini, App. Phys. Lett. 92, 213111-1-3, 2008. [6] A. J. Westphal, et al., AIP Proceedings of the ICXOM Congress, (in print) 2010. [8] A. Simionovici and CNES, patent pending.

Stardust@home: A Massively Distributed Public Search for Interstellar Dust in the Stardust Interstellar Dust Collector

NASA Technical Reports Server (NTRS)

Westphal, Andrew J.; Butterworth, Anna L.; Snead, Christopher J.; Craig, Nahide; Anderson, David; Jones, Steven M.; Brownlee, Donald E.; Farnsworth, Richard; Zolensky, Michael E.

2005-01-01

In January 2006, the Stardust mission will return the first samples from a solid solar system body beyond the Moon. Stardust was in the news in January 2004, when it encountered comet Wild2 and captured a sample of cometary dust. But Stardust carries an equally important payload: the first samples of contemporary interstellar dust ever collected. Although it is known that interstellar (IS) dust penetrates into the inner solar system [2, 3], to date not even a single contemporary interstellar dust particle has been captured and analyzed in the laboratory. Stardust uses aerogel collectors to capture dust samples. Identification of interstellar dust impacts in the Stardust Interstellar Dust Collector probably cannot be automated, but will require the expertise of the human eye. However, the labor required for visual scanning of the entire collector would exceed the resources of any reasonably-sized research group. We are developing a project to recruit the public in the search for interstellar dust, based in part on the wildly popular SETI@home project, which has five million subscribers. We call the project Stardust@home. Using sophisticated chemical separation techniques, certain types of refractory ancient IS particles (so-called presolar grains) have been isolated from primitive meteorites (e.g., [4] ). Recently, presolar grains have been identified in Interplanetary Dust Particles[6]. Because these grains are not isolated chemically, but are recognized only by their unusual isotopic compositions, they are probably less biased than presolar grains isolated from meteorites. However, it is entirely possible that the typical interstellar dust particle is isotopically solar in composition. The Stardust collection of interstellar dust will be the first truly unbiased one.

Analytical dual-energy microtomography: A new method for obtaining three-dimensional mineral phase images and its application to Hayabusa samples

NASA Astrophysics Data System (ADS)

Tsuchiyama, A.; Nakano, T.; Uesugi, K.; Uesugi, M.; Takeuchi, A.; Suzuki, Y.; Noguchi, R.; Matsumoto, T.; Matsuno, J.; Nagano, T.; Imai, Y.; Nakamura, T.; Ogami, T.; Noguchi, T.; Abe, M.; Yada, T.; Fujimura, A.

2013-09-01

We developed a novel technique called "analytical dual-energy microtomography" that uses the linear attenuation coefficients (LACs) of minerals at two different X-ray energies to nondestructively obtain three-dimensional (3D) images of mineral distribution in materials such as rock specimens. The two energies are above and below the absorption edge energy of an abundant element, which we call the "index element". The chemical compositions of minerals forming solid solution series can also be measured. The optimal size of a sample is of the order of the inverse of the LAC values at the X-ray energies used. We used synchrotron-based microtomography with an effective spatial resolution of >200 nm to apply this method to small particles (30-180 μm) collected from the surface of asteroid 25143 Itokawa by the Hayabusa mission of the Japan Aerospace Exploration Agency (JAXA). A 3D distribution of the minerals was successively obtained by imaging the samples at X-ray energies of 7 and 8 keV, using Fe as the index element (the K-absorption edge of Fe is 7.11 keV). The optimal sample size in this case is of the order of 50 μm. The chemical compositions of the minerals, including the Fe/Mg ratios of ferromagnesian minerals and the Na/Ca ratios of plagioclase, were measured. This new method is potentially applicable to other small samples such as cosmic dust, lunar regolith, cometary dust (recovered by the Stardust mission of the National Aeronautics and Space Administration [NASA]), and samples from extraterrestrial bodies (those from future sample return missions such as the JAXA Hayabusa2 mission and the NASA OSIRIS-REx mission), although limitations exist for unequilibrated samples. Further, this technique is generally suited for studying materials in multicomponent systems with multiple phases across several research fields.

Cometary Astrometry

NASA Technical Reports Server (NTRS)

Yeomans, D. K. (Editor); West, R. M. (Editor); Harrington, R. S. (Editor); Marsden, B. G. (Editor)

1984-01-01

Modern techniques for making cometary astrometric observations, reducing these observations, using accurate reference star catalogs, and computing precise orbits and ephemerides are discussed in detail and recommendations and suggestions are given in each area.

Electron impact ionization in the vicinity of comets

NASA Astrophysics Data System (ADS)

Cravens, T. E.; Kozyra, J. U.; Nagy, A. F.; Gombosi, T. I.; Kurtz, M.

1987-07-01

The solar wind interacts very strongly with the extensive cometary coma, and the various interaction processes are initiated by the ionization of cometary neutrals. The main ionization mechanism far outside the cometary bow shock is photoionization by solar extreme ultraviolet radiation.Electron distributions measured in the vicinity of comets Halley and Giacobini-Zinner by instruments on the VEGA and ICE spacecraft, respectively, are used to calculate electron impact ionization frequencies. Ionization by electrons is of comparable importance to photoionization in the magnetosheaths of Comets Halley and Giacobini-Zinner. The ionization frequency in the inner part of the cometary plasma region of comet Halley is several times greater than the photoionization value. Tables of ionization frequencies as functions of electron temperature are presented for H2O, CO2, CO, O, N2, and H.

Comets: Gases, ices, grains and plasma

NASA Technical Reports Server (NTRS)

Wilkening, L. L.

1981-01-01

The program and abstracts of the 97 papers delivered at the colloquium are presented. Cometary nuclei, comet dust, the coma, ion tails, several comet missions, and cometary origin and evolution were discussed.

Chemical Evolution of Interstellar Dust into Planetary Materials

NASA Technical Reports Server (NTRS)

Fomenkova, M. N.; Chang, S.; DeVincenzi, Donald L. (Technical Monitor)

1995-01-01

Comets are believed to retain some interstellar materials, stored in fairly pristine conditions since-their formation. The composition and properties of cometary dust grains should reflect those of grains in the outer part of the protosolar nebula which, at least in part, were inherited from the presolar molecular cloud. However, infrared emission features in comets differ from their interstellar counterparts. These differences imply processing of interstellar material on its way to incorporation in comets, but C and N appear to be retained. Overall dust evolution from the interstellar medium (ISM) to planetary materials is accompanied by an increase in proportion of complex organics and a decrease in pure carbon phases. The composition of cometary dust grains was measured in situ during fly-by missions to comet Halley in 1986. The mass spectra of about 5000 cometary dust grains with masses of 5 x 10(exp -17) - 5 x 10(exp -12) g provide data about the presence and relative abundances of the major elements H, C, N, O,Na, Mg, Al, Si, S, Cl, K, Ca, Ti, Cr, Fe, Ni. The bulk abundances of major rock-forming elements integrated over all spectra were found to be solar within a factor of 2, while the volatile elements H, C, N, O in dust are depleted in respect to their total cosmic abundances. The abundances of C and N in comet dust are much closer to interstellar than to meteoritic and are higher than those of dust in the diffuse ISM. In dense molecular clouds dust grains are covered by icy mantles, the average composition of which is estimated to be H:C:N:O = 96:14:1:34. Up to 40% of elemental C and O may be sequestered in mantles. If we use this upper limit to add H, C, N and O as icy mantle material to the abundances residing in dust in the diffuse ISM, then the resulting values for H. C, and N match cometary abundances. Thus, ice mantles undergoing chemical evolution on grains in the dense ISM appear to have been transformed into less volatile and more complex organic residues wherein the H, C and N are largely retained and ultimately accreted in cometary dust. The abundance of O is about the same for cometary dust, meteorites and interstellar dust. In all these samples, most of O in a solid phase is bonded to silicates. In dense molecular clouds, the abundance of O in dust+mantles is significantly higher then in cometary dust. This difference may reflect the greater lability of oxygenated species toward astrophysical processing. Laboratory studies show that O-bearing functional groups in organic compounds tend to be relatively easily removed by heating and/or UV and particle irradiation . In Halley's coma, O-containing organic grains, being unstable, were located closest to the nucleus. The decomposition of the organic grain component in the coma provided a significant extended source contribution to O-containing gaseous species such as CO and H2CO.

Giada improved calibration of measurement subsystems

NASA Astrophysics Data System (ADS)

Della Corte, V.; Rotundi, A.; Sordini, R.; Accolla, M.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Mazzotta Epifani, E.; Palumbo, P.

2014-12-01

GIADA (Grain Impact Analyzer and Dust Accumulator) is an in-situ instrument devoted to measure the dynamical properties of the dust grains emitted by the comet. An Extended Calibration activity using the GIADA Flight Spare Model has been carried out taking into account the knowledge gained through the analyses of IDPs and cometary samples returned from comet 81P/Wild 2. GIADA consists of three measurement subsystems: Grain Detection System, an optical device measuring the optical cross-section for individual dust; Impact Sensor an aluminum plate connected to 5 piezo-sensors measuring the momentum of impacting single dust grains; Micro Balance System measuring the cumulative deposition in time of dust grains smaller than 10 μm. The results of the analyses on data acquired with the GIADA PFM and the comparison with calibration data acquired during the pre-launch campaign allowed us to improve GIADA performances and capabilities. We will report the results of the following main activities: a) definition of a correlation between the 2 GIADA Models (PFM housed in laboratory and In-Flight Model on-board ROSETTA); b) characterization of the sub-systems performances (signal elaboration, sensitivities, space environment effects); c) new calibration measurements and related curves by means of the PFM model using realistic cometary dust analogues. Acknowledgements: GIADA was built by a consortium led by the Univ. Napoli "Parthenope" & INAF-Oss. Astr. Capodimonte, IT, in collaboration with the Inst. de Astrofisica de Andalucia, ES, Selex-ES s.p.a. and SENER. GIADA is presently managed & operated by Ist. di Astrofisica e Planetologia Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale Italiana, IT, with a support of the Spanish Ministry of Education and Science MEC, ES. GIADA was developed from a University of Kent, UK, PI proposal; sci. & tech. contribution given by CISAS, IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their outstanding work. Science support provided by NASA through the US Rosetta Project managed by JPL/California Institute of Technology. GIADA calibrated data will be available through the ESA's PSA web site (www.rssd.esa.int/index.php?project=PSA&page=index).

The Case for a Geocentric rather than Heliocentric Origin of the Late Stage Heavy Bombardment (LHB) of the Moon and Tidal Evolution of its Orbit

NASA Astrophysics Data System (ADS)

Davis, P. M.; Stacey, F. D.

2009-12-01

Melt breccia samples returned from the Apollo mission have dates that suggest that the impacts that formed major basins on the Moon occurred between 3.8 and 4.0 Ga i.e., about 0.6 G years after Lunar formation. Three models have been proposed to explain the LHB. Heliocentric models including (1) The period marked the end of large-scale impacts associated with planetary formation and (2) It corresponded to a spike in impacts associated with major reorientation of the solar system (the ‘Nice model’), when the orbits Jupiter and Saturn became resonant, causing the orbits of Uranus and Neptune to become unstable and grow, scattering cometary and asteroidal fragments into Earth-Moon crossing orbits, and a geocentric model (3) It was due to collision with the last of a series of moonlets formed during Earth accretion which were swept up by tidal regression of a large Moon that had been formed near the Earth by a giant impact. While there is no smoking gun for any of these scenarios we will discuss a possible scenario for (3). Numerical calculations show that tidal regression of a large inner Moon sequentially traps exterior smaller moonlets into 2:1 resonance. Resonant trapping rapidly increases the eccentricity of their orbits causing them to become Moon-crossing. If the orbital radii of the moonlets had a resonance or Bode's law-type distribution, for the last collision to take place at 0.6 Gy, the Moon would have been at ~40 RE when it took place. One of the implications is that the associated LHB impacts would have significantly less relative velocity than those derived from asteroidal or cometary distances associated with (1) or (2). This may explain the low content of vapor condensate in the Lunar breccias. The tidal evolution from ~40 RE at 0.6 Gy requires a lower tidal friction than at present, but this has been evident for many years from tidal rhythmite data.

Hydrothermal Habitats: Measurements of Bulk Microbial Elemental Composition, and Models of Hydrothermal Influences on the Evolution of Dwarf Planets

NASA Astrophysics Data System (ADS)

Neveu, Marc Francois Laurent

Finding habitable worlds is a key driver of solar system exploration. Many solar system missions seek environments providing liquid water, energy, and nutrients, the three ingredients necessary to sustain life. Such environments include hydrothermal systems, spatially-confined systems where hot aqueous fluid circulates through rock by convection. I sought to characterize hydrothermal microbial communities, collected in hot spring sediments and mats at Yellowstone National Park, USA, by measuring their bulk elemental composition. To do so, one must minimize the contribution of non-biological material to the samples analyzed. I demonstrate that this can be achieved using a separation method that takes advantage of the density contrast between cells and sediment and preserves cellular elemental contents. Using this method, I show that in spite of the tremendous physical, chemical, and taxonomic diversity of Yellowstone hot springs, the composition of microorganisms there is surprisingly ordinary. This suggests the existence of a stoichiometric envelope common to all life as we know it. Thus, future planetary investigations could use elemental fingerprints to assess the astrobiological potential of hydrothermal settings beyond Earth. Indeed, hydrothermal activity may be widespread in the solar system. Most solar system worlds larger than 200 km in radius are dwarf planets, likely composed of an icy, cometary mantle surrounding a rocky, chondritic core. I enhance a dwarf planet evolution code, including the effects of core fracturing and hydrothermal circulation, to demonstrate that dwarf planets likely have undergone extensive water-rock interaction. This supports observations of aqueous products on their surfaces. I simulate the alteration of chondritic rock by pure water or cometary fluid to show that aqueous alteration feeds back on geophysical evolution: it modifies the fluid antifreeze content, affecting its persistence over geological timescales; and the distribution of radionuclides, whose decay is a chief heat source on dwarf planets. Interaction products can be observed if transported to the surface. I simulate numerically how cryovolcanic transport is enabled by primordial and hydrothermal volatile exsolution. Cryovolcanism seems plausible on dwarf planets in light of images recently returned by spacecrafts. Thus, these coupled geophysical-geochemical models provide a comprehensive picture of dwarf planet evolution, processes, and habitability.

Enantioselective Analysis in instruments onboard ROSETTA/PHILAE and ExoMars

NASA Astrophysics Data System (ADS)

Hendrik Bredehöft, Jan; Thiemann, Wolfram; Meierhenrich, Uwe; Goesmann, Fred

It has been suggested a number of times in the past, to look for chirality as a biomarker. So far, for lack of appropriate instrumentation, space missions have never included enantioselective analysis. The distinction between enantiomers is of crucial importance to the question of the origin of the very first (pre)biotic molecules. If molecules detected in situ on another celestial body were found to exhibit a chiral bias, this would mean that at least partial asymmetric synthesis could take place abiotically. If this chiral bias should be found to be near 100For the currently flying ESA mission ROSETTA an enantioselective instrument was built, to try for the first time to detect and separate chiral molecules in situ. This instrument is COSAC, the Cometary Sampling and Acquisition Experiment, an enantioselective GCMS device[1,2], which is included in the lander PHLIAE that will eventually in 2014 land on the nucleus of comet 67P/Churyumov-Gerasimenko. A similar but even more powerful type of enantioselective GC-MS is in preparation for ESA's ExoMars mission. This instrument is part of MOMA, the Mars Organic Molecules Analyser. It has the objective of identifying and quantifying chiral organic molecules in surface and subsurface samples of Mars. Currently ExoMars is scheduled for 2018. The newly developed enantioselective technique utilized by both COSAC and MOMA will be described, including sample acquisition, derivatization, and separation in space-resistant chiral stationary capillary columns with time-of-flight mass spectrometric detection. Results of enantioselective analyses of representative test samples with special emphasis on amino acids[3], the building blocks of protein polymers, will be presented and we will discuss potential results of space missions Rosetta and ExoMars. [1] Thiemann W.H.-P., Meierhenrich U.: ESA Mission ROSETTA Will Probe for Chirality of Cometary Amino Acids. Origins of Life and Evolution of Biospheres 31 (2001), 199-210. [2] Goesmann F., Rosenbauer H., Roll R., Szopa C., Raulin F., Sternberg R., Israel G., Meier-henrich U., Thiemann W., Muñoz Caro G.M.: COSAC, The cometary sampling and composi-n tion experiment on Philae. Space Science Reviews 128 (2007), 257-280. [3] Meierhenrich U.J.: Amino Acids and the Asymmetry of Life -Caught in the Act of Forma-tion. Springer, Heidelberg Berlin New York (2008).

Modeling the cometary environment using a fluid approach

NASA Astrophysics Data System (ADS)

Shou, Yinsi

Comets are believed to have preserved the building material of the early solar system and to hold clues to the origin of life on Earth. Abundant remote observations of comets by telescopes and the in-situ measurements by a handful of space missions reveal that the cometary environments are complicated by various physical and chemical processes among the neutral gases and dust grains released from comets, cometary ions, and the solar wind in the interplanetary space. Therefore, physics-based numerical models are in demand to interpret the observational data and to deepen our understanding of the cometary environment. In this thesis, three models using a fluid approach, which include important physical and chemical processes underlying the cometary environment, have been developed to study the plasma, neutral gas, and the dust grains, respectively. Although models based on the fluid approach have limitations in capturing all of the correct physics for certain applications, especially for very low gas density environment, they are computationally much more efficient than alternatives. In the simulations of comet 67P/Churyumov-Gerasimenko at various heliocentric distances with a wide range of production rates, our multi-fluid cometary neutral gas model and multi-fluid cometary dust model have achieved comparable results to the Direct Simulation Monte Carlo (DSMC) model, which is based on a kinetic approach that is valid in all collisional regimes. Therefore, our model is a powerful alternative to the particle-based model, especially for some computationally intensive simulations. Capable of accounting for the varying heating efficiency under various physical conditions in a self-consistent way, the multi-fluid cometary neutral gas model is a good tool to study the dynamics of the cometary coma with different production rates and heliocentric distances. The modeled H2O expansion speeds reproduce the general trend and the speed's nonlinear dependencies of production rate and heliocentric distance, which are found in remote observations. In the multi-fluid dust model, we use a newly developed numerical mesh to resolve the real shaped nucleus in the center and to facilitate prescription of the outer boundary conditions that accommodate the rotating frame. The model studies the effects of the rotating nucleus and the cometary activity in time-dependent simulations for the first time. The result also suggests that the rotation of the nucleus explains why there is no clear dust speed dependence on size in some of the dust observations. We developed a new multi-species comet MHD model to simulate the plasma environment of comet C/2006 P1 (McNaught) over a wide range of heliocentric distances from 0.17 AU to 1.75 AU, with the constraints provided by remote and in situ observations. Typical subsolar standoff distances of bow shock and contact surface are modeled and presented to characterize the solar wind interaction of the comet at various heliocentric distances. In addition, the model is also the first one to be used to study the composition and dynamics in the distant cometary tail. The results agree well with the measured water group ion abundances from the Ulysses/SWICS 1.7 AU down-tail from the comet and the velocity and temperature measured by Ulysses/SWOOPS.

Localized aliphatic organic material on the surface of Ceres

NASA Astrophysics Data System (ADS)

De Sanctis, M. C.; Ammannito, E.; McSween, H. Y.; Raponi, A.; Marchi, S.; Capaccioni, F.; Capria, M. T.; Carrozzo, F. G.; Ciarniello, M.; Fonte, S.; Formisano, M.; Frigeri, A.; Giardino, M.; Longobardo, A.; Magni, G.; McFadden, L. A.; Palomba, E.; Pieters, C. M.; Tosi, F.; Zambon, F.; Raymond, C. A.; Russell, C. T.

2017-02-01

Organic compounds occur in some chondritic meteorites, and their signatures on solar system bodies have been sought for decades. Spectral signatures of organics have not been unambiguously identified on the surfaces of asteroids, whereas they have been detected on cometary nuclei. Data returned by the Visible and InfraRed Mapping Spectrometer on board the Dawn spacecraft show a clear detection of an organic absorption feature at 3.4 micrometers on dwarf planet Ceres. This signature is characteristic of aliphatic organic matter and is mainly localized on a broad region of ~1000 square kilometers close to the ~50-kilometer Ernutet crater. The combined presence on Ceres of ammonia-bearing hydrated minerals, water ice, carbonates, salts, and organic material indicates a very complex chemical environment, suggesting favorable environments to prebiotic chemistry.

Cometary and meteorite swarm impact on planetary surfaces

NASA Technical Reports Server (NTRS)

Okeefe, J. D.; Ahrens, T. J.

1982-01-01

The impact-induced deformation from hypothetical cometary objects having initial densities in the 0.01 to 1 g/cu cm range and heats of vaporization in the approximately 2 kJ/g (corresponding to water) to approximately 10 to the 7th J/g range is examined for impacts in the 5 to 45 km/s range. Even though the direct effect of an atmosphere is neglected, the atmosphere may in fact cause a cometary object to break up into a shower or equivalent very porous impactor. Besides examining the partitioning of impact energy into internal energy of the impacted planet and impacting cometary material, calculations are made of the relative efficiency of shock-induced melting and vaporization by comets on planetary surface materials and the mass loss from a given planet for various escape velocities.

Cometary ion dynamics observed in the close vicinity of comet 67P/Churyumov-Gerasimenko during the intermediate activity period

NASA Astrophysics Data System (ADS)

Berčič, L.; Behar, E.; Nilsson, H.; Nicolaou, G.; Wieser, G. Stenberg; Wieser, M.; Goetz, C.

2018-06-01

Aims: Cometary ions are constantly produced in the coma, and once produced they are accelerated and eventually escape the coma. We describe and interpret the dynamics of the cometary ion flow, of an intermediate active comet, very close to the nucleus and in the terminator plane. Methods: We analysed in situ ion and magnetic field measurements, and characterise the velocity distribution functions (mostly using plasma moments). We propose a statistical approach over a period of one month. Results: On average, two populations were observed, separated in phase space. The motion of the first is governed by its interaction with the solar wind farther upstream, while the second one is accelerated in the inner coma and displays characteristics compatible with an ambipolar electric field. Both populations display a consistent anti-sunward velocity component. Conclusions: Cometary ions born in different regions of the coma are seen close to the nucleus of comet 67P/Churyumov-Gerasimenko with distinct motions governed in one case by the solar wind electric field and in the other case by the position relative to the nucleus. A consistent anti-sunward component is observed for all cometary ions. An asymmetry is found in the average cometary ion density in a solar wind electric field reference frame, with higher density in the negative (south) electric field hemisphere. There is no corresponding signature in the average magnetic field strength.

Parachute Swivel Mechanism for planetary entry

NASA Technical Reports Server (NTRS)

Birner, R.; Kaese, J.; Koller, F.; Muehlner, E.; Luhmann, H.-J.

1993-01-01

A parachute swivel mechanism (PSM) for planetary entry missions such as a Mars probe (MARSNET) or return of cometary material samples (ROSETTA mission) has been developed. The purpose of the PSM is to decouple the spin of the probe from the parachute, with low friction torque, during both the deployment and descent phases. Critical requirements are high shock loads, low friction, low temperatures, and several years of storage in the deep space environment (during the cruise phase of the probe, prior to operation). The design uses a main thrust ball bearing to cope with the load requirement and a smaller thrust ball bearing for guiding of the shaft. Except for use on the Viking and Galileo swivels, it appears that this type of bearing has very rarely been employed in space mechanisms, so that little is known of its friction behavior with dry lubrication. A slip ring assembly allows the transfer of electrical power for post-reefing of the parachute. A test program has been conducted covering the environmental conditions of Mars entry and Earth reentry. This paper describes requirement constraints, model missions of planetary entries, a bearing trade-off, analyses performed, design details, the lubrication system, and test results (friction torque versus load/spin rate). In addition, the design of the test rig is addressed.

Comparison of Carbon XANES Spectra from an Iron Sulfide from Comet Wild 2 with an Iron Sulfide Interplanetary Dust Particle

NASA Technical Reports Server (NTRS)

Wirick, S.; Flynn, G. J.; Keller, L. P.; Sanford, S. A.; Zolensky, M. E.; Messenger, Nakamura K.; Jacobsen, C.

2008-01-01

Among one of the first particles removed from the aerogel collector from the Stardust sample return mission was an approx. 5 micron sized iron sulfide. The majority of the spectra from 5 different sections of this particle suggests the presence of aliphatic compounds. Due to the heat of capture in the aerogel we initially assumed these aliphatic compounds were not cometary but after comparing these results to a heated iron sulfide interplanetary dust particle (IDP) we believe our initial interpretation of these spectra was not correct. It has been suggested that ice coating on iron sulfides leads to aqueous alteration in IDP clusters which can then lead to the formation of complex organic compounds from unprocessed organics in the IDPs similar to unprocessed organics found in comets [1]. Iron sulfides have been demonstrated to not only transform halogenated aliphatic hydrocarbons but also enhance the bonding of rubber to steel [2,3]. Bromfield and Coville (1997) demonstrated using Xray photoelectron spectroscopy that "the surface enhancement of segregated sulfur to the surface of sulfided precipitated iron catalysts facilitates the formation of a low-dimensional structure of extraordinary properties" [4]. It may be that the iron sulfide acts in some way to protect aliphatic compounds from alteration due to heat.

The colors of cometary nuclei and other primitive bodies

NASA Astrophysics Data System (ADS)

Toth, I.; Lamy, P. L.

2005-12-01

Primitive minor objects like Kuiper-belt objects (KBOs), Centaurs, cometary nuclei and low-albedo asteroids contain a considerable amount of information regarding the formation of early solar system planetesimals and some of the primordial processes. Broadband colors by themselves offer limited insight into surface composition but correlations either between different color indices or with other (e.g., orbital) parameters can shed some light on the questions of the composition and the evolution of the minor objects. Furthermore, a systematic comparison of the color indices of various populations may provide clues on their relationships, and concur along with dynamical studies, to establish a scenario of their formation and evolution in the solar system. We present new color results on cometary nuclei obtained with the Hubble Space Telescope (HST) whose superior resolution enables us to accurately isolate the nucleus signals from the surrounding comae. By combining with scrutinized available data obtained with ground-based telescopes, we accumulated a sample of 39 cometary nuclei, 34 ecliptic comets (ECs) and 5 nearly-isotropic comets (NICs) using the nomenclature of Levison (1996). We analyze color distributions and color-color correlations as well as correlations with other physical parameters. We present our own compilation of colors of 282 objects in the outer solar system, separately considering the different dynamical populations, classical KBOs in low and high-inclination orbits, resonant KBOs (practically Plutinos), scattered-disk objects (SDOs) and Centaurs. We perform a systematic analysis of color distributions of all plausible parent-child combinations and conclude by synthesizing the implications of the colors for the origin of ecliptic comets. We acknowledge the support of the French "Programme National de Planétologie", jointly funded by CNRS and CNES, and of the bilateral French--Hungarian cooperation program. I. Toth further acknowledges the support of the Université de Provence, of the Hungarian Academy of Sciences through grant No. 9871.

A new hybrid particle/fluid model for cometary dust

NASA Astrophysics Data System (ADS)

Shou, Y.; Combi, M. R.; Tenishev, V.; Toth, G.; Hansen, K. C.; Huang, Z.; Gombosi, T. I.; Fougere, N.; Rubin, M.

2017-12-01

Cometary dust grains, which originate from comets, are believed to contain clues to the formation and the evolution of comets. They also play an important role in shaping the cometary environment, as they are able to decelerate and heat the gas through collisions, carry charges and interact with the plasma environment, and possibly sublimate gases. Therefore, the loss rate and behavior of dust grains are of interest to scientists. Currently, mainly two types of numerical dust models exist: particle models and fluid models have been developed. Particle models, which keep track of the positions and velocities of all gas and dust particles, allow crossing dust trajectories and a more accurate description of returning dust grains than the fluid model. However, in order to compute the gas drag force, the particle model needs to follow more gas particles than dust particles. A fluid model is usually more computationally efficient and is often used to provide simulations on larger spatial and temporal scales. In this work, a new hybrid model is developed to combine the advantages of both particle and fluid models. In the new approach a fluid model based on the University of Michigan BATSRUS code computes the gas properties, and feeds the gas drag force to the particle model, which is based on the Adaptive Mesh Particle Simulator (AMPS) code, to calculate the motion of dust grains. The coupling is done via the Space Weather Modeling Framework (SWMF). In addition to the capability of simulating the long-term dust phenomena, the model can also designate small active regions on the nucleus for comparison with the temporary fine dust features in observations. With the assistance of the newly developed model, the effect of viewing angles on observed dust jet shapes and the transportation of heavy dust grains from the southern to the northern hemisphere of comet 67P/Churyumov-Gerasimenko will be studied and compared with Rosetta mission images. Preliminary results will be presented. Support from contracts JPL #1266314 and #1266313 from the US Rosetta Project and grant NNX14AG84G from the NASA Planetary Atmospheres Program are gratefully acknowledged.

Exposed bright features on the comet 67P/Churyumov-Gerasimenko: distribution and evolution

NASA Astrophysics Data System (ADS)

Deshapriya, J. D. P.; Barucci, M. A.; Fornasier, S.; Hasselmann, P. H.; Feller, C.; Sierks, H.; Lucchetti, A.; Pajola, M.; Oklay, N.; Mottola, S.; Masoumzadeh, N.; Tubiana, C.; Güttler, C.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Bertaux, J.-L.; Bertini, I.; Bodewits, D.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B. J. R.; Debei, S.; Cecco, M. De; Deller, J.; Fulle, M.; Groussin, O.; Gutierrez, P. J.; Hoang, H. V.; Hviid, S. F.; Ip, W.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Preusker, F.; Shi, X.; Thomas, N.; Vincent, J.-B.

2018-05-01

Context. Since its arrival at the comet 67P/Churyumov-Gerasimenko in August 2014, the Rosetta spacecraft followed the comet as it went past the perihelion and beyond until September 2016. During this time there were many scientific instruments operating on board Rosetta to study the comet and its evolution in unprecedented detail. In this context, our study focusses on the distribution and evolution of exposed bright features that have been observed by OSIRIS, which is the scientific imaging instrument aboard Rosetta. Aims: We envisage investigating various morphologies of exposed bright features and the mechanisms that triggered their appearance. Methods: We co-registered multi-filter observations of OSIRIS images that are available in reflectance. The Lommel-Seeliger disk function was used to correct for the illumination conditions and the resulting colour cubes were used to perform spectrophotometric analyses on regions of interest. Results: We present a catalogue of 57 exposed bright features observed on the nucleus of the comet, all of which are attributed to the presence of H2O ice on the comet. Furthermore, we categorise these patches under four different morphologies and present geometric albedos for each category. Conclusions: Although the nucleus of 67P/Churyumov-Gerasimenko appears to be dark in general, there are localised H2O ice sources on the comet. Cometary activity escalates towards the perihelion passage and reveals such volatile ices. We propose that isolated H2O ice patches found in smooth terrains in regions, such as Imhotep, Bes, and Hapi, result from frost as an aftermath of the cessation of the diurnal water cycle on the comet as it recedes from perihelion. Upon the comet's return to perihelion, such patches are revealed when sublimation-driven erosion removes the thin dust layers that got deposited earlier. More powerful activity sources such as cometary outbursts are capable of revealing much fresher, less contaminated H2O ice that is preserved with consolidated cometary material, as observed on exposed patches resting on boulders. This is corroborated by our albedo calculations that attribute higher albedos for bright features with formations related to outbursts.

Comment on the Pioneer Venus Orbiter event of February 11, 1982 - Of cometary or solar origin?

NASA Technical Reports Server (NTRS)

Intriligator, D. S.

1986-01-01

The evidence presented by Russell et al. (1985) for the cometary origin of the Pioneer Venus Orbiter event of Febr. 11, 1982, is examined critically. It is argued that the field fluctuations and He enhancements seen at Venus and near earth, the sequence of the events, and a number of related observations all indicate that the event is of solar origin. These objections are discussed individually in a reply by Russell et al., and the claim of cometary origin is defended.

Infrared Observations of Cometary Dust and Nuclei

NASA Technical Reports Server (NTRS)

Lisse, Carey

2004-01-01

This bibliography lists citations for publications published under the grant. Subjects of the publications include cometary dust, instellar and interplanetary dust, comet nuclei and comae, Comet Hale-Bopp, infrared observations of comets, mass loss, and comet break-up.

The effect of electron collisions on rotational excitation of cometary water

NASA Technical Reports Server (NTRS)

Xie, Xingfa; Mumma, Michael J.

1991-01-01

The e-H2O collisional rate for exciting rotational transitions in cometary water is evaluated for conditions found in Comet Halley. The e-H2O collisional rate exceeds that for excitation by neutral-neutral collisions at distances exceeding 3000 km from the cometary nucleus, in the case of the O sub 00 yields 1 sub 11 transition. The estimates are based on theoretical and experimental studies of e-H2O collisions, on ion and electron parameters acquired in-situ by instruments on the Giotto and Vega spacecraft, and on results obtained from models of the cometary ionosphere. The contribution of electron collisions may explain the need for large water-water cross-sections in models which neglect the effect of electrons. The importance of electron collisions is enhanced for populations of water molecules in regions where their rotational lines are optically thick.

The effect of electron collisions on rotational populations of cometary water

NASA Technical Reports Server (NTRS)

Xie, Xingfa; Mumma, Michael J.

1992-01-01

The e-H2O collisional rate for exciting rotational transitions in cometary water is evaluated for conditions found in Comet Halley during the Giotto spacecraft encounter. In the case of the 0(00)-1(11) rotational transition, the e-H2O collisional rate exceeds that for excitation by neutral-neutral collisions at distances exceeding 3000 km from the cometary nucleus. The estimates are based on theoretical and experimental studies of e-H2O collisions, on ion and electron parameters acquired in situ by instruments on the Giotto and Vega spacecraft, and on results obtained from models of the cometary ionosphere. Thus, the rotational temperature of the water molecule in the intermediate coma may be controlled by collisions with electrons rather than with neutral molecules, and the rotational temperature retrieved from high-resolution IR spectra of water in Comet Halley may reflect electron temperatures rather than neutral gas temperatures in the intermediate coma.

Cometary material and the origins of life on earth

NASA Technical Reports Server (NTRS)

Lazcano-Araujo, A.; Oro, J.

1981-01-01

The role of cometary material in determining the environmental conditions of the prebiotic earth is reviewed. The organic synthesis pathways that occur in dense interstellar clouds and in comets are examined, and complex organic molecules believed to exist (amino acids, carboxylic acids, purines, pyrimidines and hydrocarbons) based on spectral detections of degradation products are noted. Estimates of the amount of terrestrial volatiles of cometary origin that may have been acquired in collisions during the early history of the earth are considered, and shown to dominate any estimated contributions to terrestrial carbon from other extraterrestrial sources. Current evidence that the origin and early evolution of life began about four billion years ago is discussed in relation to the cometary bombardment processes occurring at the time and the resultant shock waves, reducing atmospheres and reactive chemical species. It is thus concluded that comets contributed significantly to the processes of chemical evolution necessary for the emergence of life on earth.

Charge exchange in solar wind-cometary interactions

NASA Technical Reports Server (NTRS)

Gombosi, T. I.; Horanyi, M.; Kecskemety, K.; Cravens, T. E.; Nagy, A. F.

1983-01-01

A simple model of a cometary spherically symmetrical atmosphere and ionosphere is considered. An analytic solution of the governing equations describing the radial distribution of the neutral and ion densities is found. The new solution is compared to the well-known solution of the equations containing only ionization terms. Neglecting recombination causes a significant overestimate of the ion density in the vicinity of the comet. An axisymmetric model of the solar wind-cometary interaction is considered, taking into account the loss of solar wind ions due to charge exchange. The calculations predict that for active comets, solar wind absorption due to charge exchange becomes important at a few thousand kilometers from the nucleus, and a surface separating the shocked solar wind from the cometary ionosphere develops in this region. These calculations are in reasonable agreement with the few observations available for the ionopause location at comets.

Cometary globules in the southeast quadrant of the Rosette nebula

NASA Technical Reports Server (NTRS)

Patel, Nimesh A.; Xie, Taoling; Goldsmith, Paul F.

1993-01-01

We present a study of newly identified cometary globules in the southeast quadrant of the Rosette nebula using the J = 1-0 transition of carbon monoxide. The globules are found to be blueshifted by about 6 km/s with respect to the adjacent Rosette molecular cloud. The masses of the globules vary from 50 to 300 solar masses, and their sizes are between 1 and 3 pc. Two of the globules have cometary morphology and show velocity gradients of about 1.5 km/s/pc along their symmetry axes. These globules are associated with the IRAS sources 06314+0421, X0632+043, 06322+0427, and 06327+0423 which coincide with local maxima in the (C-13)O emission. The derived physical parameters of the globules are found to be consistent with those predicted by recent theoretical models of photoevaporating cometary clouds. We suggest that star formation induced by radiation driven implosion has occurred.

Gas Dynamics and Kinetics in the Cometary Coma: Theory and Observations

NASA Technical Reports Server (NTRS)

Combi, Michael R.; Harris, Walter M.; Smyth, William H.

2005-01-01

Our ability to describe the physical state of the expanding coma affects fundamental areas of cometary study both directly and indirectly. In order to convert measured abundances of gas species in the coma to gas production rates, models for the distribution and kinematics of gas species in the coma are required. Conversely, many different types of observations, together with laboratory data and theory, are still required to determine coma model attributes and parameters. Accurate relative and absolute gas production rates and their variations with time and from comet to comet are crucial to our basic understanding of the composition and structure of cometary nuclei and their place in the solar system. We review the gas dynamics and kinetics of cometary comae from both theoretical and observational perspectives, which are important for understanding the wide variety of physical conditions that are encountered.

The volatile composition of comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.

1988-01-01

Comets may be our best probes of the physical and chemical conditions in the outer regions of the solar nebula during that crucial period when the planets formed. The volatile composition of cometary nuclei can be used to decide whether comets are the product of a condensation sequence similar to that invoked to explain the compositions of the planets and asteroids, or if comets are simply agglomerations of interstellar grains which have been insignificantly modified by the events that shaped the other bodies in the solar system. Although cometary nuclei are not generally accessible to observation, observations of cometary comae can illuminate at least some of the mysteries of the nuclei provided one has a detailed knowledge of the excitation conditions in the coma and also has access to basic atomic and molecular data on the many species present in comets. Examined here is the status of our knowledge of the volatile composition of cometary nuclei and how these data are obtained.

First results from the Giotto magnetometer experiment at comet Halley

NASA Technical Reports Server (NTRS)

Neubauer, F. M.; Glassmeier, K. H.; Pohl, M.; Raeder, J.; Acuna, M. H.; Burlaga, L. F.; Ness, N. F.

1986-01-01

The Giotto magnetometer experiment at comet Halley has for the first time provided magnetic field measurements in all the important spatial regions characterizing the front-side interaction between the solar-wind magnetoplasma and a cometary atmosphere. Upstream waves of cometary origin have been observed at distances greater than two million km from the comet, both inbound and outbound. A cometary bow shock has been identified at 1.15 million inbound on the dawn side and a thick quasi-parallel cometary bow shock outbound. A turbulent magnetosheath has been observed further inside. A magnetic pile-up region has been identified inside 135,000 km, inbound, and 263,000 km, outbound, with fields up to 57 and 65 nT, respectively. A cavity region with essentially zero magnetic field has been discovered, with a width of 8500 km along the trajectory around closest approach.

Refractory materials in comet samples

NASA Astrophysics Data System (ADS)

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

2017-08-01

Transmission electron microscope examination of more than 250 fragments, >1 μm from comet Wild 2 and a giant cluster interplanetary dust particle (GCP) of probable cometary origin has revealed four new calcium-aluminum-rich inclusions (CAIs), an amoeboid olivine aggregate (AOA), and an additional AOA or Al-rich chondrule (ARC) object. All of the CAIs have concentric mineral structures and are composed of spinel + anorthite cores surrounded by Al,Ti clinopyroxenes and are similar to two previous CAIs discovered in Wild 2. All of the cometary refractory objects are of moderate refractory character. The mineral assemblages, textures, and bulk compositions of the comet CAIs are similar to nodules in fine-grained, spinel-rich inclusions (FGIs) found in primitive chondrites and like the nodules may be nebular condensates that were altered via solid-gas reactions in the solar nebula. Oxygen isotopes collected on one Wild 2 CAI also match FGIs. The lack of the most refractory inclusions in the comet samples may reflect the higher abundances of small moderately refractory CAI nodules that were produced in the nebula and the small sample sizes collected. In the comet samples, approximately 2-3% of all fragments larger than 1 μm, by number, are CAIs and nearly 50% of all bulbous Stardust tracks contain at least one CAI. We estimate that 0.5 volume % of Wild 2 material and 1 volume % of GCP is in the form of CAIs. ARCs and AOAs account for <1% of the Wild 2 and GCP grains by number.

Microgravity Testing of a Surface Sampling System for Sample Return from Small Solar System Bodies

NASA Technical Reports Server (NTRS)

Franzen, M. A.; Preble, J.; Schoenoff, M.; Halona, K.; Long, T. E.; Park, T.; Sears, D. W. G.

2004-01-01

The return of samples from solar system bodies is becoming an essential element of solar system exploration. The recent National Research Council Solar System Exploration Decadal Survey identified six sample return missions as high priority missions: South-Aitken Basin Sample Return, Comet Surface Sample Return, Comet Surface Sample Return-sample from selected surface sites, Asteroid Lander/Rover/Sample Return, Comet Nucleus Sample Return-cold samples from depth, and Mars Sample Return [1] and the NASA Roadmap also includes sample return missions [2] . Sample collection methods that have been flown on robotic spacecraft to date return subgram quantities, but many scientific issues (like bulk composition, particle size distributions, petrology, chronology) require tens to hundreds of grams of sample. Many complex sample collection devices have been proposed, however, small robotic missions require simplicity. We present here the results of experiments done with a simple but innovative collection system for sample return from small solar system bodies.

Isotopes and Minor Volatiles in the Coma of Comet 67P/Churyumov-Gerasimenko Observed by the Rosetta/ROSINA Instrument: Planetary Implications

NASA Astrophysics Data System (ADS)

Marty, B.; Altwegg, K.; Balsiger, H. R.; Calmonte, U.; Hässig, M.; Le Roy, L.; Rubin, M.; Bieler, A. M.; Fuselier, S. A.; De Keyser, J. M.; Mousis, O.

2015-12-01

The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) instrument suite is part of the payload of the European Space Agency's Rosetta spacecraft. Part of this suite, the Double Focusing Mass Spectrometer (DFMS) has been analyzing major (e.g., H2O,) as well as minor (CO, CO2, N2, NHx, noble gases) species and elements and some of their isotopes thanks to its high mass resolution of 3,000 at 1% peak height and its high sensitivity. In parallel to the presentation by Rubin et al. (this meeting) who discuss temporal variation of the coma composition as a function of heliospheric distance, we present here the on-going measurements done on the above species and isotopes. Besides temporal variability, one of the goals of ROSINA is to document the composition of cometary volatiles in the context of the formation of planets and of the origin of atmospheres. The first detection of a noble gas, Ar, in a cometary coma (Balsiger et al, in press), together with the measured D/H isotope ratio and carbon species, constrains the origin of the inner planet atmospheres and the terrestrial oceans. Assuming that 67P is representative of the cometary reservoir, major volatiles (H, C, N) of the inner planets are unlikely to have originated from comets, but a cometary origin for atmospheric noble gases is a viable hypothesis. However, these cometary measurements were done during a short interval of time (in autumn 2014) when the comet was at 3.5 AU from the Sun, which raises the question of how well they represent the bulk cometary composition. Further measurements of the bulk composition are planned close to the perihelion. Also of interest is the isotope composition of nitrogen in N-bearing compounds. Spectroscopic measurements of cometary HCN and NH2+ done so far indicate a two-fold enrichment in 15N, that needs to be confirmed by in-situ mass spectrometry. Measurements of other noble gases, in particular Xe (a very difficult measurement), may set stringent constraints on the nature (clathrate vs. amorphous) of cometary ice. Results from these measurements before and after the perihelion will be presented.

Comets

NASA Astrophysics Data System (ADS)

Festou, M. C.; Feldman, P. D.

Observations of comets obtained with the IUE satellite since its launch in 1978 are reviewed. The status of UV observation of comets prior to IUE is discussed, and particular attention is given to low-resolution UV spectroscopy of cometary comae, the detection of new species in the UV emission, high-dispersion spectroscopy, spatial mapping of the emissions, abundance determinations, and short-term variability. Diagrams, graphs, sample spectra, and tables of numerical data are provided.

Analyses of Cometary Silicate Crystals: DDA Spectral Modeling of Forsterite

NASA Technical Reports Server (NTRS)

Wooden, Diane

2012-01-01

Comets are the Solar System's deep freezers of gases, ices, and particulates that were present in the outer protoplanetary disk. Where comet nuclei accreted was so cold that CO ice (approximately 50K) and other supervolatile ices like ethane (C2H2) were preserved. However, comets also accreted high temperature minerals: silicate crystals that either condensed (greater than or equal to 1400 K) or that were annealed from amorphous (glassy) silicates (greater than 850-1000 K). By their rarity in the interstellar medium, cometary crystalline silicates are thought to be grains that formed in the inner disk and were then radially transported out to the cold and ice-rich regimes near Neptune. The questions that comets can potentially address are: How fast, how far, and over what duration were crystals that formed in the inner disk transported out to the comet-forming region(s)? In comets, the mass fractions of silicates that are crystalline, f_cryst, translate to benchmarks for protoplanetary disk radial transport models. The infamous comet Hale-Bopp has crystalline fractions of over 55%. The values for cometary crystalline mass fractions, however, are derived assuming that the mineralogy assessed for the submicron to micron-sized portion of the size distribution represents the compositional makeup of all larger grains in the coma. Models for fitting cometary SEDs make this assumption because models can only fit the observed features with submicron to micron-sized discrete crystals. On the other hand, larger (0.1-100 micrometer radii) porous grains composed of amorphous silicates and amorphous carbon can be easily computed with mixed medium theory wherein vacuum mixed into a spherical particle mimics a porous aggregate. If crystalline silicates are mixed in, the models completely fail to match the observations. Moreover, models for a size distribution of discrete crystalline forsterite grains commonly employs the CDE computational method for ellipsoidal platelets (c:a:b=8.14x8.14xl in shape with geometrical factors of x:y:z=1:1:10, Fabian et al. 2001; Harker et al. 2007). Alternatively, models for forsterite employ statistical methods like the Distribution of Hollow Spheres (Min et al. 2008; Oliveira et al. 2011) or Gaussian Random Spheres (GRS) or RGF (Gielen et al. 200S). Pancakes, hollow spheres, or GRS shapes similar to wheat sheaf crystal habit (e.g., Volten et al. 2001; Veihelmann et al. 2006), however, do not have the sharp edges, flat faces, and vertices seen in images of cometary crystals in interplanetary dust particles (IDPs) or in Stardust samples. Cometary forsterite crystals often have equant or tabular crystal habit (J. Bradley). To simulate cometary crystals, we have computed absorption efficiencies of forsterite using the Discrete Dipole Approximation (DDA) DDSCAT code on NAS supercomputers. We compute thermal models that employ a size distribution of discrete irregularly shaped forsterite crystals (nonspherical shapes with faces and vertices) to explore how crystal shape affects the shape and wavelength positions of the forsterite spectral features and to explore whether cometary crystal shapes support either condensation or annealing scenarios (Lindsay et al. 2012a, b). We find forsterite crystal shapes that best-fit comet Hale-Bopp are tetrahedron, bricks or brick platelets, essentially equant or tabular (Lindsay et al. 2012a,b), commensurate with high temperature condensation experiments (Kobatake et al. 2008). We also have computed porous aggregates with crystal monomers and find that the crystal resonances are amplified. i.e., the crystalline fraction is lower in the aggregate than is derived by fitting a linear mix of spectral features from discrete subcomponents, and the crystal resonances 'appear' to be from larger crystals (Wooden et al. 2012). These results may indicate that the crystalline mass fraction in comets with comae dominated by aggregates may be lower than deduced by popular methods that only emoy ensembles of discrete crystals.

Cometary science after Rosetta

PubMed Central

Knight, Matthew M.; Fitzsimmons, Alan

2017-01-01

The European Space Agency’s Rosetta mission ended operations on 30 September 2016 having spent over 2 years in close proximity to its target comet, 67P/Churyumov–Gerasimenko. Shortly before this, in summer 2016, a discussion meeting was held to examine how the results of the mission could be framed in terms of cometary and solar system science in general. This paper provides a brief history of the Rosetta mission, and gives an overview of the meeting and the contents of this associated special issue. This article is part of the themed issue ‘Cometary science after Rosetta’. PMID:28554982

'The Relation of Biology to Astronomy' and Theology: Panspermia and Panentheism; Revolutionary Convergences Advanced by Fred Hoyle and Chandra Wickramasinghe

NASA Astrophysics Data System (ADS)

Walker, Theodore, Jr.

2012-06-01

In contrast to the Copernican revolution in astro-geometry, the Hoyle-Wickramasinghe contribution to the recent and continuing revolution in astrobiology - "cometary panspermia" - features astronomy and biology converging toward theology. They employed astro-biotic reasoning (often labeled "anthropic" reasoning) to demonstrate that life is made possible by the deliberate controlling influence of the living all-embracing "intelligent universe." This is consistent with panentheism [pan-en-theos-ism, not pantheism]. As advanced by Hoyle and Wickramasinghe, cometary panspermia is panentheistic. Also, neoclassical panentheism requires generic panspermia, and favors cometary panspermia.

Evaluating some computer exhancement algorithms that improve the visibility of cometary morphology

NASA Technical Reports Server (NTRS)

Larson, Stephen M.; Slaughter, Charles D.

1992-01-01

Digital enhancement of cometary images is a necessary tool in studying cometary morphology. Many image processing algorithms, some developed specifically for comets, have been used to enhance the subtle, low contrast coma and tail features. We compare some of the most commonly used algorithms on two different images to evaluate their strong and weak points, and conclude that there currently exists no single 'ideal' algorithm, although the radial gradient spatial filter gives the best overall result. This comparison should aid users in selecting the best algorithm to enhance particular features of interest.

The pick-up of cometary protons by the solar wind

NASA Technical Reports Server (NTRS)

Neugebauer, M.; Goldstein, B. E.; Goldstein, R.; Lazarus, A. J.; Altwegg, K.; Balsiger, H.

1987-01-01

The HERS detector of the Ion Mass Spectrometer on the Giotto spacecraft measured the 3-dimensional distribution of picked-up cometary protons over a distance of about 8 million km upstream of the bow shock of comet P/Hally. The protons were observed to be elastically scattered out of their original cycloidal trajectories such that they were nonuniformly distributed over a spherical shell in velocity space. The shell radius (relative to its expected radius) and thickness increased as the bow shock was approached. Down-stream of the shock, the cometary protons could not be distinguished from the heated solar wind protons.

Comet Wild 2 and the two kinds of cometary sub-nuclei population

NASA Astrophysics Data System (ADS)

Illes-Almar, E.

On the 2nd January 2004 Stardust encountered the nucleus of comet Wild 2 by 240 km. 72 images have been collected - among them the up-till-now best views of a cometary nucleus. The "pockmarked" surface of the comet is peculiar as the "craters" are not normal craters: neither in shape nor in cross section. Their shapes are rather irregular and generally not central or axisymmetric. Furthermore they have flat bottoms and very steep walls that seem almost perpendicular to the surface. One has the feeling that they are not impact craters. In the framework of our `two kinds of cometary sub-nuclei population' hypothesis (Illés-Almár, 1995, 2002) the cavities can be explained by the stronger sublimation where the loose sub-nuclei are exposed to the surface. The almost vertical walls resemble to the vertical walls of the sublimated CO2 ice on the South polar cap of Mars. References: Illés-Almár, E.: On two different populations of cometary sub-nuclei. Antarctic Meteorites XX. June 6-8, 1995, Tokyo. Abstracts pp. 93-94, 1995. Illés-Almár, E.: Comet Borrelly and the two kinds of cometary sub-nuclei population. (submitted to Adv. Sp. Res. in 2002)

Complex Indigenous Organic Matter Embedded in Apollo 17 Volcanic Black Glass Surface Deposits

NASA Technical Reports Server (NTRS)

Thomas-Keprta, Kathie L.; Clemett, S. J.; Ross, D. K.; Le, L.; Rahman, Z.; Gonzalez, C.; McKay, D. S.; Gibson, E. K.

2013-01-01

Papers presented at the first Lunar Science Conference [1] and those published in the subsequent Science Moon Issue [2] reported the C content of Apollo II soils, breccias, and igneous rocks as rang-ing from approx.50 to 250 parts per million (ppm). Later Fegley & Swindle [3] summarized the C content of bulk soils from all the Apollo missions as ranging from 2.5 (Apollo 15) to 280 ppm (Apollo 16) with an overall average of 124+/- 45 ppm. These values are unexpectedly low given that multiple processes should have contributed (and in some cases continue to contribute) to the lunar C inventory. These include exogenous accretion of cometary and asteroidal dust, solar wind implantation, and synthesis of C-bearing species during early lunar volcanism. We estimate the contribution of C from exogenous sources alone is approx.500 ppm, which is approx.4x greater than the reported average. While the assessm ent of indigenous organic matter (OM) in returned lunar samples was one of the primary scientific goals of the Apollo program, extensive analysis of Apollo samples yielded no evidence of any significant indigenous organic species. Furthermore, with such low concentrations of OM reported, the importance of discriminating indigenous OM from terrestrial contamination (e.g., lunar module exhaust, sample processing and handling) became a formidable task. After more than 40 years, with the exception of CH4 [5-7], the presence of indigenous lunar organics still remains a subject of considerable debate. We report for the first time the identification of arguably indigenous OM present within surface deposits of black glass grains collected on the rim of Shorty crater during the Apollo 17 mission by astronauts Eugene Cernan and Harrison Schmitt.

The radiation stability of the RNA base uracil in H2O-ice and CO2-ice: in-situ laboratory measurements with applications to comets, Europa, and Mars

NASA Astrophysics Data System (ADS)

Gerakines, Perry A.; Frail, Sarah; Hudson, Reggie L.

2017-10-01

Planetary bodies of astrobiological interest, such as Mars, are often exposed to harsh incident radiation, which will influence the times that molecules can survive on them. Some or all of these bodies may well contain biologically-important organic molecules, some may even have supported life at some point in their history, and some may support life today. Future searches for organic molecules likely will include sampling the martian subsurface or a cometary surface sample return mission, where organics may be frozen in ices dominated by either H2O or CO2, which provide some protection from ionizing radiation.Recently, our research group has published studies of the radiation stability of amino acids, with a focus on glycine - in both undiluted form and in mixtures with H2O and CO2. Here, we present a similar study that focuses on the radiation-chemical kinetics of the RNA base uracil. We compare results for uracil decay for dilution in both H2O and CO2 ices. Moreover, we compare these new results with those for glycine. For each sample, we measured uracil’s destruction rate constant and half-life dose due to irradiation by 0.9-MeV protons. All measurements were made in situ at the temperature of irradiation using IR spectroscopy. Trends with dilution (up to ~300:1) and temperature (up to ~150 K) are considered, and results are discussed in the context of icy planetary surfaces.Acknowledgment: Our work is supported in part by the NASA Emerging Worlds Program and by the NASA Astrobiology Institute through the Goddard Center for Astrobiology.

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.

Physical properties of dust particles in different comets inferred from observations and experimental simulations

NASA Astrophysics Data System (ADS)

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

2007-08-01

1.Introduction Remote observations of solar light scattered by cometary dust particles provide information on the dust properties for a large variety of comets, in complement to the exceptional in-situ observations (with or without sample returns). The scattered light is partially linearly polarized, with a polarization degree depending on the geometry of observations (phase angle ?) and on the physical properties of the particles. Differences in polarization have been found in cometary comae, pointing to different physical properties of the dust (e.g. sizes of the grains, of the aggregates, structures and porosities, complex refractive indices) [1, 2]. Such differences, as well as an observed polarimetric wavelength effect, tend to show that large aggregates made of submicron-sized grains could be present in some cometary comae regions [3, 4]. On the opposite, more compact particles seem to be present in other comae regions and/or comets [5, 6]. 2. Results We will present observations of different comets. The variations of the dust properties in the coma and their evolution will be discussed. The results will be compared to the results obtained by other observational techniques. On the images of comet 9P/Tempel 1 (at ?=41°) some hours after Deep Impact, two kinds of dust particles are detected: more compact particles with small velocities and fluffy particles ejected by the impact with larger velocities. On the images of comet 73P/Schwassmann-Wachmann 3, in the tail direction of fragment B, a disruption is observed. The dust coma around fragment C is more symmetric. For both A and B, important dust jets are ejected by the nucleus, which are visible on the intensity images in the solar and antisolar directions, and on the polarization maps. 3. Interpretation and conclusion Numerical (7,8,9) and experimental simulations provide an interpretation of the observations in terms of the physical properties of the particles. Experimental simulations have been performed on numerous levitating samples (compact and fluffy) with the PROGRA2 experiment, either in reduced gravity conditions (parabolic flights) [10,11], or lifted by an air-draught (laboratory conditions) [12,13]. The variations of the polarization are correlated to variations in the size of the grains and aggregates and are a function of the complex refractive index and its evolution. The correlation between the variations of the scattered intensity and the linear polarization maps allows us to disentangle different physical properties of the dust. The results are compared to results obtained from previous observations by the same methods. References [1] E. Hadamcik and A.C. Levasseur-Regourd, JQSRT 79-80, 661-678 (2003) [2] A.C. Levasseur-Regourd, E. Hadamcik, JQSRT 79-80, 903-910 (2003) [3] E. Hadamcik, A.C. Levasseur-Regourd, A&A 403, 757- 768 (2003) [4] L. Kolokolova et al., In: Comets II, M.C. Festou et al. (eds), pp 577 (2004) [5] E. Hadamcik, A.C. Levasseur-Regourd, Icarus 166, 188-194 (2003) [6] E. Hadamcik et al., Icarus, accepted. [7] J. Lasue, A.C. Levasseur-Regourd, JQSRT 100, 220-236 (2006) [8] H. Kimura et al., A&A 449, 1243-1254 (2006) [9] A.C. Levasseur-Regourd et al., PSS, in press, available on line (2007) [10] J.-B. Renard et al. Appl. Opt 41, 609-618 (2002) [11] J.-B. Renard et al., Adv. Space Res. 31, 2511-2518 (2003) [12] E. Hadamcik et al., JQSRT 100, 143-156 (2006) [13] E. Hadamcik et al., Icarus, in press, available on line (2007)

Coordinated Analyses of Diverse Components in Whole Stardust Cometary Tracks

NASA Technical Reports Server (NTRS)

Nakamura-Messenger, Keiko; Keller, Lindsay P.; Messenger, Scott R.; Clemett, Simon J.; Nguyen, Lan-Anh N.; Frank, David

2011-01-01

Analyses of samples returned from Comet 81P/Wild-2 by the Stardust spacecraft have resulted in a number of surprising findings that show the origins of comets are more complex than previously suspected. However, these samples pose new experimental challenges because they are diverse and suffered fragmentation, thermal alteration, and fine scale mixing with aerogel. Questions remain about the nature of Wild-2 materials, such as the abundances of organic matter, crystalline materials, and presolar grains. To overcome these challenges, we have developed new sample preparation and analytical techniques tailored for entire aerogel tracks. We have successfully ultramicrotomed entire "carrot" and "bulbous" type tracks along their axis while preserving their original shapes. This innovation allowed us to examine the distribution of fragments along the track from the entrance hole all the way to the terminal particle (TP). We will present results of our coordinated analysis of the "carrot" type aerogel tracks #112 and #148, and the "bulbous" type aerogel tracks #113, #147 and #168 from the nanometer to the millimeter scale. Scanning TEM (STEM) was used for elemental and detailed mineralogy characterization, NanoSIMS was used for isotopic analyses, and ultrafast two-step laser mass spectrometry (ultra L2MS) was used to investigate the nature and distribution of organic phases. The isotopic measurements were performed following detailed TEM characterization for coordinated mineralogy. This approach also enabled spatially resolving the target sample from fine-scale mixtures of compressed aerogel and melt. Eight of the TPs of track #113 are dominated by coarse-grained enstatite (En90) that is largely orthoenstatite with minor, isolated clinoenstatite lamellae. One TP contains minor forsterite (Fo88) and small inclusions of diopside with % levels of Al, Cr and Fe. Two of the TPs contain angular regions of fine-grained nepheline surrounded by enstatite. Their O isotopic compositions are in the range of meteoritic materials, implying that they originated in the inner Solar System. Complex aromatic hydrocarbons are distributed along aerogel tracks and in TPs. These organics are likely cometary but were affected by shock heating. Three TPs of track #147 and two of track 168 have completely different mineralogy. TP2 of track #147 entirely consists of Fe-Ni alloy (5 at% Ni) and TP3 contains Fa28 with partial olivine-pyroxene intergrowth and minor albite. TP4 contains pentlandite, Fe-olivine, albite and high Ca pyroxene with Na and Cr (kosmochlor component). TP1 of #168 contains Fe-olivine, albite and pentlandite, and the concentric TP2 has a core of olivine grains with co-existing indigenous amorphous SiO2 surrounded by a carbon mantle, which in turn is surrounded by a layer of compressed aerogel. The TP of the carrot track #112 is a (16)O-rich forsteritic olivine grain that likely formed in the inner Solar System. The track also contains submicron-sized diamond grains of likely Solar System origin.

Ptolemy: in situ mass spectrometry during the Rosetta flyby of 21 Lutetia, and implications for future missions.

NASA Astrophysics Data System (ADS)

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

2011-10-01

Rosetta is the European Space Agency 'Planetary Cornerstone' mission intended to solve many of the unanswered questions surrounding the small bodies of the Solar System. Launched in March 2004 it is now over halfway through its decade long cruise, leading up to entering orbit around the nucleus of comet 67P/Churyumov-Gerasimenko in mid-2014. To date, this cruise has included three gravitational assist manoeuvres using Earth and one such manoeuvre using the gravity well of Mars. In addition, targeted flybys of two asteroids have returned a plethora of data to be compared with the comet observations to come. These flybys were of the 5.3 km diameter E-type asteroid 2867 Šteins on September 5th 2008, and a similar 3,162 km flyby of the 100 km diameter asteroid 21 Lutetia on July 10th 2010, the focus of this work. Recent ground based observations of the main belt asteroid 24 Themis have shown this body to have an organic-rich surface with exposed water ice [1]. It is also known that there at least four main belt comets - comets residing within the main belt, the prototype being 133P/Elst-Pizarro - and there are likely to be many more such bodies undergoing lower levels of cometary activity yet to be discovered [2]. The once clear-cut differentiation between volatile rich comets and volatile depleted asteroids has been somewhat eroded by these findings. Ptolemy is a miniature chemical analysis laboratory aboard the Rosetta lander 'Philae', and is intended to determine the chemical and isotopic composition of cometary material sourced from beneath, on and above the surface of the target comet. Samples are taken from the Sampler, Drill and Distribution system (SD2) and are then processed in a chemical preparation suite before delivery to a three channel gas chromatograph (GC). Elution products from the GC are passed to a quadrupole ion trap mass spectrometer for detection and quantitation [3]. As well as analysing solid samples, Ptolemy can passively adsorb coma material onto CarbosphereTM molecular sieve contained within one of the 26 SD2 sample ovens for later thermal release and analysis. Ptolemy can also make direct 'sniff' detections of the current spacecraft environment, bypassing the sample inlet and GC system, instead directly analyzing the inside of the mass spectrometer which is connected to space via a vent pipe. Based on the demonstrated instrument performance (a sensitivity of one ion count per 1x10-11 mbar for a particular mass), and knowing that the state of knowledge concerning the volatile composition and outgassing nature of main belt asteroids is only loosely constrained, it was decided to attempt to detect any extant, tenuous exosphere surrounding asteroid 21 Lutetia during the 2010 flyby opportunity. This body was thought to have both carbonaceous material and hydrated minerals on its surface - potential sources of outgassing - and therefore worthwhile of study [4].

Coordinated Analyses of Diverse Components in Whole Stardust Cometary Tracks

NASA Astrophysics Data System (ADS)

Nakamura-Messenger, K.; Keller, L. P.; Messenger, S. R.; Clemett, S. J.; Nguyen, L. N.; Frank, D.

2011-12-01

Analyses of samples returned from Comet 81P/Wild-2 by the Stardust spacecraft have resulted in a number of surprising findings that show the origins of comets are more complex than previously suspected. However, these samples pose new experimental challenges because they are diverse and suffered fragmentation, thermal alteration, and fine scale mixing with aerogel. Questions remain about the nature of Wild-2 materials, such as the abundances of organic matter, crystalline materials, and presolar grains. To overcome these challenges, we have developed new sample preparation and analytical techniques tailored for entire aerogel tracks [Nakamura-Messenger et al. 2011]. We have successfully ultramicrotomed entire "carrot" and "bulbous" type tracks along their axis while preserving their original shapes. This innovation allowed us to examine the distribution of fragments along the track from the entrance hole all the way to the terminal particle (TP). We will present results of our coordinated analysis of the "carrot" type aerogel tracks #112 and #148, and the "bulbous" type aerogel tracks #113, #147 and #168 from the nanometer to the millimeter scale. Scanning TEM (STEM) was used for elemental and detailed mineralogy characterization, NanoSIMS was used for isotopic analyses, and ultrafast two-step laser mass spectrometry (ultra L2MS) was used to investigate the nature and distribution of organic phases. The isotopic measurements were performed following detailed TEM characterization for coordinated mineralogy. This approach also enabled spatially resolving the target sample from fine-scale mixtures of compressed aerogel and melt. Eight of the TPs of track #113 are dominated by coarse-grained enstatite (En90) that is largely orthoenstatite with minor, isolated clinoenstatite lamellae. One TP contains minor forsterite (Fo88) and small inclusions of diopside with % levels of Al, Cr and Fe. Two of the TPs contain angular regions of fine-grained nepheline surrounded by enstatite. Their O isotopic compositions are in the range of meteoritic materials, implying that they originated in the inner Solar System. Complex aromatic hydrocarbons are distributed along aerogel tracks and in TPs. These organics are likely cometary but were affected by shock heating. Three TPs of track #147 and two of track 168 have completely different mineralogy. TP2 of track #147 entirely consists of Fe-Ni alloy (5 at% Ni) and TP3 contains Fa28 with partial olivine-pyroxene intergrowth and minor albite. TP4 contains pentlandite, Fe-olivine, albite and high Ca pyroxene with Na and Cr (kosmochlor component). TP1 of #168 contains Fe-olivine, albite and pentlandite, and the concentric TP2 has a core of olivine grains with co-existing indigenous amorphous SiO2 surrounded by a carbon mantle, which in turn is surrounded by a layer of compressed aerogel. The TP of the carrot track #112 is a 16O-rich forsteritic olivine grain that likely formed in the inner Solar System. The track also contains submicron-sized diamond grains of likely Solar System origin.

Chiral Sugar and Amino Acid Formation in Simulated Cometary Matter Inches Closer to Explaining the Emergence of Homochiral Life

NASA Astrophysics Data System (ADS)

Meinert, C.; Jones, N. C.; Hoffmann, S. V.; Nahon, L.; d'Hendecourt, L.; Meierhenrich, U. J.

2017-07-01

Simulated cometary ice experiments have indicated that circularly polarised light could be the initial source of life's handedness. We detected chiral sugars, amino acids and their molecular precursors within these interstellar achiral ice analogues.

Primitive bodies - Molecular abundances in Comet Halley as probes of cometary formation environments

NASA Technical Reports Server (NTRS)

Lunine, Jonathan I.

1989-01-01

The most recent results on abundances of molecules in Halley's comet are examined in the context of various models for the environment in which comets formed. These environments include molecular clouds associated with star-forming regions, the solar nebula, gaseous disks around proto-planets, and combinations of these. Of all constituents in a cometary nucleus, the highly volatile molecules such as methane, ammonia, molecular nitrogen, and carbon monoxide are most sensitive to the final episode of cometary grain formation and incorporation in the comet's nucleus; hence they likely reflect at least some chemical processing in the solar nebula. Proper interpretation requires modeling of a number of physical processes including gas phase chemistry, chemistry on grain surfaces, and fractionation effects resulting from preferential incorporation of certain gases in proto-cometary grains. The abundance of methane in Halley's comet could be a key indicator of where that comet formed, provided the methane abundance on grains in star-forming regions can be observationally constrained.

Thermal modeling of cometary nuclei

NASA Astrophysics Data System (ADS)

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

1981-09-01

A model of the sublimation of volatile ices from a cometary nucleus is presented which includes the effects of (1) diurnal heating and cooling, (2) rotation period and pole orientation, (3) the thermal properties of the ice and subsurface layers, and (4) the contributions from coma opacity, scattering and thermal emission where the properties of the coma are derived from the integrated rate of volatile production by the nucleus. In applying the model to the case of the 1986 apparition of Halley's comet, it is found that the generation of a cometary dust coma increases the total energy reaching the Halley nucleus due to the greater geometrical cross-section of the coma as compared with the bare nucleus. The calculated coma opacity of Halley is about 0.2 at 1 AU from the sun and 1.2 at perihelion. Possible consequences of the results obtained for the generation of nongravitational forces, volatile production rates for comets and cometary lifetimes against sublimation are discussed.

Physical characteristics of cometary dust from dynamical studies - A review

NASA Technical Reports Server (NTRS)

Sekanina, Z.

1980-01-01

Progress made in the determination of the physical characteristics of cometary dust particles from studies of dust tail dynamics is reviewed. Applications of the combined dynamical photometric approach of Finson and Probstein (1968) to studies of cometary tails exhibiting continuous light intensity variations are discussed, with attention given to determinations of the particle-size-related distribution function of the solar radiation pressure exerted on the particles, the contribution of comets to the interplanetary dust, calculations of dust ejection rates and a Monte Carlo approach to the analysis of dust tails. Investigations of dust streamers and striae, which are believed to be related to comet outbursts entailing brief but sharp enhancements of dust production, are then reviewed, with particular attention given to observations of Comet West 1976 VI. Finally, the question of cometary particle type is addressed, and it is pointed out that the presence of submicron absorbing particles in the striae of Comet West is not incompatible with the presence of micron-size dielectric particles in the inner coma.

The Giotto radio-science experiment

NASA Technical Reports Server (NTRS)

Edenhofer, P.; Bird, M. K.; Buschert, H.; Esposito, P. B.; Porsche, H.; Volland, H.

1986-01-01

The scientific objectives of the Giotto Radio Science Experiment (GRE) are to determine the columnar electron content of Comet Halley/s ionosphere and the cometary mass fluence from atmospheric drag by using the radio signals from Giotto during the Halley encounter. The radio science data (S and X-band Doppler and range measurements) will be collected at NASA/s deep-space 64 m tracking antenna at Tidbinbilla near Canberra, in Australia. In order to separate the effects of the terrestrial ionosphere and the interplanetary plasma, S-band Doppler measurements will also be taken at Tidbinbilla along the line-of-sight of Japan/s cometary probe Sakigake during the Giotto-Halley Encounter. The measurements of cometary electron content and mass fluence will be inverted to derive the spatial distribution of the electron and mass (dust and gas) density within Halley/s coma. The GRE is the only experiment on Giotto capable of measuring the low-energy (10 eV) electron bulk population of Halley/s ionosphere and the total cometary mass flow impacting upon the spacecraft.

Evidence of Collisional Histories of Asteroids, Comets and Meteorites: Comparisons with Shocked Minerals

NASA Technical Reports Server (NTRS)

Lederer, Susan M.; Jensen, Elizabeth; Smith, Douglas; Fane, Michael; Whizin, Akbar; Landsman, Zoe A.; Wooden, Diane H.; Lindsay, Sean S.; Cintala, Mark; Keller, Lindsay P.;

Ancient Chinese Observations and Modern Cometary Models

NASA Astrophysics Data System (ADS)

Yeomans, D. K.

1995-12-01

Ancient astronomical observations by Chinese, Japanese, and Korean observers represent the only data source for discerning the long-term behavior of comets. The primary source material is derived from Chinese astrologers who kept a vigilant celestial watch in an effort to issue up-to-date astrological forecasts for the reigning emperors. Surprisingly accurate records were kept on cometary apparitions with careful notes being made of an object's position, motion, size, color, and tail length. For comets Halley, Swift-Tuttle, and Tempel-Tuttle, Chinese observations have been used to model their motions over two millennia and to infer their photometric histories. One general result is that active comets must achieve an apparent magnitude of 3.5 or brighter before they become obvious naked-eye objects. For both comets Halley and Swift-Tuttle, their absolute magnitudes and hence their outgassing rates, have remained relatively constant for two millennia. Comet Halley's rocket-like outgassing has consistently delayed the comet's return to perihelion by 4 days so that the comet's spin axis must have remained stable for at least two millennia. Although its outgassing is at nearly the same rate as Halley's, comet Swift-Tuttle's motion has been unaffected by outgassing forces; this comet is likely to be ten times more massive than Halley and hence far more difficult for rocket-like forces to push it around. Although the earliest definite observations of comet Tempel-Tuttle were in 1366, the associated Leonid meteor showers have been identified as early as A.D. 902. The circumstance for each historical meteor shower and storm have been used to guide predictions for the upcoming 1998-1999 Leonid meteor displays.

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

NASA Technical Reports Server (NTRS)

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

1974-01-01

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

Clathrate hydrates in cometary nuclei and porosity

NASA Technical Reports Server (NTRS)

Smoluchowski, R.

1988-01-01

Possible mechanisms of formation and decomposition of CO2-clathrate hydrate in cometary nuclei are discussed. As far as it is known, this is the only clathrate hydrate which is unstable at low temperatures. Calculation shows that, in accord with other evidence, neither volume nor grain boundary diffusion in the clathrate lattice can be responsible for the rate of these reactions and that a surface mechanism with the attendant sensitivity to pressure must play a crucial role. Density changes accompanying CO2-clathrate decomposition and formation can lead to microporosity and enhanced brittleness or even to fracture of cometary nuclei at low temperatures. Other clathrate hydrates and mixed clathrates are also discussed.

Cometary atmospheres: Modeling the spatial distribution of observed neutral radicals

NASA Technical Reports Server (NTRS)

Combi, M. R.

1986-01-01

New data for the spatial distribution of cometary C2 are presented. A recompilation of the Haser scale lengths for C2 and CN resolves the previously held anomalous drop of the C2/CN ratio for heliocentric distances larger than 1 AU. Clues to the source of cometary C2 have been found through fitting the sunward-antisunward brightness profiles with the Monte Carlo particle-trajectory model. A source (parent) lifetime of 3.1 x 10,000 seconds is found, and an ejection speed for C2 radicals upon dissociation of the parent(s) of approx. 0.5 km 1/5 is calculated.

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.

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.

Early Activity of Cometary Species from ROSINA/DFMS at 67P/ Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Hässig, Myrtha; Fuselier, Stephen A.; Altwegg, Kathrin; Balsiger, Hans; Berthelier, Jean-Jacques; Bieler, André; Calmonte, Ursina; Dhooghe, Frederik; Fiethe, Björn; Gasc, Sébastien; Gombosi, Tamas I.; Jäckel, Annette; Korth, Axel; Le Roy, Léna; Rème, Henri; Rubin, Martin; Tzou, Chia-Yu; Wurz, Peter

2014-11-01

The European Space Agency’s Rosetta spacecraft arrived after a journey of more than 10 years at comet 67P/Churyumov-Gerasimenko. ROSINA is an instrument package on board Rosetta. It consists of two mass spectrometers and a COmetary Pressure Sensor (COPS). The two mass spectrometers, the Double Focusing Mass Spectrometer (DFMS) and the Reflectron Time of Flight (RTOF) complement each other with high mass resolution (e.g to resolve 13C from CH), high dynamic range (to detect low abundant isotopes and species), high mass range (to detect organics), and high time resolution. ROSINA is designed to measure the neutral gas and plasma composition in the coma of 67P/Churyumov-Gerasimenko in addition to the physical properties of the neutral component of the coma. For the first time, a comet can be observed in situ from its early activity towards and after perihelion. Little is known about what drives initial cometary activity very far from the Sun. Remote sensing observations to date are highly constrained to a limited number of a few bright comets (e.g. Hale-Bopp) and a limited number of species. Rosetta provides the first measurements of the early activity of a comet in situ and detected the first cometary molecules early August. We will focus on early activity of cometary species from the high resolution mass spectrometer ROSINA/DFMS.

Mechanical and electrostatic experiments with dust particles collected in the inner coma of comet 67P by COSIMA onboard Rosetta.

PubMed

Hilchenbach, Martin; Fischer, Henning; Langevin, Yves; Merouane, Sihane; Paquette, John; Rynö, Jouni; Stenzel, Oliver; Briois, Christelle; Kissel, Jochen; Koch, Andreas; Schulz, Rita; Silen, Johan; Altobelli, Nicolas; Baklouti, Donia; Bardyn, Anais; Cottin, Herve; Engrand, Cecile; Fray, Nicolas; Haerendel, Gerhard; Henkel, Hartmut; Höfner, Herwig; Hornung, Klaus; Lehto, Harry; Mellado, Eva Maria; Modica, Paola; Le Roy, Lena; Siljeström, Sandra; Steiger, Wolfgang; Thirkell, Laurent; Thomas, Roger; Torkar, Klaus; Varmuza, Kurt; Zaprudin, Boris

2017-07-13

The in situ cometary dust particle instrument COSIMA (COmetary Secondary Ion Mass Analyser) onboard ESA's Rosetta mission has collected about 31 000 dust particles in the inner coma of comet 67P/Churyumov-Gerasimenko since August 2014. The particles are identified by optical microscope imaging and analysed by time-of-flight secondary ion mass spectrometry. After dust particle collection by low speed impact on metal targets, the collected particle morphology points towards four families of cometary dust particles. COSIMA is an in situ laboratory that operates remotely controlled next to the comet nucleus. The particles can be further manipulated within the instrument by mechanical and electrostatic means after their collection by impact. The particles are stored above 0°C in the instrument and the experiments are carried out on the refractory, ice-free matter of the captured cometary dust particles. An interesting particle morphology class, the compact particles, is not fragmented on impact. One of these particles was mechanically pressed and thereby crushed into large fragments. The particles are good electrical insulators and transform into rubble pile agglomerates by the application of an energetic indium ion beam during the secondary ion mass spectrometry analysis.This article is part of the themed issue 'Cometary science after Rosetta'. © 2017 The Author(s).

Spectral properties of the nucleus of short-period comets

NASA Astrophysics Data System (ADS)

Toth, I.; Lamy, P. L.

2000-10-01

Comets, Edgeworth-Kuiper-Belt Objects (EKBOs), Centaurs and low albedo asteroids contain a considerable amount of information regarding some of the primordial processes that governed the formation of the early Solar System planetesimals. Opportunities to determine the colors of cometary nuclei are rare and relevant ground-based observations are difficult to perform. Color diversities and similarities between different types of small bodies have already been considered ([1] and references therein). We pursue this analysis further by introducing new BVRI colors obtained from our survey of cometary nuclei with the Hubble Space Telescope [2] as well as recent data obtained on EKBOs. We present preliminary results on the distribution of the BVRI colors (histograms, two-color diagrams) and possible relationships between the colors and orbital elements as well as the determined body sizes. The mean colors of the selected sample of the short-period (s-p) comets are: < (B-V) > = 0.91, < (V-R) > = 0.52, and < (V-I) > = 0.84. Pearson's linear correlation analysis of the (B-V) versus (V-R) and (V-R) versus (V-I) colors show significant correlations for the EKBOs+Centaurs sample while the s-p sample seems to be uncorrelated, with a few outliers. The linear regression lines of the EKBOs+Centaurs sample crosses through the sample of the s-p comets. There are no correlations of the colors versus perihelion distances, effective radii and perihelion distances as well as the (a,sin(i)) diagrams. This work was supported by grants from CNRS and CNES, France and partially by the the Hungarian Research Foundation OTKA T025049. [1] Luu, J., 1993. Icarus 104, 138. [2] Lamy, P.L. et al., this conference

The role of organic polymers in the structure of cometary dust

NASA Technical Reports Server (NTRS)

Vanysek, Vladimir; Boehnhardt, Hermann; Fechtig, H.

1992-01-01

Several phenomena observed in P/Halley and other comets indicate additional fragmentation of dust particles or dust aggregates in cometary atmospheres. The disintegration of dust aggregates may be explained by sublimation of polymerized formaldehyde - POM - which play a role as binding material between submicron individual particles.

The effect of mass loading outside cometary bow shock for the plasma and wave measurements in the coming cometary missions

NASA Astrophysics Data System (ADS)

Sagdeev, R. Z.; Shapiro, V. D.; Shevchenko, V. I.; Szego, K.

1987-02-01

The neutral gas emitted by comets is partly photoionized along its path. The interaction of the ions with the solar wind leads to observable particle and wave effects in the ambient plasma. These are described in the present paper.

Two-dimensional molecular line transfer for a cometary coma

NASA Astrophysics Data System (ADS)

Szutowicz, S.

2017-09-01

In the proposed axisymmetric model of the cometary coma the gas density profile is described by an angular density function. Three methods for treating two-dimensional radiative transfer are compared: the Large Velocity Gradient (LVG) (the Sobolev method), Accelerated Lambda Iteration (ALI) and accelerated Monte Carlo (MC).

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.;

Assemblage of Presolar Materials and Early Solar System Condensates in Chondritic Porous Interplanetary Dust Particles

NASA Technical Reports Server (NTRS)

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

2015-01-01

Anhydrous chondritic porous inter-planetary dust particles (CP IDPs) contain an assortment of highly primitive solar system components, molecular cloud matter, and presolar grains. These IDPs have largely escaped parent body processing that has affected meteorites, advocating cometary origins. Though the stardust abundance in CP IDPs is generally greater than in primitive meteorites, it can vary widely among individual CP IDPs. The average abundance of silicate stardust among isotopically primitive IDPs is approx. 375 ppm while some have extreme abundances up to approx. 1.5%. H and N isotopic anomalies are common in CP IDPs and the carrier of these anomalies has been traced to organic matter that has experienced chemical reactions in cold molecular clouds or the outer protosolar disk. Significant variations in these anomalies may reflect different degrees of nebular processing. Refractory inclusions are commonly observed in carbonaceous chondrites. These inclusions are among the first solar system condensates and display 16O-rich isotopic compositions. Refractory grains have also been observed in the comet 81P/Wild-2 samples re-turned from the Stardust Mission and in CP IDPs, but they occur with much less frequency. Here we conduct coordinated mineralogical and isotopic analyses of CP IDPs that were characterized for their bulk chemistry by to study the distribution of primitive components and the degree of nebular alteration incurred.

Discovery of Non-random Spatial Distribution of Impacts in the Stardust Cometary Collector

NASA Technical Reports Server (NTRS)

Horz, Friedrich; Westphal, Andrew J.; Gainsforth, Zack; Borg, Janet; Djouadi, Zahia; Bridges, John; Franchi, Ian; Brownlee, Donald E.; Cheng. Andrew F.; Clark, Benton C.;

Comets and the origin of life; Proceedings of the Fifth College Park Colloquium on Chemical Evolution, University of Maryland, College Park, MD, October 29-31, 1980

NASA Technical Reports Server (NTRS)

Ponnamperuma, C.

1981-01-01

Papers are presented concerning the characteristics of comets and their possible role in the origin of life. Specific topics include the characteristics, origin and structure of the cometary nucleus, cometary chemical abundances, the nature of interplanetary dust and its entry into terrestrial planet atmospheres, and the mechanism of ray closure in comet tails. Attention is also given to chemically evolved interstellar dust as a source of prebiotic material, the relation of comets to paleoatmospheric photochemistry, comets as a vehicle for panspermia, limits to life posed by extreme environments, and the status of cometary space missions as of 1980.

Korteweg-deVries-Burgers (KdVB) equation in a five component cometary plasma with kappa described electrons and ions

NASA Astrophysics Data System (ADS)

Michael, Manesh; Willington, Neethu T.; Jayakumar, Neethu; Sebastian, Sijo; Sreekala, G.; Venugopal, Chandu

2016-12-01

We investigate the existence of ion-acoustic shock waves in a five component cometary plasma consisting of positively and negatively charged oxygen ions, kappa described hydrogen ions, hot solar electrons, and slightly colder cometary electrons. The KdVB equation has been derived for the system, and its solution plotted for different kappa values, oxygen ion densities, as well as the temperature ratios for the ions. It is found that the amplitude of the shock wave decreases with increasing kappa values. The strength of the shock profile decreases with increasing temperatures of the positively charged oxygen ions and densities of negatively charged oxygen ions.

Xenon Release by the In-Vacuum Etching of Aerogel: Implications for the Study of Noble Gases in Comet Wild 2 Stardust

NASA Astrophysics Data System (ADS)

O'Mara, A.; Busemann, H.; Clay, P. L.; Crowther, S. A.; Gilmour, J. D.; Wieler, R.

2014-09-01

Xenon detection in comet Wild 2 stardust is hampered by the large adsorption of Xe on aerogel. In-vacuum etching presented here may enable the stepwise separation of terrestrial Xe, cometary Xe trapped in melted aerogel and Xe in cometary silicates.

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.

Radar meteor orbital structure of Southern Hemisphere cometary dust streams

NASA Technical Reports Server (NTRS)

Baggaley, W. Jack; Taylor, Andrew D.

1992-01-01

The Christchurch, New Zealand meteor orbit radar (AMOR) with its high precision and sensitivity, permits studies of the orbital fine structure of cometary streams. PC generated graphics are presented of data on some Southern Hemisphere Streams. Such data can be related to the formation phase and subsequent dynamical processes of dust streams.

Physical characteristics of cometary dust from optical studies

NASA Technical Reports Server (NTRS)

Hanner, M. S.

1980-01-01

Observations of the sunlight scattered and thermal emission from cometary dust, which may be used to infer the physical properties of the dust grains, are reviewed. Consideration is given to the observed wavelength dependence of the scattered light from cometary coma and tails, the average scattering function of the dust grains, the average grain Bond albedo, the polarization of the scattered light, and grain temperatures deduced from thermal infrared emission. The thermal properties of dust grains are illustrated for models based on magnetite or olivine grain materials, with consideration given to the variation of thermal properties with particle radius and heliocentric distance. Comparison of the models with observations indicates that a disordered or amorphous olivine composition can give a reasonable fit to the data for appropriate grain sizes and temperatures. The observations acquired are noted to indicate an optically important particle size of 1 micron, with silicate particles not larger than a few microns usually present although pure silicate grains can not be responsible for the thermal emission, and the cometary dust grains are most likely not spherical. Further observations needed in the infrared are indicated.

Large heterogeneities in comet 67P as revealed by active pits from sinkhole collapse.

PubMed

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

2015-07-02

Pits have been observed on many cometary nuclei mapped by spacecraft. It has been argued that cometary pits are a signature of endogenic activity, rather than impact craters such as those on planetary and asteroid surfaces. Impact experiments and models cannot reproduce the shapes of most of the observed cometary pits, and the predicted collision rates imply that few of the pits are related to impacts. Alternative mechanisms like explosive activity have been suggested, but the driving process remains unknown. Here we report that pits on comet 67P/Churyumov-Gerasimenko are active, and probably created by a sinkhole process, possibly accompanied by outbursts. We argue that after formation, pits expand slowly in diameter, owing to sublimation-driven retreat of the walls. Therefore, pits characterize how eroded the surface is: a fresh cometary surface will have a ragged structure with many pits, while an evolved surface will look smoother. The size and spatial distribution of pits imply that large heterogeneities exist in the physical, structural or compositional properties of the first few hundred metres below the current nucleus surface.

A radio source occultation experiment with comet Austin 1982g, with unusual results

NASA Technical Reports Server (NTRS)

De Pater, I.; Ip, W.-H.

1984-01-01

A radio source occultation by comet Austin 1982g was observed on September 15-16, 1982. A change in the apparent position of 1242 + 41 by 1.3 arcsec occurred when the source was 220,000 km away from the cometary ion tail. If this change was due to refraction by the cometary plasma, it indicates an electron density of the plasma of about 10,000/cu cm. When the radio source was on the other side of the plasma tail, at a distance of 230,000 km, the position angle of the electric vector of the radio source changed gradually over about 140 deg within two hours. This observation cannot be explained in terms of ionospheric Faraday rotation, and results from either an intrinsic change in the radio source or Faraday rotation in the cometary plasma due to a change in the direction and/or strength of the magnetic field. In the latter case, the cometary coma must have an electron density and a magnetic field strength orders of magnitude larger than current theories predict.

Analysis of the Cometary Plasma Environment of 67P/Churyumov-Gerasimenko Near Perihelion

NASA Astrophysics Data System (ADS)

Ostaszewski, K.; Goetz, C.; Motschmann, U.; Glassmeier, K. H.

2017-09-01

Over the course of its two year escort phase the Rosetta spacecraft has provided various observations that furthered our understanding of the cometary plasma environment. The use of numerical simulations is essential for this understanding because they allow to place the in situ measurements in a global context, in turn, through observations the numerical models can be ex- tended and improved. We use the simulation code A.I.K.E.F (Müller [7]) to simulate the cometary plasma environment of 67P/Churyumov-Gerasimenko (67P/CG). Based on observations made by the Rosetta spacecraft we extend the numerical model by electron impact ionization and the anisotropic outgassing model by Hansen et al. (2016). Both extensions result in an increase in the cometary ion production rate on the dayside. Therefore, the size of the interaction region and the contained structures increases. This causes the position of the different boundaries, e.g. bow shock, to shift further away from the comet. Considering this we can explain why no bow shock crossings could be observed during the dayside excursion of Rosetta in September 2015.

Earth as a Tool for Astrobiology—A European Perspective

NASA Astrophysics Data System (ADS)

Martins, Zita; Cottin, Hervé; Kotler, Julia Michelle; Carrasco, Nathalie; Cockell, Charles S.; de la Torre Noetzel, Rosa; Demets, René; de Vera, Jean-Pierre; d'Hendecourt, Louis; Ehrenfreund, Pascale; Elsaesser, Andreas; Foing, Bernard; Onofri, Silvano; Quinn, Richard; Rabbow, Elke; Rettberg, Petra; Ricco, Antonio J.; Slenzka, Klaus; Stalport, Fabien; ten Kate, Inge L.; van Loon, Jack J. W. A.; Westall, Frances

2017-07-01

Scientists use the Earth as a tool for astrobiology by analyzing planetary field analogues (i.e. terrestrial samples and field sites that resemble planetary bodies in our Solar System). In addition, they expose the selected planetary field analogues in simulation chambers to conditions that mimic the ones of planets, moons and Low Earth Orbit (LEO) space conditions, as well as the chemistry occurring in interstellar and cometary ices. This paper reviews the ways the Earth is used by astrobiologists: (i) by conducting planetary field analogue studies to investigate extant life from extreme environments, its metabolisms, adaptation strategies and modern biosignatures; (ii) by conducting planetary field analogue studies to investigate extinct life from the oldest rocks on our planet and its biosignatures; (iii) by exposing terrestrial samples to simulated space or planetary environments and producing a sample analogue to investigate changes in minerals, biosignatures and microorganisms. The European Space Agency (ESA) created a topical team in 2011 to investigate recent activities using the Earth as a tool for astrobiology and to formulate recommendations and scientific needs to improve ground-based astrobiological research. Space is an important tool for astrobiology (see Horneck et al. in Astrobiology, 16:201-243, 2016; Cottin et al., 2017), but access to space is limited. Complementing research on Earth provides fast access, more replications and higher sample throughput. The major conclusions of the topical team and suggestions for the future include more scientifically qualified calls for field campaigns with planetary analogy, and a centralized point of contact at ESA or the EU for the organization of a survey of such expeditions. An improvement of the coordinated logistics, infrastructures and funding system supporting the combination of field work with planetary simulation investigations, as well as an optimization of the scientific return and data processing, data storage and data distribution is also needed. Finally, a coordinated EU or ESA education and outreach program would improve the participation of the public in the astrobiological activities.

The Preservation of Cometary Organics in Stardust Aerogel

NASA Astrophysics Data System (ADS)

Clemett, Simon; Nakamura-Messenger, Keiko; Sandford, Scott; McKay, David

It has been recognized for many years that the continuous global accretion of organic matter from comets and carbonaceous asteroids, over geological timescales, to the surfaces of both Earth and Mars may have played a significant role in the prebiotic chemical evolution of these planets [1]. The dominant mass fraction of accreted meteoritic material is in the form of interplanetary dust for which the current accretion rate is estimated at ˜ 40±20 Gg·yr-1 [2]. Our understanding of the organic matter present in interplanetary dust is, however, limited by the analytical challenges involved in the molecular analysis of heterogeneous micron sized particles. We have used the technique of ultrafast two-step laser mass spectrometry (µltra-L2 MS) to investigate the nature and distribution of the aromatic organic matter present in individual dust particles from comet P81/Wild 2 collected in aerogel by the STARDUST sample return mission [3]. Complex aromatic hydrocarbons have been detected in cometary particles entrained along multiple aerogel tracks. Although terrestrial contamination from the aerogel remains a concern, a substantial fraction is interpreted as indigenous. The spectral complexity is atypical of carbonaceous and ordinary chondrites. While simple fused ring polycyclic aromatic hydrocarbon (PAHs) such as naphthalene (C10 H8 ), acenaphthalene (C12 H8 ), phenanthrene (C14 H10 ) are present along with their homologous alkylation series (Ar-(CH2 )n -H) there are additionally many prominent odd-mass species present. These are consistent with several interleaved alkylation series of N-containing PAHS (NPAHs) in the form of nitriles (Ar-CN). These species may be related to the 2.3 & 4.6 µm 'XCN' adsorption features observed in the spectra of many young stellar objects and some comets, which is believed to be synthesized by ultraviolet and/or ion bombardment of precometary ices in circumstellar environments. The presence of organo-N species is of particular importance to the organic inventory of the the early Earth since its abiotic synthesis would have been extremely slow due to the difficulty in cleaving the N≡N triple bond in the absence of biology. [1] Anders (1989) Nature 342, 255; [2] Love & Brownlee (1993) Science 262, 550; Clemett et al. MAPS (submited)

The Complex Outgassing of Comets and the Resulting Coma, a Direct Simulation Monte-Carlo Approach

NASA Astrophysics Data System (ADS)

Fougere, Nicolas

During its journey, when a comet gets within a few astronomical units of the Sun, solar heating liberates gases and dust from its icy nucleus forming a rarefied cometary atmosphere, the so-called coma. This tenuous atmosphere can expand to distances up to millions of kilometers representing orders of magnitude larger than the nucleus size. Most of the practical cases of coma studies involve the consideration of rarefied gas flows under non-LTE conditions where the hydrodynamics approach is not valid. Then, the use of kinetic methods is required to properly study the physics of the cometary coma. The Direct Simulation Monte-Carlo (DSMC) method is the method of choice to solve the Boltzmann equation, giving the opportunity to study the cometary atmosphere from the inner coma where collisions dominate and is in thermodynamic equilibrium to the outer coma where densities are lower and free flow conditions are verified. While previous studies of the coma used direct sublimation from the nucleus for spherically symmetric 1D models, or 2D models with a day/night asymmetry, recent observations of comets showed the existence of local small source areas such as jets, and extended sources via sublimating icy grains, that must be included into cometary models for a realistic representation of the physics of the coma. In this work, we present, for the first time, 1D, 2D, and 3D models that can take into account the full effects of conditions with more complex sources of gas with jets and/or icy grains. Moreover, an innovative work in a full 3D description of the cometary coma using a kinetic method with a realistic nucleus and outgassing is demonstrated. While most of the physical models used in this study had already been developed, they are included in one self-consistent coma model for the first time. The inclusion of complex cometary outgassing processes represents the state-of-the-art of cometary coma modeling. This provides invaluable information about the coma by refining the understanding of the material that constitutes comets. This helps us to comprehend the process of the Solar System formation, one of the top priority questions in the 2013-2022 Planetary Science Decadal survey.

Mass Spectum Imaging of Organics Injected into Stardust Aerogel by Cometary Impacts

NASA Technical Reports Server (NTRS)

Clemett, S. J.; Nakamura-Messenger, K.; Messenger, S.

2014-01-01

Comets have largely escaped the hydrothermal processing that has affected the chemistry and mineralogy of even the most primitive meteorites. Consequently, they are expected to better preserve nebular and interstellar organic materials. Organic matter constitutes roughly 20-30% by weight of vol-atile and refractory cometary materials [1,2]. Yet organic matter identified in Stardust aerogel samples is only a minor component [3-5]. The dearth of intact organic matter, fine-grained and pre-solar materials led to suggestions that comet 81P/Wild-2 is com-posed largely of altered materials, and is more similar to meteorites than the primitive view of comets [6]. However, fine-grained materials are particularly susceptible to alteration and destruction during the hypervelocity impact. While hypervelocity capture can cause thermal pyrolysis of organic phases, some of the impacting organic component appears to have been explosively dispersed into surrounding aerogel [7]. We used a two-step laser mass spectrometer to map the distribution of organic matter within and sur-rounding a bulbous Stardust track to constrain the dispersion of organic matter during the impact.

HUT observations of carbon monoxide in the coma of Comet Levy (1990c)

NASA Technical Reports Server (NTRS)

Feldman, P. D.; Davidsen, A. F.; Blair, W. P.; Bowers, C. W.; Dixon, W. V.; Durrance, S. T.; Henry, R. C.; Kriss, G. A.; Kruk, J.; Moos, H. W.

1991-01-01

Observations of comet Levy (1990c) were made with the Hopkins Ultraviolet Telescope during the Astro-1 Space Shuttle mission on 10 Dec. 1990. The spectrum, covering the wavelength range 415 to 1850 A at a spectral emission of 3 A (in first order), shows the presence of carbon monoxide and atomic hydrogen, carbon, and sulfur in the coma. Aside from H I Lyman-beta, no cometary features are detected below 1200 A, although cometary O I and O II would be masked by the same emissions present in the day airglow spectrum. The 9.4 x 116 arcsec aperture corresponds to 12,000 x 148,000 km at the comet. The derived production rate of CO relative to water, 0.13 + or - 0.02, compared with the same ratio derived from IUE observations (made in Sep. 1990) which sample a much smaller region of the coma, 0.04 + or - 0.01, suggests the presence of an extended source of CO, as was found in comet Halley. Upper limits on Ne and Ar abundance are within an order of magnitude or solar abundances.

Observations of Comet Levy (1990c) with the Hopkins Ultraviolet Telescope

NASA Technical Reports Server (NTRS)

Feldman, P. D.; Davidsen, A. F.; Blair, W. P.; Bowers, C. W.; Dixon, W. V.; Durrance, S. T.; Henry, R. C.; Ferguson, H. C.; Kimble, R. A.; Gull, Theodore R.

1991-01-01

Observations of Comet Levy (1990c) were made with the Hopkins Ultraviolet Telescope during the Astro-1 Space Shuttle mission on December 10, 1990. The spectrum, covering the wavelength range 415-1850 A at a spectral resolution of 3 A, shows the presence of carbon monoxide and atomic hydrogen, carbon, and sulfur in the coma. Aside from H I Lyman-beta, no cometary features are detected below 1200 A, although cometary O I and O II would be masked by the same emissions present in the day airglow spectrum. The 9.4 x 116 arcsecond aperture corresponds to 12,000 x 148,000 km at the comet. The derived production rate of CO relative to water is 0.11 + or - 0.02, compared with 0.04 + or - 0.01 derived from IUE observations (made in September 1990) which sample a much smaller region of the coma. This suggests the presence of an extended source of CO, as was found in comet Halley. Upper limits on Ne and Ar abundance are within one order of magnitude of solar abundances.

The directional dependence of cometary magnetic energy density in the quasi-parallel and quasi-perpendicular regimes

NASA Technical Reports Server (NTRS)

Miller, R. H.; Gombosi, T. I.; Gary, S. P.; Winske, D.

1991-01-01

The direction of propagation of low frequency magnetic fluctuations generated by cometary ion pick-up is examined by means of 1D electromagnetic hybrid simulations. The newborn ions are injected at a constant rate, and the helicity and direction of propagation of magnetic fluctuations are explored for cometary ion injection angles of 0 and 90 deg relative to the solar wind magnetic field. The parameter eta represents the relative contribution of wave energy propagating in the direction away from the comet, parallel to the beam. For small (quasi-parallel) injection angles eta was found to be of order unity, while for larger (quasi-perpendicular) angles eta was found to be of order 0.5.

STIP Symposium on Physical Interpretation of Solar/Interplanetary and Cometary Intervals

NASA Technical Reports Server (NTRS)

Wu, S. T.

1987-01-01

The study of travelling interplanetary phenomena has continued over a period of years. The STIP (Study of Travelling Interplanetary Phenomena) Symposium on Physical Interpretation of Solar/Interplanetary and Cometary Intervals was held in Huntsville, Alabama, on May 12-15, 1987, the first of these meetings to be held in the United States. The Symposium's objective was to coordinate and disseminate new science gained from the recent solar-terrestrial and cometary intervals which can be used to better understand the linkage of physical events to the Sun's vagaries (flares, coronal holes, eruptive prominences) from their initial detection to their consequence. Fifty-one presentations were made during the four-day period. Abstracts of these reports are included as Appendix A.

The contribution of electron collisions to rotational excitations of cometary water

NASA Technical Reports Server (NTRS)

Xie, Xingfa; Mumma, Michael J.

1992-01-01

The e-H2O collisional rate for exciting rotational transitions in cometary water is evaluated for conditions found in comet Halley during the Giotto spacecraft encounter. In the case of the O(sub 00) yields 1(sub 11) rotational transition, the e-H2O collisional rate exceeds that for excitation by neutral-neutral collisions at distances exceeding 3000 km from the cometary nucleus. Thus, the rotational temperature of the water molecule in the intermediate coma may be controlled by collisions with electrons rather than with neutral collisions, and the rotational temperature retrieved from high resolution infrared spectra of water in comet Halley may reflect electron temperatures rather than neutral gas temperature in the intermediate coma.

COMETARY SCIENCE. 67P/Churyumov-Gerasimenko surface properties as derived from CIVA panoramic images.

PubMed

Bibring, J-P; Langevin, Y; Carter, J; Eng, P; Gondet, B; Jorda, L; Le Mouélic, S; Mottola, S; Pilorget, C; Poulet, F; Vincendon, M

2015-07-31

The structure and composition of cometary constituents, down to their microscopic scale, are critical witnesses of the processes and ingredients that drove the formation and evolution of planetary bodies toward their present diversity. On board Rosetta's lander Philae, the Comet Infrared and Visible Analyser (CIVA) experiment took a series of images to characterize the surface materials surrounding the lander on comet 67P/Churyumov-Gerasimenko. Images were collected twice: just after touchdown, and after Philae finally came to rest, where it acquired a full panorama. These images reveal a fractured surface with complex structure and a variety of grain scales and albedos, possibly constituting pristine cometary material. Copyright © 2015, American Association for the Advancement of Science.

Evidence of Collisional Histories of Asteroids, Comets and Meteorites: Comparisons with Shocked Minerals

NASA Astrophysics Data System (ADS)

Lederer, Susan M.; Jensen, Elizabeth; Smith, Douglas; Fane, Michael; Whizin, Akbar; Landsman, Zoe A.; Wooden, Diane H.; Lindsay, Sean S.; Cintala, Mark; Keller, Lindsay P.; Zolensky, Michael

2017-10-01

Evidence of the collisional history of comets and asteroids has been emerging from analyses of cometary forsterite and enstatite returned from Comet Wild 2 by the Stardust mission (Keller et al.Geochim. Cosmochim. Acta 72, 2008; Tomeoka et al. MAPS 43, 2008; Jacobs et al. MAPS 44, 2009). Likewise, shock metamorphism is observed in many meteoritic forsterites and enstatites (McCausland et al. AGU, 2010), suggesting similar collisional histories for asteroids. Further exploration of the effects of collisions is slated for the upcoming Asteroid Impact Mission/Double Asteroid Redirection Test (AIM/DART) mission, expected for launch in 2020. DART will impact Didymoon, the companion of the larger 65803 Didymos (1996 G2) asteroid, and AIM will use its instrumentation to characterize the impact.A suite of relevant impact experiments have been carried out in the Experimental Impact Laboratory at the NASA Johnson Space Center at velocities ranging from ~2.0 - 2.8 km s-1 and temperatures from 25°C to -100°C. Targets include a suite of minerals typically found in cometary dust and in asteroids and meteorites: Mg-rich forsterite (olivine), enstatite (orthopyroxene), diopside (clinopyroxene), magnesite (Mg-rich carbonate), and serpentine (phyllosilicate). Transmission Electron Microscope (TEM) imaging indicates evidence of shock similar to that seen in forsterite and enstatite from Comet Wild 2. Fourier Transform Infrared (FTIR) Spectroscopy will also be used for comparisons with meteorite spectra. A quantitative analysis of the shock pressures required to induce planar dislocations and spectral effects with respect to wavelength will also be presented.Funding provided by the NASA PG&G grant 09-PGG09-0115, NSF grant AST-1010012. Special thanks to NASA EIL staff, F. Cardenas and R. Montes.

The Cosmochemistry of Pluto: A Primordial Origin of Volatiles?

NASA Astrophysics Data System (ADS)

Glein, C. R.; Waite, J. H., Jr.

2017-12-01

Pluto is a wonderland of volatiles. Nitrogen, methane, and carbon monoxide are the principal volatiles that maintain its tenuous atmosphere, and they have also created a mesmerizing landscape of icy geological features, including Pluto's iconic "heart". Recent data, particularly those returned by the New Horizons mission [1-3], allow us to begin testing hypotheses for the cosmochemical origins of these world-shaping species on Pluto. Here, we investigate if Pluto's volatiles could have been accreted in its building blocks. We take both bottom-up and top-down approaches in testing this hypothesis in terms of mass balance. We estimate Pluto's primordial inventory of volatiles by scaling a range of cometary abundances up to the ice mass fraction of Pluto. We also make estimates of the present and lost inventories of volatiles based on surface observations and interpretations, as well as different scenarios of atmospheric photochemistry and escape. We find that, if primordial Pluto resembled a giant comet with respect to volatile abundances, then the initial volatile inventory would have been sufficient to account for the estimated present and lost inventories. This consistency supports a primordial origin for Pluto's volatiles. However, the observed ratio of CO/N2 in Pluto's atmosphere [4] is several orders of magnitude lower than the nominal cometary value. We are currently using phase equilibrium and rate models to explore if volatile layering in Sputnik Planitia, or the destruction of CO in a past or present subsurface ocean of liquid water could explain the apparent depletion of CO on Pluto. References: [1] Moore et al. (2016) Science 351, 1284. [2] Grundy et al. (2016) Science 351, aad9189. [3] Gladstone et al. (2016) Science 351, aad8866. [4] Lellouch et al. (2017) Icarus 286, 289.

Propulsion Technology Development for Sample Return Missions Under NASA's ISPT Program

NASA Technical Reports Server (NTRS)

Anderson, David J.; Pencil, Eric J.; Vento, Daniel; Dankanich, John W.; Munk, Michelle M.; Hahne, David

2011-01-01

The In-Space Propulsion Technology (ISPT) Program was tasked in 2009 to start development of propulsion technologies that would enable future sample return missions. Sample return missions could be quite varied, from collecting and bringing back samples of comets or asteroids, to soil, rocks, or atmosphere from planets or moons. The paper will describe the ISPT Program s propulsion technology development activities relevant to future sample return missions. The sample return propulsion technology development areas for ISPT are: 1) Sample Return Propulsion (SRP), 2) Planetary Ascent Vehicles (PAV), 3) Entry Vehicle Technologies (EVT), and 4) Systems/mission analysis and tools that focuses on sample return propulsion. The Sample Return Propulsion area is subdivided into: a) Electric propulsion for sample return and low cost Discovery-class missions, b) Propulsion systems for Earth Return Vehicles (ERV) including transfer stages to the destination, and c) Low TRL advanced propulsion technologies. The SRP effort will continue work on HIVHAC thruster development in FY2011 and then transitions into developing a HIVHAC system under future Electric Propulsion for sample return (ERV and transfer stages) and low-cost missions. Previous work on the lightweight propellant-tanks will continue under advanced propulsion technologies for sample return with direct applicability to a Mars Sample Return (MSR) mission and with general applicability to all future planetary spacecraft. A major effort under the EVT area is multi-mission technologies for Earth Entry Vehicles (MMEEV), which will leverage and build upon previous work related to Earth Entry Vehicles (EEV). The major effort under the PAV area is the Mars Ascent Vehicle (MAV). The MAV is a new development area to ISPT, and builds upon and leverages the past MAV analysis and technology developments from the Mars Technology Program (MTP) and previous MSR studies.

Characterizing the population of Asteroids in Cometary Orbits (ACOs)

NASA Astrophysics Data System (ADS)

Tancredi, Gonzalo; Licandro, Javier; Alí-Lagoa, Victor; Martino, Silvia; Vieira Monteiro, Filipe; Silva, Jose Sergio; Lazzaro, Daniela

2015-08-01

The classification criterion between asteroids and comets has evolved in recent decades, but the main phenomenological distinction remains unchanged: comets are active objects as they present gas and dust ejection from the surface at some point of their orbits, while asteroids are inert objects as they do not show any kind of large scale gas and dust ejection.To identify the transitional objects several classification schemes based on the orbital elements have been used. They are usually based on the Tisserand’s parameter (TJ). Tancredi (2014) presents a much more restrictive criterion to identify ACOs that ensured that the objects have a dynamical evolution similar to the population of periodic comets. After applying the criteriaa to the sample of over half a million asteroids already discovered, we obtain 316 ACOs that are further classified in subclasses similar to the cometary classification: 203 objects belong to the Jupiter Family group; 72 objects are classified as Centaurs; and 56 objects have Halley Type Orbits (also known as Damocloids). These are the best-known extinct/dormant comets candidates from a dynamical point of view.We study the physical properties of this sample of ACOs. Two results will be presented:- We look for the ACOs detected by the NASA’s WISE and by fitting a thermal model to their observations, we derive: the effective diameter, beaming parameter and the visible geometric albedo, using the method described in Al-Lagoa et al (2013). We obtain these parameters for 37 of 203 ACOs in JFC orbits and 13 of 56 Damocloids. We also compute the Cumulative Size Distribution (CSDs) of these populations and compare them with the CSDs of JF Comets and Centaurs.- We have been monitoring the observable ACOs since 12/2014 up to 06/2015. Every other month we select all the ACOs with elongations >90deg and estimated magnitudes V<21. We try to observe them with the 1m IMPACTON telescope of the Observatório Astronômico do Sertão de Itaparica (OASI). By comparing the photometric profiles of the ACOs with background stars, we try to detect some hint of cometary activity. Over 20 ACOs have been observed in the six months.

Detection of CN emission from (2060) Chiron

NASA Technical Reports Server (NTRS)

Bowell, Edward

1991-01-01

Spectrophotometric observations of (2060) Chiron were obtained. Their primary goal was to look for the subtle differences in color between Chiron and its surrounding coma, and to search for possible absorption or emission features in Chiron's spectrum. The presence of the CN(0-0) emission band was identified. It proves Chiron's cometary nature and breaks the record heliocentric distance for cometary gaseous emission.

Formation of Prebiotic Molecules in Interstellar and Cometary Ices

NASA Technical Reports Server (NTRS)

Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.; Dworkin, Jason; Gilette, J. Seb; Zare, Richard N.; DeVincenzi, D. (Technical Monitor)

2000-01-01

We report here on our lab studies of ice photochemistry of large organic molecules under cometary conditions. We focus on polycyclic aromatic hydrocarbons (PAHs), their photoproducts, and their similarities to molecules seen in living systems today. We note that these kinds of compounds are seen in meteorites and we propose an explanation for both their formation and their observed deuterium enrichments.

Cometary particles - Thin sectioning and electron beam analysis

NASA Technical Reports Server (NTRS)

Bradley, J. P.; Brownlee, D. E.

1986-01-01

Thin sections (500 to 1000 angstroms thick) of individual micrometeorites (5 to 15 micrometers) have been prepared with an ultramicrotome equipped with a diamond knife. Electron microscope examination of these sections has revealed the internal structures of chondritic micrometeorites, and a subset of highly porous, fragile particles has been identified. Delicate meteoritic materials such as these are characteristic of debris from cometary meteors.

Laboratory Measurements of Cometary Photochemical Phenomena.

DTIC Science & Technology

1981-12-04

PROGFIAM ELEMENT.PROJECT TASK Laser .Chemistry Division AREA & WORK UNIT NUMaZRS Department of Chemistry - Howard University NR.051-733 Wash’ ngtQn, D. C...William M. Jackson Laser Chemistry Division Department of Chemistry Howard University .Washington, D. C. 20059 / Published by Jet Propulsion Laboratory...MEASUREMENTS OF COMETARY PHOTOCHEMICAL PHENOMENA William M. Jackson Howard University Washington, DC 20059 Abstract Laboratory experiments are described

Testing the Martian Methane from Cometary Debris Hypothesis: The Unusually Close 24 Jan 2018 Interaction Between Comet C/2007 H2 (Skiff) and Mars

NASA Technical Reports Server (NTRS)

Fries, M.; Archer, D.; Christou, T.; Conrad, P.; Eigenbrode, J.; Kate, I. L. ten; Steele, A.

2018-01-01

In previous work we proposed a hypothesis wherein debris moving along cometary orbits interacting with Mars (e.g. meteor showers) may be responsible for transient local increases of methane observed in the martian atmosphere (henceforth 'the hypothesis' ). An examination of the literature of methane detections dating back to 1997 showed that each detection was made, at most, 16 days after an interaction between Mars and one of seven small bodies (six comets and the unusual object 5335 Damocles)[ibid]. Two observations of high-altitude, transient visible plumes on Mars also correlate with cometary interactions, one occurring on the same day as the plume observation and the second observation occurring three days afterwards, and with two of the same seven small bodies. The proposed mechanism for methane production is dissemination of carbon-rich cometary material on infall into Mars' atmosphere followed by methane production via UV photolysis, a process that has been observed in laboratory experiments. Given this set of observations it is necessary and indeed conducive to the scientific process to explore and robustly test the hypothesis.

Gas flow through through a porous mantle: implications of fluidisation

NASA Astrophysics Data System (ADS)

Bentley, Mark; Koemle, Norbert; Kargl, Guenter; Huetter, Mag. Erika Sonja

Understanding the interaction of dust and gas in the upper layers of a cometary mantle is critical for understanding cometary evolution. The state of knowledge of conditions in these layers is currently rather low, and a wide range of flow conditions and phenomena can be imagined. A model is presented here that examines the conditions under which so-called "fluidized beds" might be possible in a cometary mantle. This phenomenon, well studied in industry, occurs when the weight of a bed of particles is equal to the gas drag of a gas or fluid flowing upwards through it. Wherever fluidisation occurs in a cometary mantle, it could change the dominant heat transfer mechanism by removing intimate particle contacts (creating an expanded bed) or allowing particle convection in the now fluid-like mantle. There are also implications for the stability of the Rosetta lander, Philae, if such a state were to occur in the vicinity of the deployed anchor. A two-fluid model is used, with necessarily restricted geometries, to demonstrate the conditions (gravity, pressure, gas velocity, particle size etc.) under which fluidisation could occur, and the scientific results and implications for the Rosetta mission are explored.

Cometary atmospheres: Modeling the spatial distribution of observed neutral radicals

NASA Technical Reports Server (NTRS)

Combi, Michael R.

1986-01-01

Progress during the second year of a program of research on the modeling of the spatial distributions of cometary radicals is discussed herein in several major areas. New scale length laws for cometary C2 and CN were determined which explain that the previously-held apparent drop of the C2/CN ratio for large heliocentric distances does not exist and that there is no systematic variation. Monte Carlo particle trajectory model (MCPTM) analysis of sunward and anti-sunward brightness profiles of cometary C2 was completed. This analysis implies a lifetime of 31,000 seconds for the C2 parent and an ejection speed for C2 of approximately 0.5 km/sec upon dissociation from the parent. A systematic reanalysis of published C3 and OH data was begun. Preliminary results find a heliocentric distance dependence for C3 scale lengths with a much larger variation than for C2 and CN. Scale lengths for OH are generally somewhat larger than currently accepted values. The MCPTM was updated to include the coma temperature. Finally, the collaborative effort with the University of Arizona programs has yielded some preliminary CCD images of Comet P/Halley.

Modelling of 67P cometary grains dynamic in the vicinity of the Rosetta spacecraft

NASA Astrophysics Data System (ADS)

Cipriani, F.; Altobelli, N.; Taylor, M.; Fulle, M.; Della Corte, V.; Rotundi, A.

2017-09-01

The interpretation of a number of Rosetta datasets (e.g. GIADA, COSIMA, MIDAS...), relies on the description of cometary grains dynamic in the close vicinity of the spacecraft. In particular the charged grains behaviour in the 3D spacecraft sheath open to the instrument entrances is complex and has not been described at such scales. The existence of a warm electrons population (a few 10eVs energy) in the cometary plasma as revealed during the Rendez-vous phase has been driving the spacecraft potential to negative values typically in the range -1 to -20V as inferred from RPC measurements [1]. Observation of cometary grains in the 10μm to mm range by GIADA and COSIMA[2] allowed to distinguish so called 'compact' grains of processed materials from the solar nebula from 'fluffy' aggregates of more primitive origin. When detected such grains have been observed to reach the instruments at m/s or less velocities. On particular it was inferred that fluffy aggregates are disrupted by electrostatic forces in the vicinity of the spacecraft due to the effects of local plasma hence resulting in particle showers observed by the instruments.

In Situ Plasma Measurements of Fragmented Comet 73P Schwassmann-Wachmann 3

NASA Astrophysics Data System (ADS)

Gilbert, J. A.; Lepri, S. T.; Rubin, M.; Combi, M.; Zurbuchen, T. H.

2015-12-01

The interiors of comets contain some of the most pristine material in the solar system. Comet 73P/Schwassmann-Wachmann 3, discovered in 1930, is a Jupiter-family comet with a 5.34-year period. This comet split into 5 fragments in 1995 and disintegrated into nearly 70 major pieces in 2006. In 2006 May and June, recently ionized cometary particles originating from fragments including and surrounding some of these major objects were collected with the ACE/SWICS and Wind/STICS sensors. Due to a combination of the instrument characteristics and the close proximity of the fragments passing between those spacecraft and the Sun, unique measurements regarding the charge state composition and the elemental abundances of both cometary and heliospheric plasma were made during that time. The cometary material released from some of these fragments can be identified by the concentrations of water-group pickup ions having a mass-per-charge ratio of 16-18 amu e-1, indicating that while these fragments are small, they are still actively sublimating. We present an analysis of cometary composition, spatial distribution, and heliospheric interactions, with a focus on helium, C+/O+, and water-group ions.

IN SITU PLASMA MEASUREMENTS OF FRAGMENTED COMET 73P SCHWASSMANN–WACHMANN 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilbert, J. A.; Lepri, S. T.; Combi, M.

2015-12-10

The interiors of comets contain some of the most pristine material in the solar system. Comet 73P/Schwassmann–Wachmann 3, discovered in 1930, is a Jupiter-family comet with a 5.34-year period. This comet split into 5 fragments in 1995 and disintegrated into nearly 70 major pieces in 2006. In 2006 May and June, recently ionized cometary particles originating from fragments including and surrounding some of these major objects were collected with the ACE/SWICS and Wind/STICS sensors. Due to a combination of the instrument characteristics and the close proximity of the fragments passing between those spacecraft and the Sun, unique measurements regarding themore » charge state composition and the elemental abundances of both cometary and heliospheric plasma were made during that time. The cometary material released from some of these fragments can be identified by the concentrations of water-group pickup ions having a mass-per-charge ratio of 16–18 amu e{sup −1}, indicating that while these fragments are small, they are still actively sublimating. We present an analysis of cometary composition, spatial distribution, and heliospheric interactions, with a focus on helium, C{sup +}/O{sup +}, and water-group ions.« less

Stardust impact analogs: Resolving pre- and postimpact mineralogy in Stardust Al foils

NASA Astrophysics Data System (ADS)

Wozniakiewicz, Penelope J.; Ishii, Hope A.; Kearsley, Anton T.; Burchell, Mark J.; Bradley, John P.; Price, Mark C.; Teslich, Nick; Lee, Martin R.; Cole, Mike J.

2012-04-01

The grains returned by NASA's Stardust mission from comet 81P/Wild 2 represent a valuable sample set that is significantly advancing our understanding of small solar system bodies. However, the grains were captured via impact at ˜6.1 km s-1 and have experienced pressures and temperatures that caused alteration. To ensure correct interpretations of comet 81P/Wild 2 mineralogy, and therefore preaccretional or parent body processes, an understanding of the effects of capture is required. Using a two-stage light-gas gun, we recreated Stardust encounter conditions and generated a series of impact analogs for a range of minerals of cometary relevance into flight spare Al foils. Through analyses of both preimpact projectiles and postimpact analogs by transmission electron microscopy, we explore the impact processes occurring during capture and distinguish between those materials inherent to the impactor and those that are the product of capture. We review existing and present additional data on olivine, diopside, pyrrhotite, and pentlandite. We find that surviving crystalline material is observed in most single grain impactor residues. However, none is found in that of a relatively monodisperse aggregate. A variety of impact-generated components are observed in all samples. Al incorporation into melt-derived phases allows differentiation between melt and shock-induced phases. In single grain impactor residues, impact-generated phases largely retain original (nonvolatile) major element ratios. We conclude that both surviving and impact-generated phases in residues of single grain impactors provide valuable information regarding the mineralogy of the impacting grain whilst further studies are required to fully understand aggregate impacts and the role of subgrain interactions during impact.

Amino Acids in Asteroids and Comets: Implications for the Origin of Life on Earth and Possibly Elsewhere

NASA Technical Reports Server (NTRS)

Glavin, Daniel

2012-01-01

Meteorites provide a record of the chemical processes that occurred in the early solar system before life began on Earth. The delivery of organic matter by asteroids, comets, and their fragments to the Earth and other planetary bodies in our solar system could have been an important source of the prebiotic organic inventory needed for the emergence of life. Amino acids are essential components of proteins and enzymes in life on Earth and these prebiotic organic compounds have been detected in a wide variety of carbon-rich meteorites, the majority of which have been determined to be extraterrestrial in origin. In addition, many amino acids are structurally chiral (they possess handedness) and with a few very rare exceptions, only left handed (L) amino acids are found in biology, while all known abiotic syntheses of amino acids result in equal mixtures of left and right handed (LD) amino acids. The discovery of a significant left handed amino acid imbalance of up to 20% in several different carbonaceous meteorites, could point toward a possible prebiotic contribution to the origin of biological homochirality by the exogenous delivery of extraterrestrial organic material to the early Earth. In this talk, I will focus on recent state-of-the-art measurements of the distribution, chirality, and isotopic composition of amino acids in meteorites and cometary samples carried out at the Goddard Astrobiology Analytical Laboratory. Results from the analyses of a variety of Antarctic meteorites, samples from comet Wild 2 returned by the STARDUST mission, and meteorite fragments of asteroid 2008 TC3 called Almahata Sitta recovered from northern Sudan will be discussed

Sample Returns Missions in the Coming Decade

NASA Technical Reports Server (NTRS)

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

2000-01-01

In the coming decade, several missions will attempt to return samples to Earth from varying parts of the solar system. These samples will provide invaluable insight into the conditions present during the early formation of the solar system, and possibly give clues to how life began on Earth. A description of five sample return missions is presented (Stardust, Genesis, Muses-C. Mars Sample Return, and Comet Nucleus Sample Return). An overview of each sample return mission is given, concentrating particularly on the technical challenges posed during the Earth entry, descent, and landing phase of the missions. Each mission faces unique challenges in the design of an Earth entry capsule. The design of the entry capsule must address the aerodynamic, heating, deceleration, landing, and recovery requirements for the safe return of samples to Earth.

Trajectories of charged dust grains in the cometary environment

NASA Astrophysics Data System (ADS)

Horanyi, M.; Mendis, D. A.

1985-07-01

Using a simple model of the particles and fields environment of a comet, the trajectories of the smallest (micron- and submicron-sized) dust grains that are expected to be released from a cometary nucleus are calculated. It is shown that electromagnetic forces play a crucial role in the dynamics of these particles. The present calculations indicate not only the asymmetry of the sunward dust envelopes that have been suggested earlier by other authors, but they also indicate the possible existence of wavy dust features far down the tail, reminiscent of the peculiar wavy dust feature observed in the dust tail of Comet Ikeya-Seki 1965f. The importance of these findings in studying the lower end of the cometary dust mass spectrum during the forthcoming fly-by missions to Comet Halley is underscored.

The density of cometary protons upstream of Comet Halley's bow shock

NASA Astrophysics Data System (ADS)

Neugebauer, M.; Goldstein, B. E.; Balsiger, H.; Neubauer, F. M.; Schwenn, R.; Shelley, E. G.

1989-02-01

Cometary protons picked up by the solar wind were detected by the high energy range spectrometer of the Giotto ion mass spectrometer starting at a cometocentric distance of about 12 million km. On the average, the density of cometary protons varied approximately as the inverse square of the cometocentric distance, reaching a value of 0.11/cu cm just outside the bow shock. The data can be successfully fit to models that include substantial amounts of both slow (1 km/s) and fast (8 km/s or greater) H atoms beyond the bow shock. Large local variations in the density of picked-up protons can be explained on the basis of variations in the direction of the interplanetary magnetic field in upstream regions where pitch angle scattering was weak.

Martian Methane From a Cometary Source: A Hypothesis

NASA Technical Reports Server (NTRS)

Fries, M.; Christou, A.; Archer, D.; Conrad, P.; Cooke, W.; Eigenbrode, J.; ten Kate, I. L.; Matney, M.; Niles, P.; Sykes, M.;

Unusual characteristics of electromagnetic waves excited by cometary newborn ions with large perpendicular energies

NASA Technical Reports Server (NTRS)

Brinca, A. L.; Tsurutani, B. T.

1987-01-01

The characteristics of electromagnetic waves excited by cometary newborn ions with large perpendicular energies are examined using a model of solar wind permeated by dilute drifting ring distributions of electrons and oxygen ions with finite thermal spreads. The model has parameters compatible with the ICE observations at the Giacobini-Zinner comet. It is shown that cometary newborn ions with large perpendicular energies can excite a wave mode with rest frame frequencies in the order of the heavy ion cyclotron frequency, Omega(i), and unusual propagation characteristics at small obliquity angles. For parallel propagation, the mode is left-hand circularly polarized, might be unstable in a frequency range containing Omega(i), and moves in the direction of the newborn ion drift along the static magnetic field.

Dynamics of Long-period Comets

NASA Technical Reports Server (NTRS)

Weissman, P. R.

1985-01-01

Dynamical studies of the origin and evolution of long period comets in the Oort cloud during the past year have concentrated on four areas: (1) interpretation of IRAS observations of dust shells around Vega and some 40 other main sequence stars as evidence for cometary clouds around each of these stars; (2) the dynamical plausibility of an unseen solar companion star orbiting in the Oort cloud and causing periodic cometary showers which result in biological extinction events on the earth; (3) a review of the current hypotheses for cometary formation with particular attention to how each mechanism supplies the required mass of comets to the Oort cloud; and (4) development of new dynamics software to simulate the passage of individual stars directly through the Oort cloud. Each of these efforts is described in detail.

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.

Constraining the Compositional Heterogeneity in CO-Dominated Comet C/2016 R2 (PanSTARRS)

NASA Astrophysics Data System (ADS)

McKay, Adam; Kelley, Michael; DiSanti, Michael; Womack, Maria; Wierzchos, Kacper; Biver, Nicolas; de Val-Borro, Miguel; Cordiner, Martin; Dello Russo, Neil; Feaga, Lori; Bauer, James; Cochran, Anita; Harrington Pinto, Olga

2018-05-01

Comets exhibit a primitive volatile composition, making them invaluable tools for understanding the formation of the Solar System. Constraining the compositional heterogeneity of cometary nuclei is vital for interpreting cometary composition in terms of the physical conditions operating in the protosolar disk at the time of planet formation. Some comets exhibit variability in observed coma composition over the course of their orbit. This could be indicative of a heterogeneous nucleus consisting of cometesimals formed in different parts of the protosolar nebula under differing conditions. Alternatively, the observed heterogeneity could be post-formation evolution. We propose to use Spitzer IRAC observations of CO2 in the atypically CO-rich comet C/2016 R2 (PanSTARRS) to better understand the compositional heterogeneity of cometary nuclei.

Characterization of biogenic elements in interplanetary dust particles

NASA Technical Reports Server (NTRS)

Bunch, T. E.

1986-01-01

Those particles that were designated cometary are aggregates of amorphous materials including carbon, iron-magnesium silicates, sulfides, metal and trace amounts of unusual phases. Most aggregates are carbon-rich with major and minor element abundances similar to a fine grained matrix of carbonaceous chondrites. Several particles were analyzed by a laser microprobe. The negative ionic species identified to date include carbon clusters, protonated carbon clusters, CN-, HCN-, CNO-, PO2-, PO3-, S-, S2- asnd OH-. These species are similar to those observed in cometary spectra and they support the assumption that organic materials are present. The occurance of phosphate ions suggests the presence of apatite or whitlockite. Cometary particle characteristics may indicate that the component grains represent primitive unaltered dust whose overall properties are extremely similar to altered primitive dust in carbonaceous chondrites.

Mars Sample Return Architecture Overview

NASA Astrophysics Data System (ADS)

Edwards, C. D.; Vijendran, S.

2018-04-01

NASA and ESA are exploring potential concepts for a Sample Retrieval Lander and Earth Return Orbiter that could return samples planned to be collected and cached by the Mars 2020 rover mission. We provide an overview of the Mars Sample Return architecture.

Planetary astronomy program

NASA Technical Reports Server (NTRS)

Chapman, C. R.; Hartmann, W. K.

1978-01-01

Observations and analyses of asteroids, Trojans and cometary nuclei are presented. Spectrophotometry was used to observe the cometary nuclei. The spectra are plotted as a function of semimajor axis and eccentricity. Trojans and other asteroids at great solar distances show a variety of spectra, many of them quite red despite the low measured albedoes for many of these asteroids. The asteroid spectra are grouped according to diameter and taxonomic class.

Terrestrial catastrophe caused by cometary impact at the end of Cretaceous

NASA Astrophysics Data System (ADS)

Hsü, Kenneth J.

1980-05-01

Evidence is presented indicating that the extinction, at the end of the Cretaceous, of large terrestrial animals was caused by atmospheric heating during a cometary impact and that the extinction of calcareous marine plankton was a consequence of poisoning by cyanide released by the fallen comet and of a catastrophic rise in calcite-compensation depth in the oceans after the detoxification of the cyanide.

Original and future cometary orbits. IV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marsden, B.G.

1990-06-01

The values of the original and future reciprocal semimajor axes are calulcated for 36 recent osculating cometary orbits. The results are compared with the computations of Yabushita and Hasegawa (1989). Adjustments for deriving original and future orbits are given for nine other recent comets for which only parabolic orbit determinations are available. Specific attention is given to the physical comet pair 1987 XXX/1988 III. 15 refs.

Structure and dynamics of the umagnetized plasma around comet 67P/CG

NASA Astrophysics Data System (ADS)

Henri, P.; Vallières, X.; Gilet, N.; Hajra, R.; Moré, J.; Goetz, C.; Richter, I.; Glassmeier, K. H.; Galand, M. F.; Heritier, K. L.; Eriksson, A. I.; Nemeth, Z.; Tsurutani, B.; Rubin, M.; Altwegg, K.

2016-12-01

At distances close enough to the Sun, when comets are characterised by a significant outgassing, the cometary neutral density may become large enough for both the cometary plasma and the cometary gas to be coupled, through ion-neutral and electron-neutral collisions. This coupling enables the formation of an unmagnetised expanding cometary ionosphere around the comet nucleus, also called diamagnetic cavity, within which the solar wind magnetic field cannot penetrate. The instruments of the Rosetta Plasma Consortium (RPC), onboard the Rosetta Orbiter, enable us to better constrain the structure, dynamics and stability of the plasma around comet 67P/CG. Recently, magnetic field measurements (RPC-MAG) have shown the existence of such a diamagnetic region around comet 67P/CG [Götz et al., 2016]. Contrary to a single, large scale, diamagnetic cavity such as what was observed around comet Halley, Rosetta have crossed several diamagnetic structures along its trajectory around comet 67P/CG. Using electron density measurements from the Mutual Impedance Probe (RPC-MIP) during the different diamagnetic cavity crossings, identified by the flux gate magnetometer (RPC-MAG), we map the unmagnetised plasma density around comet 67P/CG. Our aims is to better constrain the structure, dynamics and stability of this inner cometary plasma layer characterised by cold electrons (as witnessed by the Langmuir Probes RPC-LAP). The ionisation ratio in these unmagnetised region(s) is computed from the measured electron (RPC-MIP) and neutral gas (ROSINA/COPS) densities. In order to assess the importance of solar EUV radiation as a source of ionisation, the observed electron density will be compared to a the density expected from an ionospheric model taking into account solar radiation absorption. The crossings of diamagnetic region(s) by Rosetta show that the unmagnetised cometary plasma is particularly homogeneous, compared to the highly dynamical magnetised plasma observed in adjacent magnetised regions. Moreover, during the crossings of multiple, successive diamagnetic region(s) over time scales of tens of minutes or hours, the plasma density is almost identical in the different unmagnetised regions, suggesting that these unmagnetised regions may be a single diamagnetic structure crossed several times by Rosetta.

The morphology of cometary dust: Subunit size distributions down to tens of nanometres

NASA Astrophysics Data System (ADS)

Mannel, Thurid; Bentley, Mark; Boakes, Peter; Jeszenszky, Harald; Levasseur-Regourd, Anny-Chantal; Schmied, Roland; Torkar, Klaus

2017-04-01

The Rosetta orbiter carried a dedicated analysis suite for cometary dust. One of the key instruments was MIDAS (Micro-Imaging Dust Analysis System), an atomic force microscope that scanned the surfaces of hundreds of (sub-)micrometre particles in 3D with resolutions down to nanometres. This provided the opportunity to study the morphology of the smallest cometary dust; initial investigation revealed that the particles are agglomerates of smaller subunits [1] with different structural properties [2]. To understand the (surface-) structure of the dust particles and the origin of their smallest building blocks, a number of particles were investigated in detail and the size distribution of their subunits determined [3]. Here we discuss the subunit size distributions ranging from tens of nanometres to a few micrometres. The differences between the subunit size distributions for particles collected pre-perihelion, close to perihelion, and during a huge outburst are examined, as well as the dependence of subunit size on particle size. A case where a particle was fragmented in consecutive scans allows a direct comparison of fragment and subunit size distributions. Finally, the small end of the subunit size distribution is investigated: the smallest determined sizes will be reviewed in the context of other cometary missions, interplanetary dust particles believed to originate from comets, and remote observations. It will be discussed if the smallest subunits can be interpreted as fundamental building blocks of our early Solar System and if their origin was in our protoplanetary disc or the interstellar material. References: [1] M.S. Bentley, R. Schmied, T. Mannel et al., Aggregate dust particles at comet 67P/Chruyumov-Gerasimenko, Nature, 537, 2016. doi:10.1038/nature19091 [2] T. Mannel, M.S. Bentley, R. Schmied et al., Fractal cometary dust - a window into the early Solar system, MNRAS, 462, 2016. doi:10.1093/mnras/stw2898 [3] R. Schmied, T. Mannel, H. Jeszenszky, M.S. Bentley, Properties of cometary dust down to the nanometre scale, poster at the conference 'Comets: A new vision after Rosetta/Philae' in Toulouse, 14-18 November 2016.

Dynamics and Distribution of Interplanetary Dust

NASA Astrophysics Data System (ADS)

Ipatov, S. I.; Mather, J. C.

2005-08-01

We integrated the orbital evolution of 12,000 asteroidal, cometary, and trans-Neptunian dust particles, under the gravitational influence of planets, Poynting-Robertson drag, radiation pressure, and solar wind drag (Annals of the New York Academy of Sciences, v. 1017, 66-80, 2004; Advances in Space Research, in press, 2005). The orbital evolution of 30,000 Jupiter-family comets (JFCs) was also integrated (Annals of the New York Academy of Sciences, v. 1017, 46-65, 2004). For asteroidal and cometary particles, the values of the ratio β between the radiation pressure force and the gravitational force varied from <0.0004 to 0.4 (for silicates, such values correspond to particle diameters between >1000 and 1 microns). The considered cometary particles started from comets 2P, 10P, and 39P. The probability of a collision of an asteroidal or cometary dust particle with the Earth during a lifetime of the particle was maximum at diameter about 100 microns; this is in accordance with cratering records. Our different studies of migration of dust particles and small bodies testify that the fraction of cometary dust particles of the overall dust population inside Saturn's orbit is considerable and can be dominant: (1) Some JFCs can reach orbits entirely located inside Jupiter's orbit and remain in such orbits for millions of years. Such former comets could disintegrate during millions of years and produce a lot of mini-comets and dust. (2) The spatial density of migrating trans-Neptunian particles near Jupiter's orbit is smaller by a factor of several than that beyond Saturn's orbit. Only a small fraction of asteroidal particles can migrate outside Jupiter's orbit. Therefore cometary dust particles are needed to explain the observed constant spatial density of dust particles at 3-18 AU from the Sun. (3) Comparison of the velocities of zodiacal dust particles obtained in our runs with the observations of velocities of these particles made by Reynolds et al. (Ap.J., 2004, v. 612, 1206-1213) shows that only asteroidal dust particles cannot explain these observations, and particles produced by high-eccentricity comets (such as Comet Encke) are needed for such explanation. Several our recent papers are presented on astro-ph.

Mars Sample Return without Landing on the Surface

NASA Technical Reports Server (NTRS)

Jurewicz, A. J. G.; Jones, Steven M.; Yen, A. S.

2000-01-01

Many in the science community want a Mars sample return in the near future, with the expectation that it will provide in-depth information, significantly beyond what we know from remote sensing, limited in-situ measurements, and work with Martian meteorites. Certainly, return of samples from the Moon resulted in major advances in our understanding of both the geologic history of our planetary satellite, and its relationship to Earth. Similar scientific insights would be expected from analyses of samples returned from Mars. Unfortunately, Mars-lander sample-return missions have been delayed, for the reason that NASA needs more time to review the complexities and risks associated with that type of mission. A traditional sample return entails a complex transfer-chain, including landing, collection, launch, rendezvous, and the return to Earth, as well as an evaluation of potential biological hazards involved with bringing pristine Martian organics to Earth. There are, however, means of returning scientifically-rich samples from Mars without landing on the surface. This paper discusses an approach for returning intact samples of surface dust, based on known instrument technology, without using an actual Martian lander.

Field Exploration Science for a Return to the Moon

NASA Astrophysics Data System (ADS)

Schmitt, H. H.; Helper, M. A.; Muehlbberger, W.; Snoke, A. W.

2006-12-01

Apollo field exploration science, and subsequent analysis, and interpretation of its findings and collected samples, underpin our current understanding of the origin and history of the Moon. That understanding, in turn, continues to provide new and important insights into the early histories of the Earth and other bodies in the solar system, particularly during the period that life formed and began to evolve on Earth and possibly on Mars. Those early explorations also have disclosed significant and potentially commercially viable lunar resources that might help satisfy future demand for both terrestrial energy alternatives and space consumables. Lunar sortie missions as part of the Vision for Space Exploration provide an opportunity to continue and expand the human geological, geochemical and geophysical exploration of the Moon. Specific objectives of future field exploration science include: (1) Testing of the consensus "giant impact" hypothesis for the origin of the Moon by further investigation of materials that may augment understanding of the chondritic geochemistry of the lower lunar mantle; (2) Testing of the consensus impact "cataclysm" hypothesis by obtaining absolute ages on large lunar basins of relative ages older than the 3.8-3.9 Ga mascon basins dated by Apollo 15 and 17; (3) Calibration of the end of large impacts in the inner solar system; (4) Global delineation of the internal structure of the Moon; (5) Global sampling and field investigations that extend the data necessary to remotely correlate major lunar geological and geochemical units; (6) Definition of the depositional history of polar volatiles - cometary, solar wind, or otherwise; (7) Determine the recoverable in situ concentrations and distribution of potential volatile resources; and (8) Acquisition of information and samples related to relatively less site-specific aspects of lunar geological processes. Planning for renewed field exploration of the Moon depends largely on the selection, training and use of sortie crews; the selection of landing sites; and the adopted operational approach to sortie extravehicular activity (EVA). The equipment necessary for successful exploration consists of that required for sampling, sample documentation, communications, mobility, and position knowledge. Other types of active geophysical. geochemical and petrographic equipment, if available, could clearly enhance the scientific and operational return of extended exploration over that possible during Apollo missions. Equipment to increase the efficiency of exploration should include the following, helmet-mounted, systems: (1) voice activated or automatic, electronic, stereo photo-documentation camera that is photometrically and geometrically fully calibrated; (2) automatic position and elevation determination system; and (3) laser-ranging device, aligned with the stereo camera axis. Heads-up displays and controls on the helmet, activated and selected by voice, should be available for control and use of this equipment.

Structure and origin of cometary nuclei

NASA Technical Reports Server (NTRS)

Donn, B.; Rahe, J.

1981-01-01

There is strong evidence that a comet nucleus consists of a single object whose basic structure is Whipple's icy conglomerate. A number of cometary phenomena indicate that the nucleus is a low density, fragile object with a large degree of radial uniformity in structure and composition. Details of the ice-dust pattern are more uncertain. A working model is proposed which is based on theories of accumulation of larger objects from grains. This nucleus is a distorted spherical aggregate of a hierarchy of ice-dust cometesimals. These cometesimals retain some separate identity which lead to comet fragmentation when larger components break off. The outer layers of new comets were modified by cosmic ray irradiation in the Oort Cloud. The evidence for meteorite-comet association is steill controversial. Current dynamical studies do not seem to require a cometary source of meteorites.

Photodissociation Cross Sections for the Production of C2 from C2H Using Laser Induced Hg Photosensitization and Tunable Ultraviolet and Visible Lasers

NASA Technical Reports Server (NTRS)

Jackson, William M.

1996-01-01

The principle goal of our research was to understand the formation of free radicals in comets. To do this we compared laboratory results with cometary observations in attempt to make sure that the cometary observations agree with what is known about the photochemistry of the proposed parent molecule. Initially we concentrated on the CS emission in an effort to show the parent of this molecule was CS2, consistent with cometary observations of the photochemical lifetime. We then started to look into the problem of the C2 formation in comets. We set out to see if we could measure all of the nascent distributions of the C2 products in the hope that they would be a characteristic signature of the formation process.

Water/rock interactions in experimentally simulated dirty snowball and dirty iceball cometary nuclei

NASA Technical Reports Server (NTRS)

Gooding, James L.; Allton, Judith H.

1991-01-01

In the dirty snowball model for cometary nuclei, comet-nucleus materials are regarded as mixtures of volatile ices and relatively non-volatile minerals or chemical compounds. Carbonaceous chondrite meteorites are regarded as useful analogs for the rocky component. To help elucidate the possible physical geochemistry of cometary nuclei, preliminary results are reported of calorimetric experiments with two-component systems involving carbonaceous chondrites and water ice. Based on collective knowledge of the physics of water ice, three general types of interactions can be expected between water and minerals at sub-freezing temperatures: (1) heterogeneous nucleation of ice by insoluble minerals; (2) adsorption of water vapor by hygroscopic phases; and (3) freezing- and melting-point depression of liquid water sustained by soluble minerals. The relative and absolute magnitude of all three effects are expected to vary with mineral composition.

Particle emission from artificial cometary materials

NASA Technical Reports Server (NTRS)

Koelzer, Gabriele; Kochan, Hermann; Thiel, Klaus

1992-01-01

During KOSI (comet simulation) experiments, mineral-ice mixtures are observed in simulated space conditions. Emission of ice-/dust particles from the sample surface is observed by means of different devices. The particle trajectories are recorded with a video system. In the following analysis we extracted the parameters: particle count rate, spatial distribution of starting points on the sample surface, and elevation angle and particle velocity at distances up to 5 cm from the sample surface. Different kinds of detectors are mounted on a frame in front of the sample to register the emitted particles and to collect their dust residues. By means of these instruments the particle count rates, the particle sizes and the composition of the particles can be correlated. The results are related to the gas flux density and the temperature on the sample surface during the insolation period. The particle emission is interpreted in terms of phenomena on the sample surface, e.g., formation of a dust mantle.

77 FR 70835 - Centennial Challenges 2013 Sample Return Robot Challenge

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-27

... NATIONAL AERONAUTICS AND SPACE ADMINISTRATION Centennial Challenges 2013 Sample Return Robot...). SUMMARY: This notice is issued in accordance with 51 U.S.C. 20144(c). The 2013 Sample Return Robot.... The 2013 Sample Return Robot Challenge is a prize competition designed to encourage development of new...

What if chondritic porous interplanetary dust particles are not the real McCoy

NASA Astrophysics Data System (ADS)

Rietmeijer, Frans J. M.

To select a target comet for a Comet Nucleus Sample Return Mission (CNSRM) it is necessary to have an experimental data base to evaluate the extent of diversity and similarity of comets. For example, the physical properties (e.g., low density) of chondritic porous (CP) interplanetary dust particles (IDPs) are believed to resemble these properties of cometary dust although it is yet to be demonstrated that the porous structure of CP IDPs is inherent to presolar dust particles stored in comet nuclei. Porous structures of IDPs could conceivably form during sublimation at the surface of active comet nuclei. Porous structures are also obtained during annealing of amorphous Mg-SiO smokes which initially forms porous aggregates of olivine + platey tridymite and which, upon continued annealing, react to fluffy enstatite aggregates. It is therefore uncertain that CP IDPs are entirely composed of unmetamorphosed presolar dust. Conceivably, new minerals and textures may form in situ in nuclei of active comets as a function of their individual thermal history. Unmetamorphosed comet dust is probably structurally amorphous. Thermal annealing of this dust can produce ultra fine-grained minerals and this ultrafine grain size of CP IDPs should be considered in assessments of aqueous alterations that could affect presolar dust in comet nuclei between 200 and 400 K. Devitrification and hydration may occur in situ in ice-dust mixtures and the mantle of active comet nuclei. Devitrification, or uncontrolled crystallization, of amorphous precursor dust can produce a range of chemical compositions of ultrafine-grained minerals and (non-equilibrium) mineral assemblages and textures in dust contained in comet nuclei as a function of period and trajectory of orbit and number of perihelion passages (not considering internal heating). Thus, experimental data on relevant processes and reaction rates between 200 and 400 K are needed in order to evaluate comet selection, penetration depth for sampling device and curation of samples for CNSRM.

What if chondritic porous interplanetary dust particles are not the real McCoy

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.

1989-01-01

To select a target comet for a Comet Nucleus Sample Return Mission (CNSRM) it is necessary to have an experimental data base to evaluate the extent of diversity and similarity of comets. For example, the physical properties (e.g., low density) of chondritic porous (CP) interplanetary dust particles (IDPs) are believed to resemble these properties of cometary dust although it is yet to be demonstrated that the porous structure of CP IDPs is inherent to presolar dust particles stored in comet nuclei. Porous structures of IDPs could conceivably form during sublimation at the surface of active comet nuclei. Porous structures are also obtained during annealing of amorphous Mg-SiO smokes which initially forms porous aggregates of olivine + platey tridymite and which, upon continued annealing, react to fluffy enstatite aggregates. It is therefore uncertain that CP IDPs are entirely composed of unmetamorphosed presolar dust. Conceivably, new minerals and textures may form in situ in nuclei of active comets as a function of their individual thermal history. Unmetamorphosed comet dust is probably structurally amorphous. Thermal annealing of this dust can produce ultra fine-grained minerals and this ultrafine grain size of CP IDPs should be considered in assessments of aqueous alterations that could affect presolar dust in comet nuclei between 200 and 400 K. Devitrification and hydration may occur in situ in ice-dust mixtures and the mantle of active comet nuclei. Devitrification, or uncontrolled crystallization, of amorphous precursor dust can produce a range of chemical compositions of ultrafine-grained minerals and (non-equilibrium) mineral assemblages and textures in dust contained in comet nuclei as a function of period and trajectory of orbit and number of perihelion passages (not considering internal heating). Thus, experimental data on relevant processes and reaction rates between 200 and 400 K are needed in order to evaluate comet selection, penetration depth for sampling device and curation of samples for CNSRM.

Submicrometer Organic Grains: Widespread Constituents of the Early Solar System

NASA Technical Reports Server (NTRS)

Messenger, Scott; Nakamuri-Messenger, Keiko; Keller, Lindsay; Matrajt, Graciela; Clemett, Simon; Ito, Motoo

2007-01-01

Primitive meteorites and interplanetary dust particles (IDPs) contain remants of interstellar organic matter, marked by anomalous H and N isotopic ratios. These isotopic anomalies are attributed to mass fractionation during chemical reactions at cryogenic temperatures (10-100K) in a cold molecular cloud. Significant variations in the chemistry and isotopic compositions of organic compounds within and between these samples suggest varying histories of alteration and dilution of the presolar components. Recent studies have reported large H and N isotopic anomalies preserved in sub-m organic inclusions in both meteorites and IDPs. In the Tagish Lake meteorite, the largest H and N isotopic anomalies are associated with sub-m, hollow organic globules. The common physical, chemical, and isotopic characteristics of these globules suggest that they formed before being incorporated into their parent meteorite. These organic globules probably originated as organic ice coatings that formed on preexisting ice or mineral grains in a cold molecular cloud. Radiation driven photochemistry may have processed them into refractory organic grains. This model implies that submicrometer organic grains were widely distributed throughout the solar nebula during the epoch of planet formation. Submicrometer organic particles were detected by the Giotto and Vega encounters with comet Halley, termed CHON particles based on their major element chemistry. The first direct samples of cometary dust (comet Wild-2) were returned by the Stardust spacecraft in January 2006. These samples exhibit widely varying, fine grained mineralogy similar to anhydrous IDPs, including submicrometer carbonaceous grains. The submicrometer organic grains from comet Wild-2 exhibit H and N isotopic anomalies of similar magnitude to those commonly observed in primitive meteorites and IDPs. Isotopically anomalous, submicrometer organic grains have now been observed in meteorites, IDPs, the Oort-cloud comet Halley, and the Kuiper-belt comet Wild-2, suggesting that such grains were prevalent throughout the protoplanetary disk.

Isotopic analysis of cometary organic matter

NASA Technical Reports Server (NTRS)

Kerridge, John F.

1991-01-01

Carbon isotope ratios have been measured for CN in the coma of Comet Halley and for several CHON particles emitted by Halley. Of these, only the CHON-particle data may be reasonably related to organic matter in the cometary nucleus, but the true range of (C-13)/(C-12) values in those particles is quite uncertain. The D/H ratio in H2O in the Halley coma resembles that in Titan/Uranus.

CoMA: A high resolution Time-Of-Flight Secondary Ion Mass Spectrometer (TOF-SIMS) for in situ analysis of cometary matter

NASA Technical Reports Server (NTRS)

Zscheeg, Harry; Kissel, J.; Natour, G.

1992-01-01

A lot of clues concerning the origin of the solar system can be found by sending an exploring spacecraft to a rendezvous with a comet. The space experiment CoMA, which will measure the elemental, isotopic, and molecular composition of cometary dust grains is described. It will be flown on NASA's Comet Rendezvous Asteroid Flyby (CRAF) mission.

Laser induced photoluminescence spectroscopy of cometary radicals

NASA Technical Reports Server (NTRS)

Jackson, W. M.; Cody, R. J.; Sabety-Dzvonik, M.

1976-01-01

Flash photolysis together with laser excitation of the product fragments was used in laboratory studies of cometary radicals. The LIPS method has been applied to the CN radical to determine: (1) Radiative lifetimes of individual rotational levels in the zeroth vibrational level of the B state; (2) energy partitioning during photodissociation of C2N2; and (3) vibrational and rotational excitation during formation of CN radicals in the photodissociation of dicyanoacetylene.

What can meteorites tell us about comets?

NASA Technical Reports Server (NTRS)

Anders, Edward

1986-01-01

Cometary silicates, carbon, and volatiles are reviewed using data from the Halley probes, interplanetary dust particles, and cometary spectra. The origins of anhydrous Fe(2+)-bearing silicates; whether hydrated silicates, if present, were made by gaseous or liquid H2O3; sources of organic compounds: ion-molecule reactions, photochemistry, grain catalysis; sources of CO2 and of organic polymers; and interstellar molecules and grains in comets are discussed.

The Rosetta mission orbiter science overview: the comet phase

PubMed Central

Altobelli, N.; Buratti, B. J.; Choukroun, M.

2017-01-01

The international Rosetta mission was launched in 2004 and consists of the orbiter spacecraft Rosetta and the lander Philae. The aim of the mission is to map the comet 67P/Churyumov–Gerasimenko by remote sensing, and to examine its environment in situ and its evolution in the inner Solar System. Rosetta was the first spacecraft to rendezvous with and orbit a comet, accompanying it as it passes through the inner Solar System, and to deploy a lander, Philae, and perform in situ science on the comet's surface. The primary goals of the mission were to: characterize the comet's nucleus; examine the chemical, mineralogical and isotopic composition of volatiles and refractories; examine the physical properties and interrelation of volatiles and refractories in a cometary nucleus; study the development of cometary activity and the processes in the surface layer of the nucleus and in the coma; detail the origin of comets, the relationship between cometary and interstellar material and the implications for the origin of the Solar System; and characterize asteroids 2867 Steins and 21 Lutetia. This paper presents a summary of mission operations and science, focusing on the Rosetta orbiter component of the mission during its comet phase, from early 2014 up to September 2016. This article is part of the themed issue ‘Cometary science after Rosetta’. PMID:28554981

On stellar encounters and their effect on cometary orbits in the Oort cloud

NASA Astrophysics Data System (ADS)

Serafin, R. A.; Grothues, H.-G.

2002-03-01

We systematically investigate the encounters between the Sun and neighbouring stars and their effects on cometary orbits in the Oort cloud, including the intrinsic one with the star Gl 710 (HIP 89 825), with some implications to stellar and cometary dynamics. Our approach is principally based on the combination of a Keplerian-rectilinear model of stellar passages and the Hipparcos Catalogue (ESA 1997). Beyond the parameters of encounter, we pay particular attention to the observational errors in parallaxes and stellar velocities, and their propagation in time. Moreover, as a special case of this problem, we consider the collision probability of a star passing very closely to the Sun, taking also into account the mutual gravitational attraction between the stars. In the part dealing with the influence of stellar encounters on the orbital elements of Oort cloud comets, we derive new simple formulae calculating the changes in the cometary orbital elements, expressed as functions of the Jeans impulse formula. These expressions are then applied to calculate numerical values of the element changes caused by close encounters of neighbouring stars with some model comets in the Oort cloud. Moreover, the general condition for an ejection of comets from the cloud effected by a single encounter is derived and discussed.

A Model for the Breakup of Comet Linear (C/1999 S4)

NASA Technical Reports Server (NTRS)

Samarasinha, Nalin H.

2001-01-01

We propose a mechanism based on the rubble-pile hypothesis of the cometary nucleus (Weissman 1986) to explain the catastrophic breakup of comet LINEAR (C/1999 S4) observed during July-August 2000. We suggest that a solid nucleus made up of 10-100 m "cometesimals" (Weidenschilling 1997) contains a network of inter-connected voids in the inter-cometesimal regions. The production of super-volatile (i.e., species more volatile than water) gases into these voids occurs due to the thermal wave propagating through the nucleus and associated phase transitions of water ice. The network of voids provides an efficient pathway for rapid propagation of these gases within the nucleus resulting in gas pressure caused stresses over a wide regime of the nucleus. This provides a mechanism for catastrophic breakups of small cometary nuclei such as comet LINEAR (C/1999 S4) as well as for some observed cometary outbursts including those that occur at large heliocentric distances (e.g., West et al. 1991). We emphasize the importance of techniques such as radar reflection tomography and radiowave transmission tomography (e.g., Kofman et al. 1998) aboard cometary missions to determine the three dimensional structure of the nucleus in particular the extent of large scale voids.

Cometary crystalline silicate before and after perihelion passage II

NASA Astrophysics Data System (ADS)

Ootsubo, Takafumi

2014-01-01

Crystalline silicate is often observed in comets as an 11.3-micron resonant emission feature, and may be used for probing the early solar nebula. Because the formation of the crystalline silicate requires high temperature, they are thought to have been born from amorphous silicate at the inner region, and then transported toward the outer regions where comets were born. This transportation can produce the difference in the crystalline fraction in the cometary silicate dust between two dynamical types of comets, Oort-cloud comets (OCs) and Ecliptic comets (ECs), due to the different heliocentric distances of their birth places. The study of peak wavelengths in crystalline features is important to investigate the conditions of the crystalline silicate formation as well. Thus far, we don't have enough observational samples of OCs. Fortunately, we can observe comet C/2012 K1 (PanSTARRS) along with C/2013 A1 (Siding Spring) in this semester. In particular, the comet C/2012 K1 (PanSTARRS) is a bright and good target for this silicate peak feature study. Observations at pre- and post-perihelion provide us precious information on the dust evolution of the comet.

Dynamics of aspherical dust grains in a cometary atmosphere: I. axially symmetric grains in a spherically symmetric atmosphere

NASA Astrophysics Data System (ADS)

Ivanovski, S. L.; Zakharov, V. V.; Della Corte, V.; Crifo, J.-F.; Rotundi, A.; Fulle, M.

2017-01-01

In-situ measurements of individual dust grain parameters in the immediate vicinity of a cometary nucleus are being carried by the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. For the interpretations of these observational data, a model of dust grain motion as realistic as possible is requested. In particular, the results of the Stardust mission and analysis of samples of interplanetary dust have shown that these particles are highly aspherical, which should be taken into account in any credible model. The aim of the present work is to study the dynamics of ellipsoidal shape particles with various aspect ratios introduced in a spherically symmetric expanding gas flow and to reveal the possible differences in dynamics between spherical and aspherical particles. Their translational and rotational motion under influence of the gravity and of the aerodynamic force and torque is numerically integrated in a wide range of physical parameters values including those of comet 67P/Churyumov-Gerasimenko. The main distinctions of the dynamics of spherical and ellipsoidal particles are discussed. The aerodynamic characteristics of the ellipsoidal particles, and examples of their translational and rotational motion in the postulated gas flow are presented.

Status of Sample Return Propulsion Technology Development Under NASA's ISPT Program

NASA Technical Reports Server (NTRS)

Anderson, David J.; Glaab, Louis J.; Munk, Michelle M.; Pencil, Eric; Dankanich, John; Peterson, Todd T.

2012-01-01

The In-Space Propulsion Technology (ISPT) program was tasked in 2009 to start development of propulsion technologies that would enable future sample return missions. ISPT s sample return technology development areas are diverse. Sample Return Propulsion (SRP) addresses electric propulsion for sample return and low cost Discovery-class missions, propulsion systems for Earth Return Vehicles (ERV) including transfer stages to the destination, and low technology readiness level (TRL) advanced propulsion technologies. The SRP effort continues work on HIVHAC thruster development to transition into developing a Hall-effect propulsion system for sample return (ERV and transfer stages) and low-cost missions. Previous work on the lightweight propellant-tanks continues for sample return with direct applicability to a Mars Sample Return (MSR) mission with general applicability to all future planetary spacecraft. The Earth Entry Vehicle (EEV) work focuses on building a fundamental base of multi-mission technologies for Earth Entry Vehicles (MMEEV). The main focus of the Planetary Ascent Vehicles (PAV) area is technology development for the Mars Ascent Vehicle (MAV), which builds upon and leverages the past MAV analysis and technology developments from the Mars Technology Program (MTP) and previous MSR studies

Experimental Shock Chemistry of Aqueous Amino Acid Solutions and the Cometary Delivery of Prebiotic Compounds

NASA Astrophysics Data System (ADS)

Blank, Jennifer G.; Miller, Gregory H.; Ahrens, Michael J.; Winans, Randall E.

2001-02-01

A series of shock experiments were conducted to assess the feasibility of the delivery of organic compounds to the Earth via cometary impacts. Aqueous solutions containing near-saturation levels of amino acids (lysine, norvaline, aminobutyric acid, proline, and phenylalanine) were sealed inside stainless steel capsules and shocked by ballistic impact with a steel projectile plate accelerated along a 12-m-long gun barrel to velocities of 0.5-1.9 km sec^-1. Pressure-temperature-time histories of the shocked fluids were calculated using 1D hydrodynamical simulations. Maximum conditions experienced by the solutions lasted 0.85-2.7 μs and ranged from 5.1-21 GPa and 412-870 K. Recovered sample capsules were milled open and liquid was extracted. Samples were analyzed using high performance liquid chromatography (HPLC) and mass spectrometry (MS). In all experiments, a large fraction of the amino acids survived. We observed differences in kinetic behavior and the degree of survivability among the amino acids. Aminobutyric acid appeared to be the least reactive, and phenylalanine appeared to be the most reactive of the amino acids. The impact process resulted in the formation of peptide bonds; new compounds included amino acid dimers and cyclic diketopiperazines. In our experiments, and in certain naturally occurring impacts, pressure has a greater influence than temperature in determining reaction pathways. Our results support the hypothesis that significant concentrations of organic material could survive a natural impact process.

Experimental shock chemistry of aqueous amino acid solutions and the cometary delivery of prebiotic compounds.

PubMed

Blank, J G; Miller, G H; Ahrens, M J; Winans, R E

2001-01-01

A series of shock experiments were conducted to assess the feasibility of the delivery of organic compounds to the Earth via cometary impacts. Aqueous solutions containing near-saturation levels of amino acids (lysine, norvaline, aminobutyric acid, proline, and phenylalanine) were sealed inside stainless steel capsules and shocked by ballistic impact with a steel projectile plate accelerated along a 12-m-long gun barrel to velocities of 0.5-1.9 km sec-1. Pressure-temperature-time histories of the shocked fluids were calculated using 1D hydrodynamical simulations. Maximum conditions experienced by the solutions lasted 0.85-2.7 microseconds and ranged from 5.1-21 GPa and 412-870 K. Recovered sample capsules were milled open and liquid was extracted. Samples were analyzed using high performance liquid chromatography (HPLC) and mass spectrometry (MS). In all experiments, a large fraction of the amino acids survived. We observed differences in kinetic behavior and the degree of survivability among the amino acids. Aminobutyric acid appeared to be the least reactive, and phenylalanine appeared to be the most reactive of the amino acids. The impact process resulted in the formation of peptide bonds; new compounds included amino acid dimers and cyclic diketopiperazines. In our experiments, and in certain naturally occurring impacts, pressure has a greater influence than temperature in determining reaction pathways. Our results support the hypothesis that significant concentrations of organic material could survive a natural impact process.

CORSAIR (COmet Rendezvous, Sample Acquisition, Investigation, and Return): A New Frontiers Mission Concept to Collect Samples from a Comet and Return Them to Earth for Study

NASA Astrophysics Data System (ADS)

Sandford, S. A.; Chabot, N. L.; Dello Russo, N.; Leary, J. C.; Reynolds, E. L.; Weaver, H. A.; Wooden, D. H.

2017-07-01

CORSAIR (COmet Rendezvous, Sample Acquisition, Investigation, and Return) is a mission concept submitted in response to NASA's New Frontiers 4 call. CORSAIR's proposed mission is to return comet nucleus samples to Earth for detailed analysis.

Return to the Moon: A New Strategic Evaluation

NASA Technical Reports Server (NTRS)

Lowman, Paul D., Jr.

1999-01-01

This paper reviews the value of a new lunar program, initially robotic and eventually manned, in the light of developments since the 1991 Synthesis Group study of the Space Exploration Initiative. The objective is to evaluate a return to the Moon in comparison to proposed Mars programs as a focus for American space exploration with humans in the next century. The Moon is demonstrably accessible, hospitable, useful, and interesting. Lunar programs are inherently faster and less risky from a programmatic viewpoint than comparable Mars programs such as Mars Direct. The dominant reason for a resumption of manned lunar missions, focussed on a single site such as Grimaldi, is to rebuild the infrastructure for missions beyond earth orbit, the last of which was in 1972. A transitional program, corresponding to the 10 Gemini missions that bridged the gap between Mercury and Apollo, was considered absolutely essential by the Synthesis Group. Further justification for a return to the Moon is the demonstrated feasibility of a robotic lunar observatory, concentrating on optical and infrared interferometry. Many unsolved scientific questions about the Moon itself remain, and could be investigated using telerobotic lunar rovers even before the return of humans. Mars is unquestionably more interesting scientifically and far more hospitable for long-term colonization. A new lunar program would be the most effective possible preparation for the human exploration, settlement, and eventually the terraforming of Mars. Lunar and Mars programs are complementary, not competitive. Both can be justified in the most fundamental terms as beginning the dispersal of the human species against uncontrollable natural disasters, cometary or asteroidal impacts in particular, to which mankind is vulnerable while confined to a single planet. Three specific programs are recommended for the 2001-2010 period: Ice Prospectors, to evaluate polar ice or hydrogen deposits; a robotic lunar observatory; and a manned lunar base and observatory.

Return to the Moon: A New Strategic Evaluation

NASA Technical Reports Server (NTRS)

Lowman, Paul D., Jr.

1999-01-01

This paper reviews the value of a new lunar program, initially robotic and eventually manned, in the light of developments since the 1991 Synthes Group study of the Space Exploration Initiative. The objective is to evaluate a return to the Moon in comparison to proposed Mars programs as a focus for American space exploration with humans in the next century. The Moon is demonstrably accessible, hospitable, useful, and interesting. Lunar programs are inherently faster and less risky from a programmatic viewpoint than comparable Mars programs such as Mars Direct. The dominant reason for a resumption of manned lunar missions, focused on a single site such as Grimaldi, is to rebuild the infrastructure for missions beyond Earth orbit, the last of which was in 1972. A transitional prograrr@ corresponding to the 10 Gemini missions that bridged the gap between Mercury and Apollo, was considered absolutely essential by the Synthesis Group. Further justification for a return to the Moon is the demonstrated feasibility of a robotic lunar observatory, concentrating on optical and infrared interferometry. Many unsolved scientific questions about the Moon itself remain, and could be investigated using telerobotic lunar rovers even before the return of humans. Mars is unquestionably more interesting scientifically and far more hospitable for long-term colonization. A new lunar program would be the most effective possible preparation for the human exploration, settlement and eventually the terraforming of Mars. Lunar and Mars programs are complementary, not competitive. Both can be justified in the most fundamental terms as beginning the dispersal of the human species against uncontrollable natural disasters, cometary or asteroidal impacts in particular, to which mankind is vulnerable while confined to a single planet. Three specific programs are recommended for the 2001-2010 period: Ice Prospectors, to evaluate polar ice or hydrogen deposits; a robotic lunar observatory; and a manned lunar base and observatory.

Return to the Moon: A New Strategic Evaluation

NASA Technical Reports Server (NTRS)

Lowman, Paul D., Jr.

1999-01-01

This paper reviews the value of a new lunar program, initially robotic and eventually manned, in the light of developments since the 1991 Synthes Group study of the Space Exploration Initiative. The objective is to evaluate a return to the Moon in comparison to proposed Mars programs as a focus for American space exploration with humans in the next century. The Moon is demonstrably accessible, hospitable, useful, and interesting. Lunar programs are inherently faster and less risky from a programmatic viewpoint than comparable Mars programs such as Mars Direct. The dominant reason for a resumption of manned lunar missions, focused on a single site such as Grimaldi, is to rebuild the infrastructure for missions beyond Earth orbit, the last of which was in 1972. A transitional program, corresponding to the 10 Gemini missions that bridged the gap between Mercury and Apollo, was considered absolutely essential by the Synthesis Group. Further justification for a return to the Moon is the demonstrated feasibility of a robotic lunar observatory, concentrating on optical and infrared interferometry. Many unsolved scientific questions about the Moon itself remain, and could be investigated using telerobotic lunar rovers even before the return of humans. Mars is unquestionably more interesting scientifically and far more hospitable for long-term colonization. A new lunar program would be the most effective possible preparation for the human exploration, settlement and eventually the terraforming of Mars. Lunar and Mars programs are complementary, not competitive. Both can be justified in the most fundamental terms as beginning the dispersal of the human species against uncontrollable natural disasters, cometary or asteroidal impacts in particular, to which mankind is vulnerable while confined to a single planet. Three specific programs are recommended for the 2001-2010 period: Ice Prospectors, to evaluate polar ice or hydrogen deposits; a robotic lunar observatory; and a manned lunar base and observatory.

Exobiology opportunities from Discovery-class missions. [Abstract only

NASA Technical Reports Server (NTRS)

Meyer, Michael A.; Rummel, John D.

1994-01-01

Discovery-class missions that are now planned, and those in the concept stage, have the potential to expand our knowledge of the origins and evolution of biogenic compounds, and ultimately, of the origins of life in the solar system. This class of missions, recently developed within NASA's Solar System Exploration Program, is designed to meet important scientific objectives within stringent guidelines--$150 million cap on development cost and a 3-year cap on the development schedule. The Discovery Program will effectively enable "faster, cheaper" missions to explore the inner solar system. The first two missions are Mars Environmental Survey (MESUR) Pathfinder and Near Earth Asteroid Rendezvous (NEAR). MESUR Pathfinder will be the first Discovery mission, with launch planned for November/December 1996. It will be primarily a technical demonstration and validation of the MESUR Program--a network of automated landers to study the internal structure, meteorology, and surface properties of Mars. Besides providing engineering data, Pathfinder will carry atmospheric instrumentation and imaging capabilities, and may deploy a microrover equipped with an alpha proton X-ray spectrometer to determine elemental composition, particularly the lighter elements of exobiological interest. NEAR is expected to be launched in 1998 and to rendezvous with a near-Earth asteroid for up to 1 year. During this time, the spacecraft will assess the asteroid's mass, size, density, map its surface topography and composition, determine its internal properties, and study its interaction with the interplanetary environment. A gamma ray or X-ray spectrometer will be used to determine elemental composition. An imaging spectrograph, with 0.35 to 2.5 micron spectral range, will be used to determine the asteroid's compositional disbribution. Of the 11 Discovery mission concepts that have been designated as warranting further study, several are promising in terms of determining the composition and chemical evolution of organic matter on small planetary bodies. The following mission concepts are of particular interest to the Exobiology Program: Cometary coma chemical composition, comet nucleus tour, near earth asteroid returned sample, small missions to asteroids and comets, and solar wind sample return. The following three Discovery mission concepts that have been targeted for further consideration are relevant to the study of the evolution of biogenic compounds: Comet nucleus penetrator, mainbelt asteroid rendezvous explorer, and the Mars polar Pathfinder.

An Efficient Approach for Mars Sample Return Using Emerging Commercial Capabilities

NASA Technical Reports Server (NTRS)

Gonzales, Andrew A.; Stoker, Carol R.

2016-01-01

Mars Sample Return is the highest priority science mission for the next decade as recommended by the 2011 Decadal Survey of Planetary Science. This article presents the results of a feasibility study for a Mars Sample Return mission that efficiently uses emerging commercial capabilities expected to be available in the near future. The motivation of our study was the recognition that emerging commercial capabilities might be used to perform Mars Sample Return with an Earth-direct architecture, and that this may offer a desirable simpler and lower cost approach. The objective of the study was to determine whether these capabilities can be used to optimize the number of mission systems and launches required to return the samples, with the goal of achieving the desired simplicity. All of the major element required for the Mars Sample Return mission are described. Mission system elements were analyzed with either direct techniques or by using parametric mass estimating relationships. The analysis shows the feasibility of a complete and closed Mars Sample Return mission design based on the following scenario: A SpaceX Falcon Heavy launch vehicle places a modified version of a SpaceX Dragon capsule, referred to as "Red Dragon", onto a Trans Mars Injection trajectory. The capsule carries all the hardware needed to return to Earth Orbit samples collected by a prior mission, such as the planned NASA Mars 2020 sample collection rover. The payload includes a fully fueled Mars Ascent Vehicle; a fueled Earth Return Vehicle, support equipment, and a mechanism to transfer samples from the sample cache system onboard the rover to the Earth Return Vehicle. The Red Dragon descends to land on the surface of Mars using Supersonic Retropropulsion. After collected samples are transferred to the Earth Return Vehicle, the single-stage Mars Ascent Vehicle launches the Earth Return Vehicle from the surface of Mars to a Mars phasing orbit. After a brief phasing period, the Earth Return Vehicle performs a Trans Earth Injection burn. Once near Earth, the Earth Return Vehicle performs Earth and lunar swing-bys and is placed into a Lunar Trailing Orbit - an Earth orbit, at lunar distance. A retrieval mission then performs a rendezvous with the Earth Return Vehicle, retrieves the sample container, and breaks the chain of contact with Mars by transferring the sample into a sterile and secure container. With the sample contained, the retrieving spacecraft makes a controlled Earth re-entry preventing any unintended release of Martian materials into the Earth's biosphere. The mission can start in any one of three Earth to Mars launch opportunities, beginning in 2022.

NASA Curation Preparation for Ryugu Sample Returned by JAXA's Hayabusa2 Mission

NASA Technical Reports Server (NTRS)

Nakamura-Messenger, Keiko; Righter, Kevin; Snead, Christopher J.; McCubbin, Francis M.; Pace, Lisa F.; Zeigler, Ryan A.; Evans, Cindy

2017-01-01

The NASA OSIRIS-REx and JAXA Hayabusa2 missions to near-Earth asteroids Bennu and Ryugu share similar mission goals of understanding the origins of primitive, organic-rich asteroids. Under an agreement between JAXA and NASA, there is an on-going and productive collaboration between science teams of Hayabusa2 and OSIRIS-REx missions. Under this agreement, a portion of each of the returned sample masses will be exchanged between the agencies and the scientific results of their study will be shared. NASA’s portion of the returned Hayabusa2 sample, consisting of 10% of the returned mass, will be jointly separated by NASA and JAXA. The sample will be legally and physically transferred to NASA’s dedicated Hayabusa2 curation facility at Johnson Space Center (JSC) no later than one year after the return of the Hayabusa2 sample to Earth (December 2020). The JSC Hayabusa2 curation cleanroom facility design has now been completed. In the same manner, JAXA will receive 0.5% of the total returned OSIRIS-REx sample (minimum required sample to return 60 g, maximum sample return capacity of 2 kg) from the rest of the specimen. No later than one year after the return of the OSIRIS-REx sample to Earth (September 2023), legal, physical, and permanent custody of this sample subset will be transferred to JAXA, and the sample subset will be brought to JAXA’s Extraterrestrial Sample Curation Center (ESCuC) at Institute of Space and Astronautical Science, Sagamihara City Japan.

Habitation Module Technology for Mars Sample Preservation and Return

NASA Astrophysics Data System (ADS)

Humphries., Peter.; Barez., Fred.; Brant., Tom.; Gutti Shashidhar Gowda., Aishwarya.

2018-04-01

Lunar-Mars sample return is of interest to the space community such as NASA, ESA, and private industry. Collected samples of Mars need to be preserved and properly treated in returnable cache, packed to stop back-contamination prior to the return mission.

In situ energetic particle observations at Comet Halley recorded by instrumentation aboard the Giotto and VEGA 1 missions

NASA Astrophysics Data System (ADS)

McKenna-Lawlor, S.; Daly, P.; Kirsch, E.; Wilken, B.; O'Sullivan, D.; Thompson, A.; Kecskemety, K.; Somogyi, A.; Coates, A.

1989-04-01

Energetic particle data on quasi-periodic variations of cometary ion fluxes recorded by instrumentation aboard the Vega 1 and Giotto spacecraft during March 1986 are compared. It is suggested that the ion fluxes measured by the Giotto EPONA instrument were of the water group. Large fluxes of electrons and ions recorded by the EPONA instrument in the magnetic cavity appear to be cometary in origin.

Auroral and photoelectron fluxes in cometary ionospheres

NASA Astrophysics Data System (ADS)

Bhardwaj, A.; Haider, S. A.; Spinghal, R. P.

1990-05-01

The analytical yield spectrum method has been used to ascertain photoelectron and auroral electron fluxes in cometary ionospheres, with a view to determining the effects of cometocentric distances, solar zenith angle, and solar minimum and maximum conditions. Auroral electron fluxes are thus calculated for monoenergetic and observed primary electron spectra; auroral electrons are found to make a larger contribution to the observed electron spectrum than EUV-generated photoelectrons. Good agreement is established with extant theoretical works.

Asymmetric Spherical Coupled Escape Probability: Model and Results for Optically Thick Cometary Comae

NASA Astrophysics Data System (ADS)

Gersch, Alan; A'Hearn, M. F.

2012-05-01

We have adapted the Coupled Escape Probability method of radiative transfer calculations for use in asymmetrical spherical situations and applied it to modeling molecular emission spectra of potentially optically thick cometary comae. Recent space missions (e.g. Deep Impact & EPOXI) have provided spectra from comets of unprecedented spatial resolution of the regions of the coma near the nucleus, where the coma may be optically thick. Currently active missions (e.g. Rosetta) and hopefully more in the future will continue the trend and demonstrate the need for better modeling of comae with optical depth effects included. Here we present a brief description of our model and results of interest for cometary studies, especially for space based observations. Although primarily motivated by the need for comet modeling, our (asymmetric spherical) radiative transfer model could be used for studying other astrophysical phenomena as well.

The International Cometary Explorer (ICE) mission to comet Giacobini-Zinner (G/Z)

NASA Technical Reports Server (NTRS)

Brandt, J. C.; Farquhar, R. W.; Maran, S. P.; Niedner, M. B.; Von Rosenvinge, T.

1985-01-01

The primary objectives of the International Cometary Explorer (ICE) mission is to provide in situ data on the interaction between solar wind and the atmosphere of the P/Giacobini-Zinner comet (G/Z), making measurements of particles, fields, and waves while passing through the cometary tail of G/Z on September 11, 1985. Following the G/Z tail intercept, the ICE measurements will complement the later upstream measurements obtained by the Comet Halley probe. The major ICE payload includes a vector helium magnetometer, the plasma-wave experiment, the radio-wave experiment, the plasma-electron experiment, and the plasma ion experiment. Other experiments are intended to measure energetic protons, X-rays, low energy to high energy cosmic rays, cosmic ray electrons, and gamma-ray bursts. The ICE measurements of G/Z will be supplemented with ground-based measurements. Schematic diagrams are included.

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

NASA Technical Reports Server (NTRS)

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

2012-01-01

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

Cine: Line excitation by infrared fluorescence in cometary atmospheres

NASA Astrophysics Data System (ADS)

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

2017-03-01

CINE is a Python module for calculating infrared pumping efficiencies that can be applied to the most common molecules found in cometary comae such as water, hydrogen cyanide or methanol. Excitation by solar radiation of vibrational bands followed by radiative decay to the ground vibrational state is one of the main mechanisms for molecular excitation in comets. This code calculates the effective pumping rates for rotational levels in the ground vibrational state scaled by the heliocentric distance of the comet. Line transitions are queried from the latest version of the HITRAN spectroscopic repository using the astroquery affiliated package of astropy. Molecular data are obtained from the LAMDA database. These coefficients are useful for modeling rotational emission lines observed in cometary spectra at sub-millimeter wavelengths. Combined with computational methods to solve the radiative transfer equations based, e.g., on the Monte Carlo algorithm, this model can retrieve production rates and rotational temperatures from the observed emission spectrum.

Lyman-alpha observations of Comet Kohoutek 1973 XII with Copernicus

NASA Technical Reports Server (NTRS)

Drake, J. F.; Jenkins, E. B.; Bertaux, J. L.; Festou, M.; Keller, H. U.

1976-01-01

Comet Kohoutek 1973 XII was observed with a telescope-spectrometer on the Copernicus satellite on six occasions over a 1-month period starting on January 29, 1974. Positive detection of the cometary Ly-alpha emission profile was obtained on January 29 and February 2. Earlier observations of the geocoronal Ly-alpha emission profile allowed an instrumental intensity calibration and confirmation of the computed instrumental profile for an extended source at the Ly-alpha wavelength. After allowing for broadening by the instrument, a hydrogen-outflow velocity of about 10.6 km/s is derived from the width of the Ly-alpha emission on January 29. The intensity calibration combined with an appropriate cometary model led to cometary water-production rates for January 29 and February 2. Only upper limits were obtained for Ly-alpha on and after February 14. Searches for OH and D led to negative results.

Mid-infrared spectra of cometary dust: the evasion of its silicate mineralogy

NASA Astrophysics Data System (ADS)

Kimura, H.; Chigai, T.; Yamamoto, T.

2008-04-01

Infrared spectra of dust in cometary comae provide a way to identify its silicate constituents, and this is crucial for correctly understanding the condition under which our planetary system is formed. Recent studies assign a newly detected peak at a wavelength of 9.3 μm to pyroxenes and regard them as the most abundant silicate minerals in comets. Here we dispense with this pyroxene hypothesis to numerically reproduce the infrared features of cometary dust in the framework of our interstellar dust models. Presolar interstellar dust in a comet is modeled as fluffy aggregates consisting of submicrometer-sized organic grains with an amorphous-silicate core that undergoes nonthermal crystallization in a coma. We assert that forsterite (Mg2SiO4) is the carrier of all the observed features, including the 9.3 μm peak and that the major phase of iron is sulfides rather than iron-rich silicates.

Hydrogen production rate from comet Austin 1982g

NASA Technical Reports Server (NTRS)

Shih, P.; Scherb, F.; Roesler, F. L.

1984-01-01

Meaningful measurements with respect to the cometary Balmer-alpha (H-alpha) emission are difficult and require the use of special equipment. The first ground-based observations of H-alpha emission from a cometary hydrogen corona were conducted on comet Kohoutek 1973 XII with a large-aperture Fabry-Perot spectrometer installed at the McMath solar telescope at Kitt Peak National Observatory. The present investigation is concerned with the second ground-based observations of cometary H-alpha emission carried out during the apparition of comet Austin 1982g. A 150 mm dual-etalon Fabry-Perot spectrometer was employed in the experiment. Use was made of an observatory which is designed for the high spectral resolution study of faint extended sources such as interstellar and geocoronal emission lines. The investigation demonstrates that hydrogen production rates from comets as faint as about 7th magnitude can be routinely measured from the ground at minimal cost.

1548C27 - An interesting new cometary nebula

NASA Technical Reports Server (NTRS)

Craine, E. R.; Byard, P. L.; Boeshaar, G. O.

1981-01-01

The object 1548C27, a faint cometary nebula of classical form, discovered by an examination of early Near Infrared Photographic Sky Survey (NIPSS) data (1979) is presented. Direct imaging and polarimetric, photometric, and spectroscopic observations are reported. Early survey test photographs show that the object lies at R.A. 19h40m48s, Decl. +23 deg 17 arcmin 09 arc sec (1950) in the Vulpecula constellation in the immediate vicinity of the complex H II region and galactic cluster NGC 6820/6823. From the photographs, the nebula was estimated to be 15 m visual and of color class one. The object was observed spectroscopically in the region 5700-6800 A using an Image Dissector Scanner with a 1.8 m reflector, and the spectral scan, obtained on November 4, 1978, is presented. New information on cometary nebulae may further illuminate the evolutionary importance of the objects.

A tale of two telescopes: North Queensland and the 1882 transit of Venus

NASA Astrophysics Data System (ADS)

Orchiston, Wayne; Darlington, Vicki

2017-08-01

The 1882 transit of Venus offered the final opportunity for astronomers to use these rare events to pin down the distance from the Earth to the Sun. A British party based itself in southern Queensland, but total cloud cover prevented any observations being made on the critical day. In this paper we trace the preparations of the British party, and then show how they laid the foundations for the development of astronomy in Queensland by selling their two 6-in Cooke refractors before returning to Britain. Both instruments were purchased by a Townsville amateur astronomer, Edwin Norris, and although he installed one in an observatory, he made little use of it. However, he subsequently sold the other telescope to J. Ewen Davidson of Mackay, who also erected an obser-vatory for it. Davidson then used his instrument for cometary astronomy, in the process discovering two new comets, one of which now bears his name. Unfortunately, recent attempts to track down the present whereabouts of the two telescopes have failed.

Asteroid Composite Tape

NASA Astrophysics Data System (ADS)

1998-07-01

This is a composite tape showing 10 short segments primarily about asteroids. The segments have short introductory slides, which include brief descriptions about the shots. The segments are: (1) Radar movie of asteroid 1620 Geographos; (2) Animation of the trajectories of Toutatis and Earth (3) Animation of a landing on Toutatis; (4) Simulated encounter of an asteroid with Earth, includes a simulated impact trajectory; (5) An animated overview of the Manrover vehicle; (6) The Near Earth Asteroid Tracking project, includes a photograph of USAF Station in Hawaii, and animation of Earth approaching 4179 Toutatis and the asteroid Gaspara; (7) live video of the anchor tests of the Champoleon anchoring apparatus; (8) a second live video of the Champoleon anchor tests showing anchoring spikes, and collision rings; (9) An animated segment with narration about the Stardust mission with sound, which describes the mission to fly close to a comet, and capture cometary material for return to Earth; (10) live video of the drop test of a Stardust replica from a hot air balloon; this includes sound but is not narrated.

Sample Curation at a Lunar Outpost

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; Lofgren, Gary E.; Treiman, A. H.; Lindstrom, Marilyn L.

2007-01-01

The six Apollo surface missions returned 2,196 individual rock and soil samples, with a total mass of 381.6 kg. Samples were collected based on visual examination by the astronauts and consultation with geologists in the science back room in Houston. The samples were photographed during collection, packaged in uniquely-identified containers, and transported to the Lunar Module. All samples collected on the Moon were returned to Earth. NASA's upcoming return to the Moon will be different. Astronauts will have extended stays at an out-post and will collect more samples than they will return. They will need curation and analysis facilities on the Moon in order to carefully select samples for return to Earth.

78 FR 49296 - Centennial Challenges 2014 Sample Return Robot Challenge

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-13

... Return Robot Challenge AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice of Centennial Challenges 2014 Sample Return Robot Challenge. SUMMARY: This notice is issued in accordance with 51 U.S.C. 20144(c). The 2014 Sample Return Robot Challenge is scheduled and teams that wish to...

76 FR 56819 - Centennial Challenges 2012 Sample Return Robot Challenge

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-14

... Return Robot Challenge AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice. SUMMARY: This notice is issued in accordance with 42 U.S.C. 2451(314)(d). The 2012 Sample Return Robot.... The 2012 Sample Return Robot Challenge is a prize competition designed to encourage development of new...

An efficient approach for Mars Sample Return using emerging commercial capabilities

NASA Astrophysics Data System (ADS)

Gonzales, Andrew A.; Stoker, Carol R.

2016-06-01

Mars Sample Return is the highest priority science mission for the next decade as recommended by the 2011 Decadal Survey of Planetary Science (Squyres, 2011 [1]). This article presents the results of a feasibility study for a Mars Sample Return mission that efficiently uses emerging commercial capabilities expected to be available in the near future. The motivation of our study was the recognition that emerging commercial capabilities might be used to perform Mars Sample Return with an Earth-direct architecture, and that this may offer a desirable simpler and lower cost approach. The objective of the study was to determine whether these capabilities can be used to optimize the number of mission systems and launches required to return the samples, with the goal of achieving the desired simplicity. All of the major element required for the Mars Sample Return mission are described. Mission system elements were analyzed with either direct techniques or by using parametric mass estimating relationships. The analysis shows the feasibility of a complete and closed Mars Sample Return mission design based on the following scenario: A SpaceX Falcon Heavy launch vehicle places a modified version of a SpaceX Dragon capsule, referred to as ;Red Dragon;, onto a Trans Mars Injection trajectory. The capsule carries all the hardware needed to return to Earth Orbit samples collected by a prior mission, such as the planned NASA Mars 2020 sample collection rover. The payload includes a fully fueled Mars Ascent Vehicle; a fueled Earth Return Vehicle, support equipment, and a mechanism to transfer samples from the sample cache system onboard the rover to the Earth Return Vehicle. The Red Dragon descends to land on the surface of Mars using Supersonic Retropropulsion. After collected samples are transferred to the Earth Return Vehicle, the single-stage Mars Ascent Vehicle launches the Earth Return Vehicle from the surface of Mars to a Mars phasing orbit. After a brief phasing period, the Earth Return Vehicle performs a Trans Earth Injection burn. Once near Earth, the Earth Return Vehicle performs Earth and lunar swing-bys and is placed into a Lunar Trailing Orbit-an Earth orbit, at lunar distance. A retrieval mission then performs a rendezvous with the Earth Return Vehicle, retrieves the sample container, and breaks the chain of contact with Mars by transferring the sample into a sterile and secure container. With the sample contained, the retrieving spacecraft makes a controlled Earth re-entry preventing any unintended release of Martian materials into the Earth's biosphere. The mission can start in any one of three Earth to Mars launch opportunities, beginning in 2022.

An Efficient Approach for Mars Sample Return Using Emerging Commercial Capabilities.

PubMed

Gonzales, Andrew A; Stoker, Carol R

2016-06-01

Mars Sample Return is the highest priority science mission for the next decade as recommended by the 2011 Decadal Survey of Planetary Science [1]. This article presents the results of a feasibility study for a Mars Sample Return mission that efficiently uses emerging commercial capabilities expected to be available in the near future. The motivation of our study was the recognition that emerging commercial capabilities might be used to perform Mars Sample Return with an Earth-direct architecture, and that this may offer a desirable simpler and lower cost approach. The objective of the study was to determine whether these capabilities can be used to optimize the number of mission systems and launches required to return the samples, with the goal of achieving the desired simplicity. All of the major element required for the Mars Sample Return mission are described. Mission system elements were analyzed with either direct techniques or by using parametric mass estimating relationships. The analysis shows the feasibility of a complete and closed Mars Sample Return mission design based on the following scenario: A SpaceX Falcon Heavy launch vehicle places a modified version of a SpaceX Dragon capsule, referred to as "Red Dragon", onto a Trans Mars Injection trajectory. The capsule carries all the hardware needed to return to Earth Orbit samples collected by a prior mission, such as the planned NASA Mars 2020 sample collection rover. The payload includes a fully fueled Mars Ascent Vehicle; a fueled Earth Return Vehicle, support equipment, and a mechanism to transfer samples from the sample cache system onboard the rover to the Earth Return Vehicle. The Red Dragon descends to land on the surface of Mars using Supersonic Retropropulsion. After collected samples are transferred to the Earth Return Vehicle, the single-stage Mars Ascent Vehicle launches the Earth Return Vehicle from the surface of Mars to a Mars phasing orbit. After a brief phasing period, the Earth Return Vehicle performs a Trans Earth Injection burn. Once near Earth, the Earth Return Vehicle performs Earth and lunar swing-bys and is placed into a Lunar Trailing Orbit - an Earth orbit, at lunar distance. A retrieval mission then performs a rendezvous with the Earth Return Vehicle, retrieves the sample container, and breaks the chain of contact with Mars by transferring the sample into a sterile and secure container. With the sample contained, the retrieving spacecraft makes a controlled Earth re-entry preventing any unintended release of Martian materials into the Earth's biosphere. The mission can start in any one of three Earth to Mars launch opportunities, beginning in 2022.

An Efficient Approach for Mars Sample Return Using Emerging Commercial Capabilities

PubMed Central

Gonzales, Andrew A.; Stoker, Carol R.

2016-01-01

Mars Sample Return is the highest priority science mission for the next decade as recommended by the 2011 Decadal Survey of Planetary Science [1]. This article presents the results of a feasibility study for a Mars Sample Return mission that efficiently uses emerging commercial capabilities expected to be available in the near future. The motivation of our study was the recognition that emerging commercial capabilities might be used to perform Mars Sample Return with an Earth-direct architecture, and that this may offer a desirable simpler and lower cost approach. The objective of the study was to determine whether these capabilities can be used to optimize the number of mission systems and launches required to return the samples, with the goal of achieving the desired simplicity. All of the major element required for the Mars Sample Return mission are described. Mission system elements were analyzed with either direct techniques or by using parametric mass estimating relationships. The analysis shows the feasibility of a complete and closed Mars Sample Return mission design based on the following scenario: A SpaceX Falcon Heavy launch vehicle places a modified version of a SpaceX Dragon capsule, referred to as “Red Dragon”, onto a Trans Mars Injection trajectory. The capsule carries all the hardware needed to return to Earth Orbit samples collected by a prior mission, such as the planned NASA Mars 2020 sample collection rover. The payload includes a fully fueled Mars Ascent Vehicle; a fueled Earth Return Vehicle, support equipment, and a mechanism to transfer samples from the sample cache system onboard the rover to the Earth Return Vehicle. The Red Dragon descends to land on the surface of Mars using Supersonic Retropropulsion. After collected samples are transferred to the Earth Return Vehicle, the single-stage Mars Ascent Vehicle launches the Earth Return Vehicle from the surface of Mars to a Mars phasing orbit. After a brief phasing period, the Earth Return Vehicle performs a Trans Earth Injection burn. Once near Earth, the Earth Return Vehicle performs Earth and lunar swing-bys and is placed into a Lunar Trailing Orbit - an Earth orbit, at lunar distance. A retrieval mission then performs a rendezvous with the Earth Return Vehicle, retrieves the sample container, and breaks the chain of contact with Mars by transferring the sample into a sterile and secure container. With the sample contained, the retrieving spacecraft makes a controlled Earth re-entry preventing any unintended release of Martian materials into the Earth’s biosphere. The mission can start in any one of three Earth to Mars launch opportunities, beginning in 2022. PMID:27642199

STARDUST and HAYABUSA: Sample Return Missions to Small Bodies in the Solar System

NASA Technical Reports Server (NTRS)

Sandford, S. A.

2005-01-01

There are currently two active spacecraft missions designed to return samples to Earth from small bodies in our Solar System. STARDUST will return samples from the comet Wild 2, and HAYABUSA will return samples from the asteroid Itokawa. On January 3,2004, the STARDUST spacecraft made the closest ever flyby (236 km) of the nucleus of a comet - Comet Wild 2. During the flyby the spacecraft collected samples of dust from the coma of the comet. These samples will be returned to Earth on January 15,2006. After a brief preliminary examination to establish the nature of the returned samples, they will be made available to the general scientific community for study. The HAYABUSA spacecraft arrived at the Near Earth Asteroid Itokawa in September 2005 and is currently involved in taking remote sensing data from the asteroid. Several practice landings have been made and a sample collection landing will be made soon. The collected sample will be returned to Earth in June 2007. During my talk I will discuss the scientific goals of the STARDUST and HAYABUSA missions and provide an overview of their designs and flights to date. I will also show some of the exciting data returned by these spacecraft during their encounters with their target objects.

An experimental study of the isotopic enrichment in Ar, Kr, and Xe when trapped in water ice

NASA Technical Reports Server (NTRS)

Notesco, G.; Laufer, D.; Bar-Nun, A.; Owen, T.

1999-01-01

The isotopic enrichment of argon, krypton, and xenon, when trapped in water ice, was studied experimentally. The isotopes were found to be enriched according to their (m1/m2)1/2 ratio. These enrichment factors could be useful for comparison among the uncertain cosmic or solar isotopic ratios, the hopeful in situ cometary ratio, and those in Earth's atmosphere, in the context of cometary delivery of volatiles to Earth.

Workshop on Cometary Dust in Astrophysics

NASA Technical Reports Server (NTRS)

2003-01-01

The paper include contribution of each Lunar and Planetary Institute. Contents include the following: Mass flux in the ancient Earth-Moon system and benign implications for the origin of life on Earth. In-situ analysis of complex organic matter in cometary dust by ion microprobe. Pristine presolar silicon carbide. Infrared spectra of melilite solid solution. Comet observations with SIRTF. Ice and carbon chemistry in comets. The nature in interstellar dust. Modeling the infrared emission from protoplanetary dust disks.

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.

Concept Study For A Near-term Mars Surface Sample Return Mission

NASA Astrophysics Data System (ADS)

Smith, M. F.; Thatcher, J.; Sallaberger, C.; Reedman, T.; Pillinger, C. T.; Sims, M. R.

The return of samples from the surface of Mars is a challenging problem. Present mission planning is for complex missions to return large, focused samples sometime in the next decade. There is, however, much scientific merit in returning a small sample of Martian regolith before the end of this decade at a fraction of the cost of the more ambitious missions. This paper sets out the key elements of this concept that builds on the work of the Beagle 2 project and space robotics work in Canada. The paper will expand the science case for returning a regolith sample that is only in the range of 50-250g but would nevertheless include plenty of interesting mate- rial as the regolith comprises soil grains from a wide variety of locations i.e. nearby rocks, sedimentary formations and materials moved by fluids, winds and impacts. It is possible that a fine core sample could also be extracted and returned. The mission concept is to send a lander sized at around 130kg on the 2007 or 2009 opportunity, immediately collect the sample from the surface, launch it to Mars orbit, collect it by the lander parent craft and make an immediate Earth return. Return to Earth orbit is envisaged rather than direct Earth re-entry. The lander concept is essen- tially a twice-size Beagle 2 carrying the sample collection and return capsule loading equipment plus the ascent vehicle. The return capsule is envisaged as no more than 1kg. An overall description of the mission along with methods for sample acquisition, or- bital rendezvous and capsule return will be outlined and the overall systems budgets presented. To demonstrate the near term feasibility of the mission, the use of existing Canadian and European technologies will be highlighted.

Challenges of deflecting an asteroid or cometary nucleus with a nuclear burst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bradley, Paul A; Plesko, Cathy S; Clement, Ryan R C

2009-01-01

There are many natural disasters that humanity has to deal with over time. These include earthquakes, tsunami, hurricanes, floods, asteroid strikes, and so on. Many of these disasters occur slowly enough that some advance warning of which areas will be affected is possible. However, in almost all cases, the response is to evacuate the area to be affected and deal with the damage later. The evacuations for hurricanes Katrina and Rita on the US Gulf Coast in 2005 demonstrated the chaos that can result. In contrast with other natural disasters. it is likely that an asteroid or cometary nucleus onmore » a collision course with Earth is likely to be detected with enough warning time to possibly deflect it away from the collision course. 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 {approx}140 meters in the next decade. The question is how to mitigate the threat from an asteroid or cometary nucleus found to be on a collision course. We briefly review some possible methods, describing their good and bad points, and then embark on a more detailed description of using a nuclear munition in standoff mode to deflect an asteroid or cometary nucleus before it can hit Earth.« less

The contribution of cometary volatiles to the primitive Earth.

PubMed

Oro, J; Holzer, G; Lazcano-Araujo, A

1980-01-01

It has been estimated that during its early history the Earth captured a mass of cometary material of the order of 10(23) grams. Since carbon is supposed to be at least three times more abundant in comets than in carbonaceous chondrites (3.5% C in C 1 chondrites), it can be deduced that about 1 x 10(22) grams of carbon (as carbon compounds), was added by comets to the surface of the prebiotic Earth. This carbon value is of the same order of magnitude as the value of the organic carbon buried in the Earth's sedimentary shell, but approximately one order of magnitude lower than the Earth's surface total carbon (7 x 10(22) gm). The capture of comets by the Earth would also have contributed to generating the appropriate aqueous and reducing environmental conditions necessary for organic synthesis. Although it is possible that some of the cometary carbon compounds falling on the Earth survived, most of them were probably decomposed by the heat and shock waves of the cometary collision. Upon quenching to low temperatures, however, the reactive chemical species produced by the impact would have recombined, leading to the synthesis of a great variety of organic molecules. Laboratory experiments with radiation, heat and shock waves have demonstrated that some of the synthesized compounds are biochemical molecules: amino acids, sugars, purines, and pyrimidines. These are essential to all living systems.

Water Planetary and Cometary Atmospheres: H2O/HDO Transmittance and Fluorescence Models

NASA Technical Reports Server (NTRS)

Villanueva, G. L.; Mumma, M. J.; Bonev, B. P.; Novak, R. E.; Barber, R. J.; DiSanti, M. A.

2012-01-01

We developed a modern methodology to retrieve water (H2O) and deuterated water (HDO) in planetary and cometary atmospheres, and constructed an accurate spectral database that combines theoretical and empirical results. Based on a greatly expanded set of spectroscopic parameters, we built a full non-resonance cascade fluorescence model and computed fluorescence efficiencies for H2O (500 million lines) and HDO (700 million lines). The new line list was also integrated into an advanced terrestrial radiative transfer code (LBLRTM) and adapted to the CO2 rich atmosphere of Mars, for which we adopted the complex Robert-Bonamy formalism for line shapes. We then retrieved water and D/H in the atmospheres of Mars, comet C/2007 WI, and Earth by applying the new formalism to spectra obtained with the high-resolution spectrograph NIRSPEC/Keck II atop Mauna Kea (Hawaii). The new model accurately describes the complex morphology of the water bands and greatly increases the accuracy of the retrieved abundances (and the D/H ratio in water) with respect to previously available models. The new model provides improved agreement of predicted and measured intensities for many H2O lines already identified in comets, and it identifies several unassigned cometary emission lines as new emission lines of H2O. The improved spectral accuracy permits retrieval of more accurate rotational temperatures and production rates for cometary water.

The cometary and asteroidal impactor flux at the earth

NASA Technical Reports Server (NTRS)

Weissman, Paul R.

1988-01-01

The cratering records on the Earth and the lunar maria provide upper limits on the total impactor flux at the Earth's orbit over the past 600 Myr and the past 3.3 Gyr, respectively. These limits can be compared with estimates of the expected cratering rate from observed comets and asteroids in Earth-crossing orbits, corrected for observational selection effects and incompleteness, and including expected temporal variations in the impactor flux. Both estimates can also be used to calculate the probability of large impacts which may result in biological extinction events on the Earth. The estimated cratering rate on the Earth for craters greater than 10 km-diameter, based on counted craters on dated surfaces is 2.2 + or - 1.1 x 10 to the minus 14th power km(-2) yr(-1) (Shoemaker et al., 1979). Using a revised mass distribution for cometary nuclei based on the results of the spacecraft flybys of Comet Halley in 1986, and other refinements in the estimate of the cometary flux in the terrestrial planets zone, it is now estimated that long-period comets account for 11 percent of the cratering on the Earth (scaled to the estimate above), and short-period comets account for 4 pct (Weissman, 1987). However, the greatest contribution is from large but infrequent, random cometary showers, accounting for 22 pct of the terrestrial cratering.

Characteristics of Cometary Dust Tracks in Stardust Aerogel and Laboratory Calibrations

NASA Technical Reports Server (NTRS)

Burchell, M. J.; Fairey, S. A. J.; Wozniakiewicz, P.; Brownlee, D. E.; Hoerz, F.; Kearsley, A. T.; See, T. H.; Tsou, P.; Westphal, A.; Green, S. F.;

Light scattering by dust particles (PROGRA2 experiment): size and structure effects for transparent and absorbing materials

NASA Astrophysics Data System (ADS)

Hadamcik, E.; Renard, J.-B.; Lasue, J.; Levasseur-Regourd, A. C.

2007-08-01

1- Introduction Cometary and possibly interplanetary dust particles seem to be mainly made of agglomerates of submicron and micron-sized grains. These particles are among the most primitive in our solar system. Regoliths on asteroidal and planetary surfaces seem to be loose materials produced by impinging meteorites on the surface of small bodies. Comparing their physical properties is thus fundamental to understand their evolution. To interpret remote observations of solar light scattered by dust particles and regoliths, it is necessary to use numerical and experimental simulations [1,2,3]. 2- PROGRA2 experiment PROGRA2 instruments are polarimeters; the light sources are two randomly polarized lasers (632.8 nm and 543.5 nm). Levitating particles (in microgravity or lifted by an air-draught) are studied by imaging polarimetry. Details on the instruments can be found in [4,5]. 3- Samples Two kinds of samples are studied: compact particles in the (1-400) micrometer size range and fluffy aggregates in the same size range, made from submicron and micronsized grains. The materials are transparent silica and absorbing carbon. Some deposited particles are huge agglomerates of micron-sized grains produced by random ballistic deposition of single grains [6,7] or produced by evaporation of mixtures in alcohol of fluffy aggregates of submicron-sized grains. Two samples are made of silica spheres coated by a carbonaceous black compound. Cometary analogues are mixtures of silica and amorphous carbon or Mg-Fe silicates mixed with amorphous carbon. 4- Results Phase curves and their main parameters (negative polarization at small phase angles and maximum polarization, Pmax, at 90-100° phase angle) for the different materials will be compared and related to the physical properties. For example, it is well known by numerical simulations and/or by experiments that the maximum polarization decreases when the size (submicrometer range) of the grains increases [2,8,9]. An inverse rule is found for compact grains, larger than the wavelength. Mixtures of fluffy silica and fined grained amorphous carbon or better Mg-Fe silicates with amorphous carbon are excellent cometary particles analogues (as light scattering is concerned) if they are mixed with some compact micron-sized grains [9]. Nevertheless the structure of the aggregates seems to play a major role to obtain the negative branch found on the polarimetric phase curves for comets [10]. 5- Discussion and conclusions The experiments purpose is to help to disentangle the different physical properties of dust particles that can be deduced from remote observations (cometary dust, regoliths). Differences between the main parameters influencing the variations of Pmax and the presence of a negative branch on the polarimetric phase curves for lifted and deposited particles (in huge agglomerates or not) will be discussed. Acknowledgments: Technische Universität Carolo-Wilhelmina, Braunschweig, Deutschland (Pr Blum, Dr Schräpler); University of New Mexico, Albuquerque, USA (Pr Rietmeijer); NASA Goddard Space Flight Center, Maryland, USA (Dr Nuth) References [1] A.C. Levasseur-Regourd, E. Hadamcik, JQSRT 79-80, 903 (2003) [2] J. Lasue, A.C. Levasseur-Regourd, JQSRT 100, 220 (2006) [3] J.-B. Renard et al., ASR 31, 2511 (2003) [4] J.-B. Renard et al., Appl. Opt. 91, 609 (2002) [5] E. Hadamcik et al., JQSRT 106, 74 (2007) [6] J. Blum, R. Schreapler, Phys. Rev Let 93:115031 (2004) [7] J. Blum et al., Astrophys J 652, 1768 (2006) [8] R. West, Appl. Opt. 30, 5216 (1991) [9] E. Hadamcik et al., JQSRT 100, 143 (2006) [10] E. Hadamcik et al., Icarus, in press (2007)

Sample Handling Considerations for a Europa Sample Return Mission: An Overview

NASA Technical Reports Server (NTRS)

Fries, M. D.; Calaway, M. L.; Evans, C. A.; McCubbin, F. M.

2015-01-01

The intent of this abstract is to provide a basic overview of mission requirements for a generic Europan plume sample return mission, based on NASA Curation experience in NASA sample return missions ranging from Apollo to OSIRIS-REx. This should be useful for mission conception and early stage planning. We will break the mission down into Outbound and Return legs and discuss them separately.

Consideration of sample return and the exploration strategy for Mars

NASA Technical Reports Server (NTRS)

Bogard, D. C.; Duke, M. B.; Gibson, E. K.; Minear, J. W.; Nyquist, L. E.; Phinney, W. C.

1979-01-01

The scientific rationale and requirements for a Mars surface sample return were examined and the experience gained from the analysis and study of the returned lunar samples were incorporated into the science requirements and engineering design for the Mars sample return mission. The necessary data sets for characterizing Mars are presented. If further analyses of surface samples are to be made, the best available method is for the analysis to be conducted in terrestrial laboratories.

Intimate Partner Violence Exposure, Salivary Cortisol, and Childhood Asthma

ERIC Educational Resources Information Center

Bair-Merritt, Megan H.; Johnson, Sara B.; Okelo, Sande; Page, Gayle

2012-01-01

Parents were given supplies to collect 3 child salivary cortisol samples (awakening, 30-min after awakening, bedtime) at home on a typical day, and return them via mail. Medical records also were abstracted. Results: Fifty-three percent (n = 29) returned child salivary samples. Families who returned samples typically returned them within 2 weeks,…

Plasma response to a cometary outburst: Rosetta Plasma Consortium observations during comet 67P/Churyumov-Gerasimenko outburst event on 19 February 2016

NASA Astrophysics Data System (ADS)

Hajra, R.; Bruce, T.; Pierre, H.; Galand, M. F.; Heritier, K. L.; Edberg, N. J. T.; Burch, J. L.; Broiles, T. W.; Goldstein, R.; Glassmeier, K. H.; Richter, I.; Goetz, C.; Nilsson, H.; Altwegg, K.; Rubin, M.; Tanimori, T.

2016-12-01

Cometary outbursts are one of the most spectacular aspects of comet behavior. They are characterized by an abrupt increase in cometary brightness followed by a gradual fall off to the pre-event brightness. Although there are several studies on outburst events, to our knowledge, no detailed analysis on the variation of the cometary plasma environment during an outburst has ever been reported. On 19 February 2016, when comet 67P/Churyumov-Gerasimenko was at a heliocentric distance of 2.4 AU, an outburst event, characterized by two orders of magnitude increase in coma surface brightness, took place. Rosetta was at a distance of 30 km from the comet nucleus, orbiting with a relative speed of 0.17 m/s. The Rosetta Plasma Consortium (RPC) provided in-situ measurements of the cometary plasma, embedded in the solar wind, and the associated magnetic field during this outburst, as the dust and gas expelled from the comet were passing by the spacecraft. While the neutral density (ROSINA/COPS) at the spacecraft position increased by a factor of 1.5, the local plasma density (RPC/MIP) was found to increase by a factor of 3 during the outburst event, driving the spacecraft potential more negative (RPC/LAP). The event was characterized by the energy degradation of energetic (10s of eV) electrons (RPC/IES). In response to the outburst, the local magnetic field exhibited a slight increase in amplitude and a slow rotation (RPC/MAG). A weakening of 10-100 mHz magnetic field fluctuations was also observed during the outburst. The RPC instruments show that the effects of the outburst on the plasma lasted for about 4 hours, from 1000 UT to 1400 UT. Detailed analyses of the observations made by RPC along with ROSINA/COPS will be presented in the paper.

A GREAT search for Deuterium in Comets

NASA Astrophysics Data System (ADS)

Mumma, Michael

2012-10-01

Comets are understood to be the most pristine bodies in the Solar System. Their compositions reflect the chemical state of materials at the very earliest evolutionary stages of the protosolar nebula and, as such, they provide detailed insight into the physical and chemical processes operating in planet-forming disks. Isotopic fractionation ratios of the molecular ices in the nucleus are regarded as signatures of formation processes. These ratios provide unique information on the natal heritage of those ices, and can also test the proposal that Earth's water and other volatiles were delivered by cometary bombardment. Measurement of deuterium fractionation ratios is thus a major goal in contemporary cometary science and the D/H ratio of water - the dominant volatile in comets - holds great promise for testing the formation history of cometary matter. The D/H ratio in cometary water has been measured in only seven comets. Six were from the Oort Cloud reservoir and the D/H ratio was about twice that of the Earth's oceans. However, the recent Herschel measurement of HDO/H2O in 103P/Hartley-2 (the first from the Kuiper Belt) was consistent with exogenous delivery of Earth's water by comets. Outstanding questions remain: are cometary HDO/H2O ratios consistent with current theories of nebular chemical evolution or with an interstellar origin? Does the HDO/H2O ratio vary substantially among comet populations? Hartley-2 is the only Kuiper Belt comet with measured HDO/H2O, are there comets with similar ratios in the Oort cloud? These questions can only be addressed by measuring HDO/H2O ratios in many more suitable bright comets. We therefore propose to measure the D/H ratio in water in a suitable target-of-opportunity comet by performing observations of HDO and OH with the GREAT spectrometer on SOFIA. A multi-wavelength, ground-based observing campaign will also be conducted in support of the airborne observations.

A GREAT search for Deuterium in Comets

NASA Astrophysics Data System (ADS)

Mumma, Michael

2013-10-01

Comets are understood to be the most pristine bodies in the Solar System. Their compositions reflect the chemical state of materials at the very earliest evolutionary stages of the protosolar nebula and, as such, they provide detailed insight into the physical and chemical processes operating in planet-forming disks. Isotopic fractionation ratios of the molecular ices in the nucleus are regarded as signatures of formation processes. These ratios provide unique information on the natal heritage of those ices, and can also test the proposal that Earth's water and other volatiles were delivered by cometary bombardment. Measurement of deuterium fractionation ratios is thus a major goal in contemporary cometary science and the D/H ratio of water - the dominant volatile in comets - holds great promise for testing the formation history of cometary matter. The D/H ratio in cometary water has been measured in only eight comets. Seven were from the Oort Cloud reservoir and the D/H ratio was about twice that of the Earth's oceans. However, the recent Herschel measurement of HDO/H2O in 103P/Hartley-2 (the first from the Kuiper Belt) was consistent with exogenous delivery of Earth's water by comets. Outstanding questions remain: are cometary HDO/H2O ratios consistent with current theories of nebular chemical evolution or with an interstellar origin? Does the HDO/H2O ratio vary substantially among comet populations? Hartley-2 is the only Kuiper Belt comet with measured HDO/H2O, are there comets with similar ratios in the Oort cloud? These questions can only be addressed by measuring HDO/H2O ratios in many more suitable bright comets. We therefore propose to measure the D/H ratio in water in a suitable target-of-opportunity comet by performing observations of HDO and OH with the GREAT spectrometer on SOFIA. A multi-wavelength, ground-based observing campaign will also be conducted in support of the airborne observations.

Modeling cometary photopolarimetric characteristics with Sh-matrix method

NASA Astrophysics Data System (ADS)

Kolokolova, L.; Petrov, D.

2017-12-01

Cometary dust is dominated by particles of complex shape and structure, which are often considered as fractal aggregates. Rigorous modeling of light scattering by such particles, even using parallelized codes and NASA supercomputer resources, is very computer time and memory consuming. We are presenting a new approach to modeling cometary dust that is based on the Sh-matrix technique (e.g., Petrov et al., JQSRT, 112, 2012). This method is based on the T-matrix technique (e.g., Mishchenko et al., JQSRT, 55, 1996) and was developed after it had been found that the shape-dependent factors could be separated from the size- and refractive-index-dependent factors and presented as a shape matrix, or Sh-matrix. Size and refractive index dependences are incorporated through analytical operations on the Sh-matrix to produce the elements of T-matrix. Sh-matrix method keeps all advantages of the T-matrix method, including analytical averaging over particle orientation. Moreover, the surface integrals describing the Sh-matrix elements themselves can be solvable analytically for particles of any shape. This makes Sh-matrix approach an effective technique to simulate light scattering by particles of complex shape and surface structure. In this paper, we present cometary dust as an ensemble of Gaussian random particles. The shape of these particles is described by a log-normal distribution of their radius length and direction (Muinonen, EMP, 72, 1996). Changing one of the parameters of this distribution, the correlation angle, from 0 to 90 deg., we can model a variety of particles from spheres to particles of a random complex shape. We survey the angular and spectral dependencies of intensity and polarization resulted from light scattering by such particles, studying how they depend on the particle shape, size, and composition (including porous particles to simulate aggregates) to find the best fit to the cometary observations.

Cometary dust in Antarctic ice and snow: Past and present chondritic porous micrometeorites preserved on the Earth's surface

NASA Astrophysics Data System (ADS)

Noguchi, Takaaki; Ohashi, Noriaki; Tsujimoto, Shinichi; Mitsunari, Takuya; Bradley, John P.; Nakamura, Tomoki; Toh, Shoichi; Stephan, Thomas; Iwata, Naoyoshi; Imae, Naoya

2015-01-01

Chondritic porous interplanetary dust particles (CP IDPs) collected in the stratosphere are regarded as possibly being cometary dust, and are therefore the most primitive solar system material that is currently available for analysis in laboratories. In this paper we report the discovery of more than 40 chondritic porous micrometeorites (CP MMs) in the surface snow and blue ice of Antarctica, which are indistinguishable from CP IDPs. The CP MMs are botryoidal aggregates, composed mainly of sub-micrometer-sized constituents. They contain two components that characterize them as CP IDPs: enstatite whiskers and GEMS (glass with embedded metal and sulfides). Enstatite whiskers appear as <2-μm-long acicular objects that are attached on, or protrude from the surface, and when included in the interior of the CP MMs are composed of a unit-cell scale mixture of clino- and ortho-enstatite, and elongated along the [100] direction. GEMS appear as 100-500 nm spheroidal objects containing <50 nm Fe-Ni metal and Fe sulfide. The CP MMs also contain low-iron-manganese-enriched (LIME) and low-iron-chromium-enriched (LICE) ferromagnesian silicates, kosmochlor (NaCrSi2O6)-rich high-Ca pyroxene, roedderite (K, Na)2Mg5Si12O30, and carbonaceous nanoglobules. These components have previously been discovered in primitive solar system materials such as the CP IDPs, matrices of primitive chondrites, phyllosilicate-rich MMs, ultracarbonaceous MMs, and cometary particles recovered from the 81P/Wild 2 comet. The most outstanding feature of these CP MMs is the presence of kosmochlor-rich high-Ca pyroxene and roedderite, which suggest that they have building blocks in common with CP IDPs and cometary dust particles and therefore suggest a possible cometary origin of both CP MMs and CP IDPs. It is therefore considered that CP MMs are CP IDPs that have fallen to Earth and have survived the terrestrial environment.

Detection of the Water Maser Line at 1.35 cm in Exoplanetary Systems

NASA Astrophysics Data System (ADS)

Cosmovici, Christiano1, Pluchino S. 2, Pogrebenko S. 3, Montebugnoli S. 2, Bartolini M. 2, Schillirò F. 2

2012-05-01

The discovery of the first water emission in the atmosphere of Jupiter induced by a catastrophic cometary impact [1] has shown that the water Maser line at 22 GHz (1.35 cm) can be used as a diagnostic tool for cometary-[2] and also for planetary-water search outside the solar system, as comets are able to deliver very large amounts of water to planets raising the fascinating possibility of extraterrestrial life evolution. Furthermore, assuming that a sufficient amount of water may be present in the upper layers of a planetary atmosphere, it is possible to show that masing conditions may apply for a planet independently from cometary bombardment. The calculations of the feasibility of the Maser detection are reported in [3,4]. In 1999 we started the search for the water maser line on 35 targets up to 50 LY away from the Sun and by using fast multichannel spectrometers coupled to the 32 m dish of the Medicina and Noto Radiotelescopes (Italy) we carried out observations of : 1) stellar regions where either cometary clouds have been discovered, or planetary systems have been indirectly detected (up to now about 700); 2) peculiar stars, like red and brown dwarfs with sufficient IR- radiation to produce Maser emission. From the 35 targets investigated by us the following showed faint transient signals during different periods : Epsilon Eridani, Lalande 21185, EQ Peg, Ups And, 47 UMa, Tau Ceti and Gliese 581. The first two are the most reliable as we could detect signals with S/N > 4 with both telescopes. Eps Eri is particularly interesting for our purposes as it is only 10.8 LY away and among the closest star systems to the Sun. This target represents the terrestrial conditions 4 Gyr ago when cometary bombardment is supposed to have ended and life started.

DDA Computations of Porous Aggregates with Forsterite Crystals: Effects of Crystal Shape and Crystal Mass Fraction

NASA Technical Reports Server (NTRS)

Wooden, Diane H.; Lindsay, Sean S.; Harker, David; Woodward, Charles; Kelley, Michael S.; Kolokolova, Ludmilla

2015-01-01

Porous aggregate grains are commonly found in cometary dust samples and are needed to model cometary IR spectral energy distributions (SEDs). Models for thermal emissions from comets require two forms of silicates: amorphous and crystalline. The dominant crystal resonances observed in comet SEDs are from Forsterite (Mg2SiO4). The mass fractions that are crystalline span a large range from 0.0 < or = fcrystal < or = 0.74. Radial transport models that predict the enrichment of the outer disk (>25 AU at 1E6 yr) by inner disk materials (crystals) are challenged to yield the highend-range of cometary crystal mass fractions. However, in current thermal models, Forsterite crystals are not incorporated into larger aggregate grains but instead only are considered as discrete crystals. A complicating factor is that Forsterite crystals with rectangular shapes better fit the observed spectral resonances in wavelength (11.0-11.15 microns, 16, 19, 23.5, 27, and 33 microns), feature asymmetry and relative height (Lindley et al. 2013) than spherically or elliptically shaped crystals. We present DDA-DDSCAT computations of IR absorptivities (Qabs) of 3 micron-radii porous aggregates with 0.13 < or = fcrystal < or = 0.35 and with polyhedral-shaped Forsterite crystals. We can produce crystal resonances with similar appearance to the observed resonances of comet Hale- Bopp. Also, a lower mass fraction of crystals in aggregates can produce the same spectral contrast as a higher mass fraction of discrete crystals; the 11micron and 23 micron crystalline resonances appear amplified when crystals are incorporated into aggregates composed otherwise of spherically shaped amorphous Fe-Mg olivines and pyroxenes. We show that the optical properties of a porous aggregate is not linear combination of its monomers, so aggregates need to be computed. We discuss the consequence of lowering comet crystal mass fractions by modeling IR SEDs with aggregates with crystals, and the implications for radial transport models of our protoplanetary disk.

Integrating Public Perspectives in Sample Return Planning

NASA Technical Reports Server (NTRS)

Race, Margaret S.; MacGregor, G.

2001-01-01

Planning for extraterrestrial sample returns, whether from Mars or other solar system bodies, must be done in a way that integrates planetary protection concerns with the usual mission technical and scientific considerations. Understanding and addressing legitimate societal concerns about the possible risks of sample return will be a critical part of the public decision making process ahead. This paper presents the results of two studies, one with lay audiences, the other with expert microbiologists, designed to gather information, on attitudes and concerns about sample return risks and planetary protection. Focus group interviews with lay subjects, using generic information about Mars sample return and a preliminary environmental impact assessment, were designed to obtain an indication of how the factual content is perceived and understood by the public. A research survey of microbiologists gathered information on experts' views and attitudes about sample return, risk management approaches and space exploration risks. These findings, combined with earlier research results on risk perception, will be useful in identifying levels of concern and potential conflicts in understanding between experts and the public about sample return risks. The information will be helpful in guiding development of the environmental impact statement and also has applicability to proposals for sample return from other solar system bodies where scientific uncertainty about extraterrestrial life may persist at the time of mission planning.

On the petrological, geochemical, and geophysical characterization of a returned Mars surface sample and the impact of biological sterilization on the analyses

NASA Technical Reports Server (NTRS)

1974-01-01

A study was conducted: to identify those experiments that could and should be done on a returned Martian sample in order to characterize its inorganic properties; to evaluate, insofar as can be done, the effects of potential biological sterilization of the sample by heating prior to its return; to identify particular analytical techniques needing further improvement in order to make optimum use of a returned sample; and to identify experiments to be done on simulants, with and without sterilization, that better define the limits of information available about the planet from analyses of returned samples.

The study of the physics of cometary nuclei

NASA Technical Reports Server (NTRS)

Whipple, F. L.

1983-01-01

On the basis of the icy conglometate model of cometary nuclei various observations demonstrate the spotted nature of many or most nuclei, i.e., regions of unusual activity, either high or low. Rotation periods, spin axes and even precession of the axes have been determined. Narrow dust jets near the nuclei of some bright comets require that small sources be embedded in larger active areas. Certain evidence suggests that very dusty areas and very dusty comets may be less active, respectively, than surrounding areas or other comets.

The International Cometary Explorer (ICE) mission to Comets Giacobini-Zinner and Halley

NASA Technical Reports Server (NTRS)

Brandt, J. C.

1986-01-01

Use of the ISEE-3 satellite (renamed ICE) to study the interaction between the solar wind and a cometary atmosphere by passing through the plasma tail by intercepting Comet Giacobini-Zinner on 11 September 1985 is described. Details of the targeting strategy are discussed. Additional scientific objectives following the tail intercept of Comet Giacobini-Zinner include the support of Comet Halley studies through the measurement of solar-wind conditions upstream of P/Halley in October 1985 and March 1986.

The study of the physics of cometary nuclei

NASA Technical Reports Server (NTRS)

Whipple, F. L.; Marsden, B. G.; Sekanina, Z.

1976-01-01

A semiannual progress report describing the work completed during the period 1 September 1975 to 29 February 1976 on the physics of cometary nuclei was given. The following items were discussed: (1) a paper entitled ""A speculation about comets and the earth'', (2) a chapter entitled"" The physics of comets'' for ""Reviews of Astronomy and Astrophysics'', (3) continuing work on split comets, and (4) results dealing with a new application of nongravitational solar-radial forces as a measure of comet nucleus dimensions and activity.

CCD-photometry of comets at large heliocentric distances

NASA Technical Reports Server (NTRS)

Mueller, Beatrice E. A.

1992-01-01

CCD imaging and time series photometry are used to determine the state of activity, nuclear properties and eventually the rotational motion of cometary nuclei. Cometary activity at large heliocentric distances and mantle evolution are not yet fully understood. Results of observations carried out at the 2.1 telescope on Kitt Peak April 10-12 and May 15-16, 1991 are discussed. Color values and color-color diagrams are presented for several comets and asteroids. Estimations of nuclear radii and shapes are given.

Chaotic dynamics around cometary nuclei

NASA Astrophysics Data System (ADS)

Lages, José; Shevchenko, Ivan I.; Rollin, Guillaume

2018-06-01

We apply a generalized Kepler map theory to describe the qualitative chaotic dynamics around cometary nuclei, based on accessible observational data for five comets whose nuclei are well-documented to resemble dumb-bells. The sizes of chaotic zones around the nuclei and the Lyapunov times of the motion inside these zones are estimated. In the case of Comet 1P/Halley, the circumnuclear chaotic zone seems to engulf an essential part of the Hill sphere, at least for orbits of moderate to high eccentricity.

Could the Geminid meteoroid stream be the result of long-term thermal fracture?

NASA Astrophysics Data System (ADS)

Ryabova, G. O.

2015-10-01

The previous models by Ryabova have shown that the Geminid meteoroid stream has cometary origin, so asteroid (3200) Phaethon (the Geminid's parent body) is probably a dead comet. Recently (in 2009 and 2012) some week activity was observed (see Jewitt & Li, 2010, AJ, 140), but it was not the cometary activity. Recurrent brightening of Phaethon in perihelion could be the result of thermal fracture and decomposition. In this study we model the longterm dust release from Phaethon based on this mechanism.

Cometary dust at the nanometre scale - the MIDAS view after perihelion

NASA Astrophysics Data System (ADS)

Bentley, M. S.; Torkar, K.; Jeszenszky, H.; Romstedt, J.; Schmied, R.; Mannel, T.

2015-10-01

The MIDAS instrument on-board the Rosetta orbiter [1] is a unique combination of a dust collection and handling system and a high resolution Atomic Force Microscope (AFM). By building three-dimensional images of the dust particle topography with nano- to micrometre resolution, MIDAS addresses a range of fundamental questions in Solar System and cometary sciences. The greatest number of particles is expected to be collected around perihelion and the initial results of imaging these will be presented.

Linear polarization of light scattered by cometary analogs: New samples

NASA Astrophysics Data System (ADS)

Hadamcik, E.; Renard, J.; Buch, A.; Carrasco, N.; Johnson, N.; Nuth, J.

2014-07-01

Mixtures of silicates (Mg and Fe) with carbonaceous compounds (carbon and/or organics) are currently proposed as cometary analogs. The particles are fluffy aggregates of submicron-sized constituent grains and compact grains (tens of micrometers), similar to those captured in the Earth's stratosphere (interplanetary dust particles or IDPs) and deduced from the Stardust results. They are lifted or in microgravity or levitated by an air-draught. The light source is unpolarized. The linear polarization of the scattered light floating in the beam is studied as a function of the phase angle. In previous experiments with the PROGRA2 instrument (Hadamcik et al., 2011), the general shape of the cometary polarimetric phase curves is reproduced with a shallow negative branch and a more developed positive branch (maximum polarization around 20--30 %) depending on the size distributions of the particles (compact and/or aggregates) and their constituent grains. To observe the increase of polarization with wavelength, the organic materials were necessary. When fluffy aggregates (silicates and carbon black mixtures) and compact silicate grains of tens of micrometers are present, the whole cometary coma polarization phase curve is well fitted by the phase curves obtained. The maximum polarization value decreases when the ratio of compact silicates to fluffy aggregates increases. The observed differences in polarization between different coma regions may be also simulated. When only fluffy aggregates are used, the maximum polarization corresponds to the polarization in jets of 'high polarization' active comets (Hadamcik and Levasseur-Regourd, 2003). A high polarization region may exist in some 'low polarization' comets, with large slowly moving particles; using the experimental results, we suggest the presence of dark relatively compact particles larger than 20 micrometers (Hadamcik et al., 2007; 2011). When not hidden by jets, a polarimetric halo is sometimes observed in the inner coma. The negative branch can be as deep as -6% and the positive branch is smaller as compared to the whole coma (Hadamcik et al., 2003). Zubko et al. (2012) have proposed an increased fraction of silicates. From the experiments, we suggest some carbonaceous compounds with refractive indices close to those of silicates (relatively transparent). This material, if heated by the Sun after ejection, should be darker as observed when these materials are heated to 200--300°C. We are working on new analogs with mixtures of silicates and organics (not only carbon), silicates coated by organics (Johnson et al., 2004), or organics heated or not and with different elemental compositions (N/C ratios).

Geology of Potential Landing Sites for Martian Sample Returns

NASA Technical Reports Server (NTRS)

Greeley, Ronald

2003-01-01

This project involved the analysis of potential landing sites on Mars. As originally proposed, the project focused on landing sites from which samples might be returned to Earth. However, as the project proceeded, the emphasis shifted to missions that would not include sample return, because the Mars Exploration Program had deferred sample returns to the next decade. Subsequently, this project focused on the study of potential landing sites for the Mars Exploration Rovers.

The structure of cometary dust - first results from the MIDAS Atomic Force Microscope onboard Rosetta

NASA Astrophysics Data System (ADS)

Bentley, M. S.; Torkar, K.; Romstedt, J.

2014-12-01

A decade after launch the European Space Agency's Rosetta spacecraft has finally arrived at comet 67P/Churyumov-Gerasimenko. Unlike previous cometary missions, Rosetta is not a flyby, limited to taking a snapshot of the comet at a single heliocentric distance. Instead, Rosetta intercepted the comet prior to the onset of major activity and will chart its evolution during its perihelion passage and beyond. Such a unique mission requires a unique payload; as well as the more typical remote sensing instruments, Rosetta also carries sensors to sample in situ the gas and dust environment. One of these instruments is MIDAS, an atomic force microscope designed to collect dust and image it in three dimensions with nanometre resolution. Equipped with an array of sharp tips, four of which are magnetised to allow magnetic force microscopy, MIDAS exposes targets to the incident flux after which they are moved to the microscope for analysis. As well as extending coverage of the dust size distribution down to the finest particles, MIDAS has the unique capability to determine the shape of pristine particles - to determine, for example, if they are compact or fluffy, and to look for features which may be diagnostic of their formation environment or evolution. The magnetic mode lets MIDAS probe samples for magnetic material and to map its location if present. Having been operating almost continuously after hibernation imaging empty targets before exposure, the first exposures were performed when Rosetta entered 30 km bound orbits. The first MIDAS images and analyses of collected dust grains are presented here.

The morphology of cometary nuclei

NASA Astrophysics Data System (ADS)

Keller, H. U.; Jorda, L.

The sudden appearance of a bright comet stretching over a large part of the night sky must have been one of the most awesome phenomena for early humans watching the sky. The nature of comets remained obscure well into the Middle Ages. Only with the introduction of astronomical techniques and analyses in Europe was the parallax of a comet determined by Tycho Brahe for the first time. He proved that comets are not phenomena of the Earth's atmosphere but are farther away than the Moon; in other words they are interplanetary objects. Later Kepler first predicted that comets follow straight lines, then Hevelius suggested parabolic orbits roughly a hundred years later. It was Halley who suggested that the comets of the years 1531, 1607 and 1682 were apparitions of one and the same comet that would return again in 1758. The success of this prediction made it clear that comets are members of our Solar System. While it was now established that periodic comets are objects of the planetary system, their origin and nature continued to be debated. Were they formed together with the planets from the solar nebula (Kant) or were they of extrasolar origin as suggested by Laplace? This debate lasted for 200 years until well into the second half of the last century. Öpik (1932) suggested that a cloud of comets surrounded our Solar System. This hypothesis was quantified and compared to the observed distribution of orbital parameters (essentially the semi-major axes) of new comets by Oort (1950) (Section 2.1). Comets are scattered into the inner Solar System by perturbations caused by galactic tides, passing stars and large molecular clouds. The Oort cloud would have a radius of 2 105AU, a dimension comparable to the distances of stars in our neighbourhood. The lifetime (limited by decay due to activity and by perturbations caused by encounters with planets) even of the new comets on almost parabolic orbits and typical periods of the order of 106 years is short compared to the age of the planetary system (4.5 Gy). Therefore, observed comets could only recently have arrived on their orbits dipping inside the inner Solar System. This reservoir of comets must have been established during the formation process of the planetary system itself. Cometesimals were agglomerated from interstellar/interplanetary gas and dust and scattered out of the inner Solar System by the giant outer planets (Section 2.3). This scheme implies that a central part of a comet, its nucleus, is stable enough to survive these perturbations. It must also be stable enough to pass the vicinity of the sun for many times in the case of a short-period comet. Comets are bright and large when they are close to the sun and fade quickly when they recede beyond about 2AU. Only with the advent of photography and large astronomical telescopes could a comet be followed until it becomes a starlike point source. What makes comets active near the Sun, blowing their appearances up to the order of 105 km? Bright comets often develop tails two orders of magnitude longer. In an attempt to explain the cometary appearance, Bredichin (1903) introduced a mechanical model where repulsive forces drive the particles away from a central condensation. Spectroscopy revealed that dust grains reflect the solar irradiation. In addition, simple molecules, radicals and ions were found as constituents of the cometary coma and tail. The nature of the central condensation remained mysterious for a long time because of the observational dilemma. When the comet is close to the Earth and therefore to the Sun the dense coma obscures the view into its centre. When activity recedes the comet is too far away and too dim for detailed observations of its central condensation. During the middle of the nineteenth century the connection between comets and meteor streams was established. Schiaparelli (1866) calculated the dispersion of cometary dust within the orbital plane. From this time on the perception that the central condensations of comets were agglomerations of dust particles prevailed for about a century. The gas coma was explained by desorption of molecules from dust particles with large surfaces (Levin 1943). The storage of highly reactive radicals (most observed species (CN, CH, NH2, etc.) were of this category) posed a major difficulty to be explained. The inference that these radicals should be dissociation products of stable parent molecules (such as (CN)2, CH4, NH3, etc.) by Wurm (1934, 1935, 1943) led to our present understanding that these molecules are stored as ices within the central nucleus of a comet. Whipple (1950a,b) combined the astrometrical observations of changes of the orbital periods of comets with the existence of an icy cometary nucleus. The sublimation of ices cause reactive (rocket) non-gravitational forces that increase or decrease the orbital period of an active comet according to the sense of rotation of its nucleus. Evidence in support of the icy conglomerate nucleus became more and more compelling by the derived high gas production rates that could not be stored by adsorption on dust grains (Biermann and Trefftz 1964, Huebner 1965, Keller 1976a,b) and by the same account by the large quantities of dust moving into the cometary tail (Finson and Probstein 1968b). The `sand bank' model (Lyttleton 1953) was clearly dismissed in favour of a solid icy nucleus. Its formation and origin could now be explored. While there was some knowledge about the chemical composition of the nucleus, its physical properties, even the basic ones like size, shape and mass, remained largely unknown because the nucleus could not be observed. Early attempts to derive the nucleus size from the `nuclear' magnitudes of comets at large heliocentric distances while they are inactive (Roemer 1966a,b) led to a systematic overestimation of the size because their residual activity could not be eliminated. The advent of modern detectors and large ground-based telescopes revealed that most comets display residual activity or clouds of dust grains around their nuclei. Taking the residual signal into account (mostly using simple models for the brightness distribution) the size estimates of the nuclei could be improved. The (nuclear) magnitude of a comet depends on the product of its albedo and cross-section. Only in a few cases could the albedo and size of a cometary nucleus be separated by additional observation of its thermal emission at infrared wavelengths. By comparison with outer Solar System asteroids Cruikshank et al. (1985) derived a surprisingly low albedo of about 0.04. A value in clear contradiction to the perception of an icy surface but fully confirmed by the first resolved images of a cometary nucleus during the flybys of the Vega and Giotto spacecraft of comet Halley (Sagdeev et al. 1986, Keller et al. 1986). The improvements of radar techniques led to the detection of reflected signals and finally to the derivation of nuclear dimensions and rotation rates. The observations, however, are also model dependent (rotation and size are similarly interwoven as are albedo and size) and sensitive to large dust grains in the vicinity of a nucleus. As an example, Kamoun et al. (1982) determined the radius of comet Encke to 1.5 (2.3, 1.0) km using the spin axis determination of Whipple and Sekanina (1979). The superb spatial resolution of the Hubble Space Telescope (HST) is not quite sufficient to resolve a cometary nucleus. The intensity distribution of the inner coma, however, can be observed and extrapolated toward the nucleus based on models of the dust distribution. If this contribution is subtracted from the central brightness the signal of the nucleus can be derived and hence its product of albedo times cross-section (Lamy and Toth 1995, Rembor 1998, Keller and Rembor 1998; Section 4.3). It has become clear that cometary nuclei are dark, small, often irregular bodies with dimensions ranging from about a kilometre (comet Wirtanen, the target of the Rosetta comet rendezvous mission) to about 50 km (comet Hale- Bopp, comet P/Schwassman-Wachmann 1). Their albedos are very low, about 0.04. Their shapes are irregular, axes ratios of 2:1 are often derived. Even though comets are characterized by their activity, in most cases only a small fraction of the nuclear surface (in some cases less than 1%) is active. An exception seems to be comet P/Wirtanen where all its surface is required to be active in order to explain its production rates (Rickman and Jorda 1998). The detection of trans-Neptunian objects (TNOs) in the Kuiper belt (Jewitt and Luu 1993) reveals a new population of cometary bodies with dimensions an order of magnitude bigger (100 km and larger) than the typical comet observed in the inner planetary system. Little is known about the extent, density, size distribution and physical characteristics of these objects. This region is supposedly the reservoir for short-period comets, manly those controlled by Jupiter (Jupiter family comets). Our present concept of a cometary nucleus has been strongly influenced by the first pictures of the nucleus of comet Halley achieved during the Giotto flyby in 1986. While this revelation seems to be confirmed as typical by modern observations it carries the danger of prototyping new observational results and inferences. Missions and spacecraft are already on their way (Deep Space, Contour, Stardust, Deep Impact) or in preparation (Rosetta) to diversify our knowledge. The morphology of cometary nuclei is determined by their formation process in the early solar nebula, their dynamics and evolution. The physics of the processes leading to their apparent activity while approaching the Sun are still obscure in many details but determine the small- and intermediate-scale morphology. The large-scale morphology, the shape, of a cometary nucleus is determined by its fragility and inner structure and by its generally complex rotational state. These topics will be reviewed in the following sections. Chemical and compositional aspects will be only discussed where they are important in the framework of the physical evolution of cometary nuclei. More details are given in Chapter 53. A brief survey of the current modelling efforts is given. The fate of cometary nuclei and their decay products follows. A summary and outlook ends this chapter on the morphology of cometary nuclei.

Sample Return: What Happens to the Samples on Earth?

NASA Technical Reports Server (NTRS)

McNamara, Karen

2010-01-01

As space agencies throughout the world turn their attention toward human exploration of the Moon, Mars, and the solar system beyond, there has been an increase in the number of robotic sample return missions proposed as precursors to these human endeavors. In reality, however, we, as a global community, have very little experience with robotic sample return missions: 3 of the Russian Luna Missions successfully returned lunar material in the 1970s; 28 years later, in 2004, NASA s Genesis Mission returned material from the solar wind; and in 2006, NASA s Stardust Mission returned material from the Comet Wild2. [Note: The Japanese Hyabusa mission continues in space with the hope of returning material from the asteroid 25143 Itokawa.] We launch many spacecraft to LEO and return them to Earth. We also launch spacecraft beyond LEO to explore the planets, our solar system, and beyond. Some even land on these bodies. But these do not return. So as we begin to contemplate the sample return missions of the future, some common questions arise: "What really happens when the capsule returns?" "Where does it land?" "Who retrieves it and just how do they do that?" "Where does it go after that?" "How do the scientists get the samples?" "Do they keep them?" "Who is in charge?" The questions are nearly endless. The goal of this paper/presentation is to uncover many of the mysteries of the post-return phase of a mission - from the time the return body enters the atmosphere until the mission ends and the samples become part of a long term collection. The discussion will be based largely on the author s own experience with both the Genesis and Stardust missions. Of course, these two missions have a great deal in common, being funded by the same NASA Program (Discovery) and having similar team composition. The intent, however, is to use these missions as examples in order to highlight the general requirements and the challenges in defining and meeting those requirements for the final phase of sample return missions. The choices made by the Genesis and Stardust teams regarding recovery and sample handling will be discussed. These will be compared with the handling of returned lunar samples and the proposed handling of the Hyabusa samples as well. Finally, though none of these recent missions have been restricted within NASA s Planetary Protection Protocol, this is likely to change as missions venture farther from Earth. The implementation of Planetary Protection requirements will vary significantly based on mission scenario, however some of the potential implications of restricted Earth return will be considered.

New catalogue of single-apparition comets discovered in the years 1901-1950. Part I

NASA Astrophysics Data System (ADS)

Królikowska, M.; Sitarski, G.; Pittich, E.; Szutowicz, S.; Ziołkowski, K.; Rickman, H.; Gabryszewski, R.; Rickman, B.

2014-07-01

A new catalogue of cometary orbits derived using a completely homogeneous method of data treatment, accurate methods of numerical integration, and modern model of the Solar System is presented. We constructed a sample of near-parabolic comets from the first half of the twentieth century with original reciprocals of semimajor axes less than 0.000130 au^{-1} in the Marsden and Williams Catalogue of Cometary Orbits (2008, hereafter MW08), i.e., comets of original semimajor axes larger than 7700 au. We found 38 such comets in MW08, where 32 have first-quality orbits (class 1A or 1B) and the remaining 6 have second-quality orbits (2A or 2B). We presented satisfactory non-gravitational (hereafter NG) models for thirteen of the investigated comets. The four main features, distinguishing this catalogue of orbits of single- apparition comets discovered in the early twentieth century from other catalogues of orbits of similarly old objects, are the following. 1. Old cometary positional observations require a very careful analysis. For the purpose of this new catalogue, great emphasis has been placed in collecting sets of observations as complete as possible for the investigated comets. Moreover, for many observations, comet-minus-star-type measurements were also available. This type of data was particularly valuable as the most original measurements of comet positions and has allowed us to recalculate new positions of comets using the PPM star catalogue. 2. Old cometary observations were prepared by observers usually as apparent positions in Right Ascension and Declination or as reduced positions for the epoch of the beginning of the year of a given observation. This was a huge advantage of these data, because this allows us to uniformly take into account all necessary corrections associated with the data reduction to the standard epoch. 3. The osculating orbits of single-apparition comets discovered more than sixty years ago have been formerly determined with very different numerical methods and assumptions on the model of the Solar System, including the number of planets taken into account. This new catalogue changes this situation. We offer a new catalogue of cometary orbits derived using completely homogeneous methods of data treatment, accurate methods of numerical integration, and a modern model of the Solar System. 4. The osculating, original, and future sets of orbits are presented for each catalogue comet. In the case of a comet with detectable NG effects, we give both types of orbit: purely gravitational and non- gravitational. We concluded, however, that all thirteen NG orbital solutions given in the catalogue better represent the actual motions of the investigated comets. Surprisingly, the NG effects were detectable in data for five comets of second-quality-class orbits. Among these five are three comets with hyperbolic original, barycentric GR orbits. This publication will be accompanied by an online catalogue available at ssdp.cbk.waw.pl/LPCs, providing entries to orbital elements of considered comets as well as to full swarms of original and future virtual comets that formed the basis for the further analysis of dynamical evolution.

Sample Return Propulsion Technology Development Under NASA's ISPT Project

NASA Technical Reports Server (NTRS)

Anderson, David J.; Dankanich, John; Hahne, David; Pencil, Eric; Peterson, Todd; Munk, Michelle M.

2011-01-01

Abstract In 2009, the In-Space Propulsion Technology (ISPT) program was tasked to start development of propulsion technologies that would enable future sample return missions. Sample return missions can be quite varied, from collecting and bringing back samples of comets or asteroids, to soil, rocks, or atmosphere from planets or moons. As a result, ISPT s propulsion technology development needs are also broad, and include: 1) Sample Return Propulsion (SRP), 2) Planetary Ascent Vehicles (PAV), 3) Multi-mission technologies for Earth Entry Vehicles (MMEEV), and 4) Systems/mission analysis and tools that focuses on sample return propulsion. The SRP area includes electric propulsion for sample return and low cost Discovery-class missions, and propulsion systems for Earth Return Vehicles (ERV) including transfer stages to the destination. Initially the SRP effort will transition ongoing work on a High-Voltage Hall Accelerator (HIVHAC) thruster into developing a full HIVHAC system. SRP will also leverage recent lightweight propellant-tanks advancements and develop flight-qualified propellant tanks with direct applicability to the Mars Sample Return (MSR) mission and with general applicability to all future planetary spacecraft. ISPT s previous aerocapture efforts will merge with earlier Earth Entry Vehicles developments to form the starting point for the MMEEV effort. The first task under the Planetary Ascent Vehicles (PAV) effort is the development of a Mars Ascent Vehicle (MAV). The new MAV effort will leverage past MAV analysis and technology developments from the Mars Technology Program (MTP) and previous MSR studies. This paper will describe the state of ISPT project s propulsion technology development for future sample return missions.12

A Review of New and Developing Technology to Significantly Improve Mars Sample-Return Missions

NASA Technical Reports Server (NTRS)

Carsey, F.; Brophy, J.; Gilmore, M.; Rodgers, D.; Wilcox, B.

2000-01-01

A JPL development activity was initiated in FY 1999 for the purpose of examining and evaluating technologies that could materially improve future (i.e., beyond the 2005 launch) Mars sample return missions. The scope of the technology review was comprehensive and end-to-end; the goal was to improve mass, cost, risk, and scientific return. A specific objective was to assess approaches to sample return with only one Earth launch. While the objective of the study was specifically for sample-return, in-situ missions can also benefit from using many of the technologies examined.

A Review of New and Developing Technology to Significantly Improve Mars Sample-Return Missions

NASA Astrophysics Data System (ADS)

Carsey, F.; Brophy, J.; Gilmore, M.; Rodgers, D.; Wilcox, B.

2000-07-01

A JPL development activity was initiated in FY 1999 for the purpose of examining and evaluating technologies that could materially improve future (i.e., beyond the 2005 launch) Mars sample return missions. The scope of the technology review was comprehensive and end-to-end; the goal was to improve mass, cost, risk, and scientific return. A specific objective was to assess approaches to sample return with only one Earth launch. While the objective of the study was specifically for sample-return, in-situ missions can also benefit from using many of the technologies examined.

The Comet Giacobini-Zinner magnetotail: Axial stresses and inferred near-nucleus properties

NASA Technical Reports Server (NTRS)

Mccomas, D. J.; Gosling, J. T.; Bame, S. J.; Slavin, J. A.; Smith, E. J.; Steinberg, J. L.

1986-01-01

Utilizing the electron and magnetic field data from the ICE tail traversal of comet Giacobini-Zinner along with the MHD equations, a steady state, stress balance model of the cometary magnetotail was developed, and used to infer important but unmeasured ion properties within the magnetotail at ICE and upstream at the average point along each streamline where cometary ions are picked-up. The derived tailward ion flow speed at ICE is quite constant at approx. -20 to -30 km/sec across the entire tail. The flow velocity, ion temperature, density, and ion source rates upstream from the lobes (current sheet) at the average pick-up locations are approx. -75 km/sec (approx. -12), approx. 4 million K (approx. 100,000), approx. 20 cc (approx. 400), and approx. 15 cu cm/sec. Gradients in the plasma properties between the two regions are quite strong. Implications of inferred plasma properties for the near-nucleus region and for cometary magnetotail formation are examined.

Cometary water-group ions in the region surrounding Comet Giacobini-Zinner - Distribution functions and bulk parameter estimates

NASA Astrophysics Data System (ADS)

Staines, K.; Balogh, A.; Cowley, S. W. H.; Hynds, R. J.; Yates, T. S.; Richardson, I. G.; Sanderson, T. R.; Wenzel, K. P.; McComas, D. J.; Tsurutani, B. T.

1991-03-01

The bulk parameters (number density and thermal energy density) of cometary water-group ions in the region surrounding Comet Giacobini-Zinner have been derived using data from the EPAS instrument on the ICE spacecraft. The derivation is based on the assumption that the pick-up ion distribution function is isotropic in the frame of the bulk flow, an approximation which has previously been shown to be reasonable within about 400,000 km of the comet nucleus along the spacecraft trajectory. The transition between the pick-up and mass-loaded regions occurs at the cometary shock, which was traversed at a cometocentric distance of about 100,000 km along the spacecraft track. Examination of the ion distribution functions in this region, transformed to the bulk flow frame, indicates the occurrence of a flattened distribution in the vicinity of the local pick-up speed, and a steeply falling tail at speeds above, which may be approximated as an exponential in ion speed.

Characteristics of cometary picked-up ions in a global model of Giacobini-Zinner

NASA Astrophysics Data System (ADS)

Kimmel, C. D.; Luhmann, J. G.; Phillips, J. L.; Fedder, J. A.

1987-08-01

Energetic ions observed during the International Cometary Explorer (ICE) spacecraft flyby of comet Giacobini-Zinner provide information about both the constitution of comets and the plasma physical processes associated with their interaction with the solar wind. In this investigation the details of ion 'pickup,' in the limit where small-scale fluctuations in the plasma and magnetic field are neglected, are modeled by following the motion of a large number of initially cold, heavy (mass 18) ions in a global magnetohydrodynamic model of the local plasma and magnetic field. The results indicate how the background or macroscopic velocity and magnetic field structure of the comet can affect the average spatial and spectral characteristics of the observed cometary ions. These effects, which occur by virtue of forces associated with the compression and the curvature of the magnetic field in the presence of the stagnating plasma flow, can explain the double maxima in the time series of the energetic ion flux observed along the ICE trajectory.

Mission strategy for cometary exploration in the 1980's

NASA Technical Reports Server (NTRS)

Farquhar, R. W.

1974-01-01

A sequence of ballistic intercept missions to comets is proposed. The mission set is composed of a well-known group of periodic comets whose physical properties are dissimilar. In addition to full descriptions of the nominal mission profiles, earth-based sighting conditions and estimates of cometary ephemeris errors are presented for each target comet. The first mission of the sequence is a slow flyby (approximately 8 km/sec) of Encke's comet near its perihelion in 1980. Because of a near resonance in the orbital periods of Encke and the spacecraft, it is possible to retarget the spacecraft for a second Encke encounter in 1984. The second mission of the sequence also consists of two cometary encounters but in this case different comets are involved; Giacobini-Zinner in 1985 and Borrelly in 1987. The final mission of the sequence calls for a simultaneous launch of two spacecraft towards Halley's comet in 1985. One spacecraft is targeted fo a pre-perihelion intercept at a heliocentric distance of 1.37 AU.

Preshock region acceleration of implanted cometary H(+) and O(+)

NASA Astrophysics Data System (ADS)

Gombosi, T. I.

1988-01-01

A self-consistent, three-fluid model of plasma transport and implanted ion acceleration in the unshocked solar wind is presented. The solar wind plasma is depleted by charge exchange with the expanding cometary exosphere, while implanted protons and heavy ions are produced by photoionization and charge transfer and lost by charge exchange. A generalized transport equation describing convection, adiabatic and diffusive velocity change, and the appropriate production terms is used to describe the evolution of the two cometary ion components, while the moments of the Boltzmann equation are used to calculate the solar wind density and pressure. The flow velocity is obtained self-consistently by combining the conservation equations of the three ion species. The results imply that second-order Fermi acceleration can explain the implanted spectra observed in the unshocked solar wind. Comparison of measured and calculated distribution indicates that spatial diffusion of implanted ions probably plays an important role in forming the energetic particle environment in the shock vicinity.

Are comets connected to the origin of life

NASA Technical Reports Server (NTRS)

Delsemme, A. H.

1981-01-01

Possible connections between comets and the origin of life on earth are discussed. The orbital evolution of comets and their origin are considered within a framework for the origin of the solar system, with particular attention given to the origin of the biosphere, and the origin of the Oort cloud. Evidence suggesting that cometary nuclei are undifferentiated throughout is considered, and a model of the average composition of a mean new comet is obtained from observational data which is similar to that of an interstellar frost. The chemistry of the model composition giving rise to the species observed in cometary spectra is considered, as well as the relations of cometary to cosmic abundances of oxygen, carbon and sulfur. The characteristics of possible sites for prebiotic chemistry, including interstellar clouds, the protosolar nebula, comets in the Oort cloud, periodic comets and the primitive earth, are examined, and a possible role of comets in bringing the interstellar prebiotic chemistry to earth is suggested.

Extremely Low-Frequency Waves Inside the Diamagnetic Cavity of Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Madsen, B.; Wedlund, C. Simon; Eriksson, A.; Goetz, C.; Karlsson, T.; Gunell, H.; Spicher, A.; Henri, P.; Vallières, X.; Miloch, W. J.

2018-05-01

The European Space Agency/Rosetta mission to comet 67P/Churyumov-Gerasimenko has provided several hundred observations of the cometary diamagnetic cavity induced by the interaction between outgassed cometary particles, cometary ions, and the solar wind magnetic field. Here we present the first electric field measurements of four preperihelion and postperihelion cavity crossings on 28 May 2015 and 17 February 2016, using the dual-probe electric field mode of the Langmuir probe (LAP) instrument of the Rosetta Plasma Consortium. We find that on large scales, variations in the electric field fluctuations capture the cavity and boundary regions observed in the already well-studied magnetic field, suggesting the electric field mode of the LAP instrument as a reliable tool to image cavity crossings. In addition, the LAP electric field mode unravels for the first time extremely low-frequency waves within two cavities. These low-frequency electrostatic waves are likely triggered by lower-hybrid waves observed in the surrounding magnetized plasma.

Sources of Water for Oceans on Planets

NASA Astrophysics Data System (ADS)

Owen, T. C.

2001-12-01

Studies of D/H in the H2O carried by three Oort cloud comets have shown that such comets could not have contributed all of the water in the Earth's oceans. The extent of the cometary contribution depends on the value of D/H in water brought directly to the planet as hydrous minerals or adsorbed solar nebula H2O. That some cometary water was in fact delivered to the inner planets is strongly suggested by the value of D/H in Shergottite minerals when viewed in the context of other isotope geochemistry on Mars (Owen and Bar-Nun, FARADAY DISCUSSIONS 109, 453-462 (1998)). This scenario is also consistent with noble gas and siderophile element abundances on Earth. The identification of comet-produced water vapor around the aging carbon star IRC +10216 (Melnick et al., NATURE 412, 160-163 (2001)) provides concrete support for the widely held assumption that a cometary reservoir for the irrigation of inner planets should be a common feature of planetary systems throughout the galaxy.

Composition/Structure/Dynamics of comet and planetary satellite atmospheres

NASA Technical Reports Server (NTRS)

Combi, Michael R. (Principal Investigator)

1995-01-01

This research program addresses two cases of tenuous planetary atmospheres: comets and Io. The comet atmospheric research seeks to analyze a set of spatial profiles of CN in comet Halley taken in a 7.4-day period in April 1986; to apply a new dust coma model to various observations; and to analyze observations of the inner hydrogen coma, which can be optically thick to the resonance scattering of Lyman-alpha radiation, with the newly developed approach that combines a spherical radiative transfer model with our Monte Carlo H coma model. The Io research seeks to understand the atmospheric escape from Io with a hybrid-kinetic model for neutral gases and plasma given methods and algorithms developed for the study of neutral gas cometary atmospheres and the earth's polar wind and plasmasphere. Progress is reported on cometary Hydrogen Lyman-alpha studies; time-series analysis of cometary spatial profiles; model analysis of the dust comae of comets; and a global kinetic atmospheric model of Io.

Characteristics of cometary picked-up ions in a global model of Giacobini-Zinner

NASA Technical Reports Server (NTRS)

Kimmel, C. D.; Luhmann, J. G.; Phillips, J. L.; Fedder, J. A.

1987-01-01

Energetic ions observed during the International Cometary Explorer (ICE) spacecraft flyby of comet Giacobini-Zinner provide information about both the constitution of comets and the plasma physical processes associated with their interaction with the solar wind. In this investigation the details of ion 'pickup,' in the limit where small-scale fluctuations in the plasma and magnetic field are neglected, are modeled by following the motion of a large number of initially cold, heavy (mass 18) ions in a global magnetohydrodynamic model of the local plasma and magnetic field. The results indicate how the background or macroscopic velocity and magnetic field structure of the comet can affect the average spatial and spectral characteristics of the observed cometary ions. These effects, which occur by virtue of forces associated with the compression and the curvature of the magnetic field in the presence of the stagnating plasma flow, can explain the double maxima in the time series of the energetic ion flux observed along the ICE trajectory.

Cometary Matter Analyser (COMA/CRAF)

NASA Technical Reports Server (NTRS)

Buechler, K.; Igenbergs, E.; Klein, J. W.; Krueger, F. R.; Kuczera, H.; Morfill, G.; Palme, H.; Roessler, K.; Weishaupt, U.; Zerrull, R.;

The structure of a cometary type I tail - Ground-based and ICE observations of P/Giacobini-Zinner

NASA Technical Reports Server (NTRS)

Slavin, J. A.; Goldberg, B. A.; Smith, E. J.; Mccomas, D. J.; Bame, S. J.

1986-01-01

Comparison of ground-based and in situ observations of P/Giacobini-Zinner are used to investigate the morphology of a type I cometary tail. ICE magnetic field and plasma measurements show a well-defined cometary magnetotail composed of two magnetic lobes in pressure equilibrium with a central plasma sheet. A dependence of ion tail width on IMF direction is found which strongly suggests that the classical type I ion tails observed on the ground consist predominantly of emissions from the slab-shaped plasma sheet separating the magnetic lobes. The width of the G-Z magnetotail is determined to be 9.8 (+ or - 0.5) x 10 to the 3rd km with a quasi-circular cross section. The results of this study also indicate that some of the dynamical thinnings and thickenings observed in long type I tails may be caused by IMF variations changing the angle with which the plasma sheet is viewed at earth.

Curating NASA's Astromaterials Collections: Past, Present, and Future

NASA Technical Reports Server (NTRS)

Zeigler, Ryan

2015-01-01

Planning for the curation of samples from future sample return missions must begin during the initial planning stages of a mission. Waiting until the samples have been returned to Earth, or even when you begin to physically build the spacecraft is too late. A lack of proper planning could lead to irreversible contamination of the samples, which in turn would compromise the scientific integrity of the mission. For example, even though the Apollo missions first returned samples in 1969, planning for the curation facility began in the early 1960s, and construction of the Lunar Receiving Laboratory was completed in 1967. In addition to designing the receiving facility and laboratory that the samples will be characterized and stored in, there are many aspects of contamination that must be addressed during the planning and building of the spacecraft: planetary protection (both outbound and inbound); cataloging, documenting, and preserving the materials used to build spacecraft (also known as coupons); near real-time monitoring of the environment in which the spacecraft is being built using witness plates for critical aspects of contamination (known as contamination control); and long term monitoring and preservation of the environment in which the spacecraft is being built for most aspects of potential contamination through the use of witness plates (known as contamination knowledge). The OSIRIS REx asteroid sample return mission, currently being built, is dealing with all of these aspects of contamination in order to ensure they return the best preserved sample possible. Coupons and witness plates from OSIRIS REx are currently being studied and stored (for future studies) at the Johnson Space Center. Similarly, planning for the clean room facility at Johnson Space Center to house the OSIRIS-REx samples is well advanced, and construction of the facility should begin in early 2017 (despite a nominal 2023 return date for OSIRIS-REx samples). Similar development is being done, in concert with JAXA, for the return of Hayabusa 2 samples (nominally in 2020). We are also actively developing advanced techniques like cold curation and organically clean curation in anticipation of future sample return missions such as comet nucleus sample return and Mars sample return.

Mars Sample Return Orbiter Architecture Options — Results of the ESA Mars Sample Return Architecture Assessment Study

NASA Astrophysics Data System (ADS)

Derz, U.; Joffre, E.; Perkinson, M.-C.; Huesing, J.; Beyer, F.; Sanchez Perez, J. M.

2018-04-01

This paper presents the identified most promising chemical and electric propulsion architecture options of the Mars Sample Return (MSR) orbiter identified during the recent ESA MSR Architecture Assessment Study.

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.

Light scattering by low-density agglomerates of micron-sized grains with the PROGRA2 experiment

NASA Astrophysics Data System (ADS)

Hadamcik, E.; Renard, J.-B.; Lasue, J.; Levasseur-Regourd, A. C.; Blum, J.; Schraepler, R.

2007-07-01

This work was carried out with the PROGRA2 experiment, specifically developed to measure the angular dependence of the polarization of light scattered by dust particles. The samples are small agglomerates of micron-sized grains and huge, low number density agglomerates of the same grains. The constituent grains (spherical or irregularly shaped) are made of different non-absorbing and absorbing materials. The small agglomerates, in a size range of a few microns, are lifted by an air draught. The huge centimeter-sized agglomerates, produced by random ballistic deposition of the grains, are deposited on a flat surface. The phase curves obtained for monodisperse, micron-sized spheres in agglomerates are obviously not comparable to the ‘smooth’ phase curves obtained by remote observations of cometary dust or asteroidal regoliths but they are used for comparison with numerical calculations to a better understanding of the light scattering processes. The phase curves obtained for irregular grains in agglomerates are similar to those obtained by remote observations, with a negative branch at phase angles smaller than 20° and a maximum polarization decreasing with increasing albedo. These results, coupled with remote observations in the solar system, should provide a better understanding of the physical properties of solid particles and their variation in cometary comae and asteroidal regoliths.

Compact drilling and sample system

NASA Technical Reports Server (NTRS)

Gillis-Smith, Greg R.; Petercsak, Doug

1998-01-01

The Compact Drilling and Sample System (CDSS) was developed to drill into terrestrial, cometary, and asteroid material in a cryogenic, vacuum environment in order to acquire subsurface samples. Although drills were used by the Apollo astronauts some 20 years ago, this drill is a fraction of the mass and power and operates completely autonomously, able to drill, acquire, transport, dock, and release sample containers in science instruments. The CDSS has incorporated into its control system the ability to gather science data about the material being drilled by measuring drilling rate per force applied and torque. This drill will be able to optimize rotation and thrust in order to achieve the highest drilling rate possible in any given sample. The drill can be commanded to drill at a specified force, so that force imparted on the rover or lander is limited. This paper will discuss the cryo dc brush motors, carbide gears, cryogenic lubrication, quick-release interchangeable sampling drill bits, percussion drilling and the control system developed to achieve autonomous, cryogenic, vacuum, lightweight drilling.

Multiple Smaller Missions as a Direct Pathway to Mars Sample Return

NASA Technical Reports Server (NTRS)

Niles, P. B.; Draper, D. S.; Evans, C. A.; Gibson, E. K.; Graham, L. D.; Jones, J. H.; Lederer, S. M.; Ming, D.; Seaman, C. H.; Archer, P. D.;

U-Th-Pb, Sm-Nd, Rb-Sr, and Lu-Hf systematics of returned Mars samples

NASA Technical Reports Server (NTRS)

Tatsumoto, M.; Premo, W. R.

1988-01-01

The advantage of studying returned planetary samples cannot be overstated. A wider range of analytical techniques with higher sensitivities and accuracies can be applied to returned samples. Measurement of U-Th-Pb, Sm-Nd, Rb-Sr, and Lu-Hf isotopic systematics for chronology and isotopic tracer studies of planetary specimens cannot be done in situ with desirable precision. Returned Mars samples will be examined using all the physical, chemical, and geologic methods necessary to gain information on the origin and evolution of Mars. A returned Martian sample would provide ample information regarding the accretionary and evolutionary history of the Martian planetary body and possibly other planets of our solar system.

Integrating public perspectives in sample return planning.

PubMed

Race, M S; MacGregor, D G

2000-01-01

Planning for extraterrestrial sample returns--whether from Mars or other solar system bodies--must be done in a way that integrates planetary protection concerns with the usual mission technical and scientific considerations. Understanding and addressing legitimate societal concerns about the possible risks of sample return will be a critical part of the public decision making process ahead. This paper presents the results of two studies, one with lay audiences, the other with expert microbiologists designed to gather information on attitudes and concerns about sample return risks and planetary protection. Focus group interviews with lay subjects, using generic information about Mars sample return and a preliminary environmental impact assessment, were designed to obtain an indication of how the factual content is perceived and understood by the public. A research survey of microbiologists gathered information on experts' views and attitudes about sample return, risk management approaches and space exploration risks. These findings, combined with earlier research results on risk perception, will be useful in identifying levels of concern and potential conflicts in understanding between experts and the public about sample return risks. The information will be helpful in guiding development of the environmental impact statement and also has applicability to proposals for sample return from other solar system bodies where scientific uncertainty about extraterrestrial life may persist at the time of mission planning. c2001 COSPAR Published by Elsevier Science Ltd. All rights reserved.

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.

Chemical Evolution of Presolar Organics in Astromaterials

NASA Technical Reports Server (NTRS)

Nakamura-Messenger, K.; Clemett, S. J.; Messenger, Scott; Keller, L. P.

2010-01-01

Sub-micron, hollow organic globules reported from several carbonaceous chondrites, interplanetary dust particles, and comet Wild-2 samples returned by NASA?s Stardust mission are enriched in N-15/N-14 and D/H compared with terrestrial materials and the parent materials [1-4]. These anomalies are ascribed to the preservation of presolar cold molecular cloud material from where H, C, and N isotopic constraints point to chemical fractionation near 10 K [5]. An origin well beyond the planet forming region and their survival in meteorites suggests submicrometer organic globules were once prevalent throughout the solar nebula. The survival of the membrane structures indicates primitive meteorites and cometary dust particles would have delivered these organic precursors to the early Earth as well as other planets and satellites. The physical, chemical, and isotopic properties of the organic globules varies to its meteorite types and its lithologies. For example, organic globules in the Tagish Lake meteorite are always embedded in fined grained (poorly crystallized) saponite, and hardly encapsulated in coarse grained serpentine, even though saponite and serpentine are both main components of phyllosilicate matrix of the Tagish Lake meteorite. The organic globules are commonly observed in the carbonate-poor lithology but not in the carbonate-rich one. In Tagish Lake, isolated single globules are common, but in the Bells (CM2) meteorite, globules are mostly aggregated. We will review the evolutions of the organic globules from its birth to alteration in the parent bodies in terms of its own physical and chemical properties as well as its associated minerals.

Irradiation of FeS: Implications for the Lifecycle of Sulfur in the Interstellar Medium and Presolar FeS Grains

NASA Technical Reports Server (NTRS)

Keller, Lindsay P.; Loeffler, M. J.; Christoffersen, R.; Dukes, C.; Rahman, Z.; Baragiola, R.

2010-01-01

Fe(Ni) sulfides are ubiquitous in chondritic meteorites and cometary samples where they are the dominant host of sulfur. Despite their abundance in these early solar system materials, their presence in interstellar and circumstellar environments is poorly understood. Fe-sulfides have been reported from astronomical observations of pre- and post-main sequence stars [1, 2] and occur as inclusions in bonafide circumstellar silicate grains [3, 4]. In cold, dense molecular cloud (MC) environments, sulfur is highly depleted from the gas phase [e.g. 5], yet observations of sulfur-bearing molecules in dense cores find a total abundance that is only a small fraction of the sulfur seen in diffuse regions [6], therefore the bulk of the depletion must reside in an abundant unobserved phase. In stark contrast, sulfur is essentially undepleted from the gas phase in the diffuse interstellar medium (ISM) [7-9], indicating that little sulfur is incorporated into solid grains in this environment. This is a rather puzzling observation unless Fe-sulfides are not produced in significant quantities in stellar outflows, or their lifetime in the ISM is very short due to rapid destruction. The main destruction mechanism is sputtering due to supernova shocks in the warm, diffuse ISM [10]. This process involves the reduction of Fe-sulfide with the production of Fe metal as a by-product and returning S to the gas phase. In order to test this hypothesis, we irradiated FeS and analyzed the resulting material using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM).

A Review of Alfvénic Turbulence in High-Speed Solar Wind Streams: Hints From Cometary Plasma Turbulence

NASA Astrophysics Data System (ADS)

Tsurutani, Bruce T.; Lakhina, Gurbax S.; Sen, Abhijit; Hellinger, Petr; Glassmeier, Karl-Heinz; Mannucci, Anthony J.

2018-04-01

Solar wind turbulence within high-speed streams is reviewed from the point of view of embedded single nonlinear Alfvén wave cycles, discontinuities, magnetic decreases (MDs), and shocks. For comparison and guidance, cometary plasma turbulence is also briefly reviewed. It is demonstrated that cometary nonlinear magnetosonic waves phase-steepen, with a right-hand circular polarized foreshortened front and an elongated, compressive trailing edge. The former part is a form of "wave breaking" and the latter that of "period doubling." Interplanetary nonlinear Alfvén waves, which are arc polarized, have a 180° foreshortened front and with an elongated trailing edge. Alfvén waves have polarizations different from those of cometary magnetosonic waves, indicating that helicity is a durable feature of plasma turbulence. Interplanetary Alfvén waves are noted to be spherical waves, suggesting the possibility of additional local generation. They kinetically dissipate, forming MDs, indicating that the solar wind is partially "compressive" and static. The 2 MeV protons can nonresonantly interact with MDs leading to rapid cross-field ( 5.5% Bohm) diffusion. The possibility of local ( 1 AU) generation of Alfvén waves may make it difficult to forecast High-Intensity, Long-Duration AE Activity and relativistic magnetospheric electrons with great accuracy. The future Solar Orbiter and Solar Probe Plus missions should be able to not only test these ideas but to also extend our knowledge of plasma turbulence evolution.

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.

A new method for determining the mass ejected during the cometary outburst - Application to the Jupiter-family comets

NASA Astrophysics Data System (ADS)

Wesołowski, M.; Gronkowski, P.

2018-07-01

In the present article, we propose a new method of mass estimation which is ejected from a nucleus of a comet during its outburst of brightness. The phenomena of cometary outburst are often reported for both periodic and parabolic comets. The outburst of a comet brightness is a sudden increase in its brightness greater than one magnitude, average by 2-5 mag. This should not be confused with explosions such as outbreak of a bomb. The essence of the phenomenon is only a sudden brightening of the comet. Long-term observations and studies of this phenomenon lead to the conclusion that the very probable direct cause of the many outbursts is the ejection of the some part of surface layer of a comet's nucleus and an increase in the rate of a sublimation (Hughes (1990), Gronkowski (2007), Gronkowski and Wesołowski (2015)). The purpose of this article is presentation of a new simple method of the estimation of the mass which is ejected from the comet's nucleus during considered phenomenon. To estimate the mass released during an outburst, different probable coefficients of extinction for cometary matter was assumed. The scattering cross-sections of cometary grains were precisely calculated on the basis of Mie's theory. This method was applied to the outburst of a hypothetical comet X/PC belonging to the Jupiter-family comets and to the case of the comet 17P/Holmes outburst in 2007.

Mars Earth Return Vehicle (MERV) Propulsion Options

NASA Technical Reports Server (NTRS)

Oleson, Steven R.; McGuire, Melissa L.; Burke, Laura; Fincannon, James; Warner, Joe; Williams, Glenn; Parkey, Thomas; Colozza, Tony; Fittje, Jim; Martini, Mike;

Communications Relay and Human-Assisted Sample Return from the Deep Space Gateway

NASA Astrophysics Data System (ADS)

Cichan, T.; Hopkins, J. B.; Bierhaus, B.; Murrow, D. W.

2018-02-01

The Deep Space Gateway can enable or enhance exploration of the lunar surface through two capabilities: 1. communications relay, opening up access to the lunar farside, and 2. sample return, enhancing the ability to return large sample masses.

The Moon as a 100% Isolation Barrier for Earth During Exobiological Examination of Solar System Sample Return Missions

NASA Astrophysics Data System (ADS)

DiGregorio, B. E.

2018-04-01

The only 100% guarantee of protecting Earth's biosphere from a hazardous back contamination event is to use the Moon as a sample return examination facility to qualify samples for eventual return to Earth.

The Moon: A 100% Isolation Barrier for Earth During Exobiological Examination of Solar System Sample Return Missions

NASA Astrophysics Data System (ADS)

DiGregorio, B. E.

2018-02-01

The only 100% guarantee of protecting our planet's biosphere from a back contamination event is to use the Moon as a sample return examination facility to qualify samples for eventual return to Earth.

Mars Rover Sample Return mission study

NASA Technical Reports Server (NTRS)

Bourke, Roger D.

1989-01-01

The Mars Rover/Sample Return mission is examined as a precursor to a manned mission to Mars. The value of precursor missions is noted, using the Apollo lunar program as an example. The scientific objectives of the Mars Rover/Sample Return mission are listed and the basic mission plans are described. Consideration is given to the options for mission design, launch configurations, rover construction, and entry and lander design. Also, the potential for international cooperation on the Mars Rover/Sample Return mission is discussed.

Mars Sample Handling Protocol Workshop Series: Workshop 2

NASA Technical Reports Server (NTRS)

Rummel, John D. (Editor); Acevedo, Sara E. (Editor); Kovacs, Gregory T. A. (Editor); Race, Margaret S. (Editor); DeVincenzi, Donald L. (Technical Monitor)

2001-01-01

Numerous NASA reports and studies have identified Planetary Protection (PP) as an important part of any Mars sample return mission. The mission architecture, hardware, on-board experiments, and related activities must be designed in ways that prevent both forward- and back-contamination and also ensure maximal return of scientific information. A key element of any PP effort for sample return missions is the development of guidelines for containment and analysis of returned sample(s). As part of that effort, NASA and the Space Studies Board (SSB) of the National Research Council (NRC) have each assembled experts from a wide range of scientific fields to identify and discuss issues pertinent to sample return. In 1997, the SSB released its report on recommendations for handling and testing of returned Mars samples. In particular, the NRC recommended that: a) samples returned from Mars by spacecraft should be contained and treated as potentially hazardous until proven otherwise, and b) rigorous physical, chemical, and biological analyses [should] confirm that there is no indication of the presence of any exogenous biological entity. Also in 1997, a Mars Sample Quarantine Protocol workshop was convened at NASA Ames Research Center to deal with three specific aspects of the initial handling of a returned Mars sample: 1) biocontainment, to prevent 'uncontrolled release' of sample material into the terrestrial environment; 2) life detection, to examine the sample for evidence of organisms; and 3) biohazard testing, to determine if the sample poses any threat to terrestrial life forms and the Earth's biosphere. In 1999, a study by NASA's Mars Sample Handling and Requirements Panel (MSHARP) addressed three other specific areas in anticipation of returning samples from Mars: 1) sample collection and transport back to Earth; 2) certification of the samples as non-hazardous; and 3) sample receiving, curation, and distribution. To further refine the requirements for sample hazard testing and the criteria for subsequent release of sample materials from quarantine, the NASA Planetary Protection Officer convened an additional series of workshops beginning in March 2000. The overall objective of these workshops was to develop comprehensive protocols to assess whether the returned materials contain any biological hazards, and to safeguard the purity of the samples from possible terrestrial contamination. This document is the report of the second Workshop in the Series. The information herein will ultimately be integrated into a final document reporting the proceedings of the entire Workshop Series along with additional information and recommendations.

Comet Halley in 1910, as viewed from a Maltese perspective

NASA Astrophysics Data System (ADS)

Galea, Adrian

2009-07-01

Comet Halley's return in 1910 was keenly anticipated globally by scientists and the lay public alike. Although cometary science had progressed rapidly during the last quarter of the nineteenth century, superstition remained significant in different parts of the world and there were fears that people would die if the prediction that the Earth would pass through the comet's tail were correct. Malta was a small British island colony in the Mediterranean, and the inhabitants there were no exception. Local newspapers reported concerns from their readers and from foreign sources, but they also included reassuring scientific information about comets. Under the patronage of the colonial government a local amateur astronomer named Francis Reynolds reassured the public through lectures that he delivered. Overall the local population appeared to have been calm about the impending return. The first recorded sighting from Malta was on 24 April 1910 and the first naked eye sighting occurred the following day. Accounts were published in the local newspapers and in private correspondence, suggesting a high level of public interest in this object. No photographs of the comet from Malta have been traced, but the aforementioned Mr Reynolds and a well-known Maltese artist, G. Cali, did make a number of paintings. On the night when the Earth was due to pass through the comet's tail many local people congregated around the bastions of the city under an overcast sky in the early hours of the morning, but no untoward events were experienced.

NASA needs a long-term sample return strategy

NASA Astrophysics Data System (ADS)

Agee, C.

Sample return missions, as demonstrated by Apollo, can have a huge payoff for plan- etary science. Beyond NASAAfs current Discovery missions, Stardust and Genesis, there are no future U.S. sample return missions on the books. At this juncture, it would be desirable for NASA to develop a coherent, long-term strategy for sample return missions to prime targets such as Mars, Venus, and other solar system bodies. The roster of missions planned for this decade in NASAAfs Mars Program no longer includes a sample return. Arguments against an early Mars sample return (MSR) in- clude the high cost, high risk, and not knowing the Agright placeAh on the Martian surface to sample. On the other hand, answering many of the key scientific questions about Mars, including the search for life, may require sample return. In lieu of MSR, NASA plans, out to 2009, a mix of orbital and landed missions that will perform re- mote and in-situ science at Mars. One approach to MSR that may lead to success in the opportunities beyond 2009 is a series of simple missions where large rovers and complex instruments are replaced by robust Mars ascent vehicles and lander-based sampling techniques. AgMobilityAh and Agsample diversityAh in these early reconnaissance sample return missions are accomplished by sending each mission to a distinctly different location based on our understanding of Martian geology prior to launch. The expected wealth of knowledge from these simple sample return missions will help guide Mars exploration beyond 2020. Venus sample return (VSR) should also be a high priority in NASAAfs exploration of the solar system. Our understanding of the Venusian surface is fragmentary at best and the mineralogy in unknown. We have no verified meteorites from Venus and thus radiometric ages of the crust do not exist. Venusian science best done on Earth from a VSR would include (1) precise isotopic measurements of atmospheric gases, soil, and rock, (2) age dating of rock, (3) trace element chemistry of soil and rock, (4) charac- terization of very small phases, (5) characterization of complex weathering products, (6) detailed rock mineralogy and petrology.

Benefits of in situ propellant utilization for a Mars sample return mission

NASA Technical Reports Server (NTRS)

Wadel, Mary F.

1993-01-01

Previous Mars rover sample return mission studies have shown a requirement for Titan 4 or STS Space Shuttle launch vehicles to complete a sample return from a single Mars site. These studies have either used terrestrial propellants or considered in situ production of methane and oxygen for the return portion of the mission. Using in situ propellants for the return vehicles reduces the Earth launch mass and allows for a smaller Earth launch vehicle, since the return propellant is not carried from Earth. Carbon monoxide and oxygen (CO/O2) and methane and oxygen (CH4/O2) were investigated as in situ propellants for a Mars sample return mission and the results were compared to a baseline study performed by the Jet Propulsion Laboratory using terrestrial propellants. Capability for increased sample return mass, use of an alternate launch vehicle, and an additional mini-rover as payload were included. CO/O2 and CH4/O2 were found to decrease the baseline Earth launch mass by 13.6 and 9.2 percent, respectively. This resulted in higher payload mass margins for the baseline Atlas 2AS launch vehicle. CO/O2 had the highest mass margin. And because of this, it was not only possible to increase the sample return mass and carry an additional mini-rover, but was also possible to use the smaller Atlas 2A launch vehicle.

Low Cost Mars Sample Return Utilizing Dragon Lander Project

NASA Technical Reports Server (NTRS)

Stoker, Carol R.

2014-01-01

We studied a Mars sample return (MSR) mission that lands a SpaceX Dragon Capsule on Mars carrying sample collection hardware (an arm, drill, or small rover) and a spacecraft stack consisting of a Mars Ascent Vehicle (MAV) and Earth Return Vehicle (ERV) that collectively carry the sample container from Mars back to Earth orbit.

The age of the Venusian surface - Estimates using terrestrial crater data

NASA Technical Reports Server (NTRS)

Schaber, G. G.; Shoemaker, E. N.; Kozak, R. C.

1987-01-01

It is hypothesized that the age of the Venusian northern hemisphere surface studied thus far could be as great as the average age of the earth's crust (450 Myr). This possibility arises because of the uncertainty of the role of active and inactive cometary nuclei in the crateral history of the earth. If the observed Venusian surface were 1 Byr old, then there would be traces of the impacts of a half dozen or more large cometary nuclei which penetrated the atmosphere and formed craters over 100 km in diameter.

The International Cometary Explorer mission to comets Giacobini-Zinner and Halley - An update

NASA Technical Reports Server (NTRS)

Brandt, J. C.

1986-01-01

Aspects of the International Cometary Explorer (ICE) flight to the comet Giacobini-Zinner (GZ) are discussed. The most important experiments to be performed by ICE are reviewed, and the orbital parameters of GZ are described. The dust characteristics of GZ that pose a hazard to the spacecraft are addressed, and the ICE targeting strategy toward the comet is discussed. Requested ground-based coverage of GZ is indicated, and the complementarity of the GZ coverage with that given to the Halley mission is shown.

A survey of bimolecular ion-molecule reactions for use in modeling the chemistry of planetary atmospheres, cometary comae, and interstellar clouds

NASA Technical Reports Server (NTRS)

Anicich, V. G.; Huntress, W. T., Jr.

1986-01-01

All bimolecular positive ion-molecule reactions reported from 1965 to 1985 for temperatures below 1000 K are included in the present survey of those ion-molecule reactions pertinent to the chemistries of planetary atmospheres, cometary comae, and interstellar clouds. This survey is intended as an update of the first, by Huntress (1977). The tabular presentation is organized according to reactant ion, with cross-references for both the ionic and the neutral reactants as well as the ionic and neutral products.

Stability of the cometary ionopause

NASA Astrophysics Data System (ADS)

Ershkovich, A. I.; Axford, W. I.; Ip, W.-H.; Flammer, K. R.

MHD stability of the cometary ionopause is discussed in the context of the Giotto mission to comet Halley. A mechanism associated with the plasma compressibility is suggested here as being responsible for the apparent stability of the Halley ionopause: when the phase velocity of surface waves at the ionopause approaches the fast magnetoacoustic speed the unstable surface waves are transformed into stable body waves in the whole fluid resulting in an effective damping of the instability. The effects of both mass loading (due to photoionization) and dissociative recombination are also studied.

Oort's cloud evolution under the influence of the galactic field.

NASA Astrophysics Data System (ADS)

Kiryushenkova, N. V.; Chepurova, V. M.; Shershkina, S. L.

By numerical integration (Everhart's method) of the differential equations of cometary movement in Oort's cloud an attempt was made to observe how the galactic gravitational field changes the orbital elements of these comets during three solar revolutions in the Galaxy. It is shown that the cometary orbits are more elongated, even the initially circular orbits become strongly elliptical, in the outer layers of Oort's cloud it is possible for comets to turn into hyperbolic orbits and to leave the solar system. The boundaries of the solar system have been precised.

THE ROTATION PERIOD OF C/2014 Q2 (LOVEJOY)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Serra-Ricart, Miquel; Licandro, Javier, E-mail: mserra@iac.es, E-mail: jlicandr@iac.es

2015-11-20

C/2014 Q2 (Lovejoy) was observed around perihelion (2015 January 30) on 15 nights between 2015 January 21 and February 11 using the TADer 0.3-m astrograph telescope at Teide Observatory (IAC, Tenerife, Spain). Two large spiral jet structures were observed over several cometary rotations. A new method of searching for periodicities in the PA of spiral jets in the coma region at a fixed distance (20,624 km) from the cometary optocenter is presented and used to determine a nuclear rotation period of 17.89 ± 0.17 hr.

Clathrate hydrate formation in amorphous cometary ice analogs in vacuo

NASA Technical Reports Server (NTRS)

Blake, David; Allamandola, Louis; Sandford, Scott; Hudgins, Doug; Freund, Friedemann

1991-01-01

Experiments conducted in clathrate hydrates with a modified electron microscope have demonstrated the possibility of such compounds' formation during the warming of vapor-deposited amorphous ices in vacuo, through rearrangements in the solid state. Subsolidus crystallization of compositionally complex amorphous ices may therefore be a general and ubiquitous process. Phase separations and microporous textures thus formed may be able to account for such anomalous cometary phenomena as the release of gas at large radial distances from the sun and the retention of volatiles to elevated temperatures.

The origin, composition and history of cometary ices from spectroscopic studies

NASA Technical Reports Server (NTRS)

Allamandola, L. J.

1989-01-01

The spectroscopic analysis of pristine cometary material provides a very important probe of the chemical identity of the material as well as of the physical and chemical conditions which prevailed during the comet's history. Concerning classical spectroscopy, the spectral regions which will most likely prove most useful are the infrared, the visible and ultraviolet. Newer spectroscopic techniques which have the potential to provide equally important information include nuclear magnetic resonance (NMR) and electron spin resonance (ESR). Each technique is summarized with emphasis placed on the kind of information which can be obtained.

Returns to Education in Bangladesh

ERIC Educational Resources Information Center

Asadullah, Mohammad Niaz

2006-01-01

This paper reports labour market returns to education in Bangladesh using data from recent nationwide household survey. Returns are estimated separately for rural and urban samples, males, females and private-sector employees. Substantial heterogeneity in returns is observed; for example, estimates are higher for urban (than rural sample) and…

Numerical simulations of PP-SESAME/Philae/ROSETTA operations during the Descent Phase and at the surface of the Churyumov-Gerasimenko nucleus

NASA Astrophysics Data System (ADS)

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

2014-05-01

The ROSETTA probe has never been so close to its target; the comet Churyumov-Gerasimenko that it will reach later this year. Among the instruments on board the lander, Philae, the Permittivity Probe (PP) experiment, which is part of the Surface Electric Sounding and Acoustic Monitoring Experiment (SESAME) package, will measure the low frequency complex permittivity (i.e. dielectric constant and electrical conductivity) of the first 2 meters of the subsurface of the cometary nucleus. At frequencies below 10 kHz, the electrical signature of the matter is especially sensitive to the presence of water ice and its temperature behavior. PP will thus allow to determine the water ice content in the near-surface and to monitor its diurnal and orbital variations thus providing essential insight on the activity and evolution of the cometary nucleus. The PP instrument is based on the quadrupole array technique, which employs a set of transmitter and receiver electrodes for emitting alternating currents into a medium of interest. The complex permittivity of the cometary surface material is determined by measuring the magnitude and phase shift of both the emitted currents and the resulting potential difference at a pair of receiver electrodes. This technique has been used for many decades on Earth and recently helped to determine the electrical properties of the Huygens landing site on Titan (PWA/HASI experiment on Cassini-Huygens). In the case of PP, 5 electrodes can be used: 2 receiver electrodes are integrated into the lander feet while the transmitter electrodes are mounted on the third foot and on 2 other instruments. In this paper we will present results from numerical simulations performed in order to model PP operations and prepare the scientific return of this experiment. Though simple in theory, the inference of the complex permittivity from PP measurements is not straightforward in practice. In particular, the actual environment of the electrodes (lander body, feet, harpoons...) must be accounted for since the presence of nearby conducting objects will affect the data. We have thus developed a numerical model of the electrodes in their environment using COMSOL Multiphysics®. A simple version of this model was validated by comparison to laboratory measurements and analytical calculations. This model was then used to simulate PP operations during the Descent Phase of the lander (i.e. in the void and as the ground gets closer) and once at the surface of the nucleus considering different types of surfaces. The first set of simulations will be very useful to better understand the calibration data that will be acquired after separation from the ROSETTA Orbiter while the second will illustrate the idealistic sensitivity of PP to the ground electrical properties.

GeoLab Concept: The Importance of Sample Selection During Long Duration Human Exploration Mission

NASA Technical Reports Server (NTRS)

Calaway, M. J.; Evans, C. A.; Bell, M. S.; Graff, T. G.

2011-01-01

In the future when humans explore planetary surfaces on the Moon, Mars, and asteroids or beyond, the return of geologic samples to Earth will be a high priority for human spaceflight operations. All future sample return missions will have strict down-mass and volume requirements; methods for in-situ sample assessment and prioritization will be critical for selecting the best samples for return-to-Earth.

Mars Sample Return: Mars Ascent Vehicle Mission and Technology Requirements

NASA Technical Reports Server (NTRS)

Bowles, Jeffrey V.; Huynh, Loc C.; Hawke, Veronica M.; Jiang, Xun J.

2013-01-01

A Mars Sample Return mission is the highest priority science mission for the next decade recommended by the recent Decadal Survey of Planetary Science, the key community input process that guides NASAs science missions. A feasibility study was conducted of a potentially simple and low cost approach to Mars Sample Return mission enabled by the use of developing commercial capabilities. Previous studies of MSR have shown that landing an all up sample return mission with a high mass capacity lander is a cost effective approach. The approach proposed is the use of an emerging commercially available capsule to land the launch vehicle system that would return samples to Earth. This paper describes the mission and technology requirements impact on the launch vehicle system design, referred to as the Mars Ascent Vehicle (MAV).

Mars Sample Return: Mars Ascent Vehicle Mission and Technology Requirements

NASA Technical Reports Server (NTRS)

Bowles, Jeffrey V.; Huynh, Loc C.; Hawke, Veronica M.

2013-01-01

A Mars Sample Return mission is the highest priority science mission for the next decade recommended by the recent Decadal Survey of Planetary Science, the key community input process that guides NASA's science missions. A feasibility study was conducted of a potentially simple and low cost approach to Mars Sample Return mission enabled by the use of new commercial capabilities. Previous studies of MSR have shown that landing an all up sample return mission with a high mass capacity lander is a cost effective approach. The approach proposed is the use of a SpaceX Dragon capsule to land the launch vehicle system that would return samples to Earth. This paper describes the mission and technology requirements impact on the launch vehicle system design, referred to as the Mars Ascent Vehicle (MAV).

COMPASS Final Report: Near Earth Asteroids Rendezvous and Sample Earth Returns (NEARER)

NASA Technical Reports Server (NTRS)

Oleson, Steven R.; McGuire, Melissa L.

2009-01-01

In this study, the Collaborative Modeling for Parametric Assessment of Space Systems (COMPASS) team completed a design for a multi-asteroid (Nereus and 1996 FG3) sample return capable spacecraft for the NASA In-Space Propulsion Office. The objective of the study was to support technology development and assess the relative benefits of different electric propulsion systems on asteroid sample return design. The design uses a single, heritage Orion solar array (SA) (approx.6.5 kW at 1 AU) to power a single NASA Evolutionary Xenon Thruster ((NEXT) a spare NEXT is carried) to propel a lander to two near Earth asteroids. After landing and gathering science samples, the Solar Electric Propulsion (SEP) vehicle spirals back to Earth where it drops off the first sample s return capsule and performs an Earth flyby to assist the craft in rendezvousing with a second asteroid, which is then sampled. The second sample is returned in a similar fashion. The vehicle, dubbed Near Earth Asteroids Rendezvous and Sample Earth Returns (NEARER), easily fits in an Atlas 401 launcher and its cost estimates put the mission in the New Frontier s (NF's) class mission.

Nondestructive 3D confocal laser imaging with deconvolution of seven whole stardust tracks with complementary XRF and quantitative analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenberg, M.; Ebel, D.S.

2009-03-19

We present a nondestructive 3D system for analysis of whole Stardust tracks, using a combination of Laser Confocal Scanning Microscopy and synchrotron XRF. 3D deconvolution is used for optical corrections, and results of quantitative analyses of several tracks are presented. The Stardust mission to comet Wild 2 trapped many cometary and ISM particles in aerogel, leaving behind 'tracks' of melted silica aerogel on both sides of the collector. Collected particles and their tracks range in size from submicron to millimeter scale. Interstellar dust collected on the obverse of the aerogel collector is thought to have an average track length ofmore » {approx}15 {micro}m. It has been our goal to perform a total non-destructive 3D textural and XRF chemical analysis on both types of tracks. To that end, we use a combination of Laser Confocal Scanning Microscopy (LCSM) and X Ray Florescence (XRF) spectrometry. Utilized properly, the combination of 3D optical data and chemical data provides total nondestructive characterization of full tracks, prior to flattening or other destructive analysis methods. Our LCSM techniques allow imaging at 0.075 {micro}m/pixel, without the use of oil-based lenses. A full textural analysis on track No.82 is presented here as well as analysis of 6 additional tracks contained within 3 keystones (No.128, No.129 and No.140). We present a method of removing the axial distortion inherent in LCSM images, by means of a computational 3D Deconvolution algorithm, and present some preliminary experiments with computed point spread functions. The combination of 3D LCSM data and XRF data provides invaluable information, while preserving the integrity of the samples for further analysis. It is imperative that these samples, the first extraterrestrial solids returned since the Apollo era, be fully mapped nondestructively in 3D, to preserve the maximum amount of information prior to other, destructive analysis.« less

NEA Multi-Chamber Sample Return Container with Hermetic Sealing

NASA Technical Reports Server (NTRS)

Rafeek, Shaheed; Kong, Kin Yuen; Sadick, Shazad; Porter, Christopher C.

2000-01-01

A sample return container is being developed by Honeybee Robotics to receive samples from a derivative of the Champollion/ST4 Sample Acquisition and Transfer Mechanism or other samplers such as the 'Touch and Go' Surface Sampler (TGSS), and then hermetically seal the samples for a sample return mission. The container is enclosed in a phase change material (PCM) chamber to prevent phase change during return and re-entry to earth. This container is designed to operate passively with no motors and actuators. Using the rotation axis of the TGSS sampler for interfacing, transferring and sealing samples, the container consumes no electrical power and therefore minimizes sample temperature change. The circular container houses multiple isolated canisters, which will be sealed individually for samples acquired from different sites or depths. The TGSS based sampler indexes each canister to the sample transfer position, below the index interface for sample transfer. After sample transfer is completed, the sampler indexes a seal carrier, which lines up seals with the openings of the canisters. The sampler moves to the sealing interface and seals the sample canisters one by one. The sealing interface can be designed to work with C-seals, knife edge seals and cup seals. This sample return container is being developed by Honeybee Robotics in collaboration with the JPL Exploration Technology program. A breadboard system of the sample return container has been recently completed and tested. Additional information is contained in the original extended abstract.

Influence of dust on cometary radiance spectra infered from various models of Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Blecka, M. I.; Coradini, A.; Capaccioni, F.; Capria, M. T.; De sanctis, M.

2011-12-01

The work we present deals with the spectrometric measurements of VIRTIS instrument of the Rosetta mission to the Comet 67P/Churyumov-Gerasimenko (C-G). The dust important constituent of cometary environment is always present on the surface of the nucleus and in the inner coma. The cometary spectra are strongly affected by the processes taking place in the coma and by the structure and composition of cometary materials. The particles of the dust , illuminated by solar light, scatter, absorb and emit radiation. The reflected and the emitted radiation are transmitted through the coma region before being collected by instruments such as VIRTIS .The reflection, absorption, scattering, and emission processes depend on the Comet-Sun geometry and on the thermal state of the nucleus. The main purposes of the paper are: 1) short review of the published models related to the topic of presence and distribution of the solid particles in the inner coma of the Comet 67/P (C-G) 2) description of numerical calculations done by means of an radiation transfer model and comparison the simulated radiance spectra 3) discussion on influence the geometry of the measurements and the particular parameters of the thermal models taken in consideration. 4) demonstration of simulated spectra of the total directional radiance which can help to recognize the optical characteristics of constituents of the environment of Comet 67P/(C-G) References J.Agarwal; M.Müller, G.Eberhard, Dust Environment Modelling of Comet 67P/Churyumov-Gerasimenko; Space Science Reviews, 128,1-4,2007 M. I. Blecka, M.T. Capria, A. Coradini, M.C. De Sanctis; Numerical simulations of the radiance from the Comet 46P/Wirtanen in the Ivarious configuration of the measurements during "Rosetta" Mission Adv. Space Res.31,12, 2501-2510,2003 M.C.De Sanctis, J.Lasue, M.T.Capria, G. Magni, D. Turrini, A. Coradini, Shape and obliquity effects on the thermal evolution of the Rosetta target 67P/Churyumov-Gerasimenko cometary nucleus, Icarus, 207,341-358,2010 The work was supported by the grant 123/N-ESA/2008/0;

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 Impact Award from Google, and by the Alfred P. Sloan Foundation. The HSC collaboration includes the astronomical communities of Japan and Taiwan, and Princeton University.

Evolution of Cometary Dust Particles to the Orbit of the Earth: Particle Size, Shape, and Mutual Collisions

NASA Astrophysics Data System (ADS)

Yang, Hongu; Ishiguro, Masateru

2018-02-01

In this study, we numerically investigated the orbital evolution of cometary dust particles, with special consideration of the initial size–frequency distribution (SFD) and different evolutionary tracks according to the initial orbit and particle shape. We found that close encounters with planets (mostly Jupiter) are the dominating factor determining the orbital evolution of dust particles. Therefore, the lifetimes of cometary dust particles (∼250,000 yr) are shorter than the Poynting–Robertson lifetime, and only a small fraction of large cometary dust particles can be transferred into orbits with small semimajor axes. The exceptions are dust particles from 2P/Encke and, potentially, active asteroids that have little interaction with Jupiter. We also found that the effects of dust shape, mass density, and SFD were not critical in the total mass supply rate to the interplanetary dust particle (IDP) cloud complex when these quantities are confined by observations of zodiacal light brightness and SFD around the Earth’s orbit. When we incorporate a population of fluffy aggregates discovered in the Earth’s stratosphere and the coma of 67P/Churyumov–Gerasimenko within the initial ejection, the initial SFD measured at the comae of comets (67P and 81P/Wild 2) can produce the observed SFD around the Earth’s orbit. Considering the above effects, we derived the probability of mutual collisions among dust particles within the IDP cloud for the first time in a direct manner via numerical simulation and concluded that mutual collisions can mostly be ignored.

Performance of the cometary experiment MUPUS on the body Earth

NASA Astrophysics Data System (ADS)

Marczewski, W.; Usowicz, B.; Schröer, K.; Seiferlin, K.; Spohn, T.

2003-04-01

Thermal experiment MUPUS for the Rosetta mission was extensively experience in field and laboratory conditions to predict its performance under physical processes available on the Earth. The goal was not guessing a cometary material in the ground but available behavior of thermal sensor responses monitoring mass and energy transfer. The processes expected on a comet are different in composition and environmental from those met on the Earth but basically similar in physics. Nature of energy powering the processes is also essentially the same - solar radiation. Several simple laboratory experiments with freezing and thawing with water ice, with mixture of water and oil and water layers strongly diverged by salinity revealed capability of recognition layered structure of the medium under test. More over effects of slow convection and latent heat related to the layers are also observed well. Cometary environment without atmosphere makes process of sublimation dominant. Open air conditions on the Earth may also offer a change of state in matter but between different phases. Learning temperature gradient in snow layers under thawing show that effects stimulated by a cause of daily cycling may be detected thermally. Results from investigations in snow made on Spitzbergen are good proofs on capability of the method. Relevance of thermal effects to heat powered processes of mass transport in the matter of ground is meaningful for the cometary experiment of MUPUS and for Earth sciences much concerned on water, gas and solid matter transport in the terrestrial ground. Results leading to energy balance studied on the Earth surface may be interesting also for the experiment on the comet and are to be discussed.

DYNAMIC DEUTERIUM ENRICHMENT IN COMETARY WATER VIA ELEY–RIDEAL REACTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, Yunxi; Giapis, Konstantinos P., E-mail: giapis@cheme.caltech.edu

2017-01-20

The deuterium-to-hydrogen ratio (D/H) in water found in the coma of Jupiter family comet (JFC) 67P/Churyumov–Gerasimenko was reported to be (5.3 ± 0.7) × 10{sup −4}, the highest among comets and three times the value for other JFCs with an ocean-like ratio. This discrepancy suggests the diverse origins of JFCs and clouds the issue of the origin of Earth’s oceanic water. Here we demonstrate that Eley–Rideal reactions between accelerated water ions and deuterated cometary surface analogs can lead to instantaneous deuterium enrichment in water scattered from the surface. The reaction proceeds with H{sub 2}O{sup +} abstracting adsorbed D atoms, formingmore » an excited H{sub 2}DO* state, which dissociates subsequently to produce energetic HDO. Hydronium ions are also produced readily by the abstraction of H atoms, consistent with H{sub 3}O{sup +} detection and abundance in various comets. Experiments with water isotopologs and kinematic analysis on deuterated platinum surfaces confirmed the dynamic abstraction mechanism. The instantaneous fractionation process is independent of the surface temperature and may operate on the surface of cometary nuclei or dust grains, composed of deuterium-rich silicates and carbonaceous chondrites. The requisite energetic water ions have been detected in the coma of 67P in two populations. This dynamic fractionation process may temporarily increase the water D/H ratio, especially as the comet gets closer to the Sun. The magnitude of the effect depends on the water ion energy-flux and the deuterium content of the exposed cometary surfaces.« less

Fabry-Perot Observations of [OI]6300, Hα, H-Beta, and NH2 Emissions from Comet Hyakutake C/1996B2

NASA Astrophysics Data System (ADS)

Scherb, F.; Roesler, F. L.; Tufte, S.; Haffner, M.

1996-05-01

During the period 16-23 March 1996, observations of Comet Hyakutake were carried out with the new WHAM facility at the University of Wisconsin Pine Bluff Observatory, near Madison. WHAM is a second-generation double-Fabry-Perot/CCD spectrometer that is more than ten times as efficient as our previous large-aperture Fabry-Perot instruments. Specifications of WHAM in the spectral mode are: a 1-degree field of view (FOV) on the sky, 10 km/sec velocity resolution, 200 km/sec range, and 20 sigma detection of a 1-Rayleigh H-alpha emission line in about 30 seconds. WHAM can also operate in a mode in which an image of an emission source over a 1-degree FOV can be obtained at a spectral resolution of about 10 km/sec. Spectra of cometary [OI]6300, H-alpha, H-beta, and NH2 emissions were obtained with the FOV centered on the comet head and also located 3/4 degree sunward of the comet head, repectively. This was the first time that cometary H-beta emission has been detected. Images of cometary [OI]6300 and NH2 emissions were obtained with the FOV centered on the comet head. The interpretation of these observations using coma gas dynamic and photochemical models yields values of the H2O production rate from both the [OI]6300 and H-alpha data. Comparison of the cometary H-alpha and H-beta intensities provides unique ground-based information on the EUV solar Lyman-beta and Lyman-gamma emission lines. These results will be presented.

Characterizing Cometary Electrons with Kappa Distributions

NASA Technical Reports Server (NTRS)

Broiles, T. W.; Livadiotis, G.; Burch, J. L.; Chae, K.; Clark, G.; Cravens, T. E.; Davidson, R.; Eriksson, A.; Frahm, R. A.; Fuselier, S. A.;

Thermal modeling of cometary nuclei

USGS Publications Warehouse

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

1981-01-01

A new model of the sublimation of volatile ices from a cometary nucleus has been developed which includes the effects of diurnal heating and cooling, rotation period and pole orientation, and thermal properties of the ice and subsurface layers. The model also includes the contribution from coma opacity, scattering, and thermal emission, where the properties of the coma are derived from the integrated rate of volatile production by the nucleus. The model is applied to the specific case of the 1986 apparition of Halley's comet. It is found that the generation of a cometary dust coma actually increases the total energy reaching the Halley nucleus. This results because of the significantly greater geometrical cross section of the coma as compared with the bare nucleus, and because the coma provides an essentially isotropic source of multiply scattered sunlight and thermal emission over the entire nucleus surface. For Halley, the calculated coma opacity is approximately 0.2 at 1 AU from the Sun, and 1.2 at perihelion (0.587 AU). At 1 AU this has little effect on dayside temperatures (maximum ???200??K) but raises nightside temperatures (minimum ???150??K) by about 40??K. At perihelion the higher opacity results in a nearly isothermal nucleus with only small diurnal and latitudinal temperature variations. The general surface temperature is 205??K with a maximum of 209??K at local noon on the equator. Some possible consequences of the results with respect to the generation of nongravitational forces, observed volatile production rates for comets, and cometary lifetimes against sublimation are discussed. ?? 1981.

Sample Return from Small Solar System Bodies

NASA Astrophysics Data System (ADS)

Orgel, L.; A'Hearn, M.; Bada, J.; Baross, J.; Chapman, C.; Drake, M.; Kerridge, J.; Race, M.; Sogin, M.; Squyres, S.

With plans for multiple sample return missions in the next decade, NASA requested guidance from the National Research Council's SSB on how to treat samples returned from solar system bodies such as planetary satellites, asteroids and comets. A special Task Group assessed the potential for a living entity to be included in return samples from various bodies as well as the potential for large scale effects if such an entity were inadvertently introduced into the Earth's biosphere. The Group also assessed differences among solar system bodies, identified investigations that could reduce uncertainty about the bodies, and considered risks of returned samples compared to natural influx of material to the Earth in the form of interplanetary dust particles, meteorites and other small impactors. The final report (NRC, 1998) provides a decision making framework for future missions and makes recommendations on how to handle samples from different planetary satellites and primitive solar system bodies

The Composition of the Protosolar Disk and the Formation Conditions for Comets

NASA Astrophysics Data System (ADS)

Willacy, K.; Alexander, C.; Ali-Dib, M.; Ceccarelli, C.; Charnley, S. B.; Doronin, M.; Ellinger, Y.; Gast, P.; Gibb, E.; Milam, S. N.; Mousis, O.; Pauzat, F.; Tornow, C.; Wirström, E. S.; Zicler, E.

2015-12-01

Conditions in the protosolar nebula have left their mark in the composition of cometary volatiles, thought to be some of the most pristine material in the solar system. Cometary compositions represent the end point of processing that began in the parent molecular cloud core and continued through the collapse of that core to form the protosun and the solar nebula, and finally during the evolution of the solar nebula itself as the cometary bodies were accreting. Disentangling the effects of the various epochs on the final composition of a comet is complicated. But comets are not the only source of information about the solar nebula. Protostellar disks around young stars similar to the protosun provide a way of investigating the evolution of disks similar to the solar nebula while they are in the process of evolving to form their own solar systems. In this way we can learn about the physical and chemical conditions under which comets formed, and about the types of dynamical processing that shaped the solar system we see today.

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.

Cometary showers and unseen solar companions

NASA Technical Reports Server (NTRS)

Weissman, P. R.

1984-01-01

The possibility that an invisible solar companion passing through the Oort cloud every 28 Myr precipitates a sufficiently high rate of cometary collisions with the earth to account for periodic mass species extinctions recorded in the fossil record is discussed. A Monte Carlo simulation shows that any hypothesized 'death star' with a 28 Myr orbit would experience an average 10 percent change in period per orbit. Production of an 18-fold increase in cometary impacts would be associated with a 0.055 probability that a 10 km nucleus would hit the earth in a shower once every 510 Myr, longer than the proposed extinction periodicity. However, if the death star orbit has a 0.6 eccentricity and the Oort cloud is sufficiently densely populated, a 2 billion comet shower may be possible. A survey of large terrestrial impact craters indicates that 6-12 craters with diameters over 10 km originated in periodic showers. The extinctions in any case occur at 26 Myr periods and cannot be correlated with the 33 Myr period of recrossing the galactic plane, or with any other known phenomena.

The solar corona as probed by comet Lovejoy (C/2011 W3)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raymond, J. C.; McCauley, P. I.; Cranmer, S. R.

2014-06-20

Extreme-ultraviolet images of Comet Lovejoy (C/2011 W3) from the Atmospheric Imaging Assembly show striations related to the magnetic field structure in both open and closed magnetic regions. The brightness contrast implies coronal density contrasts of at least a factor of six between neighboring flux tubes over scales of a few thousand kilometers. These density structures imply variations in the Alfvén speed on a similar scale. They will drastically affect the propagation and dissipation of Alfvén waves, and that should be taken into account in models of coronal heating and solar wind acceleration. In each striation, the cometary emission moves alongmore » the magnetic field and broadens with time. The speed and the rate of broadening are related to the parallel and perpendicular components of the velocities of the cometary neutrals when they become ionized. We use a magnetohydrodynamic model of the coronal magnetic field and the theory of pickup ions to compare the measurements with theoretical predictions, in particular with the energy lost to Alfvén waves as the cometary ions isotropize.« less

Website for the Astrochemistry Laboratory, Astrophysics Branch, Space Sciences Division

NASA Technical Reports Server (NTRS)

Sandford, Scott; DeVincenzi, D. (Technical Monitor)

2002-01-01

The Astrochemistry Laboratory in the Astrophysics Branch (SSA) of the Space Sciences Division at NASA's Ames Research Center specializes in the study of extraterrestrial materials and their analogs. The staff has pioneered laboratory studies of space environments including interstellar, cometary, and planetary ices, simulations of the so-called 'Unidentified' Infrared Emission Bands and Diffuse Interstellar Bands using PAHs (Polycyclic Aromatic Hydrocarbons) and PAH-related materials, and has extensive experience with low-temperature spectroscopy and astronomical observation. Important discoveries made by the Astrochemistry Group include: (1) The recognition that polycyclic aromatic hydrocarbons and their ions are common in space; (2) The identification of a major fraction of the known molecular species frozen in interstellar/pre-cometary ices; (3) The recognition that a significant fraction of the carbon in the interstellar medium is carried by both microdiamonds and organic materials; (4) The expansion of the types of molecules expected to be synthesized in interstellar/pre-cometary ices. These could be delivered to the early Earth (or other body) and influence the origin or early evolution of life.

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.

Cometary dust at the smallest scale - latest results of the MIDAS Atomic Force Microscope onboard Rosetta

NASA Astrophysics Data System (ADS)

Bentley, Mark; Torkar, Klaus; Jeszenszky, Harald; Romstedt, Jens; Schmied, Roland; Mannel, Thurid

2015-04-01

The MIDAS instrument onboard the Rosetta orbit is a unique combination of a dust collection and handling system and a high resolution Atomic Force Microscope (AFM). By building three-dimensional images of the dust particle topography, MIDAS addresses a range of fundamental questions in Solar System and cometary science. The first few months of dust collection and scanning revealed a deficit of smaller (micron and below) particles but eventually several 10 µm-class grains were discovered. In fact these were unexpectedly large and close to the limit of what is observable with MIDAS. As a result the sharp tip used by the AFM struck the particles from the side, causing particle breakage and distortion. Analyses so far suggest that the collected particles are fluffy aggregates of smaller sub-units, although determination of the size of these sub-units and high resolution re-imaging remains to be done. The latest findings will be presented here, including a description of the particles collected and the implications of these observations for cometary science and the Rosetta mission at comet 67P.

Cometary impact and amino acid survival - Chemical kinetics and thermochemistry

USGS Publications Warehouse

Ross, D.S.

2006-01-01

The Arrhenius parameters for the initiating reactions in butane thermolysis and the formation of soot, reliable to at least 3000 K, have been applied to the question of the survival of amino acids in cometary impacts on early Earth. The pressure/temperature/time course employed here was that developed in hydrocode simulations for kilometer-sized comets (Pierazzo and Chyba, 1999), with attention to the track below 3000 K where it is shown that potential stabilizing effects of high pressure become unimportant kinetically. The question of survival can then be considered without the need for assignment of activation volumes and the related uncertainties in their application to extreme conditions. The exercise shows that the characteristic times for soot formation in the interval fall well below the cooling periods for impacts ranging from fully vertical down to about 9?? above horizontal. Decarboxylation, which emerges as more rapid than soot formation below 2000-3000 K, continues further down to extremely narrow impact angles, and accordingly cometa??ry delivery of amino acids to early Earth is highly unlikely. ?? 2006 American Chemical Society.

Highly Reduced Forsterite and Enstatite from Stardust Track 61: Implications for Radial Transport of E Asteroid Material

NASA Technical Reports Server (NTRS)

Frank, David R.; Zolensky, M. E.; Le, L.; Weisberg, M. K.; Kimura, M.

2013-01-01

The Stardust Mission returned a large fraction of high-temperature, crystalline material that was radially transported from the inner solar system to the Kuiper Belt [1,2]. The mineralogical diversity found in this single cometary collection points to an even greater number of source materials than most primitive chondrites. In particular, the type II olivine found in Wild 2 includes the three distinct Fe/Mn ratios found in the matrix and chondrules of carbonaceous chondrites (CCs) and unequilibrated ordinary chondrites (UOCs) [3]. We also find that low-Ca pyroxene is quite variable (approximately Fs3-29) and is usually indistinguishable from CC, UOC, and EH3 pyroxene as well. However, occasional olivine and pyroxene compositions are found in Wild 2 that are inconsistent with chondrites. The Stardust track 61 terminal particle (TP) is one such example and is the focus of this study. It s highly reduced forsterite and enstatite is consistent only with that in Aubrites, in which FeO is essentially absent from these phases (less than approximately 0.1 wt.% FeO) [4].

Diffuse fluid flux through orogenic belts: Implications for the world ocean

USGS Publications Warehouse

Ingebritsen, S.E.; Manning, C.E.

2002-01-01

Fifty years ago a classic paper by W. W. Rubey [(1951) Geol. Soc. Am. Bull. 62, 1111-1148] examined various hypotheses regarding the origin of sea water and concluded that the most likely hypothesis was volcanic outgassing, a view that was generally accepted by earth scientists for the next several decades. More recent work suggests that the rate of subduction of water is much larger than the volcanic outgassing rate, lending support to hypotheses that either ocean volume has decreased with time, or that the imbalance is offset by continuous replenishment of water by cometary impacts. These alternatives are required in the absence of additional mechanisms for the return of water from subducting lithosphere to the Earth's surface. Our recent work on crustal permebility suggests a large capacity for water upflow through tectonically active continental crust, resulting in a heretofore unrecognized degassing pathway that can accommodate the waer subduction rate. Escape of recycled water via delivery from the mantle through zones of active metamorphism eliminates the mass-balance argument for the loss of ocean volume or extraterestrial sources.

Implications of crustal permeability for fluid movement between terrestrial fluid reservoirs

USGS Publications Warehouse

Ingebritsen, S.E.; Manning, C.E.

2003-01-01

A classic paper by Rubey [Geol. Soc. Amer. Bull 62 (1951) 1111] examined various hypotheses regarding the origin of sea water and concluded that the most likely hypothesis was volcanic outgassing, a view that was generally accepted by Earth scientists for the next several decades. More recent work suggests that the rate of subduction of water is much larger than the volcanic outgassing rate, lending support to hypotheses that either ocean volume has decreased with time, or that the imbalance is offset by continuous replenishment of water by cometary impacts. These alternatives are required in the absence of additional mechanisms for the return of water from subducting lithosphere to the Earth's surface. Our recent work on crustal permeability suggests a large capacity for water upflow through tectonically active continental crust, resulting in a heretofore-unrecognized degassing pathway that can accommodate the water-subduction rate. Escape of recycled water via delivery from the mantle through zones of active metamorphism eliminates the mass-balance argument for the loss of ocean volume or extraterrestrial sources. ?? 2003 Elsevier Science B.V. All rights reserved.

A Draft Science Management Plan for Returned Samples from Mars: Recommendations from the International Mars Architecture for the Return of Samples (iMARS) Phase II Working Group

NASA Astrophysics Data System (ADS)

Haltigin, T.; Lange, C.; Mugnuolo, R.; Smith, C.

2018-04-01

This paper summarizes the findings and recommendations of the International Mars Architecture for the Return of Samples (iMARS) Phase II Working Group, an international team comprising 38 members from 16 countries and agencies.

Sample Return Robot Centennial Challenge

NASA Image and Video Library

2012-06-16

A judge for the NASA-WPI Sample Return Robot Centennial Challenge follows a robot on the playing field during the challenge on Saturday, June 16, 2012 in Worcester, Mass. Teams were challenged to build autonomous robots that can identify, collect and return samples. NASA needs autonomous robotic capability for future planetary exploration. Photo Credit: (NASA/Bill Ingalls)

Strategies for Investigating Early Mars Using Returned Samples

NASA Technical Reports Server (NTRS)

Carrier, B. L.; Beaty, D. W.; McSween, H. Y.; Czaja, A. D.; Goreva, Y. S.; Hausrath, E. M.; Herd, C. D. K.; Humayun, M.; McCubbin, F. M.; McLennan, S. M.;

A Sample Return Container with Hermetic Seal

NASA Technical Reports Server (NTRS)

Kong, Kin Yuen; Rafeek, Shaheed; Sadick, Shazad; Porter, Christopher C.

2000-01-01

A sample return container is being developed by Honeybee Robotics to receive samples from a derivative of the Champollion/ST4 Sample Acquisition and Transfer Mechanism or other samplers and then hermetically seal samples for a sample return mission. The container is enclosed in a phase change material (PCM) chamber to prevent phase change during return and re-entry to earth. This container is designed to operate passively with no motors and actuators. Using the sampler's featured drill tip for interfacing, transfer-ring and sealing samples, the container consumes no electrical power and therefore minimizes sample temperature change. The circular container houses a few isolated canisters, which will be sealed individually for samples acquired from different sites or depths. The drill based sampler indexes each canister to the sample transfer position, below the index interface for sample transfer. After sample transfer is completed, the sampler indexes a seal carrier, which lines up seals with the openings of the canisters. The sampler moves to the sealing interface and seals the sample canisters one by one. The sealing interface can be designed to work with C-seals, knife edge seals and cup seals. Again, the sampler provides all sealing actuation. This sample return container and co-engineered sample acquisition system are being developed by Honeybee Robotics in collaboration with the JPL Exploration Technology program.

Formation of C3 and C2 in Cometary Comae

NASA Astrophysics Data System (ADS)

Hölscher, Alexander

2015-03-01

Comets are remnants from the Solar System formation. They reside at large distances from the Sun and are believed to store deep freeze imprints of the chemical and physical conditions at the time the Solar System formed. The main ice component of a comet is H2O followed by CO and CO2 with additional small amounts of molecules with varying complexity. Comets also contain large amounts of dust. If a comet approaches the Sun the ices begin to sublimate giving rise to the cometary coma. The molecules producing the coma can be observed in the infrared, the radio wavelength range and at optical wavelengths. To constrain the formation of the Solar System, models require knowledge of the composition for a statistically significant number of comets. This favors optical observations of e.g. C3 (tricarbon) and C2 (dicarbon) since these species allow observations even of relatively faint comets and do not require space missions (infrared observations). However, one has to link these observed photodissociation product species (daughter species) to the molecules that originally sublimated from the comet nucleus surface, i.e. the so-called parent molecules, as e.g. C2H2 (acetylene) for C2. However, for C3 no parent molecules have been identified so far. This thesis investigates the formation of C3 and C2 radicals in cometary comae due to photodissociation of observed and in the literature proposed hydrocarbon parent molecules. For this purpose a one-dimensional multi-fluid coma chemistry model has been improved and applied. This work added new photo reactions to the model, updated the hydrocarbon photo rate coefficients and quantified their uncertainty. A sensitivity analysis has been carried out to determine the reactions whose uncertainty most affect the model output uncertainty. Special attention should be paid to these so-called key reactions in future laboratory experiments and quantum chemical computations to reduce the model output uncertainty more effectively. This will allow to better constrain which parent molecules are responsible for the observational C3 and C2 column densities. Based on observations of the four sample comets C/2001 Q4 (NEAT), C/2002 T7 (LINEAR), 9P (Tempel 1) and C/1995 O1 (Hale-Bopp), this work investigates which combination of the following proposed parent molecules C4H2 (diacetylene), CH2C2H2 (allene), CH3C2H (propyne), C2H4 (ethene) and observed parent molecules C2H2 and HC3N (cyanoacetylene) can best reproduce the observational C3 and C2 column densities in cometary comae, taking into account the uncertainties in photodissociation rate coefficients. It was found that the investigated photodissociation rate coefficients have large uncertainties and also a significant effect on the C3 and C2 model column densities. The responsible key reactions were determined with the sensitivity analysis. The important result of this thesis is that one can reasonably well reproduce the observations of comets with the improved model at rh = 1.00 AU (NEAT) and rh = 3.78 AU (Hale-Bopp), within the photodissociation uncertainties using realistic parent molecule production rate ratios and by various combinations of the investigated parent molecules. To confirm the agreement (NEAT, Hale-Bopp) and to clearify remaining discrepancies (LINEAR, Tempel 1) between model and observations requires additional observations of parent and daughter molecules in the coma of comets as well as in situ measurements of cometary ices (Rosetta).zeige weniger

Restricted by Whom? A Historical Review of Strategies and Organization for Restricted Earth Return of Samples from NASA Planetary Missions

NASA Technical Reports Server (NTRS)

Pugel, Betsy

2017-01-01

This presentation is a review of the timeline for Apollo's approach to Planetary Protection, then known as Planetary Quarantine. Return of samples from Apollo 11, 12 and 14 represented NASA's first attempts into conducting what is now known as Restricted Earth Return, where return of samples is undertaken by the Agency with the utmost care for the impact that the samples may have on Earth's environment due to the potential presence of microbial or other life forms that originate from the parent body (in this case, Earth's Moon).

Laser induced photoluminiscence studies of primary photochemical production processes of cometary radicals

NASA Technical Reports Server (NTRS)

Jackson, W. M.

1977-01-01

A tunable vacuum ultraviolet flash lamp was constructed. This unique flash lamp was coupled with a tunable dye laser detector and permits the experimenter to measure the production rates of ground state radicals as a function of wavelength. A new technique for producing fluorescent radicals was discovered. This technique called multiphoton ultraviolet photodissociation is currently being applied to several problems of both cometary and stratospheric interest. It was demonstrated that NO2 will dissociate to produce an excited fragment and the radiation can possibly be used for remote detection of this species.

A survey of bimolecular ion-molecule reactions for use in modeling the chemistry of planetary atmospheres, cometary comae, and interstellar clouds - 1993 supplement

NASA Technical Reports Server (NTRS)

Anicich, V. G.

1993-01-01

This is a supplement to a previous paper (Anicich & Huntress 1986). It is a survey of bimolecular positive ion-molecule reactions with potential importance to the chemistry of planetary atmospheres, cometary comae, and interstellar clouds. This supplement covers the literature from 1986 through 1991, with some additional citations missed in the original survey. Over 200 new citations are included. A table of reactions is listed by reactant ion, and cross-references are provided for both ionic and neutral reactants and also for both ionic and neutral products.

Aluminum Foils of the Stardust Interstellar Collector: The Challenge of Recognizing Micrometer-sized Impact Craters made by Interstellar Grains

NASA Technical Reports Server (NTRS)

Kearsley, A. T.; Westphal, A. J.; Burchell, M. J.; Zolensky, Michael E.

2008-01-01

Preliminary Examination (PE) of the Stardust cometary collector revealed material embedded in aerogel and on aluminium (Al) foil. Large numbers of sub-micrometer impact craters gave size, structural and compositional information. With experience of finding and analyzing the picogram to nanogram mass remains of cometary particles, are we now ready for PE of the Interstellar (IS) collector? Possible interstellar particle (ISP) tracks in the aerogel are being identified by the stardust@home team. We are now assessing challenges facing PE of Al foils from the interstellar collector.

Extended atmospheres of outer planet satellites and comets

NASA Technical Reports Server (NTRS)

Smyth, W. H.; Combi, M. R.

1985-01-01

Collisions between neutral hydrogen atoms in the interstellar medium and those in the so-called Titan hydrogen torus may provide an additional lifetime sink for atoms in the Saturn environment. Progress toward re-sorting the Voyager UVS scans of neutral hydrogen in the Saturn system to enable both a factor of two increase in the amount of data to be analyzed as well as to help identify near-Titan hydrogen is discussed. Progress toward development of the cometary carbon and oxygen models is also discussed and a preliminary model run for the H2O source of cometary oxygen is presented.

Near-tail reconnection as the cause of cometary tail disconnections

NASA Technical Reports Server (NTRS)

Russell, C. T.; Saunders, M. A.; Phillips, J. L.; Fedder, J. A.

1986-01-01

In a cometary tail disconnection event the plasma tail appears to separate from the coma and to accelerate away from it. As this occurs a new tail begins to form. It is proposed that these disconnections arise in a manner analogous to geomagnetic substorms, i.e., by the formation of a strongly reconnecting region in the near tail that forms a magnetic island in the coma and ejects the plasma tail by strengthening the magnetic 'slingshot' within the tail. This reconnection process may be triggered by several different processes, such as interplanetary shocks or variations in the Alfven Mach number.

2060 Chiron - Colorimetry and cometary behavior

NASA Technical Reports Server (NTRS)

Hartmann, William K.; Tholen, David J.; Meech, Karen J.; Cruikshank, Dale P.

1990-01-01

Ambiguities concerning the fit of the 2060 Chiron's visible spectrum to its IR spectrum have been resolved by resort to VRIJHK colorimetry obtained in 1988, which also confirms the neutrality of Chiron's taxonomic class C spectrum and indicates that Chiron has anomalously brightened since 1980-1983. This brightening, and one reported in 1978, are consistent with the hypothesis that Chiron sporadically undergoes weak cometary outbursts similar to those of comet P/Schwassmann-Wachmann 1; Chiron is further speculated to be an ice-rich object darkened by C-class carbonaceous soil, and may have been scattered from the Oort cloud in recent solar system history.

An Observational Test for Shock-induced Crystallization of Cometary Silicates

NASA Technical Reports Server (NTRS)

Nuth, J. A.; Johnson, N. M.

2003-01-01

Crystalline silicates have been observed in comets and in protostellar nebulae, and there are currently at least two explanations for their formation: thermal annealing in the inner nebula, followed by transport to the regions of cometary formation and in-situ shock processing of amorphous grains at 5 - 10 AU in the Solar Nebula. The tests suggested to date to validate these models have not yet been carried out: some of these tests require a longterm commitment to observe both the dust and gas compositions in a large number of comets. Here we suggest a simpler test.

How MIDAS improved our understanding of micrometre-sized cometary dust

NASA Astrophysics Data System (ADS)

Mannel, T.; Bentley, M. S.; Boakes, P.; Jeszenszky, H.; Levasseur-Regourd, A. C.; Schmied, R.; Torkar, K.

2017-09-01

The MIDAS atomic force microscope on the Rosetta orbiter was an instrument developed to investigate, for the first time, the morphology of nearly unaltered cometary dust. It acquired the 3D topography of about 1 - 50 µm sized dust particles with resolutions down to a few nanometres. These images showed the agglomerate character of the dust and confirmed that the smallest subunit sizes were less than 100 nm. MIDAS acquired the first direct proof of a fractal dust particle, opening a new approach to investigate the history of our early Solar System and of comets.

Possible consequences of absence of "Jupiters" in planetary systems.

PubMed

Wetherill, G W

1994-01-01

The formation of the gas giant planets Jupiter and Saturn probably required the growth of massive approximately 15 Earth-mass cores on a time scale shorter than the approximately 10(7) time scale for removal of nebular gas. Relatively minor variations in nebular parameters could preclude the growth of full-size gas giants even in systems in which the terrestrial planet region is similar to our own. Systems containing "failed Jupiters," resembling Uranus and Neptune in their failure to capture much nebular gas, would be expected to contain more densely populated cometary source regions. They will also eject a smaller number of comets into interstellar space. If systems of this kind were the norm, observation of hyperbolic comets would be unexpected. Monte Carlo calculations of the orbital evolution of region of such systems (the Kuiper belt) indicate that throughout Earth history the cometary impact flux in their terrestrial planet regions would be approximately 1000 times greater than in our Solar System. It may be speculated that this could frustrate the evolution of organisms that observe and seek to understand their planetary system. For this reason our observation of these planets in our Solar System may tell us nothing about the probability of similar gas giants occurring in other planetary systems. This situation can be corrected by observation of an unbiased sample of planetary systems.

A Survey of Rotation Lightcurves of Small Jovian Trojan Asteroids in the L4 Cloud

NASA Astrophysics Data System (ADS)

French, Linda M.; Stephens, Robert; Warner, Brian; James, David; Rohl, Derrick; Connour, Kyle

2017-10-01

Jovian Trojan asteroids are of interest both as objects in their own right and as possible relics of Solar System formation. Several lines of evidence support a common origin for, and possible hereditary link between, Jovian Trojan asteroids and cometary nuclei. Asteroid lightcurves give information about processes that have affected a group of asteroids including their density. Due to their distance and low albedos, few comet-sized Trojans have been studied. We have been carrying out a survey of Trojan lightcurve properties comparing small Trojan asteroids with comets (French et al 2015). We present new lightcurve information for 39 Trojans less than about 35 km in diameter. We report our latest results and compare them with results from the sparsely-sampled lightcurves from the Palomar Transient Factory (Waszazak et al., Chang et al. 2015). The minimum densities for objects with complete lightcurves are estimated and are found to becomparable to those measured for cometary nuclei. A significant fraction (~40%) of thisobserved small Trojan population rotates slowly (P > 24 hours), with measured periods as over 500 hours (Waszczak et al 2015). The excess of slow rotators may be due to the YORP effect. Results of the Kolmogorov-Smirnov test suggest that the distribution of Trojan rotation rates is dissimilar to those of Main Belt Asteroids of the same size.

X-Ray Computed Tomography: The First Step in Mars Sample Return Processing

NASA Technical Reports Server (NTRS)

Welzenbach, L. C.; Fries, M. D.; Grady, M. M.; Greenwood, R. C.; McCubbin, F. M.; Zeigler, R. A.; Smith, C. L.; Steele, A.

2017-01-01

The Mars 2020 rover mission will collect and cache samples from the martian surface for possible retrieval and subsequent return to Earth. If the samples are returned, that mission would likely present an opportunity to analyze returned Mars samples within a geologic context on Mars. In addition, it may provide definitive information about the existence of past or present life on Mars. Mars sample return presents unique challenges for the collection, containment, transport, curation and processing of samples [1] Foremost in the processing of returned samples are the closely paired considerations of life detection and Planetary Protection. In order to achieve Mars Sample Return (MSR) science goals, reliable analyses will depend on overcoming some challenging signal/noise-related issues where sparse martian organic compounds must be reliably analyzed against the contamination background. While reliable analyses will depend on initial clean acquisition and robust documentation of all aspects of developing and managing the cache [2], there needs to be a reliable sample handling and analysis procedure that accounts for a variety of materials which may or may not contain evidence of past or present martian life. A recent report [3] suggests that a defined set of measurements should be made to effectively inform both science and Planetary Protection, when applied in the context of the two competing null hypotheses: 1) that there is no detectable life in the samples; or 2) that there is martian life in the samples. The defined measurements would include a phased approach that would be accepted by the community to preserve the bulk of the material, but provide unambiguous science data that can be used and interpreted by various disciplines. Fore-most is the concern that the initial steps would ensure the pristine nature of the samples. Preliminary, non-invasive techniques such as computed X-ray tomography (XCT) have been suggested as the first method to interrogate and characterize the cached samples without altering the materials [1,2]. A recent report [4] indicates that XCT may minimally alter samples for some techniques, and work is needed to quantify these effects, maximizing science return from XCT initial analysis while minimizing effects.

Downselection for Sample Return — Defining Sampling Strategies Using Lessons from Terrestrial Field Analogues

NASA Astrophysics Data System (ADS)

Stevens, A. H.; Gentry, D.; Amador, E.; Cable, M. L.; Cantrell, T.; Chaudry, N.; Cullen, T.; Duca, Z.; Jacobsen, M.; Kirby, J.; McCaig, H.; Murukesan, G.; Rader, E.; Rennie, V.; Schwieterman, E.; Sutton, S.; Tan, G.; Yin, C.; Cullen, D.; Geppert, W.; Stockton, A.

2018-04-01

We detail multi-year field investigations in Icelandic Mars analogue environments that have yielded results that can help inform strategies for sample selection and downselection for Mars Sample Return.

Deciphering Martian climatic history using returned samples

NASA Technical Reports Server (NTRS)

Paige, D. A.; Krieger, D. B.; Brigham, C. A.

1988-01-01

By necessity, a Mars sample return mission must sample the upper few meters of the Martian surface. This material was subjected to a wide variety of physical processes. Presently, the most important processes are believed to be wind-driven erosion and deposition, and water ice accumulation at higher latitudes. A sample return mission represents an opportunity to better understand and quantify these important geological processes. By obtaining sample cores at key locations, it may be possible to interpret much of recent Martian climatic history.

Near-parabolic comets observed in 2006-2010 - II. Their past and future motion under the influence of the Galaxy field and known nearby stars

NASA Astrophysics Data System (ADS)

Dybczyński, Piotr A.; Królikowska, Małgorzata

2015-03-01

In the first part of this research we extensively investigated and carefully determined osculating, original (when entering Solar system) and future (when leaving it), orbits of 22 near-parabolic comets with small perihelion distance (qosc < 3.1 au), discovered in years 2006-2010. Here, we continue this research with a detailed study of their past and future motion during previous and next orbital periods under the perturbing action of our Galactic environment. At all stages of our dynamical study, we precisely propagate in time the observational uncertainties of cometary orbits. For the first time in our calculations, we fully take into account individual perturbations from all known stars or stellar systems that closely (less than 3.5 pc) approach the Sun during the cometary motion in the investigated time interval of several million years. This is done by means of a direct numerical integration of the N-body system comprising of a comet, the Sun and 90 potential stellar perturbers. We show a full review of various examples of individual stellar action on cometary motion. We conclude that perturbations from all known stars or stellar systems do not change the overall picture of the past orbit evolution of long-period comets. Their future motion might be seriously perturbed during the predicted close approach of Gliese 710 star but we do not observe significant energy changes. The importance of stellar perturbations is tested on the whole sample of 108 comets investigated by us so far and our previous results, obtained with only Galactic perturbations included, are fully confirmed. We present how our results can be used to discriminate between dynamically new and old near-parabolic comets and discuss the relevance of the so-called Jupiter-Saturn barrier phenomenon. Finally, we show how the Oort spike in the 1/a-distribution of near-parabolic comets is built from both dynamically new and old comets. We also point out that C/2007 W1 seems to be the first serious candidate for interstellar provenance.

Link between interplanetary & cometary dust: Polarimetric observations and space studies with Rosetta & Eye-Sat

NASA Astrophysics Data System (ADS)

Levasseur-Regourd, Anny-Chantal; Gaboriaud, Alain; Buil, Christian; Ressouche, Antoine; Lasue, J.; Palun, Adrien; Apper, Fabien; Elmaleh, Marc

Intensity and linear polarization observations of the solar light scattered by interplanetary dust, the so-called zodiacal light, provide information on properties of the dust particles, such as their spatial density, local changes, morphology and albedo. Earth-based polarimetric observations, with a resolution of 5° or more, have been used to derive the polarization phase curve of interplanetary dust particles and to establish that the polarization at 90° phase angle increases with increasing solar distance, at least up to 1.5 au in the ecliptic, while the albedo decreases [1, 2]. Analysis of such studies will be revisited. Numerical simulations of the polarimetric behavior of interplanetary dust particles strongly suggest that, in the inner solar system, interplanetary dust particles consist of absorbing (e.g., organic compounds) and less absorbing (e.g., silicates) materials, that radial changes originate in a decrease of organics with decreasing solar distance (probably due to alteration processes), and that a significant fraction of the interplanetary dust is of cometary origin, in agreement with dynamical studies [3, 4]. The polarimetric behaviors of interplanetary dust and cometary dust particles seem to present striking similarities. The properties of cometary dust particles, as derived from remote polarimetric observations of comets including 67P/Churyumov-Gerasimenko, the target of the Rosetta rendezvous mission, at various wavelengths, will be summarized [5, 6]. The ground truth expected from Rosetta dust experiments, i.e., MIDAS, COSIMA, GIADA, about dust particles’ morphology, composition, and evolution (with distance to the nucleus before Philae release and with distance to the Sun before and after perihelion passage) over the year and a half of nominal mission, will be discussed. Finally, the Eye-Sat nanosatellite will be presented. This triple cubesat, developed by students from engineering schools working as interns at CNES, is to be launched in 2016 [7]. Its main purpose is to study the zodiacal light intensity and polarization from a Sun-synchronous orbit, for the first time at the high spatial resolution of 1° over a wide portion of the sky and at four different wavelengths (in the visible and near-IR domains). The instrumental choices and new on-board technologies will be summarized, together with the results that may be expected on local properties of the interplanetary dust particles and thus on their similarities and differences with cometary dust particles. Support from CNES is warmly acknowledged. [1] Leinert, C., Bowyer, S., Haikala, L.K., et al. The 1997 reference of diffuse night sky brightness, Astron. Astrophys. Supp., 127, 1-99, 1998. [2] Levasseur-Regourd, A.C., Mann, I., Dumont, R., et al. Optical and thermal properties of interplanetary dust. In Interplanetary dust (Grün, E. et al. Eds), 57-94, Springer-Verlag, Berlin, 2001. [3] Lasue, J., Levasseur-Regourd, A.C., Fray, N., et al. Inferring the interplanetary dust properties from remote observations and simulations, Astron. Astrophys., 473, 641-649, 2007. [4] Nesvorny, D., Jenniskens, P., Levison, H.F., et al. Cometary origin of the zodiacal cloud and carbonaceous micrometeorites: implications for hot debris disks. Astrophys. J. 713, 816-836, 2010. [5] Levasseur-Regourd, A.C., Mukai, T., Lasue, J., et al. Physical properties of cometary and interplanetary dust, Planet. Space Sci., 55, 1010-1020, 2007. [6] Hadamcik, E., Sen, A.K., Levasseur-Regourd, A.C., et al., Astron. Astrophys., 517, A86, 2010. [7] CNES internal report. Eye-Sat end of phase A internal review, EYESAT-PR-0-022-CNES, 2013.

Synchronized Lunar Pole Impact Plume Sample Return Trajectory Design

NASA Technical Reports Server (NTRS)

Genova, Anthony L.; Foster, Cyrus; Colaprete, Tony

2016-01-01

The presented trajectory design enables two maneuverable spacecraft launched onto the same trans-lunar injection trajectory to coordinate a steep impact of a lunar pole and subsequent sample return of the ejecta plume to Earth. To demonstrate this concept, the impactor is assumed to use the LCROSS missions trajectory and spacecraft architecture, thus the permanently-shadowed Cabeus crater on the lunar south pole is assumed as the impact site. The sample-return spacecraft is assumed to be a CubeSat that requires a complimentary trajectory design that avoids lunar impact after passing through the ejecta plume to enable sample-return to Earth via atmospheric entry.

A New 3D Multi-fluid Dust Model: A Study of the Effects of Activity and Nucleus Rotation on Dust Grain Behavior at Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Shou, Y.; Combi, M.; Toth, G.; Tenishev, V.; Fougere, N.; Jia, X.; Rubin, M.; Huang, Z.; Hansen, K.; Gombosi, T.

2017-11-01

Improving our capability to interpret observations of cometary dust is necessary to deepen our understanding of the role of dust in the formation of comets and in altering the cometary environments. Models including dust grains are in demand to interpret observations and test hypotheses. Several existing models have taken into account the gas-dust interaction, varying sizes of dust grains and the cometary gravitational force. In this work, we develop a multi-fluid dust model based on the BATS-R-US code. This model not only incorporates key features of previous dust models, but also has the capability of simulating time-dependent phenomena. Since the model is run in the rotating comet reference frame, the centrifugal and Coriolis forces are included. The boundary conditions on the nucleus surface can be set according to the distribution of activity and the solar illumination. The Sun revolves around the comet in this frame. A newly developed numerical mesh is also used to resolve the real-shaped nucleus in the center and to facilitate prescription of the outer boundary conditions that accommodate the rotating frame. The inner part of the mesh is a box composed of Cartesian cells and the outer surface is a smooth sphere, with stretched cells filled in between the box and the sphere. Our model achieved comparable results to the Direct Simulation Monte Carlo method and the Rosetta/OSIRIS observations. It is also applied to study the effects of the rotating nucleus and the cometary activity and offers interpretations of some dust observations of comet 67P/Churyumov-Gerasimenko.

A new 3D multi-fluid dust model: a study of the effects of activity and nucleus rotation on the dust grains' behavior in the cometary environment

NASA Astrophysics Data System (ADS)

Shou, Y.; Combi, M. R.; Toth, G.; Fougere, N.; Tenishev, V.; Huang, Z.; Jia, X.; Hansen, K. C.; Gombosi, T. I.; Bieler, A. M.; Rubin, M.

2016-12-01

Cometary dust observations may deepen our understanding of the role of dust in the formation of comets and in altering the cometary environment. Models including dust grains are in demand to interpret observations and test hypotheses. Several existing models have taken into account the gas-dust interaction, varying sizes of dust grains and the cometary gravitational force. In this work, we develop a multi-fluid dust model based on BATS-R-US in the University of Michigan's Space Weather Modeling Framework (SWMF). This model not only incorporates key features of previous dust models, but also has the capability of simulating time-dependent phenomena. Since the model is running in the rotating comet reference frame with a real shaped nucleus in the computational domain, the fictitious centrifugal and Coriolis forces are included. The boundary condition on the nucleus surface can be set according to the distribution of activity and the solar illumination. The Sun, which drives sublimation and the radiation pressure force, revolves around the comet in this frame. A newly developed numerical mesh is also used to resolve the real shaped nucleus in the center and to facilitate prescription of the outer boundary conditions that accommodate the rotating frame. The inner part of the grid is a box composed of Cartesian cells and the outer surface is a smooth sphere, with stretched cells filled in between the box and the sphere. The effects of the rotating nucleus and the activity region on the surface are discussed and preliminary results are presented. This work has been partially supported by grant NNX14AG84G from the NASA Planetary Atmospheres Program, and US Rosetta contracts JPL #1266313, JPL #1266314 and JPL #1286489.

The discovery of cometary activity in near-Earth asteroid (3552) Don Quixote

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mommert, Michael; Harris, Alan W.; Hora, Joseph L.

The near-Earth object (NEO) population, which mainly consists of fragments from collisions between asteroids in the main asteroid belt, is thought to include contributions from short-period comets as well. One of the most promising NEO candidates for a cometary origin is near-Earth asteroid (3552) Don Quixote, which has never been reported to show activity. Here we present the discovery of cometary activity in Don Quixote based on thermal-infrared observations made with the Spitzer Space Telescope in its 3.6 and 4.5 μm bands. Our observations clearly show the presence of a coma and a tail in the 4.5 μm but notmore » in the 3.6 μm band, which is consistent with molecular band emission from CO{sub 2}. Thermal modeling of the combined photometric data on Don Quixote reveals a diameter of 18.4{sub −0.4}{sup +0.3} km and an albedo of 0.03{sub −0.01}{sup +0.02}, which confirms Don Quixote to be the third-largest known NEO. We derive an upper limit on the dust production rate of 1.9 kg s{sup –1} and derive a CO{sub 2} gas production rate of (1.1 ± 0.1) × 10{sup 26} molecules s{sup –1}. Spitzer Infrared Spectrograph spectroscopic observations indicate the presence of fine-grained silicates, perhaps pyroxene rich, on the surface of Don Quixote. Our discovery suggests that CO{sub 2} can be present in near-Earth space over a long time. The presence of CO{sub 2} might also explain that Don Quixote's cometary nature remained hidden for nearly three decades.« less

Infrared Spectroscopy of HR 4796A's Bright Outer Cometary Ring + Tenuous Inner Hot Dust Cloud

NASA Astrophysics Data System (ADS)

Lisse, C. M.; Sitko, M. L.; Marengo, M.; Vervack, R. J., Jr.; Fernandez, Y. R.; Mittal, T.; Chen, C. H.

2017-11-01

We have obtained new NASA/IRTF SpeX spectra of the HR 4796A debris ring system. We find a unique red excess flux that extends out to ˜9 μm in Spitzer IRS spectra, where thermal emission from cold, ˜100 K dust from the system’s ring at ˜75 au takes over. Matching imaging ring photometry, we find the excess consists of NIR reflectance from the ring, which is as red as that of old, processed comet nuclei, plus a tenuous thermal emission component from close-in, T ˜ 850 K circumstellar material evincing an organic/silicate emission feature complex at 7-13 μm. Unusual, emission-like features due to atomic Si, S, Ca, and Sr were found at 0.96-1.07 μm, likely sourced by rocky dust evaporating in the 850 K component. An empirical cometary dust phase function can reproduce the scattered light excess and 1:5 balance of scattered versus thermal energy for the ring with optical depth < τ > ≥slant 0.10 in an 8 au wide belt of 4 au vertical height and M dust > 0.1-0.7 M Mars. Our results are consistent with HR 4796A, consisting of a narrow shepherded ring of devolatilized cometary material associated with multiple rocky planetesimal subcores and a small steady stream of dust inflowing from this belt to a rock sublimation zone at ˜1 au from the primary. These subcores were built from comets that have been actively emitting large, reddish dust for >0.4 Myr at ˜100 K, the temperature at which cometary activity onset is seen in our solar system.

Dynamical and Physical Models of Ecliptic Comets

NASA Astrophysics Data System (ADS)

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

2005-08-01

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

Production and optical constraints of ice tholin from charged particle irradiation of (1:6) C2H6/H2O at 77 K

NASA Astrophysics Data System (ADS)

Khare, B. N.; Thompson, W. R.; Cheng, L.; Chyba, C.; Sagan, C.; Arakawa, E. T.; Meisse, C.; Tuminello, P. S.

1993-06-01

Fifty separate irradiations of a 6:1 mixture of H2O/C2H6 ice conducted over a 5-month period have yielded sufficient tholin for the determination of its physical constants in the 0.06 to 40 micron range. While the imaginary part of the refractive index k was obtained by transmission measurements on thin-film samples and Kramers-Kronig analysis (KKA), the real part of the refractive index was obtained by KKA and ellipsometry; these data may prove useful in cometary and outer solar system spectrometric interpretation.

Comparing the biocidal properties of non-thermal plasma sources by reference protocol

NASA Astrophysics Data System (ADS)

Khun, Josef; Jirešová, Jana; Kujalová, Lucie; Hozák, Pavel; Scholtz, Vladimír

2017-10-01

The previously proposed reference protocol enabling easy comparison of biocidal properties of different non-thermal plasma sources has been followed and discussed. For inactivation tests the reference protocol has used spores of Gram positive bacterium Bacillus subtilis (ATCC 6633) deposited on a polycarbonate membrane as reference sample. In this work, biocidal properties of a negative glow corona, positive streamer corona, positive transient spark and cometary discharges are being compared in both open air and closed apparatus. Despite the total number of bacteria surviving 1 h exposure has decreased by up to 7 orders in closed apparatus, in open one, only weak inhibition bactericidal effect has been observed.