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NASA NTRS1991

Allegheny Observatory search for planetary systems

The newly developed Multichannel Astrometric Photometer (MAP) and a rebuilt red light 0.76 meter Thaw refractor are used in an astrometric observational program to detect Jupiter-like planets in orbit about nearby stars. The program includes 15 stars and is obtaining approx. 12 good observations per year of each of them, sufficient to assure an annual normal point precision of 0.001 arcsec (1 mas) per object. The observational program will yield the first astrometric information about planetary systems in general. The astrometric technique is most sensitive to nearby planetary systems and to massive planets that have orbits that place them within the regions around a star where the temperature is sufficiently low to permit the existence of water ice grains. Thus it covers a different search space than that of radial velocity techniques. Currently the only astrometric survey program, it is complementary to other detection programs and some target stars have been included to assure overlap with them. The minimum detectable mass varies with the particular target star from objects almost twice as massive as Neptune to bodies almost twice as massive as Jupiter.

Gatewood, George D.↗

NASA NTRS1993

A model for the hydrologic and climatic behavior of water on Mars

An analysis is carried out of the hydrologic response of a water-rich Mars to climate change and to the physical and thermal evolution of its crust, with particular attention given to the potential role of the subsurface transport, assuming that the current models of insolation-driven change describe reasonably the atmospheric leg of the planet's long-term hydrologic cycle. Among the items considered are the thermal and hydrologic properties of the crust, the potential distribution of ground ice and ground water, the stability and replenishment of equatorial ground ice, basal melting and the polar mass balance, the thermal evolution of the early cryosphere, the recharge of the valley networks and outflow, and several processes that are likely to drive the large-scale vertical and horizontal transport of H2O within the crust. The results lead to the conclusion that subsurface transport has likely played an important role in the geomorphic evolution of the Martian surface and the long-term cycling of H2O between the atmosphere, polar caps, and near-surface crust.

Clifford, Stephen M.↗

NASA NTRS2006

NASA Laboratory Astrophysics Workshop 2006 Introductory Remarks

NASA Laboratory Astrophysics Workshop 2006, is the fourth in a series of workshops held at four year intervals, to assess the laboratory needs of NASA's astrophysics missions - past, current and future. Investigators who need laboratory data to interpret their observations from space missions, theorists and modelers, experimentalists who produce the data, and scientists who compile databases have an opportunity to exchange ideas and understand each other's needs and limitations. The multi-wavelength character of these workshops allows cross-fertilization of ideas, raises awareness in the scientific community of the rapid advances in other fields, and the challenges it faces in prioritizing its laboratory needs in a tight budget environment. Currently, we are in the golden age of Space Astronomy, with three of NASA s Great Observatories, Hubble Space Telescope (HST), Chandra X-Ray Observatory (CXO), and Spitzer Space Telescope (SST), in operation and providing astronomers and opportunity to perform synergistic observations. In addition, the Far Ultraviolet Spectroscopic Explorer (FUSE), XMM-Newton, HETE-2, Galaxy Evolution Explorer (GALEX), INTEGRAL and Wilkinson Microwave Anisotropy Probe (WMAP), are operating in an extended phase, while Swift and Suzaku are in their prime phase of operations. The wealth of data from these missions is stretching the Laboratory Astrophysics program to its limits. Missions in the future, which also need such data include the James Webb Space Telescope (JWST), Space Interferometry Mission (SIM), Constellation-X (Con-X), Herschel, and Planck. The interpretation of spectroscopic data from these missions requires knowledge of atomic and molecular parameters such as transition probabilities, f-values, oscillator strengths, excitation cross sections, collision strengths, which have either to be measured in the laboratory by simulating space plasma and interactions therein, or by theoretical calculations and modeling. Once the laboratory data are obtained, a key step to making them available to the observer is the creation and maintenance of critically compiled databases. Other areas of study, that are important for understanding planet formation, and for detection of molecules that are indicators of life, are also supported by the Laboratory Astrophysics program. Some examples are: studies of ices and dust grains in a space environment; nature and evolution of interstellar carbon-rich dust; and polycyclic aromatic hydrocarbons. In addition, the program provides an opportunity for the investigation of novel ideas, such as simulating radiative shock instabilities in plasmas, in order to understand jets observed in space. A snapshot of the currently funded program, mission needs, and relevance of laboratory data to interpreting observations, will be obtained at this workshop through invited and contributed talks and poster papers. These will form the basis for discussions in splinter groups. The Science Organization Committee will integrate the results of the discussions into a coherent White Paper, which will provide guidance to NASA in structuring the Laboratory Astrophysics program in subsequent years, and also to the scientific community in submitting research proposals to NASA for funding.

Hasan, Hashima↗

NASA NTRS2008

Mars Mapping Technology Brings Main Street to Life

The Red Planet has long held a particular hold on the human psyche. From the Roman god of war to Orson Welles infamous Halloween broadcast, our nearest planetary neighbor has been viewed with curiosity, suspicion, and awe. Pictures of Mars from 1965 to the present reveal familiar landscapes while also challenging our perceptions and revising our understanding of the processes at work in planets. Frequent discoveries have forced significant revisions to previous theories. Although Mars shares many familiar features with Earth, such as mountains, plains, valleys, and polar ice, the conditions on Mars can vary wildly from those with which we are familiar. The apparently cold, rocky, and dusty wasteland seen through the eyes of spacecraft and Martian probes hints at a dynamic past of volcanic activity, cataclysmic meteors, and raging waters. New discoveries continue to revise our view of our next-door neighbor, and further exploration is now paving the way for a human sortie to the fourth stone from the Sun. NASA s Mars Exploration Program, a long-term effort of robotic exploration, utilizes wide-angle stereo cameras mounted on NASA s twin robot geologists, the Mars Exploration Rovers (MERs), launched in 2003. The rovers, named "Spirit" and "Opportunity," celebrated 4 Earth years of exploration on January 3, 2008, and have sent back a wealth of information on the terrain and composition of the Martian surface. Their marathon performance has far outlasted the intended 90 days of operation, and the two intrepid explorers promise more images and data.

Source record↗

NASA NTRS2016

Volatile Analysis by Pyrolysis of Regolith (Vapor) for Planetary Resource Prospecting

Measuring the chemical composition of planetary bodies and their atmospheres is key to understanding the formation of the Solar System and the evolution of the planets and their moons. In situ volatile measurements enable a ground-truth assessment of the distribution and abundance of resources such as water-ice and oxygen, important for a sustained human presence on the Moon and beyond. The Volatile Analysis by Pyrolysis of Regolith (VAPoR) instrument is a compact pyrolysis mass spectrometer designed to detect volatiles released from solid samples that are heated to elevated temperatures and is one technique that should be considered for resource prospecting on the Moon, Mars, and asteroids.

regolith↗

NASA NTRSDate not supplied

Researching the Planetary Environment with an Interstellar Probe

In 2018, a study originated with the idea of a mission that would be feasible to launch in the 2030s, targeting 1000 AU within 50 years using current technology. While the primary objective of such an Interstellar Probe would be to understand the heliosphere and interstellar medium, this probe offers an excellent opportunity for rock, dust, and ice sciences. In the initial stages of its journey through the solar system, this Interstellar Probe would carry out a wide range of potential observations to study the planetary environment, particularly focusing on dust/ice analysis and planetary science through fly-bys of critical science targets, especially in the trans-Neptunian region. A flyby of a trans-Neptunian dwarf planet, such as Quaoar, would provide further geological, compositional, and geophysical context for Earth-based observations. Aside from in-situ remote sensing techniques, VISIR and dust analyses would also benefit in this region of the solar system to determine (i) dominant ice and dust compositions and potential variations depending on heliocentric distance (e.g., chemical or irradiated products); (ii) collections and identification of PAH-type components; and (iii) solar nebula chemical and mechanical processing, such as collisions. The purpose of our poster is to provide a background of the Interstellar Probe’s objectives and possible instrumentation to offer insight on current questions about the planetary environment.

C J Ahrens↗

NASA NTRS1994

Evidence, age, and thickness of a frozen Paleolake in Utopia Planitia, Mars

Recent mapping studies west of Elysium Mons, Mars, have pinpointed subice features that suggest the existence of a frozen paleolake in Utopia Planitia as recently as 1.8 billion years ago. The subice features are interpreted to be hyaloclastic ridges and hills, table moutains, associated joekulhalaup deposits, and fluvial channels. Photoclinometric studies of these features and of a basal scarp around the northwest flank of Elysium Mons interpreted to have been an ice-sheet boundary indicate that the maximum thickness of ice within the basin may have been about 180 m. This thickness of ice during a relatively late stage of Martian geologic history would have important implications concerning the atmospheric, the climatic, and possibly the exobiologic history of the planet.

Chapman, Mary G.↗

NASA NTRS2005

Astrobiological and Geological Implications of Convective Transport in Icy Outer Planet Satellites

The oceans of large icy outer planet satellites are prime targets in the search for extraterrestrial life in our solar system. The goal of our project has been to develop models of ice convection in order to understand convection as an astrobiologically relevant transport mechanism within icy satellites, especially Europa. These models provide valuable constraints on modes of surface deformation and thus the implications of satellite surface geology for astrobiology, and for planetary protection. Over the term of this project, significant progress has been made in three areas: (1) the initiation of convection in large icy satellites, which we find probably requires tidal heating; (2) the relationship of surface features on Europa to internal ice convection, including the likely role of low-melting-temperature impurities; and (3) the effectiveness of convection as an agent of icy satellite surface-ocean material exchange, which seems most plausible if tidal heating, compositional buoyancy, and solid-state convection work in combination. Descriptions of associated publications include: 3 published papers (including contributions to 1 review chapter), 1 manuscript in revision, 1 manuscript in preparation (currently being completed under separate funding), and 1 published popular article. A myriad of conference abstracts have also been published, and only those from the past year are listed.

Pappalardo, Robert T.↗

NASA NTRS2015

The Formation of Complex Organic Compounds in Astrophysical Ices and their Implications for Astrobiology

Ices in astrophysical environments are generally dominated by very simple molecules like H2O, CH3OH, CH4, NH3, CO, CO2, etc, although they likely contain PAHs as well. These molecules, particularly H2O, are of direct interest to astrobiology in-and-of themselves since they represent some of the main carriers of the biogenic elements C, H, O, and N. In addition, these compounds are present in the dense interstellar clouds in which new stars and planetary systems are formed and may play a large role in the delivery of volatiles and organics to the surfaces of new planets. However, these molecules are all far simpler than the more complex organic compounds found in living systems.

UV Irradiation↗

NASA NTRS1994

The determination of the mass and mean density of Enceladus from its observed shape

Application of limb-fitting methods to the 11 best Voyager 2 images of Enceladus has shown that the shape of this satellite is closely represented by a triaxial ellipsoid. The observed ratio of the differences of the principal axes F = (b - c)/(a - c) is 0.23 (sup +0.04 sub - 0.01), consisting with the value F = 0.23 expected for a synchronously rotating satellite in hydrostatic equilibrium. We also deduce from the Voyager observations, after allowing for limb topography, that the mean radius of the satellite is 249.4 +/- 0.2 km. For satellites of known mass, measurement of the size and shape leads to a determination of the satellite's mean density and moment of inertial. We have used this method to determine the moments of inertia of Mimas (1988) and Tethys (1991). Enceladus appears to be hydrostatically relaxed, making it an ideal candidate for this type of analysis. However, none of the Pioneer or Voyager spacecraft had a close encounter with this satellite and thus its mass is effectively unknown. Enceladus is trapped in a 2:1 orbit-orbit resonance with Dione, but the amplitudes of libration are too small to allow a useful mass determination. Using the observed shape alone, without any other assumptions other than that the satellite is in hydrostatic equilibrium at its present orbital radius, we place an upper bound on the mean density of 1.12 +/- 0.05 g/cu cm. Thus, the mean density of Enceladus is probably little more than that of water-ice and we conclude that this satellite is markedly deficient in rock. If the mass of a satellite is unknown, but the satellite is differentiated and has a deep mantle of known composition, then we show that measurement of the shape alone can lead to a determination of the satellite's mass, mean density, and moment of inertia. Application of this method to Enceladus, assuming that the satellite has a deep mantle of water-ice of density 0.93 g/cu cm, gives the result that the mean density of the satellite is 1.00 +/- 0.03 g/cu cm. This result fills the one remaining gap in our knowledge of the structure of the Saturnian satellite system. We now know the mean densities of all the primary Saturnian satellites in the sequence from the coorbital satellites, Janus and Epimetheus, through to the outer satellite Iapetus (the densities of the small, secondary satellites in Trojan-type orbits are still unknown). The Saturnian system possesses two striking features. (1) Because of significant porosity, the mean material densities of the satellites Janus, Epimetheus, and Mimas could be substantially greater than the apparent mean densities of these satellies. (2) The densities of the satellites are not correlated with their distances from the planet; in particular, the satellites Enceladus and Tethys have lower mean densities than their interior and exterior neighbors, Mimas and Dione. This may be the result of gross postformation redistribution of rock and ice, possibly due to satellite disruptions are suggested by Smith et al. (1982).

Dermott, Stanley F.↗

NASA NTRS1996

Spectroscopic Evidence for Interstellar Ice in Comet Hyakutake

Volatile compounds in comets are the most pristine materials surviving from the time of formation of the Solar System, and thus potentially provide information about conditions that prevailed in the primitive solar material. Moreover, comets may have supplied a substantial fraction of the volatiles on the terrestrial planets, perhaps including organic compounds that played a role in the origin of life on Earth. Here we report the detection of hydrogen isocyanide (HNC) in comet Hyakutake. The abundance of HNC relative to hydrogen cyanide (HCN) is very similar to that observed in quiescent interstellar molecular clouds, and quite different from the equilibrium ratio expected in the outermost solar nebula, where comets are thought to form. Such a departure from equilibrium has long been considered a hallmark of gas-phase chemical processing in the interstellar medium, suggesting that interstellar gases have been incorporated into the comet's nucleus, perhaps as ices frozen onto interstellar grains. If this interpretation is correct, our results should provide constraints on the temperature of the solar nebula, and the subsequent chemical processes that occurred in the region where comets formed.

Irvine, W. M.↗

NASA NTRS1996

Spectroscopic evidence for interstellar ices in comet Hyakutake

Volatile compounds in comets are the most pristine materials surviving from the time of formation of the Solar System, and thus potentially provide information about conditions that prevailed in the primitive solar nebula. Moreover, comets may have supplied a substantial fraction of the volatiles on the terrestrial planets, perhaps including organic compounds that played a role in the origin of life on Earth. Here we report the detection of hydrogen isocyanide (HNC) in comet Hyakutake. The abundance of HNC relative to hydrogen cyanide (HCN) is very similar to that observed in quiescent interstellar molecular clouds, and quite different from the equilibrium ratio expected in the outermost solar nebula, where comets are thought to form. Such a departure from equilibrium has long been considered a hallmark of gas-phase chemical processing in the interstellar medium, suggesting that interstellar gases have been incorporated into the comet's nucleus, perhaps as ices frozen onto interstellar grains. If this interpretation is correct, our results should provide constraints on the temperature of the solar nebula, and the subsequent chemical processes that occurred in the region where comets formed.

Non-NASA Center↗

NASA NTRS2001

Water Ice and Life's Roots in Space

Nearly three decades ago as Voyager 2 spacecraft raced out of the Solar System. NASA engineers turned its camera arm around (at the request of the American astronomer Carl Sagan) to take a parting snapshot of Earth. Earth's image was a single pale blue pixel, its color caused by the Rayleigh scattering of sunlight in the water of our oceans. Earth is a water planet, and this is the color of life. No matter how far we travel on our planet, no matter how high or deep, if we find liquid water, we find some form of life that manages to survive there. And yet there is a cruel irony. Water in its solid crystalline form is hostile to life. Organisms can roost in geysers, wallow in brine and gulp down acid, but they cowered from ice. The rigid ordering of water molecules in ice crystals expels impurities and tears organic tissue beyond repair. In fact, about the only good thing you can say about ice is that it gets out of the way: Its low density ensures that it floats and leaves the water dwelling creatures in peace. Recent discoveries have caused us to rethink this basic premise. New lines of evidence both observational and experimental - suggest that prebiotic organic compounds are not only comfortable in, but in fact had their origin in a peculiar form of solid water ice that is ubiquitous in interstellar space, but completely absent from Earth. Only recently have we been able to create even submicroscopic quantities of this ice in terrestrial laboratories, yet it constitutes the most abundant form of water in the universe. Interstellar ice is a far cry from the ice we are so familiar with on Earth. This interstellar ice has no crystalline structure, and despite the fact that its temperature is a scant few degrees above absolute zero (where all molecular motion ceases), it is highly reactive and can flow like water when exposed to radiation. It is in fact this ice's similarity to liquid water that allows it to participate in the creation of the very first organic compounds.

Blake, David↗

NASA NTRS1984

The rheology of icy satellites

High-temperature creep in orthoenstatite under conditions of controlled oxygen fugacity was studied. It was found that creep was conttrolled by the extremely thin layer of SiO2 which wetted the grain boundaries. Slight reduction of the (Mg, Fe)SiO3 enstatite during hot pressing produced microscopic particles of Fe and the thin film of intergranular SiO2. This result highlights another complication in determining the flow properties of iron bearing silicates which constitute the bulk of terrestrial planets and moons. The Phenomenon may be important in the ductile formation of any extraterrestrial body which is formed in a reducing environment. The rheology of dirty ice was studied. This involves micromechanical modeling of hardening phenomena due to contamination by a cosmic distribution of silicate particles. The larger particles are modeled by suspension theory. In order to handle the distribution of particles sizes, the hardening is readed as a critical phenomenon, and real space renormalization group techniques are used. Smaller particles interact directly with the dislocations. The particulate hardening effect was studied in metals. The magnitude of such hardening in ice and the defect chemistry of ice are studied to assess the effects of chemical contamination by methane, ammonia, or other likely contaminants.

Sammis, C. G.↗

NASA NTRS1985

Dust emission of Comet Halley at large heliocentric distances

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

Gruen, E.↗

NASA NTRS1999

South Polar Region of Mars: Topography and Geology

The polar layered deposits of Mars represent potentially important volatile reservoirs and tracers for the planet's geologically recent climate history. Unlike the north polar cap, the uppermost surface of the bright residual south polar deposit is probably composed of carbon dioxide ice. It is unknown whether this ice extends through the entire thickness of the deposit. The Mars Polar Lander (MPL), launched in January 1999, is due to arrive in December 1999 to search for water and carbon dioxide on layered deposits near the south pole (SP) of Mars. Additional information is contained in the original extended abstract.

Schenk, P. M.↗

NASA NTRS1989

The case for planetary sample return missions. 2. History of Mars

Principal science goals for exploration of Mars are to establish the chemical, isotopic, and physical state of Martian material, the nature of major surface-forming processes and their time scales, and the past and present biological potential of the planet. Many of those goals can only be met by detailed analyses of atmospheric gases and carefully selected samples of fresh rocks, weathered rocks, soils, sediments, and ices. The high-fidelity mineral separations, complex chemical treatments, and ultrasensitive instrument systems required for key measurements, as well as the need to adapt analytical strategies to unanticipated results, point to Earth-based laboratory analyses on returned Martian samples as the best means for meeting the stated objectives.

NASA Center ARC↗

NASA NTRS2005

Saturn Satellite Densities and the C/O Chemistry of the Solar Nebula

The composition of material condensed in the outer solar system is very dependent on the state of carbon and oxygen in the solar or circumplanetary nebula, since oxygen is the dominant solid-forming element in a solar composition gas (in the form of silicates and water ice), and carbon is about half as abundant. Past discussions of solid material formed in these regions have focused on differences expected between material formed near giant planets where carbon is generally expected to be in the reduced, CH4, form and material formed in the outer protoplanetary solar nebula where CO is believed to be the dominant form [1]. The composition and expected density of these materials are quite sensitive to the C and O solar abundances in all these models. We discuss here the effects of recently suggested modifications to solar abundances on the interpretation of the mean densities for satellites in the Saturn system.

Johnson, T. V.↗