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NASA NTRS1985

Impact Cratering Calculations

Impact cratering, both normal and oblique, on planetary surfaces is discussed and energy partitioning, ejecta distribution, (both with regard to size, velocity, energy content, and size sorting), the condensation physics of impact induced vapor, and the loss of planetary atmospheres during accretion of terrestrial and icy planets are considered. The possible origin of SNC meteorites, impact into porous regolith, equation of state of water and ice, and a possible model for the accretion of the Jovian and Saturnian satellites are examined.

Ahrens, T. J.↗

NASA NTRS1986

Research in planetary astronomy and operation of the 2.2-meter telescope

The turn-around in the secular change in brightness of Pluto was detected, the planet is now beginning to brighten. The spectral signature was found of an ammonia bearing compound in the surface ices of Europa. Specific Io volcanic hotspots were detected from infrared photometry of the mutual events of the Jovian satellites. The polarized emission from the volcanic hotspots on Io was discovered and the locations of those hotspots were determined. The orbit of Charon was refined from speckle observations of the Pluto-Charon system. The spectral properties of liquid nitrogen-methane mixtures with reference to the infrared spectrum of Triton were studied. Major progress was made in modeling asteroid lightcurves from a modern theory of photometric properties of the asteroid surfaces. Several additional olivine-rich asteroids from near-infrared spectrophotometry were discovered. Important photometric, spectroscopic, narrow-band imaging data on Comet P/Halley was acquired, along with Schmidt photographs of Comet P/Halley and its tail.

Hall, D. N. B.↗

NASA NTRS1991

Studies of volatiles and organic materials in early terrestrial and present-day outer solar system environments

A review and partial summary of projects within several areas of research generally involving the origin, distribution, chemistry, and spectral/dielectric properties of volatiles and organic materials in the outer solar system and early terrestrial environments are presented. The major topics covered include: (1) impact delivery of volatiles and organic compounds to the early terrestrial planets; (2) optical constants measurements; (3) spectral classification, chemical processes, and distribution of materials; and (4) radar properties of ice, hydrocarbons, and organic heteropolymers.

Sagan, Carl↗

NASA NTRS1999

Global Topography of Mars with the MGS Laser Altimeter (MOLA): Latest Results

After acquiring topographic measurements of the northern hemisphere of Mars last Spring and Summer the Mars Global Surveyor (MGS) spacecraft will begin to observe the rest of Mars from its planned mapping orbit in early March of this this year. After successfully completing the aerobraking phase of the mission in February, the spacecraft will be finally placed into the near circular, 400 km polar, mapping orbit for almost continuous observation of the planet for one Mars year. Of particular interest in the early phases will be the structure of the southern ice cap, the cratered southern highlands and the topography in the region of the landing sites of the Mars 98 and the Mars 01 missions.

Smith, David E.↗

NASA NTRS2005

Morphology and Elemental Composition of Recent and Fossil Cyanobacteria

Cyanobacteria (cyanophyta, cyanoprokaryota, and blue-green algae) are an ancient, diverse and abundant group of photosynthetic oxygenic microorganisms. Together with other bacteria and archaea, the cyanobacteria have been the dominant life forms on Earth for over 3.5 billion years. Cyanobacteria occur in some of our planets most extreme environments - hot springs and geysers, hypersaline and alkaline lakes, hot and cold deserts, and the polar ice caps. They occur in a wide variety of morphologies. Unlike archaea and other bacteria, which are typically classified in pure culture by their physiological, biochemical and phylogenetic properties, the cyanobacteria have historically been classified based upon their size and morphological characteristics. These include the presence or absence of heterocysts, sheath, uniseriate or multiseriate trichomes, true or false branching, arrangement of thylakoids, reproduction by akinetes, binary fission, hormogonia, fragmentation, presence/absence of motility etc. Their antiquity, distribution, structural and chemical differentiation, diversity, morphological complexity and large size compared to most other bacteria, makes the cyanobacteria ideal candidates for morphological biomarkers in returned Astromaterials. We have obtained optical (nomarski and phase contrast)/fluorescent (blue and green excitation) microscopy images using an Olympus BX60 compound microscope and Field Emission Scanning Electron Microscopy images and EDAX elemental compositions of living and fossil cyanobacteria. The S-4000 Hitachi Field Emission Scanning Electron Microscope (FESEM) has been used to investigate microfossils in freshly fractured interior surfaces of terrestrial rocks and the cells, hormogonia, sheaths and trichomes of recent filamentous cyanobacteria. We present Fluorescent and FESEM Secondary and Backscattered Electron images and associated EDAX elemental analyses of recent and fossil cyanobacteria, concentrating on representatives of the genera Calothnx, Leptolyngbya, Lyngbya, Planktolyngbya and Oscillatoria.

SaintAmand, Ann↗

NASA NTRS2004

Remote-Raman and Micro-Raman Studies of Solid CO2, CH4, Gas Hydrates and Ice

It is well known that on Mars CO2 is the principal constituent of the thin atmosphere and on a seasonal basis CO2 snow and frost coats the polar caps. Also over 25% of the Martian atmosphere freezes out and sublimes again each year. The Mars Odyssey Emission Imaging system (THEMIS) has discovered water ice exposed near the edge of Mars southern perennials cap. In recent years, it has been suggested that in Martian subsurface CO2 may exist as gas hydrate (8CO2 + 44 H2O) with melting temperature of 10C. Since the crust of Mars has been stable for enough time there is also a possibility that methane formed by magmatic processes and/or as a byproduct of anaerobic deep biosphere activity to have raised toward the planet s surface. This methane would have been captured and stored as methane hydrate, which concentrates methane and water. Determination of abundance and distribution of these ices on the surface and in the near surface are of fundamental importance for understanding Martian atmosphere, and for future exploration of Mars. In this work, we have evaluated feasibility of using remote Raman and micro-Raman spectroscopy as potential nondestructive and non-contact techniques for detecting solid CO2, CH4 gas, and gas hydrates as well as water-ice on planetary surfaces.

Sharma, S. K.↗

NASA NTRS2004

Analysis of Organic Compounds in Mars Analog Samples

The detailed characterization of organic compounds that might be preserved in rocks, ices, or sedimentary layers on Mars would be a significant step toward resolving the question of the habitability and potential for life on that planet. The fact that the Viking gas chromatograph mass spectrometer (GCMS) did not detect organic compounds should not discourage further investigations since (a) an oxidizing environment in the near surface fines analyzed by Viking is likely to have destroyed many reduced carbon species; (b) there are classes of refractory or partially oxidized species such as carboxylic acids that would not have been detected by the Viking GCMS; and (c) the Viking landing sites are not representative of Mars overall. These factors motivate the development of advanced in situ analytical protocols to carry out a comprehensive survey of organic compounds in martian regolith, ices, and rocks. We combine pyrolysis GCMS for analysis of volatile species, chemical derivatization for transformation of less volatile organics, and laser desorption mass spectrometry (LDMS) for analysis of elements and more refractory, higher-mass organics. To evaluate this approach and enable a comparison with other measurement techniques we analyze organics in Mars simulant samples.

Mahaffy, P. R.↗

NASA NTRS2004

Jet Propulsion Laboratory: Annual Report 2003

If you stepped outdoors on the final evening of 2003 and looked up into the night sky, many celestial events were taking place. A hundred million miles away from Earth, a dust storm swirled across the terracotta peaks and gullies of Mars, as two six-wheeled robots bore down on the planet. They were soon to join two orbital sentries already stationed there. A few hops across the inner solar system, another spacecraft was closing in on a ball of ice and rock spewing forth a hailstorm of dust grains, heated as it swung in toward the Sun. Closer in, two newly lofted space telescopes scanned the skies, their mirrors gathering photons that had crossed the empty vastness of space for billions of years, recording ancient events in unimaginably distant galaxies. And streaking overhead every few minutes directly above our home planet, a handful of satellites was recording the unfolding events of a tropical cyclone off the east coast of Africa and a blizzard that carpeted the northwestern United States. As 2003 drew to a close, the Jet Propulsion Laboratory was on the cusp of an extraordinarily busy period, a time when JPL will execute more fly-bys, landings, sample returns and other milestones than at any other time in its history. The exploration we undertake is important for its own sake. And it serves other purposes, none more important than inspiring the next generation of explorers. If the United States wishes to retain its status as a world leader, it must maintain the technological edge of its workforce. What we do here is the stuff of dreams that will inspire a new generation to continue the American legacy of exploration.

Jet Propulsion Laboratory (JPL)↗

NASA NTRS1990

Triton, Pluto and Charon

On the eve of the Voyager encounter with Neptune and Triton, the knowledge of the surface and atmosphere of the satellite has made some progress. Methane, and perhaps molecular nitrogen, appears to dominate the surface and atmospheric chemistry. Sketchy evidence suggests changes in the disposition and state of the volatile materials on this body in the past few years, perhaps in response to the extreme seasons. Pluto and its satellite Charon are at last revealed in some detail, chiefly resulting from observations of the mutual transits and occultations of 1985-1990. A stellar occultation by Pluto in 1988 has given the first detailed information on the planet's atmosphere. The density of the Pluto-Charon system indicates a bulk composition consisting of silicates and water ice, suggesting formation directly from the solar nebula.

Cruikshank, D. P.↗

NASA NTRS1991

Laboratory and observational study of the interrelation of the carbonaceous component of interstellar dust and solar system materials

By studying the chemical and isotopic composition of interstellar ice and dust, one gains insight into the composition and chemical evolution of the solid bodies in the solar nebula and the nature of the material subsequently brought into the inner part of the solar system by comets and meteorites. It is now possible to spectroscopically probe the composition of interstellar ice and dust in the mid-infrared, the spectral range which is most diagnostic of fundamental molecular vibrations. We can compare these spectra of various astronomical objects (including the diffuse and dense interstellar medium, comets, and the icy outer planets and their satellites) with the spectra of analogs we produce in the laboratory under conditions which mimic those in these different objects. In this way one can determine the composition and abundances of the major constituents of the various ices and place general constraints on the types of organics coating the grains in the diffuse interstellar medium. In particular we have shown the ices in the dense clouds contain H2O, CH3OH, CO, perhaps some NH3 and H2CO, we well as nitriles and ketones or esters. Furthermore, by studying the photochemistry of these ice analogs in the laboratory, one gains insight into the chemistry which takes place in interstellar/precometary ices. Chemical and spectroscopic studies of photolyzed analogs (including deuterated species) are now underway. The results of some of these studies will be presented and implications for the evolution of the biogenic elements in interstellar dust and comets will be discussed.

Allamandola, L. J.↗

NASA NTRS1994

The origin of carbon monoxide in Neptunes's atmosphere

The CO abundance in the observable atmosphere of Neptune can be plausibly explained by rapid vertical mixing from the deeper atmosphere if Neptune has a greater complement of water than Uranus. Thermochemical equilibrium and kinetic calculations reveal that Neptune must and Uranus may have about 10 times more oxygen than carbon, whereas for Jupiter and Saturn equal enrichments of carbon and oxygen are satifactory to explain the observed CO abundances by deep vertical mixing. Relative to hydrogen and solar composition, the respective enrichment factors for carbon and oxygen are 41, 440 (Neptune); 32, less than or equal 260 (Uranus); 6.6, 6.6 (Saturn); and 2.8, 2.8 (Jupiter). Because water ice is the most refractory ice among the ices assumed to be present in the outer solar nebula, the most massive H2O enrichment is expected for the outermost planet of this group. Thus, Neptune can indeed be regarded as the 'god of the seas.'

Lodders, K.↗

NASA NTRS1998

Theories of Giant Planet Formation

An overview of current theories of planetary formation, with emphasis on giant planets, is presented. The most detailed models are based upon observations of our own Solar System and of young stars and their environments. While these models predict that rocky planets should form around most single stars, the frequency of formation of gas giant planets is more difficult to predict theoretically. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant planets begin their growth as do terrestrial planets, but they become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. Most models for extrasolar giant planets suggest that they formed as did Jupiter and Saturn (in nearly circular orbits, far enough from the star that ice could), and subsequently migrated to their current positions, although some models suggest in situ formation.

Lissauer, Jack J.↗

NASA NTRS2011

Mars In-Situ Resource Utilization Technology Evaluation

We have examined the technologies required to enable Mars Tn-Situ Resource Utilization (ISRU) because our understanding of Mars resources has changed significantly in the last five years as a result of recent robotic missions to the red planet [1-4]. Two major developments, (1) confirmation of the presence of near-surface water in the form of ice in very large amounts at high latitudes by the Phoenix Lander and (2) the likely existence of water at lower latitudes in the form of hydrates or ice in the top one meter of the regolith, have the potential to change ISRU technology selection. A brief technology assessment was performed for the most promising Mars atmospheric gas processing techniques: Reverse Water Gas Shift (RWGS) and Methanation (aka Sabatier), as well as an overview of soil.processing technology to extract water from Martian soil.

Santiago-Maldonado, Edgardo↗

NASA NTRS2016

40 Years of Processing Pieces of Space

This year marks the 40th year anniversary for the Antarctic Search for Meteorite (ANSMET) program. In 1976, the ANSMET program led the first expedition to Antarctica. The ANSMET program is a US-led field-based science project that recovers meteorite samples from Antarctica. Once a year from late November to late January, a field team consisting of 8 to 12 people, spends 6-8 weeks camping on the ice and collecting meteorites. Since 1976, more than 22,000 meteorite samples have been recovered. These meteorites come from asteroids, planets and other bodies of the solar system. Once collected, the Antarctic meteorites are shipped to NASA/Johnson Space Center (JSC) Houston, TX. in a refrigerated truck and are kept frozen to minimize oxidation until they are ready for initial processing. In Antarctica each meteorite is given a field tag which consists of numbers, once in the lab, this is replaced by an official tag, consisting of the Antarctic field location and year collected. The types and numbers of meteorites that have been classified include 849 carbonaceous chondrites, 135 enstatites, 512 achondrites, 64 stony, 115 irons, 48 others (27 R chondrites, 7 ungrouped), 6,161 H chondrites, 7,668 L chondrites, and 4,589 LL chondrites. Although 80-85 percent of the collected meteorites fall in the ordinary chondrite group, the other approximately 15 percent represent rare types of achondrites and carbonaceous chondrites. These rare meteorites include 25 lunar meteorites, 15 Martian meteorites, scores of various types of carbonaceous chondrites, and unique achondrites. The Antarctic meteorites that have been collected are processed in the Meteorite Processing Lab at JSC in Houston, TX. Initial processing of the meteorites begins with thawing/drying the meteorites in a nitrogen glove box for 24 to 48 hours. The meteorites are then photographed, measured, weighed and a description of the interior and exterior of each meteorite is written. The meteorite is broken and a representative sample, either a 1-3 gram chip or thin section is sent to the Smithsonian Institution for classification. After Antarctic meteorites have been classified and approved by the Nomenclature Committee of the Meteoritical Society, they are announced in the Antarctic Meteorite Newsletter, which is published twice per year (fall and spring) so that scientists may review which meteorites are available to study. Requests for Antarctic Meteorite samples are welcomed from research scientists, regardless of their current state of funding for meteorite studies. Since its inception over 3,300 requests have been made for pieces of these meteorites and over 400 investigators worldwide are active in the study of meteorites.. Research on these samples has been published in more than1500 peer reviewed articles; a listing of papers for any meteorite sample can be generated by accessing http://curator.jsc.nasa.gov/antmet/referencesearch.cfm. Antarctic meteorite samples requested by scientists are prepared several different ways. Most samples are prepared as chips, either using a rock splitter or using a chisel and chipping bowl. In special situations, a researcher may request a meteorite slab in which case the samples are cut using a diamond-bladed bandsaw inside of a dry nitrogen glove box. The meteorites are always cut in a 100 percent liquid-free environment. Additionally, thin/thick sections of Antarctic meteorites are also prepared at JSC. The meteorite thin section lab at JSC can prepare standard 30-micron thin sections, thick sections of variable thickness (100 to 200 microns), or demountable sections using superglue, all section are prepared without using water. Although many of the techniques used back in the '70's are still used today, advances in computers, software, databases, available tools and instrumentation have helped to streamline and shorten the duration of the classification process. In conjunction with present day missions to asteroids and other planets, meteorite studies have not only led to a better understanding of the complex histories of these bodies but have also tied certain meteorite groups to particular asteroid bodies. New meteorite discoveries by the ANSMET program provide a cost effective method for obtaining samples of previously unsampled bodies, allowing scientists to learn more about the origin, composition, and evolution of the solar system. Preservation in our cleanrooms at NASA allows material to be archived for future generations and advances in instrumentation and analysis.

Satterwhite, C. E.↗

NASA NTRS2020

Future Missions to the Giant Planets that Can Advance Atmospheric Science Objectives

Other papers in this special issue have discussed the diversity of planetary atmospheres and some of the key science questions for giant planet atmospheres to be addressed in the future. There are crucial measurements that can only be made by orbiters of giant planets and probes dropped into their atmospheres. To help the community be more effective developers of missions and users of data products, we summarize how NASA and ESA categorize their planetary space missions, and the restrictions and requirements placed on each category. We then discuss the atmospheric goals to be addressed by currently approved giant-planet missions as well as missions likely to be considered in the next few years, such as a joint NASA/ESA Ice Giant orbiter with atmospheric probe. Our focus is on interplanetary spacecraft, but we acknowledge the crucial role to be played by ground-based and near-Earth telescopes, as well as theoretical and laboratory work.

Mark D Hofstadter↗

NASA NTRS1993

The evolution of the early Martian climate and the initial emplacement of crustal H2O

Given the geomorphic evidence for the widespread occurrence of water and ice in the early Martian crust, and the difficulty involved in accounting for this distribution given the present climate, it has been suggested that the planet's early climate was originally more Earth-like, permitting the global emplacement of crustal H2O by direct precipitation as snow or rain. The resemblance of the Martian valley networks to terrestrial runoff channels and their almost exclusive occurrence in the planet's ancient (approximately 4-b.y.-old) heavily cratered terrain are often cited as evidence of just such a period. An alternative school of thought suggests that the early climate did not differ substantially from that of today. Advocates of this view find no compelling reason to invoke a warmer, wetter period to explain the origin of the valley networks. Rather, they cite evidence that the primary mechanism of valley formation was groundwater sapping, a process that does not require that surface water exists in equilibrium with the atmosphere. However, while sapping may successfully explain the origin of the small valleys, it fails to address how the crust was initially charged with ice as the climate evolved towards its present state. Therefore, given the uncertainty regarding the environmental conditions that prevailed on early Mars, the initial emplacement of ground ice is considered here from two perspectives: (1) the early climate started warm and wet, but gradually cooled with time, and (2) the early climate never differed substantially from that of today.

Clifford, S. M.↗

NASA NTRS1993

Mars: The initial emplacement of ground ice in response to the thermal evolution of its early crust

Given the geomorphic evidence for the widespread occurrence of water and ice in the early martian crust, and the difficulty involved in accounting for this distribution given the present climate, it has been suggested that the planet's early climate was originally more Earth-like, permitting the global emplacement of crustal H2O by direct precipitation as snow or rain. The resemblance of the martian valley networks to terrestrial runoff channels, and their almost exclusive occurrence in the planet's ancient (approximately 4 billion year old) heavily cratered terrain, is often cited as evidence of just such a period. An alternative school of thought suggests that the early climate did not differ substantially from that of today. Advocates of this view find no compelling reason to invoke a warmer, wetter period to explain the origin of the valley networks. Rather, they cite evidence that the primary mechanism of valley formation was ground water sapping, a process that does not require that surface water exist in equilibrium with the atmosphere. However, while sapping may successfully explain the origin of the small valleys, it fails to address how the crust was initially charged with ice as the climate evolved towards its present state. Therefore, given the uncertainty regarding the environmental conditions that prevailed on early Mars, the initial emplacement of ground ice is considered from two perspectives: (1) that the early climate started warm and wet, but gradually cooled with time; and (2) that it never differed substantially from that of today.

Clifford, Stephen M.↗

DOE OSTI2025

Wave ripples formed in ancient, ice-free lakes in Gale crater, Mars

Symmetrical wave ripples identified with NASA’s Curiosity rover in ancient lake deposits at Gale crater provide a key paleoclimate constraint for early Mars: At the time of ripple formation, climate conditions must have supported ice-free liquid water on the surface of Mars. These features are the most definitive examples of wave ripples on another planet. The ripples occur in two stratigraphic intervals within the orbitally defined Layered Sulfate Unit: a thin but laterally extensive unit at the base of the Amapari member of the Mirador formation, and a sandstone lens within the Contigo member of the Mirador formation. In both locations, the ripples have an average wavelength of ~4.5 centimeters. Internal laminae and ripple morphology show an architecture common in wave-influenced environments where wind-generated surface gravity waves mobilize bottom sediment in oscillatory flows. Their presence suggests formation in a shallow-water (<2 meters) setting that was open to the atmosphere, which requires atmospheric conditions that allow stable surface water.

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