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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 217 records · Page 12

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NASA NTRS1992

Distribution of Martian ground-ice table: Preliminary results about climatic variations

Rampart craters seem to have been emplaced by flows around craters over the surface just after the impact event by melting of volatiles. Such rampart craters are considered to be good ground-ice indicators. A map shows a latitudinal distribution of Martian ground-ice with a deep ground-ice table at equatorial latitudes and subsurface ground-ice tables at mid and high latitudes. Some studies suggest the presence of large amounts of ground-ice on Mars, with near surface ground-ice in the northern plains and a permafrost at low latitudes containing a large amount of volatiles at depth. Spatial variations in the spin axis of the planet affect the latitudinal distribution of the Sun's isolation, and therefore the Martian ground-ice distribution.

Costard, F. M.↗

NASA NTRS1986

Europa

Europa, the second major satellite outward from Jupiter, is a lunar-sized object in synchronous rotation about that planet. Its high albedo and spectral characteristics indicate the presence of surface water ice and/or frost. Its density suggests a substantial silicate component of at least 85 percent by volume. A limited variety of landforms is seen in Voyager images, most likely because of poor spatial resolution of these data. The absence of numerous impact craters is interpreted as indicating a youthful surface and /or surface regenerating processes. A planet-wide lineament system has been interpreted to result from tectonic stresses induced by evolution of Europa's orbit and interior. Present data do not permit unambiguous tests of such interpretations. Greater insight may come from analytical or numerical models and future spacecraft observations.

Malin, Michael C.↗

NASA NTRS2015

Giant-Planet Chemistry: Ammonium Hydrosulfide (NH4SH), Its IR Spectra and Thermal and Radiolytic Stabilities

Here we present our recent studies of proton-irradiated and unirradiated ammonium hydrosulfide, NH4SH, a compound predicted to be an important tropospheric cloud component of Jupiter and other giant planets. We irradiated both crystalline and amorphous NH4SH at 10-160 K and used IR spectroscopy to observe and identify reaction products in the ice, specifically NH3 and long-chained sulfur-containing ions. Crystalline NH4SH was amorphized during irradiation at all temperatures studied with the rate being the fastest at the lowest temperatures. Irradiation of amorphous NH4SH at approximately 10-75 K showed that 60-80% of the NH4 + remained when equilibrium was reached, and that NH4SH destruction rates were relatively constant within this temperature range. Irradiations at higher temperatures produced different dose dependence and were accompanied by pressure outbursts that, in some cases, fractured the ice. The thermal stability of irradiated NH4SH was found to be greater than that of unirradiated NH4SH, suggesting that an irradiated giant-planet cloud precipitate can exist at temperatures and altitudes not previously considered.

Jupiter↗

NASA NTRS1984

An experimental investigation of the angular scattering and backscattering behaviors of the simulated clouds of the outer planets

A cryogenic, 50 liter volume Planetary Cloud Simulation Chamber has been constructed to permit the laboratory study of the cloud compositions which are likely to be found in the atmospheres of the outer planets. On the basis of available data, clouds composed of water ice, carbon dioxide, and liquid and solid ammonia and methane, both pure and in various mixtures, have been generated. Cloud microphysical observations have been permitted through the use of a cloud particle slide injector and photomicrography. Viewports in the lower chamber have enabled the collection of cloud backscattering data using 633 and 838 nm laser light, including linear depolarization ratios and complete Stokes parameterization. The considerable technological difficulties associated with the collection of angular scattering patterns within the chamber, however, could not be completely overcome.

Sassen, K.↗

NASA NTRS1985

Thermodynamics of clathrate hydrate at low and high pressures with application to the outer solar system

The thermodynamic stability of clathrate hydrate is calculated to predict the formation conditions corresponding to a range of solar system parameters. The calculations were performed using the statistical mechanical theory developed by van der Waals and Platteeuw (1959) and existing experimental data concerning clathrate hydrate and its components. Dissociation pressures and partition functions (Langmuir constants) are predicted at low pressure for CO clathrate (hydrate) using the properties of chemicals similar to CO. It is argued that nonsolar but well constrained noble gas abundances may be measurable by the Galileo spacecraft in the Jovian atmosphere if the observed carbon enhancement is due to bombardment of the atmosphere by clathrate-bearing planetesimals sometime after planetary formation. The noble gas abundances of the Jovian satellite Titan are predicted, assuming that most of the methane in Titan is accreted as clathrate. It is suggested that under thermodynamically appropriate conditions, complete clathration of water ice could have occurred in high-pressure nebulas around giant planets, but probably not in the outer solar nebula. The stability of clathrate in other pressure ranges is also discussed.

Lunine, J. I.↗

NASA NTRS1986

Non-solar noble gas abundances in the atmosphere of Jupiter

Lunine, Jonathan I.↗

NASA NTRS1991

Water on Mars: Volatile history and resource availability

The existence of water on Mars is undisputed today. Measurements of atmospheric water vapor have shown that the abundance varies with location and season in a systematic way which depends on processes of exchange with the polar caps, regolith, and atmosphere. Channels, which give the appearance of having been carved by water or of having had water involved in their formation, appear in various locations on the surface; some were formed by catastrophic outflow of water from beneath the surface, while others form valley networks which give the appearance of having formed over long periods of time primarily early in the planet's history. The north polar residual cap consists of water ice, possibly containing an amount of water equivalent to a global layer several tens of meters thick. Finally, water is observed within the regolith, as adsorbed water or as water of hydration.

Jakosky, Bruce M.↗

NASA NTRS1999

Return to the Moon: A New Strategic Evaluation

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.

Lowman, Paul D., Jr.↗

NASA NTRS1999

Return to the Moon: A New Strategic Evaluation

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.

Lowman, Paul D., Jr.↗

NASA NTRS1999

Return to the Moon: A New Strategic Evaluation

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.

Lowman, Paul D., Jr.↗

NASA NTRS2000

Measuring Geologic Time on Mars

Recent images from Mars show compelling evidence of near-surface flowing water, aeolian activity slope processes, and ice cap evolution that underscores the dynamic geologic history of the planet. Establishing an accurate chronology for Martian planetary features is critical for addressing fundamental questions about the evolution of the planet's surface and atmosphere and the differentiation of its interior. For example, how long was standing water on the surface? If life did evolve on Mars, did it occur before or after the evolution of life on Earth? These are arguably some of the most profound questions currently being asked by the planetary science community. Yet answers will not be forthcoming without an absolute chronology of Mars history, enabling the construction of a timescale comparable to Earth's. Discussion of methods for establishing such a chronology is particularly timely in light of new missions to Mars that are being planned to return in situ measurements or samples to Earth.

Source record↗

NASA NTRS2013

The Aqua-planet Experiment (APE): Response to Changed Meridional SST Profile

This paper explores the sensitivity of Atmospheric General Circulation Model (AGCM) simulations to changes in the meridional distribution of sea surface temperature (SST). The simulations are for an aqua-planet, a water covered Earth with no land, orography or sea- ice and with specified zonally symmetric SST. Simulations from 14 AGCMs developed for Numerical Weather Prediction and climate applications are compared. Four experiments are performed to study the sensitivity to the meridional SST profile. These profiles range from one in which the SST gradient continues to the equator to one which is flat approaching the equator, all with the same maximum SST at the equator. The zonal mean circulation of all models shows strong sensitivity to latitudinal distribution of SST. The Hadley circulation weakens and shifts poleward as the SST profile flattens in the tropics. One question of interest is the formation of a double versus a single ITCZ. There is a large variation between models of the strength of the ITCZ and where in the SST experiment sequence they transition from a single to double ITCZ. The SST profiles are defined such that as the equatorial SST gradient flattens, the maximum gradient increases and moves poleward. This leads to a weakening of the mid-latitude jet accompanied by a poleward shift of the jet core. Also considered are tropical wave activity and tropical precipitation frequency distributions. The details of each vary greatly between models, both with a given SST and in the response to the change in SST. One additional experiment is included to examine the sensitivity to an off-equatorial SST maximum. The upward branch of the Hadley circulation follows the SST maximum off the equator. The models that form a single precipitation maximum when the maximum SST is on the equator shift the precipitation maximum off equator and keep it centered over the SST maximum. Those that form a double with minimum on the equatorial maximum SST shift the double structure off the equator, keeping the minimum over the maximum SST. In both situations only modest changes appear in the shifted profile of zonal average precipitation. When the upward branch of the Hadley circulation moves into the hemisphere with SST maximum, the zonal average zonal, meridional and vertical winds all indicate that the Hadley cell in the other hemisphere dominates.

AGCM↗

NASA NTRS1997

Carbon dioxide warming of the early Earth

Svante Arrhenius' research in atmospheric physics extended beyond the recent past and the near future states of the Earth, which today are at the center of sociopolitical attention. His plan encompassed all of the physical phenomena known at the time to relate to the formation and evolution of stars and planets. His two-volume textbook on cosmic physics is a comprehensive synopsis of the field. The inquiry into the possible cause of the ice ages and the theory of selective wavelength filter control led Arrhenius to consider the surface states of the other terrestrial planets, and of the ancient Earth before it had been modified by the emergence of life. The rapid escape of hydrogen and the equilibration with igneous rocks required that carbon in the early atmosphere prevailed mainly in oxidized form as carbon dioxide, together with other photoactive gases exerting a greenhouse effect orders of magnitude larger than in our present atmosphere. This effect, together with the ensuing chemical processes, would have set the conditions for life to evolve on our planet, seeded from spores spreading through an infinite Universe, and propelled, as Arrhenius thought, by stellar radiation pressure.

NASA Discipline Exobiology↗

NASA NTRS2001

A Proposal for an Integrated Geophysical Strategy to "Follow the Water" on Mars

The search for subsurface water has become a primary focus of Mars exploration. Its abundance and distribution (both as ground ice and groundwater) have important implications for understanding the geologic, hydrologic, and climatic evolution of the planet; the potential origin and continued survival of life; and the accessibility of a critical in situ resource for sustaining future human explorers. For these reasons, a principal goal of the Mars science, astrobiology, and the HEDS programs is to determine the 3-D distribution and state of subsurface H2O, at a resolution sufficient to permit reaching any desired volatile target by drilling. The three targets most often discussed are: groundwater, massive deposits of near-surface ground ice (associated with the ponded discharge of the outflow channels or the relic of a former ocean), and ice-saturated frozen ground. Based on the present best estimates of mean annual surface temperature, crustal thermal conductivity, geothermal heat flow, and groundwater freezing temperature, the mean thickness of frozen ground on Mars is expected to vary from approx. = 2.5 - 5 km at the equator to approx. = 6.5 - 13 km at the poles. However, natural variations in both crustal heat flow and thermal conductivity are likely to result in significant local departures from these predicted values. The recent discovery of "young" fluvial-like features, emanating from the slopes of local scarps, raises the possibility that liquid water may also exist episodically at shallow (approx. = 100 - 500 m) depth; however, the true nature and absolute age of these features remains highly uncertain. Although the belief that Mars is water-rich is supported by a wide variety geologic evidence, our ignorance about the heterogeneous nature and thermal evolution of the planet's crust effectively precludes geomorphic or theoretical attempts to quantitatively assess the current geographic and subsurface vertical distribution of ground ice and groundwater . For this reason, any exploration activity (such as drilling) whose success is contingent on the presence of subsurface water, must be preceded by a comprehensive high-resolution geophysical survey capable of assessing whether local reservoirs of water and ice actually exist. Terrestrial experience has demonstrated that the accurate identification of such targets is likely to require the application of multiple geophysical techniques. In this abstract we propose an integrated strategy for the geophysical exploration of Mars that we believe represents the fastest, most cost-effect, and technically capable approach to identifying the state and distribution of subsurface water. Additional information is contained in the original extended abstract.

Clifford, S. M.↗

NASA NTRS1993

The RNA World: Life Before DNA and Protein

All of the life that is known, all organisms that exist on Earth today or are known to have existed on Earth in the past, are of the same life form: a life form based on DNA and protein. It does not necessarily have to be that way. Why not have two competing life forms on this planet? Why not have biology as we know it and some other biology that occupies its own distinct niche? Yet that is not how evolution has played out. From microbes living on the surface of antarctic ice to tube worms lying near the deep-sea hydrothermal vents, all known organisms on this planet are of the same biology. Looking at the single known biology on Earth, it is clear that this biology could not have simply sprung forth from the primordial soup. The biological system that is the basis for all known. life is far too complicated to have arisen spontaneously. This brings us to the notion that something else something simpler, must have preceded life based on DNA and protein. One suggestion that has gained considerable acceptance over the past decade is that DNA and protein-based life was preceded by RNA-based life in a period referred to as the 'RNA world'. Even an RNA-based life form would have been fairly complicated - not as complicated as our own DNA- and protein-based life form - but far too complicated, according to prevailing scientific thinking, to have arisen spontaneously from the primordial soup. Thus, it has been argued that something else must have preceded RNA-based life, or even that there was a succession of life forms leading from the primordial soup to RNA-based life. The experimental evidence to support this conjecture is not strong because, after all, the origin of life was a historical event that left no direct physical record. However, based on indirect evidence in both the geological record and the phylogenetic record of evolutionary history on earth, it is possible to reconstruct a rough picture of what life was like before DNA and protein.

Joyce, Gerald F.↗

NASA NTRS1993

Acoustic oscillations of Jupiter

We calculate low-degree l acoustic (p-mode) oscillations of the giant planet Jupiter. We use two Jupiter models, both of which contain a rocky core, an ice mantle, and a hydrogen-rich envelope. One of the models incorporates the 'plasma phase transition' of hydrogen, a first-order phase transition that yields a density discontinuity in the hydrogen-rich envelope. Our calculations of the acoustic oscillation spectrum of Jupiter have taken account of the effects of the rapid rotation of the planet: the Coriolis force, centrifugal force, and deformation of the equilibrium state. The p-mode frequency spectra of the Jupiter models are summarized in several echelle diagrams. We show that the frequency spectra of the low-degree p-modes are strongly affected by the existence of the rocky core and by avoided crossings among high radial-order p-modes with different l's.

Lee, Umin↗

NASA NTRS1993

Radio observations of the planets - The importance of laboratory measurements

Laboratory data on the line broadening parameters of H2S gas under Uranian/Neptunian conditions, on the far wings of the H2S and NH3 line profiles, and on the dielectric properties of CH4-, NH3-, H2S-, and NH4SH-ice are needed to constrain elemental abundances and understand the dynamics and cloud physics in the atmospheres of the giant planets. Measurements of the absorption coefficient of gaseous H2SO4 at millimeter wavelengths are needed in order to obtain a better understanding of Venus' atmosphere. To determine wind velocity fields in Venus' and Mars' atmospheres, accurate measurements of the center frequencies of the CO lines are necessary. The absorption and scattering properties of lunar soils and/or terrestrial rock powders at frequencies from approximately 1 to 200 GHz, determined in laboratory experiments, would provide a valuable addition to existing data at 450 MHz, 35 GHz, and far infrared frequencies. These data would be used to analyze the microwave spectra of planetary surfaces. Such studies may be helpful in distinguishing the effects of radiative transfer from those of nonlinear heat conduction and internal heat sources.

De Pater, Imke↗

NASA NTRSDate not supplied

Investigating the Applications of In-Situ Resource Utilization for Future Crewed Mars Missions

There are significant gaps in knowledge regarding the water ice on Mars and future preparation for human missions. So far, six rovers have traversed Mars’ rocky surface, aiming to understand the planet’s composition and search for signs of life. A rover mission set to explore the high northern latitudes of Mars with the goal of analyzing ice cores could greatly advance scientific knowledge to better understand Mars’s ancient climate and geochemistry. As of now, little has been accomplished in the exploration of colder regions and the extraction of water ice apart from the Phoenix lander and the Viking 2 mission; however, the science potential of the Phoenix and Viking landers was limited due to their inability to explore terrain like rovers. The exploration of the near-polar region Arcadia Planitia and its water ice deposits could reveal signs of past microbial life through preserved biosignatures. Additionally, to prepare for permanent human habitation on Mars, this proposed rover could continue the characterization of Mars’s current land and mineral composition, and search for materials that future humans may need on Mars (such as water for habitation, basalt for construction, and olivine for manufacturing purposes). This would increase understanding of the potential for in-situ resource utilization (ISRU) on Mars. The use of ISRU will reduce the amount of material needed on the initial flight, and similarly will reduce fuel costs. The mission to Arcadia Planitia incorporates the use of various mineral-extracting and imaging instruments (Martian Ice Core Analyzer, ground-penetrating radar, NavCam, Mars Environmental Dynamics Analyzer, SuperCam, etc.) to collect data from water ice and geologic samples. A near-polar rover mission to Mars would illuminate Mars’ past and present, while learning more about martian resources to benefit human explorers in the future.

Annika Sachdeva↗