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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Search for volatiles on icy satellites. I - Europa

NASA IRTF reflectance spectra of unprecedented precision, obtained for the leading and trailing sides of Europa, are presently noted to no longer show the apparent absorptions seen in 1980 and 1985. It is presently suggested that if the weak absorptions seen in the 1980 and 1985 data are real, they may indicate the transient spectroscopic presence of a molecular component on Europa's trailing side that differs from the water ice known to be the dominant constituent of the surface.

Brown, Robert Hamilton↗
NASA NTRS1988

Volatiles on Triton - The infrared spectral evidence, 2.0-2.5 microns

The new IR spectra presented for Triton exhibit the 2.3-micron methane band as well as Cruikshank et al.'s (1984) 2.15-micron spectral band. It is found on the basis of comparisons with methane ice spectra, and laboratory spectra of methane dissolved in liquid nitrogen, that the former band cannot be exclusively due to methane's presence. Also, the strength of the 2.3-micron band does not allow any obvious correlation with the satellite's orbital position in the new data set.

Cruikshank, Dale P.↗
NASA NTRS1987

Photochemical weathering and contemporary volatile loss on Mars

In an earlier series of papers by the author it was proposed that photochemical weathering of Fe(2+) in magnetite and in mafic silicates may be occurring in the contemporary surface environment with a resultant loss of O2 from the atmosphere. Morris and Lauer challenged the photochemical weathering model, proposing that oxidation by radiant heating rather than UV photoelectron emission induced oxidation may have dominated in the authors experiments. Subsequent laboratory studies of photochemical weathering of magnetite described here support the authors original proposal that UV illunimation can indeed drive the oxidation of magnetite under contemporary Martian surface conditions. The negative results of the Morris and Lauer study can now be explained.

Huguenin, R. L.↗
NASA NTRS1989

Cosmogenic helium and volatile-rich fluid in Sierra Leone alluvial diamonds

Noble gas measurements were carried out on two identical splits of a finely powdered harshly acid-washed sample derived from fragments of a single alluvial diamond from Sierra Leone, with essentially identical results obtained for both splits. Isotopic ratios for Ar, Kr, and Xe were found to be atmospheric. Their elemental abundances were high relative to published data, owing to the effect of shock implantation in the crushing step, as was verified in a supplementary experiment. No Ne was detected above the blank level. The He-3 was exceptionally abundant, while He-4 was exceptionally depleted, possibly due to the acid wash. The He-3/He-4 ratio was anomalously high at an R/Ra value of 246 + or - 16. The results support the hypothesis that the He-3 excess in diamonds is cosmogenic.

Mcconville, P.↗
NASA NTRS1991

Coproduction of volatiles and metals from extraterrestrial materials

Two main efforts in support of the general goals of SERC/culpr are presented. Investigations of processes for the coproduction of metals from extra-terrestrial materials in conjunction with plausible schemes for oxygen extraction continue. The principal emphasis was on the extraction and purification of iron from the ilmenite reduction process for oxygen, from the cathode metal deposits made in the magma electrolysis process for oxygen, and from native ferrous metal alloys on the moon and asteroids. All work on the separation and purification of ferrous metals was focussed upon the gaseous carbonyl process, a scheme that involves only temperatures attainable by passive thermal control. The exploration of a variety of schemes was initiated, involving the use of several different propulsion options and both propulsive and aerobraking capture at earth, for return of extraterrestrial resources to earth orbits. In addition, the search for new opportunities in space resource utilization continues. Examples include the continuation of work underway on: (1) the feasibility of locating solar power satellites in highly eccentric earth orbit; (2) the energetics of extracting the potential clean fusion fuel He-3 from the atmosphere for return to earth; and (3) the utility of a nuclear steam rocket (using non-terrestrial water as the working fluid) for transportation in the inner solar system.

Lewis, John S.↗
NASA NTRS1989

Extraction of volatiles and metals from extraterrestrial ores

Extraterrestrial materials, processes, and products were identified which are associated with the production of propellants in space, including the most complete possible conversion of the feedstocks for propellant production into useful products with the minimum feasible expenditure of energy. Laboratory research was identified and begun on several processes that promise very large increases in the mass of useful products at the cost of only modest increases in energy consumption. Processes for manufacturing propellants then become processes for making propellants plus metals and refractories. It is the overall yield of useful materials per unit expended energy that matters, not simply the yield of propellants. Three tasks have been undertaken to date: (1) Literature search and compilation of a dBase 3 data base on space materials processing; (2) Gaseous carbonyl extraction and purification of ferrous metals; and (3) Characterization of lunar ilmenite and its simulants.

Lewis, John S.↗
NASA NTRS1990

Extraction of volatile and metals from extraterrestrial materials

Since March 1, 1989, attention was concentrated on the extraction of ilmenite from extraterrestrial materials and on the planning and development of laboratory facilities for carbonyl extraction of ferrous metal alloys. Work under three subcontracts was administered by this project: (1) electrolytic production of oxygen from molten lunar materials; (2) microwave processing of lunar materials; and (3) production of a resource-oriented space science data base.

Lewis, John S.↗
NASA NTRS1991

Infrared remote sensing of cometary parent volatiles from the ground, air, and space

A balanced view of the present generation of infrared instruments for cometary compositional studies is presented. Ground-based instruments are compared with airborne and spaceborne capabilities. An attempt to give examples of the unique science achievable with each is made, and particular emphasis is on the unique aspects of a dedicated Cometary Composition Telescope in earth orbit for investigating the chemical and structural heterogeneity of the cometary nucleus.

Mumma, Michael J.↗
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 NTRS1990

Water on Mars - Volatile history and resource availability

An attempt is made to define the available deposits of water in the near-surface region of Mars which will be available to human exploration missions. The Martian seasonal water cycle is reviewed, and geochemical and geological constraints on the availability of water are examined. It is concluded that the only sure source of water in amounts significant as a resource are in the polar ice deposits.

Jakosky, Bruce M.↗
NASA NTRS1990

Volatile compounds in shergottite and nakhlite meteorites

Shergottites ALHA77005, EETA79001, and Shergotty, and the nakhlite Nakhla are all found to contain oxidized sulfur (sulfate) of preterrestrial origin, In EETA79001, which is composed of three different lithologies, the degree of sulfur oxidation increased from A to C. Significant bulk carbonate was confirmed in Nakhla and trace carbonate was confirmed for EETA79001, all of which seems to be preterrestrial in origin. Chlorine in shergottites and Nakhla is found to covary with oxidized sulfur, whereas carbonate and sulfate are related inversely. Sulfate and carbonate in shergottites and Nakhla were probably formed by aqueous geochemistry in a highly oxidizing environment sometime near the late-stage histories of the rocks that are now represented as meteorites.

Gooding, James L.↗
NASA NTRS1992

Mars: Compositional variability of ferric/ferrous minerals and polar volatiles from groundbased imaging spectroscopy

In an attempt to further constrain the ferric and ferrous mineralogy of Mars, Bell et al. (1989; 1990) obtained high resolution imaging spectroscopic data of much of the Martian surface in the visible and near-infrared (0.4-1.1 micron) during the 1988 opposition. Preliminary analysis of these data showed further evidence of crystalline hematite absorption features at 0.8-0.9 microns and 0.6-0.7 microns. Additionally, the 0.6-0.7 micron Fe(III) band was shown to vary across the surface, with a substantial correlation with albedo in the region studied. Calibration of this 1988 data set (along with a similar data set obtained during the 1990 opposition) has been ongoing, and some of the most recent results of the analysis of these data using linear spectral mixture modeling are reported.

Bell, James F., III↗
NASA NTRS1992

Infrared imaging of Mars for volatile distribution and seasonal variability between 2.4 and 5.1 microns

Recent advances in ground-based infrared imaging now allow for sub-arc second spectral imaging. Data collected at the NASA Infrared Telescope Facility using protocam, a 62 x 58 InSb array camera with a circular variable filter and a plate scale 0.2 arc-seconds/pixel, are discussed. These images are a first attempt at extended seasonal infrared coverage of Mars to look for seasonal variations. Currently, data collected in Jun. 1990 at Ls = 241 (southern spring) and in Jan. 1991 Ls = 360 (late southern summer) are being reduced and analyzed. The 3 micron bound water band is the strongest surface absorption feature on Mars in the infrared. Infrared spectroscopy can also be useful in the detection of ice and frost deposits, especially in the polar regions. While imaging and spectroscopy at visible wavelengths allows for the detection of condensates, infrared information is needed to distinguish between water and CO2 ice/frost deposits. In the Jun. images, the southern polar cap totally disappears in the 3.4 micron CO2 frost band and is bright in the 3.1 micron water ice band, indicating that water ice is not a detectable component of the southern polar cap at this season. Further investigations are currently under way to look for residual water ice after the disappearance of the seasonal south polar cap in the Jan. images. The Jun. images that were focused on had a sub-earth point located at 184 longitude, and 23.8 S latitude which put the center of the disk in the southern highland region between Elysium and Amazonis. Examination of the Jun. images show that there are four surface units identifiable: a CO2 frost deposit, a northern plains unit, an equatorial unit, and a southern highland unit. At this resolution there does not appear to be any latitudinal variations in the 3 micron band that is independent of the 2.4 micron albedo features. The northern planes unit and the southern highland unit have very similar 'color' in the three micron band as demonstrated by the rise out of the band, but different brightness levels. The equatorial unit has a distinct three micron color implying a compositional difference. The albedo features at 2.4 microns have decreased contrast at longer wavelengths, till they are unrecognizable at 4 microns.

Blaney, Diana L.↗
NASA NTRS1992

Volatile tracers of Martian atmospheric evolution: Present measurement status and requirements for future investigations

One of the most significant contributions to the detailed characterization of the molecular, atomic, and isotopic composition of the Martian atmosphere came from the Viking mass spectrometer experiments. Measurement of the abundance of the noble gases Ne, Ar, Kr, and Xe, as well as major molecular species was achieved together with some of the important isotopic compositions such as N-15/N-14, Ar-36/Ar-40, and others. The isotopic characterization, a key element to an understanding of atmospheric evolution, advanced further with recent measurements of the deuterium/hydrogen (D/H) ratio from HDO as well as the detailed study of gases contained in meteorites thought to be Martian origin.

Mahaffy, Paul↗
NASA NTRS1992

Hydrogen and carbon isotopic composition of volatiles in Nakhla: Implications for weathering on Mars

Gases were collected at 120, 200, 300, 415, and 600 and 850 C. Hydrogen yields for the 600 and 850 C aliquots were measured separately and then the gases were combined for isotopic analysis. CO2 samples collected at the two lowest temperature steps amounted to less than 0.5 mu mole and were not analyzed isotopically. Excluding the 120 C temperature step, the bulk delta D of the sample was + 187 percent. Delta D values increase from -91 percent in the 120 C step to +518 percent in the 315 to 850 C step. The hydrogen content is greatest in the 120 C step and is roughly constant in the 200, 300, and 415 C aliquots. Between 415 C and 850 C, the yield drops off considerably. From 850 C to 950 C, virtually no H2 and only minor CO2 (less than 1 mu mole) were extracted. Using the isotopic analysis from the 300, 415, 600, and 850 C temperature collections, the bulk delta C-13 sub (PDB) is 0.0 percent. The heaviest component (delta C-13 sub (PDB) of +29 percent) was collected between 300 and 415 C. The release of hydrogen at the low temperatures reported here is consistent with the breakdown of the phases that constitute the alteration product between approx. 250 and 650 C. Although not as high as the present Martian atmosphere, the high delta D values are consistent with a Martian origin for the meteorites in question.

Watson, L. L.↗
NASA NTRS1991

Mars volatile evolution - Evidence from stable isotopes

In the most strongly favored of the scenarios presently considered for Martian atmospheric evolution, oxygen fractionation by escape into space is diluted by exchange by a nonatmospheric reservoir as polar ice-water deposits exchange with atmospheric water over geologic time. The exchange of oxygen between atmospheric CO2 and H2O may account for the fractionation observed between those two species. Observations and numerical modeling efforts that may test the present results are suggested.

Jakosky, Bruce M.↗
NASA NTRS1992

Mineralization on the moon? Theoretical considerations of Apollo 16 'rusty rocks', sulfide replacement in 67016, and surface-correlated volatiles on lunar volcanic glass

Theoretical considerations of vapor-rock interactions in the lunar environment are a useful supplement to petrologic studies of mineralization or alteration in rocks from the moon. They also provide insights into the potential for the existence of more extensive mineralization on the moon than is found in the limited sample set. Discussed in this paper are the coexistence and textural association in 66095 of the phases lawrencite, troilite, schreibersite, iron metal, and sphalerite; the replacement of olivine in certain clasts of 67016 by troilite and enstatite; and the existence of Zn + S deposits on the surfaces of volcanic glass beads. Particular attention is given in each case to whether the observed mineralization implies that metals, as well as S, P, or Cl, have been mobilized in the vapor. Vapor species that might mobilize metals in the absence of H2O are considered. Most importantly, the suggestion is made that in the dry lunar environment carbonyl species may be important carriers of S and metals. The implications of this possibility are discussed.

Colson, Russell O.↗