Engineering topics

Huguenin, R. L.

Publications and source records attributed to Huguenin, R. L..

At least 19 records

NASA NTRS1988

Regolith water vapor sources on Mars: A historical bibliography

The regolith as a potential source and sink of atmospheric water is examined bibliographically. The controversy surrounding Solis Lacus, a region on Mars first identified by R. Huguenin as a possible regolith source of atmospheric water vapor, is reviewed. The publications listed describe the initial debate over the existence of a regolith source of atmospheric water vapor in Solis Lacus. The debate over Solis Lacus has motivated a rigorous examination of several important data sets, and helped define the limits of their interpretation.

Clifford, Stephen M.↗

NASA NTRS1987

The silicate component of Martian dust

Absorption features in telescopic reflectance spectra of Mars obtained during 1978, and absorption features in Mariner 7 and Mariner 9 spectra, are analyzed which are assigned to structural hydroxyl within a strongly hydrogen-bonded acidic material suggested to be a silicate. Deduced fundamentals indicate that the Si-O(b)-Si bond angle may be approximately linear, and that the estimated Si-O(b) bridge length may be about 1.61 A. Viking compositional data indicate that Mg(2+), rather than Ca(2+) may be the dominant cation in the Martian material. The results suggest that the silicate component of the dust may be an incipient hydrolysis product of olivine-rich ultramafic or mafic material, involving a process that resulted in minimum loss of mobile cations and that maintained the high O/Si ratio of the starting material.

Huguenin, R. L.↗

NASA NTRS1987

Chemical frost weathering of olivine: Experimental study and implications

New experimental results are reported on the frost weathering of olivine. After first weathering, a decrease in Fe sup 2(+)M(2) absorption bands were noted. This decrease is related to the protonation of O(+) in the mineral. It is contented that this reaction may result in the regolith storage of 100 to 1000 m of H(sub 2) over the history of Mars.

Harris, S. L.↗

NASA NTRS1987

Mars low albedo regions: Possible map of near-surface

A freeze/thaw desorption mechanism is proposed in certain low albedo areas which could be the factor that instigated dust storms. It is widely accepted that the bulk of the episodic gas evolution (not necessarily the oxygen release) experienced during the humidification process in the Viking Gas Exhange Experiment (GEX) was caused by a familiar process in which more polar H2O molecules replace large quantities of other preadsorbed gas molecules on adsorption sites. The author suggests that a similar process could produce high pore pressures in soil that could disrupt the soil and eject dust at high velocity. The author also argued that association of sites of dust storms initiated with high thermal inertial areas may simply reflect repeated dust depletion.

Huguenin, R. L.↗

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 NTRS1986

Injection of dust into the Martian atmosphere - Evidence from the Viking Gas Exchange experiment

The hypothesis that predawn midlatitude storms are triggered by a soil humidification process is examined. A freeze/thaw model of the process is evaluated in the Viking Gas Exchange experiments conducted on Mars. The humidification-driven desorption and desiccation state of Martian soil samples are analyzed. The periodic humidification of equatorial regolith soil is studied in terms of pore space pressure during desorption events and soil diffusivity; the thermal properties of the regolith surface layer are modeled using the program of Clifford (1984). Consideration is given to the diurnal and seasonal cycles of the humidification process, the permanent, low-albedo features in the midlatitudes, and the production of H2SO4 and HCl aerosols.

Huguenin, R. L.↗

NASA NTRS1986

Intelligent information extraction from reflectance spectra Absorption band positions

A multiple high-order derivative analysis algorithm has been developed which can automatically extract absorption band positions from low-quality reflectance spectra with little degredation of accuracy. Overlapping bands with comparable widths and intensities can be resolved whose centers are as close as 0.3-0.5 W, with safer resolution limits of 0.6-1.0 W band center separations suggested for overlapping bands that are dissimilar. The segment length for smoothing is continually adjusted to about 0.5 W to minimize signal distortion, and a spectral pattern recognition algorithm predicts the signal spectrum and calculates approximate W across the spectrum using its second derivative. A single-pass cubic spline is applied to the smoothed data, and a sliding segment sixth-order polynomial is fit to the spectrum, with the length of the segment being continuously locally adjusted to 1.0 W across the spectrum. Good reliability and consistency of the algorithm is demonstrated with application to laboratory and earth-based telescope spectra.

Huguenin, R. L.↗

NASA NTRS1985

Basalts of Mars: Constraints on Volatile Evolution

The mineralogy of relatively unweathered rocks on Mars place important constraints on models of planetary oxidation state, volcanism and associated outgassing, accretion and associated volatile inventory, and geochemical changes over time. Reflectance spectra (300 to 2500 nm) provide direct mineralogic information about the surface materials. Spectra measured using Earth-based telescopes were analyzed by a multiple high-order derivative spectroscopy technique. Nine areas, measured during the 1978 opposition, were analyzed by the technique. Each contained suites of well-defined absorption bands. These bands can be interpreted in terms of constituent mineralogy by the technique of Adams. Among the features extracted from the spectra were bands attributed to iron oxides. Other bands can be attributed to silicates within chemically unweathered rocks/fines. Absorption features suggest the presence of Mg-olivine and plagioclase feldspar.

Huguenin, R. L.↗

NASA NTRS1985

Iron Oxides of Mars: Evidence for Contemporary Weathering

Reflectance spectra of Mars were analyzed using a multiple high order derivative spectroscopy technique. Among the results of the analysis was the presence of suites of bands in each of the spectra that can be attributed to Fe(3e) phases. Several of the spectra contained bands that are very close to the band positions in the laboratory spectra of goethite, an hexagonal hydrated ferric oxide. Spectra of other areas showed absorption bands that were within 3% of the positions for hematite, and hexagonal close packed unhydrated Fe203. Remaining areas showed bands that are intermediate in position to the goethite and hematite bands, suggesting that there may be mixtures of goethite and hematite, and/or intermediate (partially dehydrated goethite) phases present in those areas. Both bright areas and dark areas showed suites of goethite bands and hematite bands, and there does not therefore appear to be a correlation with albedo. The areas that showed the goethite bands are, however, within zones of ongoing or historically frequent dust cloud activity, and the areas with the hematite bands were outside of the zones of frequent dust cloud activity. This suggests the possiblility that the more hydrated phase may occur within a mobile dust component.

Huguenin, R. L.↗

NASA NTRS1985

Automated Extraction of Absorption Bands from Reflectance Special

A multiple high order derivative spectroscopy technique has been developed for deriving wavelength positions, half widths, and heights of absorption bands in reflectance spectra. The technique is applicable to laboratory spectra as well as medium resolution (100-200/cm) telescope or spacecraft spectra with moderate (few percent) noise. The technique permits absorption band positions to be detected with an accuracy of better than 3%, and often better than 1%. The high complexity of radiative transfer processes in diffusely reflected spectra can complicate the determination of absorption band positions. Continuum reflections, random illumination geometries within the material, phase angle effects, composite overlapping bands, and calibration uncertainties can shift apparent band positions by 20% from their actual positions or mask them beyond detection. Using multiple high order derivative analysis, effects of scattering continua, phase angle, and calibration (smooth features) are suppressed. Inflection points that characterize the positions and half widths of constituent bands are enhanced by the process and directly detected with relatively high sensitivity.

Huguenin, R. L.↗

NASA NTRS1985

Oxidation states of iron in the terrestrial planets: Evidence and implications for accretion models

Analyses of Mars spectra reveal that primary minerals may be more iron rich than average basalts on Earth, and the oxidation state of iron in the pyroxines suggests equally high or higher oxygen fugacities on Mars than Earth. Analysis of Mercury spectra reveal that silicate iron contents are substantially lower than those on Mars. Mercury, however, probably has a substantial iron core. This is consistent with a lower oxidation state of iron on Mercury than on Mars. These findings are consistent with predictions of models of equilibrium condensation and homogeneous accretion. Those models predict that Mercury would have negligible Fe(2+) in silicates (Fe/Fe+Mg approx. 0.5). For Mercury iron should be virtually all metallic, while for Mars the iron would be all oxidized as FeS and silicate. Surface measurements of Fe/Fe+Mg on Venus, Earth, and Mars further support the predicted relative increase in Fe/Fe+Mg ratio (increased oxidation state) with distance from the Sun. The implied high oxygen fugacities on Mars (Fe(3+) in silicates) provide additional consistence with the model predictions.

Huguenin, R. L.↗

NASA NTRS1983

Mars - A contamination potential?

Three regions on Mars, Solis Lacus, Noachis-Hellespontus, and the Syrtis Major border areas, would appear to have generally less hostile environments than at the Viking lander sites. Significant soil moisture may extend to within about 1 cm of the surface. Water vapor pressures within the pore spaces may be near saturation, and brines may be physically segregated from pockets of relatively pure H2O. Temperatures reach above 0 C during southern spring and summer, with peak temperatures reaching +22 C. These regions should contain fewer oxidants, and primary synthesis of organics may occur. The potential for contamination of these sites by microbes transported from existing spacecraft should be assessed. The adequacy of proposed new planetary protection procedures for possible future United States Mars Surface Sample Return missions should also be assessed in light of these findings.

Huguenin, R. L.↗

NASA NTRS1982

Chemical weathering and the Viking biology experiments on Mars

Since the publication of studies describing models that do not require external energy sources, new LR (labeled release) test standards module studies have been reported by Levin and Straat (1981). These studies impose important constraints on the various models, and they offer strong support for the 'frost-weathering' model. These findings are discussed here, and it is proposed that the activity of all three biology experiments can now adequately be explained as a consequence of a single active agent produced by contemporary chemical weathering. Some of the possible consequences and implications of contemporary weathering for the current state and evolution of the regolith and atmosphere are briefly discussed.

Huguenin, R. L.↗

NASA NTRS1982

Mars: Definition and characterization of global surface units with emphasis on composition

Viking 2 approach maps of red and violet normal albedo are used to define units of similar optical properties for a large area of the Martian surface. Computer processing of these data reveals clusters of albedo values relating to specific, contiguous regions of the planet, with some unit boundaries being of a gradational nature while others are more discrete. A study of the albedo properties of analog materials measured in the laboratory, and of telescopic spectrophotometry of Mars, indicates that both hydroxylated and hematitic oxidized materials exist on the surface. The most probable surface expression of global dust and/or high albedo soils is in the classical bright region, Arabia. Most low albedo features in the region studied have red and violet albedos that are consistent with a dark substrate, such as basalt, coated by, or mixed with, a fine grained alteration product.

Mccord, T. B.↗

NASA NTRS1982

Remote sensing evidence for regolith water vapor sources on Mars

McCord et al. (1977) have presented earth-based photometric imaging data of an event associated with the 1973 dust storm on Mars. The initial dust cloud in Solis Lacus and two regions to the north and south appeared anomalously bright at blue wavelengths. Water frosts, hazes, and/or clouds were identified, and it was suggested that the water responsible for these findings may have originated from Solis Lacus. More recently, a more intensive review of the observational record of Mars was undertaken. Earth-based telescope observations and data from the Mariner and Viking missions have revealed that Solis Lacus has been a center of repeated activity. Persistent activity in the vicinity of Noachis-Hellespontus and in the border regions of Syrtis Major was also discovered. A review of the observations is provided and possible interpretations are discussed. The obtained results appear to support the original proposal that Solis Lacus may be a source of water vapor. Noachis-Hellespontus seems to be a similar vapor source

Huguenin, R. L.↗

NASA NTRS1981

Remote sensing at the University of Massachusetts

The projects, faculty, and computer resources involved in remote sensing research at the University of Massachusetts are discussed. Field instrumentation and technology transfers from other disciplines are also described.

Huguenin, R. L.↗

NASA NTRS1979

Mars surface composition from reflectance spectroscopy - A summary

Visible and near-infrared reflectance spectra and multispectral maps of the Martian surface are discussed, and implications of the data for the composition of the Martian surface are considered. Spacecraft and earth-based telescopic observations have confirmed the generally bimodal albedo distribution of the planet, dividing the surface into bright and dark regions. Mars spectra are characterized by the presence of strong Fe(+3) absorption, which is attributed to various ferric oxide minerals. Interpretations of the spectra from the dark regions indicate a basaltic or ultramafic source rock. Evidence for water ice or a highly desiccated metal hydrate has been obtained, along with evidence for CO2-ice only in the south polar cap. Mariner 9 observations of Martian dust suggest the presence of rather acidic rock or mineral particles, or a montmorillonite-type clay. Prospects for the future study of Martian surface composition include continuing earth-based spectrophotometric studies, and high-spectral-resolution mapping of a significant portion of the surface by the Galileo spacecraft and the next Mars mission.

Singer, R. B.↗

NASA NTRS1979

Frost-weathering on Mars - Experimental evidence for peroxide formation

The weathering of silicates by frost is investigated in relation to the formation of surface peroxides to which Viking biology experiment results have been attributed. Samples of the minerals olivine and pyroxene were exposed to water vapor at -11 to -22 C and resultant gas evolution and pH were monitored. Experiments reveal the formation of an acidic oxidant upon interaction of the mineral and H2O frost at subfreezing temperatures, which chemical indicators have suggested to be chemisorbed hydrogen peroxide. A model for the formation of chemisorbed peroxide based on the chemical reduction of the mineral by surface frost is proposed, and it is predicted that the perioxide would decay at high temperatures to H2O and adsorbed O, consistent with the long-term storage and sterilization behavior of the soil oxidants observed in the Viking Gas Exchange and Labeled Release experiments.

Huguenin, R. L.↗