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A suite of sulfate minerals were characterized spectrally, compositionally, and structurally in order to develop spectral reflectance-compositional-structural relations for this group of minerals. Sulfates exhibit diverse spectral properties, and absorption-band assignments have been developed for the 0.3-26 [micro]m range. Sulfate absorption features can be related to the presence of transition elements, OH, [H.sub.2]O, and S[O.sub.4] groups. The number, wavelength position, and intensity of these bands are a function of both composition and structure. Cation substitutions can affect the wavelength positions of all major absorption bands. Hydroxo-bridged [Fe.sup.3+] results in absorption bands in the 0.43, 0.5, and 0.9 [micro]m regions, while the presence of [Fe.sup.2+] results in absorption features in the 0.9-1.2 [micro]m interval. Fundamental S-O bending and stretching vibration absorption bands occur in the 8-10, 13-18, and 19-24 [micro]m regions (1000-1250, 550-770, and 420-530 [cm.sup.- 1]). The most intense combinations and overtones of these fundamentals are found in the 4-5 [micro]m (2000-2500 [cm.sup.-1]) region. Absorption features seen in the 1.7-1.85 [micro]m interval are attributable to H-OH/O-H bending and translation/rotation combinations, while bands in the 2.1-2.7 [micro]m regions can be attributed to [H.sub.2]O- and OH-combinations as well as overtones of S-O bending fundamentals. OH- and [H.sub.2]O-bearing sulfate spectra are fundamentally different from each other at wavelengths below ~6 [micro]m. Changes in [H.sub.2]O/OH content can shift S-O band positions due to change in bond lengths and structural rearrangement. Differences in absorption band wavelength positions enable discrimination of all the sulfate minerals used in this study in a number of wavelength intervals. Of the major absorption band regions, the 4-5 [micro]m region seems best for identifying and discriminating sulfates in the presence of other major rock-forming minerals. Keywords: Asteroids, composition; Europa; Mars, surface; Meteorites; Mineralogy; Spectroscopy

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2005.01.015 Byline: Ashley Gerard Davies, Dennis L. Matson, Glenn J. Veeder, Torrence V. Johnson, Diana L. Blaney Abstract: The modeling of thermal emission from active lava flows must account for the cooling of the lava after solidification. Models of lava cooling applied to data collected by the Galileo spacecraft have, until now, not taken this into consideration. This is a flaw as lava flows on Io are thought to be relatively thin with a range in thickness from [approximately equal to]1 to 13 m. Once a flow is completely solidified (a rapid process on a geological time scale), the surface cools faster than the surface of a partially molten flow. Cooling via the base of the lava flow is also important and accelerates the solidification of the flow compared to the rate for the 'semi-infinite' approximation (which is only valid for very deep lava bodies). We introduce a new model which incorporates the solidification and basal cooling features. This model gives a superior reproduction of the cooling of the 1997 Pillan lava flows on Io observed by the Galileo spacecraft. We also use the new model to determine what observations are necessary to constrain lava emplacement style at Loki Patera. Flows exhibit different cooling profiles from that expected from a lava lake. We model cooling with a finite-element code and make quantitative predictions for the behavior of lava flows and other lava bodies that can be tested against observations both on Io and Earth. For example, a 10-m-thick ultramafic flow, like those emplaced at Pillan Patera in 1997, solidifies in [approximately equal to]450 days (at which point the surface temperature has cooled to [approximately equal to]280 K) and takes another 390 days to cool to 249 K. Observations over a sufficient period of time reveal divergent cooling trends for different lava bodies [examples: lava flows and lava lakes have different cooling trends after the flow has solidified (flows cool faster)]. Thin flows solidify and cool faster than flows of greater thickness. The model can therefore be used as a diagnostic tool for constraining possible emplacement mechanisms and compositions of bodies of lava in remote-sensing data. Author Affiliation: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099, USA

Polar brightness temperatures on Io are higher than expected for any passive surface heated by absorbed sunlight. This discrepancy implies large scale volcanic activity from which we derive a new component of Io's heat flow. We present a 'Three Component' thermal background, infrared emission model for Io that includes active polar regions. The widespread polar activity contributes an additional ~0.6 W [m.sup.-2] to Io's heat flow budget above the ~2.5 W [m.sup.-2] from thermal anomalies, Our estimate for Io's global average heat flow increases to ~3 [+ or -] 1 W [m.sup.-2] and ~1.3 [+ or -] 0.4 x [10.sup.14] watts total. Keywords: Io; Volcanism; Thermal; Infrared

Modeling of an infrared outburst on the Jovian satellite reveals that the outburst is caused by the flow of lava from a large volcanic eruption. The lava has an initial temperature of 1,225 Kelvin, which later cools down to 555 Kelvin. Many volcanic eruptions such as this have contributed to the absence of intact craters on the Jovian satellite.

On the upcoming Mars‐2020 rover two remote sensing instruments, Mastcam‐Z and SuperCam, and two microscopic proximity science instruments, Scanning for Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) and Planetary Instrument for X‐ray Lithochemistry (PIXL), will collect compositional (mineralogy, chemistry, and organics) data essential for paleoenvironmental reconstruction. The synergies between and limitations of these instruments were evaluated via study of a Mars analog field site in the Mojave desert, using instruments approximating the data that will be returned by Mars‐2020. A ground truth data set was generated for comparison to validate the results. The site consists of a succession of clay‐rich mudstones of lacustrine origin, interbedded tuffs, a carbonate‐silica travertine deposit, and gypsiferous mudstone strata. The major geological units were mapped successfully using simulated Mars‐2020 data. Simulated Mastcam‐Z data identified unit boundaries and Fe‐bearing weathering products. Simulated SuperCam passive shortwave infrared and green Raman data were essential in identifying major mineralogical composition and changes in lacustrine facies at distance; this was possible even with spectrally downsampled passive IR data. Laser‐induced breakdown spectroscopy and simulated PIXL data discriminated and mapped major element chemistry. Simulated PIXL revealed millimeter‐scale zones enriched in zirconium, of interest for age dating. Scanning for SHERLOC‐like data mapped sulfate and carbonate at submillimeter scale; silicates were identified with increased laser pulses/spot or by averaging of hundreds of spectra. Fluorescence scans detected and mapped varied classes of organics in all samples, characterized further with follow‐on spatially targeted deep‐UV Raman spectra. Development of dedicated organics spectral libraries is needed to aid interpretation. Given these observations, the important units in the outcrop would be sampled and cached for sample return.Plain Language Summary: The Mars‐2020 rover will land at Jezero Crater, where it will search for signs of past life and seek to refine our understanding of the geologic history of Mars. The ability to measure the minerals, chemical composition, and organic molecules present at the landing site is vital to these investigations. There are four instruments on the Mars‐2020 rover which can make these measurements: SuperCam, Mastcam‐Z, Scanning for Habitable Environments with Raman and Luminescence for Organics and Chemicals, and Planetary Instrument for X‐ray Lithochemistry. We undertook a field study using instruments that approximate the same data that the Mars‐2020 instruments will produce to discern (1) how the data from these instruments will inform and complement the discoveries from other instruments, (2) what limitations might exist for this suite of instruments and what important features may be missed because of these limitations, and (3) strategies to use the rover and its instruments most efficiently while lessening the gaps in knowledge that could result from these limitations. The data used to address these objectives compared favorably with a complete understanding of the field site using the full range of measurements available on Earth, indicating that accurate and complete information about the Mars landing site can be obtained while using the instruments in the modes described in this study.Key Points: Color imaging and multispectral data allow remote unit definition and passive IR adds key remote mineralogical identification capabilityMost mineral phases present identified but discriminating amorphous phases, clay minerals, and oxides sometimes required dedicated proceduresFluorescence mapping and deep‐UV Raman spectra detect organics in several sample locations, although organics spectral libraries need expansion [ABSTRACT FROM AUTHOR]

The Urey organic and oxidant detector consists of a suite of instruments designed to search for several classes of organic molecules in the martian regolith and ascertain whether these compounds were produced by biotic or abiotic processes using chirality measurements. These experiments will also determine the chemical stability of organic molecules within the host regolith based on the presence and chemical reactivity of surface and atmospheric oxidants. Urey has been selected for the Pasteur payload on the European Space Agency's (ESA's) upcoming 2013 ExoMars rover mission. The diverse and effective capabilities of Urey make it an integral part of the payload and will help to achieve a large portion of the mission's primary scientific objective: "to search for signs of past and present life on Mars." This instrument is named in honor of Harold Urey for his seminal contributions to the fields of cosmochemistry and the origin of life.