ABSTRACT: Diviner has detected several features on the Moon with highly silicic
compositions. These geologic settings of these features suggest
formation of highly evolved lithologies from both extrusive volcanic and
Geology. 01/2010; 33:809-812.
ABSTRACT: TES and GRS provide unique and complementary insights into martian
surface compositions. TES measures the composition of the upper hundred
microns of the surface while GRS measures the upper few tens of
centimeters. We examine TES oxide abundances of low-albedo surfaces and
compare distributions to GRS element abundances to constrain the
relative roles of igneous and alteration processes on Mars. The bulk
variability of compositions measured by TES is accounted for by two
spectral endmembers (ST1 and ST2). TES oxide abundances (wt. %) (SiO2,
Na2O, K2O, CaO, MgO, FeO, Al2O3) are calculated by combining
compositions of spectral endmembers in proportion to their relative
modeled abundances (vol. %). Recent GRS studies report Si, K, Fe, Th,
and K/Th for 'regions' dominated by TES ST1 (RT1) and ST2 (RT2)
materials. The most significant TES chemical trends are higher
abundances of FeO for ST1 (ST1 15.2 % vs. ST2 12.4 %) and higher
abundances of SiO2 for ST2 (ST2 57.9 % vs. ST1 53.9 %). Results from
OMEGA are in agreement with TES oxides. OMEGA pyroxene maps are closely
correlated with the distribution of ST1 (High FeO) while ST2 materials
lack evidence of mafic bands and are consistent with an enrichment of
high-silica phases. GRS RT2 chemistries have higher abundances of FeO
(RT2 20.1 % vs. RT1 17.6 %), K, and Th compared to RT1. Abundances of
SiO2 (RT1 44.7 % and RT2 45.8 %) and K/Th ratio do not show significant
spatial variations. Chemical trends from TES and GRS appear to be in
disagreement. TES ST1 is enriched in FeO while GRS RT1 is depleted in
FeO. TES ST2 is enriched in SiO2 while GRS RT2 shows no enrichment in
SiO2. One can account for these discrepancies, and constrain igneous
and alteration processes, by considering the sampling depth differences
between TES and GRS. The constant K/Th ratio across RT1 and RT2 is not
consistent with subaqueous or deep subaerial aqueous weathering of
basalt as K would fractionate from Th. Fractional crystallization and
subduction zone magmatism could enrich K and Th, however GRS does not
detect an enrichment of Si as would be expected. The lack of any
significant enrichment in SiO2 between GRS RT1 and RT2 indicates that
evolved volcanics (andesites) are not present in high-abundances within
the upper few tens of centimeters at global scales. The favored model
from the GRS team is thus initial bulk differentiation processes on Mars
producing compositionally distinct magma source regions in the mantle.
RT1 and RT2 basaltic provinces with distinct trace element compositions
could then be produced. However, the differences in SiO2 between TES
ST1 and ST2 must be taken into consideration. Thin coatings or rinds of
secondary high-silica phases (tens of microns) significantly affect the
shape and position of absorptions in thermal emission spectra of basalt.
Such coatings on Mars may form from near-surface ice and/or
surface-atmosphere interactions with little to no water penetrating or
cycling into the surface. Limited degrees of alteration in only the
upper few tens of microns of the surface could affect TES derived
chemistries and be undetectable to GRS due to a deep sampling depth. GRS
and TES chemistries support: 1) Distinct magma source regions and
basaltic compositions for ST1-RT1 and ST2-RT2 and 2) Thin secondary
coatings or rinds of amorphous high-silica phases on ST2-RT2 basalt.
AGU Spring Meeting Abstracts. 04/2007; -1:07.
ABSTRACT: Mineralogy and chemistry of the Martian surface are derived from Thermal
Emission Spectrometer (TES) data by linear deconvolution using a
spectral library containing the infrared spectra of a variety of phases
[e.g. 1]. Obtaining successful results relies on utilization of a
spectral library containing an accurate representation of the phases
measured on the Martian surface. In order to explore the influence of a
variety of glass compositions on the deconvolution of TES spectra, we
synthesized five pristine glasses, obtained their thermal infrared
spectra and conducted preliminary TES spectral deconvolutions using a
spectral library containing the new glass spectra. The five new glasses
have compositions relevant to Martian igneous processes. One basalt has
a high-FeO, low-Al2O 3 composition linked to several Martian meteorites
[refs in 3]. A second basalt is based on the Deccan Trap basalt that
serves as a spectral analog to the TES Surface Type 1 (ST1) spectrum
. Similarly, one andesite is based on the Medicine Lake andesite that
serves as a spectral analog to the TES Surface Type 2 (ST2) spectrum
. A second andesite represents the interstitial melt composition
resulting from 90% crystallization of an anhydrous Martian meteorite
basalt (described above) . A dacitic glass represents the
interstitial melt composition resulting from 80% crystallization of a
hydrous Martian meteorite basalt . Each glass was fused in either Pt
or AgPd tubing vacuum sealed in SiO2 glass tubing for 72-96 hours. We
collected thermal infrared spectra of the ≥500 μm fraction of the
glasses at the Hawai'i Institute of Geophysics and Planetology with a
ThermoElectron Nexus 470 FTIR interferometric spectrometer in thermal
emission mode . We obtained data from 200-4000 cm-1 at 2 cm-1
spectral sampling. Preliminary deconvolutions of ST1 and ST2 spectra
indicate that the newly synthesized glasses may represent significant
components in the Martian surface. ST1 and ST2 are modeled with high
abundances of the andesitic interstitial melt endmember (17 vol% ST1 and
23 vol% ST2); ST2 is also modeled with 11 vol% of the analog TES basalt
glass and 13 vol% of a high-silica and potassium glass . Addition of
the new glass spectral endmembers results in an overall increase in the
total abundance of modeled glasses at the expense of plagioclase,
pyroxenes and olivine. Modeling of distinct glass compositions does not
necessarily indicate that each glass is present on the Martian surface.
Different glass compositions and abundances may represent average glass
chemistry much the way different plagioclase compositions are modeled to
reflect average plagioclase composition in rocks. Average derived
chemistries for glasses in ST1 (59 wt% SiO2 and 15.7 wt% FeO) and ST2
(64.2 wt% SiO2 and 10.5 wt%FeO) are influenced by inclusion of the new
glass compositions in deconvolutions. Total derived bulk chemistries
for ST1 and ST2, however, do not significantly change (e.g. ±1-2
wt% SiO2) with the addition of the new glass spectral endmembers. This
likely reflects the partial substitution of chemically similar minerals
with newly synthesized glasses.  M.S. Ramsey and P.R. Christensen
(1998) JGR, 103, 577 596.  J.L. Bandfield et al. (2000) Science, 287,
1626 1630.  M.E. Minitti and M.J. Rutherford (2000) GCA, 64, 2535-
2547.  V.E. Hamilton and P.G. Lucey (2005) LPSC XXXVI, #1272. 
M.B. Wyatt et al. (2001) JGR, 106, 14,711-14,732.
AGU Fall Meeting Abstracts. 11/2006; -1:0067.
Journal of Geophysical Research 01/2006; 111. · 3.02 Impact Factor
ABSTRACT: Compositional mapping of Mars at the 100-metre scale with the Mars Odyssey Thermal Emission Imaging System (THEMIS) has revealed a wide diversity of igneous materials. Volcanic evolution produced compositions from low-silica basalts to high-silica dacite in the Syrtis Major caldera. The existence of dacite demonstrates that highly evolved lavas have been produced, at least locally, by magma evolution through fractional crystallization. Olivine basalts are observed on crater floors and in layers exposed in canyon walls up to 4.5 km beneath the surface. This vertical distribution suggests that olivine-rich lavas were emplaced at various times throughout the formation of the upper crust, with their growing inventory suggesting that such ultramafic (picritic) basalts may be relatively common. Quartz-bearing granitoid rocks have also been discovered, demonstrating that extreme differentiation has occurred. These observations show that the martian crust, while dominated by basalt, contains a diversity of igneous materials whose range in composition from picritic basalts to granitoids rivals that found on the Earth.
Nature 07/2005; 436(7050):504-509. · 36.28 Impact Factor
ABSTRACT: Impure evaporitic sedimentary rocks preserved on Meridiani Planum
preserve textural, mineralogical and geochemical evidence for a
protracted and complex history of syndepositional through burial
diagenesis dominated by phreatic meteoric conditions.
Lunar and Planetary Science XXXVI, Lunar and Planetary Institute (2005). 02/2005;
ABSTRACT: The Miniature Thermal Emission Spectrometer (Mini-TES) has provided remote measurements of mineralogy, thermophysical properties, and atmospheric temperature profile and composition of the outcrops, rocks, spherules, and soils surrounding the Spirit and Opportunity Rovers. The mineralogy of volcanic rocks provides insights into the composition of the source regions and the nature of martian igneous processes. Carbonates, sulfates, evaporites, and oxides provide information on the role of water in the surface evolution. Oxides, such as crystalline hematite, provide insight into aqueous weathering processes, as would the occurrence of clay minerals and other weathering products. Diurnal temperature measurements can be used to determine particle size and search for the effects of sub-surface layering, which in turn provide clues to the origin of surficial materials through rock disintegration, aeolian transport, atmospheric fallout, or induration. In addition to studying the surface properties, Mini-TES spectra have also been used to determine the temperature profile in the lower boundary layer, providing evidence for convective activity, and have determined the seasonal trends in atmospheric temperature and dust and cloud opacity.
ABSTRACT: The Miniature Thermal Emission Spectrometer (Mini-TES) on Opportunity investigated the mineral abundances and compositions of outcrops, rocks, and soils at Meridiani Planum. Coarse crystalline hematite and olivine-rich basaltic sands were observed as predicted from orbital TES spectroscopy. Outcrops of aqueous origin are composed of 15 to 35% by volume magnesium and calcium sulfates [a high-silica component modeled as a combination of glass, feldspar, and sheet silicates (approximately 20 to 30%)], and hematite; only minor jarosite is identified in Mini-TES spectra. Mini-TES spectra show only a hematite signature in the millimeter-sized spherules. Basaltic materials have more plagioclase than pyroxene, contain olivine, and are similar in inferred mineral composition to basalt mapped from orbit. Bounce rock is dominated by clinopyroxene and is close in inferred mineral composition to the basaltic martian meteorites. Bright wind streak material matches global dust. Waterlain rocks covered by unaltered basaltic sands suggest a change from an aqueous environment to one dominated by physical weathering.
Science 01/2005; 306(5702):1733-9. · 31.20 Impact Factor
ABSTRACT: The soils at the Opportunity site are fine-grained basaltic sands mixed with dust and sulfate-rich outcrop debris. Hematite is concentrated in spherules eroded from the strata. Ongoing saltation exhumes the spherules and their fragments, concentrating them at the surface. Spherules emerge from soils coated, perhaps from subsurface cementation, by salts. Two types of vesicular clasts may represent basaltic sand sources. Eolian ripples, armored by well-sorted hematite-rich grains, pervade Meridiani Planum. The thickness of the soil on the plain is estimated to be about a meter. The flatness and thin cover suggest that the plain may represent the original sedimentary surface.
Science 01/2005; 306(5702):1723-6. · 31.20 Impact Factor
ABSTRACT: The Miniature Thermal Emission Spectrometer (Mini-TES) experiments
provide remote measurements of mineral abundances and compositions at
the Spirit and Opportunity landing sites of Gusev Crater and Meridiani
Planum. Olivine basaltic sands and rocks are identified at Gusev
Crater, along with variable amounts of fine-grained dust and other
possible coatings. Olivine basaltic sands and coarse crystalline
hematite, a clinopyroxene-rich basaltic rock, fine-grained dust, and
outcrops composed of sulfates, hematite, and sheet silicates/glass are
identified at Meridiani Planum. The occurrence of olivine basalt was
predicted at both landing sites by observations from the orbiting Mars
Global Surveyor (MGS) Thermal Emission Spectrometer (TES) and Mini-TES
spectra of basaltic sands are very similar to a global average TES
basalt spectrum in the overall spectral shape and positions of spectral
features. Ground-truth observations of the mineralogy and chemistry of
olivine basalt from the Mini-TES, Alpha Particle X-ray Spectrometer
(APXS), and Mössbauer Spectrometer (MB) are significant because of
the extensive distribution and high-abundance of olivine basalt on Mars
and the inferred petrogenesis and evolution of a basaltic crust. In
this study, we calculate bulk chemical oxide abundances of surface
materials from Mini-TES derived mineral abundances and compositions and
compare results to APXS and MB observations to examine the accuracy of
thermal emission derived chemistry. We also examine methods to
constrain APXS derived normative minerals using multivariate regression
with Mini-TES and MB mineral abundances and compositions. We focus on
comparisons of Mini-TES and TES derived chemistries of basalt to
determine the limits to which we can constrain bulk compositions and the
depth and degree of partial melting of their source regions. Local
ground-truth observations of the bulk mineralogy and chemistry of a
global basaltic unit provide insight to the degree of differentiation
of the crust and mantle.
AGU Fall Meeting Abstracts. 11/2004; -1:04.
ABSTRACT: The Miniature Thermal Emission Spectrometer (Mini-TES) on Spirit has studied the mineralogy and thermophysical properties at Gusev crater. Undisturbed soil spectra show evidence for minor carbonates and bound water. Rocks are olivinerich basalts with varying degrees of dust and other coatings. Dark-toned soils observed on disturbed surfaces may be derived from rocks and have derived mineralogy (+/-5 to 10%) of 45% pyroxene (20% Ca-rich pyroxene and 25% pigeonite), 40% sodic to intermediate plagioclase, and 15% olivine (forsterite 45% +/-5 to 10). Two spectrally distinct coatings are observed on rocks, a possible indicator of the interaction of water, rock, and airfall dust. Diurnal temperature data indicate particle sizes from 40 to 80 microm in hollows to approximately 0.5 to 3 mm in soils.
Science 09/2004; 305(5685):837-42. · 31.20 Impact Factor
ABSTRACT: The Spirit landing site in Gusev Crater on Mars contains dark, fine-grained, vesicular rocks interpreted as lavas. Pancam and Mini-Thermal Emission Spectrometer (Mini-TES) spectra suggest that all of these rocks are similar but have variable coatings and dust mantles. Magnified images of brushed and abraded rock surfaces show alteration rinds and veins. Rock interiors contain </=25% megacrysts. Chemical analyses of rocks by the Alpha Particle X-ray Spectrometer are consistent with picritic basalts, containing normative olivine, pyroxenes, plagioclase, and accessory FeTi oxides. Mössbauer, Pancam, and Mini-TES spectra confirm the presence of olivine, magnetite, and probably pyroxene. These basalts extend the known range of rock compositions composing the martian crust.
Science 08/2004; 305(5685):842-5. · 31.20 Impact Factor
Science 01/2004; 306:1723-1726. · 31.20 Impact Factor
ABSTRACT: A gradation of surface units represents either (1) an influx of basaltic sediment from southern highlands, deposited on andesitic volcanics, or (2) incompletely weathered basalt marking the geographic extent of submarine alteration of basaltic crust. Additional information is contained in the original extended abstract.
ABSTRACT: Basalt and andesite surface compositions are identified within individual low albedo intracrater features and adjacent dark wind streaks. High resolution mapping of compositional heterogeneities may help constrain origin hypotheses for these features. Additional information is contained in the original extended abstract.
Meteoritics and Planetary Science Supplement. 06/2000; 35:171.
Meteoritics and Planetary Science Supplement. 06/1999; 34:123.
ABSTRACT: 1] Gusev crater, previously interpreted as the depocenter for the Gusev-Ma'adim Vallis fluvio-lacustrine system, is a proposed landing site for one of the Mars Exploration Rovers (MER). Here we use new remote-sensing data from the Thermal Emission Imaging System (THEMIS) supplemented by data from the Thermal Emission Spectrometer (TES), Mars Orbiter Camera (MOC), and Mars Orbiter Laser Altimeter (MOLA) to characterize the geology of Gusev crater. Thermal infrared data from THEMIS and TES were used to map thermophysical units on the basis of relative albedos and diurnal temperature variations. THEMIS and MOC visible images were used to map unit morphologies and to estimate crater density ages. MOLA data were used to identify unit contacts and stratigraphic relationships. Various data were then combined to construct a new surface unit map and stratigraphy for units on the floor of Gusev. Seven surface units were identified in Gusev, mostly Hesperian in age, but with two showing evidence of later modification and redistribution. Five or more surface units and layering are present within the MER-A landing ellipse, attesting to the geologic diversity of this site. Surface units show features that could be consistent with fluvio-lacustrine, aeolian, and/or volcanoclastic deposition, but the spatial resolution of visible/infrared data does not allow for the identification of unambiguous volcanic or fluvio-lacustrine textures. However, a MER landing in Gusev may provide the opportunity to analyze multiple units, distinguish rock types, examine stratigraphic relationships, and shed light on the ancient depositional environment.
J. Geophys. Res. 108(8078).
ABSTRACT: Impure reworked evaporitic sandstones, preserved on Meridiani Planum, Mars, are mixtures of roughly equal amounts of altered siliciclastic debris, of basaltic provenance (40 ± 10% by mass), and chemical constituents, dominated by evaporitic minerals (jarosite, Mg-, Ca-sulfates ± chlorides ± Fe-, Na-sulfates), hematite and possibly secondary silica (60 ± 10%). These chemical constituents and their relative abundances are not an equilibrium evaporite assemblage and to a substantial degree have been reworked by aeolian and subaqueous transport. Ultimately they formed by evaporation of acidic waters derived from interaction with olivine-bearing basalts and subsequent diagenetic alteration. The rocks experienced an extended diagenetic history, with at least two and up to four distinct episodes of cementation, including stratigraphically restricted zones of recrystallization and secondary porosity, non-randomly distributed, highly spherical millimeter-scale hematitic concretions, millimeter-scale crystal molds, interpreted to have resulted from dissolution of a highly soluble evaporite mineral, elongate to sheet-like vugs and evidence for minor synsedimentary deformation (convolute and contorted bedding, possible teepee structures or salt ridge features). Other features that may be diagenetic, but more likely are associated with relatively recent meteorite impact, are meter-scale fracture patterns, veins and polygonal fractures on rock surfaces that cut across bedding. Crystallization of minerals that originally filled the molds, early cement and sediment deformation occurred syndepositionally or during early diagenesis. All other diagenetic features are consistent with formation during later diagenesis in the phreatic (fluid saturated) zone or capillary fringe of a groundwater table under near isotropic hydrological conditions such as those expected during periodic groundwater recharge. Textural evidence suggests that rapidly formed hematitic concretions post-date the primary mineral now represented by crystal molds and early pore-filling cements but pre-date secondary moldic and vug porosity. The second generation of cements followed formation of secondary porosity. This paragenetic sequence is consistent with an extended history of syndepositional through post-depositional diagenesis in the presence of a slowly fluctuating, chemically evolving, but persistently high ionic strength groundwater system.
Earth and Planetary Science Letters.