The Distribution of Crystalline Hematite on Mars from the Thermal Emission Spectrometer: Evidence for Liquid Water
ABSTRACT Crystalline hematite on Mars has been mapped using the MGS TES. Two major, and several minor areas of significant accumulation are identified. We favor precipitation models involving Fe-rich water, providing direct mineralogic evidence for large-scale water interactions.
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ABSTRACT: The Thermal Emission Imaging System (THEMIS) on 2001 Mars Odyssey will investigate the surface mineralogy and physical properties of Mars using multi-spectral thermal-infrared images in nine wavelengths centered from 6.8 to 14.9μm, and visible/near-infrared images in five bands centered from 0.42 to 0.86μm. THEMIS will map the entire planet in both day and night multi-spectral infrared images at 100-m per pixel resolution, 60% of the planet in one-band visible images at 18-m per pixel, and several percent of the planet in 5-band visible color. Most geologic materials, including carbonates, silicates, sulfates, phosphates, and hydroxides have strong fundamental vibrational absorption bands in the thermal-infrared spectral region that provide diagnostic information on mineral composition. The ability to identify a wide range of minerals allows key aqueous minerals, such as carbonates and hydrothermal silica, to be placed into their proper geologic context. The specific objectives of this investigation are to: (1)determine the mineralogy and petrology of localized deposits associated with hydrothermal or sub-aqueous environments, and to identify future landing sites likely to represent these environments; (2)search for thermal anomalies associated with active sub-surface hydrothermal systems; (3)study small-scale geologic processes and landing site characteristics using morphologic and thermophysical properties; and (4)investigate polar cap processes at all seasons. THEMIS follows the Mars Global Surveyor Thermal Emission Spectrometer (TES) and Mars Orbiter Camera (MOC) experiments, providing substantially higher spatial resolution IR multi-spectral images to complement TES hyperspectral (143-band) global mapping, and regional visible imaging at scales intermediate between the Viking and MOC cameras. The THEMIS uses an uncooled microbolometer detector array for the IR focal plane. The optics consists of all-reflective, three-mirror anastigmat telescope with a 12-cm effective aperture and a speed of f/1.6. The IR and visible cameras share the optics and housing, but have independent power and data interfaces to the spacecraft. The IR focal plane has 320 cross-track pixels and 240 down-track pixels covered by 10 ∼1-μm-bandwidth strip filters in nine different wavelengths. The visible camera has a 1024×1024 pixel array with 5 filters. The instrument weighs 11.2kg, is 29cm by 37cm by 55cm in size, and consumes an orbital average power of 14W.Space Science Reviews 12/2003; 110(1):85-130. · 5.52 Impact Factor
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ABSTRACT: The concentrated crystalline hematite is a unique composition on Mars. A GIS-based study of regional MGS and Viking data sets is underway to shed light on the mysterious mineral deposit. The abstract presents the results of the study.03/2002;
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ABSTRACT: 1] Low-frequency sounding radars should be able to probe the Martian subsurface layers down to varying depths, depending on the geoelectrical properties of the sounded sites. We present in this work four frequency-dependent geoelectrical models of the Martian subsurface in the 1–20 MHz frequency band, based on laboratory electromagnetic characterization of Martian soil analogues. Those models correspond to local Martian sites that we considered to be of particular interest in the search for water using mainly the Ground-Penetrating Radar (GPR) instrument of the Netlander mission. Results and discussion are also valid for both sounding experiments MARSIS and SHARAD. The four models of the Martian subsurface are designed to represent terrains where recent fluvial-like features suggest the presence of near-subsurface ground ice and probably liquid water. We performed measurements on volcanic and sedimentary materials that may be present on these sites under the appropriate geophysical conditions that may exist in those terrains. We then simulated the backscattered radar echo arising from each site in the 2 MHz frequency band, using the Finite Difference Time Domain (FDTD) algorithm, in order to evaluate the instrument performances to probe the subsurface stratigraphy of each site. Our results confirm that the near-subsurface rich iron oxide mineralogy controls the instrument performances in terms of penetration depth and signal-to-noise ratio in the 2 MHz frequency band. We finally discuss the geophysical and geoelectrical sounding conditions that could lead to an ambiguous detection of shallow subsurface water on Mars for the Netlander GPR. geoelectrical models of the Martian subsurface for shallow groundwater detection using sounding radars, J. Geophys. Res., 108(E4), 8030, doi:10.1029/2002JE001871, 2003.Journal of Geophysical Research 01/2003; 108. · 3.17 Impact Factor
THE DISTRIBUTION OF CRYSTALLINE HEMATITE ON MARS FROM THE THERMAL EMISSION
SPECTROMETER: EVIDENCE FOR LIQUID WATER. P.R.Christensen
One of the primary objectives of the Thermal
Emission Spectrometer (TES) instrument on the
Mars Global Surveyor (MGS) spacecraft is to
determine and map the mineralogic composition of
the Martian surface. Of particular interest is the
search for minerals formed through interaction with
water, either by low-temperature precipitation or
weathering, or by hydrothermal mineralization.
Over 50 x10
from the MGS mapping orbit. These spectra
observed from orbit are a complex combination of
surface and atmospheric emitted and transmitted
energy. The spectral features resulting from
atmospheric CO2, dust, and water ice have been
removed using a radiative transfer model [1, 2].
Using these atmospherically-corrected spectra we
have identified two major accumulations of
crystalline hematite (α-Fe2O3) . Crystalline
hematite is uniquely identified by the presence of
fundamental vibrational absorption features centered
near 300, 450, and >525 cm
silicate fundamentals in the 1000 cm
depth and shape of the hematite fundamental bands
show that the hematite is crystalline and relatively
coarse grained (>5-10 µm). Diameters up to and
greater than 100s of micrometers are permitted
within the instrumental noise and natural variability
of hematite spectra. The spectrally-derived areal
abundance of hematite varies with particle size from
~10% (>30 µm diameter) to 40-60% (10 µm
diameter). Crystalline hematite has been previously
reported using visible/near-IR observations , and
nanophase hematite is widely thought to be an
important component of the materials that give Mars
its red color [5-8]. The hematite in Sinus Meridiani
is distinct, however, from the fine-grained (diameter
<5-10 µm), red, crystalline hematite considered, on
the basis of visible, near-IR data, to be a minor
spectral component in Martian bright regions.
Crystalline hematite has been mapped over an
area in Sinus Meridiani approximately 500 km in
longitude extending approximately 200 km in
latitude . The extent of this deposit very closely
matches the geomorphic boundary of a smooth,
layered, friable unit that is interpreted to be sedi-
Christensen, Separation of atmospheric and surface
1, M. Malin
3, D. Morris
5, J. Band-
1, M. Lane
2U.S.Geological Survey, Denver, CO;
5Johnson Space Center, TX;
1, K. Edgett
1Dept. of Geology, Campus Box 871404, Arizona State University, Tempe, AZ 85287-
3Malin Space Science Systems, CA;
6Ames Research Center, Moffet Field, CA,
4U. S. Geological Survey, Flag-
7Goddard Space Flight Center,
6 spectra have been observed to date
-1, and by the absence of
-1 region. The
mentary in origin [3, 9]. This material may be the
uppermost surface in the region, indicating that it
might be a later-stage sedimentary unit, or alterna-
tively a layered portion of the heavily cratered
A second accumulation of hematite approxi-
mately 60 x 60 km in size is observed in Aram
Chaos (2° N, 21° W). This site is also associated
with layered materials and a water-rich environ-
We consider five possible mechanisms for the
formation of coarse-grained, crystalline hematite.
These processes fall into two classes depending on
whether they require a significant amount of near-
surface water: (1) chemical precipitation that
includes origin by (a) precipitation from standing,
oxygenated, Fe-rich water (oxide iron formations),
(b) precipitation from Fe-rich hydrothermal fluids,
(c) low temperature dissolution and precipitation
through mobile ground water leaching, and (d)
formation of surface coatings; and (2) thermal
oxidation of magnetite-rich lavas . We favor
chemical precipitation models involving precipita-
tion from Fe-rich water based on the probable
association with sedimentary materials, large
geographic size, distance from regional heat sources,
and lack of evidence for extensive groundwater
processes elsewhere on Mars.
The TES results provide mineralogic evidence
for probable large-scale water interactions. The
Sinus Meridiani region may be an ideal candidate
for future landed missions searching for biotic and
pre-biotic environments, and the physical character-
istics of this site satisfy the engineering require-
ments for the missions currently being considered.
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Christensen, Spectral dataset factor analysis and
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Lunar and Planetary Science XXXI
HEMATITE ON MARS: P.Christensen, M. Malin, D. Morris, J. Bandfield, M. Lane, K. Edgett
spectral features in Mars Global Surveyor Thermal
Emission Spectrometer (TES) spectra: Models and
atmospheric properties. J. Geophys. Res., in press.
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crystalline hematite mineralization on Mars by the
Thermal Emission Spectrometer: Evidence for near-
surface water. J. Geophys. Res., in press.
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Lunar and Planetary Science XXXI