96 research outputs found
Mars Express measurements of surface albedo changes over 2004 - 2010
The pervasive Mars dust is continually transported between the surface and
the atmosphere. When on the surface, dust increases the albedo of darker
underlying rocks and regolith, which modifies climate energy balance and must
be quantified. Remote observation of surface albedo absolute value and albedo
change is however complicated by dust itself when lifted in the atmosphere.
Here we present a method to calculate and map the bolometric solar
hemispherical albedo of the Martian surface using the 2004 - 2010 OMEGA imaging
spectrometer dataset. This method takes into account aerosols radiative
transfer, surface photometry, and instrumental issues such as registration
differences between visible and near-IR detectors. Resulting albedos are on
average 17% higher than previous estimates for bright surfaces while similar
for dark surfaces. We observed that surface albedo changes occur mostly during
the storm season due to isolated events. The main variations are observed
during the 2007 global dust storm and during the following year. A wide variety
of change timings are detected such as dust deposited and then cleaned over a
Martian year, areas modified only during successive global dust storms, and
perennial changes over decades. Both similarities and differences with previous
global dust storms are observed. While an optically thin layer of bright dust
is involved in most changes, this coating turns out to be sufficient to mask
underlying mineralogical near-IR spectral signatures. Overall, changes result
from apparently erratic events; however, a cyclic evolution emerges for some
(but not all) areas over long timescales
Water ice at low to midlatitudes on Mars
In this paper, we analyze water ice occurrences at the surface of Mars using
near-infrared observations, and we study their distribution with a climate
model. Latitudes between 45{\deg}S and 50{\deg}N are considered. Data from the
Observatoire pour la Min\'eralogie, l'Eau, les Glaces et l'Actitit\'e and the
Compact Reconnaissance Imaging Spectrometer for Mars are used to assess the
presence of surface water ice as a function of location and season. A modeling
approach combining the 1-D and 3-D versions of the General Circulation Model of
the Laboratoire de M\'et\'eorologie Dynamique de Jussieu is developed and
successfully compared to observations. Ice deposits 2-200 \mu m thick are
observed during the day on pole facing slopes in local fall, winter and early
spring. Ice extends down to 13{\deg} latitude in the Southern Hemisphere but is
restricted to latitudes higher than 32{\deg} in the north. On a given slope,
the pattern of ice observations at the surface is mainly controlled by the
global variability of atmospheric water (precipitation and vapor), with local
ground properties playing a lower role. Only seasonal surface ice is observed:
no exposed patches of perennial ground ice have been detected. Surface seasonal
ice is however sensitive to subsurface properties: the results presented in
this study are consistent with the recent discovery of low latitude subsurface
ice obtained through the analysis of CO2 frost
Near-tropical subsurface ice on Mars
Near-surface perennial water ice on Mars has been previously inferred down to
latitudes of about 45{\deg} and could result from either water vapor diffusion
through the regolith under current conditions or previous ice ages
precipitations. In this paper we show that at latitudes as low as 25{\deg} in
the southern hemisphere buried water ice in the shallow (< 1 m) subsurface is
required to explain the observed surface distribution of seasonal CO2 frost on
pole facing slopes. This result shows that possible remnants of the last ice
age, as well as water that will be needed for the future exploration of Mars,
are accessible significantly closer to the equator than previously thought,
where mild conditions for both robotic and human exploration lie
Evidence for an Ancient Buried Landscape on the NW Rim of Hellas Basin, Mars
Hellas basin is the largest (2000+ km across) well-preserved impact structure on Mars and its deepest depositional sink [e.g., 1]. The Hellas rim and adjacent highlands are of special interest given the possibility of paleolakes on the basin floor [2-4], recent studies of potential localized fluvial/lacustrine systems [2, 5-17], and evidence for phyllosilicates around and within impact craters north of the basin [18-26]. We are producing a 1:1.5M-scale geologic map of eight MTM quadrangles (-25312, -25307, -25302, -25297, -30312, -30307, -30302, -30297) along Hellas NW rim. The map region (22.5-32.5degS, 45- 65degE) includes a transect across the cratered highlands of Terra Sabaea, the degraded NW rim of Hellas, and basin interior deposits of NW Hellas Planitia. No previous mapping studies have focused on this region, although it has been included in earlier global and regional maps [27-29]
New near-IR observations of mesospheric CO2 and H2O clouds on Mars
Carbon dioxide clouds, which are speculated by models on solar and
extra-solar planets, have been recently observed near the equator of Mars. The
most comprehensive identification of Martian CO2 ice clouds has been obtained
by the near-IR imaging spectrometer OMEGA. CRISM, a similar instrument with a
higher spatial resolution, cannot detect these clouds with the same method due
to its shorter wavelength range. Here we present a new method to detect CO2
clouds using near-IR data based on the comparison of H2O and CO2 ice spectral
properties. The spatial and seasonal distributions of 54 CRISM observations
containing CO2 clouds are reported, in addition to 17 new OMEGA observations.
CRISM CO2 clouds are characterized by grain size in the 0.5-2\mum range and
optical depths lower than 0.3. The distributions of CO2 clouds inferred from
OMEGA and CRISM are consistent with each other and match at first order the
distribution of high altitude (>60km) clouds derived from previous studies. At
second order, discrepancies are observed. We report the identification of H2O
clouds extending up to 80 km altitude, which could explain part of these
discrepancies: both CO2 and H2O clouds can exist at high, mesospheric
altitudes. CRISM observations of afternoon CO2 clouds display morphologies
resembling terrestrial cirrus, which generalizes a previous result to the whole
equatorial clouds season. Finally, we show that morning OMEGA observations have
been previously misinterpreted as evidence for cumuliform, and hence
potentially convective, CO2 clouds.Comment: Vincendon, M., C. Pilorget, B. Gondet, S. Murchie, and J.-P. Bibring
(2011), New near-IR observations of mesospheric CO2 and H2O clouds on Mars,
J. Geophys. Res., 116, E00J0
BC-SIM-TR-032 HRIC ICO4 REPORT
The present document has been issued to describe the Instrument Check Out Phase (ICO#4) Tests of HRIC, channel of the Spectrometers and Imagers for MPO BepiColombo Integrated Observatory SYStem (SIMBIO-SYS)
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