1,422 research outputs found
Gliese 581d is the first discovered terrestrial-mass exoplanet in the habitable zone
It has been suggested that the recently discovered exoplanet GJ581d might be
able to support liquid water due to its relatively low mass and orbital
distance. However, GJ581d receives 35% less stellar energy than Mars and is
probably locked in tidal resonance, with extremely low insolation at the poles
and possibly a permanent night side. Under such conditions, it is unknown
whether any habitable climate on the planet would be able to withstand global
glaciation and / or atmospheric collapse. Here we present three-dimensional
climate simulations that demonstrate GJ581d will have a stable atmosphere and
surface liquid water for a wide range of plausible cases, making it the first
confirmed super-Earth (exoplanet of 2-10 Earth masses) in the habitable zone.
We find that atmospheres with over 10 bar CO2 and varying amounts of background
gas (e.g., N2) yield global mean temperatures above 0 degrees Celsius for both
land and ocean-covered surfaces. Based on the emitted IR radiation calculated
by the model, we propose observational tests that will allow these cases to be
distinguished from other possible scenarios in the future.Comment: Accepted to the Astrophysical Journal Letters; 9 pages, 1 table, 4
figure
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
A reanalysis of ozone on Mars from assimilation of SPICAM observations
We have assimilated for the first time SPICAM retrievals of total ozone into a Martian global circulation model to provide a global reanalysis of the ozone cycle. Disagreement in total ozone between model prediction and assimilation is observed between 45°S–10°S from LS=135–180° and at northern polar (60°N–90°N) latitudes during northern fall (LS=150–195°). Large percentage differences in total ozone at northern fall polar latitudes identified through the assimilation process are linked with excessive northward transport of water vapour west of Tharsis and over Arabia Terra. Modelling biases in water vapour can also explain the underestimation of total ozone between 45°S–10°S from LS=135–180°. Heterogeneous uptake of odd hydrogen radicals are unable to explain the outstanding underestimation of northern polar total ozone in late northern fall.
Assimilation of total ozone retrievals results in alterations of the modelled spatial distribution of ozone in the southern polar winter high altitude ozone layer. This illustrates the potential use of assimilation methods in constraining total ozone where SPICAM cannot observe, in a region where total ozone is especially important for potential investigations of the polar dynamics
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The latest (version 4.3) Mars Climate Database
Introduction: The Mars Climate Database (MCD) is a database of meteorological fields derived from General Circulation Model (GCM) numerical simulations of the Martian atmosphere and validated using available observational data. The MCD includes complementary post-processing schemes such as high spatial resolution interpolation of environmental data and means of reconstructing the variability thereof. The GCM is developed at Laboratoire de Météorologie Dynamique du CNRS (Paris, France) [1,2] in collaboration with the Open University (UK), the Oxford University (UK) and the Instituto de Astrofisica de Andalucia (Spain) with support from the European Space Agency (ESA) and the Centre National
d'Etudes Spatiales (CNES)
Simulations of atmospheric phenomena at the Phoenix landing site with the Ames General Circulation Model
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95144/1/jgre2784.pd
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Modeling the martian atmosphere with the LMD global climate model
Introduction: For several years we have been developing a 3D Global Climate Model (GCM) for Mars derived from the models used on Earth for weather forecasting or climate changes studies [1]. The purpose of such a project is ambitious: we wish to build a 'Mars simulator' based only on physical equations, with no tailor-made forcing, but able to reproduce all the available observations of the Martian climate (temperatures, winds, but also clouds, dust, ices, chemical species, etc...).
The GCM is constantly evolving, thanks to a contnuous collaboration between several teams based in France (LMD, SA), the UK (The Open University, University of Oxford) and Spain (Instituto de Astrofisica de Andalucia), and with the support of ESA and CNES.
We are currently working on an improved version of the model. Several new parametrisation are included in the heart of the model (radiative transfer, surface and subsurface processes, dynamics) and the applications of the GCM are in contnuous development (Water, dust, CO2, radon cycles, photochemistry, thermosphere, ionosphere, etc...
A high resolution study of the Martian water cycle with a global climate model
International audienceThe martian water cycle's main source is the northern polar cap. Running high resolution models, up to 360° per 180°, help better resolve this ice cap, and better mimic the gradual retreat of the seasonal cap. Atmospheric circulation is also better resolved. Water vapor advection and the subsequent formation of clouds quite differ when we compare these brand new high resolution simulations and the usual lower resolution ones at 64 per 48 grid points
A Cloud Greenhouse Effect on Mars: Significant Climate Change in the Recent Past
The large variations in Mars orbit parameters are known to be significant drivers of climate change on the Red planet. The recent discovery of buried CO2 ice at the South Pole adds another dimension to climate change studies. In this paper we present results from the Ames GCM that show within the past million years it is possible that clouds from a greatly intensified Martian hydrological cycle may have produced a greenhouse effect strong enough to raise global mean surface temperatures by several tens of degrees Kelvin. It is made possible by the ability of the Martian atmosphere to transport water to high altitudes where cold clouds form, reduce the outgoing longwave radiation, and drive up surface temperatures to maintain global energy balance
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