170 research outputs found
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
An Extremely Elongated Cloud Over Arsia Mons Volcano on Mars: I. Life Cycle
We report a previously unnoticed annually repeating phenomenon consisting of the daily formation of an extremely elongated cloud extending as far as 1,800 km westward from Arsia Mons. It takes place in the solar longitude (Ls) range of ∼220°–320°, around the Southern solstice. We study this Arsia Mons Elongated Cloud (AMEC) using images from different orbiters, including ESA Mars Express, NASA MAVEN, Viking 2, MRO, and ISRO Mars Orbiter Mission (MOM). We study the AMEC in detail in Martian year (MY) 34 in terms of local time and Ls and find that it exhibits a very rapid daily cycle: the cloud growth starts before sunrise on the western slope of the volcano, followed by a westward expansion that lasts 2.5 h with a velocity of around 170 m/s in the mesosphere (∼45 km over the areoid). The cloud formation then ceases, detaches from its formation point, and continues moving westward until it evaporates before the afternoon, when most sun-synchronous orbiters make observations. Moreover, we comparatively study observations from different years (i.e., MYs 29–34) in search of interannual variations and find that in MY33 the cloud exhibits lower activity, while in MY34 the beginning of its formation was delayed compared with other years, most likely due to the Global Dust Storm. This phenomenon takes place in a season known for the general lack of clouds on Mars. In this paper we focus on observations, and a theoretical interpretation will be the subject of a separate paper.This work has been supported by the Spanish project AYA2015-65041-P and PID2019-109467GB-I00 (MINECO/FEDER, UE) and Grupos Gobierno Vasco IT-1366-19. JHB was supported by ESA Contract No. 4000118461/16/ES/JD, Scientific Support for Mars Express Visual Monitoring Camera. The Aula EspaZio Gela is supported by a grant from the Diputación Foral de Bizkaia (BFA). We acknowledge support from the Faculty of the European Space Astronomy Center (ESAC). Special thanks are due to the Mars Express Science Ground Segment and Flight Control Team at ESAC and ESOC. The contributions by K.C and N.M.S were supported by NASA through the MAVEN project
Inventory of detached layers detected by Omega/Mex
International audienceINVENTORY OF DETACHED LAYERS DETECTED BY OMEGA/MEX B. Gondet, J.-P Bibring, M. Vincendon Institut d'Astrophysique Spatiale, Université Paris-Sud, Paris, Orsay France ([email protected] The dynamic of solid particles transport and condensation/sublimation in the Martian atmosphere results in the formation of high altitude detached layers of dust and/or ice. Recent studies have highlighted the complexity and diversity of formation mechanisms for detached layers, which are thus difficult to predict and simulate in climate models. The capability to orient Mars Express (MEX) allows a great diversity of observations modes, in particular nadir and limb. During day and night limb's observations, 4 out of 7 MEX instruments (the spectrometers: SPICAM, OMEGA, PFS and the high-resolution camera HRSC) work together to provide spectra (0.12 µm to 45 µm) of the Martian atmosphere, at each altitude step, with the associated image [1]. Since the beginning of the mission (2004) Omega has observed a large numbers of detached aerosols layers at different locations, time and altitude. We can quantify the effective particle size of each layers using the visible channel of OMEGA (0.5 µm to 0.95 µm), and thanks to the mid-IR channels (0.9 µm to 5.2 µm) of we can infer the dominant composition of particles (dust, H2O ice, CO2 ice). We will present an inventory of 8 Martian years of detections. We hope that this inventory will improve our ability to understand and model these detached layers. [1] The Mars Express limbs observations database Gondet et al, EGU 201
The Mars Express limbs observations database
The capability to orient Mars Express allows a great diversity of observations modes, in particular nadir and limb. During day and night limb’s observations, 4 out of 7 MEX instruments (the spectrometers: SPICAM, OMEGA,
PFS and the high-resolution camera HRSC) work together to provide spectra (.12 µ�m to 45 �µm) of the Martian
atmosphere, at each altitude step, with the associated image. We will present the limbs database of more than 10 years in orbit with striking results (dust and clouds detached layers, day and night emissions). The database is now accessible to the scientific community via the ESA/PSA website (www.rssd.esa.int/PSA)
Mapping the mesospheric CO<sub>2</sub> clouds on Mars
International audienceThis climatology of martian clouds will enable us to better characterise the mesospheric structure and dynamics, as very specific conditions (especially low temperatures and a source of condensation nuclei) are required for CO2 ice condensation
Mars CO2 ice clouds: results of 4 Martian years of monitoring by OMEGA/Mars Express
An important achievement of the ESA/MarsExpress mission is the detection and characterization of mesospheric CO2 ice clouds, by indirect (PFS and SPICAM) and direct (OMEGA and HRSC) observations, as discussed by Clancy et al.. These clouds have been recently detected by CRISM and MCS on board MRO. Back in 2007, OMEGA provided the first non ambiguous discovery and characterization of high altitude CO2 ice clouds in Mars atmosphere, at specific locations and times, through their diagnostic reflectance signature at 4,26 m. They were monitored, in their space/time evolution, during 4 consecutive Martian years. They offer a unique possibility to understand the processes involved in cloud formation, both on Mars and Earth. We will present an overview of the properties of these clouds in terms of location, altitude, seasonal variation, and opacity. Although no definite explanation for their formation can be proposed yet, we will suggest potential processes and conditions to account for
First Detection of O2 Recombination Nightglow Emission at 1.27 µm in the Atmosphere of Mars With OMEGA/MEX and Comparison with Model
Le fichier pdf est un "extended abstract" de 3 pages en libre acces: http://www-mars.lmd.jussieu.fr/paris2011/abstracts/bertaux_paris2011.pdfInternational audiencesan
Solar Albedo High Resolution Global Map of the Martian Surface from OMEGA/MEX
International audienceWe present a global map of solar albedo derived from OMEGA data. It is the highest resolution map of this key parameter for climate modelling and TI retrievals
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