Subvisible CO2 ice clouds detected in the mesosphere of Mars
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Authors
Montmessin, F.
Bertaux, J.-L.
Quémerais, E.
Korablev, O.
Rannou, P.
Forget, F.
Perrier, S.
Fussen, D.
Lebonnois, S.
Rébérac, A.
Dimarellis, E.
Discipline
Physical sciences
Audience
Scientific
Date
2006Metadata
Show full item recordDescription
The formation of CO2 ice clouds in the upper atmosphere of Mars has been suggested in the past on the basis of a few temperature profiles exhibiting portions colder than CO2 frost point. However, the corresponding clouds were never observed. In this paper, we discuss the detection of the highest clouds ever observed on Mars by the SPICAM ultraviolet spectrometer on board Mars Express spacecraft. Analyzing stellar occultations, we detected several mesospheric detached layers at about 100 km in the southern winter subtropical latitudes, and found that clouds formed where simultaneous temperature measurements indicated that CO2 was highly supersaturated and probably condensing. Further analysis of the spectra reveals a cloud opacity in the subvisible range and ice crystals smaller than 100 nm in radius. These layers are therefore similar in nature as the noctilucent clouds which appear on Earth in the polar mesosphere. We interpret these phenomena as CO2 ice clouds forming inside supersaturated pockets of air created by upward propagating thermal waves. This detection of clouds in such an ultrararefied and supercold atmosphere raises important questions about the martian middle-atmosphere dynamics and microphysics. In particular, the presence of condensates at such high altitudes begs the question of the origin of the condensation nuclei.
Citation
Montmessin, F.; Bertaux, J.-L.; Quémerais, E.; Korablev, O.; Rannou, P.; Forget, F.; Perrier, S.; Fussen, D.; Lebonnois, S.; Rébérac, A.; Dimarellis, E. (2006). Subvisible CO2 ice clouds detected in the mesosphere of Mars. , Icarus, Vol. 183, Issue 2, 403-410, DOI: 10.1016/j.icarus.2006.03.015.Identifiers
scopus: 2-s2.0-33746047130
Type
Article
Peer-Review
Yes
Language
eng