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| Titel |
Investigations of selected areas of the south seasonal cap of Mars in early 2009 |
| VerfasserIn |
Y. Langevin, C. Hansen, N. Thomas, M. Vincendon, T. Titus, S. Piqueux, J.-P. Bibring, B. Gondet |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026279
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| Zusammenfassung |
| A coordinated campaign of observations of the retreating South seasonal cap of Mars is under
way, combining observations in the near IR (OMEGA, CRISM) and the thermal IR
(THEMIS) with high resolution observations with HIRISE (30 cm IFOV). This
will be the 3rd set of observations with OMEGA/Mex, providing information on
interannual variations of the evolution of the seasonal cap. The pericenter of the orbit of
Mex is now at high southern latitudes, so that OMEGA observes the seasonal cap
with an IFOV of 300 m (similar to that of the pushbroom mode of CRISM but
with a better spectral sampling), while HR observations with CRISM provide a
much higher spatial resolution (IFOV 18 m) on selected areas. Previous observation
campaigns have demonstrated that two types of areas could be identified in the “cryptic
region” (dark and cold in mid-spring): those with a significant CO2 ice signature
(type “A”) with clear evidence for a venting process (spots, fans, spiders) and those
which become heavily contaminated with surface dust shortly after equinox (type
“B”), with little evidence for large scale venting. Shortly after equinox, there is a
widespread surface contamination by H2O frost. During early spring, H2O frost becomes
restricted to a few locations around the cryptic region . These patches disappear after
mid-spring.
The main focus of this contribution is on the evolution of two end-members of the
seasonal cap: cryptic region type “B” and the evolution of H2O frost patches. One of the
major issues is the role of several candidate processes for surface dust contamination in
cryptic region B:
- venting similarly to region A, but on smaller spatial scales
- direct dust sedimentation on the surface
- scavenging of airborne dust by condensation of H2O frost
Previous OMEGA observations have indeed shown that regions corresponding to H2O
frost deposition are depleted in aerosols when compared to a well-mixed model for the lower
10 km of the martian atmosphere. The evolution of H2O frost patches is of particular interest
when compared to that in previous martian years, as these features are linked to topography
and wind patterns.
References : H.H. Kieffer et al., JGR 105, 9653 (2000) ; Y. Langevin et al., Nature
442, 790 (2006)Â ; Y. Langevin et al., JGR 112, E08S08 (2007) ; H.H. Kieffer et
al., Nature 442, 793 (2006)Â ; S. Piqueux et al., JGR 108, E8 3-1 (2003)Â ; H.H.
Kieffer, JGR 112 E08005 (2007)Â ; M. Vincendon et al., Icarus 196, 488 (2008) |
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