Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p13g..05b&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P13G-05
Astronomy and Astrophysics
Astronomy
[6225] Planetary Sciences: Solar System Objects / Mars, [6949] Radio Science / Radar Astronomy
Scientific paper
Most of classic remote-sensing methods probe the surface and very close subsurface of the Martian crust and are thus only sensitive to processes that occurred under the Amazonian climate. Sounding radar has the potential to probe deeper into the crust, revealing processes that occurred in a distant past.We report here on the completion and improvement of dielectric maps of the Martian polar regions assembled from MARSIS measurements, building upon the initial work of [1]. New data collected by MARSIS since 2008 have been incorporated to greatly increase the level of details in the northern hemisphere. In our presentation, we will briefly discuss the method used to extract values of dielectric con-stant from MARSIS measurements which was explained in details by [1]. As a reasonable ap-proximation, we show that these maps are representative of the average dielectric constant of the first 50 to 100 meters below the surface. We compare the dielectric maps of the northern and southern polar regions of Mars and note a stricking difference between both hemispheres. In the south, a strong decrease of the dielectric constant is consistent with the inferred limit for the presence of stable water ice in the ground. In the north, a similar decrease of dielectric constant is observed but it compasses a much broader area than the one where water ice is at equilibrium under the current climate. The dielectric constant pattern displays a much better correlation with the global topography and, to some extent, with the putative shorelines of the past ocean. Ancient water activity is likely responsible for the observed dielectric pattern. To test the link between the geologic nature of the terrains and the value of dielectric con-stant, we produced a composite geologic / dielectric map from the geologic map of [2] and our dielectric map. A detailed examination of this map confirms the strong link between the geologic nature of the formations and their dielectric constant. Hesperian units that are interpreted as sedimentary systematically show lower dielectric constants than recent and ancient volcanic units. Two hypotheses can be proposed to explain the pattern of dielectric constant observed in the northern plains: the sedimentary nature of the units located inside the putative shoreline (VBF in particular) or the presence of massive amounts of ice buried at large depth below the surface (> 20 m) and thus protected from sublimation and redistribution over long periods of time. Both possibilities point toward the existence of a past ocean over the northen plains, which remnants are still detectable today, underneath a layer affected by more recent climatic change.
Beck Paul
Clifford Stephen M.
Kofman Wlodek
Mouginot Jérémie
Pommerol Antoine
No associations
LandOfFree
Dielectric Maps of the Martian Polar Regions from MARSIS/Mex Surface Reflectivity Measurements does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Dielectric Maps of the Martian Polar Regions from MARSIS/Mex Surface Reflectivity Measurements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Dielectric Maps of the Martian Polar Regions from MARSIS/Mex Surface Reflectivity Measurements will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-868634