Dielectric map of the Martian northern hemisphere and the nature of plain filling materials

Jérémie Mouginot , Antoine Pommerol , Pierre Beck (1) , Wlodek Kofman (1) , Stephen M. Clifford

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

A number of observations suggest that an extended ocean once covered a significant part of the Martian northern hemisphere. By probing the physical properties of the subsurface to unprecedented depth, the MARSIS/Mars Express provides new geophysical evidences for the former existence of a Late Hesperian ocean. The Vastitas Borealis formation, located inside a putative shoreline of the ancient ocean, has a low dielectric constant compared with that of typical volcanic materials. We show that the measured value is only consistent with low-density sedimentary deposits, massive deposits of ground-ice, or a combination of the two. In contrast, radar observations indicate a distribution of shallow ground ice in equilibrium with the atmosphere in the south polar region. We conclude that the northern plains are filled with remnants of a late Hesperian ocean, fed by water and sediments from the outflow channels about 3 Gy ago.

Domains: Sciences of the Universe [physics]

Jérémie Mouginot, Antoine Pommerol, Pierre Beck, Wlodek Kofman, Stephen M. Clifford. Dielectric map of the Martian northern hemisphere and the nature of plain filling materials. Geophysical Research Letters, 2012, 39, ⟨10.1029/2011GL050286⟩. ⟨insu-03612455⟩