MARSIS Finds Buried Basins in Chryse Planitia
Top: Radargrams for MARSIS orbits 1903 (a) and 1892 (b) that both cross Chryse Planitia. Radar sounding echo intensities are plotted in grey scale as a function of time-delay versus position along the orbit track (north is to the right). The peak surface return is corrected to agree with the MOLA topography.
Bottom: Ground-range projections of the orbit 1903 (c) and 1892 (d) radargrams are overlaid on MOLA colour-coded shaded relief. Parabolic echoes in the radargrams that project as arcs on the surface are interpreted to be from the near and far rim walls (relative to the orbit track) of buried impact basins. The dashed white circles are approximate fits to the arcs (echoes labelled in radargrams).
By comparing the echoes of the two adjacent ground track, the left-right ambiguity of the location of the sub-surface basins is resolved.
The echoes are interpreted to be from the far rim wall of a ~220-km-diameter basin (corresponding echoes in a and b labelled 'Far wall') superimposed on a larger ~310-km-diameter basin that may have echoes from the top (t) and bottom (b) of the near rim wall (corresponding echoes in a and b labelled 'Near wall').