This image shows a ground-range projection of the ‘radargram’ obtained by the MARSIS sounding radar on board ESA’s Mars Express on 6 July 2005 (orbit 1892), when the spacecraft was flying over the Martian lowland plains of Chryse Planitia.

Rim walls and interior ring structures of impact basins produce parabolic-shaded echoes. The inset shows that parabolic-shaped echoes in the radargram project to circular arcs, indicating the presence of a buried impact basin.