Example of SHARAD data used in the study. SHARAD data is presented as radargrams which depict the delay time of the return signal against distance along the martian surface. From this we can identify the surface and subsurface structure. Throughout eastern Elysium Planitia two parallel subsurface reflectors are present (L1R and L2R) which we interpret to be boundaries between extensive geologic layers. The formation of Marte Vallis cut channels through these boundaries. Thus from identifying where the reflectors are absent, we were able to map out the shape and scale of the Marte Vallis channels.