Signs of Flowing Water on Mars 1 2 3 4 5 6 7 8 9 10 Groundwater May Be Responsible Gullies beneath a small crater on the rim of a larger crater. This image supports the hypothesis that the fluid responsible for the gullies came from beneath the ground, either as groundwater or melting of subsurface ice. The impact that created the larger crater caused an initial set of subsurface fractures. Then, fractures from the second, smaller impact provided pathways for groundwater to reach the surface on the wall of the larger crater and spill down the slope. + Full image and caption     Jet Propulsion Laboratory    California Institute of Technology