It may be difficult to see how deep these craters go, but in the above image from Mars Express’ High Resolution Stereo Camera (HRSC), a piece of Martian terrain fell more than four kilometers. Here’s more on the astonishing dynamisn of the surface of our red neighbors, from Phys.Org:

A scattering of impact craters, formed as incoming bodies from space collided with Mars’ surface, can be seen to the left of the frame; the floor of the largest and uppermost basin spans about 40 kilometers, and contains some fractures and markings that formed just after the crater itself. Hot, molten rock is thought to have been thrown up during the crater-forming collision, after which it cooled and settled to form the scar-like features visible here.

Toward the middle of the frame, the surface is relatively smooth and featureless—however, two broad channels have worked their way through the landscape, and can be seen as meandering, branching indentations in the surrounding terrain. These channels are reminiscent of so-called ‘sapping valleys’ on Earth, which form as water consistently seeps and flows through sediment to carve out a natural drainage network.

See and learn more!