Martian Chasm

A small tributary of the Grand Canyon of Mars, Hebes Chasma is pictured in this high-resolution image taken by the European Space Agency's Mars Express orbiter on October 10.

Nearly 8 kilometers deep, Hebes Chasma forms a giant trough of Valles Marineris, the largest canyon system in the solar system.

Some 125 kilometers across at its widest point, the feature stretches to a length of roughly 315 kilometers. Mars scientists believe that flowing water may have carved out the entire canyon system more than a billion years ago.