This small fossa segment cuts the channel of Athabasca Valles, and post-dates the youngest of Mars' outflow channels. A "fossa" is a cavity or depression.
Floods of water and lava are thought to have emanated from the larger fossae nearby, perhaps forming the Athabasca channel and later filling it with lava. Comparison with the larger fossa segments at the Athabasca Valles head may reveal whether this will be a source of a future flood.
Photo credit: NASA/JPL/University of Arizona