Signs of ancient erosion—most likely caused by liquid water—are preserved in the Ares Vallis outflow channel, a feature that meanders for more than 1,056 miles (1,700 kilometers) across the southern highlands of Mars.
Above, an angled view of part of Ares Vallis shows streamlined "islands," which indicate which way water likely moved in the channel.
The high-resolution image, recently released by the European Space Agency, was taken from about 185 miles (300 kilometers) above the surface by the Mars Express Orbiter.
Space Pictures This Week: Pulsing Crab, Moon Halo, More
Gamma-ray pulses from a nebula, a ring around the moon, and newfound "failed" stars feature among this week's best space pictures.