Impact craters are usually round, but the European Space Agency's Mars Express orbiter recently sent back this image of a long, oval crater pocking the Red Planet's southern hemisphere. What happened here?

ESA scientists think
a series of impacts created this unusual shape. First, two projectiles—or possibly two halves of one projectile that broke in transit—plowed into this spot at a shallow angle, creating the crater. Deeper areas inside the crater suggest even more projectiles hit afterward.

Spread out in wings around the crater is the "ejecta blanket," which was formed from the material that the projectiles threw aside when they hit. The blanket includes several small channels. Scientists think these features may be evidence that this area of Mars was once covered with material—possibly water—that would have melted or boiled when exposed to the heat from the impacts and then flowed, carving the channels.

–Francie Diep