Dramatic explosions deep under the Mars surface, possibly involving ice, are believed to have created a pair of massive craters spotted side-by-side in satellite images taken in January by the European Space Agency.
What makes the twin craters remarkable is the central pit found in each, which indicate the presence of water on or just below the surface of the red planet.
The smaller rectangle shows the region covered by the two craters. The northernmost is called Arima, while the southernmost remains unnamed.
In a report on the craters published on April 11, ESA scientists proposed a range of theories on what caused them.
"When an asteroid hits the rocky surface of the planet, both it and the surface are compressed to high densities," scientists with the ESA reported last week. "Immediately after the impact, the compressed regions rapidly de-pressurize, exploding violently."
The crater pits may form when the ice or rock in a meteor melts after impact, draining away through fissures in the crater. Another theory researchers proposed is that ice just under the surface rapidly heats up on impact, and vaporizes in an explosion immediately after.