A “crazy-looking” crater on Mars caught the attention of scientists. A simple calculation cleared up how it got its strange shape, but also raised a few questions about past weather on Mars.
“Craters should be bowl shaped, but this one had terraces in the wall,” says Ali Bramson, a graduate student in the Lunar and Planetary Laboratory (LPL) at the University of Arizona. Terraces can form when there are layers of different materials in the planet’s subsurface, such as dirt, ice, or rock.
“When the crater is forming, the shock wave from an object hitting a planet’s surface propagates differently depending on what substrates are beneath the area of impact,” Bramson says. “If you have a weaker material in one layer, the shock wave can push out that material more easily, and the result is terracing at the interface between the weaker and stronger materials.”
‘Something Weird Is Going On’
“It’s worth mentioning that terraced craters of this size are quite rare,” says Shane Byrne, associate professor in LPL. “But in this area of Mars (Arcadia Planitia), there are a lot of terraced craters. The craters may have formed at different times, but they all have terraces, which indicates something weird is going on in the subsurface.”
