Be sure to look where you’re walking on Mars.
NASA’s Mars Reconnaissance Orbiter (MRO) last week stumbled upon a hole in the surface of the Red Planet’s South Pole.
In the late summer sun, the southern hemisphere’s topography is “accentuated in orbital images,” according to NASA’s Tony Greicius.
“We see many shallow pits in the bright residual cap of carbon dioxide ice (also called ‘Swiss cheese terrain’),” he explained in a recent update. “There is also a deeper, circular formation that penetrates through the ice and dust.”
The dimple (upper right corner of above image) is most likely the effect of a collapse pit—formed when the ground sinks into a void below—or an impact crater (i.e. something slamming into the planet).
The multipurpose MRO, equipped with the University of Arizona’s HiRISE camera, launched in August 2005 and arrived on Mars seven months later. The spacecraft takes detailed pictures of the Martian surface using the High-Resolution Imaging Science Experiment (HiRISE) shooter.
Last week’s slideshow also included an elongated depression from three merged craters, and active flow deposits emanating from rocky alcoves.
This isn’t the first time NASA was puzzled by a “circular feature” on the south pole of Mars: In April, the organization released a photo of what “might be an impact structure.”
“Craters in icy terrain are modified by processes that flatten and change them in such a manner that it is hard to say for sure if it had an impact origin,” Greicius said at the time.
NASA made a breakthrough in 2015, providing evidence that water may still exist on the surface of Mars.
The longer and harder they looked, though, the less H2O scientists believe there is: The latest findings tip about the same volume as Earth’s Atacama Desert or the Antarctic Dry Valleys.
Analysts were stumped, however, by new climate data, released in February, which suggests the Red Planet’s atmosphere may not have been warm enough to melt ice into water.