A City-Sized 'Eye' Has Been Discovered on Mars

If you stare long enough at Mars, Mars might start to stare back. 

That’s the eerie effect of a huge Martian crater that resembles an eye in a new image captured from outer space by the European Space Agency (ESA) orbiter Mars Express. It follows a slew of other intriguing snapshots taken by rovers on the surface of Mars this year, including a rock formation that looks like a doorway, as well as spikes shaped like plant stems.    

Snapped by the orbiter on April 25, the image reveals some of the mysterious features of the unexplored and unnamed crater, which stretches across a city-sized 18 miles of a region called Aonia Terra, located in the southern highlands of Mars, according to ESA. The formation is surrounded by ancient evidence of water flowing across the Martian surface in channels, when the red planet was warmer, wetter, and potentially habitable.

“Conjuring images of veins running through a human eyeball, these channels are likely to have carried liquid water across the surface of Mars around 3.5–4 billion years ago,” ESA said in the statement. “The channels appear to be partly filled with a dark material, and in some places, seem to actually be raised above the surrounding land.”

The agency said that these strange features, which are still not understood, could be the result of either hardy sediments or lava flows filling the channels. 

The crater is just one of many fascinating formations in Aonia Terra, a region that may have been doused with periodic flows of liquid meltwater within the last million years, a finding that “points to more habitable recent environments than previously predicted” on the red planet, according to a 2015 paper in Nature Communications.