If a future earth ever needs a place to send convicts, the high-resolution camera on the Mars Reconnaissance Orbiter may have found it a few nights back.

A black spot on a bright dusty lava plain shocked the image team at the University of Arizona when they locked onto it at a resolution of 25 cms per pixel, enough to make out objects as wide as a frisbee.

It is a seemingly bottomless black pit, 150 metres wide. The edge shows sand chutes about seven metres long, and then … nothing. A free-fall into the darkest place ever seen in broad daylight, on the fourth rock from the Sun.

This is what the team noted on its blog.

The HiRISE camera is very sensitive and we can see details in almost any shadow on Mars, but not here. We also cannot see the deep walls of the pit. The best interpretation is that this is a collapse pit into a cavern or at least a pit with overhanging walls. We cannot see the walls because they are either perfectly vertical and extremely dark or, more likely, overhanging.

The pit must be very deep to prevent detection of the floor from skylight, which is quite bright on Mars.

And here’s a picture of the 150m-wide Marshole itself:

Media credit: Image courtesy NASA/JPL/University of Arizona

And now, a further mystery? Is this the entrance to a Mars Underworld teeming with life? For several decades scientists have been perplexed by the amount of methane detected in the red planet’s atmosphere.

Methane rapidly breaks down in sunlight which means something is making the gas down on the red planet itself. Is it being vented from buried volcanic hot spots, or is it biological in origin, or maybe a combination of both, from organisms that draw heat and chemical sources of energy from underground springs? Do Martian cows f-rt like Earth cows? OK, we can probably scratch the last possibility.

Someone is going to have to go over the lip of the black hole of Mars one day to find out. Who knows what the darkness holds.