by Matthew Cobb
We’ve featured the amazing images from the HiRISE Mars orbiter before. Here’s a stunning crater that was captured in 2011, on the slopes of Pavonis Mons, one of the massive extinct volcanoes on the Red Planet.:
Shane Byrne at the HiRise site run jointly by the University of Arizona says that the hole at the bottom is 35 m across, and about 20 m below bottom of the crater (they worked this out by the movement of the shadows) (All photos NASA/JPL/University of Arizona). The cavern that we are looking into is of unknown size. Shane writes:
Caves often form in volcanic regions like this when lava flows solidify on top, but keep flowing underneath their solid crust. These, now underground, rivers of lava can then drain away leaving the tube they flowed through empty. (…) The origin of the larger hole that this pit is within is still obscure. You can see areas where material on the walls has slid into the pit. How much of the missing material has disappeared via the pit into the underground cavern?
Here’s a larger version (click to see the stunning full size image). Imagine you are an explorer on Mars – could you walk down the slope of the crater, and then use a rope to get down into the bottom of the cavern, and look back up? Or is the surface of the crater thin and would it break under your weight?
Here’s the original image that caught the attention of the HiRISE team:
Of course, it might not be a crater and a cavern at all. Here are two other options: