The Mars Reconnaissance Orbiter’s HiRISE instrument has captured another image of those mysterious caves on Mars. When you catch one of these at high noon, you won’t get too much perspective, just a dark hole in a bright landscape. In the image above, you can see the illumination on the interior wall from a mid-afternoon sun. The opening is decent-sized, about five hundred feet.
This confirms that this pit is essentially a vertical shaft cut through the lava flows on the flank of the volcano. Such pits form on similar volcanoes in Hawaii and are called “pit craters.” They generally do not connect to long open caverns but are the result of deep underground collapse. From the shadow of the rim cast onto the wall of the pit we can calculate that the pit is at least 78 meters (255 feet) deep.
Dust storms are less common on the high slopes and peaks of Mars’ great shield volcanoes, but I have questions. Would sand and dust tend to fill these pits, if the volcanoes have been dormant? Are these pits broad enough to permit winds to blow dust and sand out of them?
Here’s the close-up: