Caves and Craters
NASA/JPL/University of Arizona

Caves and Craters
ESP_023531_1840  Science Theme: Impact Processes


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Earlier this year (2011), the CTX camera team saw a crater containing a dark spot on the dusty slopes of the Pavonis Mons volcano. We took a closer look at this feature with HiRISE and found this unusual geologic feature.

The dark spot turned out to be a “skylight,” an opening to an underground cavern, that is 35 meters (115 feet) across. 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. We can use the shadow cast on the floor of the pit to calculate that it is about 20 meters (65 feet) deep.

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?

UPDATE: March 2014
From a second observation, creating a stereo pair, we now know the topography much better. From the characteristic angles of the slopes, it looks like loose granular material has drained into a cave (probably a lava tube in an area like this).

This is a conical collapse pit (approximately 50 meters or 165 feet deep) implies a conical pile of debris of equal height sitting in the cave and the top of this pile is (approximately 30 meters or 100 feet) below the rim of the hole. So this is a pretty enormous cave.: approximately 80 meters or 265 feet from floor to ceiling!

Written by: Shane Byrne   (17 August 2011)

This is a stereo pair with ESP_023953_1840.

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Acquisition date:04 August 2011 Local Mars time: 2:08 PM
Latitude (centered):3.735° Longitude (East):248.485°
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