Fantastic picture of sandpit/cavern on Mars

[Godhumor]

From Bad Astronomy's description:

This was taken by the Mars Reconnaissance Orbiter in July 2011. See the hole in the bottom? You can tell from the lighting that this is an underground opening to a cavern — a skylight. Quite a few of these have been found on Mars, actually. We see them on Earth and even on the Moon. Given the angle of the shadows, the vertical distance from the bottom of the pit to the floor of the cavern is about 20 meters (65 feet). Watch your step!

Here’s how we think skylights like this form. In the distant past, Mars was geologically active. Rivers of lava ran across the surface. If the surface of the lava hardens it can form a roof, allowing the lava underneath to continue flowing; these are called lava tubes and there are bazillions of them in Hawaii, for example. Eventually, the source of the lava chokes off and the lava flows away, leaving the empty tube underground. If the roof is thin in one spot it can collapse. Sometimes that just leaves a hole, but apparently in this case it was under a sand field. Some of the sand must have fallen into the chamber below and eventually blown away, leaving the pit and the hole. The pit is located not too far from Pavonis Mons, a known (long-dead) Martian volcano.

The hole is about 35 meters (115 feet) across, so the pit is about 175 meters (nearly 600 feet) across the rim. I love how it sits in an otherwise nearly featureless sand field; the contrast is beautiful. In the high-res image you can see boulders perched on the pit wall, having rolled part of the way down as well. The inside of the pit has lines and furrows that are instantly recognizable to anyone who has tried to dig a hole at the beach and had sand continually flow down from the rim.


http://blogs.discovermagazine.com/badastronomy/

[Fumesucker]

1. Reminds me of this..

[Broderick]

2. alien home

[Godhumor]

5. The blog post actually mentioned that these caverns might be living areas when we go there

Better protected from the elements, so to speak.

[Buns_of_Fire]

3. Sandworms!

Oh noez!:woohoo:

[DirkGently]

4. The Eyeballs of Mars. Clearly, this is where they're hiding the atmosphere converters.

[eppur_se_muova]

6. What are you staring at ?

[Shagbark Hickory]

7. I think we all know that's a boobie.

[MineralMan]

8. There's a bigass ant lion at the bottom of that thing.

Careful where you walk....