Mars: Lava Tubes & 'Skylights'

[eburacum]

This text excerpted from:
https://forums.forteana.org/index.php?threads/the-lcross-impact.39601/
... to preface / introduce this new thread.
-------------------------

Talking about underground cavities on the Moon (which we were, a number of posts back) here's a possible hole into one
http://www.newscientist.com/article/dn1 ... -moon.html ...

Journal reference: Geophysical Research Letters (in press)

Similar things have been seen on Mars. The low gravity seems to allow unusually large lava tubes on both worlds- in theory, I suppose the lava tubes on the Moon could be proportionally larger due to the lower gravity.

 

[EnolaGaia]

... Similar things have been seen on Mars. The low gravity seems to allow unusually large lava tubes on both worlds- in theory, I suppose the lava tubes on the Moon could be proportionally larger due to the lower gravity.

Interest in these large lava tubes is driven by the proposition they might provide the most convenient and safe locations for operational bases protecting personnel from radiation and other hazards on the surface.

This recent article describes one of the more notable skylight features found on Mars.

What Is The Deal With This Weird Hole on Mars?

Mars is a pretty wild and wonderful place, and an image posted to the NASA science blog and Astronomy Photo of the Day this week is a brilliant example. It shows what appears to be a mountain... but completely hollowed out.

While it's not actually the product of some strange mining experiment, the formation is indeed hollow. What you're looking at is a lava tube 'skylight', the product of ancient volcanic activity below the surface of Mars.

The feature is on the western slopes of a shield volcano called Pavonis Mons, the surrounding regions of which show some pretty breathtaking geological features. There are long, snaking lava tubes, fault features called grabens, and, of course, the large volcanic crater itself.

The image above was taken by the Mars HiRise orbiter in 2011, and captured the attention of Mars scientists just because it was so unusual.

A closer look revealed it to be a skylight - that is, a surface opening to a lava tube below. It's hollow because sometimes lava flows can solidify on the surface while the flow continues below. Then, the flowing lava can drain away, leaving behind lava tube caves.

As time goes by, sections of the roof can collapse, creating the skylight.

Analysis of this skylight revealed the opening to be about 35 metres (115 feet) across. The top of the collapsed rubble pile that you can see through the opening is at a depth of about 28 metres (92 feet).

Lava tube caves like this are exciting because they offer some protection from the harsh radiation that bombards Mars. This means that they could be good sites to establish underground bases (if they are accessible; this particular one doesn't look like it's easy to get in and out of).

But there's another implication, too. If we're going to look for signs of life on Mars, caves might be the best option. ...

FULL STORY: https://www.sciencealert.com/what-is-the-deal-with-this-weird-hole-on-mars

See Also:

https://en.wikipedia.org/wiki/Martian_lava_tube

 

[Mythopoeika]

It's a Sarlacc's nest.

 

[blessmycottonsocks]

It's a Sarlacc's nest.

Is that concave or convex - can't quite make it out?

 

[EnolaGaia]

Is that concave or convex - can't quite make it out?

Concave, based on the shadows.

 

[blessmycottonsocks]

Concave, based on the shadows.

Astonishing. The sort of structure you'd love to fly a camera-drone into.

 

[madmath]

The question of why there is a cone of sand around it - perhaps sand accumulated over time around the original lava tube, naturally dropping down the hole in the middle with natural forces slump-sloping the sand around the hole, as in an hourglass. Sandstorms are common occurrences on Mars, and there's been millions to billions of years for sand to accumulate.
Or there was a colony of giant Martian ants, which died off long enough ago for their footprints to be erased...

It would also be interesting the sample the atmosphere just above the hole looking for unexpected gases escaping.