Starship Asterisk*

A Hole in Mars

Explanation: What created this unusual hole in Mars? The hole was discovered by chance in 2011 on images of the dusty slopes of Mars' Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars. The hole appears to be an opening to an underground cavern, partly illuminated on the image right. Analysis of this and follow-up images revealed the opening to be about 35 meters across, while the interior shadow angle indicates that the underlying cavern is roughly 20 meters deep. Why there is a circular crater surrounding this hole remains a topic of speculation, as is the full extent of the underlying cavern. Holes such as this are of particular interest because their interior caves are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are therefore prime targets for possible future spacecraft, robots, and even human interplanetary explorers.

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What is the white material thought to be ?
Its a little disconcerting that the text doesn't address obvious issues like this.

Future explorers, robot or human, will need to watch their step around there... !

{qoute}What is the white material thought to be ?{/qoute}

If it were the devil's dandruff, space exploration would never suffer a lack of funding.

I'm rather certain that manufacturing it locally and then smuggling it to various locations is a lot cheaper than making a round trip to Mars. Anyway, the soil is not actually white. Here is an RGB image of the hole and surrounding region. Some more examples of Martian soil (regolith, if you want to be fancy) can be seen at this Wikipedia article.

It looks like your basic, plain, ordinary low-gravity sink hole. There's another just like it on one of Mar's moons.

For me, it is not the crater of a volcano, it is a crater certainly, probably due to an impact and we can see a lake at the bottom in which this reflects something…
Moreover, we can see, on the edges of the crater, the various laminated layers of surface.

zaqs wrote:For me, it is not the crater of a volcano, it is a crater certainly, probably due to an impact and we can see a lake at the bottom in which this reflects something…
Moreover, we can see, on the edges of the crater, the various laminated layers of surface.

I think I see something trolling in the lake.

The crater is most likely a small collapsed lava tube, on the side slopes of the Pavonis Mons volcano. I've seen images of quite a few on Mars and the Moon.

If you look closely you might see several Corvettes in there.

Holey Mars, Batman, a Martian pub!

I do not understand the illumination of this picture.

The external shadow of the cone is on the same direction as the illuminated bottom of the hole. It is as there are two sources of light.

Guest wrote:I do not understand the illumination of this picture.

The external shadow of the cone is on the same direction as the illuminated bottom of the hole. It is as there are two sources of light.

I think you're being fooled by the famous concave/convex optical illusion. There is no cone here. The hole is at the bottom of a depression.

bobfang wrote:If you look closely you might see several Corvettes in there.

Or, perhaps the remains of a giant Martian Antlion! Don't know what an Antlion is? https://www.google.com/#q=wikipedia-Antlion

geckzilla wrote: Anyway, the soil is not actually white.

Thank you for this clarification regarding the color of the soil, geckzilla. I was going to ask the same question. The APOD image definitely makes it look white.

smitty wrote:

geckzilla wrote: Anyway, the soil is not actually white.

Thank you for this clarification regarding the color of the soil, geckzilla. I was going to ask the same question. The APOD image definitely makes it look white.

Although it is less common with planet surface images, which are often rendered more realistically (since we all know what images from Earth's surface look like), most astronomical images are contrast stretched so that the lightest pixels are white and the darkest black. That brings out the maximum amount of detail, even though it isn't photorealistic in some cases.

This is a repeat of the July 18, 2012 APOD. No further explanation is offered beyond what was posted then.
It's a big universe. Is there nothing new?

twoknoy wrote:This is a repeat of the July 18, 2012 APOD. No further explanation is offered beyond what was posted then.
It's a big universe. Is there nothing new?

There is so much new, awesome stuff that I bet if you started your own astronomy picture website you could feature all images and descriptions that were never featured on APOD even once. But then you might also find out that sometimes you just want a day off and on those days it's great to revisit old pictures that some people may not have seen before.

And that sometimes, have up-dated information also.
I'm waiting for the "Icy Finger of Death" to come around again.

Beyond wrote:
And that sometimes, have up-dated information also.

These pits are therefore prime targets for possible future APODs.

Beyond wrote:
I'm waiting for the "Icy Finger of Death" to come around again.

I'm waiting for the "The Flying Fickle Finger of Fate Award" to come around again.

No need to speculate about the circularity of the hole, both large
http://gizmodo.com/5551916/the-gates-of ... -guatemala
and small
http://www.cumberlandnewsnow.com/News/L ... r-Oxford/1

But why a crater, most seem to be holes, with near vertical sides?
John

The circular "crater" around the hole is obviously due to unconsolidated material falling into the hole. There's even a slightly more durable layer visible about a quarter of the way down. The slope is about 100 meters wide (assuming the central hole is 35 meters in diameter) so if the angle of repose is 30 degrees (a typical value), the blanket of unconsolidated material is about 58 meters deep. Multiple images under different lighting can probably pin down the exact slope and perhaps provide clues about the mechanical properties of the sand.

Steve Dutch wrote:
The circular "crater" around the hole is obviously due to unconsolidated material falling into the hole. There's even a slightly more durable layer visible about a quarter of the way down. The slope is about 100 meters wide (assuming the central hole is 35 meters in diameter) so if the angle of repose is 30 degrees (a typical value), the blanket of unconsolidated material is about 58 meters deep. Multiple images under different lighting can probably pin down the exact slope and perhaps provide clues about the mechanical properties of the sand.

What is that "slightly more durable layer visible about a quarter of the way down"?

• A volcanic eruption?

http://www.tulane.edu/~sanelson/Natural_Disasters/volclandforms.htm wrote:
<<Cinder cones are small volume volcanic cones consisting predominantly of tephra that result from strombolian eruptions. They usually consist of basaltic to andesitic material. Slopes of the cones are controlled by the angle of repose (angle of stable slope for loose unconsolidated material) and are usually between about 25º & 35º.>>

http://en.wikipedia.org/wiki/Angle_of_repose wrote:

Code: Select all

Material (condition)   Angle of Repose (degrees)
--------------------------------------------------------
Coconut (shredded) 	    45°
Bark (wood refuse) 	    45°
Flour (wheat) 	         45°
Chalk 	                 45°
.................................
Sand (wet) 	            45°
Sand (dry) 	            34°
.................................
Earth 	               30–45°
.................................
Gravel (loose dry) 	  30–45°
Gravel (natural w/sand) 25–30°
.................................
Clay (dry lump) 	     25–40°
Clay (wet excavated) 	  15°
.................................
Ashes 	                 40°
Snow 	                  38°
.................................
Clover seed 	           28°
Wheat 	                 27°
Urea (Granular) 	       27°

Ant lion ?

Humans or Rovers or Robots....they are going to have to watch out for the SARLACC down there!!!!!!!!

After clicking on the photo....and magnifying the view.....I think we are looking at an illusion. I don't think this is a cavern....I do not see a wall going down into anything....I see a floor with a crescent moon shadow, and a part of the floor of the crater....I don't think we are actually looking inside something. The EDGES of the bottom are too consistent...and do not appear to drop into anything....
In other words...it is like a Frozen Lake at the bottom...and what we see is Shoreline and contrast....
Just my observation.

I do observe, that if you look long enough...it can change appearance to look LIKE A CONE...and not a crater....but I think that too is an illusion, as the upper right shadows are on the outer edge where they should be, while the lower left, has few shadows....
I think the light source...is from the lower left....

:---[===] *

Boomer12k wrote:After clicking on the photo....and magnifying the view.....I think we are looking at an illusion. I don't think this is a cavern....I do not see a wall going down into anything....I see a floor with a crescent moon shadow, and a part of the floor of the crater....I don't think we are actually looking inside something.

This is no illusion. There are other images of the same thing, taken under different lighting. You don't see any walls because they are well away from the hole, out of view. This is a hole in a roof of the cavern, not a well-shaped hole.

Chris Peterson wrote:

Guest wrote:I do not understand the illumination of this picture.

The external shadow of the cone is on the same direction as the illuminated bottom of the hole. It is as there are two sources of light.

I think you're being fooled by the famous concave/convex optical illusion. There is no cone here. The hole is at the bottom of a depression.

Yes, I assumed the other variant too, but if this is a depression, the light is consistent, but the semicircular shadow looks kind of weird. A better resolution maybe will clear away my confusion.