APOD: An Unusual Hole in Mars (2017 Jun 12)

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APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by APOD Robot » Mon Jun 12, 2017 4:07 am

Image An Unusual Hole in Mars

Explanation: What created this unusual hole in Mars? Actually, there are numerous holes pictured in this Swiss cheese-like landscape, with all-but-one of them showing a dusty, dark, Martian terrain beneath evaporating, light, carbon-dioxide ice. The most unusual hole is on the upper right, spans about 100-meters, and seems to punch through to a lower level. Why this hole exists and why it is surrounded by a circular crater remains a topic of speculation, although a leading hypothesis is that it was created by a meteor impact. Holes such as this are of particular interest because they might be portals to lower levels that extend into expansive underground caves. If so, these naturally-occurring tunnels 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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Bob

Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by Bob » Mon Jun 12, 2017 4:34 am

Any chance of developing a 3D anaglyph image?

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by wolfie138 » Mon Jun 12, 2017 6:17 am

What's the darker smear leading off to the North-East? Looks like something was surrounding the crater and has been blown by winds, but it seesm to cover a far greater surface area than i'd expect.

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by distefanom » Mon Jun 12, 2017 6:52 am

In lots of Martian "holes" I can clearly see that "coma" imprinted on the soil, just as there is something "continuously venting" out of the crater itself.
I wonder if it's not something like volcanic (or maybe criovulcanic) activity there...
I can hardly image some kind of robotic rover that could crawl down there inside...
Maybe something more like a drone could make something like a speleology research or a maneuverable balloon... (can't imagine if anything like that could work on Mars)... :shock:

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by ygmarchi » Mon Jun 12, 2017 7:56 am

I'm really impressed by the perfectly geometrical round shape.

Alex_333

Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by Alex_333 » Mon Jun 12, 2017 9:21 am

Sublimations patterns like the ones on Pluto.

pacman

Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by pacman » Mon Jun 12, 2017 10:46 am

I would be interested to know how thick is the ice sheet.

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by Whiskybreath » Mon Jun 12, 2017 10:51 am

Instantly reminded of the craters left in Arctic regions by methane eruptions during the melt of permafrost. Photographs of these are startlingly similar.

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by saturno2 » Mon Jun 12, 2017 11:06 am

It´s a strange hole.
Looks like an old truck tire.

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by smitty » Mon Jun 12, 2017 11:51 am

Can anyone offer an explanation for the amazingly uniform, almost leather-like nature of the terrain underlying the ice sheet? Thanks!

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by De58te » Mon Jun 12, 2017 12:29 pm

I am guessing that the hole is not a crater, but an accumulation of CO2 sublimated gas that became explosive and acted as a geyser. The south pole is a combination of water ice and CO2 ice. During spring heating sunlight penetrates the still relatively clear water ice layer and heats the dry ice. But in the meantime global dust storms occur and the pole gets a layer of dust deposit. The CO2 geyser than picks up the dust and with the prevailing wind at the time produces the dark fan debris. The Swiss Cheese effect could be collapse of the water ice layer as the Co2 sublimates.

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by warmingwarmingwarming » Mon Jun 12, 2017 3:42 pm

De58te wrote:I am guessing that the hole is not a crater, but an accumulation of CO2 sublimated gas that became explosive and acted as a geyser. The south pole is a combination of water ice and CO2 ice. During spring heating sunlight penetrates the still relatively clear water ice layer and heats the dry ice. But in the meantime global dust storms occur and the pole gets a layer of dust deposit. The CO2 geyser than picks up the dust and with the prevailing wind at the time produces the dark fan debris. The Swiss Cheese effect could be collapse of the water ice layer as the Co2 sublimates.
You're probably correct. Similar holes appear in farm fields which are heavily manured by cattle dung .. the dung emits gas, which can be trapped, until it explodes through the surface. But I didn't know there were cattle on Mars. Good news for our Marsnauts when they get there .. take a barbecue.
I think I think, though I'm not sure if I all the thoughts I think I think, or if they come to me from .. goodness knows where. :)

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by Chris Peterson » Mon Jun 12, 2017 4:11 pm

warmingwarmingwarming wrote:
De58te wrote:I am guessing that the hole is not a crater, but an accumulation of CO2 sublimated gas that became explosive and acted as a geyser. The south pole is a combination of water ice and CO2 ice. During spring heating sunlight penetrates the still relatively clear water ice layer and heats the dry ice. But in the meantime global dust storms occur and the pole gets a layer of dust deposit. The CO2 geyser than picks up the dust and with the prevailing wind at the time produces the dark fan debris. The Swiss Cheese effect could be collapse of the water ice layer as the Co2 sublimates.
You're probably correct. Similar holes appear in farm fields which are heavily manured by cattle dung .. the dung emits gas, which can be trapped, until it explodes through the surface. But I didn't know there were cattle on Mars. Good news for our Marsnauts when they get there .. take a barbecue.
What kind of barbecue is required for cattle whose exploding dung creates 100 meter craters?!
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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by ta152h0 » Mon Jun 12, 2017 4:43 pm

swiss cheesery
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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by Baby's Back » Mon Jun 12, 2017 4:55 pm

Chris Peterson wrote: What kind of barbecue is required for cattle whose exploding dung creates 100 meter craters?!
Something like this? - https://imgur.com/I6wAZbh

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by chuckster » Mon Jun 12, 2017 6:38 pm

There are a lot of photos of Mars, from orbiters and rovers, that look remarkably like Earth desert terrain. And then along come photos like today's and a few others like this : https://apod.nasa.gov/apod/ap120422.html , that would be completely appropriate for a "Rocketship XM" movie-style Theremin score !

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by hscribner@spp.org » Mon Jun 12, 2017 6:42 pm

The hole looks like it could have come from an electric plasma discharge.

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by JohnD » Mon Jun 12, 2017 7:13 pm


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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by Chris Peterson » Mon Jun 12, 2017 7:45 pm

hscribner@spp.org wrote:The hole looks like it could have come from an electric plasma discharge.
The largest electrical discharges on Mars are lightning, which is probably pretty minor compared with the lightning on Earth (which does not, of course, create giant holes in the ground).
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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by distefanom » Mon Jun 12, 2017 9:04 pm

Let's imagine inside the hole there is a mixture of water ice & CO2 (Hipotetical: I dont' know if those can stay mixed together down there).
Temperature needed to have a stable mixture should be (seeing the triple point diags attached) at least below -80°C
If not less, since at lower pressure, CO2 needs even lower temperatures to stay "solid".
Have a comparison btw the two phase diagrams:
https://drive.google.com/open?id=0ByisW ... FFGT3BFcXc
https://drive.google.com/open?id=0ByisW ... TJ5YVMzRjg
Now let's imagine temperature increases and goes over the CO2 Triple point which is around -55°C.
Water in the mixture is still ROCK-SOLID at this temperature, or maybe liquid, for the soil pressure exherted by the soil above; so the CO2 gas has to literally explode (or BURST) to get free...
Also, this "BURST" cannot happen on the Mar's SURFACE level, since water needs the soil pressure to not sublimate: only underground all the conditions are met.
Having Mars gravity, and the pressure needed to have liquid water, one could also infer how much the pit is deep...
I think this is at least reasonable to explain the crater-like feature we see.

(sorry I don't know how to correctly post images here)
Last edited by bystander on Mon Jun 12, 2017 10:19 pm, edited 1 time in total.
Reason: All <img> tags require image urls not page urls

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by MarkBour » Tue Jun 13, 2017 12:34 am

Looking away from the most interesting spot to the rest of the field of "holey" dry ice, I grabbed a few parts of this image to represent what I would guess the short-term progression is. Left-to-right, I would guess we have an evaporative process that proceeds like:
Captures.png
It would seem that we have a base terrain that has been described as "leathery" at this resolution, and on top of that appear to be two layers, most clearly visible in the 4th frame above. The lower layer appears darker, much like water ice, and the upper layer appears like snow on Earth, but I'm assuming that it is frozen CO2. The last frame shows a place that leads me to believe the CO2 layer sublimates away and then the ice layer also eventually disappears somewhat later. You can still see significant residue of the lower darker layer, but it also evidently recedes to nothing over time.

Looking at the edges of the holes, it actually looks like there are 3 layers in some places: light-dark-light. But I am suspecting that the lower light layer is really just a "temporary snowbank" of top-layer material that forms along the edge of the growing openings from time to time. This conclusion is based on looking at the overall pattern and region and seeing lots of variation in those thin strips of light color.

Has this region been undergoing a warming period?
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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by warmingwarmingwarming » Tue Jun 13, 2017 3:23 pm

Baby's Back wrote:
Chris Peterson wrote: What kind of barbecue is required for cattle whose exploding dung creates 100 meter craters?!
Something like this? - https://imgur.com/I6wAZbh
I kin smell the savoury aroma drifting on the Martian air!
I think I think, though I'm not sure if I all the thoughts I think I think, or if they come to me from .. goodness knows where. :)

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by doribeans » Wed Jun 14, 2017 8:38 pm

I'm sorry that this isn't a serious question but...
isn't human exploration of tunnels on other planets the subject of about half of scary sci-fi thrillers?

be interesting to see what happens...

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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by neufer » Wed Jun 14, 2017 10:59 pm

doribeans wrote:
I'm sorry that this isn't a serious question but...
isn't human exploration of tunnels on other planets the subject of about half of scary sci-fi thrillers?
  • "it seems such an obvious thing."
----------------------------------------------------------------------------------------
THE FIRST MEN IN THE MOON by H.G. Wells (1901) Chapter 13
............................................
"We are some way in," he said. "I mean—perhaps a couple of thousand feet or more."

"Why?"

"It's cooler. And our voices are so much louder. That faded quality—it has altogether gone. And the feeling in one's ears and throat."

I had not noted that, but I did now.

"The air is denser. We must be some depths—a mile even, we may be—inside the moon."

"We never thought of a world inside the moon."

"No."

"How could we?"

"We might have done. Only one gets into habits of mind."

He thought for a time.

"Now," he said, "it seems such an obvious thing."

"Of course! The moon must be enormously cavernous, with an atmosphere within, and at the centre of its caverns a sea.

"One knew that the moon had a lower specific gravity than the earth, one knew that it had little air or water outside, one knew, too, that it was sister planet to the earth, and that it was unaccountable that it should be different in composition. The inference that it was hollowed out was as clear as day. And yet one never saw it as a fact. Kepler, of course—"

His voice had the interest now of a man who has discerned a pretty sequence of reasoning.

"Yes," he said, "Kepler with his sub-volvani was right after all."

"I wish you had taken the trouble to find that out before we came,"
----------------------------------------------------------------------------------------
https://en.wikipedia.org/wiki/Phobos_(moon)#Shklovsky.27s_.22Hollow_Phobos.22_hypothesis wrote:
<<Around 1958, Russian astrophysicist Iosif Samuilovich Shklovsky, studying the secular acceleration of Phobos's orbital motion, suggested a "thin sheet metal" structure for Phobos, a suggestion which led to speculations that Phobos was of artificial origin. Shklovsky based his analysis on estimates of the upper Martian atmosphere's density, and deduced that for the weak [aerodynamic] braking effect to be able to account for the secular acceleration, Phobos had to be very light—one calculation yielded a hollow iron sphere 16 kilometers across but less than 6 cm thick. In a February 1960 letter to the journal Astronautics,[climate change denier] Fred Singer, then science advisor to U.S. President Dwight D. Eisenhower, said of Shklovsky's theory: If the satellite is indeed spiraling inward as deduced from astronomical observation, then there is little alternative to the hypothesis that it is hollow and therefore Martian made. The big 'if' lies in the astronomical observations; they may well be in error. Since they are based on several independent sets of measurements taken decades apart by different observers with different instruments, systematic errors may have influenced them.

Subsequently, the systemic data errors that Singer predicted were found to exist, and the claim was called into doubt, and accurate measurements of the orbit available by 1969 showed that the discrepancy did not exist. Singer's critique was justified when earlier studies were discovered to have used an overestimated value of 5 cm/yr for the rate of altitude loss, which was later revised to 1.8 cm/yr. The secular acceleration is now attributed to tidal effects, which had not been considered in the earlier studies.

The density of Phobos has now been directly measured by spacecraft to be 1.887 g/cm3. Current observations are consistent with Phobos being a rubble pile. In addition, images obtained by the Viking probes in the 1970s clearly showed a natural object, not an artificial one. Nevertheless, mapping by the Mars Express probe and subsequent volume calculations do suggest the presence of voids and indicate that it is not a solid chunk of rock but a porous body. The porosity of Phobos was calculated to be 30% ± 5%, or a quarter to a third being empty.>>
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Re: APOD: An Unusual Hole in Mars (2017 Jun 12)

Post by MartynW » Thu Jun 22, 2017 6:05 pm

These holes seem to be the result of surface collapse, a "pothole" of sorts. If you look carefully at the patch of ice inside the hole, you can see piles of dirt covering an edge, indicating very recent collapse.

I agree that it would be really interesting to make a closer study of that brown stuff that seems to be quietly emanating from the hole and drifting downwind. The simplest, and most boring answer, is that it's the dust raised when part of the side falls in at intervals.