May 23, 2007, HiRISE release

Ustrax - finally - you have what you asked for

http://hiroc.lpl.arizona.edu/images/PSP/di...PSP_003647_1745

http://hiroc.lpl.arizona.edu/images/2007/d..._1745_cut_b.jpg

THAT...is an abyss.

Doug

Well, just look at that great big hole in the ground !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

If I knew the service was so fast I could have ordered one earlier...

EDITED: A view:
Click to view attachment

It's obvious that's an Acme Portable Hole that Wile E. Coyote left behind....

Beep Prepared 1961

Wow!!!

Is that the entrance or exit?

..okay, THIS made my jaw drop! Why so circular? Almost looks like a meteor punched right through a thin surface crust & into a deep dark chamber (undoubtedly making the patented Wile E. Coyote as he goes off a cliff "bomb dropping" whistle all the way down in the thin Martian air...)

Either that, or we finally found the ejection end of the linear accelerator that launched H.G. Wells' invading cylinders...

The imagination runs wild. If these things are really deep, you could have some interestingly high atmospheric pressure down there...

Well - unless its many many km's - then there are other places which will have higher atmos.press at 'ground' level. But it's still a very very exciting and interesting feature

Doug

Looks to me like one of Kim Stanley Robinson's Mars moholes.

Alternatively, we could extrapolate wildly from Titan and assume that anything that dark and featureless has to be liquidish, sort-of. Or not.

I wonder what IR will show us, especially at night. I don't think we'll be able to look down the hole directly, unless MRO's orbit is modified, right? Maybe we need to wait for a nice, strong dust storm to kick up the tau, so that more light is sent down the hole from all around. Pretty amazing that it is pitch black!

I'm sure it's possible with to make an estimate of the minimum size and depth of the cavern based on that. Maybe we'll get lucky and something interesting will show up on IR, like the extent of the roof over the cavern. Do either of the radars on Mars have the resolution to check this out?

I don't quite understand why the incidence angle != angle of the sun above the horizon; only thing I can think of is that we're looking at a slope.

Anyone locate a wider context shot of that location? I couldn't see any lava-tube features, but the whole image might be one.

EDIT: Looks like this is Jeanne:

http://themis-data.asu.edu/img/browse/V183...&stretch=S2

Took me a bit to convince myself it's the same location.

Can someone less lazy than I do the calculations on this? If we know the angle of the sun and the angle of this photo it should be easy to calculate a minimum depth for this chasm if we assume that sunlight illuminating the bottom of this hole would be visible in the image. Since nothing is visible, the depth must exceed that minimum.

See this topic for more information and links to context images from Odyssey:
http://www.unmannedspaceflight.com/index.php?showtopic=4036

--Emily

The excitement in this thread is one thing. Just wait till the kooks get wind of this image.

Given this image's location on Mars, I would presume this is a skylight of an old lava tube. Very interesting though.

Yes, but it must be a very large tube since the hole is more than 100 meters across. I can't remember ever seeing a window into a lava tube that big on Earth. I wonder if lava tubes scale with gravity somehow.

(groan)...don't remind me. I'm traveling now, but next week one of my consipiracy-minded co-workers is going to jump me on this for sure if it hits Hoaxland...at least he's retiring soon!

Who? Your co-worker or Hoagland?

The former; maybe he's tight enough with the latter to persuade him to follow suit? </wishful thinking mode>

38 degrees. Call it 130m across - sohcahtoa and all that - 101 metres is the cutoff at which we wouldn't see light at the bottom.

Doug

According to the caption on the image, though, HiRISE should be able to see deeper than that:

--Emily

Just for grins, I went to HRSCview and located the HRSC image that contains this skylight. Here's a crop from that:
Click to view attachment
I also noticed another skylight in the same HRSC view:
Click to view attachment
It doesn't look to me like that one's on the Cushing et al list (see my blog entry for that list and image). Or is it?

--Emily

Nice find, Emily! Seems like it's right in line with that (apparent) collapsed lava tube to the upper right...

Ouch!

Am I the only one that didn't immediately see the pun??


GROAAAAAAAN!

Ahh, they finally released this picture. The one's got all of the scientists perplexed, we've come to a conclusion it's likely an overhanging of some kind, meaning that the lava tube is really big... I think we've figured it must be at least 200 m deep as well. Still, it's certainly quite a mystery.

Oh, for those of you wanting to overlay MOLA data, it's already been tried, without any luck.

Were any THEMIS images taken?

Of course, that's what prompted us to take the picture in the first place. Besides, THEMIS has photographed just about everywhere on Mars.

OK now I see the history of this with Odyssey. Sorry been out of the loop with assorted obligations the past few months.



Good to know. Mike has yet to impliment the Midnight THEMIS Browser , so I haven't been able to keep up on that instrument either.

Looks like a good landing site for MSL -- if it stood for the Mars Spelunking Laboratory...

-the other Doug

Martian bungee jumping anyone?

Surely this will kick off a more systematic look at the slopes of the Tharsis and Elysium volcanoes, if it isnt already happening. Who know how many of these things might turn up, and who knows how big they might be? Hmmmmm, 0.38 gravity.....

P

Actally, regardless of how deep these things are, at SOME time of the day at SOME time of the year (given their near equatorial location, around local mid day and around the equinoxes) the sun will illuminate the floors of these caverns. Being lucky enough to have an MRO overpass at one of these short periods is another matter of course...

P

MRO is in sun-synchronous orbit so the nadir point below is either early morning or late afternoon local time to provide decent shadowing for most imaging. The orbit would have to be substantially adjusted to get a fly over noon local time.

What is the range of illumination angles due to seasonal variations from axial tilt?

I don't see it in the seven that they show. I think antipode is correct, suggesting, "Who know how many of these things might turn up, and who knows how big they might be?"

I took a hint from your discovery and started panning over that region with HRSCview, and I thought I saw several very small skylights that were not very convincing. I also came across the one you posted an image of, and then finally another apparently "new" one that was large enough to be convincing. It's actually a pair, but the second one is rather small.
Click to view attachment

Excellent. ~100m across? >200m deep? What a place to dome over and start building.

Andy

Is it really impossible to dig out something from the black?

So this can only be a fantasy...

What I did was an attempt to enhance some features that were already visible in the image shown here on the right but that also come out from the original one.

Note: I know that it has already a name but Cernunnos, the Celtic God of Fertility, Life, Wealth and the Underworld sounded just perfect for the occasion...

Yes - it really is impossible. That's not details - that's noise.

Doug

Judging from the non-sense making overhangs visible in the picture, I vote for liquid.

What sort of liquid at .006 bar and -80degC? Would a liquid not have specular reflection etc. Orbital images of lakes and seas on earth are not black. Do not confuse the 'black lakes' of Cassini Radar imagery with the optical wavelengths of HiRISE.

There is nothing nonsensical in the concept of overhangs. We see them on Earth - they could be even more extreme in the 1/3rd G of Mars.

Doug

I can't imagine anything else than a hole in a (lava) tube.
I don't remember the width of the path of MOLA. Somebody suggested that the depth can be find in the data. Is that possible?

Regarding that overhang:

We are told that the sun was 38 degrees above the horizon, or 52 degrees from zenith. This means that if the angle of overhang was less than 52 degrees from the vertical the sun would be directly illuminating part of the overhang wall surface underneath the visible rim. This would add significantly to the level of downward illumination inside, so my guess is it's not happening. That makes the angle of overhang quite severe and the rim quite thin. The direct sunlight entering through the skylight would then be falling on the floor of the cavern some distance down-sun. The light scattered from that bright spot would then be shining upward, illuminating the interior roof but not the part of the floor in our line of sight.

^

"Oh, for those of you wanting to overlay MOLA data, it's already been tried, without any luck."

Doug

There must be some liquids (carbon based) that absorb most /all visible light (independent of the light frequency). Is there any evidence that this hole is a hollow tube / entrance to a cave / ? Why is there no light on one of the walls?

Because the ceiling is overhanging. It's a collapse to a lava tube. We've seen other hirise images that take this to the extreme just leaving a single piece over the top of the old lava tube - itself with overhanging edges (the 'bridge' picture). The mechanism behind a formation like this is certainly not that unusual and indeed terrestrial analogues are not uncommon either.

http://www.texasbeyondhistory.net/plateaus/images/ap17.html

We're looking almost straight down it - so in actual fact it wouldn't take that much of an overhang to mean we don't see the sides even if they're lit.

That opening is 11,000 sq m . If there were 11,000 sq m of an unusual liquid - CRISM would have found it and we'd know about it. It's 8 or so Crism pixels across.

Doug

It's mostly noise, but on the scale of the whole hole, the upper part of the circle is lighter than the lower part. This might be the floor showing.

They just need to increase the exposure time for the next pass.

Thanks Doug, not even a tiny single chance?

I've justaposed what I got to the original image and that damn noise has the ability to act as if following some features in the contour of the rim...
Click to view attachment

I'm not saying that you're not pulling out three different shades from an 8 bit greyscale image, for which some photons from the bottom my be responsible. I'm saying it's impossible to say "that's the bottom". Lest we forget, similar techniques turned a black dunefield into all sorts of things.

I'm not sure that HiRISE can take longer exposures - 4x4 binning might help but of course we can do that with the image on the ground already

Doug

Neither am I, I was not saying "look how dark is the bottom, it might even be a pond!"
I was focusing on the "walls"...
For now...

The problem of that dunefield was being a dunefield, let's remember that the techniques applied to Ultreya were accurately developed specifically to deal with an abyss...

EDITED:

Yes, I found that curious because it seems to be an extension of the disturbed lighter soil patch outside the hole:
Click to view attachment

Binning done in the electronics before AD transformation is a lot more effective than in software, and I think this is what they talk about when some Hirise image is 2x2 binned etc.

Increasing is exposure time is of course problematic because Hirise has a scanning type detector. It will be interesting to see what the future plan is.

Will we have to wait until there is a laser altimeter or radar that can look to the bottom? How soon
can that be? I'm guessing a camera sensitive enough to see down there would not be worth it.

True. But we had good times imagining what "those sort of things" might be.

It's not an abyss, it's a martian oubliette!

And when we finally get illumination down there we'll find both Mars Polar Lander and Beagle 2 at the bottom!



( "My God, I see stars....")





[This image has totally tickled me pink. Aside from it's sheer image impact, a collapsed lava tube is a great way to get a peek at relatively protected Martian basalt.]

-Mike