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August 29, 2007, HiRISE release

Interesting new image of the Arsia Mons pit.

The polar pit gullies image is pretty good, too.
"interesting" is quite an understatement! Mark my words, that hole will be in the news headlines a couple of days from now.
Click to view attachment
The structure of the wall is fascinating.
Big enough to get a few CRISM pixels in there smile.gif

I did a five layer contour trace. Still not much detail beyond that wall.
Here's a related press release:

HiRISE Camera Returns New View of Dark Pit on Mars
UA News
August 29, 2007
You know, it's really interesting and cool to look into such a Martian pit. But, guys -- it's all basalt. Garden-variety basalt. You can look at the exact same kind of rock all over the Earth, and if you want to get some from off-Earth, there's a quadrillion tons more just 400,000 km away...

In other words, while the feature really looks interesting, it doesn't tell the story about Mars that I want to hear. The rock beds I want to see a sharp cut through are a lot older than this stuff.

-the other Doug
Sense of wonder, other Doug! Sense of wonder! Doesn't the thought of kilometers-long, tens of meters-high Martian caverns still your breath for just a tiny bit?

And I do wonder at the potential of Martian caverns as ecosystems. Yeah, they'd be cold, but the temperature would be stable, which counts for something; there'd be none of that pesky UV and less of those nasty superoxides.

While I am inclined to agree that the action's in the really ancient rocks, I have to wonder - might there be lava tubes at the sites of recent eruptions involving water? What might they hold?
QUOTE (Gsnorgathon @ Aug 30 2007, 03:25 PM) *
Sense of wonder, other Doug! Sense of wonder!

Sense of wonder, indeed.

Being of the generation that remembers Mariner 4, these images just blow me away.
Mariner 4 laid to rest the Lowelian Barsoom. There were reputable scientists at that time who just wrote Mars off as nothing but another Luna with a wisp of air. "Mars is Dead" proclaimed the NYT.

Mariner 4 killed the fantasy, but in place of that, gave us a real world. And that world just gets more complex with each added mission. Look at the HRISE south pole spider imaging.

Is this "just" a vertical shaft into the basalt, or a doorway into a nether realm of caverns (fantasy again... or not). Let's find out, and not just write it off.

Oh, trust me, I'd be first in line if they were asking for volunteers to go spelunking down into that hole. As far as sense of wonder, and also human-habitable volumes, are concerned, the place is a wonder. And I don't write it off as being *completely* uninteresting from a geological point of view.

But, hey -- if Steve Squyres can write about (paraphrasing here) "nothing but boring, uninteresting chunks of lava as far as the eye can see" about the floor of Gusev, I figure I've at least a little support for the idea that the real action truly is in the much older rocks.

I do admit, though, that Martian caverns would be the perfect places for medium-term and long-term human habitats. Their interiors are protected from solar and cosmic radiation (a very important consideration), and the application of enough heat (plus a little Yankee building ingenuity) could seal up cavern walls and allow a section of a cavern to be pressurized with a livable atmosphere. Heck, with enough native water, you might even be able to make indigenous concrete...

-the other Doug
Just on the principle of dropping a rock into a mineshaft & counting the seconds until you hear the echo, would LOVE to do a precision ranging radar/lidar pass over these holes for even an approximate depth estimation...wouldn't it be interesting if some were deep enough to have estimated bottom atmospheric pressures >= 20mb, which IIRC is the minimum threshold for maintaining liquid water at average Martian equatorial temps...
20mb would occur at a depth of about 12 kilometres below the Mars nominal "sea level".

Your rock needs to fall for about 80 seconds. ohmy.gif

Andy, neglecting air resistance, as is traditional.
Unfortunately, most of the pits which may lead into lava tubes are located on the flanks of Tharsis volcanic piles, which are located significantly higher than median. Even if these "caverns" bottomed out a km below the local surface, they would be higher above the median than, say, is the floor of Hellas. So, unless there is some other mechanism concentrating the atmosphere, I can't see how it would be significantly higher in pressure down in these tubes than we see at, say, Meridiani.

-the other Doug
Just messing about... smile.gif

Click to view attachment
I barely noticed this picture myself, sometimes I miss the days of working with HiRISE and finding out about all of this a week and a half before the general public. Still, I do occasionally get to glimpse at things from a HiRISE perspective, it does help to have worked there.

It does indeed seem to be fairly near straight down. One thing that makes this unusual as compared to Earth is it's large size, I believe this is much larger than anything found on Earth.
QUOTE (Stu @ Aug 31 2007, 07:52 AM) *
Just messing about... smile.gif

Waiting for Soup Dragon? cool.gif
And the Polar Pit Gullies are fascinating.

Polar Pit Gullies

Especially the enlarged sub-image...

Polar Pit Gullies - enlargement

Looks like Scottish hillside gullies, with apparent "sheep tracks" crossing obliquely between the gullies... smile.gif

QUOTE (AlexBlackwell @ Aug 29 2007, 09:15 AM) *
Interesting new image of the Arsia Mons pit.

Perfect timing. And wouldn't you know it? I understand that the Cushing et al. paper ("THEMIS observes possible cave skylights on Mars") should be published online tomorrow in Geophysical Research Letters. biggrin.gif
QUOTE (kenny @ Sep 4 2007, 10:09 AM) *
Looks like Scottish hillside gullies, with apparent "sheep tracks" crossing obliquely between the gullies... smile.gif


Though these are thoat tracks of course. smile.gif
Hej tty,

I think you mean "goat" ?

Do you have mountain goats in Sweden? I didn't see any when I climbed Kebnekaise.
No, he definitely means thoat. smile.gif

Yep -- as someone else here once said, I would absolutely adore to see images from a Barsoom Reconnaisance Orbiter. BRO could resolve the great spires of the city of Helium, after all... smile.gif

-the other Doug
Ah! Thanks Emily. I've obviously not been reading enough science fiction...

If we are VERY lucky, we may see the spires of the towers of Helium, thoats, green martians, and Deja Thoris in a few years. Pixar has the rights now and is apparently SERIOUSLY planning "John Carter of Mars".

For those that don't know, A Princess of Mars is the first, precedent setting and archtype creating "Planetary Romance", one of the two roots of modern Space Opera.

A Princess of Mars is an Edgar Rice Burroughs science fiction novel, the first of his famous Barsoom series. It is also Burroughs' first novel, predating any of his famous Tarzan novels. He wrote it between July and September 28, 1911, going through four working titles. finished story was first published under the last of these titles in All-Story as a six-part serial in the issues for February-July 1912. The finished story was first published under the last of these titles in All-Story as a six-part serial in the issues for February-July 1912.

Anyways, I was just wondering about MRO resolution, and the maximum possible. I know there were rumblings before the arrival that MRO's additional resolution wouldn't help any due to the limiting factor of Mars' atmosphere. Now that we're there and all, are there any new idea on the reasonable resolution limit from orbit? If we had a 5/2/1cm per pixel capability, when would we start getting dimishing returns?
Well, it all depends on how big of a camera you want to send there. I think HiRISE is mostly diffraction-limited, and it's mirror is 50cm, I think. If you want to double the resolution, you have to double the size of the mirror, or get closer to the surface. I don't think NASA would like the latter option very much, so you're stuck with a larger mirror.

HiRISE's max resolution is near 20-30cm, although I think there's some pixel-blurring at the highest resolution (I haven't studied the optical system, and I'm no optical engineer anyways, but this is from my memory). Anyways, assuming you would want a 5cm resolution, you'd need to send a 2m mirror! I can't see that happening for a long while yet, HiRISE resolution is good enough for 99% of the things we could think of, I rarely have seen anyone asking for much higher. I could see another HiRISE being sent before they send another higher-resolution (As I understand, there's another HiRISE camera that's half-built on the ground, it's not out of the realm to send another one there, just thought you'd like to know that.) Anyways, just thought I'd through in my $.02
A study document for the 2013 Mars Science Orbiter (available at the MEPAG website) weighed the advantages/disadvantages of sending a camera with 10 to 15 cm resolution. To eliminate pixel smear, they considered moving the CCD array during image acquisition, rather than moving the entire camera or entire spacecraft.
Ultimately, they decided that the weight of such a camera would be excessive and a HiRISE-class camera would be sufficient, given how little of Mars will be imaged by HiRISE itself during its lifetime. BTW, a HiRISE camera is not guaranteed for 2013, and will be competing for payload inclusion against things like an imaging SAR and advanced atmospheric instruments.

A resolution of at least 10 cm should be technically achievable from Mars orbit. Unclassified sources estimate that U.S. reconnaissance satellites get at least 10 cm resolution, and the Earth's atmosphere should be more of a challenge to compensate for than Mars'. Except during planet-wide dust storms, of course.
QUOTE (monitorlizard @ Sep 18 2007, 04:50 PM) *
Unclassified sources estimate that U.S. reconnaissance satellites get at least 10 cm resolution,

Actually they acquired images better than that. There are anecdotes from the latter cold war years of espionage agencies being able to identify individual license plates on vehicles. The letters on my California plates (assuming they are typical) are about 6 cm tall. Clearly you'd need resolution on the order of 2cm or finer to read them
I've always heard that those were just that -- anecdotes. However, from what I've heard, the more recent orbital reconaissance assets are multi-spectral, able to return images in color and in non-visible frequencies.

I've heard that the rumors of being able to read license plates were apocryphal, but that you could, in many cases, determine the issuing state of a given license plate from its unique color combination. You could also determine the rank of a given officer by the color of his shoulderboards (depending on the particular uniform specifications of the government you're observing).

Infrared imaging, of course, has very obvious benefits.

-the other Doug
Perhaps I am missing something obvious, but with license plates being mounted vertically on fenders, I never understood how they could be read from above... even if you are right next to the car.
You obviously observe vertical and near-vertical surfaces from a slant angle. Now, as good planetary imaging afficienados, we tend to think of getting the greatest resolution, and the greatest resolution (and most useful angle for projecting our images onto DEMs or using them for mapping) is from directly above.

But especially in the game of reconaissance spacecraft, what you want to look at might not pass directly underneath the resource(s) you have in place. So, you end up working a series of compromises; do you want 15-cm resolution of the ground 112 miles away from what you really need to look at, or do you want 23-cm resolution of what you need to see, at a slant angle of, say, 17 degrees?

And, of course, there are times in the recon biz when you *want* to see things from a slant angle, when you need to analyze an object or a construct in three dimensions. There is only so much you can do to reconstruct something's shape from a direct overhead shot and a short shadow...

-the other Doug
Recon sats can look at targets at way off verticle slant angles. An infamous pair <near vertical and 45'ish deg slant angle> of recon sat images leaked about or a little before 1990 of a Soviet shipyard (the leaker was imprisoned for it) show good slant angle capability.

The basic fact is that recon sats have had hubble size mirrors, basically. An Aries-5 could or Saturn 5 could have launched much bigger optics. You can play with clean, oversampled high signal to noise ratio diffraction-limited images to extract about 2 times the apparent raw resolution out of the data, but that's about it.
Hugh P
Moved to correct thread - Mod

No one seems to have noticed details in this pit -
Click to view attachment

I tweaked the levels in Photoshop and applied a slight blur to reduce the scan line artifacts, and tweaked the levels again.
It seems that there an extra shelf below the eastern wall, which may be an overhang or even a tunnel, or more likely rubble that's fallen off the eastern wall.
There's a shadow gradient from top left to bottom right which cannot be a camera artifact, and is either caused by the slope and/or from the light reflecting off the opposite side wall.

There also appears to be chunks of rubble at the base of the pit, although this may well be in part noise from the HiRISE camera. See this image to compare how light plays off rubble in the bottom of a pit, and it seems fairly similar. However the gradient is in the opposite direction possibly because this hole is shallower relative to the width.

I'm very surprised no one has spotted this before as it had quite widespread media coverage when the image was captured in 2007 and I have been unable to find any other reference to this. Here is the link to the HiRISE source - the details are only visible on the non-map projected image.
Here are the original musings about it on my blog and I would be very interested to know what the experts think smile.gif
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