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Del Miller

The orbital surveys of Mars depict millions of craters with dusty bottoms and often a few dunefields scattered across them. I find it puzzling that the dustiest and sandiest planet imaginable - one that has, for billions of years, had raging, planet-wide dust storms on a regular basis - still has mostly empty craters.

Even if these dust storms had deposited only a fraction of a millimeter per year, the net result over the last two or three billion years ought to have resulted in craters that have been completely filled in and the ramparts being totally covered.

I can't believe that the Martian winds can scour these basins so effectively as to remove that much of the dust and sand and the occasional dust devils surely couldn't be that powerful enough of a vacuum cleaner to empty the craters.

Has anybody looked at this question? Where has the dust gone?

Bruce Moomaw

I'll look into this in more detail -- but the evidence, as I understand it, is that the dust devils (which are not "occasional", but one of the commonest phenomena on Mars) are extremely good at picking up and moving dust around. The logical explanation would seem to be that they keep the dust distribution more or less evenly spread all over Mars, instead of having it accumulate in depressions as one might expect. (One abstract at March's LPSC suggested, on the basis of lab tests, that a single devil passing over one of the rovers might give it a new lease on life by neatly vacuuming most of the dust off its solar panels -- although the same devil might fuzz up its Hazcam lenses to some degree.)

Thanks for the compliment on my articles, Oliver. The real key question is whether that underlying basalt sandstone layer found at Endurance Crater shows ANY chemical signs of having come in contact with significant amounts of normal, un-acidified water. If it does, there remains a possibility that all the sediments at Meridiani were indeed laid down by liquid water -- but it would still have had to be a quite short-lived exposure to it, since even 100,000 years of exposure to ordinary neutral water breaks down the minerals in basalt very nicely. That's why we so rarely see dark sand on Earth.

Also, a closeup inspection of the ripples in the basalt-sandstone layer is crucial, to determine whether that particular layer of sediments ever had water running across it before it lithified, or whether it was laid down by winds and then hardened gradually due to exposure to repeated small traces of liquid water. In any case, I think the later acid-modified sediments were laid down only after the lower sediment layers had already hardened into relatively waterproof sandstone, which explains why they resisted being acid-modified as well. (The very fact that we're seeing ripples in the upper acid-modified stuff indicates that those sediments were NOT laid down on a stable lake bottom, but either laid down originally or stirred up afterwards by shallow rivulets of acidified water running across them or through them. The lake-bottom deposition theory is, I think, one that we can rule out right now on the basis of what we already know.)

Bruce Moomaw

I should also clarify that I think the reason Opportunity has been sent down into Endurance several weeks ahead of the earlier plans is that I think they want good CLOSEUP compositional maps of the basalt-sandstone layer with Mini-TES before it breaks down. (This was pure deduction on my part -- I haven't seen any actual statements from them to that effect -- but I can't think of any other reason for them to change their plans so drastically. Mini-TES' nitghtime temperatures during Deep Sleep are now down below -52 deg C, and clearly it is not long for this world.)

By the way, James Oberg has sent me the latest status reports. As of Sol 137, the rover was fully 5 meters down into the crater at a tilt of 19 deg, and things continued to go well. It has already tested its ability to back up from that kind of slope, and it is now preparing to begin the full regimen of arm operations on a rock called "Tennessee" (including 2.5 hours of RATting) -- after which it will proceed deeper into the crater.

Also: I can't say anything more about this for fear that Oliver may beat me to an article; but pay very careful attention to tomorrow morning's press conference (10 AM Pacific time) I have good reason to believe that Spirit has found something Very Big at the Columbia hills -- bigger than anyone expected, in fact (although we're not talking about visible fossils).

Oliver Morton

Bruce -- is that press conference going to be webcast? and while I'm asking, did you ever post a third (magnetite?) report from the astrobiology conference?


Having cross posted your very tantalising discussion to Adots Notblog it was pointed out there that there are some very interesting new PanCam images from Gusev.

Any chance this is related to the Sol 158\159 PanCam images like this one
This stuff looks a lot more like the material at Meridiani than anything that has cropped up at Gusev far.
It certainly looks "sedimentary" to me.

Bruce Moomaw

(1) Yep, it will be webcast.

(2) Nope, I'm still working on part 3 -- mostly because the evidence for and against fossil evidence in ALH84001 has now become so convoluted, and so dependent on who you talk to, that I'm still trying to make sure I have all my facts straight.

(3) Ah, so somebody else noticed the Gusev Blueberries too! At any rate, that's exactly what these isolated hunks of stuff scattered around the foot of the hills look like -- finely layered sedimentary rock with little round concretions in it -- and I have received advance word that the main focus of tomorrow's conference will concern some kind of major finding at Gusev.

They're the last thing I expected to see at Gusev, and of course we don't know yet whether they are gray hematite like the Meridiani berries, or some other mineral. But if Benton Clark and Jeffrey Kargel are right and sulfuric acid solution of various strenghts has been quite a common feature of the surface history of Mars, these things may be scattered all over Mars in various quantities -- with Meridiani just the most spectacular concentration of them currently exposed on the surface.

Bruce Moomaw

That isn't the only picture of them -- there were some taken the day before, although it took me until today to fully realize what I was looking at. Here's the full list (including some photos from yesterday's sequence that I didn't notice until today):

(1) http://qt.exploratorium.edu/mars/spirit/pancam/2004-06-13/2P140388061ESF6800P2594L2M1.JPG , and several following frames in the http://qt.exploratorium.edu/mars/spirit/pancam/2004-06-13/ sequence. (If you have trouble fidning them there, the first one has a size of 83k.)

(2) http://qt.exploratorium.edu/mars/spirit/pancam/2004-06-14/2P140478538EFF6830P2597L5M1.JPG http://qt.exploratorium.edu/mars/spirit/pancam/2004-06-14/2P140478588EFF6830P2597L7M1.JPG

(3) http://qt.exploratorium.edu/mars/spirit/pancam/2004-06-13/2P140386989ESF6800P2595L7M1.JPG

(4) A whole series of Microscopic Imager closeups of what appears to be a rock surface unlike anything I've seen at Gusev before:

All the frames at http://qt.exploratorium.edu/mars/spirit/micro_imager/2004-06-13/ , except the first one.

Once again, this stuff looks eerily like the Meridiani acid-modified sedimentary rock.


I'm very curious about the location of this deposit (assuming it is sedimentary or an evaporite). Spirit appears to have been climbing slightly over the past few weeks. If it has then the fact that there was no evidence (found) of such deposits on the main Gusev crater floor area seems to indicate either [a] This stuff doesn't necessarily form in standing water or [b] these particular Gusev rocks are very old or [c] These have been scattered in from elsewhere or [d] Something moves hills about fairly significantly on Mars which I didn't think was likely without active plate tectonics or [e] I should probably leave these conjectures to the experts.

Bruce Moomaw

The probable truth is (B) -- it was known long before the landing that these hills of "Etched" terrain are actually considerably older than the surrounding lower plain, judging from their crater count. This is precisely why the rover headed for them the moment it became clear that Bonneville Crater wasn't deep enough to expose any interesting material.

Wht happened is that they are apparent remnants of the original floor of Gusev, which was largely eroded away -- after which the crater was refilled with other kinds of material: windblown sand, basalt ejecta from other nearby craters, maybe volcanic ash from the big Apollinaris Patera volcano 250 km north -- maybe even actual basalt lava flows from vents either outside or inside Gusev. At any rate, the floor material -- at least on that side of Gusev -- is thoroughly uninteresting. (The floor material extending up the crater's west side looks distinctly different, and may consist of material swept up the crater by Ma'adim Vallis -- but it's out of reach.) The Etched Hills are intriguing islands of an older surface; but I had just convinced myself that they were probably just going to be older lava flows when THIS stuff turned up. Oh ye of little faith...

Oliver Morton

Great exchange, people. As I said, I believe detailed mapping by people at USGS Flagstaff shows the hills as being part of the rim of a crater within the basin, standing proud of a later layer of lava or ash filling in the rest of the basin and the bowl of the crater. If true I'd take that as meaning Gusev is a very low erosion place, since I find it hard to imagine the ash or lava being stripped away from the surface preferentially and thus uncovering hills that would have to be made of harder material. More likely that they were never covered at all, I suspect.


I'm also interested in the 'rotten' rock to the right of the 'bluebery' one(see pic)

The vertical sides look like standard wind-erosion as see all over the place out on the plains, but then the middle appears to be dissolving from the top down . . . vey strange!

Then there's the 'cobra hoods' http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20040615a/fragile2.gif

Could that be due to saltation? (dust grains bouncing along the surface in the wind preferentially eroding the lower portions of the rock) If so, then the fact that such things are seen here and not on the plains must add weight to the argument that the surface of the hills are older than the plains.


I think I recall reandig that Opportunity could take as long as 2 years to travel the 15 or so kilometers to the larger crater it's aiming for. Of course it's stopping to rubber neck along the way. But still, at that rate, travelling roughly a quarter of the way around Mars to meet Spirit which has also had to travel another quarter of the way, dragging a bum wheel and running backwards I suspect it would be a while before we'd see the hug. We might be able to get to Mars, start a colony, and be running tour buses to see their progress before they reached each other.But what an Odyssey it would be!


ok, for everyone that's like she sohuldn't have done it, you can tell it's fake , it's her choice, it has nothing to do with you. i understand it's your opinion, but if it makes her happy then that's all that matters.I think they look fine, and if she's happy with it, then good for her=)


love this post marc i SO often feel the same way in fact, a lot of my investment stgrteay was devised to work around this tragic flaw of my personality basically, i limit my first check to a small amount, then followup with a bigger 2nd check if it turns out i was right after all.the challenge is that as an investor, i'm no longer the entrepreneur even when i see the upside in the business, i can only help advise, i'm not running the show anymore. it's ultimately up to the business founder to deliver on that optimism and turn vision into reality. that doesn't mean i'm less optimistic, but it does change how i participate / interact with the team. i still try to provide useful help & resources, but i can't press my vision onto the founder; they have to discover and find their own way. still, like you i like to believe they will be successful. and maybe that's not a flaw, it's just a good perspective for someone who wants to help regardless, great post & appreciate the sentiment and honesty.

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