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As Homer says, Woohoo! We're getting to the point that explaining an absence of life, past or present, on Mars is going to be a challenge.

Do we understand enough about those little ripples to use them as a baseline for an order of magnitude guess about the lifetime of the body of water that formed them? E.g., do you get ripples in 5 minutes, 5 years, 5 millenia?

Or, is it the case that ripples form rapidly all the time and that the rover found the ripples that happened to be left behind when the last bit of water disappeared?

Keith Cowing

At the press conference today I was about to bring up stromatolites and other mega- manifestations of microorganisms as a follow-up to my follow-up question - but I'd already pushed the point - and Steve was not going to go there ....

Have my write up online at


"Beachcombing On the Shores of Barsoom"



Oliver Morton

I should have added to this post a reiteration of something I said about the first announcement: a fundamental discovery being made here is that by using all the instruments on the rover together, and its mobility too, it's possible to make complex, multifaceted geological interpretations. This was clearly assumed, but that doesn't mean it's not extremely exciting to see it prove true.

Carl Zimmer

From what I understand about stromatolites, there are a lot of ways they can be formed without microbes, and robot-eyeballing probably won't be able to distinguish between biotic and abiotic ones. But it can certainly find some good candidates for sample return! Amazing stuff.

Charles Schmidt

Though I'm no geologist, it had occured to me that the msss MGS MOC image here, at the center of the landing ellipse - some kilometers west of Eagle crater - is reminiscent on earth of springtime salt, when the salt which has been used for deicing leaves a white tracery of salt crystals over dark asphalt. The units on Mars bear a striking visual resemblance.


Surely, someone in the know had predicted that the white areas on Meridiani Planum would be found to be a salt flat, with salty outcroppings...
The image also underscores how lucky we were to find an outcrop in the western part of the landing ellipse, for here in the center of the ellipse the outcroppings (the high albedo areas, I presume) appear to be pervasive and large, while easterly by Spirit the outcroppings are precious few, but for moderate craters like Endurance, or the impossibly propitious Eagle Crater.

Hey, when did Terra Meridiani become Meridiani Planum? Does the new name supplant the old, or do other places on Mars bear dual proper nouns? I still like the old Terra Meridiani.

The discussion by M. Morton on methane (4/25)is well, awesome, like everything else here, wow thank you so much Oliver.

Fred Mills

Speaking of NASA and possible cover-ups does anyone remember the perfect epsilon noted on the surface of a rock being among the very first pictures received from the martian surface? Even before the face. Reference to it seems to have disappeared in the intervening years.

Either someone from NASA or elsewhere had a good sense of humor or "somebody" from Mars did. Just curious.


DC: The ultimate socrue of the oxygen is carbon dioxide from volcanoes [water, actually - thanks to everyone who corrected me]. This is then split into oxygen and reduced organic carbon by photosynthesis, and if the carbon is then kept separated by burial, and the oxygen left behind is produced faster than it can be consumed by other oxidation processes (especially reacting with iron and sulphur) it will build up.Regarding the amount of carbon, organic carbon is incorporated into all marine sediments as dead algae etc. settle out of the water column, and whilst the concentrations are low compared to something like coal, when you integrate over the volume of all that sedimentary rock you get a very large number indeed. To quote: Organic matter in shales is the dominant reduced carbon reservoir. The earth's crust contains 1.1 x 10^21 moles of reduced carbon The total amount of organic carbon needed to account for all the oxygen in the atmosphere is only 0.038 x 10^21 moles.Of course, these marine sediments are then mainly subducted back into the mantle and thus really buried.As for the iron formations, as I understand it, what they're actually telling us is not quite as simple as them being a huge oxygen sink not least because, as I mentioned in the post, their present mineralogy is largely the result of later alteration. It's one of those subjects where you're perfectly happy until you start reading the literature, and then you develop a headache.Robert: the Late Heavy Bombardment ended about 3.8 billion years ago; these rocks formed 300 million years later. That's a lot of time to play with enough in recent geological history for life to go through 2 major mass extinctions and subsequent evolutionary radiations. Spontaneous' should used lightly, methinks.

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