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Wednesday, November 21, 2012

Curiosity, killing us all

Yesterday, on NPR, NASA dropped a kind of big bomb, maybe.

John Grotzinger, who is the principal investigator for the Mars rover Curiosity mission for JPL, hinted pretty loudly yesterday that Curiosity had made a discovery of monumental importance. But they couldn't talk abut it just yet. The preliminary results from a series of soil samples taken at Rocknest (pictured above) a few weeks ago, if confirmed, will be "one for the history books."

The NPR article is here, for whatever details there are.


So, lots of space blogs are now speculating that Opportunity has discovered (drum roll, please) Life ... On ... MARS!!!(tm).


So, alright. First off, this wouldn't be the first time that NASA gave a teaser for an announcement that turned out to be something other than the obvious conclusion informed people would likely come to based on the teaser. This isn't even the first time this has happened regarding the possibility of a discovery of life on Mars. It wouldn't even be the first time space blogs, including this one (cough), had made this sort of speculation which later proved wildly erroneous. To their credit, usually the actual announcements are pretty important, just not always as newsworthy to the general public. Remember the arsenic bacteria in Mono Lake? Incredibly important discovery from the standpoint of exobiology, but the average person on the street wasn't likely to care very much. Add to this the sad fact that the NASA budget is very much in the cross-hairs of the Sequestration ("Fiscal Cliff") negotiators, and the possibility that NASA is up to similar shenanigans is not entirely out of the question.

But maybe, just maybe, this is the time that Lucy isn't going to snatch the football away. Maybe.

Okay, let's look at what we actually know here.

Two different laboratories on board Curiosity have now studied soil samples from Rocknest. The first laboratory is called CheMin, which is NASA-ese for Chemistry and Mineralogy. It determines which types of minerals are in a soil sample. The second laboratory, which is the one generating all the excitement, is called SAM, for Sample Analysis at Mars. SAM is designed to analyze the chemical makeup of Martian soil and atmosphere, specifically to determine if there are organic molecules present.

In the past few weeks, these two laboratories have shown that water was once abundant on the surface of Mars (we knew that already, but it was a good confirmation), and that, at least at the sample site, there are not measurable amounts of methane, which on earth is mostly produced by biological processes. What SAM is really looking for is carbon and oxygen, and it has the ability to analyze these using laser spectrometry to determine if the carbon and oxygen it finds is of geological or biological origin.

This is what SAM does. It does not have the ability to directly monitor for metabolic change in the soil chemistry (as the Labeled Release experiment on the Viking missions did back in 1976), but it can and does analyze the basic chemical composition of the soil and atmosphere. Sam has been doing this at Rocknest on Mars for the past several weeks now. And NASA is really, really excited with whatever the preliminary results of that are.

As minimum, one can reasonably conclude that they have in fact found carbon and oxygen which seem to be of biological origin. By itself, that's a pretty big deal, because it would indicate pretty strongly that life of some sort has lived on Mars at some point in its history. That would be an awfully important discovery. But "one for the history books"? Well, yes, for a book about the history of exobiology. But for the average person on the street, probably not all that terribly interesting.

However, and this is purely speculative on my part, if there were really actual living micro-organisms in the soil samples, SAM might detect this as standard ratios of the CHONPS (carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur) elements which are the signature of life on earth. Or, as a similar ratio of organic chemicals which replace these, such as arsenic apparently does for some amount of phosphorus in the Mono Lake halobacteria. It is possible that this is what NASA has discovered on Mars this week.

And that would unequivocally be one for the history books.

But we wouldn't know anything else about that life. But that's ok, because once we know that there is definitely microbial life in the Martian soil, we have plenty of means to further study it. The most important of these will be genotyping, assuming that any organisms found there actually have genes to type.

There are essentially two possible (hypothetical) outcomes of this. One is that we will find that we share common ancestry with the Martian micro-organisms, either because they originated on earth, or we originated on Mars, or both Martian and terrestrial life originated from someplace else. Any of these are possible. The other outcome is that Martian life arose on Mars completely independently of terrestrial life, either with its own unique DNA or RNA, or else some other truly alien biochemistry. Either of these outcomes could provide tantalizing clues as to the relative ubiquity of life in the universe.

NASA will be announcing the results of the SAM soil experiments in the first week of December, once the data has been verified and re-verified. Until then, the media and blogs like this one are left to their own guesswork. I'll be posting here as soon as anything is known. Until then...


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