Sunday, August 10, 2008


Last Saturday, I noted that there was a buzz about some discovery on Mars that had implications for the possibility of life on that planet. I've been meaning to get to this for a while, but on Monday or Tuesday, NASA held a hastily-arranged press conference and announced that Phoenix had discovered- wait for it- Chocolate-Covered Strawberries!

Ok, Ok, not really. The chocolate covered strawberries gag was put together to lampoon the over-reaction by bloggers and commenters like me that had taken this story and amplified it into something a little more noisy than a Saturn V liftoff: maybe more like a medium-yield strategic nuke. In my own defense, I have to say that while I was excited, I was careful not to speculate. I was going to say, "speculate beyond the available information," but looking back over that post, I pretty much laid out the parameters of what we knew then and what we might be capable of discovering with the instruments available. I didn't really speculate at all. Although I made it clear that any possible discovery of evidence of life was a very exciting idea that would be the most momentous thing science had ever accomplished.

Turns out what they think they've discovered is evidence of perchlorate, a combination of oxygen and chlorine. Perchlorate is a strong oxidizer that at first glance might seem to argue against the probability of living organisms. Just as bleach (sodium hyperchlorite- a similar oxygen-chlorine compound) kills bacteria by creating an oxidizing solution that chemically "burns" them and breaks down the complex organic molecules that create pigments and stains, so perchlorate in high concentration would be very damaging to living things. However it turns out that in lower concentration, there are bacteria that use perchlorate as a source of oxygen just as we use free oxygen in the air. Furthermore, in the Atacama Desert, the driest desert in the world, where an inch or two of rain might fall once in a decade, perchlorate can build up as a result of UV light interacting with salts and the atmosphere. (Rains wash it away, and allow it to react in solution with other materials). So perchlorate is neither totally adversarial to life, nor is it's presence evidence that life cannot or does not exist in the neighborhood.

So what happened? Looks like this was one of those "A little bit of knowledge can be dangerous" situations. Someone told a reporter that there was a discovery, but didn't provide enough information for even a knowledgeable reporter to draw reasonable conclusions- I'll ignore the fact that most science reporters don't know enough science to report anything but what they're told. The report that the White House had been briefed, for example, was overstated. The president's science advisor was briefed. But the president doesn't even know he has a science advisor, so it's unlikely he ever heard about this issue. As noted above, depending on how you approach the issue, the existence of perchlorate could be an important indicator of an environment's hostility or hospitality toward life... or not. What the reporter apparently heard- correctly or not- was that the purported discovery had a direct bearing on Mars' ability to support life. This might have been an error on the part of the reporter or the leaker, who knows, and who cares? It was an easy mistake. I don't harbor anger toward either, but it does highlight the idea that clarity of communication is of utmost importance.

Some have made a big fuss over the kerfluffle sometimes with wry humor, sometimes with righteous indignation- how dare amateurs get excited and run with unsubstantiated rumors. This is science: a grave and serious business best left to the professionals. I call bullshit. In my opinion, his was a case of no harm, no foul. Wry humor is appropriate.

And to add to the confusion, the wording is that there is "substantial evidence" of the presence of perchlorate. The two wet-lab runs picked up evidence of the substance, but the TEGA (Thermal Evolved Gas Analyzer) instrument did not. This might be because it was not run in such a way as to detect chlorine, or because some perchlorate compounds would not break down under the conditions that samples in the TEGA are subjected to. More tests of both types will be run over the next few weeks to clarify the results.

So in the end, you could characterize this as a false alarm. An interesting one. One that tells you quite a bit about how science moves forward, and quite a bit more about its strengths and weaknesses.

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