Nov 28, 2009
Fresh data from ALH 84001 rules out nonbiological origin for carbon
This story is far from over. The latest analysis of the tiny specks of magnetite found deep inside the Martian meteorite ALH 84001 appear to have ruled out nonbiological explanations for their origin. This on the heels of an August paper that showed that the rock had originally come from an area of Mars that was warm and bathed in liquid water.
What does all this mean? Nothing conclusive. The evidence is definitely tipped in the direction of life, though; for instance, there's methane on Mars, but no obvious geological mechanism that could produce it. (Since methane can only survive for a few years under Martian conditions, it must be continuously replenished from some source.) There's now known to be an enormous amount of water right under the surface in the Northern hemisphere, which increasingly looks like it was the location of an ocean at one time. And in the past couple of years we've seen direct photographic evidence of subsurface water in the form of fresh gulleys in crater walls.
All of this could have been learned in a matter of weeks or months, thirty years ago, had NASA gone to Mars after Apollo. As it is, I may be dead and gone before this particular controversy is resolved. But at least there's progress.
Aug 03, 2008
Rumours are flying. But the truth may lead us to reexamine past missions
Aviation Week has created a shitstorm on the web by publishing this article. They claim that the White House has been briefed about a forthcoming announcement from the Phoenix Mars lander team--something significant, apparently, that will blow the doors off the recent confirmation of water and even the revelation that Martian soil would be capable of growing Earth plant life.
On sites like Slashdot, people are lining up to speculate about what the news is. Is it life? Ideas range from the possibility that Phoenix's microscopes have spotted fossils, to actual confirmation of life. NASA, however, was careful in its statement to state that no direct sign of life, past or present, has been found.
Many others are jumping in with sober reminders that Phoenix isn't even equipped to find life--just water and maybe organic substances. The most likely scenario is, in fact, that Phoenix has discovered organics in the Martian soil.
This would be a big discovery, true; it would make an unequivocal statement that Mars is a habitable planet, only the second one in the universe known. If our very next-door-neighbour is hospitable to life, then how much more likely is it that many other worlds also are?
...Of course, such a discovery isn't as world-shaking as it sounds. After all, for a very long time now, we've known that there's no known reason why other planets wouldn't be habitable--Mars included. This would just be confirming what we've already deduced from the available evidence: that safe havens for life are abundant in the universe.
From this point of view, the Phoenix team briefing the White House is really just a piece of grandstanding--a last-ditch attempt to squeeze money from a science-hostile administration before the expected recession/depression gets the space program killed.
But there is one other possibility.
The recent discovery that the soil at the Phoenix lander site could support some earthly plants would appear to contradict the findings of the Viking landers from the 1970s. Those craft deployed sophisticated experiments to determine whether life is present on Mars, yet the instruments returned ambiguous results. There was a strong signal indicating life from some of the instruments, yet no evidence of biological material in the soil. The official interpretation that has become orthodoxy as a result, is that the Martian soil is highly oxidizing, ie. that it contains compounds such as hydrogen peroxide that destroy biological materials.
But if Phoenix has found that you could grow earthly plants in the soil at its site, doesn't this cast serious doubt on that interpretation?
Here's the logic in its most direct form:
- The Viking experiments indicated the presence of metabolism, but did not find biological materials. The failure to find organics was puzzling, and meant either that the instrument failed or there were no organics. But the metabolism tests did indicate life.
- A strongly-oxydizing soil was the only consistent interpretation other than life+instrument failure to account for the test results.
- Phoenix has found water and soil that can apparently support plant growth. This would appear to contradict the hypothesis of strongly oxydizing soil. If Phoenix has found organics, or has at least found that there is little likelihood of a strongly oxydizing soil existing anywhere on Mars, we are then left with:
- The Viking landers detected life in 1976. One of their instruments failed to do its job and did not correctly characterize the chemical makeup of the soil, leading to thirty years of muddied waters in the quest for life on Mars.
By this hypothesis, NASA is being coy by saying that Phoenix has not detected life. It hasn't; what it's done is confirm that the Vikings already found it!
Now, NASA's not actually going to say this. Scientists are (rightly) conservative with their pronouncements, and even vindication of the Viking experiments doesn't actually prove anything. A Mars sample-return mission would have to be undertaken to do that. But maybe that's the funding that NASA is looking to get here.
Because the fact remains that if you can grown vegetables in Martian soil, it can't be the kind of hostile chemical bleach that would be necessary to invalidate the Viking experiments. Even without any data beyond what's already been released, the evidence now points to life on Mars, and fairly cries out for a follow-up investigation. And that, I suspect, is what NASA is going to call for.