Thursday, January 18, 2007

Martian Mistakes?

For man must strive, and striving he must err. ~ Goethe

There's something about Mars that seems to tie into strange things happening. So many probes have been lost that there are those who think that they are being shot down by ticked-off Martians who think we're spying on them. No such luck. Recently, two more instances of mistakes were raised, one of which could well be true, the other of which is more doubtful.

Not too long ago, I wrote a paean to Mars Global Surveyor, which ceased communications last November. MGS radioed a problem with one of its solar panels and went into safe mode. Repeated attempts to resurrect the onboard computer and to locate MGS (even using Mars Reconnaissance Orbiter to try to find it) were in vain. As is usually the case in such events, NASA initiates an investigation to try to figure out what went wrong.

Early indications are that it may have been a software glitch, introduced when an update was uploaded to MGS. Now those of us who use Microsoft products, this is not an unusual occurrence. But, in the world of satellite operations, software is very single-purposed, so one would expect rigorous testing prior to an upload. It appears, in a preliminary finding, that the uploaded commands, sent up in June which were supposed to synchronizing the two processors, had incorrect memory addresses. This caused the solar arrays to drive to a “hard stop” which is why MGS went into safe mode.

Unfortunately, at this point the radiator for the battery was pointed at the Sun which overheated, causing battery failure. As a result, insufficient power was available to the satellite, with the result that communications could not be re-established.


It's difficult to understand, with the testing that normally occurs before any change is made to a system, how such an error could have gone undetected. But, that's why we have post-mortem investigations. And, it may yet turn out that something else was to blame, like a micrometeorite strike or component failure.

The other possible mistake involves the Viking landers. A geology professor at Washington State University, one Dirk Schultze-Makuch, thinks that the very tests used to discover signs of life on Mars may have killed it. According to his theory, based on data obtained from more recent satellites and landers, Martian life could have a chemistry based on a mix of water and hydrogen peroxide. The tests weren't designed to look for hydrogen-peroxide-based structures, so the microbes could have been drowned or cooked.

Well, maybe.

Interestingly, not very long ago, another group had thought the landers may have found life after all. Looking at the Viking data, two of the three tests did, in fact, give evidence of life, but the third test, the gas chromatograph mass spectrometer (GCMS) that was supposed to be the most determinative of the tests, failed to show any evidence of microbial activity. In a recent re-evaluation of the GCMS, it was found that it didn't do such a good job of detecting life on Earth, much less on Mars. Lest we get hypercritical of the Viking experimenters, we should keep in mind that they wanted to be absolutely sure that what they found was conclusive.

Their methods were thoroughly tested based on assumptions about what Martian soil was like. Based on data returned from the Rovers, a group decided to use the GCMS on the Mars-like soils on Earth, where it failed to find any signs of life.

So we have one investigator telling us that data indicates Martian chemistry is different enough that the tests destroyed it, while another group tells us that it wouldn't have been detected by the key test anyway.

Ultimately, I have to lean toward the GCMS-doubters because Mr. Schultze-Makuch does not mention the two positive tests, one of which included “drowning” the microbes in water. It's possible that he, like some, doesn't regard the first two positive tests as meaningful, or, as a geologist, he's operating out of his specialty a bit and isn't familiar with the details of the tests.

Finding extraterrestrial life is no picnic. Many people think that life on other worlds could be based on silicon, copper, or some other mix of chemicals. But silicon bonds are not as sturdy as carbon bonds, and copper is not as efficient an oxidizer as iron (despite Mr. Spock's green blood). That is not to say that there may not be some exotic chemical makeup for life elsewhere, but within our own solar system it would seem less likely.

Everything in our solar system is made of essentially the same stuff. Even Titan has been seen to have a makeup that would seem to be very similar to the early Earth. It would seem that life in our neck of the woods would tend to be of stuff we can recognize, even though its exact form and behavior may be exotic to our way of thinking.

A mistake may have been made in the Viking search-for-life tests, but it's open to debate which, if either, of these explanations describes what it may have been.

Guess we'll just have to bring back some Mars dirt and find out.

No comments: