Little green microbes?

Life on Mars Found by NASA's Viking Mission?

Science reporting in the news is always a bit sketchy; a reporter gets more attention by making bold claims than by reporting on maybe and possibly. Whenever you read in the news about a scientific discovery, it should be taken with a sizeable grain of salt. Even so, this one is pretty damned cool.

Back in 1976 there was some evidence of life-processes taking place in Martian soil. Now, researches have done some math and found that those life-like-processes seem to be on a circadian rhythm that is consistent with the length of the Martian day. What does that really mean, though?

The search for life on other planets is a difficult thing; we can't know how similar or different it would be from life here on Earth. We can make some assumptions-- it would probably be carbon-based, simply because carbon is so abundant and so easy to combine with other things. All the life we know of is carbon-based. Some scientists have thought that if a life form existed that was not carbon-based, it would probably be silicon-based, simply because silicon has a lot of the same properties as carbon. But we don't know-- biologists, for this purpose, have a sample size of one. All the life they have ever observed is terrestrial life, carbon-based and built on DNA. Would life elsewhere be the same?

Some people think that life on Earth began when a meteorite from Mars crashed here and brought Martian life with it. If that is the case (and it is possible, though a little improbable), then life on Mars would be very similar to life here. We could assume that it would have DNA and be carbon-based and be very like the life we have here, just evolved in different ways. But what if it didn't? What if life began twice, in our solar system? Life on Mars needn't have anything in common with life on Earth. It probably would have some similarities-- I mentioned carbon above, and there are other factors that are similar enough on Mars and Earth that some things would likely be the same-- but we couldn't make any assumptions.

So how do you look for life? The original 1976 results showed that a Martian soil sample reacted the way one on Earth would, if that Earth soil sample contained microbial life. They ran several control experiments as well, which would not have elicited a result with the life-rich Earth soil, and they failed to do so with the Martian soil, either. How many assumptions are inherent in that test? Is it possible something other than life could have produced that result? Is it possible the rover brought microbes with it, and they contaminated the experiment? Too many factors, too many unknowns. But one has been eliminated now. It is not possible that Earth microbes produced the result-- Earth microbes would have had a different circadian rhythm. The fact that the results showed a circadian rhythm that would be consistent with the circadian rhythm Martian life would have if it did exist is fascinating, but is not proof of anything.

Is there life on Mars? Possibly. That's the best answer we have for now. The possibility has not been eliminated, and there are some tantalizing results that indicate that it might be true. And that's pretty damned cool.