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Sunday, September 25, 2005

Life and Landing On Mars

posted by Mr.B
In the considerations of scientists over the last 100 years, whether or not there might be life on Mars has been most mutable. Recent discoveries on Mars: evidence of liquid water in Mars' past, water ice on and probably beneath the martian surface, methane in the atmosphere, as well as earthly discoveries of life in what we consider extreme conditions, have brought us to where we are today -- thinking that Mars may harbor life. That Mars may be lifeless is indisputable. That it could have life, given what little we know, is also indisputably possible.

Nowadays, when we send out space probes, we sterilize them. What little I know of this seems to indicate that our sterilization processes may be far from perfect. Regardless, the rationale for sterilization is sound -- whether or not life exists or has existed at the probe's destination, sending some of Earth's life to the destination would potentially muck things up beyond repair. When we fear a spacecraft might not be sterile, we purposefully destroy it while it still has fuel enough to perform a fatal maneuver, as we did with the Galileo probe to protect the potential life on Jupiter's moon Europa from earthy microbes possibly riding on the probe. These are real concerns that govern our use of current robotic space probes.

Suppose we didn't worry about such things. Suppose there is life, an ecosystem, where we send a space probe. Suppose further, that some hardy bacteria or fungus stowed away on the space probe and is thereby introduced into the alien ecosystem. Chances are it will die out. However, there's a slim chance that such stowaways could find habitat, potentially altering or even destroying an existing alien ecosystem.

On earth, science has shown that all life is related. It seems every lichen, bacteria, fern, and fish have a common ancestor. Given how small our solar system is, and the fact that meteor impacts and volcanoes can throw material from one planet, into space, and subsequently onto another planet, and given that some life can be dormant, frozen, for a very very long time, it is conceivable, however improbable, that if there is life elsewhere in our solar system, that we might be related through common ancestry.

Such a scenario was alluded to when a few years ago scientists found what are possibly fossilized bacteria in an Antarctic meteorite of martian origin. Despite the fact that this discovery has not generally been, in any sense of the word, "proven" or even substantiated as being of biological formation, the discovery has brought to light and into the public imagination the fact that even without a rocket ship, life transfer between planets is at least conceivable.

So if we find bacteria or even their fossils on Mars, one of the greatest and most interesting unknowns we'd want to pin down is whether these are related to terrestrial life.

If we inadvertently "pollute" Mars with earth life before we get a chance to either confirm Mars' lifelessness or study its ecologies, then we mess up a huge chance at understanding and studying the nature of life on the grandest scale yet.

I'm not saying that we should hold martian bacteria as sacred, so that were they ever discovered, we'd never send earth life to the martian surface. But surely we'd want to study any extraterrestrial life thoroughly before risking biological cross contamination, either way.

But in all the heady talk of sending people to Mars in our lifetimes, and the potential of discovering life there, no one seems to mention that the two are at some odds with each other ( at least not in what I read ).

Given the rather difficult challenge of sterilizing robot probes, keeping a biologically impermeable set of seals around all astronauts, their habitats, and their waste seems impossible. If people go to Mars it seems to me unavoidable that we will bring earth's biology into the Martian landscape. Do we not care about this? Is it somehow known that every living thing we might drop there will die in Mars' thin and cold atmosphere? Is it known that in looking for life on Mars we'll be able to with certainty determine whether a dead or dormant bacterium is Martian or an earthly stowaway? Given the possibility that Earth and Mars could previously naturally have shared organisms, it seems imperative that until we know with certainty that Mars is barren, we don't risk making it not so.

There is, of course, another reason for caution. H. G. Wells predicted it in War of the Worlds. But in his story the Martians visited Earth first. Their doom was earthly bacteria. He might have got it partly right, as in a few years, we might be the invaders brought low by some unexpected effect of mixing martian biology with our own. Or is this just the stuff of science fiction? What do you think?
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