Angry in the Great White North

Are people going to start protesting this?

NASA is planning a return to the Moon and eventually to send manned spacecraft to Mars, and the National Research Council warned Monday that if life forms from Earth were able to survive the trip they could contaminate the Red Planet.

I can imagine people who are against the space program, either in its entirety, or on specific reasons such as the use of nuclear fuels on some probes (eg, Cassini), enlisting environmentalists to start a movement to save the Martian equivalent of the spotted owl.

There are good scientific reasons to be concerned:

That could interfere with investigations to detect any life that might be native to Mars, said the council, an arm of the National Academy of Sciences.

"Ongoing Mars missions have shown that the planet may have environments where some Earth microbes could grow," Christopher Chyba, professor of astrophysics at Princeton University, said in a statement.

The article ends it there, but I see the potential for problems moving in several directions.

First, suppose there is no life on Mars. Contamination might make that determination more difficult, at least in the short term, while scientists work on being certain that a microbe found actually came from the probe or spacecraft. Contamination could leave lingering doubt. Of course, if it is determined postively that there is no life on Mars, it probably doesn't matter.

Second, there is Earth-like life on Mars, that is, DNA-based. Possible, of course. We just don't know if life is always DNA-based. We don't know if DNA-based life started on Mars, then contaminated Earth via meteorite collisions, then died out (mostly) on Mars. But if there is DNA-based life on Mars, there is a potential for real danger. I'm not certain what the chances of an infectious agent existing on Mars that is entirely Martian -- two billion years or so of divergent evolution means that Martian microbes are not designed to deal with human defenses against infection (though of course it also means that human defenses have never seen a Martian microbe). But if we bring Earth microbes to Mars and the Earth microbes thrive, there is very good chance that DNA-swapping will occur. A hyrid Earth-Martian microbe might evolve that combines the possibly unique protein machinery of a Martian bug with the infectious power of a Terran germ. Nasty.

Third, there is life on Mars, but it uses an entirely different scheme for encoding genetic information and passing it on to the next generation. As such, this non-DNA-based microbe is unlikely to form a threat to either humans or Earth germs. I say unlikely, because we really don't know. Just because it doesn't use DNA (and so the chance of a viral infection is nil), the Martian equivalent of a bacterium might still be infectious, since it's not clear that the human immune system would know what to do with one if it entered the body through a wound, for example. Antibiotics might also be ineffective. And even if the Martian bug found the human body an inhospitable host beyond the short term, which is quite possible, upon dying, like Terran bacteria, the Martian germ might release all sorts of toxins, the effects of which might be very bad. In this situation, the presence of Earth microbes is unlikely to be a factor one way or another...except...that if Earth microbes turn out to be effective colonists, they might push back these dangerous non-DNA Martian microbes by taking over their environmental niches. In this case, contamination is our friend, though we risk losing out on important scientific knowledge about non-DNA life, especially if this colonization takes place before we even notice.