[X] My Assistant

[remcook]

http://www.timesonline.co.uk/article/0,,2089-1697332,00.html

FAR from discovering life on Mars, Nasa may have put it there. The American space agency believes the two rover spacecraft scuttling across the red planet are carrying bacteria from Earth, writes John Harlow.

Probably isn't the first time either. Can't believe old russian probes had any policy with that respect.

[tedstryk]

I think that the big reason that the contamination of Mars is a big deal is that it is possible that life evolved on its own there. Also, it might have naturally transmigrated via meteors and taken hold there. Unlikely, but possible. Contaminating it via spacecraft might lead to a situation in which we will never know if the life we are studing, should we find it, came from Earth via meteors, is indigenous to Mars, or was carried by our own missions. Thus, it is a big deal. This recent story however isn't. This did not come from the scientific community, but an author shamelessly trying to promote his book, and a hapless journalist who fell for it. Also, wouldn't it be tragic to find the remains of dead martian bacteria, and to discover that its end was brought about by agressive bacteria brought by us!

[dvandorn]

Well, yes -- introducing strains of bacteria that are more successful than native Martian bacteria, up until the point where you've learned as much as you can from the native stuff and preserved it in laboratories and protected zones, is not a good idea.

But consider -- it is really, really unlikely that present-day Martian bacteria live anywhere near the surface of mars. Especially not near enough to the surface for any of the chicken-scratchings our probes have made to get anywhere close to it.

It's been mentioned that the real threat would be for terrestrial organisms to find nutrient-rich environments (which, I will add, must be protected from the surface radiation environment) and overcome any native forms. And I ask, with all sincerity -- just where would one find a nutrient-rich and radation-protected environment near enough the surface of Mars to allow terrestrial bacteria to move from a landed probe into them? And remember, the radiation environment at the surface is a pretty good sterilizer -- any transport mechanism you postulate would have to figure out how to get terrestrial organisms to the protected environments quickly, before the radiation environment destroyed them.

I would be fascinated to hear about any theories of such a transport mechanism that don't depend, at some point or another, on the infamous "and then a miracle occurs" step in the process...

-the other Doug