[T'Aerwynd]

Time: http://www.time.com/time/health/arti...877434,00.html

Cute references to Trek, interesting topic.

Star Trek fans know it as the Prime Directive: that there should be no interference with the internal affairs of other civilizations. (Given the frequency with which Captains Kirk, Picard, et. al., violate it, however, the Prime Directive seems more like a Prime Suggestion.) Since human beings have yet to explore very far beyond Earth, pondering an interplanetary non-interference policy of our own may seem a little premature — at least until we've mastered warp drives and phasers.

But in fact such a directive already exists in some form — the international Outer Space Treaty of 1967, which governs the legal framework for activities in space. Best known for banning governments from putting nuclear weapons in orbit, the treaty also requires spacefaring nations to avoid "harmful contamination" of other worlds while exploring the solar system. Human beings have yet to step foot on other planets, so the risk today comes from bacteria that can hitch a ride on unmanned spacecraft like NASA's Mars Phoenix Lander, which arrived on the red planet's surface last May.

Even though Phoenix was assembled in a special clean room to minimize bacterial contamination — and the lander's arm, which would have direct contact with Martian ice, was heat-sterilized before launch — it's likely that dozens or more species of microbes hitched a ride on Phoenix's 10-month trip to Mars. Once on Mars, it's possible that bacteria shielded by the structure of the spacecraft from the harsh Martian UV radiation could stay alive, in dormancy, for hundreds of thousands of years. And if native microbes do exist on Mars — nothing has been found yet, but scientists hold out hope that the ice present on parts of the planet harbors life — there's a risk that foreign bacteria could contaminate or somehow change the development of their Martian counterparts. But beyond the broad language of the Outer Space Treaty, we don't really have set guidelines for how we should treat microbial life on another planet, should we run across it.

That's why NASA planetary scientist Christopher McKay, in an article in this week's Science, suggests the need for a stronger policy that ensures all exploration of Mars be "biologically reversible" — meaning we would be required to effectively wipe away our footprints and remove any possibility of contamination, by leaving behind nothing that could foster alien microbial growth. Such a policy would be especially necessary if we discover that life on Mars has emerged independently from life on Earth — what McKay calls a "second genesis" (as opposed to Martian life that arose because of meteorites exchanged between Mars and a hospitable Earth, a condition in which the two planets would share a tree of life and contamination would be less of a concern). If there really were a second genesis on Mars, "contamination by even one Earth bacterium may be a serious issue of environmental ethics," McKay writes. We only have to look back at the damage that invasive species have inflicted on virgin territory on our planet — like the infamous cane toads that ravaged Australia — to know what Earth bacteria could do on an alien surface.

For now, it's not that difficult to make sure that we avoid squashing new life as we search it out — although doing so could add considerable cost to any space mission. Probes like Phoenix can be more fully sterilized before launch, and debris from any unmanned craft could eventually be recovered. The real challenge will occur if and when humans step foot on Mars or any other planet, and begin establishing a more permanent presence, especially if we explore beneath the surface, out of the reach of the sterilizing solar UV radiation. When the day comes, we'll need to step carefully to make sure that native life on Mars — yes, I'm sorry, I have to say it — "lives long and prospers."

[mmoore]

I bet that McKay guy was a Boy Scout. You always leave a campsite cleaner than you found it.

[MissionTrek08]

It's a fine point and goal for missions, but on the other hand once the ship/device leaves our hands, it's also 'fair game' to anything floating around out there. Precautions are just fine and they certainly avoid the ignominy of interplanetary contamination due to laziness, but there's a certain point where the "observer effect" must take hold: by sending anything to another planet, we inevitably change the environment simply by the probe's presence.

The impact can never truly be zero because the act itself cannot be erased, even the 'cleaning up of the act' has an effect. The only way to leave it as it was is to not go at all, which pretty much negates any exploration outside of a telescope. A good, "safe" balance exists between.

[Big D]

On the other hand... if Mars has truly become completely extinct, with no remaining life of its own, then there's the tiny chance that Earth microbes could take root. A first, tiny step toward terraforming in the distant future...

[MissionTrek08]

I have a question for the brilliant scientific minds here: the article said something about microbes being shielded from Mars UV Radiation by the probe as a scenario for contaminating the planet.

But would it be as simple as all that? This would seem to imply that Mars, with practically no atmosphere to shield the planet, is only vulnerable to UV radiation (I assume they're implying from the sun?).

Wouldn't there also be all kinds of gamma rays and such hurtling through space that would strike such a vulnerable planet from all sides?

Basically, the article makes it sound like if you stand in the shade on Mars, you're good to go, despite the numerous other hostile conditions of the local and extraplanetary environment. Sounds unlikely to me, but thought I'd ask others better trained to know such things.