Have we already hopelessly contaminated the search for extraterrestrial life?

Every time we send spacecraft to explore the solar system, we send along lots of tiny microbes. In fact, we may have deposited a trillion microbial spores on Mars. How will we ever discover alien life through all that haze?

That's the problem Barry E. DiGregorio, the director of the International Committee Against Mars Sample Return, wrestles with over at the New Scientist. He points out that humanity at least set out to protect the rest of the solar system from contamination, as a 1967 United Nations treaty set down an agreement among all spacefaring nations to keep other planets and moons free of Earthly contamination.

But early efforts to sterilize all rockets sent into space proved incredibly expensive, and over the years nations became lax in their enforcement of the treaty. And now a Russian space mission might completely rip apart the last lingering shreds of the treaty's intent. DiGregorio explains:

The Russian Federal Space Agency's Phobos Sample Return Mission (formerly known as Phobos-Grunt) will send not just microbial spores but live bacteria into the solar system for the first time...The mission will fly to Mars, study it from orbit and then land on Phobos, the larger of Mars's two moons. On board will be two sealed capsules containing live micro-organisms. Some months later the craft will embark on the return journey carrying the still-sealed capsules, plus samples of soil scooped up from the surface of Phobos. All being well it will return to Earth in 2014.

So why are scientists doing this? As DiGregorio explains, it's meant as a test of transpermia, the idea that life can be transferred between planets from rocks that are ejected from the planet in meteorite or asteroid collisions. Of course, this isn't exactly a test of the full theory - most meteorites take millions of years travelling in space between Mars and Earth before they crash back down.

As DiGregorio explains, a lot could go disastrously wrong, just to prove a very minor scientific point:

In order to justify their experimental goals, one of the groups involved in the experiment, The Planetary Society of Pasadena, California, argues that rocks larger than 100 grams are transferred from Mars to Earth in only two to three years. No direct evidence exists for this claim. Is the transpermia question really so important that it is worth risking the contamination that would surely happen if the spacecraft malfunctioned and crashed on Mars? This is no small risk. Of 38 craft launched towards Mars, only 19 succeeded. At least three crash-landed on the planet's surface.

DiGregorio further argues that this is a very complicated mission, which raises the risk of the Martian atmosphere getting contaminated by a rocket crash, and that we've already got a lot of evidence of microbial survival in space conditions from earlier space experiments and those performed in simulated environment.

His full argument is well worth a read, whether you agree with his conclusions or not. You can check that out over at The New Scientist, and the scientific paper exploring the presence of Earth microbes on the Martian surface is available here.