NASA's Planetary Protection Officer Catharine A. Conley says that we've already contaminated the Red Planet with organisms from EarthThe tantalizing possibility of of life on Mars, our planetary neighbor, has been a cultural fixation going back at least as far as the publication of H.G. Wells's The War of the Worlds in 1898. If they were out there, what would they be like? Who would they be?
As the saying goes, we've met the enemy, and they is us.
Well not exactly. We haven't found any martian life, but there is life on Mars: life we sent there, says NASA's planetary protection officer, Catharine A. Conley. Bacteria, pollen spores, and other pieces of life have traveled millions of miles inside our spacecraft, and we have reason to believe they could have survived the journey (life on the outsides of the craft would have been killed by exposure to UV light outside of Earth's atmosphere), and are now persisting on the Red Planet. "The saving grace to all this," Conley says, "is that the surface conditions on Mars are pretty hostile to Earth life, so it's not very likely that those organisms could actually reproduce, or even survive if they came off the spacecraft." If they're doing anything at all, they're just sitting there.
As NASA's planetary protection officer, it's Conley's job to spearhead our efforts (such as pre-baking spacecraft to kill off as much life on-board as possible) to ensure that life from Earth does not contaminate other solar-system bodies (planets, moons, comets, and asteroids), and to protect life on Earth from any possible life that may be brought here on returning spacecraft. Considering the implications of Earthly contamination, it's a big responsibility. NASA is required to take these precautions by the 1967 United Nations' Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Bodies.
Conley had a realization about the need to prevent transfer of life between planets in 2003, after the destruction of the Space Shuttle Columbia upon its re-entry into the Earth's atmosphere. Conley had had an experiment aboard the space ship involving worms. After the shuttle's destruction, five of the six worm canisters were recovered. Of those five, four still had worms alive inside them.