Dr. Catharine Conley's job is to make sure that if we ever discover life on Mars, it's actually Martian and not our own dirty fingerprints. “If we’re going to look for life on Mars, it would be really kind of lame to bring Earth life and find that instead,” she tells the New York Times. Conley is NASA's planetary protection officer, charged with preventing the "harmful contamination" of other planets, moons, and more. Millions of bacteria travel through space via spacecraft, and it could take many years for even Mars' harsh environment to kill them all off. Conley says some Earth microbes can even eat the salts that are keeping the red planet's water liquid. “The environment on Mars potentially is basically one giant dinner plate for Earth organisms,” she tells the Times.
This is actually a serious problem for NASA right now because its Curiosity rover isn't considered clean enough to visit the sites of recently discovered liquid water on Mars announced last week, the Japan Times reports. Four decades ago, NASA's Viking lander was thoroughly sterilized before it landed on Mars. But that process can add an extra $100 million or so to a mission, and NASA has decided to forgo it since, particularly in light of the fact that Viking's data pointed to Mars being "lifeless," the Times notes. “We’re treading new ground,” one NASA official says. “The issue of planetary protection has gone very much from one where we’re just trying to be careful to one that has very real, near-term consideration.”