Almost every probe ever sent into space has been equipped to detect oxygen, liquid water, and organic chemicals--key signs of the potential for life. But unless a large, preferably green alien walks past the camera of an unsuspecting rover, actually finding a pulse out in space will be a difficult proposition. Piloting a robot from millions of miles away is hard enough to begin with. And even if the robot detects an intriguing chemical, how do you tell whether the molecules came from a microbe or from complex but nonbiological chemistry? Right now, you don't.
NASA's current best hope in the E.T. hunt is Curiosity, a $2 billion Mars rover that launches later this year. Curiosity's ChemCam will fire a laser at rocks up to 30 feet away and analyze the color of the vaporizing mass to determine its chemical composition. Should the ChemCam identify an interesting sample, the whole rover can move in for a closer look, clutching samples with a robotic arm and using a battery of sensors to catalog the chemicals inside them. Looking farther ahead, a team at MIT and Massachusetts General Hospital-Harvard is designing an instrument that will be able to scan for alien DNA and RNA. "This experiment would be the first to look for life by targeting the molecules specific to life as we know it," says Christopher Carr, the lead engineer on the project. If a probe finds something to sequence, that would be almost definitive proof that life took hold on Mars and very likely is thriving there right now. Carr hopes his device will fly on a NASA Mars mission within the next decade.