Mars once held conditions suitable for life, NASA announced today, based on data from the Curiosity rover. The car-sized robot found a variety of enticing chemicals — sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon — within a sample rock on the Red Planet, indicating past conditions consistent with microbial activity. As the mission’s project scientist, John Grotzinger, put it at today’s press conference: “We’ve found a habitable environment that is so benign and supportive of life that probably, if this water was around, and you had been on the planet, you would have been able to drink it.”
The rover, also known as the Mars Science Laboratory, is currently exploring an area dubbed Yellowknife Bay within the larger Gale Crater. Past analysis suggested the area was once covered with water, perhaps a lake or streams, and these findings make that even more likely. The area’s rocks, which the rover drilled into to study, contained clay minerals produced in reactions with water. Curiosity’s findings suggest this area, in the past, could have been much more temperate, and life-friendly, than Mars’ current harsh environment. That means that, for all of the promise of possible life on other worlds, the Red Planet is currently our best bet for the existence (past or present) of non-Earth life. “This is probably definitively the only habitable environment that we have recorded,” said David Blake, principal investigator for Curiosity’s Chemistry and Mineralogy instrument.
The rover’s primary mission was to determine if Mars could ever have supported life, and the answer now seems to be yes. As Grotzinger explained, that required finding evidence of three specific conditions: a neutral pH balance, high water activity, and energy available within minerals (which microbes could treat as a battery). Curiosity found evidence of all three with its first use of its drill: an unexpectedly lucky stroke. The mission will continue to search for more evidence of Mars’ past habitability, including a close look at what was originally expected to be the main site of scientific discovery: Mount Sharp, also within Gale Crater. After drilling and analyzing more samples to verify these results, the Curiosity team expect to continue the months-long trek to the mountain.
So no, NASA did not find any evidence of actual life on Mars. Curiosity’s instruments aren’t even looking for it. “We’re not a life detection mission,” Grotzinger said. Still, the discovery is a major milestone not just for the MSL mission, but for Mars research as well, and even planetary science in general. Whether or not the Red Planet held life, we now know it probably could have done so — and that’s already a game changer.