Ever since we started landing probes on Mars in 1997, we've dreamed of discovering extraterrestrial life there. The Soviet Union made an attempt at landing probes on Mars in the '70s, but America was the first to land a working rover when Sojourner landed successfully on July 4, 1997.
Since then, we landed Spirit and Opportunity on the Red Planet in 2004. Then, we followed that up with a bigger, better rover named Curiosity in 2011. Curiosity only had a two-year mission, but it's been so successful that it's outlived its expiration date by almost a year!
In March 2013, Curiosity found new evidence that proved Mars once provided conditions that could support microbial life. That's no definitive proof that there is or ever was life on Mars. It just means that at one point in time, Mars could have had life, in theory.
But now, the Curiosity rover has stumbled onto these weird methane pulses. Methane levels in Gale Crater, where Curiosity has been exploring, are actually lower than expected. But every once in a while, the methane readings go off the charts for some reason.
The short answer is we don't know. All the methane spikes prove is that there's probably something happening below the surface of Mars. Here's how one scientist put it:
It's exciting that methane is definitely in Mars' atmosphere, Curiosity Project Scientist John Grotzinger said during a news conference at the American Geophysical Union Meeting on Tuesday, even though it's not proof of life on its own.
“We now have full confidence that there is methane," Grotzinger said. "And that there are organics preserved in rocks [around the planet]... those things are both consistent with the former or existing presence of life."
Even if we don't find out whether the methane pulses indicate former or current life, the information is invaluable for a future manned mission to the planet. Want to see what it's like to drive a rover around Mars? Try NASA's cool Curiosity simulator.