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.