Scientists detected methane in Mars’s atmosphere. In fact, they’ve been detecting it for years. Methane should dissipate from the atmosphere in that time, but it didn’t. This means something on Mars is creating more methane. There are two giant ways to make methane:
1) Life (you know, even at the cellular level)
2) Geology (chemical reaction)
Either one of these is cool. We know there is a little geologically happening on Mars, but it seems fairly dead. Finding methane means that there are chemical processes going on.
It does NOT mean there is life on Mars. It could, but it’s WAAAAY more likely to be geology.