The intrepid Mars rover Curiosity has already confirmed that water once flowed on Mars, but that it’s long since dried up. Still, that doesn’t mean there’s not flowing water now, too.
NASA data has long supported the idea that a seasonal, briny water may be flowing on the Red Planet. In 2011, scientists noted that landscape formations showing up in the planet’s warmer months were caused by flowing water–or, at least, that was the “best explanation for these observations so far.” Now, the Mars Reconnoissance Orbiter has spotted more of those “dark, finger-like features” near the Martian equator, offering tantalizing evidence of briny water–or some other liquid substance–that appears in the winter but evaporates in the warm season.
Flowing water on Mars, of course, hasn’t yet been confirmed, and there are competing theories on what, exactly, the formations could mean. (There’s even been some theories put forward that there’s no liquid at all, and the formations are caused by winds.) But finding water moving today could fundamentally change our understanding of the environment on Mars, and it’s our best bet at finding life still lurking under the surface.