The surface of Mars might not look like the most inviting landscape, but it's apparently a completely different picture underneath. New evidence found by NASA's Curiosity rover suggests the Martian planet may have liquid water below its exterior.

Curiosity has stumbled across a bevy of evidence suggesting water exists on the Red Planet, and scientists have long believed Mars was once covered in a huge, deep ocean. It just shows that you can't exactly judge a book by its cover.

The breakthrough came when Curiosity discovered the substance calcium perchlorate in a soil sample. As Popular Science notes, the discovery is significant due to "perchlorate's relationship with water."

Calcium perchlorate can absorb water vapor from the atmosphere given the right conditions. And when it's mixed with H20, the compound lowers the freezing point of water, allowing it to exist in liquid form at very low temperatures. In this liquid state, the water is considered a brine—an extremely salty solution.

Scientists believe that, under the right conditions, water vapor in the Martian atmosphere turns into frost at night, and that frost then melts into water. When this happens, scientists think that the water then seeps below the Red Planet's surface, collecting into what could be an underground oasis.

While the discovery is big news, it doesn't make Mars any more hospitable for life due to its levels of radiation. But it does give us more proof that, yes, water is out there, and that alone is changing how we view space and beyond.