Astronauts and scientists have been keen to push the reaches of humanity as far as Mars for decades now, but there have been obvious stumbling blocks.

One of those is whether or not there could be sources of water on Mars – and this new discovery could be a game changer in that regard.

That’s because geophysicists have discovered what amounts to a huge ocean just below the surface – one that could even harbor life.

They used seismic data taken by NASA’s InSight Lander and determined it holds enough liquid to cover the planet in a mile of water.

The catch?

It’s too deep to access by any means we currently have.

The ocean is inside a layer of rock that’s 7-13 miles deep, beneath Mars’ outer crust, which would mean drilling to a depth no one ever has before on Earth.

Armageddon flashbacks, anyone?

If we could access it, though, researchers like study co-author Michael Manga think it could be harboring life on the red planet.

“Water is necessary for life as we know it. I don’t see why the underground reservoir is not a habitable environment. It’s certainly true on Earth – deep, deep mines host life, the bottom of the ocean hosts life.”

We know water once existed on the surface, due to the existence of dried-up river channels, deltas, and lake beds that are visible. An abrupt change of climate 3.5 billion years ago changed all of that.

Theories on what happened range from a loss of magnetic field, an asteroid impact, or microbial life that led to climate change.

Finding out which of these theories are accurate has been an important mystery to solve.

That is what led to using the data from the InSight lander to search for clues.

They used it to map out the “thickness of the crust, the depth of the core, the composition of the core, even a little bit about the temperature within the mantle.”

The deeper crust seems to be fragmented igneous rock that contains more than enough liquid water to fill the oceans. So instead of disappearing all of those millions of years ago, the water seeped below the surface.

The deepest hole ever dug on earth was 7.6 miles deep (the Kola Superdeep Borehole), so we have a ways to go if we’re going to search for life down there.

NASA is on it, though, and is soliciting proposals from private companies that could help speed up a mission timeline.

If you thought that was interesting, you might like to read about a second giant hole has opened up on the sun’s surface. Here’s what it means.