A hidden body of water is tucked away between layers of fractured rock, 4 to 8 miles beneath the planet’s outer crust, according to a new study published in the journal Proceedings of the National Academy of Sciences (PNAS). The ocean is large enough to cover all of Mars with water a mile deep, but it’s also far too deep to be accessible by any known means.

The possibility of life on Mars is increasing!

“As far as we know, water is essential for life,” said Michael Manga, a professor of earth and planetary science at UC Berkeley and co-author of the study . “I don’t understand why an underground reservoir wouldn’t be habitable. We know there’s life deep in the mines and on the ocean floor on Earth .” Manga said there’s no evidence of life on Mars yet, but theoretically, they’ve identified a place where life could exist.

Dried-up riverbeds, deltas, and lake beds on Mars’ surface suggest that the planet once had abundant water. But about 3.5 billion years ago, a sudden change in Mars’ climate wiped out all water on the surface.

While the cause of this rapid drying is not yet clear, scientists have suggested possible causes include the sudden loss of the planet’s magnetic field, an asteroid impact, or ancient microbial life disrupting the planet through climate change.

Examination of the deeper crust revealed that it likely contains fragmented igneous rocks that contain enough liquid water to fill the Martian oceans, suggesting that billions of years ago, water did not escape into space but instead seeped into the planet’s crust.

Reaching the hidden ocean is currently beyond humanity’s technical capabilities, but scientists are continuing their search for life on Mars elsewhere. The Perseverance rover has been exploring the surface of Jezero crater since 2021, collecting samples of Martian dust and even evidence of ancient life. NASA is planning a mission to bring back the samples and is seeking offers from private companies to speed up the mission.