Mars water

Mars is a dusty, barren, dried up planet. But it didn't used to be that way.

New research suggests an ocean up to one mile deep once occupied over half of the Martian planet's surface, painting a completely different picture compared to what we know today. This isn't the first time scientists have hypothesized Mars was once a water-world, but the evidence just keep stacking up.

The new research was presented by planetary scientist Geronimo Villanueva, who made his observations at the European Southern Observatory's Very Large Telescope in Chile.

"With these powerful instruments, the researchers distinguished the chemical signatures of two slightly different forms of water in Mars' atmosphere," NASA explained. "One is the familiar H2O. The other is HDO, a naturally occurring variation in which one hydrogen is replaced by a heavier form, called deuterium."

The study measured and mapped the different H2O and HDO levels over a six-year period—or about three martian years. Although Mars is a wasteland today, researchers were able to create maps that revealed "regional variations called microclimates and seasonal changes," suggesting the environment of Mars was much different billions and billions of years ago. NASA said there was a "wet Noachian period" on Mars, though it ended almost 4 billion years ago.

Evidence of water on Mars has popped up on numerous occasions, most notably in tests performed by NASA's Curiosity rover over the past few years. And even though there's no water on the planet today, it begs the question: Was Mars more Earth-like in its formative years? It's a mystery scientists are earnestly trying to uncover.