Ancient Rivers And Lakes On Mars Hint The Red Planet Used To Be A Lot Like Earth

Mars isn’t nearly as simple as scientists once believed. Only weeks ago, they discovered that briny water once existed on the red planet. And now, NASA has announced that rivers and lakes once did, too.

Scientists once thought Earth was pretty simple, too, and the evidence is pointing them to an unbelievable conclusion: Mars used to look a lot like home, the Washington Post reported.

“The more you look into it, questions come up because you’re beginning to fathom the real complexity of what we see… This is a good time to go back to reevaluate all our assumptions. Something is missing somewhere,” said John Grotzinger, a Professor of Geology at Caltech.

The briny water that flows on Mars today only shows up occasionally and wets the dirt like a sponge. But, billions of years ago, the planet may have flowed with even more water.

The case for the existence of rivers and lakes on Mars is compelling. NASA’s Curiosity rover has spent lots of time studying the Gale Crater, and it recently found an interesting layer of sediment inside the ancient depression. This layer could only have been formed by lots and lots of water.

In other words, the sediment suggests that in the past, the environment was teeming with rivers, river deltas, and lakes, Smithsonian Air and Space Magazine added.

The evidence suggests that a lake system existed at the Gale Crater 3.5 billion years ago and lasted for millions of years. And each lake in this system would’ve been filled with water for at least 100 years, and even as long as 10,000 years at a time.

This may be long enough for life to have evolved.

Besides these tantalizing signs of rivers and lakes, NASA made an interesting discovery about the planet’s three-mile-high peak, Aeolis Mons, or Mount Sharp; scientists have long wondered how it got so high. According to the Christian Science Monitor, deposits from rivers and lakes formed the bottom layers of Mount Sharp over 500 million years.

The theory is that sediment layers from rivers and lakes were deposited at Gale Crater and then eventually eroded; the wind carried the sediment and formed the peak.

In a tantalizing detail, the presence of rivers and lakes on Mars suggests that the environment there used to be a bit like Earth. In addition to being wetter, it was also a bit warmer. NASA didn’t discover any glaciated sediments or other signs of a cold climate, which is odd because they’ve long believed that the red planet was a frigid place 3.5 billion years ago.

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The problem: Back then, the Sun was up to 30 percent weaker than it is today, so Mars wasn’t getting nearly as much solar heat. To make up for that, the atmosphere was thicker. Right now, scientists can’t explain why the planet was warmer — and covered in rivers and lakes — at a time it should’ve been colder.

The climate back then would’ve been pretty mild and possibly a good place for life to thrive. Gale Crater, at least, was quite Earth-like, and the water was neutral — not too acidic or basic. That’s the perfect recipe for basic life — like ours — to get started. It doesn’t prove microbes ever did live there, but it suggests something Earth-like could’ve survived.

Does that mean life could make it there now? Grotzinger said that even though the rivers and lakes are gone, a groundwater table would remain. If life evolved on Mars, this could provide the right habitat.

But many questions still remain, said NASA scientist Michael Meyer.

“What we thought we knew about water on Mars is constantly being put to the test. It’s clear… billions of years ago [it] more closely resembled Earth than it does today. Our challenge is to figure out how this more clement Mars was even possible, and what happened to that wetter Mars.”

[Photos Courtesy NASA / Getty Images]