Mars was once covered with wide rivers

Mars was wet, until suddenly it was.

Scientists have long found that dry riverbeds crisscross the surface of Mars as evidence that water once flowed freely on the planet. And in 2012, NASA's Curiosity space robot returned images of smooth, round pebbles from the bottom of a riverbed, their absence of rough edges proving that the water had once sunk them. Now, a new study published today (March 27) in the journal Science Advances lists these rivers and indicates that their waters probably flowed a lot until the last time, before Mars was completely drained.

"It's already hard to explain the rivers or lakes based on the information we have," said Edwin Kite, scientist in planetary science at the University of Chicago and lead author of the study in a statement. "It makes a difficult problem even more difficult." [7 Most Mars-Like Places on Earth]

If the rivers had been brief or if they had sunk only part of the time, it would have always been difficult to explain their existence. But scientists simply do not know where all the liquid water that formed these important flows comes from.

Mars is today freezing and mostly dry, with just a thin atmosphere on the surface. In the distant past, it seems that the weather should have been even colder, because sunlight reaching the surface of the planet would have been weaker. And yet, billions of years ago, water seems to have flowed freely and freely on Mars, sometimes in rivers wider than Earth's. These waters seem to have sunk so much that they would have been in motion all day, not just at peak rush hours or in small nets.

Scientists simply do not know how much time the red planet would have produced these rivers, but the study showed that the very flowing water has been around for over a billion years, at the beginning of Martian history. .

This implies, at the very least, that Mars had a strong greenhouse effect at the time to capture the limited sunlight energy on the planet and melt its water, which was then flowed into the channels of the river. [‘4-Billion-Year Old’ Mars Fly-Over Shows Water and Blue Skies | Video]

Kite said that this work implies that something in the current science of planets and the early solar system is wrong, because all that scientists know suggests that the rivers on Mars should have been small and temporary or nonexistent. The long-term, heavy flows that last millions of years simply do not correspond to current scientific knowledge.

Research also shows that when the red planet has cooled, it has not slowly dried up. Instead, at the end of the wet Martian era, the rivers became shorter, but they always underwent significant runoff before disappearing – almost immediately -.

Originally published on Science live.