Science

Huge rivers flowed on Mars

Huge rivers flowed on Mars”

That's because the sun was 25 to 30 percent less bright than it is today, keeping the planet relatively cool. We know water in the form of ice and vapor is present on Mars, and there are signs it also exists in liquid form: it's believed these dark streaks were created by minerals binding to water running over the alien world's surface during summertime.

"We infer that climate-driven runoff that was both intense and globally distributed persisted late in the history of the drying out of Mars", the study said. "The largest river in our database has a width of around one kilometer [0.6 miles], which is wider than the MS at St. Louis", study author Edwin Kite, from the University of Chicago, told Newsweek.

A preserved river channel on Mars appears in this photo taken by NASA's Mars Reconnaissance Orbiter, with color overlaid to indicate elevation.

Scientists have long known that rivers once ran on the surface of the Red Planet, but now they reveal that their existence was relatively recent in Mars' history.

The new findings complicate the picture for other scientists trying to figure out the history of the planet's climate - and its drastic transition from wet to dry, the university researchers said. Presently, a new study published March 27 in the journal Science Advances lists those rivers and reports that their waters likely streamed vigorously well into the last epoch, before Mars completely evaporated. Between 3.6 and 1 billion years ago, and likely after 1 billion years ago, there was intense runoff in these channels, amounting to 3 to 20 kilograms per meter squared each day. What's more, these organisms could have been living for millions of years and if it can be proven that water remains beneath Mars' surface, then they could be living even up to now. And yet, billions of years ago, water seems to have flowed heavily and freely across Mars, in rivers that were sometimes wider than those on Earth.

The two scientists concluded that fractures within some of Mars' craters, enabled water springs to rise up to the surface as a result of pressure deep below. For example, the width and steepness of the riverbeds and the size of the gravel tell scientists about the force of the water flow, and the quantity of the gravel constrains the volume of water coming through. Based on the size of the rivers, the researchers say the water was flowing continuously. Kite explains in a statement that climate models of ancient Mars need to include a strong greenhouse effect that would maintain an average temperature above the freezing point of water.

The rivers also show strong flow up to the last geological minute before the wet climate dries up. "You would expect them to wane gradually over time, but that's not what we see", Kite says in a press release. "The wettest day of the year is still very wet".

It's also possible the climate had a sort of "on/off" switch, which tipped back and forth between dry and wet cycles, Kite speculated.



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