Saturday, 24 August, 2019

Water could be flowing deep underground around the equator of Mars

This self-portrait of NASA's Curiosity Mars rover shows the vehicle on Vera Rubin Ridge in Gale crater on Mars. North is on the left and west is on the right with Gale crater's rim on the horizon of both edges. This mosaic was assembled from dozens of Ancient Mars rivers were twice as wide as those on earth, study indicates
Sandy Nunez | 30 March, 2019, 14:30

That implies, at a minimum, that Mars had a strong greenhouse effect back then to trap the energy of limited sunlight on the planet and melt its water - which then ran off into river channels.

Mars once had huge rivers wider than the MS that flowed intensely up until around one billion years ago, scientists discovered.

The new study also shows that scientists still have a lot to learn about Mars' climate evolution.

The findings are a mystery, because scientists had thought the Red Planet was losing its atmosphere and drying out during this time.

In a paper published today in Science Advances, researchers took multiple angles of the same rivers gathered together by the Mars Reconnaissance Orbiter's HIRISE camera.

Intense flow may have occurred in the river channels between 3.6 and 1 billion years ago, and even after that, researchers found.

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It's possible that either volcanism, a strong magnetic field that protected the atmosphere or the unique composition of its atmosphere allowed Mars to support liquid H2O longer than hypothesized. But, billions of years prior, water appears to have streamed vigorously and freely across Mars, in rivers that were sometimes wider than those on Earth. It could mean that now accepted dates for late-stage rivers are wrong, that late-stage atmospheric removal processes were faster than now thought, or that some other mechanism allowed for precipitation in low-atmosphere conditions. Mount Sharp's many rock layers hold clues about Mars' climate shifts, mission scientists have said.

It is a puzzle why ancient Mars had liquid water, researchers said. 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. This complicates the picture for scientists trying to model the ancient Martian climate, said lead author Edwin Kite, Assistant Professor at the University of Chicago. "Things were always kind of right at the edge of being able to have water flowing across the surface", Alan Howard of the Planetary Science Institute in Tucson, not involved in the study, says.

The confusion on climate modeling for the planet is in part because the planet wouldn't have had enough light to keep water warm enough for a liquid state. Rivers also exhibited strong flow until right before Mars' wet climate ended when it dried up nearly instantly.

"You would expect them to wane gradually over time, but that's not what we see", Kite said in a statement. Rather, at the end of the Martian epoch, rivers became shorter, yet at the same time carried heavy runoff before - very quickly - vanishing.

One possibility is that the Martian climate had an "on/off" switch that tripped back and forth between dry and wet cycles, he added. "Which is wrong: the climate models, the atmosphere evolution models or our basic understanding of inner solar system chronology?"