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Why did Mars dry out? New study points to unusual answers
phys.org ^ | 5/26/2022 | Louise Lerner

Posted on 05/26/2022 8:27:59 AM PDT by LibWhacker

Billions of years ago, a river flowed across this scene in a Mars valley called Mawrth Vallis. A new study examines the tracks of Martian rivers to see what they can reveal about the history of the planet’s water and atmosphere. Credit: NASA/JPL Caltech/University of Arizona Mars once ran red with rivers. The telltale tracks of past rivers, streams and lakes are visible today all over the planet. But about three billion years ago, they all dried up—and no one knows why.

"People have put forward different ideas, but we're not sure what caused the climate to change so dramatically," said University of Chicago geophysical scientist Edwin Kite. "We'd really like to understand, especially because it's the only planet we definitely know changed from habitable to uninhabitable."

Kite is the first author of a new study that examines the tracks of Martian rivers to see what they can reveal about the history of the planet's water and atmosphere.

Previously, many scientists had assumed that losing carbon dioxide from the atmosphere, which helped to keep Mars warm, caused the trouble. But the new findings, published May 25 in Science Advances, suggest that the change was caused by the loss of some other important ingredient that maintained the planet warm enough for running water.

But we still don't know what it is.

Water, water everywhere, and not a drop to drink

In 1972, scientists were astonished to see pictures from NASA's Mariner 9 mission as it circled Mars from orbit. The photos revealed a landscape full of riverbeds—evidence that the planet once had plenty of liquid water, even though it's dry as a bone today.

Since Mars doesn't have tectonic plates to shift and bury the rock over time, ancient river tracks still lie on the surface like evidence abandoned in a hurry.

This allowed Kite and his collaborators, including University of Chicago graduate student Bowen Fan as well as scientists from the Smithsonian Institution, Planetary Science Institute, California Institute of Technology Jet Propulsion Laboratory, and Aeolis Research, to analyze maps based on thousands of pictures taken from orbit by satellites. Based on which tracks overlap which, and how weathered they are, the team pieced together a timeline of how river activity changed in elevation and latitude over billions of years.

Then they could combine that with simulations of different climate conditions, and see which matched best.

For years, researchers have debated whether Mars once even had enough water to form an ocean, as depicted in this concept illustration. Credit: NASA/GSFC Planetary climates are enormously complex, with many, many variables to account for—especially if you want to keep your planet in the "Goldilocks" zone where it's exactly warm enough for water to be liquid but not so hot that it boils. Heat can come from a planet's sun, but it has to be near enough to receive radiation but not so near that the radiation strips away the atmosphere. Greenhouse gases, such as carbon dioxide and methane, can trap heat near a planet's surface. Water itself plays a role, too; it can exist as clouds in the atmosphere or as snow and ice on the surface. Snowcaps tend to act as a mirror to reflect away sunlight back into space, but clouds can either trap or reflect away light, depending on their height and composition.

Kite and his collaborators ran many different combinations of these factors in their simulations, looking for conditions that could cause the planet to be warm enough for at least some liquid water to exist in rivers for more than billion years—but then abruptly lose it.

But as they compared different simulations, they saw something surprising. Changing the amount of carbon dioxide in the atmosphere didn't change the outcome. That is, the driving force of the change didn't seem to be carbon dioxide.

"Carbon dioxide is a strong greenhouse gas, so it really was the leading candidate to explain the drying out of Mars," said Kite, an expert on the climates of other worlds. "But these results suggest it's not so simple."

There are several alternative options. The new evidence fits nicely with a scenario, suggested in a 2021 study from Kite, where a layer of thin, icy clouds high in Mars' atmosphere acts like translucent greenhouse glass, trapping heat. Other scientists have suggested that if hydrogen was released from the planet's interior, it could have interacted with carbon dioxide in the atmosphere to absorb infrared light and warm the planet.

"We don't know what this factor is, but we need a lot of it to have existed to explain the results," Kite said.

There are a number of ways to try to narrow down the possible factors; the team suggests several possible tests for NASA's Perseverance rover to perform that could reveal clues.

Kite and colleague Sasha Warren are also part of the science team that will be directing NASA's Curiosity Mars rover to search for clues about why Mars dried out. They hope that these efforts, as well as measurements from Perseverance, can provide additional clues to the puzzle.

On Earth, many forces have combined to keep the conditions remarkably stable for millions of years. But other planets may not be so lucky. One of the many questions scientists have about other planets is exactly how lucky we are—that is, how often this confluence exists occurs in the universe. They hope that studying what happened to other planets, such as Mars, can yield clues about planetary climates and how many other planets out there might be habitable.

"It's really striking that we have this puzzle right next door, and yet we're still not sure how to explain it," said Kite.


TOPICS: Astronomy; Science
KEYWORDS: dry; mars; water
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To: Billthedrill
And what happened to the subways under the canals?

(Heinlein reference.)

41 posted on 05/26/2022 9:41:41 AM PDT by Publius (It wasn't easy being a young conservative. It's easier being an old conservative.)
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To: LibWhacker

They don’t know what mars-ological force caused the red planet to become a lifeless desert, yet some individuals cling to the belief that they can “terraform” Mars, generating oxygen and, that the unknown force will not eliminate the oxygen that the scientists work so hard to generate.


42 posted on 05/26/2022 9:51:04 AM PDT by I want the USA back (A totally corrupt media willingly lies to protect a totally corrupt administration. )
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To: dsrtsage

How could the Martian environment be reverse engineered? Wouldn’t it be cool to have a habitable planet close by?


43 posted on 05/26/2022 9:53:01 AM PDT by GOPJ (Thank God for Texas Law Enforcement and our brave Border Patrol..)
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To: LibWhacker

More than likely the reason Mars lost it’s liquid water was that it progressively lost its atmosphere. And probably it lost its atmosphere because it wasn’t geologically active as earth was/is. What does Earth have that Mars doesn’t? A molten iron core that creates a magnetic field that deflects solar winds.


44 posted on 05/26/2022 10:17:41 AM PDT by Tallguy
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To: Tallguy

Lack of mass may also have had something to do with it.


45 posted on 05/26/2022 10:25:04 AM PDT by Reily
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To: Reily

I wouldn’t discount that. There is also the accepted theory that early in its life Earth was struck by an asteroid/planetoid with a high iron composition. This added to the mass & density of the planet while creating a disk of lighter debris that eventually condensed into our Moon.


46 posted on 05/26/2022 10:30:13 AM PDT by Tallguy
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To: LibWhacker
Why, the Martian SUVs of course.


47 posted on 05/26/2022 10:36:25 AM PDT by Rinnwald
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To: Tallguy

Yes I know.


48 posted on 05/26/2022 10:40:20 AM PDT by Reily
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To: LibWhacker

How the heck does these scientists know what happened billions of years ago?

Why are we trying to find life on a planet that has close to 96% CO2 atmosphere?

According to climate change scientists our planet is going to end and we have a .06-.04% CO2 in our atmosphere...


49 posted on 05/26/2022 10:42:59 AM PDT by Pez149 (Time to stop saying a theory is fact....)
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To: LibWhacker

dehydration


50 posted on 05/26/2022 10:44:03 AM PDT by bert ( (KWE. NP. N.C. +12) Promoting Afro Heritage diversity will destroy the democrats)
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To: LibWhacker

“Carbon dioxide is a strong greenhouse gas, so it really was the leading candidate to explain the drying out of Mars,” said Kite, an expert on the climates of other worlds. “But these results suggest it’s not so simple.”


and the science shows it is a LAGGING Indicator, but don’t pay attention to the science..................


51 posted on 05/26/2022 10:45:55 AM PDT by PeterPrinciple (Thinking Caps are no longer being issued but there must be a warehouse full of them somewhere.)
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To: PeterPrinciple

CO2’s molar mass is 44. O2 is 32. CO2 is heavier than air, and thus it sinks.

It’s why we have phytoplankton, seaweed, etc in our oceans. Were it not the case, there would be no sustainable food chain in the ocean.

Leaving one important scientific question:

Who did this person sleep with to get this job?


52 posted on 05/26/2022 10:48:48 AM PDT by RinaseaofDs
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To: dsrtsage

Never had water. It didn’t go anywhere.

Liquid CO2 flowed. Now all gas or crystallized below (that’s ice in water terms).


53 posted on 05/26/2022 10:57:47 AM PDT by If You Want It Fixed - Fix It ( )
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To: LibWhacker

Not really much of a mystery. Mars has no Magnetic field to speak of.

The solar winds pretty much has swept away any atmosphere that could be on Mars.

To terraform that world, you would first have to get a strong magnetic field going.


54 posted on 05/26/2022 11:00:39 AM PDT by Conan the Librarian (Conan the Sailing Librarian)
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To: LibWhacker

Not enough fluid or electrolytes?

My best guess.

5.56mm


55 posted on 05/26/2022 11:02:11 AM PDT by M Kehoe (Quid Pro Joe and the Ho need to go.)
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To: LibWhacker
"Sorry Earthling but there are no duck ponds here."
56 posted on 05/26/2022 11:02:43 AM PDT by N. Theknow (Kennedys-Can't drive, can't ski, can't fly, can't skipper a boat-But they know what's best for you.)
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To: LibWhacker

Prohibition


57 posted on 05/26/2022 11:04:57 AM PDT by N. Theknow (Kennedys-Can't drive, can't ski, can't fly, can't skipper a boat-But they know what's best for you.)
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To: LibWhacker

Putin.


58 posted on 05/26/2022 11:23:45 AM PDT by o-n-money (Not my president: WRONG Not the president: RIGHT)
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Simple…use of fossil fuels by Martians…just ask Algore and Greta…


59 posted on 05/26/2022 11:27:47 AM PDT by TnTnTn
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To: Boogieman

Excellent Point.


60 posted on 05/26/2022 11:42:34 AM PDT by Sergio (An object at rest cannot be stopped! - The Evil Midnight Bomber What Bombs at Midnight)
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