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.
“Wouldn’t it be cool to have a habitable planet close by?”
Yeah. Dreamy.
Until the first f’n Democrat shows up and S@#$ts in the pool.
But, MAYBE we could send ALL the Democrats there, instead.
Concoct some Earth crisis story requiring evacuation, and — of course — all the Democrats get to go on the first ship out since they’re OBVIOUSLY the Most Important People. And we’ll paint the entire ship to look like a gigantic pride flag, just to make them even more excited to be going on this historic journey. Then we send all the Democrats off to Mars to ensure they’re safely out of harm’s way; saved from the coming calamity here on Earth.
Oh, and did I neglect to mention it’s a one-way trip?
Silly me.
Anyway, they all live self-loathingly on Mars ever after.
And the Earth calamity? We “discover” a flaw in our model that, once corrected, shows it was all a false alarm. Ha-ha! Imagine that!
With all the Democrats gone off to Mars, San Francisco might become habitable, again. Or even Chicago. Lots of potential benefits to this scenario...
This!🤔
Our white liberal ‘elites’ could even invite the DAVOS group to evacuate with them... We can dream.
Transfer the excess atmosphere from Venus to Mars, bring water from the outer solar system, put genetically engineered bacteria in place to break down the poisons in the soil and mars can be terraformed.
For awhile anyway.🤔
Yep, start simple...
Immanuel Velikovsky opines that the loss of Martian water was much more recent and due to a near approach of a wandering body with a greater gravity that stripped away the atmosphere and most water. Worlds in Collision, written in 1950.
A part of the puzzle solution, no doubt. To hold an atmosphere the gasses have to be a certain ratio. while water is flowing and raining down on Mars, all that is needed to upset the balance is a meteoric rain which would heat the atmosphere sufficiently to evaporate water into clouds no longer heavy enough for the gravity of the planet to hold the atmosphere. Half of Mars is pocked with craters, while another half is relatively scoured. IF Mars was a moon of a much larger watery planet which disintegrated forming the asteroid belt, then the catastrophes can explain the changes to Martian atmosphere. 9Tiamat anyone?)
Only Venus spins “backwards”. You would see orbits become far more eccentric before you would get tipping effects from magnetic fields. Only Pluto has a wildly eccentric orbit.
If you look at Mars’ atmospheric composition, it looks pretty much like a solar-wind stripped result if you started with an atmosphere similar to Earth’s.
The CO2 is essentially the heaviest gas in the mix. Some of the oxygen and most of the carbon available early on would have stayed CO2 since there is no plant life to decompose it and store the carbon. The argon is the product of potassium beta decay and is stripped by the solar wind, keeping it in an equilibrium or at least present. And the oxygen and nitrogen are the remnant that still have not been completely stripped by the solar wind, even the ratio is reasonable given that nitrogen is a bit lighter than oxygen. And water vapor is even less dense than either, so it would be gone as well. So, it is not a wildly fantastic claim that the current Mars atmosphere is the solar wind ravaged dregs of a once-Earthlike atmosphere.
In a different post you claim that Mars has no magnetic field so it should have lost its atmosphere much faster than it apparently did. That would be a valid argument if Mars had never possessed a magnetic field, however, it almost certainly did possess one early on given the amount of iron present. Thus the loss of atmosphere would have begun slowly and accelerated as the magnetic field dissipated once the cooling of the planet progressed. And Mars, being much smaller than the Earth, would have cooled considerably faster than Earth, so it is not at all peculiar that Earth still has an atmosphere while Mars does not. Given enough time, we will look like Mars in terms of dryness and thinness of the atmosphere.
“Only Venus spins “backwards”.”
Venus and Uranus spin backwards.
Well, he was wrong. To strip the atmosphere and water such a passage would have caused massive disruption and there would be visible evidence (since there was no water or atmosphere to erode it away...)
However, when the moon initially formed it was so close to the Earth that all the gasses and dust on its surface were vacuumed off. Proximity to the Earth is why it became tidally locked and why the nearside is so much different than the farside. If a near passage stripped Mars there would be features visible to indicate that.
Uranus rotates mostly on its side. I don’t think you can count it either way. Its axis of rotation is more or less in the ecliptic (more so than Earth’s is perpendicular to it, by a factor of three). At one point in Uranus’ year the planet appears to rotate clockwise from the perspective of the Sun, and half a Uranus year later, it is rotating counter-clockwise. At the quarter-year points it is either rotating “up” or rotating “down”.
“So, it is not a wildly fantastic claim that the current Mars atmosphere is the solar wind ravaged dregs of a once-Earthlike atmosphere.”
I didn’t dispute that the solar wind stripped the atmosphere from Mars, I dispute the claim that the solar wind had somehow stripped the CO2 from the atmosphere faster than the rest of the constituents, which is ludicrous for both the reason you cited, that the CO2 is heavier than other gases, and also for the reason that the CO2 right now remains the majority constituent of the atmosphere.
“In a different post you claim that Mars has no magnetic field so it should have lost its atmosphere much faster than it apparently did.”
Not I. You’ve confused me with another poster, I’m afraid. Perhaps when I quoted a portion of Mr. K’s post when I replied to him you thought that was my own thoughts.
Plant some algae and see if it grows.
You know there will be people that will say leave Mars alone.
Before NASA went all woke they did real.science.
https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html
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