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superficei de Marte/Europa Press
< /ul> CO2 does not seem to be the culprit that caused Mars to dry up
A new study examines the traces of Martian rivers to see what caused them What they can reveal about the history of the planet’s water and atmosphere has come to an unexpected answer: CO2 was not the key.
The revealing traces of rivers, streams and lakes in the past are visible today all over the planet Mars. But about three billion years ago, they all dried up, and no one knows why.
“People have come up with different ideas, but we’re not sure what. caused “I wonder if the climate would change so drastically,” University of Chicago geophysical scientist Edwin Kite, lead author of the research, said in a statement. “We’d really like to understand, especially since it’s the only planet that we definitely know changed.” from habitable to uninhabitable.”
Previously, many scientists had assumed that the loss of carbon dioxide from the atmosphere,that helped keep Mars warm, was causing the problem. But the new findings, published May 25 in Science Advances, suggest the change was caused by the loss of some other important ingredient that kept the planet warm enough for running water.
In 1972, scientists were shocked to see images from NASA’s Mariner 9 mission as it orbited Mars. The photos revealed a landscape filled with riverbeds, evidence that the planet once had abundant liquid water.
Since Mars doesn’t have tectonic plates to move and bury rock over time, traces of ancient rivers are still on the surface. Kite and his collaborators analyzed maps based on thousands of images taken from satellite orbit. Depending on what As tracks overlap and erode, the team put together a timeline of how the river’s activity changed. in elevation and latitude over billions of years.
They were then able to combine that with simulations of different weather conditions and see which one matched best.
Planetary climates are hugely complex, with many, many variables to take into account, especially if you want to keep your planet in the “Goldilocks” zone, where it’s just warm enough for water to be liquid. liquid, but not so much that it boils. Heat can come from a planet’s sun, but it has to be close enough to receive radiation, but not so close that the radiation washes out of the atmosphere.
Greenhouse gases, such as carbon dioxide and methane, can trap heat near the surface of a planet. The water itself itself also plays a role; it can exist as clouds in the atmosphere or as snow and ice on the surface. Snow caps tend to act like a mirror to reflect sunlight back into space, but clouds can either catch or reflect light, depending on their height and composition.
Kite and his collaborators ran many used different combinations of these factors in their simulations, looking for conditions that could cause the planet to warm enough for at least some liquid water to exist in the rivers for more than a billion years, but then lose it abruptly.
CO2 WAS NOT THE DRIVING FORCE
But when comparing different simulations, they saw something surprising. Changing the amount of carbon dioxide in the atmosphere did not change the amount of carbon dioxide in the atmosphere. The result. That is, the driving force of change did not seem to be carbon dioxide.
“Carbon dioxide is a strong greenhouse gas, so it really was the leading candidate to explain the desiccation of Mars,” said Kite, an expert on otherworldly climates. “But these results suggest that it’s not that simple.”
There are several alternative options. The new evidence fits nicely with a scenario, suggested in a 2021 Kite study, where a layer of thin, icy clouds high in Mars’ atmosphere acts like a greenhouse of translucent glass, trapping the heat. Other scientists have suggested that if it was released hydrogen from the planet’s interior, could have interacted with carbon dioxide in the atmosphere to absorb infrared light and heat the planet.
“We don’t know what that is. this factor, but we need a lot to have existed to explain the results,” Kite said.
There are several 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.