How did Mars go from wet to dry? New study provides unusual answers

Study raises theory that Mars had a thin atmosphere throughout its era of river formation and became uninhabitable as a result of constant pressure cooling

Representative picture

Mars once had rivers and ponds, but the water evaporated about three billion years ago. No one knows why this happened and a new study by scientists at the University of Chicago has provided some unusual answers to the wet-to-dry transition.

Previously, many scientists had assumed that the loss of carbon dioxide from the atmosphere, which helps keep Mars warm, was causing problems. But the new findings, published in Scientists progress, suggest the shift was caused by the loss of “another important ingredient” that kept the planet warm enough for running water. But we still don’t know what it is, according to the University of Chicago.

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According to the latest study, titled “Change in Spatial Distribution of Water Flow Patterns, Major Change in Mars Greenhouse Effect”, Mars’ atmosphere is now so thin that it is close to the point triple the water, so the lakes of early March probably formed under a thicker atmosphere. Carbon dioxide (CO2) is, in the modern inner solar system, a key greenhouse gas for the regulation of climate change.


Alternate explanation

However, even when H2O vapor feedback is taken into account, additional warming without CO2 is needed to warm Mars early enough for rivers. Therefore, changes in non-CO2 radiative forcing are another explanation for Mars’ wet-dry transition. The relative importance of these two mechanisms has not been studied, so the dominant explanation for the wet-to-dry transition remains untested, he added.

The researchers reconstructed Mars’ greenhouse history using geological proxies for past river activity that resolve Mars’ desertification in time. They also compared the proxy data to a climate model to retrieve changes in the greenhouse effect and also to assess to what extent the changes were the result of changes in CO2 radiative forcing versus non-CO2 radiative forcing.

“People have come up with different ideas, but we don’t know exactly what caused such dramatic climate change,” said Edwin Kite, a geophysicist at the University of Chicago.

“We would really like to understand, especially because it’s the only planet that we know for sure went from habitable to uninhabitable,” he added.

Kite and his collaborators ran many different combinations of various factors in their simulations, looking for conditions that could make the planet warm enough for at least some liquid water to exist in rivers for more than billions of years. years – but then suddenly loses her. But when comparing different simulations, they saw something surprising. Changing the amount of CO2 in the atmosphere did not change the result. In other words, the driving force for change does not appear to be carbon dioxide, according to the University of Chicago.

Greenhouse gas

Researchers first thought the reason Mars was drying up was due to greenhouse gases.

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

“We don’t know what this factor is, but we need it to have existed in large part to explain the results. It’s really striking that we have this puzzle right next to it, and yet we still don’t know how to explain it,” Kite added.

“Mars is the only world whose surface is known to have become uninhabitable…Our results raise the possibility that Mars had a thin atmosphere throughout the era of river formation and that Mars became uninhabitable following constant-pressure cooling. This study does not rule out the hypothesis that the end of surface habitability on Mars was ultimately caused by atmospheric decay, but suggests that the loss of non-CO2 radiative forcing (not CO2 loss) played a dominant role in changing the spatial distribution of water fluxes,” the researchers said.

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