Mars had ponds and rivers, now it’s getting dry; study explains unusual reasons

Study puts forward theory that Mars had a thin atmosphere during the river-forming era and became uninhabitable due to cooling under constant pressure

Representative image

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 unusual answers to the transition from wet to dry.

Previously, many scientists had assumed that the loss of carbon dioxide from the atmosphere, which helped keep Mars warm, was causing the problems. But the new findings, published in scientific progress, suggest the change was caused by the loss of an “other key 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.

Also read: A house on Mars: IISc, ISRO researchers develop technology for space rocks

According to the latest study, titled “Changing spatial distribution of water flow charts major change in Mars’ greenhouse effect,” Mars’ atmosphere is so thin today that it’s close to the triple point of water, so lakes likely formed on early Mars. under a thicker atmosphere. Carbon dioxide (CO2) is an important greenhouse gas for regulating climate change in the modern inner solar system.


alternative explanation

But even when H2O vapor feedback is considered, additional non-CO2 warming is needed to warm Mars early enough for rivers. Therefore, changes in non-CO2 radiative forcing are an alternative explanation for the wet-to-dry transition of Mars. The relative importance of these two mechanisms has not been explored, so the prevailing explanation of the wet-to-dry transition remains untried, it added.

The researchers reconstructed the history of Mars’ global warming using geologic proxies for past river activity that resolve Martian desertification over time. They also compared the proxy data to a climate model to find out changes in global warming and also to assess to what extent the changes were due to changes in CO2 radiative forcing versus non-CO2 radiative forcing.

“People have put forward different ideas, but we’re not sure why the climate has changed so drastically,” said University of Chicago geophysical scientist Edwin Kite.

“We’d really like to understand it, especially since it’s the only planet that we know for sure has changed from habitable to uninhabitable,” he added.

Kite and his collaborators used many different combinations of different 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 billion years — but then to lose abruptly. But when they compared different simulations, they saw something surprising. Changing the amount of CO2 in the atmosphere did not change the outcome. That is, the driving force behind the change did not appear to be carbon dioxide, according to the University of Chicago.

Greenhouse gases

The researchers first thought that the reason for the drying of Mars was due to greenhouse gases.

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

“We don’t know what this factor is, but we must have had a lot of it to explain the results. It’s really striking that we have this puzzle next door, 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 during the river-forming epoch and that Mars became uninhabitable due to cooling under constant pressure. This study concludes 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 the loss of CO2) played a dominant role in the changing spatial distribution of water flow,” the researchers said.

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