Martian glaciers may have carved their valleys

Today, Mars is a dry world, but missions to the Red Planet have indicated that it may have contained liquid water early in its life. Whether that water ran freely or was trapped in the ice remains a matter of debate.

According to new research, the answer may be both. Arihiro Kamada, a planetary scientist at Japan’s Tohoku University and first author of the new research, which is published in the journal, said Icarus.

"Resolving how and why surface water flowed when surface temperatures were likely below freezing for the majority of the year is the key question for understanding the evolution of the climate of Mars and, by extension, the climates of other habitable terrestrial planets."

Kamada and his team created a global atmospheric model of Mars during the Noachian period, nearly 4 billion years ago. At the time, the water would have been trapped in ice layers a few kilometers thick. As Mars warmed with the changing seasons, the base of those glaciers could have melted, draining their waters away, carving out intricate valley networks.

"Resolving how and why surface water flowed when surface temperatures were likely below freezing for most of the year is a key question for understanding the evolution of the climate of Mars and, by extension, the climates of other habitable terrestrial planets," said Bethany Elman. from the California Institute of Technology, who was not involved in the research.

Melting glaciers, carving valleys

Hundreds of valleys intersect with the southern highlands of Mars. Only a few kilometers away on average, narrow channels are intertwined together, bearing a strong resemblance to features cut by the flow of water on land. In the decades since their discovery, valley networks have provided some of the strongest evidence that liquid water was flowing across the surface of Mars. Other hints of water on the Red Planet have also appeared, including signs of oceans and suggestions of clays and silicates that require water to form.

Canyon networks, such as those captured by NASA’s Viking mission, were among the first indications of water flowing on ancient Mars. credit: NASA

Today, Mars has a thin atmosphere and a temperature that is too cold to tolerate liquid surface water. Polar ice caps trap some of the fluid, and groundwater may sometimes make its way through the crust, only to be instantly sublime into the gas at the surface.

Scientists think that Mars' atmosphere was thicker and may have been able to support liquid water in the past, but "once you start forming ice layers, it’s really hard to stop and stop building them," said Anna Grau Gallover, a researcher at the French National Center for Research. The scientist who was not involved in the new study. She said the new model "correlates very well" with Grau Galofre’s previous work analyzing the geomorphology and properties of the Martian valley network.

Mars in … war?

The new research is not without criticism. For Ramses Ramirez, who simulates the atmosphere of Mars at the University of Central Florida, the authors themselves have highlighted one of the biggest problems – the projected valley networks do not align well with the actual observed valleys.

I don’t see a good deal [between the results and observations] Ramirez said.

Kamada and colleagues note that this discrepancy may be due to other processes forming some of Mars' valleys. They concluded that melting glaciers could have created a large number of valleys, while forces such as volcanic eruptions and meteorite impacts could have played a role in shaping others.

Grau Galofre noted that the new study compared its results to all observed valley networks, rather than focusing on those believed to have formed during the Noachian period. "They’re trying to model the early climate but they’re comparing it to the whole history," she said. She suspects that the narrowing of the time frame for the observed tributaries would make a stronger argument for glacier runoff.

Ramirez also noted that the ice sheets must have created glacial features in the southern highlands, features he said do not exist. "It doesn’t match the geological evidence we see," he said.

But previous research by Grau Gallofre identified possible glacial features in the valley networks, leading her team to conclude that there is evidence that the ice sheets formed some branches. Other researchers argue that these features were created by flowing water rather than flowing ice.

The new research adds more data to an ongoing divide in Mars science, with some scientists falling firmly on the side of a red, semi-arid planet with occasional rain and others standing firm with a cold Mars of ice and snow. Some referred to the separation as war, although the participating researchers soon noted that it was a case of healthy debate rather than outright hostility.

“This is a really new and complex approach. The climate of Mars in its early days may not have been one extreme or the other but somewhere in between.”

Although the idea of ​​cold, wet Mars initially seems to bridge the gap, Ramirez is not convinced that the new research provides conclusive evidence. "I don "t think so [the debate] It really moved a lot at all.” “I think people are in a good place one way or the other.”

Grau Galofre is more optimistic.

“This is a really new and complex approach,” she said. "It is possible that the climate of early Mars was not extreme or the other but somewhere in between."

—Nola Taylor Tillman (Tweet embed), a science writer

the quote: Tillman, NT (2022), Martian glaciers may have carved their valleys, Eos, 103, Posted on August 2, 2022.
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