Today, Mars is a desiccated world, but missions to the Red Planet have suggested that it may have had liquid water early in its life. Whether that water was free flowing or trapped in ice is still a matter of debate.
According to new research, the answer may be both. “If the early Martian climate was warm enough to cause glacial ice to melt, the meltwater could create river systems in downstream regions,” he said. kamada arihiroplanetary scientist at Japan’s Tohoku University and first author of the new research, which was published in the journal icarus.
“Solving how and why surface water flowed when mean surface temperatures were likely below freezing for most of the year is the key question in understanding the evolution of the Mars climate and, by extension, climates.” of other habitable terrestrial planets”.
Kamada and his team created a global atmospheric model of Mars during the noahic period, about 4 billion years ago. At that time, the water could have been trapped in ice sheets a few kilometers thick. As Mars warmed with the changing seasons, the base of those glaciers could have melted, their water draining away and carving out intricate networks of valleys.
“Solving how and why surface water flowed when mean surface temperatures were likely below freezing for most of the year is the key question in understanding the evolution of the Mars climate and, by extension, climates.” from other habitable terrestrial planets,” he said. Bethany Ehlmann from the California Institute of Technology, which was not involved in the research.
Glacial melting, valley carving
Hundreds of valleys run through the southern highlands of Mars. Only a few kilometers wide on average, the narrow channels intertwine, bearing a strong resemblance to features cut by flowing water on Earth. In the decades since their discovery, valley networks have provided some of the strongest evidence that liquid water ever flowed across the Martian surface. Other hints of water on the Red Planet have also emerged, including signs of the oceans and suggestions of clays and silicas that required water to form.
Today, Mars has a thin atmosphere and a frigid temperature that cannot support liquid surface water. The polar ice caps trap some liquid, and groundwater can occasionally work its way through the crust, only to immediately sublimate into gas at the surface.
Scientists think the Martian atmosphere was thicker and possibly capable of supporting liquid water in the past, but “once you start forming ice sheets, it’s actually very difficult to shut them down and stop building them,” he said. Anna Grau Galofre, a researcher at the French National Center for Scientific Research who was not involved in the new study. The new model “fits quite well” with that of Grau Galofre previous work analyzing the geomorphology and characteristics of the Martian valley network, he said.
Mars in… War?
The new research is not without its critics. For Ramses Ramirezsimulating the atmospheres of Mars at the University of Central Florida, the authors themselves highlight one of the biggest problems: the predicted trough networks do not align well with the actual observed troughs.
I don’t see a good deal [between the results and observations] even in the best of cases,” Ramírez said.
Kamada and his colleagues point out that this discrepancy may be due to other processes that form some of the Martian valleys. Glacial melting could have created a significant number of valleys, they conclude, while forces such as volcanic eruptions and meteorite impacts could have played a role in the formation of others.
Grau Galofre pointed out that the new study compared its results with all observed valley networks, rather than focusing on those thought to have formed during the Noahide period. “They’re trying to model early climate but comparing it to all of history,” he said. She suspects that narrowing the time frame for observed tributaries would make a stronger case for glacial runoff.
Ramírez also noted that the ice sheets should have created glacial features in the southern highlands, features that he said are not present. “It doesn’t square with the geological evidence we see,” he said.
But Grau Galofre’s earlier research did identify potential glacial features in the valley networks, leading his team to conclude there was evidence that ice sheets had formed some of the branches. Other researchers argue that those features were made by flowing water rather than ice.
The new research adds more data to the ongoing schism in Martian science, where some scientists fall firmly on the side of a semi-arid red planet with occasional rain showers and others stand firm with a cold Mars of ice and snow. Some have referred to disconnection as a waralthough the investigators involved were quick to note that it is more a case of healthy debate than open hostility.
“This is a really novel and intricate approach. The climate of early Mars was probably neither one extreme nor the other, but somewhere in between.”
Although the idea of a cold, wet Mars initially appears to bridge the gap, Ramirez isn’t convinced the new research offers conclusive evidence. “I don’t think so [the debate] it has really moved a lot at all,” he said. “I think people are quite willing one way or the other.”
Grau Galofre is more optimistic.
“This is a really novel and intricate approach,” he said. “The climate of early Mars was probably neither one extreme nor the other, but somewhere in between.”
—Nola Taylor Tillman (@Nola_T_Tillman), science writer