Thin Ice May Have Helped Ancient Lakes Survive on Mars
One of the mysteries of the Martian landscape is the presence of numerous valleys and lakebeds, which appear to have been shaped by flowing water in ancient times. Simulations of what Mars might have looked like eons ago suggest the red planet was likely too cold to support liquid water. A new analysis has identified a solution that may explain how icy Mars hosted watery lakes.
The study was published in AGU Advances.
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Where’s The Ice On Mars?
Mars’s ancient lake basins had confused many previous planetologists, who expected to find evidence of chunky ice sheets on the planet’s surface.
“Seeing ancient lake basins on Mars without clear evidence of thick, long-lasting ice made me question whether those lakes could have held water for more than a single season in a cold climate,” said Eleanor Moreland, a planetologist at Rice University and co-author of the study, in a press release.
Moreland and colleagues’ new analysis used a climate model adapted for Martian weather patterns. On Earth, researchers can reconstruct the past using biological proxies, such as patterns in tree rings, to study ancient climates. The treeless wastes of Mars contain no easy records to analyze, so the team instead used data collected from the Mars rover Curiosity as it scuttled across the Gale Crater, a former impact site found on Mars’ equator. These machines had previously collected rock and mineral samples that could serve as proxies.
Over years of work, the authors tweaked their model’s parameters until it resembled Mars as it was 3.6 billion years ago. The research team focused on how Martian lakes might have existed at this time and named their new model Lake Modeling on Mars with Atmospheric Reconstructions and Simulations (LakeM2ARS).
The model showed that lakes, like those found in Gale Crater, didn’t need thick ice to survive as long as climate conditions were stable.
“When our new model began showing lakes that could last for decades with only a thin, seasonally disappearing ice layer, it was exciting that we might finally have a physical mechanism that fits what we see on Mars today,” said Moreland.
The simulations essentially created a virtual Martian lake and then tested its durability over a 30-Martian-year (56 Earth-year) period under different climate conditions.
“It was fun to work through the thought experiment of how a lake model designed for Earth could be adapted for another planet, though this process came with a hefty amount of debugging when we had to change, say, gravity,” said planetologist and co-author Sylvia Dee, who originally designed the model, in a press release.
Martian Lakes Survive On Thin Ice
In some simulations, a thin layer of ice atop the lake acted as an insulator — minimizing water loss, while still allowing enough sunlight through to heat the lake during warmer periods. Although the average air temperature in the simulations remained below zero for much of the time, the lake water remained at a similar depth. Importantly, such a thin ice sheet would leave little trace, explaining why there’s no evidence of thick ice sheets or glaciers on Mars.
The researchers now plan to apply their model to other Martian landscapes that show signs of ancient water. They also want to enhance their simulation by adding factors such as atmospheric change and groundwater flow.
“If similar patterns emerge across the planet, the results would support the idea that even a quite cold early Mars could sustain year-round liquid water, a key ingredient for environments to be suitable for life,” Moreland said.
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