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Old Mars may have been less wet than expected



A collage picture showing Mars valleys (in gray) overlaid with channels on Devon Island (in brown) and showing striking similarities.

A collage picture showing Mars valleys (in gray) overlaid with channels on Devon Island (in brown) and showing striking similarities.
image:: Anna Grau Galofre / Arizona State University

According to scientists, ice sheets and no rushing rivers have formed many Martian valleys. The new research suggests that old Mars was not as warm and wet as we thought, but an expert we spoke to remains unconvinced.

New research published in Nature Geoscience suggests that rushing rivers were not responsible for the characteristic shape of certain Martian valleys in the southern highlands of the planet. Rather, these geological features were forged by melting water that flows beneath giant glaciers in a geological process known as subglacial erosion. Old Mars, according to new research, was probably cold and icy, not the temperate humid planet that is often believed to be.

“Our study questions the widely held view that most valley networks on Mars are formed by rivers fed by precipitation,” said Gordon Osinski, co-author of the new paper and planetary geologist at Western University, in a Western Press release. “While we found evidence consistent with a small handful of valley networks formed in this way, our observations suggest that the majority have formed among ice sheets.”

Interestingly, these results, although surprising, seem to agree with the results of climate models. computer Simulations of ancient Mars indicate that the Red Planet was cold and covered with ice about 3.8 billion years ago.

For the new study, Osinski, together with Anna Grau Galofre from Arizona State University and Mark Jellinek from the University of British Columbia, examined satellite photos of 10,276 individual valleys in 66 valley networks on Mars, which they made with customized software. Their algorithm was able to adapt surface features to certain erosion processes, including glacier, subglacial, river (surface water) and sapping (groundwater) erosion.

“When you look at Earth from a satellite, you see a lot of valleys: some of rivers, some of glaciers, others of other processes, and each type has its own shape,” said Grau Galofre in an ASU Press release. “Mars is similar in that the valleys look very different, which suggests that many processes were involved in carving them.”

Mars valleys have also been compared to known subglacial features on Earth. Devon Island in the Canadian Arctic is “one of the best analogues we have for Mars here on Earth,” said Osinski, since it is a “cold, dry polar desert and we know that the icing is largely due to the cold “.

Of the 66 valley systems examined, the researchers identified 22 as formed by subglacial erosion: 14 fluvial, nine glacial, three sapping and 18 undetermined. These results are “the first evidence of extensive subglacial erosion caused by channeled meltwater drainage under an old ice sheet on Mars,” said Jellinek in the ASU press release, adding that these results “show only a fraction of the.” Valley nets with typical patterns correspond to surface water erosion, which is in marked contrast to the conventional view. “

Bruce Jakosky, geology professor at the University of Colorado and principal investigator for the Mars Atmosphere and Volatile Evolution (MAVEN) mission, described the new analysis as “interesting” but not “final”.

“Based on their numbers, there seems to be a smooth gradation between the properties of the individual valley nets,” said Jakosky in an email. “A smooth gradation of properties, but the division into a limited number of educational processes seems to be open to considerable uncertainties.”

As a result, Jakosky is not very confident about the numbers used in the study. He was also unimpressed by the relatively small sample size of 66 given the authors’ statement that “HundredsThere are valley nets on Mars.

“Except for the small number of erosion sagging, this appears to be compatible with a random distribution between the other processes,” he said. “That said, although subglacial erosion is most pronounced, it is not so dominant that it justifies the conclusion that it is the main process. That is, they state that subglacial and fluvial dominate, but it looks about the same in all processes. ”

He added, “Your conclusions should have been that all of the processes you investigated mattered, and we need to find a climate / environment that could support them all.”

Scott King, a geotechnical scientist from Virginia Tech, found the new result reasonable and even likely.

“I think the problem is that it is Mars and we have some pretty strong ideas about Mars, and sometimes that hinders our observation of the observations,” King wrote in an email. “This is one of those studies that makes us special stop and ask us Why did we accept that? everything The valley nets on Mars were fluid? Why wouldn’t there have been both river and glacier erosion on Mars? The climate models tell us that Mars was cold and icy, so these researchers asked a very logical question: “What kind of valley networks do we see?”

Indeed, the new data must be reconciled with other geological evidence from old Mars, such as the locations of former lakes and river deltas (inclusive). Jezero crater, the destination for the Mars Perseverance Rover), sound formations (as discovered from the Curiosity Rover) and even testimonials from an old one Mega tsunami on the Mars.

Old Mars was wet, but the new paper complicates our understanding of the planet’s past by showing how erosion processes other than free-flowing surface water can shape certain geological features. In the future, planetary scientists should remember this paper well, even if it is somewhat incomplete. However, it is becoming increasingly clear that ancient Mars was a complex and dynamic place.


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