An Alternate Explanation for Geological Evidence of Flowing Water on Mars

[Recusant]

Maybe Mars didn't have as many open-air rivers on its surface as its geology seems to suggest. The study described in this article presents evidence in support of the idea that the features we see that we had previously thought were river beds are in fact mostly channels created by melt flow under ice caps. So, still rivers of a sort, but not necessarily as we know them.

"Early Mars was covered in ice sheets, not flowing rivers, researchers say" | ScienceDirect

A large number of the valley networks scarring Mars's surface were carved by water melting beneath glacial ice, not by free-flowing rivers as previously thought, according to new UBC research published today in Nature Geoscience. The findings effectively throw cold water on the dominant "warm and wet ancient Mars" hypothesis, which postulates that rivers, rainfall and oceans once existed on the red planet.

To reach this conclusion, lead author Anna Grau Galofre, former PhD student in the department of earth, ocean and atmospheric sciences, developed and used new techniques to examine thousands of Martian valleys. She and her co-authors also compared the Martian valleys to the subglacial channels in the Canadian Arctic Archipelago and uncovered striking similarities.

"For the last 40 years, since Mars's valleys were first discovered, the assumption was that rivers once flowed on Mars, eroding and originating all of these valleys," says Grau Galofre. "But there are hundreds of valleys on Mars, and they look very different from each other. If you look at Earth from a satellite you see a lot of valleys: some of them made by rivers, some made by glaciers, some made by other processes, and each type has a distinctive shape. Mars is similar, in that valleys look very different from each other, suggesting that many processes were at play to carve them."

[. . .]

In total, the researchers analyzed more than 10,000 Martian valleys, using a novel algorithm to infer their underlying erosion processes. "These results are the first evidence for extensive subglacial erosion driven by channelized meltwater drainage beneath an ancient ice sheet on Mars," says co-author Mark Jellinek, professor in UBC's department of earth, ocean and atmospheric sciences. "The findings demonstrate that only a fraction of valley networks match patterns typical of surface water erosion, which is in marked contrast to the conventional view. Using the geomorphology of Mars' surface to rigorously reconstruct the character and evolution of the planet in a statistically meaningful way is, frankly, revolutionary."

[Continues . . .]

Only the abstract of the paper is available:

Abstract:

The southern highlands of Mars are dissected by hundreds of valley networks, which are evidence that water once sculpted the surface. Characterizing the mechanisms of valley incision may constrain early Mars climate and the search for ancient life. Previous interpretations of the geological record require precipitation and surface water runoff to form the valley networks, in contradiction with climate simulations that predict a cold, icy ancient Mars. Here we present a global comparative study of valley network morphometry, using a principal-component-based analysis with physical models of fluvial, groundwater sapping and glacial and subglacial erosion. We found that valley formation involved all these processes, but that subglacial and fluvial erosion are the predominant mechanisms. This is supported by predictions from models of steady-state erosion and geomorphological comparisons to terrestrial analogues. The inference of subglacial channels among the valley networks supports the presence of ice sheets that covered the southern highlands during the time of valley network emplacement.

[Tank]

Interesting. It makes Perseverances mission a little less likely to find evidence of life.

[Recusant]

This doesn't rule out liquid surface water though. They say that the valley formation appears to have been mostly subglacial, but they also note "fluvial" processes. That is, rivers and streams as we know them, at least according to Wikipedia, which describes "glaciofluvial" or "fluvioglacial" as proper terms for subglacial flow, while "fluvial" relates to rivers and streams.

Perhaps there never was a warm Mars, but it seems there was a wet Mars.

[Tank]

It must have been warm in places around the volcanoes. Which on Earth do host a range of extremophile organisms. The question this raises is did the extremophiles evolve from 'normal' organisms or visa versa. If the former were the case there may never have been the more benevolent conditions to kick life off in the first place.

[Randy]

I wouldn't rule out the possibility of finding life just yet. I don't know which came first on Earth, life as we commonly know it, or life that is found in extreme environments which, until fairly recently, we didn't think was possible. Maybe Mars is one of those. Of course it depends on if there is water somewhere. Otherwise they might at least find fossils. Either would be a boon to the world.