Thursday, 25 April, 2019

River water persisted on Mars much later than thought

Expose R2 in space The Expose R2 facility
Cary Marshall | 30 March, 2019, 14:31

To understand how Martian rivers even existed, scientists analyzed satellite snaps of more than 200 ancient Martian riverbeds spanning over a billion years.

Satellite images and data from Nasa's Curiosity rover indicate that numerous rivers were twice as wide as those on Earth.

This complicates the picture for scientists trying to model the ancient Martian climate, said lead study author Edwin Kite, assistant professor of geophysical sciences and an expert in both the history of Mars and climates of other worlds.

They may also have persisted until less than one billion years ago, the evidence suggests. Geological features show that the land had been sculpted by flowing water, while NASA's rovers collected evidence in support of an ancient wet climate-including a Martian rock with clay minerals.

Heggy and Abotalib, who have long studied subsurface aquifers and groundwater flow movement on Earth and in desert environments, found similarities between the groundwater moving mechanisms in the Sahara and on Mars. What's more, these organisms could have been living for millions of years and if it can be proven that water remains beneath Mars' surface, then they could be living even up to now.

The planet has had a very thin atmosphere throughout its history and only received a third of the sunlight of present-day Earth, which shouldn't be enough heat to hold liquid water.

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Now, researchers at the USC Arid Climate and Water Research Center (AWARE) have published a study that suggests deep groundwater could still be active on Mars and could originate surface streams in some near-equatorial areas on Mars. By measuring the steepness, width, and size of the rounded pebbles found in each canal, the researchers were able to learn more about how much water flowed through them and at what speed.

The findings are a mystery, because scientists had thought the Red Planet was losing its atmosphere and drying out during this time.

"It actually makes the problem of what's allowed early Mars to be warm and wet-which is already a hard problem-more difficult", Edwin Kite, a planetary scientist at the University of Chicago who authored the study, said. Ironically, the lack of water and atmosphere responsible for this slow erosion allowed researchers to better study these former rivers. That suggests the average daytime temperatures were above the freezing point, pointing toward a strong greenhouse effect. You would expect them to wane gradually over time, but that's not what we see. The rivers get shorter-hundreds of kilometers rather than thousands-but discharge is still strong. That lasted right up until the end of Mars' more wet era, which ended around a billion years ago.

"It's possible the climate had a sort of on/off switch, which tipped back and forth between dry and wet cycles".

"Our work answers some existing questions but raises a new one". The new findings make scientists wonder which of the theories is wrong- the climate models, the atmosphere evolution models, or the basic understanding of inner solar system chronology.

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