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Lakes, snowmelt-fed streams formed on Mars much later than previously thought: NASA report

The region on Mars where the researchers focused their observations is called Arabia Terra on the planet’s northern side

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Valleys much younger than well-known ancient valley networks on Mars are evident near the informally named "Heart Lake" on Mars. (NASA/JPL-Caltech/ASU)
  • Mars may have been wet much later than previously thought, upping the chance the Red Planet could have hosted microbial life
  • The region on Mars where the researchers focused their observations is called Arabia Terra on the planet’s northern side
  • They determined the area was likely wet between two and three billion years ago, which is considerably later than what most scientists previously thought

Sept 18, 2016: Mars may have been wet much later than previously thought, upping the chance the Red Planet could have hosted microbial life.

Using data from NASA’s Mars Reconnaissance Orbiter, researchers say lakes and streams appeared on Marks a “billion years after a well-documented, earlier era of wet conditions on ancient Mars.” The study appears in the Journal of Geophysical Research, Planets.

“We discovered valleys that carried water into lake basins,” said Sharon Wilson of the Smithsonian Institution, Washington, and the University of Virginia, Charlottesville. “Several lake basins filled and overflowed, indicating there was a considerable amount of water on the landscape during this time.”

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The region on Mars where the researchers focused their observations is called Arabia Terra on the planet’s northern side.

“One of the lakes in this region was comparable in volume to Lake Tahoe,” Wilson said, referring to a California-Nevada lake that holds about 45 cubic miles (188 cubic kilometres) of water. “This particular Martian lake was fed by an inlet valley on its southern edge and overflowed along its northern margin, carrying water downstream into a very large, water-filled basin we nicknamed ‘Heart Lake.’

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Researchers say the Heart Lake valley system is about 150 kilometres long. Heart Lake, they say could have held 2,790 cubic kilometres of water, more than Lake Ontario.
The region may not have been wet year round, perhaps depending on seasonal melting of ice and snow to replenish the liquid water.

To come up with a timescale of when the water was there, the researchers examined 22 impact craters and “assessed whether or not the valleys carved into the blankets of surrounding debris ejected from the craters, as an indicator of whether the valleys are older or younger than the craters.”

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They determined the area was likely wet between two and three billion years ago, which is considerably later than what most scientists previously thought.

“The rate at which water flowed through these valleys is consistent with runoff from melting snow,” Wilson said, “These weren’t rushing rivers. They have simple drainage patterns and did not form deep or complex systems like the ancient valley networks from early Mars.”

So while Mars might have been wet later, the question still remains if the planet was habitable.

“A key goal for Mars exploration is to understand when and where liquid water was present in sufficient volume to alter the Martian surface and perhaps provide habitable environments,” said Mars Reconnaissance Orbiter Project Scientist Rich Zurek of NASA’s Jet Propulsion Laboratory, Pasadena, California. “This paper presents evidence for episodes of water modifying the surface on early Mars for possibly several hundred million years later than previously thought, with some implication that the water was enplaced by snow, not rain.” (VOA)

 

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Heavy Rain shaped the Martian Landscape Billions of Years Ago: Study

The rain appears to have slowly changed over time, researchers said, noting that changes in the Martian atmosphere influenced how heavy the rain was, particularly the size of the raindrops.

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The Hubble Space Telescope took this close-up of Mars when it was just 88 million kilometers away. This image was assembled from a series of exposures taken over 36 hours. A new study posits that heavy rain may have once fallen on the Red Planet. (NASA). VOA

Washington DC, May 21, 2017: Heavy rain shaped the Martian landscape billions of years ago, according to a new study.

According to researchers at the Smithsonian Institution and the Johns Hopkins University Applied Physics Laboratory, rain on Mars once carved river beds and created valleys much like rain on Earth has, and does. It no longer rains on the Red Planet, and the water that remains is mostly in the form of ice.

The rain appears to have slowly changed over time, researchers said, noting that changes in the Martian atmosphere influenced how heavy the rain was, particularly the size of the raindrops.

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When Mars formed 4.5 billion years ago, it had a much thicker atmosphere and higher atmospheric pressure. Pressure, researchers say, influences the size of raindrops.

A view of the surface of Mars taken at the "Intrepid" crater by the Opportunity Mars Rover on November 11, 2010. (NASA/JPL-Caltech/Cornell University)

A view of the surface of Mars taken at the “Intrepid” crater by the Opportunity Mars Rover on November 11, 2010. (NASA/JPL-Caltech/Cornell University)

They say that early in the planet’s history, the rain would have actually been more like fog, so it would unlikely have made much of an impact on the terrain. But as the atmosphere thinned over time, larger raindrops could form and were heavy enough to “cut into the soil” changing the shape of craters and leading to running water that could have carved valleys.

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Specifically, researcher say the atmospheric pressure on the Red Planet was about four bars, compared to one bar on Earth today. This means the raindrops could not have been bigger than three millimeters across. Over time the pressure dropped to 1.5 bars allowing for larger drops measuring about 7.3 millimeters across.

Water-carved valleys on Mars appear to have been caused by runoff from precipitation, likely meltwater from snow. Early Martian precipitation would have fallen on mountainsides and crater rims.

Water-carved valleys on Mars appear to have been caused by runoff from precipitation, likely meltwater from snow. Early Martian precipitation would have fallen on mountainsides and crater rims.

“By using basic physical principles to understand the relationship between the atmosphere, raindrop size and rainfall intensity, we have shown that Mars would have seen some pretty big raindrops that would have been able to make more drastic changes to the surface than the earlier fog-like droplets,” said Ralph Lorenz of John Hopkins APL.(VOA)