[meteorite-list] Ancient Martian Air 'Too Cold and Thin' for Liquid Water

[Ron Baalke]

http://www.ibtimes.co.uk/ancient-martian-air-too-cold-thin-liquid-water-1444741

Ancient Martian Air 'Too Cold and Thin' for Liquid Water
By Hannah Osborne 
International Business Times
April 14, 2014 

The air on Mars 3.6 billion years ago was too cold and thin for liquid 
water to form, scientists have said.

Nasa's Rover explorers had found evidence that water was present on the 
Red Planet in its liquid state billions of years ago and there was enough 
for rivers and lakes to exist.

However, research published in the journal Nature Geoscience suggests 
that water formation on Mars was the result of occasional warm spells

According to Nature magazine, researchers are increasingly finding evidence 
to suggest that Mars was not warm and wet during its early history, which 
would have required an atmosphere much thicker than modern times.

Edwin Kite, a planetary scientist from Princeton University, said it is 
very unlikely Mars was able to hold a thick atmosphere for more than a 
few thousand years at a time.

He said the size of the planet's craters provide evidence to support their 
theory. Using images from the Mars Reconnaissance Orbiter, the team catalogued 
over 300 craters over 84,000 square kilometres.

If Mars had a thicker atmosphere, small objects would have broken up as 
they passed through, like they do with Earth, rather than surviving intact 
to create big blast craters.

Only 10% of the craters had diameters of 50m or less, with many believed 
to be the remnants of ancient craters being 21m or smaller.

After using a computer model to look at a simulation of incoming objects 
striking Mars with different atmospheric densities, the researchers found 
it was probably no more than 150 times its current state. This means it 
was about a third as thick as it needed to be to host liquid water and 
consistently keep the surface temperature above freezing.

James Head, from Brown University in Rhode Island, said: "This is an excellent 
paper. It bolsters previous studies that suggest early Mars was icy."

Kite said the most likely scenario for water on Mars was the red planet 
being intermittently warm through greenhouse gasses from volcanic activity 
- enough to thicken the atmosphere for a few millennium: "That's plenty 
enough to get fluid flowing [on Mars]," he said.