Friday, January 8, 2010

If I can't sleep at night, I get up and read about Mars... it was wet and warm a very long time ago.

Contrary to what most people think, Mars was a warm and wet planet 3 billion years ago, new research suggests. Writing in the journal Geology, scientists from Imperial College London and University College London (UCL) in the UK speculate that the 'red planet' was actually home to huge lakes (each some 20km wide) generated by melted ice during the Hesperian Epoch, the second of three Martian geologic epochs marked by lava flows.

Past studies suggested that Mars was indeed wet and warm, but the loss of most of its atmosphere between 4 billion and 3.8 billion years ago, before the Hesperian Epoch, triggered a cold and arid environment. Thanks to this latest research, fuelled by detailed images from NASA's Mars Reconnaissance Orbiter that is currently orbiting the red planet, the scientists deduce that Mars actually sustained warm and wet periods.

The new images show a number of small, winding channels that connect 'flat-floored depressions' in the surface of the planet, located specifically above Ares Vallis - a huge, 2,000km gorge across the equator. The researchers speculate that only running water could have created these channels. Ice turning directly into gas could not have been responsible, they add.

Experts at NASA (National Aeronautics and Space Administration) also believe that these channels were generated by Martian lake water flowing between the depressions around 3 billion years ago.

Scientists in the past believed that the depressions were created by sublimation, a process where an element or compound such as ice changes from its solid state into a gas without becoming liquid.

So what could have elicited the warmer and wetter environment? Shifts in the planet's orbit, stronger volcanic activity or even meteorite impacts were probably responsible for the planet's warmer and wetter periods, the researchers say. The higher temperature generated gases that thickened the atmosphere for a short period, effectively trapping more sunlight and making it warm enough for water to be sustained.

'Most of the research on Mars has focused on its early history and the recent past,' said Dr Nicholas Warner from Imperial College London's Department of Earth Science and Engineering, the lead author of the study. 'Scientists had largely overlooked the Hesperian Epoch as it was thought that Mars was then a frozen wasteland. Excitingly, our study now shows that this middle period in Mars' history was much more dynamic than we previously thought.'

For his part, UCL's Professor Jan-Peter Muller, who was responsible for mapping the 3D (three dimensional) shape of Mars' surface, said, 'We can now model the 3D shape of Mars' surface down to sub-metre resolution, at least as good as any commercial satellite orbiting the Earth. This allows us to test our hypotheses in a much more rigorous manner than ever before.'

The findings of this study could be a boon for scientists investigating the possibility of life on Mars. According to the researchers, the lake beds indicate regions on Mars that could have been warm and wet, and which could have been ideal locations for microbial life. 'These areas may be good targets for future robotic missions,' they say.

The researchers plan to investigate other areas along the planet's equator in order to determine the breadth of the lakes' existence during the Hesperian Epoch. Next on their list is 'Chryse Planitia', a region at the mouth of Ares Vallis. Initial data suggest lakes existed in this area as well.

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