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New, ‘strong’ evidence for ancient ocean on Mars

Posted by in Space

 

 

Courtesy of ESA and World Science staff

 

The European Space Agency’s Mars Express spacecraft has picked up strong new evidence that Mars once had an ocean, though this ocean would have been relatively short-lived, scientists say.

 

Using radar, the orbiting spacecraft detected what researchers called sediments reminiscent of an ocean floor within the bounds of previously noted, ancient shorelines.

 

Scouring more than two years of data, scientists found the Red Planet’s northern plains are covered in a light material that appears to consist of ‘sedimentary deposits, maybe ice-rich,’ said Jérémie Mouginot, one of the researchers.

 

‘It is a strong new indication that there was once an ocean here,’ added Mouginot, of the Planetary and Astrophysical Institute of Grenoble and France and the University of California, Irvine.

 

The existence of oceans on ancient Mars has been suspected before. Features reminiscent of shorelines have been tentatively identified in images from various spacecraft. However, it remains a controversial issue. Two oceans have been proposed: four billion years ago, when warmer conditions prevailed, and three billion years ago when subsurface ice melted, possibly due to heat-generating processes underground. These would have created outflow channels that drained water into low-lying areas.

 

Evidence of an ocean

 

Mars Express’s MARSIS radar instrument ‘penetrates deep into the ground, revealing the first 60-80m of the planet’s subsurface,’ said Wlodek Kofman, leader of the radar team at the Grenoble institute. ‘Throughout all of this depth, we see the evidence for sedimentary material and ice.’

 

Radar is a system for mapping unseen objects by analysing short radio waves that are sent out, then reflected back from those objects. Radar imaging can also penetrate underground.

 

‘Previous Mars Express results about water on Mars came from the study of images and mineralogical data, as well as atmospheric measurements,’ said Olivier Witasse, the space agency’s Mars Express project scientist. ‘Now we have the view from the subsurface radar,’ he added. ‘This adds new pieces of information to the puzzle but the question remains: where did all the water go?’ Mars Express is scheduled to continue investigating.

 

The newfound sediments show up as areas of low radar reflectivity, the researchers said, adding that such sediments are typically light, grainy materials that have been eroded away by water and carried to their destination.

 

This later ocean would have been temporary, though. Within a million years or less, Mouginot estimates, the water would have either frozen back in place and been preserved underground again, or turned into vapour and lifted gradually into the atmosphere. ‘I don’t think it could have stayed as an ocean long enough for life to form,’ he said, adding that to find evidence of life scientists will have to look even further back in Mars’ history when liquid water persisted for much longer periods.

 

 

A map of a proposed ocean that would have covered Mars’ northern plains around three billion years ago. (Credits: ESA, C. Carreau)

 

Source: World Science, http://www.world-science.net