Andrew Purcell, online producer
(Image: ESA/DLR/FU Berlin (G. Neukum))
Now in the ninth year of its mission, the European Space Agency's Mars Express orbiter has sent back images of the Red Planet's mysterious Syrtis Major region - once thought to be a shallow sea.
Syrtis Major was first discovered in 1659 by physicist and astronomer Christaan Huygens, who used its appearance during the planet's rotation to help calculate the length of a day on Mars.
We now know that it is not water, but sand and dust which cause the
region's shape to change over time. The dispersal patterns of the
lighter-toned dust and darker-toned sand in the image show the
prevailing direction of the wind.
The region is also now known to have volcanic origins, with lava
flows and partly-filled impact craters visible in the image. The number
and size of these impact craters has enabled scientists to calculate
that the Syrtis Major region is approximately 3 billion years old.
Despite notions of present-day oceans on Mars having long been
dismissed, Mars Express has also recently added to the evidence
suggesting that there may indeed have once been oceans on the Red
Planet. Features resembling ancient shorelines have previously been
identified in images from several spacecraft and Mars Express has now
used radar to detect sediments reminiscent of an ocean floor within the
boundaries of these previously identified ancient shorelines.
"It is a strong new indication that there was once an ocean here," says Jérémie Mouginot of the Grenoble Institute of Planetology and Astrophysics (IPAG) and the University of California, Irvine.
Mouginot
says an ocean first existed 4 billion years ago, when warmer conditions
prevailed on Mars. A second ocean may have formed a billion years later
when subsurface ice melted following a large impact, creating outflow
channels that drained the water into areas of low elevation. The search for life, meanwhile, goes on.
http://www.newscientist.com/
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