Mysterious dark patches dot Mercury's surface

The Messenger probe's second flyby of Mercury earlier this month has provided the first global view of the pockmarked planet, hinting at a complicated mineral structure beneath the surface and more glimpses of the planet's volcanic history.
Messenger flew just 200 kilometres above the planet's surface on 6 October to image 30% of the planet that had never been photographed by spacecraft. The manoeuvre was the second of three flybys designed to place the probe into orbit around Mercury in 2011.
The pass revealed more patches of an unknown dark, bluish material that had previously been seen on the planet's surface

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