THE MOON'S HUGE HIDDEN VALLEY SYSTEM

A new study reported in Nature magazine identifies a huge rectangular buried feature on the Moon:
http://www.bbc.co.uk/news/science-environment-29447159

The 2,500 km wide structure is believed to be the remains of old rift valleys that late became filled with lava. Centred on the Procellarum region, the feature is revealed in gravity maps  acquired by Nasa's grail mission in 2012. However, it is possible to trace the outline of the rectangular region in ordinary photographs.

Professor Jeffery Andrews-Hanna said 'It's really amazing how big this feature is. It covers about 17% of the surface of the Moon.' He notes that the Procellarum  region contains a lot of naturally occurring radioactive elements, including uranium, thorium and potassium. On the early Moon these would have heated the crust which, when cooled, would have contracted. This shrinking would have ripped the surface, opening deep valleys.

This study is further proof of the value of the Grail mission, led from MIT. The two Grail satellites mapped changes in the pull of the Moon's gravity.

Comment: Recent exploration of the solar system has shifted away from the Moon, to Mars and beyond. It's good news to find scientific discoveries continuing on our closest neighbour in space.