Two faces: Maps show differences between the topography and gravity on both sides of the Moon. The lower layer shows areas of high (red) to low (blue) gravity. The upper layer in the image shows topography; the near side is mostly flat (green) while red areas on the far side represent cratered highlands at higher altitude (red).
Credit: Science/AAAS
"The abundance of water is a key parameter to understanding the formation and evolution of the Moon," said co-author of one study Araki Hiroshi, an astronomer at the National Astronomical Observatory of Japan in Tokyo.
The lack of water suggested by SELENE supports the theory that the Moon was formed in a giant collision between a still-molten Earth and a wandering proto-planet. Astronomers believe that such an impact would have heated the debris that became the Moon, evaporating off its water and explaining why the Moon is dry even though it is close to a watery Earth.
Astrophysicist Sarah Maddison, of Swinburne University in Melbourne, Australia, said that getting a good map of the whole Moon was an important step, because knowing the exact shape of the Moon gave researchers better information about its gravity.
"We really didn't have any data on the far side [before this]," said Maddison who was not involved with the study.
