Nasa on the track of lunar Grail

NASA has launched twin probes called Grail to the Moon to map tiny variations in the pull of gravity.

The information should give scientists fresh insight into the internal structure of Earth’s satellite and is expected to help explain many mysteries, such as why the far side of the Moon looks so different from that of the near side, with its swathe of dark volcanic plains. The data also will be an invaluable navigation tool for future exploration, enabling more precise landings.

A Delta rocket sent the Grail twins on their way from Cape Canaveral in Florida yesterday. The journey is a slow cruise, however. The duo are not expected to enter into the Moon’s orbit until the turn of the year.The near side of the Moon is covered in smooth, dark material created by magma flooding on to the surface. The far side is more rugged, with a thicker crust pock-marked by impact craters.

“The improvement that Grail will have for the gravity field on the nearside is a factor of 100 better than we have now, and on the farside it is a factor of 1,000,” said Grail programme scientist Dr Robert Fogel.

“Imagine trying to see something microscopic with your own eyes and then putting a lens in front of them that has 100 times power or 1,000 times power – it becomes a different world; and that’s what we’ll get with Grail.”

Grail is an acronym for gravity recovery and internal laboratory.