NASA Grail probes ready to orbit moon

Two NASA spacecrafts launched from Florida in September are set to enter orbit around moon over the New Year's weekend to measure the gravity field and lunar interior, according to media reports on Tuesday. NASA scientists want to know the most uneven gravitational field they know of in the solar system since it will shed light on what is going on beneath the lunar surface. The twin spacecrafts are named Grail-A and Grail-B. Grail-A will enter the moon’s orbit on New Year’s Eve, Grail-B will follow on New Year’s Day. "The purpose of the GRAIL mission is to obtain gravity data on the Moon. And with that data, the scientists are able to determine the structure of the lunar interior, from crust to core," said David Lehman of NASA's Jet Propulsion Laboratory. Once in orbit, the pair will spend two months following each other around the moon. Data collection won’t begin until March. Using the gravity information, scientists can deduce what’s below or at the lunar surface such as mountains and craters and may help explain why the far side of the moon is more rugged than the side that faces Earth.