Both GRAIL craft orbiting the moon

Cheers erupted in mission control at the Jet Propulsion Laboratory in California as an engine firing appeared successful Sunday evening to put a second GRAIL spacecraft in orbit around the moon, where it will fly with its twin to map the moon's gravity field.

A 39-minute engine firing slowed the craft so the moon’s gravity could capture it. The first craft dropped into orbit after a similar maneuver on Dec. 31.

"NASA greets the new year with a new mission of exploration," said NASA Administrator Charles Bolden in a statement. "The twin GRAIL spacecraft will vastly expand our knowledge of our moon and the evolution of our own planet."

A twitter feed for JPL announced the mission's latest success Sunday and read, "It's going to be a great 2012!"

The unmanned probes on the $496-million GRAIL mission, short for Gravity Recovery and Interior Laboratory, will start in March to map the moon's lumpy gravity field in detail 100 to 1,000 times better than existing surveys.

The two craft will fly about 34 miles above the moon’s surface, measuring how gravity affects the distance between them. The precise map of the gravitational field will reveal what is going on below the moon’s surface, from the crust to the core. The knowledge could help scientists learn more about the Earth.

For more information about GRAIL visit: http://www.nasa.gov/grail.