Article Posted on : - Sep 11, 2011

NASA's GRAIL mission blasts off from Cape Canaveral Air Force Station, Fla. Photo: NASA,

WASHINGTON (AFP): NASA on Saturday has launched a USD 500 million pair of washing-machine-sized satellites on a mission to map the Moon's inner core for the first time.

The twin spacecraft took off from Cape Canaveral Air Force Station in Florida on a three-month journey to the Moon at 9:08 am local time aboard a Delta II rocket.

"Liftoff of the Delta II with GRAIL, on a journey to the center of the moon," NASA commentator George Diller said upon blast-off of the GRAIL mission, which stands for Gravity Recovery and Interior Laboratory.

High upper level winds delayed the first launch attempt on Thursday, and also briefly set back Saturday's launch.

The duo will travel to the Moon for more than three months, arriving into a polar lunar orbit one after the other around New Year's Day.

With one spacecraft trailing the other, the plan is for the two to use gravity tools to map the terrain beneath, revealing the contents of the inner core of the Moon, about which little is known.

The mission should also shed light on the unexplored far side of the Moon, and perhaps tell scientists whether there was once a second Moon that fused with ours.

"GRAIL will be the first mission to determine the internal structure of the Moon," programme scientist Bobby Fogel told reporters this week.

"We have used gravity science before to try to gain some insight as to what is going on inside the Moon, however these have been very primitive attempts.

"If those previous attempts could be likened to a magnifying glass, GRAIL by contrast would be a high-powered microscope."

Scientists believe that the Moon was formed when a planet-sized object crashed into the Earth, throwing off a load of material that eventually became what we now recognize as our planet's airless, desolate satellite.

How it heated up over time, creating a magma ocean that later crystallized, remains a mystery, despite 109 past missions to study the Moon since 1959, and the fact that 12 humans have walked on its surface.

A recent hypothesis that there may have been two Moons that slowly merged into each other can also be tested with this mission, said principal investigator Maria Zuber.

"If we want to reconstruct the evolution of the Moon over time, we certainly need to reconstruct the temperature structure of the Moon right now," she said.

Little is known for certain about what lies inside the Moon. The widely held belief that there is a small solid iron core surrounded by a liquid iron core is unproven, said Zuber.