US probes begin journey to try and find out what's inside the Moon

Two US spacecraft rocketed towards the Moon on the first mission dedicated to measuring lunar gravity and determining what's inside.

CAPE CANAVERAL, FLORIDA // Two US spacecraft rocketed towards the Moon yesterday on the first mission dedicated to measuring lunar gravity and determining what's inside Earth's orbiting companion.

The US space agency Nasa launched the near-identical probes, named Grail-A and Grail-B, aboard a small Delta II rocket to save money. It will take nearly four months for the unmanned spacecraft to reach the Moon, a long, roundabout journey compared with the three-day trip that Apollo astronauts took four decades ago.

"Grail, simply put, is a journey to the centre of the Moon," said Ed Weiler, the head of Nasa's science mission directorate.

The world has launched more than 100 missions to the Moon since the Soviet Union's Luna probes in 1959. That includes Nasa's six Apollo moon landings that put 12 men on the lunar surface.

Nasa's Grail spacecraft - each the size of a washing machine - will not land on the Moon but will conduct their science survey from lunar orbit.

Beginning in March, once the spacecraft are orbiting just 55 kilometres above the Moon's surface, scientists will monitor the slight variations in distance between the two to map the Moon's entire gravitational field. The measurements will continue until May.

"It will probe the interior of the Moon and map its gravity field 100 to 1,000 times better than ever before. We will learn more about the interior of the Moon with Grail than all previous lunar missions combined," Mr Weiler said.

At the same time, four cameras on each spacecraft will offer schoolchildren the opportunity to order up whatever pictures of the Moon they want.

The entire Grail mission costs US$496 million (Dh1.82bn).