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Second U.S. Moon Probe Enters Orbit

The GRAIL mission will fly twin spacecraft in tandem orbits around the moon to measure its gravity field in unprecedented detail. (undated NASA artist image)
The U.S. space agency NASA says two unmanned spacecraft are now orbiting the moon as part of a mission to measure lunar gravity and investigate how the moon evolved.

NASA said the second GRAIL spacecraft on January 1 joined the first GRAIL probe, which went into lunar orbit the day before.

The twin GRAIL probes – GRAIL being short for “Gravity Recovery And Interior Laboratory” – arrived near the moon after launching from earth in September and making a 3.5-month flight.

Scientists say they hope the probes will help them gain insight into how the moon was formed and what the moon’s interior may resemble.

The two probes are planned to fly above the moon and, using measuring instruments, map the moon’s uneven gravitational fields.

Scientists say the mission should provide more information about the mountainous far side of the moon that doesn’t face earth, and also test a hypothesis that earth once had two moons that collided and formed one.

compiled from agency reports