NASA has postponed the launch of twin moon gravity-mapping spacecrafts until Saturday to give engineers time to investigate a glitch with the Delta 2 rocket that will carry the probes into space.

The Gravity Recovery and Interior Laboratory (GRAIL) was originally slated to blast off Thursday, but strong winds forced NASA to stand down for the day.

The agency was hoping to make a liftoff attempt Friday, but the Delta 2's propulsion system developed a problem that was detected while the rocket was drained of fuel after Thursday's scrubbed launch, NASA said.

NASA now plans to wait until the weekend to allow time to review data from the propulsion system.

Current forecasts predict more favorable launch weather over the weekend, with a 60 percent chance of acceptable conditions on Saturday.

The twin satellites, named GRAIL-A and GRAIL-B, will spend several months orbiting the moon.

The $496 million GRAIL mission will study the interior of the moon and construct accurate and detailed maps of its gravity field.

Scientists will measure the entire gravity field of the moon by keeping a precise track of the distance between the two probes.

Observations from the three-month mission are expected to help scientists understand the origin of the moon, its composition and its evolutionary history.

It is hoped to figure out what's beneath the moon's surface, all the way down to the core.

Earlier this week, NASA released new images of the 1969-72 lunar landing sites, which the space agency said were the sharpest photos ever taken from space.

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