The Gravity Recovery and Interior Laboratory satellites launched Saturday morning aboard a Delta II rocket, bound on a mission to study the interior of the moon. (Credit Thom Baur, United Launch Alliance)

The launch comes after several days of delays due to weather, though the Dec. 31 and Jan 1. arrivals of the satellites are not expected to change.

From the Christian Science Monitor:

The $496 million mission relies on a pair of identical orbiters that will swing, single-file, around the moon's poles for some 82 days gathering exquisitely precise measurements of the moon's gravity field. (GRAIL stands for Gravity Recovery and Interior Laboratory.)

NASA hopes the information about the lunar gravity will reveal more about the interior structure of the moon and its formation, also showing whether the core is made of solid iron or titanium oxide.

NASA says the moon presents a good opportunity to study formation of early planets, since its lack of forceful internal geological processes preserves its early formations.

The satellites will also carry four cameras that will allow schoolchildren to order pictures of the moon.  Over 1,100 schools signed up as of Saturday, according to the Associated Press.

Reach writer Shea Huffman here.