The astronomers had successfully uncovered the secret of the moon's irregular gravity using the data of the Grail spacecrafts.

The Gravity Recovery and Interior Laboratory, shortly known as Grail, was NASA's science mission formed to study the gravitational field of the moon. The mission sent two spacecrafts which will work together to measure the varying distance between each other. The measurements gathered will be used to map the gravitational field of the moon. The spacecrafts ended their mission in December 2012 by crashing into the moon to collect data about the 'mascons'.

The mascons, short term for mass concentrations, are sitting in the surface of the moon. They are so dense that they can vary the gravity of the moon. The variations were captured by the spacecrafts which NASA interpreted as measurements. Mascons were nothing new since the astronomers were already aware of it since the Apollo mission but they haven't figured out the cause of it.

In a journal Science published last May 30, a study explained the cause of the irregular gravity of the moon. Jay Melosh, lead author of the study and a geophysicist at Purdue University in West Lafayette, Ind., and his team showed the exact location of the mascons and used computer technology to create a model of it.

The mascons are located in two huge craters of the moon that may have been formed when an asteroid hit the moon billions of years ago. The first crater is on the lunar nearside-the side of the moon facing the Earth-while the other is on the far side-the dark side.

The researchers concluded that the asteroids that the asteroids that hit the moon were the cause of the irregular gravitational field. The more craters formed in the moon, the more mascons are deposited, thus resulting to more variations.

The team is still in the process of developing new models for the presentation of this discovery.