NASA's latest mission aims to find out what goes on beneath the Moon's surface

Two of NASA's spacecraft have just reached lunar orbit, which means they are circling around our Moon. The mission, which is the first of the year 2012, focuses on measuring the strength of gravity caused by lunar mass. We can use this information to tell what goes on beneath the surface of the Moon. In turn, our newfound knowledge will need to explain how the Earth and Moon came to be in our part of the Solar System.

Radio signals
The two lunar orbiters, named Grail-A and Grail-B will be communicating with each other by sending out radio signals. That enables them to measure the distance between them, which will vary because of the changing gravitational field. Grail-A and Grail-B are currently circling the Moon at an altitude of 55 kilometres, and will start performing measurements in March. 

Hidden masses

Differences in gravity can be caused by large collections of mass, such as a mountain. However, when such features are absent, an increase in the gravitational force field points at larger masses beneath the surface, which tells us something about the composition of the Moon. According to NASA, finding out what goes beneath the surface will also tell us the history of how the Moon, and correspondingly the Earth, came to be during the creation of the Solar System.

Outlook
It is intriguing how a relatively simple experiment, measuring the distance between two points by conventional radio transmission can tell us something about the history of the Solar System, provided measurements go well. Additionally, in an effort to make the project known among us Earth dwellers, NASA will allow American students to request photos from the moon, taken by the two spacecraft. It is likely that it will take quite a while before we can draw the first solid conclusions based on the data Grail-A and Grail-B gather.