What Was the GRAIL Mission About?

What Was the GRAIL Mission About?

GRAIL spacecraft Ebb and Flow


You may have heard about NASA's GRAIL mission but what was it about and why did they then deliberately crash the spacecrafts into the moon afterwards. Read on for more information.


What Was the GRAIL Mission?


GRAIL stands for Gravity Recovery and Interior Laboratory. It was designed to map how gravity changes over the entire surface of the moon. This has been done before but this mission aimed to do it 100 to 10,000 times more detailed. The mission was a great success and has provided some incredible detailed images of the moon's gravity.

Image credit: NASA/JPL


How Did They Make Such Detailed Maps?


The maps were created by flying two spacecraft called Ebb and Flow in a tight formation about 35 miles above the moon's surface. They were able to precisely measure the distance between themselves many times a second. If the front craft was pulled toward an area with more gravity it would accelerate as it was drawn toward the surface. This change in speed would be detected. Here are some of the maps they produced. The first one is called "free-air gravity" and demonstrates the changes in gravity across the moon. The next one is the crustal thickness of the moon. The images are credited to: NASA's Goddard Space Flight Center Scientific Visualization Studio.

grail free air gravity map
grail thickness of moon crust map


What Do These New Maps Mean?


These new maps demonstrated some amazing unknown facts about the moon. It is now evident that the crust is much thinner than thought. It was always thought to be about 40 miles thick. However, the GRAIL mission has identified the crust is probably less than 27 miles thick. The GRAIL mission has also shown that the moon is more like a pile of rubble rather than a solid mass of rock. It has large spaces within it. This is probably as a result of the heavy bombardment of meteorites over the years. This new information wil help determine how other celestial bodies may have formed in our Solar System.


So Why Did NASA Crash Ebb and Flow Into the Moon?


Ebb and Flow were deliberately crashed into the moon at a speed of 3,760 mph. This was because they didn't have enough fuel or altitude to continue the mission. The spacecraft emptied their remaining fuel loads just before impact. This should help to calculate the amount of fuel required for future missions. A great end to a great mission. 

You can all the information you desire about this mission here:

http://solarsystem.nasa.gov/grail/home.cfm


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