How did the Moon form?
To help find out, NASA launched the twin
Gravity Recovery and Interior Laboratory (GRAIL)
satellites in 2011 to orbit and map the Moon's surface gravity in
Pictured above is a resulting GRAIL gravity map, with regions of
slightly lighter gravity shown in blue and regions of slightly stronger gravity shown in red.
Analysis of GRAIL data indicates that the moon has an unexpectedly shallow
crust than runs about 40 kilometers deep, and an overall composition similar to the Earth.
Although other surprising structures
have been discovered that will continue to be investigated, the results generally bolster the hypothesis that the
Moon formed mostly from Earth material
following a tremendous collision
in the early years of our Solar System, about 4.5 billion
After completing their mission and running low on fuel, the two GRAIL
Ebb and Flow,
were crashed into a lunar crater at about 6,000 kilometer per hour.
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