The incredible images that reveal the full extent of the moon's battered past
Nasa says images show lunar surface is 'far more broken up' than previously thoughtGravity maps were produced by twin Nasa spacecraft
19:59 GMT, 5 December 2012
The moon took quite a beating in its early days, more than previously believed, scientists reported Wednesday.
This surprising new view of the moon comes from detailed gravity mapping by twin NASA spacecraft, which slipped into orbit around the celestial body earlier this year to peer into the interior.
Researchers have long known that the moon and rocky planets – including the Earth – suffered heavy bombardment from asteroids and comets during their formative years billions of years ago.
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The variations in the lunar gravity field as measured by NASA's Gravity Recovery and Interior Laboratory (GRAIL) during its primary mapping mission from March to May 2012
These maps of the moon show the 'Bouguer' gravity anomalies on the lunar surface caused by collisions
HOW IT WAS CREATED
The map was created by the dual GRAIL spacecraft transmitting radio signals to define precisely the distance between them as they orbit the Moon in formation.
As they fly over areas of greater and lesser gravity caused by visible features, such as mountains and craters, and masses hidden beneath the lunar surface, the distance between the two spacecraft will change slightly.
Now they are just starting to realize the extent.
The moon is 'far more broken up and shattered than we've seen before,' said mission chief scientist Maria Zuber of the Massachusetts Institute of Technology.
Measurements by the NASA spacecraft called Ebb and Flow also found that the moon's crust, or outermost layer, is much thinner than scientists thought – only about 25 miles thick.
Results were presented Wednesday at a meeting of the American Geophysical Union meeting in San Francisco and published online in the journal Science.
Though past missions have measured lunar gravity – about one-sixth Earth's pull – Ebb and Flow are the first spacecraft dedicated to this pursuit.
To collect data, the washing machine-size spacecraft flew in formation, orbiting about 35 miles above the moon's surface.
Their positions allowed them to look deep inside.
Underground lunar dykes identified by GRAIL are 50 times longer and 1,000 times wider than the dyke on Earth seen here on the left
The resulting gravity maps revealed an exceptionally smooth lunar interior – consistent with it being pulverized by impacts.
Fracturing extended deep into the crust and may have penetrated the mantle, scientists said.
The maps also exposed numerous lunar features in greater detail than before including volcanoes, basins and craters.
A provocative paper published last year hypothesized that Earth once had two moons that collided early on in the solar system's history to create the orb that graces the sky today.
But Zuber said high-resolution mapping by the spacecraft did not find evidence for that.
The mission is scheduled to end later this month when Ebb and Flow crash into the moon.
A 300-mile-long (500 kilometer-long) linear gravity anomaly on the far side of the moon revealed by gravity gradients measured by NASA's GRAIL mission
A linear gravity anomaly intersecting the Crisium basin on the nearside of the moon has revealed by the GRAIL mission
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