New Scars Found on Moon, Hint at "Recent" Tectonic Activity
Long trenches called graben suggest early moon wasn't fully melted.
The presence of the long, thin valleys—known as graben—suggests that the moon has undergone relatively recent tectonic activity, within the past 50 million years or so.
That activity in turn hints that the moon may not have been entirely melted when it first formed roughly 4.6 billion years ago. Instead the early moon likely had a solid core covered by a global ocean of molten rock.
(Related: "Earth Had Two Moons, New Model Suggests.")
The young graben were discovered on the moon's far-side highlands and in volcanic plains using images from NASA's Lunar Reconnaissance Orbiter Camera (LROC), a high-resolution instrument aboard the orbiting spacecraft, which launched in 2009.
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