GRAIL Explores the Moon
Measurements of the Moon's gravity field by radio tracking of NASA's two GRAIL spacecraft have provided our most detailed view ever of the interior structure of a planetary body other than Earth.
The densities of Apollo lunar rocks were measured using a laser scanner in the Lunar Sample Laboratory at NASA's Johnson Space Center. The results were used in modeling GRAIL gravity observations. This Apollo 14 sample is a breccia produced during the formation of the Imbrium impact basin.
The Marius Hills basaltic dome field is the largest volcanic field on the Moon. GRAIL gravity data reveal that the domes were fed by a magma chamber that was 200 to 250 kilometers across and 3 to 6 kilometers thick.
The Gruithuisen volcanic domes are 13 to 20 kilometers across and 1 to 1.3 kilometers tall. GRAIL gravity data show that these domes have a low density that is consistent with porous rhyolite (a type of volcanic rock similar to granite).
The Orientale basin is the youngest large impact basin on the Moon. GRAIL gravity data show that the impact melt sheet in the basin center is 10 kilometers thick and also reveal the presence of faults beneath some of the mountainous basin rings. This image shows the gravity data draped over a shaded relief topography image of the basin (red is higher than average gravity, blue is lower than average gravity).
Dr. Walter Kiefer
Walter Kiefer is the associate director at the Lunar and Planetary Institute. He uses computer models to study the internal structure and thermal evolution of the Moon, Mars, and differentiated asteroids. He was a member of the science team for NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission and is helping to design possible future missions to explore Venus.
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