Dense molten rocks in the interior of the moon

A 2011 NASA study [1] of moonquakes, based on seismometer measurements made during the Apollo missions, revealed a surprising new view of the lunar interior: the deepest parts of the rocky mantle of the Moon, at depths between 1200 and ~1350 km, appear to contain large amounts of molten rock (magma). In fact, up to 30 per cent of this deep layer may be molten. On Earth, such melt percentages would be accompanied by the formation of volcanoes, because magma formed in the interior of the Earth is less dense than the rock it originates from. This density difference provides a driving force for upward transport, leading to volcanic eruptions at the surface. However, despite the presence of large amounts of magma in its interior, the Moon has no active volcanoes. We have found an explanation for this apparent discrepancy by subjecting synthetic Moon rocks to extreme pressures and temperatures and measuring the density of the resulting magma using in situ techniques at beamline ID27