IT HAS long been a mystery why most lunar “seas”—which are actually
ancient lava flows—are on the side of the Moon nearest Earth.
Now researchers at the Massachusetts Institute of Technology and Brown
University in Rhode Island suggest that as the Moon solidified 4 million years
ago, radioactive heating near the core formed an unstable layer of lava. Because
of the small size of the Moon’s metallic core, says researcher Shijie Zhong,
only a single plume rose towards the surface, causing the asymmetry (Earth
and Planetary Science Letters, vol 177, p 131). He speculates that the
higher…
