A new map of lunar craters by NASA's Lunar Reconnaissance Orbiter is stoking a long-smouldering debate about whether the moon was hit by a sudden barrage of impactors early in its life.
The Astronomical Research Center A.R.C mentioned taht the moon is thought to have formed about 4.5 billion years ago, from the debris of a collision between Earth and a Mars-sized body. Its pockmarked surface records a lifetime of impacts, the rate of which, researchers agree, has fallen over time.
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At issue is whether there was a sudden spike of impacts 3.9 billion years ago, and if so, what caused it. The evidence for this "late heavy bombardment" comes from rocks collected by Apollo astronauts at several lunar sites, many of which appear to have been melted by impacts at around that time.
A 2005 study led by Robert Strom at the University of Arizona in Tucson suggested these early impactors came from a different source than what hit the moon afterwards. The researchers found a larger proportion of big craters in the moon's oldest "highlands" areas compared to those in younger areas of solidified lava.