Researchers question Apollo-era evidence for the Late Heavy Bombardment
(Phys.org)—Many scientists believe that a cataclysmic series of impact events called the Late Heavy Bombardment (LHB) occurred around 4.1 to 3.9 billion years ago, during which there was a spike in asteroids colliding with the planets of the inner solar system. Among the possible explanations for the LHB is the migration of large planets to the outer solar system, disrupting objects in the asteroid belt and the Kuiper belt and flinging them toward the inner solar system. The Earth is constantly resurfaced by erosion and cratonic growth, and as a result, can't contribute much geologic data about the existence of the LHB. Much of the evidence is therefore derived from the moon—specifically, from Apollo-era lunar samples returned to Earth in the 1960s and 1970s. Researchers used argon dating to determine age spectra of lunar rocks found in three major lunar basins. The so-called "plateau ages" of these rocks, as determined from...