Nectarian System(nek-tair -ee-ăn) One of the stratigraphic systems of the Moon, defined by the deposits of the Nectaris Basin and covering the period from 3.92 to 3.85 billion (109) years ago. It includes nearly four times as many large craters as the Imbrium Basin, and possibly some volcanic deposits. The Pre-Nectarian System is the oldest lunar stratigraphic system, covering the period from the Moon's origin and formation of the lunar crust to the Nectaris impact, i.e. 4.6 to 3.32 billion years ago. It includes crater and basin deposits from this period. See also Copernican System; Imbrian System.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006