A 8.2 Ma Age for the Lunar

Introduction: The 22 km ∅ crater “Giordano Bruno” is the youngest lunar crater of its size or larger [1]. The crater is located at 36N / 103E in the Th-poor lunar highlands and has a prominent ejecta ray system. According to urban ledgend formation of the Giordano Bruno crater was observed by medieval monks on June 18, 1178 A.D [2]. However, formation of a 22 km sized crater on the Moon would have resulted in an intense storm of lunar meteorites onto Earth [3]. An intense meteor shower is not recorded in the historical chronicals around the world, and thus Withers [3] concluded that the crater was not formed in 1178 A.D. For an efficient delivery of lunar impact ejecta to Earth, and the similar number of lunar (134) and matian (94) meteorites [4], it was previously argued that Giordano Bruno crater is certainly older than 1 Ma [5]. This interpretation was recently confirmed by crater statistics that assigned an 1 10 Ma age for the emplacement of the Giordano Bruno ejecta blanket onto the lunar surface [1]. Considering that the Giordano Bruno crater is the largest crater that formed during the last 10 Ma, and hence ejected the greatest amont of material from the Moon, it appears likely that fragments of that ejecta are present in our collection of lunar meteorites. In addition, it is discussed the likelyhood that the Giordano Bruno crater delivered suficient 3He-rich lunar material to Earth to produce a significant spike in the extraterrestrial 3He-record of Earth’s sediments [6].