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Searching for Supernova Debris on the Moon: 60Fe and 53Mn measurements in Lunar samples by means of accelerator mass spectrometry (AMS)

Leticia Fimiani (TUM, Physik-Department E12, Garching)

Date:  July 5, 2012 16:00  – 17:00 

Place: Am Coulombwall 1, Garching
Lecture Hall (ground floor)

The enhanced deposition of 60Fe in a deep ocean ferro-manganese crust about (2.1 +/- 0.4) Myr ago (Knie et al., PRL 93, 171103 (2004), Fitoussi et al., PRL 101, 121101 (2008)) indicate that one or more supernova (SN) explosions occurred in the vicinity of the Solar System.  That observation was only possible with the ultrasensitive AMS technique at the MLL, where we are able to measure concentrations of 60Fe/Fe down to a level of 10^-16. Because of its lacking atmosphere and negligible sedimentation rate, the Lunar surface is an excellent quantitative reservoir for SN debris. We searched for live 60Fe and 53Mn in different samples from 3 Apollo missions. 53Mn is, similar as 26Al and 60Fe, a tool to trace nucleosynthesis activities. It is formed primarily during the explosive silicon-burning of the inner shells of SNe via 53Fe which beta-decays to 53Mn with an 8.51 min. halflife. Samples where we found an enhanced 60Fe concentration showed also an enhancement of 53Mn. If confirmed, this could be the first detection of live 53Mn originating from nucleosynthesis. In this talk I will briefly describe the measuring technique and show the results of the measurements made so far. I will discuss in detail the possible origins of the measured concentrations.