Basu S, Stuart F M, Schnabel C, Klemm V
Isotope Geosciences Unit, Scottish Universities Environmental Research Centre, East Kilbride G75 0QF, United Kingdom.
Phys Rev Lett. 2007 Apr 6;98(14):141103. doi: 10.1103/PhysRevLett.98.141103. Epub 2007 Apr 2.
An excess of 60Fe in 2.4-3.2 x 10(6) year old ferromanganese crust (237 KD) from the deep Pacific Ocean has been considered as evidence for the delivery of debris from a nearby supernova explosion to Earth. Extremely high ;{3}He/;{4}He (up to 6.12 x 10(-3)) and 3He concentrations (up to 8 x 10(9) atoms/g) measured in 237 KD cannot be supernova-derived. The helium is produced by galactic cosmic rays (GCR) and delivered in micrometeorites that have survived atmospheric entry to be trapped by the crust. 60Fe is produced by GCR reactions on Ni in extraterrestrial material. The maximum (3)He/(60)Fe of 237 KD (80-850) is comparable to the GCR (3)He/(60)Fe production ratio (400-500) predicted for Ni-bearing minerals in iron meteorites. The excess 60Fe can be plausibly explained by the presence of micrometeorites trapped by the crust, rather than injection from a supernova source.
在来自太平洋深处的237 KD、年龄为240万至320万年的铁锰结壳中，过量的60Fe被认为是附近超新星爆炸产生的碎片抵达地球的证据。在237 KD中测得的极高的3He/4He（高达6.12×10-3）和3He浓度（高达8×109原子/克）并非来自超新星。氦是由银河宇宙射线（GCR）产生的，并通过微陨石输送，这些微陨石在进入大气层后幸存下来并被结壳捕获。60Fe是由GCR在外层物质中的镍上发生反应产生的。237 KD的最大3He/60Fe（80-850）与铁陨石中含镍矿物预测的GCR 3He/60Fe产生率（400-500）相当。过量的60Fe可以合理地解释为结壳捕获了微陨石，而不是来自超新星源的注入。
