HR: 08:30h
AN: P41E-01 INVITED     [Abstracts]
TI: Moon as a Recorder of Early Earth Evolution; A new Perspective.
AU: * Ozima, M
EM: EZZ03651@nifty.ne.jp
AB: SW implanted in lunar regolith has been a major source of information on the solar elemental and isotopic abundances (i.e. Solar abundance). In fact, light elements such as N and noble gases (including 129I-induced radiogenic 129Xe and Pu-induced fission Xe) in lunar soils are surface- correlated and clearly implanted from outside. The straightforward interpretation is that theses elements are implanted solar wind, but this explanation has difficulties accounting for both the abundance of N and isotopic ratios. We urge consideration of a hypothesis which stipulates that most of the N and some of the other volatile elements in lunar soils are actually from the Earth's atmosphere rather than the solar wind. This suggestion is quantitatively reasonable if the escape of atmospheric gases, and implantation into lunar soil grains, occurred at a time when the Earth had essentially no geomagnetic field. Thus, the evidence preserved in lunar soils might resolve the question of when the geomagnetic field first appeared. This hypothesis could be tested by examination of lunar farside soils, which should lack the terrestrial component. However, it remains to see if the radiogenic 129Xe and fission Xe are also attributable to terrestrial contamination. 1. Ozima M. et al. Nature 436, 655- 659, 2005. 2. Ozima M., Miura Y.N. & Podosek F.A., Icarus 170, 17-23, 2004.
DE: 1714 Geomagnetism and paleomagnetism
DE: 2152 Pickup ions
DE: 2780 Solar wind interactions with unmagnetized bodies
DE: 5210 Planetary atmospheres, clouds, and hazes (0343)
DE: 6250 Moon (1221)
SC: Planetary Sciences [P]
MN: Fall Meeting 2005