Basic Study on Remote SIMS Method for Lunar Surface Observation

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This report describes the results of basic study on the lunar surface observation using Remote SIMS (Secondary Ion Mass Spectrometry) method. Evidence of the water ice in permanently shadowed craters at the lunar poles was detected by Lunar Prospector's neutron spectrometer experiment. Because of the low spatial resolution and the uncertainty in indirect observations of the water ice, the direct exploration mission is expected. Remote SIMS is considered to be a candidate for the in-situ observation method on the moon in order to obtain a credible evidence of the ice occurrence. Irradiation of the lunar surface by the ion beams from the Lander will induce secondary and back scattered radiation. Generated secondary ions can be detected by a mass spectrometer installed on the Lander. We carried out the experiments of the secondary ion generation using a plate of the water ice and a porous alumina with the water attached on the cooling target that simulates the permanently shaded region of the lunar surface. Mass spectra of the water ice by the fast ion bombardment were measured. It was confirmed that secondary ion yield of the water ice under the various conditions of the primary ion beam. Our results showed a possibility of the observations of the volatiles such as water ice concerning the lunar surface by R-SIMS installed on the Lander.