Earth Planets Space, Vol. 60 (No. 4), pp. 293-297, 2008
Yoko Maruyama1,2, Kazunori Ogawa1,3, Tatsuaki Okada1,4, and Manabu Kato1,2,3
1Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan
2Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan
3Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Ookayama, Tokyo 152-8550, Japan
4Department of Space and Astronautical Science, Sokendai, Sagamihara, Kanagawa 229-8510, Japan
(Received March 30, 2007; Revised October 29, 2007; Accepted October 29, 2007; Online published April 9, 2008)
We performed laboratory experiments to investigate the effect of particle size in X-ray fluorescence (XRF) with respect to interpreting remote X-ray spectrometry. To simulate microscopic roughness of the uppermost surface of lunar regolith, we used powdery specimens of crashed rocks ranging 25 to 500 μm in size and flat rock plates for comparison. Our results show that XRF intensities from powdery specimens decrease relative to those from flat plates by up to 50%, especially for larger particle size and at increasing source-to-surface-to-detector angle (phase angle). Corrections should be required for elemental analysis by XRF spectrometry in the SELENE "Kaguya" and other planetary orbiter missions.
Key words: X-ray fluorescence, particle size effect, regolith, elemental composition, phase angle.