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Open Access

Complexities of gamma-ray line intensities from the lunar surface

  • Naoyuki Yamashita110Email author,
  • Nobuyuki Hasebe110,
  • Takashi Miyachi110,
  • Masanori Kobayashi210,
  • Osamu Okudaira110,
  • Shingo Kobayashi110,
  • Takeshi Ishizaki110,
  • Kunitomo Sakurai110,
  • Mitsuhiro Miyajima110,
  • Robert C. Reedy310,
  • Claude d’Uston410,
  • Sylvestre Maurice410 and
  • Olivier Gasnault410
Earth, Planets and Space200860:BF03352796

Received: 19 March 2007

Accepted: 20 October 2007

Published: 9 April 2008


Assuming different abundances of the Apollo lunar soil samples and the average spectrum of galactic cosmic ray protons, energy spectra of neutrons and gamma rays and emission rates of gamma-ray lines from major elements have been estimated by using the reviewed Monte Carlo simulation library Geant4 and nuclear data. Previously, such libraries were not able to reproduce gamma-ray lines properly for the planetary application. Results clearly show that the emission rate of gamma rays heavily depends not only on the chemical abundance but also neutron flux within the lunar subsurface. While the intensities of gamma-ray lines are mostly proportional to elemental abundances, the intensity per unit elemental abundance can vary. Such a complex correlation is attributed to the change in neutron flux within the lunar subsurface and petrological restriction of elemental variation.

Key words

Gamma rayneutronlunar and planetary spectroscopymoonGRSSELENE