Research ArticleSPACE SCIENCES

KAGUYA observation of global emissions of indigenous carbon ions from the Moon

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Science Advances  06 May 2020:
Vol. 6, no. 19, eaba1050
DOI: 10.1126/sciadv.aba1050
  • Fig. 1 Pickup ion observation by KAGUYA above the Moon.

    (A) Schematic view of the observation in the Selenocentric Solar Ecliptic coordinates. The solar wind (SW) blows around to the –x direction. Two ion sensors, IEA and IMA, on the three-axis stabilized KAGUYA measure mainly solar wind ions and ions emitted from the lunar surface and exosphere, respectively. The solar wind electric and magnetic fields (E and B) transport (pickup) ions emitted from the Moon. The length, L, between the points of origin of measured pickup ions and spacecraft’s positions is determined by L = κ/∣E∣, where κ indicates the measured ion energies. Blue arrows denote fluxes of pickup ions. (B) Schematic of C+ emissions due to the solar wind, solar UV, and micrometeoroids. Secondary C+ emitted from the surface and photoionized exospheric C+ are picked up by the solar wind to space. The solar wind and micrometeoroids supply carbon to the lunar surface. Indigenous carbon contained in the lunar surface and interior materials contribute substantially to C+ emissions.

  • Fig. 2 Observation data by IMA on KAGUYA on 21 October 2008.

    (A) Energy TOF/mass profile of ions. PACE, Plasma energy Angle and Composition Experiment. (B) TOF/mass profile of low-energy (<~500 eV) ions derived from data in (A). The black curve is the sum of all calibration curves (colored lines) with random noise to fit the observation data (rectangles). The error bars indicate a confidence interval of 68% (1σ). Three TOF peaks are generated by one sort of incident ions, since ultrathin foil was used for start signals, which resulted in their charge state being converted to negative, neutral, or positive particles in the TOF chamber (21). For the incident C+, the peaks at 140 and 200 ns were made by C and a combination of C and C+, respectively.

  • Fig. 3 Orthogonal views of distribution map of C+ emissions from the Moon.

    Positions are normalized by the lunar radius (Rm); colors indicate the flux intensity; each pixel size is 5° × 5°. The mean statistical error (1σ) of the C+ emissions in the pixels is 27%, which is determined with respect to the number of C+ observations obtained.

Supplementary Materials

  • Supplementary Materials

    KAGUYA observation of global emissions of indigenous carbon ions from the Moon

    Shoichiro Yokota, Kentaro Terada, Yoshifumi Saito, Daiba Kato, Kazushi Asamura, Masaki N. Nishino, Hisayoshi Shimizu, Futoshi Takahashi, Hidetoshi Shibuya, Masaki Matsushima, Hideo Tsunakawa

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