First measurements of low-energy cosmic rays on the surface of the lunar farside from Chang’E-4 mission

• DOI: 10.1126/sciadv.abk1760
• Publication Date: 2022-01-14T20:38:10Z
• Authors: Pengwei Luo; Xiaoping Zhang; Shuai Fu; Yong Li; Cunhui Li; Jinbin Cao
• Keywords: Earth, Environmental, Ecological, and Space Sciences; 13. Climate action; 0103 physical sciences; 7. Clean energy; 01 natural sciences; 0105 earth and related environmental sciences

Human activities on the lunar surface are severely constrained by space radiation dominated cosmic rays (CRs). Here, we report first measurements of low-energy (about 10 to 100 MeV/nuc) CR spectra from China’s Chang’E-4 (CE-4) mission around solar minimum 24/25. The results show that for proton, helium, CNO, and heavy-ion groups, ratios (ratio errors) CE-4 fluxes those near-earth spacecraft 1.05 (0.15), 1.30 (0.18), 1.08 (0.16), 1.24 (0.21), respectively, predicted models [CRÈME96 CRÈME2009] instead [1.69 (0.17), 2.25 (0.23)], [1.66 1.76 (0.18)], [1.08 (0.11), 1.07 (0.11)], [1.33 1.17 (0.15)]. Moreover, a notable enhancement 3He/4He ratio is observed at ~12 MeV/nuc, dawn-dusk symmetry confirmed. These provide valuable insights into CRs farside will benefit future exploration.