title: Mysterious abrupt carbon-14 increase in coral contributed by a comet.
abstract: A large and sudden increase in radiocarbon ((14)C) around AD 773 are documented in coral skeletons from the South China Sea. The (14)C increased by ~ 15‰ during winter, and remain elevated for more than 4 months, then increased and dropped down within two months, forming a spike of 45‰ high in late spring, followed by two smaller spikes. The (14)C anomalies coincide with an historic comet collision with the Earth's atmosphere on 17 January AD 773. Comas are known to have percent-levels of nitrogen by weight, and are exposed to cosmic radiation in space. Hence they may be expected to contain highly elevated (14)C/(12)C ratios, as compared to the Earth's atmosphere. The significant input of (14)C by comets may have contributed to the fluctuation of (14)C in the atmosphere throughout the Earth's history, which should be considered carefully to better constrain the cosmic ray fluctuation.
authors.affiliation: 1] CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China [2].
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.affiliation: 1] State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences, Guangzhou 510640, China [2].
authors.forename: Zhao-feng
authors.initials: ZF
authors.lastname: Zhang
authors.affiliation: CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China.
authors.forename: Zi-cheng
authors.initials: ZC
authors.lastname: Peng
authors.affiliation: State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences, Guangzhou 510640, China.
authors.forename: Ming-xing
authors.initials: MX
authors.lastname: Ling
authors.affiliation: High-Precision Mass Spectrometry and Environment Change Laboratory (HISPEC), Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan.
authors.forename: Chuan-Chou
authors.initials: CC
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, The Chinese Academy of Sciences, Xi'an 710075, China.
authors.forename: Wei-guo
authors.initials: WG
authors.lastname: Liu
authors.affiliation: Institute for the History of Natural Sciences, The Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Xiao-chun
authors.initials: XC
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences, Guangzhou 510640, China.
authors.forename: Cheng-de
authors.initials: CD
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Nuclear Physics and Technology & Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871, China.
authors.forename: Ke-xin
authors.initials: KX
authors.lastname: Liu
authors.affiliation: CAS Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences, Guangzhou 510640, China.
authors.forename: Weidong
authors.initials: W
authors.lastname: Sun
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000737:chemistry*; D002250:Carbon Radioisotopes / Q000737:chemistry*; D002681:China; D003359:Cosmic Radiation
chemical_list: D002250:Carbon Radioisotopes