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  • 标题:A possible anorthositic continent of early Mars and the role of planetary size for the inception of Earth-like life
  • 本地全文:下载
  • 作者:James M. Dohm ; Shigenori Maruyama ; Motoyuki Kido
  • 期刊名称:Geoscience Frontiers
  • 印刷版ISSN:1674-9871
  • 出版年度:2018
  • 卷号:9
  • 期号:4
  • 页码:1085-1098
  • DOI:10.1016/j.gsf.2016.12.003
  • 语种:English
  • 出版社:Elsevier
  • 摘要:AbstractThe Moon has an anorthositic primordial continental crust. Recently anorthosite has also been discovered on the Martian surface. Although the occurrence of anorthosite is observed to be very limited in Earth's extant geological record, both lunar and Martian surface geology suggest that anorthosite may have comprised a primordial continent on the early Earth during the first 600 million years after its formation. We hypothesized that differences in the presence of an anorthositic continent on an Earth-like planet are due to planetary size. Earth likely lost its primordial anorthositic continent by tectonic erosion through subduction associated with a kind of proto-plate tectonics (PPT). In contrast, Mars and the Moon, as much smaller planetary bodies, did not lose much of their anorthositic continental crust because mantle convection had weakened and/or largely stopped, and with time, they had appropriately cooled down. Applying this same reasoning to a super-Earth exoplanet suggests that, while a primordial anorthositic continent may briefly form on its surface, such a continent will be likely transported into the deep mantle due to intense mantle convection immediately following its formation. The presence of a primordial continent on an Earth-like planet seems to be essential to whether the planet will be habitable to Earth-like life. The key role of the primordial continent is to provide the necessary and sufficient nutrients for the emergence and evolution of life. With the appearance of a “trinity” consisting of (1) an atmosphere, (2) an ocean, and (3) the primordial continental landmass, material circulation can be maintained to enable a “Habitable Trinity” environment that will permit the emergence of Earth-like life. Thus, with little likelihood of a persistent primordial continent, a super-Earth affords very little chance for Earth-like life to emerge.Graphical abstractDisplay OmittedHighlights•A logic to identify habitable planet is proposed.•Difference in the presence of an anorthositic primordial continent is due to the size of planet.•The presence of the primordial continent is one of the most significant factors to be a habitable planet.•There is very little chance for life to emerge on a super-Earth.
  • 关键词:KeywordsenAnorthosite on MarsMoonHabitable trinitySuper-EarthPlate tectonicsOrigin of life
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