PerspectivePlanetary Science

Dwarf planet Ceres and the ingredients of life

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Science  17 Feb 2017:
Vol. 355, Issue 6326, pp. 692-693
DOI: 10.1126/science.aal4765

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  • Why many planets are ellipsoid?
    • Qiuyun Liu, Professor, Guangdong Provincial Key Laboratory of Improved Variety Reproduction in Aquatic Economic Animals, Sun Yat-sen University
    • Other Contributors:
      • Zi-Wei Ye, students, School of Biological Sciences, the University of Hong Kong, Hong Kong
      • Kai Wang, student, Division of Life Science, the Hong Kong University of Science and Technology, Hong Kong
      • Ye Gao, students, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA

    Take the Earth as an example. The Earth self-rotates at immense speed in the solar and lunar gravitational fields. Since the Earth has curvature, the tangential force caused by inertia (or fictitious centrifugal force = mv*v/r) acts on preceding mass by trailing mass, and it can be divided into a vertical component and tangential component in the preceding-trailing mass interface. The vertical component can lift up masses when it is large enough. Since the tangential force is proportional to linear speed, the radius is largest in the equator which renders the Earth an ellipsoid. By a similar principle, earthquakes occur when potential energies are present (1), which flattens the Earth surface over geological time.

    Zi-Wei Ye, 2,5 Kai Wang, 3,5 Ye Gao, 4,5 Qiuyun Liu, 1*
    1 Guangdong Provincial Key Laboratory of Improved Variety Reproduction in Aquatic Economic Animals, Biomedical Center, State Key Laboratory of Biocontrol, Lab of Microbial Metabolic Engineering and Synthetic Biology, Lab for Earthquake Perception Genes, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China.
    2 School of Biological Sciences, the University of Hong Kong, Hong Kong.
    3 Division of Life Science, the Hong Kong University of Science and Technology, Hong Kong, China.
    4 Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
    5 Equal contributions.

    *Correspondence author.
    E-mail address:...

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    Competing Interests: None declared.
  • RE: Planetary volatiles and prebiotic synthesis

    Küppers review (1) of the paper of De Sanctis et al. (2) suggests there have been (and are) difficulties with providing a source of Earth’s volatiles because Earth “formed dry”. There can be little doubt that Earth certainly has fewer volatiles than it would have if formed from some kind of average mix of “modern” meteoritic material (3, 4), which may or may not indicate formation from anhydrous sources. The source of the known volatiles may well be late-accreting objects from the asteroid belt, as suggested by the presence of abundant volatiles on Ceres, but accretion almost certainly involved late additions of various sized objects, from small meteorites to asteroids. This probably added a percent or more of Earth’s total mass in an accretionary tail (5) over 100 million years or more, following a much more energetic early phase, which possibly involved a moon-forming impact within the first 50-100 million years of Earth’s formation (6). In fact, a meteorite mix similar to the inventory of Antarctic meteorites, which may be our best guess at average compositions for late-accreting material, is sufficient to explain all of Earth’s volatiles without the need for a large, volatile-rich object or objects (3, 4). It is also clear that the presence of specific classes of organic compounds on potentially accreting bodies, in particular amino acids, etc., is not required as a source of pre-biotic molecules (3, 4). The conditions of accretion, and the nature of likely accreting...

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    Competing Interests: None declared.