New insights on Saturn's formation from its nitrogen isotopic composition

Olivier Mousis, Jonathan I. Lunine, Leigh N. Fletcher, Kathleen E. Mandt, Mohamad Ali-Dib, Daniel Gautier, Sushil Atreya

    Research output: Contribution to journalArticlepeer-review


    The recent derivation of a lower limit for the 14N/15N ratio in Saturn's ammonia, which is found to be consistent with the Jovian value, prompted us to revise models of Saturn's formation using as constraints the supersolar abundances of heavy elements measured in its atmosphere. Here we find that it is possible to account for both Saturn's chemical and isotopic compositions if one assumes the formation of its building blocks at ∼45 K in the protosolar nebula, provided that the O abundance was ∼2.6 times protosolar in its feeding zone. To do so, we used a statistical thermodynamic model to investigate the composition of the clathrate phase that formed during the cooling of the protosolar nebula and from which the building blocks of Saturn were agglomerated. We find that Saturn's O/H is at least ∼34.9 times protosolar and that the corresponding mass of heavy elements (∼43.1 M⊕) is within the range predicted by semi-convective interior models.

    Original languageEnglish (US)
    Article numberL28
    JournalAstrophysical Journal Letters
    Issue number2
    StatePublished - Dec 1 2014


    • Planets and satellites: Atmospheres
    • Planets and satellites: Composition
    • Planets and satellites: Formation
    • Planets and satellites: Individual (saturn)
    • Protoplanetary disks
    • Solid state: Volatile

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science


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