1I/‘Oumuamua as an N2 Ice Fragment of an Exo-Pluto Surface II: Generation of N2 Ice Fragments and the Origin of ‘Oumuamua

S. J. Desch, A. P. Jackson

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


The origin of the interstellar object 1I/‘Oumuamua has defied explanation. In a companion paper (Jackson & Desch, 2021), we show that a body of N2 ice with axes 45 m × 44 m × 7.5 m at the time of observation would be consistent with its albedo, nongravitational acceleration, and lack of observed CO or CO2 or dust. Here we demonstrate that impacts on the surfaces of Pluto-like Kuiper belt objects (KBOs) would have generated and ejected ∼1014 collisional fragments—roughly half of them H2O ice fragments and half of them N2 ice fragments—due to the dynamical instability that depleted the primordial Kuiper belt. We show consistency between these numbers and the frequency with which we would observe interstellar objects like 1I/‘Oumuamua, and more comet-like objects like 2I/Borisov, if other stellar systems eject such objects with efficiency like that of the Sun; we infer that differentiated KBOs and dynamical instabilities that eject impact-generated fragments may be near-universal among extrasolar systems. Galactic cosmic rays would erode such fragments over 4.5 Gyr, so that fragments are a small fraction (∼0.1%) of long-period Oort comets, but C/2016 R2 may be an example. We estimate ‘Oumuamua was ejected about 0.4–0.5 Gyr ago, from a young (∼108 yr) stellar system, which we speculate was in the Perseus arm. Objects like ‘Oumuamua may directly probe the surface compositions of a hitherto-unobserved type of exoplanet: “exo-Plutos.” ‘Oumuamua may be the first sample of an exoplanet brought to us.

Original languageEnglish (US)
Article numbere2020JE006807
JournalJournal of Geophysical Research: Planets
Issue number5
StatePublished - May 2021


  • 'Oumuamua
  • Kuiper Belt
  • Pluto
  • exoplanets

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science


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