Origin Of Water In The Terrestrial Planets: Insights From Meteorite Data And Planet Formation Models

By Keith Cowing
Status Report
February 7, 2023
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Origin Of Water In The Terrestrial Planets: Insights From Meteorite Data And Planet Formation Models
Dynamical evolution of the Solar System and different episodes of water delivery to the terrestrial planets. (A) Jupiter’s and Saturn’s cores grow via pebble accretion. (B) Jupiter’s core starts to accrete its gaseous envelope from the disk and scatter nearby planetesimals towards the inner and outer Solar System. (C) Saturn’s core starts to accrete its gaseous envelope and scatter planetesimals. (D) A fraction of the planetesimals scattered by Jupiter and Saturn is implanted into the asteroid belt, while another fraction reaches the terrestrial planets’ water delivery zone (green region), delivering water to the growing terrestrial planets. (E) Ice protoplanets beyond Saturn grow via pebble and planetesimal accretion, migrate inwards due to planet-disk gravitational interactions scattering planetesimals, and eventually collide with other ice protoplanets. (F) Collisions among ice protoplanets lead to the formation of three ice giant planets beyond Saturn. (G) The sun’s natal disk dissipates. In the absence of dissipative forces from the disk, the giant planets’ orbits become dynamically unstable, leading to the ejection of one of the ice giants from the Solar System. The dynamical instability sculpts the planetesimal disk beyond the orbit of Neptune and scatters a fraction of these objects (magenta planetesimals) towards the inner Solar System. (H) The Solar System giant planets reach their current orbits and the terrestrial planets continue to grow. Terrestrial planets complete formation roughly 30 to 150 My after the beginning of the Solar System formation (not illustrated). — astro-ph.EP

Water condensed as ice beyond the water snowline, the location in the Sun’s natal gaseous disk where temperatures were below 170 K. As the disk evolved and cooled, the snowline moved inwards.

A low temperature in the terrestrial planet-forming region is unlikely to be the origin of water on the planets, and the distinct isotopic compositions of planetary objects formed in the inner and outer disks suggest limited early mixing of inner and outer Solar System materials.

Water in our terrestrial planets has rather been derived from H-bearing materials indigenous to the inner disk and delivered by water-rich planetesimals formed beyond the snowline and scattered inwards during the growth, migration, and dynamical evolution of the giant planets.

Andre Izidoro, Laurette Piani (CRPG)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)
Cite as: arXiv:2302.02674 [astro-ph.EP] (or arXiv:2302.02674v1 [astro-ph.EP] for this version)
Journal reference: Elements, 2022, 18 (3), pp.181-186
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Submission history
From: Laurette Piani
[v1] Mon, 6 Feb 2023 10:24:30 UTC (1,881 KB)

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