A holistic approach to understand Earth formation

  grant N. 101019380



The preliminary analyses made for the preparation of the HolyEarth proposal have led to two results, one on Contemporary formation of early solar system planetesimals at two distinct radial locations, the other on  Terrestrial planet formation from lost inner solar system material, published in Nature Astronomy and Science Avances respectively.

The first paper shows that the first planetesimals, related to the iron meteorite parent bodies, may have formed at the sites of the snowline and the silicate sublimation line, at about 5 and 1 au respectively. This explains the isotopic dichotomy of iron meteorites, revealed in Kruijer et al. (2017), and also why the cores of the iron meteorite parent bodies isotopically related to carbonaceous chondrites (CC) had a smaller core than those related to non-carbonaceous chondrites (NC), which suggest that the former were more oxidized (i.e. contained more water).

The second paper analyzes the isotopic dichotomy of meteorites using the largest possible number of elements, and shows that there is no common trend of NC meteorites towards CC meteorites, unlike what had been originally proposed (e.g. Schiller et al., 2018) by looking at a more restricted sample of isotopes, like Ca, Ti and Cr only. Also, the Earth does not appear intermediate between the NC and CC group. These measurements constrain the amount of CC material accreted by the Earth (and equivalently by Mars). This must be less than 10% by mass, with a more probable fraction of 4%. This result rules out the hypothesis that the terrestrial planets may have grown substantially by pebble accretion, because pebbles would have drifted from the outer disk, carrying a strong CC signature.

Please visit the publication page to access these papers.