Formation of the terrestrial planets from planetesimals originated at different distances from the Sun
Abstract
The evolution of disks consisting of planetesimals and planets (or embryos of planets) was simulated [1]. The difference between initial semi-major axes of planetesimals in one run usually did not exceed 0.2 AU. In different calculations initial semi-major axes varied from 0.3 to 2 AU. Initial eccentricities of planetesimals equaled to 0.05 or 0.3, and initial inclinations in radians equaled to a half of initial eccentricities. In the first series of calculations, all planets were considered. In the second series, initial masses of the embryos of the planets, moved in orbits of the terrestrial planets, were equal to 0.3 of the masses of these planets. In the third series of calculations, initial masses of embryos of the planets, moved in orbits of the terrestrial planets, were equal to 0.1 of the masses of these planets, and Uranus and Neptune were excluded. The motion of planetesimals was integrated under the gravitational influence of the Sun, planets or their embryos. Collisions of planetesimals with planets were not simulated. The orbital elements of the migrated bodies were recorded in computer memory with a step of 500 years. Based on these arrays for several considered time intervals (from 0.5 to 50 Myr), I calculated the probabilities of collisions of planetesimals with planets, the Moon, and with their embryos. The results of calculations showed that at masses of the embryos of the terrestrial planets of about 0.1 of the masses of the planets, an embryo grew mainly by accumulation of bodies from its neighborhood, and the embryos of the Earth and Venus grew faster than the embryos of Mercury and Mars. The amounts of material from different parts of the zone from 0.7 to 1.5 AU from the Sun, which entered into almost formed the Earth and Venus, differed, probably, by no more than 2 times. The Earth and Venus could acquire more than a half of their masses in 5 million years. The formation of embryos of Mars and Mercury with masses that were several times smaller than those of these planets, as a result of the compression of rarefied condensations, was supposed. The features of the formation of terrestrial planets can be explained with a relatively smooth decrease of the semi-major axis of Jupiter caused by its ejection of planetesimals into hyperbolic orbits, without considering Jupiter's migration to Mars's orbit and back (the Grand Tack model) and without sharp changes in orbits of the giant planets for the Nice model. At the ratio of the masses of the embryos of the Earth and the Moon equaled to 81 (the ratio of the masses of the Earth and the Moon), the ratio of probabilities of planetesimals collided with the embryos of the Earth and the Moon in the considered variants did not exceed 54 and was maximum at the masses of embryos about three times smaller than the present masses of the Earth and the Moon. The work was carried out as a part of the state assignments of the Vernadsky Institute of RAS. Studies of the growth of the Earth were supported by the grant 13.1902.21.0039 of the Russian Ministry of Education and Science. [1] Ipatov S.I. Solar System Research, 2019, 53, 332-361, https://rdcu.be/bRVA8.
- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E.148I