Formation of Saturn and distribution of its growth times

Abstract

The work presented here encompasses the intriguing evolution of our celestial neighborhood, the solar system. This study centers on the formation of giant planets in the outer region of the solar system. Apart from the Cassini mission to Saturn, Jupiter has garnered the majority share of research attention, leaving little room for inquiry into the formation and evolution of its lesser-explored counterpart, Saturn. This project aims to investigate the conditions and parameters of the protoplanetary disk that led to the formation of Saturn and its distribution of formation times. The study explores the implications of the simplest disc and pebble accretion model, with steady-state accretion, on the formation of gas giants. We conducted a statistical survey of different disk parameters and initial conditions to establish which combination best reproduces the present outer solar system. The parameter space is large: we examined the effect of the initial planetesimal disk mass, the number of planetesimals and their size-frequency distribution, the coagulation, and dust settling timescales, planet migration, and the feedback of gas disk that will govern the overall dynamics of the final sizes, compositions, and positions of the planets. The results reveal that pebble accretion is sensitive to various parameters and initial conditions of the disk, and in the absence of a planetesimal disk, the giant planets will be highly eccentric. Moreover, it is challenging to replicate the formation of all four giant planets in the outer solar system in a single simulation. The study estimates the average formation time for Saturn to be ⟨tSaturn⟩ = 3.09 ± 1.33 Myrs, which aligns closely with the Hf-W reset age of the Eagle Station pallasite, an achondritic meteorite from the outer solar system. This study plays a pivotal role in understanding the configuration of the contemporary solar system as we perceive it. The emergence of gas giants in the outer solar system bears implications for the inflow of matter towards the inner regions, influencing the terrestrial planets and the makeup of the asteroid and Kuiper belts. This work contributes to the dynamic evolution of these planets, which are responsible for molding the composition of the inner solar system and the terrestrial planets.