Origin of water in the inner Solar System: Planetesimals scattered inward during Jupiter and Saturn's rapid gas accretion

TL;DR

The paper proposes that water in the inner Solar System originated from planetesimals scattered inward during the rapid gas accretion phase of Jupiter and Saturn, providing a universal mechanism for water delivery.

Contribution

It introduces a new model showing that giant planet formation naturally scatters water-rich planetesimals inward, explaining the origin of terrestrial water without relying on orbital migration.

Findings

Outer main belt populated with C-type asteroids from broad disk regions

Water delivery to Earth occurs as scattered planetesimals reach terrestrial orbits

Mechanism is independent of giant planets' migration history

Abstract

There is a long-standing debate regarding the origin of the terrestrial planets' water as well as the hydrated C-type asteroids. Here we show that the inner Solar System's water is a simple byproduct of the giant planets' formation. Giant planet cores accrete gas slowly until the conditions are met for a rapid phase of runaway growth. As a gas giant's mass rapidly increases, the orbits of nearby planetesimals are destabilized and gravitationally scattered in all directions. Under the action of aerodynamic gas drag, a fraction of scattered planetesimals are deposited onto stable orbits interior to Jupiter's. This process is effective in populating the outer main belt with C-type asteroids that originated from a broad (5-20 AU-wide) region of the disk. As the disk starts to dissipate, scattered planetesimals reach sufficiently eccentric orbits to cross the terrestrial planet region and deliver water to the growing Earth. This mechanism does not depend strongly on the giant planets' orbital migration history and is generic: whenever a giant planet forms it invariably pollutes its inner planetary system with water-rich bodies.