Volatile Delivery to Planets from Water-rich Planetesimals around Low Mass Stars

TL;DR

This study investigates how higher water content in primitive bodies beyond the water line affects planetary formation around low-mass stars, using N-body simulations to predict trends in habitable zone planets.

Contribution

It introduces a model with water-rich planetesimals based on chemical equilibrium, contrasting traditional water-depleted assumptions, to better understand volatile delivery during planet formation.

Findings

Higher water content leads to more water-rich planets in habitable zones.

Planetary system architectures vary with stellar mass and initial water content.

Model predictions can be tested against ongoing exoplanet data.

Abstract

Most models of volatile delivery to accreting terrestrial planets assume that the carriers for water are similar in water content to the carbonaceous chondrites in our Solar System. Here we suggest that the water content of primitive bodies in many planetary systems may actually be much higher, as carbonaceous chondrites have lost some of their original water due to heating from short-lived radioisotopes that drove parent body alteration. Using N-body simulations, we explore how planetary accretion would be different if bodies beyond the water line contained a water mass fraction consistent with chemical equilibrium calculations, and more similar to comets, as opposed to the more traditional water-depleted values. We apply this model to consider planet formation around stars of different masses and identify trends in the properties of Habitable Zone planets and planetary system architecture which could be tested by ongoing exoplanet census data collection. Comparison of such data with the model predicted trends will serve to evaluate how well the N-body simulations and the initial conditions used in studies of planetary accretion can be used to understand this stage of planet formation.