Mass Inventory of the Solar System Beyond the Sun: A Systematic Compilation with Uncertainty Budget

TL;DR

This paper provides a comprehensive mass inventory of the Solar System excluding the Sun, using a Monte Carlo approach to quantify uncertainties and identify key sources of variance.

Contribution

It offers the first systematic compilation of Solar System mass with an uncertainty budget, highlighting the dominant uncertainty from the inner Oort cloud.

Findings

Total non-solar mass is approximately 462 Earth masses.

Giant planets account for over 96% of the total mass.

Uncertainty is mainly due to the inner Oort cloud, with no direct observational constraints.

Abstract

We compile a systematic mass inventory of the Solar System excluding the Sun, drawing on spacecraft measurements, planetary ephemerides, and population surveys of small-body populations including main-belt asteroids and trans-Neptunian objects. Using a Monte Carlo simulation with 100,000 realisations, and treating poorly constrained components (scattered disc, Oort cloud) as log-normal distributions, we obtain a total non-solar mass of 462 Earth masses (median), with a 68% credible interval of [451, 515] Earth masses and a 90% credible interval of [449, 642] Earth masses. The giant planets dominate the mass budget (96.2% of the total). A variance decomposition shows that 98.2% of the total uncertainty is attributable to a single component: the inner Oort cloud (Hills cloud), for which no direct observational constraints exist. The current small-body populations retain only ~0.2% of the primordial trans-Neptunian disc mass inferred from Nice model simulations, and ~0.04% of the primordial asteroid belt mass implied by the Grand Tack hypothesis. We identify constraints on the Oort cloud from the Vera C. Rubin Observatory and improved long-period comet surveys as the primary path toward a better-determined total mass budget.