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

Mario Menichella

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.

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

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.
Paper Structure (35 sections, 1 equation, 3 figures, 4 tables)

This paper contains 35 sections, 1 equation, 3 figures, 4 tables.

Table of Contents

  1. Introduction
  2. Methodology
  3. Source selection
  4. Uncertainty characterisation
  5. Monte Carlo uncertainty propagation
  6. Unit conventions and scope
  7. Component Mass Estimates
  8. The Planets
  9. Natural Satellites and Ring Systems
  10. Large planetary-mass moons
  11. Mid-sized moons and rings
  12. The Main Asteroid Belt
  13. The dominant objects
  14. Total belt mass
  15. The Kuiper Belt and Trans-Neptunian Region
  16. ...and 20 more sections

Figures (3)

  • Figure 1: Mass of Solar System components (excluding planets and major moons) on a logarithmic scale, with $1\sigma$ uncertainty bars. Blue: inner Solar System populations. Green: trans-Neptunian populations (excluding Oort cloud). Red: Oort cloud components. The Oort cloud error bars span more than one order of magnitude, dominating the total uncertainty budget.
  • Figure 2: Monte Carlo probability distribution of the total non-solar mass of the Solar System ($N = 10^5$ realisations). The distribution is strongly right-skewed, with a median of $462.4\,M_{\oplus}$, 68% credible interval $[451,\,515]\,M_{\oplus}$ (dark shading), and 90% credible interval $[449,\,642]\,M_{\oplus}$ (light shading). The asymmetry is a direct consequence of the log-normal uncertainty in the Hills cloud mass.
  • Figure 3: Complete mass inventory of the Solar System on a single logarithmic bar chart, spanning eleven orders of magnitude from Jupiter ($444.6\,M_{\oplus}$) to the small satellite and ring populations ($\sim$$5 \times 10^{-6}\,M_{\oplus}$). Colour progression from dark blue (giant planets) to light green (inner trans-Neptunian) to orange/red (Oort cloud) reflects increasing uncertainty.