Rare Event Sampling Improves Mercury Instability Statistics

TL;DR

This paper introduces a new rare event sampling method, QDMC, which significantly improves the efficiency of estimating Mercury's orbital instability probability within 2 billion years.

Contribution

The paper presents QDMC, a novel rare event sampling technique that provides unbiased probability estimates at a fraction of the computational cost of traditional simulations.

Findings

Estimated Mercury instability probability as ~10^-4 in 2 billion years

QDMC reduces computational cost by up to 100 times compared to direct simulation

QDMC is easy to implement and applicable to planetary dynamics problems

Abstract

Due to the chaotic nature of planetary dynamics, there is a non-zero probability that Mercury's orbit will become unstable in the future. Previous efforts have estimated the probability of this happening between 3 and 5 billion years in the future using a large number of direct numerical simulations with an N-body code, but were not able to obtain accurate estimates before 3 billion years in the future because Mercury instability events are too rare. In this paper we use a new rare event sampling technique, Quantile Diffusion Monte Carlo (QDMC), to estimate that the probability of a Mercury instability event in the next 2 billion years is approximately $10^{-4}$ in the REBOUND N-body code. We show that QDMC provides unbiased probability estimates at a computational cost of up to 100 times less than direct numerical simulation. QDMC is easy to implement and could be applied to many problems in planetary dynamics in which it is necessary to estimate the probability of a rare event.