Pre-LHB Evolution of the Earth's Obliquity

TL;DR

This paper investigates Earth's obliquity evolution, suggesting it remained stable despite past orbital changes, and was likely established during Moon formation, avoiding secular resonant encounters.

Contribution

It provides a detailed analysis of Earth's obliquity stability through Solar System dynamical history, emphasizing the role of Moon formation in setting current obliquity.

Findings

Earth's obliquity remained stable despite past orbital perturbations.

The system avoided secular resonant encounters throughout its evolution.

Current obliquity was likely established during Moon formation.

Abstract

The Earth's obliquity is stabilized by the Moon, which facilitates a rapid precession of the Earth's spin-axis, de-tuning the system away from resonance with orbital modulation. It is however, likely that the architecture of the Solar System underwent a dynamical instability-driven transformation, where the primordial configuration was more compact. Hence, the characteristic frequencies associated with orbital perturbations were likely faster in the past, potentially allowing for secular resonant encounters. In this work we examine if at any point in the Earth's evolutionary history, the obliquity varied significantly. Our calculations suggest that even though the orbital perturbations were different, the system nevertheless avoided resonant encounters throughout its evolution. This indicates that the Earth obtained its current obliquity during the formation of the Moon.