Mare versus highland lunar impact flash light curve dichotomy

TL;DR

This study analyzes lunar impact flash light curves over 9 years, revealing significant differences in decay behavior between mare and highland impacts, linked to lunar terrain and impact physics.

Contribution

It provides a comprehensive classification and modeling of lunar impact flash light curves, highlighting terrain-dependent differences in impact processes.

Findings

Highland LIFs decay more slowly than mare LIFs.

Impact light curve profiles depend on lunar terrain lithology.

Dual-size ejecta model explains extended impact flash durations.

Abstract

We perform a comprehensive analysis of lunar impact flash (LIF) light curve shapes and their dependence on the lunar terrain, using the large sample of LIFs detected by NELIOTA over the last 9 years. We classified 124 multi-frame light curves into mare, highland and `border' regions. Subsequently, we derived analytical expressions for single-size and dual-size ejecta cooling models, which were fitted to the observational data to estimate their physical properties. While impacts on both terrains yield similar peak magnitude distributions, their decay behaviour differs significantly; highland LIFs exhibit a shallower and longer-lasting decay compared to mare flashes, which are faster and steeper. The dual-size model suggests this extended duration is primarily driven by the fine droplets of the ejecta. The profile and duration of the LIF light curves represent the initial stages of the impact cratering process. The observed dichotomy between highland and mare LIFs demonstrates that the initial stages of the impact cratering process are fundamentally dependent on lunar lithology.