First determination of the temperature of a lunar impact flash and its evolution

TL;DR

This study presents the first measurement of temperature evolution in a lunar impact flash using near-infrared and visible data, revealing a maximum temperature of about 4000 K and estimating impact parameters.

Contribution

It provides the first direct temperature measurement of a lunar impact flash and estimates near-infrared emission efficiency for sporadic meteoroids impacting the Moon.

Findings

Maximum impact temperature ~4000 K

Near-infrared emission efficiency ~56% higher than visible

Impact origin likely from sporadic background meteoroids

Abstract

We report the first analysis of a flash produced by the impact of a meteoroid on the lunar surface and recorded both in the near-infrared and in the visible. Despite the fact that similar data have been recently published by other team during the refereeing process of our manuscript (Bonanos et al. 2018), our result still forms the first measurement of the temperature of a telescopic lunar impact flash (Madiedo and Ortiz 2016, 2018). The flash exhibited a peak magnitude of 5.1 $\pm$ 0.3 in the near-infrared I band and 7.3 $\pm$ 0.2 in the visible, and the total duration of the event in these bands was 0.20 s and 0.18 s, respectively. The origin of the meteoroid was investigated, and we inferred that the most likely scenario is that the impactor that belonged to the sporadic background. The analysis of this event has provided for the first time an estimation of the emission efficiency in the near-infrared {\eta}I for sporadic meteoroids impacting the Moon. We have determined that this efficiency is around 56% higher than in the visible band and we have found a maximum impact plume temperature of ~4000 K at the initial phase followed by temperatures of around 3200 K after the peak brightness. The size of the crater produced as a consequence of this impact is also calculated.