Trajectory, recovery, and orbital history of the Madura Cave meteorite

TL;DR

This paper reports the recovery and analysis of the Madura Cave meteorite, detailing its trajectory, orbit, and origin, revealing it as an Aten-type asteroid with a long near-Earth space history, originating from the inner asteroid belt.

Contribution

It provides the first detailed trajectory, orbit, and origin analysis of the Madura Cave meteorite, including its classification as an L5 chondrite and its Aten-type orbit.

Findings

Madura Cave is an L5 ordinary chondrite.

It has an Aten-type orbit, rare among meteorites.

The meteoroid's dynamical lifetime in near-Earth space is approximately 87 million years.

Abstract

On the 19th June 2020 at 20:05:07 UTC, a fireball lasting 5.5 s was observed above Western Australia by three Desert Fireball Network observatories. The meteoroid entered the atmosphere with a speed of $14.00 \pm 0.17$ km s$^{-1}$ and followed a $58^{\circ}$ slope trajectory from a height of 75 km down to 18.6 km. Despite the poor angle of triangulated planes between observatories (29$^{\circ}$) and the large distance from the observatories, a well constrained kilo-size main mass was predicted to have fallen just South of Madura in Western Australia. However, the search area was predicted to be large due to the trajectory uncertainties. Fortunately, the rock was rapidly recovered along the access track during a reconnaissance trip. The 1.072 kg meteorite called Madura Cave was classified as an L5 ordinary chondrite. The calculated orbit is of Aten type (mostly contained within the Earth's orbit), the second time only a meteorite is observed on such an orbit after Bunburra Rockhole. Dynamical modelling shows that Madura Cave has been in near-Earth space for a very long time. The NEO dynamical lifetime for the progenitor meteoroid is predicted to be $\sim87$ Myr. This peculiar orbit also points to a delivery from the main asteroid belt via the $\nu6$ resonance, and therefore an origin in the inner belt. This result contributes to drawing a picture for the existence of a present-day L chondrite parent body in the inner belt.