Deepest ever photographed Geminid with small but not negligible terminal mass

TL;DR

This paper reports the deepest atmospheric penetration of a Geminid fireball, likely resulting in meteorite landings, with detailed analysis of its unique trajectory, deceleration, and survival, challenging previous claims of similar events.

Contribution

It presents the first detailed observation of a Geminid fireball penetrating to 32.5 km, surviving to land, and provides new insights into meteoroid behavior and survivability during atmospheric entry.

Findings

Record depth of atmospheric penetration at 32.5 km.

Survivability of a small meteoroid with initial mass 0.25 kg.

Comparison showing terminal altitude remains constant for larger Geminids.

Abstract

We report an instrumental observation of the very exceptional Geminid fireball which was observed in scope of the Czech part of the European Fireball Network (EN) on 13 December 2012 at 4h12m59.4s UT. The uniqueness of this Geminid fireball consists of the record depth of its penetration in the atmosphere (to the height of 32.5 km) and in the fact that most likely a very small fraction of its initial mass survived severe deceleration in the atmosphere and landed on the ground. Such deeply penetrating Geminid with so precise and reliable data has not yet been observed. From a comparison with a large number of Geminids observed by the European Fireball Network and all brightest Geminids from the Prairie Fireball Network in USA and the Canadian MORP Network, we have shown that for Geminids with an entry mass greater than approximately 10 grams, the terminal altitude limit does not decrease further as it does for smaller Geminids, but remains constant at around 38 km. In this comparison, we have shown that there is only one exception, and that is the Geminid presented here. This one penetrated nearly 6 km deeper with very low terminal speed for Geminids. During the atmospheric flight this Geminid meteoroid slowed down from its original speed of 35.75 km/s to 6.8 km/s. This small meteoroid with initial mass of only 0.25 kg is probably the fastest candidate for a meteorite dropping event ever observed. This solid meteoroid belonging to the meteor shower survived a significant dynamic pressure of almost 2 MPa and thus ranks among the interplanetary bodies of asteroidal origin that caused the observed meteorite fall. Although a similar Geminid event has been previously presented in the literature, we demonstrate here that this claim was flawed.