Fragmentation and Volatile Depletion in Meteor Head Echo Measurements

Abstract

The main source of mass influx to Earth is thought to come from microgram sized meteoroids. These micro-meteoroids are indirectly detectable by high powered large aperture radars through the plasma they generate while ablating. A subset of meteor head echoes is known to contain abrupt drops in radar cross section (RCS). These drops can indicate meteor fragmentation, depletion of volatile elements, and the pyrolysis of organic material. Relatively few such detections have been studied in depth, as they must be manually identified among all other meteor detections without sudden decreases in signal strength. This study uses deep learning methodology to systematically classify the MAARSY meteor head echo catalogue, which contains meteor head echo detections between 2016-2024. The deep learning method achieved an accuracy of 86% and a precision of 91% in the task of identifying drops in RCS. Of the 1.6 million catalogued meteors 12% contain a distinct drop in RCS. Through subsequent analysis of the classified meteoroids, it was found that sporadic meteoroids originating from the narrow Apex source—associated with comet 55P/Tempel-Tuttle—are overrepresented by 50% among the group of meteoroids with distinct drops in RCS. In contrast, Helion and anti-Helion meteors—associated with comet 2P/Encke—are less likely to exhibit a drop in RCS. A statistical analysis indicates that meteors with a drop in RCS appear to be low in volatiles, leading to the hypothesis that this could be a result of space weathering. This depletion would leave the meteoroids more porous and fragile, making them more susceptible to destructive fragmentation, detected by MAARSY as a distinct drop in the received signal power. The results show that there are significant differences in how different populations of micro-meteoroids ablate in the atmosphere, which can be linked to the origin of the meteoroids. This information can grant further insight into the composition and structure of micro-meteoroids, as well as the effect of space weathering processes on meteoroids in the solar system.