The Maribo CM2 meteorite fall - survival of weak material at high entry speed

TL;DR

This study analyzes the high-speed atmospheric entry of the fragile CM2 Maribo meteorite, revealing its ability to survive fragmentation pressures comparable to ordinary chondrites due to its inhomogeneous structure and internal cracks.

Contribution

It demonstrates that fragile, high-speed CM2 meteorites can survive atmospheric entry pressures similar to more robust meteorites, challenging previous assumptions about their survivability.

Findings

30-40% of the meteoroid mass was destroyed at low dynamic pressures (~0.02 MPa)

25-40% of the mass survived until pressures of 3-5 MPa

Survivability is linked to inhomogeneity and lack of internal cracks in CM2 meteorites

Abstract

High entry speed (> 25 km/s) and low density (< 2500 kg/m3) are two factors that lower the chance of a meteoroid to drop meteorites. The 26 g carbonaceous (CM2) meteorite Maribo recovered in Denmark in 2009 was delivered by a superbolide observed by several instruments across northern and central Europe. By reanalyzing the available data, we confirmed the previously reported high entry speed of (28.3 +/- 0.3) km/s and trajectory with slope of 31 degrees to horizontal. In order to understand how such a fragile material survived, we applied three different models of meteoroid atmospheric fragmentation to the detailed bolide light curve obtained by radiometers located in Czech Republic. The Maribo meteoroid was found to be quite inhomogeneous with different parts fragmenting at different dynamic pressures. While 30 - 40% of the (2000 +/- 1000) kg entry mass was destroyed already at 0.02 MPa, another 25 - 40%, according to different models, survived without fragmentation until relatively large dynamic pressures of 3 - 5 MPa. These pressures are only slightly lower than the measured tensile strengths of hydrated carbonaceous chondrite (CC) meteorites and are comparable with usual atmospheric fragmentation pressures of ordinary chondritic (OC) meteoroids. While internal cracks weaken OC meteoroids in comparison with meteorites, this effects seems to be absent in CC, enabling meteorite delivery even at high speeds, though in the form of only small fragments.