The Maribo CM2 meteorite fallSurvival of weak material at high entry speed

High entry speed (>25kms(-1)) and low density (<2500kgm(-3)) are the two factors that lower the chance of a meteoroid to drop meteorites. The 26g carbonaceous (CM2) meteorite Maribo recovered in Denmark in 2009 was delivered by a bright bolide 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) kms(-1) and trajectory with slope of 31 degrees to the 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 up to the 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 effect seems to be absent in CC, enabling meteorite delivery even at high speeds, though in the form of only small fragments.