Impact disruption of Bjurb\"ole porous chondritic projectile

TL;DR

This study examines the catastrophic fragmentation of a Bjurb"ole chondrite projectile upon impact, revealing unique size, shape, and distribution characteristics that differ from smaller impact experiments and asteroid boulders.

Contribution

It provides new insights into the disruption process and fragment properties of porous chondritic projectiles at impact velocities around 200 m/s.

Findings

Fragments follow power law size and mass distributions.

Bjurb"ole fragments are more equidimensional than smaller impact fragments.

Differences may be due to projectile properties, impact velocity, or erosion effects.

Abstract

The ~200 m/s impact of a single 400-kg Bjurb\"ole L/LL ordinary chondrite meteorite onto sea ice resulted in the catastrophic disruption of the projectile. This resulted in a significant fraction of decimeter-sized fragments that exhibit power law cumulative size and mass distributions. This size range is underrepresented in impact experiments and asteroid boulder studies. The Bjurb\"ole projectile fragments share similarities in shape (sphericity, and roughness at small and large scale) with asteroid boulders. However, the mean aspect ratio (3D measurement) and apparent aspect ratio (2D measurement) of Bjurb\"ole fragment is 0.83 and 0.77, respectively, indicating that Bjurb\"ole fragments are more equidimensional compared to both fragments produced in smaller scale impact experiments and asteroid boulders. These differences may be attributed either to the fragment source (projectile vs. target), to the high porosity and low strength of Bjurb\"ole, to the lower impact velocity compared with typical asteroid collision velocities, or potentially to fragment erosion during sea sediment penetration or cleaning.