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3‐D laser images of splash‐form tektites and their use in aerodynamic numerical simulations of tektite formation

Abstract: 

Ten splash-form tektites from the Australasian strewn field, with masses ranging from 21.20 to 175.00 g and exhibiting a variety of shapes (teardrop, ellipsoid, dumbbell, disk), have been imaged using a high-resolution laser digitizer. Despite challenges due to the samples’ rounded shapes and pitted surfaces, the images were combined to create 3-D tektite models, which captured surface features with a high fidelity (Approx. 30 voxel mm-2 ) and from which volume could be measured noninvasively. The laser-derived density for the tektites averaged 2.41 +/- 0.11 g cm-3 . Corresponding densities obtained via the Archimedean bead method averaged 2.36 +/- 0.05 g cm-3 . In addition to their curational value, the 3-D models can be used to calculate the tektites’ moments of inertia and rotation periods while in flight, as a probe of their formation environment. Typical tektite rotation periods are estimated to be on the order of 1 s. Numerical simulations of air flow around the models at Reynolds numbers ranging from 1 to 106 suggest that the relative velocity of the tektites with respect to the air must have been <10 m/s-1 during viscous deformation. This low relative velocity is consistent with tektite material being carried along by expanding gases in the early time following the impact.

Authors: C Samson, S Butler, C Fry, PJA McCausland, RK Herd, O Sharomi, RJ Spiteri, M Ralchenko

Download: Tektites