Oblique impact jetting of geological materials

To understand jetting of earth materials, gabbro slabs (5 mm thick) were accelerated to 1.5–2 km/s and impacted inclined gabbro (5–10 mm thick), novaculite (10 mm thick) and porous sandstone (12 mm thick) targets at angles of 30°–60°. The ejecta were collected using a catcher box filled with styrofoam and the particles were extracted using chloroform. The mass of the ejected particles per unit area (∼50 mg/cm^2) remains almost independent of impact velocity, inclination angle, thickness of the target and sample mineralogy and density. Based on this result, we predict that a 500 m diameter asteroid will produce only ∼10^7 gm tektite material. This is negligible comparing to an estimated 2×10^(13) gm in the Ivory Coast tektite strewn field. The recovered ejecta, unlike most tektites, contains both target and impactor materials. Both of the above results suggest that the tektites are not produced by jetting.