Olivine origination in lunar Das crater through three-dimensional numerical simulation

Abstract

Mineral olivine and Mg-rich spinel observed in Das crater were previously attributed to the excavation from the lunar lower crust or even mantle. To test this hypothesis, we developed a three-dimensional hydrocode SALEc to simulate the formation of such an elliptical crater. The hydrocode SALEc was examined and verified by comparing its results with experimental data and another code iSALE-2D. Based on the comparison between our SALEc's numerical results and observations, we found that Das crater can be formed by an impact with the projectile of 6.0 km in diameter, impact velocity of 10 km/s, and impact angle of 70° relative to the vertical. In the impact, the excavation depth of Das crater is ∼3.0 km, much less than the lunar crust thickness, hence the mineral olivine and Mg-rich spinel observed in this crater is unlikely originated from lunar lower crust or mantle. Numerical simulation results also show that some projectile materials can survive in this impact and are distributed in the downrange crater floor. Given the abundant olivine in many asteroids, we propose that olivine observed in Das crater is most probably originated from projectile remnants instead of excavation from the depth.