Modelling the survival of meteoritic material exchanged between planetary bodies: scientific and commercial implications

Halim, Samuel Hickson (2023) Modelling the survival of meteoritic material exchanged between planetary bodies: scientific and commercial implications. PhD thesis, Birkbeck, University of London.

Abstract

Impacts are the most ubiquitous process across the Solar System, with every solid planetary surface we see marked by evidence of this process in some regard. Some impacts provide enough energy for the transfer of material between planetary bodies. Using the iSALE shock physics code, the survival of projectile material after impact with the Moon is investigated. The work within this thesis also explores the transfer of ejecta from Earth to the Moon, as well as investigating the survival of a particular set of larger asteroids (carbonaceous chondrites) that impact the lunar surface. This thesis investigates the potential for terrestrial material (i.e., terrestrial meteorites) to be transferred to the Moon by a large impact on Earth and subsequently survive impact with the lunar surface. Three-dimensional impact simulations show that a typical basin-forming impact on Earth can eject solid fragments at speeds sufficient to transfer them from Earth to the Moon. The importance of considering temperature when assessing the survival of biomarkers within the projectile is shown with the inclusion of a strength model that can resolve both shock and shear heating. This work shows that, assuming survival after launch from Earth, some biomarker molecules within terrestrial meteorites are likely to survive impact with the Moon, especially at the lower end of the range of typical impact velocities for terrestrial meteorites (2.5 km s−1). Long-term survival of biomarkers depends heavily upon where the projectile material lands, whether it is buried or remains on the surface, and the related cooling timescales. Carbonaceous chondrites contain relatively large quantities of carbon and nitrogen, two elements that are particularly depleted in the lunar crust. This work assesses the viability of surviving carbon and nitrogen within the impacted asteroids at a range of impact angles and velocities. At impact velocities of 5 km s−1, up to 86% of the impactor remains solid with the potential to retain carbon- and nitrogen-based compounds. Highly oblique impacts (15°) lead to material concentrating out of the crater rim, downrange in the direction of impact. Increasing impact velocity and angle decreases the proportion of surviving solid material. However, less oblique impacts concentrate surviving material within or close to the crater rim, which may be beneficial for resource utilisation.

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