SPS Seminar - Atom Probe of Impacts, and the Impact of Atom Probe

When:  Thursday 25 May at 14.00

Where:  Microsoft Teams – Robert Hooke/Online

Speaker:  Lee White (SPS)

Hosted by: Alexander Barrett

Abstract:

Constraining the timing, duration, and intensity of planetary bombardment is critical to understanding the origins and evolution of life on Earth. Beyond the quintessential planetary-scale extinction events, meteorite impacts can also nurture microbial life, potentially delivering amino acids and water to the early inner Solar System and providing the thermal and kinetic energies required to support habitable environments. Continued crustal recycling on Earth leaves precious little evidence of the ancient (> 4 Gyr ago) impacts that drove the evolution of isotopic and volatile reservoirs, hindering our ability to place empirical constraints on the pressure and temperature conditions experienced by budding microbial communities in shallow crustal environments. Instead, we examine meteoritic and returned planetary samples (such as those from NASA’s Apollo missions) to constrain bombardment events throughout the inner Solar System and place implied constraints on the conditions experienced on Earth. Given the small abundances and irreplaceable nature of these materials, techniques which maximise scientific yield while minimising destructive consumption are increasingly important. Atom probe tomography (APT), a technique that measures both the abundance and distribution of individual atoms from < 100 nm scale domains, has slowly revolutionised our ability to date impact events, constrain isotopic fractionation and diffusion in shocked minerals, and support interpretation of more traditional (e.g. SIMS) geochronological data. In concert with correlative microstructural techniques such as EBSD and TEM, atom probe has provided a deeper understanding of the nanoscale effects of planetary bombardment events and shifted our understanding of the impact flux in the turbulent early Solar System, opening the door for microbial life on Mars as early as 4.48 billion years ago. The continued application of APT to planetary, environmental and biological materials promises improved understanding of the fundamental mechanisms driving many natural systems, here including new constraints for the origin of life on Earth.

BIO:

Dr. Lee Francis White is a postdoctoral researcher at The Open University studying the distribution, abundance and composition of volatiles in lunar materials.  After completing his PhD at the University of Portsmouth, studying shock deformation in terrestrial impact structures, Dr. White spent 4 years at the University of Toronto (Canada) unravelling chemical and structural complexities in meteorite samples. He is an expert on the application of electron backscatter diffraction (EBSD) and atom probe tomography (APT) to geological materials, with a focus on linking geochronology with mineral and whole rock structure. He has published on a wide range of planetary samples, including martian meteorites, lunar meteorites, returned Apollo samples, and carbonaceous chondrites, and has spear headed a number of technique developments, including U-Th-Pb chronology by APT, utilising accessory mineral microstructure as a shock barometer, and extracting grains in-situ for dissolution analysis (FIB-TIMS). He is a current committee member of the UK Planetary Forum, and has organised conferences (BPSC 2022), conference sessions (including Goldschmidt), and workshops focused on the nanoscale analysis of planetary materials.