PS Planetary and Solar System Sciences
The 2023 Division Outstanding Early Career Scientist Award is awarded to Tim Lichtenberg for outstanding research in cosmochemistry and planet formation, with emphasis on volatile cycling between atmospheres and planetary interiors, and especially with regard to magma oceans.
Tim Lichtenberg’s research is wide-ranging, and we begin this citation with his work on the importance of short-lived radionuclides in desiccating the planetary building blocks of rocky planets and exoplanets (termed planetesimals). Lichtenberg’s scientific results are important because they indicate an important control on whether rocky planets are at the one extreme “born dry” or at the other born with a volatile inventory substantially in excess of what is known on Earth or Venus. This work connects the volatile inventory with the galactic environment in which planets form, as a planet such as Earth may need to form in a disk quite near an object such as a supernova or Wolf-Rayet star in order to get an appreciable inventory of short-lived radionuclides, such as Al-26, to heat and devolatilize it in the first few million years. Lately, Lichtenberg’s work on this topic has extended to carbon species and water in the context of the chemical composition of planetesimals and thermodynamic structure of protoplanetary disks.
Lichtenberg has also investigated the bifurcation of planetary building blocks in the inner and outer Solar System, by going significantly beyond earlier work on volatile delivery to tackle the role of the inhomogeneous cosmochemical environment in protoplanetary disks. He has taken on the long-standing ‘Big Question’ concerning an evident dichotomy in the reservoirs from which the Solar System planets are made, establishing him as one of the world’s key emerging players in the quest to understand what determines the volatile inventory of planets (a key aspect of habitability, among other things). An example is his 2021 Science paper that shows an outstanding ability to connect theoretical concepts of disk dynamics and planet formation with geophysical models and meteoritic data on isotopic gradients in the Solar System. Tim Lichtenberg is very productive, and his citation metrics are excellent for his stage of career and research field.
Magma oceans form an important determinant of subsequent planetary evolution, and Lichtenberg’s recent papers were significant in exploring the extent to which this stage of planetary evolution could be characterized by exoplanet observations, and in the fluid mechanics of magma ascent, respectively. Furthermore, Lichtenberg has become conversant with the atmospheric modeling side of things, which he early recognized as crucial to his research programme since the blanketing effect of atmospheres determines how rapidly a planetesimal or young planet can cool off; atmospheres also exchange with planetary interiors, both during the magma ocean stage, and subsequently after the solidification of the melt. His recent works on the magma ocean epoch coupled state-of-the-art interior geophysical models with radiative-convective atmospheres, connecting interior dynamics to volatile cycling and atmospheric models with relevance to exoplanets. Elucidating core segregation in super-Earth magma oceans, Lichtenberg demonstrated a novel path to form coreless rocky exoplanets, potentially hosting secondary reduced atmospheres.
Beyond these remarkable research achievements, Tim Lichtenberg has also been dedicated to service to the planetary science community. In particular he was the lead organiser for the 2022 Rocky Worlds II conference and the ongoing Rocky Worlds Discussions virtual meeting series, and is very active in advising graduate and undergraduate students. He is a rising star in the interdisciplinary field connecting planetary science and exoplanet astronomy, and richly deserves the Planetary Sciences Division’s Outstanding Early Career Scientist Award.