Forschungsinteressen
I am an isotope geo- and cosmochemist studying the formation and evolution of the early Solar System and the accretion and differentiation history of the terrestrial planets. My work focuses on understanding the timing and mechanisms of mixing and fractionation processes in the earliest Solar System, as well as the formation and thermal evolution of asteroids and planetary precursors. A central goal is to reconstruct how, when, and where planetary building blocks assembled to form Earth and other bodies.
To address these questions, I analyze isotopic and chemical signatures in meteorites and terrestrial rocks. I combine radiometric dating to establish chronology, nucleosynthetic isotope anomalies to trace genetic heritage, and elemental and mass-dependent isotope fractionations to constrain kinetic and equilibrium processes, thereby reconstructing the sequence and conditions of nebular and planetary evolution.
Vita
Awards and Fellowships:
2022 Bradley Paper Award (Runner-up) – The Geological Society of Washington
2021 Paul Pellas-Graham Ryder Award – The Meteoritical Society and the Geological Society of America
2018 Outstanding Student Presentation Award – American Geophysical Union
2018 Wiley Award – The Meteoritical Society
Education and Employment:
2024–Present: Scientist, Max Planck Institute for Solar System Research, Göttingen, Germany
2021–2024: Post-Doctoral Associate, University of Maryland, Department of Geology, USA
2021: Post-Doctoral Researcher, University of Münster, Institute for Planetology, Germany
2016–2020: Doctor of Natural Sciences and Research Assistant, University of Münster, Institute for Planetology
2014–2016: Master of Science – Geosciences / Earth Sciences and Student Assistant, University of Münster
2011–2014: Bachelor of Science – Geosciences / Earth Sciences, University of Münster
Selected Publications:
Hellmann, J.L., Van Orman, J.A. and Kleine, T. (2024) Hf-W isotope systematics of enstatite chondrites: Parent body chronology and origin of Hf-W fractionations among chondritic meteorites. Earth and Planetary Science Letters 626, 118518.
doi:10.1016/j.epsl.2023.118518
Hellmann, J.L., Schneider, J.M., Wölfer, E., Drążkowska, J., Jansen, C. A., Hopp, T., Burkhardt, C. and Kleine, T. (2023) Origin of isotopic diversity among carbonaceous chondrites. The Astrophysical Journal Letters 946, L34.
doi:10.3847/2041-8213/acc102
Hellmann, J.L., Hopp, T., Burkhardt, C., Becker, H., Fischer-Gödde, M. and Kleine, T. (2021) Tellurium isotope cosmochemistry: Implications for volatile fractionation in chondrite parent bodies and origin of the late veneer. Geochimica et Cosmochimica Acta 309, 313-328.
doi:10.1016/j.gca.2021.06.038
Hellmann, J.L., Hopp, T., Burkhardt, C. and Kleine, T. (2020) Origin of volatile element depletion among carbonaceous chondrites. Earth and Planetary Science Letters 549, 116508.
doi:10.1016/j.epsl.2020.116508
Hellmann, J.L., Kruijer, T.S., Van Orman, J.A., Metzler, K. and Kleine, T. (2019) Hf-W chronology of ordinary chondrites. Geochimica et Cosmochimica Acta 258, 290-309.
doi:10.1016/j.gca.2019.05.040