Lunchtime Seminar Schedule

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Laura Sammon from Department of Geology
The Ghost Particles: How we use geoneutrinos to study Earth and other bodies

Abstract: Geoneutrinos, electron antineutrinos emitted from the decay of radionuclides within Earth, tell us information about Earth's composition and heat budget. These chargeless, ghost-like particles rarely interact with matter, traveling unimpeded from their sources deep within Earth. Geoscientists team up with particle physicists to measure geoneutrino fluxes using large (kiloton-sized) vats of scintillating fluid. We relate geoneutrino fluxes to Earth's absolute U and Th content, the only two radionuclides whose geoneutrinos we can detect. U and Th, though, are refractory lithophile elements which occur in virtually constant ratios to >25 other elements. By constraining U and Th content, we can also constrain these other refractory lithophiles. Geoneutrinos from the crust are indistinguishable from mantle geoneutrinos, forcing us to create new models and methods for separating the crust and mantle signals. The study of neutrinos and antineutrinos, in general, is a growing field of Nobel-prize-winning science that can inform us about Earth's core, distant stars, and perhaps even the very beginning of our universe.

Yasmina Martos from UMD / NASA
Revealing geothermal heat flux in Earth’s polar regions – geodynamic evolution and impact on ice sheet dynamics

Abstract: Geothermal heat flux, or heat escaping Earth’s interior, is an indicator of geology and tectonic history of a region. Additionally, the patterns described by this parameter impact the elements located above the surface. This is especially important in Earth’s polar regions, Antarctica and Greenland, which are covered in its vast majority by ice sheets. Geothermal heat flux controls the melting or freezing at the base of the ice and in turn, the ice dynamics and associated sea-level changes, which depends primarily on the amount of ice mass loss. Here, the geothermal heat flux in Earth’s polar regions will be discussed with special emphasis on magnetically derived models. The patterns, signatures and values of this parameter reveal the subglacial geology and geodynamics, and provide an input for deriving the thermal conditions at the base of the ice, influencing the generation of subglacial lakes or subglacial hydrological systems.

Peng Ni from Carnegie Institution of Washington
Heavy iron isotope composition of iron meteorites caused by core crystallization

Abstract: Magmatic iron meteorites - core remnants of extinct asteroids – record critical information on planetary differentiation processes in the early Solar System. Isotopic analyses on these meteorites found their Fe isotopic composition to be heavier than chondritic by ~ 0.1‰, indicating a planetary-scale process causing the isotope fractionation that remains poorly understood. In this talk, I will present recent solid/liquid metal equilibrium experiments to simulate the planetary core crystallization process, and demonstrate how core crystallization could lead to enrichment of heavy iron isotopes in the iron meteorites.

Samuel Crossley from Department of Geology
Brachinites record divergent pathways of differentiation

Abstract: Brachinite family meteorites (brachinites and related ungrouped achondrites) are minimally melted asteroidal materials that are related by the oxidation state and sulfur content of their precursors. These initial factors significantly affect the evolutionary pathway of planetary materials at the onset of differentiation and ultimately yield distinct igneous products. We present petrologic and geochemical evidence for these relationships and processes, their resolvable effects on laboratory-based remote sensing measurements, and implications for the interpretation of oxidation states among Main Belt asteroids.