Research

Through high-pressure experiments, we investigate rocks from exoplanets, whose compositions can differ significantly from Earth. These compositional differences can affect the evolution and dynamics of rocky, Earth-like exoplanets.

Recent examples: diamond-rich planets (Horn et al., 2020, Planetary Science Journal), silicon-carbide planets (Nisr et al., 2016, JGR-Planets), and spin state of Fe in basal magma oceans of super-Earths (Shim et al., 2023, Science Advances).

Sub-Neptunes are common in our galaxy and may have either rocky interiors with dense hydrogen-rich atmospheres or thick water layers. The relationship between these two types remains unclear.

We study reactions between silicate/oxide minerals and dense hydrogen, which can release oxygen from silicates and produce water. Recent examples: Horn et al., 2023, Planetary Science Journal, Horn et al., 2025, Nature, and Kim et al., 2023, PNAS.

Uranus and Neptune are water-rich planets, and some sub-Neptune exoplanets are also likely water worlds. In these planets, water interacts with rocks under extreme pressure-temperature conditions.

We use high-pressure experiments to constrain internal structure and geochemical cycles. Recent examples: Nisr et al., 2020, PNAS and Kim et al., 2021, Nature Astronomy.

Seismic imaging reveals complex structures in Earth’s deep interior. Geodynamic simulations show that formation and destruction of these structures can influence surface tectonics and volcanism.

We provide physical and chemical constraints for these processes in collaboration with experts in seismology, geodynamics, and planetary dynamics.

Recent examples: Chen et al., 2020, EPSL, Kim et al., 2020, GRL, Bindi et al., 2020, Science Advances, and Ko et al., 2022, Nature.

Water likely reaches the core-mantle boundary and facilitates reactions between lower-mantle minerals and outer-core liquid iron alloys under extreme conditions.

We investigate these reactions to explain fine-scale features such as ultra-low velocity zones, core-rigidity zones, and the E’ layer in the outer core.

Recent examples: Ko et al., 2022, Geophysical Research Letters and Kim et al., 2022, Nature Geoscience.

Hydrogen is the most abundant element in the solar system, but its storage in Earth’s deep interior remains poorly constrained.

We investigate how hydrogen affects the chemistry, structure, and dynamics of Earth’s core. Recent examples: Fu et al., 2022, PRB, Fu et al., 2022, American Mineralogist, and Fu et al., 2023, Nature.

To understand early Earth volatile evolution, we study atmosphere-magma ocean interactions.

Using hydrogen gas loading and microsecond pulse laser heating, we investigate reactions between hydrogen and silicate melts or iron liquids under deep magma-ocean conditions.

Recent example: Piet et al., 2023, GRL.

Mars’ dynamo stopped abruptly, potentially linked to its shift from wet to dry surface conditions. The mechanism remains uncertain.

We investigate water- and hydrogen-mediated core-mantle interactions in Mars. Recent examples: O’Rourke and Shim, 2019, JGR-Planets and Piet et al., 2021, JGR-Planets.

Diamond-anvil cells compress materials between gem-quality diamonds to reach extreme pressures (about 1-5,000,000 bar). Diamond transmits X-rays, infrared, and visible light, enabling in situ diffraction and spectroscopy at high pressure-temperature conditions.

Laser heating raises sample temperatures to ~1,000-5,000 K. Our lab uses both fiber laser (1070 nm) and CO2 laser (10,000 nm) systems. Recent examples: Ko et al., 2022, Nature, Fu et al., 2023, Nature, and Horn et al., 2025, Nature.

Our gas loading system supports hydrogen, helium, neon, oxygen, and gas mixtures in diamond-anvil cells, enabling volatile-silicate/metal reaction experiments at high pressure.

Recent examples: Fu et al., 2023, Nature, Horn et al., 2023, Planetary Science Journal, Kim et al., 2023, PNAS, and Horn et al., 2025, Nature.

Multi-anvil presses allow larger-volume synthesis at ~0-28 GPa. Two 1100-ton presses are available at ASU, with additional presses installed at FORCE for expanded experimental capability.

Recent examples: Kulka et al., 2020, Minerals and Chen et al., 2020, American Mineralogist.

We use dynamic compression of silicates and metals to investigate melt structure and properties at extreme pressure-temperature conditions, including super-Earth regimes.

Recent examples: Hwang et al., 2020, Science Advances, Morard et al., 2020, PNAS, and Shim et al., 2023, Science Advances.

Synchrotron facilities provide bright X-ray beams for in situ diffraction and spectroscopy in diamond-anvil cell experiments.

Recent examples: Ko et al., 2022, Nature, Fu et al., 2023, Nature, and Shim et al., 2017, PNAS.

XFEL sources provide ultrabright pulses with high time resolution. We perform dynamic and static experiments at LCLS and PAL-XFEL.

Recent examples: Hwang et al., 2020, Science Advances, Morard et al., 2020, PNAS, and Shim et al., 2023, Science Advances.

Raman spectroscopy enables phase identification and thermodynamic constraints and is especially effective for icy and volatile-rich materials (H2O, NH3, CH4, CO2).

Recent examples: Allen-Sutter et al., 2020, Planetary Science Journal and Ko et al., 2022, GRL.

Aberration-corrected electron microscopy allows nanometer to atomic-scale chemical analysis with high spectral resolution (EDX/EELS).

Recent examples: Shim et al., 2017, PNAS, Kim et al., 2021, Nature Astronomy, and Kim et al., 2023, Nature Geoscience.

Secondary ion mass spectrometry (including NanoSIMS) supports isotopic and volatile measurements of high-pressure synthesized samples.

Recent example: Nisr et al., 2020, PNAS.

We pair high-pressure experiments with density functional theory to improve coverage and interpretation when direct measurements are limited.

Recent examples: Nisr et al., 2020, PNAS and Piet et al., 2023, GRL.