Research

Through high pressure experiments, we investigate rocks from exoplanets, as their compositions can vary significantly from those of Earth. These compositional differences have the potential to 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 the basal magma oceans of super-Earths (Shim et al., 2023, Science Advances).

Sub-Neptunes are commonly found in our galaxy, and they can either have a rocky interior with a dense hydrogen-rich atmosphere or a thick layer of water. The relationship between these two types of sub-Neptunes remains unclear. To investigate, we study the chemical reactions between silicate and oxide minerals and dense hydrogen, which could release oxygen from silicates and create water.

Recent examples: formation of water from reaction between oxide melt and dense hydrogen ( Horn et al., 2023, Planetary Science Journal; Horn et al., 2025, Nature), and formation of hydride from reaction between oxide melt and dense hydrogen ( Kim et al., 2023, PNAS).

Uranus and Neptune are the two water-rich planets in our solar system, and some sub-Neptune exoplanets are also believed to be water worlds. On these planets, water exists under extreme conditions of high pressure and high temperature, interacting with minerals and rocks. We use high pressure experiments to gain insights into the internal structure and geochemical cycles of these water-rich planets.

Recent examples: water-silica mixing ( Nisr et al., 2020, PNAS; Kim et al., 2021, Nature Astronomy).

Fascinating structures have been unveiled within the Earth’s interior through seismic imaging investigations. Dynamic simulations have demonstrated that the formation and destruction of these structures can have a significant impact on surface tectonics and volcanic activities. Our research offers crucial physical and chemical parameters that aid in comprehending the origins of these structures.

At ASU, we collaborate with a diverse group of experts, including Ed Garnero (seismology), Mingming Li (geodynamics), and Joe O’Rourke (dynamics), spanning geophysics, geology, and planetary science to foster a holistic understanding of the Earth’s interior.

Recent examples: deep water transport (Chen et al., 2020, EPSL), deep melting (Kim et al., 2020, GRL), nanocrystalline metal iron in shocked meteorite (Bindi et al., 2020, Science Advances), and new mineralogy of the deep Earth (Ko et al., 2022, Nature).

Water is likely transported to the core-mantle boundary. Water can facilitate the chemical reaction between mineral phases of the lower mantle and the liquid iron of the outer core at the core-mantle boundary. Our research investigates the chemical reactions that occur between hydrous minerals and liquid iron alloys under high-pressure and high-temperature conditions relevant to the Earth’s core-mantle boundary.

This research aims to provide insight into the origin of the fine-scale structures observed in the region, including ultra-low velocity zones, core-rigidity zones, and the E′ layer located in the outer core.

Recent examples: diamond at the core-mantle boundary (Ko et al., 2022, Geophysical Research Letters), and hydrogen-silica exchange at the core-mantle boundary induced by deeply transported water (Kim et al., 2022, Nature Geoscience).

Although hydrogen is the most abundant element in our solar system, the storage of hydrogen within the Earth’s deep interior is not well understood. Our research focuses on investigating how the presence of hydrogen affects the chemistry, structure, and dynamics of the Earth’s core.

Recent examples: discovery of a new Fe-Si-H alloy (Fu et al., 2022, PRB), hydrogen solubility in FeSi alloys (Fu et al., 2022, American Mineralogist), and snow in the Earth’s outermost core (Fu et al., 2023, Nature).

To understand the early geological history and the storage of volatiles, it is crucial to examine the interplay between the atmosphere and magma ocean. With the aid of a hydrogen loading system and micro-second pulse laser heating technique, we can now attain temperatures high enough to investigate the chemical reactions that occur between hydrogen and silicate melts, as well as between hydrogen and iron liquids, under the pressure-temperature conditions of the deep magma ocean.

Recent examples: super-stoichiometric Fe-H liquid (Piet et al., 2023, GRL).

The Mars dynamo stopped abruptly, which may have played a role in its transition from a wet environment to the current dry environment on its surface. The reason for the sudden halt in dynamo from the Martian core is unknown. Our research focuses on investigating the interaction between the core and mantle of Mars, facilitated by water and hydrogen, to shed light on this.

Recent examples: water and dynamo in deep Mars (O’Rourke and Shim, 2019, JGR-Planets), and hydrogen in the Martian core (Piet et al., 2021, JGR-Planets).

In diamond-anvil cells, materials are compressed between two gem-quality diamond anvils to generate extremely high pressures ranging from 1-5,000,000 bars. Diamond is the strongest material known to date and transmits a wide range of electromagnetic radiation, including X-rays, infrared, and visible light. These properties allow us to conduct in situ diffraction or spectroscopy measurements under high-pressure and high-temperature conditions.

Laser heating systems are employed to raise the temperature of the samples in the diamond-anvil cells to temperatures between 1,000-5,000 K. The temperature can be estimated by analyzing the black-body radiation of the samples. Our lab has both fiber optic laser (1,070 nm) and CO2 laser (10,000 nm) heating systems. Recent examples: Ko et al. (2022, Nature), Fu et al. (2023, Nature), and Horn et al. (2025, Nature).

The gas loading system in our lab is capable of loading a variety of gases into diamond-anvil cells, including hydrogen, helium, neon, oxygen, and gas mixtures. This allows us to conduct high-pressure experiments on the chemical reactions between volatiles and silicates/metals. 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).

A multi-anvil press allows for the synthesis of a large amount of sample at 0-28 GPa. Two 1100-ton multi-anvil presses are available at ASU (PI: Leinenweber). Four more presses are being installed at FORCE (Facility for Open Research in a Compressional Environment), ASU. A 6000-ton press will allow us to study petrology of the Earth's lower mantle and alloying at the Martian core.

A 1500-ton DIA type press will enable large-volume experiments to the pressure conditions of the lowermost mantle. Recent examples: Kulka et al. (2020, Minerals) and Chen et al. (2020, American Mineralogist).

We conduct dynamic compression of silicates and metals to understand the atomic-scale structures and the properties of the melts at extreme pressures and temperatures. We use laser systems for dynamic compression at LCLS-XFEL to study metals and silicates up to pressures expected for the super-Earth exoplanets. Recent examples: Hwang et al. (2020, Science Advances), Morard et al. (2020, PNAS), and Shim et al. (2023, Science Advances).

Synchrotron facilities provide extremely bright X-ray beams for diffraction and spectroscopy measurements in diamond-anvil cells. We perform diffraction and spectroscopy at synchrotron facilities (Advanced Photon Source, Advanced Light Source, and National Synchrotron Light Source). Recent examples: Ko et al. (2022, Nature), Fu et al. (2023, Nature), and Shim et al. (2017, PNAS).

X-ray free electron laser sources provide extremely bright X-ray pulses with very high time resolution. We have conducted both dynamic and static experiments at XFEL sources (Linac Coherent Light Source at Stanford University and Pohang Accelerator Laboratory X-ray Free Electron Laser). ASU's compact XFEL source will enable us to conduct some unique experiments in near future. Recent examples: Hwang et al. (2020, Science Advances), Morard et al. (2020, PNAS), and Shim et al. (2023, Science Advances).

The phonon spectra allow for phase identification and estimation of thermodynamic properties. Raman spectroscopy is particularly powerful for studying icy materials such as H2O, NH3, CH4, and CO2, along with volatile components in materials. Our system is capable of 2D scan of the samples, both in diamond-anvil cells and multi-anvil press experiments, as well as in situ high-pressure measurements in diamond-anvil cells. Recent examples: Allen-Sutter et al. (2020, Planetary Science Journal) and Ko et al. (2022, GRL).

Aberration corrected electron microscopy provides exciting new opportunities to measure chemical properties of extremely small samples with atomic to nanometer-scale spatial resolution and superb spectral resolutions (EDX and EELS). We have access to new STEM systems in the LeRoy Eyring Center for Solid State Science at ASU. Recent examples: Shim et al. (2017, PNAS), Kim et al. (2021, Nature Astronomy), and Kim et al. (2023, Nature Geoscience).

Secondary ion mass spectrometry allows for the measurements of isotopic ratios and volatile contents of the samples synthesized at high pressure. ASU has a secondary ion mass spectrometry system and a NanoSIMS instrument. Recent examples: Nisr et al. (2020, PNAS).

Although high-pressure techniques have facilitated a plethora of remarkable in situ measurements, the resulting data quality and coverage are often incomplete. This shortcoming can be resolved by conducting experimental measurements in conjunction with density functional theory calculations. Recent examples: Nisr et al. (2020, PNAS) and Piet et al. (2023, GRL).