Scientific Areas
Earth’s Deep Interior
Understanding the deep interior of Earth and other planets requires experimental investigations of the physical and chemical properties of materials at extreme pressures and temperatures. For example, convection of the liquid iron-rich metal outer core produces Earth’s magnetic field, which is crucial for life. Still, little is known about the detailed chemical composition, viscosity, or melting behavior of the liquid outer core to adequately model and understand this phenomenon.
Plate tectonics is a direct consequence of the dynamic interior of the Earth, driven by heat exchange between the core and lower mantle. While the basic structure and mineralogy of the mantle and core are well-established, there are many unanswered questions about how heat and chemicals are exchanged between the core and mantle, and what effect light and volatile elements may have on the elastic properties of the minerals in the mantle.
SEES beamlines provide cutting-edge instruments with extremely bright, high-energy X-rays enabling Earth scientists from across the US and the world use SEES beamlines to investigate these sorts of fundamental questions about the physical and chemical composition and properties of materials and the extremely high-pressure and temperature conditions of the Earth’s interior.
Earth’s Upper Mantle and Crust
The Earth’s upper mantle and transition zone are the engines that drive the redistribution of critical life-giving and economically important elements between Earth’s surface and interior. Crustal processes such as sedimentary cycling, volcanic degassing, and hydrothermal circulation drive seismicity and volcanism, help regulate the climate and create the conditions on the Earth’s surface required for life to thrive.
While geoscientists have relied on bulk measurements of electronic and structural properties of natural and synthetic glasses and minerals for decades, synchrotron methods can probe these materials at the microscale, allowing earth scientists to untangle problems that were previously too complex. Synchrotron X-ray spectroscopic methods are particularly useful in determining the oxidation state of reactive transition metals such as iron, titanium, chromium, and vanadium. With these methods, geochemists can answer questions about how the oxidation state of the mantle has changed over the course of Earth’s history, and how the minerals formed at different pressures, temperatures, and oxidation states affected the evolution of the Earth’s ocean and atmosphere. Understanding this interplay of pressure, temperature, and chemical state is also vital for understanding the intensity and frequency of volcanic eruptions, and how ore deposits form.
Fluid-Rock Interaction
Fluids such as water exert important controls on the formation and evolution of the Earth. Water is incorporated into rocks deep into the Earth’s crust, and affects how the crust fractures and flows, and so can greatly impact the seismic activity of the Earth.
Earth scientists use SEES beamlines to study the rates at which faults in the Earth’s crust propagate, and how pressurized pore fluids influence the strength in a fault zone throughout the earthquake cycle. This understanding will lead to a better understanding of the physics of earthquakes and lead to more reliable assessment and mitigation of geohazards.
Earth’s Near-Surface and Environmental Science
The distribution and cycling of chemical elements depend on molecular-scale geochemical processes that take place in the continental and oceanic crusts, oceans, and the atmosphere that comprise the Earth’s envelope. The interactions of the chemical elements that are critical for supporting life derive from a complex balance of thermodynamic and kinetic forces that span length scales from nano- to mega-meters and time scales from picoseconds to millions of years.
Geochemists use a variety of synchrotron X-ray methods at SEES beamlines to study the atomic-scale structure and chemistry of minerals, soils, biofilms, micro-organisms, and mixtures of solids, fluids, and gases. The advances in our understanding of the chemistry of the Earth from these scientific studies give vital information for mineral exploration and extraction and for waste disposal of these elements that are vital for a sustainable modern civilization.
Many geophysical tools such as seismic, radar, gravity, electrical, and magnetic imaging are used to characterize the Earth’s surface and crust. Connecting the large-scale geophysical data of subsurface properties to the molecular level is very challenging, especially given the heterogeneous and complex mineralogy, pore structures, and multiphase fluids that comprise the crust and surface of the Earth. The SEES beamlines are used by geoscientists to combine imaging with measurements of the chemical and mechanical properties and the interactions between rock and pore-fluids at laboratory length and time scales that are invaluable for creating models to better understand the near-surface geophysics.
Planetary Science
While we know quite a bit about the formation and composition of the planets and other bodies in our solar system, there are mony open questions. For example, as with the Earth, the chemical compositions and especially oxidation levels of the moon, asteroids, Mars, and other planets will determine which minerals will be present. In addition, chemical analysis of precious samples such as meteorites, asteroids, and comets can give invaluable information about the composition of the early solar system.
Astro- and Geochemists use the SEES beamlines for non-destructive analysis of the physical and chemical states of samples from many NASA missions that have returned samples from the moon, comets, and asteroids.