Steve Jacobsen
Department of Earth and Planetary Sciences
Northwestern University
Evanston, IL 60208
Tel 847.467.1825
Email


Research

Steve Jacobsen, Associate Professor in the Department of Earth and Planetary Sciences is a mineralogist specializing in the field of mineral physics, which explores the materials science of geophysical processes.

Liquid water covers almost 75% of Earth's surface, but contitutes only 0.025% of the entire planet's mass; far less H2O than found in primitive meteorites, thought to represent Earth's bulk composition. Could there exist a hidden, much larger geochemical reservoir of H2O in Earth's interior? Jacobsen investigates water in minerals and the role hydrated minerals may play in plate tectonics and the evolution of our planet into a habitable world. Deep water, dissolved at the atomic scale into the solid rocks and minerals of the mantle at extreme conditions of pressure and temperature may constitute the planet's largest reservoir of H2O. Hydrated minerals display modified physical properties, such as density and elastic properties, which may allow remote detection of water cycling in the mantle from seismic waves. Jacobsen's lab is working towards understanding the whole-Earth water cycle, and the influence of water on the physical properties of Earth materials from atomic to geophysical scales.

In mineral physics, students and postdocs are working on a wide range of projects, including design and synthesis of superhard materials, elastic properties of diamond and related materials, equations of state of materials at extreme conditions, hydrogen bonding in silicates, thermodynamic modeling of hydrated minerals in the mantle, spectroscopy of water in minerals, cement mineralogy, CO2 sequestration, and IR-reflectivity of hydrocarbon ices and liquids. Much of the group's research is carried out at the Advanced Photon Source of Argonne National Laboratory and the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory.


Funding

This research is supported by a Fellowship for Science and Engineering by the David and Lucile Packard Foundation and grants from the US National Science Foundation EAR-0651173 (Instrumentation and Facilities), EAR-0721449 (Geophysics Program), and a Faculty Early Career Development Award (CAREER) EAR-0748707. Support is also provided by the Carnegie/DOE Alliance Center (CDAC), a Stewardship Science Academic Alliance Program of the Department of Energy and the National Nuclear Security Administration.


Selected Publications

Complete List

Earth's Deep Water Cycle


Steven D. Jacobsen and Suzan van der Lee, Editors

This interdisciplinary volume, available through AGU books, covers recent discoveries on the origin, distribution, and influence of water in the Earth. High-pressure silicates have a remarkable ability to incorporate water as OH-defects into their crystal structures, with some major consequences for their physical properties. Minerals within a remote mantle layer from 410-660 km depth could contain the majority of our planet's water and acted to control surface waters over geologic time. If so, could deep geochemical reservoirs of water be detected remotely using seismology? What role has water played in the evolution of plate tectonics and our habitable planet? This volume integrates studies from mineral physics, seismology, experimental petrology, geochemistry, and geodynamics.

View the Table of Contents



High-pressure science and technology

In the Northwestern Mineral Physics Laboratory, using gem diamonds as superhard transparent anvils, we simulate conditions deep inside the Earth and use pressure to modify the structure and physical properties of materials. The anvils, each about 2.5 mm in height, are precisely cut and aligned to support static pressures at their tips in excess of 100 gigapascals (or 1 Mbar, about the pressure 3000 km deep in the Earth). Samples inside are compressed within a tiny sample chamber made by forming a hard, rhenium-metal gasket around the anvil tips. A pressure transmitting medium such as helium surrounds the sample to compress it without being crushed between the diamond tips, which remain apart. The diamonds, transparent to visible, infrared, and X-radiation, allow us to probe the structures and physical properties of materials formed under extreme conditions.

One of the questions we are exploring is how much water the Earth's interior might store, in the form of OH-defects inside high-pressure silicate minerals. The image above right, shows a blue crystal of hydrous ringwoodite (g-Mg2SiO4) at about 30 GPa, just after laser heating to 2000 K. By reacting minerals with water under deep mantle conditions, we are studying the hydrogen storage capacity of the mantle, and the influence of OH-related defects on the physical properties of Earth's mantle. For example, hydrated silicates of the mantle appear to transmit seismic waves more slowly than dry rock, suggesting that seismology might be used as a remote probe to test for "deep oceans" in the interior.


GHz-ultrasonic interferometry

I am developing a high-frequency acoustic method called gigahertz (GHz) ultrasonic interferometry. This ultrasonic probe has been interfaced with the diamond-anvil cell (DAC) to measure the compressional and shear-wave velocities in single-crystal samples that were previously too small for ultrasonic methods. GHz-frequency shear waves are produced by P-to-S conversion inside a single-crystal gem. Elastic properties of samples as thin as 20 microns have been measured, or about four times thinner than a human hair. The elastic tensor of materials relates stress to strain and is used in mineral physics to understand how seismic waves propagate through the solid Earth. In that sense, we simulate tiny earthquakes in the Northwestern Mineral Physics Laboratory (though at much higher frequency, and shorter wavelengths).

Seismograms from a real earthquake (top) and from inside the diamond-anvil cell.

Research Keywords

Mineral physics and applications to solid-Earth geophysics and geochemistry, planetary science, high-pressure physics and chemistry, and materials science. Keywords include: material structure and properties; elasticity; crystal chemistry; hydrogen in minerals; interpretation of Earth's seismic structure; Earth's deep water cycle; hydrogen bonding; planetary ices; Titan; iron in minerals; electronic structure; superhard materials; high-pressure science and technology; ultrasonic testing; X-ray and neutron diffraction; infrared and Raman spectroscopy; diamond-anvil cell; single-crystal synthesis; Synchrotron radiation; National Synchrotron Light Source of Brookhaven National Laboratory; Advanced Photon Source of Argonne National Laboratory.

Courses at Northwestern

EARTH-101: Earth Science for the 21st Century
EARTH-102: The Future of Renewable Energy
EARTH-300: Earth and Planetary Materials
EARTH-301: Petrology: Evolution of Crustal and Mantle Rocks
EARTH-438: Advanced Topics in Geophysics: Water in the Solar System
EARTH-438: Advanced Topics in Geophysics: Mineral Physics From Crust to Core
EARTH-440: Advanced Topics in Geochemistry: Metamorphic and Sedimentary Petrology

Honors

2013 Northwestern University Weinberg College Distinguished Teaching Award
2008 Presidential Early Career Award for Scientists and Engineers (PECASE), see a photo
2008 Packard Fellowship for Science and Engineering, David and Lucile Packard Foundation
2008 Faculty Early Career Development Award, National Science Foundation
2007 Mineralogical Society of America Distinguished Lecturer

Education

Ph.D. Geophysics; University of Colorado
M.S. Geology; University of Colorado
B.A. Geology; University of Colorado

Positions Held

Associate Professor, 2011-present
Department of Earth and Planetary Sciences, Northwestern University, Evanston, IL

Assistant Professor, 2006-2011
Department of Earth and Planetary Sciences, Northwestern University, Evanston, IL

Research Scientist (Principal Investigator), 2005-2006
Carnegie Institution of Washington, Geophysical Laboratory, Washington D.C.

Barbara McClintock Fellow; 2005
Carnegie Institution of Washington, Geophysical Laboratory, Washington D.C.

Alexander von Humboldt Fellow and Research Associate, 2002-2004
Bayerisches Geoinstitut, University of Bayreuth, Germany

CIRES Graduate Research Fellow, 1999-2000
Cooperative Institute for Research in Environmental Sciences (CIRES) and Department of Geological Sciences, University of Colorado

Links


My favorite rock shop: Dave's Down to Earth Rock Shop.


RRUFF Project: Database of Raman spectra, X-ray diffraction, and chemical data for minerals.


Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.