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 mineral physics, which uses principles of condensed matter physics and materials science to understand geophysical processes.

Liquid water covers almost 75% of Earth's surface, but constitutes only 0.025wt% of the planet's mass. This is far less water than is found in primitive meteorites, thought to represent building blocks of the terrestrial planets. Earth's deep water cycle is connected to the rock cycle through plate tectonics. Could there exist a hidden, much larger geochemical reservoir of H2O in Earth's interior?

Little is known about how much H2O the Earth contains as a whole, or how the oceans developed. Was Earth's water delivered by comets, or did most of it degass out of the primitive mantle? 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.

Hydrated minerals containing OH defects 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 influence of water on the physical properties of Earth and planetary 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, 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.


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 Alliances (SSAA) Program of the Department of Energy, 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 research on the origin, distribution, and influence of water in the Earth. High-pressure silicates can incorporate water as OH-defects into their crystal structures, with some major consequences for their physical properties. Minerals within the transition region of the mantle from 410-660 km depth could contain the majority of our planet's water and acted to control surface waters over geologic time.

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 found deep inside the Earth and use pressure to modify the structure and physical properties of materials. The diamond 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. 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 deep inside, in the form of OH-defects in 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 1600 C (orange spots). 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 materials. 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 search 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.

Professional Interests

Mineral physics and solid-Earth geophysics; geochemistry, geology, planetary science, materials science, condensed matter physics, and physical chemistry, with emphasis on how pressure and temperature modifies fundamental properties of materials such as structure, bonding, and elasticity; Earth’s deep water cycle from atomic to geophysical scales; water in the solar system; extrasolar planets, superhard materials, cement minerals, role of minerals and materials in energy technology; science outreach at all levels.

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

2014 Bessel Award, Alexander von Humboldt Foundation
2013 Distinguished Teaching Award, Weinberg College of Arts and Sciences, Northwestern University
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
2005 Barbara McClintock Fellowship, Carnegie Institution of Washington
2002 Alexander von Humboldt Fellowship, Bayerisches Geoinstitut

Education

Ph.D. Geophysics; 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.