Peter

DriscollHe/His

The geodynamo is the process by which Earth generates its magnetic field by convection in the liquid iron-rich outer core. Evidence supporting the existence of the ancient geodynamo extends back to at least 3.5 billion years ago—possibly as far back as 4.2 billion years, nearly the age of the Earth itself. 

How has Earth maintained a dynamo-generated magnetic field for so long? No one knows for sure, but the answer is intertwined with how Earth has maintained a habitable surface for so long.  

The geodynamo that creates the magnetic field is a critical component of Earth's prolonged habitability. It shields the surface of our planet from high-energy particles that are harmful to life. It might even be important for protecting the atmosphere from erosion by solar wind.  Understanding what drives the geodynamo and how it may have evolved over Earth's history is central to understanding the evolution of life, the atmosphere, and what makes planets habitable in general.

Earth is the only planet known to have maintained an internally generated magnetic field in its core over most, if not all, of its history.  The presence of a core-generated planetary magnetic field is commonplace in the Solar System, with nearly every planet either maintaining a present-day core dynamo (Earth, Mercury, Jupiter, Saturn, Uranus, Neptune) or showing evidence of one in the past (Mars). Although there is presently no evidence for a dynamo in Venus, it could have maintained one in the past.  Even satellites are capable of dynamo action: lunar rocks show evidence of a now-extinct dynamo in the Moon, and Ganymede, the largest satellite of Jupiter, maintains a dynamo today.

There are three general requirements to maintaining a planetary magnetic field:

1. The presence of a liquid that is electrically conductive—like Earth’s iron-rich liquid outer core
2. Planetary rotation
3. Fluid motion—often generated by the convection of the fluid

Factors (1) and (2) are common but the presence of convection is less of a guarantee. 

To drive convection in the core there must be a continuous source of buoyancy to keep the fluid moving.  In the modern-day core, this is thought to be predominantly supplied by the release of light elements at the base of the outer core, where the iron-rich liquid solidifies onto the solid inner core. During the solidification, light elements—such as oxygen, silicon, or sulfur—are rejected from the solid and accumulate in the liquid, where they rise and drive convective currents.  However, Earth’s inner core, and the solidification process, is likely only about a billion years old based on the cooling rate of the planet’s interior, which is significantly younger than the geodynamo.

Peter Driscoll is currently working on modeling the thermal evolution of the Earth to better constrain the timing of inner core solidification and the cooling rate of the interior, which is critical to understanding what was driving the geodynamo in the deep past.

He is also working with Computational Scientist Cian Wilson on first principles 3D dynamo models that generate magnetic fields from rotating convection in a spherical shell. In particular, they are testing how the thermal and chemical buoyancy fields interact and are coupled to each other as the core cools. Ultimately their goal is to better quantify what kinds of magnetic fields are generated from different driving forces and apply that knowledge to better understand the Earth’s thermal evolution from the paleomagnetic record.

• Chair, Computational Infrastructure for Geodynamics, Dynamo Working Group 2019-present
• Associate Editor, Frontiers in Geophysics, 2018-present
• Carnegie Venture Grant 2019, 2017
• Yale University Bateman Fellowship, 2010-12
• NASA Ames Honor Award 2002

• Ph.D., Earth & Planetary Sciences, Johns Hopkins University, Baltimore, MD, 2010
• M.A., Earth & Planetary Sciences, Johns Hopkins University, Baltimore, MD, 2008
• M.S., Physics & Astronomy, San Francisco State University, San Francisco, CA, 2006
• B.S., Physics & Astronomy, Dickinson College, Carlisle, PA,  2003

• Staff Scientist, Earth & Planets Lab, Carnegie Institution for Science, 2015-present
• Postdoctoral Fellow, NASA Virtual Planetary Laboratory, University of Washington, 2013-2015
• NSF FESD Postdoctoral Researcher, Yale University, 2012-2013
• Bateman Postdoctoral Associate, Yale University, 2010-2012
• NSF Graduate Research Associate, Johns Hopkins University, 2006-2010
• Graduate Teaching Associate, Johns Hopkins University, Spring 2008
• NASA/NSF Graduate Research Associate, California Planet Search, San Francisco State U., 2003-2006
• Graduate Teaching Associate, San Francisco State University, 2003-2006
• Education Associates Internship, NASA Ames Research Center, Summer 2002
• Teaching Assistant & Laboratory Consultant, Dickinson College, 2001-2002
• NSF Summer Internship, Scitefair International, Inc., Philadelphia, PA, Summers 2000-2001

• Planetary Habitability, Guest Lecturer, University of Washington, Fall 2013, 2017
• Early Earth Seminar, CoOrganizer, Yale University, Spring 2013
• Life in the Universe, Guest Lecturer, Yale University, Fall 2011
• Habitable Planets Seminar, Co-Organizer, Yale University, 2010-2011
• Natural Catastrophes, Assistant, Johns Hopkins University, Spring 2008
• Physical Sciences, Guest Lecturer, Johns Hopkins School of Education, Spring 2007
• Introductory Astronomy Lab, Instructor, San Francisco State University, 2004-2006
• Introductory Physics Lab, Instructor, San Francisco State University, Fall 2003
• Workshop Physics, Assistant, Dickinson College, 2002-2003