Joseph G. O'Rourke

Earth and Planetary Scientist

Dr. Joseph G. O'Rourke is an Assistant Professor in the School of Earth and Space Exploration at Arizona State University, specializing in the long-term evolution of Earth and other worlds.

Representative Sketches of Ongoing Projects

Structure and Evolution of Earth's Core and Magnetic Field

I proposed that precipitation of magnesium-bearing minerals could power Earth's dynamo—especially before the inner core started growing. This new source of chemical convection is necessary to reconcile models with observational and experimental constraints on core/mantle heat flow and radiogenic heating. At present, I am modeling the putative layer with low density and seismic velocity atop the core.

News & Views for O'Rourke & Stevenson (2016)

Prospects for Crustal Remanent Magnetism on Venus

Venus lacks an internally generated magnetic field today. However, future missions (ideally an aerial platform) should perform the first-ever magnetometer measurements below the ionosphere to search for crustal remanent magnetism. My numerical simulations predict dynamo activity within the surface age if and only if Venus has an Earth-like core, which would imply a similar birth for these celestial cousins.

Concept from 2015 KISS Report on "Probing the Interior Structure of Venus" (Stevenson et al.).

Suppressing the Martian Dynamo with Hydrogenation of the Core

I formulated a new story for the demise of Mars' global magnetic field roughly 4 billion years ago. After a delay caused by phase changes or compositional stratification in the lower mantle, hydrogen from hydrated minerals like ringwoodite begins partitioning into the core. Hydrogenation represents a sink of gravitational energy that kills the dynamo even if core/mantle heat flow is rather high, which is useful to explain the apparent longevity of mantle plumes.

InSight w/ deployed instruments (NASA/JPL-Caltech).

Athena: A SmallSat Mission to (2) Pallas

I am the Principal Investigator of a SmallSat mission (ESPA-class) called Athena, which would perform the first-ever encounter with (2) Pallas—the most off-ecliptic and largest unexplored protoplanet in the main asteroid belt and the parent of a populous impact family that includes several notable near-Earth asteroids such as (3200) Phaethon. Athena was evaluated as Category 1 in the 2018 NASA SIMPLEx competition but not selected. We eagerly await the next opportunity to propose this exciting concept!

Artist's rendition by B. E. Schmidt and S. C. Radcliffe.