Doug Hemingway
Postdoctoral Fellow

DougHemingway

Research Interests

Planetary geophysics; interior modeling from gravitational and magnetic field data; icy ocean worlds; planetary magnetism; space weathering

Academics

BASc, 2001, Systems Design Engineering, University of Waterloo, Canada
MSc, 2009, Space Studies, International Space University, Strasbourg, France
PhD, 2015, Earth & Planetary Sciences, University of California Santa Cruz, USA

Contact & Links

  • (202) 478-8815
  • dhemingway@carnegiescience.edu
  • Department of Terrestrial Magnetism
    Carnegie Institution of Washington
    5241 Broad Branch Road, NW
    Washington, DC 20015-1305
  • curriculum vitae
  • Personal Website

Overview

HemingwayImages
Figure 1 (top): Depiction of the approximate interior structure of Saturn's ~250 km radius icy moon Enceladus, comprising a ~190 km radius low density rocky core, surrounded by a global liquid water ocean, and an outer ice shell of laterally variable thickness [Hemingway and Mittal, 2018]. Figure 2 (bottom): Lunar Reconnaissance Orbiter Camera view of a lunar swirl—an optical anomaly on the lunar surface that coincides with a crustal magnetic anomaly [Hemingway and Tikoo, 2018].

I study the geophysical processes that drive the evolution and behavior of planetary interiors. I do this by developing models that are constrained by spacecraft-based observations, especially those relating to gravitational and magnetic fields.

Part of my research focusses on icy ocean worlds in the outer solar system. Where sufficiently precise measurements can be made, much about the interior structures of these bodies can be deduced from asymmetries in their figures and gravitational fields, and from their responses to tidal forces. I have been using observations from the Cassini spacecraft (which was orbiting Saturn until 2017) to place constraints on the interiors of some of the large moons of Saturn, including Titan, Enceladus (Figure 1), Rhea, and Dione. With its surprising level of geologic activity—namely its ongoing eruptions of organic-rich water ice—Enceladus is perhaps the most compelling of these moons, and is presently our best opportunity for developing an understanding of icy ocean worlds in general. Enceladus’s ice shell structure is important for understanding the nature of the ongoing eruptions and how the moon responds to tidal forces. The shell structure also tells us about the energy budget. How and where is heat dissipated internally? Is the ice so thin that Enceladus is cooling faster than it can dissipate heat internally? Can the internal liquid water ocean be sustained over geologic time? More generally, how does the presence or absence of an internal liquid water ocean change the dominant geodynamical processes on icy moons, and what accounts for the major differences we see across the solar system?

Another track of my research involves planetary magnetism and the origins of the crustal magnetic anomalies on the Moon, Mars, and Mercury. An enduring mystery since Apollo is that, in spite of the Moon's lack of a global magnetic field, the surface is nevertheless dotted with regional magnetic fields strong enough to be detected from orbit. Did the Moon once have an intrinsic global field that magnetized parts of the crust but has since decayed away? This is a question of fundamental importance to understanding the formation and thermal evolution of solid planetary bodies, and yet it remains unresolved due in part to limitations in our knowledge of these crustal magnetic anomalies. A useful clue comes from an intriguing series of optical anomalies known as lunar swirls (Figure 2). Swirls appear to be places where the presence of strong crustal magnetic fields interfere with the way the solar wind plasma can access the surface—the solar wind is a stream of charged particles coming from the sun and participates in the poorly understood process of ‘space weathering’ whereby the optical properties of surfaces are altered over time due to exposure to solar wind and micrometeoroids. To the extent that they track near-surface magnetic field structure, the swirls can be used to probe crustal magnetic fields on scales that are much finer than what can be resolved from orbit, helping to constrain the origins of the underlying magnetic anomalies and, in turn, to better understand the Moon’s magnetic history. More generally, investigations starting from patterns in the crustal magnetic anomalies on the Moon, Mars, and Mercury have the potential to offer important insights into the deep internal structure and early thermal history of these bodies.