The School of Earth and Atmospheric Sciences Presents Dr. Hao Cao, Harvard University

A Magnetic Perspective on the Interiors of Saturn and Mercury

Magnetic fields are windows into planetary interiors. The existence and properties of the planetary magnetic fields reflect the interior structure, dynamics, and evolution of the host planets. Recent observations from the MESSENGER, the Cassini, and the Juno missions have revealed many surprising features in the magnetic fields and interiors of Mercury, Saturn, and Jupiter, respectively. 

In this talk, I will mainly present my analyses and interpretations of the magnetic fields of Saturn and Mercury. For Saturn, the new features of the planet’s magnetic field revealed by the Cassini Grand Finale will be reported, including the small-scale axisymmetric magnetic structures and the new upper limit on the non-axisymmetry of the field. Implications on deep zonal flows (differential rotation) and stable stratification inside Saturn will be discussed. 

For Mercury, with the help of numerical dynamo experiments, I will show that the peculiar north-south asymmetry in Mercury’s magnetic field can be reconciled with the slow rotation of Mercury, extensive iron snow within Mercury’s liquid core, and a relatively small solid inner core. 

In closing, I will highlight the magnetic aspects of the ongoing Juno mission and a few upcoming planetary missions (e.g. Psyche mission to asteroid 16 Psyche, Clipper to Europa, BepiColombo to Mercury, JUICE to Ganymede, and a possible mission to Uranus/Neptune) and how they will help answer questions ranging from the thermal evolution history of asteroid 16 Psyche to the salinity of Europa’s ocean.