Planetary Magnetic Fields

A Public lecture presented by:  Professor Richard Holme

Internally generated magnetic fields are a feature of most planetary bodies. That of the Earth is best characterised and studied, with study from recent dedicated satellite missions, an extensive historical record, and probing of its geological history from recordings in rocks. However, all the outer planets (Jupiter, Saturn, Uranus and Neptune) also have currently active internal magnetic fields, as does Mercury, and Mars and the Moon show evidence of having had fields generated in the past. Even a moon of Jupiter, Ganymede, has its own field, and induced fields from the main field of Jupiter have provided the primary evidence of subsurface oceans in this and two other moons, leading to discussions of the possible presence of life. The Messenger mission to Mercury is currently revolutionising our understanding of this field, while in the last phase of its Mission, Cassini is due to probe the details of Saturn's enigmatic, axisymmetric field by going into a very close orbit.

The Juno mission is due to provide unprecedented coverage of the jovian field from 2016, while the ESA mission Juice, recently accepted, will answer many questions concerning Ganymede (although sadly only in 2033!) Finally, there is growing discussion as the possible detection and use of magnetic fields of extra-solar planets. In this talk, I provide an observational perspective on the magnetic fields of planets, drawing on my own work on the Earth, Jupiter, Uranus, Neptune and Mercury, and discuss what further information knowledge of planetary magnetic fields can yield.

Professor Richard Holme is a professor of Geophysics at the University of Liverpool. His research interests focus on modelling of the magnetic fields of planets from data, and the use of such models to infer details of internal planetary structure and processes. For the Earth models cover timescales from days to millions of years, drawing upon satellite data, historical measurements, and records from archaelogical artefacts and rocks. For the other planets he uses available mission data: his past work has focused on Jupiter, Uranus and Neptune, and he is now focusing on Mercury and Ganymede.