Planetary magnetic fields from satellite data

Earth's magnetic field has been used for navigation for centuries. Even nowadays, most mobile phones have a magnetic compass built in which is used to determine the direction in which the phone points. This magnetic field is generated deep inside Earth, in our planet's outer core.

But the core magnetic field is not the only magnetic field coming from within our Earth. Certain rocks can become magnetic when they heat up and cool down, or water and rock interactions can create magnetic minerals. The magnetic field from these rocks in Earth's crust was a key evidence to understand plate tectonics.

Earth is not the only planet that has a magnetic field. Most rocky planets have at least a magnetic field from their crust, such as for example Mars and Mercury. For Venus, we simply do not know. Mars does not have a core field but had one in the past. Mercury has a weak and surprisingly-shaped core field. It looks like the magnetic field of a bar magnet aligned with the planet's rotation axis, but "shifted" toward the north pole by 20% of Mercury's radius. Jupiter's moon Ganymede also has a core magnetic field.

Our research group studies planetary magnetic fields from data collected by satellites operated by NASA, ESA, JAXA, etc, with the goal to understand the internal structure and geologic history of the various planetary bodies. For Earth, understanding its magnetic field has revolutionized our understanding of our home planet. Doing the same for other planetary bodies is the new frontier.

Graduate students working with me on planetary magnetic field research should have basic programming skills and be comfortable with mathematical topics such as linear algebra and vector calculus. The vast majority of our research funding comes from NASA.


Near-surface geophysics

Archaeology, groundwater studies, mining prospection, and many other disciplines all have in common that they need to know what is buried within the top few tens of feet below the subsurface. This knowledge should be gained without or only with minimal excavation to reduce cost and, in the case of groundwater studies and archaeology, to avoid disturbing the site. This is where near-surface geophysics comes into play. We collaborate with colleagues in archaeology, biology, hydrology, etc, and use ground penetrating radar, electrical resistivity tomography and time-domain induced polarization to image the shallow subsurface.

A near-surface research project typically starts with detailed planning on how to collect field data. Such planning will involve computer simulations of how what we expect to find will look like in the geophysical data. Field data collection requires carrying equipment and long days of work in the field. But the reward when we study the data we collected in the field is incredible. It is like x-ray vision super power.

Funding for small-scale regional near-surface geophysical projects is difficult to come by, so graduate students working on a near-surface geophysical project are typically funded through a teaching-assistantship, meaning they teach lab components of intro to geology courses. On the other hand, students in near-surface geophysics are typically much less set on a specific project compared to the NASA-funded planetary science students in our group.

Our research group has at its disposal: A ground penetrating radar system (PulseEKKO Ultra) with 50 MHz, 100 MHz, and 200 MHz antennae, an electrical resistivity tomography / time-domain induced polarization system (ABEM Terrameter LS 2) with 48 electrodes and maximum electrode spacing 5m, a differential GPS system with a rover and base station, and high-performance computers for data analysis and inversion.

Alain Plattner
Department of Geological Sciences
University of Alabama
201 7th Avenue
Room 2023 Bevill Building
Tuscaloosa, AL 35487

Email: amplattner (at) ua (dot) edu