Data collected during the MESSENGER mission indicates Mercury has a solid inner core. Image: Antonio Genova
Using sophisticated software to precisely analyse how Mercury’s gravity affected the trajectory of NASA’s MESSENGER spacecraft during multiple low-altitude orbits, researchers have been able to show the small planet must have a large, solid-iron inner core measuring some 2,000 kilometres (1,260 miles) across, almost as large as Earth’s.
Including its molten metal outer layer, Mercury’s metallic core fills nearly 85 percent of the planet’s volume, huge compared to the cores of the solar systems other terrestrial planets.
“Mercury’s interior is still active, due to the molten core that powers the planet’s weak magnetic field, relative to Earth’s,” said Antonio Genova, an assistant professor at Sapienza University of Rome who led the research. “Mercury’s interior has cooled more rapidly than our planet’s. Mercury may help us predict how Earth’s magnetic field will change as the core cools.”
To determine the nature of Mercury’s inner core, researchers used radio observations from MESSENGER to determine the precise position of the planet’s rotational pole and incorporated ground-based radar data collected in 2007 showing small shifts in the planet’s 58-day spin, called librations, that indicated the presence of at ...