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Some scientists compare Mercury to a cannonball because its metal core fills nearly 85 percent of the volume of the planet. This large core -- huge compared to the other rocky planets in our solar system -- has long been one of the most intriguing mysteries about Mercury. Scientists had also wondered whether Mercury might have a solid inner core.
The findings of Mercury's solid inner core, published in AGU's journal Geophysical Research Letters, help scientists better understand Mercury but also offer clues about how the solar system formed and how rocky planets change over time.
Mercury - Interior - Molten - Core - Planet
"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 while at NASA Goddard Space Flight Center in Greenbelt, Maryland. "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 figure out what Mercury's core is made of, Genova and his colleagues had to get, figuratively, closer. The team used several observations from NASA's MESSENGER mission to probe Mercury's interior. The researchers looked, most importantly, at the planet's spin and gravity.
MESSENGER - Spacecraft - Orbit - Mercury - March
The MESSENGER spacecraft entered orbit around Mercury in March 2011 and spent four years observing this nearest planet to our Sun until it was deliberately brought down to the planet's surface in April 2015.
Scientists used radio observations from MESSENGER to determine Mercury's gravitational anomalies (areas of local increases or decreases in mass) and the location of its rotational pole, which allowed them to understand the orientation of the planet.
Planet - Axis - Pole - Mercury - Earth
Each planet spins on an axis, also known as the pole. Mercury spins much more slowly than Earth, with its day lasting about 58 Earth days. Scientists often use...
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