The smallest planet in our solar system has a massive solid inner core.
In its final trip around Mercury before crash-landing in 2015, NASAs MESSENGER mission zoomed in close to the planet, enabling scientists to make detailed measurements of its gravity, spin and internal structure. Those data, researchers report April 10 in Geophysical Research Letters, suggest Mercury has a solid inner core about 2,000 kilometers in diameter, making up about half of Mercurys entire core.
Scientists already knew that Mercurys core was huge, taking up about 85 percent of the planet (SN: 4/21/12, p. 8). In 2007, radar observations made from Earth detected small oscillations in Mercurys spin rate that suggested the core was at least partially liquid (SN: 5/5/07). Then MESSENGER data revealed that the planet has a weak magnetic field generated by circulation of molten metal in that liquid core (SN Online: 5/7/15). But it wasnt clear if Mercury, like Earth, also has a solid inner core.
To study the planets interior structure, MESSENGER measured Mercurys distribution of mass by tracking tiny shifts in the spacecrafts orbiting speed caused by subtle variations in gravitational pull. Using those data, scientists were able to estimate what sort of interior composition would best explain how Mercury spins.
Big heart
Measurements of gravity anomalies within Mercury suggest that the planets solid inner core makes up about half of the total core. The entire core is about 85 percent of the planet.
The smallest planet in our solar system has a massive solid inner core.
In its final trip around Mercury before crash-landing in 2015, NASAs MESSENGER mission zoomed in close to the planet, enabling scientists to make detailed measurements of its gravity, spin and internal structure. Those data, researchers report April 10 in Geophysical Research Letters, suggest Mercury has a solid inner core about 2,000 kilometers in diameter, making up about half of Mercurys entire core.
Scientists already knew that Mercurys core was huge, taking up about 85 percent of the planet (SN: 4/21/12, p. 8). In 2007, radar observations made from Earth detected small oscillations in Mercurys spin rate that suggested the core was at least partially liquid (SN: 5/5/07). Then MESSENGER data revealed that the planet has a weak magnetic field generated by circulation of molten metal in that liquid core (SN Online: 5/7/15). But it wasnt clear if Mercury, like Earth, also has a solid inner core.
To study the planets interior structure, MESSENGER measured Mercurys distribution of mass by tracking tiny shifts in the spacecrafts orbiting speed caused by subtle variations in gravitational pull. Using those data, scientists were able to estimate what sort of interior composition would best explain how Mercury spins.
Big heart
Measurements of gravity anomalies within Mercury suggest that the planets solid inner core makes up about half of the total core. The entire core is about 85 percent of the planet.
