What is the structure of Mercurys core?
The biggest surprise from the Mariner 10 flybys was that Mercury has a global magnetic field, making it the only terrestrial (rocky) planet besides Earth to have one. Mercury’s magnetic field is weak – about 100 times weaker than Earth’s at the surface – but that it exists at all raises interesting questions about activity deep inside the planet. Earth’s magnetic field is generated by the swirling motions of molten liquid in our planet’s outer core. But Mercury is so much smaller than Earth – 4,878 kilometers in diameter vs. Earth’s 12,714 kilometers (3,031 miles vs. 7,900 miles) – that its core should have cooled and solidified long ago. Its many long scarps suggest that the planet has contracted and the core has cooled, so how could Mercury’s now stagnant core generate a magnetic field? One potential answer is that the observed magnetic field is a fossil remaining from Mercury’s earliest years; perhaps rocks were magnetized long ago when there was a magnetic field, and Mariner 10’s m
