KATLENBURG-LINDAU, Germany, Dec. 23 (UPI) -- Mercury, the smallest planet and the closest to the sun, has an unexpectedly weak magnetic field, and European researchers have fingered the sun as the culprit.
Planetary magnetic fields are generated by flows in the hot, liquid iron cores of rocky planets. Based on its size and density, Mercury should field strengths similar to those on Earth -- yet the planet's field is 150 times weaker than Earth's.