SPACE
Why doesn’t Mercury orbit on a wonky axis?
Emlyn Morris
© NASA
■ All the planets in the Solar System have a tilted spin axis relative to their orbit around the Sun, but in Mercury’s case the tilt is tiny – less than a 30th of a degree. Another peculiarity is that due to Mercury’s proximity to the Sun, strong tidal forces over billions of years have locked it into a 3:2 spin-orbit resonance. It’s possible that similar tidal effects are responsible for the reduced axial tilt.