Wednesday, December 21, 2011

Science Changes

Huh. I thought Mercury was tidally locked with the sun. Apparently not:

Scientists had long assumed that Mercury was tidally locked with the sun — the planet's tiny size and proximity to the sun suggested the star's gravitational pull would quickly force Mercury into such a state. However, radar observations of Mercury surprisingly revealed that the planet led a far stranger life, rotating three times on its axis for every two orbits it completes around the sun.

An asteroid impact likely broke the lock at some point.

I'm glad that is finally settled.