13 October 2011

Mercury's day is longer than its year

A solar day (noon to noon) on Mercury is as long as 176 Earth days.  But its year (one orbit around the sun) takes only 88 Earth days.  So the day is two years long...  (Details here).

Photo from the Messenger spacecraft, which is mapping the planet, via NASA's Astronomy Photo of the Day.


  1. Yep. Mercury has a stable 2:3 Spin-orbit resonance with the Sun.

  2. Whoops. That ratio should be 3:2 not 2:3.

  3. Sufferers of 'Seasonal Affective Disorder' (SAD) should avoid Mercurean nights, then....

  4. I'm 257 Mercury years old and this is the first time I've heard of this.


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