Mercury’s Shadowy North Pole

[muriel_volestrangler]

9. I'd never heard of that, but I see what you mean

because the orbit is very eccentric, Mercury's angular velocity around the Sun is more, for a short time, than its rotational angular velocity, so the Sun would appears to go backwards. The Wikipedia explanation:

At certain points on Mercury's surface, an observer would be able to see the Sun rise about halfway, then reverse and set before rising again, all within the same Mercurian day. This is because approximately four Earth days before perihelion, Mercury's angular orbital velocity exactly equals its angular rotational velocity so that the Sun's apparent motion ceases; at perihelion, Mercury's angular orbital velocity then exceeds the angular rotational velocity. Thus, to a hypothetical observer on Mercury, the Sun appears to move in a retrograde direction. Four days after perihelion, the Sun’s normal apparent motion resumes at these points.

http://en.wikipedia.org/wiki/Mercury_%28planet%29