How does Mercury's rotation relate to the Sun?
A) Its rotation rate is 2/3 as long as its year, due to tidal resonances.
B) It always keeps one face tidally locked toward the Sun, as our Moon does with us.
C) Its day is the same length as its year.
D) Its year is much shorter, only 88 days, than its slow rotation of 243 days on its axis.
E) It does not spin at all, being tidal stopped by the solar tides.

Question

Quizplus · Accepted Answer

Mercury's rotation period is 2/3 of its orbital period due to a 3:2 spin-orbit resonance, meaning it rotates three times on its axis for every two orbits around the Sun.

How Does Mercury's Rotation Relate to the Sun