Mercury's Moon – Caloris

Hypothesis: That Mercury once had a moon.
Mercury's parameters
Mercury has a 3:2 spin:orbit resonance, rotating three times (3 × 58.7 days) for every two revolutions (2 × 88 days) around the Sun; the eccentricity of Mercury’s orbit makes this resonance stable — at perihelion, when the solar tide is strongest, the Sun is nearly still in Mercury’s sky. The orbit of Mercury has the greatest eccentricity of all the Solar System planets, but has the smallest axial tilt.

It so happens that every second orbit around the sun, perihelion is exactly over the Caloris Basin. At perihelion on the in-between orbits, the Caloris Basin is at the antipodal point.

Mercury ----- Caloris ----- Sun
Caloris ----- Mercury ----- Sun

Top | Home