Station Info :: Nine Planet Solar System ::
Space Mercury :: Mercury Orbit
Mercury orbit has high eccentricity, with the planet's distance from the Sun. Among the major planets only Pluto has a more eccentric orbit. However, because of the smallness of Mercury's orbit, all of the planets except the Earth and Venus have a larger spread between perihelion and aphelion (Mars' is 42.6 Gm to Mercury's 23.8 Gm, for example); there are even several outer planet satellites that beat Mercury's spread: Saturn's S/2004 S 18 (with 30.8 Gm) and Neptune's S/2003 N 1 and S/2002 N 4 (42.0 and 47.9 Gm, respectively).
A study indicates that the eccentricity of Mercury's orbit varies frantically from 0 (circular) to a very high 0.47 over millions of years. This is thought to explain Mercury's 3:2 spin-orbit resonance (rather than the more usual 1:1), because this state is more likely to happen through a period of high eccentricity.
Also see the
Physical Characteristics of Mercury
Understanding Of Mercury
Exploration Of Mercury