Sunlight is therefore more effective at raising the temperature of the northern hemisphere . This results in the surprising fact that northern summer is a little warmer than southern summer even though Earth is farther from the Sun in July. On planets like Mars with orbits much more eccentric than ours, the varying distance to the Sun can have a big influence on seasonal conditions. For example, northern summer on Mars lasts 24 days longer than winter because the planet is close to aphelion when the north pole is tilted toward the Sun. This won't happen on Earth because our orbit is more nearly circular than the Red Planet's.
Earth has one of the most circular orbits in the solar system.
Only Neptune and Venus follow more perfectly circular paths around the Sun. The other six planets trace paths that are significantly elliptical. Pluto, the planet with the greatest orbital eccentricity, follows a path so lopsided that it sometimes travels closer to the Sun than Neptune. Just last year Pluto ended a 20-year stint as the eighth planet when it crossed Neptune's orbit in February on its way back to the outer solar system. After Pluto, the second and third most elliptical orbits belong to Mercury and Mars, respectively.