The distance between Earth and Mars varies greatly because both planets are orbiting the Sun in elliptical paths.

* At their closest: Earth and Mars are about 0.5 astronomical units (AU) apart.

* At their furthest: They can be as far as 2.5 AU apart.

Important Note: An astronomical unit (AU) is the average distance between the Earth and the Sun, which is approximately 93 million miles or 150 million kilometers.