Answer: On average, Mars is about 225 million kilometers (140 million miles) away from Earth.

The distance between Mars and Earth varies continuously as both planets follow elliptical orbits around the Sun. When Mars is at its closest approach to Earth then a phenomenon known as opposition takes place which means that Mars can come as close as approximately 54.6 million kilometers or 33.9 million miles. This event occurs approximately every 26 months and during opposition Mars appears brighter and larger in the night sky. when Mars is on the opposite side of its orbit from Earth then it is at its farthest distance reaching approximately 401 million kilometers or 249 million miles away.

Space agencies take advantage of these favorable oppositions to launch missions to Mars with reduced travel times and fuel requirements. For example, the launch window for the shortest trip from Earth to Mars occurs approximately every 26 months.