On the opposite end of the scale, Mars and Earth can be 401 million km apart (249 million miles) when they are in opposition and both are at aphelion. The average distance between the two is 225 million km. When Mars and Earth are at their closest, you have your launch window. read more
The answer to that question changes from moment to moment because Earth and Mars are orbiting the Sun. read more
Distance from Earth to Mars - How long would it take to travel from Earth to Mars - what is the distance in miles and kilometers read more