Here's why:

* The Sun is the center of our solar system. Earth orbits the Sun at an average distance of 93 million miles (150 million kilometers).

* Mars is a planet that orbits the Sun further out than Earth. The average distance between Mars and the Sun is 142 million miles (228 million kilometers).

While Mars's orbit is elliptical, meaning its distance from the Sun varies, it's always farther away from the Sun than Earth. Therefore, it's closer to Earth than the Sun.