Mars opposes Earth?
It's not really a rivalry. About every 26 months planet Earth passes between the Sun and sister planet Mars. It's also a time when the two worlds are closer together than normal. Because the orbits of the planets are not perfectly circular, the date of opposition and the date of closest approach aren't usually the same and the distance at its closest also varies.
This year the closest approach of Earth and Mars will take place on December 18 when they will be just shy of 55 million miles apart. Opposition takes place December 24 and Mars will be at its brightest for Earth-bound viewers. The close approach and brightness makes viewing the Red Planet its best during opposition and near-opposition periods.