Mars Set to Make Closest Approach to Earth in 11 Years

— -- If Martians exist, they'll be closer to Earth on Memorial Day than they have been in 11 years.

This Monday, around 5:34 p.m. EDT, when many Americans may be enjoying a holiday barbecue, the Red Planet will be the closest it has been to Earth in more than a decade, coming within 46.8 million miles, according to NASA. The relatively close encounter with Earth comes a week after the Martian opposition, when Mars and the sun lined up on exact opposite sides of the Earth.

Every two years, Earth catches up to Mars’ orbit and aligns with the planet and the sun in a straight line. While Earth takes 365 days to orbit the sun, Mars takes 687 Earth days. As a result, the opposition occurs about every 26 months.

The close approach, however, varies between 35 million and 63 million miles, according to NASA, since Mars is on an elliptical orbit around the sun. Mars will be even closer in 2018, coming within 35.8 million miles of Earth, according to NASA.

While Mars will be closer than it has been in a long time, viewing details of the Red Planet may require a powerful telescope. For those wanting to check out Mars' close approach, online observatory Slooh will host a live look at the Red Planet beginning at 9 p.m. EDT.