Earth and Mars to scale in terms of size and color. Mars is shown in winter, with polar icecaps. Image credit: NASA, with modifications by Wikimedia Commons user Jcpag2012.

Mars gears up for its closest approach to Earth in over a decade

You’ll get another good chance in two years, and then not again until the 2030s!

“This is the plan. Get your ass to Mars, and go to the Hilton Hotel and flash the fake Brubaker I.D. at the front desk, that’s all there is to it. Just do as I tell you.” –Total Recall

Relative to the stars in the sky, planets generally move slightly towards the east from night-to-night.

The retrograde motion of Mars relative to the background stars from March to May, 2014. Image credit: E. Siegel, using Stellarium.

But beginning tonight, Mars will move to the west, commencing retrograde motion, which continues until June 30th.

The geocentric (L) and heliocentric (R) pictures of our Solar System. The planets all orbit the Sun (R), and it is only due to the faster speeds of the inner worlds that this retrograde phenomenon appears to occur. Image credit: E. Siegel.

This isn’t due to Mars changing its motion, but rather to Earth, orbiting inner to Mars, overtaking it due to Earth’s faster path around the Sun.

Earth’s and Mars’ orbits, to scale, as viewed from the Solar System’s north direction. Image credit: Wikimedia Commons user Areong under a c.c.a.-s.a.-2.5 license.