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.

Both orbits are elliptical, and Earth is approaching aphelion, our farthest point from the Sun, while Mars approaches perihelion, its closest.

Mars as seen from the Hubble Space Telescope, with its polar icecap and clouds. Image credit: ESA/Hubble.

On May 30th, Mars will be only 0.51 A.U. (or 76 million km) from Earth, the closest our two worlds have been since 2005.

Earth, as seen from the surface of Mars by the Curiosity rover on January 31, 2014. Image credit: NASA/JPL-Caltech/MSSS/TAMU.

Summer approaches on both worlds: Earth’s from its axial tilt, pointing one hemisphere towards the Sun; Mars’ owing to its orbit’s ellipticity, as it receives 45% more sunlight at perihelion than aphelion.

Mars pre (L) and post (R) dust storm, which are common occurrences during the martian summers. Image credit: NASA/JPL/Malin Space Science Systems, from Mars Global Surveyor.

Mars rises in the southeast around midnight, providing outstanding views through a telescope.

Varying views of Mars near opposition over the course of many years, from 1995–2005. Image credit: NASA/Hubble Heritage team, via https://www.flickr.com/photos/hubble-heritage/3195427662.

Twice the Moon’s diameter but 200 times as distant, Mars is always point-like to human eyes.

Even at its closest, Mars (lower left) still appears nearly 100 times smaller than the Moon. Image credit: Wikimedia Commons user Luisalvaz, under a c.c.a.-s.a.-4.0 International license.

The only superior show comes in July of 2018, when Mars comes within 0.386 A.U. (58 million km) of us, appearing its largest and brightest until 2035.


Mostly Mute Monday tells the story of a single astronomical phenomenon or object primarily in visuals, with no more than 200 words of text.

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