Mars 2018 Opposition


drawing by Denis Fell

Every 2 years and about 50 days, the planet Mars appears opposite the Sun in our sky, shining brighter and appearing larger than usual. Some Mars oppositions are much closer than others, owing to the large eccentricity of the planet's orbit. The 2018 Opposition of Mars is the best apparition since August 2003, 15 years ago. With opposition on July 27 and closest approach on July 31, for much of the summer the disk of Mars will appear larger than that of Saturn, and for a time will even outshine Jupiter. Read all about it in the RASC Observer's Handbook 2018, in the article The Planets in 2018—Mars by Murray Paulson.


Mars will be larger than 24'' in diameter between July 23 and August 9, nearly as large as the 2003 opposition size of 25"; however, visual observing in the months leading up to opposition trains the eye and reveals the changing face of Mars as it moves from the Mars autumnal equinox on May 22 to the Mars winter solstice on October 16.

Below, you will find downloadable resources for observing and drawing Mars with the aid of a telescope, including an observing form, courtesy of RASC member and Mars watcher Denis Fell. RASC members can read his article in the June 2018 issue of the Journal of the RASC.

Mars 2018 Highlights
May 9 12" Look for North Polar Hood, Hellas darkening, atmospheric clouds, and South Polar Hood (thinning).
May 22 14" Autumnal Equinox (northern hemisphere)—South Polar Cap at maximum, look for polar hoods.
Jun 26 21" Retrograde (east–west) motion begins—Syrtis Major darkens, check for clouds.
Jul 27 24" Opposition—look for the dark rifts Rima Augusta and Rima Australis in South Polar Cap.
Jul 31 24" Closest approach to Earth—check for dust clouds.
Aug 27 22" Retrograde motion ends.
Sep 15 18" Perihelion—look for dust clouds over Serpentis–Hellespontus.
Oct 16 14" Winter Solstice (northern hemisphere) Summer Solstice (southern hemisphere).
Oct 31 12" Check for North Polar Hood growth.
Last modified: 
Sunday, April 29, 2018 - 11:48am