On any of these next few nights – July 25 to 27, 2018 – watch for the moon and the very bright red object near it. That red “star” is really a planet, Mars. On July 27, Mars comes to opposition in our sky for the first time since May 22, 2016. That’s when our planet Earth, in its smaller orbit around the sun, passes more or less between the sun and Mars. The 2018 Martian opposition happens on July 27 around 05:00 UTC (1 a.m. EDT … 10 p.m. PDT on July 26; translate UTC to your time).
Opposition is a special time for any superior planet. Around the time of opposition, a superior planet comes closest to Earth for the year and, in turn, shines at its brightest best in Earth’s sky. Moreover, any planet at opposition – being opposite the sun – rises in the east at sunset, climbs to its highest point in the sky at midnight, and sets in the west around sunrise.
And so Mars, now opposite the sun, shines brightly all night long.
On July 27, when Mars is at opposition, the full moon will be near Mars in the sky. And – as seen from Earth’s Eastern Hemisphere – there will be a total eclipse of the full moon. Click here to learn more about the July 27 total lunar eclipse.
Oppositions of Mars happen about every two years. That makes sense because Earth takes a year to orbit the sun, and Mars takes about two years. About every two years, we gain a lap on Mars, passing between it and the sun.
Not all Mars’ oppositions are equal, and 2018 brings Mars’ brightest appearance in our sky since 2003. Since early July, Mars has shone more brightly than the king planet Jupiter, which is generally the fourth-brightest sky object after the sun, moon and planet Venus. In 2018, Mars shines more brightly than Jupiter from about July 7 to September 7, 2018. You can’t miss Mars right now! On July 25 to 27, even the drenching moonlight won’t wash the red planet from the nighttime sky.
Extra-close oppositions of Mars (less than 37 million miles or 60 million km) recur in periods of 15 to 17 years. The last extra-close Martian opposition happened on August 28, 2003, and the next one will occur on September 15, 2035.
Extra-close oppositions happen when we go between Mars and the sun around the time Mars is near perihelion – its closest point to the sun. That makes sense, too, right?
An extra-far opposition (over 62 million miles or 100 million km) last took place on March 3, 2012, when Mars was near aphelion – its farthest point from the sun. As a basis of comparison, the 2018 opposition of Mars finds the planet about 28 million miles (45 million km) closer than the extra-far opposition of 2012.
Extra-far oppositions also recur in periods of 15 to 17 years, and the next one will happen on February 19, 2027.
By the way, Mars will come closest to Earth some four days after opposition, on July 31, 2018.
If Earth and Mars orbited the sun in perfect circles and on the same exact plane, Earth would come closest to Mars right at opposition. However, the orbits of both Earth and Mars are not perfect circles; they are ellipses, like circles someone sat down on.
Mars always comes closest to Earth near (but not necessarily on) opposition. The time interval between opposition and Mars’ nearest point to Earth is no greater than 8.5 days, and can be as little as 10 minutes.
Bottom line: July 2018 is the best time in nearly 15 years to see Mars. Earth passes between Mars and the sun on July 27, 2018, the Martian opposition. Earth and Mars will be closest on July 31, 2018.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.