We use cookies to create a secure and effective website. By using our website you agree to our use of cookies in accordance with our cookie policy - hide this message

Astronomy Events Guide

Mars Opposition 2018


Get ready to see the Red Planet up close this summer: When Mars reaches opposition with the sun, observers on Earth will have their closest view of the planet since 2003.


Mars and Earth both orbit the sun, but at different distances, and thus, different speeds. Every two years or so, Mars, Earth and the sun form a straight line during the course of their orbits, with Earth in the middle — an event known as opposition


This summer, opposition occurs on July 27, and Mars will reach its closest approach to Earth 7:50am on July 31. The Red Planet will also be at its brightest since 2003, when Mars made its closest approach to Earth in almost 60,000 years. 


Closest since 2003


View photos

Mars reaches opposition, as in this artist's illustration, when it's opposite from the sun in Earth's sky. NASA







During the Mars opposition in 2003, the Red Planet was only 34.6 million miles (55.8 million kilometers) from Earth. This was the closest the two planets had come to each other in almost 60,000 years, and this record won't be broken until August 28th, 2287, according to NASA. 


In comparison, when Mars is on the other side of the sun and thus at its greatest distance from Earth, it is about 250 million miles (401 million km) away. However, the average distance between the two planets is roughly 140 million miles (225 million km).


Leading up to this year's opposition in July, Mars will continue to brighten in our sky. By June 26, Mars will be just 44 million miles (70.8 million km) away, and from the perspective of watchers on Earth, it will appear five times brighter than usual. By the time the Red Planet reaches its closest point to Earth, it will be a mere 35.8 million miles (57.6 million km) away and will have nearly doubled in brightness since June 26.


What, exactly, is an opposition?


Mars orbits the sun at a greater distance than Earth. As the distances increase, the orbital period also increases, so Mars takes about two Earth years to complete one orbit around the sun. Due to these different orbital speeds, every two years or so, Earth passes between Mars and the sun. This means that Mars and the sun are on directly opposite sides of Earth. 


Also, because Mars is directly opposite the sun during opposition, Mars rises as the sun sets, and it sets as the sun rises. As a result, the Red Planet shines prominently in our night sky.


In addition, this year, Mars will reach what is called "perihelic opposition". Perihelion refers to the point in Mars' orbit when it's closest to the sun. Therefore, when Mars is closest to the sun, it is even closer to Earth during opposition. 


How to see Mars 


For about two months, between July 7th and September 7th this year, Mars will brighten dramatically, outshining Jupiter and moving up in rank as the fourth-brightest object in Earth's sky after Venus, the moon and the sun. Throughout May, both Mars and Saturn will be visible, and the best views will be in the predawn hours of the Northern Hemisphere. Mars is easily distinguished by its reddish colour, while Saturn appears golden. Mars will move east of Saturn by mid-May, into the constellation Capricornus. Starting in mid-June, Mars will officially enter the evening sky and noticeably brighten and grow in size, leading up to opposition on July 27. The planet will appear brightest between July 21 and Aug. 3. As sunsets occur earlier in late summer and early autumn, viewers will be able to see the planet higher in the evening sky.