In 2018, Mars will appear brightest from July 27 to July 30. Mars closest approach will be July 31, 2018. That is the point in Mars’ orbit when it comes closest to Earth. Mars will be at a distance of 35.8 million miles (57.6 million kilometres). It reaches its highest point around midnight — about 35 degrees above the southern horizon, or one-third of the distance between the horizon and overhead. Mars will be visible for much of the night. By mid-August, it will become fainter, as Mars and Earth travel farther away from each other in their orbits around the Sun. Miss seeing Mars Close Approach in 2018? The next Mars Close Approach is Oct. 6, 2020.
Close is a relative term. The minimum distance from the Earth to Mars is about 33.9 million miles (54.6 million kilometres). However, that doesn’t happen very often. If Earth and Mars had perfectly circular orbits, their minimum distance would always be the same. However, they have elliptical (egg-shaped) paths. Also, gravitational tugging by planets constantly changes the shape of their orbits a little bit. Giant Jupiter especially influences the orbit of Mars. The orbits of Mars and Earth are also slightly tilted concerning each other. All of these factors mean that not all close encounters are equal. In 2003, Mars made its closest approach to Earth in nearly 60,000 years! It won’t be that close again until the year 2287. When Mars and Earth are close to each other, Mars appears very bright in our sky. It also makes it easier to see with telescopes or the naked eye. The Red Planet comes close enough for exceptional viewing only once or twice every 15 or 17 years.
When does Mars Close Approach Occur?
Mars Close Approach happens about every 26 months. It is closely related to Mars Opposition and Mars Retrograde. Since Mars and Earth are at their closest, it’s generally the best time to go to Mars. Many Mars missions have taken advantage of the close distance to visit the red planet. That’s why, depending on budgets, you’ll often see that Mars missions launch about every two years:
2001: Mars Odyssey
2003: Mars Exploration Rovers
2005: Mars Reconnaissance Orbiter
2007: Mars Phoenix Lander
2009: (skipped opportunity)
2011: Mars Science Laboratory/Curiosity Rover
2016: (skipped opportunity)
2020: Mars 2020
After this event, the next Mars Close Approach is Oct. 6, 2020, when the Red Planet will be only 38.6 million miles (62.07 million kilometres) from Earth.