35.8 million miles is definitely not what most of us would consider “close.” But in planetary terms, close is definitely relative! On July 31, Mars will be 35.8 million miles from Earth, which is the closest it has been to Earth in 15 years. What does this mean for sky watchers? It means the Red Planet will appear super bright, and with its orange-red color, will be hard to miss in the nighttime sky. From July 27-30, the point in Mars’ orbit will come closest to Earth, and will be closest to Earth before sunrise Eastern Time on July 31.
What defines a “close approach?” The minimum distance from the Earth to Mars is about 33.9 million miles and does not happen very often. Because Earth and Mars have elliptical orbits and are slightly tilted to each other, all close approaches are not equal. When Mars slowly approaches what astronomers call opposition, it and the Sun are on opposite sides of the Earth. Earth and Mars align in opposition about every two years (fun fact: this is why most NASA missions to the Red Planet are at least two years apart – to take advantage of the closer distance). Opposition to Mars is at its closest to the Sun every 15 to 17 years, when excellent views of the Red Planet from Earth can occur. This is what is happening on the early morning hours of July 31.
Is 35.8 million miles the closest Mars has ever been to Earth? Nope. In 2003, Mars was 34.6 million miles from Earth and the closest it had been in nearly 60,000 years. This type of proximity won’t occur again until 2287. But, there will be another close approach in October 2020 when the distance between the Red Planet and Earth will be 38.6 million miles.
Now that we’ve gotten all of that out of the way, what does this mean for you, the novice astronomer or general sky-watcher? It means that if you have clear skies where you live, go outside on the overnight hours of July 30 or early morning hours of July 31 and look up. The planet will be brighter than usual and will have an orange or red haze. You can also look through a telescope. If weather is bad where you are, NASA will be streaming live from the Griffith Observatory.
Good luck and happy viewing!