Mars Arrives At Opposition!

In October the planet Mars makes another of its once every 26 month visits to the Earth and blazes like a ruddy-orange beacon above the eastern horizon after sunset. Normally the most disappointing of the five bright naked-eye planets (see below), it now takes center stage and dominates the night sky!

On the evening of October 13th Mars reaches opposition (or “opposite” the Sun in the sky). Because it has a very elliptical orbit, which can take it as much as 250,000,000 miles from us, coupled with it relatively small size (at 4,200 miles in diameter—only about half that of the Earth) makes it a difficult telescopic target much of the time as far as seeing any of its features. BUT this month it will approach to within 39,000,000 miles. And this is actually as close as it will be again for the next 15 years at an opposition.

At such times, a magnification of just 25X will make Mars appear as big as the full Moon. Impressive as this might sound it’s very misleading, since everyone over-estimates the size of the Moon. It’s actually smaller than a dime held at arm’s length! While the unaided eye and binoculars will show nothing of the planet’s polar caps or surface markings (which will require a magnification of at least 100X), they will reveal two things of interest. Mars’ tiny disk makes

it decidedly non-star-like, shining with a steady light (unlike a twinkling star). And its color is quite intense. However, Mars is not red, as most people believe (leading to it often being referred to as the “Red Planet”) but rather ruddy-orange. Much of the planet is covered with deserts whose sand is of that hue. And the cause of the color is that Mars is heavily oxidized—or rusted! This means that it contains oxygen and water which could be utilized—something those planning to colonize the planet are counting on doing.

October brings to mind for many the famous War of the Worlds CBS radio broadcast on the evening of October 30th, 1938. An adaptation by Orson Welles of the classic H.G. Wells’s novel of the same title, it was intended as a fictional Halloween offering of “The Mercury Theater on the Air.” But its amazing realism (thanks to Welles’ acting genius) resulted in something of a panic, as many listeners actually believed that the Earth was being invaded by Martians! You may well laugh at this given our knowledge today of conditions on the planet as definitely not being life-friendly. But back in 1938 it was still widely thought that Mars was possibly inhabited. I’ve personally listened to the original broadcast several times on Halloween nights and can tell you that I for one would have believed that it was happening!

— James Mullaney
Former assistant editor at Sky & Telescope magazine & author of 10 books on stargazing. His latest, Celebrating the Universe!, is available from