If no one has asked you about it yet, they probably will. A bogus e-mail chain letter, sometimes titled "Mars Spectacular," has been circulating around the Internet, as it did two years ago. It claims that on August 27th the planet Mars will dazzle the world, appearing brighter than ever in history and "as large as the full Moon to the naked eye."

The problem is that "August 27th" is actually August 27, 2003. Mars did make a historically close pass by Earth at that time. In August 2006, though, the Red Planet is invisible, hidden behind the glare of the Sun. And, of course, to the naked eye Mars will always looks like a bright star, not the full Moon.

As they orbit the Sun, the Earth and Mars make a close approach every 2-1/4 years or so. This time is called "opposition," because from our perspective on Earth, Mars then appears opposite the Sun in the sky. On average the two planets come within 48 million miles of each other. But because their orbits are elliptical (oval) rather than perfectly circular, the minimum separation between the two planets varies from one opposition to the next.

In late August 2003 Mars came within 35 million miles of Earth, and in late October and early November 2005 it came within 43 million miles. Mars's next opposition will come in December 2007, when it will be farther still, 55 million miles from Earth. For reference, the Moon orbits the Earth at an average distance of about 240,000 miles, and the average Earth–Sun distance is about 93 million miles.

"The Mars chain letter gets revived every August," says Alan MacRobert, a senior editor of Sky & Telescope. "I see it as a good thing, not a bad thing. It's an immunization. If you make a fool of yourself by sending it to your friends and family, you'll be less likely to send them the next e-mail chain letter you get, which may not be so harmless."

The first place to check for facts about any Internet rumor, hoax, or urban legend is www.snopes.com. Bookmark it!

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