Quashing the Myth of a Moon-Sized Mars

The infamous Mars hoax that widely circulated on the Internet since its first appearance in the summer of 2004 is rearing its head again. It comes in the form of an e-mail message titled "Mars Spectacular," originating from an unknown source.

The Mars hoax e-mail has been passed on to countless others who haven't been able to resist forwarding it to their entire address book. In some cases, the message has been turned into a full-blown PowerPoint presentation, accompanied by snazzy-looking graphics seemingly providing a sense of authenticity to the message.

The e-mail declares that on the night of Aug. 27, the planet Mars will come closer to Earth than it has in 60,000 years, thereby offering spectacular views of the Red Planet. The commentary even proclaims, with liberal use of exclamation marks, that Mars will appear as bright as (or as large as) the full moon.

The problem is that "Aug. 27" is actually Aug. 27, 2003. Mars made a historically close pass by Earth that night (34.6 million miles, or 55.7 million km). The Hubble Space Telescope used the opportunity to make some great images of Mars. But even then, to the naked eye Mars appeared as nothing more than an extremely bright yellowish-orange star, not at all like the full moon.

It is impossible for Mars to ever appear as large at the moon. [Amazing Mars Photos]

This Mars sky map shows the location of Mars in the night sky on Friday, Aug. 27 at 9 p.m. EDT as seen from the northeastern United States, weather permitting.

As Neil deGrasse Tyson, director of New York's Hayden Planetarium, puts it: "The proximity of Mars to Earth in 2003, while indeed closer than in the past 60,000 years, was nonetheless no more meaningful than me swimming a hundred yards out from the California coast (instead of my usual seventy yards) and then declaring to the world, "I have never been this close to China before."

Where's Mars now?

This year Mars is actually much dimmer and far less conspicuous than in 2003.

If you want to find Mars right now in the early evening sky, you should use the brilliant planet Venus as your guide. Face the west-southwest about 45 minutes after sunset.

You can't miss Venus. Mars will be situated about 2 to 3 degrees above and to the right of it.

As a reminder, your clenched fist, held at arm's length measures roughly 10 degrees. So Mars is about one-third of a fist above and to the right of Venus.

Currently, Mars sets at about the same time as Venus, about 90 minutes after sundown. But at magnitude +1.5, Mars is about six magnitudes and 250 times less bright than Venus, so you might need binoculars to pick it up in the twilight sky.

In terms of actual size, Mars (approximately 4,213 miles, or 6,780 km in diameter) is almost twice the size of our moon (about 2,160 miles, or 3,475 km). But the great distance between Mars and Earth never allows it to appear anywhere near as large as the moon in our sky.

The average distance of the moon from Earth is 238,000 miles (382,900 km). For Mars to appear to loom as large as the moon does, it would have to be about twice the Moon's distance, or roughly 476,000 miles (766,000 km).

In fact, this week the Red Planet is 198 million miles (318 million km) from Earth.

Duped by the hoax

To give you some idea of how many people have fallen for this over the years, back on Aug. 27, 2007, one of nature's great sky shows, a total eclipse of the moon, occurred across the United States.

On the day before the eclipse, the Hayden Planetarium's Answer-Line expected a heavy volume of phone inquiries from the general public concerning advice on how to view the eclipse. Fifty-one calls were logged, but amazingly, only three concerned the upcoming eclipse; the other 48 were calls (some breathless) asking where and when would be the best times to see Mars when it was due to appear as large as the moon.

Not a few of those calls actually started off chiding the planetarium for not scheduling a public viewing session for the "Big Mars Event!"

So, plain and simple, if you have already received this infamous Mars e-mail — or eventually receive it during the next few days — be advised that it is totally bogus. And please, don't pass it on.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.

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