Mars As Big as Full Moon Tonight? All a Hoax

In case you haven’t heard: Mars will be as big as the full moon tonight. Or so goes the e-mail that’s circulating the internet. It’s all a hoax, however, one that’s been perpetrated every year since 2003.

Among the claims in the Mars hoax e-mail:

  • "The Red Planet is about to be spectacular."
  • "Earth is catching up with Mars [for] the closest approach between the two planets in recorded history."
  • "On August 27th … Mars will look as large as the full moon."
  • "Two Moons on August 27."

Each year, the e-mail (said by some to have innocent roots) replicates itself like a virus and is forwarded by unwitting (and sometimes amazed) internet users.

The hoax has its origins in an event that occurred on Aug. 27, 2003, when Mars was closer to Earth than it had been in 60,000 years. The event was hyped — some say overhyped — as being a great opportunity to see the red planet. Indeed it was a great opportunity. With Mars being (34.6 million miles, or 55.7 million km) away, it was ever-so-slightly larger and brighter than usual. The Hubble Telescope snapped some excellent Mars globe photos.

But Mars did not then, and cannot ever, appear as large as the moon. Astronomer Neil deGrasse Tyson, director of New York's Hayden Planetarium, put the 2003 close pass in cosmic perspective:

"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.'"

Right now, Mars is faint and barely visible in the western evening sky [Sky Map] just after the sun goes down. It sets about 90 minutes after the sun does. Near Mars, you will see a very bright "star." That’s Venus, which is so close and so bright that with binoculars or a small telescope, you can actually see it is in a crescent phase (Venus, like the moon, goes through phases from our vantagepoint).

Mars is faint tonight because it’s not at all close to us. And here's why: The red planet’s trip around the sun is longer than that of Earth. When the two planets are on the same side of the sun, with Earth passing Mars on the inside track, they’re at their closest. When the two planets are on opposite sides of the sun, the distance between them is at its greatest.

"On August 27, 2010, Mars will be 314 million km [195 million miles] from Earth, about as far away as it can get," according to NASA.