July 7, 2005: Just when you thought it was safe to read your email....
There's a rumor about Mars going around the internet. Here are some snippets from a widely-circulated email message:
"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."
And finally, "NO ONE ALIVE TODAY WILL EVER SEE THIS AGAIN."
Only the first sentence is true. The Red Planet is about to be spectacular. The rest is a hoax.
Here are the facts: Earth and Mars are converging for a close encounter this year on October 30th at 0319 Universal Time. Distance: 69 million kilometers. To the unaided eye, Mars will look like a bright red star, a pinprick of light, certainly not as wide as the full Moon.
Disappointed? Don't be. If Mars did come close enough to rival the Moon, its gravity would alter Earth's orbit and raise terrible tides.
Sixty-nine million km is good. At that distance, Mars shines brighter than anything else in the sky except the Sun, the Moon and Venus. The visual magnitude of Mars on Oct. 30, 2005, will be -2.3. Even inattentive sky watchers will notice it, rising at sundown and soaring overhead at midnight.
You might remember another encounter with Mars, about two years ago, on August 27, 2003. That was the closest in recorded history, by a whisker, and millions of people watched as the distance between Mars and Earth shrunk to 56 million km. This October's encounter, at 69 million km, is similar. To casual observers, Mars will seem about as bright and beautiful in 2005 as it was in 2003.