"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."
Those are snippets from a widely-circulated email. 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.
Although closest approach is still months away, Mars is
already conspicuous in the early morning. Before the sun comes up, it's the
brightest object in the eastern sky, really eye-catching. If you have a
telescope, even a small one, point it at Mars. You can see the bright icy South
Polar Cap and strange dark markings on the planet's surface.
One day people will walk among those dark markings, exploring
and prospecting, possibly mining ice from the polar caps to supply their
settlements. It's a key goal of NASA's Vision for Space Exploration: to return
to the Moon, to visit Mars and to go beyond.
By
Tony Phillips
Science.NASA.gov
