Note: This article was published in June of 2003. The event it discusses occured in August of 2003. For more information on any email you may receive on the subject, see the article called: Mars Closest to Earth Email.
August of 2003 is a special time for scientists and amateur astronomers. Our red neighbor, will move closer than its been in 50,000 years. On August 27, 2003, the "red planet" will be less than 55.76 million kilometers (34.65 million miles) away from the Earth. That sounds like a huge distance, but in stellar terms, thats a stones throw. Just six months before, Mars was about five times that distance.
"Think of Earth and Mars as two race cars going around a track," said Dr. Myles Standish, an astronomer from NASAs Jet Propulsion Laboratory, Pasadena, Calif. "Earth is on a race track that is inside the track that Mars goes around, and neither track is perfectly circular. There is one place where the two race tracks are closest together. When Earth and Mars are at that place simultaneously, it is an unusually close approach, referred to as a 'perihelic opposition'."
The term "opposition" means that Earth and another planet are lined up in the same direction from the Sun. "Perihelic" comes from perihelion, the orbital point when a celestial body is closest to the Sun. This event brings Mars to its perihelion to the Sun opposition with Earth at the same time.
Opposition occurs about every two years, when Earth with its faster orbit passes Mars. In 1995, the opposition brought Mars 101.1 million kilometers (62.8 million miles) from the Earth, twice as far as this most recent approach.
"It gets more complicated as the race tracks are changing shape and size and are rotating, changing their orientation," Standish explains. "So this place where the two tracks are closest together constantly changes, changing the opposition closeness as well. This is why a 'great' approach, like the one this month, hasnt happened in 50,000 years. But with the tracks closer together now, there will be even closer approaches in the relatively near future."