Earth's orbit is carrying it to a rendezvous with a planetary neighbor in August that is virtually unprecedented in all of human history.
On Aug. 27, Earth and Mars will share what in celestial terms could be considered a face-off when the planets pass within 34.7 million miles of each other in a phenomenon astronomers call opposition -- when Earth reaches a point on a direct line between the sun and one of the other planets.
Although opposition is a routine event -- it occurs between Mars and Earth about every two years and 50 days -- this particular one carries a special distinction. Astronomers have calculated it will be the closest proximity of Earth and the red planet in 73,000 years.
Because Mars grows larger and brighter as it moves closer, the August opposition has created a buzz among professional and amateur astronomers alike. By then the planet will appear five times larger than normal and its brightness, astronomers said, will increase nearly 60-fold -- enough to reveal new details usually concealed from Earth-based telescopes.
"By any measure, 2003 will be the best year for Mars observing this decade," said Francis Reddy, a veteran science writer and astronomy book author who lives in Newberry, S.C.
Reddy has assembled a series of graphics and animation on his Web site depicting Martian changes in appearance. The online displays plot changes in the planet's phase and angular size every 14 days for the rest of the year.
Reddy said the maps are based on the U.S. Geological Survey's digital Mars mosaic, which is derived from data gathered during the Viking spacecraft missions of the 1970s. "As such, they represent a better view of Mars from space than through a telescope" and therefore should present excellent guides for studying the planet's surface, he explained.
"If you are an observer in the Northern Hemisphere, this is your year for Mars," said P. Clay Sherrod, an astronomer with the Arkansas Sky Observatory. The planet is "fairly high in the sky and only about 35 million miles away from the base of your telescope," he said.
Sherrod, who also has prepared an online Mars-observing guide for amateur sky watchers, said many uncertainties still exist "regarding the visible phenomena of the Martian surface and atmosphere," which is why Mars continues to appeal to the amateur astronomer.
Deemed the symbol of the god of war in ancient times, Mars has been a subject of human fascination since 19th-century Italian astronomer Giovanni Schiaparelli focused his relatively crude telescope on the red planet and discovered what he thought were channels of water.
In a huge and unfortunate misunderstanding, Schiaparelli's word for channels -- canali -- was interpreted by the English-speaking world to mean canals had been dug on the planet's surface by Martian engineers. The possibility became the inspiration for the classic novel, "The War of the Worlds," written in 1898 by H.G. Wells.
"Since the Viking and Mariner spacecraft (have) visited the vicinity of the mysterious planet Mars, some of the wonder and mystique have disappeared from our attitudes toward the red planet," Sherrod said. "We have now closely examined the surface, and it appears that there are no creatures there. Indeed, not even the basic organics necessary for life exist in the Martian environment."
Yet there still is reason to observe the red planet closely, Sherrod noted. "We can rationalize in our human way that the spacecraft may "have missed something."
For example, he explained, scientists still do not know why the maria, or dark areas, of the Martian plains appear to darken when the planet's polar caps melt. They also do not know what causes a mysterious phenomenon called the "blue clearing," in which the Martian atmosphere seems to change color. Nor do they understand why the darker features on the surface seem to change shape and size erratically, a development that caused scientists to abandon the Marian canals idea -- because the features ceased to appear to Earth-bound astronomers.
Less dramatic, perhaps, but just as fascinating scientifically, Sherrod said, data from orbiting spacecraft and successful landings have revealed Mars at one time "was quite active both geologically and meteorologically, considerably more so than at present."
Near the beginning of the 20th century, American astronomer Percival Lowell -- still forwarding the assumption the red planet was population -- developed the theory that Mars was a dying world, Sherrod said, "one in which its inhabitants were starving and dehydrating from the lack of water."
Lowell theorized that Martians had built the canals to bring melting water from the planet's polar ice caps to thirsty cities. "We now know that Mars does not have canals and that there are no inhabitants who wait eagerly for the advent of spring," Sherrod said. "Yet Lowell was correct about one point of his theory -- Mars is, indeed, a dying world."
(Reddy's Mars observing guide can be found at: home.mindspring.com/%7Efjr1/mars2003.html. Sherrod's guide is part of the Arkansas Sky Observatory site: arksky.org/mars2003.htm)