Astronomers Ready for Close Encounter of a Mars Kind

John Roach
for National Geographic News
August 12, 2003

On August 27, the orbits of Earth and Mars will bring the two planets the closest they have been in nearly 60,000 years. For the weeks surrounding this celestial event, the red planet will be the brightest star in the night sky.

Precisely 34,646,418 miles (55,758,006 kilometers) will separate Earth and Mars during the event. Mars won't approach the Earth as closely again for another 284 years, at which time it will approach even closer, according to astronomers.

Mars rises in the southeastern sky progressively earlier each night in August and September. By late August, Mars will be visible after 9 or 10 p.m. local time. As the night progresses, the planet climbs higher and shifts to the south.

The planet will look like a "very bright red star" said Robert Zubrin, president of the Indian Hills, Colorado-based Mars Society. Most people should be able to see it, even from the most light-polluted cities.

Close Orbits

To explain why Mars and Earth are so cozy at this point in time, Zubrin likened the orbits of the planets around the Sun to the minute and hour hands on a clock.

"Sometimes they are close to each other, and sometimes not," he said. "On a clock, the two hands make a close pass about once an hour. Earth and Mars make a close pass every 26 months. But since Earth's orbit is almost circular and Mars's is somewhat elliptical, some passes are closer than others. This one is the best."

Myles Standish, an astronomer at NASA's Jet Propulsion Laboratory in Pasadena, California, likens the phenomenon to two race cars, Earth and Mars, speeding around two race tracks with Earth orbiting the inside track.

Neither track is perfectly circular. But there is one place where the tracks are closest together. When Mars and Earth happen to reach that place simultaneously, it makes for an unusually close approach.

"It gets more complicated, because the race tracks are changing shape and size, and they are rotating, changing their orientation," said Standish. "So this place where the two tracks are closest together changes."

Standish added that over the past 60,000 years the point of the shortest distance between Mars's and Earth's orbits has been decreasing and will continue to do so for the next several hundred years.

Mars Observations

Continued on Next Page >>




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