On August 27, 2003, at 9:51 UTC, the centers of Earth and Mars will be only 55,758,006 kilometers (34,646,418 miles) apart. The U.S. Naval Observatory?s MICA software and the Jet Propulsion Laboratory?s DE406 planetary ephemeris agree on this value for the true geometric distance.
According to a calculation by the Association of Lunar and Planetary Observers' Jeffrey Beish and James DeYoung, Mars came a little closer to Earth in 57,537 BC. Aldo Vitagliano, an expert in computational celestial mechanics at the University of Naples, Italy, has confirmed that there was indeed a close approach in the year 57,538 BC (not 57,537 BC), but it did not quite beat the AD 2003 value.
Vitagliano?s calculation took about three hours on an 800mhz computer, and it involved a simultaneous numerical integration of the motions of all nine planets, the Earth's moon, and three major asteroids (Ceres, Pallas, and Vesta). At first he adopted JPL?s DE406 as the starting point; then he repeated the calculation using JPL?s earlier DE200. He also tried omitting the asteroids and Pluto to see if that would make a significant difference ? it didn't. Vitagliano concludes that the last time Mars came so close was in 57,617 BC, when it passed within 55.718 million km of Earth, a little closer than this year?s 55.758 million km.
So the upcoming approach is the closest in 59,620 years.
However, an even closer approach than this one will take place in 2287.
In terms of visual astronomy, of course, even a difference of a million km is pretty much insignificant. So it's not like Mars is going to look any more detailed at this approach than it does at the typical close approach.
Still, Mars is sure to be a popular target at star parties and public observing sessions later this summer.
Personally, I find Jupiter and Saturn to be much more interesting planetary subjects than is Mars. But to each his own.
To find an astronomy club near you (so that you can go to a public viewing session and look at stuff through other people's telescopes, without going into debt to buy your own $5000 scope which you might not even know how to use), click
here.
To read a little more about observing Mars, click
here.
If you're anywhere near Harrisburg, PA, the Astronomical Society of Harrisburg has free public viewing sessions every Sunday this summer (weather permitting). For details, click
here.