Many folks would like to see us back on the Moon and developing its resources.

Thursday, July 31, 2003

A Mars Record for the Ages: "This is a special year for Mars. Already the planet is shining big and bright in the southeastern sky before dawn, and it's drawing closer to us week by week. For four weeks from mid-August through early September, Mars will be nearer to Earth, and appear bigger in a telescope, than it has since 1988. And at its very closest, it will be a hair closer than it has been in many, many years.
But how many? Various different figures are being reported in different places; some are clearly wrong. Sky & Telescope sorted through the situation to find the authoritative answer.
On August 27, 2003, at 9:51 Universal Time, 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.
There has been some confusion about this because another authoritative source, JPL Horizons gives a time five minutes earlier and a separation 86 km closer. But Horizons expresses all solar-system distances in 'apparent' rather than geometric form, which takes into account the motions of Earth and Mars during the time it takes for light to travel between the two bodies. There is no actual discrepancy.
Mars will indeed be truly close. As Belgian astronomers Edwin Goffin and Jean Meeus wrote long ago, 'In August, 2003, Mars will come closer to Earth than at any time in the last several thousand years, and an even slightly closer approach will take place in the year 2287' (Sky & Telescope: August 1978, page 107). They also explained why. During recent millennia Mars's orbit has been getting slightly more eccentric (elongated) due to the gravitational attractions of other planets. Each passing century brings Mars a little closer to the Sun at perihelion, and a little farther from the Sun at aphelion.

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