We are in the home stretch of the historic 2003 close encounter with the planet Mars, which occurs officially at 5:51 a.m. ET on Wednesday, Aug. 27. Earth has been approaching Mars ever since Aug. 10 of last year. At that time Mars was situated on the opposite side of the Sun at a distance of 248 million miles (400 million kilometers) from the Earth. When it finally emerged into the morning sky some weeks later, Mars was shining no brighter than a mundane second magnitude star. But we have been slowly creeping up on Mars ever since, catching it on the inside of a celestial racetrack around the Sun.