Two Views of Mars
In 2005, the Mars closest approach and opposition occurred within a week of each other. On October 28/29 (depending on what time zone one lived), Mars was the closest it has been in the last two years, reaching a distance of only 43 million miles from Earth. On this date, the Mars, Earth, Sun angle was almost lined up but not quite, resulting in a slight shadow on the eastern edge of Mars. On November 7, the Mars, Earth, Sun angle was perfectly aligned, and Mars was in opposition with the Sun as seen from Earth. This resulted in a perfect globe of Mars viewed from Earth and from the Hubble Space Telescope on November 8. Two different detectors were used on the two dates that Hubble observed the Red Planet, the first image being taken on October 28 with the Advanced Camera for Surveys High Resolution Channel, and the second image on November 8 with the Wide Field Planetary Camera 2. Slightly different filters on the two detectors pick up subtly different features on the Martian surface and in the Martian atmosphere. More cloud structure appears in the opposition image, making the planet appear somewhat wider at the equator.