Prior to the Mariner 4 flyby in 1965, all we knew about Mars came from Earth-based telescopic observations. At best, Mars is a challenging object to observe, due to its small size, low contrast, and turbulence in Earth's atmosphere. The best times to see the planet are around its closest approaches to Earth, which occur near "opposition," when the two planets are roughly in a line on one side of the Sun. This occurs about every 26 months, when Mars can appear to grow (in the night sky) to as large as about 20 arc-seconds in size. (20 arc-seconds is about the apparent size of a dime seen from 190 meters, or about the length of two football fields, away; it is about the size of a crater 40 kilometers (25 miles) in diameter on the Moon.)
In 2001, Mars is at opposition on June 13-14 and makes its closest approach to Earth on June 21, when it is about 67 million kilometers (~42 million miles) away and subtends 20.8 arc-seconds in the sky. For observers in the northern hemisphere, it can be seen as a bright (magnitude -2) red object, low in the southern sky near the constellation Scorpius, in the evening. Southern hemisphere observers have a better view, as Mars is higher in the sky from that vantage.
Not only is Mars at opposition June 13-14, 2001, and making its closest approach to Earth since 1988 on June 21st, on June 17-18 Mars will be at equinox, with the southern hemisphere turning to spring and the northern hemisphere begins autumn. The diagrams below illustrate the opposition and equinox configurations of Mars.
The Image above is one of a series of simulated views of Mars as it would be seen from the Mars Global Surveyor spacecraft. To view the rest of these images please go to the June 2001: Mars Opposition and Equinox page at the Malin Space Science Systems web site.
Animation of simulated Earth-based views of Mars.