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Mars Opposition and Equinox | by NASA on The Commons
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Mars Opposition and Equinox

Description: 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 was at opposition on June 13-14 and made its closest approach to Earth on June 21, when it is about 67 million kilometers (~42 million miles) away and subtended 20.8 arc-seconds in the sky. For observers in the northern hemisphere, it could be seen as a bright(magnitude -2) red object, low in the southern sky near the constellation Scorpius, in the evening. Southern hemisphere observers had a better view, as Mars was higher in the sky from that vantage.


The Image above is one of a series of simulated views of Mars as it would be seen from the Mars Global Surveyor spacecraft.


Image #: PIA03229

Date: June 13, 2001

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Taken on June 13, 2001