Mars generally moves west to east (right to left) on the background of stars. But every 780 days it goes through period of 83 days during which it moves east to west against the stars, the retrograde motion. The retrograde period is centered around the time when Mars is in opposition - Mars is directly opposite the Sun.

The movie begins on October 1, 1996 and lasts until September 4, 1999 with 6 days between each frame. Two complete retrograde events are shown. The view is about 30 degrees in height and 90 degrees in width. The line of the ecliptic is shown in green for reference. The Sun, Moon, Mercury and Venus also pass through your field of view during the movie. The movie was created using Starry Night, by Sienna Software.

The left hand view is from above the sun (in yellow) looking down on the earth (in green) and Mars (in read). The right hand view is looking up at Mars in the sky from the earth. The movie begins on March 1st, 1998 and ends on October 31,1999 with 3 days between frames.

Further question: Why isn't the retrograde loop a flat line?

Page created by David Cebula