Sunset over Ares Vallis, taken by NASA's Mars Pathfinder in 1997.

Every several days, Mars Pathfinder will image the sunrise and sunset on Mars. Future images will show a larger area -- we have a higher data rate than we expected when we planned this image, so we can get more information. Images taken at sunset, like this, and up to two hours later, will be used to investigate the distribution of dust within the Martian atmosphere. Already, we can see some dust layers in the images. By seeing how the twilight fades with time -- it lasts for over two hours -- we can determine that the dust extends high into the atmosphere.

Photojournal note: Sojourner spent 83 days of a planned seven-day mission exploring the Martian terrain, acquiring images, and taking chemical, atmospheric and other measurements. The final data transmission received from Pathfinder was at 10:23 UTC on September 27, 1997. Although mission managers tried to restore full communications during the following five months, the successful mission was terminated on March 10, 1998.

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