The rounded knobs (arrows) up to 3 or 4 cm wide on 'Shark' and 'Half Dome' and in the foreground could be pebbles in a cemented matrix of clays, silts, and sands; such rocks are called conglomerates. Image captured by NASA's Sojourner Rover.

The rounded knobs (arrows) up to 3 or 4 cm wide on "Shark" (left; approximately 70 cm wide)) and "Half Dome" (upper right) and in the foreground could be pebbles in a cemented matrix of clays, silts, and sands; such rocks are called conglomerates. Well-rounded objects like these were not seen at the Viking sites.

NOTE: original caption as published in Science magazine.

Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

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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