Twenty-five years ago, on July 20, 1976, NASA's Viking 1 lander soft-landed on the surface of Mars, becoming the first successful mission to land on the red planet, as well as the first successful American landing on another planet.

With a second lander later joining the first on the surface and with two orbiters circling the planet, the Viking project changed our understanding of that alien world. Its treasure trove of images and data covering the entire Martian globe remains a valuable scientific resource for the study of Mars.

The Viking 1 lander operated on the Plain of Chryse (Chryse Planitia) until November 1982. The Viking 2 lander set down on the Plain of Utopia (Utopia Planitia) on Sept. 3, 1976, and operated until April 1980. The two landers took 4,500 unprecedented images of the surrounding surface and more than three million weather-related measurements, while the two orbiters took 52,000 images representing 97 percent of the Martian globe.

Viking will probably be most remembered for its search for life on Mars. Each lander contained a suite of biology instruments designed to detect evidence of life in the Martian soil. Scientists concluded that the Viking experiments found no evidence of life at either landing site, but the data didn't rule out the possibility that life may have existed in the past or may still exist in other, more hospitable places.

"The Viking landing sites are extremely dry desert environments where it would be unlikely to find present-day biological activity on the surface," said Dr. Jim Garvin, Mars program scientist at NASA Headquarters. "Other sites on Mars, such as nearer the polar caps or other places where liquid water may be found, are far more likely places to look for signs of present or past life. Our long-term plans call for missions to find liquid water on or under the surface, which will be the best places to begin a search for signs of life."

NASA's Langley Research Center was responsible for managing Project Viking. "We didn't really know what Mars was all about. Mars had been examined from orbit by the Mariners and we had a pretty good picture, but the images were on the scale of a football field," said former Viking project manager James Martin. "That was the smallest thing we could see and that's not very distinct when you consider the landers are only in the order of six or eight feet across. We didn't have the slightest idea what was on the surface in that scale."

In April 1978, Langley turned Project Viking over to NASA's Jet Propulsion Laboratory. Today, JPL manages the NASA Mars Exploration Program, a two-decade-long effort to answer fundamental questions about Mars' early evolution and its ability to support life.

"JPL designed and built the two Viking orbiters and we are extremely proud of the Lab's history with Project Viking. The success of that mission set the stage for our current and future slate of spacecraft," said Dr. Firouz Naderi, manager of the Mars Exploration Program at JPL. "NASA's new Mars Exploration Program, unveiled last year, will build on the foundation secured by Viking."

Since Viking, NASA's missions to Mars have included the ill-fated Mars Observer, the successful Mars Pathfinder lander and Sojourner rover, the prolific Mars Global Surveyor (still operating in orbit around Mars), and the Mars Climate Orbiter and Mars Polar Lander, both of which failed as they neared Mars. The 2001 Mars Odyssey is more than halfway to the red planet and is due to enter Mars orbit on October 23.

In 2003, NASA plans to launch twin geology-laboratory rovers to the surface, each the size of a desk and capable of traveling up to 110 yards a day from their respective landing sites. Other missions, including landers and orbiting missions, will follow every 26 months.

On Thursday, July 19, NASA Administrator Daniel S. Goldin delivers the keynote address at "Continuing the Quest -- Celebrating Viking and Looking to the Future of Mars Exploration," a symposium hosted by Lockheed Martin Corp. at the National Geographic Society's Grosvenor Auditorium, Washington, D.C., from 1 p.m. to 5:30 p.m. EDT.

On Friday, July 20, from 1:30 p.m. to 3 p.m. EDT, NASA Television will broadcast live a panel discussion, "Viking: The First Encounter," from NASA's Langley Research Center, Hampton, Va. NASA TV is broadcast on GE-2, transponder 9C, C-Band, located at 85 degrees West longitude. The frequency is 3880.0 MHz. Polarization is vertical and audio is monaural at 6.8 MHz.

More information about NASA's Mars Exploration Program is available on the Internet at

JPL manages the Mars Exploration Program for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology.

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