Twenty years ago, on July 20, 1976, the Viking 1 lander became the first spacecraft to successfully land on the surface of Mars. Several events this week will examine the legacy and impact of Viking on future international Mars missions and the two U.S. robotic missions scheduled for launch to Mars in November and December. The events are:
- NASA Administrator Daniel Goldin and Dr. Chris McKay of NASA's Ames Research Center, Mountain View, CA, will discuss the history and future of Mars exploration in a public lecture organized by The Planetary Society at 7 p.m., Thursday, July 18, at the National Academy of Sciences (NAS) in Washington, DC.
- NASA, The Planetary Society and the Lockheed Martin Corp. are co-hosting a symposium entitled, "Mars Revisited: A Look Forward" at the NAS from 9 a.m. to 4 p.m., Friday, July 19.
- The Smithsonian Institution's National Air and Space Museum in Washington, DC, will present "Mars Day," a day-long family program offering hands-on activities and science demonstrations from 10 a.m. to 4 p.m., Saturday, July 20. Events and activities include views of the Martian surface and Viking landing sites in 3-D, one-on-one talks with experts about the Viking landing sites and NASA's upcoming Mars Surveyor program, an interactive computer flyover of Valles Marineris in the 'Mars Virtual Exploration Control Center,' and other activities.
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 Aug. 7, 1976, and operated until April 1980. The two landers took 4,500 unprecedented images of the surrounding surface and radioed more than 3 million weather-related measurements back to Earth, while their two companion orbiters took 52,000 images of sections of the Martian globe, imaging 97 percent of it.
The Viking missions provided numerous new insights into the nature and history of Mars, producing a vivid overall picture of a cold weathered surface with reddish volcanic soil under a thin, dry carbon dioxide atmosphere, clear evidence for the existence of ancient river beds and vast floods, and no detectable seismic activity.
Viking probably will be most remembered for its tantalizing search for signs of life on Mars. Each Viking lander conducted experiments using cameras, a gas chromatograph/mass spectrometer and a suite of biology instruments capable of detecting evidence of life in the Martian soil. State-of-the-art at the time, the biology experiment package contained instruments that searched the Martian soil for evidence of metabolic processes like those found in bacteria, green plants and animals on Earth.
"Scientists finally concluded that we found no evidence of life on Mars," said Viking Project Scientist Dr. Gerald Soffen, now director of the Office of University Programs at NASA's Goddard Space Flight Center, Greenbelt, MD. "But this doesn't prove there is not life on Mars. It simply says that, in the two distinct places on the planet that we landed, there are probably no living organisms."
Although no traces of life were found, analysis of the Martian atmosphere and soil indicated that all elements essential to life on Earth -- carbon, nitrogen, hydrogen, oxygen and phosphorus -- were present on Mars. Liquid water is also considered an essential requirement for life. Viking found ample evidence of water in two of its three phases -- vapor and ice -- and evidence for large amounts of permafrost. But it is impossible for water to exist in its liquid phase on the surface of Mars under current conditions.
NASA's Langley Research Center, Hampton, VA, had overall responsibility for managing Project Viking, based partly on the center's successful management of the Lunar Orbiter project. James Martin, who had been the assistant project manager for the Lunar Orbiter project, was chosen to lead the Viking project. Israel Taback was chosen as deputy project manager.
"One of the biggest engineering challenges of the Viking project was designing and testing the flight computer on Viking," Taback said. "In those times the computers were a lot more difficult to obtain than they are now. In fact, we battled for about three years to get about 18,000 words into the computer. Nowadays, of course, you can get megabytes for just a few pennies."
Langley turned Project Viking over to NASA's Jet Propulsion Laboratory (JPL), in Pasadena, CA, in April 1978. Today, JPL is leading the development of the Mars Global Surveyor orbiter, due for launch on November 6, and the Mars Pathfinder lander and rover, due for launch on December 2, with landing in July 1997.
The Mars Global Surveyor and the Mars Pathfinder lander and rover missions begin a decade-long program of Mars exploration designed to answer key questions about the role of water in Mars' early evolution, and whether the planet could have supported life very early in its history. The missions will measure elements in the Martian atmosphere to help deduce conditions in the planet's early history, and observe surface volatiles such as frosts and dust as they migrate from the northern to the southern hemisphere.
"This time we will go back to make a detailed survey of the planet over an entire Martian year, to observe changes in the surface and atmosphere as Mars goes through seasonal cycles," said Dr. Arden Albee, Project Scientist on the Mars Global Surveyor mission.
"We'll get down to a new level of detail about Mars, understanding the planet rather than simply observing it," said Dr. Daniel McCleese, chief scientist for the decade-long Mars Surveyor program. "We've got fantastic reconnaissance data from Viking to work with, and with modern technologies emerging in the next 10 years, we will be able to address a variety of topics about Mars in depth."
Headquarters, Washington, DC July 15, 1996
Goddard Space Flight Center, Greenbelt, MD
Jet Propulsion Laboratory, Pasadena, CA
Langley Research Center, Hampton, VA