The first truly successful landings on Mars took place in 1976 when the Viking mission used two identical spacecraft, each consisting of a lander and an orbiter. Launched on August 20, 1975, from the Kennedy Space Center in Florida, Viking 1 spent nearly a year cruising to Mars, placed an orbiter in operation around the planet, and landed on July 20, 1976, on the Chryse Planitia (Golden Plains). Viking 2 was launched on September 9, 1975, and landed on September 3, 1976. The Viking project’s primary mission ended on November 15, 1976, 11 days before Mars’s superior conjunction (its passage behind the sun), although the Viking spacecraft continued to operate for six years after first reaching Mars. The last transmission from the planet reached Earth on November 11, 1982.
One of the most important scientific activities of this project involved an attempt to determine whether there was life on Mars. Although the three biology experiments discovered unexpected and enigmatic chemical activity in the Martian soil, they provided no clear evidence for the presence of living microorganisms in soil near the landing sites. According to mission biologists, Mars was self-sterilizing. They concluded that the combination of solar ultraviolet radiation that saturates the surface, the extreme dryness of the soil, and the oxidizing nature of the soil chemistry had prevented the formation of living organisms in the Martian soil.
The failure to find evidence of life on Mars devastated the optimism present for astrobiology in an era of great expectations. Collectively, these missions led to the development of two essential reactions. The first was a questioning by a significant minority of scientists that complex life might not exist elsewhere in the Solar System, but that did not mean that it was not present throughout the universe. While scientists grew discouraged, it was a disappointment that did not remain for many of them. JPL director Bruce Murray believed that the legacy of failure to detect life, despite the billions spent and a succession of overoptimistic statements, would spark public disappointment and perhaps a public outrage.
An aftermath of the Viking landings in 1976 was that the prospects for discovering extraterrestrial life on Mars had been oversold. Planetary scientist and JPL director Bruce Murray complained at the time of Viking about the landers being ballyhooed as a definite means of ascertaining whether or not life existed on Mars. The public expected to find it, and probably so did many of the scientists, and what would happen when hopes were dashed? Murray argued in his memoir that “the extraordinarily hostile environment revealed by the Mariner flybys made life there so unlikely that public expectations should not be raised.” Carl Sagan, who fully expected to find something there, accused Murray of pessimism. Murray accused Sagan of far too much optimism. And the two publicly jousted over how to treat the Viking mission.
Murray, as well as other politically savvy scientists and public intellectuals, argued that the legacy of failure to detect life, despite billions spent on research since the beginning of the space age and overoptimistic statements that a breakthrough was just around the corner, would spark public disappointment and perhaps an outrage manifested in reduced public funding for the effort.
The failure of Viking to find evidence of life on Mars revealed a core problem of overselling possibilities for extraterrestrial life and its discovery. The disappointment was palpable, at least if missions are sparked by success. Thereafter, no spacecraft went to Mars for more than twenty years after Viking. Not until 1988 did the Soviet Union, just a year away from collapse and the end of the Cold War, sent Phobos 1 and 2 to Mars, while one failed en-route the second completed part of its mission prior to failure. The Mars Observer launched by the United States on September 25, 1992, fared little better. Intended to provide the most detailed data available about Mars as it orbited the planet since what had been collected by the Viking explorers of the mid-1970s, the mission was progressing smoothly until August 21, 1993, three days before the spacecraft’s capture in orbit around Mars. Suddenly and without warning, controllers lost contact with it.
The engineering team working on the project at the Jet Propulsion Laboratory responded with a series of commands to turn on the spacecraft’s transmitter and to point the spacecraft’s antennas toward Earth. No signal came from the spacecraft, however, and the Mars Observer was not heard from again. The loss of the nearly $1 billion Mars Observer probably came as a result of an explosion in the fuel lines of the space vehicle. One wit offered an alternative explanation, suggesting that after the landing by the Vikings in 1976 the Martians had developed a planetary defense system and it was now knocking out everything aimed at the red planet.
We now know that was never the case, of course, but the question of life on Mars at some time in the distant past remains open.