From positions in orbit and on ground, Viking orbiters and landers tried to detect the existence or the remains of life on Mars. Thorough and revolutionary experiments on the Martian atmosphere and soil were conducted, but unfortunately, after years of work, no definitive conclusion could be reached.
The biology experiments performed by the landers yielded positive results. But equipment searching for organic molecules could not detect even the slightest presence of organic material, and without organic material, there was very little chance of finding life. Yet it was incomprehensible that Mars did not have organic material; organic compounds are essentially carbon based and for billions of years Mars had been bombarded with cosmic debris made up largely of carbon. Moreover, it seemed strange that a planet containing all the necessary components for life -- carbon, nitrogen, hydrogen, oxygen, phosphorus, and water (in two of its three phases) could be entirely dead.
The Mars that Viking saw baffled scientists: the planet had indications of life but no life; it had shown evidence of running water to earlier Mariner probes, but Viking's close look confirmed that Mars could not sustain water in its liquid form; Mars had volcanoes, a sign of plate tectonics, yet Lander 2's seismometer did not record a single tremor in 1,200 hours of study.
The Viking mission provided a wealth of information on Mars that opened up new avenues of investigation -- to explain Viking's bizarre findings scientists began to suggest that perhaps a very different Mars once existed. Viking supplied the data for future inquiries into Mars and fueled the fire of Martian intrigue. The distant red planet that had fascinated Earthlings since the very early days of astronomy was found to be even more enchanting and mystifying when the Viking mission brought Mars into close range.
