Background
NASA’s Viking project was a two-part mission that sent spacecraft to Mars to map its surface, collect atmospheric data, and search for signs of life (1440 Topics: NASA).
Named after the Norse explorers, the identical Viking 1 and 2 spacecraft launched in 1975. Each consisted of a lander with scientific instruments and an orbiter with high-resolution cameras and communication relays to transmit data.
The landers were the first in history to transmit data from the Martian surface, and both they and the orbiters operated for years—far beyond the 90-day project lifetime—uncovering geological activity and evidence of past surface water (see the first photos).
Technology
Both Viking spacecraft were launched using Titan-Centaur rockets, the same system used for the Voyager probes (1440 Topics: Voyager Mission).
Each orbiter was equipped with a visual imaging system of twin cameras for redundancy, an infrared thermal mapper to measure atmospheric and surface temperatures, radio science and communication systems, and a spectrometer designed to detect water (how spectroscopy works).
The landers included two 360-degree cameras, environmental and meteorological sensors to collect atmospheric data, a seismometer to measure geological activity, and custom biological experiments designed to detect changes in gases produced or consumed by potential organisms in captured soil samples (learn more).
Solar panels and radioisotope thermoelectric generators—devices that convert the heat from the radioactive decay of plutonium-238 into electricity—powered the orbiters and landers, respectively, and nickel-cadmium batteries provided backup power for both.
Once each spacecraft arrived, it orbited Mars looking for an optimal landing site before the orbiter released the lander, which safely descended to the surface using a novel parachute that could withstand supersonic speeds without tearing and three retrorockets (watch explainer).
Findings
The Viking 1 and 2 orbiters combined to orbit Mars more than 2,100 times, capturing its surface and identifying two contrasting regions—lowlands in the northern hemisphere and highlands in the southern hemisphere—known as the Martian dichotomy.
The southern highlands are full of craters, magnetized rocks, and frozen lava flows above a thick crustal layer, while the northern lowlands are smooth, flat, and free of significant magnetization (1440 Topics: Mars).
The orbiters directly observed volcanoes, lava plains, and geological features like river valley networks and canyons. These features—some much larger than any seen on Earth—are created from rainfall and flooding, indicating the presence of significant surface water in Mars’ past (watch explainer). Seasonal dust storms and polar caps of frozen water in the north and frozen carbon dioxide in the south were also observed.
Analysis of both landers’ life-detection experiments provided no definitive evidence of life. Read NASA’s overview of the results here.
Legacy
The Viking orbiters sent back 52,663 images, mapping 97% of the Martian surface in addition to Phobos and Deimos, the Martian moons.
The landers’ biology experiments set the stage for the future discipline of astrobiology as the first mission dedicated to the field.
Many protocols and technologies developed for Viking were foundational to future planetary exploration, including heat shielding, sterilization protocols, and the parachute system, whose successors have become world-record holders.
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