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Balky Device. If scientists can fix another balky device—the lander's 10-ft.-long telescoping arm, which last week jammed in a partially extended position—Viking's most dramatic experiments should begin this week; the lander will start its search for life in the soil of Mars. Shortly after sunrise, eight days after the landing, an electric motor will whine in the thin air, and the slender arm, tipped with a shovel no bigger than a child's beach toy, will slide slowly out of the lander. Scooping up some 6 cu. cm. of soil (about a heaping tablespoonful), the arm will then lift, retract and twist, dumping the contents of its shovel into a round, sievelike opening in the lander's top. From there, the soil will go into a rotating carrousel, or distributor, that will feed carefully measured samples into what must certainly rate as one of the age's technological masterpieces—the Viking Lander Biology Instrument.
Built by TRW of Redondo Beach, Calif., at a cost of about $50 million and housing some 40,000 components—pumps, chambers, filters and electronic parts—the biology instrument is the equivalent of a university biology laboratory in capability—but not in size. The entire package—including much of the equipment to transmit its findings back to earth—is crammed into a box occupying only 1 cu. ft., about the dimensions of the average automobile battery.
The biology lab will be looking for the signs of the kind of life that scientists believe is most likely to exist on Mars: microorganisms that live in the planet's red soil. In three separate experiments, each of which can be run four times for confirmation and control purposes, the Viking biology lab will test for evidence of:
GROWTH. On earth, plants depend on photosynthesis, the process by which they remove carbon dioxide from the air and, using sunlight as their energy source, convert the carbon to organic matter. Viking's first life-seeking experiment—called pyrolytic release—will attempt to determine whether Mars has organisms that can do the same. The biology instrument will take a ¼-cu.-cm. soil sample and incubate it for up to five days under simulated Martian sunlight in a chamber filled with carbon dioxide and carbon monoxide containing radioactive carbon 14. Any organisms present in the sample should assimilate carbon—and thus radioactive carbon 14 from the atmosphere in the chamber.
At the end of the incubation period, the chamber atmosphere will be flushed (into a special container in order to avoid contaminating the Martian atmosphere) to remove any carbon 14 that has not been ingested by the organisms. Then the soil sample will be heated to a temperature of 625° C. (1057° F.) to break down the organisms' cells and vaporize the organic material. The cooking will release whatever carbon 14 has been assimilated during the incubation period, providing Viking's sensitive detectors with at least initial evidence that organisms are growing on Mars.