Looking for Life on Mars

Space shots may be old hat to launch crews at the Kennedy Space Center. But there was an unusual air of excitement as technicians made final preparations for the blast-off of the first of two Viking spacecraft bound for Mars. Each of the ships carries a lander, the first ones designed specifically to seek evidence of life beyond the earth. Viking I, scheduled to take off this week, will follow an arcing, 460-million-mile path for more than ten months before it goes into orbit around Mars in mid-June 1976.* The spacecraft will circle the Red Planet for two weeks or more, reconnoitering landing sites and radioing information back to the Jet Propulsion Laboratory in Pasadena, Calif.

Then, on the Fourth of July, Viking Orbiter I will cut loose Lander I for its descent to Mars' surface. The lander, almost 10 ft. wide and 7 ft. tall overall, will start work at once. In the Martian atmosphere, only 1% as dense as earth's, its radio reports on atmospheric pressure, composition, temperature and ion concentrations will be relayed to earth by the Viking orbiter. Slowed by a parachute, the lander will spread its three spidery legs and will be braked by retrorockets for what is hoped will be a gentle setdown near the mouth of a 2,500-mile-long canyon, perhaps the site of a former drainage basin. (Viking II's lander is targeted for an area near the planet's north polar hood, where moisture may still exist.) Instead of jet fuel, which would contaminate Mars with hydrocarbons, the landers' descent rockets are powered by purified hydrazine, a nitrogen-hydrogen compound. This, explains Richard S. Young, chief program scientist for the mission, will cause minimal pollution of the Martian environment.

To make certain that Mars does not suffer a more significant contamination (and that the life-seeking devices are not confused by terrestrial organisms), both landers were heat sterilized and sealed on earth. All of the components had to be miniaturized to an incredible degree, yet remain capable of working under a wide range of temperatures. Only when such problems had been solved could the exobiologists and their engineer colleagues finally assemble the life-detection laboratory (see diagram), in a space of only one cubic foot.

Soil Scoop. On Mars, the laboratory will be served by a mechanical arm, which will reach out and scoop soil up from the surface. One small sample of soil will be dropped into a vessel containing natural Martian atmosphere. Then water vapor and carbon dioxide tagged with radioactive carbon 14 will be added. After five days of incubation under simulated Martian sunlight, the atmosphere will be removed, and the soil heated to 1160DEG F., hot enough to vaporize organic material. If any organism in the soil has incorporated the radioactive carbon dioxide by a process similar to terrestrial photosynthesis, the vaporized gases will contain radioactive carbon 14. That would be a sign of some kind of life.

On the chance that Mars may be the home of primitive living things something like bacteria, a soil sample in another chamber will be slightly moistened by a nutrient solution laced with carbon 14. The sample will be incubated, then tested to learn whether anything in the soil has consumed the nutrient and released waste gases containing the telltale carbon 14.

In a third vessel, a soil sample will be incubated after being given a generous serving of a richer nutrient (but one containing no radiocarbon), which the experimenters call "chicken soup." If any organisms thrive in the nutrient, they should give off familiar metabolic gases--oxygen, nitrogen, methane or carbon dioxide--that would then be identified by an analyzer. If there are living organisms in the vicinity of the landing sites, this fine biochemical screen should trap them.

If all goes according to plan, U.S. viewers should see closeup and panoramic stills of the Martian surface in black and white within hours after the lander touches down. There will also be transmissions from the Viking I Orbiter, and then another flood of data and pictures from Orbiter II and Lander II. All told, the cost of Project Viking will be a staggering $1 billion. But if scientists on earth receive the first hard evidence that life exists elsewhere in the solar system, that startling revelation will be well worth the cost.

* Viking II, to be launched ten days after its twin, will travel a slightly longer course and not reach Mars until early in August.

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