Racing Toward Mars

For more than five months, the three unmanned spacecraft have been racing almost neck and neck through the cold blackness of the interplanetary void. Now, as the target looms ever larger ahead of the ships, there is a growing air of anticipation in control rooms back on earth. For the three robot voyagers--one American, two Russian --should this week begin giving man his closest and most penetrating look yet at the planet Mars.

At 7:16 p.m.. E.S.T., on Saturday, Nov. 13, the U.S. entry in the Martian sweepstakes--a 1,300-lb. windmill-shaped instrument package called Mariner 9--will begin a series of crucial maneuvers. Acting on preprogrammed commands sent from the huge, 210-ft. Goldstone tracking antenna in California's Mojave Desert, Mariner's onboard computer will ignite the spacecraft's small liquid-fuel engine for a precise 15-minute "burn," reducing the ship's velocity from about 11,000 m.p.h. to just over 8,000 m.p.h. As it slows down, Mariner will be captured by Martian gravity, thereby becoming the first man-made object to go into orbit around another planet. The three previous U.S. Mars missions were designed to make their observations during the brief time that they were passing close to the planet on the way into perpetual orbit around the sun.

Strange Wave. After it is captured, Mariner will be sent into a huge lopsided orbit tilted at an angle of about 65DEG to the Martian equator. Making a full circuit every twelve hours, the spacecraft will come as close as 750 miles to the Martian surface, then soar out to a distance of some 10,500 miles. During its expected three-month working life --longer if the power supply holds out--Mariner will radio back more than 5,000 television pictures, mapping at least 70% of the planetary surface. In addition, its two cameras will take the first relatively closeup pictures of the two little Martian moons, Deimos and Phobos. But photography will only be part of the mission's objective, the most sophisticated in the history of planetary exploration.

Packed with ultraviolet and infrared sensors, Mariner will also keep a continual watch on the Martian surface and atmosphere. Thus, for the first time, scientists will be able to observe on a day-to-day basis the mysterious changes that occur on the Red Planet, including the strange seasonal wave of darkening that was once regarded by astronomers as a sign of earthlike vegetation. Equally important, more may be learned about the Martian physical features discovered by earlier Mariners: moonlike craters, the virtual lack of a magnetic field and the extremely low atmospheric pressure (only one one-hundred-fiftieth that of the earth's). Finally, although many scientists are becoming increasingly pessimistic about the prospect of finding life on Mars, Mariner will look for telltale evidence (water vapor, temperature) that the planet could possibly support rudimentary biological activity.

Soviet Reticence. In contrast to NASA, Soviet space officials have been far less talkative about their two unmanned probes, Mars 2 and 3. But some U.S. observers have concluded from the size of the spacecraft--which weighed about 8,000 Ibs. more at lift-off than their American counterpart--that the Russians may be attempting an actual touchdown on the Martian surface, perhaps landing an automated Mars rover similar to their highly successful Lunokhod I, which roamed the moon for ten months. (The first U.S. Mars landing mission will not be launched until 1975.)

Despite their reticence about their goals, the Soviets have cooperated with the U.S. in establishing a "hot line" between Mariner's mission controllers at Caltech's Jet Propulsion Laboratory in Pasadena and Moscow, where the Russian Mars program is directed by the Soviet Academy of Sciences. Thus if the American spacecraft or either of the Russian probes radios back some particularly intriguing observation, the information could be quickly exchanged by Teletype, giving both nations an opportunity to study the same phenomenon.

The Soviets and the U.S. are already fully aware of one dramatic Martian occurrence. Since the end of September, astronomers have observed a dust storm on the planet. Spreading at the rate of 20 or 30 m.p.h., the yellowish cloud now obscures much of the planet's surface and is one of the most severe blowups ever witnessed through terrestrial telescopes. Some scientists are delighted with this rare chance of witnessing close up one of Mars' puzzling storms, which seem to occur when the planet moves closest to the sun and the Martian surface heats up. Others are equally concerned that the dust may obscure the view through Mariner's twin cameras. Says Project Scientist Robert H. Steinbacher: "The mappers are just sick, while those people looking at dynamic changes on the planet are hoping the storm lasts long enough for them to study it."

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