Farewell to the Red Planet

A faithful robot orbiting Mars finally runs out of gas

Precisely on schedule one day last week, controllers at Caltech's Jet Propulsion Laboratory in Pasadena, Calif., sent an electronic command leaping across 164 million miles of space. With that, Viking Orbiter 1, which has been faithfully circling Mars once every 47 1/2 hours for the past four years, expelled its last puff of steering gas. No longer maneuverable, its electrical systems silenced, the unmanned spacecraft will now slowly sink until it finally crashes into Mars some time after the year 2019.

Even the cool NASA professionals in the control room were not unmoved. With the orbiter's death came the end of another phase of the $1 billion Project Viking, the most ambitious mission to another planet to date. Back in 1975, twin spacecraft, each consisting of an orbiter and a lander, were sent off to Mars. A key objective: to determine if the Red Planet harbors life. After going into Martian orbit ten months later, the mated spacecraft split apart. Their spider-legged landers touched down on the surface, while the orbiters continued patrolling overhead, mapping the planet with their cameras and acting as relay stations for the instrument packages below.

The ships were superb performers. Because of a surprisingly effective design and careful use of fuel, they far exceeded their anticipated lifetime of 90 days. Before the demise of the orbiters--the first went silent in 1978--they sent back 51,539 photographs, including a final series of color views of Tharsis Ridge, site of three major volcanoes with an average elevation of 17 km (10.8 miles) and two smaller ones. Besides confirming past volcanic activity, Viking provided closeup glimpses of the reddish, rocky Martian soil, monitored weather changes including violent dust storms and discovered significant quantities of water (as atmospheric vapor, polar ice and permafrost). But Viking failed to find any signs of life, although biological tests showed certain quirky chemical activity in the soil.

Despite the orbiter's death last week, the JPL controllers will still get occasional glimpses from the Martian surface. One lander remains operational and, although it has lost its partner in the Martian sky, it has been programmed to keep its antenna pointed directly to earth and send a weekly report from Mars until it too finally runs out of fuel in 1994.

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