The Life Detector

SPACE EXPLORATION

Some time in 1966, if U.S. space exploration sticks to schedule, a strange device the size of a milk bottle will plop onto the dry crust of Mars, set itself up on three self-adjusting legs, and begin a search for life. The detector will not be looking for bug-eyed monsters or giant, exotic plants. It will be satisfied with nothing more than a faint, fluorescent glow in its own compartmented innards.

Known as a "multivator" (for multiple evaluator), the life detector was developed by Dr. Joshua Lederberg, Stanford University's Nobel-winning geneticist, Physicist Elliott Levinthal and Electrical Engineer Lee Hundley. In its current version, which may be further miniaturized, the multivator stands just under 10 in. tall, weighs less than 2 Ibs. But despite its small size, it is more than equal to its momentous mission.

When the first Mariner capsule soft-lands on Mars, the multivator will be tossed out at the end of an electronic umbilical cord. After settling its tripod feet firmly on the Martian surface, a miniature vacuum cleaner will suck dust into a thin-lipped opening in the multivator's base. As the dust filters through the multivator's 15 tiny chambers, it will stick to their adhesive-coated walls. Then the chambers will be automatically sealed and filled with water from a small external tank.

Into this mixture the multivator will squirt a shot of test chemicals--fluorescein spiked with phosphate. The fluorescein cannot give off its telltale glow until the phosphate has been removed, and nothing can remove phosphate better than the enzyme phosphatase, which is common to all life on earth.

If phosphatase is present in the Martian dust, it will eat away the inhibiting phosphate, and the fluid in the multivator's chambers will begin to glow. That glimmer will then be picked up by a photomultiplier tube, converted into a radio signal in the Mariner capsule, and relayed back to earth.

Phosphatase itself is not alive, but Lederberg reasons that if the enzyme shows up in the dust of Mars, its presence must mean that microscopic living organisms exist--or have recently existed--on the distant planet just as they do on earth. The actual identification of these creatures will have to wait for larger, more elaborate spacecraft. But in the meantime, to ensure that Mars is not contaminated by earthly microbes carried there aboard the multivator, Lederberg is working on a technique for sterilizing his life detector.

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