Harpooning A Comet--And Other New Space Probes

Over the next 25 years or so, NASA hopes to launch between 30 and 40 small probes to explore planets and other celestial bodies. Scientists used to send up one gigantic, astronomically expensive craft every 10 years or so. If it malfunctioned or di dn't reach its destination--as was the case with the Mars Observer project, lost in the early '90s--a decade's worth of work and countless dollars would disappear into a black hole. Today's new generation of space vehicles will take on more narrowly targ eted missions. They're smaller--about the size of a refrigerator--and comparatively cheap: most cost less than $200 million. Within a decade or so, they'll be smaller and cheaper still. Here are a few of the more ambitious projects planned:

Stardust: Set to launch in early 1999, the craft will travel 242 million miles and fly through the path of Comet Wild-2. An arm, looking something like a giant fly swatter, will extend to capture icy dust and organic compounds from the comet and return them to Earth seven years later. Scientists believe that comets ma y have carried the building blocks of life to Earth billions of years ago; they hope to recover traces.

Champollion/Deep Space 4 will launch in the summer of 2003, headed for Comet Tempel 1, some 233 million miles from Earth. If all goes well, a harpoon will be shot from the spacecraft and anchor itself to the comet. Then a drill will dig in and retr ieve something scientists have never seen--a sample of a comet's frozen core.

Mars Global Surveyor is a mission comprising about nine individual spacecraft scheduled to drop in on the Red Planet over the next seven years, culminating in a return voyage complete with Martian rocks and dirt. Each consecutive mission will bore deeper into the planet's surface, looking for water and other organic material. Scientists hope to establish with certainty whether life ever existed on the planet, and if water is still present underground. The missions will pave the way for eventual hu man visits.

Fire and Ice: Our white-hot sun, the icy extremes of Pluto and Jupiter's moon Europa are the targets for this ambitious series of space missions. Astronomers believe that Europa is entirely covered by an ice-crusted ocean about 60 miles deep. Since oceans may harbor life, scientists ultimately plan to send a probe that will melt a hole in the ice and then deploy a submarine--Buck Rogers meets Jules Verne. Another craft will visit Pluto, which scientists call the Mount Everest of planetary explorat ion; it will take about 13 years for a one-way journey. On a separate visit to the sun, a craft will take continuous measurements of organic elements and radiation levels before it hurls itself, like a cosmic kamikaze, onto the molten surface.

Why explore the heavens? ""We're going to answer two basic questions," says Goldin. ""How did these planets and galaxies evolve and how does this knowledge help us to rewrite the chemistry, physics, biology and geology textbooks? The second questio n is whether life, either single-cell or carbon-based, is unique to planet Earth." For the moment, our search will be limited to Earth's immediate surroundings, but in time, perhaps, we'll be able to venture farther. ""Over the next 10 to 20 years, we're going to find the potential habitable planets within 100 light-years from us," says NASA scientist Charles Beichman. ""Whether we actually can send a spacecraft to visit those places is a question for the rocket scientists. But at least we'll have the a ddresses of where we want to go." Will anyone be home when we get there?