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After decades of space exploration, there are now more than 500,000 pieces of artificial debris greater than half an inch in size. (Courtesy of NASA Orbital Debris Program Office)

Space Garbage: The Dark Cloud Above

A mass of debris from satellites and space missions is orbiting our planet—and it may be growing all the time

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(Continued from page 1)

These constant collisions produce ever more pieces of debris, which then lead to even more collisions. As a result, the number of orbiting objects might actually continue to increase even if we stop producing debris entirely. In 1978, NASA scientist Donald J. Kessler postulated that if the density of objects in low-earth orbit hit a tipping point, it would trigger such a chain reaction. This phenomenon is now known as the Kessler syndrome, and a report released by the National Academy of Sciences in September indicates that we may well have already passed the point of no return for space junk.

This has prompted some to consider a drastic step: actively cleaning up earth’s orbit. A range of plans—from the practical to the seemingly harebrained—have been proposed to accomplish this feat. “There’s the classic technique, where you simply have a vehicle, it goes up, it rendezvous with a derelict object and it latches onto it,” says Johnson. “Once you've captured it, you bring it down to a lower altitude or all the way into the earth's atmosphere.” This approach would likely be prohibitively costly, though, so more innovative schemes abound. Suggestions include ground-based lasers, unmanned orbiting clean-up vehicles, mesh nets suspended by inflatable space booms, adhesive gels and even “sails” that could be attached to pieces of debris and increase their drag enough to bring them down.

These plans are presently the stuff of science fiction—the technologies are nowhere near advanced enough to capture tiny pieces of junk moving at 17,000 miles per hour or more. With so much at stake, though, it’s imperative that scientists find a solution. “Some really valuable orbits—like maybe a weather satellite orbit, or a spy satellite orbit—could just be off limits because they’re so congested,” Allen says. “Space is incredibly valuable, so we really don't want to lose it.”

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