By Dr. Robert Thorson

Bikini atoll? Agent Orange? Cape Cod toxics? Humans have polluted the Earth in the name of national security. Why not the heavens as well?

That was my first thought after reading about last month’s anti- satellite test by the Chinese. In the name of national security, they wanted to make sure they could take one out if need be. So on Jan. 11 they did some target practice by shooting a rocket at a one- ton satellite 530 miles above the Earth.

Bull’s-eye for them! Bad news for us! The resulting debris will accelerate an inevitable chain reaction that will likely pollute space for millennia and threaten peaceful uses of this international frontier.

Given the conditions at that altitude — little gravity, no air friction and an impact at 18,000 mph — the targeted satellite quickly broke up into about 1,000 large pieces, each defined as being more than 4 inches across, large enough to be tracked. (No one is even attempting to track the smaller pieces.) The debris scattered into higher and lower orbits, forming a band similar to one of Saturn’s rings, but with a much lower concentration. There it will remain for at least the rest of my lifetime, possibly longer than the human species will survive on Earth.

The United States and the former Soviet Union performed more than 20 such tests during the 1970s and 1980s as part of their Cold War military programs. Fortunately, they did their target practice at lower orbits where the Earth’s gravity is stronger. Hence, most of the resulting debris soon descended through the atmosphere, either burning up or falling with little notice. A surprising thing about the recent Chinese test, however, is that the Chinese are leading members of an international organization called the Inter-Agency Space Debris Coordinating Committee, which advocates for the reduction of man-made objects in orbit.

We civilians create space junk too in the name of astronomy, communication, observation and exploration. An astronaut lost a wrench once, so I was told. Perhaps it’s now on a collision course with the Hubble Telescope. Someone else lost a camera. Is it circling around to hit the International Space Station?

Also out there are more than 10,000 objects capable of damaging important things like the space shuttle. On Earth we have rules about parking dead cars in public places. Not so in space, where somewhere near 2,000 dead satellites are parked unattended. Space has become a junkyard.

And now for the problem space scientists have worried about for decades: a chain reaction, or, more properly, an event cascade. Large objects are capable of smashing much larger objects into smaller pieces, thereby creating additional large objects. The recent Chinese test, for example, began with two but ended up with nearly 1,000 pieces counted by sky-watchers.

Many of these new large objects are capable of striking other much larger ones to produce — you guessed it — even more large objects, and so forth. Such an event cascade will accelerate until most of the big things parked or traveling up there have been smashed into dangerous fragments.

The result will be permanent veil of junk that will that will jeopardize the billions of dollars we’ve invested in working satellites, and make the peaceful use of space more difficult, risky and costly.

For years, I’ve known space was being cluttered with junk. But before I read William Broad’s article in last week’s New York Times Science Section, I had no concept that a chain reaction could “expand for centuries, spreading chaos through the heavens.” The only sure way to mitigate this problem, according to Nicholas L. Johnson, NASA’s chief scientist for orbital debris, is to perform the “environmental remediation” of space.

A cynic might claim this as great news: that space can be our new and exciting frontier for out-of-control pollution. Indeed, we have fouled the groundwater of the lithosphere, the oceans of the hydrosphere, the tissues of the biosphere and the gasses of the atmosphere. It’s only logical that our next step should be the serious pollution of the heavens.

I wonder what God thinks about this.