Ng Han Guan, AP
The Shenzhou 9 spacecraft rocket lifts off from the launch pad at the Jiuquan Satellite Launch Center in Jiuquan, China, Saturday, June 16, 2012.

The world may be a long way from experiencing a “Kessler syndrome,” but the Chinese space station that will fall from the sky sometime this weekend is a strong reminder that earth’s orbit is filled with flying junk.

Donald J. Kessler is an American astrophysicist and former NASA scientist who coauthored a scholarly paper in 1978 describing what could happen if a large manmade object began a cascading series of collisions in space. Each collision would create countless tiny fragments that together would form a belt around earth’s orbit that could hinder space travel for hundreds of years.

Experts say the world is nowhere near such a moment. Despite thousands of pieces of floating debris, earth’s orbit is vast. However, those tiny fragments, traveling in frictionless space at about 17,500 mph, already have come in contact with spacecraft. One created a tiny hole in the space shuttle Endeavour.

The U.S. already tracks the orbits of about 23,000 pieces of debris that are larger than a softball, according to Business Insider. It knows which nations are responsible for each, and can warn spacecraft when they are approaching danger.

But many smaller pieces of junk are difficult to track, and with private companies now getting into space travel, the problem is expected to intensify. Experts estimate as many as 17 million pieces of junk larger than the size of a paint fleck may be in orbit.

In case you’re wondering, Elon Musk’s red Tesla convertible is leaving earth’s orbit and heading toward Mars, so it won’t cause any trouble for space stations or satellites.

China’s Tiangong-1 space station, however, is getting closer to Earth every day. Because of a variety of variables, it’s impossible to know where it will enter the atmosphere and where pieces of it that don’t burn up in re-entry will land.

Luckily, the Earth is a desolate place, worries about overpopulation not withstanding. Chances are good these pieces will end up in the ocean or in some uninhabited desert or forest.

But there are no guarantees.

The odds of a person being hit by such debris is about one in a trillion, and yet it happened 20 years ago to Lottie Williams as she walked through a park in Tulsa, Oklahoma. A six-inch piece of blackened metal hit her in the shoulder, according to ABC News. The object was light and thin and did not injure her.

11 comments on this story

After Tiangong-1 makes its final descent, the next large object to leave orbit will be the Hubble Telescope in 2021. It, however, is equipped with technology allowing it to be manually deorbited and pointed toward a remote part of the Pacific Ocean, far away, one hopes, from any unsuspecting cargo ships.

All new spacecraft should be equipped with such technology, for the safety of those of us below. Keeping everyone safe high above, however, will require an international effort with an eye toward keeping Kessler’s vision of a catastrophic future from ruining space for everyone.