The topic of trash and potentially harmful waste polluting the environment here on Earth has never been more mainstream. For example, you may have heard about the Great Pacific Garbage Patch, a vast island of plastic three times the size of France floating in the pacific ocean. But what about waste outside our planet? We first launched an object, a satellite, to be precise, into space in 19571. And since then, scientists around the world have been launching things beyond Earth's atmosphere. Most of these objects and the spacecraft that carry them never return to Earth. But just how much space junk is there, and why is it causing such a problem?
Space debris is classed as both meteoroid (natural rocky or metallic objects) and artificial orbital debris. Orbital debris is any human-made object that is no longer in operation or serves a useful function; for example, retired satellites that no longer work. Other orbital debris examples include fragments from rockets, solidified liquids from spacecraft, explosions of objects, and even tiny paint flecks.
Scientists track all space debris passing around Earth, but human-made orbital debris is particularly concerning. Why? Because meteoroid debris typically travels around the sun, it rarely comes close enough to Earth to cause a problem. However, the exact opposite is true of orbital debris - it's typically in a very low orbit around the Earth.
The space debris traveling close to our planet is moving very fast, up to 18,000 miles per hour - almost seven times faster than a bullet. When objects traveling this quickly collide, they can create explosions that further break up into more junk.
Scientists estimate that there are approximately 23,000 pieces of space junk larger than a softball orbiting our planet. And those are just the large ones. There's also an estimated half a million pieces of debris the size of a marble or larger, and around 100 million pieces of debris approximately 0.4 inches (1 millimeter) in size2.
Space debris the size of paint flecks might not sound like a huge issue. After all, if you were hit by a paint fleck here on Earth, you might not even notice. However, paint flecks traveling 18,000 miles per hour can cause some severe damage. In fact, several space shuttle windows had to be replaced because they were damaged by a material that turned out to be paint flecks. It's such a problem that NASA considers millimeter-sized debris to be the most significant mission-ending risk for spacecraft in low Earth orbit.
Naturally, much larger pieces of space debris cause problems too. For example, in 1996, a French satellite was hit and harmed by a rocket that had exploded ten years earlier. And in 2009, a defunct Russian spacecraft collided with an operational US commercial spacecraft, adding more than 2,300 additional pieces of debris.
While large pieces of debris are trackable, smaller pieces are not. This means scientists can time launches to avoid collisions with large space junk but are often in the dark about smaller waste in the vicinity. As our technology continues to advance, it could be possible to track increasingly small pieces of debris to eliminate any damage to functional spacecraft.
However, managing the space debris problem is becoming increasingly challenging. A primary goal is to reduce any additional debris but to do this, all space-faring nations need to be on board. For example, in 2007, China launched an anti-satellite test where they used a missile to destroy an old weather satellite. This mission resulted in more than 3,500 additional pieces of large debris and many more pieces of small debris. Missions like this are not sustainable. At present, there are no international laws to clean up space debris3.