At any given time, there are over half a million pieces of marble-sized debris floating in orbit around Earth. There are also upwards of 20,000 larger pieces of debris, ranging from an astronaut’s glove to a disused rocket stage. Bits of debris left behind from human-led expeditions or crafts launched into space are often called “space junk,” and they can pose a serious threat to future space travel. In total, there are over 7,600 tons of space junk in Earth’s orbit.

While there is not an immediate concern affecting launches that are scheduled to occur this year or next, scientists are becoming increasingly worried about the future of spacecraft and exploration. In particular, they worry about the damage that could be caused to spacecraft as a result of passing through the belt of space junk surrounding the planet.

Smaller pieces of debris, the ones that are about a millimeter or so in size, tend to be the most dangerous, due to their high penetration risk. Smaller objects have a much faster impact speed, especially when they come into contact with spacecrafts in low-Earth orbit. The smallest pieces can move as fast as 30,000 miles per hour. NASA scientists estimate that there are tens of millions of pieces of space junk that are too small for satellites to track, posing a huge risk to crewed and uncrewed missions.

Additionally, many worry about the Kessler Effect. This occurs when a piece of space debris hits a satellite, breaking off another piece of space debris. This second piece of debris then hits another satellite, creating a dangerous domino effect, potentially damaging an entire constellation of satellites. Since satellites control a large part of essential communications, this could create a very dangerous situation.

Space junk is not a problem for American astronauts alone. While NASA has a debris sensor aboard the International Space Station that it uses to blast any detectible debris to a smaller size, other agencies are also developing solutions. For example, Russia’s space agency plans to develop and use a tracking telescope it has agreed to install in Brazil. In addition, Space Insight in the UK and the Deimos Sky Survey in Spain monitor and track space debris.

One plan to deal with this type of debris, especially larger pieces, is to use a removal system. The European Active Debris Removal mission is scheduled to launch in April aboard a Falcon 9 rocket. Its purpose is to release simulated pieces of debris, and then test various methods of retrieval. Ultimately, researchers hope that private companies can improve upon their technology, finding cost-effective ways to clean up space.

The space race is becoming busier than ever before, with countries like China and India joining the United States and Russia in developing and launching spacecraft, satellites, and other flotsams. As each country becomes more advanced, the number of objects launched into space is only expected to climb. Private companies becoming equally as involved in space exploration also adds to the amount of debris littering Earth’s orbit. As space innovation moves forward, there is an increased and urgent need to find ways to remove or at least mitigate the risks posed by space junk.