Space debris, also known as space junk, continues to orbit around the Earth primarily in low Earth orbit (LEO) due to a combination of factors:
Large Number of Objects: Over the years, numerous satellites, spent rocket stages, fragments from explosions, and other debris have accumulated in LEO. This dense population increases the chances of collisions between objects, generating more debris in the process.
Lack of Atmospheric Drag: While LEO is within Earth's atmosphere, it is still a very thin atmosphere. The density of the atmosphere decreases with altitude, and at the altitudes where most space debris resides, the atmospheric drag is not significant enough to cause rapid decay or immediate reentry for smaller debris.
Orbital Mechanics: Objects in orbit around the Earth are moving at very high speeds horizontally, which helps maintain their orbital path. Even if they experience some atmospheric drag, their forward velocity prevents them from falling back to Earth immediately. Instead, the drag gradually lowers their orbit over time.
Collisions and Fragmentation: Collisions between space debris can result in fragmentation, creating even more debris. These fragments can continue to orbit and pose a threat to operational satellites. The Kessler Syndrome, a theoretical scenario, suggests that if enough collisions occur, the density of space debris could reach a point where it becomes self-sustaining, making LEO increasingly hazardous.
Although some larger or more massive space debris may eventually reenter the denser parts of Earth's atmosphere and burn up, smaller debris can persist in orbit for extended periods. The management and mitigation of space debris are ongoing challenges for space agencies and organizations worldwide, as it is crucial to minimize the generation of new debris and actively track and remove existing debris to ensure the long-term sustainability of space activities.