The rings around planets like Saturn and Uranus are indeed formed by the debris of colliding asteroids, comets, and other objects in their respective planetary systems. However, there are several factors that prevent space junk from forming rings around Earth:
Gravity: Earth's gravity is much stronger compared to the gravity of asteroids and other small debris in space. This gravitational force pulls most of the space junk towards Earth, causing it to enter the atmosphere and burn up upon reentry. The debris that survives reentry typically falls into the oceans or lands in remote areas.
Atmospheric drag: Earth has a dense atmosphere that exerts drag on objects in orbit. This atmospheric drag causes the orbit of space junk to decay over time, leading to its eventual reentry and destruction. As a result, space debris does not accumulate in orbit around Earth for long periods to form a stable ring.
Space debris removal: Various space agencies and organizations actively work to mitigate the issue of space debris. They track larger pieces of space junk and sometimes perform controlled deorbit maneuvers to bring them down into the Earth's atmosphere. Additionally, there are proposed initiatives for capturing and removing space debris from orbit. These efforts help prevent the accumulation of debris and the formation of a significant ring-like structure.
It's important to note that while space junk doesn't form rings around Earth, the problem of space debris is a significant concern. The increasing amount of debris in space poses risks to operational satellites, spacecraft, and even the International Space Station. Efforts are being made to address this issue through improved space debris management and mitigation strategies.