When satellites fall off the Earth's orbit, their fate depends on a few factors such as their altitude, speed, and the atmospheric conditions they encounter. Here are a few possible outcomes:
Reentry and Burnup: Satellites that are in low Earth orbit (LEO) and experience atmospheric drag will gradually lose altitude. Eventually, they will enter the denser parts of Earth's atmosphere. Friction with the air will cause them to heat up, and if they are not designed to withstand reentry forces, they will burn up and disintegrate. This is the most common fate for satellites falling from orbit.
Ocean Impact: If a satellite falls from orbit over an ocean, it will likely crash into the water. This is a relatively safe outcome, as the vast majority of Earth's surface is covered by oceans. However, the impact can still generate debris and pose potential hazards to marine life or shipping routes.
Land Impact: In some cases, satellites may reenter and crash onto land. Depending on their size and composition, they can cause damage upon impact. However, given that Earth's surface is predominantly covered by water and uninhabited areas, the chances of a satellite falling on a populated area are relatively low.
It is worth noting that many satellites are designed with controlled deorbit mechanisms or propulsion systems that allow them to be maneuvered into a designated "graveyard" orbit or directed toward a safe reentry path to minimize risks and potential debris generation.
Space agencies and organizations also make efforts to track and predict the reentry of large satellites to ensure that necessary precautions can be taken if there is a higher chance of debris impacting populated areas.