Scientists are using earthquake sensors to track space debris falling to Earth. By detecting sonic booms from re-entering debris, researchers can precisely locate where objects break apart, improving safety as satellite re-entries become more frequent
Researchers have identified a new way to monitor dangerous space junk as it re-enters Earth’s atmosphere by using the planet’s existing network of earthquake sensors. Scientists from Johns Hopkins University and Imperial College London found that seismometers can detect the sonic booms created by falling space debris, offering a more precise method for determining where objects break apart or hit the ground.
The study, published January 22 in the journal Science, highlights the growing risk of satellite re-entries. As more human-made objects circle the planet, the frequency of these events has increased to multiple occurrences per day. Current radar-based tracking often results in predictions that are off by thousands of miles. This seismic approach provides independent verification and near-real-time data to fill those gaps.
Tracing the Path of the Shenzhou-15
To test the method, lead author Benjamin Fernando and coauthor Constantinos Charalambous analysed the re-entry of China’s Shenzhou-15 orbital module. On April 2, 2024, the 1.5-ton module entered the atmosphere at speeds between Mach 25 and Mach 30. Travelling ten times faster than the world’s fastest jet aircraft, the debris generated intense shock waves.
By analysing data from 127 seismometers across southern California, the team traced the module as it moved northeast over Santa Barbara and Las Vegas. The seismic signals revealed that the debris actually travelled 25 miles north of the path predicted by U.S. Space Command. This data also allowed researchers to pinpoint exactly when the module disintegrated.
Environmental and safety implications
Improved tracking is essential for public safety and environmental protection. When space debris burns up, it can release toxic particles that drift through the atmosphere. Accurate pathing helps scientists understand which populations might be exposed to these materials.
Furthermore, some debris contains hazardous or radioactive components. Fernando cited the 1996 Mars 96 spacecraft incident, where a radioactive power source was lost and later suspected of contaminating a glacier in Chile. Identifying the landing site within seconds rather than months allows for the fast recovery of such dangerous materials.
Enhancing global monitoring networks
While radar remains the primary tool for monitoring objects in orbit, seismic measurements offer a vital secondary record once an object enters the atmosphere. This methodology turns a global network of earthquake sensors into a secondary defence system. As satellite deployments continue to rise, these existing tools will play a critical role in managing the hazards falling from the sky.
