Space junk is becoming a serious problem. Old satellites and parts of rockets reenter our atmosphere more than three times a day. When they burn up, they can release harmful substances, and if they reach the ground, they might even hit buildings or people.
Tracking these falling objects is tough. They can drop from space at speeds up to 18,000 miles per hour. Current methods, like using radar and optical tracking, often struggle to pinpoint where debris might land. Sometimes, objects break apart during reentry, making predictions even harder. This uncertainty can hinder cleanup efforts for any toxic materials that land.
Recently, scientists from Johns Hopkins University and Imperial College London came up with a new way to track space junk. They’re using seismometers—the same devices that detect earthquakes—to listen for sonic booms made by falling debris. Benjamin Fernando, a researcher, explained that space junk makes sonic booms, similar to meteoroids and supersonic aircraft.
Fernando has experience using seismic data on Mars to understand meteoroids. He noted that techniques developed for tracking other objects can be applied to space debris. However, space junk behaves differently. It often enters the atmosphere at a shallower angle and can break up more unpredictably, posing more risks to people on the ground.
To test this method, researchers focused on the uncontrolled reentry of China’s Shenzhou-15 mission. As it fell through the atmosphere, its sonic booms created vibrations detected by seismometers. By analyzing data from 125 instruments, they could trace the object’s path. Interestingly, their findings differed from a prediction made by the US Space Force, indicating their method could be better.
There’s still a lot of work to do, but the goal is to develop a tool that could help locate falling debris quickly. Immediate information could aid recovery efforts, especially in places worried about debris falling from the sky.
Fernando highlighted two significant incidents involving falling debris that impacted the environment. The first was the Soviet satellite Kosmos 954, which dispersed radioactive materials over Canada in 1978—much of which remains uncollected. The second involved a SpaceX Starship rocket that exploded in 2025, affecting both aviation and marine areas with hazardous debris.
Experts are increasingly concerned about the atmospheric effect of these reentries. Chemicals in spacecraft can be toxic, sometimes even depleting the ozone layer. Hugh Lewis from the University of Birmingham praised the new method as a low-cost solution that makes use of existing seismometer networks. Moriba Jah from the University of Texas also pointed out how it offers new insights during the chaotic reentry phase of space objects.
However, there are limitations. Jah cautioned that not all objects create the strong sonic booms needed for detection. Additionally, differentiating between signals from debris and natural or artificial events, like aircraft noise, can be challenging. Still, with proper validation, this method might be a valuable tool alongside current tracking technologies.
Ultimately, improving tracking of reentering objects is essential. It could enhance recovery operations and give us a clearer picture of how space activities affect life on Earth. Future citizen-science projects could even emerge, empowering the public to help track and identify debris through sonic boom detection.
As we continue to expand our activities in space, we must consider the possible impacts on our environment. This growing area of research highlights the need for more robust and innovative methods to tackle the issue of space debris.
For more details on the challenges posed by space debris, you can read the European Space Agency’s report here.
