A shower of fireballs illuminated the night skies over Los Angeles, Central and Southern California on 2 April. The curious onlookers were unsure if they had seen a UFO, a meteor or a rocket that failed to launch.
Later, astronomers confirmed that these fireballs came from space debris in the orbital module of the Chinese Shenzhou-15 spacecraft launched first in November 2022. This uncontrolled spacecraft reentry caused international outrage about space debris falling to Earth. However, the event inspired seismologists with a way to monitor the fate of this space junk using ground signals. Seismometers in the Los Angeles basin picked up sonic booms. A team of researchers has now reconstructed a spacecraft’s path through the atmosphere using seismic data. Researchers could use this new method to detect space debris anywhere on the planet, without having to observe it visually. Benjamin Fernando, a planetary scientist at Johns Hopkins University Baltimore and the lead author of this study, said
“I’m not aware of work that’s been done to try to track and characterize space debris using seismic measurements,” . Fernando and colleagues presented their work at the AGU Annual Meeting in Washington, D.C. on 9th December.
Space debris is a growing danger
Up until recently, space debris that was out of control was an uncommon phenomenon. “Increasing space missions have led to larger and more spaceships being launched that subsequently deorbit,” Fernando said. Fernando was interested by the event of 2 April after learning that Los Angeles residents had heard debris burn high above them. Supposedly, he thought, if people could hear the debris, then supersensitive seismometers would have also picked up on signals. Receive the most exciting discoveries from around the globe in your email. He said. Fernando and his co-workers downloaded seismic data from Los Angeles stations that recorded the same night and discovered similar seismic signals traveling inland. They spent several months analysing data in order to determine the speed of the debris and its trajectory, as well as the population it passed through before it broke up.
Fernando (19659012) was part of a plan to track a human-made object that entered Earth’s airspace: a capsule containing samples taken from the asteroid Bennu, as part NASA’s Origins, Spectral Interpretation, Resources Identification, and Security-Regolith Explorer mission (OSIRIS-REx). In September 2023, seismometers tracked the hypersonic booms of the capsule and its blazing trajectory over Utah’s desert. Fernando pointed out that seismologists used the ground station to track the Shenzhou-15’s reentry for the first time without warning.
He said that this method would be able to detect other objects in less-populated areas if enough seismic stations picked up atmospheric signals. Fernando said that researchers can track the speed, trajectory and size of an object and determine how it has broken up. Fernando said that if the method is applied to fireballs quickly, it could help predict whether or not debris will hit an area of population once they have entered Earth’s atmospheric layer.
Challenges of moving targets
This new method is an innovative use of seismic data. McKee, who works as a volcano geologist at Vanderbilt University, Nashville, Tenn., uses the waves from seismic sensors to monitor magma, gas, and other subsurface movements. McKee said that reducing the dangers to public safety from objects returning into Earth’s atmospheric is a major goal. But it comes with challenges. She said that the changing weather and wind conditions could affect scientists’ ability to pinpoint where space debris is likely to crash. She said that it is a worthwhile challenge for applied research. The original article for this “It is a hard problem to solve, but definitely one worth pursuing.”
