An unexpected “visitor from beyond” struck the home of a resident in Naples, Florida, USA. On the afternoon of March 8th Eastern Standard Time, resident Alejandro Botero was on a trip away from home when he received a phone call from his son, who was alone at home, reporting that the roof had been penetrated by an unidentified flying object. The incident caused significant damage to the home, with the object even piercing through two floors all the way to the ground level. Botero said that the falling object made a loud noise, and his son was fortunately not hit.
The initial suspicion was that the disaster might have been caused by a meteorite. However, upon returning home to inspect, Botero found that the piece of metal looked more like some sort of man-made object. Judging by its partially charred shape, it seemed to have originally been cylindrical but was deformed after burning through the atmosphere. At the time of the incident, Botero was shocked by the force with which the object fell and the extent of the damage caused.
Tracing the origin of this “visitor from beyond,” one cannot help but look toward the International Space Station, about 400 kilometers above the Earth. This accident may be related to an incident in October 2018. At that time, NASA astronaut Nick Hague and Russian cosmonaut Aleksey Ovchinin were scheduled to take the Soyuz rocket to the International Space Station. Unfortunately, due to issues with the rocket’s booster, the launch failed. The two astronauts did not reach their planned orbit and could not travel to the International Space Station as intended.
Nick Hague was originally scheduled to participate in a mission that included upgrading the power system of the International Space Station, replacing the old nickel-hydrogen batteries with new lithium-ion batteries. Because he did not reach the space station in time, the planned spacewalk to change the batteries had to be canceled. The nickel-hydrogen batteries, which were supposed to be removed and sent back to Earth on the HTV cargo spacecraft, may have been left in space. The object that fell is very likely to have originated from this incomplete battery replacement process.
The report investigated some of the conditions of the HTV cargo spacecraft during its service to the International Space Station, with a focus on a series of events related to battery replacement. The report pointed out that, since the HTV cargo spacecraft could only carry a limited number of batteries, it could not take away all the replaced old nickel-hydrogen batteries at once. With each new batch of lithium-ion batteries, the HTV cargo spacecraft could only take away the previously replaced old batteries. Until the final HTV spacecraft completed its mission in 2020, there were still nickel-hydrogen batteries left on the International Space Station that were not taken away, these batteries coded EP9, weighing as much as a large SUV.
As Japan began to use other new types of carrier spacecraft and stopped using the HTV cargo spacecraft to transport materials to the International Space Station, NASA made a decision on how to handle this large object that had been left behind, the EP9 pallet. Since space is extremely precious on the International Space Station, NASA planned to dump EP9 directly into space as space debris, making it the largest piece of space junk discarded by the International Space Station to date.
On March 11, 2021, when the International Space Station was about 418 kilometers above the Pacific Ocean west of Central America, NASA’s ground control operators used the station’s robotic arm to release EP9 into space. According to NASA’s prediction at the time, EP9 would float in space for 2 to 3 years before re-entering the atmosphere and completely burning up.
Years have passed in the blink of an eye, and as of March 8 this year, EP9 has ended its orbiting journey around the Earth, beginning to burn up violently as it entered the atmosphere above the Gulf of Mexico. The European Space Agency’s relevant departments had been following the fate of EP9 closely. The European Space Agency stated that the total mass of EP9 was about 2.6 tons, and although most parts would burn up upon re-entering the atmosphere, it was still possible that some debris could fall back to the Earth’s surface, though the probability of hitting people was extremely low.
Ultimately, some fragments of EP9 indeed did not dissipate completely during re-entry, and an unexpected piece fell towards Florida in the United States, unfortunately striking the house of a resident named Alejandro Botero. To identify this unexpected visitor, NASA later contacted Mr. Botero and sent the fragment to the Kennedy Space Center in Florida. Through detailed analysis of the fragment’s size, characteristics, and materials, and comparison with similar hardware on EP9, NASA confirmed that this 0.7kg fragment with a length of 10cm and a diameter of 4cm was originally a chromium-nickel-iron alloy strut used to secure batteries on the tray.
The National Aeronautics and Space Administration (NASA) and the International Space Station conducted an in-depth analysis, where scientists are studying the phenomena of heating and combustion caused by the re-entry of space debris EP9 into the atmosphere through the establishment of physical models, to further understand why such struts can survive and ultimately reach the ground.
With the increasing frequency of human space activities, the problem of space debris has also become more serious. According to data provided by the European Space Agency (ESA), as of October 6, 2023, about 6500 rockets have been launched into space, approximately 16990 satellites have been placed in Earth’s orbit, of which 9000 are still in working condition. The defunct satellites, rocket boosters, spacecraft remnants, and items discarded by space stations, etc., all make up space debris orbiting the Earth.
According to statistics, there are about 35150 pieces of space debris that the Space Surveillance Network (SSN) in the United States routinely tracks, and the actual number may be much higher. The accumulation of these space debris is making the orbits above Earth increasingly crowded, posing various challenges to current and future space missions. For example, the International Space Station has had to adjust its orbit multiple times to avoid space debris.
The ESA points out that an average of one larger space object re-enters the Earth’s atmosphere every week, and although most of the fragments burn up completely before reaching the ground. The design purpose of most spacecraft and rockets is to ensure that they can burn up as much as possible upon returning to the atmosphere to minimize risks to the ground. However, the survival of EP9 warns us that space debris can also pose a threat to the ground.
Throughout history, there have been occurrences where space debris has fallen to the ground and posed a threat. In 1969, a fragment from a former Soviet spacecraft fell and struck a Japanese ship near the coast of Siberia, injuring five people. In 1997, a piece of rocket debris struck a female resident in Oklahoma, USA, who was lucky to have not been injured. With the increasing number of spacecraft being launched into space by humans, the frequency of such incidents may rise in the future.
