A massive space probe is expected to fall back into Earth's atmosphere years earlier than previously predicted. NASA said that while most of the spacecraft will likely burn up during reentry, some fragments could survive and pose a potential risk on the ground.

NASA and the United States Space Force said preliminary analysis suggests the roughly 600-kilogram spacecraft could reenter the atmosphere at around 7:45 p.m. Eastern Time on March 10, though the timing carries an uncertainty window of about 24 hours. According to NASA, the probability of debris causing injury to people on the ground is about 1 in 4,200.

NASA described the risk as "low," noting that about 70% of Earth's surface is covered by oceans, making it far more likely that any surviving debris will fall into open waters rather than populated areas.

The spacecraft is the retired Van Allen Probe A, one of the twin Van Allen Probes launched in 2012 to study the Van Allen radiation belts – zones of high-energy charged particles trapped by Earth's magnetic field. The probes operated in highly elliptical orbits ranging from about 640 to 58,000 kilometers above Earth.

NASA said the radiation belts help shield Earth from harmful cosmic radiation, solar wind and solar storms that could threaten humans and damage technological systems. Data collected by the probes has been critical for understanding how solar activity affects satellites, astronauts, and infrastructure on Earth such as communications, navigation and power grids.

Originally designed for a two-year mission, the two spacecraft far exceeded expectations and continued operating until 2019, when they ran out of fuel. NASA had planned for them to gradually descend and burn up in Earth's atmosphere during reentry, which typically generates enough heat to destroy most spacecraft.

Under NASA guidelines, US-launched spacecraft must either reenter Earth's atmosphere or be safely disposed of within 25 years after their missions end. Disposal methods include deorbiting the spacecraft or moving it to a so-called "graveyard orbit," a designated region where defunct satellites can remain in space. However, even graveyard orbits cannot completely eliminate the risk of collisions that could create space debris threatening operational satellites.

Unexpectedly strong solar activity has altered the original timeline for the probe's return. NASA had previously predicted the spacecraft would reenter around 2034, but those calculations were made before the current solar cycle began.

In 2024, scientists confirmed the sun had reached a period of solar maximum, triggering intense space-weather events. According to NASA, the heightened solar activity increased atmospheric drag on the spacecraft more than anticipated, causing it to descend and reenter the atmosphere earlier than expected.

Solar activity has also shortened the orbital lifetime of the twin spacecraft, Van Allen Probe B, though to a lesser degree. NASA currently estimates that Probe B will not reenter Earth's atmosphere before 2034.