NASA has revealed that an old satellite fell from orbit on Wednesday and reentered Earth’s atmosphere. Most of the spacecraft is expected to burn up during reentry, but some parts may survive, NASA said, per CNN. The agency said there is a 1 in 4,200 chance of people being injured by debris from the falling satellite.

“We’ve had things that have reentered have a 1 in 1,000 chance, and nothing happened; if we have a few that are 1 in 4,000 or 5,000, it’s not a horrible day for mankind,” Dr. Darren McKnight, a senior technical fellow at space-tracking company LeoLabs, told CNN.

When did the NASA satellite fall from orbit?

NASA said the 1,323-pound spacecraft reentered Earth’s atmosphere at 6:37 a.m. on Wednesday. The probe was spotted south of Mexico and west of Ecuador.

The satellite’s twin, the Van Allen Probe B, is no longer functioning but continues to orbit Earth, The Associated Press reported.

NASA launched the two spacecraft in 2012 to study a pair of cosmic bands of energy particles known as the Van Allen radiation belts. According to NASA, the radiation belts “shield Earth from cosmic radiation, solar storms and the constantly streaming solar wind that are harmful to humans and can damage technology.”

“So understanding them is important,” NASA said in a statement, per CNN.

Although the satellites ran out of fuel in 2019, the agency expected the probes to remain in orbit until 2034.

Why did the NASA satellite fall from orbit?

NASA said Probe A reentered earlier than expected due to increased solar activity in recent years.

Probe B, however, will likely reenter Earth’s atmosphere after 2030, the agency said.

According to NASA, data from the probes made it possible for scientists to understand how “the radiation belts operate during its lifetime, including the first data showing the existence of a transient third radiation belt, which can form during times of intense solar activity.”