A heavy space probe is falling to Earth today (March 10), eight years earlier than expected, according to NASA.
The 1,300-pound (600 kilograms) Van Allen Probe A should mostly burn up as it enters Earth's atmosphere, but some components are expected to remain intact. The spacecraft poses a low risk to humans, with a 1-in-4,200 chance of it causing harm, NASA said in a statement released Monday (March 9).
U.S. Space Force calculations have the probe reentering Earth's atmosphere at about 7:45 p.m. EDT today, according to NASA. However, that prediction carries a 24-hour margin of error, so the reentry could have happened already. As of this writing, there have been no reports of a reentry.
Intense solar activity is forcing the probe down much earlier than initially forecast. When the spacecraft ran out of fuel in 2019, NASA predicted it would remain in orbit until 2034. However, that was before the sun entered its current solar cycle in late 2019, and that cycle has been much more active — and peaked sooner — than scientists expected.
The sun's roughly 11-year cycle peaks with an explosive period of activity known as solar maximum, which triggers more intense space weather events. These events created more atmospheric drag for the fuelless Van Allen Probe A, pulling it out of orbit.
Van Allen Probe A is one of two Van Allen Probes that have been in space for almost 14 years. NASA launched the satellites in 2012 to study Earth's two permanent radiation belts, which were named after American physicist James Van Allen.
The radiation belts are made up of charged particles trapped by Earth's magnetic field. They essentially act as natural shields, protecting Earth from cosmic radiation, solar storms and solar wind.
The Van Allen Probes were designed for a two-year mission but ended up lasting around seven years. The mission eventually ended in 2019, when the probes ran out of fuel. Van Allen Probe A's twin, Van Allen Probe B, is expected to stay in space until 2030, according to NASA.
The probes made a series of scientific discoveries during their tenure. For example, the spacecraft found that electrons in the radiation belts can be accelerated to near light speed by surfing on waves of plasma ejected from the sun. They also detected a third radiation belt that forms only during periods of intense solar activity.
