A heavy space probe fell toward Earth on March 10, eight years earlier than expected, according to NASA.
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The 1,300-pound (600-kilogram) probe, Van Allen Probe A, was expected to burn up largely upon re-entry into Earth's atmosphere, although some components would likely remain intact. According to a statement issued by NASA on Monday (March 9), the spacecraft poses very little risk to humans, with a chance of causing harm of about 1 in 4,200.
Intense solar activity pushed the craft to fall much earlier than originally predicted. When the spacecraft ran out of fuel in 2019, NASA estimated it would remain in orbit until 2034.However, that prediction was made before the Sun entered its current solar cycle in late 2019, which turned out to be much more intense — and peaked earlier — than scientists had expected.
The Sun's roughly 11-year cycle culminates in an explosive period of activity called solar maximum, during which space weather events become more intense. These events increased atmospheric drag on the Van Allen Probe A, which was running out of fuel, causing it to gradually lose its orbit and head toward Earth.
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Van Allen Probe A is one of two Van Allen Probes that have been in space for nearly 14 years. NASA launched the satellites in 2012 to study Earth's two permanent radiation belts, named after American physicist James Van Allen.
These belts are made up of charged particles trapped by Earth's magnetic field. They essentially act as a natural shield, protecting the planet from cosmic rays, solar storms, and solar wind. The Van Allen Probes were originally designed for a two-year mission, but ended up operating for about seven years. The mission ended in 2019, when the spacecraft ran out of fuel. Van Allen Probe A's "twin," Van Allen Probe B, is expected to remain in space until 2030, according to NASA.
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During their operation, the detectors made important scientific discoveries. Among other things, they found that electrons in the radiation belts can be accelerated to almost the speed of light, "surfing" on waves of plasma ejected from the Sun. In addition, they identified a third radiation belt, which forms only during periods of intense solar activity.
