The Van Allen belts surrounding the Earth protect our planet from dangerous radiation, and new research from NASA is revealing more information about this invisible shield, essential for life on our planet.

Researchers from the Massachusetts Institute of Technology and University of Colorado at Boulder conducted an extensive study of data collected by the Van Allen probes orbiting around the Earth.

For decades, researchers believed the Van Allen belts consisted of just a pair of doughnut-shaped magnetic belts surrounding the planet. In 2013, a third band of electromagnetic force was discovered in the system.

The Van Allen probes have now detected an additional invisible shield, protecting Earth from high-energy electrons whizzing around the planet. This barrier is located roughly 7,000 miles above the planet, at the underside of the outermost belt. This phenomenon, dubbed "plasmaspheric hiss," is characterized by the sound it makes in radios. This feature works as a shield around the planet, protecting Earth from the most dangerous particles, called ultra-relativistic electrons, as they approach our world. This barrier prevents even the most energetic particles from coming within 6,900 miles of the planetary surface.

"It's almost like these electrons are running into a glass wall in space. Somewhat like the shields created by force fields on Star Trek that were used to repel alien weapons, we are seeing an invisible shield blocking these electrons. It's an extremely puzzling phenomenon," Daniel Baker, director of the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder, said.

Detection of the Van Allen radiation belts was the first major discovery of the space age. The features were discovered by James Van Allen of the University of Iowa in 1958. These belts extend as far as 25,000 miles above the surface of Earth.

The pair of Van Allen probes were launched into space on August 30, 2012, on a mission to study the magnetic belts. With a mission lifespan estimated to last between two and four years, investigators hope to study new ways of protecting human space travelers during long-duration missions to Mars and beyond. The third belt, discovered in 2013, disappeared over a few months.

"It's a very unusual, extraordinary, and pronounced phenomenon. What this tells us is if you parked a satellite or an orbiting space station with humans just inside this impenetrable barrier, you would expect them to have much longer lifetimes. That's a good thing to know," John Foster, associate director of the Haystack Observatory, operated by the MIT, said.

Discovery of the invisible barrier detected between layers of the Van Allen Belt is detailed in the journal Nature.

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