NASA’s Van Allen Probes have discovered some strange radio wave activity in the space around Earth. On Wednesday, NASA Goddard Space Center announced that the two probes had helped scientists identify an envelope of very low frequency (VLF) radio waves encircling Earth. Radiation around Earth isn’t strange in and of itself, as the Van Allen Belts are the loci of strong radiation surrounding our planet. What’s strange about this new discovery is that it’s human-made. Because of course it is.

VLF radio waves are produced by human-made communication devices, specifically those used by submarines. True to their name, VLF radio waves have very low frequencies — between 3 kHz and 30 kHz —and therefore also extremely long wavelengths — between 100 and 10 kilometers. For comparison, the wavelength of visible light is measured in nanometers (with corresponding high frequencies), so we’re talking super long wavelengths and low frequencies here.

Since VLF radio waves are very good at penetrating 40 meters or more into saltwater, they’re ideal for submarine communications. Something we’re only just learning, though, is how far beyond Earth they can travel, too. This newly discovered VLF radio wave envelope seems to be the unintended consequence of all the VLF waves traveling all over the globe.

In another plot twist, it seems that this bubble, which ends just at the inner edge of the Van Allen Belts, may actually provide Earth with an additional layer of protection against particle radiation coming from space, deflecting other types of harmful radiation.

In the paper associated with this announcement, published in the journal Space Science Reviews, scientists explain that the lower limits of the Van Allen Belts have actually gotten farther away from Earth since the 1960s, likely as a result of this expanding VLF radio wave envelope, creating further protection from these regions of high radiation.

Scientists suspect that further study will help us understand how VLF can be used to protect Earth from the radiation that results from space weather events like solar storms.

Photos via NASA