The strange radio pulses were detected by the Antarctic Impulsive Transient Antenna (ANITA), an array of instruments designed to detect elusive particles called neutrinos.

Rather than detecting these cosmic particles, the researchers were baffled to find signals emerging from the ice at seemingly impossible angles.

Worryingly, they have no idea what could be causing them.

In a paper, published in Physical Review Letters, an international team of researchers explained that these findings cannot be explained by the current understanding of particle physics.

This might mean there are entirely new forms of particles and interactions at play or that these unusual signals are the product of mysterious dark matter.

Dr Stephanie Wissel, an astrophysicist from The Pennsylvania State University who worked on the ANITA team, says: ‘The radio waves that we detected were at really steep angles, like 30 degrees below the surface of the ice.

‘It’s an interesting problem because we still don’t actually have an explanation for what those anomalies are.’

Scientists have been baffled to discover mysterious radio signals emerging from deep beneath Antarctica’s ice

The ANITA experiment was designed to hunt for an elusive type of particle called a neutrino, the smallest of all the subatomic particles.

Neutrinos are typically created by high-energy events like the Big Bang or a supernova and are extremely common throughout the universe.

However, since they are so small and don’t have a charge, they don’t affect the objects they pᴀss through, which makes them extremely difficult to spot.

Dr Wissel says: ‘You have a billion neutrinos pᴀssing through your thumbnail at any moment, but neutrinos don’t really interact.

‘So, this is the double-edged sword problem. If we detect them, it means they have travelled all this way without interacting with anything else. We could be detecting a neutrino coming from the edge of the observable universe.’

Like opening a time capsule from the distant past, examining the signal from a neutrino could reveal more information about the cosmos than data from the world’s most powerful telescopes.

To try and find them, the ANITA experiment uses balloons floating 18 to 24 miles (30-39km) above the Antarctic, where other signals are rare, to look for radio waves caused by neutrinos hitting the ice.

‘We point our antennas down at the ice and look for neutrinos that interact in the ice, producing radio emissions that we can then sense on our detectors,’ says Dr Wissel.

The signals were detected by the Antarctic Impulsive Transient Antenna (ANITA), an array of instruments designed to detect elusive particles called neutrinos

This experiment’s sensor balloons detected radio signals emerging from beneath the ice at such steep angles that they could not have been made by neutrinos

Just as a ball thrown to the ground will always bounce at a particular angle, scientists can use the trajectory of these signals to track the neutrino back to its origin.

However, the scientists were shocked to discover a set of signals which could not be traced back to any possible origin.

These radio signals were coming from the the ice at an impossibly steep angle, something that a neutrino-produced signal could never do.

Even stranger, rather than bouncing off the ice, the pulses appear to be coming from below the horizon.

That would mean the radio waves would have had to travel through thousands of miles of rock and ice before reaching ANITA’s balloons, which should have rendered them undetectable.

After analysing the data from multiple flights and comparing it to simulations of cosmic rays, the researchers were able to filter out the background noise.

However, after eliminating the possibility of any other known particle-based signals, the anomalous radio pulses remained stubbornly unexplained.

Additionally, other detectors, the IceCube Experiment and the Pierre Auger Observatory didn’t detect anything that could explain what the scientists were seeing.

Scientists currently don’t know what is causing these signals to emerge or how they can pᴀss through so much rock and ice. It could be a new type of particle interaction or the interference of dark matter (stock image)

According to scientists’ current understanding of how particles interact, these signals shouldn’t be possible.

This has led scientists to speculate that they may have stumbled onto a type of particle interaction previously unknown to science.

Dr Wissel says: ‘My guess is that some interesting radio propagation effect occurs near ice and also near the horizon that I don’t fully understand, but we certainly explored several of those, and we haven’t been able to find any of those yet either.

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‘So, right now, it’s one of these long-standing mysteries.’

To learn more, scientists are currently building an even bigger detector, dubbed PUEO, which will be better at spotting hidden particles.

That could help scientists understand the origins of these baffling signals from beneath the ice.

Dr Wissel concludes: ‘I’m excited that when we fly PUEO, we’ll have better sensitivity. In principle, we should pick up more anomalies, and maybe we’ll actually understand what they are.’