Mysterious Radio Signal Rising From Antarctica's Ice Baffles Scientists

Newsweek

a day ago

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Mysterious radio signals detected emanating from Antarctica's ice have left particle physicists baffled.
The pulses were detected by the Antarctic Impulsive Transient Antenna (ANITA)—an array of radio instruments flown high above the southernmost continent via air balloon.
ANTIA was designed to detect the radio waves generated when neutrinos from space hit the Antarctic ice, with the aim of learning more about distant cosmic phenomena.
In contrast, these strange new signals appear to be coming from below the horizon, a source direction that cannot be reconciled with our current understanding of particle physics.
To reach the detector, the team explained, the signal must have traveled through thousands of miles of rock first, which should have attenuated it down to nothing.
"The radio waves that we detected were at really steep angles, like 30 degrees below the surface of the ice," said paper author and physicist Stephanie Wissel.
"It's an interesting problem because we still don't actually have an explanation for what those anomalies are, but what we do know is that they're most likely not representing neutrinos."
The ANITA Experiment prepares for launch.
The ANITA Experiment prepares for launch.
Stephanie Wissel / Penn State
Perhaps the most ironic aspect of this discovery is that ANITA was launched over Antarctica in part because this remote location should limit the risk of interference from other signals.
The team's analysis of the strange new signals ruled out the possibility that they were caused by neutrinos, regular cosmic rays, or other known particle-based signals.
"My guess is that some interesting radio propagation effect occurs near ice and also near the horizon that I don't fully understand," said Wissel.
"But we certainly explored several of those—and we haven't been able to find any of those yet either. So, right now it's one of those long-standing mysteries."
The researchers are currently developing the next big ultra-high energy particle detector, the Payload for Ultrahigh Energy Observations, or "PUEO" for short.
When PUEO launches, Wissel added, "we should pick up more anomalies, and maybe we'll actually understand what they are. We also might detect neutrinos, which would in some ways be a lot more exciting."
Neutrinos are electrically neutral elementary particles that are abundant in the universe, being emitted from high-energy sources such as stars, supernovas, and even the Big Bang.
Despite the presence of neutrino signals throughout the cosmos, they are notoriously difficult to detect. This is because these particles typically pass straight through regular matter, as they interact weakly with it via gravity and the weak nuclear force.
"You have a billion neutrinos passing through your thumbnail at any moment, but neutrinos don't really interact," Wissel explained.
"So, this is the double-edged sword problem. If we detect them, it means they have traveled all this way without interacting with anything else. We could be detecting a neutrino coming from the edge of the observable universe."
Because of this, the detection of even one neutrino offers a veritable trove of information, the researchers explained.
"We use radio detectors to try to build really, really large neutrino telescopes so that we can go after a pretty low expected event rate," said Wissel.
In the case of ANITA, the researchers are hunting for signs of a flavor of neutrino—the tau neutrino—which can interact with ice to form a "tau lepton." When tau leptons decay, they break down and produce emissions known as showers. By projecting backward from these signals, physicists are able to determine the nature of the neutrinos that triggered them.
Unfortunately, the same does not apply to the new, strange signals, however, as their angle of flight is outside that predicted by existing models.
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Reference
Pierre Auger Collaboration, Abdul Halim, A., Abreu, P., Aglietta, M., Allekotte, I., Almeida Cheminant, K., Almela, A., Aloisio, R., Alvarez-Muñiz, J., Ammerman Yebra, J., Anastasi, G. A., Anchordoqui, L., Andrada, B., Andringa, S., Apollonio, L., Aramo, C., Araújo Ferreira, P. R., Arnone, E., Arteaga Velázquez, J. C., ... Zeolla, A. (2025). Search for the Anomalous Events Detected by ANITA Using the Pierre Auger Observatory. Physical Review Letters, 134(12). https://doi.org/10.1103/PhysRevLett.134.121003