Neutrinos are ghostly particles—no charge, barely any mass, and yet they flood the cosmos. Born in places like the Sun, exploding stars, and even the Big Bang itself, they race through us by the trillions every second, silently.
But here’s the twist: they’re almost impossible to catch. That’s why scientists build ultra-sensitive detectors, buried deep underground or beneath ice, in an attempt to hear just a faint “ping” from these elusive messengers. Even a single neutrino signal could reveal secrets about the universe’s most dramatic events.
ANITA, a balloon-borne radio detector flying over Antarctica, was designed to eavesdrop on ghostly particles, such as neutrinos, far from the noisy human signals. But recently, it picked up something far weirder: strange radio pulses rising from beneath the ice when signals should’ve been coming from above.
This discovery has scientists scratching their heads. Could it be new particles? Or unknown physics rewriting what we thought we knew?
The strange radio waves ANITA picked up came from way below the ice, at angles so steep —like 30 degrees —that they should have traveled through thousands of kilometers of solid rock.
That’s a problem because rock usually swallows up signals like that. By the time a normal radio wave made it through, it’d be gone entirely. And yet… this one showed up, loud and clear. How? That’s the mystery.
Stephanie Wissel, associate professor of physics, astronomy, and astrophysics who worked on the ANITA team searching for signals from elusive particles called neutrinos, said, “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.”
To figure out what ANITA had really heard, scientists didn’t just take the data at face value. They compared it with computer models and ran countless simulations of known space particles, such as regular cosmic rays and strange bursts from below known as “upward air showers.” That helped them rule out the usual suspects.
Antarctica had rainforests 90 million years ago
But they didn’t stop there. When scientists checked with other detectors, such as IceCube and the Pierre Auger Observatory, they came up empty—none had picked up anything that could explain ANITA’s strange radio signal.
That was a big red flag. It meant this wasn’t a familiar visitor like a neutrino slipping through unnoticed. Hence, scientists described the signal as ‘anomalous’.
Wissel said, “The signals do not fit within the standard picture of particle physics, and while several theories suggest that it may be a hint of dark matter, the lack of follow-up observations with IceCube and Auger really narrow the possibilities.”
Wissel believes there might be some unusual effect in how radio waves travel near the ice and the horizon—something we don’t fully understand yet. Scientists have tested a bunch of theories, but none of them have explained it so far. That’s why this strange signal remains one of science’s lingering mysteries.
Journal Reference
- A. Abdul Halim, P. Abreu et al. Search for the Anomalous Events Detected by ANITA Using the Pierre Auger Observatory. Physical Review Letters. DOI: 10.1103/PhysRevLett.134.121003
