What Unknown Particles Could Explain ANITA’s Baffling Radio Signals?

06-14-2025, ANTARCTICA— What mysterious particles are producing the perplexing radio signals detected by the Antarctic Impulsive Transient Antenna (ANITA) experiment? The balloon-borne detector, floating 37 kilometers above Antarctica, has recorded radio pulses emerging from deep beneath the ice at steep angles, challenging the Standard Model of particle physics and sparking urgent speculation about undiscovered particles or interactions, according to a study published Friday in Physical Review Letters.

What Did ANITA Detect?

Between 2016 and 2018, ANITA’s array of radio antennas captured two anomalous radio pulses, appearing to originate 30 degrees below the ice surface. These signals, detected during flights over Antarctica’s vast ice sheets, suggest particles traveled through thousands of kilometers of Earth’s rock—behavior that defies known physics, as high-energy particles like neutrinos should be absorbed by such dense material.

“The radio waves we detected were at really steep angles,” said Stephanie Wissel, associate professor of physics at Penn State and ANITA team member. “It’s an intriguing problem because we still don’t have an explanation.”

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Why Do These Signals Challenge Physics?

The Standard Model, the framework describing all known particles and forces, predicts that high-energy neutrinos—the primary focus of ANITA—cannot traverse the Earth at such steep angles due to their large interaction cross-sections. Unlike low-energy neutrinos, which zip through matter unscathed, high-energy neutrinos are likely to collide with atoms, making ANITA’s detections “anomalous.”

Researchers ruled out neutrinos as the source after cross-referencing data with the IceCube Neutrino Observatory and Pierre Auger Observatory, which detected no similar signals.

Could New Particles Be the Culprit?

The signals have fueled speculation about unknown particles. One theory suggests tau leptons, produced by tau neutrinos interacting just below the ice, could decay and emit radio waves. However, the steep angles observed are inconsistent with Standard Model neutrino properties.

Some physicists propose exotic particles, such as sterile neutrinos or supersymmetric particles like sleptons, which could pass through Earth with minimal interaction.

“If these events are real, they could point to physics beyond the Standard Model,” said Alex Pizzuto, an astrophysicist at the University of Wisconsin-Madison.

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Are Dark Matter or Cosmic Accelerators Involved?

Another hypothesis links the signals to dark matter, the mysterious substance comprising 27% of the universe’s mass. Heavy dark matter particles or new interactions could produce the observed radio pulses. Alternatively, cosmic accelerators—such as blazars, gamma-ray bursts, or supernovae—might generate high-energy particles capable of such feats.

A 2014 supernova was considered a possible source for one ANITA event, but no clear candidates exist for others, leaving these theories speculative.

Could Antarctic Ice Be Misleading Scientists?

Some researchers caution that the signals may stem from glaciological effects rather than new particles. Subglacial lakes or thin ice layers could reflect radio waves, mimicking upward-moving particle signals without phase inversion.

A 2020 study suggested that complex ice structures, like double layers of ice over hoar, might explain the anomalies, but the hypothesis remains unconfirmed. “ANITA could have discovered something intriguing about glaciology instead of particle physics,” said Ian Shoemaker of Virginia Tech.

Did you know?
ANITA’s radio pulses, detected at 30 degrees below Antarctica’s ice, suggest particles traveled through Earth’s core, defying known physics and hinting at new particles or ice effects.

How Will PUEO Advance the Search?

NASA’s upcoming Payload for Ultrahigh Energy Observations (PUEO), set to launch in 2026, promises greater sensitivity and better noise isolation to clarify ANITA’s findings. “PUEO may detect more of these signals and help us understand whether they’re new physics or rare environmental effects,” Wissel said. The instrument’s advanced antennas aim to capture additional events, potentially confirming or ruling out exotic particle theories.

Why Does This Matter for Science?

If confirmed, these signals could herald a paradigm shift in physics, revealing particles or interactions not accounted for in the Standard Model. Even if attributed to ice phenomena, the findings could enhance our understanding of Antarctica’s subsurface. The scientific community awaits PUEO’s results to resolve whether these signals are a glitch, a geological quirk, or a window into new physics.