The Antarctic Radio Signal That Scientists Still Can’t Fully Explain

In 2006, an experiment called ANITA (Antarctic Impulsive Transient Antenna) was launched on a high-altitude balloon over Antarctica to study extremely high-energy cosmic particles. ANITA detects radio waves produced when high-energy particles interact with the atmosphere and Antarctic ice.

Normally, the process looks like this:
Cosmic ray from space
↓
Enters Earth's atmosphere
↓
Creates a particle shower (cosmic-ray air shower)
↓
Radio signals reflect off the Antarctic ice surface
↓
Detected by ANITA
However, ANITA detected several unusual events that did not match the expected pattern. In 2006 and 2014, the experiment recorded radio pulses that appeared to come from an angle below the horizon, as if they were coming from beneath the Antarctic ice. This created a scientific puzzle. If the signal truly came from particles traveling through the Earth, those particles would have had to pass through thousands of kilometers of rock and matter. Even extremely weakly interacting particles like neutrinos should face significant absorption at certain energies. Scientists have proposed several possible explanations:

Could it be an unusual reflection or interaction with the Antarctic ice?
Could the direction of the signal have been misinterpreted?
Could there be an unknown particle process involved?
Could it point toward physics beyond the current Standard Model?
Several exotic physics ideas have been proposed, but no explanation has been universally accepted as the final answer.