A few years ago, the Antarctic Impulsive Transient Antenna (ANITA) experiment detected baffling radio signals that appeared to travel upward through the Earth, an observation that seemingly defies the known laws of physics. This anomaly hinted at new particles not described by the Standard Model, but a new, exhaustive search has failed to find any corroborating evidence, deepening the puzzle.

The ANITA experiment, a balloon-borne antenna array, detected mysterious radio signals that sparked a physics puzzle.

(Wissel/Penn State, 2025)

In response to the ANITA findings, an international team at the Pierre Auger Observatory in Argentina conducted a dedicated search for similar phenomena. Using a vast array of instruments, scientists re-analyzed 15 years of data to look for “air showers”—cascades of secondary particles—that appeared to be traveling upward from below the horizon at extreme angles.

The single detection is statistically consistent with the expected background noise—a standard, downward-traveling cosmic ray misidentified by the system. Scientific models predicted that if the ANITA signals were real, the Auger Observatory should have detected at least eight similar events. The fact that it found none, statistically speaking, creates a strong disagreement with the original exotic explanation.

The lack of corroborating signals from a different, highly sensitive observatory challenges the initial interpretation of the ANITA data.

(Wissel/Penn State, 2025)

The results from the Pierre Auger Observatory, published in *Physical Review Letters*, place the original ANITA observations in a challenging new context. While the study does not solve the puzzle of what ANITA detected, it strongly suggests the answer is not a flux of exotic particles traveling through the planet. This leaves the baffling Antarctic anomaly an even more profound mystery for physicists to solve.