Signals coming from beneath Antarctica have been detected. They appear to have passed through the Earth as if its matter didn't exist.
These strange radio waves weren't captured as usual by bouncing off the ice, but rather coming directly from the depths. The ANITA experiment, suspended from a stratospheric balloon above Antarctica, intercepted these unexpected signals at an altitude of 25 miles (40 km), with no known explanation justifying their trajectory.
According to current particle physics laws, a radio signal that has traveled thousands of kilometers through rock should be too weakened to remain detectable. But here, these pulses arrive clearly, and most importantly are oriented 30° below the horizon—an angle normally impossible to reach without significant loss.
The first suspects are naturally neutrinos. Nicknamed "ghost particles," they usually pass through all matter without reacting, and their detection is exceptionally rare. ANITA is specifically designed to track them by identifying their interactions in the ice.
But researchers from the project, including Stephanie Wissel from Penn State University, clarify that these signals don't resemble those of the expected neutrinos. Their shape, angle of arrival, and intensity don't match existing models. Even other detectors like IceCube or Pierre Auger haven't seen anything similar.
The usual mechanism involves so-called "tau" neutrinos hitting the ice, producing secondary particles that eventually generate "particle showers." These events, oriented upwards, are captured by ANITA's antennas. But the abnormal signals seem to come from below, as if they were emitted through the Earth.
No propagation model can explain such a trajectory. Neither edge effects nor known reflections in the ice can justify the origin. It could be new, still unknown particles, or unexpected interactions between exotic particles.
Another, bolder hypothesis suggests a form of dark matter. Invisible yet massive, these entities would make up 85% of the Universe's matter. If the signals came from there, it would be a major discovery.
Researchers are now awaiting the commissioning of a more sensitive detector: PUEO, still in development. It could help shed light on these anomalies or even detect the true neutrinos ANITA has been tracking all along.
What is dark matter?
Dark matter represents about 85% of the Universe's total matter, but it remains invisible to traditional telescopes. Its existence is inferred from its gravitational effects on galaxies and galaxy clusters.
Scientists believe dark matter is composed of particles that don't interact with light, making them extremely difficult to detect. Experiments like ANITA search for indirect evidence of these particles.
Despite decades of research, the exact nature of dark matter remains a mystery. The anomalies detected by ANITA could provide valuable clues to solving this cosmic enigma.
How does the ANITA experiment work?
ANITA is a series of instruments suspended from balloons floating at high altitude above Antarctica. These instruments are designed to detect neutrinos and other high-energy cosmic particles.
By observing the radio signals produced when these particles interact with the ice, ANITA can trace their origin. This method allows the study of distant and extremely energetic cosmic phenomena.
Antarctica's isolation and the purity of its radio environment make it an ideal location for this type of research. The collected data helps scientists better understand the mechanisms at work in the Universe.