Instruments flying high over Antarctica have detected mysterious radio bursts coming from deep below the ice—signals that current scientific models say shouldn’t exist.
The Antarctic Impulsive Transient Antenna, or ANITA, first recorded the pulses. This NASA experiment uses 24 radio antennas attached to a balloon flying more than 18 miles (29 kilometers) above the continent. The setup is designed to capture data in a location with little signal interference.
Researchers found the bursts appeared to originate from about 30 degrees below the surface—an angle that should block such signals. According to existing science, any radio waves from that depth would have to pass through thousands of miles of solid rock.
That rock, researchers say, should have absorbed the signals long before they reached the surface. Yet the signals arrived clearly, puzzling scientists and prompting new studies.
Neutrinos ruled out as the source of signals
“It’s an interesting problem because we still don’t actually have an explanation for what those anomalies are,” said Stephanie Wissel, a physicist and co-author of the study, which was published March 27 in Physical Review Letters.
The ANITA experiment was originally designed to study neutrinos, tiny particles that can pass through matter with almost no interaction. Sometimes called “ghost particles,” neutrinos are notoriously difficult to detect. But the direction and behavior of the signals ANITA captured don’t match what scientists expect from neutrinos.
Wissel explained that neutrino signals would not typically emerge from such sharp angles below the surface. The research team used computer models and data from other detectors, including the Pierre Auger Observatory in Argentina, to test different explanations. They ruled out neutrinos, background noise, and known particle behaviors.
Unusual findings hint at new physics
Since the signals don’t fit with what the Standard Model of particle physics predicts, they may point to something entirely new.
“More research needs to be done on this,” said Benjamin Flaggs, a physics graduate student at the University of Delaware and another co-author of the study. “There are theorists proposing some beyond-standard-model interactions from different types of particles.”
Some theories suggest the signals could be linked to dark matter, the invisible substance thought to make up about 27% of the universe. Others, including Wissel, believe the answer might lie in an unknown behavior of radio waves. But so far, no theory has clear evidence to support it.
New balloon experiment may offer answers
Scientists are preparing to launch a new balloon experiment from Antarctica this December to help solve this mystery. The upgraded tool is called the Payload for Ultrahigh Energy Observations, and is designed to detect even more of these unusual signals.
“The more data we can get, the better we can get our statistical error,” Flaggs said. “It’s exciting for researchers because these are problems that no one else has figured out before.”