The exploration of Antarctica is an ongoing exercise. The South pole is not just a treasure trove of information for the Earth’s formation and eras, it is also a very interesting place from which to study space and its interactions with Earth through electromagnetic waves and other invisible cosmic rays. It houses plenty of bases from many countries around the world and a lot of antennas that aim to capture signals from outer space. One of the most renowned ones is the Antarctic Impulsive Transient Antenna (ANITA for short).
While ANITA was meant to pick up those space signals, the cluster of antennas strapped to a giant balloon picked up something a lot more interesting and closer to home, waves that shot upwards from Earth. While not its job, its job is to detect radio waves created when high-energy particles like cosmic rays slam into the ice or atmosphere, when it detected these strange signals, scientists new that they had to investigate and discover what laid beneath the ice and was causing the disturbance.
The signals captured by ANITA in Antarctica, an unexpected scientific breakthrough
Like many discoveries through the ages, this one was accidental and just fell into researcher’s laps. The waves captured by ANITA had all the intensity expected from a powerful cosmic particle except that they did not flip polarity the way they would if they had bounced off a surface. What that meant is that they likely were not reflections, which meant that they came upward through the Earth.
The explanation still leaves a lot to be desired, as physics says that if an ultra-energetic neutrino traveled through Earth and triggered a particle cascade just as it popped out of the Antarctic ice, you might see a signal like that. But that theory has a major flaw, and that is that neutrinos almost never interact with matter, and getting through thousands of kilometers of dense rock without reacting is highly unlikely.
Researchers at the Pierre Auger Observatory in Argentina were not satisfied with he explanation and looked into fifteen years’ worth of data to see if something similar had occurred before, and although they did find some similar instances, they were not exactly the same and were deemed just background noise, which means that this event could be a first recording of something. What that something is, is still to be determined.
If these signals are not from neutrinos punching through the planet, we do not know what they are. Some scientists have suggested that we could be seeing new forms of particle interaction, others think we might be witnessing some kind of strange radio wave behavior or Earth-specific magnetic quirk we do not understand yet.
The paper reporting on all this does not leave any room for optimism when it comes to theories and past data being able to explain the phenomenon, stating quite directly “No simple mechanism can be anticipated that produces distributions of this type.”
The framework that has been used until now to try to decipher what this phenomenon is, known as the Standard Model, has been incredibly successful at explaining the behavior of fundamental particles but it is not perfect and does not account for things like gravity or dark matter. So when data like this shows up, scientists get excited even if they are unable to come up with an explanation right away.
But they are not giving up and are hoping that this seemingly isolated event will repeat itself this time on a new project. Named PUEO (Payload for Ultrahigh Energy Observations), it is basically ANITA 2.0, designed to be more sensitive and better equipped to catch these rare signals. As Penn State’s Stephanie Wissel puts it “It’s one of those long-standing mysteries, and I’m excited because when we launch PUEO, we’ll have better sensitivity. In principle, we should detect more anomalies, and perhaps understand them.”