Over the course of its data-taking, ANITA has been seeing three events that look like neutrinos at very high energy. One was in 2006, the year ANITA started taking data, one in 2014, and one in 2015. ANITA doesn't take data continuously, it makes separate flights over the Antarctic summer. There is nothing sudden about these events.
The first events triggered interest in the particle physics community when it happened, and the 2014 event made this much more interesting. They do not have to come from high energy neutrinos, there is always a chance that events are mis-classified as no experiment is perfect. It's not expected that three events are mis-classified but we can't rule it out either.
We don't know what makes neutrinos achieve such a high energy, but we have been measuring high energy neutrinos for as long as we have detectors to do so. IceCube in particular with its giant size can measure many of them. They are interesting for particle physicists but they rarely make big headlines.
What makes the ANITA events more interesting: At these energies Earth absorbs almost all neutrinos going through it. The 2015 event came from above the horizon - its energy seems to be is really high, but it came from above the horizon, so no problem from that side. The 2006 and the 2014 events come from below the horizon - they would have to travel through Earth, and they can't do that according to our current theories.
Something must be wrong, and some of the possible options are exciting:
- The events were not caused by neutrinos, but came from noise in the detector or whatever - the most boring option.
- The events were caused by neutrinos but the estimate of the direction was wrong. That still gives us the task to find the origin of them and to figure out how they reach this energy.
- The events were caused by neutrinos that did travel through Earth and we underestimate that probability - this would be a very remarkable discovery, changing our knowledge of neutrinos in many ways.
- The events were caused by some other particles that travel through Earth - no known particle can do it, so this would be something fundamentally new. Even more exciting.
How can we figure out which one is correct? We try to measure similar events with other detectors. If they can also measure neutrinos at high energy traveling through Earth then we can rule out measurement problems of ANITA. IceCube did so, and didn't find similar events, in an analysis they made public a month ago. There are scenarios where ANITA would see something but IceCube can't find it, but they are much more exotic. This makes the first two options more likely - the more boring options.
All this has zero impact on our lives. It's studied to learn more about the universe only.
