People often wonder what activities occur at the South Pole during the winter, or to phrase it differently, why are we here? Over the course of the next couple of months I will tell you about some of the scientific investigations underway at Amundsen-Scott South Pole Station in such diverse fields as earth science, astronomy, astrophysics, cosmology, and climatology.
Perhaps one of the most unique investigations being conducted is that of the IceCube Laboratory (ICL), more formally known as the IceCube Neutrino Observatory. Construction of the $276,000,000 project started in 2004 and was just recently completed. The structure shown in the picture above is just the “tip of the iceberg”, for deeply buried in the ice below the laboratory are about five thousand Digital Optical Modules or DOMs designed to detect the traces of sojourners from outer space. No, not the sort of aliens depicted in the various movie versions of “The Thing”, but rather subatomic particles known as neutrinos.
Neutrinos (Italian for “small neutral one”) are constantly bombarding Earth and can result from radioactive decay, nuclear reactions, or energetic cosmic events. Unlike many other particles of cosmic origin, they have a very small mass and are electrically neutral, so they are not affected by the magnetic fields of stars and planets. As a matter of fact, they interact very little with other matter and are able to pass right through the Earth unimpeded. Since they travel in a straight line it is possible for scientists to trace their trajectory back to their point of origin. This makes neutrinos one of the best tools for uncovering mysteries in the farthest reaches of the universe. But neutrinos are notoriously difficult to detect and it takes very special instruments in a very special environment to have any hope of success.
IceCube’s detector array took six years to construct and consists of eighty-six cables, each strung with 60 basketball-sized DOM light detectors which were lowered into in 2.4 kilometer (8000 feet) deep holes melted in the ice with hot water. The melted ice was allowed to refreeze, creating a detector array one cubic kilometer (a little more than half a mile) in size. Each DOM is enclosed in a thick glass sphere strong enough to withstand the enormous pressure of the deep ice. The DOM contains a photomultiplier tube and other electronics able to detect and record the faint blue light (“Cherenkov radiation”) emitted when a neutrino strikes a hydrogen or oxygen atom in the ice and produces a muon. Because the deep ice at the South Pole is exceptionally clear, dozens of sensors will see each muon created and scientists can triangulate the neutrino’s exact path through the ice.
Neutrinos are thought to result from exploding stars or super novas, black holes that eject intense jets of particles, or even the mysterious dark matter that is thought to make up the majority of the universe. It is ironic that to help solve the mysteries of the outer reaches of the universe, we have come to what Captain Robert Falcon Scott called “this awful place” at the end of the Earth.