A long winter in Antarctica

18 April 2019

Physicist Dr. Benjamin Eberhardt from Mainz is living and conducting research at the South Pole for an entire year. Together with his colleague Dr. Kathrin Mallot, he is overseeing the IceCube Neutrino Observatory. The observatory is operated by an international consortium in which Johannes Gutenberg University Mainz (JGU) is a major participant.
 

The satellite is in a favorable position. Dr. Benjamin Eberhardt now has an hour in which to call his native city, Mainz. The connection is astonishingly good. Every now and then he gets briefly cut off, but the 34-year-old's voice rapidly becomes crystal clear again. It is scarcely believable that he is sitting in the international Amundsen–Scott Research Station, just 50 meters from the geographical South Pole.

The sun is shining 24 hours a day in Antarctica at present. "But it's already low in the sky," explains Eberhardt, "the shadows are getting longer." Soon it will disappear behind the horizon for half a year. "The last supply aircraft has just taken off, and we are clearing away the runway." The thermometer is now showing minus 45 degrees Celsius. For some time yet, temperatures will continue to fall. The lowest temperature ever recorded here was minus 82 degrees Celsius.

Hunting for neutrinos with the IceCube

"The real adventure is just about to start," says Eberhardt's colleague Dr. Kathrin Mallot from Berlin. Both are actually looking forward to spending winter at the South Pole. "We are wondering how things will go in the next six months." Just 42 of the base's 150 regular occupants are staying. But those 42 winterovers, a term coined for those who stay at the South Pole over winter, are quickly knitting together as a group. "We are preparing an extensive leisure time program," says Mallot. "Some of our colleagues asked us to teach them some German. For my part, l want to learn to play the guitar." "And a unicycle course is about to start," Eberhardt adds.

That may sound like the winterovers will be enjoying a lot of free time in the months to come, but in fact Mallot and Eberhardt have a lot on their plate. They underwent extensive training at the University of Wisconsin-Madison for several months before heading off to Antarctica in October 2018. "The station is home to a wide spectrum of experiments in the fields of atmospheric and climate research, earthquake detection, and astrophysics," explains Eberhardt. "We are a team and support each other. We work every single weekday, and if there are problems we are also busy at night." Talking about day and night at the South Pole is, in any event, a rather academic exercise since all time zones genuinely meet up here. "For purely practical reasons, we operate on New Zealand time."

Mallot and Eberhardt are responsible for the successful operation of one experiment in particular: the IceCube Neutrino Detector. It took six years before this extraordinary observatory was completed at the end of 2010. A total of 86 vertical boreholes were drilled into the 3,000-meter thick ice sheet at the South Pole containing 5,160 digital optical modules. They are arrayed at depths of 1,450 to 2,450 meters in a clear ice cube that is one kilometer on each side.

Scientists all over the world are using these sensors to search for high-energy neutrinos, these electrically neutral, virtually massless particles. Unlike light, there is almost nothing that can block them. Some 300 trillion of them hurtle unnoticed through each of our bodies every second. They react with the medium they pass through at a phenomenally low rate, but then, and only then, can they be detected. Most neutrinos that pass straight through the Earth were formed in the Sun, but a few originate from much further away. And these are the ones that IceCube is looking for. In 2017, for instance, a neutrino was detected that originated from a galaxy 3 billion light years away.

Data for scientists from twelve countries

"I first went to the South Pole in 2014," Benjamin Eberhardt recalls. "At the time I was writing my doctoral thesis on IceCube. But I only stayed four weeks in summer." Eberhardt was born and raised in Mainz. He started studying physics at Mainz University, where he encountered the IceCube research group led by Professor Sebastian Böser and Professor Lutz Köpke. Several semesters in Paris and Vancouver followed, before he returned for his dissertation. "I can hardly imagine life without IceCube anymore," he smirks.

Kathrin Mallot was born in Koblenz. She spent her childhood in France, studied physics in Freiburg, and learned about IceCube as a postgraduate from the research group she worked with at the Humboldt-Universität zu Berlin. "When I heard about the opportunity to spend a year working at the South Pole, I jumped at the chance." Her parents took a bit of convincing at first, she remembers. "But my friends provided me with a lot of encouragement right away."

And that's how they both ended up at the South Pole being in charge of IceCube. There is a small surface station on stilts directly above IceCube. "The station is about a kilometer from here," explains Eberhardt. "If there is some kind of malfunction, we have to go out into the cold. Clearly, we can't get to the sensors in the ice itself, but at the station we can adjust them and update the software to teach them new tricks."

The project is managed by the National Science Foundation (NSF), with Germany providing the second largest research contingent. Some 300 scientists from twelve countries are involved. The detector provides them all with a flood of data. "The data is filtered here on site before being transmitted on," Mallot explains. "We send emails to 40 to 50 telescopes around the world to coordinate their observations."

Wintering over in the most isolated spot in the world

In total there are three satellites for communication. They can also relay telephone calls and provide a very impressive Internet connection for four hours a day. "Recently, we had a direct connection to an Italian school class," reports Mallot. "We would love to do things like that more often." And Eberhardt adds: "We are of course officially considered to be at the most isolated location on the planet, but modern technology makes things much easier." With the new satellites that are planned, round-the-clock Internet access is coming. But that's verging on too much of a good thing, they both agree. They are keen to feel and experience the remoteness. "I also want to use this time for personal contemplation," says Mallot.

The station is at an altitude of almost 3,000 meters on top of the massive Antarctic ice sheet known as the Polar Plateau. "Believe it or not, but this is the driest desert in the world," Benjamin Eberhardt points out. "There are no hills, everything is flat. The coast is 1,300 kilometers away." The station crew has to comply with stringent environmental standards. "There are, for example, areas we are not allowed to drive into." The daily routine also takes some getting used to. "Water is a problem. Obtaining it costs an enormous amount of energy. That is why two showers a week for two minutes is the limit."

In the polar night, Mallot and Eberhardt will not just be doing research. "Everyone in our community has to take on additional tasks," Mallot states. "We are both in charge of maintaining the greenhouse and managing the fuel for the station."

When asked what they are missing in Antarctica, they are both quick to respond. "I have a cat at home and I would really like to stroke her again," Mallot says. A dog would do the trick, too. "I miss the plants and the trees," declares Eberhardt, "and especially all kinds of scents." But that's not their main concern right now, with the polar night rapidly drawing on. "We are very excited about the challenge," Mallot says. "That's what we came for."