November 6, 2018 report
Using neutrinos detected by IceCube to measure mass of the Earth
A trio of researchers from CSIC-Universitat de València and Universitat de Barcelona has used data from the IceCube detector in Antarctica to measure Earth's mass. In their paper published in the journal Nature Physics, Andrea Donini, Sergio Palomares-Ruiz and Jordi Salvado describe using data describing neutrinos passing through the Earth to learn more about the interior of the planet. Véronique Van Elewyck with Paris Diderot University has written a News and Views piece on the work done by the team in the same journal issue.
Currently, scientists use calculations based on gravitational pull and readings from seismic detectors to measure the mass of the Earth and its density. In this new effort, the researchers have taken a different approach—looking at the number of neutrinos that make their way through the planet.
The IceCube Neutrino Observatory was established back in 2005. It is made up of thousands of sensors situated under the ice to detect neutrinos that have passed through the Earth. Neutrinos are weakly interacting particles—those that pass through the Earth are known as atmospheric neutrinos because they arise from collisions between cosmic rays and the Earth's atmosphere. In this new effort, the researchers used data from IceCube from 2011 to 2012—it was not publicly released until 2016. IceCube detects low-energy neutrinos—high-energy neutrinos are not able to make it all the way through the planet.
To calculate the Earth's mass, the researchers measured how much of the neutrino stream produced by atmospheric collisions made it through the planet. To calculate the density of Earth's layers, they counted how many neutrinos were able to get through the planet at different angles to IceCube.
The researchers report that their findings agreed with measurements of the planet taken using traditional methods. But they also note that as the years pass and IceCube collects more data, measurements of the planet using neutrinos will become more precise. Van Elewyck suggests that as other neutrino-sensing stations are set up in other places, it should be possible to conduct a full tridimensional analysis of the planet offering information not available through other means.
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