https://phys.org/news/2018-11-neutrinos-icecube-mass-earth.html

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.