On September 29, 2022, NASA’s Juno spacecraft flew past Europa at an altitude of 360 km (220 miles). “The 29-km estimate relates to the cold, rigid, conductive outer-layer of a pure water ice shell,” Dr. Levin said. These scatterers are estimated to be no bigger than a few inches in diameter and appear to extend to depths of hundreds of feet below Europa’s surface. “How thick the ice shell is and the existence of cracks or pores within the ice shell are part of the complex puzzle for understanding Europa’s potential habitability,” said Juno’s principal investigator Dr. Scott Bolton, a researcher at the Southwest Research Institute. Europa’s ice thickness and subsurface structure characterized by the Juno microwave radiometer.