Juno Microwave Radiometer Observations of Europa’s Subsurface Ice Shell 

<p>On 29 Sep 2022, Juno had a close flyby of Jupiter&#8217;s moon Europa, flying within 500 km of the surface. During the flyby, Juno&#8217;s Microwave Radiometer (MWR) observed Europa, obtaining several swaths across Europa using Juno&#8217;s spin to map Europa&#8217;s subsurface ice shell at six frequencies ranging from 600 MHz to 22 GHz.&#160; The ice transparency at microwave frequencies is dependent on purity; assuming pure ice, the observations probe depths ranging from meters to kilometers.&#160;The MWR observations represent the first resolved interrogation of Europa&#8217;s subsurface ice shell revealing new constraints on porosity, fracturing, differences in terrain type and possibly the thickness of the conductive ice shell.&#160; These unprecedented measurements on Europa and Ganymede will provide new insights into the &#160;comparative nature of the surfaces and interiors of the Jovian satellites.</p>