This graphic illustrates the areas of Jupiter’s moon Io sampled by the Microwave Radiometer (MWR) instrument aboard NASA’s Juno spacecraft during two close flybys. The black overlapping lines show the instrument’s footprints during Perijove 57 on Dec. 30, 2023, when the spacecraft primarily mapped the northern hemisphere. The blue lines represent Perijove 58 on Feb.

This map represents data captured by the Microwave Radiometer (MWR) aboard NASA’s Juno spacecraft, indicating heat rising from just beneath the surface of Jupiter’s moon Io. While infrared instruments measure the temperature of the moon’s surface, the lowest frequency microwave channels (0.6 and 1.25 gigahertz) on the MWR can penetrate between about 6 and 20