This map represents data captured by the Microwave Radiometer (MWR) aboard NASA’s Juno spacecraft, indicating the heat rising just below the surface of Jupiter’s moon Io. While infrared instruments measure the temperature of the moon’s surface, the MWR’s lower frequency microwave channels (0.6 and 1.25 gigahertz) can penetrate 6 to 20 feet (2 to 6 meters) into the crust. The colors of this map illustrate a clear temperature gradient on the Moon, with the most extreme heat production located in red.

The most prominent red anomaly at the top left (between 60 and 120 degrees west longitude) reveals subsurface temperatures 18 to 36 degrees Fahrenheit (10 to 20 degrees Celsius, or 10 to 20 Kelvin) warmer than the surrounding area. This huge regional heat source coincides with the Zal Montes Patera complex, an area where the Juno Stellar Reference Unit observed an active lava flow. A second major underground heat source is also visible near the equator, extending from 0 to 50 degrees west longitude. Together, these distinct microwave anomalies indicate significant internal heating occurring within the upper tens of meters of Io’s crust.

In contrast to these intense hot spots are the yellow and green regions, which reflect more common temperatures across the moon. The yellow areas represent intermediate temperatures that naturally warm to about -190°F (-123°C or 150 Kelvin) as they approach the equator. Meanwhile, the green areas, visible primarily toward higher northern latitudes, indicate the coldest subsurface temperatures, which fall to around -298°F (-183°C or 90 Kelvin) near the pole.

NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Juno mission for principal investigator Scott Bolton of the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington. The MWR was built by JPL. Lockheed Martin Space in Denver built and operates the spacecraft.

More information about Juno is at: http://www.nasa.gov/juno