NASA’s Juno mission has provided the first measurements of the temperature below the surface of Jupiter’s moon Io, revealing significant heating within the shallow subsurface of the most volcanically active world in the solar system. Collected during two close flybys, the data also shows that most of Io’s surface is remarkably smooth and composed of material of very low density.
Published Wednesday in the Journal of Geophysical Research: Planets, these findings break new observational ground for both fiery and icy worlds beyond our planet.
Io’s extreme volcanism is powered by tidal heating. The moon is constantly stretched and squeezed by Jupiter’s immense gravity as it travels its slightly elliptical orbit, generating internal heat output many times greater than Earth’s. Until now, virtually everything known about that heat came from infrared observations, which sense only the temperature of the top surface. The latest findings are derived from data collected by the spacecraft’s Microwave Radiometer (MWR) instrument.
“The Juno Microwave Radiometer directly observed Io’s heat output by looking below the surface,” said Scott Bolton, study coauthor and Juno’s principal investigator at Southwest Research Institute in San Antonio. “The surprising discovery that we could see below a rocky moon’s surface has important implications for studying Earth’s volcanoes. Juno has taught us that if we look with an MWR-type instrument near a volcano on Earth, we might see a similar signature in the subsurface temperature gradient, providing new information on how terrestrial volcanoes work.”
