As Voyager 1 approached Jupiter in the 1970s, scientists expected the spacecraft to find a world not unlike our moon. Io, the innermost of Jupiter’s largest moons, is about the same size and mass as the moon. It seemed reasonable to predict Io would turn out to be a cold, rocky world studded with craters, too.
Instead, Voyager found a world alive with volcanoes. The first plume was spotted by Linda Morabito, an engineer on Voyager’s imaging team at NASA’s Jet Propulsion Laboratory, as she sorted through the spacecraft’s data. The photograph was the first evidence of volcanic activity somewhere besides Earth.
Today, Io is known to be the most volcanically active place in the solar system. The moon is teeming with hundreds of volcanoes, some of which can spew lava dozens of miles into the moon’s thin atmosphere of sulfur dioxide, a chemical compound that is sometimes used to preserve foods on Earth.
A number of different NASA spacecraft have flown by Io since Voyager and captured their own photographs of the moon. But one of the best views of Io is outside of the capabilities of the typical camera.
The photo at the top of this story shows Io in all its volcanic glory in infrared light, which the human eye can’t see, captured by the Juno spacecraft’s Jovian Infrared Auroral Mapper instrument. Each bright spot is the glow from a volcanic feature on the moon’s surface. The image was created by Roman Tkachenko, an amateur astronomer and music producer in Kursk, Russia, and one of the dozens of people who assembles raw data from the Juno spacecraft, which has been orbiting Jupiter since 2016, to produce beautiful photos of the planet and its moons.