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Io

The left half of the roughly spherical-shaped moon Io appears in this image, with the right half in complete darkness, blending completely into a black background. The surface is a mottled pale reddish-brown color, with some darker brown-gray patches and some lighter cream-colored patches.
Posted inResearch Spotlights

Io’s Hidden Heat Revealed for the First Time

Sarah Stanley, Science Writer by Sarah Stanley 24 July 202623 July 2026

Data from the Juno spacecraft also suggest that Jupiter’s moon has a relatively smooth, low-density surface.

Three images of the Jovian moon Io show different distributions of colors. The far left image has a spot of red and yellow at bottom left, and the other two images each have a spot of red and yellow in the top half.
Posted inResearch Spotlights

Webb Telescope Spies Io’s Volcanic Activity and Sulfurous Atmosphere

Sarah Stanley, Science Writer by Sarah Stanley 4 November 20254 November 2025

New James Webb Space Telescope images reveal cooling lava, volcanic sulfur monoxide gas, and sulfur gas emissions created by interactions between plasma and the moon’s atmosphere.

A hemisphere image of a pink-tinged volcanic world
Posted inNews

Io Probably Doesn’t Have a Global Magma Ocean After All

Kimberly M. S. Cartier, News Writing and Production Intern for Eos.org by Kimberly M. S. Cartier 12 December 202410 January 2025

Data from the Juno spacecraft may have answered a decades-old question about Jupiter’s moon.

The mountain Telegonus Mensae on Io. In the bottom center of the image is a dark spot that could be an impact crater.
Posted inENGAGE, News

Amateur Astronomer Finds a Possible Crater on Io

by Chiara Villanueva 15 December 202315 December 2023

The most volcanically active body in the solar system may have an impact crater, a discovery spotted by a curious nonprofessional scientist.

Illustration of Jupiter’s magnetosphere and innermost planets
Posted inResearch Spotlights

Two Moons and a Magnetosphere

Sarah Stanley, Science Writer by Sarah Stanley 21 April 202018 October 2022

Decades of research have illuminated how Io and Europa shape—and are shaped by—Jupiter’s giant magnetosphere.

Ganymede, Europa, and Io are in resonant orbits around Jupiter
Posted inFeatures

Does Io Have a Magma Ocean?

by A. McEwen, K. de Kleer and R. Park 18 October 201911 April 2023

Future space missions will further our knowledge of tidal heating and orbital resonances, processes thought to create spectacular volcanism and oceans of magma or water on other worlds.

Composite satellite images of Jupiter’s Galilean moons: Io, Europa, Ganymede, and Callisto
Posted inNews

Jupiter’s Galilean Moons May Have Formed Slowly

Mara Johnson-Groh, Science Writer by Mara Johnson-Groh 30 September 201922 July 2024

A new model is the first to simultaneously explain many of the moons’ characteristics, including their mass, orbits, and icy composition

The Tvashtar volcano erupts on Io
Posted inResearch Spotlights

No Underground Magma Ocean on Jupiter’s Fiery Moon?

by E. Underwood 22 May 201911 May 2022

A new study suggests alternative explanations for Io’s unusual magnetic field.

Researchers look at satellite data to analyze the oxygen cloud around Io
Posted inResearch Spotlights

The Oxygen Neutral Cloud Surrounding Jupiter’s Volcanic Moon

Kate Wheeling, freelance science writer by Kate Wheeling 20 June 201827 July 2022

Japan’s Hisaki satellite takes measurements of faint oxygen emissions from Io.

Jupiter’s moon Io
Posted inNews

Scientists Discover Stromboli-Like Eruption on Volcanic Moon

JoAnna Wendel, freelance science writer and illustrator by JoAnna Wendel 27 December 20175 January 2022

Jupiter’s moon Io is known for its lava fountains and roiling lava lakes, but scientists had never seen such an intense eruption in their data until now.

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