NASA's Juno spacecraft has delivered the most detailed thermal observations yet of Jupiter's volcanic moon Io, offering scientists new insights into the internal processes powering the most geologically active world in the solar system. The findings, published in the Journal of Geophysical Research: Planets, provide a high-resolution thermal map of Io's surface and reveal how heat is distributed beneath its volcano-filled landscape.

Io, which is slightly larger than Earth's Moon, is constantly reshaped by intense volcanic activity driven by powerful gravitational forces. Orbiting Jupiter, the moon experiences a continuous gravitational tug-of-war between the giant planet and its neighbouring moons, Europa and Ganymede. This interaction causes Io to stretch and compress repeatedly, a process known as tidal flexing, generating enormous amounts of internal heat through friction.

According to the study published on Wednesday, the relentless tidal heating turns Io's interior into a vast reservoir of molten rock, fuelling hundreds of active volcanoes across its surface. Scientists have long sought to understand how this heat is produced and transported within the moon. The latest observations from Juno are expected to help researchers refine models of Io's internal structure while shedding light on how tidal forces influence planetary bodies elsewhere in the solar system.

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During its recent close flybys of Io, Juno used its Jovian Infrared Auroral Mapper (JIRAM) instrument to capture highly detailed thermal images of the moon. The instrument measured heat radiating from lava lakes, volcanic fissures and enormous calderas, enabling scientists to create one of the most comprehensive thermal profiles of Io to date. The data also revealed how temperatures vary across different volcanic regions, offering clues about the depth and movement of magma beneath the surface.

In addition to JIRAM's infrared observations, Juno's Microwave Radiometer (MWR) examined Io at longer wavelengths, allowing researchers to peer beneath the surface. The observations showed that Io's surface appears relatively smooth when viewed at these microwave wavelengths, indicating that heat may be rising from below in a more uniform manner than previously believed. This capability enables scientists to study subsurface temperatures and better understand how volcanic materials accumulate and evolve over time.

Researchers say the combined observations from JIRAM and the Microwave Radiometer represent a significant advance in the study of Io's volcanic activity. By combining infrared and microwave data, scientists can investigate both surface and subsurface thermal behaviour, helping them determine how magma is generated, stored and transported within the moon. The findings could also improve understanding of geological processes on other rocky worlds influenced by tidal heating, including some icy moons that may harbour subsurface oceans.

Launched in 2011 and orbiting Jupiter since 2016, NASA's Juno mission was originally designed to study the giant planet's atmosphere, magnetic field and internal structure. Its extended mission has allowed the spacecraft to conduct close flybys of Jupiter's major moons, including Io, Europa and Ganymede, significantly expanding its scientific objectives. The latest results from Io highlight Juno's continuing role in revealing new details about the Jovian system and the dynamic processes shaping some of the solar system's most extraordinary worlds.

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