NASA hasn’t finished its work on Mars, but its search for water now extends across the solar system. Ice is widespread, especially near the south poles of planets and on many moons. Some of Jupiter’s moons have shown signs of possible subsurface water, with activity suggesting that liquid may be reaching the surface in the near future. While these environments aren’t candidates for human habitation, they continue to offer valuable targets for observation and research.
Why is NASA looking for water on moons?
Moons aren’t the main focus, but they’re part of a broader effort to understand how key elements — like helium, carbon, and oxygen — behave across the universe. All of them play critical roles on Earth and are found in abundance beyond it.
NASA’s Juno mission, launched to study Jupiter, is investigating the planet’s water content by looking for molecular traces of hydrogen and oxygen. Jupiter’s atmosphere is mostly hydrogen and helium, but previous studies have also detected methane and ammonia. In 1995, data from the Galileo probe surprised researchers by revealing that Jupiter was warmer than expected and had less water than predicted. Since then, attention has shifted to its 95 moons, particularly Io, known for its extreme volcanic activity.
During two recent flybys, Juno captured high-resolution images of Loki Patera, the largest lava lake ever observed. It spans around 200 kilometers, with a surface that appears smooth and reflective, signs of rapid cooling, and the possible presence of volcanic glass.
NASA’s Juno Mission reveals volcanic depressions
Infrared data from Juno’s JIRAM instrument revealed several volcanic depressions on Io, with cooler crusts at the center and hotter edges. This pattern suggests constant resurfacing as molten lava breaks through the crust. According to a NASA scientist from the Juno mission, Alessandro Mura, roughly 3% of Io’s surface may be covered by active lava lakes. Some regions appear to show textures consistent with obsidian, a volcanic glass formed from quickly cooled lava.
Most of these lakes appear hottest along their edges, a sign that a solid crust may cover their centers while molten lava remains exposed at the margins. Researchers suggest this pattern is shaped by the lakes’ steep-walled basins. As lava rises or falls, the crust scrapes against the caldera walls, breaking apart and revealing fresh material.
The moons of Jupiter are different
Jupiter’s moons fall into two categories: the four Galilean moons — Io, Ganymede, Europa, and Callisto — and a group of smaller, irregular ones. Ganymede, the largest, may have a liquid metallic core. Io, although smaller and structurally weaker, is the most geologically active. The gravitational forces from Jupiter, Europa, and Ganymede generate constant tidal stress, heating Io’s interior and powering its ongoing eruptions.
No central hotspots were detected, which may indicate that magma isn’t surfacing directly beneath each lake. Instead, scientists are exploring the idea that multiple lakes could be connected to a shared reservoir — a possibility that could help explain how Io’s volcanic system is supplied and maintained.
The impact of NASA’s discovery
NASA’s discovery of the Loki Patera and other active lava lakes on Io reinforces the idea that intense volcanic activity isn’t unique to Earth. It offers a real-time case study of how tidal heating — driven by gravitational forces from Jupiter and nearby moons — can fuel large-scale geological processes. On Earth, volcanic eruptions are typically triggered by plate tectonics. On Io, the mechanism is different: constant gravitational flexing heats the interior and drives magma to the surface. Due to the size of the planet, Jupiter has a strong gravitational field, and its moons do too. They are thousands of times bigger than our natural satellite, and can have more impact than we previously thought.