In 1997, Galileo mapped a 400-kilometer patch of Europa; a later analysis found ammonia-bearing compounds near fractures in the ice

Europa appears plain when viewed from afar. It is a small and icy moon in orbit around Jupiter, appearing like a pale ball cracked with fissures, smaller even than our own moon. Below the icy crust lies a hidden ocean of liquid water, kept liquid by Jupiter’s tidal forces. This makes Europa an important target in the search for signs of habitability.

This image is based on imagery captured by NASA’s Galileo spacecraft in 1997 during its 11th orbit around Jupiter. The dataset covers an area about 250 miles (400 kilometres) wide on Europa. Galileo’s Solid-State Imaging camera supplied the black-and-white surface imagery, while its Near-Infrared Mapping Spectrometer provided spectral data that could be used to identify ammonia-bearing compounds. A later analysis of the Galileo data, reported by NASA in 2026, combined the imagery and spectral data to show where the compounds were detected in relation to Europa’s fractures. The Galileo spacecraft was launched on October 18, 1989, aboard Space Shuttle Atlantis and was managed by NASA’s Jet Propulsion Laboratory. It entered orbit around Jupiter in December 1995, and its extended mission continued until September 21, 2003, when Galileo was deliberately plunged into Jupiter’s atmosphere.

Clues within the cracks of the ice


A glance at Europa shows a surface marked by dark, crosshatched bands. Scientists have studied these fractures to understand whether they are confined to the surface or could provide pathways for material from beneath the ice to reach the surface. A new analysis of an older dataset offered further clues about where the ammonia-bearing compounds may have originated. The compounds clustered near the cracks rather than being spread evenly across the surface.

The importance of ammonia traces on Europa

Ammonia is not expected to persist for long on an icy moon exposed to space for millions of years. Being near Jupiter, Europa faces intense radiation that can break down the compound relatively quickly. The traces may be relatively recent and could reflect local activity. According to NASA Science, researchers led by JPL’s Al Emran suggest that the ammonia-bearing compounds may have reached Europa’s surface through geologically recent cryovolcanic processes. Cryovolcanism is similar to volcanic activity, but it involves water pushing through cracks in the ice and reaching the surface. In this case, cracks might be active vents connecting the ocean and the surface of the moon.

Nitrogen is one element found in ammonia and is important in the chemistry of life as we know it. This doesn't mean that there is life on Europa in any way, but rather that the presence of nitrogen near a potential route connecting Europa's ocean with its surface simply adds another piece to a long-running puzzle that planetary scientists have been putting together for some time now. The finding suggests the ocean beneath Europa's surface may be chemically more complex than previously thought.

Implications for the future

In practice, findings like these help guide future study, and Europa has drawn renewed attention from missions focused on its ice, cracks, and subsurface ocean. NASA’s Europa Clipper mission launched on October 14, 2024, and is currently travelling to Jupiter, where it is expected to arrive in April 2030. Once there, the spacecraft will make nearly 50 close flybys of Europa, using nine science instruments to study its ice shell, suspected ocean, surface composition, and geology. Rather than scanning all of Europa at once, researchers can now prioritize specific fracture zones. That kind of detection can help future studies focus on the most promising regions from the start.

The discovery is notable because it came from reexamining existing data. The new finding did not require another spacecraft to make the journey to Jupiter. Instead, researchers reexamined NASA archive data collected nearly 30 years ago using newer analysis methods. The ammonia trace was identified in Galileo’s infrared spectrometer data rather than in the spacecraft’s visible-light images. Nearly three decades after Galileo collected the data, the ammonia finding was reported by NASA in January 2026, adding another intriguing clue to what lies beneath Europa’s icy surface.