A newly published analysis of a striking surface formation on Jupiter’s moon Europa sheds light on the potential for subsurface activity and the search for extraterrestrial life. Dubbed “Damhán Alla“-Irish for “spider” or “wall demon”-the unusual, spider-web-like structure first observed by NASA’s Galileo spacecraft in the late 1990s is now believed too have formed by a unique interplay of impact fracturing and saltwater upwelling, according to research published in The Planetary Science Journal.The findings, led by scientists with Irish ties, offer a compelling glimpse into the dynamic processes occurring beneath Europa’s icy shell and are informing preparations for the upcoming Europa Clipper mission.
A striking formation resembling a spider’s web has captured the attention of planetary researchers studying the icy moon Europa, orbiting Jupiter. The unusual structure, nicknamed “Damhán Alla” – Irish for “spider” or, more evocatively, “wall demon” – was first spotted in images taken by NASA’s Galileo spacecraft in the late 1990s, but a new analysis suggests how it formed and hints at potential subsurface activity on the moon.
Located within the Manannán crater, Damhán Alla appears as a network of branching cracks extending across Europa’s frozen surface. For years, it remained an unexplained anomaly in one of the solar system’s most intriguing environments, a world believed to harbor a vast ocean beneath its icy shell. The discovery is particularly relevant as scientists search for environments beyond Earth capable of supporting life.
The renewed interest stems from a study published in The Planetary Science Journal, led by physicist Lauren McKeown of the University of Central Florida and researchers from NASA’s Jet Propulsion Laboratory, Brown University, and the Planetary Science Institute. The team proposes that the formation resulted from an impact that fractured the ice, allowing saltwater from below to briefly surface and refreeze, creating the distinctive pattern.
To understand the origin of Damhán Alla, researchers looked to Earth for analogous formations. They found a match in “lake stars” – radial patterns that appear when snow covers a frozen lake and liquid water breaks through, melting the snow and forming branch-like structures. While these terrestrial formations typically measure just a few meters across, Damhán Alla spans approximately a kilometer on Europa.
The team conducted field tests at Ollie’s Pond and Maggie Pond in Colorado, identifying similar formations, and complemented these observations with laboratory experiments simulating the process using ice simulators and temperature-controlled chambers. They also developed computer models and analyzed images from the Galileo probe to understand the geometry and formation mechanism of the structure on Jupiter’s moon.
A Name Rooted in Irish Heritage
The name Damhán Alla is no coincidence. The study was led by Professor McKeown, originally from Churchtown, Dublin, Ireland, and included other Irish scientists, including Dr. Jennifer Scully, also a Trinity College Dublin graduate. “As Jen and I are Irish, and given that many geographical features on Europa already bear Irish and Celtic names – including the Manannán crater, referencing the ‘son of the sea’ from Irish mythology – we decided to name it with the Irish word for spider,” explains McKeown in a Trinity College statement.
The name also serves a practical purpose: distinguishing this structure from “spiders” on Mars, visually similar formations but created by entirely different processes. As previously reported by DW, these Martian spiders are formed by flows of gas associated with the sublimation of carbon dioxide (CO₂), a mechanism unrelated to the saltwater theorized to have shaped Damhán Alla.
Europa’s Subsurface Ocean and the Potential for Life
Europa has long been considered one of the most promising candidates for extraterrestrial life in the solar system. Scientists believe a global ocean of saltwater exists beneath its icy crust, and formations like Damhán Alla could indicate that this ocean isn’t entirely isolated, but occasionally interacts with the surface. This finding underscores the importance of continued exploration of ocean worlds.
Europa also exhibits some of the most unique surface features in the solar system. Unlike other rocky bodies covered in impact craters, Europa is remarkably smooth, displaying features like “chaos terrain” – broken and disordered ice that has shifted and reassembled over time – and now, these spider-like formations, as reported by Universe Today.
Europa Clipper Mission: Mapping the Icy Moon
Currently, the study of Europa relies heavily on images taken by the Galileo probe over two decades ago. However, that is expected to change with the NASA Europa Clipper mission, scheduled to enter orbit around Jupiter in 2030. The spacecraft will search for evidence of liquid water beneath the ice and map Europa’s surface with unprecedented resolution.
According to Universe Today, Europa Clipper is expected to cover up to 95% of the moon’s surface, compared to the 10–14% available so far. Identifying more formations like Damhán Alla would strengthen the hypothesis of subsurface activity and potentially favorable conditions for life.
McKeown continues this research in a new laboratory called FROSTIE, where she will conduct low-pressure experiments designed to simulate environments like those on Europa. The goal is to determine if these structures can form naturally under a frozen crust, similar to how lava moves beneath the Earth’s surface.
While questions remain – such as whether Damhán Alla is a rare occurrence or one of many similar structures hidden beneath the ice – the study opens new avenues for understanding Europa’s internal dynamics and reinforces the idea that a potentially active world may lie beneath its icy exterior.
Edited by Felipe Espinosa Wang with information from Trinity College Dublin, Space.com and Universe Today.
