In a discovery that significantly boosts the search for alien life, scientists have identified a colossal, star-shaped feature on Jupiter's icy moon Europa. Nicknamed the 'wall demon', this formation is a preserved record of briny water that once flowed to the surface, offering a tantalising clue that life-sustaining material from the moon's hidden ocean could be accessible.
The 'Damhán Alla' and Its Earthly Twin
The unique feature, found inside the 13-mile-wide Manannán crater, was spotted in images from NASA's Galileo spacecraft. The US-based research team, led by physicist Lauren Mc Keown from the University of Central Florida, believes the 1.8-mile-wide pattern is not merely surface cracks. Instead, it represents frozen brine—salty liquid water—that welled up and solidified.
This dark, branching formation, given the Gaelic nickname 'Damhán Alla' (spider or wall demon), bears a striking resemblance to transient 'lake stars' on Earth. These patterns appear on frozen ponds when water pushes through ice, melting and refreezing the snow above in a radial design. "Lake stars are really beautiful, and they are pretty common on snow or slush-covered frozen lakes and ponds," said Mc Keown. "It is wonderful to think that they may give us a glimpse into processes occurring on Europa."
A Window into Europa's Hidden Ocean
The researchers' analysis suggests the wall demon formed when a meteor impact created the Manannán crater. The heat from the impact melted part of Europa's icy shell, creating a subsurface pocket of brine up to 12 miles wide, sitting roughly 3.7 miles down. This brine then rose and spread, freezing into the distinctive pattern seen today.
This process is crucial because it indicates that material from Europa's vast subsurface ocean—believed to contain twice as much liquid water as all of Earth's oceans combined—can reach the surface. If that ocean harbours life, its chemical signatures or even microbial life could be frozen near the surface, making it far easier for future probes to detect than if it were trapped deep below.
Europa is considered a prime candidate for life alongside Saturn's moon Enceladus. It is thought to possess all key ingredients: a liquid water ocean, chemical building blocks like carbon and salts found in its ice, and a potential energy source from hydrothermal vents on its seafloor. The heat needed to keep the ocean liquid is generated by the immense tidal forces from Jupiter's gravity.
Proving the Theory from Lab to Colorado Lakes
To confirm their hypothesis, the scientific team undertook a multi-year project. They examined old Galileo photos, mapped the crater, and compared the pattern to similar 'spiders' on Mars. Crucially, they also recreated Europa-like conditions in a cold chamber at NASA's Jet Propulsion Laboratory, cooled by liquid nitrogen.
Furthermore, they studied real lake stars at frozen ponds in Breckenridge, Colorado. The lab simulations and earthly comparisons proved that the giant 'wall demon' was indeed a legitimate extraterrestrial lake star. "Surface features like these can tell us a lot about what's happening beneath the ice," explained Mc Keown. "If we see more of them with Europa Clipper, they could point to local brine pools below the surface."
This discovery sets the stage for NASA's upcoming Europa Clipper mission, which will conduct detailed reconnaissance. By identifying more such features, scientists hope to pinpoint the best locations to search for the ultimate prize: evidence that we are not alone in the solar system.
