A spider-like scar haunts Jupiter's moon Europa — and scientists think they know why

A strange, spider-like scar on Jupiter's icy moon Europa may mark where salty water once surged up through its fractured crust.

NASA's Galileo spacecraft (whose mission ended in 2003) spotted the unique feature — officially named Damhán Alla, an Irish word meaning "spider" or "wall demon" — within Europa's Manannán crater. The starburst-like pattern first appeared in images captured by the spacecraft in the late 1990s, but scientists are only now piecing together how it may have formed, according to a statement from Trinity College Dublin.

The spider-like features exhibit branching ridges and troughs that resemble "lake stars" on Earth — delicate, dendritic patterns carved into snow and ice by flowing meltwater. This resemblance, combined with field observations, lab experiments and computer modelling, suggests that the Damhán Alla features may have formed from briny water eruptions beneath the moon's ice, offering clues about subsurface liquid water and the potential for life on Europa.

"The significance of our research is really exciting," Lauren Mc Keown, lead author of the study, said in the statement. "Surface features like these can tell us a lot about what's happening beneath the ice. If we see more of them with Europa Clipper, they could point to local brine pools below the surface."

On Earth, lake stars emerge when snow falls on frozen lakes and holes form in the ice, allowing water to flow upwards and melt surrounding snow, carving radial, branching channels as it spreads. Such patterns are common in nature, from lightning scars to tidal channels, illustrating the movement of fluids and energy through different surfaces.

The researchers suggest that Europa's version might form the same way — except the liquid in this case would be salty brine forced upward after an impact disrupted the ice shell. Under Europa's frigid conditions, such brine could briefly flow, etching star-like tendrils before freezing in place. If correct, features like Damhán Alla could hint at localized pockets of liquid water trapped within Europa's crust.

While current research is limited to images from the Galileo spacecraft, higher-resolution imagery from NASA's Europa Clipper mission, scheduled to arrive at the Jupiter system in April 2030, could reveal new clues about the icy moon.

"Lake stars are really beautiful, and they are pretty common on snow or slush-covered frozen lakes and ponds," McKeown said in the statement. "It is wonderful to think that they may give us a glimpse into processes occurring on Europa and maybe even other icy ocean worlds in our solar system."

Their findings were published Dec. 2 in the Planetary Science Journal.