Europa, Jupiter’s frigid moon, is an oceanic environment that stands out as a key player in the quest for extraterrestrial life. Its surface is characterized by various landforms believed to originate from salty water sources beneath its icy crust, potentially making it the most accessible body of liquid water in the solar system. Notably, the asterisk-shaped “spider” located in the center of Manannan Crater was identified during NASA’s Galileo mission. Planetary scientists have recently introduced a novel hypothesis regarding the formation of this spider-like structure, drawing on morphological analysis and initial analog modeling. They propose that it may have formed through a process akin to the creation of dendritic “lake stars,” a seasonal phenomenon observed in frozen terrestrial ponds and lakes.

“The spider-like feature may have resulted from an eruption of molten salt water following the Manannan impact,” explains Dr. Elodie Lesage from the Planetary Science Institute.

“This presents an opportunity to understand the subsurface characteristics and the salt water composition at the impact’s time.”

Dr. Lesage and colleagues are also researching similar “spiders” on Mars, which are tree-like formations in the regolith near the planet’s south pole.

Their findings on Mars have been applied to other celestial bodies, including Europa.

Martian spiders develop as a result of gases escaping beneath a seasonal dry ice layer; however, the Europa study speculates that the “asterisk-shaped” features could have emerged post-impact.

“Lake stars are radial branching designs that occur when snow accumulates on a frozen lake, creating holes in the ice due to the snow’s weight, allowing water to flow through and spread out energetically,” stated Dr. Lauren McCune from the University of Central Florida and NASA’s Jet Propulsion Laboratory.

“We believe a similar process could have happened on Europa, with subsurface brine erupting after the impact and dispersing through the porous surface ice.”

The research team has informally designated the Europa feature as Damhan Alla, which translates to “spider” in Irish, differentiating it from Martian spider formations.

To validate their hypothesis, they studied lake stars in Breckenridge, Colorado, and conducted field as well as lab experiments using a cryogenic glovebox equipped with a Europa ice simulator cooled by liquid nitrogen.

“In our experiments where we passed water through these simulants at various temperatures, we observed similar star-like formations even at extremely low temperatures (-100 degrees Celsius or -148 degrees Fahrenheit), lending support to the idea that such mechanisms could occur on Europa after the impact,” Dr. McCune remarked.

Scientists also created models showing how the saltwater beneath Europa’s surface would react following an impact, including an animation illustrating the process.

While observations of Europa’s icy features are primarily reliant on images captured by the Galileo spacecraft in 1998, the researchers aim to explore this further with high-resolution images from NASA’s Europa Clipper mission, anticipated to arrive at the Jupiter system in April 2030.

“Although lake stars offer significant insights, terrestrial conditions differ vastly from those on Europa,” Dr. McCune notes.

“Earth possesses a nitrogen-rich atmosphere, while Europa’s environment features extremely low pressures and temperatures.”

“This investigation combined field data and laboratory trials to better simulate Europa’s surface conditions.”

The team will further examine how low-pressure systems affect the formation of these landforms and explore whether such structures can form beneath Europa’s icy crust, akin to how flowing lava generates smooth, rope-like textures known as pahoehoe on Earth.

While the primary focus was geomorphology, this discovery sheds light on subsurface activity and habitability, crucial for future astrobiological studies.

“By employing numerical modeling of saline reservoirs, we assessed the potential depth of the reservoir (up to 6 km, or 3.7 miles below the surface) and its longevity (potentially several thousand years post-impact),” Dr. Lesage stated.

“This data is invaluable for upcoming missions investigating viable ecosystems beneath ice shells.”

The team’s results were published in Planetary Science Journal.

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Lauren E. McCune et al. 2025. A lake star as an Earth analogue of Europa’s Manannan Crater Spider feature. Planet. Science. J 6,279; doi: 10.3847/PSJ/ae18a0