![\"Manann\u00e1n\u2019s](\"https:\/\/cdn.sci.news\/images\/enlarge13\/image_14411e-Damhan-Alla.jpg\")
<\/a><\/p>\nManann\u00e1n\u2019s Damh\u00e1n Alla geomorphologic map. Image credit: Mc Keown et al., doi: 10.3847\/PSJ\/ae18a0.<\/p>\n
\u201cThis spider-like feature might have formed through the eruption of melted brines following the Manann\u00e1n impact,\u201d said Dr. Elodie Lesage, a researcher at the Planetary Science Insititute.<\/p>\n
\u201cThis would mean that it can inform us on subsurface properties and brine composition at the time of the impact.\u201d<\/p>\n
Dr. Lesage and colleagues also study Martian \u2018spiders,\u2019 which are branching, tree-like features that form in the regolith near Mars\u2019 south pole.<\/p>\n
They applied that knowledge to other planetary surfaces, including Jupiter\u2019s icy moon Europa.<\/p>\n
While Martian spiders form when dust and sand are eroded by escaping gas below a seasonal dry ice layer, the team\u2019s Europa work asserts that the \u2018asterisk-shaped\u2019 feature may have formed after impact.<\/p>\n
\u201cLake stars on Earth are radial, branching patterns that form when snow falls on frozen lakes and the weight of the snow creates holes in the ice, allowing water to flow through the snow, melting it and spreading in a way that is energetically favorable,\u201d said Dr. Lauren Mc Keown, a researcher at the University of Central Florida and NASA\u2019s Jet Propulsion Laboratory.<\/p>\n
\u201cOn Europa, we believe a subsurface brine reservoir could have erupted after an impact and spread through porous surface ice, producing a similar pattern.\u201d<\/p>\n
The researchers informally named Europa\u2019s feature Damh\u00e1n Alla, Irish for \u2018spider,\u2019 to distinguish it from Martian spider formations.<\/p>\n
To test their formation hypothesis, they also conducted field and lab experiments, observing lake stars in Breckenridge, Colorado, and recreating the process in a cryogenic glovebox, using Europa ice simulants cooled with liquid nitrogen.<\/p>\n
\u201cWe flowed water through these simulants under different temperatures and found that similar star-like patterns formed even under extremely cold temperatures (minus 100 degrees Celsius, or minus 148 degrees Fahrenheit), supporting the idea that the same mechanism could occur on Europa after impact,\u201d Dr. Mc Keown said.<\/p>\n
The scientists modeled how a brine pool might behave beneath Europa\u2019s surface after this impact, and the team created an animation illustrating the process.<\/p>\n
Observations of Europa\u2019s icy feature have been limited to images from the Galileo spacecraft from 1998, but the authors hope to resolve this question with higher-resolution imagery from the Europa Clipper mission, a NASA spacecraft scheduled to arrive at the Jupiter system in April 2030.<\/p>\n
\u201cWhile lake stars have provided valuable insight, Earth\u2019s conditions are very different from Europa\u2019s,\u201d Dr. Mc Keown said.<\/p>\n
\u201cEarth has a nitrogen-rich atmosphere, while Europa\u2019s environment is extremely low in pressure and temperature.\u201d<\/p>\n
\u201cIn this study, we combined field observations with lab experiments to better simulate Europa\u2019s surface conditions.\u201d<\/p>\n
Looking ahead, the team plans to investigate how low pressure affects the formation of these features and whether they could form beneath an icy crust, similar to how lava flows on Earth to create smooth, ropy textures called pahoehoe.<\/p>\n
Although geomorphology was the main focus of this study, the findings offer important clues about subsurface activity and habitability, which are crucial for future astrobiology research.<\/p>\n
\u201cUsing numerical modelling of the brine reservoir, we obtained constraints on the reservoir potential depth (up to 6 km, or 3.7 miles, below the surface) and lifetime (up to a few thousands of years post-impact),\u201d Dr. Lesage said.<\/p>\n
\u201cThis is valuable information for future missions looking for habitable environments within icy shells.\u201d<\/p>\n