Europa has a vast, salty ocean covered by a thick shell of ice
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Europa’s liquid ocean is believed to be shielded beneath a frozen crust that is possibly six times thicker than the deepest ice in Antarctica, posing challenges in detecting any potential life forms residing there.
Recognized for its abundant liquid water, Jupiter’s moon Europa is a primary target in the quest for alien life.
Prior assessments of the ice covering Europa’s ocean ranged from under 10 kilometers to nearly 50 kilometers, with the assumption that fractures, crevices, and pores in the icy layer could facilitate the transport of nutrients between the surface and the ocean.
A recent study led by Steven Levin at the California Institute of Technology analyzed data gathered by the Juno spacecraft, which has been orbiting Jupiter since 2016.
During a close flyby on 29 September 2022, Juno passed within 360 kilometers of Europa, scanning the surface using its microwave radiometer to provide direct measurements of the ice. This instrument assessed the heat emitted by Europa’s frozen shell, enabling the team to determine the ice’s temperature at various depths and identify variations caused by imperfections in the ice sheet.
The research team estimated the most likely thickness of the ice sheet to be around 29 kilometers, potentially thicker than previous estimates, ranging from 19 to 39 kilometers in thickness.
Importantly, the study revealed that imperfections such as cracks and pores likely extend only hundreds of meters into the ice, with pores having a radius of a few centimeters.
“The imperfections we observed with the microwave radiometer are too shallow and small to facilitate significant nutrient exchange between the ocean and the surface,” Levin explained.
However, the absence of direct transport channels between Europa’s surface and its ocean does not necessarily diminish the possibility of life existing there. Levin suggested that alternative mechanisms for nutrient transport could be at play, and unexplored regions of the moon might exhibit different characteristics.
Ben Montet from the University of New South Wales in Sydney remarked that the thick ice layer could pose challenges in the search for life. “While the ice shield could protect life for extended periods, it also presents obstacles in accessing and studying the ocean,” Montet noted.
Helen Maynard-Casely from Australia’s Nuclear Science and Technology Organisation added that although direct communication between Europa’s surface and sub-ice ocean is not mandatory for life to thrive, a transport mechanism could enhance the likelihood. Without such conduits, the ecosystem within the ocean may have remained static since its inception.
NASA’s Europa Clipper mission, launched in 2024 and scheduled to arrive at Jupiter’s moon in 2030, is expected to provide more definitive insights into the nature of Europa’s ice composition, according to Maynard-Casely.
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