How Europa’s Thick Ice May Obstruct the Hunt for Ocean Life

Europa, one of Jupiter’s intriguing moons, features a liquid ocean possibly encased beneath a thick layer of ice, estimated to be six times the depth of Antarctica’s icy crust, complicating our efforts to detect any potential lifeforms.

This moon is a leading candidate in the search for extraterrestrial life, primarily due to its significant volume of liquid water.

Previously, estimates regarding the thickness of Europa’s ice have varied dramatically—ranging from under 10 kilometers to nearly 50 kilometers. Researchers initially believed certain defects in the ice might permit nutrient exchange between the surface and the ocean below.

Now, a research team, led by Stephen Levin from the California Institute of Technology, has analyzed data collected by the Juno spacecraft, which has been orbiting Jupiter since 2016.

On September 29, 2022, Juno came within 360 kilometers of Europa, utilizing its microwave radiometer to scan the surface and perform the first direct measurements of the ice layer. Levin noted that this instrument assessed the heat emitted by Europa’s icy exterior, enabling the measurement of ice temperatures at various depths and detecting temperature fluctuations resulting from imperfections in the ice sheet.

The researchers estimate that the most accurate thickness of the ice sheet is approximately 29 kilometers, aligning with the higher range of previous estimates while presenting a possible thickness that could range from 19 kilometers to 39 kilometers.

Crucially, their findings indicate that the fissures, pores, and other imperfections likely extend only a few hundred meters beneath the surface, with pore diameters measuring only a few centimeters.

“This indicates that the observed defects in the microwave radiometers are insufficiently deep or expansive to facilitate significant nutrient transport between the ocean and the surface,” asserts Levin.

Nonetheless, this does not diminish the potential for life on Europa. Levin further explains, “Though the observed pores and cracks are too minute and shallow to transport nutrients, alternative transportation mechanisms may exist.”

There may also be unexplored regions of the moon where conditions differ, he adds.

Researchers including Ben Montet from the University of New South Wales in Sydney, express concerns that the ice thickness could hinder life’s search. “While this protection may sustain life for extended durations, it complicates our ability to penetrate the ice and study the ocean beneath,” he notes.

He argues that life could exist without a direct link between Europa’s surface and its subterranean ocean, though such a connection would enhance the chances of discovering life. Helen Maynard-Casley of the Australian Nuclear Science and Technology Agency emphasizes that without that transport link, “you’re essentially confined to whatever was in the ocean initially.”

NASA has plans to launch the Europa Clipper spacecraft in 2024, aiming to embark on its mission to Jupiter’s moons in 2030. This spacecraft is expected to provide clearer insights into Europa’s icy layer, according to Maynard-Casley.

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