Europa’s thick ice may hinder the search for life in its oceans

Europa's liquid ocean may be isolated from the surface by a frozen layer six times thicker than the deepest Antarctic ice, making it difficult to detect any life there.

Thanks to its abundance of liquid water, Jupiter's moon Europa is considered a high-priority target in space. search for extraterrestrial life.

Previous estimates of the thickness of the ice covering the ocean range from less than 10 kilometers to nearly 50. But it has also been thought that cracks, fissures, pores and other defects in the frozen cover could help transport nutrients between the surface and the ocean.

Now the team is under the leadership Stephen Levine at the California Institute of Technology studied data collected by the Juno spacecraft, which has been in orbit around Jupiter since 2016.

September 29, 2022 the probe flew within 360 kilometers of Europe and scanned the surface with a microwave radiometer, providing the first direct measurements of ice. According to Levin, this instrument measured the heat emitted by Europa's frozen shell, effectively measuring the temperature of the ice at various depths. He was also able to detect temperature changes caused by imperfections in the ice sheet.

The team estimated that the most likely thickness of the ice sheet was about 29 kilometers – thicker than most previous estimates – but it could be thinner than 19 kilometers or 39 kilometers.

Importantly, cracks, pores and other defects likely extend only hundreds of meters deep into the ice, and the pore radius is only a few centimeters, they found.

“This means that the defects we see with the microwave radiometer are not deep enough or large enough to transport much of anything between the ocean and the surface,” Levine says.

But this does not necessarily mean that the chances of life on Europa are diminishing. “The pores and cracks we see are too small and shallow to transport nutrients to and from the ocean, but there may be other transport mechanisms,” he says.

There may also be unexplored regions of the Moon where the situation is different, he adds.

Ben Montet from the University of New South Wales in Sydney, Australia, say the thickness of the ice could make the search for life more difficult. “This protection may help life persist for long periods of time, but it makes it more difficult for us to reach and study the ocean,” he says.

While there doesn't need to be a “connection” between Europa's surface and the ocean beneath the ice for life to exist, transport links could increase the likelihood, he says. Helen Maynard-Caisley at the Australian Nuclear Science and Technology Organisation. Without such connections, “you would essentially say you were trapped by whatever was in the ocean in the beginning,” she says.

NASA launched Europa Clipper probe in 2024, and it should reach Jupiter's moon in 2030. This mission should more accurately answer the question of the nature of Europa's ice, says Maynard-Caisley.

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