The icy moons circling Saturn and Jupiter are the top places scientists are looking for life beyond Earth. Now, a study shows that the ice that shoots out from these moons may actually contain signs of life that could be detected by instruments sent to explore them.

For the first time, researchers found that even a tiny bit of material from living things could be spotted by the instruments on spacecraft, this gives scientists more hope that they’ll be able to find life similar to what we have on Earth when they send probes to study the icy moons.

The Cassini spacecraft discovered cracks near the south pole of Saturn’s moon Enceladus, where jets of gas and ice grains shoot out. NASA’s upcoming Europa Clipper mission will take a closer look at Jupiter’s icy moon Europa, and to get ready for these missions, researchers are figuring out what the new instruments might be able to find.

This image shows red streaks on the surface of Europa, the smallest of Jupiter's four large moons. The upcoming Europa Clipper mission will send instruments to investigate this moon. New research shows that one of these instruments destined for the upcoming mission could find traces of a single cell in a single grain of ice ejected from the interior of the planetary body
This image shows red streaks on the surface of Europa, the smallest of Jupiter’s four large moons. The upcoming Europa Clipper mission will send instruments to investigate this moon. New research shows that one of these instruments destined for the upcoming mission could find traces of a single cell in a single grain of ice ejected from the interior of the planetary body. Credit: NASA / JPL/Galileo

It’s too difficult to recreate the conditions where ice grains would slam into the instruments at high speed in space, so instead, the scientists sprayed water into a vacuum to see how the droplets would behave and what the instruments could detect. The results show that the instruments planned for future missions can find signs of tiny organisms in individual ice grains.

The researchers focused on a common bacteria found in Alaska that is well-suited for living in cold, nutrient-poor environments like icy moons. These bacteria are extremely small, so they could potentially get trapped in the ice that shoots out from ocean worlds like Enceladus and Europa.

The study found that looking at individual ice grains, where the biological material can concentrate, works better than just looking at a big sample with billions of grains. Previous research by the same team also found evidence of phosphate on Enceladus.

The drawing on the left shows Enceladus and its ice-covered ocean, with cracks near the south pole thought to penetrate through the icy crust. The middle panel shows where the authors believe life could thrive: on top of the water, in a proposed thin layer (shown in yellow) as in Earth's oceans. The right panel shows that, as gas bubbles rise and burst, bacterial cells could be launched into space with droplets that would then become the ice grains detected by Cassini
The drawing on the left shows Enceladus and its ice-covered ocean, with cracks near the south pole thought to penetrate through the icy crust. The middle panel shows where the authors believe life could thrive: on top of the water, in a proposed thin layer (shown in yellow) as in Earth’s oceans. The right panel shows that, as gas bubbles rise and burst, bacterial cells could be launched into space with droplets that would then become the ice grains detected by Cassini. Credit: European Space Agency

This means the moon has the key ingredients for life – energy, water, phosphate, other chemicals, and organic carbon-based material, and this makes it more likely that some form of life could exist there.

The scientists think that if there are bacterial cells on these moons, they may form a layer on the surface of the subsurface oceans, then, when the ice cracks open, the vacuum of space would cause the ocean water to boil and release bubbles that could carry the cells into the ice plumes.

The instruments on the Europa Clipper will be even better than past ones at detecting signs of life, like fatty acids and lipids, which may be more stable than DNA. With the right tools, it could be easier than expected to find life, or evidence of it, on these icy moons.

The left panel shows the kilometers-thick icy crust believed to encapsulate Saturn's moon Enceladus. The crack is filled with salt water with a thin layer (in orange) on its surface. The right panel shows that as gas bubbles rise and burst, they combine with organic material and are ejected into the dew
The left panel shows the kilometers-thick icy crust believed to encapsulate Saturn’s moon Enceladus. The crack is filled with salt water with a thin layer (in orange) on its surface. The right panel shows that as gas bubbles rise and burst, they combine with organic material and are ejected into the dew. Credit: Postberg et al. (2018) / Nature

Sources

University of Washington | Fabian Klenner, Janine Bönigk, et al., How to identify cell material in a single ice grain emitted from Enceladus or Europa. Science Advances, vol.10 no.12, DOI:10.1126/sciadv.adl0849

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