Ice geysers could spew alien microbes into space from the ocean of Enceladus

Ice geysers could spew alien microbes into space from the ocean of Enceladus

Ice geysers could spew alien microbes into space from the ocean of Enceladus

While on a In a world like Mars, we may have to dig underground for life, or walk miles under the ice on Europa, Jupiter’s moon, one of the best targets for finding extraterrestrial life could send life to a passing space probe. This is according to an article published last month in the Journal of Planetary Sciencewho discovers that ice geysers on Saturn’s moon Enceladus could propel its potential life forms straight into space.

From its discovery in 1789 until the Voyager probes were rocked by Saturn in the early 1980s, Enceladus was just another moon of an outer planet, twinkling from inside Saturn’s wide E ring. . Voyager 2 saw Enceladus covered in fresh, new ice – at least geologically – as it passed, and astronomers began to suspect that the faint E ring might have something to do with the tiny icy moon in its center.

Enceladus got much more interesting in 2005, when the Cassini mission finally arrived after an eight-year journey from Earth. Cassini discovered that the south pole of Enceladus was covered in strange stripes, long ridges much younger and hotter than the rest of the moon’s surface.

These “tiger stripes” appear to have been the result of cryovolcanoes. As Saturn tugs at Enceladus, powerful tides pull the aquatic interior upward until huge plumes of water explode through the ice. And water isn’t the only thing Cassini found in these plumes: she also detected methane, which on Earth may be a sign of life or a sign of hydrothermal vents where life could thrive.

The team’s work focuses on modeling a hypothetical biosphere for Enceladus, given what Cassini was able to observe of the moon as it passed. Hypothesizing that life on Enceladus might be akin to relatively familiar – albeit still quite extreme – methanogenic microorganisms that cluster around hydrothermal vents on Earth, they believe the tiny moon might be able to support an ecosystem built around less than 10 tons of carbon, a total environment about as massive as a single whale.

Enceladus tiger stripes.Nasa

While that’s not a lot of life, it’s still more than enough for it to be detectable without having to go down and look for it. Talk with Reverselead author Antonin Affholder notes that applying ecosystem theory to a potentially habitable environment like Enceladus could allow future missions to move from finding “very indirect biosignatures to slightly less indirect biosignatures.”

While there are ways to mistake a lifeless system for one teeming with alien microbes or ways a system actually full of life is mistaken for something lifeless, examining the composition and concentration of other molecules in the cryovolcanic explosions of Enceladus provide a way to focus astrobiology research.

“To seek life, we must build the tools to refute his existence. We can only rely on circumstantial evidence and the best we can do to advance the search for life is not to disprove its existence,” said Paul Byrne, planetary geologist at Washington University in St. Louis. . Reverse“it is extremely difficult to be sure that what we see is the result of biology and not of an abiogenic process.”

It gets even trickier on Enceladus. The moon has been the target of numerous proposals since its highlights in 2005, and a future mission has been named one of the top targets in the latest US Decade Survey. But landing on Enceladus would risk contaminating an alien environment with life from Earth.

These concerns explain why, in 2017, Cassini himself was sent to dive into Saturn rather than stay in orbit: it’s possible that a particularly tough microbe remained on the nuclear-heated spacecraft during its twenty-four-year mission. years, and scientists didn’t want to risk potential contamination. And beyond that, says Byrne, “even if you land on Enceladus and enter the ocean, somehow melt in 10 years, unless something comes out of the darkness and attacks you – which would be pretty compelling evidence of life there – just because you haven’t found the microbe doesn’t mean there isn’t life there.

Although an Enceladan biosphere would likely be tiny, the team’s model indicates that it would be large enough to be easily detected from orbit. The waste – part of the system’s total biomass – as well as living and dead cells would be ejected into the moon’s icy plumes, high enough for an orbiting mission to collect without having to land.

The team estimates that one would need to take a tenth of a milliliter – about a tenth of a raindrop – of material from the plume to have a good chance of determining whether there is life or not. It may not seem like much, but it still represents hundreds of flights through Enceladus eruptions.

“If you had the ability to see with a microscope something swimming in a drop of water, that would be pretty compelling evidence of life – that’s probably not going to be,” Byrne says. If you’re flying through the plumes of Enceladus, you “have to time the speed of that flyby just right – if you go too slow, you won’t catch much; if you go too fast, you might end up encountering a microbe, but detonating it at the speed you hit it.

“There are a bunch of concepts for the return to Enceladus, but it’s still an open field,” adds Affholder, “It’s very difficult to say what the next mission on Enceladus will be.” Most important for now, he says, is to emphasize that we cannot rule out life there: “To seek life, we must build the tools to refute his existence. We can only rely on circumstantial evidence and the best we can do to continue the search for life is not to disprove its existence.

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