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Frozen world: scientists are seeking a way to detect life on Enceladus

April 25, 2024 · Comment icon 9 comments

Is there life on Enceladus ? Image Credit: NASA/JPL-Caltech/Space Science Institute
Saturn's icy moon is thought to be home to an ocean of liquid water, meaning that it might also be home to alien life.
Fabian Klenner: Saturn has 146 confirmed moons - more than any other planet in the solar system - but one called Enceladus stands out. It appears to have the ingredients for life.

From 2004 to 2017, Cassini - a joint mission between NASA, the European Space Agency and the Italian Space Agency - investigated Saturn, its rings and moons. Cassini delivered spectacular findings. Enceladus, only 313 miles (504 kilometers) in diameter, harbors a liquid water ocean beneath its icy crust that spans the entire moon.

Geysers at the moon's south pole shoot gas and ice grains formed from the ocean water into space.

Though the Cassini engineers didn't anticipate analyzing ice grains that Enceladus was actively emitting, they did pack a dust analyzer on the spacecraft. This instrument measured the emitted ice grains individually and told researchers about the composition of the subsurface ocean.

As a planetary scientist and astrobiologist who studies ice grains from Enceladus, I'm interested in whether there is life on this or other icy moons. I also want to understand how scientists like me could detect it.

Ingredients for life

Just like Earth's oceans, Enceladus' ocean contains salt, most of which is sodium chloride, commonly known as table salt. The ocean also contains various carbon-based compounds, and it has a process called tidal heating that generates energy within the moon. Liquid water, carbon-based chemistry and energy are all key ingredients for life.

In 2023, I and others scientists found phosphate, another life-supporting compound, in ice grains originating from Enceladus' ocean. Phosphate, a form of phosphorus, is vital for all life on Earth. It is part of DNA, cell membranes and bones. This was the first time that scientists detected this compound in an extraterrestrial water ocean.

Enceladus' rocky core likely interacts with the water ocean through hydrothermal vents. These hot, geyserlike structures protrude from the ocean floor. Scientists predict that a similar setting may have been the birthplace of life on Earth.

Detecting potential life

As of now, nobody has ever detected life beyond Earth. But scientists agree that Enceladus is a very promising place to look for life. So, how do we go about looking?

In a paper published in March 2024, my colleagues and I conducted a laboratory test that simulated whether dust analyzer instruments on spacecraft could detect and identify traces of life in the emitted ice grains.

To simulate the detection of ice grains as dust analyzers in space record them, we used a laboratory setup on Earth. Using this setup, we injected a tiny water beam that contained bacterial cells into a vacuum, where the beam disintegrated into droplets. Each droplet contained, in theory, one bacterial cell.

Then, we shot a laser at the individual droplets, which created charged ions from the water and the cell compounds. We measured the charged ions using a technique called mass spectrometry. These measurements helped us predict what dust analyzer instruments on a spacecraft should find if they encountered a bacterial cell contained in an ice grain.
We found these instruments would do a good job identifying cellular material. Instruments designed to analyze single ice grains should be able to identify bacterial cells, even if there is only 0.01% of the constituents of a single cell in an ice grain from an Enceladus-like geyser.

The analyzers could pick up a number of potential signatures from cellular material, including amino acids and fatty acids. Detected amino acids represent either fragments of the cell's proteins or metabolites, which are small molecules participating in chemical reactions within the cell. Fatty acids are fragments of lipids that make up the cell's membranes.

In our experiments, we used a bacteria named Sphingopyxis alaskensis. Cells of this culture are extremely tiny - the same size as cells that might be able to fit into ice grains emitted from Enceladus. In addition to their small size, these cells like cold environments, and they need only a few nutrients to survive and grow, similar to how life adapted to the conditions in Enceladus' ocean would probably be.

The specific dust analyzer on Cassini didn't have the analytical capabilities to identify cellular material in the ice grains. However, scientists are already designing instruments with much greater capabilities for potential future Enceladus missions. Our experimental results will inform the planning and design of these instruments.

Future missions

Enceladus is one of the main targets for future missions from NASA and the European Space Agency. In 2022, NASA announced that a mission to Enceladus had the second-highest priority as they picked their next big missions - a Uranus mission had the highest priority.

The European agency recently announced that Enceladus is the top target for its next big mission. This mission would likely include a highly capable dust analyzer for ice grain analysis.

Enceladus isn't the only moon with a liquid water ocean. Jupiter's moon Europa also has an ocean that spans the entire moon underneath its icy crust. Ice grains on Europa float up above the surface, and some scientists think Europa may even have geysers like Enceladus that shoot grains into space. Our research will also help study ice grains from Europa.

NASA's Europa Clipper mission will visit Europa in the coming years. Clipper is scheduled to launch in October 2024 and arrive at Jupiter in April 2030. One of the two mass spectrometers on the spacecraft, the SUrface Dust Analyzer, is designed for single ice grain analysis.

Our study demonstrates that this instrument will be able to find even tiny fractions of a bacterial cell, if present in only a few emitted ice grains.

With these space agencies' near-future plans and the results of our study, the prospects of upcoming space missions visiting Enceladus or Europa are incredibly exciting. We now know that with current and future instrumentation, scientists should be able to find out whether there is life on any of these moons.

Fabian Klenner, Postdoctoral Scholar in Earth and Space Sciences, University of Washington

This article is republished from The Conversation under a Creative Commons license.

Read the original article. The Conversation

Source: The Conversation | Comments (9)




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Recent comments on this story
Comment icon #1 Posted by Ell 24 days ago
Some engineers appear to want to send a probe to Enceladus. Boys and their toys. How to get politicians to finance their desired toy? Simply tell them that there might be life on Enceladus and the suckers will pay up.   I am all for sending a probe to Enceladus, but tell it as it is: "We want to play with our toy!" It is obvious that the 'searching for life' fib is a hoax intended to fool the sucker politicians.
Comment icon #2 Posted by Abramelin 24 days ago
If life forms will be found on a tiny moon like Enceladus, then the universe must be teeming with life.
Comment icon #3 Posted by Abramelin 24 days ago
You're nowhere near of being an explorer, eh?
Comment icon #4 Posted by Waspie_Dwarf 24 days ago
What is obvious is that you don't know what you are talking about. There are good reasons to believe that the icy moons of the giant planets may have liquid oceans beneath an icy surface. There are good reasons to believe that there could be volcanic activity beneath the surface of these moons (in Enceladus' case it's a near certainty). There are good reasons to suspect that at least some of these moons have the right organic chemicals for life (again a near certainty in the case of Enceladus). There are good reasons to believe that it was at such volcanic vents on the Earth's ocean floor wher... [More]
Comment icon #5 Posted by Waspie_Dwarf 24 days ago
The key word here is "if", we don't know if life exists anywhere else in the solar system other than Earth, but of course, if we don't look we'll never know. It doesn't necessarily follow that life on Enceladus means that the universe is teaming with life. There are methods of panspermia by which life could evolve once in the solar system and spread out to other planets and moons. In that case it could still be extremely rare in other solar systems. Of course. once again, if we don't look we'll never know.
Comment icon #6 Posted by Ell 24 days ago
Well, I know that such believers are most likely wrong.   On the other hand it would be fun to have a robot make some ice sculptures on Enceladus, so let's do that. I propose a sculpture of a fighting dog and cat.
Comment icon #7 Posted by Abramelin 23 days ago
But whatever you post here, you are far, far away of being an explorer, a discoverer, a guy with brass balls to put on a space suit and do whatever astronauts did. You're just an annoying bug with 'an opinion'. Btw., you're not alone here on UM. There's another one here I forgot the name of. 'Quick' - something.
Comment icon #8 Posted by Piney 23 days ago
My sisters couldn't get me in SCUBA gear, let alone a space suit. 
Comment icon #9 Posted by joc 23 days ago
Yeah, there is no way I would ever put on SCUBA gear either.  And...all one really has to do is to watch a Saturn V rocket liftoff.  In the first place you'd never even get me up to the top to the capsule.  The thing was 363 feet tall.  It takes a certain kind of person to even want to do that...plus, the physical training involved, plus the mathematics and science one has to know to become an astronaut is unbelievable. To minimize the work and effort of NASA to 'boys with their toys' is just stupid.  Not ignorant...STUPID! sometimes I just shake my head   


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