Far beneath the frozen crust of Saturn's moon Enceladus, a dark ocean may hold conditions that echo the earliest chapters of life on our own planet. In a laboratory on Earth, researchers recreated that hidden seafloor and found that a deep-sea archaeon, an ancient kind of microbe that feeds on hydrogen and carbon dioxide, continued to grow and release methane. The finding does not confirm that anything lives out there, but it reveals that a place once thought hostile may be more welcoming than we imagined. Whether the answer lies in those distant waters will depend on the patient reach of futu
Saturn's Moon Enceladus May Be More Hospitable to Life Than Thought, Lab Study Finds
It kept growing, and it produced methane.
Mark
So what did the researchers actually do here?
Mimi
They built a chamber with oxygen about 10,000 times lower than Earth's air, simulated Enceladus's alkaline ocean and rocky seafloor, and dropped in a deep-sea archaeon called Methanothermococcus okinawensis.
Mark
And it survived?
Mimi
It grew and produced methane, using hydrogen from water-rock reactions. That environment had been assumed to be lethal to such organisms.
Luke
Let's be clear about the limits, though. This is a lab simulation with one organism from Earth. Nobody has shown anything living on Enceladus.
Mimi
The lead scientists say the same. William Orsi said the study doesn't prove life there, only that key geochemical features could enable one of the oldest metabolic forms.
Mark
Why does the carbon dioxide matter so much?
Mimi
The ocean's high pH leaves very little CO2. That was a major challenge for potential life, and the archaeon adapted by using the tiny amounts available.
Luke
Worth noting that the description of the results as astonishing comes from the university's own statement, so it's the institution's framing.
Mark
So how would anyone find out for real?
Mimi
ESA's planned L4 mission, targeted for 2042, would sample the plumes from geysers in the ice crust and analyse them for microbial life.
Luke
And that's a plan, not a launched mission. Until then, this stays a well-supported possibility.
Der Puls
- A chamber with almost no oxygen was built to mimic a moon's buried ocean floor, and scientists waited to see whether a microbe would survive.
- The archaeon kept growing and making methane, defying the assumption that a high-pH, carbon-starved ocean would be lethal.
- Scarce carbon dioxide, the moon's most serious obstacle to life, was overcome by the microbe's ancient hydrogen-based metabolism.
- Researchers are cautious: the results prove nothing about life on Enceladus, and the real test awaits ESA's L4 mission in 2042, which will sample geyser plumes.
Far beneath the frozen crust of Saturn's moon Enceladus, a dark ocean may hold conditions that echo the earliest chapters of life on our own planet. In a laboratory on Earth, researchers recreated that hidden seafloor and found that a deep-sea archaeon, an ancient kind of microbe that feeds on hydrogen and carbon dioxide, continued to grow and release methane. The finding does not confirm that anything lives out there, but it reveals that a place once thought hostile may be more welcoming than we imagined. Whether the answer lies in those distant waters will depend on the patient reach of future spacecraft.
Inside a sealed laboratory chamber, the air held about ten thousand times less oxygen than ours. The scientists had built it deliberately, to imitate the seafloor of an ocean hidden beneath the ice of Enceladus, a moon of Saturn. They placed in it a single-celled organism pulled from the deep sea on Earth, and then they watched, expecting it to fail.
It did not fail. The organism, Methanothermococcus okinawensis, kept growing and produced methane, drawing its energy from hydrogen released by reactions between water and rock. Its team, drawn from universities in the United States and Germany, reported the work in Science Advances. The microbe needs only hydrogen and carbon dioxide to live, a pathway its researchers describe as one of the most primordial still found on Earth.
The chamber also reproduced the moon's alkaline ocean, where carbon dioxide is extremely scarce. Before this study, that scarcity was thought to be a fatal barrier. The archaeon adapted, making use of the trace amounts available. The lead author, Vanessa Helmbrecht, said the results suggest Enceladus may be even more favourable to microbes than believed.
The geobiologist William Orsi, the corresponding author, was careful to temper the excitement. The study does not show that life exists there, only that the chemistry could support one of the oldest forms of life known. The answer may eventually arrive from space: the European Space Agency's planned 2042 L4 mission would collect samples from the geyser plumes rising through the ice, samples that could be examined for signs of microbes.
Inside a specially built chamber in a laboratory, the air contained about 10,000 times less oxygen than Earth's atmosphere. Researchers had engineered it that way on purpose, to mimic the floor of an ocean hidden beneath the ice of Enceladus, one of Saturn's moons. Into that setting they introduced a single-celled organism from the deep sea on Earth, and then they waited to see whether it would die.
It didn't. According to a statement from Ludwig Maximilian University of Munich, the organism kept growing in the simulation and produced methane, using hydrogen generated by reactions between water and rock. The work was done by a team from universities in the United States and Germany and was published in the journal Science Advances in September.
The organism is Methanothermococcus okinawensis, an archaeon, one of the groups often described as ancient bacteria. It is a hydrogen-consuming, methane-producing microbe, and it needs only two gases to make energy: hydrogen and carbon dioxide. The researchers describe that as one of the most primordial metabolic pathways still found in living things on Earth. Because it is anaerobic, it does not need oxygen at all.
The chamber was meant to recreate two features of Enceladus. Researchers believe the moon holds a global ocean of liquid water beneath its icy crust, with a deeper rocky core below. In the experiment, the team simulated both the alkaline ocean and the rocky seafloor. Before this work, it had been assumed that such an environment would be lethal to these single-celled organisms.
One of the biggest obstacles for any life there, the university noted, is the extremely low concentration of carbon dioxide, a result of the ocean's high pH. The team showed that the archaeon could adapt, using the tiny amounts of available CO2 through its distinctive metabolism.
Vanessa Helmbrecht, the study's lead author, said in the university statement that Enceladus is considered one of the most promising places to search for extraterrestrial life, and that the experiments suggest its geochemistry could be even more favourable to microbes than previously assumed. The university described the results as astonishing.
The researchers were careful about what the findings do not say. Geobiologist William Orsi, the study's corresponding author, said the work does not prove there is life on Enceladus. What it does show, he said, is that key geochemical features there could enable one of the oldest metabolic forms of life.
An answer may eventually come from space. According to the statement, the European Space Agency recently announced that its planned 2042 mission, known as L4, would collect samples from the plumes that geysers send through the moon's ice crust into space. Those samples could then be analysed for signs of microbial life, which would turn a laboratory possibility into something that can actually be tested.
Bemerkenswerte Zitate
Our study does not prove that there is life on Enceladus, but it does show that key geochemical features there could enable one of the oldest metabolic forms of life.— William Orsi, geobiologist and corresponding author
Enceladus is considered one of the most promising places to search for extraterrestrial life.— Vanessa Helmbrecht, lead author
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