Saturn moon Enceladus harbors key ingredient for life

the top of a planetary body rises in black and white from the bottom. light illuminates streaks of geysers spewing from the surface near the top.
(Image credit: NASA/JPL-Caltech/Space Science Institute)

A new investigation of data collected by NASA's Cassini mission, which ended six years ago, has revealed that the spacecraft spotted a key ingredient needed for life on Saturn's icy moon Enceladus. The Cassini observations have revealed a powerful energy source for potential lifeforms deep below the icy shell of this moon. 

Enceladus blasts out plumes of ice and water from fissures in its icy shell, and scientists have known for some time that organic molecules — some of which may have the right chemistry to be important for life as we know it — are contained in these jets. In 2017, scientists found carbon dioxide, methane, and hydrogen in Enceladus' plumes, indicative of a metabolic process called methanogenesis. As its name suggests, methanogenesis produces methane, which is widespread here on Earth and could be a sign of life on other worlds.

The new confirmation of hydrogen cyanide — a crucial precursor for some molecules that needed to be present on Earth for life to arise  —  takes the concept that Enceladus could be habitable to a whole new level, however. 

The same research team also discovered that the subsurface ocean of Enceladus, from which the plumes apparently originate, could be the source of several other organic compounds, some of which serve as fuel sources for terrestrial organisms. This indicates that there may be more energy available for life on Enceladus than was previously thought. 

"Our work provides further evidence that Enceladus is host to some of the most important molecules for both creating the building blocks of life and for sustaining that life through metabolic reactions," lead author and Harvard University doctoral student Jonah Peter said in a statement. "Not only does Enceladus seem to meet the basic requirements for habitability, we now have an idea about how complex biomolecules could form there, and what sort of chemical pathways might be involved."

Related: Signs of life shooting from Saturn's moon Enceladus would be detectable by spacecraft, scientists say 

The Swiss Army Knife of life 

To get started, life as we know it needs compounds like amino acids as its essential building blocks. The team behind the new findings describes hydrogen cyanide as the Swiss Army Knife of amino acids because of the variety of ways the molecule can be stacked to help construct amino acids. 

"The discovery of hydrogen cyanide was particularly exciting, because it's the starting point for most theories on the origin of life," Peter said. "The more we tried to poke holes in our results by testing alternative models, the stronger the evidence became. Eventually, it became clear that there is no way to match the plume composition without including hydrogen cyanide."

This newfound source of chemical energy is more powerful and diverse than the methanogenesis process, study team members said. This means that there are various chemical pathways available for organisms (if they exist) in the moon's subsurface ocean. 

"If methanogenesis is like a small watch battery, in terms of energy, then our results suggest the ocean of Enceladus might offer something more akin to a car battery, capable of providing a large amount of energy to any life that might be present," research co-author Kevin Hand, a scientist at NASA's Jet Propulsion Laboratory (JPL) in Southern California, said in the same statement. 

The team used statistical analysis to arrive at their results. Armed with the new findings; scientists can now investigate these chemical pathways for life in the lab as they attempt to discover if Enceladus really has the right stuff for life. 

"We used math and statistical modeling to figure out which combination of puzzle pieces best matches the plume composition and makes the most of the data without overinterpreting the limited dataset," Peter said. "There are many potential puzzle pieces that can be fit together when trying to match the observed data."

The research also demonstrates that the Cassini mission keeps delivering important insights about Saturn and its moons, despite having made a suicide dive into the atmosphere of the gas giant in September 2017

"Our study demonstrates that while Cassini's mission has ended, its observations continue to provide us with new insights about Saturn and its moons  —  including the enigmatic Enceladus," said Cassini team member Tom Nordheim, also of JPL. 

The team's research was published on Thursday (Dec. 14) in the journal Nature Astronomy. 

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Robert Lea
Contributing Writer

Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.

  • rod
    "The new confirmation of hydrogen cyanide — a crucial precursor for some molecules that needed to be present on Earth for life to arise  —  takes the concept that Enceladus could be habitable to a whole new level, however."

    This report jarred my brain. Here is another report where HCN is used for abiogenesis to create life on Earth.

    The first life on Earth depended on a deadly poisonous gas, study suggests, https://forums.space.com/threads/the-first-life-on-earth-depended-on-a-deadly-poisonous-gas-study-suggests.53849/
    "Could the toxic gas used in chemical weapons today have been involved in the birth of life on Earth?"…"A messy birth
    In the new study, researchers developed a complex model of the early Earth. It goes a little something like this: The massive collision that created the moon just happened. Earth's surface cooled from the aftermath, with the oceans just beginning to form and the continents starting to emerge. It was still a pretty nasty place..."

    Apparently HCN via abiogenesis created life on Earth, and now perhaps Enceladus too. At the moment, I have not read reports where HCN created a single cell that represents life and then continued to evolve, onwards, and upwards. Apparently Charles Darwin warm little pond in his 1871 letter can now use HCN for abiogenesis or on Enceladus too.
    Reply
  • mikeash
    Why not build a probe and put it in a geosynchronos orbit around Enceladus near to the plumes.
    Reply
  • billslugg
    The proposed Enceladus Life Finder (ELF) mission would go into orbit around Saturn and would pass through the plumes of Enceladus 8 times over three years. If it orbited only Enceladus, perhaps it would be limited in what science it got.
    Reply
  • rod
    I read this interesting report this morning about the giant impact model with Theia and abiogenesis on the early earth.

    Planetary scientists simulate oxidation of iron by giant impact during atmospheric evolution of early Earth, https://phys.org/news/2023-12-planetary-scientists-simulate-oxidation-iron.html
    Ref - Oxidation of iron by giant impact and its implication on the formation of reduced atmosphere in the early Earth, https://www.science.org/doi/10.1126/sciadv.adi6096, 15-Dec-2023. "Abstract Giant impact–driven redox processes in the atmosphere and magma ocean played crucial roles in the evolution of Earth..."
    My observation. Apparently now the giant impact model using Theia is good for a reducing atmosphere created on the early earth so abiogenesis can take place. What about abiogenesis on other planets like Mars, Encledaus moon? Interesting how a giant impact on Earth using Theia can help aid in abiogenesis taking place on Earth because of the early earth atmosphere arising after the giant impact. Does this scenario apply to other planets in the Milky Way and in our solar system too?
    Reply