The Enigma of Enceladus

Mar 27, 2008 4:47pm

In 2005, NASA’s Cassini probe, orbiting Saturn, made a remarkable and tantalizing discovery: Enceladus, one of Saturn’s moons, was venting something — possibly liquid water — into the frozen space around it. Enceladus.  Even the name, coming from Greek mythology, rolls off the tongue mysteriously.  En-CELL-a-dus.  Now, as we’ve reported, Cassini has added to the mystery. Controllers at the Jet Propulsion Laboratory sent the ship racing through the plume of Enceladus’ geysers, and found them rich in organic compounds.  They were also warmer than scientists had expected.  "Could microbial life exist inside Enceladus, where no sunlight reaches, photosynthesis is impossible and no oxygen is available?" ask Chris McKay and Dennis Matson in an essay on the Cassini site. "To answer that question, we need look no farther than our own planet to find examples of the types of exotic ecosystems that could make life possible on Saturn’s geyser moon. The answer appears to be, yes, it could be possible." They continue, "In recent years, life forms have been found on Earth that thrive in places where the sun doesn’t shine and oxygen is not present because no photosynthesis takes place. Microbes have been discovered that survive on the energy from the chemical interaction between different kinds of minerals, and others that live off the energy from the radioactive decay in rocks. The ecosystems are completely independent of oxygen or organic material produced by photosynthesis at Earth’s surface. These extraordinary microbial ecosystems are models for life that might be present inside Enceladus today."  The full essay is HERE. Of course, a reality check is in order.  They did find water vapor, methane, carbon monoxide, a whole brew of organic molecules — but the Saturn system (see our slide show HERE) is far out in the solar system, and there may be many things going on that we cannot see.  They’re the ingredients for life.  That doesn’t necessarily mean anything there actually is alive. Mckay and Matson: "the evidence points to the feasibility of life in Enceladus. But how would it get its start? A major problem in answering that question is that we don’t know how life originated on Earth, nor have we been able to reproduce Earth’s first spark of life in the laboratory. But here’s the good news: there are a lot of theories for how life originated on Earth. Now the question is — do they apply to Enceladus?" Those are questions we cannot answer for now.  But they certainly send minds racing.  (False-color image of venting near Enceladus’ south pole, imaged by Cassini spacecraft.)

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