The Cassini space probe has detected sodium salts near the south pole of Enceladus, one of the larger moons of Saturn. To astrobiologists, sodium is an indirect sign of liquid water, as liquid water will leach sodium out of rock over a period of time.
To astrobiologists, sodium is an indirect sign of liquid water.
Scientists already knew water vapor and ice were actively emanating from Enceladus, and this discovery only fuels their hopes of finding conditions for life on the planet. The researchers believe the water may exist in underground caverns, with the vapors and salt released through cracks in the surface. They even speculate the existence of a subsurface ocean.
The amount of salt is minimal, however: less than two percent of the expelled ice, too little to be detected from Earth. Cassini researcher Frank Postberg of the Max Planck Institute for Nuclear Physics explained, “Water droplets are probably lifted by gas bubbles in the water (like the spray you see above sparkling water).”
But Nicholas Schneider of the University of Colorado–Boulder cautioned that the existence of water was only one of several possibilities: “It could still be warm ice vaporizing away into space. It could even be places where the crust rubs against itself from tidal motions and the friction creates liquid water that would then evaporate into space.” He added, “These are all hypotheses but we can’t verify any one with the results so far.” Yet in a recording on BBC News, Postberg declares, “I’m sure we have [liquid water].”
Schneider’s skepticism may not extend to the entire astrobiology community. Cassini researcher John Spencer of Colorado’s Southwest Research Institute told the BBC, “We need three ingredients for life, as far as we know—liquid water, energy, and the basic chemical building blocks—and we seem to have all three at Enceladus, including some fairly complex organic molecules. That’s not to say there is life on Enceladus but certainly the ‘feedstock’ is there for life to use if it does exist.”
Any hint that liquid water could exist elsewhere in space, even without confirmation—or even that water once may have existed—attracts a pack of evolutionary speculation. The speculation is rooted in the unproven idea that (as Spencer said) life needs only water, energy, and “basic chemical building blocks.” Yet no scientific experiment shows that life could arise from only those ingredients; such is the required speculation of metaphysical naturalism.
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