Paul Gilster at Centauri Dreams writes of a scientific paper he’s reviewing that analyzes the potential oxygenation in Europa’s sub-crustal ocean.
We know Europa has liquid water beneath its icy veneer. The challenge for those seeking off-Earth life is considerable. There may well be water, but life as we know it still needs oxygen to breathe. Where would it come from?
We’ve seen evidence for processes by which water is broken down into its constituent elements: the hydrogen and oxygen clouds above the Earth, oxygen in the rings of Saturn, to name two. Radiation might break down the Europan surface ice, and some transport mechanism might deliver the oxygen to the inner ocean.
That ocean is considerably deeper than Earth’s. Notice the inner layers of rock and metal. That part of Europa’s interior is more guesswork, but we know how much that moon weighs, and we can extrapolate from there the percentages of ice, water, stone, and metal.
Gilster quotes from the abstract, “Such an ocean would be energetically hospitable for terrestrial marine macrofauna. The availability of reductants could be the limiting factor for biologically useful chemical energy on Europa.”
Then adds the understatement:
If the term ‘macrofauna’ doesn’t get your attention, nothing will.
It sure got my attention. Examples of macrofauna would include giant squid, sharks, and whales. The latter would be impossible to find swimming the Europan ocean (whales evolved from land animals) but animals the size of these creatures would have no lack of oxygen or energy to live on this moon. And depending on the mineral content, possibly without environmental suits.
Another interesting point: there might be far more extra-terrestrial environments hospitable for dolphins and whales than for humans.