Sciency Words: (proper noun) a special series here on Planet Pailly focusing on the definitions and etymologies of science or science-related terms. Today’s Sciency Word is:
EUPHOTIC ZONES
Based on what Google ngrams has to tell me, it looks like “euphotic” and “euphotic zone” entered the English lexicon right at the start of the 20th Century, then really caught on circa 1940.
The word euphotic is a combination of Greek words and means something like “good lighting” or “well lit.” In the field of marine biology, the euphotic zone refers to the topmost layer of the ocean, or any body of water, where there’s still enough sunlight for photosynthesis to occur.
My first encounter with this term was in this paper by astrophysicists Carl Sagan and Edwin Salpeter. Sagan and Salpeter sort of co-opted this term from marine biologists and applied it to the layer of Jupiter’s atmosphere where—hypothetically speaking—Jupiterian life might exist.
I don’t see any reason why the term could not also by used for other planets as well. There’s a euphotic zone just above the cloud tops of Venus. The same could be said about Saturn or Uranus. Or maybe if the ice is thin enough, we may find euphotic zones right beneath the surfaces of Europa or Enceladus.
Of course just because a planet has a euphotic zone, that doesn’t mean photosynthetic organisms are living there. And also there are plenty of ecosystems here on Earth that do not depend on photosynthesis and that don’t exist anywhere near a euphotic zone.
Still, I’m very glad to have picked up this term. The concept of euphotic zones can be very helpful in any discussion of where alien life may or may not be hiding.
Planet Pailly 
I believe there are starfish which can survive these zones of the dark deep here on earth where pressures are exceedingly amazing so like equivalent to having 50 jumbo jets stacked one on top of the other on you. weird huh?
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There are so many weird creatures down there, totally cut off from the sun. And I think that is highly suggestive of what we might find living on other planets and moons.
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Thanks for this – I’ve not heard the term before…
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It’s a good one, isn’t it? Not all forms of life have to live in euphoric zones, but it’s a useful concept when we’re talking about certain kinds of life.
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Well we need to find other life in such a zone first… which we’re struggling with.
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True. Those other forms of life might be too strange for us to identify as living. At least until we learn a whole lot more about what life is.
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Well quite…. Are stones life?
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I can’t find it now, but there was an article a few years back about a rock on the deep sea floor. It sat there for years, and nobody thought anything of it. Then one day, the rock got up and scuttled away on little legs. It was a previously unknown organism.
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Oh yes this rings a bell, it wasn’t an actual stone but it looked like one.
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Yeah, it was a case of really good camouflage, not a totally new form of life. But still, it’s a good demonstration of how easily we can miss stuff that’s sitting right in front of us.
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Yes we need to keep our eyes open more!
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