Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us all expand our scientific vocabularies together. Today’s term is:
SHADOW BIOSPHERE
Crazy Talk
We are not alone on planet Earth. There are aliens among us. Their existence has gone unnoticed and unsuspected for millions of years.
Truth be told, I shouldn’t call them “aliens.” They evolved here on Earth, side by side with what we, in our arrogance, call “organic life.”
They’re everywhere. There’s a whole biosphere of these weird creatures sharing our planet with us. It’s called the shadow biosphere.
Not Crazy Talk
I first heard about the shadow biosphere on an episode of SciShow, and I’ve been seeing the term more and more lately. It seems like some sort of astrobiology buzzword at the moment.
The idea is that an alternative form of life could have evolved here on Earth, and we just haven’t discovered it yet. Maybe it lives in areas totally inaccessible to us, like deep beneath the Earth’s crust. Or maybe it’s so different from us that we don’t yet recognize it as a life form.
Personally, I take this as more of an astrobiology thought experiment than a serious hypothesis about life on our planet. It’s a way of reminding us how limited our understanding of life is and show how difficult it might be to identify alien life should we happen to find it.
You see, to determine if something is alive, we must try to identify ways in which it is similar to other living things. Does it move? Grow? Reproduce? On a more fundamental level, is it cellular in structure? Does it have a carbon-based biochemistry? A DNA-like genetic code?
But all these questions presuppose that newly discovered life forms will be similar to life forms we already know about. What if we’re dealing with a life form totally dissimilar to life as we know it? What if they’re non-cellular, non-carbon-based organisms that don’t have anything resembling DNA?
Why, such organisms might be so strange to us that they could exist all around us, even right here on Earth, and we wouldn’t know it. Or so this type of thought experiment may lead you to conclude.
Back to Crazy Talk
It’s not just a thought experiment. The shadow biosphere is real. It’s real, I tell you! Wait, where are you taking me? No, I don’t want to take my medicine. Are you working for them? Did the pet rocks send you?
Planet Pailly 
Nature has a way of ignoring our little categories, like the distinction between life and non-life. Viruses are a good example. They are molecules that replicate, but because they hijack the replicating mechanisms of other organisms, many don’t consider them to be alive.
I suspect when we do find the first truly alien life, it will challenge our very notions of what life is supposed to be. We may end up having an extended debate on whether we’ve really found actual life, or some new type of complex chemical phenomenon.
From I’ve read, many at NASA define life as anything that replicates and evolves. I think that’s a good definition, although it may someday leave us debating whether an extraterrestrial form of clay is alive.
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That’s basically how I think things will play out too.
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This is a great thought experiment (or non-thought experiment). I often wonder what science is missing by putting so much emphasis on finding places in the habitable zone of distant stars, places where liquid water can exist. When we write, we start with what we know. Same goes for science, we need a familiar place to start, right? So, a place where there can be liquid water is a reasonable starting point. There are extremophiles here on Earth, though, that live in deep, dark places near undersea vents where the water is full of chemicals that would kill most life we know very quickly. I love the idea of a biosphere because it makes us think outside the… water. I wonder what places could hold life that thrives in scorchingly hot worlds, or words with an arsenic atmosphere. Who knows?
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Those hydrothermal vents are a great example. Apparently when they first started studying those vents, they brought geologists and chemistists and such on the expedition, but no one thought to bring a biologist because no one ever imagined they might find life there. It was a complete surprise.
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First Contact with intelligent alien life could infect the evolution of earths timeline. I do believe Astronaut Gordon Cooper has already reported that Aliens, bless them, have landed on Earth! So I reported our search for alien lifeforms 7 years ago.Trekkers probably figured I had gone stark raving mad, ha ha.
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