So you want to design an extrasolar planet for your hard-SF story, and cast about your house looking for ideas. There, you find all manner of of man-made materials: polystyrene coffee cups, polycarbonate eyeglass lenses, PVC pipes. Nothing could be farther from the natural, organic compounds of life, right?
Polystyrene, polycarbonate, and PVC are all examples of polymers, a class of chemical compounds made by bonding sequences of smaller chemicals (“mers”) together into long chains. We didn’t think of this concept first, though. Consider the following examples of polymers from life:
- Cellulose, the building block of trees and the roughage in your whole wheat bread, is a polymer made up of sugar molecules strung together into long chains. It is a polysaccharide.
- Proteins, which provide structure to cells and control the chemistry of life, are built from sequences of amino acids linked together. They are polypeptides.
- DNA, the design template of life, is built from long chains of base-pair sequences. It is a polynucleotide.
It would seem, therefore, that whenever a big molecule was needed in nature, a polymer was used.
What does this mean for the chemistry of world building? Pretty much any polymer chemical invented by man might exist naturally in the life chemistry of a distant world. Imagine a world where animals use lightweight PVC as a skeletal material instead of the protein collagen. Suddenly the need for calcium in the diet is greatly reduced, but the need for dietary chloride is increased.
Of course, a world that makes use of PVC is going to be subject to all the chemical problems that PVC might have. For example, PVC is degraded by exposure to ultraviolet light. It might, therefore, not work well on earth, but might be effective on a world that orbits a red dwarf sun, or one with an extremely dense atmosphere.
If a compound exists naturally, however, it is more likely to be part of the food web. We can’t digest cellulose, but cows can—and so can many bacteria. If animals use PVC as a structural material, there will certainly be other animals and bacteria with the enzymes to digest it.
Modern man is surrounded by polymers: Nylon, Lexan, Teflon, Kevlar, Dacron, and many others. Any one of these could be a starting point for the design of an original life chemistry on your planet.
Note to regular readers: I plan to work through the exercises in #blogging101 when it starts next week. I have no idea what kind of assignments will be required, so please forgive me if my blog becomes suddenly inhabited by posts about sentient protozoa or the potential of Rick Moranis to star as the romantic lead in your next non-comedy action film.