Hello, friends! Welcome back to Sciency Words, a special series here on Planet Pailly where we take a closer look at interesting and new scientific terms in order to expand our scientific vocabularies together! Today’s Sciency Word is:
So is there life on Mars? Well, there could be. It’s not totally impossible. But as I’ve said before on this blog, I think the odds of us finding living things on Mars are pretty low. The odds of us finding dead things on Mars, however… I think those odds are much better!
Or at least I did think that until I read this paper, entitled “A Field Guide to Finding Fossils on Mars.” That paper introduced me to the concept of “preservation potential,” and subsequent research led me to learn about something paleontologists call “preservation bias.”
Basically, turning into a fossil isn’t easy. A lot of factors have to come together just right in order for a dead organism to become preserved in the fossil record. As that Martian fossil field guide explains:
On Earth, most organisms fail to fossilize because their remains are physically destroyed, chemically oxidized or dissolved, digested by their own enzymes, or consumed by other organisms. Fossilization only occurs when processes of preservation outpace degradation.
Preservation bias refers to the fact that certain organisms—or certain parts of certain organisms—stand a better chance of fossilizing than others. Preservation bias can also refer to the fact that some environments (rivers and lakes, for example) do a better job creating and preserving fossils than others (for example, deserts).
A lot of factors can get involved in this, but as a quick and easy example, think of the dinosaurs. Dinosaur bones fossilize easily enough. Other parts of the dinosaur… not so much. That, my friends, is preservation bias at work, favoring hard tissue, like bone, over soft tissue, like muscle or fat.
Now imagine what would have happened if dinosaurs somehow evolved without bones (that’s a weird concept, I know, but just bear with me a moment). How much would we know about those boneless dinosaurs today? Would we know about them at all? Those hypothetical boneless dinosaurs could have roamed the earth for billions of years and left hardly a trace of evidence for us modern humans to find!
Which brings us back to Mars. There was a time, very long ago, when Mars was a much warmer and wetter planet than he is today. It’s possible—no, I’d say it’s probable!—that life of some kind developed on ancient Mars, just as it did on ancient Earth. But would that ancient Martian life have left us any fossils to find? Maybe. Maybe not. It depends on the various factors involved in preservation bias.
P.S.: Boneless dinosaurs are delicious.