Sciency Words: Panspermia

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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:


What if bacteria have their own space program? What if microorganisms can travel from planet to planet all by themselves?

Ap13 Panspermia Adventures Part 1

Admittedly, this bacterial space program is a poor man’s way to explore the universe. Single-celled astronauts don’t know when they’ll be launched into space, nor can they predict where they’ll be going. There are no rocket ships. There’s no mission control.

And if you think a lot of human astronauts have died in the name of space exploration, the fatality rate for bacterial astronauts is way, way higher.

Ap13 Panspermia Adventures Part 2

Panspermia comes from the Greek words for “all” and “seeds.” It can be loosely translated as “seeds in all places” or “seeds everywhere.” As a scientific concept, panspermia hypothesizes that microorganisms can hop from one world to another via asteroid impacts.

There’s very little proof for panspermia, but scientists have gathered plenty of circumstantial evidence.

  • Many asteroids (especially C-type asteroids) contain water and amino acids. It’s not much, but very simple organisms might be able to eek out an existence there.
  • Life didn’t appear on Earth until after an event known as the late heavy bombardment, when loads of asteroids pummeled our planet. Mars and Venus, the moons of Jupiter and Saturn… they all got pummeled too. Life could have been seeded across the whole Solar System at that time.
  • The earliest fossilized microbes on Earth appear to have already developed a certain degree of complexity. Maybe they evolved this complexity before coming to Earth.
  • Tardigrades have become famous for their ability to survive in space, but a surprising number of other microorganisms can survive in space too. Some apparently grow better up there than they do here. Why are these life forms are so well adapted to space? Maybe it’s because they’re from space.
  • Plenty of meteorites found here on Earth originate from other places in the Solar System, and there’s good reason to suspect that Earth rocks have made it to other planets too. Any of these rocks could have had microscopic passengers aboard.

So how seriously should we take the panspermia hypothesis? Even if we accept the possibility that bacteria could travel between worlds, that doesn’t mean they do or that such things are common occurrences.

But as a science fiction writer who’s in the middle of world-building for a new story, I think panspermia is a great place to start. If I decide panspermia is true, I can have a universe where life is everywhere—and perhaps where all life is genetically similar in some respects. If I decide panspermia is false (within my fictional reality), I’ll have a universe where life is rare, separated by strange and wildly dissimilar genetic structures.

Both options offer intriguing storytelling opportunities. Which to choose? Which to choose….


Panspermia: A Promising Field of Research from the 2010 Astrobiology Science Conference.

Tiny Animals Survive Exposure to Space from ESA.

Bacteria in Space! from Scientific American.

The Continuing Controversy of the Mars Meteorite from Astrobiology Magazine.

Earth and Mars Could Share a Life History from Mars Daily.

8 thoughts on “Sciency Words: Panspermia

  1. It’s certainly an interesting theory, but it might be hard to prove or disprove. It would certainly help explain why all the aliens in Star Trek look a lot like us. Then again, maybe it had something to do with production budgets too.

    Liked by 1 person

  2. I actually did a paper (not academic, just for bio class) on panspermia and abiogenesis. Turns out there’s a lot of speculation that ancient Mars would have been better suited environmentally for the development of an RNA world, which is the current popular theory on how the first lifeforms arose.

    Liked by 1 person

  3. I don’t really have a stand one way or the other on panspermia from Mars or somewhere else in the solar system. Though it seems much more of a leap to entertain that it might have come from other star systems.

    On whether to include it in the story, I think it totally depends on what kind of story you want to tell. It seems like that story has to come first, and you assume whatever science you need for it. (How plausible that science needs to be depends on how hard you want your sci-fi to be.)

    Liked by 1 person

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