Sciency Words: Panspermia

sciency_words_slimSciency Words is an ongoing series here on Sci-Fi Ideas celebrating the rich and colorful world of science and science-related vocabulary. For today’s special Alien August edition of Sciency Words, we turn our attention to the term:


Last week we met the extremophiles: organisms that not only can survive under the harshest of conditions but actually thrive in them. Some live in acid. Some prefer boiling water. Some even live in highly radioactive environments. But are any organisms “extreme” enough to survive in space?

Yes, as it turns out. Most notably: tardigrades (a.k.a. “water bears”). These tiny critters enter a state of suspended animation when exposed to the vacuum of space. Tardigrades don’t exactly thrive like this, so they’re generally not considered extremophiles, but their ability to survive in space is still impressive.

A cute little tardigrade virtually begging you to tickle its tummy.

A cute little tardigrade virtually begging you to tickle its tummy.

Meanwhile, several species of bacteria apparently grow better in zero gravity than they do here on Earth, and it’s estimated that bacterial spores can remain viable for millions of years in space so long as they’re shielded from direct sunlight.

All this begs the question: why would terrestrial organisms develop the ability to survive in space… unless at some point in their evolutionary history, their ancestors came from space?

This brings us to the scientific hypothesis of panspermia, which loosely translates from Greek as “all seeds” or “seeds everywhere.” According to panspermia, life – in the form of bacterial spores, tardigrades, or whatever – spreads promiscuously through space, hopping from planet to planet, hitching rides on meteorites and comets.

A meteorite from Mars, like the controversial ALH84001 meteorite, could have delivered the first seeds of life to Earth; or perhaps a similar meteorite brought the seeds of life from Earth to Mars. Or maybe these seeds were planted all over the Solar System and originated somewhere else entirely.

It’s worth mentioning that the earliest evidence of life on Earth coincides with an event called the Early Heavy Bombardment, during which Mercury, Venus, Earth, and Mars all got pummeled by asteroids and comets from the outer Solar System.

Obviously panspermia remains highly speculative, but if we ever do find life elsewhere in the Solar System and if that life bears eerie genetic similarities to life on Earth, that would be compelling evidence in panspermia’s favor. It could also mean that as humanity seeks out new life and new civilizations, boldly going where no man has gone before, we may find out that we share a common ancestor with the aliens we meet.


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.

Article by James Pailly. Check out James’ blog for more great science articles.

  • Kirov

    I was wondering if this word would come up. Interesting note, I was reading up on RNA world earlier, and apparently conditions on Mars were thought to be better for an RNA world than on Earth. There’s a theory that abiogenesis occurred on Mars, where an RNA world developed, and then life migrated to Earth via panspermia.

  • Leonardo Faria

    I suggest to drop the locution “zero gravity”, in favor of the more accurate “microgravity”.

    There’s no such a thing as zero gravity.

    • Aidan903

      Well, not in our universe.

      In a universe in which there was no mass, it might be possible.

    • I’m not exactly an expert but i was under the assumption that there are areas in which the forces of gravity cancel each other out (lagrange points) please tell me if I’m wrong though.

  • didn’t fred hoyle use panspermia as an argument against natural selection (interesting fact, Fred hoyle coined the term “big bang” during a debate, dismissing the idea as unintelligent)