Background: It is sometime in the late 21st century. Several unmanned probes have recently been sent to land on and investigate Jupiter and Saturn's moons. Two sites in particular, Europa and Titan, are being monitored closely and have been declared by the world government as manned "no go zones" due to their potential of life.

The question(s): What forms of life could exist on Europa/Titan?

How advanced would any such life have to be to motivate a crewed expedition to the outer planets?

Any and all answers will be appreciated. Thank you!

  • $\begingroup$ Have you read Arthur C. Clarke's Space Odyssey series? It answers the first question you have. (In the third book, I think.) $\endgroup$
    – Halfthawed
    Commented Nov 17, 2019 at 21:57
  • $\begingroup$ The first and second(the Discovery story arc) I remember well. After that I vaguely remember there was a crash landing on Europa and some big diamond mountain from Jupiter's core. I don't recall the detailed description of life though. $\endgroup$
    – Lelu
    Commented Nov 18, 2019 at 1:00
  • $\begingroup$ Life starts developing on Europa when Jupiter gets lit on fire. (Maybe 3001: Final Odyssesy would have it?) $\endgroup$
    – Halfthawed
    Commented Nov 18, 2019 at 1:11

1 Answer 1


First of all:

How advanced would any such life have to be to motivate a crewed expedition to the outer planets?

Any life form of any type would motivate a crewed expedition - from the simplest, most basic cellular life on up. If we found any life on any celestial body, we would be thrilled.

As for Europa, it has a fair amount of water, and an atmosphere of oxygen. There are theories that it has water underneath it's ice-sheets that could support life as we know it. If this theory is correct, then most marine life as we know it today could theoretically live on Eurpoa.

Titan, however, has a mostly nitrogen and methane atmosphere, so most life forms as we know them on earth would not be able to survive on Titan. That said, we have found life forms that don't need oxygen. In fact, some scientists from Cornell believe methane-based life could exist on Titan. It's unclear what exactly that type of life form would look like, as we would have to define how an oxygen-free cell would perform, but it does appear to be possible, at least in theory.

Until science gives us more answers as how such cells can/do/might behave, you'll have to use your imagination and some hand-waiving to get life on Titan. Europa could/would be more like life on earth's seas. Regardless, any life at all of any kind would motivate a crewed expedition for sure.

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    $\begingroup$ A trick with Europa would be the darkness under the ice. Water life would have to be of the deep sea vent chemolithotropic producers variety. $\endgroup$
    – Willk
    Commented Nov 17, 2019 at 14:06
  • $\begingroup$ Thank you for your wonderful answer! @Willk Is it possible that such life could be multicellular, similar to a jellyfish, octopus, or other similar varieties? Though even unicellular bacteria would be fascinating for scientific study, I don't imagine it would look as impressive. $\endgroup$
    – Lelu
    Commented Nov 17, 2019 at 18:27
  • 1
    $\begingroup$ @Lelu: sure. There are lots of multicellular creatures around deep sea vents. Down there the primary producers that capture the chemical energy are unicellular and a lot are unicellular up in the sun as well. But the herbivores and carnivores can be multicellular. You could also have a multicellular chemolithotroph primary producer in analogy to a plant. There is stuff about that concept here on WB Stack. $\endgroup$
    – Willk
    Commented Nov 17, 2019 at 21:15
  • $\begingroup$ Given the low energy environment, the vast majority of the putative biosphere would resemble pond scum huddled around hydrothermal vents. It is possible that there will be some multi cellular life that can move about and feed on the pond scum, and even higher order predators that feed on them. Life will be very slow compared to our own, however. $\endgroup$
    – Thucydides
    Commented Nov 18, 2019 at 2:34

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