NASA recently released the news that there are hydrothermal vents in a great ocean beneath the icy crust of Saturn’s moon, Enceladus. The exciting thing about this is that hydrothermal vents beneath Earth’s ocean are the home to non-photosynthetic based ecosystems; in other words, hydrothermal vents on Earth give rise to chemoautotrophic life. And to me, this is the most plausible “potential life on another planet” story I’ve ever heard. (Some people believe that hydrothermal vents gave rise to all life on Earth…I’m haven’t picked a side on this issue, but it’s interesting.)
Given hydrothermal vents and a liquid ocean, there’s every potential for Enceladus to have life. Furthermore, it doesn’t just have to be microbial life: our own hydrothermal vent ecosystems are complex and include many animals reliant on the autotrophic bacteria that synthesize energy from chemical reactions with compounds released by the vents.
I learned about these hydrothermal vents from a friend of mine who studies them and I was always fascinated by the ecosystems that form around them. Here are some photos of hydrothermal vent life (stolen from the internet as I’ve never been in a submarine before (yet!)).
Vulcanoctopus thermoventalis (Source: https://uk.pinterest.com/pin/471892867176409645/)
Riftia tube worms (Source: http://www.uniprot.org/taxonomy/6426)
The cousin of Riftia, Lamellibrachia, is way prettier, but I think they only live on cold seeps, which are of course biochemically very distinct. They are both in the Annelid phylum, which includes your friendly backyard earthworm! (Here’s a photo of Lamellibrachia, because it’s so pretty: https://upload.wikimedia.org/wikipedia/commons/5/5d/Lamellibrachia_luymesi1.png).
The scaly-foot gastropod (Chrysomallon squamiferum) has an iron coating and will actually stick to magnets! (Source: https://en.wikipedia.org/wiki/File:Three_populations_of_Chrysomallon_squamiferum.jpg)
There are also Pompeii worms (Alvinella pompejana), which are covered in episymbionts (the symbionts are epsilonproteobacteria (say that three times fast))! (Source: http://www.arkive.org/pompeii-worm/alvinella-pompejana/)
Here’s a picture of a hydrothermal vent community (Source: http://invertebrates.si.edu/Features/stories/vestimentifera.html)
So, if those are some of the weird and wonderful things we find on our own ocean floor, imagine** (what if!) the kinds of living things we could find on another world!
Of course, it could be extremely difficult to sample these vents on another world*…we not only have to design a ship to travel across space, but also deep into the ocean. It would need to withstand a total vacuum and incredibly high pressure from the ocean. And it would somehow need to send its findings back to us! My father (who works for NASA) says, “It is an interesting technical problem for Communications and Navigation since we not only need to get a probe to Enceladus, but we need to land, drill through the crust and then operate a submersible under the ice. Not easy to keep a comm path back to Earth with something under the ice that far away. I do think there is a chance for life there; it may not resemble any life on earth.”
*Am I allowed to call Enceladus a planet? I don’t think so…
**You can’t even imagine!