How to Build an Alien: Extremophiles

by Melanie Marttila
published in Writing

A few columns ago, I took you on a tour of the solar system in search of world building ideas. I hope you’ve had a chance to explore some of these ideas to create new worlds of your own, because this time on Speculations, we’re going to look at populating those imagined worlds.

Just like we didn’t have to go very far, relatively speaking, to find some interesting ideas for created worlds, we don’t have to stray far from home to find some interesting ideas for beings that might be able to survive in different or extreme environments. In fact, we don’t have to leave Earth at all.

Enter the Extremophiles

“Extremophiles” refers to a group of organisms that have found ways to not only survive, but thrive, in extreme environments. There are those creatures that live in high pressure, like those that live in the deepest ocean trenches. There are creatures that have learned to survive in the high heat of volcanic vents. Others have learned to live in high saline environments or thrive in areas of high radiation. Some animals thrive in multiple extremes. And then, there’s my absolute favourite, the tardigrade, which technically isn’t an extremophile at all.

I’m only going to introduce you to a handful of these fascinating beings, but I’ve included some links at the end of the column where you can go to learn more about these life forms.

Atacama Desert Archaea

When scientists found DNA in the Atacama Desert in Chile, they wondered whether it was just some remnant from a previously living species, or a dormant, but still living organism. You see, the Atacama might see rain once a decade. It’s bathed in ultraviolet radiation and salt has rendered the soil inhospitable to life…until a freak 2015 storm revealed the bizarre truth.

The scientific team found organisms that were tolerant of the high aridity, salinity, and UV radiation. In effect, they desiccated and survived, like microbial mummies, until the conditions that would wake them up arose. Scientists returned in 2016 and 2017 to study the archaea (an ancient domain of life separate from bacteria, plants, and animals) and watch their return to dormancy.

It’s theorized that some of these microbes could remain dormant for up to 50,000 years! The Atacama is a lot like Mars, and astrobiologists are interested in what the archaea there can teach them about life on other planets.

Black Smoker Microbes

In the deepest parts of the ocean floors, where the pressure is intense and the temperatures are frigid, where everything is so far from the surface that there is absolutely no light, where hydrothermal vents spew a super-heated chemical cocktail that gives them the name “black smokers”…there is life. And that life is critical to the continuance of the deep-sea ecosystem.

Plants photosynthesize light and carbon dioxide to produce energy and oxygen. The microbes living around the black smokers, in the temperature gradient between the super-heated stacks and the surrounding frigid water, chemosynthesize energy from the mineral and chemical compounds emerging from the vents.

These microbes become the basis of the food chain and produce the chemicals other deep-sea dwellers need to live. Methanopyrus kandleri harvests energy from hydrogen gas and produces methane. Pyrolobus and Pyrodictium produce hydrogen sulfide. Green sulfur bacteria actually do manage to photosynthesize, but they use the weak radioactive glow emitted by geothermally heated rock to do it instead of sunlight.

How’s that for adaptation?

Methanogens at the Bottom of Lake Ace

Like Methanopyrus kandleri, Methanogenium frigidum and Methanococcoides burtonii are methanogens, that is, they are organisms that produce methane. Unlike M. kandleri, M. frigidum and M. burtonii thrive at the bottom of Ace Lake in Antarctica where there is no oxygen, light, or carbon, and the temperature is stable around 33 degrees Fahrenheit. Brrr!

Both organisms have been found to contain flexible proteins, which allow them to function at freezing temperatures. M. frigidum also has cold shock proteins, which also help them to thrive in the cold. They grow very slowly, however, so slowly that researchers often think they’ve died.

The Department of Energy is interested in them as a potential fuel source. NASA is interested in them because they offer the hope of finding life on other planets and moons in the solar system, where similar circumstances (no oxygen, light, or carbon) pertain.


As I mentioned above, tardigrades aren’t extremophiles. They don’t need high pressure, salinity, or hydrogen gas to live, as the other organisms I’ve discussed do. But they’re survivors. Tardigrades are one of the most resilient life forms on the planet…or not.

Tardigrades are also known as water bears or moss piglets, and that’s where they typically make their homes: in moss and lichen. They feed on algae and small invertebrates. Very small. Tardigrades are only 0.02 inches in length, so anything they feed on has to be considerably smaller.

The thing is that tardigrades have also been found in dunes, marine or freshwater sediments, or living on barnacles. That’s not all. Tardigrades have also been found at the tops of mountains, in mud volcanoes, and at the bottom of the ocean. They’re hardy little things, able to withstand exposure to extreme temperatures, pressures, air deprivation, radiation, dehydration, and starvation. They’ve even survived exposure to space.

Tardigrades have most recently been the inspiration for Star Trek: Discovery’s giant, fungal-spore space-faring aliens and the key to Discovery’s spore drive technology.  

Taking it to the Page

NASA has been studying extremophiles in the hope of being able to recognize life on other planets, or moons, when we find it. Speculative fiction is all about extrapolating what we know into a feasible story element. In this case, aliens, or fantasy creatures.

What if something similar to one of the archaea formed the basis of life on another planet? On earth, the conditions they need to live are considered extreme, but what about on a world where the atmosphere consists primarily of hydrogen gas? In Cixin Liu’s The Three Body Problem, the aliens coming to invade Earth have survived on their volatile planet by periodically dehydrating. Could they have evolved from something like the archaea living in the Atacama Desert?

With a little research, the possibilities will open before you. Just remember that the alien is not the story, but alien building could yield a great character, or antagonist, to propel the narrative.

Until next time, keep speculating and see where it leads you!


Melanie Marttila creates worlds from whole cloth. She’s a dreamsinger, an ink alchemist, and an unabashed learning mutt. Her speculative short fiction has appeared in Bastion Science Fiction Magazine, On Spec Magazine, and Sudbury Ink. She lives and writes in Sudbury, Ontario, Canada, where she spends her days working as a corporate trainer. She blogs at and you can find her on Facebook and Twitter.

Enjoyed this article?