Terraforming and maintaining a biosphere suitable for humans is tough, but no worries, Protogon is here! Collaborating with Providence, our scientists have created Hygiea, a series of rapidly growing organisms used to turn the slightly not so dead husk into a Earth-like environment.

Hygiea itself is a set of rapidly growing symbiotic organisms who "work" together (basically growing) and seed a planet with life (plants mainly) that in turn produce a habitable environment.

Would something like Hygiea ever work? In my mind it would basically speed up evolution on the planet, moon, or biosphere in question. To work, however, a fragile atmosphere and basic building blocks for life must be present already. However it turns centuries of work terraforming into mere years.

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    $\begingroup$ I'll remove it then. My bad $\endgroup$ Feb 13, 2019 at 2:47
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    $\begingroup$ Isn't this exactly what caused the great oxygenation event on Earth? Once the planet is terraformed, the organisms doing the terraforming die down because the planet is now hostile to them. $\endgroup$
    – pojo-guy
    Feb 13, 2019 at 3:36
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    $\begingroup$ First. Fastest. Furthest. $\endgroup$
    – Joe Bloggs
    Feb 13, 2019 at 7:16
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    $\begingroup$ What are you asking? "If it's a good idea" is an inappropriate question because SE isn't a discussion forum. "Would it ever work?" is silly because, given enough time and money, almost anything can be made to work (whether it makes sense or not). As a reality-check, there isn't enough information to judge the solution. Are you merely asking us to approve your basic idea? This is the wrong place for that. SE's model is one-specific-question/one-best-answer. What do you imagine the best answer to be? $\endgroup$
    – JBH
    Feb 13, 2019 at 17:28
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    $\begingroup$ @JoeBloggs I see I'm not the only one who got the reference. $\endgroup$
    – Gryphon
    Feb 13, 2019 at 18:15

5 Answers 5


a set of rapidly growing symbiotic organisms who "work" together (basically growing) and seed a planet with life

The closest to a sterile environment we have here on Earth is the surrounding of a volcano after an eruption.

What happens then? Well, usually the first life form to colonize the place are lichens. And what are lichens?

A lichen (/ˈlaɪkən/, LEYE-ken but in UK often /ˈlɪtʃən/, LICH-en) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship

Lichens grow on and in a wide range of substrates and habitats, including some of the most extreme conditions on earth. They are abundant growing on bark, leaves, and hanging from branches "living on thin air" (epiphytes) in rain forests and in temperate woodland. They grow on bare rock, walls, gravestones, roofs, and exposed soil surfaces. They can survive in some of the most extreme environments on Earth: arctic tundra, hot dry deserts, rocky coasts, and toxic slag heaps. They can live inside solid rock, growing between the grains, and in the soil as part of a biological soil crust in arid habitats such as deserts. Some lichens do not grow on anything, living out their lives blowing about the environment.

When growing on mineral surfaces, some lichens slowly decompose their substrate by chemically degrading and physically disrupting the minerals, contributing to the process of weathering by which rocks are gradually turned into soil. While this contribution to weathering is usually benign, it can cause problems for artificial stone structures. For example, there is an ongoing lichen growth problem on Mount Rushmore National Memorial that requires the employment of mountain-climbing conservators to clean the monument.

Coming to your question:

Hygiea itself is a set of rapidly growing symbiotic organisms who "work" together (basically growing) and seed a planet with life (plants mainly) that in turn produce a habitable environment. Would something like Hygiea ever work?

If it is anything close to a lichen, it surely will.

  • $\begingroup$ Love a good lichen. +1 $\endgroup$
    – Joe Bloggs
    Feb 13, 2019 at 7:17
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    $\begingroup$ Lichens are not a bad option once you've already made the planet reasonably habitable. Even a fresh lavaflow on Earth benefits in terms of habitability from the presence of microbial biota, the oxygenated atmosphere, and the presence of water. $\endgroup$ Feb 13, 2019 at 17:51

The creation of genetically engineered microorganisms for industrial and high-tech applications such as terraforming is certainly within the realm of possibility. However, there are several hurdles that they will face.

First problem: The target planet needs to have an initial environment upon which at the very least the most extreme microorganisms of Earth are able to survive. Mars for instance, does not meet these criteria, so you're need to do some physical modifications prior to setting loose your terraformers. If the planet was a reasonable Earth analogue to begin with (in that is had suitable insolation and surface water) you can skip this step.

Second problem: Your terraformers are going to grow so rapidly as to outpace the supply of nutrients. This can be mitigated somewhat by making the organism capable of nitrogen fixing, and can be strongly mitigated if you are willing to undertake nutrient seeding throughout the process.

Third problem: Your target planet will likely lack an ozone layer at the point you introduce your terraformers, so they will either need to be able to resist UV irradiation, or be restricted to marine environments.

Fourth problem: The rapid growth of your terraformers will cause the environment to shift from an anaerobic one to an aerobic one reasonably quickly. Their metabolisms need to be able to function in both of these regimes.

While there are probably many more issues that I've not thought of, solving these four will be a big step on the way to designing your terraformation microbes. My suggestion would be to use Rhodopseudomonas palustris as the basis of your microbe as it is able to shift between four different modes of metabolism based on the conditions it finds itself in, maybe with a bit of Deinococcus radiodurans thrown in for radiation resistance.

  • $\begingroup$ Would Europa serve as a suitable candidate? I assume if you cleaned up Venus' atmosphere so its not hellish it would be a nice project for Protogon. $\endgroup$ Feb 13, 2019 at 3:58
  • $\begingroup$ Assuming Europa doesn't already have a biosphere, it is a potential candidate. One issue you'd have there is that is doesn't receive much insolation, so photosynthesis may not be possible. Venus has... issues. Even if you stripped the atmosphere off it, the planet's rotation is pretty extreme, and it is probably too far inside the inner edge of the sun's habitable zone to be made permanently habitable. It'd require constant management not to have it go runaway greenhouse again. $\endgroup$ Feb 13, 2019 at 17:48
  • $\begingroup$ If I remember correctly you could build a big solar shade to cool off Venus. Plus cover the other side with solar panels. Now the constant management isn't a issue gives me an excuse to build massive coolant towers and employe people. $\endgroup$ Feb 13, 2019 at 18:59

Let's define the core goals of terraforming:

1) HABITABLE -- An atmosphere of appropriate chemical composition and temperature for humans to live in it unassisted.

2) STABLE -- A biosphere containing a self-perpetuating life & food webs that act to maintain the habitability of the planet. Barring extreme scenarios we expect a mixed soil-ocean-atmosphere system that generates human food.

The tasks required to do this depend on your starting environment. More tasks = longer terraforming time.

  • Do we need to actively engineer the radiative properties of the atmosphere to control temperature?
  • Does the atmosphere need gases added? Removed?
  • Do we need to add/remove liquid water?
  • Do we need to create viable soil for macroscale plants to grow in?

These tasks can all, theoretically, be performed by engineered organisms that act to move chemical elements between planetary reservoirs --- your Hygiea. The speed at which it can be done depends on how much modification is needed and how accessible the right chemical elements are.

At a minimum, you need to allow a microbe/plant enough time to grow across the planet and process enough material to move GIGATONNES of the right element to where you want it to be. Probably followed by another wave of GM organisms to make the next adjustment. Eventually leading to trying to create a full, stable foodweb on this new world.

I would honestly expect it to take decades for any individual organism to grow across a planet (even if aggressively seeded across the world via spaceship) and appreciably adjust its atmospheric composition.

If conditions are "hard", like freezing cold or processing shitty soil into better soil, then it will take longer.

Assuming no systematic failures or ecosystem collapses (which seem quite likely -- disease could easily affect a planet-wide monoculture of near genetically identical plants) I'd peg this as a 100 year process at a minimum. Longer if the planet doesn't start off pretty habitable to begin with.

Prototyping this story idea, I'd consider having a probe that can be sent to promising candidate worlds ahead of a human presence. The probe contains remote sensors, an AI and vats of GM microbes/plants (plus some limited capability to gene-edit these on the the fly). The probe can scan the atmosphere from orbit and then plan a suitable series of terraforming steps (eg. add 5 Gt of radiative blocker molecule X to atmosphere via organism Y, Kill organism Y via disease vector Z; allow 5 years for temperature to adjust, introduce organisms A,B to liberate oxygen and nitrogen from rock deposits; etc...).

This automated process takes many decades, but creates a passable human environment for low investment prior to any humans arriving.


In practice - if you want to wait for less than millions of years, fast growing organisms are likely the only practical solution. It is unlikely that an existing organism is optimal for any of the steps I suggest below, so almost certainly the organisms would need to be extensively engineered. Alternatives, such as big mechanical factories pumping out O2 doesn't seem at all realistic.

First though, I think it is worth commenting that any conceivable terraforming process is likely to take many millennia to produce a livable stable atmosphere/climate. But with that niggle over, I think that an efficient solution may be a multi-step process. The exact process would obviously depend on the starting point environment, but as an example, take something a bit like a possible primordial earth: N2, CO2, a bit of NH3 and CH4 and H2O, but no free O2. Assume that most of the H2O is vapour as all that CO2 produces a moderate greenhouse effect.

Step1: Seed with single cell organisms that mop up the ammonia and methane, and breath CO2. The atmosphere may be fairly opaque so photosynthesis is not necessarily an op-tion - organisms might 'eat' sulphur or use some other novel metabolism. Design them so that when they die a significant part of the CO2 they have respired remains 'fixed'. For example, they produce a carbonate shell, or just coat the ground with a growing peat-like carbon sink. Because there is no competition in the environment, these organisms will multiply to form a significant biomass only limited by available space. After a long time...CO2 is significantly down and the planet cols sufficiently for precipitation to occur.

Step 2: Probably more CO2 breathers but now aquatic ones. Potentially more efficient and easier to sequester carbon in deep oceans. Much more time passes....

Step 3: Add robust O2 producers. The atmosphere shifts from reducing to oxidizing, so there will be enormous changes in rock weathering, mineral deposition etc. Hopefully the air is clear enough now for photosynthesis of some form to be the main mechanism for organism growth. More time passes...

Step 4: Now sufficient O2, but may need to add/subtract various organisms to ensure that you don't go too far either way in green-house effect. There may be periods of high temperature and/or a snow-ball earth effect that you have to manage by careful injection of organisms that raise or lower green-house gasses or alter the albedo of the planet. This won't be just a simple formulaic solution - active management will be required.

Step 5: You now have a planet with a limited number of single cell organisms that is not too hot or cold, surface erosion has more or less stabilised, and you have an at least approximately breathable atmosphere. In a number of planned steps, start introducing macro-plants and the first animals (initially microscopic). This will need very active management as any imbalance could produce a plague of frogs effect or an unwanted extinction.

Step 6: Now you can possibly introduce you colonizing community. The environment is still probably miserable to live in - too hot/too dry/too cold/too wet/hurricanes on a weekly basis/too much UV/everyobe eats tofu 'cos that's all we can grow/but the settlers' great great great.......grand-children might have a comfortable life in a few more millennia - if you can maintain and slowly improve the necessarily knife-edge balance in the environment


What you would have is a series of life forms for each stage and once the planet hit a milestone, you'd release the next batch of lifeforms. The speed is actually in you seeding the entire planet so it doesn't need to spread and the plants and animals already existing so not needing to evolve.

Most of these lifeforms already exist and might only need some minor DNA tweaking to increase survivability.

You'd start off with simple lichen and algae to build biomass and start building the correct atmosphere. Next is grasses and seaweeds. You'd then bring in insects and simple sea life to eat said plantlife and make biomass. Then things to eat those things and so on. Seeding in plants with matching animals.

Your terraforming ship would be a giant ark of plants and animals ready to be seeded across the new planet.

You're still going to take centuries to finish the job but that's nothing considered the Earth took billions of years to do the same.

It might only take decades to get the planet to the level a human could walk across the surface without a spacesuit on but still centuries for a new Earth like planet

  • $\begingroup$ The time constraints as perfect! Although I'm thinking you might be able to speed up the evolution of the later stages by some sort of bioengineering. $\endgroup$ Feb 14, 2019 at 4:34
  • $\begingroup$ Actually you'd engineer the earlier stages for the speed. Lichen grows pretty slow. You'd engineer growth speed and a failsafe into it so it dies once the oxygen levels get high enough $\endgroup$
    – Thorne
    Feb 14, 2019 at 4:46

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