How long would it take to terraform a lifeless but somewhat earthlike planet using bacteria, fungus, seeds and eggs?

Question

What are realistic time-schedule expectations for far-future terraforming and developing earth-like plant and animal/fish/bird populations on distant planets, by means of robotic space probes with "seed" technology such as bacteria that converts atmosphere, seeds, bionegineered eggs, etc.?

The idea is that robot probes would be sent to distant star systems with equipment to analyze local planets and asteroids, set up automated production of bacteria and/or fungus to drop onto the best planets, designed to be able to survive and convert local materials into a biosphere, and later to drop other bacteria, fungus, then seeds and eventually eggs for insects, fish, birds, and even animals.

The question is, assuming it's conceivably possible to develop this technology given enough time and resources, how long might it take to advance a lifeless alien planet with otherwise earth-like properties (i.e. .7 to 1.5 earth mass, some existing atmosphere, magnetic field, not utterly frozen nor too hot) to the next stages such as:

1. Atmosphere that can support more than bacterial life. This would obviously be highly-dependent on the starting atmosphere and materials available, but in general, how fast might this be doable by dropping purposely-chosen bacteria onto a planet?
2. Some earth plants/insects can survive somewhere on the planet.
3. Some earth fish/animals can survive somewhere on the planet.
4. Most earth animals/humans can survive on the planet.

For each level, would it take decades? Centuries? Millennia?

Background information:

• Time/setting: Up to 20,000 years in the future, following optimistic peaceful resolution of current self-destructive stupidity on Earth.
• Technology: Realistic extrapolations of modern science. There may or may not be FTL technology, but it is limited - distances are still an issue and it requires significant time and resources to travel to other star systems.
• Space program: Space stations with large permanent human populations, "domed" planetary colonies, and various space industries have been developed. Some colonization of other star systems has occurred.

Related idea from an answer by Black to a question about terraforming:

It would be nice to have biomass on a planet before you got there. As well as any target byproducts you might engineer them to make. I'd add that Deinococcus radiodurans can survive anywhere you can't engineer other bacteria to. So you're pretty much guaranteed to be able to just launch a can across the universe at any planet, even if you can't quite fly to it yet. If your lucky the locals may have evolved before you got there and be able to contribute to science with their "un-poisoned" paradigms. (Panspermia anyone?)

Answer 1

Cort said: it took us 3.5 billion years to go from single-celled creatures to land plants. That would be the upper bound on this process.

Which is not precisely true. It is one upper-bound on evolving a solution. ie: one data point. It may take a lot longer than that if you want to evolve solutions; perhaps Earth is on the fastest of all possible evolutionary paths.

Anyways, the point is: you're not evolving anything. You're taking already evolved solutions, and selectively inserting them.

Dronz said: with imported/engineered microbes pre-developed on Earth, might be much faster than what evolved naturally out of the primordial ooze.

Precisely.

You're probably going to want to start with some monitoring. Did the planet you select already have life? You'd said you wouldn't know what you've got until you get there - it might be considered a hostile act to come in with an automated probe and try converting someone else's planet :) Besides the ethical considerations of eliminating life that's evolving itself (depends on your society's ethical constraints).

You'd probably want at least a decade to see what types of climate variations you're going to get from orbital perturbations, as well as a study of the star - some of the star's output can be analyzed from afar, but some may need in system analysis. This may determine what life you want to seed to moderate effects that exist in your system. You might be able to skip this, and play catch-up when you get surprised by events. But that will lead to increased failure rates.

I'd give it a century of study, if you've got time to burn.

The biggest thing, besides being in the habitable zone, having roughly Earth-like mass, and a carbon-dioxide atmosphere, is having enough liquid water.

Liquid water is going to get you a chance to get your autotrophs and cyanobacteria started. Which will start getting you organics from inorganics and an oxygen-based atmosphere. Once you got those started, introducing something with chloroplasts (algae most likely) is going to be the big thing - you want your Great Oxygenation Event to happen ASAP. Time-scale on that is unknown, and may depend on conditions. But you're going to want your autotrophs to have had some time to work. How many are you seeding initially? Are you setting up reactors to make tons of them in orbit? Or just injecting a nanoliter (microliter?, milliliter?, liter?) worth of them in selected spots (how many spots?).

Turning over your atmosphere into the ocean to get the CO2 out and O2 in, is going to be a thing. It's a pretty complex field of study. One key driver is do you have polar ice caps (or, can you make them?)? That drives thermohaline circulation, and will take a ton of CO2 into the ocean (although with a primarily CO2 atmosphere, the ocean may already be saturated...). Iron is a limiting nutrient, and if you've got the tech, pulverizing nickel-iron asteroids and drifting the dust down on the oceans (or dispersing from flyers) may greatly speed up your algae/oxygen production.

http://benmatthews.eu/benphd/chap1.html For a lot of info on Earth's exchange, ie: not exactly what we're talking about - but we do 92 GtC in and 90 GtC out in our oceans.

Once you've got the ocean / atmosphere work started, you're going to want to start on the land-mass. Cyanolichens and lichens are what you want to start breaking down rock to get soil, and to put the organics into your starter level soil. You can be dumping these on any rocks. No dams necessary. In fact, without plants respiring, you may not have a lot of freshwater to be working with, once you get inland.

At phases in here, you're going to have to choose some types of lifeforms to manage cloud seeding / cloud-cover and albedo. You're going to need some satellite coverage and computer monitoring to figure this out. This is going to require some pretty robust computer programming, or a human that's in and out of stasis once a year/decade. I'm assuming you're not sending humans, since the cheapest way to do this is to send something the size of a football with DNA codes a fabricator, and some expandable vats (it'll collect shielding in-system, to protect from flares/gamma rays).

This is about as far as you can (easily) go with a football. Your probe would have to be able to vastly expand itself in order to make tons of seed, and/or animal life. You might be able to store some insect life, and micro-shrimp / fish eggs - but you're probably looking at something more the size of a room - and you could easily fail the insects and fish if you are carrying too few eggs. Your first set(s) may be put down too early, and all fail because of not enough supporting substrate. Any time you drop eggs, expect to lose some of the drops because of errors / bad placement. You can take plant seeds with you, but like the animals, you'll have a tough time taking enough to make a big dent soon. Best bet is to set up an automated farm in orbit and harvest seed. This is going to make your probe a lot more complex.

Anyways, once you get some organics in the soil, then you're going to want to go with some plants. A lot of seeds, and little return to start with. You'll want stuff that handles aridity and low-to-no soil. Once you've given that some time to work, and maybe get a freshwater cycle setup, then you can think about insects and other stuff.

You can probably have seeded the ocean with fishes prior to this.

If you've got fishes, you can move rapidly up to birds and mammals which hunt fishes, and some herbivores. Landing those from orbit is going to be a trick. A lot of the other stuff can be dropped with a heat-shield / cooling apparatus and a micro-chute, and let it bounce. A mammal or a bird, not so much. Training your bird to fly in orbit... also tricky. You're not going to drop bird eggs, unless you're also dropping incubators. You may need robot mothers to teach some skills.

Scifi: The Forgotten Planet is a story of terraforming gone awry.

Answer 2

It is very much a function of the state of the planet on arrival, how ample a power supply you have to start and the degree to which your robots are capable of advanced nanotechnology. I'll assume you have both water-based oceans in your world and artificial controlled nanotech, it'd be a rather hopeless endeavor without (relying on biological nanotech, aka microbes, would take hundreds of thousands to millions of years).

1. State of the planet.

   • Atmosphere: The mass of a Venusian atmosphere is about $5\times10^{20}kg$, while Earth's is around a hundred times lighter at $5\times10^{18}kg$, and Mars' is about 200 times lighter than that at $2.5\times10^{16}kg$. If you want unadapted humans to live on the surface you may need to flare out or to bring in substantial amounts of volatiles. Needless to say, flaring out is hard, and enriching depends on how much volatiles you can find in the local asteroid belts and outer (Oort-style) frozen outskirts. Obviously, either would require a massive industrial enterprise orders of magnitude higher than anything mankind has done up to now. For comparison, 150 years of industrial activities have changed Earth's atmosphere by altering the ratios of gases to the order of perhaps 200 parts per million, aka "trace amounts." And that's with our industry burning oil and coal literally as fast as we can get it out of the earth. Depending on the initial composition, you'd literally need a process literally 10,000 times more intensive than Earth's current combined industrial activity.

   • Soil. Let's assume a similar land area of ~$100,000,000 km^2$, and that we need to process a 10 meter layer (although runoff into the ocean would realistically be a problem). At $10^{15}m^3 \times 2\times10^3kg/m^3$, that's about the same amount of mass at the atmosphere.

   • Life. With sufficiently advanced nanotech, life forms can be manufactured and seeded into the soil as part of the regular soil processing. However, the process will likely be rather, um, energetic, and thus more likely to leave an organic ash behind rather than the kind of soil we're used to. Perhaps a second set of processor can follow the first wave and use giant vats of bacterial and viral soup to seed the soil in their wake. Life is about 10^12 kg, so many orders of magnitude less. Delicate second wave nanobot constructors will do.

2. Power supply.

   • Obviously, if Humanity's footprint on our own atmosphere over a century amounts to trace amount modification, the process might seem a tad daunting. Fear not, the power of exponential growth will ride to the rescue. Over the past century, the cilivizations at the edge of the technological boom (i.e not playing catchup and simply copying preexisting tech) have grown at around 2-5% per year.
   • Let's assume you want to pull this off in a century or two. If we take the 4% as median and extrapolate out (assuming no dark ages in the future, it is a conservative assumption, given probable orders of magnitude increases given currently imaginable AGI and nanotech molecular-time manufacturing capacities), we get (post-?)humanity to output roughly the production amount needed to pull this off in a few centuries in, um, about 2.5 centuries from today.
   • Of course, Humanity being what it is, it is unlikely that we'll get to the point where a full year's worth of production can be invested into manufacturing probes and supplies for colonizing a new world. We'll be busy fighting each other, turning planets into paperclips, drilling into Heaven, whatever. Let's bring it down a notch or two. The Apollo missions were a significant expense, and when they were launched, they output so much energy that it amounted to about 2 seconds' worth of Humanity's entire energy output that year. So, if we keep assuming 4% exponential growth, humanity's output will be high enough for a terraforming to be equivalent to the Apollo program in about 700 year, circa 2,700 AD (or 750 Epoch time)

That said, planets, with their deep gravity wells are far from optimal real estate for a space faring civilization. Mining asteroids and harvesting volatile from the satellites of gas giants seems a lot easier in terms of the energy-in energy out ratio.

Answer 3

The answer is very dependent on how Earth-like the planet is. Evolution works at evolution's pace, so if the bacteria and fungi need to adapt, they may need a few million or billion years.

Let's assume you find Earth 2.0 (Like in Hithchiker's Guide to the Galaxy), so no evolution is needed, just the mere act of bacteria and fungi "doing their thing."

The first hard thing is going to be balance. At every step of the way, you are going to need to balance the ecosystem. A completely empty world is going to reward the most aggressively multiplying organisms. Our modern ecosystem is very dependent on this balance: life will survive once you seed it, but it may be hard to introduce higher life like plants and humans if the balance is substantially different.

Your goal would be to critically damp all multiplication, a differential equations term which seeks to achieve stability in the shortest time constants. You would have to constantly seed different organisms to "favor" one over another in a short run to yield balance in the long run.

Once there is soil, we have documented evidence of low long it takes: centuries. Modern naturalism has found that a forest can reboot itself after a massive fire within a few linfetimes. There is a well understood process for it: grasses come first, then ferns, then short trees, then tall trees. This part of nature is amazingly robust!

However, it needs soil. Your Earth will be a mass of sand and rock. This is not an easy landscape. No nitrogen fixing bacteria or anything. Massive erosion issues. Depending on the landscape, you may need a long time to fix this: it took us 3.5 billion years to go from single-celled creatures to land plants. That would be the upper bound on this process.

Now, to give you a time-domain that isn't horribly pessimistic like that (3.5billion years + 100 years!), I'd like to point out that your planet already has one complex creation on it:

Your robots

While you may not have "living" robots, they certainly can help seed life. If your robots seek to accomplish a fixed plan, written into their code before they were launched, they could seek to replicate on the surface of the planet, digging into the rocks to mine the reosurces they need.

Once you have a large volume of controlled power to wield, you can help the organisms along. You can do in minutes what takes centuries of erosion and bacterial activity to pulverize. You can construct artificial dams (like the straw ones we use to control drainage) to keep the soil where it needs to be until the organisms can lock it down themselves.

With this capability, you bring the task into the timeline of land-reclamation, a human-lead activity that is on the time period of decades or centuries.

Accordingly with an almost but not quite Von Neuman probe replicating to help the organisms along, it would take centuries to terraform a planet.

Interestingly enough, this blending of life and machine is not unique to this problem. Modern day Chess programs have finally reached the point where they crush every human player out there. A laptop is more than enough to beat a top-tier grandmaster. However, combined solutions: a human with a laptop, are so much stronger than either a computer or a human, that the combined forces are explicitly forbidden at almost every level of competition.

Answer 4

Given soil and an earthlike planet to start, some things would be more rapid. If you have to break rocks to get the soil, then you need things to break rocks, and that takes as long as it takes. You could likely start with a small area and a dome, then expand it from there. Best would probably be to have a sleeper colony with a few people awake from time to time to keep things on track, and just let the machines work. You should be able to gather materials from the planet to keep things going while you're making soil, and spreading things from there. From one spot would take quite a while, but multiple spots..?
To limit moral quandaries, let's assume no native life exists here. Factories could exist to simply make air until the plants get themselves to that point. Balancing things shouldn't take that long, given that we have an example of a system that works already. Some tweaking to keep up with random mutations and the new planet's paradigm would certainly be necessary, but not an impassible ( :) ) problem.
Once a spot is cleared for living, things would progress a bit more rapidly, as there would be people to assist and push things along. Not just the once-a-year nudges, but actual innovation. What that would do to any social structure existing could be interesting, too.
I don't think it would take that long to get to 'inhabitable' status, but it depends on a lot of givens: Soil, atmosphere, gravity, temperature, radiations, etc. Adjustments to all of these would be important, and could easily change the nature of the planet/story/game/etc. Going to science fiction here, a type of radiation that makes it easier for plants to grow, but hinders/changes the development of animals, insects, etc. would cut down on the time needed, and change the balance for itself.
Thank you to everyone who answered.

Answer 5

Probably in the order of a billion years, but possibly tens of millions

The problem you have is that there are massive inorganic sinks that will absorb oxygen before you can produce a stable, life-friendly, planet. On Earth, Oxygen production proceeded for somewhere around 1.6 billion years before the atmospheric Oxygen rose to habitable levels (see the Great Oxygenation Event), and this scale of time is likely to be required for your planet.

It is possible that this could be dramatically shortened by adopting genetic engineering methods, providing nutrient sources, and carefully selecting the strains of bacteria used but I find it unlikely that you could produce oxygen fast enough to produce habitable conditions faster than the tens of millions.

Terrestrial plants will make oxygen, but they are unable to survive in an atmosphere without oxygen so could not be deployed until late in the process, so you would be reliant on bacteria. To get faster results you would need to adopt heavy industrial processes, not rely on simply seeding with organic life.