Discussions of the ethics of terraforming often touch on  rights of planets or extraterrestrial lifeforms, or near term utilitarian values. But what about our responsibilities to terraformed worlds, and their long term future? I suggest that we are nowhere near mature enough as a civilization to be responsible parents to a newly terraformed world with a gestation period of millennia and an "adult life" of hundreds of millions of years. Though we could be reasonable parents to Moon city domes or Stanford Torus type habitats and the like.

Mars is the planet most people think about when it comes to terraforming, but these issues apply generally to any planets, dwarf planets or moons. And our responsibilities extend, I think, to unterraformed planets as well. I'm going to start with those first, then move on to our responsibilities for terraformed or partially terraformed planets.

First of all, if there is life there, even if just microbes, we could learn a huge amount from them if they evolved differently from Earth life. Even more so if they have a different biochemistry or details of how they work internally differ. I've talked about that before, see my Will We Meet ET Microbes On Mars? Why We Should Care Deeply About Them - Like Tigers

It's easy to see that we may have some responsibilities towards a planet with extraterrestrial microbes on it. We would become like adoptive parents of the planet and all the lifeforms on it. But what's not so easy to see, perhaps, are our responsibilities to a planet without life.


A planet might have something in between life and non life such as autopoetic cells (metabolism but no exact replication) or an RNA world (exact replication but no metabolism or anything resembling a living cell), or something that imperfectly reproduces.

Diagram of an autopoetic cell, from "Chemical Approaches to Synthetic Biology: From Vesicles Self-Reproduction to Semi-Synthetic Minimal Cells" There, L is the cell boundary, lipids in case of Earth life. P and Q are the basic ingredients of cell growth and W, Z the waste materials. E is the genetic and metabolic network, which converts the ingredients into the cell wall as well as the internal components of the cell creating waste products that leave the cell.

An autopoetic cell is not alive, but it has a metabolism, can also reproduce when daughter vesicles inside escape, and has many of the properties of life. Some scientists think life may have started as autopoetic cells. If so, if life hasn't evolved on Mars, it may still have got as far as autopoetic cells. Or as far as various other precursors to life that have been suggested. These could be especially vulnerable to contamination by Earth life.

See also my "Super Positive" Outcomes For Search For Life In Hidden Extra Terrestrial Oceans Of Europa And Enceladus


For that matter it is not clear how to define life anyway. Viruses reproduce but in other respects don't count as life. Crystals also "reproduce" after a fashion.

This is how NASA attempts to define it:

"Living things tend to be complex and highly organized. They have the ability to take in energy from the environment and transform it for growth and reproduction. Organisms tend toward homeostasis: an equilibrium of parameters that define their internal environment. Living creatures respond, and their stimulation fosters a reaction-like motion, recoil, and in advanced forms, learning. Life is reproductive, as some kind of copying is needed for evolution to take hold through a population's mutation and natural selection. To grow and develop, living creatures need foremost to be consumers, since growth includes changing biomass, creating new individuals, and the shedding of waste."

Life's Working Definition: Does It Work?

What we find there could push the boundaries of what we count as life. It might "almost" satisfy some of those conditions and not others.

Perhaps forms of "almost life" can't reproduce, or only imperfectly but have some of the other characteristics of what we count as life here on Earth.

I'd like to suggest, any new thing which is like life but not quite is also of great interest, and we should preserve these "almost life" forms or conditions just as we do life, until we know more about them.

So, there's lots more to consider than whether it has life or not.

These in-between forms of life, if they exist may be especially vulnerable to being, e.g. eaten by Earth life or even just seeded by a fragment of DNA or a dead cell that might trigger them into a new step so we can't study them as the were before our introduction of even dead Earth life.

So, we have responsibilities towards them, like adoptive parents have responsibilities towards any children they adopt - to make sure Earth life doesn't just gobble them up or transform them. You could say we have that responsibility irrespective of whether they are of value to humans. But in any case, for purely pragmatic reasons, we have that responsibility because of their value to future humans, and perhaps also even to future beings that may evolve long after we are extinct, millions of years into the future.


Then, if it has conditions for life but doesn't have life - or had it in the past but no longer has it, then a big question is, why doesn't it have life now? Terraform it and you can no longer look into that, especially not study how a planet works without life on it. This is something we may have the opportunity to do now, on Mars if it is uninhabited. We'd deny that opportunity to all future generations.

Then apart from that, even if it is of no scientific interest at all, or you have a hundred copies and can afford to set one aside for experimental terraforming (that's not true of Mars but could be for Kuiper belt dwarf planet sub surface oceans for instance in the future) the problem is that terraforming is irreversible.

Especially once you introduce life, you can't undo that, no matter what, not on something as big as a planet or dwarf planet or large habitable or semi-habitable moon.


Then just to mention it, there may well be interesting natural processes. For instance on Mars the Martian geysers may be unique to Mars. If we warm up the planet we can no longer study this possibly unique natural phenomenon.

Artist's impressions of Geysers on Mars - so far we haven't been able to study them on the surface but evidence from orbit suggests that every spring in polar regions, dry ice below the surface turns into carbon dioxide gas as it warms up, causing these spectacular geysers. We see the dust and debris they spread across the surface from orbit.

Higher res image - image details (see bottom of page) with even higher resolution image.

If we warm up Mars, then it will no longer have these geysers, which as far as we know are unique to Mars.


Then - what if successful terraforming requires introducing life forms in some particular sequence? Or some way to prepare the planet first that doesn't involve life before you introduce the very first lifeform to it?

Or what if our attempt to terraform it produces some problematical species - one that evolves out of whatever you seed it with. Microbes can evolve quickly because of their short generation times. Or what if it is introduced by mistake? We are nowhere near to having the capability to list all the microbe species present even in spacecraft assembly clean rooms. Most microbial life on Earth is not only unsequenced, but not cultivable and not been classified. It's thought that there are even entire genera, as different from each other as plants are from animals, not yet discovered. This is the problem of "Microbial dark matter" ( Mining the microbial dark matter - Nature )

Or what if you introduce a microbe or creature which you don't even realize is going to be problematical, like the way humans deliberately introduced rabbits to Australia? What are the microbial equivalent of rabbits that may be harmful for terraforming?


And an attempted terraforming may lead the planet into an end state that is undesirable in many ways. What if you intend an oxygen rich atmosphere but it instead trends towards an atmosphere rich in methane or hydrogen sulfide, say, and you can't stop it?

When we can't even adjust the CO2 content of our atmosphere and required decades of large scale production of CO2 world wide to raise it by 0.01%, we are not going to be able to "fix" an atmosphere that goes wrong. Or a biosphere that goes in an unexpected direction.

Mars: White, Red, Purple, Green, Blue, Black, Or None Of The Above

From my Imagined Colours Of Future Mars - What Happens If We Treat A Planet As A Giant Petri Dish?
These images are meant as visual coat pegs to attach the discussion to. I don't claim that they show scientifically accurate simulations of the visual appearances of possible future Mars.


And you need a world that can go into your desired end state. In our solar system, only Earth is in a suitable orbit to support a terrestrial biosphere without megatechnology such as artificial greenhouse gases or planet scale mirrors or shades.

The "blanket" of our atmosphere is not warm enough for Mars and is too warm for Venus even if we could somehow set Venus rotating and compensate for Mars' lower gravity, lack of continental drift and lack of magnetic field.

Photograph of the Earth's atmosphere - taken from Space Shuttle Columbia on its final mission in 2003 - this ia a poignant photograph as they all died on re-entry.

Our atmosphere is just right for our world, keeps it at a temperature ideal for us. But the same "blanket" would be too warm for Venus and not warm enough for Mars.

If we made Venus and Mars into clones of present day Earth but left them in their different orbits, only Earth would survive for any length of time.

Venus would soon go into a similar state to the one it is in now. All its oceans would boil away in a runaway greenhouse effect. This fate will happen to Earth also about half a billion years from now - unless we use mega technology such as artificial shades orbiting Earth to cut the sunlight.

For Mars, the oceans would all freeze over and trees wouldn't be able to grow even at the equator. It's somewhat mysterious how it kept its oceans liquid in the early solar system. Perhaps it did this through greenhouse gases such as methane in its atmosphere. CO2 would not be strong enough as a greenhouse gas to do this by itself.


And you need an "end game". If your biosphere works, but you get it working only after much effort and mega-engineering after, say, 100,000 years - have you set it up in such a way that it can continue maintenance free for say half a billion years? Or only for another 100,000 years (say). Will it just "unterraform" as rapidly as it was terraformed?

(That 100,000 years is one estimate for the time to get Mars to an oxygen rich atmosphere - this is with ongoing engineering using greenhouse gases mining of order one cubic kilometer of fluorite rock per decade for all future time to keep it warm. Or it could be planet sized areas of thin film mirrors to double the solar radiation)

Those future beings are separated from us only by time.

If you terraform a planet, I'd say you have similar responsibilities to parents with newborn babies.

It is not enough to be able to give birth to a brand new terraformed planet - if that is possible at all.

You also have to be able to bring it to maturity and then continue to support it through adulthood or at least make sure you have set it off in a direction where it can support itself through its future.

Being a twin means you always have a pillow or blanket handy

A newly terraformed planet - if it is possible for us at all - is like a baby. We still have responsibilities to our babies after their mother gives birth.

In my view anyway, we must not terraform a planet until we know how to give birth successfully (we are nowhere near to knowing enough for confidence there).

Then we have to be able to act as responsible parents. Which for planets involves a multi million year future.

I don't know if we will ever be ready for this, but I'd be surprised if it happens in the next century say, unless through external assistance such as contact with ETIs. (Extra Terrestrial Intelligences).

I don't think a responsible ETI would permit us as adoptive parents of a brand new terraformed planet. Probably the first question would be "Will your civilization continue for at least a million years into the future?"

So far we find it hard to sustain a mega technology project even for several decades. We can do it sometimes, as with the ISS. But it is hard in the US to sustain the same direction in space exploration through multiple presidencies even.

The idea of embarking on a project that requires megatechnology, and advanced supervision, billions of dollars commitment per year, and a high level of competence and understanding for even several centuries, never mind 100,000 years seems absurd. And that is just the stage of giving birth. To stop after 100,000 years would be like parents abandoning new born children thinking they have done all that is needed to be done. There may be nobody else around to adopt the new-born planet.


I think we need to first find out how to make closed system Stanford Torus type habitats. That is a multi decade project perhaps, but within our capability. With earlier experiments first of course with smaller habs, for instance to make a space station similar in size to the ISS which is able to grow all its own food and recycle its oxygen.

Video fly through of a Stanford Torus style space habitat by Uzi Bento

This may seem a mega technology project rather beyond what we can do at present. But the Stanford study suggested it was feasible even with 1970s technology. This is something we could complete in decades. Long before we are anywhere near the capability to terraform a planet, we may be able to create Stanford Torus type habitats in space.

The atmosphere inside can be adjusted in hours if something goes wrong. Problematical gases and microbes removed. Light levels adjusted, even the amount of gravity changed. If the worst comes to worse, we can evacuate the air, sterilize the soil, and start again. And the whole thing can be completed in decades - it doesn't require a commitment to mega technology continuing year in, year out, for thousands of years.

For more on this see my Asteroid Resources Could Create Space Habs For Trillions; Land Area Of A Thousand Earths

I think we could already, in near future, be responsible parents of a Stanford Torus type habitat. After all, if worst comes to worse, we can evacuate everybody back to Earth.

Later on we could try larger scale projects. But I can't see us having the knowledge to tackle terraforming in a responsible way soon, probably not this century at least. That is, apart from some huge leap forward such as being contacted by ETIs that have done it before, or absolutely enormous leaps forward in understanding of biology, biospheres, exoplanets (probably), closed systems and probably many topics we don't even realize we need to master yet.

Though thinking about it is something we can do. It does no harm to work on it theoretically. Or write and read sci. fi. stories so long as we realize they are imaginative explorings of possibilities, rather than accurate foretelling of the future.

All this can help in many ways including greater appreciation of our planet which is already "terraformed" for us, and to help with healing it.


Sometimes enthusiasts suggest we should bash ahead and do it as an experiment. But we don't have hundreds of copies of Mars to terraform after our first experiment turns up flaws in our methods. And as well as that, an experiment needs a context, a hypothesis to test, a control, etc.

It's not an experiment for instance to just throw some mud into a pond or jump into a swimming pool and try to splash onlookers :).That's just "mucking about" and you may not learn much from it.

This is not an experiment, it is just playful "mucking around" :). Ideas to just add a bunch of lifeforms to Mars are about as scientific as jumping into a swimming pool to see what happens.

To be an experiment it needs to follow carefully thought out following protocols and with a hypothesis and objective and rationale for the experiment.

And experiments have to follow ethical guidelines and don't get you out of the need for ethical considerations.


If we just randomly add microbes and hope for the best, or even if we terraform carefully, to best of our knowledge, but can't keep it up for thousands of years, or we make a mistake, it's like letting our newly remade planet drift out to sea like this:

We shouldn't terraform a planet, in my view until we can bring it up properly through childhood, then we may get a happy baby terraformed planet like this:

A baby girl in India

and then we need to continue to support it to adulthood until we are able to leave it to fend for itself.

We can't do this until we have a civilization that we know will be stable for at least a hundred thousand years and probably much longer, of the order of millions of years.


Instead, we should start with Stanford torus type habitats, also city domes on the Moon, or anything like that, and before that, ISS sized habitats and spacecraft making all their own oxygen and food.

There we can experiment in a meaningful way, since we can control the parameters, and indeed, start again.

We can adjust the atmosphere in hours, remove or reduce levels of problematic microbes and other lifeforms, purge problematical gases like methane, hydrogen sulfide etc, increase or decrease CO2 levels, introduce emergency oxygen if needed, and tweak the amount of solar radiation just by using shades or mirrors.

We can even vary the amount of gravity in a rotating habitat.

If it comes to it we can purge the air, sterilize the habitat and start again.

We can never do any of that with a planet. At least not with current technology.

See also my science blog posts (most also available now as kindle booklets):

This originated as my answer to a question on Quora - Is it ethical to terraform planets?