# How would we choose which species to populate Mars with?

As has been shown many times, once a species "escapes" into an environment, there's no reeling it in. So choosing the right species to terraform Mars is incredibly important.

How would we choose the mix of class/order/family?
Do we chose just one of each class/order/family?
Which bacteria do we chose?
Is there a "first wave" of species that quickly get the biological ball rolling, then a second wave to make it all "work" nicely?
What about genetically modified species?
How restrictive should/can we be?

I realise this is quite broad - if you feel so, please feel free to narrow it.

• How will we terraform? Nukes? Asteroids? – Mormacil Mar 21 '17 at 22:46
• @Mormacil by releasing stuff that can survive and which makes a positive change, etc – Bohemian Mar 21 '17 at 23:00
• Creating oxygen that way will be to slow with the lack of a stronger magnetic field to keep it trapped. It will simply fly away as fast as you can make it. You need to kickstart the process somehow. – Mormacil Mar 21 '17 at 23:34
• @Mormacil I challenge your statement that Mars' atmosphere will fly away as fast as you can make it. In fact, I assert that Mars will lose atmosphere at 100 tons per year. Do you have any evidence to the contrary? – kingledion Mar 22 '17 at 0:47
• @userLTK sure, but mars might look a whole lot better after a cataclysmic asteroid impact with Earth. Hope for the best, but plan for the worst – Bohemian Mar 22 '17 at 3:38

## 5 Answers

Red Mars (and its followups, Green Mars and Blue Mars) is the best treatment in fiction I know of regarding the terraforming of Mars.

Your objectives for terraforming are primarily to generate an atmosphere. to introduce something that will start making oxygen, while being able to handle the cold and dry and radiation. Both Red Mars and other authorities suggest that lichens are the way to go, and could be adapted to Mars' hostile environment in short order. Lichens should be distributed widely over the planet, where they will start he process of both generating oxygen.

The next priority, is some type of decomposer to start turning the dead bits of lichen into usable soil. This would be some combination of fungus and bacteria.

After that, you have to wait until conditions get better. This would take forever by its own; you would probably want to hit the planet with a few comets full of useful volatiles like carbon dioxide (to help the plants, provide pressure, and cause a greenhouse effect), water (also important for the greenhouse effect) and nitrogen compounds (to start a nitrogen cycle). Eventually, the combination of heat from impacts and greenhouse effect will start melting the water and carbon dioxide ice caps.

Once the planet has some more water, nitrogen, and atmospheric pressure, things would be improved. Vascular plants could survive once carbon dioxide partial pressure gets high enough and water is available. Plants with deep roots, particularly trees, will be important to extract useful minerals from deep in the soil and add them to the available bio-cycles. They will be much more efficient oxygen generators than lichen. Also, if enough liquid water can form lakes or oceans, then various plankton will also contribute a lot of oxygen.

That's the moral of the story. I don't see any reason to introduce plants to the planet that aren't wheat, and animals that aren't cows. Why go through all the effort to remake the planet, if you don't remake it for us?

Edit for :

According to Kass and Yung, 1995, solar wind induced sputtering on Mars could potentially remove 2.4e24 molecules of CO$_2$ and 8.6e25 molecules of H$_2$0 per second. This amounts of 6kg and 93kg per second, respetively.

This may seem like a lot of materials, however, the Earth's atmosphere is 5.15e18 kg. The ratio Mars:Earth surface area is 0.53, so an Earth-like Martian atmosphere might have mass 1.46e18 kg. For this mass, the half-life at the above rates of sputtering are 500 million years for $H_20$, and 7.3 billion years for CO$_2$.

Of course, the Martian atmosphere will lose less mass as its density goes down. Instead of losing 6 kg of CO$_2$ a second, according to Edberg et al, 2010, quoting Barabash et al, 2009 (which I do not have access to), the actual loss rate in the Martian atmosphere is 0.01-1 kg per second, depending on solar conditions as discussed in their paper. But with a nice full atmosphere, the higher rates of sputtering losses would be observed.

The question then becomes, if the CO$_2$ half-life is 7.2 billion years, then how did Mars lose its atmosphere? This is the purpose of the Kass and Yang paper. The Sun's UV output was higher in the past, even as its overall luminosity was lower. According to their paper, 3.5 Gyr ago, the UV incidence on Mars was six times higher than present, and 2.5 Gyr ago, it was 3 times higher. At these higher UV exposures, the loss rate of CO$_2$ was about three and two orders of magnitude higher than current, respectively. The conclusion of their paper is that, integrated over 4.5 billion years, Mars has lost about 3 bar of CO$_2$.

However, for our purposes starting in the current day, that loss will not be repeated because the sun's ability to strip Mars' atmosphere is significantly reduced.

# Conclusion

If we added an atmosphere to Mars, it would take on the scale of billions of years for it to be removed. If we can add an atmosphere in thousands of years, there will be no problem retaining it.

• I love the Mars trilogy, but it ignores the fact that Mars cannot hold an atmosphere without the magnetosphere that it once had. :( – Mikey Mar 22 '17 at 8:06
• @Mikey This is a terrible comment. How does Venus have an atmosphere then? What about Titan? You should delete this comment, because it is wrong. – kingledion Mar 22 '17 at 11:57
• @kingledion Venus is larger than Mars, and Titan is further away from the sun, so it doesn't need a magnetosphere to protect it from solar rays. In addition, both Venus and Titan have active volcanic activity which continually pump heavy gases into the atmosphere. While Mars does have an atmosphere, it is much thinner than Earth's due to its low gravity and lack of magnetosphere, and even if we could convert its CO2 to oxygen, finding a way to make it thick enough to breathe is one of the main obstacles in terraforming. – IndigoFenix Mar 22 '17 at 13:36
• @IndigoFenix We are not talking about what Mars currently has. I don't need geological processes. I'm going to slam a few peta-tons of ices from comets into the planet. Nothing you said indicates that Mars would not be able to retain those vaporized ices. – kingledion Mar 22 '17 at 13:47
• @IndigoFenix See edit. The scientific evidence does not support your viewpoint. – kingledion Mar 22 '17 at 14:35

The main problem with escaping species on Earth is they tend to destroy the local ecosystem. When you're terraforming Mars you don't care about the local ecosystem.

Our first big issue is how are we colonizing? Are we slamming large icy bodies into the surface or do we work entirely with the ice we find on Mars? Do we have a thicker atmosphere or is that still being worked on? That would imply how much radiation resistance our species need.

Regardless I'm confident our species will be genetically tailored to living on Mars. The first plants will likely be very hardy. Evergreens, moss and algae. Our first fauna will probably be related to keeping those plants alive. Something like worms and moles for the soil.

As for what we choose specifically? Whatever is easiest to work with probably. Species A is a great fit the the genetic modification hits a snag? We probably take species B that works almost as well. Time is money after all.

Really this question is pretty dang broad. But likely the order will be like this:

• some bacteria
• some simple hardy plants
• some small creatures to support the plants
• insects in general
• bigger plants
• small animals like rabbits, ferrets and lizards
• etc.

Good answers from kingledion & Mormacil. I'd add that humans would be desperate to exclude a whole bunch of species from whatever ecosystems they create. We won't want anything which causes disease in us or our crops or our domestic animals, for instance. Or which we just consider to be a nuisance! So no malaria-carrying mosquitoes, for instance - partly because we don't want malaria, and partly because people just don't like getting itchy bites from mosquitoes, midges and the like.

So no poisonous snakes, biting insects, parasites, crop pests, garden pests, and so on. This will have all sorts of knock on effects. No midges and mosquitoes means no (or fewer) dragonflies, swifts, swallows and bats, since those all eat flying insects, and fewer lake fish, since those eat the mosquito larvae. No greenfly (aphids) means healthier plants but no ladybirds and none of those ants which 'milk' greenfly for honeydew.

Whatever ecosystems we build on Mars will be very species poor compared to Earth. The terraformed planet should be regarded as a giant garden or planetary scale greenhouse rather than as a natural biosphere. Mars may look like pockets of a tidier version of the modern British farming landscape, set in a largely animal-free steppe or forest.

Whether wild animals like deer, bison, wildebeest, wild horses and the like roam free will depend on the political clout of agribusiness versus the hunting lobby versus wildlife lovers. Farmers really don't like herds of deer and flocks of finches eating their crops and cutting into their profits. Big predators - lions, wolves, leopards - have a glamorous appeal, but also have a nasty habit of eating our goats and cows, and occasionally eating us. There may be a ban on introducing anything dangerous to 'the wild'.

All of these answers appear to be decent starts tot the question but even if we could fill out Mars' atmosphere with the necessary gasses (there are many means to do this, very few of which we have established technology to accomplish) the fact does not change that mars' magnetosphere is simply to weak to hold it all stable. Mar's core is completely or almost completely dormant and thus has a weak pull on the atmosphere it is trying to retain. Every time a solar wind comes by, it blasts some of the atmosphere away and some molecules just drift a little to far and float off. If we increased the density of the atmosphere all it would do would be to increase pressure which would make it easier for gasses to get pushed further away and drift out of Mar's reach. Also for clarification purposes from an early post- lichens are decomposers and one of their main purposes on mars would be to break down rocks and minerals into more usable forms in the soil for plants to use. That is why they are so important, not because they produce tons of oxygen on their own- though they would breath out some. Also as for the what species' would we bring question, a stable ecosystem does not exist between lichens, wheat, and cows alone. Cows need grass, and grass needs a whole host of soil fungi (mycorrhizal fungi) and symbiotic bacteria to gain anything from the soil, decomposers are also required to break down the dead grass and bones and such of cows. It is also important to note that mars is a planet. That means that is does not consist of one uniform ecosystem. I dont know about everyone else here but I am not aware of any cows farms on antarctica. And the grasses that grow in different climates are completely different and also degrade the soil in varying amounts. Other organisms are also pivotal to fixing nitrogen from the atmosphere and conducting pollination, cycling other nutrients, changing atmospheric composition etc. So in short, we would definitely need more than one or two organisms to form a stable ecosystem (a key word because it means literally the interactions between lifeforms). Insects help keep other bugs, plants etc. in check and you have to have different species of grass and the like in case a blight comes through and kills all of one type of grass- insects are necessary to make sure that certain types of those plants don't take over and kill off the others, and even animals are necessary to keep those bugs in check.

• I'm delighted with the effort you put into this response, but it doesn't answer the OP's question. It's primarily commentary on other answers and a small frame challenge. +1 for the wonderful effort. -1 for not answering the question (and for the wall-of-text, which is really hard to read). – JBH Apr 18 at 19:38
• Welcome to WorldBuilding.SE! Please break this up into paragraphs so it's easier to read. – F1Krazy Apr 18 at 21:00

## Genetically modified grass.

Not your average tall fescue, but grass modified with genes that will allow it to survive on Mars. Anti-freeze genes, uv protectant genes and the like. Hopefully it will be edible, and tasty, too! Because, once you get there and kneel down to kiss Martius firmus, you might be just a tad peckish from months of shipboard fodder.

I literally just turned off the tele (Science Channel) and they were describing experiments with plants actually being grown in a Mars like atmosphere.