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I am trying to figure out how to build a human colony on a moon (75% of Earth size) of a gas giant.

Some details of the planetary system chosen for colonisation:

  • K-type main sequence star (about 60% of Sun size; orange; lower radiation emission than Sun);
  • large asteroid belt which can be mined for all and any necessary materials;
  • a gas giant is in the Goldilocks zone (closer to the star than in our Solar system);
  • this gas giant does not have a strong magnetosphere;
  • it has 3 moons, the largest of which is being colonised;
  • this moon is the only candidate in the entire star system for establishing a colony.

The colonists do not have contact with Earth and cannot receive supplies or technology updates. The majority of them are scientists (not just STEM, social sciences as well) and engineers. The team is very small — under 200 people.

Their genetic engineering technologies are higher level than today, but not at the level of magic. For example:

  • Corrective genetic therapies that modify all cells over a relatively short time are available, but their effectiveness is limited to fixing/changing small chunks of DNA. Changes in adult organisms at chromosomal level and massive tissue transformations (like a sex change) are not possible.
  • Utilization of techniques like CRISPr allow permanent inheritable genetic changes even when a therapy is administered to adults (not sure about women, but males definitely).
  • "Designer-babies" are not only possible but the technology will be widely used to avoid population bottleneck and Founders effect.
  • Decoded genomes of various species are readily available in a digital form and can be synthesised in a lab.
  • The overall understanding of human genome (what genes and their groups are responsible for) is much higher than today's but is not 100%. Thus it is not possible to create a race of highly intelligent super-human beings with a precise set of characteristics.

The colonists do not have moral or ethical restrictions on experiments. But they would like to avoid creating human chimaeras as much as possible. Their main objective is to ensure the survival of the colony while still keeping it human.


There are some radiation resistant species on Earth, notably Deinococcus radiodurans and Thermococcus gammatolerans. Both microorganisms can repair DNA damage even after receiving very high acute radiation doses. Theoretically, we can use their genome to figure out what genes are responsible for radiation resistance and then modify genomes of all other species (humans, flora, fauna, etc.). Perhaps the first generation of colonists will not be able to undergo such a drastic transformation and will be confined to the radiation shelters. But all the following generations and ecosystem will be protected.

I wonder if this is a feasible strategy. Are there any other considerations that I have to keep in mind (for example, the moon's atmosphere deteriorating at a rate higher than robotic asteroid miners can replenish it)?

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Here is the thing: Human cells and DNA already have a lot of DNA repair mechanisms. The main reason why those bacteria are so much better at it then our cells is because they're so simple and uncomplicated compared to us. Unfortunately these big differences mean that whatever nifty mechanism the Bacteria uses just won't work in Human cells. You're better off making your scientists design a completely new human-specific defence mechanism and edit that in instead.

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  • $\begingroup$ What should I look into? It seems that the most effective DNA repair mechanisms rely on copying from the already existing template. I am not sure if it is a good idea to have backup genome copies in human cells. $\endgroup$
    – Olga
    Commented Aug 26, 2017 at 23:22
  • $\begingroup$ I'm not sure that DNA repair is why radiodurans is resistant. If radiodurans is resistant because it can modify its cell wall, then that would have zero use to humans. $\endgroup$
    – SFWriter
    Commented Aug 27, 2017 at 0:39
  • $\begingroup$ @Olga Simple. Have them create a mechanism to let's a damaged cell copy the DNA from a neighboring but healthy cell. Backup chromosomes in the same cell would really complicate cell replication, this won't. $\endgroup$
    – Wissieze
    Commented Aug 27, 2017 at 20:02
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If at all available such a DNA-preserving technology would be invaluable for tons of usages, including, but not limited to:

  • Cancer prevention.
  • Retrovirus containment (AIDS)
  • Antiaging.

Main difficulty is such methods are deeply ingrained in cellular metabolism; it is unclear what other effect they would have on overall building of complex organism as we are.

Please note we have much less genes than phenotypic characteristics (by orders of magnitude), this means a single gene has effects on many areas (this is different, e.g. in arthropods); it is not possible to change a single trait in a complex vertebrate.

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  • $\begingroup$ I understand the practical difficulties of genetic engineering. Only a few traits (like eye colour) can be reliably changed. But this is not the goal. Although, experimenting with genetic manipulations and associated moral challenges would be great for story and character development. I will have to resort to suspended disbelieve in order to allow radiation resistance in all life forms in the colony. But I want to try to avoid making obvious mistakes in physics. $\endgroup$
    – Olga
    Commented Aug 26, 2017 at 13:43
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I think engineering from bacteria wouldn't be our first approach.

I think we'd try to enhance or own DNA repair mechanisms before engineering in new mechanisms, from bacteria to boot. I forget if D. radiodurans (etc) is radiation resistant because of DNA repair or because of some novel feature of its cell wall - Being able to sporulate, for example. Look into that. If they are resistant because they make a special cell coat, that would definitely not work in humans.

We humans can repair radiation damage to some extent. Think about people who are more susceptible to UV damage (Xeroderma pigmentosum). They are less good at innate repair mechanisms.

If I lived in your colony I'd suggest to my colleagues that we genetically amplify our innate ability to repair DNA (and other radiation damage) rather than introduce bacterial genes.

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  • $\begingroup$ D. radiodurans seems to use several different mechanisms: 1) several copies of its genome in its cell; 2) copying DNA of another D. radiodurans cell; 3) a slightly different way the DNA itself is stored. $\endgroup$
    – Olga
    Commented Aug 26, 2017 at 22:55
  • $\begingroup$ OK you are up to speed on how they work. $\endgroup$
    – SFWriter
    Commented Aug 27, 2017 at 0:45
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Instead of preventing cancer through genetic engineering which would be hard, difficult, and would take a lot of effort for 200 scientists; consider simply fixing cancer that occurs in between normal safety steps. Two important things to note is that you have the mechanism to store huge DNA codes and pull them back out for genetic engineering. Another thing is that you can hit every single cell in a body. Cancer is caused by mutations in the gene. If we have the tools to live on another place we'll have the tools to do individual genetic sequencing which already exist though on a small scale and we've already determined we can store it digitally and recall it as well. First thing these people would do is remove oncogenes in everyone and their offspring. Oncogenes are basically genes that make someone predisposed to cancer. This is a form of prevention and could probably just be done on the way over to the space planet. You'd probably also just want to ramp up melanin production as a preventive measure. The second thing is that every couple of days, the person would get their DNA sequence reuploaded. This would also stop loading. If you argue that genetic engineering is not, in fact, genetic replacement and therefore not allowed; there are alternatives. One could instead have genetic screening every couple of days which would be processed and errors would be corrected. This wouldn't prevent aging but it would be probably be a little resource intensive.

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The question is moot: a magnetosphere protects the atmosphere, not the surface life. Specifically, it protects water vapor in the atmosphere from being split by the particles of the stellar wind, allowing the hydrogen to more easily escape...see Venus, which has lost most of its hydrogen to this process, and Earth, which regularly goes through periods without a strong, global magnetic field, without major impacts on life.

As far as surface life goes, a deep enough atmosphere to be breathable at the surface will provide ample radiation shielding, especially considering that a moon will likely have lower gravity and require a greater mass of atmosphere (thus more shielding) to achieve the same surface pressure.

Genetic engineering for radiation protection or cancer resistance would actually be more relevant if the gas giant had a magnetosphere. A magnetosphere would mean radiation belts, a gas giant means very large and strong radiation belts filling the nearby orbital space and perhaps even surrounding the moon. Those who stay on the surface might be protected by the atmosphere, but if the colonists wish to remain spacefaring, they will have to pass through that harsh radiation environment.

Conveniently, this is also a bit more realistic, as it would be rather odd for a gas giant to not have a magnetic field.

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