Questions for scientifically knowledgeable posters.

[Akka]

I'm trying to make a somewhat hardish SF context, and for this I'd like to have some solid answers, especially about radiations and biology.

The idea is to have a species thriving in a medium which is radioactively lethal for human. As such, I thought about a planet lacking a/with a very weak magnetic field, and exposed to a star throwing intense radiations.
Here are my questions :

- What exactly do kill humans when exposed to quickly-lethal (something that would kill you in less than 24 hours) amount of radiations ? I understand it's the ionizing radiations which are messing about your cells, but I'd like to understand better what happens exactly and why people aren't fried instantly but will die quickly.

- I'm trying to get which kind of star and planet-star distance is required to have a star which can live at least for 1000 million years before changing significantly and a planet which is big enough to have at least 0,5 G, with the planet having a non-scorching surface temperature but an amount of radiation intense enough to fulfill the previous criterium (killing unprotected human in less than 24 hours if they endure about 30 mn of exposure, so I surmise something like 25 to 50 sievert ?).

- What would be the effect of such amount of radiation on radio communication ?

- What kind of chemical process a species could use to be actually powered up (even if it kills them in about one or two years) by such radiation ?

Yes, I know, I'm a nitpicking freak. But I'd very much appreciate informed and detailed answers about all these

Thanks !

 

[Lohrenswald]

I've kinda forgotten a lot of stuff
Like I used to know the details of ionization, but I don't recall it well enough to say much
It has to do with like, the ionization process making the atoms want to make new connections, so that like breaks up cell structure

one thing though

a star which can live at least for 1000 million years before changing significantly

Our own sun is a type of star that can exist for nearly ten times that amount of time before changing significantly

 

[Akka]

Our own sun is a type of star that can exist for nearly ten times that amount of time before changing significantly

Oh yeah, I know I can safely use any star up to class F for the longevity part, but my problem is more about the combination of all the requirements (radiation + longevity + planet at a distance allowing for being bathed in such radiation but not scorched by regular heat).

 

[Kyriakos]

Another scenario - and i suppose easier to compute?- would be a species living in the aftermath of a nuclear war, or living in a planet with nuclear detonations from time to time (due to whatever reason).
I can't help with the chemistry, but the overall factor can be a bit ambiguous and still ok for sci-fi.

That said - and going from what Lohren posted- is it even possible for an actual material-based being to survive constant exposition to chemical-connection-altering factors? Maybe if it is a very simple (?) life form.

 

[Lohrenswald]

Well I'm pretty sure you could just take a planet like earth and remove the magnetic field

IIRC, neither Venus or Mars has magnetic fields (while Mercury I think does)

 

[Bootstoots]

I'm trying to make a somewhat hardish SF context, and for this I'd like to have some solid answers, especially about radiations and biology.

The idea is to have a species thriving in a medium which is radioactively lethal for human. As such, I thought about a planet lacking a/with a very weak magnetic field, and exposed to a star throwing intense radiations.
Here are my questions :

- What exactly do kill humans when exposed to quickly-lethal (something that would kill you in less than 24 hours) amount of radiations ? I understand it's the ionizing radiations which are messing about your cells, but I'd like to understand better what happens exactly and why people aren't fried instantly but will die quickly.

- I'm trying to get which kind of star and planet-star distance is required to have a star which can live at least for 1000 million years before changing significantly and a planet which is big enough to have at least 0,5 G, with the planet having a non-scorching surface temperature but an amount of radiation intense enough to fulfill the previous criterium (killing unprotected human in less than 24 hours if they endure about 30 mn of exposure, so I surmise something like 25 to 50 sievert ?).

- What would be the effect of such amount of radiation on radio communication ?

- What kind of chemical process a species could use to be actually powered up (even if it kills them in about one or two years) by such radiation ?

Yes, I know, I'm a nitpicking freak. But I'd very much appreciate informed and detailed answers about all these

Thanks !

Ah, as the forum's #1 connoisseur of radioactive things, I love being asked these sorts of questions. The Wiki article on acute radiation syndrome has a lot of the answers you're looking for, as does the shorter one Biological timeline of radiation poisoning.

High doses of radiation kill in a variety of ways. One thing that happens is that the bone marrow is really radiation-sensitive, and white blood cell production collapses, leaving the victim extremely vulnerable to infection. It also messes with the ability of cells to divide properly, which produces major effects everywhere that a relatively fast turnover of cells is needed, such as the gastrointestinal system. The result is that people who have absorbed a fatal or near-fatal dose of radiation actually sometimes improve for a week or two and feel basically fine, until the cells that are supposed to be replaced aren't replaced and then they go into a rapid decline, dying at the 2 or 3 week mark. The effect on cell division is great if it's targeted at a tumor because we don't want tumors reproducing, but it increases the risk of cancerous mutations in non-cancer cells that do manage to divide as well, and at high short-term dose rates, the inability of cells that are supposed to divide rapidly, like bone marrow and the GI lining, leads to survival for a little while followed by a slow and painful death after a couple weeks.

At the sorts of extreme doses you are talking about, in the >25 Sv range (death in <48 h), ionizing radiation causes severe neurological damage as well. Victims here usually die of neurological complications before they die of the other ones. Cancer patients who have whole-brain radiotherapy to deal with multiple brain tumors will usually complain of a mental fog that eventually goes away, but at ten times that dose, the brain just starts shutting down pretty rapidly. I don't know the details of why this is, though.

There absolutely are life forms on Earth that thrive in high-radiation environments, even feeding off the ionizing radiation as an energy source while having extremely good DNA repair mechanisms. Some Wiki links about fungi that grow inside the Chernobyl sarcophagus: Radiotrophic fungus and one of the most successful ones, C. neoformans.
https://en.wikipedia.org/wiki/Biological_timeline_of_radiation_poisoning
I can think of two types of planet/moon where this sort of situation may pop up. One is around Flare stars, which are generally dim red dwarfs like Proxima Centauri or the recent one a planetary system was found around (the name escapes me now). They have a tendency to emit enormous solar flares and resultant bursts of ionizing radiation, which would be a problem for most, but not all, life as we know it. The other situation is when a moon orbits within a radiation belt of a giant planet. A few hours on Europa and you'll absorb a fatal dose from Jupiter's monster radiation belts, and Io is even worse. However, it should be noted that most ionizing radiation doesn't penetrate very deep - a few meters of water, rock, or concrete (to say nothing of lead) goes a long way. So high doses of radiation may mess with life a bit, but they don't make it impossible.

 

[Honor]

Let's not forget Conan the Bacterium: https://en.wikipedia.org/wiki/Deinococcus_radiodurans

And the good ole Tardi: https://en.wikipedia.org/wiki/Tardigrade

 

[The_J]

- What exactly do kill humans when exposed to quickly-lethal (something that would kill you in less than 24 hours) amount of radiations ? I understand it's the ionizing radiations which are messing about your cells, but I'd like to understand better what happens exactly and why people aren't fried instantly but will die quickly.

Short summary for this, 2 things:
#1
- enzymes are transcribed from DNA
- radiation causes mutations in the DNA
- this might render enzymes functionless (if there are enough mutations then for sure)
- which means that all basic cell functions will break down. You cannot degrade sugars anymore if the necessary enzymes are mutated (e.g.; and well, everything else in the cell)
#2
- if the radiation is high enough, this might directly lead to DNA breakdown
- which will either directly lead to cell malfunctioning (because no enzymes), or
- will lead to re-assembly of the DNA in a different state, which is also lethal (wrong enzymes; even if not, regulation will be messed up, which can also lead to serious diseases)

The basic problem is that the cell systems for mutation control/fixing mutations will not be able to keep up with the high amount of mutations caused by the radiation.
You're exposed to a certain amount of radiation each day, but you don't die from it, because the DNA repair systems can deal with this little amount of mutations.
That's e.g. also what's causing skin cancer. Higher exposure to radiation (UV light) will cause more damage, which is not possible to be repaired in time. This might damage certain systems in the cell (e.g. control for cell growth), which will then lead to cancer. Some cells might also have different mutations, but that normally doesn't matter too much, since skin dies and is shed regularly.
Death by high radiation is caused because not only the skin is affected (bootstoots gives some examples what could happen, and this basically relates to which part of your body is affected first; if your brain cells break down first, you'll get neurological problems, etc.)

- What kind of chemical process a species could use to be actually powered up (even if it kills them in about one or two years) by such radiation ?

Even though there is the cryptococcus neoformans (linked higher up), this is actually not clear.
Gamma radiation (that is, the actually deadly radiation) is the energy which gets free when the atom core breaks down.
Reverting this into nuclear fusion is not really possible (unless I missed something in physics).
Using alpha radiation (the helium cores; not actually deadly unless you ingest radioactive stuff; your skin normally shields you enough from it) could be a theoretical idea. Since the positively charged helium cores could sort of build up a proton gradient, this one could be used to power energy systems (cells already use proton gradients, but these are normally powered by hydrogen or sodium ions, not helium ones).
Never cite me on this, this is crazy feces ^^, and I'm sure that there is a half ton of theoretical impossibilites within these 2 sentences.


EDIT: Just in case, doing a PhD in a genetics related field ^^.

 

[Valka D'Ur]

I've kinda forgotten a lot of stuff
Like I used to know the details of ionization, but I don't recall it well enough to say much
It has to do with like, the ionization process making the atoms want to make new connections, so that like breaks up cell structure

one thing though

Our own sun is a type of star that can exist for nearly ten times that amount of time before changing significantly

It's not that significant to the Sun, but several months ago I read an article on one of the astronomy sites (forget which one) where the author hypothesized that realistically the human race has about 600,000 years left on Earth and then we'll absolutely have to leave to avoid the increasing temperatures, decreasing water, and a bunch of other stuff that was so horribly depressing that I'm not surprised I don't immediately recall where I read it. Suffice to say that our planet is not getting out of this alive.

 

[Lohrenswald]

It's not that significant to the Sun, but several months ago I read an article on one of the astronomy sites (forget which one) where the author hypothesized that realistically the human race has about 600,000 years left on Earth and then we'll absolutely have to leave to avoid the increasing temperatures, decreasing water, and a bunch of other stuff that was so horribly depressing that I'm not surprised I don't immediately recall where I read it. Suffice to say that our planet is not getting out of this alive.

based on global warming or diminishing magnetic field or?

 

[warpus]

All I wanted to say is, two thumbs up, I approve of this type of thread. Very interesting stuff

 

[Valka D'Ur]

based on global warming or diminishing magnetic field or?

I'd have to find the article again to give you an informed answer. I honestly don't recall.

 

[innonimatu]

There absolutely are life forms on Earth that thrive in high-radiation environments, even feeding off the ionizing radiation as an energy source while having extremely good DNA repair mechanisms. Some Wiki links about fungi that grow inside the Chernobyl sarcophagus: Radiotrophic fungus and one of the most successful ones, C. neoformans.

I was thinking Stanislaw Lem had done something similar, but no. He only did the fungus civilization stuff, but that was a plot device used only for a final twist in one of his books.

 

[Akka]

Thanks a lot for the informative answers, guys !

Too many things to quote to thank individually, but be sure I read every single line of every post ^^

Flare stars look nice, and would be low-heat enough to allow a planet to be close enough without being cooked, but it seems these flares are irregular, while I was counting more on a permanent basking in a sea of radiations. Orbiting in the radiation belt of a gaz giant look even more promising.
One thing I'd like to know though : would such radiations be able to jam/shut down/parasite radio communications for a space station orbiting the planet ?

Short summary for this [...] neurological problems, etc.)

Pretty interesting and thorough, but is it about radiation poisoning in general, or specifically about receiving enough radiation to kill you in 24 or so hours ?
I understand why we get cancer if we are irradiated, but what I want to dig up info is more about what kills in a matter of hour - Bootstoots says it seems it basically shut down the brain, for example.

Samely, interesting points about the lifeforms who can endure radiations, and especially the ones which seems to thrive in radiations, but they look more like species which can repair radiation damage than those which would evolve by being based on using radiations to sustain themselves. The stuff about the proton gradient aspect look an interesting way to look into though


To give more context : I'd like to build up an extraterrestrial species which would be utterly and fondamentally different from life as we know it. At the same time, I'm very much of a hard SF guy, so I want to get as much as possible realistic, or at least grounded in real facts. Due to the events planned in the story, I want them to be able to interact with radiowave/electricity at the biological level (so using radiation as a source of energy seemed sensical). I'm looking for the most exotic processes which would end up giving the most alien perspective - the goal is to have reasons why the species acts or looks which are entirely and fundamentally different from what we would expect, but that would make total sense from its own point of view.

It's not that significant to the Sun, but several months ago I read an article on one of the astronomy sites (forget which one) where the author hypothesized that realistically the human race has about 600,000 years left on Earth and then we'll absolutely have to leave to avoid the increasing temperatures, decreasing water, and a bunch of other stuff that was so horribly depressing that I'm not surprised I don't immediately recall where I read it. Suffice to say that our planet is not getting out of this alive.

That's due to the fact that stars have output which slowly increases during their lifespan, and as such over very long period of time, the Earth receives more and more heat from the Sun.
From memory, though, it's not 600 000 years but 600 millions before we reach such kind of temperatures.

I was thinking Stanislaw Lem had done something similar, but no. He only did the fungus civilization stuff, but that was a plot device used only for a final twist in one of his books.

He also did the "force of nature" aliens in The Invincible. In fact, I'm trying something that is rather in the same vein as he did - he's one of the few authors who actually reach for truly "aliens" aliens, and not just human with weird faces.

 

[Bootstoots]

It's not that significant to the Sun, but several months ago I read an article on one of the astronomy sites (forget which one) where the author hypothesized that realistically the human race has about 600,000 years left on Earth and then we'll absolutely have to leave to avoid the increasing temperatures, decreasing water, and a bunch of other stuff that was so horribly depressing that I'm not surprised I don't immediately recall where I read it. Suffice to say that our planet is not getting out of this alive.

600,000 years is too short a period of time, but 600 million years is quite plausible. Estimates I've heard are generally around the ballpark of one billion years of complex surface life remaining. I'll tell you what my current understanding of the distant future is.

The Sun is heating up slowly, about 10% per billion years IIRC. Initially, the Earth's geology will compensate (and has been compensating) for this by increased rates of silicate weathering and other ways to sequester CO2 geologically, lowering global GHG levels and keeping the planet relatively constant temperature-wise. We're worried right now about the coming several-thousand-year-long warm period caused by a bunch of pyromaniac apes getting loose and lighting things on fire, but in geological time this will be over pretty quickly and the extra CO2 will all be sequestered within a couple of tens of thousands of years, reestablishing the longer-term equilibrium. The long-term trend is for CO2 levels to drop. In fact, although it's not possible to prove this absolutely, I strongly suspect that the lowest CO2 concentrations in the history of the world have occurred during the glacial periods of the current ice age, when it was down to about 190 ppm. They will continue dropping for the next few hundred million years, for the most part, excluding occasional periods of high volcanism or clathrate releases or human descendants/other animals getting loose and lighting buried carbon on fire again.

Over the last few million years, plants have been evolving new photosynthetic pathways to deal with the low CO2 levels. C4 carbon fixation allows plants that use it to utilize CO2 more efficiently, allowing them to do pretty well during the low-CO2 glacial periods. The older C3 plants are still all over the place and are doing fine, but the balance will shift more towards C4 and whatever other more carbon-efficient mechanisms evolve. With a little more evolution, they could probably survive all the way down to something like 10 ppm.

But eventually, sometime a few hundred million years to a billion years from now, we hit a floor as to how low the CO2 and other GHG levels can go. I'm not sure exactly where this floor is; it may be so low that not even C4 plants survive and the world is barren of photosynthetic life already at that point, it may be high enough that there are still C4-based forests and algae with associated ecosystems and so on. Either way, at this point temperatures begin an inexorable increase over the next couple hundred million years. Once the average global temperature passes a critical level - about 47 C - a runaway moist greenhouse effect begins, in which so much water vapor is in the atmosphere that it traps more IR light and warms the Earth still further, evaporating more water and so on. The oceans and all other surface water boils away, and global temperatures shoot up still higher.

Some water will continue seeping out from the mantle for quite some time, and there may well be extremophile life living in these little superheated pools for another billion+ years depending on exactly what happens on Earth's surface. They may even be oxygen-dependent, because the water vapor will slowly be broken down in the stratosphere, leaving oxygen on the planet but shooting the hydrogen off into space. But eventually they die too, the surface temperature passes something like 300 C as the Sun continues to warm up, and the equilibrium favoring carbonate formation reverses. All limestone and other carbonate rocks evaporate to release CO2, and Earth completes its transition into Venus, probably well before the Sun reaches the red giant stage and destroys the planet once and for all.

Venus was probably an Earth-like watery world ~4 billion years ago too, and it is believed to have undergone the same sort of transformation. The smoking gun is that the ratio of deuterium (hydrogen-2) to normal hydrogen (protium, hydrogen-1) is like 100x higher than they are on Earth. For an atom in the far upper atmosphere of a planet, the chance of getting blasted into space is a strong function of the atom's mass, and when water vapor gets blasted into its constituent atoms by UV light, deuterium is much more likely to come back than normal hydrogen. So we have some evidence that Venus was once a moist greenhouse that slowly lost most of its water vapor to solar breakdown, implying that still earlier in the Solar System's history it was probably Earth-like.

 

[Birdjaguar]

Just recently, the robot cameras sent into the Japanese mess died within 2 hours because of the radiation. The articles didn't say why. You should keep in mind that high does will also affect no living things.

 

[AppleDumplingHead]

Venus doesn't have a strong, intrinsic magnetic field, as Earth's, but it has a sort of external magnetic field where the pressurized cloud layer interacts with the "solar wind".
http://sci.esa.int/venus-express/50246-a-magnetic-surprise-for-venus-express/
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You would not presume complex carbon, or even silicon, based life and just plop it in an environment with heavily ionizing radiation. It "dies". Its components are quickly and wildly adversely affected from the order necessary to function systems. You'd backtrack to basics and imagine an evolution of life not so quickly manipulated by, or even shielded (hidden?) from, that aspect of the environment. My best guess is "proteins" (for lack of a better word) composed of hypothetical particles which do not interact with the Higgs field, but rather a "parallel field", rendering mass to hypothetical bosons, which therefore do not interact with identifiable (to us) particles with such properties. They would "appear" as mass-less, "invisible" phantoms, without a properly calibrated device to register their "frequency". What "we call" radiation would pass through them as harmlessly as "neutrinos" to us.

The question may become, "who becomes aware of whom, first".

Well, you said "hard" sci-fi.

 

[Honor]

You could make a hybrid species which is not radiation-based per se, but radiation-resistant (repairs itself really fast) and able to use radioactive energy to power its metabolic functions. The mitochondria may have evolved to function like a nuclear reactor, etc.

 

[SS-18 ICBM]

To add to the last post, I'm thinking maybe some sort of photosynthesis that uses gamma rays (read: high-energy photons). Essentially have antenna complex molecules that can capture such photons and funnel them into th electron transport chain.

For radiation resistance, maybe the organism can readily metabolize heavy metals and incorporate them into proteins or deposit them like bone minerals.

 

[uppi]

- What would be the effect of such amount of radiation on radio communication ?

Nuclear radiation is much more energetic than the radio waves used for communication and thus have a much higher frequency. So in principle, radio communication is no problem in a highly radioactive area, with two caveats: First, your communication equipment needs to be able to withstand the radiation (see below). Second, if the radiation source is a star, it might also emit other radiation at lower frequencies that does interfere with the communication. But you could always get around that by using radio waves in a narrow band with high power.

Short summary for this, 2 things:
Gamma radiation (that is, the actually deadly radiation) is the energy which gets free when the atom core breaks down.
Reverting this into nuclear fusion is not really possible (unless I missed something in physics).

Technically, gamma radiation is emitted when the nucleus changes its state (a very similar process to light being emitted when an electron in the atom changes its state). If a nucleus breaks apart or decays, it is often left in an excited state and will then emit a gamma photon. Theoretically, this is perfectly reversible, if you would send the gamma photon back in exactly the same way. In practice, we do not have enough control over photons at this frequency to really do that. You would want some kind of gamma-ray laser (graser?) for that, which is - again - theoretically possible, but very hard to realize.

Just recently, the robot cameras sent into the Japanese mess died within 2 hours because of the radiation. The articles didn't say why. You should keep in mind that high does will also affect no living things.

If you build semiconductor electronics, you intentionally introduce defects in the semiconductors. Given the right pattern of these defects, the circuit will do what you intended. Nuclear radiation will introduce additional defects in the semiconductor, thereby altering the pattern. If the radiation alters the pattern too much, the circuit will do something else than intended, usually resulting in a breakdown. if you keep this in mind, you can design circuits that are not as susceptible to radiation than usual equipment, but fundamentally, every semiconductor circuit will fail if subjected to too much radiation.