Alien biology based on toxic/corrosive chemicals

[garak1a]

Hello all,

I was considering a sci-fi premise where Humans visited a planet that had a thriving ecosystem (nothing sapient), whose biochemistry was based on something that was either toxic, or ideally [to the plot] even corrosive to Earth life. Not just a matter of producing indigestible L-proteins or toxins in their blood; I'm thinking along the lines of animals that breathe a gas like fluorine or chlorine.

So: is it hypothetically possible to have a non-Earth ecosystem, which presumably still relies on photo- or chemo-synthetic autotrophs, using a gas like fluorine in place of oxygen?

Thank you!

[Izawwlgood]

Like this;

Spoiler:

So... thirsty!

ammonia alien.jpg (8.08 KiB) Viewed 6089 times

I realize it's a bit small. The Alien's crawling through the desert, going 'ammonia! ammonia!'

[++$_]

Liquid ammonia is probably the most likely candidate to replace water, since it is readily formed and can dissolve a lot of things. There are other solvents, like acetone, but they are less likely to be present naturally, so I don't see how you would accumulate enough of them on a planet to form an ocean, at least without living things creating them first. Maybe you can have a planet with "second-generation" acetone oceans, having been pumped out as waste by a previous generation of water-based life, or something.

Either type of ocean would be much less compatible with atmospheric oxidizing gases than water. Maybe a lower concentration of oxygen would work, or perhaps another gas like nitrous oxide or chlorine would have to be used instead.

As for fluorine: No, probably not. It is scarce in the universe compared to oxygen, and it will react instantly with almost anything other than fluorine, fluorides, platinum-group metals, or noble gases. If you were to pump some fluorine into the atmosphere of an ordinary planet, it would quickly be used up oxidizing the rocks. In this video a brick is lit on fire using fluorine.

[Jessica]

Well, there is the microbes we found on earth which are toxic (arsenic).

also http://en.wikipedia.org/wiki/Hypothetic ... ochemistry

[charonme]

we found

allegedly...

Also, the alien in this story needs to add cyanide into the air he breathes on Earth because of the different way his blood works.

[ikrase]

Perhaps elevate some of our extremophile bacteria to the level of multicellular animals?

[Quizatzhaderac]

You could have the atmosphere be mostly reductive (for example made of methane/ CO2, helium mixtiure) and biological "fuel" be oxidative. As I understand it the Earth used to be like that before photosynthesis became popular. Conversely our atmosphere would probably be poisonous to the life of that planet.

[Tass]

Liquid ammonia is probably the most likely candidate to replace water, since it is readily formed and can dissolve a lot of things. There are other solvents, like acetone, but they are less likely to be present naturally, so I don't see how you would accumulate enough of them on a planet to form an ocean, at least without living things creating them first. Maybe you can have a planet with "second-generation" acetone oceans, having been pumped out as waste by a previous generation of water-based life, or something.

Either type of ocean would be much less compatible with atmospheric oxidizing gases than water. Maybe a lower concentration of oxygen would work, or perhaps another gas like nitrous oxide or chlorine would have to be used instead.

As for fluorine: No, probably not. It is scarce in the universe compared to oxygen, and it will react instantly with almost anything other than fluorine, fluorides, platinum-group metals, or noble gases. If you were to pump some fluorine into the atmosphere of an ordinary planet, it would quickly be used up oxidizing the rocks. In this video a brick is lit on fire using fluorine.

Yes. Fluorine is more oxidizing than oxygen and therefore attacks even oxides like water and sand, which notably does not burn in oxygen because they are already oxidized. Do you know what fluorine does not attack? Things that are already heavily fluorinated. In order for this to have any chance of working fluorine would have to completely substitute oxygens role on the planet. The rocks of crust and mantle would be fluoride crystals, the oceans would be HF and so on.

Of course it fail because of the negligible likelihood of a planet getting that much of such a rare element, but maybe that could be handwaved. Getting a biochemistry to work would also be very hard. It took a lot of evolution for life on earth to be able to handle the deadly poisonous and corrosive oxygen. Fluorine is a thousand times worse.

Temperature would probably have to be lower (which would also facilitate the HF oceans). The skin of organisms would still need to be made of especially fluorination resistant compounds, maybe mostly per-fluorocarbon chains (we are lucky that regular carbohydride chains are resistant to oxidation at room temperature). Spontaneous combustion would happen a lot more to them than it does to us.

So fluorine for oxygen might work, but it is a long shot. Ammonia as solvent is more likely.

[PM 2Ring]

FWIW, the Terro-Human Future History series of H. Beam Piper occasionally mentions the planet Niflheim, which has a fluorine-based ecosystem.

Niflheim

Niflheim is the 4th planet of Nu Puppis. It's about 5 AU from its primary, with about 1g surface gravitation and one atmosphere of pressure. Ambient temperature is about -60C. It was discovered by the Terran Federation Space Navy. The atmosphere is 4-5% free fluorine with some inert components. The bulk of the atmosphere is the result of the reaction of fluorine with other materials: CF4, BF3, SiF4, PF5, SF6 and others. There is also a little free oxygen. The planet's rocks are weak and consist exclusively of fluorides. The only free liquid on the surface was liquid hydrofluoric acid (HF). It is rich in uranium.
Niflheim's native plants and animals metabolize fluorine. Their harder tissues are long-chain fluorocarbons (e.g., Teflon). Trees are described as "topped with huge ragged leaves, looking like hundred-foot stalks of celery." Other plants as "a mat of wormlike colorless or pastel sprouts". Animals are described as "Little round things, four inches across, gnawing at the vegetation, and bigger things, two feet long, with articulated shell-armor and sixteen legs which fed on the smaller herbivores."

From the introduction to Uller Uprising by H. Beam Piper:

Probably the most surprising and interesting thing about the Twayne edition is the essay that forms the introduction to that volume, and is reprinted here. The essay is by Dr. John D. Clark, an eminent scientist of the forties and fifties and one of the discoverers of sulfa, the first "miracle drug." It describes in great detail the planetary system of the star Beta Hydri, and gives the names of those planets: Uller and Niflheim. A publisher's note states that Clark's essay was written first, and given to the contributors as background material for a novel they would then write.

The fans of H. Beam Piper seem to owe a great debt to Dr. Clark. Uller Uprising became the foundation of Piper's monumental Terro-Human Future History; the first story where we encounter the Terran Federation. In it we learn about Odin, the planet that will one day be the capital of the First Galactic Empire; and humble Niflheim, which in more decadent times will become a common expletive, a word meaning hell.

Here's a link to that Introduction by Dr. John D. Clark mentioned above. The material about Niflheim is in section II, The Fluorine Planet.

Unfortunately, the fluorine chemistry & biology of Niflheim is only incidental to the plot of the stories it's mentioned in. Personally, I'm highly sceptical of the possibility of a fluorine-based planet, but if you like reading 70 year old sci-fi, the stories of H. Beam Piper can be quite engaging even if the science content isn't very rigorous.

[Codemasterc]

Judging by the microbe evidence here on earth it seems as long as there is a chemical combination that allows for self replication readily available in mass then there should be life. The problem then is overcoming the threat of interacting with these toxic creatures. Though that can be mostly acheived by via specialty made suits it would make immigrating into an alien society hard if not nigh impossible.

Edit: However depending on whatever chemical composition it would be very easy to destroy such beings. Especially if they disentigrate in water. We could conquer a whole world with nothing more than high powered water guns.

[Sleeper]

The books 2061 and 3001 by Arthur C Clarke focus on life-forms based on a different chemistry that has evolved (or been guided into evolving) on Jupiter's moon Europa. That chemistry is poisonous to people.

[madd0ct0r]

how to get such a concentration of flourine though?

Oxygen is far more common, slightly less reactive and also slightly heavier. hmmm

A planet has flourine and oxygen, with the flourine getting bound up in salts on the surface and driving the oxygen off.

Along comes a nova shockwave (or something) and strips the atmosphere off. Bye Bye oxygen.

Over time, the flourine salts slowly separate (how? photosynthesis?) and flourine becomes a larger component of the atmosphere again.

[PM 2Ring]

how to get such a concentration of flourine though?

Oxygen is far more common, slightly less reactive and also slightly heavier. hmmm

A planet has flourine and oxygen, with the flourine getting bound up in salts on the surface and driving the oxygen off.

Along comes a nova shockwave (or something) and strips the atmosphere off. Bye Bye oxygen.

Over time, the flourine salts slowly separate (how? photosynthesis?) and flourine becomes a larger component of the atmosphere again.

It's "fluorine".

But yes, it's not easy to see how a planet could have large amounts of free fluorine hanging around. The situation is worse than that of oxygen. It's currently believed that a planet is unlikely to have much free oxygen in its atmosphere unless its being produced by biological processes, so it's reasonable to make similar claims for fluorine. However, fluorine bonds to other atoms tend to be much stronger than the equivalent oxygen bonds, so it would be significantly harder for biological mechanisms to liberate free fluorine.

And as you mention, fluorine is much rarer than oxygen: according to Wikipedia, the ratio of oxygen to fluorine in the solar system is 8800:1. Stars that are hot enough to cook fluorine tend to destroy it in short order, so it takes somewhat unusual circumstances to make it in any appreciable quantity.

From the perspective of cosmology, fluorine is relatively rare with 400 ppb in the universe. Within stars, any fluorine that is created is rapidly eliminated through nuclear fusion: either with hydrogen to form oxygen and helium, or with helium to make neon and hydrogen. The presence of fluorine at all—outside of temporary existence in stars—is somewhat of a mystery because of the need to escape these fluorine-destroying reactions.

Three theoretical solutions to the mystery exist. In type II supernovae, atoms of neon are hit by neutrinos during the explosion and converted to fluorine. In Wolf-Rayet stars (blue stars over 40 times heavier than the Sun), a strong solar wind blows the fluorine out of the star before hydrogen or helium can destroy it. In asymptotic giant branch (a type of red giant) stars, fusion reactions occur in pulses and convection lifts fluorine out of the inner star. Only the red giant hypothesis has supporting evidence from observations.

For more details, see Fluorine: An Element-ary Mystery by Ken Croswell. Published in Sky and Telescope (September 2003--cover story).

[madd0ct0r]

gah- clearly i need to brush my teeth less often

- so put alien planet in orbit around binary system including specific type of red giant.

Red giant is spewing out fluorine* into planet's orbit, and it all gets hoovered up by the planet, incidentally slightly poisoning the existing ecosystem. Red Giant dwindles away, and the loss of mass causes the system to unbalance, with the older star falling into the younger one. Big boom strips planet of existing atmosphere, with life being cut back to a few extremophiles in the crust. Cue a relatively long period where different branches of organisms compete, their waste products alternately poisoning or feeding their neighbors. Eventually, perhaps by chance more then anything, fluorine, liberated by silicate lichens becomes the reactant gas of choice.

complete rubbish, but moderate technobabble.

* and presumably other elements, which might also go some way to explaining why the planet is so toxic to humans

[idobox]

What about significantly higher levels of ozone?
If the planet has life relatively similar to Earth, and much more UV, the concentration of ozone could much higher, to the point of being harmful to earth life, and usable by local life forms.

[oxoiron]

how to get such a concentration of flourine though?

Oxygen is far more common, slightly less reactive and also slightly heavier. hmmm

What do you mean when you say oxygen is slightly heavier than fluorine?

[idobox]

fluorine is a rare compound in the universe, and it reacts very strongly with pretty much anything.
Getting a high concentration of it is going to be difficult to justify

[oxoiron]

Neither abundance nor reactivity of fluorine (both of which I am well aware, thank you) have anything to do with the question I posed. I'm curious why madd0ct0r thinks oxygen is heavier than fluorine, although I suspect s/he may never be back to supply an answer.

EDIT: removed extra use of the word "answer"

[PM 2Ring]

how to get such a concentration of flourine though?

Oxygen is far more common, slightly less reactive and also slightly heavier. hmmm

What do you mean when you say oxygen is slightly heavier than fluorine?

Oops! How did I miss that? I guess I just got distracted by other stuff...

[zatnaas]

After hearing some rather uneventful biology questions over the last couple of years, I think I can safely say that biology question-writing in general lags behind writing in the physical sciences and math.

[ikrase]

In the dragons thread I outlined an idea for a (probably heavily radioactive and plutonium-dusted) ecology based on nuclear fission instead of sunlight. The producer was a fungus that enriched uranium and decomposed dead animals, and bore fruit containing subcritical quantities of mixed oxide fuel.

[Cyberax]

That idea of fission-based ecology was explored in Robert Forward's "Camelot 30K". It also has aliens with blood made of F2O.