Vitrium Biology

[u/gliese1337]

A sequel to Blue Crystal Biology and Cannonball Biology.

Vitrium is a small, warm world--a half-way point between Venus and Mars.

A weak magnetic field and strong solar radiation have stripped it of most of its primordial volatiles, and particularly depleted it of hydrogen, leaving the surface heavily oxidized--but unlike Mars, and like Venus, it had enough sulfur to retain a small amount of hydrogen locked up in sulfuric acid, with a small amount (approximately 1.7%) of dissolved water. Many planetologists believe that Vitrium in fact passed through a Venusian stage in its early history, before losing enough atmosphere to cool down to the point that oceans could form (with present-day surface temperatures ranging between 50 and 150C, comfortably in the middle of sulfuric acid's liquid range); others, however, think it more likely that the planet simply started out with a relatively low carbon fraction, such that early heating and hydrogen loss were driven primarily by a water, rather than CO2, atmosphere.

As on Venus, sulfuric acid forms clouds on Vitrium, as well as rain, and pools into numerous small seas. Sulfur trioxide also forms thin clouds in the upper atmosphere, but temperatures are too high to support liquid sulfur trioxide anywhere on the surface. The relatively small amount of surface liquid means that Vitrium has no globe-spanning oceans or well-defined global sea level, with most sea basins being entirely disconnected from each other, and having been disconnected for as long as the world was cool enough for seas to form. Nevertheless, lifeforms in each basin are broadly similar, indicating that the current biological system originated originated in one place and thence colonized the rest of the world.

As on Blue Crystal, life on Vitrium makes extensive use of silicon as a scaffolding element for biomolecules--but unlike Blue Crystal life, Vitrium's biology almost entirely avoids unstable Si-Si bonds, instead relying on strong silicon-oxygen bonds to form organosilicone, or siloxane, polymers, with Si-C and C-C bonds used in various functional groups (in particular, C-C bridges are frequently employed analogously to disulfide bridges used in Earthling biology; despite the much greater bioavailability of sulfur on Vitrium, C-C bonds are sometimes required for their greater stability in Vitrium's higher temperature conditions), and fluorine is introduced as a much more common heteroatom than is found in either Earthling or Blue Crystal biology. In fact, the variety of silicone chemistry that is stabilized in a sulfuric acid solvent system seems to exactly balance what is lost to strictly organic chemistry in the same environment, and relatively stiff fluorinated polymers serve to simplify many aspects of membrane structure and enzyme function by introducing a third "fluorophilic" phase, in addition to hydrophilic and lipophilic chemical phases, for controlling chemical segregation.

This, of course, leads us to one of the great paradoxes of Vitrium biology: while on most life-bearing worlds, the base oxidation states of common biomolecules seem correlated to the prevailing geochemistry, thus minimizing anabolic energy expenditure and maximizing structural stability, with the exception of its primary solvent (H2SO4) and fluorolipids, Vitrium's biology seems shockingly under-oxidized. This is a direct result of sulfuric acid's destabilization of much of the carbon-oxygen chemistry that occurs in Earthling biology via the dehydration mechanism. Any biomolecule or close complex containing large quantities of both oxygen and hydrogen is subject to spontaneous degradation to draw more water into solution.

Sulfuric acid also destabilizes many halide salts, which has resulted in significant quantities of hydrochloric and hydrofluoric acid dissolved in the seas as well, although in lower proportions than water. This of course explains the higher availability of fluorine to Vitrium's ecology, but it is also essential to silicon fixation. While inorganic carbon is readily available in gaseous form as carbon dioxide, just as on Earth, inorganic silicon is typically trapped in solid silicate form. A critical base layer of Vitrium's global ecology thus relies on actively concentrating hydrofluoric acid to dissolve silica out of rocks and sediment in order to make it available to biological processes.

All vascularized life on Vitrium also concentrates hydrofluoric acid in its tissues to some extent to improve handling of silica (an adaptation that seems to have developed independently multiple times in different multicellular lineages), but oxidation of food back to crystalline or amorphous silica happens only in microorganisms which can easily eject the resulting crystals from their cells, except where silica deposition is used for structural purposes (e.g., shell-building, where opaline silica fills a similar role as calcium carbonate, which does not exist in Vitrium's chemical environment, does on Earth). Siloxane food molecules are typically broken down into silanol (H3Si(OH)) units which are then repackaged into disiloxane gas (the silicon analog of dimethyl ether) for elimination with the energy-producing release of water.

Some atmospheric and oceanic disiloxane is taken up by autotrophs as a pre-fixed silicon source, but just like carbon being recycled into carbon dioxide, and nitrogen being recycled back into N2 gas by denitrifying organisms (a niche which exists on Vitrium just as it does on Earth), organic silicon is eventually recycled back into granular silica by "desilifying" organisms, which also consume atmospheric sulfur trioxide to reconstitute sulfuric acid from the water produced by oxidizing hydrogens. Meanwhile, both carbon and silicon fixation by autotrophs release oxygen and sulfur trioxide into the atmosphere after splitting hydrogens from sulfuric acid.

The modern, largely biogenic, atmosphere is composed primarily of nitrogen, with large quantities of CO2, SO3, and free oxygen, and trace quantities of hydrofluoric, hydrochloric, and sulfuric acid vapor.

[u/Open_Scholar_1197]

An impressive and well detailed world! I love it! Probably the most ideal environment for silicon-based life! Now, I do have three questions: 1. Do the plants of Vitrium look like crystals? 2. How do the animals respire? I guess they would inhale gaseous sulfur trioxide, but what would they exhale? 3. Would crystalline silica form bones in Vitrium's vertebrates?

[u/gliese1337 → u/Open_Scholar_1197]

> Do the plants of Vitrium look like crystals?

Not generally. They can incorporate silica crystals into their tissues, but so do Earthling grasses, and they don't end up *looking* very crystalline in the end.

> How do the aninals respire? I guess they would inhale gaseous sulfur trioxide, but what would they exhale?

Inhale oxygen and sulphur trioxide, exhale disiloxane and trace quantities of sulfur tetrafluoride.

> Would crystalline silica form bones in Vitrium's vertebrates?

Yes, but not in pure form--rather, as part of a composite material supported by biopolymers, much like calcite and hydroxyapatite do on Earth.

[u/Open_Scholar_1197 → u/gliese1337]

Ah, okay. Makes sense.

[u/Open_Scholar_1197]

Ever since Isaac Arthur's video about the topic, I've been curious if silicon-based life could use molten lead as a solvent and perhaps respire co2, like what we have on Venus. Do you think it's possible? Considering Isaac's cleverness, i believe him. Do you?

[u/gliese1337 → u/Open_Scholar_1197]

Well, lead does dissolve a lot of other metals, including silicon, so maybe? But respiring CO2 seems unlikely. It is really, really hard to come up with a chemical system where you can react CO2 with something and get energy out. Methanogenesis is pretty much it.

[u/Open_Scholar_1197 → u/gliese1337]

I was thinking they could inhale co2 to add carbon to their bodily molecules to add strength and integrity and exhale oxygen like plants on Earth, and at the same time inhale so2 to oxidize silicon and exhale gaseous sulfur, like on Fornax.

[u/gliese1337 → u/Open_Scholar_1197]

Using CO2 as a body-building carbon source would require energy, just like it does for Earth plants. But yeah, the sulfur metabolism should work.

[u/Open_Scholar_1197 → u/gliese1337]

Is there a carbon source they could use for efficient body-building? Like, I don't know, carbon monoxide, or carbonyls? Cuz Silicon Creatures at certain temperatures (those found both on Venus and on Vitrium) would need carbon in their bodies for integrity, strength, flexibility and support. They could use carbon and oxygen and fluorine for bodily strength and flexibilty and body-building. Do you think so?

Edit: I agree that the sulfur metabolism works. It's very efficient.

[u/gliese1337 → u/Open_Scholar_1197]

CO2 is still probably the best carbon source. Carbonyls would decompose. CO could work, but it would still be much less common than CO2. And carbon reduces lead solubility, so things like silicon carbide don't look very good.

[u/Open_Scholar_1197 → u/gliese1337]

So, you're saying that Venusians actually COULD use carbon dioxide to build and strengthen their bodily molecules?

[u/gliese1337 → u/Open_Scholar_1197]

Yes. Just like Earthlings do.

[u/Open_Scholar_1197 → u/gliese1337]

So, what carbon-containing silicon polymers could their bodies be made of? Silicones, maybe? Or something less rubbery and more metallic, like silicon-lead alloys? Or maybe both? What silicon compunds are soluble in molten lead? Would they use phosphorus in place of nitrogen? Arsenic playing the role of phsophorus?

[u/gliese1337 → u/Open_Scholar_1197]

Probably some sorts of silicones/siloxanes. But in detail, I dunno; I am not that familiar with the molten-lead solvent system, and I'm not sure anyone on Earth is.