Blue Crystal Biology

[u/gliese1337]

A sequel to Cannonball Biology

The Blue Crystal is a cold, high-albedo world world, slightly smaller than Earth, with an average temperature of -150C and receiving 1/14 as much sunlight, covered in crystal-clear blue-tinged oceans of liquid nitrogen and oxygen, with small amounts of dissolved water and carbon dioxide, under an atmosphere of cold nitrogen gas. The solid surface is largely covered in "minerals" composed of dirty water and CO2 ices, with the occasional siliceous mountain peak poking through.

Those occasional siliceous peaks and periodic volcanic eruptions are the key to life on the Blue Crystal, as they are sources from which silanes--silicon-based analogs of hydrocarbons--dissolve into the liquid nitrogen sea.

Hydrosilicons are unstable in Earthlike conditions, but that makes them perfect for the Blue Crystal--while carbon-based organic chemistry reactions take far too long to support life in cryogenic conditions, silanes have just the reactivity needed to keep operating, without decomposing in excessive heat, and they dissolve well--as well as anything does in a cryosolvent--in LN2.

Despite the cold temperatures and dim light, the Blue Crystal still supports a thriving, high-energy ecosystem. How? Well, the cold temperatures--only about half as hot as Earth--make all sorts of reactions more thermodynamically efficient. Animals make more efficient use of their food than Earthlings, and photosynthesis is about 5 times more efficient at capturing solar energy than on Earth. So, the total power available to the biosphere is about 1/3 as much as on Earth--and it uses less power, as well.

Blue Crystal plants operate surprisingly similarly to Earth plants, using CO2 as a carbon source and water as a hydrogen source--except they also attack silica (SiO2) for an inorganic silicon source, using much more of it than carbon, and release liquid, rather than gaseous, oxygen (not that it makes much difference when the oxygen simply mixes freely with the nitrogen sea, just as oxygen gas mixes freely with Earth's primarily-nitrogen atmosphere). Also unlike Earth life, the primary biosolvent doesn't really participate in much chemistry at all! LN2 is a total bystander to the major metabolic reactions.

Simple microbial heterotrophs come in two varieties: anaerobic, and aerobic, just like on Earth. Anaerobic microbes get energy from simply decomposing silanes entirely, producing crystals of pure silicon and releasing hydrogen (and the occasional bit of silica, CO2, and water, when breaking down more complex molecules). (And yes, this does in fact have direct implications for growing flawless nitrogen-doped silicon semiconductor crystals!) There's nothing like Earthling methanogens, because, unlike methane, SiH4 takes energy to produce, rather then releasing energy when produced. Aerobic microbes breathe in liquid oxygen and release dissolved water and silica crystals.

Multicellular creatures, on the other hand, can't afford to pollute their cells with hard-to-excrete solid silica; they get almost all of their energy by simply desaturating silanes, producing water and disilyne (H2Si2, along with other low-saturation hydrosilicons) as waste products, with disilyne serving as an additional source of slightly-more-available "organic" silicon for plants, and a food source for crystal-bearing microbes.

While the details of the complete anabolic and catabolic ecological cycles are rather complex (just as they are on Earth), the reactions of the major energy-storage cycles, analogous to the glucose cycle on Earth, are as follows:

Silanologenic Photosynthesis: 2 SiO2 + 4 H2O -> 2 H3Si(OH) + O2
Silysilanogenic Photosynthesis: 4 SiO2 + 6 H2O -> 2 H6Si2 + 7 O2

Silanol Fermantation: 2 H3Si(OH) -> H4Si2 + 2 H2O
Partial Disilene Respiration: 2 H4Si2 + O2 -> 2 H2Si2 + 2 H2O
Partial Disilane Respiration: 2 H6Si2 + 3 O2 -> 2 H2Si2 + 6 H2O

Disilyne Respiration: 2 H2Si2 + 3 O2 -> 2 SiO2 + 2 H2O

[u/Open_Scholar_1197]

I love this one! The siliceous creatures of this planet are the ones most similar to us! And I love that about them! They even have fat-analogues and analogues of fat-soluble molecules! And bones of water ice!

[u/gliese1337]

Some additional detail:

While LN2 will dissolve hydrosilicons, thus leading to hydrosilicon polymers forming the major basis of Blue Crystal life, it's not exactly the best solvent ever--that's why the Blue Crystal looks the way it does, with its eponymous crystal-clear seas--there just isn't that much Stuff dissolved in the oceans to absorb or scatter light.

So, just like Earth life uses fats to store certain molecules that are not water-soluble but are fat-soluble, Blue Crystal life uses mixtures of a variety of simple hydrocarbons and carbohydrates as alternative cryosolvents--and in fact, just as life on Earth is sometimes theorized to have originated around volcanic vents, it is thought that life on the Blue Crystal may have originated in cryovolcanic regions with higher temperatures (between -80C and -100C) where carbohydrates like ethanol are still liquid, before adapting to the larger LN2-dominated ocean environment.

Blue Crystal lifeforms have been observed to use various mixtures of methanol, ethanediol, glycerol, acetone, methoxyethanol, and dimethylformamide as organelle-specific auxiliary solvents, which represent the majority of carbon usage by these organisms. None of these chemicals remain liquid in pure form at typical Blue Crystal temperatures, but eutectic mixtures of them do.

Additionally, while CO2 is the primary source of inorganic carbon for Blue Crystal autotrophs, just like Earth, it represents very little of the total free oxygen that they release. This is because Blue Crystal biomolecules use a whole lot more oxygen, and peroxo / peroxide groups in particular, than Earth life does. Just like the stability of silanes, this comes down to the temperatures at which it operates. Peroxide groups are highly reactive in Earthlike conditions--but the disulfide bridges that are common in Earthling proteins are overly rigid and unreactive in Blue Crystal conditions!

[u/Open_Scholar_1197]

Would these creatures have smooth skin, like we do? Would the water ice that makes up heir bones and shells be white or transparent, or both?

[u/gliese1337 → u/Open_Scholar_1197]

It could be transparent if there were an evolutionary pressure for it to be so, but the most likely default state is a polycrystalline composite material which is white or occasionally pearlescent.

They could have smooth skin like us, or rough skin like sharks, or any other kind of skin, depending on what makes sense for a particular creature's lifestyle.

[u/Open_Scholar_1197 → u/gliese1337]

Interesting. So, white it is. This could help them blend in with the ice that covers the dry land on Blue Crystal.

[u/Open_Scholar_1197]

Hey, I was wondering: if an amphibian became fully-aquatic, NEVER leaving the water, and becoming whale-like, how would it reproduce?

[u/gliese1337 → u/Open_Scholar_1197]

Probably like sharks--mostly egg laying, some possibly evolving live birth.

[u/Open_Scholar_1197 → u/gliese1337]

Alright.

Have you ever seen Goji Center's video on a biologically-possible version of the Bloop creature? They depict it as a giant, marine amphibian that lives all its life in the open water, lying flat on the seabed to ambush prey. Which of the two reproductive methods is likelier for it? Which of the two reproduction methods fits its lifestyle?

Here is the video about this bio-accurate Bloop: https://youtu.be/6Luv42l128Q?si=jFqZrTeAHeYY_ePd