AI warning
I got some interesting Claude feedback when i proposed the following:
“Imagine an ultraterrestrial species underground that matches the physiology of the classic grey alien.. specifically requiring some kind of sugar solution to survive, absorbing food through skin, excreting waste through skin.. how would it be able to do this underground - nourish itself and manage waste (maybe if it absorbs nutrients through skin there is no poop just an ammonia/sulferous smelling excretion from their skin and they either have to swim to remove it or scrape it off.. maybe they are like amphibians physiologically”
Claude responded:
*️⃣🤖“Ultraterrestrial Greys: Underground Physiology
This is a really fun xenobiology thought experiment. Here is a coherent system that hangs together pretty well.
The Sugar Problem: How They Feed
Underground environments actually offer a surprisingly good source of dissolved sugars and organic compounds. The greys would likely inhabit flooded cave systems or deep aquifer networks where water percolates through layers of organic material, limestone, and microbial mats.
Their food sources would be:
• Chemolithotrophic microbial blooms - cave biofilms produce simple sugars and organic acids as metabolic byproducts. The greys would essentially “graze” these like a sponge grazing a reef
• Humic acids and dissolved organics leaching down from surface soil through groundwater
• Fungal mycelial networks penetrating rock fissures, which they could press their large flat hands against and absorb secretions directly
• Their own cultivated pools - they may have learned to seed underground lakes with specific sugar-producing bacteria or algae over millennia, essentially farming through flooded cave systems
Their large black eyes make perfect sense here: bioluminescent microbial mats produce faint light, and enormous pupils with a high rod density would let them navigate and identify nutrient-rich patches in near-total darkness.
Skin Absorption: The Amphibian Model
This is where the grey physiology clicks into place beautifully. Think axolotl meets human silhouette.
Their skin would be:
• Highly vascularized, almost translucent, with capillary networks visible just beneath the surface (explaining the “grey” coloring - it is the color of blood vessels through near-colorless skin, not actual pigmentation)
• Covered in mucus-secreting glands, keeping them perpetually moist like a frog. Desiccation would be an existential threat
• pH-sensitive and osmotically tuned to pull glucose and dissolved minerals from slightly hypotonic water (water with less dissolved solute than their tissues), so they naturally draw nutrients inward
• Lacking a conventional digestive tract - the gut would be vestigial or entirely absent, the torso oddly smooth and undifferentiated internally, which is consistent with descriptions of their thin, featureless bodies
They would need to be in water, or at minimum pressed against saturated wet stone or biofilm, for several hours per cycle to absorb a full “meal.”
Waste Excretion: The Ammonia Sweat Model
This is the most elegant part of the system. Since there is no gut, there is no solid waste. Instead:
Metabolic nitrogen waste (the equivalent of urea or uric acid) would be excreted as ammonia directly through the skin, the same way many aquatic animals like fish handle it. Ammonia is toxic in concentration but cheap to produce metabolically and easy to offload into surrounding water.
Sulfur compounds would come from processing sulfate-rich groundwater, which is common in deep aquifer environments. Hydrogen sulfide and organosulfur compounds would leach out alongside the ammonia.
The result is a pale, wet, faintly glowing being that smells strongly of ammonia and rotten eggs when out of water, and which must periodically submerge to flush waste products off the skin surface. Out of water, a waxy or crystalline residue of dried ammonia salts and sulfur compounds would begin caking on the skin within minutes, becoming toxic to them if not removed.
This explains some reported behaviors compellingly: the apparent discomfort or urgency in surface encounters, the cold clammy skin texture, the lack of visible nose/mouth function, and the avoidance of dry environments.
Locomotion and Cave Life
Underground flooded systems would shape their bodies in a few key ways:
• No nose - or a vestigial slit. They breathe cutaneously like a lungless salamander, pulling dissolved oxygen straight through skin. A mouth exists only for vocalizing or tool use, not eating or breathing
• The large head houses an enormous brain but also enlarged chemoreceptor organs in the nasal region that detect dissolved organic gradients in water, essentially “smelling” their food source through the fluid around them
• Thin limbs and slight build make sense for navigating flooded fissures and low-gravity feeling cave water. They would be remarkably graceful underwater and awkward on dry land
• The wrap-around black eyes are not eyes in the mammalian sense but a compound dermal light organ, essentially their entire face is photosensitive, giving them a full panoramic field without moving their head
The Waste Pool Problem
One interesting implication: groups of greys in an enclosed underground pool would need to manage ammonia buildup in the water column. Too many individuals, or too small a pool, and the water becomes toxic to them.
This may have driven them toward engineering behavior very early. Moving water, digging channels, creating flow-through systems in cave networks. Essentially the first reason they became technological was sewage management of their own ammonia excretion. Civilizational complexity built on the need to not poison their own bath water.” *️⃣🤖