A detailed Eridian physiology and biochemistry model inspired by Project Hail Mary - It's a speculative model independently developed by me. So it serves as an alternative model for how Eridian breath is not canon to the Novels or the movie.
Recently, I have watched Andy Weir's novel based movie named Project Hail Mary, and it got me thinking about their metabolism and physiology, like what their energycycle is or what could be the atmospheric composition of their planet, and I independently developed a model with diagrams and chemical reactions which could answer this purely out of enthusiasm and respect. I purely built this from first principles.
Given Erid's constraints (Liquid NH₃ solvent, P ≈ 28 atm, T ≈ 210°C, no stable liquid H₂O), here's what the model proposes: Eridians absorb H2 transdermally and inhale CO2. Internally, H2 feeds an electron transport chain where N2 acts as terminal electron acceptor producing NH3 and ATP. That NH3 reacts with CO2 forming ammonium carbamate, which converts to urea — their primary excretory product. Surface bacteria decompose urea back into NH3, CO2 and H2, closing the planetary cycle completely.
The key conclusion: Eridians probably don't breathe ammonia at all. Their ammonia atmosphere is geological-scale metabolic waste — exactly like Earth's O2 was cyanobacterial waste but at macroscopic scale their planet physics allows this.
The biochemical reasoning is mine, diagram design assisted by Claude (Anthropic).
correct - Project Hailmary movie was released in 2026 not 2021.