The Tunnel
Ammonia as a life solvent, radiative cooling, and contact engineering
The Eridians build a xenonite tunnel between both ships. Grace deduces they live in high-pressure, high-temperature ammonia, confirming life can use solvents other than water. Physical first contact is about to happen.
Ammonia as a life solvent
Grace deduces the Eridians live at high temperature and pressure. Ammonia is their "water."
The science behind it
Ammonia (NH₃) is liquid between -77°C and -33°C at atmospheric pressure. But under high pressure, its boiling point rises. At 29 atmospheres, it could be liquid above 100°C.
As a solvent, NH₃ can dissolve many compounds. It forms hydrogen bonds (like water, but weaker). Theoretically, it could support complex biochemical reactions.
Life needs a solvent where molecules move, interact, and react. Water is excellent, but not the only option. Other candidates: liquid methane (Titan), sulfuric acid (Venus), ammonia.
The Stefan-Boltzmann law (P = σAT⁴) lets you calculate how long an object takes to cool in vacuum. Higher temperature = faster radiation. If the cylinder was still hot after 40 minutes, its initial temperature exceeded 200°C.
Key terms
Try it yourself
Radiative Cooling in Vacuum
Rocky's cylinder was still hot after 40 min → initial temp >200°C
The xenonite tunnel: engineering first contact
Eridians build a xenonite tunnel and glue it to the Hail Mary's aluminum hull with alien adhesive. Each side has its own atmosphere.
The science behind it
Bonding two completely different materials (alien xenonite + human aluminum) without knowing the other's exact composition implies an extraordinarily versatile adhesive.
The tunnel has a dividing wall supporting the pressure difference: 1 atm of oxygen (Grace's side) vs 29 atm of ammonia (Eridian side). Catastrophic failure would kill both.
Wall knocking ("knock, knock, knock") is the most primitive communication technology possible: requires no language, no electronics, just transmits "I'm here and I'm intelligent."