Chapter 23

Chapter 23 — "Nitrogen Kills It"

TL;DR: Earth's air is 78% nitrogen and Erid's is 8%, so Grace and Rocky must breed two separate Taumoeba strains: one tough enough for Venus's atmosphere, one tough enough for Erid's lower stratum.

Summary: The two engineers narrow the targets. Earth doesn't actually need a fully Earth-tolerant Taumoeba — they need one that can survive the Venus environment, where Astrophage breeds, because that is where the predator must do its work. Venus's lower atmosphere holds about 3.5% nitrogen, far less than Earth surface. Erid's deeper "strata" — where Astrophage will eventually breed in 40 Eridani's system as it dims — runs around 8%. So they need two strains: Taumoeba-3.5 (call it Taumoeba-35) for Venus and Taumoeba-8 (call it Taumoeba-82.5 in scaled notation) for Erid. They start the long, patient work of evolutionary selection.

Key scenes:

• A whiteboard with Venus, Earth, and Erid as three rectangles labeled with nitrogen percentages
• Petri-dish arrays multiplying on the workbench in a grid, each labeled with a round number
• Grace and Rocky flipping through generation after generation of survivors, taking notes
• A montage time-passes shot — calendar pages of lab dates ticking forward, dish gradients sliding higher

Characters present: Ryland Grace, Rocky

Locations / settings:

• The Hail Mary lab, now organized as a long-running breeding facility

Visual motifs: a grid of Petri dishes glowing amber under hood-lights — pattern of life and death, an evolutionary fitness chart climbing slowly across a whiteboard, time-lapse calendar marks, Rocky's sphere parked beside the workbench like a partner at the same machine

Emotional tone: patient, methodical, marathon-long, hopeful

Confidence: high — the dual-strain breeding setup and the specific 3.5% / 8% nitrogen targets are consistent across summaries.