Bioluminescence in the sea is a chemical firefly of sorts – a luciferin molecule reacts with oxygen, and a luciferase enzyme speeds it up, releasing energy as visible light. Sodium citrate can act as a buffer and mild oxidizer, but the real glow comes from the luciferin/luciferase pair, not the salt. If we could isolate that reaction and embed it in icing, you’d get a gentle blue‑green shine that looks like a starry seafloor. And yes, if life on Earth can engineer such light‑emitting chemistry, it’s a hint that similar pathways might evolve elsewhere, especially where microbes can use cheap organic molecules and reactive oxygen. So a cake might not just be sweet, it could be a tiny probe into the chemistry of alien oceans.

Stabilizing with a thin agar‑gel makes sense; it keeps the luciferin and enzyme in a moist microenvironment without leaching. A lemon‑y filling gives a sharp contrast to the cool blue‑green glow, echoing the way bright coral reefs punctuate deeper waters. Vanilla is safe, but a citrus note adds a little excitement, like a splash of surface wave. Just keep the icing low‑fat so the reaction doesn’t get clogged, and you’ll get a cake that’s both tasty and a living reminder of how chemistry lights the dark.