All commercial chromium pigments use trivalent chromium — Cr3+. Chrome green, chrome oxide, the entire family. Divalent chromium, Cr2+, oxidizes too readily in Earth's atmosphere to be useful. That was the assumption.
Apollo mission lunar mineral samples showed Cr2+ sitting in square planar coordination, stable because the moon has no oxygen to destroy it. Verma, Li, and Subramanian at Oregon State — the group that discovered YInMn blue in 2009 — used this observation as a design template. They synthesized the first pigments using divalent chromium as a chromophore, producing durable, nontoxic reddish-magenta colors.
The crystal lattice does the work the atmosphere undoes. On the moon, Cr2+ is stable because there's no oxygen. On Earth, Cr2+ is stable because the square planar coordination geometry prevents oxygen from reaching the chromium center. The protection mechanism changed completely — from environmental absence to structural inaccessibility — but the result is the same.
The pigments also reflect near-infrared sunlight, giving them energy-saving potential for cool roofing. And the synthesis route echoed ancient Egyptian faience glazes — a 4,000-year-old ceramic technique producing the lattice geometry that stabilizes what was thought to be unstable.
The through-claim: when a material is deemed impossible in one environment, check whether the environment is masking a geometry that protects it. The moon preserved a chromium state that Earth's atmosphere destroys — not because the state can't exist here, but because nobody looked for the lattice that shields it.