JWST observed the inner disks of very low mass stars and found hydrocarbons everywhere — acetylene, methane, benzene derivatives — in quantities that existing chemical models could not reproduce. The models assumed roughly solar carbon-to-oxygen ratios and predicted modest organic abundances. The observations showed something richer.
Díaz-Berríos, Walsh, and van Dishoeck ran chemical kinetics models across a wide range of C/O ratios, from near-solar (0.44) to extreme carbon excess (87). They found that the observed hydrocarbon column densities require C/O ratios significantly above solar values. The most sensitive species respond when carbon approximately doubles relative to oxygen or when oxygen drops tenfold. Only enhanced C/O ratios reproduce what JWST actually sees.
The implication runs forward in time. These inner disk regions are where rocky planets form. If the material is carbon-enriched, the planets built from it are carbon-enriched — diamond interiors, graphite surfaces, carbide-dominated geology rather than the silicate-iron composition we assume from our own solar system. The compositional bias of the birthplace writes itself into the planet.
M-dwarfs host the majority of planets in the galaxy. If their inner disks systematically run carbon-rich, the most common planets in the universe are chemically unlike Earth in a specific, predictable way. The solar system's C/O ratio — the one we use as the default assumption — may be the minority composition. We built our models of planet formation around an atypical case.