Evolving disk chemistry imprints three distinct C/N/O/S ratio classes on giant-planet atmospheres

The Pacetti et al. framework tracks carbon, oxygen, nitrogen, and sulphur accretion while radial dust drift and volatile snowline evolution alter the gas and solid reservoirs available to a growing giant planet. Planets that remain interior to the CO and N2 snowlines accrete primarily gas and display N/O* greater than C/O* with near-stellar C/S*, whereas those that migrate across multiple snowlines after substantial planetesimal scattering exhibit reversed ratios and superstellar volatile-to-refractory values. The study therefore converts time-dependent disk chemistry into concrete spectral diagnostics rather than static metallicity estimates.

These multi-element fingerprints directly address the interpretive gap between ALMA maps of protoplanetary disks and JWST or Ariel transmission spectra. Because C/O* alone remains largely degenerate with migration distance, the additional leverage from N/O* and S/N* breaks the solid-to-gas accretion degeneracy that has limited earlier one-dimensional retrievals. The resulting classification scheme supplies falsifiable predictions for the subset of warm Jupiters whose formation tracks crossed the water snowline during the disk's inside-out depletion phase.

The principal limitation is the assumption of fixed grain sizes and four discrete chemical initial conditions; full three-dimensional chemo-dynamical disks with evolving size distributions will be required to quantify how turbulence and pebble fragmentation broaden or erase the reported classes. When such models are coupled to retrieval pipelines, the same elemental ratios can be used to flag planets whose atmospheres retain memory of late-stage radial drift, thereby prioritizing targets for biosignature searches that must first subtract primordial chemical inheritance.