Top: Fig 12 in Colmenares et al. (2026) Middle: Fig. 1 in Colmenares et al. (2024b), Bottom: M.J. Colmenares

I work in Prof. Ted Bergin’s group studying the chemistry of protoplanetary disks, with a focus on the carbon-to-oxygen ratio (C/O) as a tracer of disk composition and planet formation. As part of the JDISCS collaboration, I use observations from the James Webb Space Telescope (JWST) to investigate how chemistry evolves in the planet-forming regions of young disks.

In Colmenares et al. (2026), we used JWST/MIRI to study ISO-Oph 37, a very young, highly inclined disk with strong molecular absorption. We found an unusually carbon-rich chemistry, with abundant hydrocarbons relative to CO and HCN, and evidence for a warm, stratified disk wind. These observations suggest that processes such as inward drift of icy material and the thermal processing of carbon-rich grains can establish carbon-rich chemistry early in disk evolution.

In Colmenares et al. (2024b), we studied DoAr 33, a T Tauri star with similarly hydrocarbon-rich chemistry. Its strong C₂H₂ emission is consistent with a carbon-enriched inner disk (C/O ≈ 2–4), potentially produced by the destruction of carbon-rich grains near the soot line. The detection of crystalline silicates provides additional evidence for substantial thermal processing in this region.

This observations led us to propose that hydrocarbon-rich chemistry may be sustained by unusually low accretion rates, which allow carbon released by grain destruction to persist in the inner disk. We are now testing this idea with our JWST Cycle 4 program, which will observe 14 disks spanning a wide range of stellar accretion rates. By comparing these systems, we can investigate how accretion shapes the chemistry of planet-forming regions.

Solar System meteorites exhibit a fundamental isotopic dichotomy between non-carbonaceous (NC) and carbonaceous (CC) groups. The existence of this dichotomy hints at two separate reservoirs from which planets could accrete material during the formation of the Solar System. In Colmenares et al. (2024a), we studied how an accretion outburst can set a thermal gradient in the protoplanetary disk and impart an isotopic signature.  We modeled how these two distinct reservoirs evolve, and found that the combination of viscous mixing and radial drift of the pebble populations is consistent with isotopic signatures in the current-day meteorites, specifically in supernovae-origin isotopes like 54Cr, 30Si,48Ca, among others.  This contrasts the idea that Jupiter formed in-situ and served as a barrier between the two reservoirs. 

Fig. 7 in Colmenares et al. (2024a)