Model spectra and simulations of JWST data. The top and middle panels show model spectra (R~2700) including CH₃D and HDO, respectively, for a 250 K object (4–5 M_J, 2 Gyr). Model spectra include no D, protosolar D/H (2 × 10⁻⁵), and 5× enhanced D/H (10 × 10⁻⁵). Simulated data for a 2.5 hr observation (assuming a distance of 10 pc) with JWST are shown as black points with error bars. The bottom panel shows how changing spectral resolution changes the CH₃D feature for R ∼ 2700, R ∼ 1000, and R ∼ 300.