JWST COMPASS: A NIRSpec/G395H Transmission Spectrum of the Sub-Neptune TOI-836c NICOLE L. WALLACK, NATASHA E. BATALHA, LILI ALDERSON, NICHOLAS SCARSDALE, JEA I. ADAMS REDAI, ARTYOM AGUICHINE, MUNAZZA K. ALAM, PETER GAO, ANGIE WOLFGANG, NATALIE M. BATALHA, JAMES KIRK, MERCEDES LÓPEZ-MORALES, SARAH E. MORAN, JOHANNA TESKE, HANNAH R. WAKEFORD, AND NICHOLAS F. WOGAN Abstract: The study presents results from the JWST NIRSpec G395H transit observation of TOI-836c, a sub-Neptune planet. The results show a featureless transmission spectrum, ruling out atmospheric metallicities below 175 times solar in the absence of aerosols at ~1 millibar. The study also leverages microphysical models to determine that aerosols at such low pressures are physically plausible. The results represent the first observation from the COMPASS program, which includes TOI-836b and aims to compare the presence and compositions of atmospheres for 12 super-Earths/sub-Neptunes. Keywords: Exoplanet atmospheric composition; Exoplanet atmospheres; Exoplanets; Infrared spectroscopy Introduction: The study focuses on the atmospheres of super-Earths and sub-Neptunes, which are common in the Galaxy. The study uses the JWST to measure the atmospheres of these planets to better understand their evolutionary trajectories. The study presents results from the JWST NIRSpec G395H transit observation of TOI-836c, a sub-Neptune planet. The results show a featureless transmission spectrum, ruling out atmospheric metallicities below 175 times solar in the absence of aerosols at ~1 millibar. The study also leverages microphysical models to determine that aerosols at such low pressures are physically plausible. The results represent the first observation from the COMPASS program, which includes TOI-836b and aims to compare the presence and compositions of atmospheres for 12 super-Earths/sub-Neptunes. Observations: The study presents results from the JWST NIRSpec G395H transit observation of TOI-836c. The results show a featureless transmission spectrum, ruling out atmospheric metallicities below 175 times solar in the absence of aerosols at ~1 millibar. The study also leverages microphysical models to determine that aerosols at such low pressures are physically plausible. The results represent the first observation fromJWST COMPASS: A NIRSpec/G395H Transmission Spectrum of the Sub-Neptune TOI-836c NICOLE L. WALLACK, NATASHA E. BATALHA, LILI ALDERSON, NICHOLAS SCARSDALE, JEA I. ADAMS REDAI, ARTYOM AGUICHINE, MUNAZZA K. ALAM, PETER GAO, ANGIE WOLFGANG, NATALIE M. BATALHA, JAMES KIRK, MERCEDES LÓPEZ-MORALES, SARAH E. MORAN, JOHANNA TESKE, HANNAH R. WAKEFORD, AND NICHOLAS F. WOGAN Abstract: The study presents results from the JWST NIRSpec G395H transit observation of TOI-836c, a sub-Neptune planet. The results show a featureless transmission spectrum, ruling out atmospheric metallicities below 175 times solar in the absence of aerosols at ~1 millibar. The study also leverages microphysical models to determine that aerosols at such low pressures are physically plausible. The results represent the first observation from the COMPASS program, which includes TOI-836b and aims to compare the presence and compositions of atmospheres for 12 super-Earths/sub-Neptunes. Keywords: Exoplanet atmospheric composition; Exoplanet atmospheres; Exoplanets; Infrared spectroscopy Introduction: The study focuses on the atmospheres of super-Earths and sub-Neptunes, which are common in the Galaxy. The study uses the JWST to measure the atmospheres of these planets to better understand their evolutionary trajectories. The study presents results from the JWST NIRSpec G395H transit observation of TOI-836c, a sub-Neptune planet. The results show a featureless transmission spectrum, ruling out atmospheric metallicities below 175 times solar in the absence of aerosols at ~1 millibar. The study also leverages microphysical models to determine that aerosols at such low pressures are physically plausible. The results represent the first observation from the COMPASS program, which includes TOI-836b and aims to compare the presence and compositions of atmospheres for 12 super-Earths/sub-Neptunes. Observations: The study presents results from the JWST NIRSpec G395H transit observation of TOI-836c. The results show a featureless transmission spectrum, ruling out atmospheric metallicities below 175 times solar in the absence of aerosols at ~1 millibar. The study also leverages microphysical models to determine that aerosols at such low pressures are physically plausible. The results represent the first observation from