JWST-TST DREAMS : quartz clouds in the atmosphere of WASP-17b

Abstract

Funding: D.G. acknowledges funding from the UKRI STFC Consolidated grant No. ST/V000454/1. H.R.W. was funded by UK Research and Innovation (UKRI) under the UK government's Horizon Europe funding guarantee (grant No. EP/Y006313/1). A.G. acknowledges support from the Robert R. Shrock Graduate Fellowship. J.G. acknowledges funding from SERB research grant No. SRG/2022/000727. R.J.M. is supported by NASA through the NASA Hubble Fellowship grant No. HST-HF2-51513.001, awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. We acknowledge the MIT SuperCloud and Lincoln Laboratory Supercomputing Center for providing high performance computing resources that have contributed to the research results reported within this paper. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center. N.E.B. acknowledges support from NASA's Interdisciplinary Consortia for Astrobiology Research (grant No. NNH19ZDA001N-ICAR) under award number 19-ICAR19_2-0041.Clouds are prevalent in many of the exoplanet atmospheres that have been observed to date. For transiting exoplanets, we know if clouds are present because they mute spectral features and cause wavelength-dependent scattering. While the exact composition of these clouds is largely unknown, this information is vital to understanding the chemistry and energy budget of planetary atmospheres. In this work, we observe one transit of the hot Jupiter WASP-17b with JWST's MIRI LRS and generate a transmission spectrum from 5-12 μm. These wavelengths allow us to probe absorption due to the vibrational modes of various predicted cloud species. Our transmission spectrum shows additional opacity centered at 8.6 μm, and detailed atmospheric modeling and retrievals identify this feature as SiO2(s) (quartz) clouds. The SiO2(s) clouds model is preferred at 3.5-4.2σ versus a cloud-free model and at 2.6σ versus a generic aerosol prescription. We find the SiO2(s) clouds are comprised of small ~0.01 μm particles, which extend to high altitudes in the atmosphere. The atmosphere also shows a depletion of H2O, a finding consistent with the formation of high-temperature aerosols from oxygen-rich species. This work is part of a series of studies by our JWST Telescope Scientist Team (JWST-TST), in which we will use Guaranteed Time Observations to perform Deep Reconnaissance of Exoplanet Atmospheres through Multi-instrument Spectroscopy (DREAMS).Peer reviewe