Cloudy mornings and clear evenings on a gas giant exoplanet
The spectra of exoplanet atmospheres are affected by aerosols (clouds and hazes) of uncertain origin. Proposed aerosol formation mechanisms include gas condensation or photochemical reactions. We measured the transmission spectrum of the tidally locked gas giant exoplanet WASP-94A b and identified asymmetry in its atmosphere. The morning limb is cooler and cloudy, whereas the evening limb is hotter and exhibits gaseous water absorption features. We interpret this difference as being due to the formation of cloud droplets near the morning limb, which evaporate during circulation to the evening limb. The dominant aerosols are clouds cycling between the day and night sides of the atmosphere, not photochemical hazes. The resulting asymmetry can severely bias chemical abundance measurements, unless limb-resolved spectroscopy is available.
Authors
- Katherine A. Bennett (ORCID: https://orcid.org/0000-0002-9030-0132)
- Carlos Gascón (ORCID: https://orcid.org/0000-0001-5097-9251)
- Duncan Christie (ORCID: https://orcid.org/0000-0002-4997-0847)
- Erin May (ORCID: https://orcid.org/0000-0002-2739-1465)
- Kevin B. Stevenson (ORCID: https://orcid.org/0000-0002-7352-7941)
- Guangwei Fu (ORCID: https://orcid.org/0000-0002-3263-2251)
- Stephen P. Schmidt (ORCID: https://orcid.org/0000-0001-8510-7365)
- Patrick McCreery (ORCID: https://orcid.org/0000-0003-0473-6931)
- Natalie H. Allen (ORCID: https://orcid.org/0000-0002-0832-710X)
- Maria Zamyatina (ORCID: https://orcid.org/0000-0002-9705-0535)
- Jacob Lustig‐Yaeger (ORCID: https://orcid.org/0000-0002-0746-1980)
- Joshua D. Lothringer (ORCID: https://orcid.org/0000-0003-3667-8633)
- Zafar Rustamkulov (ORCID: https://orcid.org/0000-0003-4408-0463)
- Lakeisha M. Ramos Rosado (ORCID: https://orcid.org/0000-0002-1056-3144)
- Mei Ting Mak (ORCID: https://orcid.org/0000-0002-1624-3360)
- David K. Sing (ORCID: https://orcid.org/0000-0001-6050-7645)
- Harry Baskett
- Le Wang (ORCID: https://orcid.org/0000-0002-6379-3816)
- Kevin C. Schlaufman (ORCID: https://orcid.org/0000-0001-5761-6779)
- Éric Hébrard
- L. C. Mayorga
- N J Mayne
- Mercedes López-Morales (ORCID: https://orcid.org/0000-0003-3204-8183)
- Daniel Thorngren (ORCID: https://orcid.org/0000-0002-5113-8558)
- Kristin S. Sotzen (ORCID: https://orcid.org/0000-0001-7393-2368)
- Jayesh Goyal (ORCID: https://orcid.org/0000-0002-8515-7204)
- Henrique Reggiani (ORCID: https://orcid.org/0000-0001-6533-6179)
- Sagnick Mukherjee (ORCID: https://orcid.org/0000-0003-1622-1302)
Institutions
- Space Telescope Science Institute (US)
- Planetary Science Institute (US)
- Johns Hopkins University (US)
- National Institute of Science Education and Research (IN)
- University of California, Santa Cruz (US)
- Homi Bhabha National Institute (IN)
- University of Exeter (GB)
- Johns Hopkins Medicine (US)
- Johns Hopkins University Applied Physics Laboratory (US)
- NOAA Oceanic and Atmospheric Research (US)
- Institut d'Estudis Espacials de Catalunya (ES)
- Max Planck Institute for Astronomy (DE)
- Gemini South Observatory (CL)
- Center for Astrophysics Harvard & Smithsonian (US)
- Arizona State University (US)
Publication Details
- Journal
- Science
- Published
- 2026-05-21
- DOI
- https://doi.org/10.1126/science.adx5903
- Citations
- 1
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 12.01
Funders
- National Science Foundation
- John Templeton Foundation
- Heising-Simons Foundation
- Science and Technology Facilities Council