1,2,1,1,4,6,7,8,9,1,1,10- 1School of Physics and Astronomy, University of Leicester
- 2Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Santiago, Chile
- 3AURA, Washington, DC
- 4Jet Propulsion Laboratory
- 5Royal Astronomical Society
- 6University of Oxford
- 7Space Science Institute
- 8University of California, Berkeley
- 9Northumbria
- 10NASA Goddard Space Flight Center
We present observations and analysis of Neptune’s atmosphere from JWST, providing new constraints on hydrocarbon abundances, cloud properties, and temperature structure across the planet’s disk.
JWST observed Neptune in June 2023 (program1249) as part of the Solar System Guaranteed Time Observations (GTO). Integral field spectroscopy (IFS) with the Near-Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument/Medium Resolution Spectrometer (MIRI/MRS) were combined to provide nearly simultaneous and continuous spatial and spectral data between 1.66 and 28.70 microns.
We show how wavelengths sensitive to the atmospheric temperatures reveal a structure consistent with Voyager [1] and ground-based imaging [2,3], with a sharply defined warm polar vortex. In contrast, wavelengths sensitive to stratospheric hydrocarbons (namely acetylene and ethane) show a marked enhancement in the northern winter hemisphere.
Finally, we examine the distribution and vertical structure of clouds in context of the temperature and chemical structure. Scattered light in NIRSpec observations indicate variable discrete clouds extend to pressures of roughly 50 mbar at the northernmost latitudes and south pole.
[1] Conrath, B. J., F. M. Flasar, and P. J. Gierasch. "Thermal structure and dynamics of Neptune's atmosphere from Voyager measurements." Journal of Geophysical Research: Space Physics 96, no. S01 (1991): 18931-18939.
[2] Fletcher, Leigh N., Imke de Pater, Glenn S. Orton, Heidi B. Hammel, Michael L. Sitko, and Patrick GJ Irwin. "Neptune at summer solstice: zonal mean temperatures from ground-based observations, 2003–2007." Icarus 231 (2014): 146-167.
[3] Roman, Michael T., Leigh N. Fletcher, Glenn S. Orton, Thomas K. Greathouse, Julianne I. Moses, Naomi Rowe-Gurney, Patrick GJ Irwin et al. "Subseasonal variation in Neptune’s mid-infrared emission." The Planetary Science Journal 3, no. 4 (2022): 78.
How to cite: Roman, M., Fletcher, L., Hammel, H., King, O., Orton, G., Rowe-Gurney, N., Irwin, P., Moses, J., de Pater, I., Melin, H., Harkett, J., Toogood, S., and Milam, S.: Temperature, Composition, and Cloud structure in Atmosphere of Neptune from MIRI-MRS and NIRSpec-IFU Observations, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–12 Sep 2025, EPSC-DPS2025-1261, https://doi.org/10.5194/epsc-dps2025-1261, 2025.
