Evidence of pure ammonia clouds in Jupiter’s Northern Temperate domain from Juno/JIRAM infrared spectral data

ABSTRACT In this work, we analyse data from the Jovian Infrared Auroral Mapper (JIRAM) imaging spectrometer on board the NASA mission Juno, to investigate the presence of spectrally identifiable ammonia clouds (SIACs). Focusing on the data from the first perijove passage, we found that a white vortex structure near 40 $^{\circ }$N provides the best candidate. Implementing atmospheric retrieval thanks to the planetary spectrum generator, we fit the JIRAM spectra (in the 2.5–3.1 $\mu$m range) inside and outside the vortex, varying the gaseous ammonia profiles, and the clouds and hazes properties and composition. We found that outside the vortex, the best fit is achieved using main clouds composed of tholins (approximation of an unknown contaminant material). Inside the vortex the best fit is achieved when main cloud decks are composed of pure ammonia ice, or ammonia-coated tholins. We therefore claim the detection of 38 SIACs, all detected over the white vortex structure. With respect to the external regions, the retrieved parameters distributions inside the vortex show: (i) higher altitude hazes and clouds, (ii) smaller haze’s effective radii, and (iii) higher gaseous ammonia relative humidity values. Both the detection of pure ammonia ice clouds and the retrieved physical parameters are consistent with the vortex being the result of a moist convection storm that uplifted fresh ammonia from the deep troposphere which in turn either condensed or became a possible source of coating material for existing cloud particles. This work confirms the trend established by space and ground-based observations, for which ammonia clouds on Jupiter are rare and connected to strong convective episodes.

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Publication Details

Journal
Monthly Notices of the Royal Astronomical Society
Published
2025-03-05
DOI
https://doi.org/10.1093/mnras/staf381
Citations
2
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
2.31
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article

Evidence of pure ammonia clouds in Jupiter’s Northern Temperate domain from Juno/JIRAM infrared spectral data

R. Sordini, D. Grassi, A. Mura, Francesco Biagiotti et al.
2 citations
Monthly Notices of the Royal Astronomical Society
Astro and Planetary Science
2.31
article

Evidence of pure ammonia clouds in Jupiter’s Northern Temperate domain from Juno/JIRAM infrared spectral data

R. Sordini, D. Grassi, A. Mura, Francesco Biagiotti, G. Piccioni, S. K. Atreya, A. Cicchetti, Luis Guillermo Villanueva, F. Tosi, S. Levin, R. Noschese, T. Guillot, Giuseppe Sindoni, Glenn S. Orton, Christina Plainaki, Leigh N. Fletcher, Federico Oliva, Giuliano Liuzzi, C. J. Hansen, Gerald Eichstädt, S. J. Bolton, Shawn Brueshaber, C Li, A. Adriani, C. Castagnoli, E. D’Aversa
article en
2 citations

Abstract

ABSTRACT In this work, we analyse data from the Jovian Infrared Auroral Mapper (JIRAM) imaging spectrometer on board the NASA mission Juno, to investigate the presence of spectrally identifiable ammonia clouds (SIACs). Focusing on the data from the first perijove passage, we found that a white vortex structure near 40 $^{\circ }$N provides the best candidate. Implementing atmospheric retrieval thanks to the planetary spectrum generator, we fit the JIRAM spectra (in the 2.5–3.1 $\mu$m range) inside and outside the vortex, varying the gaseous ammonia profiles, and the clouds and hazes properties and composition. We found that outside the vortex, the best fit is achieved using main clouds composed of tholins (approximation of an unknown contaminant material). Inside the vortex the best fit is achieved when main cloud decks are composed of pure ammonia ice, or ammonia-coated tholins. We therefore claim the detection of 38 SIACs, all detected over the white vortex structure. With respect to the external regions, the retrieved parameters distributions inside the vortex show: (i) higher altitude hazes and clouds, (ii) smaller haze’s effective radii, and (iii) higher gaseous ammonia relative humidity values. Both the detection of pure ammonia ice clouds and the retrieved physical parameters are consistent with the vortex being the result of a moist convection storm that uplifted fresh ammonia from the deep troposphere which in turn either condensed or became a possible source of coating material for existing cloud particles. This work confirms the trend established by space and ground-based observations, for which ammonia clouds on Jupiter are rare and connected to strong convective episodes.

Monthly Notices of the Royal Astronomical SocietyVol. 538(3)
University of Rome Tor Vergata (IT), Michigan Technological University (US), Southwest Research Institute (US), Planetary Science Institute (US), Goddard Space Flight Center (US), Jet Propulsion Laboratory (US), University of Leicester (GB), University of Basilicata (IT), University of Michigan (US), Agenzia Spaziale Italiana (IT), Stuttgart Technical University of Applied Sciences (DE), Institute of Atmospheric Sciences and Climate (IT), Institute for Space Astrophysics and Planetology (IT), Université Bourgogne Franche-Comté (FR), Film Independent (US), Institute of Organic Synthesis and Photoreactivity (IT), Observatoire de la Côte d’Azur (FR), Bologna Research Area (IT), Sapienza University of Rome (IT)
Openalex Percentile: Top 13%
Astro and Planetary Science
2.31
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