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Storms and the Depletion of Ammonia in Jupiter: I. Microphysics of "Mushballs"

Guillot, Tristan and Stevenson, David J. and Atreya, Sushil K. and Bolton, Scott J. and Becker, Heidi N. (2020) Storms and the Depletion of Ammonia in Jupiter: I. Microphysics of "Mushballs". Journal of Geophysical Research. Planets, 125 (8). Art. No. e2020JE006403. ISSN 2169-9097. https://resolver.caltech.edu/CaltechAUTHORS:20200820-125847066

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Abstract

Microwave observations by the Juno spacecraft have shown that, contrary to expectations, the concentration of ammonia is still variable down to pressures of tens of bars in Jupiter. We show that during strong storms able to loft water ice into a region located at pressures between 1.1 and 1.5 bar and temperatures between 173 and 188 K, ammonia vapor can dissolve into water ice to form a low‐temperature liquid phase containing about one‐third ammonia and two‐third water. We estimate that, following the process creating hailstorms on Earth, this liquid phase enhances the growth of hail‐like particles that we call mushballs. We develop a simple model to estimate the growth of these mushballs, their fall into Jupiter's deep atmosphere, and their evaporation. We show that they evaporate deeper than the expected water cloud base level, between 5 and 27 bar depending on the assumed abundance of water ice lofted by thunderstorms and on the assumed ventilation coefficient governing heat transport between the atmosphere and the mushball. Because the ammonia is located mostly in the core of the mushballs, it tends to be delivered deeper than water, increasing the efficiency of the process. Further sinking of the condensates is expected due to cold temperature and ammonia‐ and water‐rich downdrafts formed by the evaporation of mushballs. This process can thus potentially account for the measurements of ammonia depletion in Jupiter's deep atmosphere.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1029/2020je006403DOIArticle
http://doi.org/10.5281/zenodo.3749609DOICode
https://doi.org/10.1002/essoar.10502154.1DOIDiscussion Paper
ORCID:
AuthorORCID
Guillot, Tristan0000-0002-7188-8428
Stevenson, David J.0000-0001-9432-7159
Atreya, Sushil K.0000-0002-1972-1815
Bolton, Scott J.0000-0002-9115-0789
Becker, Heidi N.0000-0001-5777-9850
Additional Information:© 2020 American Geophysical Union. Issue Online: 05 August 2020; Version of Record online: 05 August 2020; Manuscript accepted: 17 April 2020; Manuscript revised: 14 April 2020; Manuscript received: 03 February 2020. This paper is dedicated to the memory of our friend and colleague Adam Showman, curious mind, great scientist and wonderful man. We thank the referees and particularly Kensuke Nakajima for helpful comments. TG thanks Stéphanie Cazaux, Yohai Kaspi, Ravit Helled, the IWG and AWG Juno teams for discussions that led to this work and Gaël Guillot and Flora Bellone for experimental tests on milk downdrafts and on ice melting in the family oven. Data Availability Statement: T.G. acknowledges support from the Centre National d'Etudes Spatiales and the Japan Society for the Promotion of Science. The codes used to make the figures in this paper are available online (http://doi.org/10.5281/zenodo.3749609).
Group:Astronomy Department
Funders:
Funding AgencyGrant Number
Centre National d'Études Spatiales (CNES)UNSPECIFIED
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
Subject Keywords:Jupiter's atmosphere; Ammonia; Water; Storms; cloud microphysics; Phase diagram
Issue or Number:8
Record Number:CaltechAUTHORS:20200820-125847066
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20200820-125847066
Official Citation:Guillot, T., Stevenson, D. J., Atreya, S. K., Bolton, S. J., & Becker, H. N. (2020). Storms and the depletion of ammonia in jupiter: I. Microphysics of “Mushballs”. Journal of Geophysical Research: Planets, 125, e2020JE006403. https://doi.org/10.1029/2020JE006403
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105045
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:20 Aug 2020 20:09
Last Modified:22 Oct 2020 17:34

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