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First observations of CH4 and H3+ equatorial detached layers, as seen by JIRAM/Juno
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  • Alessandra Migliorini,
  • Bianca Maria Dinelli,
  • Chiara Castagnoli,
  • Maria L. Moriconi,
  • Francesca Altieri,
  • Sushil K. Atreya,
  • Alberto Adriani,
  • Alessandro Mura,
  • Federico Tosi,
  • Alessandro Moirano,
  • Giuseppe Piccioni,
  • Davide Grassi,
  • Roberto Sordini,
  • Raffaella Noschese,
  • Andrea Cicchetti,
  • Scott J Bolton,
  • Giuseppe Sindoni,
  • Christina Plainaki,
  • Angelo Olivieri
Alessandra Migliorini
INAF
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Bianca Maria Dinelli
Istituto di Scienza dell'Atmosfera e del Clima - CNR

Corresponding Author:[email protected]

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Chiara Castagnoli
INAF-IAPS
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Maria L. Moriconi
CNR-ISAC
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Francesca Altieri
INAF
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Sushil K. Atreya
University of Michigan-Ann Arbor
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Alberto Adriani
IAPS-INAF
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Alessandro Mura
INAF-IAPS
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Federico Tosi
INAF-IAPS
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Alessandro Moirano
INAF-IAPS
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Giuseppe Piccioni
INAF
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Davide Grassi
INAF
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Roberto Sordini
IAPS-INAF
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Raffaella Noschese
Istituto Nazionale di Astrofisica
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Andrea Cicchetti
Istituto Nazionale di Astrofisica
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Scott J Bolton
Southwest Research Institute
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Giuseppe Sindoni
Agenzia Spaziale Italiana
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Christina Plainaki
Agenzia Spaziale Italiana
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Angelo Olivieri
Agenzia Spaziale Italiana
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Abstract

In this work we present the detection of CH4 and H3+ emissions in the atmosphere of Jupiter as two well separated layers, located, respectively, at a tangent altitudes of about 200 km and 500-600 km above the 1-bar level. We studied the vertical distribution of the two species retrieving their Volume Mixing Ratio (VMR) and temperature simultaneously or allowing only one quantity to vary. From this analysis, it is not possible to firmly conclude if the observed H3+ and CH4 features are due to an increase of their VMR or rather to variations of the temperature of the two molecules. However, our retrieval indicates that CH4 is in non-Local Thermal Equilibrium (non-LTE) condition, considering that the retrieved temperature values at about 300 km, where the maximum CH4 concentration lies, is always about 100 K higher than the Galileo measurements.
We suggest that vertically propagating waves is the most likely explanation for the observed VMR and temperature variations in the JIRAM (Jovian InfraRed Auroral Mapper) data. Other possible phenomena could explain the observed evidences, for example a dynamical activity driving chemical species from lower layers towards the upper atmosphere, like the advection-diffusion processes responsible for the enhancement observed by Juno/MWR (MicroWave Radiometer), or soft electrons precipitation, although a better modeling is required to confirm these hypothesis.
The characterization of CH4 and H3+ species, simultaneously observed by JIRAM, offers the opportunity for better constraining the atmospheric models of Jupiter and understanding the planetary formation.