Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 – 23 September 2022
Europlanet Science Congress 2022
Palacio de Congresos de Granada, Spain
18 September – 23 September 2022

OPS4

OPS
Jupiter and Giant Planet System Science: New Insights From Juno 

The Juno mission is providing crucial new data sets addressing Jupiter's origin, interior, atmosphere, satellites, rings and magnetosphere that challenge current theories of formation, evolution and dynamics of both Jupiter and giant planets in general. The Juno results when combined with data sets from previous missions and ground based observations is providing a new opportunity for the study of comparative planetology. Juno’s results on Jupiter also provide key insights important for our understanding of exoplanet systems. This session welcomes contributions on a wide variety of topics regarding Jupiter and other giant planets in general: gravity and magnetic field analysis and interpretation, giant planet magnetospheres, aurorae, radiation environments, atmospheric dynamics, planet interiors and the Galilean satellites. The session also welcomes remote observations acquired in support of Juno, and discussions of formation scenarios and evolutionary pathways of planetary bodies in our Solar System and beyond.

Convener: Scott Bolton | Co-conveners: Yamila Miguel, Yasmina M Martos, Corentin Louis, Stavros Kotsiaros, Kimberly Moore
Orals
| Thu, 22 Sep, 12:00–13:30 (CEST), 15:30–18:30 (CEST)|Room Andalucia 2, Fri, 23 Sep, 10:00–11:30 (CEST)|Room Andalucia 3
Posters
| Attendance Thu, 22 Sep, 18:45–20:15 (CEST) | Display Wed, 21 Sep, 14:00–Fri, 23 Sep, 16:00|Poster area Level 1

Session assets

Discussion on Slack

Orals: Thu, 22 Sep | Room Andalucia 2

Chairperson: Corentin Louis
12:00–12:10
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EPSC2022-95
Heidi Becker, Meghan Florence, Martin Brennan, Candice Hansen, Paul Schenk, Michael Ravine, John Arballo, Scott Bolton, Jonathan Lunine, Alexandre Guillaume, and James Alexander

Juno’s low-light sensitive Stellar Reference Unit (SRU) navigation camera has embarked on Juno’s Extended Mission as a full-fledged member of the science payload. SRU images from Juno’s Prime Mission led to multiple discoveries within the Jovian system, inspiring new objectives that the orbit’s evolution will soon put within reach. SRU images of Jupiter’s dark side revealed the presence of “shallow lightning” flashes with origins in high altitude ammonia-water clouds above the 2 bar level. These observations fortify theories in which ammonia-water hailstones (“mushballs”) transport ammonia into Jupiter’s deep atmosphere, accounting for the ammonia variability observed at depth by Juno’s Microwave Radiometer (MWR). Images of Jupiter’s faint dust ring have been acquired from unique vantage points while inside the ring looking out, and while observing the shadow line cast by Jupiter across the dust. In June 2021, the SRU imaged Ganymede’s dark side at >79 degrees illumination angle and <920 m/pixel resolution while the surface was illuminated only by Jupiter-shine. This novel use of a low-light star tracker resolved multiple craters, surface features (such as grooved terrain), and an unusual elongated ejecta deposit in Xibalba Sulcus. These features are not resolved in the Voyager and Galileo imagery used for the USGS global geologic map of Ganymede. Our discussion will focus on proposed updates to Ganymede’s geologic record and SRU ring science. A preview of upcoming SRU observations to investigate the influence of Jupiter’s shallow thunderstorms on Jupiter’s deep atmospheric dynamics (during the dark side perijoves starting in 2023) will also be included.

How to cite: Becker, H., Florence, M., Brennan, M., Hansen, C., Schenk, P., Ravine, M., Arballo, J., Bolton, S., Lunine, J., Guillaume, A., and Alexander, J.: Jovian Satellite and Ring Observations from the Juno Stellar Reference Unit, plus Plans for the Dark Side Perijoves, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-95, https://doi.org/10.5194/epsc2022-95, 2022.

12:10–12:20
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EPSC2022-145
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ECP
Miriam Estefanía Cisneros González, Manuel López-Puertas, Justin Erwin, Ann Carine Vandaele, Clément Lauzin, François Poulet, and Séverine Robert

The study of Jupiter’s atmosphere, its composition, evolution, distribution, structure, and dynamics around the planet, is of interest to the scientific community. Several missions, space observatories, and ground-based telescopes (even if limited by the telluric bands of water vapor), have studied Jupiter’s atmosphere. Some of them, such as Juno, the Hubble Space Telescope (HST), and the Very Large Telescope (VLT), continue providing information about the vertical structure and distribution of the atmosphere around the planet [1-3]. Although the main chemical composition of Jupiter’s atmosphere has been unraveled, many questions remain open, such as the global abundance of water, or the responsible chemistry for the coloration of the clouds [4]. Besides, a remarkable potential of VIS-NIR spectrometry for characterizing the composition and dynamics of planetary atmospheres has been demonstrated in the last years [5].

The next mission to the Jovian system from the European Space Agency (ESA) is the Jupiter Icy Moons Explorer (JUICE), to be launched in April 2023 with an arrival date on July 2031 [6]. One of the key scientific instruments onboard is the Moons And Jupiter Imaging Spectrometer (MAJIS), which will provide hyperspectral capabilities through two channels: VIS-NIR (0.5μm-2.35μm), and IR (2.25μm-5.54μm) [7]. We would like to perform simulations of different test cases with respect to the viewing geometries of MAJIS and assess its capabilities [8-9] to characterize the vertical structure of the Jovian atmosphere. For this purpose, we upgraded ASIMUT-ALVL, a Radiative Transfer (RT) code developed at BIRA-IASB, that has been extensively used to characterize Mars and Venus atmospheres [10-11].

During the implementation phase of the new Jupiter case in ASIMUT-ALVL, we applied the current knowledge of the physical and chemical characteristics of Jupiter, including the Rayleigh scattering contribution due to dominant atmospheric species, the refractive index of Jupiter’s atmosphere, and the Collision-Induced Absorption (CIA) due to H2-H2 and H2-He molecular systems. The typical temperature profile and atmospheric composition of Jupiter were retrieved from [12], although in our next studies we might use the CH4 abundance from the Volume Mixing Ratio (VMR) profile from [13], which is similar to that from [14]. The required line-lists were implemented from the HITRAN online database with line parameters adequate for an H2 and He dominant atmosphere, following the 2020 version release [15]. The extinction coefficient due to Rayleigh Scattering is obtained based on the calculation of its cross-section from [16], by considering the refractive indexes of H2 and He, obtained from the refractivities measured by [17] and [18], respectively. The atmospheric King correction factor is obtained from an adapted version of the formula of [19], considering the depolarization ratio of H2 as measured by [20]. To model the aerosols and hazes present in the atmosphere, we used the microphysical parameters defined by [21].

We validated the updated performances of ASIMUT-ALVL by individually comparing the main spectroscopic features of Jupiter’s atmosphere in the VIS-NIR range against KOPRA, an RT code originally developed for studying Earth’s atmosphere but later adapted to the atmospheres of Titan, Mars, and Jupiter [22]. We used the same geometry of observation, assuming solar occultations with a tangential altitude between 50km and 360km, a resolution of 0.3cm-1, a Signal-to-Noise Ratio (SNR) of 100, and an orbit around the planet of 5000km high. The mean difference in transmittance obtained between both models is below 3%.

The next step was to validate our RT model against observational spectroscopic data, which was obtained from the Visible and Infrared Mapping Spectrometer (VIMS) observations during the Cassini flyby to Jupiter [23]. This imaging spectrometer consists of two channels: VIS (0.35µm-1.07µm) and IR (0.85µm-5.1µm). In this presentation, we will discuss the results we obtained from the complete validation of our RT model, and the perspectives for the future implementation of the performances and viewing geometries of MAJIS/JUICE.

Acknowledgements

We acknowledge the kind support of Gianrico Filacchione who provided the calibrated data of the VIMS/Cassini observations. This project also acknowledges the funding provided by the Scientific Research Fund (FNRS) through the Aspirant Grant: 34828772 MAJIS detectors and impact on science.

References

[1] Bolton, S.J., et al., Space Science Reviews, 2017. 213(1): p. 5-37.
[2] Nichols, J.D., et al., Geophysical Research Letters, 2017. 44(15): p. 7643-7652.
[3] Antuñano, A., et al., The Astronomical Journal, 2019. 158(3): p. 130 (28).
[4] MAJIS Team, JUICE Definition Study Report, 2014.
[5] Langevin, Y., et al., Lunar and Planetary Science Conference, 2014. No. 1777: p. 2493.
[6] Grasset, O., et al., Planetary and Space Science, Vol. 78, pp. 1-21, 2013.
[7] Piccioni, G. et al., International Workshop on Metrology for AeroSpace, IEEE, 2019. pp. 318-323.
[8] ESA, Consolidated Report on Mission Analysis (CReMA), Tech. Rep. 5.0b23.1. https://www.cosmos.esa.int/web/spice/spice-for-juice
[9] Cisneros-González, M. E. et al., Space Telescopes and Instrumentation in Proc. SPIE 2020, 11443, 114431L.
[10] Vandaele, A.C., et al., Planetary and Space Science, 2015. 119: p. 233-249.
[11] Vandaele, A.C., et al., Optics Express, 2013. 21(18): p. 21148-21161.
[12] Moses, J.I., et al., Journal of Geophysical Research: Planets, 2005. 110(E8).
[13] Sánchez-López, et al., Astronomy & Astrophysics, 2022. Forthcoming article (ArXiv:2203.10086).
[14] Seiff, A., et al., Journal of Geophysical Research: Planets, 1998. 103(E10): 22857-22889.
[15] Gordon, I.E., et al., Journal of Quantitative Spectroscopy and Radiative Transfer, 2022. 277: p. 107949.
[16] Sneep, M., et al., Journal of Quantitative Spectroscopy and Radiative Transfer, 2005. 92(3): p. 293-310.
[17] Peck, E.R. et al., Journal of the Optical Society of America, 1977. 67(11): p. 1550-1554.
[18] Mansfield, C.R., et al., Journal of the Optical Society of America, 1969. 59(2): p. 199-204.
[19] Tomasi, C., et al., Applied optics, 2005. 44(16): p. 3320-3341.
[20] Parthasarathy, S., Indian Journal of Physics, 1951. 25: p. 21-24.
[21] López-Puertas, M., et al., The Astronomical Journal, 2018. 156.4: 169.
[22] Stiller, G.P., et al., Optical Remote Sensing of the Atmosphere and Clouds, SPIE 2000, 3501.
[23] Brown, R.H., et al., Icarus, 2003. 164(2): p. 461-470.

How to cite: Cisneros González, M. E., López-Puertas, M., Erwin, J., Vandaele, A. C., Lauzin, C., Poulet, F., and Robert, S.: Validation of ASIMUT-ALVL against observational data of Jupiter’s atmosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-145, https://doi.org/10.5194/epsc2022-145, 2022.

12:20–12:30
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EPSC2022-174
Scott Bolton and the Juno MWR Science Team

As observed for over 100 years, Jupiter's atmosphere has been characterized by a well-organized system of zones and belts disrupted by storms and vortices such as the Great Red Spot (GRS).  Jupiter’s meteorologically-active weather layer, where storms, vortices, and convective clouds are observed, was expected to be constrained to relatively shallow depths above the levels where water condensation and latent heat release might be an important driver of convection.  Early results from Juno extended the puzzle by discovering that both ammonia and water vary across most of the planet at much greater depths than their expected saturation levels.

 

The Microwave Radiometer (MWR) instrument on the Juno spacecraft provides a new and unique view into giant planetary atmospheres, using a set of radiometers operating at a range of frequencies that interrogate depths from the upper troposphere down to more than 600 km beneath the visible cloud tops.  As part of Juno, an unprecedented collaboration between ground- and space-based observations has been organized to help interpret the MWR and other Juno data.  Infrared images and spectroscopy from Juno’s Jovian Infrared Auroral Mapper (JIRAM) instrument, as well as from Earth-based observatories, provide compositional boundary conditions for the interpretation of the MWR data.  Spatial context comes from color imaging by JunoCam on Juno and from HST, together with ground-based imaging spanning the UV to the IR.  We present preliminary results of a study on the dynamics inside Jupiter’s atmosphere relating the cloud and storm features observed at shallow depths to the deeper atmospheric dynamics detected by the MWR.

How to cite: Bolton, S. and the Juno MWR Science Team: Exploring the depth of weather storms and vortices in Jupiter’s atmosphere, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-174, https://doi.org/10.5194/epsc2022-174, 2022.

12:30–12:40
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EPSC2022-220
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MI
Ricardo Hueso, Marc Delcroix, Agustín Sánchez-Lavega, Mikel Sánchez-Arregui, Csaba Palotai, and Mark Boslough

Since 2010 several amateur astronomers have discovered flashes of light that result from the collision of objects of 5-20 m in diameter, impacting in Jupiter’s atmosphere at velocities higher than 60 km/s. These objects release energies of the order of 1015-1016 J, or 200-1000 kiloton [1] and become observable even with small-size telescopes. Up to 2019, 6 such impact flashes have been observed by amateur astronomers [2-3]. In one case, the quality of the light-curve allowed to investigate the physical composition of the impacting object through the effect of its density when comparing with models of impacts and with the likely conclusion of a stony composition [4]. An important step forward has been the availability of software tools that allow to check video files of Jupiter to automatically search for the faint trace of an impact. The software DeTeCt is a free-software designed for the task [5] and available at: http://www.astrosurf.com/planetessaf/doc/project_detect.php

Here we report the characteristics of 3 additional impacts detected in 2020-2021. These were a very bright flash discovered on 13 September, which was simultaneously observed by at least 9 observers from Brazil to Germany. A new impact was discovered by Kothji Arimatsu from Kyoto University on 15 October 2021, running a dedicated telescope with two CMOS cameras, and also observed by amateur astronomers in Japan and Singapore. After finding this impact, one of these observers used the DeTeCt software on past observations acquired one year earlier on 11 Aug. 2020 finding an additional impact that had passed unnoticed. These 3 impacts in 2020 and 2021 were observed by a variety of cameras with different sensitivities to color. This allows a good quantification of the effective brightness temperature of the impact and a more accurate measurement of the energy released, and thus, a better estimation of the mass of the impactor. The event observed on 13 September 2021 was the brightest flash observed in Jupiter. The 15 October 2021 event was also brighter than most previous flashes and it impacted Jupiter in an area observed by the Junocam instrument 28 hours later. However, Junocam did not observe a remnant even at a spatial resolution over the impact area of ~30 km/pix. We present light-curves of these three impacts and their brightness temperatures from multi-wavelength observations. Brightness temperatures compare well with the spectra of a smaller impact observed in 2018 by the Juno mission [8]. From the light-curves and brightness temperatures we deduce masses, sizes and how these 3 new objects,  and the combined data of the DeTeCt project set ups new constrains in the current impact rate in the Jupiter System [3, 7]. We also evaluate the quality of the structures observed in the simultaneous lightcurves and their capability to constrain models of bolides impacting Jupiter’s atmosphere [2,4].

 

Figure: Composite images of the three impacts discussed in this work together with multi-wavelength lightcurves of the central impact from one of the colour videos obtained. The rate between blue and red is indicative of a high brightness temperature.

Acknowledgments

We are very grateful to all the observers of these impacts supplying the observations and reports used in this analysis. These are: (1) Victor PS Ang (Singapore), who observed the 2020-08-11 impact and was one of the 3 amateur observers of the 2021-11-15 impact. (2) Jose Luis Pereira (Brazil), Harald Paleske (Germany), Jean-Paul Arnould (France), Didier Walliang (France), Michel Jacquesson (France), Cosmin Sabdu Val (Romania), Jean-Christophe Griveau (France), who all observed and recorded videos of the 2020-09-13 impact together with additional colleagues operating their telescopes. In addition Maciej Libert (Germany), Simone Galelli (Italy) both reported visual observations of the impact looking at the eyepiece of their telescopes. (3) “Yotsu” (Japan) and Yasunobu Higa (Japan) who were two of the observers of the 2021-11-15 impact. We are also grateful to Kothji Arimatsu and the PONCOTS team from Kyoto Observatory for comments on the October 2021 impact they originally discovered and announced making possible its detection in amateur videos acquired from Singapore and Japan. In addition, we are extremely grateful to the many amateur astronomers taking part in the DeTeCt project and committing a large amount of their time to look for impacts.

References

[1] Hueso, R., Wesley A. et al. (2010). First Earth-based detection of a superbolide on Jupiter, The Astrophysical Journal Letters (721), 2010.

[2] Hueso, R. et al. (2013). Impact flux on Jupiter: From superbolides to large-scale collisions. Astronomy & Astrophysics, 560, A55.

[3] Hueso, R., Delcroix, M. et al. (2018). Small impacts on the giant planet Jupiter, Astronomy & Astrophysics, A68.

[4] Sankar, R. et al. (2020). Fragmentation modelling of the August 2019 impact on Jupiter, Montly Notices of the Royal Astronomical Society, 493, 4622-4630.

[5] Hueso, R. Et al. (2018). Detectability of possible space weather effects on Mars upper atmosphere and meteor impacts in Jupiter and Saturn with small telescopes. Journal of Space Weather and Space Climate, 8, A57.

[6] Delcroix, M. et al. (2019). Jupiter impact detection project, Europlanet Science Conference, EPSC2019-970.

[7] Delcroix, M. et al. (2020). Impact detection on Jupiter through amateur’s processing of their own videos using DeTeCt, Europlanet Science Conference, EPSC2020-775.

[8] Giles, R. S. et al. (2021). Detection of a Bolide in Jupiter’s atmosphere with Juno UVS, Geophysical Research Letters, 48, e2020GL091797.

How to cite: Hueso, R., Delcroix, M., Sánchez-Lavega, A., Sánchez-Arregui, M., Palotai, C., and Boslough, M.: Bolide Impacts in Jupiter’s Atmosphere in 2020-2021, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-220, https://doi.org/10.5194/epsc2022-220, 2022.

12:40–12:50
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EPSC2022-221
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ECP
José Eduardo Silva, Pedro Machado, Francisco Brasil, Ruben Gonçalves, and Miguel Silva

The thousands of exoplanets that have already been discovered launched an unprecedent drive towards the exploration of these new worlds, particularly their atmospheres. Many of these new planets fit the profile of a gas giant, although with a wide range of characteristics. To study these far away objects, we often use the Solar System as a starting point, thus a good knowledge of the atmospheres of these objects is paramount to understand these other worlds. In this regard, Jupiter often serves as model gas giant, due to its size and mass combination, among other parameters. However, despite numerous interplanetary and orbiting spacecraft combined with a long record of Earth-based observations, some fundamental questions regarding dynamical processes in Jupiter's atmosphere remain [Fletcher et al. (2020)]. The vertical structure of the colourful clouds we see with a small-sized telescope and their circulation mechanisms are still elusive [Sanchez-Lavega (2011)]. Also, to study the atmosphere dynamics of solar system planets, particularly its behaviour and evolution with time, continuous observations are required [Hueso et al. (2020)].

Multiple records of detailed observations span across more than 30 years, from first analysis of the zonal winds [Limaye et al. (1986), Vasavada et al. (1998)] using Pioneer and Galileo data, to more detailed views from the Cassini flyby [Porco et al. (2003), Salyk et al. (2006), Garcia-Melendo et al. (2011), Galperin et al. (2014)]. The most recent efforts in this regard are attributed to the Juno mission, which contributes with very high spatial resolution images [Hansen et al. (2017)], supported by observation campaigns from the Hubble Space Telescope [Garcia-Melendo et al. (2001), Tollefson et al. (2017), Hueso et al. (2017), Johnson et al. (2018)]. Although an impressive volume of data, winds at tropospheric levels have mostly been obtained with cloud-tracking techniques, which follow large patterns moving in the observable atmosphere of Jupiter. Recent efforts in studying the dynamics of the tropospheric region of Jupiter with other techniques such as high-resolution spectroscopy are gaining momentum, with the improvement of facilities which enable increased spectral resolution [Gaulme et al. (2018), Goncalves et al. (2019)].

Different techniques, such as high resolution spectroscopy applied to planetary atmospheres of the Solar System to study dynamics, can be complementary to the usually employed cloud-tracking method, by targeting slightly different levels of the atmosphere [Machado et al. (2021)], with the possibility therein to study the vertical wind shear. The technological capabilities of modern facilities that were designed to discover exoplanets can also be taken advantage of to observe Solar System atmospheres, achieving unprecedent levels of precision from the ground [Gonçalves et al. (2020)]. One such facility is ESPRESSO, assembled on the Very Large Telescope, at ESO. ESPRESSO is able to get two simultaneous spectra in a wavelength range between 378.2 and 788.7 nm with a resolving power that ranges from 70,000 in the Medium Resolution mode (MR) to more than 190,000 in the Ultra High Resolution mode (UHR) [Pepe et al. (2021)]. ESPRESSO was originally designed for exoplanet hunting and atmospheric characterisation, however, just as was demonstrated in [Gonçalves et al. (2020)] for HARPS-N, using these very high resolution spectrographs on solar system atmospheric characterisation can open new horizons on what is possible to achieve with ground-based instruments to study large objects in our cosmic vicinity.

We present an optimised Doppler velocimetry method, originally used to retrieve winds on Venus' cloud top region in the visible part of the spectrum [Widemann et al. (2008), Machado et al. (2012), Machado et al. (2014), Machado et al. (2017)]. With its successful application to Venus, this work presents an exploration of other targets within the solar system with our method. It is also an opportunity to investigate the effectiveness of ESPRESSO in the study of Solar System atmospheres, since it was used for this purpose for the first time. We show zonal wind speeds at equatorial latitudes using all the lines in the visible spectrum, from solar radiation backscattered on Jupiter’s atmosphere. These results are compared with the plethora of wind velocity data already retrieved in Jupiter’s troposphere for validation, finding consistency between both methods, despite our limited spatial and temporal coverage.

This work promotes another step in the exploration of other Solar System targets with ground-based observations, to fill the gap left by the limited availability of interplanetary space missions, ensuring continuous monitoring of the evolution of the atmospheric circulation on those planets at high spectral resolutions.

References

  • Fletcher, L.N., et al. (2020), PSJ, 216, article id. 30, DOI: 10.1007/s11214-019-0631-9;
  • Galperin, B., et al. (2014), Icarus, 229, pp. 295-320, DOI: 10.1016/j.icarus.2013.08.030;
  • Garcia-Melendo, E., Sanchez-Lavega, A., (2001), Icarus, 152, pp 316-330, DOI: 10.1006/icar.2001.6646;
  • Gaulme, P., et al. (2018), A&A, 617, article id. A41, DOI: 10.1051/0004-6361/201832868;
  • Gonçalves, I., et al. (2019), Icarus, 319, pp. 795-811, DOI: 10.1016/j.icarus.2018.10.019;
  • Gonçalves, R., et al. (2020), Icarus, 335, article id. 113418, DOI: 10.1016/j.icarus.2019.113418;
  • Hansen, C.J., et al., (2017), Spc. Sci. Rev., 243, pp. 475-506, DOI: 10.1007/s11214-014-0079-x;
  • Hueso, R., et al. (2017), Geophys. Res. Lett., 44, pp. 4669-4678, DOI: 10.1002/2017GL073444
  • Johnson, P.E., et al. (2018), Nat. Lett., 155, pp. 2-11, DOI: 10.1016/j.pss.2018.01.004;
  • Limaye, S.S., (1986), Icarus, 65, pp. 335-352, DOI: 10.1016/0019-1035(86)90142-9;
  • Machado, P., et al. (2012), Icarus, 221, pp. 248-261, DOI: 10.1016/j.icarus.2012.07.012;
  • Machado, P., et al. (2014), Icarus, 243, pp. 249-263, DOI: 10.1016/j.icarus.2014.08.030;
  • Machado, P., et al. (2017), Icarus, 285, pp. 8-26, DOI: 10.1016/j.icarus.2016.12.017;
  • Machado, P., et al. (2021), Atmosphere, 12, nº506, DOI: 10.3390/atmos12040506;
  • Pepe, F., et al. (2021), A&A, 645, A96, DOI: 10.1051/0004-6361/202038306;
  • Porco, C., et al. (2003), Science, 299, nº1541, DOI: 10.1126/science.1079462;
  • Salyk, C., et al. (2006), Icarus, 185, pp. 430-442, DOI: 10.1016/j.icarus.2006.08.007;
  • Sanchez-Lavega, A. (2011), CRC Press, 1st, Taylor & Francis Group;
  • Tollefson, J., et al. (2017), Icarus, 296, pp. 163-178, DOI: 10.1016/j.icarus.2017.06.007;
  • Vasavada, A.R., et al. (1998), Icarus, 135, pp. 265-275, DOI: 10.1006/icar.1998.5984;
  • Widemann, T., et al. (2008), Planet. Space Sci., 56, pp. 1320-1334, DOI: 10.1016/j.pss.2008.07.005.

How to cite: Silva, J. E., Machado, P., Brasil, F., Gonçalves, R., and Silva, M.: Jupiter's banded circulation through the eyes of VLT/ESPRESSO, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-221, https://doi.org/10.5194/epsc2022-221, 2022.

12:50–13:00
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EPSC2022-257
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ECP
José Ribeiro, Pedro Machado, Santiago Pérez-Hoyos, João Dias, and Patrick Irwin

The study of the thermal spectrum of Jupiter gives us the possibility to study the elements that constitute the Jovian atmosphere, allowing us to infer the formation history and conditions of the giant planet (Taylor et al., 2004). Determining the abundance of chemical species and isotopic ratios is fundamental in this regard. For this, we reanalyse 1997 Jupiter data obtained by the ESA mission Infrared Space Observatory (ISO) (Kessler et al., 1996) in the 793.65-3125 cm-1 (3.2-12.6 µm) region using the Short-Wave Spectrometer (SWS) (de Graauw et al., 1996).  Despite the age of this data, we argue that it warrants a revisit and reanalysis since it was an important step in the study of Jupiter’s atmosphere and there have since been advancements in atmospheric models and line data.

In this work we used the NEMESIS radiative transfer suite (Irwin et al. 2008) to reproduce the observations from Encrenaz et al. (1999), which will also work as a validation of our method. Using the Cassini/CIRS model as a starting point, we adapted the template for the ISO/SWS data. We compiled correlated k-tables from the spectral line database from Fletcher et al. (2018) for a NH3, PH3, 12CH3D, 12CH4, 13CH4, C2H2, C2H6, C2H4, C4H2, He and H2 atmosphere.

Figure 1: Plot of ISO/SWS and CIRS observations showing the discrepancy between both (no offset applied)

We first compare the spectrum obtained by ISO/SWS with the a priori model in order to find discrepancies between them as well as how each molecule individually impacts the forward model (Figure 1).

Our current work is focused on the 793.65-1500 cm-1 (6.7-12.6 µm) region of the spectrum, for comparison reasons between the CIRS and ISO-SWS data, with the 793.65-1200 cm-1 (8.3-12.6 µm) region showing the best fit.

We present here our preliminary results of the study of abundances of 12CH3D, 12CH4, 13CH4, C2H2 and C2H6 of Jupiter’s atmosphere as well as our study of the pressure-temperature profile of Jupiter obtained using NEMESIS retrievals. We also compare our results with the profiles and abundances from Neimann et al. (1998) and Fletcher et al. (2016) with the aim of constraining the number of possible best fit profiles.

As consequence of the former study, we also present our initial study of the H/D and 12C/13C isotopic ratio of the Jovian atmosphere from the abundances of 12CH3D, 13CH4 and 12CH4 following the methodology from Fouchet et al. (2000).

We hope with this work to advance the understanding of the atmosphere of Jupiter and the physical and chemical processes that occur, as well as better determining its vertical distribution of chemical species and thermal profile. As future work, we expect to extend our frequency domain to the full range of ISO/SWS observations, study the 15N/14N ratio and compare our finding with other relevant results.

 

 

References:

  • de Graauw et al., Observing with the ISO short-wavelength spectrometer, A&A 315, L49-L54, 1996
  • Encrenaz et al., The atmospheric composition and structure of Jupiter and Saturn form ISO observations: a preliminary review, Planetary and Space Science 47, 1225-1242, 1999
  • Fletcher et al., Mid-infrared mapping of Jupiter’s temperatures, aerosol opacity and chemical distributions with IRTF/TEXES, Icarus 278, 128–161, 2016
  • Fletcher et al., A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex, Nature Communications, Volume 9, 2018.
  • Fouchet et al., ISO-SWS Observations of Jupiter: Measurement of the Ammonia Tropospheric Profile and of the 15N/14N Isotopic Ratio, Icarus 143, 223–243, 2000
  • Irwin et al., The NEMESIS planetary atmosphere radiative transfer and retrieval tool, Journal of Quantitative Spectroscopy & Radiative Transfer 109, 1136–1150, 2008
  • Kessler et al., The Infrared Space Observatory (ISO) mission, A&A 315, L27, 1996
  • Neimann et al., The composition of the Jovian atmosphere as determined by the Galileo probe mass spectrometer, Journal of Geophysical Research Atmospheres 103(E10):22831-45, 1998
  • Taylor et al., Jupiter, The Planet, Satellites and Magnetosphere, Ch.4, Cambridge Planetary Science, Eds. Bagenal, Dowling, McKinnon, 2004

 

Acknowledgements:

We thank Thérèse Encrenaz, from LESIA, Observatoire de Paris, for providing the data for this work, Patrick Irwin, from the University of Oxford (UK), for the help with the NEMESIS radiative transfer suite and Maarten Roos-Serote for guidance and help in analysing the data and retrieval results.

We acknowledge support from the Portuguese Fundação Para a Ciência e a Tecnologia (ref. PTDC/FIS-AST/29942/2017) through national funds and by FEDER through COMPETE 2020 (ref. POCI-01-0145 FEDER-007672) and through a grant of reference 2021.04584.BD. 

How to cite: Ribeiro, J., Machado, P., Pérez-Hoyos, S., Dias, J., and Irwin, P.: Preliminary atmospheric study of Jupiter using ISO/SWS data, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-257, https://doi.org/10.5194/epsc2022-257, 2022.

13:00–13:10
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EPSC2022-324
Asier Anguiano-Arteaga, Santiago Pérez-Hoyos, and Agustín Sánchez-Lavega

Introduction

The Great Red Spot of Jupiter (GRS) is the largest and longest-lived anticyclone in the Solar System. First observed probably in the XVII century, it is one of the most remarkable dynamical phenomena in any known atmosphere. The structure, coloration and dynamical behavior of the Jovian anticyclone are severely affected by the formation and evolution of the GRS upper hazes, making them a relevant field of study.

The distinctive reddish color of the GRS (see Figure 1) is due to the nature and vertical distribution of the hazes over it. Carlson et al. (2016) proposed a possible chromophore to explain the GRS coloration: the products from photolyzed ammonia reacting with acetylene. Sromovsky et al. (2017) showed that this species was able to explain the reddish colorations all over the planet, despite being of very different intensity. This chromophore must be located on top of the tropospheric haze, in the so called “crème brûlée” model. Anguiano-Arteaga et al. (2021) performed a radiative transfer analysis that showed the existence of a stratospheric haze that could be compatible with the chromophore agent proposed by Carlson et al. (2016), although their study also suggested another chromophore located below that, in the upper tropospheric levels. However, every single color in the region shown in Figure 1 was also explained with those two chromophores.  In a recent paper (Anguiano-Arteaga et al., 2022) we find that the results of Anguiano-Arteaga et al. (2021) remain valid at least from 2015 to 2021, and no major temporal variations are expected in years close to such time span.

                                          

Figure 1. Map showing Jupiter’s Great Red Spot in December 2016. The RGB images are constructed from HST/WFC3 images with R=F631N, G=F502N and B=F395N. Image taken from Anguiano-Arteaga et al. (2022).

Vertical structure of the GRS

Images taken in filters sensitive to the altitude of the clouds and hazes show that the cloud top of the GRS is higher than its environment. The altitude of the hazes plays a major role in the coloration and dynamics. For example, in the scheme proposed by Carlson et al. (2016) material in the GRS raises to upper pressure levels and undergoes photochemical reactions that lead to the creation of the coloring agent. The amount of material high in the atmosphere would be then a fundamental factor to determine the production rate of chromophore species. Radiative transfer analyses give some insight on the altitude of the clouds and hazes. In Figure 2, we show maps of cloud top effective altitudes obtained from radiative transfer spectral modeling, as shown in Anguiano-Arteaga et al. (2021, 2022). However, radiative transfer analyses cannot provide some important information on the hazes, such as chromophore production rates or timescales of the undergoing atmospheric processes (e.g., coagulation, condensation and sedimentation). Because of this, microphysical considerations should be also taken into account in order to get a more complete description of the nature, structure and evolution of the hazes.

                                              

Figure 2. Map of the GRS area in December 2016 showing the pressure levels (in mbar) where the optical depth at 900 nm equals unity. This map is interpreted as the cloud top effective altitude.

Microphysical study

In this work, we perform microphysical simulations of the GRS hazes in the stratosphere and upper troposphere (P < 500 mbar). For this purpose, we develop a 1-D numerical code that takes into account the effects of particle sedimentation, coagulation, eddy diffusion and aerosol growth by molecular condensation. We report here results on the particle size distribution as a function of altitude, together with aerosol concentrations and timescale analysis regarding different microphysical processes. This constrains the mass production rates required to explain the chromophore model and hence serves as a test for any given proposed candidate. The results are interpreted according to prior findings following radiative transfer analysis on the GRS.

References

- Anguiano-Arteaga, A., Pérez-Hoyos, S., Sánchez-Lavega, A., Sanz-Requena, J. F., & Irwin, P. G. J. (2021). Vertical distribution of aerosols and hazes over Jupiter's Great Red Spot and its surroundings in 2016 from HST/WFC3 imaging. J. Geophys. Res. Planets., 126, e2021JE006996 https://doi.org/10.1029/2021JE006996

- Anguiano-Arteaga, A., Pérez-Hoyos, S., Sánchez-Lavega, A., Sanz-Requena, J. F., & Irwin, P. G. J. (2022). Temporal variations in vertical cloud structure of Jupiter’s Great Red Spot, its surroundings and oval BA from HST/WFC3 imaging. Submitted to J. Geophys. Res. Planets.

- Carlson, R.W., Baines, K.H., Anderson, M.S., Filacchione, G., & Simon, A.A. (2016). Chromophores from photolyzed ammonia reacting with acetylene: Application to Jupiter’s Great Red Spot. Icarus, 274, 106-115. https://doi.org/10.1016/j.icarus.2016.03.008

- Sromovsky, L.A., Baines, K.H., Fry, P.M., & Carlson, R.W. (2017). A possibly universal red chromophore for modeling color variations on Jupiter. Icarus, 291, 232-244. https://doi.org/10.1016/j.icarus.2016.12.014

How to cite: Anguiano-Arteaga, A., Pérez-Hoyos, S., and Sánchez-Lavega, A.: Formation and structure of hazes over Jupiter’s Great Red Spot, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-324, https://doi.org/10.5194/epsc2022-324, 2022.

13:10–13:20
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EPSC2022-355
Thibault Cavalié, Ladislav Rezac, Raphael Moreno, Emmanuel Lellouch, Thierry Fouchet, Bilal Benmahi, Thomas K. Greathouse, James A. Sinclair, Vincent Hue, Paul Hartogh, Michel Dobrijevic, Nathalie Carrasco, and Zoé Perrin

Jupiter's stratospheric chemistry and dynamics are poorly understood as a function of latitude. The Shoemaker-Levy 9 comet impacts in Jupiter's atmosphere in 1994 have offered us with a unique means to characterize Jupiter's stratospheric chemistry and dynamics. We can indeed use the delivery at 44°S of the long-lived species HCN, CO, H2O, and CS and the subsequent temporal evolution of their spatial distribution as constraints for vertical and meridional mixing, zonal winds and chemistry as a function of latitude. 
We mapped HCN and CO in Jupiter's stratosphere with ALMA in March 2017. These observations have already been used in Cavalié et al. (2021) and Benmahi et al. (2021) to derive the stratospheric zonal wind field. In this paper, we use the same observations to retrieve the vertical and meridional distributions of HCN and CO, almost 25 years after the comet impacts. We will present the spatial distributions of both species and discuss the implications on Jupiter's stratospheric chemistry, and vertical and horizontal mixing.

How to cite: Cavalié, T., Rezac, L., Moreno, R., Lellouch, E., Fouchet, T., Benmahi, B., Greathouse, T. K., Sinclair, J. A., Hue, V., Hartogh, P., Dobrijevic, M., Carrasco, N., and Perrin, Z.: ALMA observations of the spatial distribution of CO and HCN in the stratosphere of Jupiter, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-355, https://doi.org/10.5194/epsc2022-355, 2022.

13:20–13:30
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EPSC2022-427
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ECP
Sho Shibata, Ravit Helled, and Hiroshi Kobayashi

Introduction

The detailed observations by the NASA Juno spacecraft has advanced Jupiter’s interior structure models which can be used to improve our understanding of Jupiter’s origin. In this study, we investigate the potential origin of Jupiter's enriched atmosphere. We revisit the planetesimal accretion during Jupiter’s formation: in previous studies, the planetesimal accretion rate is calculated using N-body simulations that model the swam of planetesimals around proto-Jupiter. It was concluded that the heavy-element enrichment in Jupiter's envelope can be explained by the planetesimal accretion if Jupiter formed in a planetesimal disk that is at least five times more massive than the minimum mass solar nebulae (MMSN). However, this conclusion was inferred under the assumption that the total mass of captured planetesimals linearly increases with the surface density of planetesimals. In reality, in such a massive disk the gravitational interactions between planetesimals and embryos becomes so strong that the initial eccentricity and inclination are excited to 〜0.1 at most. In this study, we investigate this scenario in detail accounting for the change of the eccentricity and inclination of the planetesimals and show its affect off Jupiter’s growth rate and final composition.

 

Model

Figure 1: The surface density of planetesimals used in this study. This surface density profile is obtained by Kobayashi & Tanaka (2021).

 

We adopt a planetesimal disk obtained by Kobayashi & Tanaka (2021) where the collisional evolution of dust grains in the protoplanetary disk results in a dense-compact planetesimal disk because of pebble drift from the outer disk. Figure 1 shows the surface density profile of planetesimals we use in this study. We start the N-body simulations with a swam of planetesimals around proto-Jupiter which enters the runaway gas accretion phase and increases its mass from 10 M to 318 M. During its formation, we assume that proto-Jupiter slightly migrates inward due to type II migration. If a planetesimal collides on the surface of proto-Jupiter or loses its escape energy from Jupiter's Hill sphere, we assume that the planetesimal is captured by proto-Jupiter.

We set the initial eccentricities and inclinations of planetesimals as input parameters. Since the choice of the planetesimal’s size can significantly affect the accretion rate we consider various planetesimal sizes.

 

Results

Figure 2: The cumulative mass of captured planetesimals as a function of time. Black, red, green and blue lines show correspond to different assumed initial eccentricities of ‹e01/2=10-3,10-2,10-1, and 0.4, respectively. The initial inclination is set as   ‹i01/2=0.5‹e01/2.

 

In a massive planetesimal disk, proto-Jupiter accretes tens Earth-masses of heavy elements by the end of runaway gas accretion. Figure 2 shows the cumulative mass of captured planetesimals vs. time. We find that the increase of the initial eccentricity and inclination:

  • weakens resonant trapping and leads to an enhancement of planetesimal accretion,
  • reduces the capture probability of planetesimals.

Due to the combination of these effects, the captured mass of planetesimals decreases with the increase of the initial eccentricity and inclination.

 

Discussion

Figure 3: Total mass of captured planetesimals as a function of planetesimal size and the initial eccentricity. The initial inclination is set as   ‹i01/2=0.5‹e01/2. The solid and dashed black line shows the equilibrium eccentricity of planetesimals with and without embryos, respectively.

 

The initial eccentricity and inclination of planetesimals are determined by the scattering from other planetesimals/embryos. In a massive planetesimal disk as assumed here, embryos other than proto-Jupiter would form and be in the “oligarchic regime”. Considering the eccentricity and inclination excitation from the embryos, we conclude that the total mass of captured planetesimals is about 5-10 M, and is larger for larger planetesimals.

The bulk metallicity of Jupiter is still a matter of debate (e.g., Stevenson 2020). Planetesimal accretion could explain structure models with ~10 M of heavy elements in Jupiter’s outer envelope. However, if Jupiter’s enrichment is found to be higher, as suggested by some structure models (e.g., Miguel et al. 2022), an additional enrichment mechanism would be required. Such an enrichment could be a result of giant impacts of embryos. Such impacts have been suggested by Liu et al. (2019) for the formation of Jupiter’s fuzzy core.

We also compare our results with those presented by Shibata & Helled (2022), where planetesimal accretion was considered for the case of a migrating Jupiter from 20 au to 5 au. We find that the timing of planetesimal accretion must occur earlier for the in-situ formation case, which enriches Jupiter's interior rather than the outer envelope or atmosphere. We suggest that a determination of the heavy-element distribution in Jupiter’s envelope could constrain Jupiter’s formation location and formation history.

 

References

Kobayashi, H., & Tanaka, H. 2021, ApJ, 922, 16, doi: 10.3847/1538-4357/ac289c

Liu, S.-F., Hori, Y., M ̈uller, S., et al. 2019, Nature, 572, 355, doi: 10.1038/s41586-019-1470-2

Miguel, Y., Bazot, M., Guillot, T., et al. 2022, arXiv e-prints, arXiv:2203.01866. https://arxiv.org/abs/2203.01866

Shibata, S., & Ikoma, M. 2019, MNRAS, 487, 4510, doi: 10.1093/mnras/stz1629

Shibata, S., & Helled, R. 2022, ApJL, 926, L37, doi: 10.3847/2041-8213/ac54b1

Stevenson, D. J. 2020, Annu. Rev. Earth Planet. Sci., 48, 465

 

 

How to cite: Shibata, S., Helled, R., and Kobayashi, H.: Revisiting Planetesimal Accretion onto Proto-Jupiter, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-427, https://doi.org/10.5194/epsc2022-427, 2022.

Lunch break
Chairperson: Jack Connerney
15:30–15:40
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EPSC2022-475
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MI
Leigh Fletcher, Fabiano Oyafuso, Glenn Orton, Zhimeng Zhang, Shawn Brueshaber, Michael Wong, Cheng Li, Alessandro Mura, Davide Grassi, Henrik Melin, Steve Levin, Scott Bolton, John Rogers, and Shannon Brown

Jupiter’s cyclonic features are known to undergo transitions between quiescent states with smooth edges (often appearing as dark brown ‘barges’) to states with convective outbursts of billowing white clouds, chaotically churned into filamentary structures.  Cyclones in the latter state are known as ‘Folded Filamentary Regions’ (FFRs), and Voyager images (Ingersoll+1979, doi: 10.1038/280773a0) revealed them to be rapidly-varying turbulent regions, occurring in cyclonic domains on the poleward side of Jupiter’s prograde jets.  JunoCam visible-light observations (Orton+2017, doi:10.1002/2016GL072443, Rogers+2021, doi:10.1016/j.icarus.2021.114742), reveal the increasing prevalence of FFRs at mid-to-high latitudes.  They dominate the polar domain alongside smaller anticyclonic white ovals, drifting westward in latitude bands between the narrow prograde jets, and rapidly evolving over timescales of days. 

The present study makes use of Juno’s ever-improving microwave observations of the north polar domain, as the latitude of closest-approach (“perijove”) moves northward.  We therefore focus on FFRs in the northern hemisphere, where we find them to occur in zonally-organised latitude bands even at high latitudes.  Statistics of the FFRs suggest that they occur on the poleward sides of the N4 (43.3oN, centric), N5 (52.3oN), and N7 (66.1oN) prograde jets (N6 at 61.2oN coincides with a ‘bland zone’ lacking notable FFRs), and scattered in the polar domain up to the octagon of circumpolar cyclones at 85oN.  JIRAM 5-µm imaging of both poles reveal FFRs as generally dark structures with elevated aerosol opacity blocking thermal infrared emission from the 4-6 bar level, coinciding with the white stratiform clouds observed by JunoCam. Clusters of small cumulus-like clouds, as well as curvilinear cloud streaks, provide texture to the flat stratiform clouds to give the appearance of a network of filaments.  Visibly-dark lanes border the brighter filaments, creating an intricate network of narrow, aerosol-free, and 5-µm-bright striations within each FFR.  This is in contrast to cyclonic features such as barges at lower latitudes, where an absence of overlying aerosols generally renders them 5-µm bright. 

A survey of 1.4-50 cm observations acquired by Juno’s Microwave Radiometer (MWR) between PJ20 (May 2019) to PJ37 (October 2021) reveals that FFRs share a key characteristic with their low-latitude counterparts:  they are microwave-bright in channels sounding the 0.6-2.0 bar range (1.4-3.0 cm), become hard to distinguish from their surroundings near 5 bars (5.75 cm), but are then microwave-dark in the channel sounding 10-15 bar (11.5 cm). This suggests FFRs are depleted in ammonia gas and/or locally warmer at levels above the putative location of Jupiter’s water cloud, the latter implying a decay of cyclonic winds with altitude.  This shallow ammonia depletion is surprising, given the apparent convective nature of the FFRs - maybe NH3-rich plumes occupy a sufficiently small area of the cyclonic structure, so that they have negligible impact on the warm emission observed by MWR.  This shallow depletion is balanced by a local NH3 enrichment (or local cooling) at depth, below the water cloud, like a cyclonic lens.  However, the extension of FFR signatures to deeper levels (p>20 bars) is currently unclear due to insufficient spatial coverage and resolution at the longest-wave channels, and confusion arising from auroral contributions to the MWR dataset at 50 cm.  

An inversion in microwave brightness with depth was previously identified for Jupiter’s larger-scale belts and zones (Fletcher+2021, doi:10.1029/2021JE006858) and mid-latitude discrete features (Bolton+2021, doi:10.1126/science.abf1015), and now appears to be common at high latitudes as well.  Geostrophy implies that cyclonic circulations (low-pressure centers) cause a rise in potential-temperature surfaces in deeper layers, potentially triggering moist convection in the water cloud (e.g., Dowling & Gierasch, 1989 Bull. Amer. Astron. Soc 21, 946; Fletcher+2017, doi:10.1016/j.icarus.2017.01.001), producing the distinct convective cloud structure observed by visible and infrared imaging: juxtaposed tall convective towers, deep water clouds, and narrow clear lanes (Imai+2020, doi:10.1029/2020GL088397). Lightning sferics measured by MWR at 50 cm/600 MHz are more frequent in the N4, N5, and N7 domains where FFRs are common (Brown+2018, doi:10.1038/s41586-018-0156-5), and are further clustered in FFRs themselves (Wong+2020, doi:10.3847/1538-4365/ab775f).  Thus the evolution of the cyclonic FFRs, and their penetration to the moist depths below the water condensation level, may hold the key to understanding the distribution of lightning activity on Jupiter.

How to cite: Fletcher, L., Oyafuso, F., Orton, G., Zhang, Z., Brueshaber, S., Wong, M., Li, C., Mura, A., Grassi, D., Melin, H., Levin, S., Bolton, S., Rogers, J., and Brown, S.: Juno Characterisation of Cyclonic “Folded Filamentary Regions” within Jupiter’s Polar Domains, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-475, https://doi.org/10.5194/epsc2022-475, 2022.

15:40–15:50
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EPSC2022-534
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ECP
Corentin Louis, Caitriona Jackman, Aoife O’Kane Hackett, Elliot Devon-Hurley, William Kurth, George Hospodarsky, Philippe Louarn, Frederic Allegrini, John Connerney, Dale Weigt, Sean McEntee, Alexandra Fogg, James Waters, and Scott Bolton

During its 53-day polar orbit around Jupiter, Juno often crosses the boundaries of the Jovian magnetosphere, namely the magnetopause and bow shock, as well as the plasma disc (located at the centrifugal equator). The positions of the magnetopause and bow shock allow us to determine the dynamic pressure of the solar wind (using both the updated model of Joy et al. 2002 by Ranquist et al., 2020 and/or in situ data) which allows us to infer magnetospheric compression or relaxation, while the observations of plasma disc perturbations allows us to infer magnetospheric reconfigurations.

The aim of this study is to examine Jovian radio emissions during magnetospheric perturbations. We then use our analysis to determine the relationship between the solar wind and Jovian radio emissions (observed and emitted from different regions of the magnetosphere, from different mechanisms, and at different wavelengths from kilometers to decameters).

In this presentation, we show case studies for each typical case (bow shock, magnetopause and plasma disk crossings) and show that the activation of new radio sources is related to magnetospheric disturbances. By performing a statistical study of these crossings, we hope to be able to show the relationship between the activation of new radio sources (emission intensity and extension, source positions) and the solar wind (dynamic pressure, magnetic intensity, ...), with the aim of being able to use observations of planetary radio emission as a proxy for the solar wind.

How to cite: Louis, C., Jackman, C., O’Kane Hackett, A., Devon-Hurley, E., Kurth, W., Hospodarsky, G., Louarn, P., Allegrini, F., Connerney, J., Weigt, D., McEntee, S., Fogg, A., Waters, J., and Bolton, S.: Effect of magnetospheric disturbances on Jovian radio emissions: an in situ case study from Juno data, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-534, https://doi.org/10.5194/epsc2022-534, 2022.

15:50–16:00
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EPSC2022-535
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ECP
Deborah Bardet, Padraig Donnelly, Leigh N. Fletcher, Arrate Antuñano, Michael T. Roman, Glenn S. Orton, Sandrine Guerlet, Henrik Melin, and Jake Harkett


Ground- and space-based remote sensing, from Voyager, to Galileo, Cassini and Juno, has revealed the existence of circulation cells in the troposphere of Jupiter. These circulation cells, which may be similar to terrestrial Ferrel cells [1], show properties that vary significantly as a function of depth, showing circulations of opposing directions above and below the expected level of the water condensation cloud near 4-6 bar [2]. Moreover, the location of each vertical branch of the Ferrel-like cells are correlated to the Jupiter's temperature belt/zone contrast, suggesting a dynamical and thermal link between winds, temperatures, aerosols, and composition. 

To provide infrared support for Juno spacecraft observations, we have been observing Jupiter with the VISIR mid-infrared instrument on the Very Large Telescope (VLT) since 2016.  We analyse images at multiple wavelengths between 5 and 20 µm  to study the thermal, chemical and aerosol structure of Jupiter's belts, zones, and polar domains. In particular, an observing run in May 2018 (conciding with Juno's 13 perijove) provided global coverage of Jupiter in  thirteen narrow-band filters.  These data sense stratospheric temperature (7.9 µm), tropospheric temperature via the collision-induced hydrogen-helium continuum (13, 17.6, 18.6, 19.5 µm), aerosol opacity (8.6 and 8.9 µm), and the distribution of ammonia gas (10.5, 10.7 and 12.3 µm).  These wavelengths primarily sound the upper troposphere at p<0.7 bar, above the cloud tops, so are sensitive to the upper cell of the belt/zone Ferrel-like circulations.  By stacking the data in all 13 filters, we invert the data using the optimal-estimation retrieval algorithm NEMESIS [3] to derive temperature, aerosol and chemical structure over the whole planet. Meridional gradients of temperature, wind shear (derived from thermal balance equation) and chemical species will be examined to understand the upper-tropospheric circulation cells.  

We confirm that the pattern of cool anticyclonic zones and warm cyclonic belts persists throughout the mid-latitudes, up to the boundary of the polar domains.  This implies, via thermal wind balance, the decay of the zonal jets as a function of altitude throughout the upper troposphere. Aerosol opacity is often (but not always) highest in the anticyclonic zones, suggesting condensation of saturated vapours, but we caution that aerosol opacity is not a good proxy for atmospheric circulation on any giant planet.  The thermal and compositional gradients derived from the VISIR maps are consistent with those from Voyager and Cassini, but opposite to what would be inferred for the Ferrel-like circulations of the deeper cell of [1], which was suggested by [2] to exist only below the water-cloud layer based on Juno microwave observations.

Concerning the Jovian polar regions, the analysis of VISIR imaging shows a large region of mid-infrared cooling poleward ~67˚S, co-located with the reflective aerosols observed in methane-band imaging by JunoCam, suggesting that they play a key role in the radiative cooling at the poles, and that this cooling extends from the upper troposphere into the stratosphere.  These VISIR observations also reveal thermal contrasts across polar features, such as numerous cyclonic and anticyclonic vortices, as well as evidence of high-altitude heating by auroral precipitation. Comparison of zonal mean thermal properties and high-resolution visible imaging from Juno allows us to study the variability of atmospheric properties as a function of altitude and jet boundaries, particularly in the cold southern polar vortex.  To investigate the radiative processes and influence of auroral precipitation on the southern cold vortex, a radiative-convective model tailored for Jupiter's atmosphere [4], with an updated polar aerosol distribution from Juno mission results, will be used to determine the aerosol distribution needed to reproduce the thermal structure of the cold polar vortex of Jupiter.   

 

[1] Duer, K., Gavriel, N., Galanti, E., Kaspi, Y., Fletcher, L. N., Guillot, T., Bolton, S. J., Levin, S. M., Atreya, S. K., Grassi, D., Ingersoll, A. P., Li, C., Li, L., Lunine, J. I., Orton, G. S., Oyafuso, F. A., Waite, J. H.: Evidence for Multiple Ferrel-Like Cells on Jupiter, Geophysical Research Letters, 2021.


[2] Fletcher, L. N., Oyafuso, F. A., Allison, M., Ingersoll, A., Li, L., Kaspi, Y., Galanti, E., Wong, M. H., Orton, G. S., Duer, K., Zhang, Z., Li, C., Guillot, T., Levin, S. M., Bolton, S: Jupiter's Temperate Belt/Zone Contrasts Revealed at Depth by Juno Microwave Observations, Journal of Geophysical Research: Planets, 2021

[3] Irwin, P. G. J., Teanby, N. A., de Kok, R., Fletcher, L. N., Howett, C. J. A., Tsang, C. C. C., Wilson, C. F., Calcutt, S. B., Nixon, C. A., Parrish, P. D.: The NEMESIS planetary atmosphere radiative transfer and retrieval tool, Journal of Quantitative Spectroscopy & Radiative Transfer, 2008


[4] Guerlet, S., Spiga, A., Delattre, H., Fouchet, T.: Radiative-equilibrium model of Jupiter's atmosphere and application to estimating stratospheric circulations, Icarus, 2020

How to cite: Bardet, D., Donnelly, P., Fletcher, L. N., Antuñano, A., Roman, M. T., Orton, G. S., Guerlet, S., Melin, H., and Harkett, J.: Investigating Thermal Contrasts Between Jupiter's Belts, Zones, and Polar Vortices with VLT/VISIR, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-535, https://doi.org/10.5194/epsc2022-535, 2022.

16:00–16:10
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EPSC2022-855
Olivier Mousis, Antoine Schneeberger, Jonathan Lunine, Christopher Glein, Alexis Bouquet, Steven Vance, and Vassilissa Vinogradoff

A key feature among the Galilean satellites is their monotonic decrease in density, indicating an ice fraction that is zero in the innermost moon Io, and about half in the outer moons Ganymede and Callisto. So far, there is no formation scenario that explains this gradient while considering the moons grew in a water-depleted circumplanetary disk. Here, we investigate the possibility that the jovian circumplanetary disk was fueled with ice-free chondritic minerals, including phyllosilicates. To do so, we use a standard one-dimensional gas-starved accretion disk model derived from the literature [1, 2] coupled with gas and solids transport modules [3, 4] to investigate the evolution of vapors released by the dehydration of phyllosilicates. We show that the dehydration of such particles and the outward diffusion of the released water vapor allows condensation of significant amounts of ice in the formation region of Ganymede and Callisto in the Jovian circumplanetary disk. This mechanism naturally explains the presence of ice-rich moons around a water-depleted Jupiter.

[1] Canup, R.M., Ward, W.R. 2002. Formation of the Galilean Satellites: Conditions of Accretion. The Astronomical Journal 124, 3404–3423. doi:10.1086/344684

[2] Sasaki, T., Stewart, G.R., Ida, S. 2010. Origin of the Different Architectures of the Jovian and Saturnian Satellite Systems. The Astrophysical Journal 714, 1052–1064. doi:10.1088/0004-637X/714/2/1052

[3] Birnstiel, T., Klahr, H., Ercolano, B. 2012. A simple model for the evolution of the dust population in protoplanetary disks. Astronomy and Astrophysics 539. doi:10.1051/0004-6361/201118136

[4] Anderson, S.E., Mousis, O., Ronnet, T. 2021. Formation Conditions of Titan's and Enceladus's Building Blocks in Saturn's Circumplanetary Disk. The Planetary Science Journal 2. doi:10.3847/PSJ/abe0ba

How to cite: Mousis, O., Schneeberger, A., Lunine, J., Glein, C., Bouquet, A., Vance, S., and Vinogradoff, V.: The role of phyllosilicates in shaping the Galilean moons' density gradient, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-855, https://doi.org/10.5194/epsc2022-855, 2022.

16:10–16:20
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EPSC2022-267
J. Hunter Waite, Philip Valek, Thomas Greathouse, Frederic Allegrini, Robert Ebert, Randall Gladstone, and Scott Bolton

Measurements by Juno as the spacecraft flew by Ganymede on June 7th of 2021 from the JADE instrument when combined with images from UVS of the aurora can be used to significantly advance our knowledge of the atmosphere and ionosphere. JADE measures the ion outflow composition that results from downgoing plasma electrons in the polar cap region and also measures the downward electrons associated with the reconnection at the boundary of Ganymede’s magnetosphere with the Jupiter magnetosphere. Modeling can help to check the consistency between the electron energy influx in the polar cap and the resulting ionospheric outflow and can also be used to set constraints on how reconnected electrons form the auroral atmosphere and the auroral emissions measured by UVS.

How to cite: Waite, J. H., Valek, P., Greathouse, T., Allegrini, F., Ebert, R., Gladstone, R., and Bolton, S.: What the JADE electron and ionospheric measurements told us about the aurora and atmosphere of Ganymede, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-267, https://doi.org/10.5194/epsc2022-267, 2022.

16:20–16:30
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EPSC2022-719
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ECP
Yasmina M Martos, Norberto Romanelli, Jared Espley, Jack Connerney, and Stavros Kotsiaros

On June 7, 2021 Juno performed a close flyby of Ganymede. Here we study the high-resolution magnetic field spectrum which indicates that Juno travelled within Ganymede’s closed magnetic field line region for around 3 minutes during the closest approach. This result is supported by two main facts. 1) The harmonic structure in the spectrum of the high-resolution magnetometer data agrees very well with the frequencies predicted for resonances of a dipole field. 2) The inferred plasma density near the equator at 1.7 RG (L-shell of the closest approach) is approximately 25 amu/cm3, which is much lower than the local density of the plasma sheet near Ganymede (~100 amu/cm3). We also discuss our results together with those obtained by other Juno instruments and theoretical models.

How to cite: Martos, Y. M., Romanelli, N., Espley, J., Connerney, J., and Kotsiaros, S.: Field line resonances in Ganymede’s magnetosphere observed by Juno, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-719, https://doi.org/10.5194/epsc2022-719, 2022.

16:30–16:40
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EPSC2022-691
Francesca Zambon, Alessandro Mura, Julie Rathbun, Rosaly Lopes, Federico Tosi, Roberto Sordini, Raffaella Noschese, Alberto Adriani, Mauro Ciarniello, Gianrico Filacchione, Davide Grassi, Giuseppe Piccioni, Christina Plainaki, Giuseppe Sindoni, Diego Turrini, Shawn Brooks, Candice Hansen-Koharcheck, and Scott Bolton

Io is the Solar System body showing the largest number of active volcanic centers, primarily generated by tidal heating [1]. Many ground based and remote sensing observations have revealed spatial and temporal variabilities, important to define the characteristics of tidal heating and the mechanisms by which heat escapes from the interior [2, 3, 4].

The Jovian Infrared Auroral Mapper (JIRAM), the imager/spectrometer onboard JUNO mission, mainly devoted to the study of Jupiter’s atmosphere, had the opportunity to acquire data of the Galilean satellites, including Io. JIRAM is composed of a slit spectrometer covering a range of wavelengths between 2 and 5 μm and an imager equipped with two filters, L and M, centered at 3.4 and 4.7 μm, respectively [1]. 

In this work, we mapped the Io hot spots by using JIRAM M filter images from orbits 7, 9, 10, 16, 17, 18, 20, 24, 25, 26, 27, 32, 33, with a spatial scale ranging from ∼ 48 up to ~150 km/pixel (Fig. 1), updating the work by [5]. For each orbit, we consider a set of images (referred to as “super images”) which contain the average radiance of several JIRAM contiguous observations. This approach minimizes the effects due to spurious pixels, reducing the detection of false hot spots [5].

JIRAM data cover almost the entire surface of Io, with a redundancy up to 43 super images per pixel in the northern and equatorial regions (Fig. 2), improving the observations of the polar areas. To identify Io hot spots, we first filtered each super image for emission angles > 75°. Then, since JIRAM data have been acquired at different incidence angles, including Io dayside, nightside, and eclipse (Fig. 1), to select the hot spots, we divided the images in three categories: day (i≤ 70°), dawn/dusk (70° < i < 90°) and night i≥ 90°. For each super image, we calculated the median value of the radiance for the dayside, nightside and dawn/dusk background. Hence, we considered as hot spots’ detection limit the radiance values larger than the median radiance for the night side, and median background radiance plus 0.003 for dawn/dusk and day side. 

We identified 242 hot spots, many of which had already been included in other databases (e. g. [6, 7, 8, 9]). Among the hot spots revealed by JIRAM, 24 have not been observed before, and half of these are located at the poles.  The comparison between our results and the last Io global heat flow power output map published by [8] suggests that the highest power heat flow hot spots are still active, indicating their activity lasts for decades or more, while a large part of the intermediate power heat flow hot spots are still present, as only 15 of them are not included in our map. We found the larger discrepancies in the lower heat flow hot spots, given that many of those listed as active by [8] have not been observed by JIRAM. 

The study of Io hot spots variation and distribution, is worthwhile in helping to constrain the interior models and the magma distribution in its subsurface. The Io hot spots map presented here is the most up-to-date one produced by remote sensing datasets. The future JIRAM higher spatial resolution observations will be fundamental to extend and confirm our results, better distinguish close hot spots and improve our overall knowledge of Io volcanic processes and evolution.

Figure 1: Example of Io JIRAM M filter images for the orbits JM 24 and 25.

Figure 2: JIRAM M filter data coverage of Io for JIRAM orbits 10, 11, 16, 17, 18, 20, 24, 25, 26, 27, 32, 33.

Acknowledgments

This work is supported by Agenzia Spaziale Italiana (ASI). JIRAM is funded by ASI contract 2016-353 23-H.0. 

References

[1] Peale, S. J.,  et al., 1979, Science, 203. [2] Davies et al., 2015, Icarus, 262. [3] de Kleer et al., 2019, The Astronomical Journal, 158. [4] Adriani et al., 2017, Space Science Review, 213. [5] Mura, A., et al., 2020, Icarus, 241. [6] Lopes and Spencer, Eds, 2007, Praxis-Springer. [7] Williams, D. A., et al., 2011, Icarus, 214. [8] Veeder, G. J., et al., 2015, Icarus, 245. [9] Cantrall, C., et al., 2018, Icarus, 312.

How to cite: Zambon, F., Mura, A., Rathbun, J., Lopes, R., Tosi, F., Sordini, R., Noschese, R., Adriani, A., Ciarniello, M., Filacchione, G., Grassi, D., Piccioni, G., Plainaki, C., Sindoni, G., Turrini, D., Brooks, S., Hansen-Koharcheck, C., and Bolton, S.: Io hot spots detection as revealed by JUNO/JIRAM data, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-691, https://doi.org/10.5194/epsc2022-691, 2022.

16:40–16:50
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EPSC2022-733
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ECP
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MI
Shawn Brueshaber, Glenn Orton, Zhimeng Zhang, Fabiano Oyafuso, Alessandro Mura, Davide Grassi, Gerald Eichstadt, Candice Hansen, Leigh Fletcher, Shinji Mizumoto, Thomas Momary, Steve Levin, and Scott Bolton

The Juno spacecraft’s polar orbit with periapses (perijove; PJ) within a few thousand kilometers of the 1-bar level has allowed for detailed observations of Jupiter’s thunderstorms from multiple instruments at unprecedented resolution.  Here, we detail the observations of a 2,500-km wide thunderstorm feature located in the North Equatorial Belt (at planetocentric latitude 9°N; Fig. 1) from the six channels of the Microwave Radiometer Instrument (MWR), from JunoCam’s RGB filters, from the Jovian Infrared Auroral Mapper’s (JIRAM) 5-micron band, and from supporting Earth-Based images taken during near the time of the 38th perijove. Juno flew over one such thunderstorm complex at close range (~5,000 km) on 29 Nov. 2021 for the first time with a favorable alignment to observe such a feature at low emission angles. JunoCam and MWR observations were taken nearly simultaneously while JIRAM’s data was collected approximately 4.5 hours prior. 

Moist convection is widely thought to play a large role in transporting heat from Jupiter’s interior through the weather layer (here defined as 10 to 0.7 bar) and then to space. In the process, heat transport allows for moist convection, which powers thunderstorms and generates small-scale turbulence that, through the inverse-cascade mechanism, generates large-scale vortices and zonal jets.  Convective instability allows for strong updrafts that carry volatiles such as NH3 and H2O from the base of the water-cloud (and deeper) upwards to form cumulonimbus (CB) clouds.  The tops of these CB towers diverge outwards and are shaped by local winds to form an icy anvil cloud much as they do on Earth.

 

Lightning is a defining characteristic of CB clouds and the MWR instrument detected numerous flashes in and around the bright white feature with a storm-like morphology clearly observed by JunoCam. JIRAM’s M-band filter images clearly show the structure of the cloud tops, matching observations from JunoCam once the zonally-averaged motion over the 4.5-hour time separation is accounted for. Figure 2 is a JIRAM image with a noticeable dark ‘notch,’ which is where the optically thick storm clouds are located. Preliminary spectral analysis from JIRAM shows a slightly enhanced signal of H2O and PH3 near the anvil top but NH3 ice is undetectable in these night-time JIRAM observations.

 

Gaseous NH3 and H2O are partially opaque to wavelengths sensed by the MWR instrument.  Each of the six channels of MWR have a sensitivity that peaks at different altitudes in the atmosphere, which allows us to sound the brightness temperature and the vertical structure from the cloud tops down to many tens of bars.  The brightness temperature is a combination of air temperature and humidity, and, at present, we are unable to deconvolve these two measurements. Nevertheless, sounding the brightness temperature provides information on the depth and structure of a tall atmospheric feature and we present brightness temperature maps for all six channels.

We observe that this particular thunderstorm complex is visible from the cloud tops (~0.7 bar) down to approximately the level of the water cloud. Below this level, the thunderstorm signal is no longer apparent, which indicates that any dry convective updraft carrying MWR opacity-inducing vapor is either not present, or its air temperature and humidity are combined in such a way to mask its presence perfectly. If this thunderstorm is a result of dry convection from below the base of the water cloud lifting moist air to the level of free convection (LFC) then the effect of the dry convection is to lift vapor already located around the base of the water-cloud level rather than bringing up significantly moist air from deep below the base of the water cloud, or otherwise a signal would be detected in the short wavelength channels of MWR (See Fig. 3 for a cloud-top MWR map).

The next several perijoves will feature an orientation for the MWR instrument that is conducive for low emission angle observations. Additionally, the latitude of perijove is slowly migrating northward and, if Juno does fly over new thunderstorms, we may have the opportunity to compare the vertical structure of multiple thunderstorms taken from different regions of the planet at high resolution from multiple instruments.

Figure 1: PJ38 Thunderstorm from JunoCam Image JNCE_2021333_38C00030_V01 (left) and close-up  (right: Image Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill)

Figure 2: Map-Projected Processed Close-Up Image of PJ38 Thunderstorm from JIRAM M-Band Image (Image Credit: NASA/JPL-Caltech/INAF-IAPS). Circle denotes location of optically thick storm clouds.

Figure 3: Map-Projected MWR Ch 6 Brightness Temperature

How to cite: Brueshaber, S., Orton, G., Zhang, Z., Oyafuso, F., Mura, A., Grassi, D., Eichstadt, G., Hansen, C., Fletcher, L., Mizumoto, S., Momary, T., Levin, S., and Bolton, S.: Dissecting Jupiter’s Thunderstorms: Results from JIRAM, JunoCam, MWR and Earth-Based Observations, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-733, https://doi.org/10.5194/epsc2022-733, 2022.

16:50–17:00
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EPSC2022-741
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ECP
Jamey Szalay, George Clark, George Livadiotis, David McComas, Don Mitchell, Jamie Rankin, Ali Sulaiman, Frederic Allegrini, Fran Bagenal, Rob Ebert, Randy Gladstone, Bill Kurth, Barry Mauk, Phil Valek, Rob Wilson, and Scott Bolton

We present a discrete observation of diverse plasma populations and evidence of closed magnetic topology at Jupiter’s polar cap. Two distinct populations of protons are observed over Jupiter’s southern polar cap: a ~1 keV core population and ~1-300 keV dispersive conic population at 6-7 Jovian radii planetocentric distance. We find the 1 keV core protons are likely the seed population for the higher-energy dispersive conics. Transient wave-particle heating in a “pressure-cooker” process is likely responsible for this proton acceleration. The plasma characteristics and composition during this period show Jupiter's polar-most field lines can be topologically closed, with conjugate magnetic footpoints connected to both hemispheres. Finally, these observations demonstrate energetic protons can be accelerated into Jupiter's magnetotail via wave-particle coupling.

How to cite: Szalay, J., Clark, G., Livadiotis, G., McComas, D., Mitchell, D., Rankin, J., Sulaiman, A., Allegrini, F., Bagenal, F., Ebert, R., Gladstone, R., Kurth, B., Mauk, B., Valek, P., Wilson, R., and Bolton, S.: Closed Fluxtubes and Proton Conics in Jupiter’s Polar Cap, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-741, https://doi.org/10.5194/epsc2022-741, 2022.

Coffee break
Chairperson: Yasmina M Martos
17:30–17:40
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EPSC2022-761
Glenn Orton, Leigh Fletcher, Fabiano Oyafuso, Cheng Li, Zhimeng Zhang, Shawn Brueshaber, Michael H. Wong, Thomas Momary, Steven Levin, Scott Bolton, Kevin Baines, Emma Dahl, and James Sinclair

The Juno Microwave Radiometer (MWR) has extended our knowledge of the structure and composition of Jupiter's atmosphere down to several hundred bars, revealing meridional variability at great depths (e.g. Li et al. 2017, Fletcher et al. 2021). It has revealed that some cyclonic and anticyclonic vortices may have roots at depths of hundreds of bars of pressure (Bolton et al. 2022), but 5-µm hot spots and associated plumes are restricted to shallow depths above the water cloud (Fletcher et al. 2021). We report ongoing work on evolution of axisymmetric bands, concentrating on two regions where large-scale changes have been observed in the visible and infrared.

One of these is the Equatorial Zone (EZ), for which Figure 1 illustrates a dramatic color change. The color change in the central component (EZc, ~3°S – 1°N, planetocentric latitude) is more prominent than the northern component (EZn, ~2° - 6°N).  This change began in 2018, and by 2019 was as prominent as shown in 2021. In near-infrared bands of strong gaseous absorption, the EZc reflectivity increased dramatically (Fig. 2), but only temporarily for the EZn.

Another region is the northern component of the North Equatorial Belt (NEBn, ~12°N to 15°N), whose change from a visibly dark to a bright region is also illustrated in Figure 1, with the southern component (NEBs, ~7°N to 11°N) remaining its typical dark color.  Figure 3 shows that this color is associated with a remarkable drop of its 5-µm brightness which dropped down to the faint emissions of the nearby cloudy and visually bright zones. This implies a major increase in the opacity of 0.7-5 bar clouds that are similar but more extreme than the quasi-periodic northward expansions of the NEB (Fletcher et al. 2017). This transformation took place in early 2021 when Jupiter was in solar conjunction.

The very preliminary results of our initial examination of MWR observations (Fig. 4) plot antenna temperatures derived using averages over all longitudes sensed in which the center of the field of view lay within specified latitude ranges. Observations were selected only if 99% or more of the field of view included the planet and the emission angle was limited to 65° or less, after which they were converted to a nadir-equivalent emission using limb-darkening models that were fit to every latitude and each channel. All observations were made at close approaches of the spacecraft to Jupiter, known as ‘perijoves’ or PJs. Many perijoves between 2019 and 2022 did not contain any measurements of these regions meeting those selection criteria, due to unfavorable spacecraft pointing. Exceptions included special spacecraft orientations.    

The EZc appears invariable in time, but the EZn underwent a ~7K drop in Channel-3 antenna temperatures - sensitive to conditions near ~9 bars - starting in early 2017, reaching a minimum in late 2017, then returning to its original values by early 2019.  Similar variability is evident in Channel 4, sensitive to the ~3-bar level, and a smaller one in Channel 5, which is sensitive to the ~1.5-bar level.  No change is detectable in Channel 6, sensitive to the ~0.7-bar level. The 2017 temperature drop has no obvious counterpart in reflected sunlight, although its “recovery” occurs during the reflectivity changes in 2019 (Figs. 1-2). To link the two, one must devise a causal relationship between a short-lived variation of absorber, likely gaseous ammonia, at 1.5-9 bars at 2016-2019 between 2°N and 6°N, and conditions at higher altitudes over a wider latitude range.

If the NEBn variability between 2020 and 2021 (Figs. 1, 3) implies an increase of ammonia absorption, we would expect a decrease in antenna temperatures between our last trustworthy observation in 2019 April and observations in late 2021. This is indeed the case at 0.7 bars, represented by the 6-7K drop in Channel-6 antenna temperatures for the NEBn. This is also present in Channel 5 as a ~5K drop, but it is not detectable above the noise in the deeper-sounding channels, so this is not substantially present at pressures higher than ~1.5 bars. A ~5K drop in antenna temperatures in late 2016 is followed by a slower rise to its previous range by the end of 2017 in both Channels 5 and 6. Other channels do not show this variability, so this is another “shallow” phenomenon with no obvious connection to changes in cloud reflectivity.

We will continue to examine variability in cloud reflectivity associated with these changes,  observe with increasingly favorable geometries for the next few perijoves, and examine other latitudes for variability.

References:

Bolton, et al. 2021. Science 374, 968-972.

Fletcher, et al. 2017. Geophys. Res. Lett. 44, 7140-7148

Fletcher, et al. 2020. J. Geophys. Res. 125, E06399.

Fletcher, et al. 2021. J. Geophys. Res. 126, E06858.

Li, et al. 2017. G. Res. Lett. 44, 5317-5325.

Simon, et al. 2015. Ap. J. 812, 55.

 

Figure 1. Color-composite cylindrical maps of Jupiter from the Hubble Space Telescope OPAL program (Simon et al. 2015). Note the darkening of the EZ central and northern components, which began in 2018. Note also that in 2021 the northern part of the North Equatorial Belt has become lighter in color compared with 2017, a process that took place in early 2021.

 

Figure 2. Reflectivity of the central and northern components of the Equatorial Zone vs time at 2.166 µm, a wavelength sensitive to reflected sunlight from ~80-mbar aerosols. This plot implies that the EZn contained a denser population of aerosols near this level, most likely from more vigorous lofting.

 

Figure 3. Images of Jupiter at 5.1 µm: these and data in Fig. 2 were taken using NASA’s Infrared Telescope Facility (IRTF) SpeX guide camera. Note the drop in radiance of the northern section of the North Equatorial Belt from 2020 to 2021.

 

Figure 4. Preliminary results on radiances measured by Juno’s Microwave Radiometer (MWR). Channels 3 and 6 sense radiances at 2.6 and 22 GHz, respectively. For clarity, other channels are not shown. Error bars represent the standard deviation of antenna temperatures included in the latitude bin.

 

 

 

How to cite: Orton, G., Fletcher, L., Oyafuso, F., Li, C., Zhang, Z., Brueshaber, S., Wong, M. H., Momary, T., Levin, S., Bolton, S., Baines, K., Dahl, E., and Sinclair, J.: Exploring the Depth of Planetary-Scale Changes in Jupiter from Juno Microwave Radiometer Observations, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-761, https://doi.org/10.5194/epsc2022-761, 2022.