•We developed a forward radiative transfer model to describe Saturn's atmosphere.•We developed an inversion algorithm to retrieve clouds properties from VIMS-V data.•We verified that no NH3 ice cloud ...is needed to reproduce the vortex spectra.•We propose a spectral modification of the tropospheric haze refractive index.•We infer that the atmospheric dynamics in the vortex region is weakening.
We studied the evolution of a giant tropospheric vortex formed in the wake of the storm that encircled Saturn from December 2010 to July 2011 (Fletcher et al. 2011a Science, 332, 1413–1417; Fletcher et al. 2012 Icarus, 221, 560–586; Sánchez-Lavega et al. 2011 Nature, 475, 71–74; Sánchez-Lavega et al. 2012 Icarus, 220, 561–576; Sayanagi et al. 2013 Icarus, 223, 460–478; Fischer et al. 2011 Nature, 475, 75–77) taking advantage of the observations acquired by the instruments on board the Cassini spacecraft. In particular, the Visual and Infrared Mapping Spectrometer (VIMS) imaged the vortex several times. In this work we analyzed two observations registered by the visual channel of VIMS (VIMS-V) on 08/24/2011 and 01/04/2012, both after the active phase of the storm, and characterized quantitatively the vertical structure of the clouds and hazes above the vortex. Until now, VIMS-V dataset has been scarcely exploited to perform such an analysis. The IR channel of VIMS has always been preferred since it covers wavelengths containing spectral information on a wider range of altitudes in the atmosphere. Nevertheless, in our analysis we investigate the information content of VIMS-V observations and demonstrate that the covered spectral range contains valuable information that are helpful to improve our knowledge on the properties of Saturn's upper atmosphere.
We developed a forward radiative transfer model to describe Saturn's atmosphere and simulate VIMS-V spectra in the 0.35–1.05µm wavelength range. The analysis has then been performed by means of an inverse model that we built on the basis of the Bayesian approach. Spatial distributions of effective radii, column number densities and top pressures of the cloud decks have been mapped and as a by-product of our analysis we also suggest a modified spectral shape for the imaginary part of the refractive index of the tropospheric haze, with respect to the shape described in the study of Karkoschka and Tomasko (2005 Icarus, 179, 195–221).
The results suggest that the processes responsible for the formation and persistence of the vortex weakened between August 2011 and January 2012, even if the differences that we observe could be due to the fact that the vortex has moved in different positions between the two dates. We found that in August 2011 the upper haze was arranged in a dome like structure with the center at 8mbar and the boundaries at 12mbar; moreover we detected a zone in the lower haze at 135mbar characterized by higher optical thickness with respect to the surrounding regions located at 85mbar. In January 2012 the dome in the upper layer has diluted into a more homogeneous structure and the haze appears to be overall shifted to less than 6mbar. Similarly, the 135mbar high optical depth zone previously detected in the lower layer has disappeared.
During the first perijove passage of the Juno mission, the Jovian InfraRed Auroral Mapper (JIRAM) observed a line of closely spaced oval features in Jupiter's southern hemisphere, between 30°S and ...45°S. In this work, we focused on the longitudinal region covering the three ovals having higher contrast at 5 μm, i.e., between 120°W and 60°W in System III coordinates. We used the JIRAM's full spectral capability in the range 2.4–3 μm together with a Bayesian data inversion approach to retrieve maps of column densities and altitudes for an NH3 cloud and an N2H4 haze. The deep (under the saturation level) volume mixing ratio and the relative humidity for gaseous ammonia were also retrieved. Our results suggest different vortex activity for the three ovals. Updraft and downdraft together with considerations about the ammonia condensation could explain our maps providing evidences of cyclonic and anticyclonic structures.
Key Points
JIRAM data from first Juno orbit highlighted the presence of several ovals in Jupiter's southern hemisphere
Column densities and altitudes for an NH3 cloud and an N2H4 haze have been retrieved for three ovals in the region between 60–120°W and 30–45°S
Evidences of cyclonic and anticyclonic structures inside the ovals have been found
The Jupiter InfraRed Auroral Mapper (JIRAM) instrument on board the Juno spacecraft performed observations of two bright Jupiter hot spots around the time of the first Juno pericenter passage on 27 ...August 2016. The spectra acquired in the 4–5 µm spectral range were analyzed to infer the residual opacities of the uppermost cloud deck as well as the mean mixing ratios of water, ammonia, and phosphine at the approximate level of few bars. Our results support the current view of hot spots as regions of prevailing descending vertical motions in the atmosphere but extend this view suggesting that upwelling may occur at the southern boundaries of these structures. Comparison with the global ammonia abundance measured by Juno Microwave Radiometer suggests also that hot spots may represent sites of local enrichment of this gas. JIRAM also identifies similar spatial patterns in water and phosphine contents in the two hot spots.
Key Points
Hot spots are confirmed as very dry regions in the atmosphere of Jupiter
Consistent spatial patterns are found in the distributions of water and phosphine
Ammonia shows local enhancements in the southern parts of hot spots
ABSTRACT
We analyse spectra measured by the Jovian Infrared Auroral Mapper (JIRAM, a payload element of the NASA Juno mission) in the 3150–4910 cm−1 (2.0–3.2 μm) range during the perijiove passage ...of 2016 August. Despite modelling uncertainties, the quality and the relative uniformity of the data set allow us to determine several parameters characterizing the Jupiter’s upper troposphere in the latitude range of 35°S–30°N. Ammonia relative humidity at 500 millibars varies between 5 per cent to supersaturation beyond 100 per cent for about 3 per cent of the processed spectra. Ammonia appears depleted over belts and relatively enhanced over zones. Local variations of ammonia, arguably associated with local dynamics, are found to occur in several locations on the planet (Oval BA, South Equatorial Belt). Cloud altitude, defined as the level where aerosol opacity reaches unit value at 3650 cm−1 (2.74 μm), is maximum over the Great Red Spot (>20 km above the 1 bar level) and the zones (15 km), while it decreases over the belts and towards higher latitudes. The aerosol opacity scale height suggests more compact clouds over zones and more diffuse clouds over belts. The integrated opacity of clouds above the 1.3-bar pressure level is found to be minimum in regions where thermal emission of the deeper atmosphere is maximum. The opacity of tropospheric haze above the 200-mbar level also increases over zones. Our results are consistent with a Hadley-type circulation scheme previously proposed in literature for belts and zones, with clear hemisphere asymmetries in cloud and haze.
The Jupiter InfraRed Auroral Mapper (JIRAM) aboard Juno observed the Jovian South Pole aurora during the first orbit of the mission. H3+ (trihydrogen cation) and CH4 (methane) emissions have been ...identified and measured. The observations have been carried out in nadir and slant viewing both by a L‐filtered imager and a 2–5 μm spectrometer. Results from the spectral analysis of the all observations taken over the South Pole by the instrument are reported. The coverage of the southern aurora during these measurements has been partial, but sufficient to determine different regions of temperature and abundance of the H3+ ion from its emission lines in the 3–4 μm wavelength range. Finally, the results from the southern aurora are also compared with those from the northern ones from the data taken during the same perijove pass and reported by Dinelli et al. (2017).
Key Points
H3+ intensity, column density, and temperature maps of the Jupiter southern aurora are derived from Juno/JIRAM data collected on the first orbit
Emissions from southern aurora are more intense than from the North
Derived temperatures are in the range 600°K to 1400°K
Dawn storms are among the brightest events in the Jovian aurorae. Up to now, they had only been observed from Earth‐based observatories, only showing the Sun‐facing side of the planet. Here, we show ...for the first time global views of the phenomenon, from its initiation to its end and from the nightside of the aurora onto the dayside. Based on Juno's first 20 orbits, some patterns now emerge. Small short‐lived spots are often seen a couple of hours before the main emission starts to brighten and evolve from a straight arc to a more irregular one in the midnight sector. As the whole feature rotates dawn‐ward, the arc then separates into two arcs with a central initially void region that is progressively filled with emissions. A gap in longitude then often forms before the whole feature dims. Finally, it transforms into an equatorward‐moving patch of auroral emissions associated with plasma injection signatures. Some dawn storms remain weak and never fully develop. We also found cases of successive dawn storms within a few hours. Dawn storms thus share many fundamental features with the auroral signatures of the substorms at Earth, despite the substantial differences between the dynamics of the magnetosphere at the two planets.
Plain Language Summary
Polar aurorae are a direct consequence of the dynamics of the plasma in the magnetosphere. The sources of mass and energy differ between the Earth's and Jupiter's magnetospheres, leading to fundamentally distinct auroral morphologies and very different responses to solar wind variations. Here, we report on the imaging of all development stages of spectacular auroral events at Jupiter, called dawn storms, including, for the first time, their initiation on the nightside. Our results reveal surprising similarities with auroral substorms at Earth, which are auroral events stemming from explosive magnetospheric reconfigurations. These findings demonstrate that, whatever their sources, mass and energy do not always circulate smoothly in planetary magnetospheres. Instead they often accumulate until the magnetospheres reconfigure and generate substorm‐like responses in the planetary aurorae, although the temporal and spatial scales are different for different planets.
Key Points
Juno's observations provide the first global description of dawn storms in Jupiter's aurorae, from their initiation to their end
Examples of nonisolated dawn storms and smaller events named pseudo‐dawn storms have been identified
Jovian dawn storms and terrestrial auroral substorms share many morphological and temporal characteristics
The Radiation Monitoring Investigation of the Juno Mission will actively retrieve and analyze the noise signatures from penetrating radiation in the images of Juno’s star cameras and science ...instruments at Jupiter. The investigation’s objective is to profile Jupiter’s
>
10
-MeV
electron environment in regions of the Jovian magnetosphere which today are still largely unexplored. This paper discusses the primary instruments on Juno which contribute to the investigation’s data suite, the measurements of camera noise from penetrating particles, spectral sensitivities and measurement ranges of the instruments, calibrations performed prior to Juno’s first science orbit, and how the measurements may be used to infer the external relativistic electron environment.
The aim of this study was to revealthe in vitro gas profile of basal diet added with Coleus amboinicus lour (CAL). The basal diet was added with CAL extracted with different solvent of each water and ...ethanol. There were four treatments of this experiment namely P0: basal diet (control), P1: basal diet added with 2 % of CAL powder, P2:basal diet added with 2 % of CAL extracted with water, P3 basal diet added with 2 % of CAL extracted withethanol. Each sample was incubated for 48 h following the Reading Gas technique methods with slight modification. Gas was collected at 2, 4, 6, 8, 12, 18, 36 and 48 h. The parameters measured were the total gas production (P), potential gas production (b) and rate of gas production (c). The results of this experiment showed that P and b were significant (P<0.05) different. The total gas production was 122.16, 94.78, 122.34 and 62.34 ml/g for P0, P1, P2 and P3 respectively and b was 124.88, 100.13, 117.05 and 80.76 ml/g for P0, P1, P2 andP3 respectively. The value of c was not significant (P>0.05) among four treatments. The value of c was 0.0625, 0.0525, 0.0525 and 0.0425 for P0, P1, P2 andP3 respectively. It could be concluded that the use of water to extract CAL was the best among four treatments.
In this paper we report the mapping of H3+, C2H2, and CH4 as derived by an unexploited Galileo/Near‐Infrared Mapping Spectrometer (NIMS) data set. As previously observed, hydrocarbons emissions ...appear to be located in the internal part of the auroral main oval, where CH4 3 µm vibrational band intensity ratios suggest that nonthermal excitation mechanisms, such as auroral particle precipitation and/or Joule heating, are responsible for the observed emissions. Temperature estimation are in good agreement for the CH4‐emitting region on the hot spot, while the values obtained for H3+ are lower in comparison with Cassini/visual and infrared mapping spectrometer and ground‐based data. C2H2 emission overlaps the CH4 one only at higher latitudes >75°N, indicating that different energetic particles are at work inside the main oval polar ward. CH4 is also found on the northern section of the main oval (135°< longitude <190°, 60°< latitude <90°N). The present investigation results have implications on the Juno/Jovian InfraRed Auroral Mapper observation planning as well as on the codes that will be used to retrieve temperatures and densities of all the emitting species involved in the Jupiter auroral processes.
Key Points
Maps of H3+, C2H2, and CH4 as derived by unexploited Galileo/NIMS data
H3+ and CH4 temperatures and column densities derived for specific mean spectra. H3+ temperatures lower than previously reported
Hydrocarbons emissions overlap only for latitudes >75°N indicating different energies of impacting particles polar ward
We compare Jupiter observations made around 27 August 2016 by Juno's JunoCam, Jovian Infrared Auroral Mapper (JIRAM), MicroWave Radiometer (MWR) instruments, and NASA's Infrared Telescope Facility. ...Visibly dark regions are highly correlated with bright areas at 5 µm, a wavelength sensitive to gaseous NH3 gas and particulate opacity at p ≤5 bars. A general correlation between 5‐µm and microwave radiances arises from a similar dependence on NH3 opacity. Significant exceptions are present and probably arise from additional particulate opacity at 5 µm. JIRAM spectroscopy and the MWR derive consistent 5‐bar NH3 abundances that are within the lower bounds of Galileo measurement uncertainties. Vigorous upward vertical transport near the equator is likely responsible for high NH3 abundances and with enhanced abundances of some disequilibrium species used as indirect indicators of vertical motions.
Key Points
A high correlation between visibly dark clouds and 5‐micron radiation extends only partially to microwave radiation
Five‐micron spectroscopy and microwave radiometry yield a 5‐bar NH3 abundance not inconsistent with Galileo results
Meridional dependence of deep atmospheric opacity is dynamically consistent with most other vertical‐motion tracers
Plain Language Summary
Comparison of observations of Jupiter by different Juno and ground‐based instruments verified some long‐standing relationships, such as those between visibly dark regions and clear, dry parts of the atmosphere. But Juno saw significant exceptions. Different instrument results for the abundance of ammonia gas, a condensate similar to water in the Earth's atmosphere, at 5 bars of pressure were self‐consistent and within the uncertainty of Galileo results. The substantial upwelling of ammonia detected by the Microwave Radiometer from great depth near the equator is consistent with other indirect tracers of vertical winds.
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