The Jovian InfraRed Auroral Mapper (JIRAM) on board the NASA Juno spacecraft is a dual‐band imager and spectrometer in the 2–5 μm range with 9‐nm spectral sampling, primarily designed to study the ...Jovian atmosphere and aurorae. In addition to these goals, JIRAM is used to obtain images and spectra of the Galilean satellites, every time the spacecraft attitude is favorable. Here we present JIRAM images and spectra of Ganymede obtained during the first 4 years of the mission. In particular, on 26 December 2019, during a relatively close passage of Juno with the moon, a dedicated reorientation of the spacecraft was performed to achieve optimized observations of Ganymede by Juno's remote sensing instruments, including JIRAM. In the outbound phase of the flyby, observing the northern polar regions of Ganymede at a distance of roughly 100,000 km, JIRAM collected infrared images and spectra of the surface at a spatial resolution as high as 23 km per pixel, covering high northern latitudes that were scarcely mapped previously. A photometric model of Ganymede reflectance is produced, which diverges from the Lambert model. The spatial distribution of the obtained spectra complements the available coverage of the surface, with particular regard to the 2.0‐µm water ice absorption band and, to a lesser extent, to the 4.26‐µm spectral feature diagnostic of CO2 trapped in water ice. The water ice distribution is compatible with sputtered‐induced water ice grain enrichment at high latitude (>45°). Several minor species (hydrated salts, trapped H2, CO2, and acids) are also identified in the measured spectra.
Plain Language Summary
The Jovian Infrared Auroral Mapper (JIRAM) is a dual‐band imager and spectrometer on the NASA Juno spacecraft. It works in the range of 2–5 μm and its spectral sampling is 9 nm. JIRAM is mainly used to study the Jovian atmosphere and aurora. JIRAM is also used to obtain images and spectra of the moons of Jupiter, every time the spacecraft has a favorable attitude. Here, we show Ganymede images and spectra obtained during the first 4 years of the mission. On 26 December 2019, during a close passage of Juno to Ganymede, JIRAM observed it at a distance of approximately 100,000 km. In this occasion, JIRAM collected infrared images and surface spectra with a spatial resolution of up to 23 km per pixel. This data covers North polar regions that were not mapped before. A photometric model of Ganymede's reflectance was produced, and it is different from the Lambert model. The spatial distribution of the obtained spectrum can supplement the available coverage of the surface, especially for the 2.0 µm water ice absorption band. At high latitudes (>45°), the distribution of water ice is compatible with the enrichment of water ice particles induced by sputtering. Several minor species (hydrated salts, trapped H2, CO2, and acids) were also identified in the measured spectra.
Key Points
Water ice distribution for previously unmapped regions
Latitudinal variability of CO2 spectral feature
New photometric model for Ganymede reflectance
We observed the evolution of Jupiter's polar cyclonic structures over two years between February 2017 and February 2019, using polar observations by the Jovian InfraRed Auroral Mapper, JIRAM, on the ...Juno mission. Images and spectra were collected by the instrument in the 5‐μm wavelength range. The images were used to monitor the development of the cyclonic and anticyclonic structures at latitudes higher than 80° both in the northern and the southern hemispheres. Spectroscopic measurements were then used to monitor the abundances of the minor atmospheric constituents water vapor, ammonia, phosphine, and germane in the polar regions, where the atmospheric optical depth is less than 1. Finally, we performed a comparative analysis with oceanic cyclones on Earth in an attempt to explain the spectral characteristics of the cyclonic structures we observe in Jupiter's polar atmosphere.
Plain Language Summary
The Jovian InfraRed Auroral Mapper (JIRAM) is an instrument on‐board the Juno NASA spacecraft. It consists of an infrared camera, for mapping both Jupiter's auroras and atmosphere, and a spectrometer. In February 2017, the complex cyclonic structures that characterize the Jupiter's polar atmospheres were discovered. Here, we report the evolution of those cyclonic structures during the 2 years following the discovery. We use for this purpose infrared maps built by the JIRAM camera images collected at wavelengths around 5 μm. The cyclones have thick clouds that obstruct most of the view of the deeper atmosphere. However, some areas, near the cyclones, are only covered by thin clouds allowing the spectrometer to see deeper in the atmosphere. In those areas, the instrument was able to detect spectral signatures that permitted estimation of abundances of water vapor, ammonia, phosphine, and germane. Those gases are minor but significant constituents of the atmosphere. Finally, the dynamics of the Jupiter's polar atmosphere are not well understood and are still under study. Here, to suggest possible mechanisms that governs the polar dynamics, we attempted a comparative analysis with some Earth oceanic cyclones that show similarities with the Jupiter ones.
Key Points
The Jupiter's polar cyclonic structures did not change much in two years of observations from February 2017 to February 2019
Abundances of some atmospheric minor constituents measured in the hottest spots of the polar regions, higher values registered in the south
Earth oceanic cyclones analogies suggest a well‐mixed upper boundary layer on Jupiter's Poles
We have analyzed limb daytime observations of Titan's upper atmosphere at 3.3 μm, acquired by the visual‐infrared mapping spectrometer (VIMS) on Cassini. They were previously studied by García‐Comas ...et al. (2011) to derive CH4 densities. Here, we report an unidentified emission peaking around 3.28 μm, hidden under the methane R branch. This emission is very strong, with intensity comparable to the CH4 bands located in the same spectral region. It presents a maximum at about 950 km and extends from 600 km up to 1250 km. It is definitely pumped by solar radiation since it vanishes at night. Our analysis shows that neither methane nor the major hydrocarbon compounds already discovered in Titan's upper atmosphere are responsible for it. We have discarded many other potential candidates and suggest that the unidentified emission might be caused by aromatic compounds.
Key Points
We observe an unknown emission in VIMS spectra of Titan's upper atmosphere
The feature is persistent, very strong, present at daytime and peaks at 950 km
Not caused by known Titan gases, aromatic hydrocarbons are likely carriers
In this work, we present the detection of CH4 and H3+ ${\mathrm{H}}_{3}^{+}$ emissions in the equatorial atmosphere of Jupiter as two well‐separated layers located, respectively, at tangent altitudes ...of about 200 and 500–600 km above the 1‐bar level using the observations of the Jovian InfraRed Auroral Mapper (JIRAM), on board Juno. This provides details of the vertical distribution of H3+ ${\mathrm{H}}_{3}^{+}$ retrieving its Volume Mixing Ratio (VMR), concentration, and temperature. The thermal profile obtained from H3+ ${\mathrm{H}}_{3}^{+}$ shows a peak of 600–800 K at about 550 km, with lower values than the ones reported in Seiff et al. (1998), https://doi.org/10.1029/98JE01766 above 500 km using VMR and temperature as free parameters and above 650 km when VMR is kept fixed with that model in the retrieval procedure. The observed deviations from the Galileo's profile could potentially point to significant variability in the exospheric temperature with time. We suggest that vertically propagating waves are the most likely explanation for the observed VMR and temperature variations in the JIRAM data. Other possible phenomena could explain the observed evidence, for example, dynamic activity driving chemical species from lower layers toward the upper atmosphere, like the advection‐diffusion processes, or precipitation by soft electrons, although better modeling is required to test these hypothesis. The characterization of CH4 and H3+ ${\mathrm{H}}_{3}^{+}$ species, simultaneously observed by JIRAM, offers the opportunity for better constraining atmospheric models of Jupiter at equatorial latitudes.
Plain Language Summary
The Jovian Infrared Auroral Mapper (JIRAM) is the infrared imager and spectrometer on board the Juno mission, designed to investigate Jupiter's atmosphere. A key objective of JIRAM is the investigation of the minor species, such as CH4 and H3+ ${\mathrm{H}}_{3}^{+}$ that are very important to understanding the energy balance of the middle and upper atmosphere of Jupiter. These species have strong signatures in the 3.3–3.8 μm spectral region, well within the nominal wavelength range of the instrument. We present the analysis of recent images and spectra obtained by JIRAM, in the period December 2018–September 2020, plus additional measurements in March 2017, to study methane and H3+ ${\mathrm{H}}_{3}^{+}$ vertical distribution at equatorial latitudes. We find that CH4 is localized around 200 km above the 1‐bar level, while a distinct layer of H3+ ${\mathrm{H}}_{3}^{+}$ is observed around 500–600 km (0.04–0.016 μbar). The observed vertical distribution and intensity variation of H3+ ${\mathrm{H}}_{3}^{+}$ is likely to be the result of vertically propagating waves. However, other possible phenomena can be invoked to explain these findings, like for example, an uplifting of chemical species from lower layers toward the upper atmosphere, or soft electrons precipitation, although a rigorous modeling is needed to confirm the latter hypothesis.
Key Points
Detection of CH4 and H3+ ${\mathrm{H}}_{3}^{+}$ emissions over Jupiter's disc as two well separated layers in the equatorial region at 200 and 600 km
The H3+ ${\mathrm{H}}_{3}^{+}$ temperature profile shows a peak of 600–800 K at about 600 km with some differences with respect to the Galileo's profile
The observed features point out the presence of localized variability with altitude, perhaps indicative of wave activities
The electromagnetic coupling between the Galilean satellites at Jupiter and the planetary ionosphere generates an auroral footprint, which is detected with high spatial resolution in the infrared L ...band by the Jovian InfraRed Auroral Mapper (JIRAM) onboard the Juno spacecraft. We report the JIRAM data acquired since 27 August 2016 until 23 May 2022, which are used to compute the average position of the footprint tracks of Io, Europa and Ganymede. The result of the present analysis help to test the reliability of magnetic field models, to calibrate ground‐based observations and to highlight the variability in the footprint positions, which can be used to probe the plasma environment at the orbit of the satellites. The determination of the plasma properties around the moons is particularly relevant to complement the Juno flybys of the moons during its extended mission, and to support the future Juice and Europa Clipper missions. Lastly, we report no clear evidence of the auroral footprint of Callisto, which is likely due to a combination of its low expected brightness and its position very close to the main Jovian aurora.
Plain Language Summary
The Jovian InfraRed Auroral Mapper onboard the Juno spacecraft around Jupiter has now been gathering 6 years of observations. Here, we report the position of the auroral infrared emission associated with the orbital motion of Io, Europa and Ganymede. The position of this emission ‐ called footprint ‐ carries information on the magnetic field geometry and the distribution of charged particles along the magnetic field. Therefore, the footprint tracks provided here can be used to test and constrain magnetic field models, and to improve the calibration of ground based observations of Jupiter: this can help better understand the source region of the main Jovian aurora and its variations. Lastly, by surveying the data acquired over 40 Juno orbits, we point out variations in the footprint position, which reflect the variability in the plasma conditions near the moons: this monitoring may help determine the mass loading of the magnetosphere, which affects the intensity of the main aurora. The possibility of investigating the plasma environment at the orbit of the satellites is important to complement the satellite flybys performed during the extended mission of Juno and to support the future Juice and Europa Clipper missions, which are dedicated to the Galilean moons.
Key Points
The position of the Io, Europa and Ganymede footprints based on Juno‐JIRAM observations are reported with unprecedented spatial resolution
The positions of the footprints support the Juno‐based magnetic field models and the calibration of ground‐based observation
The transversal shift of the Ganymede footprint suggests variations of the plasmadisk; the shift appears to be correlated with local time
To evaluate in the follow-up the sensory-motor recovery and quality of life patients 2 months after completion of the Nintendo Wii console intervention and determine whether learning retention was ...obtained through the technique.
Five hemiplegics patients participated in the study, of whom 3 were male with an average age of 54.8 years (SD = 4.6). Everyone practiced Nintendo Wii therapy for 2 months (50 minutes/day, 2 times/week, during 16 sessions). Each session lasting 60 minutes, under a protocol in which only the games played were changed, plus 10 minutes of stretching. In the first session, tennis and hula hoop games were used; in the second session, football (soccer) and boxing were used. For the evaluation, the Fulg-Meyer and Short Form Health Survey 36 (SF-36) scales were utilized. The patients were immediately evaluated upon the conclusion of the intervention and 2 months after the second evaluation (follow-up).
Values for the upper limb motor function sub-items and total score in the Fugl–Meyer scale evaluation and functional capacity in the SF-36 questionnaire were sustained, indicating a possible maintenance of the therapeutic effects.
The results suggest that after Nintendo Wii therapy, patients had motor learning retention, achieving a sustained benefit through the technique.
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The JUNO mission, launched on August 2011 with the goal of investigating the origin and evolution of Jupiter, reached Jupiter in July 2016. The months preceding the JUNO orbit insertion have been ...crucial for all the instrument teams to check the status and working abilities of the respective experiments. JIRAM (Jupiter Infrared Auroral Mapper), with its imager and slit spectrometer operating over the 2-5μm spectral range will attempt to reveal the deep atmospheric composition --3 to 7 bars-- in hot spots, to analyze the infrared auroral emissions of the H
3
+
molecules ionized by the Jovian magnetosphere currents and to detect the morphology and vertical structure of the clouds. Many different processing tools are in preparation to exploit the incoming JIRAM data. Here some results pertaining to the image quality optimization and the visualizations that can be obtained from the spectrometer data management are reported.
We present multiwavelength measurements of the thermal, chemical, and cloud contrasts associated with the visibly dark formations (also known as 5‐μm hot spots) and intervening bright plumes on the ...boundary between Jupiter's Equatorial Zone (EZ) and North Equatorial Belt (NEB). Observations made by the TEXES 5‐ to 20‐μm spectrometer at the Gemini North Telescope in March 2017 reveal the upper‐tropospheric properties of 12 hot spots, which are directly compared to measurements by Juno using the microwave radiometer (MWR), JIRAM at 5 μm, and JunoCam visible images. MWR and thermal‐infrared spectroscopic results are consistent near 0.7 bar. Mid‐infrared‐derived aerosol opacity is consistent with that inferred from visible‐albedo and 5‐μm opacity maps. Aerosol contrasts, the defining characteristics of the cloudy plumes and aerosol‐depleted hot spots, are not a good proxy for microwave brightness. The hot spots are neither uniformly warmer nor ammonia‐depleted compared to their surroundings at p<1 bar. At 0.7 bar, the microwave brightness at the edges of hot spots is comparable to other features within the NEB. Conversely, hot spots are brighter at 1.5 bar, signifying either warm temperatures and/or depleted NH3 at depth. Temperatures and ammonia are spatially variable within the hot spots, so the precise location of the observations matters to their interpretation. Reflective plumes sometimes have enhanced NH3, cold temperatures, and elevated aerosol opacity, but each plume appears different. Neither plumes nor hot spots had microwave signatures in channels sensing p>10 bars, suggesting that the hot spot/plume wave is a relatively shallow feature.
Plain Language Summary
To date, our only direct measurement of Jupiter's gaseous composition came from the descent of the Galileo probe in 1995. However, the results from Galileo appeared to be biased due to the unusual meteorological conditions of its entry location: a dark, cloud‐free region just north of the equator, known as a hot spot. One of the aims of NASA's Juno mission was to place the findings of the Galileo probe into broader context, which requires a detailed characterization of these equatorial hot spots and their neighboring plumes. We combine (a) data from Juno (microwave observations sounding conditions below the clouds and visible/infrared observations revealing variations in cloud opacity) with (b) observations from amateur observers (to track the hot spots over time) and (c) observations from the TEXES infrared spectrometer mounted on the Gemini‐North telescope. The latter provides the highest‐resolution thermal maps of Jupiter's tropics ever obtained and reveals contrasts within and between the individual hot spots and plumes. We find that the hot spots are distinguishable from their surroundings for relatively shallow pressures but that the deep measurements from Juno and Galileo are probably more representative of Jupiter's North Equatorial Belt than previously thought.
Key Points
Gemini TEXES spectral mapping reveals temperature, aerosol, and ammonia contrasts associated with plumes and hot spots on Jupiter's NEB jetstream
Juno microwave measurements are consistent with the infrared mapping and reveals that hot spot ammonia contrasts are confined to pressures less than 8–10 bars
Hot spots and plumes are primarily contrasts in aerosols, with only subtle upper‐tropospheric ammonia and temperature variations
► We present the first concentration retrieval of HCN by Cassini-VIMS limb observations of the Titan upper atmosphere. ► HCN is thought to play an important role in the chemistry and in determining ...the thermal structure of Titan’s thermosphere. ► A model for non-LTE HCN emission in Titan atmospheric condition has been developed for the purpose.
Cassini/VIMS limb observations have been used to retrieve vertical profiles of hydrogen cyanide (HCN) from its 3
μm emission in the region from 600 to 1100
km altitude at daytime. While the daytime emission is large up to about 1100
km, it vanishes at nighttime at very low altitudes, suggesting that the daytime emission originates under non-LTE conditions. The spectrally integrated radiances around 3.0
μm shows a monotonically decrease with tangent altitude, and a slight increase with solar zenith angle in the 40–80° interval around 800
km.
A sophisticated non-LTE model of HCN energy levels has been developed in order to retrieve the HCN abundance. The population of the HCN 0
0
0
1 energy level, that contributes mostly to the 3.0
μm limb radiance, has been shown to change significantly with the solar zenith angle (SZA) and HCN abundance. Also its population varies with the collisional rate coefficients, whose uncertainties induced errors in the retrieved HCN of about 10% at 600–800
km and about 5% above. HCN concentrations have been retrieved from a set of spectra profiles, covering a wide range of latitudes and solar zenith angles, by applying a line-by-line inversion code. The results show a significant atmospheric variability above ∼800
km with larger values for weaker solar illumination. The HCN shows a very good correlation with solar zenith angles, irrespective of latitude and local time, suggesting that HCN at these high altitudes is in or close to photochemical equilibrium. A comparison with UVS and UVIS measurements show that these are close to the lower limit (smaller SZAs) of the VIMS observations above 750
km. However, they are in reasonable agreement when combining the rather large UV measurement errors and the atmospheric variability observed in VIMS. A comparison of the mean profile derived here with the widely used profile reported by Yelle and Griffith (Yelle R.V., Griffith, C.A. 2003. Icarus 166, 107–115) shows a good agreement for altitudes ranging from 850 to 1050
km, while below these altitudes our result exhibits higher concentrations.
The spatial distribution of water, ammonia, phosphine, germane, and arsine in the Jupiter's troposphere has been inferred from the Jovian Infrared Auroral Mapper (JIRAM) Juno data. Measurements allow ...us to retrieve the vertically averaged concentration of gases between ~3 and 5 bars from infrared‐bright spectra. Results were used to create latitudinal profiles. The water vapor relative humidity varies with latitude from <1% to over 15%. At intermediate latitudes (30–70°) the water vapor maxima are associated with the location of cyclonic belts, as inferred from mean zonal wind profiles (Porco et al., 2003). The high‐latitude regions (beyond 60°) are drier in the north (mean relative humidity around 2–3%) than the south, where humidity reaches 15% around the pole. The ammonia volume mixing ratio varies from 1 × 10−4 to 4 × 10−4. A marked minimum exists around 10°N, while data suggest an increase over the equator. The high‐latitude regions are different in the two hemispheres, with a gradual increase in the south and more constant values with latitude in the north. The phosphine volume mixing ratio varies from 4 × 10−7 to 10 × 10−7. A marked minimum exists in the North Equatorial Belt. For latitudes poleward 30°S and 30°N, the northern hemisphere appears richer in phosphine, with a decrease toward the pole, while the opposite is observed in the south. JIRAM data indicate an increase of germane volume mixing ratio from 2 × 10−10 to 8 × 10−10 from both poles to 15°S, with a depletion centered around the equator. Arsine presents the opposite trend, with maximum values of 6 × 10−10 at the two poles and minima below 1 × 10−10 around 20°S.
Key Points
Horizontal variations of gases are dominated by latitudinal components; longitudinal variations are relatively more important for water
Phosphine and germane abundances fit well the model of disequilibrium species transported upward from deep troposphere by vertical mixing
Strong upturn of arsine at polar latitudes seen by JIRAM cannot be explained by the diffusion‐kinetics model
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