► We combine IR (VIRTIS) and smm/mm (MIRO) data to constrain the thermal properties of Asteroid Lutetia. ► VIRTIS dayside temperature measurements in excess of 240K indicated thermal inertias less ...than 20. ► MIRO 2-channel polar night measurements indicated a Lutetia thermal inertia increasing with depth. ► Comparisons of model predictions with VIRTIS dayside temperatures indicated roughness effects. ► Addition of a model of 50% coverage of mini-craters resolves the model vs. measurement offsets.
The European Space Agency’s Rosetta spacecraft is the first Solar System mission to include instrumentation capable of measuring planetary thermal fluxes at both near-IR (VIRTIS) and submillimeter–millimeter (smm–mm, MIRO) wavelengths. Its primary mission is a 1year reconnaissance of Comet 67P/Churyumov–Gerasimenko beginning in 2014. During a 2010 close fly-by of Asteroid 21 Lutetia, the VIRTIS and MIRO instruments provided complementary data that have been analyzed to produce a consistent model of Lutetia’s surface layer thermal and electrical properties, including a physical model of self-heating. VIRTIS dayside measurements provided highly resolved 1K accuracy surface temperatures that required a low thermal inertia, I<30J/(Km2s0.5). MIRO smm and mm measurements of polar night thermal fluxes produced constraints on Lutetia’s subsurface thermal properties to depths comparable to the seasonal thermal wave, yielding a model of I<20J/(Km2s0.5) in the upper few centimeters, increasing with depth in a manner very similar to that of Earth’s Moon. Subsequent MIRO-based model predictions of the dayside surface temperatures reveal negative offsets of ∼5–30K from the higher VIRTIS-measurements. By adding surface roughness in the form of 50% fractional coverage of hemispherical mini-craters to the MIRO-based thermal model, sufficient self-heating is produced to largely remove the offsets relative to the VIRTIS measurements and also reproduce the thermal limb brightening features (relative to a smooth surface model) seen by VIRTIS. The Lutetia physical property constraints provided by the VIRTIS and MIRO data sets demonstrate the unique diagnostic capabilities of combined infrared and submillimeter/millimeter thermal flux measurements.
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
One of the striking features about Venus atmosphere is its temporal variability and dynamics, with a chaotic polar vortex, large-scale atmospheric waves, sheared features and variable winds that ...depend on local time and possibly orographic features. The aim of this research is to combine data accumulated over several years and obtain a global mean state of the atmosphere focusing in the global structure of the clouds using the cloud opacity and upper cloud temperatures.
We have first produced global maps using the integrated radiance through the infrared atmospheric windows centred around 1.74 μm and 2.25 μm, that show the spatial variations of the cloud opacity in the lower clouds around 44–48 km altitude and also provide an indirect estimation of the possible particle size. We have also produced similar global maps using the brightness temperatures seen in the thermal region at 3.8 μm and 5.0 μm, which provide direct indication of the temperatures at the top of the clouds around 60–70 km altitude.
These maps have been generated using the complete dataset of the Visible and InfraRed Thermal Imaging Spectrometer mapping channel (VIRTIS-M) on board Venus Express, with a wide spatial and long temporal coverage in the period from May 2006 until October 2008.
Our results provide a global view of the cloud opacity, particle size and upper cloud temperatures at both hemispheres, showing the main different dynamical regions of the planet. The profiles obtained also provide the detailed dependencies with latitude, local time and longitude, diagnostic of the global circulation flow and dynamics at various altitude layers, from about 44 up to 70 km over the surface.
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•Full Venus nightside atmosphere seen with VIRTIS-Venus Express complete Infrared dataset.•Global view of nightside cloud opacity, particle size and cloud top temperature.•Detailed latitudinal and local time profiles show symmetric features on both hemispheres.•Polar views show global behaviour of Venus mid-latitude clouds and cold collar region.
Increasing evidence suggests that uric acid (UA) is a relevant risk factor for arteriolosclerosis and recent studies have demonstrated the positive relationship between UA concentrations and the ...severity of leukoaraiosis. However, the association between lacunar infarcts (LI) and UA levels has seldom been reported in the literature. The aim of our study was to assess whether serum UA levels may be related to the presence of LI. We recruited 242 patients (113 males and 129 females, aged 82.83 ± 6.49 years) from our Geriatric Department for whom CAT scans (CT) were available. Clinical and laboratory data was collected. Patients CT images were examined to identify the presence, the size, the number, and the location of LI. LI without neurological symptoms were considered silent LI. Serum UA levels were found to be positively associated with the presence (
p
= 0.0001), the number (
p
= 0.001), the size (
p
= 0.001), and the location of LI in the basal ganglia (
p
= 0.0038), the deep white matter (DWM) (
p
< 0.0001), and the pons (
p
= 0.0156). A significant association was also found between UA and silent LI (
p
= 0.0002). The prevalence of LI increased starting from UA levels of 5.7 mg/dl. Stepwise multiple regression analysis confirmed that UA was independently related with the presence, the number, the size, LI in the basal ganglia, the DWM, the pons, and with silent LI. Our study suggests a positive association between UA levels and LI, which is independent of traditional cardiovascular risk factors. This data suggests that UA plays an influential role on the physiopathology of LI and could represent a potential target to prevent cerebral microinfarcts.
•Dust particles sizes, optical depth and top altitude maps of a local dust storm.•Evidence for connections between the storm dynamics and the region topography.•Hints on the storm origins from ...thermal inertia, GCM and surface mafic features.
In this study we present the analysis of the dust properties of a local storm imaged in the Atlantis Chaos region on Mars by the OMEGA imaging spectrometer on March 2nd, 2005. We use the radiative transfer model MITRA to study the dust properties at solar wavelengths between 0.5 µm and 2.5 µm and infer the connection between the local storm dynamics and the topography.
We retrieve maps of effective grain radius (reff), optical depth at 9.3 µm (τ9.3) and top altitude (ta) of the dust layer. Our results show that large particles (reff = 1.6 µm) are gathered in the centre of the storm (lat = 33.5° S; lon = 183.5° W), where the optical depth is maximum (τ9.3 > 7.0) and the top altitude exceeds 18 km. Outside the storm, we obtain τ9.3 < 0.2, in agreement with the estimates derived from global climate models (GCM).
We speculate that a low thermal inertia region at the western border of Atlantis Chaos is a possible source of the dust storm. Moreover, we find evidence that topography plays a role in confining the local storm in Atlantis Chaos. The vertical wind component from the GCM does not provide any hint for the triggering of dust lifting. On the other hand, the combination of the horizontal and vertical wind profiles suggests that the dust, once lifted, is pushed eastward and then downward and gets confined within the north-east ridge of Atlantis Chaos.
From our results, the thickness of the dust layer collapsed on the surface ranges from about 1 µm at the storm boundaries up to more than 100 µm at its centre. We verify that a layer of dust thicker than 1 µm, deposited on the surface, can prevent the detection of mafic absorption features. However, such features are still present in OMEGA data of Atlantis Chaos registered after the storm. Hence, we deduce that, once the storm is over, the dust deposited on an area larger than the one where it has been observed.
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
•Full analysis VIRTIS-Venus Express Visible dataset in the night side of Venus.•Most comprehensive search of lightning conducted so far with Venus Express data.•Thousands of signal detections, but ...they can all be explained by cosmic rays.•Statistical analysis shows random wavelength distribution consistent with cosmic rays.•No clear evidence of lightning in the data adds constrains for future research.
In this study we describe a dedicated analysis of luminous transient events on Venus night side atmosphere with the visible channel of the VIRTIS instrument (280–1100nm), this being the most comprehensive search of lightning conducted so far with Venus Express data. Our search results in thousands of signal detections, but unfortunately they can be all explained by cosmic rays impinging on the detector, and further statistical analysis shows that all of the events are randomly distributed along the spectral dimension, therefore not showing any clear evidence of signal coming from lightning emission in the Venus atmosphere. This does not exclude the existence of lightning, but imposes some constraints on their occurrence that are important for future research.
The mapping IR channel of the Visual and Infrared Thermal Imaging Spectrometer (VIRTIS‐M) on board the Venus Express spacecraft observes the CO2 band at 4.3 μm at a spectral resolution adequate to ...retrieve the atmospheric temperature profiles in the 65–96 km altitude range. Observations acquired in the period June 2006 to July 2008 were used to derive average temperature fields as a function of latitude, subsolar longitude (i.e., local time, LT), and pressure. Coverage presented here is limited to the nighttime because of the adverse effects of daytime non‐LTE emission on the retrieval procedure and to southernmost latitudes because of the orientation of the Venus‐Express orbit. Maps of air temperature variability are also presented as the standard deviation of the population included in each averaging bin. At the 100 mbar level (about 65 km above the reference surface), temperatures tend to decrease from the evening to the morning side despite a local maximum observed around 20–21LT. The cold collar is evident around 65S, with a minimum temperature at 3LT. Moving to higher altitudes, local time trends become less evident at 12.6 mbar (about 75 km) where the temperature monotonically increases from middle latitudes to the southern pole. Nonetheless, at this pressure level, two weaker local time temperature minima are observed at 23LT and 2LT equatorward of 60S. Local time trends in temperature reverse about 85 km, where the morning side is the warmer. The variability at the 100 mbar level is maximum around 80S and stronger toward the morning side. Moving to higher altitudes, the morning side always shows the stronger variability. Southward of 60S, standard deviation presents minimum values around 12.6 mbar for all the local times.
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