Potential vorticity of the south polar vortex of Venus

©2016. American Geophysical UnionVenus' atmosphere shows highly variable warm vortices over both of the planet's poles. The nature of the mechanism behind their formation and properties is still unknown. Potential vorticity is a conserved quantity when advective processes dominate over friction and diabatic heating and is a quantity frequently used to model balanced flows. As a step toward understanding the vortices' dynamics, we present maps of Ertel's potential vorticity (EPV) at Venus' south polar region. We analyze three configurations of the south polar vortex at the upper cloud level (P ~ 240 mbar; z ~ 58 km), based on our previous analyses of cloud motions and thermal structure from data acquired by the Visual and InfraRed Thermal Imaging Spectrometer instrument on board Venus Express. Additionally, we tentatively estimate EPV at the lower cloud level (P ~ 2200 mbar; z ~ 43 km), based on our previous wind measurements and on static stability data from Pioneer Venus and the Venus International Reference Atmosphere (VIRA) model. Values of EPV are on the order of 10−6 and 10−8 K m2 kg−1 s−1 at the upper and lower cloud levels, respectively, being 3 times larger than the estimated errors. The morphology observed in EPV maps is mainly determined by the structures of the vertical component of the relative vorticity. This is in contrast to the vortex's morphology observed in 3.8 or 5 µm images which are related to the thermal structure of the atmosphere at the cloud top. Some of the EPV maps point to a weak ringed structure in the upper cloud, while a more homogenous EPV field is found in the lower cloud

Solar Tides in the winds of the southern polar region of Venus using VIRTIS-M/Venus Express images

The effect of the solar tides on the winds at the top of the clouds in Venus has been studied using cloud tracking technique applied to the Venus Express/VIRTIS-M images taken at wavelengths of 3.8 and 5.0 μm. Both these wavelengths probe about the same altitude on the clouds top, allowing for the first time to retrieve winds in the dayside and nightside simultaneously. The dataset included observations from 17 orbits, covering a time span of 290 days and a latitude range between 70ºS and 85ºS, a region where resides the so called cold collar. Both the diurnal (wavenumber 1) and the semidiurnal (wavenumber 2) tides are present, with the diurnal tide being the dominant harmonic for both the zonal and meridional components of the wind. The diurnal tide induces wind oscillations with amplitudes of about 4.5 m/s and 8.0 m/s for the zonal and meridional winds respectively. These amplitudes are in good accordance with the Rayleigh friction expected for this level of the Venus atmosphere, and support the important role of the diurnal tide in the maintenance of the mean zonal flow and in determining the sense of the meridional flow. While the tidal amplitude seems not to undergo important changes, the phase displays a temporal variability of about 1.4 hours in the local time coordinate. The rate of change of the phase seems different for the diurnal and semidiurnal component, indicative of a dispersive character of the solar tides, and is consistent with the expected change due to the tidal vertical propagation. Finally, a persistent lag is apparent in most cases between the tidal phases of zonal and meridional disturbances, implying that the diurnal tides tend to force equatorward winds when in the sense of the mean flow, and poleward winds when in the opposite sense

Dynamics of Jupiter’s atmosphere

Giant planet atmospheres provided many of the surprises and remarkable discoveries of planetary exploration during the past few decades. Studying Jupiter's atmosphere and comparing it with Earth's gives us critical insight and a broad understanding of how atmospheres work that could not be obtained by studying Earth alone

Acoustics Reveals Short-Term Air Temperature Fluctuations Near Mars’ Surface

Acoustics is new on Mars: it allows the characterization of turbulence at smaller scales than previously possible within the lowest part of the Planetary Boundary Layer. Sound speed measurements, by the SuperCam instrument and its microphone onboard the NASA Perseverance rover, allow the retrieval of atmospheric temperatures at 0.77 m above the ground, at 3 Hz, with a ∼10 ms response time that is 20–100 times shorter than for typical thermocouple sensors used on Mars. Here we report on the first measurements of the sound speed-derived temperature and its fluctuations near the surface. Data highlight large and rapid fluctuations up to ±7 K/s, whose amplitude over such a timescale has never been reported, nor predicted by atmospheric models. These fluctuations follow the daytime pattern of the turbulence and highlight occasional high amplitude events that are likely due to the conjunction of low thermal inertia and strong winds.Plain Language SummaryThe atmospheric surface layer of Mars, is prone to various interactions between the surface and the atmosphere, which control most of the climate and the weather of the red planet. There, large temperature gradients generate an intense turbulence during the daytime. Hence, the measurement of the air temperature variations close to the surface is important to understand the spatial and temporal scales of this turbulence. The SuperCam instrument onboard the NASA Perseverance rover enables the retrieval of the near-surface atmospheric temperatures, and their fluctuations, at an unprecedented short timescale. Sound speed-derived temperatures, also call sonic temperatures, collected over the Northern spring and summer of Martian Year 36 reveal large and rapid thermal fluctuations up to ±7 K/s, whose amplitude over such a timescale is not reported by any weather station sensors, nor predicted by models that simulate small-scale eddies. These fluctuations follow the daytime pattern of the turbulence with a maximum amplitude early afternoon. Some occasional high temperature fluctuation events are observed, suggesting a complex effect of ground properties and local meteorological conditions on the turbulence. Overall, acoustics is a new and promising technique that records a unique view of atmospheric temperature variations near the surface of Mars.Key PointsSound speed derived temperature is used to study the microscale turbulence at an unprecedented short response timeAir temperature experiences fluctuations as high as ±7 K/s, which has never been reported in situ, nor resolved by mesoscale atmospheric modelsSonic temperature fluctuations follow the daytime turbulence pattern and find their origin in complex surface-atmosphere interactionsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/175247/1/grl64948.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/175247/2/grl64948_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/175247/3/2022GL100333-sup-0001-Supporting_Information_SI-S01.pd

Acoustics Reveals Short-Term Air Temperature Fluctuations Near Mars' Surface

International audienceAcoustics is new on Mars: it allows the characterization of turbulence at smaller scales than previously possible within the lowest part of the Planetary Boundary Layer. Sound speed measurements, by the SuperCam instrument and its microphone onboard the NASA Perseverance rover, allow the retrieval of atmospheric temperatures at 0.77 m above the ground, at 3 Hz, with a ∼10 ms response time that is 20-100 times shorter than for typical thermocouple sensors used on Mars. Here we report on the first measurements of the sound speed-derived temperature and its fluctuations near the surface. Data highlight large and rapid fluctuations up to ±7 K/s, whose amplitude over such a timescale has never been reported, nor predicted by atmospheric models. These fluctuations follow the daytime pattern of the turbulence and highlight occasional high amplitude events that are likely due to the conjunction of low thermal inertia and strong winds

Acoustics Reveals Short-Term Air Temperature Fluctuations Near Mars' Surface

International audienceAcoustics is new on Mars: it allows the characterization of turbulence at smaller scales than previously possible within the lowest part of the Planetary Boundary Layer. Sound speed measurements, by the SuperCam instrument and its microphone onboard the NASA Perseverance rover, allow the retrieval of atmospheric temperatures at 0.77 m above the ground, at 3 Hz, with a ∼10 ms response time that is 20-100 times shorter than for typical thermocouple sensors used on Mars. Here we report on the first measurements of the sound speed-derived temperature and its fluctuations near the surface. Data highlight large and rapid fluctuations up to ±7 K/s, whose amplitude over such a timescale has never been reported, nor predicted by atmospheric models. These fluctuations follow the daytime pattern of the turbulence and highlight occasional high amplitude events that are likely due to the conjunction of low thermal inertia and strong winds

Measurements of sound propagation in Mars' lower atmosphere

Acoustics has become extraterrestrial and Mars provides a new natural laboratory for testing sound propagation models compared to those ones on Earth. Owing to the unique combination of a microphone and two sound sources, the Ingenuity helicopter and the SuperCam laser-induced sparks, the Mars 2020 Perseverance rover payload enables the in situ characterization of unique sound propagation properties of the low-pressure CO2-dominated Mars atmosphere. In this study, we show that atmospheric turbulence is responsible for a large variability in the sound amplitudes from laser-induced sparks. This variability follows the diurnal pattern of turbulence. In addition, acoustic measurements acquired over one Martian year reveal a variation of the sound intensity by a factor of 1.8 from a constant source due to the seasonal cycle of pressure and temperature that significantly modifies the acoustic impedance and shock-wave formation. Finally, we show that the evolution of the Ingenuity tones and laser spark amplitudes with distance is consistent with one of the existing sound absorption models, which is a key parameter for numerical simulations applied to geophysical experiments on CO2-rich atmospheres. Overall, these results demonstrate the potential of sound propagation to interrogate the Mars environment and will therefore help in the design of future acoustic-based experiments for Mars or other planetary atmospheres such as Venus and Titan

Debris Field of the July 19, 2009, Impact in Jupiter and Its Long-term Evolution

A multi-platform suite of imaging and spectroscopic observations of Jupiter\u27s atmosphere tracked the evolution of the debris field of an unknown impactor on 2009 July 19. The initial debris field is similar to those of intermediate Shoemaker-Levy 9 fragments, suggesting a body hundreds of meters in size, if icy, entering from the west and slightly north. The field is detectable in the visible as dark material and in the near-IR by high-altitude particulate reflectivity; it was quickly redistributed by different zonal flows across its latitudinal range. At first, the particulate field was highly correlated with areas of enhanced temperatures and enhanced ammonia and ethane emission, but this was no longer true by mid-August. As of Sept. 2, the debris field was undetectable in the thermal, detectable in the visible with good seeing, and still prominent near 2 microns wavelength. Visibly, the impact scar consists of two dark regions along the same latitude, ostensibly different from the central bright region associated with the near-IR debris pattern. Both morphologies show eastern and western extensions propagating away from the original impact site, which appear to be influenced by flows around vortices previously undetected in Jupiter atmosphere. These observations define the flow field just north of Jupiter\u27s southern polar vortex at higher altitudes than tracked in Jupiter\u27s main cloud deck

Jupiter Science Enabled by ESA's Jupiter Icy Moons Explorer

ESA's Jupiter Icy Moons Explorer (JUICE) will provide a detailed investigation of the Jovian system in the 2030s, combining a suite of state-of-the-art instruments with an orbital tour tailored to maximise observing opportunities. We review the Jupiter science enabled by the JUICE mission, building on the legacy of discoveries from the Galileo, Cassini, and Juno missions, alongside ground- and space-based observatories. We focus on remote sensing of the climate, meteorology, and chemistry of the atmosphere and auroras from the cloud-forming weather layer, through the upper troposphere, into the stratosphere and ionosphere. The Jupiter orbital tour provides a wealth of opportunities for atmospheric and auroral science: global perspectives with its near-equatorial and inclined phases, sampling all phase angles from dayside to nightside, and investigating phenomena evolving on timescales from minutes to months. The remote sensing payload spans far-UV spectroscopy (50-210 nm), visible imaging (340-1080 nm), visible/near-infrared spectroscopy (0.49-5.56 $μ$m), and sub-millimetre sounding (near 530-625\,GHz and 1067-1275\,GHz). This is coupled to radio, stellar, and solar occultation opportunities to explore the atmosphere at high vertical resolution; and radio and plasma wave measurements of electric discharges in the Jovian atmosphere and auroras. Cross-disciplinary scientific investigations enable JUICE to explore coupling processes in giant planet atmospheres, to show how the atmosphere is connected to (i) the deep circulation and composition of the hydrogen-dominated interior; and (ii) to the currents and charged particle environments of the external magnetosphere. JUICE will provide a comprehensive characterisation of the atmosphere and auroras of this archetypal giant planet