Rovers and landers on Mars have experienced local, regional, and planetary‐scale dust storms. However, in situ documentation of active lifting within storms has remained elusive. Over 5–11 January ...2022 (LS 153°–156°), a dust storm passed over the Perseverance rover site. Peak visible optical depth was ∼2, and visibility across the crater was briefly reduced. Pressure amplitudes and temperatures responded to the storm. Winds up to 20 m s−1 rotated around the site before the wind sensor was damaged. The rover imaged 21 dust‐lifting events—gusts and dust devils—in one 25‐min period, and at least three events mobilized sediment near the rover. Rover tracks and drill cuttings were extensively modified, and debris was moved onto the rover deck. Migration of small ripples was seen, but there was no large‐scale change in undisturbed areas. This work presents an overview of observations and initial results from the study of the storm.
Plain Language Summary
Mars commonly has local and regional dust storms, some of which grow into global dust storms. Until now, no lander or rover on Mars has observed the meteorology and processes within an active lifting storm center. The Perseverance rover experienced a large regional storm in Jezero crater over six sols (Martian days) in January 2022. It documented active dust lifting and winds reshaping the Martian sediment. Winds increased as the storm approached but were only directly monitored until the afternoon of the first sol, when the wind sensor failed during high winds. Winds, even after the loss of the wind sensor, were powerful enough to blow sand and lift dust around the rover. Rover imaging showed 21 dust devils and other dust lifting events near noon of the first sol. Images of the rover and terrain showed that there were several incidents of sediment mobilization immediately around the rover. Rover tracks were erased or heavily modified, cuttings from a recent drilling were removed, and sediment was deposited across the rover's deck. The changes wrought by the storm were concentrated on areas where the rover had previously modified the terrain, except for sand motion including the migration of small sand ripples.
Key Points
The Perseverance rover documented the meteorology and effects of a dust storm as it passed over Jezero crater, Mars
The storm brought damaging winds and wide‐spread dust lifting, while modifying the pressure amplitudes and thermal cycle at the site
Winds extensively modified previously disturbed areas, while sand motion and small‐scale ripple migration occurred all around the rover
Aim
The microbial metabolic quotient (MMQ; mg CO2‐C/mg MBC/h), defined as the amount of microbial CO2 respired (MR; mg CO2‐C/kg soil/h) per unit of microbial biomass C (MBC; mg C/kg soil), is a key ...parameter for understanding the microbial regulation of the carbon (C) cycle, including soil C sequestration. Here, we experimentally tested hypotheses about the individual and interactive effects of multiple nutrient addition (nitrogen + phosphorus + potassium + micronutrients) and herbivore exclusion on MR, MBC and MMQ across 23 sites (five continents). Our sites encompassed a wide range of edaphoclimatic conditions; thus, we assessed which edaphoclimatic variables affected MMQ the most and how they interacted with our treatments.
Location
Australia, Asia, Europe, North/South America.
Time period
2015–2016.
Major taxa
Soil microbes.
Methods
Soils were collected from plots with established experimental treatments. MR was assessed in a 5‐week laboratory incubation without glucose addition, MBC via substrate‐induced respiration. MMQ was calculated as MR/MBC and corrected for soil temperatures (MMQsoil). Using linear mixed effects models (LMMs) and structural equation models (SEMs), we analysed how edaphoclimatic characteristics and treatments interactively affected MMQsoil.
Results
MMQsoil was higher in locations with higher mean annual temperature, lower water holding capacity and lower soil organic C concentration, but did not respond to our treatments across sites as neither MR nor MBC changed. We attributed this relative homeostasis to our treatments to the modulating influence of edaphoclimatic variables. For example, herbivore exclusion, regardless of fertilization, led to greater MMQsoil only at sites with lower soil organic C (< 1.7%).
Main conclusions
Our results pinpoint the main variables related to MMQsoil across grasslands and emphasize the importance of the local edaphoclimatic conditions in controlling the response of the C cycle to anthropogenic stressors. By testing hypotheses about MMQsoil across global edaphoclimatic gradients, this work also helps to align the conflicting results of prior studies.
Planetary‐scale waves are thought to play a role in powering the yet unexplained atmospheric superrotation of Venus. Puzzlingly, while Kelvin, Rossby, and stationary waves manifest at the upper ...clouds (65–70 km), no planetary‐scale waves or stationary patterns have been reported in the intervening level of the lower clouds (48–55 km), although the latter are probably Lee waves. Using observations by the Akatsuki orbiter and ground‐based telescopes, we show that the lower clouds follow a regular cycle punctuated between 30°N and 40°S by a sharp discontinuity or disruption with potential implications to Venus's general circulation and thermal structure. This disruption exhibits a westward rotation period of ∼4.9 days faster than winds at this level (∼6‐day period), alters clouds' properties and aerosols, and remains coherent during weeks. Past observations reveal its recurrent nature since at least 1983, and numerical simulations show that a nonlinear Kelvin wave reproduces many of its properties.
Plain Language Summary
One of the biggest mysteries of Venus is its atmospheric superrotation that allows the atmosphere to rotate 60 times faster than the solid planet. Atmospheric waves are among one of the possible mechanisms thought to feed this superrotation by pushing energy to different locations of the atmosphere. In fact, the upper clouds of Venus located at 65–70 km exhibit varied giant waves, like the so‐called Y feature or the more recently discovered bow‐shaped wave that keeps “stationary” over Aphrodite mountains. In contrast, these planetary‐scale waves are missing at the deeper lower clouds (48–55 km). This is especially puzzling in the case of the stationary waves since the lower clouds are located between the upper clouds and the surface, where they are thought to be generated. Thanks to the high‐quality observations of Venus from JAXA's space mission Akatsuki and NASA's IRTF telescope, we discovered at the lower clouds an intriguing sharp discontinuity that propagates to the west faster than the winds while altering the clouds' properties and suffering little distortions during weeks. A reanalysis of past observations revealed that this is a recurrent phenomenon that has gone unnoticed since at least the year 1983. Numerical simulations evidence that an atmospheric wave generated below the clouds and probably pumping energy to the upper clouds can explain many of its properties.
Key Points
Discovery of an equatorial cloud discontinuity at the middle and lower clouds of Venus, where no planetary wave had been found before
This disruption propagates to the West faster than the winds, keeps coherent for weeks, and alters clouds' properties and aerosols
Past observations confirm its existence since 1983; numerical simulations suggest a physical origin as a nonlinear Kelvin wave
The Venus Express mission has provided a long-term monitoring of Venus atmosphere including the morphology and motions of its upper clouds. Several works have focused on the dynamics of the upper ...cloud visible on the day-side in ultraviolet images sensitive to the 65–70km altitude and in the lower cloud level (50km height) observable in the night-side of the planet in the 1.74μm spectral window. Here we use VIRTIS-M spectral images in nearby wavelengths to study the upper cloud layer in three channels: ultraviolet (360–400nm), visible (570–680nm) and near infrared (900–955nm) extending in time the previous analysis of VIRTIS-M data. The ultraviolet images show relatively well contrasted cloud features at the cloud top. Cloud features in the visible and near infrared images lie a few kilometers below the upper cloud top, have very low contrast and are distinct to the features observed in the ultraviolet. Wind measurements were obtained on 118 orbits covering the Southern hemisphere over a six-year period and using a semi-automatic cloud correlation algorithm. Results for the upper cloud from VIRTIS-M ultraviolet data confirm previous analysis based on images obtained by the Venus Monitoring Camera (Khatuntsev et al. (2013)). At the cloud top the mean zonal and meridional winds vary with local time accelerating towards the local afternoon. The upper branch of the Hadley cell circulation reaches maximum velocities at 45° latitude and local times of 14–16h. The mean zonal winds in the ultraviolet cloud layer accelerated in the course of the 2006–2012 period at least 15ms−1. The near infrared and visible images show a more constant circulation without significant time variability or longitudinal variations. The meridional circulation is absent or slightly reversed in near infrared and visible images indicating that, either the Hadley-cell circulation in Venus atmosphere is shallow, or the returning branch of the meridional circulation extends to levels below the cloud level sensed in near infrared images. At subpolar to polar latitudes the three wavelength ranges show similar features and motions which is a signature of small vertical wind shear and may be affected by vertical convergence of both layers. At the clod top level observed in UV images there are signatures of a long-term acceleration of the zonal winds at afternoon hours when comparing zonal winds from the first years of Venus Express observations (2006–2008) to later dates (2009–2012) with a mean acceleration of zonal winds of 17±6ms−1 between both time periods.
•We measure Venus winds from VIRTIS on Venus Express over six years.•Winds at cloud top have a large variability with tides and a long-term acceleration.•Winds from near infrared images have a regular behavior.•We find high vertical wind shear at low-mid latitudes but not at subpolar latitudes.
In June 2015, Cassini high-resolution images of Saturn's limb southwards of the planet's hexagonal wave revealed a system of at least six stacked haze layers above the upper cloud deck. Here, we ...characterize those haze layers and discuss their nature. Vertical thickness of layers ranged from 7 to 18 km, and they extended in altitude ∼130 km, from pressure level 0.5 bar to 0.01 bar. Above them, a thin but extended aerosol layer reached altitude ∼340 km (0.4 mbar). Radiative transfer modeling of spectral reflectivity shows that haze properties are consistent with particles of diameter 0.07-1.4 μm and number density 100-500 cm
. The nature of the hazes is compatible with their formation by condensation of hydrocarbon ices, including acetylene and benzene at higher altitudes. Their vertical distribution could be due to upward propagating gravity waves generated by dynamical forcing by the hexagon and its associated eastward jet.
► We retrieved Saturn’s winds from ISS Cassini CB and MT images from 2004 to 2009. ► Differences between CB and MT zonal winds are due to vertical thermal wind shear. ► We supply tabular data of the ...ISS Cassini CB and MT Cassini wind profiles. ► Outside the equator zonal winds have remained stable during a complete Saturn’s year. ► There is a major change in the equatorial winds possibly after the 1990 GWS event.
Five years of Cassini Imaging Science Subsystem images, from 2004 to 2009, are analyzed in this work to retrieve global zonal wind profiles of Saturn’s northern and southern hemispheres in the methane absorbing bands at 890 and 727
nm and in their respective adjacent continuum wavelengths of 939 and 752
nm. A complete view of Saturn’s global circulation, including the equator, at two pressure levels, in the tropopause (60
mbar to 250
mbar with the MT filters) and in the upper troposphere (from ∼350
mbar to ∼500
mbar with the CB filter set), is presented. Both zonal wind profiles (available at the
Supplementary Material Section), show the same structure but with significant differences in the peak of the eastward jets and the equatorial region, including a region of positive vertical shear symmetrically located around the equator between the 10°
<
|
φ
c
|
<
25° where zonal velocities close to the tropopause are higher than at 500
mbar. A comparison of previously published zonal wind sets obtained by Voyager 1 and 2 (1980–1981), Hubble Space Telescope, and ground-based telescopes (1990–2004) with the present Cassini profiles (2004–2009) covering a full Saturn year shows that the shape of the zonal wind profile and intensity of the jets has remained almost unchanged except at the equator, despite the seasonal insolation cycle and the variability of Saturn’s emitted power. The major wind changes occurred at equatorial latitudes, perhaps following the Great White Spot eruption in 1990. It is not evident from our study if the seasonal insolation cycle and its associated ring shadowing influence the equatorial circulation at cloud level.
Even though many missions have explored the Venus atmospheric circulation, its instantaneous state is poorly characterized. In situ measurements vertically sampling the atmosphere exist for limited ...locations and dates, while remote sensing observations provide only global averages of winds at altitudes of the clouds: 47, 60, and 70 km. We present a three‐dimensional global view of Venus's atmospheric circulation from data obtained in June 2007 by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) and Venus Express spacecrafts, together with ground‐based observations. Winds and temperatures were measured for heights 47–110 km from multiwavelength images and spectra covering 40°N–80°S and local times 12 h–21 h. Dayside westward winds exhibit day‐to‐day changes, with maximum speeds ranging 97–143 m/s and peaking at variable altitudes within 75–90 km, while on the nightside these peak below cloud tops at ∼60 km. Our results support past reports of strong variability of the westward zonal superrotation in the transition region, and good agreement is found above the clouds with results from the Laboratoire de Météorologie Dynamique (LMD) Venus general circulation model.
Plain Language Summary
The atmosphere of the Earth or Mars globally rotates with a speed similar to the rotation of the planet (approximately 24 h). The rotation of Venus is of about 243 days, much slower than the Earth, but when scientists measured the winds by tracking the clouds of Venus, they discovered that the atmosphere rotates 60 times faster! No one has explained yet what originates this “superrotation,” and we do not know well what happens either above or below the clouds. The technique of “Doppler shift” has been used to measure winds above the clouds, but results are “chaotic” and different to interpret. Thanks to a worldwide collaboration in June 2007 between NASA (MESSENGER), ESA (Venus Express), and many observatories (VLT in Chile, JCMT in Hawaii, HHSMT in Arizona, or IRAM in Spain), the authors combined the different data to obtain, for the first time, the instantaneous 3‐D structure of the winds on Venus at the clouds and also above, very important for new Venus models to start “forecasts” of the Venus weather with “data assimilation”. We also discovered that the superrotation seems unexpectedly different on the night of Venus and that it varies its altitude depending on the day.
Key Points
The 3‐D quasi‐simultaneous winds on Venus's day and night from combining space and ground observations
We detect and quantify day‐to‐night and temporal wind changes between altitudes 50 and 120 km
Comparison between wind data and GCM predictions indicates good agreement, but deviations occur at 60–70 km in nighttime
In situ measurements by the Curiosity rover provide a unique opportunity for studying the effects of dust on assets placed at the surface of Mars. Here we use in situ measurements of solar UV ...radiation to quantify the seasonal and interannual variability of dust accumulation on the sensor on the rover deck. We show that the amount of dust accumulated on the sensor follows a seasonal cycle, with net dust removal during the perihelion season until L
~ 300°, and net dust deposition until the end of the aphelion season (L
~ 300°-180°). We use independent in situ measurements of atmospheric opacity and pressure perturbations in combination with numerical modeling, showing that daytime convective vortices and nighttime winds are likely responsible for the seasonal dust cleaning, with the role of nighttime wind being more important in Martian Year (MY) 32 than in MY 33 and that of daytime convective vortices being more important in MY 33 than in MY 32. The fact that the UV sensor is cleaner in MY 33 than in MY 32 indicates that natural cleaning events make solar energy an excellent candidate to power extended (multiannual) Mars missions at similar latitudes as the Curiosity rover.
We have used high-resolution images obtained with JunoCam onboard the Juno spacecraft during its close flyby of Jupiter on 2017 July 11, to study the dynamics of the Great Red Spot (GRS) at the upper ...cloud level. We have measured the horizontal velocity and vorticity fields using the clouds as tracers of the flow. We have analyzed a variety of cloud morphologies that serve to characterize different underlying dynamic processes. Long undulating dark gray filaments (2000-10000 km) circulate around the outer part of the vortex moving at high speed (∼120-140 m s−1) where mesoscale waves (wavelength 75 km) indicate stable conditions in this region. At mid distance from the center, a large eddy (radius ∼500 km) is observed in a region of intense horizontal wind shear whereas on the opposite side, compact cloud clusters with cell sizes of ∼50 km, indicative of shallow convection, are observed. The core of the GRS (∼5000 × 3000 km2) is turbulent where the circulation has weakly cyclonic and anticyclonic regions. This variety of phenomena occurs in the upper ammonia cloud layer and haze (thickness ∼20-50 km) that represents the top of a dynamical system with a much deeper circulation.
We describe a huge planetary‐scale disturbance in the highest‐speed Jovian jet at latitude 23.5°N that was first observed in October 2016 during the Juno perijove‐2 approach. An extraordinary ...outburst of four plumes was involved in the disturbance development. They were located in the range of planetographic latitudes from 22.2° to 23.0°N and moved faster than the jet peak with eastward velocities in the range 155 to 175 m s−1. In the wake of the plumes, a turbulent pattern of bright and dark spots (wave number 20–25) formed and progressed during October and November on both sides of the jet, moving with speeds in the range 100–125 m s−1 and leading to a new reddish and homogeneous belt when activity ceased in late November. Nonlinear numerical models reproduce the disturbance cloud patterns as a result of the interaction between local sources (the plumes) and the zonal eastward jet.
Key Points
A planetary‐scale disturbance developed in the highest‐speed Jupiter jet at 23.5°N latitude during October and November 2016
Four “plumes” were involved in the outbreak moving with speeds between 155 and 175 m s−1, the fastest features at cloud level
Nonlinear numerical models reproduce the disturbance from the interaction between local sources (the plumes) and the zonal eastward jet
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