The COVID-19 pandemic and global environmental change: Emerging research needs

The outbreak of COVID-19 raised numerous questions on the interactions between the occurrence of new infections, the environment, climate and health. The European Union requested the H2020 HERA project which aims at setting priorities in research on environment, climate and health, to identify relevant research needs regarding Covid-19. The emergence and spread of SARS-CoV-2 appears to be related to urbanization, habitat destruction, live animal trade, intensive livestock farming and global travel. The contribution of climate and air pollution requires additional studies. Importantly, the severity of COVID-19 depends on the interactions between the viral infection, ageing and chronic diseases such as metabolic, respiratory and cardiovascular diseases and obesity which are themselves influenced by environmental stressors. The mechanisms of these interactions deserve additional scrutiny. Both the pandemic and the social response to the disease have elicited an array of behavioural and societal changes that may remain long after the pandemic and that may have long term health effects including on mental health. Recovery plans are currently being discussed or implemented and the environmental and health impacts of those plans are not clearly foreseen. Clearly, COVID-19 will have a long-lasting impact on the environmental health field and will open new research perspectives and policy needs.     

AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR). With independent delivery and direct-to-Earth communications, AVIATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan??s global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments??2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector??AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan??s atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earth-year nominal mission. We propose a novel ??gravity battery?? climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead of using gimbaled cameras. AVIATR would climb up to 14?km altitude and descend down to 3.5?km altitude once per Earth day, allowing for repeated atmospheric structure and wind measurements all over the globe. An initial Team-X run at JPL priced the AVIATR mission at FY10 $715M based on the rules stipulated in the recent Discovery announcement of opportunity. Hence we find that a standalone Titan airplane mission can achieve important science building on Cassini??s discoveries and can likely do so within a New Frontiers budget.     

In-flight calibration of the Cassini imaging science sub-system cameras

We describe in-flight calibration of the Cassini Imaging Science Sub-system narrow- and wide-angle cameras using data from 2004 to 2009. We report on the photometric performance of the cameras including the use of polarization filters, point spread functions over a dynamic range greater than 10⁷, gain and loss of hot pixels, changes in flat fields, and an analysis of charge transfer efficiency. Hot pixel behavior is more complicated than can be understood by a process of activation by cosmic ray damage and deactivation by annealing. Point spread function (PSF) analysis revealed a ghost feature associated with the narrow-angle camera Green filter. More generally, the observed PSFs do not fall off with distance as rapidly as expected if diffraction were the primary contributor. Stray light produces significant signal far from the center of the PSF. Our photometric analysis made use of calibrated spectra from eighteen stars and the spectral shape of the satellite Enceladus. The analysis revealed a shutter offset that differed from pre-launch calibration. It affects the shortest exposures. Star photometry results are reproducible to a few percent in most filters. No degradation in charge transfer efficiency has been detected although uncertainties are large. The results of this work have been digitally archived and incorporated into our calibration software CISSCAL available online.     

Ozone abundance on Mars from infrared heterodyne spectra: II. Validating photochemical models

Ozone is an important observable tracer of martian photochemistry, including odd hydrogen (HO_x) species important to the chemistry and stability of the martian atmosphere. Infrared heterodyne spectroscopy with spectral resolution ?¹⁰⁶ provides the only ground-based direct access to ozone absorption features in the martian atmosphere. Ozone abundances were measured with the Goddard Infrared Heterodyne Spectrometer and the Heterodyne Instrument for Planetary Wind and Composition at the NASA Infrared Telescope Facility on Mauna Kea, Hawai'i. Retrieved total ozone column abundances from various latitudes and orbital positions (LS=40°, 74°, 102°, 115°, 202°, 208°, 291°) are compared to those predicted by the first three-dimensional gas phase photochemical model of the martian atmosphere [Lefèvre, F., Lebonnois, S., Montmessin, F., Forget, F., 2004. J. Geophys. Res. 109, doi:10.1029/2004JE002268. E07004]. Observed and modeled ozone abundances show good agreement at all latitudes at perihelion orbital positions (LS=202°, 208°, 291°). Observed low-latitude ozone abundances are significantly higher than those predicted by the model at aphelion orbital positions (LS=40°, 74°, 115°). Heterogeneous loss of odd hydrogen onto water ice cloud particles would explain the discrepancy, as clouds are observed at low latitudes around aphelion on Mars.     

Crystallochemistry and origin of pyroxenes in komatiites

We present a detailed mineralogical and major- and trace-element study of pyroxenes in two Archean komatiitic flows in Alexo, Canada. The pyroxenes in spinifex-textured lavas commonly are zoned with cores of magnesian pigeonite and rims of augite. Concentrations of incompatible trace elements are low in pigeonite and jump to higher values in the augite mantles, a variation that can be modelled using accepted partition coefficients and assuming crystallization from komatiitic liquids. Crystallization sequences are very different in different parts of both flows. In the flow top, the sequence is olivine followed by augite: deeper in the spinifex sequence, pigeonite crystallizes after olivine, followed by augite; in lower cumulates, orthopyroxene or augite accompany olivine. In spinifex lavas, pigeonite crystallizes sooner than would be predicted on the basis of equilibrium phase relations. We propose that contrasting crystallization sequences depend on the position in the flow and on the conditions of crystal growth. In the flowtop, rapid cooling causes quench crystallization. Deeper in the spinifex layer, constrained growth in a thermal gradient, perhaps augmented by Soret differentiation, accounts for the early crystallization of pigeonite. The cumulus minerals represent a near-equilibrium assemblage. Augites in Al-undepleted Archean komatiites in various localities in Canada and Zimbabwe have high moderate to high Wo contents but their Mg# (Mg/(Mg + Fe) are lower than in augites in komatiites from Barberton, South Africa. We attribute the combination of high Wo and high Mg# in Barberton rocks to the unusually high CaO/Al₂O₃ of these Al-depleted komatiites.     

Seismic images and rock properties of the very shallow structure of Campi Flegrei caldera (southern Italy)

In September 2001, an extensive active-seismic investigation (Serapis experiment) was carried out in the Gulfs of Naples and Pozzuoli, with the aim of investigating and reconstructing the shallow crustal structure of the Campi Flegrei caldera, and possibly identifying its feeding system at depth. The present study provides a joint analysis of the very shallow seismic reflection data and tomographic images based on the Serapis dataset. This is achieved by reflection seismic sections obtained by the 3D data gathering and through refined P-velocity images of the shallowest layer of Pozzuoli Gulf (z < 1,000 m). From the refined Vp model, the overall picture of the velocity distribution confirms the presence of a complex arc-shaped anomaly that borders the bay offshore. The deeper part of the anomaly (beneath 700 m, with Vp > 3,500 m/s) correlates with units made up of agglomerate tuffs and interbedded lava, which form the southern edge of the caldera, which was probably formed following the two large ignimbritic eruptions that marked the evolutionary history of the area under study. The upper part of the anomaly that tends to split into two parallel arcs is correlated with dikes, volcanic mounds and hydrothermal alteration zones noted in previous shallow reflection seismic analyses. The depth of the transition between the upper and lower parts of the anomaly is characterized by an abrupt Vp increase on the one-dimensional (1D) profiles extracted from the 3D tomographic model and by the presence of a strong reflector located at about 0.6/0.7 s Two Way Time (TWT) on Common Mid Point gathers. The move-out velocity analysis and stack of the P–P and P–S reflections at the layer bottom allowed to estimate relatively high Vp/Vs values (3.7 ± 0.9). This hypothesis has been tested by a theoretical rock physical modeling of the Vp/Vs ratio as a function of porosity suggesting that the shallow layer is likely formed by incoherent, water saturated, volcanic and marine sediments that filled Pozzuoli Bay during the post-caldera activity.     

The COVID-19 pandemic and global environmental change: Emerging research needs

The outbreak of COVID-19 raised numerous questions on the interactions between the occurrence of new infections, the environment, climate and health. The European Union requested the H2020 HERA project which aims at setting priorities in research on environment, climate and health, to identify relevant research needs regarding Covid-19. The emergence and spread of SARS-CoV-2 appears to be related to urbanization, habitat destruction, live animal trade, intensive livestock farming and global travel. The contribution of climate and air pollution requires additional studies. Importantly, the severity of COVID-19 depends on the interactions between the viral infection, ageing and chronic diseases such as metabolic, respiratory and cardiovascular diseases and obesity which are themselves influenced by environmental stressors. The mechanisms of these interactions deserve additional scrutiny. Both the pandemic and the social response to the disease have elicited an array of behavioural and societal changes that may remain long after the pandemic and that may have long term health effects including on mental health. Recovery plans are currently being discussed or implemented and the environmental and health impacts of those plans are not clearly foreseen. Clearly, COVID-19 will have a long-lasting impact on the environmental health field and will open new research perspectives and policy needs.     

Computer simulation of electron transfer at hematite surfaces

Molecular dynamics simulations in combination with ab initio calculations were carried out to determine the rate of electron transfer at room temperature in bulk hematite (α-Fe₂O₃) and at two low-index surfaces, namely the (012) and (001) surfaces. The electron transfer reactions considered here involve the II/III valence interchange between nearest-neighbor iron atoms. Two electron transfer directions were investigated, namely the basal plane and c direction electron transfers. Electron transfer rates obtained in bulk hematite were in good agreement with ab initio electronic structure calculations thus validating the potential model. The surfaces were considered both in vacuum and in contact with an equilibrated aqueous solution. The reorganization energy is found to increase significantly at the first surface layer and this value is little affected by the presence of water. In addition, in the case of the (012) surface, the electronic coupling matrix element for the topmost basal plane transfer was calculated at the Hartree-Fock level and was found to be weak compared to the corresponding electron transfer in the bulk. Therefore, most surfaces show a decrease in the rate of electron transfer at the surface. However, where iron atoms involved in the electron transfer reaction are directly coordinated to water molecules, water lowers the free energy of activation to a great extent and provides a large driving force for electrons to diffuse toward the bulk thus opposing the intrinsic surface effect. The surfaces considered in this work show different electron transfer properties. Hematite has been shown to exhibit anisotropic conductivity and thus different surfaces will show different intra- and inter-layer rates depending on their orientation. Moreover, the calculations of electron transfers at the hydroxyl- and iron-terminated (001) surfaces revealed that surface termination has a significant effect on the electron transfer parameters in the vicinity of the surface. Finally, our findings indicate that undercoordinated terminal iron atoms could act as electron traps at the surface.     

Impact of the LMDZ atmospheric grid configuration on the climate and sensitivity of the IPSL-CM5A coupled model

The IPSL-CM5A climate model was used to perform a large number of control, historical and climate change simulations in the frame of CMIP5. The refined horizontal and vertical grid of the atmospheric component, LMDZ, constitutes a major difference compared to the previous IPSL-CM4 version used for CMIP3. From imposed-SST (Sea Surface Temperature) and coupled numerical experiments, we systematically analyze the impact of the horizontal and vertical grid resolution on the simulated climate. The refinement of the horizontal grid results in a systematic reduction of major biases in the mean tropospheric structures and SST. The mid-latitude jets, located too close to the equator with the coarsest grids, move poleward. This robust feature, is accompanied by a drying at mid-latitudes and a reduction of cold biases in mid-latitudes relative to the equator. The model was also extended to the stratosphere by increasing the number of layers on the vertical from 19 to 39 (15 in the stratosphere) and adding relevant parameterizations. The 39-layer version captures the dominant modes of the stratospheric variability and exhibits stratospheric sudden warmings. Changing either the vertical or horizontal resolution modifies the global energy balance in imposed-SST simulations by typically several W/m² which translates in the coupled atmosphere-ocean simulations into a different global-mean SST. The sensitivity is of about 1.2 K per 1 W/m² when varying the horizontal grid. A re-tuning of model parameters was thus required to restore this energy balance in the imposed-SST simulations and reduce the biases in the simulated mean surface temperature and, to some extent, latitudinal SST variations in the coupled experiments for the modern climate. The tuning hardly compensates, however, for robust biases of the coupled model. Despite the wide range of grid configurations explored and their significant impact on the present-day climate, the climate sensitivity remains essentially unchanged.