No detection of methane on Mars from early ExoMars Trace Gas Orbiter observations

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today. A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations. These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere, which-given methane's lifetime of several centuries-predicts an even, well mixed distribution of methane. Here we report highly sensitive measurements of the atmosphere of Mars in an attempt to detect methane, using the ACS and NOMAD instruments onboard the ESA-Roscosmos ExoMars Trace Gas Orbiter from April to August 2018. We did not detect any methane over a range of latitudes in both hemispheres, obtaining an upper limit for methane of about 0.05 parts per billion by volume, which is 10 to 100 times lower than previously reported positive detections. We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally

Martian dust storm impact on atmospheric H₂O and D/H observed by ExoMars Trace Gas Orbiter

Global dust storms on Mars are rare but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere, primarily owing to solar heating of the dust. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes, as well as a decrease in the water column at low latitudes. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere

Flash flood forecasting within the PREVIEW project : value of high-resolution hydrometeorological coupled forecast

PREVIEW is an European Commission FP6 Integrated Project which aims at developing, on an European level, new geo-information services for natural and industrial risk management. The work package WP4340 focuses on forecast of Mediterranean flash floods. Phase 1 was devoted to the assessment of the usefulness of kilometric scale atmospheric model forecast for hydrological applications and to the development of hydro-meteorological coupled systems based on high-resolution atmospheric models and hydrological models able to reproduce the hydrological behaviour of Mediterranean catchments. Four high-resolution models at 2–3 km resolution have been run on five flash-flood cases over the French Cévennes-Vivarais and Italian Piedmont regions; models are MM5 (by NOA), COSMO-2 (by MeteoSwiss), MESO-NH (by Météo-France) and COSMO-LAMI (by Arpa Piemonte). To investigate the benefit of coupling atmospheric and hydrological models, the quantitative precipitation forecasts (QPF) have been verified against observations using both classical and categorical statistical scores, while the sensitivity of the QPF to the model initial conditions has been also examined. In addition, the various hourly precipitation forecasts were supplied as input to hydrological models to evaluate through the simulated discharges the value of high resolution forecasts for hydrological forecast purposes. Clearly the hydrological verification conclusions differ from the QPF verification ones and show the usefulness of developing such hydrological verification as the one performed here