References of "Kasaba, Y"
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See detailMartian dust storm impact on atmospheric H 2 O and D/H observed by ExoMars Trace Gas Orbiter
Vandaele, A. C.; Korablev, O.; Daerden, F. et al

in Nature (2019), 568

Global dust storms on Mars are rare 1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere 3 , primarily owing to ... [more ▼]

Global dust storms on Mars are rare 1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere 3 , primarily owing to solar heating of the dust 3 . 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 4 . 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 5,6 , as well as a decrease in the water column at low latitudes 7,8 . 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 2 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 H 2 O 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 3 . The observed changes in H 2 O 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. © 2019, The Author(s), under exclusive licence to Springer Nature Limited. [less ▲]

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See detailNo detection of methane on Mars from early ExoMars Trace Gas Orbiter observations
Korablev, O.; Vandaele, A. C.; Montmessin, F. et al

in Nature (2019), 568

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today 1 . A number of different measurements of methane show evidence of ... [more ▼]

The detection of methane on Mars has been interpreted as indicating that geochemical or biotic activities could persist on Mars today 1 . A number of different measurements of methane show evidence of transient, locally elevated methane concentrations and seasonal variations in background methane concentrations 2–5 . These measurements, however, are difficult to reconcile with our current understanding of the chemistry and physics of the Martian atmosphere 6,7 , which—given methane’s lifetime of several centuries—predicts an even, well mixed distribution of methane 1,6,8 . 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 2,4 . We suggest that reconciliation between the present findings and the background methane concentrations found in the Gale crater 4 would require an unknown process that can rapidly remove or sequester methane from the lower atmosphere before it spreads globally. [less ▲]

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See detailNOMAD, an Integrated Suite of Three Spectrometers for the ExoMars Trace Gas Mission: Technical Description, Science Objectives and Expected Performance
Vandaele, A. C.; Lopez-Moreno, J.-J.; Patel, M. R. et al

in Space Science Reviews (2018), 214

The NOMAD ("Nadir and Occultation for MArs Discovery") spectrometer suite on board the ExoMars Trace Gas Orbiter (TGO) has been designed to investigate the composition of Mars' atmosphere, with a ... [more ▼]

The NOMAD ("Nadir and Occultation for MArs Discovery") spectrometer suite on board the ExoMars Trace Gas Orbiter (TGO) has been designed to investigate the composition of Mars' atmosphere, with a particular focus on trace gases, clouds and dust. The detection sensitivity for trace gases is considerably improved compared to previous Mars missions, compliant with the science objectives of the TGO mission. This will allow for a major leap in our knowledge and understanding of the Martian atmospheric composition and the related physical and chemical processes. The instrument is a combination of three spectrometers, covering a spectral range from the UV to the mid-IR, and can perform solar occultation, nadir and limb observations. In this paper, we present the science objectives of the instrument and explain the technical principles of the three spectrometers. We also discuss the expected performance of the instrument in terms of spatial and temporal coverage and detection sensitivity. [less ▲]

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See detailThe Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter
Korablev, O.; Montmessin, F.; Trokhimovskiy, A. et al

in Space Science Reviews (2018), 214

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared ... [more ▼]

The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7-1.6 μm spectral range with a resolving power of ˜20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2-4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7-17 μm with apodized resolution varying from 0.2 to 1.3 cm[SUP]-1[/SUP]. TIRVIM is primarily dedicated to profiling temperature from the surface up to ˜60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described. [less ▲]

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See detailWeakening of Jupiter's main auroral emission during January 2014
Badman, S. V.; Bonfond, Bertrand ULiege; Fujimoto, M. et al

in Geophysical Research Letters (2016), 43(3), 988-997

In January 2014 Jupiter's FUV main auroral oval decreased its emitted power by 70% and shifted equatorward by ∼1°. Intense, low-latitude features were also detected. The decrease in emitted power is ... [more ▼]

In January 2014 Jupiter's FUV main auroral oval decreased its emitted power by 70% and shifted equatorward by ∼1°. Intense, low-latitude features were also detected. The decrease in emitted power is attributed to a decrease in auroral current density rather than electron energy. This could be caused by a decrease in the source electron density, an order of magnitude increase in the source electron thermal energy, or a combination of these. Both can be explained either by expansion of the magnetosphere or by an increase in the inward transport of hot plasma through the middle magnetosphere and its interchange with cold flux tubes moving outward. In the latter case the hot plasma could have increased the electron temperature in the source region and produced the intense, low-latitude features, while the increased cold plasma transport rate produced the shift of the main oval. © 2016. The Authors. [less ▲]

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See detailWeakening of Jupiter’s main auroral emission in response to magnetospheric hot plasma injections
Badman, Sarah; Bonfond, Bertrand ULiege; Fujimoto, M. et al

Conference (2014, September 11)

We present images of Jupiter’s northern UV aurorae taken by the Hubble Space Telescope as part of a large observing campaign in January 2014. The high time resolution observations allow the dynamics of ... [more ▼]

We present images of Jupiter’s northern UV aurorae taken by the Hubble Space Telescope as part of a large observing campaign in January 2014. The high time resolution observations allow the dynamics of the different components of the aurorae to be observed. Particular features of interest are large regions of diffuse emission, which occurred equatorward of the main oval, enveloping the auroral footprint of Ganymede. These diffuse, low latitude emissions are caused by the injection of hot plasma from the outer magnetosphere, a process which has previously been related to interchange between the flux tubes from the outer magnetosphere and outward-moving flux tubes loaded with iogenic plasma. Over the two-week observing interval the auroral signatures of two large injection events were observed, while the main oval generally decreased in intensity. We suggest that the overall dimming of the main oval results from the weakening of the corotation-enforcement currents that drive the main emission, following the replacement of the radially-stretched, mass-loaded flux tubes by more dipolar flux tubes containing rarefied hot plasma. [less ▲]

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