The Experts below are selected from a list of 7719 Experts worldwide ranked by ideXlab platform
A Sanchezlavega - One of the best experts on this subject based on the ideXlab platform.
-
Dust particle size shape and optical depth during the 2018 my34 martian global Dust Storm retrieved by msl curiosity rover navigation cameras
Icarus, 2021Co-Authors: H Chenchen, S Perezhoyos, A SanchezlavegaAbstract:Abstract Martian planet-encircling Dust Storms or global Dust Storms (GDS), resulting from the combined influence of local and regional Storms, are uncommon aperiodic phenomena: with an average frequency of approximately one every 3–4 MY, they produce a substantial rise in the atmospheric Dust loading that lasts from weeks to months and have a significant impact on the atmospheric properties, energy budget, and global circulation. During the 2018/MY34 global Dust Storm, initiated at LS = 185° (30–31 May 2018), an intensive atmospheric science campaign was carried out by the Mars Science Laboratory (MSL) rover to monitor the environmental parameters at Gale Crater. We contribute to previous studies with independent retrievals to constrain the Dust opacity and characterise the aerosol particle properties, including: size, shape and single scattering phase function. An iterative radiative transfer retrieval procedure was implemented to determine the aerosol parameters that best fit the angular distribution of sky radiance at forward and backward scattering regions observed by MSL Navigation Cameras (Navcams) during the 2018/MY34 GDS. The MOPSMAP aerosol database and Double Henyey-Greenstein (DHG) analytical single scattering phase functions were used to model the Martian Dust aerosol. Outcomes of this study show a steep rise in Dust opacity from pre-Storm levels of 1.2 up to τ > 9, correlated to particle size variations from 1 to 4 μm. DHG phase functions are characterised with an average asymmetry parameter of g = 0.60 ± 0.11 during the Storm, diverging from values of around 0.71 ± 0.06 for the same period in previous MY. Best fitting simulations to backscatter observations for high-opacity periods were generated by a mixture of spheroids following a log-normal distribution of aspect ratios centred on 2.8 ± 0.9, in contrast to values of 1.8 in post-Storm sols, thus pointing to more irregular particle shapes at the peak of the Dust Storm.
-
strong increase in Dust devil activity at gale crater on the third year of the msl mission and suppression during the 2018 global Dust Storm
Icarus, 2020Co-Authors: I Ordonezetxeberria, R Hueso, A SanchezlavegaAbstract:Abstract The Rover Environmental Monitoring Station (REMS) instrument in the Mars Science Laboratory (MSL) mission has collected atmospheric data from Gale crater for more than three Martian years. These data correspond to a path travelled by the Curiosity rover of 18 km in length with differences in altitude of 400 m through a variety of terrains in terms of the thermal inertia and nearby topography in the complex environment formed by Gale crater and Aeolis Mons. Pressure measurements obtained by REMS contain sudden drops on day-time hours caused by convective vortices passing nearby, which in some cases raise Dust and become Dust devils. Pressure measurements also contain pressure drops at night-time possibly caused by atmospheric turbulence and showing a strong seasonality. We present an analysis of these pressure drops for 2224 sols of the MSL mission extending previous results. The new data obtained over the third Martian year of the mission show a large increase in the frequency and intensity of vortices accompanied by a dramatic increase of Dust devils that are simultaneously detected by lower values of UV radiation measured with REMS photodiodes. These Dust devil events increased from one to two per Martian year in the two first Martian years of the MSL mission to 36 events in the third Martian year of the mission. We argue that this increase in Dust devil activity is related to two different factors: (i) more intense vortices produced by a combination of the higher elevation of the terrain and lower thermal inertia of the environment favouring larger thermal differences between the ground and the air close to the terrain; (ii) a higher Dust availability in the terrains traversed during the third Martian year of the MSL mission. An alternative explanation is that Dust devils may need a minimum central pressure drop threshold to raise Dust, and that a slightly enhanced convective activity after the second Martian year of the mission largely increased the Dust devil events. Our observations suggest a minimum pressure drop of 3.5 Pa value for high Dust loads in the terrain studied with the MSL mission. The new measurements also cover the period of activity of the Global Dust Storm of 2018. During the roughly 100 sols that the Storm lasted, all Dust devil activity ceased. Nocturnal pressure drops similar to daytime convective vortices continued to be a strongly seasonal effect and were not affected by the Global Dust Storm.
Bruce M. Jakosky - One of the best experts on this subject based on the ideXlab platform.
-
Dust Storm enhanced gravity wave activity in the martian thermosphere observed by maven and implication for atmospheric escape
arXiv: Space Physics, 2021Co-Authors: Erdal Yigit, Alexander S Medvedev, Mehdi Benna, Bruce M. JakoskyAbstract:Lower atmospheric global Dust Storms affect the small- and large-scale weather and variability of the whole Martian atmosphere. Analysis of the CO$_2$ density data from the Neutral Gas and Ion Mass Spectrometer instrument (NGIMS) on board NASA's Mars Atmosphere Volatile EvolutioN (MAVEN) spacecraft show a remarkable increase of GW-induced density fluctuations in the thermosphere during the 2018 major Dust Storm with distinct latitude and local time variability. The mean thermospheric GW activity increases by a factor of two during the Storm event. The magnitude of relative density perturbations is around 20% on average and 40% locally. One and a half months later, the GW activity gradually decreases. Enhanced temperature disturbances in the Martian thermosphere can facilitate atmospheric escape. For the first time, we estimate that, for a 20% and 40% GW-induced disturbances, the net increase of Jeans escape flux of hydrogen is a factor of 1.3 and 2, respectively.
-
effect of the 2018 martian global Dust Storm on the co 2 density in the lower nightside thermosphere observed from maven iuvs lyman alpha absorption
Geophysical Research Letters, 2020Co-Authors: Jeanyves Chaufray, M S Chaffin, Justin Deighan, Sonal Jain, N M Schneider, Majd Mayyasi, Bruce M. JakoskyAbstract:The MAVEN/IUVS instrument measures Lyman‐α emissions from interplanetary and martian hydrogen at the limb and through the extended corona of Mars. In June 2018, a Global Dust Storm (GDS) surrounded Mars for a few months, heating the lower atmosphere and leading to an expansion of the Martian atmosphere. Nightside IUVS observations before and throughout this GDS showed the altitude of CO2 absorption of Lyman‐α photons in the thermosphere to increase by 4.5±1.0 km on 8 June 2018. This shift is attributed to an increase of the CO2 density by a factor 1.9±0.2 at 110 km due to the heating of the lower atmosphere. These nightside observations, not previously used to study Dust Storms, in an altitude range not sampled by other instruments, are consistent with dayside MAVEN observations and allow for more comprehensive determination of the global changes produced by the GDS on the Martian thermosphere.
Lucio Baggio - One of the best experts on this subject based on the ideXlab platform.
-
Martian water ice clouds during the 2018 global Dust Storm as observed by the ACS-MIR channel onboard the Trace Gas Orbiter
Journal of Geophysical Research. Planets, 2020Co-Authors: Aurélien Stcherbinine, Franck Montmessin, M. Vincendon, M. J. Wolff, A. Fedorova, Alexander Trokhimovskiy, A. Patrakeev, Gaetan Lacombe, Lucio BaggioAbstract:The Atmospheric Chemistry Suite (ACS) instrument onboard the ExoMars Trace Gas Orbiter (TGO) ESA-Roscosmos mission began science operations in March 2018. ACS Mid InfraRed (MIR) channel notably provides solar occultation observations of the martian atmosphere in the 2.3 – 4.2 μm spectral range. Here we use these observations to characterize water ice clouds before and during the MY 34 Global Dust Storm (GDS). We developed a method to detect water ice clouds with mean particle size ≤ 2 μm, and applied it to observations gathered between Ls = 165◦ and Ls = 243◦. We observe a shift in water ice clouds maximum altitudes from about 60 km before the GDS to above 90 km during the Storm. These very high altitude, small-sized (reff ≤ 0.3 μm) water ice clouds are more frequent during MY34 compared to non- GDS years at the same season. Particle size frequently decreases with altitude, both locally within a given profile and globally in the whole dataset. We observe that the maximum altitude at which a given size is observed can increase during the GDS by several tens of km for certain sizes. We notably notice some large water ice particles (reff ≥ 1.5 μm) at surprisingly high altitudes during the GDS (50 – 70 km). These results suggest that GDS can significantly impact the formation and properties of high altitude water ice clouds as compared to the usual perihelion Dust activity.
Jeanyves Chaufray - One of the best experts on this subject based on the ideXlab platform.
-
effect of the 2018 martian global Dust Storm on the co 2 density in the lower nightside thermosphere observed from maven iuvs lyman alpha absorption
Geophysical Research Letters, 2020Co-Authors: Jeanyves Chaufray, M S Chaffin, Justin Deighan, Sonal Jain, N M Schneider, Majd Mayyasi, Bruce M. JakoskyAbstract:The MAVEN/IUVS instrument measures Lyman‐α emissions from interplanetary and martian hydrogen at the limb and through the extended corona of Mars. In June 2018, a Global Dust Storm (GDS) surrounded Mars for a few months, heating the lower atmosphere and leading to an expansion of the Martian atmosphere. Nightside IUVS observations before and throughout this GDS showed the altitude of CO2 absorption of Lyman‐α photons in the thermosphere to increase by 4.5±1.0 km on 8 June 2018. This shift is attributed to an increase of the CO2 density by a factor 1.9±0.2 at 110 km due to the heating of the lower atmosphere. These nightside observations, not previously used to study Dust Storms, in an altitude range not sampled by other instruments, are consistent with dayside MAVEN observations and allow for more comprehensive determination of the global changes produced by the GDS on the Martian thermosphere.
H Chenchen - One of the best experts on this subject based on the ideXlab platform.
-
Dust particle size shape and optical depth during the 2018 my34 martian global Dust Storm retrieved by msl curiosity rover navigation cameras
Icarus, 2021Co-Authors: H Chenchen, S Perezhoyos, A SanchezlavegaAbstract:Abstract Martian planet-encircling Dust Storms or global Dust Storms (GDS), resulting from the combined influence of local and regional Storms, are uncommon aperiodic phenomena: with an average frequency of approximately one every 3–4 MY, they produce a substantial rise in the atmospheric Dust loading that lasts from weeks to months and have a significant impact on the atmospheric properties, energy budget, and global circulation. During the 2018/MY34 global Dust Storm, initiated at LS = 185° (30–31 May 2018), an intensive atmospheric science campaign was carried out by the Mars Science Laboratory (MSL) rover to monitor the environmental parameters at Gale Crater. We contribute to previous studies with independent retrievals to constrain the Dust opacity and characterise the aerosol particle properties, including: size, shape and single scattering phase function. An iterative radiative transfer retrieval procedure was implemented to determine the aerosol parameters that best fit the angular distribution of sky radiance at forward and backward scattering regions observed by MSL Navigation Cameras (Navcams) during the 2018/MY34 GDS. The MOPSMAP aerosol database and Double Henyey-Greenstein (DHG) analytical single scattering phase functions were used to model the Martian Dust aerosol. Outcomes of this study show a steep rise in Dust opacity from pre-Storm levels of 1.2 up to τ > 9, correlated to particle size variations from 1 to 4 μm. DHG phase functions are characterised with an average asymmetry parameter of g = 0.60 ± 0.11 during the Storm, diverging from values of around 0.71 ± 0.06 for the same period in previous MY. Best fitting simulations to backscatter observations for high-opacity periods were generated by a mixture of spheroids following a log-normal distribution of aspect ratios centred on 2.8 ± 0.9, in contrast to values of 1.8 in post-Storm sols, thus pointing to more irregular particle shapes at the peak of the Dust Storm.
