Periodic Reporting for period 2 - ROADMAP (ROle and impAct of Dust and clouds in the Martian Atmosphere: from lab to space)
Période du rapport: 2021-11-01 au 2023-10-31
Dust is present everywhere on Mars, yet its abundance, physical properties and impact on the atmosphere have today only barely been understood. Dust is lifted from the surface up into the atmosphere by several processes. 3 transport regimes are usually considered: suspension (the grain remains aloft in the atmosphere), saltation (the particle will fall back to the surface), and creep (the particle undergoes rolling and sliding on the surface). When large particles return to the surface, they impact dust grains which in turn can be injected into the atmosphere.
Dust storms can span different spatial and time scales. Sometimes, Global Dust Storms occur. The processes that control the creation, expansion, and decay of global dust storms depend on the radiative–dynamic feedback between dust lifting, heating of the atmosphere, and circulation. The dust and water cycles are coupled through cloud condensation processes. Dust also modifies the thermal structure of the atmosphere.
The concept of the RoadMap project (ROle and impAct of Dust and clouds in the Martian AtmosPhere) is based on an integrated approach of different scientific aspects (laboratory, modelling, space data analysis) to improve our vision of the Martian atmosphere and provide a new generation of high-level data which will increase the science return of the past and current missions to Mars, but will also shape and help future planetary missions.
This will be done through the analysis of existing data to obtain abundances and properties of gases, dust and clouds through analysis tools improved thanks to laboratory experiments. General Circulation Models will be updated with the latest results from the lab (lifting, aggregation, radiative properties), to better understand the Martian atmosphere.
Dust storms can span different spatial and time scales. Sometimes, Global Dust Storms occur. The processes that control the creation, expansion, and decay of global dust storms depend on the radiative–dynamic feedback between dust lifting, heating of the atmosphere, and circulation. The dust and water cycles are coupled through cloud condensation processes. Dust also modifies the thermal structure of the atmosphere.
The concept of the RoadMap project (ROle and impAct of Dust and clouds in the Martian AtmosPhere) is based on an integrated approach of different scientific aspects (laboratory, modelling, space data analysis) to improve our vision of the Martian atmosphere and provide a new generation of high-level data which will increase the science return of the past and current missions to Mars, but will also shape and help future planetary missions.
This will be done through the analysis of existing data to obtain abundances and properties of gases, dust and clouds through analysis tools improved thanks to laboratory experiments. General Circulation Models will be updated with the latest results from the lab (lifting, aggregation, radiative properties), to better understand the Martian atmosphere.
One of the first challenges of the RoadMap project was to produce samples of analogues for Martian dust. Different analogues were chosen: JSC Mars-1, MMS-2, and MGS-1.
Key achievement (KA) 1 optimised method for producing of samples with specified size distributions.
Key result (KR) 1 Samples with different particle sizes, some with very narrow size distribution were produced.
These samples were fully characterized in the lab through different experiments.
KA2 Experimental set-ups designed to fully characterize the dust to a level never achieved before. Systems were built for depositing dust under Martian conditions upon sand beds. A modular wind tunnel was implemented into an environmental wind tunnel capable of resuspending dust.
KR2 The experiment on dust lifting showed that even fine dust that can stay in suspension in the Martian atmosphere on long-time scales is lifted in saltating impacts.
KR3 The aerodynamical properties experiment showed that most particles ejected in saltating impacts are round; Particles are compact but can be porous.
KR4 The electrical properties of particles ejected in saltating impacts show partially strong electrification. Lifted particles being charged could create a field between ground and lifted dust and thus further aid lifting. This was proposed earlier but could never be proved.
KR5 For the first time, direct dust remobilisation under Martian conditions was demonstrated. Dust depth is a key factor: direct dust remobilization threshold for thick dust layers is comparable to that of sand. Thin dust layers cannot be removed even at an order of magnitude increase in wind stress. Dust removal occurred via rolling of large dust aggregates and lifting of smaller ones.
KR6 For the first time, direct dust resuspension was observed under Martian conditions.
KR7 For the first time, saltation-induced dust remobilization was observed under Martian conditions. The unexpected generation of abrasion-induced dust was observed.
KR8 The abrasion process results from sand being carried high above the sand bed and reaching high velocity, collisions caused sand grain fracture and dust generation. This is important for understanding sand transport and dust generation on Mars.
Based on these measurements, several models and parameterizations could be improved. Some were tested on real space data to estimate their impact and importance on Martian processes.
KR9 A comprehensive dust lifting model was developed and implemented into a Martian GCM.
Some of the samples were also subjected to specific experiments to characterize their radiative properties.
KR10 Scattering matrices at two wavelengths were obtained for different analogues. They are available in the Codulab database.
KR11 Diffuse reflectance spectra (200 - 2000 nm) of the samples are available in the Codulab database.
Based on these measurements, different models were used to test the validity of scattering databases such as the triaxial ellipsoid and the hexahedra scattering.
KR12 The hexahedra model produced the best fits to the experimental data and is thus recommended to be further used in Martian studies.
KR13 Optical constants of the analogues were retrieved. This retrieval is not sensitive to changes in the real part of the refractive index, but well to the particle shapes. Four shapes were considered. The GRS2 shapes should be considered.
KR14 The measured scattering matrices were modelled by using the new sets of optical constants and the hexahedra model. The model is sensitive to changes in the real part of the refractive index. It can then be used to retrieve scattering properties for various particle size distributions.
KA3 Retrieval techniques were devised to improve the analysis of space data (dust and trace gasses).
KA4 A 1D microphysical model for aerosols was built. A new size-resolved dust bin algorithm was implemented into the 3D GCM.
KR15 Using NOMAD-UVIS solar occultation observations, an unprecedented dataset of dust/cloud vertical profiles has been obtained.
KR16 Using NOMAD-UVIS nadir observations we showed that none of the analogues could improve the retrieval of dust indicating that these are good analogues for the dynamical behaviour of the dust, but not for its radiative properties. We need dust samples from Mars.
KR17 Using NOMAD solar occultation observations an unprecedented dataset of vertical profiles of several atmospheric species and temperature has been built.
KR18 Improved climatology obtained with the GCM was prepared, 3 Mars Years with a model output frequency of ~30 minutes.
KA5 Exploitation and dissemination:
papers in international refereed Journals; results shown at international conferences. 3 PhD
New high-level data, tools and methods: see roadmap.aeronomie.be/index.php/data-portal.
dedicated exhibition displayed at the Astropolis Space Science Center in Oostende and the Museo Nacional de Ciencia y Tecnología in Madrid.
Mars in a Box educational project sent to schools in Europe and to the Ethiopian Space Science and Technology Institute. The online box: www.marsinabox.eu.
Making planetary research inclusive through art. Researchers in the atmosphere of Mars and students of LUCA School of Arts worked together on data visualization - art projects exhibited at the final workshop of RoadMap
Key achievement (KA) 1 optimised method for producing of samples with specified size distributions.
Key result (KR) 1 Samples with different particle sizes, some with very narrow size distribution were produced.
These samples were fully characterized in the lab through different experiments.
KA2 Experimental set-ups designed to fully characterize the dust to a level never achieved before. Systems were built for depositing dust under Martian conditions upon sand beds. A modular wind tunnel was implemented into an environmental wind tunnel capable of resuspending dust.
KR2 The experiment on dust lifting showed that even fine dust that can stay in suspension in the Martian atmosphere on long-time scales is lifted in saltating impacts.
KR3 The aerodynamical properties experiment showed that most particles ejected in saltating impacts are round; Particles are compact but can be porous.
KR4 The electrical properties of particles ejected in saltating impacts show partially strong electrification. Lifted particles being charged could create a field between ground and lifted dust and thus further aid lifting. This was proposed earlier but could never be proved.
KR5 For the first time, direct dust remobilisation under Martian conditions was demonstrated. Dust depth is a key factor: direct dust remobilization threshold for thick dust layers is comparable to that of sand. Thin dust layers cannot be removed even at an order of magnitude increase in wind stress. Dust removal occurred via rolling of large dust aggregates and lifting of smaller ones.
KR6 For the first time, direct dust resuspension was observed under Martian conditions.
KR7 For the first time, saltation-induced dust remobilization was observed under Martian conditions. The unexpected generation of abrasion-induced dust was observed.
KR8 The abrasion process results from sand being carried high above the sand bed and reaching high velocity, collisions caused sand grain fracture and dust generation. This is important for understanding sand transport and dust generation on Mars.
Based on these measurements, several models and parameterizations could be improved. Some were tested on real space data to estimate their impact and importance on Martian processes.
KR9 A comprehensive dust lifting model was developed and implemented into a Martian GCM.
Some of the samples were also subjected to specific experiments to characterize their radiative properties.
KR10 Scattering matrices at two wavelengths were obtained for different analogues. They are available in the Codulab database.
KR11 Diffuse reflectance spectra (200 - 2000 nm) of the samples are available in the Codulab database.
Based on these measurements, different models were used to test the validity of scattering databases such as the triaxial ellipsoid and the hexahedra scattering.
KR12 The hexahedra model produced the best fits to the experimental data and is thus recommended to be further used in Martian studies.
KR13 Optical constants of the analogues were retrieved. This retrieval is not sensitive to changes in the real part of the refractive index, but well to the particle shapes. Four shapes were considered. The GRS2 shapes should be considered.
KR14 The measured scattering matrices were modelled by using the new sets of optical constants and the hexahedra model. The model is sensitive to changes in the real part of the refractive index. It can then be used to retrieve scattering properties for various particle size distributions.
KA3 Retrieval techniques were devised to improve the analysis of space data (dust and trace gasses).
KA4 A 1D microphysical model for aerosols was built. A new size-resolved dust bin algorithm was implemented into the 3D GCM.
KR15 Using NOMAD-UVIS solar occultation observations, an unprecedented dataset of dust/cloud vertical profiles has been obtained.
KR16 Using NOMAD-UVIS nadir observations we showed that none of the analogues could improve the retrieval of dust indicating that these are good analogues for the dynamical behaviour of the dust, but not for its radiative properties. We need dust samples from Mars.
KR17 Using NOMAD solar occultation observations an unprecedented dataset of vertical profiles of several atmospheric species and temperature has been built.
KR18 Improved climatology obtained with the GCM was prepared, 3 Mars Years with a model output frequency of ~30 minutes.
KA5 Exploitation and dissemination:
papers in international refereed Journals; results shown at international conferences. 3 PhD
New high-level data, tools and methods: see roadmap.aeronomie.be/index.php/data-portal.
dedicated exhibition displayed at the Astropolis Space Science Center in Oostende and the Museo Nacional de Ciencia y Tecnología in Madrid.
Mars in a Box educational project sent to schools in Europe and to the Ethiopian Space Science and Technology Institute. The online box: www.marsinabox.eu.
Making planetary research inclusive through art. Researchers in the atmosphere of Mars and students of LUCA School of Arts worked together on data visualization - art projects exhibited at the final workshop of RoadMap
RoadMap has characterized martian dust samples from the laboratory to their use for space data analysis, improving the description of physical and radiative processes in which dust is involved. RoadMap established links between different communities (Laboratory, Modeling, data analysis). See KR above for the beyond the state-of-the-art results.