Franzese, Gabriele (2018) Characterisation of dust events on Earth and Mars the ExoMars/DREAMS experiment and the field campaign in the Sahara desert. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Resource language: English
Title: Characterisation of dust events on Earth and Mars the ExoMars/DREAMS experiment and the field campaign in the Sahara desert
Date: 10 June 2018
Number of Pages: 135
Institution: Università degli Studi di Napoli Federico II
Department: dep06
Dottorato: phd028
Ciclo di dottorato: 30
Coordinatore del Corso di dottorato:
Esposito, FrancescaUNSPECIFIED
Date: 10 June 2018
Number of Pages: 135
Keywords: Dust lifting process; Dust Devils; Dust Storms; Atmospheric Electricity; Terrestrial Atmosphere; Martian Atmosphere; Meteorology
Settori scientifico-disciplinari del MIUR: Area 02 - Scienze fisiche > FIS/05 - Astronomia e astrofisica
Date Deposited: 13 Jun 2018 15:24
Last Modified: 06 Mar 2019 08:55

Collection description

Atmospheric dust plays an important role on the terrestrial climate, regulating the amount of solar radiation coming to the surface, affecting the development and the life time of the clouds and providing fundamental nutrients to the growth of the terrestrial and oceanic biomes. On Mars, the global effect of dust is even stronger due to the widespread presence of sources and the lack of vegetation and oceans able to mitigate its contribution. Hence, in the frame of the Martian exploration, the study of the dust proprieties and of the dust lifting phenomena covers a key role, representing one of the goals of the present and future missions. The ExoMars 2016-2020 programme aims to search for signs of past or present life on Mars, and investigates the Martian atmosphere and the long-term climate changes. The DREAMS station and the Dust Complex, on board of the ExoMars 2016 and 2020 mission respectively, have been specifically developed for the study of the airborne dust. During my Phd I joined the team that lead the DREAMS experiment and the MicroMed sensor of the Dust Complex. As a part of the instruments developing and the acquisition of martian analogous data, our team has carried out various campaigns in the Sahara desert, to study the environment and the lifting phenomena that are expected on Mars. Indeed, there are still many open questions regarding the dust processes physics, largely due to the lack of proper field surveys. Among the other, many uncertainties are still related to the electric proprieties of the dust grains, that are able to acquire charge by triboelectricity. Our station was able to monitor the dust lifting events by acquiring, for the first time in literature, synchronous measurement of meteorological data (vertical and horizontal wind speed, pressure, air and soil humidity and temperature) and the atmospheric electric field, coupling also the observations of the saltation activity and suspended dust concentration. Currently, we have acquired the most complete data set available for the study of the dust lifting processes. One of the aim of this PhD work has been the development of proper detection algorithms to individuate the dust events acquired in the surveys. The methods could be applied also to future martian missions. We focused also on the development of a technique to evaluate the morphological proprieties of the dust devils using the tracks leaved in the meteorological data. We studied the characteristic of the observed dust storm and dust devils activity, focusing on their electric proprieties. We performed the first statistical study of the electric proprieties of the dust devils observing how the induced E-field is linearly related to the vortex pressure drop, rotatory speed and the vertical air flow speed. We found that during both dust storms and dust devils the induced E-field is linearly related to the numeric concentration of lifted grains with a compatible slope for the two dust processes. We observed also how the induced electric field is heavily influenced by the air and soil humidity and how the grains ability to acquire and hold the electric charge is probably affected by the deliquescence of the evaporites. In addition, we obtained the first experimental indication of how the induced electric field has a positive feedback on the lifting process, enhancing the amount of suspended grains when a critical value is overcome. We compared the terrestrial results with the martian data available in literature, founding a lot of points in common between the dust processes populations of the two planets. This allow to understand how the results here presented are fundamental not only for the study of the terrestrial dust proprieties but also for the analysis of the future ExoMars data.


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