G. G. Ori

The role of the atmospheric electric field in the dust-lifting process

Mineral dust particles represent the most abundant component of atmospheric aerosol in terms of dry mass. They play a key role in climate and climate change, so the study of their emission processes is of utmost importance. Measurements of dust emission into the atmosphere are scarce, so that the dust load is generally estimated using models. It is known that the emission process can generate strong atmospheric electric fields. Starting from the data we acquired in the Sahara desert, here, we show for the first time that depending on the relative humidity conditions, electric fields contribute to increase up to a factor of 10 the amount of particles emitted into the atmosphere. This means that electrical forces and humidity are critical quantities in the dust emission process and should be taken into account in climate and circulation models to obtain more realistic estimations of the dust load in the atmosphere.

Tectonic evolution of the eastern margin of the Thaumasia Plateau (Mars) as inferred from detailed structural mapping and analysis

[1] The eastern margin of the Thaumasia Plateau (EMTP) is characterized by a diversity of tectonic features, which recorded its complex, and still controversial, tectonic history. A detailed structural survey and analyses have been carried out in order to assess the kinematics and relative age of the main deformational events. Combining results from statistics of lineament orientations and density of fault length for each geologic unit and taking into account crosscutting relationships among tectonic structures, three main deformational events have been recognized. The early stage of the tectonic evolution of EMTP is recorded by Noachian units at the southern edge of Melas Dorsa and is represented by N-S oriented grabens sutured by Early Hesperian formations. Starting from Late Noachian, the extensional stress field became NE-SW oriented and resulted in the formation of NW-SE striking sets of grabens. At the boundary between Noachian and Hesperian, the most important change in tectonic regime occurred. The Hesperian tectonics are characterized by an E-W shortening possibly related to an eastward motion of the Thaumasia Plateau. This tectonic phase likely produced a N-S-oriented wrinkle ridges as well as regional folds and thrust faults. E-W-oriented preexisting tectonic lineaments could have been reactivated forming regional transfer zones. In this scenario, Coprates Rise, Melas Dorsa, and Thaumasia Ridge could be interpreted as mountain belts resulting from buckling and thrust faulting of the eastern and southern margins of the Thaumasia plateau. The proto-Valles Marineris could have experienced a left-lateral component of displacement and played a role of a transfer shear zone.