The possibility and feasibility of future drone-based shallow subsurface GPR radar survey for Mars have been examined. SHARAD data indicates shallower features are expected to be present, while HiRISE based analysis of outcrops confirm there are several target features, waiting for radar identification. Targets for an airborne shallow subsurface radar were evaluated including ice content of indurated dunes, internal layering of fluvial deposits, mid- and high latitude ice containing features, former crater lake sediments and lava caves; as well as expected dielectric constant values. The proposed instrument will be able to explore discontinuities in the underground to measure thickness, volume and stratigraphic sequence. Airborne GPR is expected to provide such information what is not achievable by rovers with limited traverse capability and inability of crossing several terrain types.The radar penetration will be increased compared to those characteristics on the Earth by the low humidity expected in the Martian subsurface, while the iron-oxides could decrease the signal with scattering effect and the normal attenuation due to imaginary part of dielectric constant. As radar signals are strongly affected by the presence of liquid water that is very common of Earth, the FlyRadar instrument will be tested mostly in dry areas that are arid hot deserts, karsts or cold arid areas where water is frozen. The suggested trade off according to the geology of the investigated areas was found for the survey of the top 50 m of subsurface could be done at 20 MHz of bandwidth with 80 MHz of transmitted frequency. The mass of such an instrument could reach kilogram payload. The drone technology is available to do survey at 10 km scale distances, what neither an orbiter nor a surface rover could achieve, in order to support next missions for science and ISRU activities.

The FlyRadar Project involves a collaboration between various University institutions and Companies to develop and evaluate a multi-mode (penetrating and SAR) multi-frequency radar system mounted on a UAV designed for exploration on Mars and conducting surveys on Earth. This project has received funding from the European Commission under the H2020-MSCA-RISE framework. The FlyRadar project is structured based on technical, scientific, and qualification tasks. Radar characteristics have been determined based on scientific expectations. The radar is a versatile radar system that operates at multiple modes and frequencies. Specifically, it operates at a frequency of 435 MHz for short-range operations and is designed to be installed on an electric quadcopter UAV. The radar system includes SAR (Synthetic Aperture Radar) and echo sounder modes. These modes enable a wide range of applications in remote sensing exploration, particularly in the fields of geology, agronomy, subsurface artifacts, hydrology, archaeology, and more, both on Earth and other planetary environments. Compared to other radar tools like SHARAD and MARSIS, which operate at lower frequencies, the FlyRadar tool offers a higher resolution but has a lower penetration depth. This means that it can provide detailed characterization of shallower features in the crust, typically within tens of meters, with enhanced clarity. The design of the radar system takes into account various aspects, including mechanical, electrical, electronic, optical, sensor, software control, and thermal analysis. Furthermore, scientific and operational considerations are also incorporated. Additionally, an efficient data processing chain has been implemented to handle the radar data effectively. The Unmanned Aerial Vehicle (UAV) has been specifically engineered to accommodate the weight and size of the FlyRadar instrument. Both the airborne and ground components, including mechanical, electrical, electronic, and sensor systems, have been meticulously integrated, taking into account scientific and operational requirements. A comprehensive qualification program was implemented to assess the performance of each individual element as well as the entire system. FlyRadar was developed for the purpose of studying planetary surfaces, including Earth. The system can be utilized on our planet for detailed analysis using synthetic aperture data to map out archaeological sites, conduct high-resolution surveys of surfaces and the immediate subsurface. The penetration mode is capable of collecting data on the subsurface up to a few tens of meters deep, depending on the water content of the materials in the subsurface. In addition to its applications on Earth, FlyRadar aims to serve as a prototype for planetary exploration by offering surface characterization and subsurface support. It has the potential to be a valuable tool for mapping lava tunnels, identifying ice covered by debris (particularly in glacial regions), determining the thickness of regolith, and more. Mars is an ideal candidate for exploration utilizing advanced technology. The surface of Mars is covered with a diverse range of rocks, including volcanic, sedimentary, and impact rocks, which are clearly visible. Additionally, Mars boasts two permanent polar ice caps and various ice masses hidden beneath the surface in the mid-latitude region. The 3D structure of these geological formations remains largely unexplored, but can be investigated using a GPR-SAR tool. The effectiveness of Ground Penetrating Radar (GPR) has already been proven on Mars, as demonstrated. Over the past two decades, two orbital radar instruments, MARSIS on Mars Express and SHARAD on MRO, have successfully provided the first subsoil images of Mars. The RimFax instrument on the Perseverance rover has been active, delivering high-resolution images of the Jezero delta on Mars. The FlyRadar system, which will be mounted on a UAV and operate several tens of meters above the Martian surface, will provide precise and detailed data essential for future Mars sample return missions and human expeditions.

On April 19, 2021, the first controlled extraterrestrial flight of a drone, or unmanned aerial vehicle, took place on Mars. This drone, also known as the Mars helicopter, was produced as part of NASA's Mars2020 mission and is called Ingenuity, nicknamed Ginny. It demonstrated that flight is possible in Mars' extremely thin atmosphere, ushering in a new stage of exploration of Mars (drone-based stage). Currently, drones such as Mars Sample Recovery Helicopters (NASA) and Martian Boundary Layer Explorer (MARBLE; Indian Space Research Organization) are being developed for use in upcoming missions. It is obvious that the use of these drones in particular and drones in general in the exploration of Mars will provide new information and data, and perhaps even revolutionize certain areas of research.This paper discusses the potential of drone usage to study so-called viscous flow features (VFFs) which are widespread in the mid-latitudes of Mars with the maximum density between ∼30° and ∼50° N and S. This term is used as “an umbrella term for all glacial-type formations exhibiting evidence of viscous flow” (Souness et al., 2012). Their surface morphology is represented by lineation, ridges, troughs, mounds and pits (oriented both parallel and transverse to the slope). Rock glaciers and debris-covered glaciers are considered analogues of the VFFs on Earth (Squyres, 1978; Holt et al., 2008).Results from the Shallow Radar (SHARAD) on board the Mars Reconnaissance Orbiter showed that the bulk of the LDA reveal radar properties entirely consistent with massive water ice (Holt et al., 2008). This fact makes VFFs part of the Martian cryosphere, so their study is one of the most important issues in the research of Mars, and they also could be a source of water for future human exploration in situ, as well as a source of hydrogen and oxygen for fuel. Besides, ice contains historical records of climatic and geologic changes and can preserve ancient microbial life or even living organisms. However, there are still no detailed studies on the thickness and structure of the VFF cover. The use of drones, or unmanned aerial vehicles (UAVs), on Mars, could partially fill this gap and also help in preparing the future missions to drill interpreted VVF ice at further stages of the Mars exploration. Therefore, in this work we discuss what types of observations could a drone make on mid-latitude VFFs.1. High-resolution images (aerial view). Currently, the highest-resolution images of VFFs are HiRISE images (0.25 m/pixel). Thus, only large boulders and blocks can be identified on them. The main disadvantage of HiRISE images is the limited spatial coverage, which does only partially cover VFFs. The use of drones at further stages of the Mars exploration could improve resolution and partially solve the problem of limited spatial coverage. UAVs makes possible acquisition of images of resolution up to several centimetres per pixel (and even more detailed, depending on the camera and survey height). It makes possible to estimate the proportion of coarse fractions (pebbles and small boulders) in the surface sediments covering the supposed ice. Spatial coverage encompasses the entire object of interest, not just part of it, but only in the area of rover landing and/or operation. An important advantage is that the drone can fly over places that are inaccessible to rover exploration.2. Digital terrain models (DTMs) and 3D topography. Typically, DTMs derived from HiRISE imagery can achieve vertical resolution ranging from a few meters, depending on the specific terrain and the accuracy of the processing methods. Horizontal resolution is generally determined by the original imagery's resolution, which is around 50 centimetres per pixel for HiRISE images. DTMs generated from high-resolution drone imagery are able to achieve better resolution (from a few centimetres to several decimetres both vertical and horizontal). The main advantage of drones is the ability to use ground control points with known coordinates and elevations for georeferencing of images and elevation data. Geometrically corrected aerial images (orthophotos) draped over the DTMs will create informative and visually appealing high-resolution 3D topography. DTMs and 3D topography generated from drone imagery can be used for accurate and detailed measurements as well for studying small-scale landforms of VFF surfaces. They will provide new information on the processes and dynamics of VFF deposits formation and will allow a better understanding of their cover origin.3. Ground penetrating radar (GPR) profiling. This is probably one of the main tasks on the way to searching for subsurface water and ice on Mars. Radar data on the structure of the upper part of the crust obtained from orbit (SHARAD, MARSIS) provide information only deeper than 15-50 m from the surface. Metre – decimetre scale spatial resolution of radar data for studying the uppermost subsurface is challenging and could not be gained from orbit, but close to the surface. However, the mobility of rovers is limited, and their scanning capabilities are limited to thin lines over a moderate distance. In contrast, a drone-based GPR survey has the potential to overcome these limitations. It can cover larger areas and provide more flexibility in data collection. GPR survey will provide information on the thickness of sediments covered the ice, the thickness and internal structure of the ice, as well as stratigraphic correlation with adjacent units.All these types of observations will be useful for choosing site to drill ice at further stages of the Mars exploration. In addition, they will provide a better understanding of VFF origin. To implement them, there is a number of challenges related primarily to the remote control of the drone and limitations on the data transmission rate between the drone, the rover, and Earth. However, the first experience of using a drone on Mars (Ingenuity) shows that these challenges can be partially resolved. AcknowledgementThis work was supported by the FlyRadar EU Horizon 2020 project (grant agreement No 101007973). ReferencesHolt et al. 2008. Science, 322 (5905).Souness et al. 2012. Icarus 217, 243–255.Squyres 1978. Icarus, 34 (3). 600–613.

The Danakil depression in Ethiopia, at the southern end of the Red Sea, has been the place of volcanic crises in 2004–10, with emplacement of at least 15 dykes. One of them, non-emergent, occurred in dry lake Asale next to Black Mountain and south of Mount Dallol during fall 2004. We report on the opening of a 4.5 km-long fissure in the ground at the same time the Black Mountain dyke was intruding the crust 2 km westward and parallel to it. The fissure, located north and south of Yellow Lake (Gaet’ale) and trending NNW-SSE, is still hydrothermally active. First, we describe the remarkable diversity of morphologic expressions of the fissure, made possible by development in an evaporite sequence. Satellite image monitoring reveals that its formation is coeval with the latest intrusion stage of the Black Mountain dyke. Hydrothermal activity in the fissure area is, however older than ∼60 years. It is suggested that hydrothermal activity is primarily a side effect of the igneous processes, probably sill intrusion, that resulted in the uplift of Mount Dallol area, in a ∼400 m thick, fluid-saturated evaporite pile. We suggest that, in 2004, emplacement of the Black Mountain dyke caused dilation within the evaporite pile overlying it, where extension was also facilitated by pressured pore fluids. This study documents the delicate intermingling of magmatic, tectonic, hydrothermal, and geomorphologic processes in evaporitic environments at the transition between continental rifting and oceanic spreading.

<p>Shalbatana Vallis is a valley located in the Oxia Palus quadrangle, characterized by a simple system and a homogeneous coverage. Shalbatana vallis flows into the Chryse Planitia basin, alongside Ares Vallis, Kasei Valles, Simud Valles and Tiu Valles. The valley is affected in different points by landslides with various surfaces and elongations. Landslides on Mars are a topic already studied by other authors. However, the problem of the dynamic of such structures remains debated. The landslides of Shalbatana Vallis occurred in a homogeneous lithology and in a valley with a quite constant depth. We first present the ages of the landslide and discuss the age distribution. The, we present a geometrical analysis of the landslides (surface, elongation, volume, runout, etc….) and use these parameters to constrain some dynamical properties (possible velocity, possible loss of volatiles) and to discuss possible triggering mechanisms.</p>

<p>This research deals with the detailed study of some global-scale geomorphological structures on Mars to identify possible current or fossil methane emission points. For years, attempts have been made to understand the mechanism that led to the formation of methane on Mars and how it may have been stored to date in subsurface reservoirs. From the data recently received from satellites (Tracer Gas Orbiter on board of ExoMars, Planetary Fourier Spectrometer on Mars Express) and rovers (Mars Science Laboratory Curiosity in Gale crater) on Mars, it is possible to infer that the methane on Mars is gradually emitted into the atmosphere and most of the times is detected by these instruments. Thanks to these dataset of methane emissions during the years (since 2004 with the PFS first detections) it is possible to trace the possible points in which the upper limit concentration of methane are equal to or greater than 10 p.b.b.v. so as to select a few areas where to begin the geomorphological and mineralogical analyses for this research in order to create a global map of possible areas where current methane emissions from subsurface methane reservoirs may be recorded. For this study the focus will be on hectometric to kilometric mounds of volcanic or sedimentary origin (mud volcanoes and/or pingos like structures), chaotic terrains and fracture fields in sedimentary piles. The areas selected for this research are Coprates and Candor Chasma (Valles Marineris, Mars), Nili Fossae (Mars), Vernal crater and the surrounding of Arabia Terra (Mars) and Gale crater (Mars). All of these locations have key characteristics such as proximity to a boundary zone (Gale crater), the presence of a fracture system (Nili Fossae), presence of mud volcanoes or pingoes (Valles Marineris and Utopia Planitia): all possible incentives for the presence of methane emission spots. The aim of this project, as already mentioned, will therefore be to analyse these areas in detail, trying to understand whether they could be or have been methane emission points, with the help of the planetary analogues that can be found in Azerbaijan regarding mud volcanoes, in Canada for pingos or fracture systems in China.</p>

Abstract Plagioclase‐bearing rocks were first detected in the vicinity of large impact basins on Mars using visible/near‐infrared (VNIR) data. The geologic context is consistent with excavated plutons or ancient crustal outcrops. Our analyses reveal plagioclase outcrops exposed in a 200 m thick, sub‐horizontal layer in the 8 km deep walls of the Valles Marineris canyon. These plagioclase‐bearing rocks are consistent with either a sill, a volcano‐clastic layer, or a porphyritic lava flow, in contrast with the previous understanding that plagioclase feldspar signatures must be indicative of nearly pure, anorthositic rocks inherited from a primary flotation crust or granitoids from either plutonic activity or ancient continental crust. We present here evidence of possibly effusive, volcanic rocks bearing plagioclase VNIR spectral signatures, expanding the geologic setting of these unique and uncommon martian rocks to include multiple lithologies. This has direct implications for Mars magmatic processes and for the nature of its crust.

We develop a phenomenological model of suspended sediment transport on the basis of data acquired in the Capesterre river, which drains a small tropical catchment in Guadeloupe. The model correctly represents the concentration of suspended sediment during floods, provided that the relation between concentration and water level forms a counterclockwise loop. In the model, the properties of the sediment and of the river are all lumped into four parameters: a settling velocity related to the size of the suspended sediment, a threshold water level which acts as a proxy for the threshold shear stress, a characteristic entrainment rate, and a dimensionless exponent. The value of the parameters changes from one flood to the next, probably reflecting changes in the characteristics of the river and the fine sediment. Finally, a test of the model against data acquired in a small catchment in the French Alps suggests that the model is versatile enough to be used in diverse hydrological settings.

Bedload transport, entrainment of coarse sediment by a river, is inherently a stochastic and intermittent process whose monitoring remains challenging. Here, we propose a new method to characterize bedload transport in the field. Using an uncrewed aerial vehicle (UAV) equipped with a high-resolution camera, we recorded yearly images of a bar of the Grande Rivière des Vieux-Habitants, a gravel bed river located on Basse-Terre Island (Guadeloupe, French West Indies). These images, combined with high-frequency measurements of the river discharge, allow us to monitor the evolution of the population of sediments of a diameter between 0.5 and 0.75 m on the riverbed. Based on this dataset, we estimate the smallest discharge that can move these boulders and calculate the duration of effective transport. We find that the transport of boulders occurs for approximately 10 h yr−1. When plotted as a function of the effective transport time, a given population of boulders decreases exponentially with an effective residence time of approximately 17 h. This exponential decay suggests that the probability of dislodging a grain from the bed is proportional to the number of grains at repose on the bed, an observation consistent with laboratory experiments. Finally, the residence time of bedload particles on a riverbed can be used to evaluate bedload discharge.

Methane has been detected these last years in the Martian atmosphere both from orbit (TGO-ExoMars mission - still active) and from ground (Curiosity rover – Mars Science laboratory mission). The sources of methane remain undetected. As the life time of methane in the Martian atmosphere should be less than few months, these sources are currently active at the Martian surface. The localization and the geometry of these sources remain an open question. Emission centers could be localized in peculiar zones on which it is possible to detect methane. Methane could also be emitted in wide areas and be locally concentrated by atmospheric processes. The aim of this study is to compare the geology and geomorphology three impact craters (Gale, Gusev and Vernal) in which methane has been detected from orbit and/or from ground. Satellite and in situ hyperspectral data (for Gusev, hyperspectral data from Spirit - for Gale, data from Curiosity), as well as high-resolution Context Camera (CTX) and HiRISE images (MRO mission) were also considered. Digital Elevation Models (DEM) were calculated from the highest resolution images that are available. Geomorphological maps were drawn for each crater through GIS projects. For each crater, the possible areas of emission are defined from criteria defined on terrestrial analogs located in Chile and Antarctica. Differences and similarities between the three selected craters are discussed.

A leucogranite sill in the footwall of the extensional Pilat shear zone (PSZ) Eastern French Massif Central was emplaced and sheared in a short time interval, between 301.8 +/- 3.1 and 303.0 +/- 1.6 Ma (zircon U-Pb and mica 40Ar/39Ar ages, respectively). Extension ended at 298.5 +/- 1.5 Ma (40Ar/39Ar on mica) as shown by a non deformed dike cross cutting the sheared zone. On the hanging wall of the fault, the opening of the St. Etienne Basin filled by coarse clastic sedimentation confirms the existence of a relief south of the PSZ. U-Pb dating of a lithic-rich ignimbrite at the bottom of the basin and of a volcanic layer at the top delivered ages of 310.5 +/- 3.4 Ma and 299.3 +/- 1.3 Ma, respectively. Close U-Pb and 40Ar/39Ar ages from syn-to post-tectonic granites indicate very fast cooling (similar to 150 degrees C/Myr) and exhumation rate (6 mm/yr) corresponding to the emplacement of granites in the middle crust immediately followed by their fast tectonic exhumation and cooling into the upper crust. The development of the Pilat fault in the thermally softened crust is responsible for the rapid exhumation of the Velay dome, a Metamorphic Core Complex localized in the footwall of the sheared zone. Here we propose that its rapid exhumation was due to localized sub crustal lithospheric mantle dripping. These new data show that there was only one extensional phase in the PSZ coeval with the opening of the St. Etienne coal Basin. Finally, the new chronology obtained in this study is challenging previous ages suggesting 20 Ma activity for the Pilat shear zone. Published by Elsevier B.V. on behalf of International Association for Gondwana Research.

THE EARTH. F. Mancini, G.G. Ori, G. Alberti, P. Allemand, P. Grandjean, A. Kreszturi, D. Mège, A.Tullo , S. Augier, W. Kofman, E. Mariani,, C. Orlanducci, T. Senez, V. Steinman, K. Villavicencio, 1 International Research School of Planetary Sciences, Università Gabriele D’Annunzio, Viale Pindaro 42, Pescara, Italy, 2 CO.RI.S.T.A., 80143 Naples, Italy, 3 UCBL, CNRS, UMR 5276 LGL-TPE, France, 4 Hyperion Seven, Claix, F-38640, 5 CSFK Sopron 9400, Hungary, 6 Departimento Ingenieria e geologia, Università “G. D’Annunzio” of ChietiPescara, Viale Pindaro 42, Pescara, Italy, 7 Centrum Badań Kosmicznych Polskiej Akademii Nauk (CBK PAN), Bartycka 18A, 00-716 Warszawa, Poland, 8 Exploration Sarlau, Marrakech, Morocco.

Hyperspectral sensors offer the opportunity of analysing the chemical and physical composition of the remote sensed scene thanks to their ability of measuring the spectrum of the observed pixels in a large number of contiguous and narrow spectral channels [1]. Despite the technological advances, hyperspectral satellites are still poorly represented in spaceborne missions for Earth Exploration compared to multispectral ones [2]. In this context, the Italian Space Agency (ASI) EO mission named PRISMA (PRecursore IperSpettrale della Missione Applicativa, [3]) offers a great opportunity to improve the knowledge about the scientific and commercial applications of spaceborne hyperspectral data. PRISMA, launched in March 2019, includes a pushbroom hyperspectral camera covering the portion of the electromagnetic spectrum ranging from 400 nm to 2500 nm with 10 nm spectral sampling. Precisely, the PRISMA satellite comprises a high-spectral resolution Visible Near InfraRed (VNIR) and Short Wave InfraRed (SWIR) imaging spectrometer with 30 m ground sampling distance (GSD) and a panchromatic camera with 5 m GSD [4]. One of the critical issues in the exploitation of hyperspectral remotely sensed data is represented by the distortion effects due to the atmosphere in the radiative transfer path [5]. The products systematically produced by the PRISMA ground processor and made available to users consist of: Level 1 TOA radiometrically and geometrically calibrated radiance images; Level 2 geolocated and geocoded atmospherically corrected images. Details can be found in the PRISMA Products Specification Document [6]. Our analysis of PRISMA imagery was mainly performed on an arid environment in NE Ethiopia (Dallol; Long: 40.299351, Lat: 14.244367). One advantage of this area is that the nebulosity is generally low, in fact the image selected during the dry season has a cloud coverage percentage less than 1%. In the selected site, a salt suite was deposited and re-worked by hydrothermalism. The characteristic minerals of the area are: carbonate, halite, carnallite, anhydrite, gypsum, native sulfur of hydrothermal origin (7; 8). The unique lithological and geochemical features of Dallol and, specifically, the Mesozoic and Tertiary sedimentary cover, offer the opportunity to test PRISMA data at first order to delineate carbonates from salts. The main objectives of this study are (1) to implement the atmospheric corrections for Level 1 data and compare the results with Level 2 data and (2) to test the capabilities of Prisma cubes to map an environment made of various sedimentary rocks and to differentiate and identify characteristic salt minerals. References: [1] Chang, C.I., 2007. John Wiley & Sons. DOI: 10.1002/0470124628 [2] Transon, J., et al. 2018. Remote Sensing, 10(2), 157. DOI: 10.3390/rs10020157 [3] Candela, L., et al. 2016. IEEE international geoscience and remote sensing symposium (IGARSS), 253-256. DOI: 10.1109/IGARSS.2016.7729057 [4] Loizzo, R., et al. 2019. IEEE International Geoscience and Remote Sensing Symposium (IGARSS), 4503-4506. DOI: 10.1109/IGARSS.2019.8899272 [5] Schott, J.R., 2007. Oxford University Press on Demand [6] ASI, 2020. PRISMA Products Specification Document Issue 2.1 [7] Cavalazzi, B., et al. 2019. Astrobiology, 19(4), 553-578. DOI: 10.1089/AST.2018.1926 [8] López-García, J.M., et al. 2020. Frontiers in Earth Science, 7, 351. DOI: 10.3389/FEART.2019.00351

Introduction Studying planetary field analog environments is a key point in order to define the physical and chemical parameters that favor life on Earth and other planets. Terrestrial hydrothermal springs have long been considered among the most significant planetary analogs searching for traces of life on Mars [1]. Hyperspectral data have been recognised to be more suitable for the detailed mapping and identification of rocks and minerals identification of land surface, especially for minerals [2]. Notwithstanding the technological advances, hyperspectral satellites are still poorly represented in spaceborne missions for Earth Exploration compared to multispectral ones. In this context, the Italian Space Agency (ASI) EO mission named PRISMA (PRecursore IperSpettrale della Missione Applicativa, [3]) offers a great opportunity to improve the knowledge about the scientific applications of spaceborne hyperspectral data. PRISMA, launched in March 2019, includes a panchromatic and a hyperspectral camera with 239 spectral bands. Specifically, the PRISMA satellite comprises a high-spectral resolution Visible Near InfraRed (VNIR) and Short-Wave InfraRed (SWIR) imaging spectrometer, ranging 400-2500 nm, with 30 m ground sampling distance (GSD) and 5 m GSD for the panchromatic camera [4]. Our analysis with PRISMA images was mainly performed on an arid environment in a remote region of NE Ethiopia (Dallol; Long: 40.299351, Lat: 14.244367), representing an exceptional Mars analog due to diffuse hydrothermal alteration and the sulfate deposits evocative of past hydrothermal activity on Mars. This work aimed to obtain an identification map of minerals and their relative abundance using hyperspectral imaging to understand the potential of PRISMA as analog probe of Mars orbital instruments to detect and study possible analogs on Earth. Study Area Dallol is situated in the Danakil Depression, which is part of the East African Rift System. Principal geothermal features of the central crater area of Dallol are salt pillars, circular manifestations and acidic ponds. The northern and southern part is dominated by a salt dome structure and Salt pinnacles in the SW salt canyon area. The Black Mountain and the super-saline Black Lagoon, just south-southwest of Dallol, is an area of salt extrusions, geothermal manifestations and brine upflows. One advantage of this area is that the nebulosity is generally low, in fact the image selected during the dry season has a cloud coverage percentage of less than 1%. A salt suite was deposited and re-worked by hydrothermalism in the selected site. The characteristic minerals of the area are: carbonate, halite, carnallite and bischofite, anhydrite, gypsum, native sulfur of hydrothermal origin [5; 6]. Flooding episodes from the Lake Assale to the north due to intense winds acting over the flat topography of the depression. The PRISMA SWIR Land/Water band combinations on the image selected, helped us to choose the region of interest around the Dallol area. Operational Hyperspectral Processing PRISMA images have three different levels of processing. Level 2C and 2D geolocated and atmospherically corrected images were used in this work and dated 21 August 2021. it is worth noticing that the images acquired on Dallol prior to the image selected for analysis had several preprocessing problems, particularly for stripe removal. The operational hyperspectral processing is composed of three main processing steps: (1) dimensionality reduction; (2) endmember identification and (3) mineral map distribution and abundance estimation. An unexpected result was obtained by applying an additional atmospheric correction, the Internal Average Relative Reflectance with Dark Subtraction, on the L2C image already corrected during the principal component analysis (PCA). The corrected atmospheric PCA allows better highlighting of geomorphological features. As for step (1), since hyperspectral images are composed of hundreds of extremely correlated bands, it is possible, and indeed beneficial, to reduce the effective dimension of the input data by removing bad bands. Step (2) was performed using the THOR Hyperspectral Material Identification (in ENVI 5.6) to identify unknown spectral signatures by comparing them with spectral libraries. This tool considers background statistics and image endmembers and can therefore provide accurate responses and spectra plots for rare or sub-pixel targets. Finally, the Spectral Angle Mapper (SAM) and the Linear Spectral Unmixing (LSU) tools were adopted for step (3). SAM determines the spectral similarity between two spectra by calculating the angle between the spectra and treating them as vectors in a space with dimensionality equal to the number of bands. LSU is a standard technique for spectral mixture analysis that infers a set of endmembers and fractions of these, called abundances. The mineral distribution and the abundance maps are shown respectively in Fig.1 and Fig.2. Conclusion Six minerals have been recognised with the SAM classification from ENVI spectral library, in excellent agreement with the previous studies: carnallite, jarosite, kainite, polyhalite, gypsum and nontronite. The results confirm the mineralogical variability typical of the Dallol; in Fig.2, high mineral abundance values are shown in blue. The error calculated with the RMS is very low over the entire area of interest, except for the central zone where there are sulphur pools and therefore the presence of water does not favour this type of analysis. To better constrain the mineralogical mapping, future work will be conducted by a field exploration campaign to collect spectral signatures to be added to the ENVI library used, which so far could not be organised due to the ongoing civil war in Dankalia. To sum up, the study of terrestrial analogs can provide insights into the probable presence and nature of spring deposits on Mars, as well as help develop methods for classifying them from remote sensing data. PRISMA represents a valuable satellite for distinguishing not only the geometric characteristics of observed objects, but also the chemical-physical composition of the surface of the Earth. References: [1] Walter, M.R. and Des Marais, D.J., 1993. Icarus 101:129–143 [2] Chang, C.I., 2007. John Wiley & Sons. 10.1002/0470124628 [3] Candela, L., et al. 2016. IEEE international geoscience and remote sensing symposium (IGARSS), 253-256. 10.1109/IGARSS.2016.7729057 [4] Loizzo, R., et al. 2019. IEEE (IGARSS), 4503-4506. 10.1109/IGARSS.2019.8899272 [5] Cavalazzi, B., et al. 2019. Astrobiology, 19(4), 553-578. 10.1089/AST.2018.1926 [6] López-García, J.M., et al. 2020. Frontiers in Earth Science, 7, 351. 10.3389/FEART.2019.00351

The Danakil depression in Ethiopia, at the end of the southern Red Sea, has been the locus of volcanic crises in 2004-10, with emplacement of 15 dykes: one, non-emergent, in Lake Asale next to Blac...

On November 11, 2019, a M$_{\mathrm{w}}$ 4.9 earthquake hit the region close to Montelimar (lower Rhône Valley, France), on the eastern margin of the Massif Central close to the external part of the Alps. Occuring in a moderate seismicity area, this earthquake is remarkable for its very shallow focal depth (between 1 and 3 km), its magnitude, and the moderate to large damages it produced in several villages. InSAR interferograms indicated a shallow rupture about 4 km long reaching the surface and the reactivation of the ancient NE–SW La Rouvière normal fault in reverse faulting in agreement with the present-day E–W compressional tectonics. The peculiarity of this earthquake together with a poor coverage of the epicentral region by permanent seismological and geodetic stations triggered the mobilisation of the French post-seismic unit and the broad French scientific community from various institutions, with the deployment of geophysical instruments (seismological and geodesic stations), geological field surveys, and field evaluation of the intensity of the earthquake. Within 7 days after the mainshock, 47 seismological stations were deployed in the epicentral area to improve the Le Teil aftershocks locations relative to the French permanent seismological network (RESIF), monitor the temporal and spatial evolution of microearthquakes close to the fault plane and temporal evolution of the seismic response of 3 damaged historical buildings, and to study suspected site effects and their influence in the distribution of seismic damage. This seismological dataset, completed by data owned by different institutions, was integrated in a homogeneous archive and distributed through FDSN web services by the RESIF data center. This dataset, together with observations of surface rupture evidences, geologic, geodetic and satellite data, will help to unravel the causes and rupture mechanism of this earthquake, and contribute to account in seismic hazard assessment for earthquakes along the major regional Cévenne fault system in a context of present-day compressional tectonics.

Submarine hydrothermal activity is responsible for heat and chemical exchanges through the seafloor. Shallow-water hydrothermal systems (SWHS), while identified around the globe, are often studied in a way that is less comprehensive than their deep-ocean counterparts (e.g., along ridges), where systematic optical and acoustic mapping is more prevalent and coupled to in situ observations and sampling. Using aerial drones, an AUV, and temperature measurements at 10-40 cm subseafloor, we investigated in 2019 one of the most extensive SWHS known to date, in Paleochori and nearby Spathi and Agia Kyriaki Bays (south of Milos, Greece). Hydrothermal venting, found from the shore to water depths of almost 500 m, shows emissions of gases and high-temperature fluids, often associated with bacterial mats and/or hydrothermal mineral precipitates. This study provides extensive drone mapping coupled with local AUV surveys for seafloor characterization and ground-truthing from the shore to similar to 20 m water depth. Seafloor photomosaics also provide a detailed context to samples, measurements and observations carried in situ. We interpret the photomosaics to define distinct seafloor types, linked to this hydrothermal activity. White hydrothermal patches (WHPs) often show a clear polygonal organization, together with outflow areas that are both more dispersed and distributed. Polygonal patterns likely result from fluid convection in a sandy porous medium heated from below. These WHPs display elevated subseafloor temperatures, typically >50 degrees C, with maximum values of similar to 75 degrees C. Photomosaics also display textures of biological origin, including seagrass and bioturbation patterns. Widespread bioturbation by burrowing shrimps is often associated with WHPs, bounding them, but also occurs on sandy seafloor away from hydrothermal patterns. Subseafloor temperatures at these bioturbated areas are of similar to 30-40 degrees C, and are thus transitional between hot WHPs and sedimented seafloor unaffected by hydrothermal activity (similar to 24 degrees C). In addition to linking subseafloor temperature data and interpreted seafloor photomosaics, our results provide a comprehensive general overview of this SWHS, of the organization of its hydrothermal outflow through the seafloor, and of the underlying subseafloor fluid circulation. This paper also gives the first perspectives on the heat fluxes of the system, and constitutes a background for other studies on the nature and distribution of microbial communities, controlled by this hydrothermal activity.