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Overall surface‐subsurface model and structural features. (a) The reconstruction of the subsurface mechanical layering, interpreted fluid and sediment reservoir locations and pathways, and putative geometrical relationship between TPT and possible N‐S faults. (b) Fault traces observed in the study area are highlighted with dashed white lines while black solid traces indicate mapped thumbprint terrains.
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The Martian northern hemisphere displays mounds interpreted to be the result of sediment and water erupting onto the surface. We analyzed the mounds spatial distribution and found patterns that reflects the extent at depth of the subsurface conduits that fed those mounds (array of fractures, i.e., high permeability pathways)...
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... S21). However, the higher path-averaged velocities we observe in the upper 10 km would require lower porosity, which could result from viscous closure of pore spaces due 5 to thermal annealing expected to accompany volcanic resurfacing processes (23,39), partial filling of pore spaces by the deposition of precipitated minerals from a briny ancient aquifer system (40), or the presence of a deep cryosphere or substantial water table beneath the thick Amazonian lava flows along the R1 path (19,41,42) (Fig. 3). We note that images from the High Resolution Imaging Science Experiment of the S1094b impact crater show large blocks of pure ice ejected 10 from the shallower layers (20). ...
We detected surface waves from two meteorite impacts on Mars. By measuring group velocity dispersion along the impact-lander path, we obtained a direct constraint on crustal structure away from the InSight lander. The crust north of the equatorial dichotomy had a shear wave velocity of approximately 3.2 kilometers per second in the 5- to 30-kilometer depth range, with little depth variation. This implies a higher crustal density than inferred beneath the lander, suggesting either compositional differences or reduced porosity in the volcanic areas traversed by the surface waves. The lower velocities and the crustal layering observed beneath the landing site down to a 10-kilometer depth are not a global feature. Structural variations revealed by surface waves hold implications for models of the formation and thickness of the martian crust.
Subtle mounds have been discovered in the source areas of Martian kilometer‐sized flows and on top of summit areas of domes. These features have been suggested to be related to subsurface sediment mobilization, opening questions regarding their formation mechanisms. Previous studies hypothesized that they mark the position of feeder vents through which mud was brought to the surface. Two theories have been proposed: (a) ascent of more viscous mud during the late stage of eruption and (b) expansion of mud within the conduit due to the instability of water under Martian conditions. Here, we present experiments performed inside a low‐pressure chamber designed to investigate whether the volume of mud changes when exposed to a Martian atmospheric pressure. Depending on the mud viscosity, we observe a volumetric increase of up to 30% at the Martian average pressure of ∼6 mbar. The reason is that the low pressure causes instability of the water within the mud, leading to the bubble formation that increases the volume of the mixture. This mechanism bears resemblance to the volumetric changes associated with the degassing of terrestrial lava or mud volcano eruptions caused by a rapid pressure drop. We conclude that the mounds associated with putative Martian sedimentary volcanoes might indeed be explained by volumetric changes in the mud. We also show that mud flows on Mars and elsewhere in the Solar System could behave differently to those found on Earth because mud dynamics are affected by the formation of bubbles in response to the different atmospheric pressures.
Extensive fields of sub-kilometre- to kilometre-scale mounds, cones, domes, shields, and flow-like edifices cover large parts of the martian lowlands. These features have been compared to structures on Earth produced by sedimentary volcanism – a process that involves subsurface sediment/fluid mobilisation and commonly releases methane to the atmosphere. It was proposed that such processes might help to explain the presence of methane in the martian atmosphere and may also have produced habitable, subsurface settings of potential astrobiological relevance. However, it remains unclear if sedimentary volcanism on Earth and Mars share genetic similarities and hence if methane or other gases were released on Mars during this process. The aim of this review is to summarise the current knowledge about mud-volcano-like structures on Mars, address the critical aspects of this process, identify key open questions, and point to areas where further research is needed to understand this phenomenon and its importance for the Red Planet's geological evolution. We show here that after several decades of exploration, the amount of evidence supporting martian sedimentary volcanism has increased significantly, but as the critical ground truth is still lacking, alternative explanations cannot be ruled out. We also highlight that the lower gravity and temperatures on Mars compared to Earth control the dynamics of clastic eruptions and surface emplacement mechanisms and the resulting morphologies of erupted material. This implies that shapes and triggering mechanisms of mud-volcano-like structures may be different from those observed on Earth. Therefore, comparative studies should be done with caution. To provide a better understanding of the significance of these abundant features on Mars, we argue for follow-up studies targeting putative sedimentary volcanic features identified on the planet's surface and, if possible, for in situ investigations by landed missions such as that by the Zhurong rover.
Landforms with characteristic flow-like morphology are distributed across the southwestern portion of Utopia Planitia, Mars. Although some of the features have previously been interpreted as mud flows associated with a former presence of partly frozen muddy ocean based on their morphologies and similarities with terrestrial analogues (Ivanov et al., 2014, Icarus 228; Ivanov et al., 2015, Icarus 248), such interpretations remain ambiguous. This is because a) the evidence supporting the presence of such an ocean has been disputed by many, b) models of evolution of Utopia Planitia do not sufficiently explain the emplacement mechanisms of the flow-like landforms, and c) no in-situ measurements are available to confirm their sedimentary origin. Here we present results of a mapping exercise that focused on a field of flow-related landforms spread across a ~ 500 × 1300 km large area centered around Adamas Labyrinthus in the attempt to provide additional insight about their formation mechanism. We mapped the distribution of 312 edifices and classified them based on their areal extent, shape, and morphological properties. We assert that these features can be grouped into four classes with distinct shapes and sizes. Their shapes are consistent with the ascent and the subsequent movement of liquid over the Martian surface. We interpret an evolutionary sequence among the classes as the differences in their morphologies can be explained by different effusion rates of the source material and the duration of the discharge at the time of their emplacement. As the result of our analysis and considering previous studies focusing on the area of our interest, we propose that all the >300 studied features were formed by subsurface sediment mobilization and that the material likely originated from the same subsurface source area. Consequently, we argue for the presence of a large body of mud within this region in the past. Finally, we note that there are several previously unconsidered sequences of events which could have resulted in such sedimentary-volcanic activity within Adamas Labyrinthus.
Following the dramatic events of 2020, the year 2021 was marked by a slow recovery to prepandemic conditions. The previously deserted department building became populated
again; students were finally allowed to attend lectures in class, conferences and meetings
could be attended in person. In this third edition of the Yearbook of the Department of
Geosciences, we wish to bring to light the numerous activities that we managed to organise and host during this transitional year, along with what we have learned from the pandemic period. First, a few numbers. In 2021, the Department of Geosciences counted 16 full professors, 30 associate professors and 12 researchers (including RU, RTDa ed RTDb), 44 postdoc and 47 PhD students. This staff provided teaching in 17 BSc and 35 MSc courses; however, our main commitment was devoted to the three courses hosted by the department, these being the BSc degree in Geological Sciences, the MSc degree in Geology and Technical Geology and the recently established MSc degree in Geophysics for Natural Risks and Resources. Altogether, these three degrees are attended by 287 students.
Also in 2021, the pandemic called for restrictions on teaching activity that were especially limiting during the springtime. Laboratories and field activities, crucial elements in the education of young geoscientists, were partly impeded. Fortunately, the situation
ameliorated in due course, and the new academic year provided the opportunity to start fresh. A total of 31 and 36 students received their degrees in Geological Sciences (BSc) and in Geology and Technical Geology (MSc), respectively, and 43 additional students were
supervised by our researchers to obtain their degrees in other courses from other departments. High-quality research carried out at the department attracted graduate students from abroad: in 2021, 13 out of 45 postdocs and 6 out of 14 PhD students were foreign citizens. The department could rely on 34 research laboratories that yielded a huge number of sample preparations and analyses.
Part of the research activities were supported by 56 research projects. The department also hosts CIRCe, which is the only centre in Italy for investigating cement materials and the formulation of construction binders. This centre not only collaborates with several
companies and institutions at the national and international levels, but it is also involved in the training and support of African students and researchers and in consultancy for small companies in line with UNESCO’s Sustainable Development Goals. The efficiency of our laboratories, combined with successful activities in fundraising, allowed the department to develop and maintain a relevant number of collaborations, which are estimated to include more than 102 European and extra-European and 46 Italian universities, institutions and private companies. A total of 192 papers were published in 2021, and our department ranked first in Italy in the Nature Index international ranking, which is only based on the number of papers published in high-impact journals; we have the 92nd position in the world in terms of score. The department is also involved in the museum network of the University of Padua, thanks to its collection of Italian and foreign rocks, fossils and minerals housed in the Museum of Geology and Palaeontology and in the Museum of Mineralogy. Finally, the department has been actively committed to promoting and offering the dissemination and divulgation of scientific knowledge through TV and radio interviews and laboratories with local schools and exhibits. In total, more than 60 events were organised, such as the Night of the Research 2021, thus demonstrating the specific dedication of the department to outreach and communication.
Kilometre-sized flows (KSFs) have been observed in many regions on Mars and have been typically interpreted as lava flows. However, sedimentary volcanism has been proposed as an alternative origin for some KSFs. Remarkable examples of such hypothesized sedimentary KSFs are located at the southern margin of Chryse Planitia. There, the flows are associated with conical and dome-shaped edifices; however their formation mechanism remains enigmatic due to the absence of ground truth. Previous studies revealed that these KSFs consist of three morphological elements: a central depression, leveed central channels, and a distal portion of the fading channel(s). Here, we present new morphological results obtained on these KSFs using seven newly available Digital Elevation Models computed from HiRISE stereo pairs. Our investigation confirms that these features are aggradational and formed by the transport of a liquid. This material emerged from identified depressions and the presence of subtle mounds inside them is interpreted to mark the position of feeder vents. We also observe that the margins surrounding the central large channels are not continuous. They are cut by meter-sized troughs linking the central channels to units which have distinctive albedo and roughness compared to their surroundings. These bright units do not have a clear topographical expression, suggesting that the effused material originally flowing away from the central channel was easily removed after its emplacement. Such surface features are unlikely to be related to igneous deposits, since once lava is released from a main channel, it would rapidly solidify due to the heat loss and hence result in topographically distinct features. In contrast, such morphological expressions are more likely related to sedimentary volcanism and the emplacement of low viscosity water-rich mud. Sublimation, evaporation, infiltration or a combination of these processes should lead to water loss from the flows without leaving a detectable topographic expression but changing the roughness and hence albedo of the surface. The southern part of Chryse Planitia is a region on Mars where subsurface sediment mobilization could have operated in the past and hence represents a promising site for future exploration where deeper-sourced sedimentary deposits are exposed at the surface.
