Inferring the high velocity of landslides in Valles Marineris on Mars from morphological analysis

The flow characteristics and velocities of three landslides in Valles Marineris on Mars are investigated using detailed morphological analyses of high-resolution images and dynamical calculations based on the run-up and curvature of the landslide deposits. The morphologies of the landslides are described, especially concerning those characteristics that can provide information on the dynamics and velocity. The long runout and estimated high velocities, often exceeding 100 m/s, confirm a low basal friction experienced by these landslides. Because subaqueous landslides on Earth exhibit reduced friction, we explore the scenario of sub-lacustrine failures, but find little support to this hypothesis. The environmental conditions that better explain the low friction and the presence of longitudinal furrows suggest an aerial environment with a basal soft and naturally lubricating medium on which friction diminished gradually; in this perspective, ice is the most promising candidate

The Large Dendritic Morphologies in the Antoniadi Crater (Mars) and Their Potential Astrobiological Significance

Mars has held large amounts of running and standing water throughout its history, as evidenced by numerous morphologies attributed to rivers, outflow channels, lakes, and possibly an ocean. This work examines the crater Antoniadi located in the Syrtis Major quadrangle. Some parts of the central area of the crater exhibit giant polygonal mud cracks, typical of endured lake bottom, on top of which a dark, tens of kilometers-long network of dendritic (i.e., arborescent) morphologies emerges, at first resembling the remnant of river networks. The network, which is composed of tabular sub-units, is in relief overlying hardened mud, a puzzling feature that, in principle, could be explained as landscape inversion resulting from stronger erosion of the lake bottom compared to the endured crust of the riverine sediments. However, the polygonal mud cracks have pristine boundaries, which indicate limited erosion. Furthermore, the orientation of part of the network is the opposite of what the flow of water would entail. Further analyses indicate the similarity of the dendrites with controlled diffusion processes rather than with the river network, and the presence of morphologies incompatible with river, alluvial, or underground sapping processes, such as overlapping of branches belonging to different dendrites or growth along fault lines. An alternative explanation worth exploring due to its potential astrobiological importance is that the network is the product of ancient reef-building microbialites on the shallow Antoniadi lake, which enjoyed the fortunate presence of a heat source supplied by the Syrtis Major volcano. The comparison with the terrestrial examples and the dating of the bottom of the crater (formed at 3.8 Ga and subjected to a resurfacing event at 3.6 Ga attributed to the lacustrine drape) contribute to reinforcing (but cannot definitely prove) the scenario of microbialitic origin for dendrites. Thus, the present analysis based on the images available from the orbiters cannot be considered proof of the presence of microbialites in ancient Mars. It is concluded that the Antoniadi crater could be an interesting target for the research of past Martian life in future landing missions

Mysteries of Mars

This book introduces the reader to the wonders of Mars, covering all aspects from our past perceptions of the planet through to the latest knowledge on its history, its surface processes such as impact cratering, volcano formation, and glaciation, and its atmosphere and climate. In addition, a series of ten intriguing open issues are considered in a more advanced way. These include such thought-provoking questions as What turned off the planet’s magnetic field?, Why are the northern and southern hemispheres so different?, What was the fate of the once abundant water?, and Is there, or was there, life on Mars? Numerous original figures, unavailable elsewhere, reproduce details of images from Viking, CTX, MOC, HiRISE, THEMIS, and HRSC.  The book will appeal especially to general readers interested in planetary sciences, astronomy, astrogeology, and space exploration and to students of Earth Sciences and Natural and Environmental Sciences. The higher-level material on the remaining mysteries of Mars will also be of interest to astrogeologists and other researchers

Mysteries of Mars

This book introduces the reader to the wonders of Mars, covering all aspects from our past perceptions of the planet through to the latest knowledge on its history, its surface processes such as impact cratering, volcano formation, and glaciation, and its atmosphere and climate. In addition, a series of ten intriguing open issues are considered in a more advanced way. These include such thought-provoking questions as What turned off the planet’s magnetic field?, Why are the northern and southern hemispheres so different?, What was the fate of the once abundant water?, and Is there, or was there, life on Mars? Numerous original figures, unavailable elsewhere, reproduce details of images from Viking, CTX, MOC, HiRISE, THEMIS, and HRSC.  The book will appeal especially to general readers interested in planetary sciences, astronomy, astrogeology, and space exploration and to students of Earth Sciences and Natural and Environmental Sciences. The higher-level material on the remaining mysteries of Mars will also be of interest to astrogeologists and other researchers

The dynamics of coastal landslides: insights from laboratory experiments and theoretical analyses

Laboratory experiments have been carried out to study the dynamics of landslides commencing sub-aerially and ending inside a water basin. A comparison between experiments with and without water shows differences in the final deposits. In the subaqueous experiments the grains did not spread out from the mass in the same way as in the subaerial movement. It is suggested that air can be trapped inside the mass which, released during the final stage of the underwater mass propagation, modifies the buoyancy forces. Other effects observed during the air to water transition include the "jumping" and "tilting" of grains. It is concluded that the air to water transition plays a key role in the dynamics of combined subaerial/subaqueous landslides. The information obtained from the experiments may also be useful in the consideration of tsunami generation and the sedimentological analyses of landslide deposits

Landslides surfing on water: A preliminary study

We conjecture that in some cases, landslides impacting onto a water surface might acquire a vertical momentum that makes them slide horizontally at the water level, instead of plunging immediately into deep water, a process that we name surfing. An example of this behavior could be the recent (2002) landslide from the Sciara del Fuoco (Stromboli, Italy), which caused a tsunami with 10-15 meters high run-up waves. By examination of photographs, laboratory experiments, theoretical estimates, and numerical calculations, we preliminarily investigate the surfing conditions for landslides. The effect might also have an impact on the generation and propagation of tsunami waves. © 2013 Sapienza Universitá Editrice

Subaerial and subaqueous dynamics of coastal rockfalls

In spite of the hazard represented by rockfalls in coastal areas, few investigators have studied the movement of rocks failing in water. This work describes a model for the propagations of coastal rockfalls, i.e., blocks detaching from a subaerial cliff, propagating initially in air, impacting against the water surface, and finally coming to rest in the water basin. Application of the model to two real cases in Italy shows a satisfactory agreement between the predicted rockfall run-out and the field data. Some scattering observed in the data is explained as the consequence of different heights of the source area. It is shown that largest boulders usually reach a longer distance. However, the schematic shape for blocks adopted in the model likely results in a much more regular behaviour compared to reality. (C) 2009 Elsevier B.V. All rights reserved