Monica Pondrelli

Sequence of infilling events in Gale Crater, Mars: Results from morphology, stratigraphy, and mineralogy

Gale Crater is filled by sedimentary deposits including a mound of layered deposits, Aeolis Mons. Using orbital data, we mapped the crater infillings and measured their geometry to determine their origin. The sediment of Aeolis Mons is interpreted to be primarily air fall material such as dust, volcanic ash, fine-grained impact products, and possibly snow deposited by settling from the atmosphere, as well as wind-blown sands cemented in the crater center. Unconformity surfaces between the geological units are evidence for depositional hiatuses. Crater floor material deposited around Aeolis Mons and on the crater wall is interpreted to be alluvial and colluvial deposits. Morphologic evidence suggests that a shallow lake existed after the formation of the lowermost part of Aeolis Mons (the Small yardangs unit and the mass-wasting deposits). A suite of several features including patterned ground and possible rock glaciers are suggestive of periglacial processes with a permafrost environment after the first hundreds of thousands of years following its formation, dated to ~3.61 Ga, in the Late Noachian/Early Hesperian. Episodic melting of snow in the crater could have caused the formation of sulfates and clays in Aeolis Mons, the formation of rock glaciers and the incision of deep canyons and valleys along its flanks as well as on the crater wall and rim, and the formation of a lake in the deepest portions of Gale.

Insight into the development of a carbonate platform through a multi-disciplinary approach: a case study from the Upper Devonian slope deposits of Mount Freikofel (Carnic Alps, Austria/Italy)

The development and behavior of million year-scaled depositional sequences recorded within Palaeozoic carbonate platform has remained poorly examined. Therefore, the understanding of palaeoenvironmental changes that occur in geological past is still limited. We herein undertake a multi-disciplinary approach (sedimentology, conodont biostratigraphy, magnetic susceptibility (MS), and geochemistry) of a long-term succession in the Carnic Alps, which offers new insights into the peculiar evolution of one of the best example of Palaeozoic carbonate platform in Europe. The Freikofel section, located in the central part of the Carnic Alps, represents an outstanding succession in a fore-reef setting, extending from the Latest Givetian (indet. falsiovalis conodont zones) to the Early Famennian (Lower crepida conodont zone). Sedimentological analysis allowed to propose a sedimentary model dominated by distal slope and fore-reef-slope deposits. The most distal setting is characterized by an autochthonous pelagic sedimentation showing local occurrence of thin-bedded turbiditic deposits. In the fore-reef slope, in a more proximal setting, there is an accumulation of various autochthonous and allochthonous fine- to coarse-grained sediments originated from the interplay of gravity-flow currents derived from the shallow-water and deepwater area. The temporal evolution of microfacies in the Freikofel section evolves in two main steps corresponding to the Freikofel (Unit 1) and the Pal (Unit 2) limestones. Distal slope to fore-reef lithologies and associate changes are from base to top of the section: (U1) thick bedded litho- and bioclastic breccia beds with local fining upward sequence and fine-grained mudstone intercalations corresponding, in the fore-reef setting, to the dismantlement of the Eifelian–Frasnian carbonate platform during the Early to Late Frasnian time (falsiovalis to rhenana superzones) with one of the causes being the Late Givetian major rift pulse; (U2) occurrence of thin-bedded red nodular and cephalopod-bearing limestones with local lithoclastic grainstone intercalations corresponding to a significant deepening of the area and the progressive withdrawal of sedimentary influxes toward the basin, in relation with Late Frasnian sea-level rise. MS and geochemical analyses were also performed along the Freikofel section and demonstrate the inherent parallel link existing between variation in MS values and proxy for terrestrial input. Interpretation of MS in terms of palaeoenvironmental processes reflects that even though distality remains the major parameter influencing MS values, carbonate production and water agitation also play an important role.

Evolution of periglacial landforms in the ancient mountain range of the Thaumasia Highlands, Mars

Abstract Possible periglacial and relict glacial landforms in the ancient mountain range of the Thaumasia Highlands, Mars, are described. The landforms include large-scale mantling, lineated crater and valley-fill materials, debris aprons, protalus lobes and ramparts. The most pristine ice-related landforms appear to be small-scale protalus lobes and ramparts with no visible distinct impact craters at both medium (High Resolution Stereo Camera (HRSC)) and high (Mars Orbiter Camera (MOC) narrow angle (NA), Context Camera (CTX)) spatial resolution. These small landforms are possibly active at present and post-date more extensive features such as crater fills, possibly formed during high obliquity climatic periods. In contrast to the rock glacier-like landforms with distribution preferentially occurring on south-facing slopes, possibly controlled by enhanced exposure to the Sun, older, less pristine lineated fill materials show a less systematic distribution of flow directions, suggesting a more generalized periglacial and possibly glacial environment in the Thaumasia Highlands.

Geology of Aeolis Dorsa alluvial sedimentary basin, Mars

ABSTRACT Aeolis Dorsa is a topographic depression, ∼800 km east of Gale Crater, located along the Mars’ dichotomy boundary. This area hosts a set of fluvial sedimentary rocks displaying an exceptional record of depositional environments and fluvial channels patterns that suggest the presence of a large amount of surface and/or subsurface water. We interpreted the plain as an ancient waterlogged environment, a sedimentary basin passing into distal depositional environments. Regional mapping of the area revealed the presence of a large-scale fluvial system that points to a long-term and extensive hydrological cycle. A significant wet period with changing environmental conditions in Hesperian/Amazonian occurred in the study area diverging from the present-day climate. Our map (Main Map) contributes to the understanding of past climatic conditions on Mars. Moreover, it provides an interesting perspective for future missions looking for evidence of present-day and/or past extraterrestrial organisms as the life as we know it needs liquid water.

Fluvio-Lacustrine Sedimentation and Tectonic Influence, Lunae Planum (Mars)

This area of Lunae Planum (centred around 4°S and 298°E) has been studied by various authors, who have described the presence of exhumed channels (sinuous lineations), Light Layered Deposits (LLD), and detected hydrated sulphates associated with LLDs. We performed sedimentological, geomorphological, and stratigraphic analyses of the LLDs and produced geological maps of the area. The geological maps can serve as a guide for scientific or landing site analyses, and they represent a tool for making lateral correlations and for detecting different units in the vertical dimension. Our aim is to contribute to the debate about processes associated with the presence of water, the factors controlling these processes, and the residence time of liquid water on the surface of Mars. The significant element that emerges from this work is the complex evolutionary history of the study area and, to our knowledge, the area represents a unique example on Mars of clear evidence of tectonic influence on sedimentation.

Equatorial Layered Deposits in Arabia Terra, Mars: Stratigraphy and Process Variability

The equatorial layered deposits of Arabia Terra are investigated to understand their genesis and the controls on their evolution. We interpret the deposits found within the craters as having been formed by spring deposition based on the large-scale geometry, the presence of morphologies consistent with fluid expulsion, the composition, and the sedimentary structures. Outside of the craters, we found evidence of dune forms and cross-stratification suggestive of aeolian activity, possibly associated with playa deposition. Groundwater fluctuations are suggested as the control on deposition.

Application of Sequence-Stratigraphic Concepts to Mars: Eberswalde Crater

Sedimentary deposits within Eberswalde Crater are generally interpreted as having formed in a fluviolacustrine depositional environment. The Eberswalde fan delta consists of five lobes (four deltaic), the relative stratigraphy of which can be unravelled through simple cross-cutting relationships, allowing inferences to be made of the approximate water level from the transition between delta plain and delta front. Switching between different lobes is inferred to have been controlled by allogenic control. We distinguish three water-level fluctuations, possibly associated with system tracts, on which a higher order regressive trend is superimposed. The three lower-order cycles may partly reflect control by transient and/or localized processes, but the cyclic behaviour suggests the presence of climatic control.

New Concepts and Tools for Geological Mapping of Mars: Geological Mapping of Mars: A Workshop on New Concepts and Tools; Tuscany, Italy, 12–14 October 2009

Geological mapping is a key tool for understanding the evolution of any planetary surface. The availability of ever growing data sets (e.g., multispectral and hyperspectral imaging and subsurface radar sounding) requires increasing effort in analyzing, integrating, and exploiting them for mapping purposes. To discuss these issues, about 80 planetary geoscientists gathered in Italy at a workshop co-organized by the Italian Space Agency (ASI), the International Research School of Planetary Sciences (IRSPS), and the U.S. Geological Survey (USGS). The workshop focused on both data and concepts and covered a range of scientific and technical topics.