The Argyre Region as a Prime Target for in situ Astrobiological Exploration of Mars

At the time before ∼3.5 Ga that life originated and began to spread on Earth, Mars was a wetter and more geologically dynamic planet than it is today. The Argyre basin, in the southern cratered highlands of Mars, formed from a giant impact at ∼3.93 Ga, which generated an enormous basin approximately 1800 km in diameter. The early post-impact environment of the Argyre basin possibly contained many of the ingredients that are thought to be necessary for life: abundant and long-lived liquid water, biogenic elements, and energy sources, all of which would have supported a regional environment favorable for the origin and the persistence of life. We discuss the astrobiological significance of some landscape features and terrain types in the Argyre region that are promising and accessible sites for astrobiological exploration. These include (i) deposits related to the hydrothermal activity associated with the Argyre impact event, subsequent impacts, and those associated with the migration of heated water along Argyre-induced basement structures; (ii) constructs along the floor of the basin that could mark venting of volatiles, possibly related to the development of mud volcanoes; (iii) features interpreted as ice-cored mounds (open-system pingos), whose origin and development could be the result of deeply seated groundwater upwelling to the surface; (iv) sedimentary deposits related to the formation of glaciers along the basin's margins, such as evidenced by the ridges interpreted to be eskers on the basin floor; (v) sedimentary deposits related to the formation of lakes in both the primary Argyre basin and other smaller impact-derived basins along the margin, including those in the highly degraded rim materials; and (vi) crater-wall gullies, whose morphology points to a structural origin and discharge of (wet) flows

Formation and degradation of chaotic terrain in the Galaxias regions of Mars: implications for near-surface storage of ice

Galaxias Chaos is a region of low plateaus separated by narrow fractures – a chaotic terrain. Galaxias Mensae and Galaxias Colles are characterised by mesa and knobby terrains of individual landforms, or small assemblages, separated by plains. Galaxias Chaos has been attributed to ground disturbance due to sublimation in shallow subsurface ice-rich deposits, Galaxias Mensae and Galaxias Colles to sublimation and degradation of icy surface materials, without production of chaotic terrain. Liquid water has not been regarded as a product of the degradation of these icy terrains. This paper asks two research questions: (1) what was the total extent of the different modes of landscape degradation, especially chaotic terrain, involved in producing the present landscapes of Galaxias Chaos and Galaxias Mensae–Colles; (2) can the generation of liquid water as a product of landscape degradation be ruled-out? Using a morphological-statistical approach, including power spectrum analysis of relief, our observations and analyses show that present mesa-knobby terrains of Galaxias Mensae–Colles evolved from a landscape that had the same directional pattern and relief as presently found in Galaxias Chaos. This terrain extended across ∼440,000 km2 but ∼22,000 km3 (average thickness, 77 m) have been lost across ∼285,000 km2. This represents a significant loss of ice-bearing deposits. Moreover, this surface degradation was spatially partitioned by landforms associated with elevated ground heating and the transmission of a fluid in the shallow subsurface towards a distal channel. In answer to research question 2, it cannot be determined definitively if the fluid involved was groundwater, generated by the thermal destabilisation of the icy deposits, or low viscosity lava. However, it is likely that the degradation of Galaxias Mensae–Colles was not a consequence of sublimation alone. These findings underscore the significance of cryo-volcanic interactions in the cycling of water between the Martian surface and the atmosphere

Programme Dementia Prevention (pdp): A Nationwide Program for Personalized Prevention in Luxembourg.

peer reviewedBACKGROUND: With continuously aging societies, an increase in the number of people with cognitive decline is to be expected. Aside from the development of causative treatments, the successful implementation of prevention strategies is of utmost importance to reduce the high societal burden caused by neurodegenerative diseases leading to dementia among which the most common cause is Alzheimer's disease. OBJECTIVE: The aim of the Luxembourgish "programme dementia prevention (pdp)" is to prevent or at least delay dementia in an at-risk population through personalized multi-domain lifestyle interventions. The current work aims to provide a detailed overview of the methodology and presents initial results regarding the cohort characteristics and the implementation process. METHODS: In the frame of the pdp, an extensive neuropsychological evaluation and risk factor assessment are conducted for each participant. Based on the results, individualized multi-domain lifestyle interventions are suggested. RESULTS: A total number of 450 participants (Mean age = 69.5 years; SD = 10.8) have been screened at different recruitment sites throughout the country, among whom 425 participants (94.4%) met the selection criteria. CONCLUSIONS: We provide evidence supporting the feasibility of implementing a nationwide dementia prevention program and achieving successful recruitment of the target population by establishing a network of different healthcare providers.3. Good health and well-bein

Sub-kilometre (intra-crater) mounds in Utopia Planitia, Mars: character, occurrence and possible formation hypotheses

At the middle latitudes of Utopia Planitia (∼35–45°N; ∼65–101°E) hundreds of small-sized mounds located in sub-kilometre impact craters dot the landscape. Their shape varies from circular to crescentic and their height ranges from ∼10 to 50 m. Often, metre to decametre pitting is observed, as is metres-thick banding or stratification. Mound albedo is relatively high, i.e. ∼0.16. The plain’s terrain in the region, previously linked to the latitude-dependent mantle (LDM) of ice–dust, displays pitting and albedo similar to the small intra-crater mounds. Some workers have suggested that the mounds and the plain’s terrain share a common ice–dust origin. If so, then scrutinising the mounds could provide analogical insight on the key geological characteristics and spatial distribution of the LDM itself. Other workers have hypothesised that the mounds are eroded sedimentary landforms or periglacial mounds underlain by a perennial ice-core (closed-system pingos). In this article we develop and then discuss each of the three mound-hypotheses in a much more substantial manner than has been done hitherto. Towards this end we use high-resolution images, present a detailed regional-map of mound distribution and establish a regional platform of topographical analysis using MOLA data superposed on a large-scale CTX mosaic. Although the ice–dust hypothesis is consistent with some observations and measurements, we find that a (loess-based) sedimentary hypothesis shows greater plausibility. Of the three hypotheses evaluated, the pingo or periglacial one is the weakest

Introduction to the Current and recent landscape evolution on Mars special issue

International audienceThe early views of Mars, derived of the Mariner and Viking missions, hinted at a surface environment that was invariably cold, extremely dry (at least in the relatively-recent past), low in atmospheric pressure and, largely, inanimate. Repeat orbital observations combined with the collection of in situ data have revealed a contrary geological facet. Mars is unrelentingly in flux, it seems, at temporal and geological scales ranging from micro- to macro- and, bi-hemispherically, at polar and non-polar latitudes

Martian thermal-contraction polygons as sounders of subsurface properties in Utopia Planitia

International audienceOn Earth, temperature decreases can cause the thermal contraction of ice-cemented ground. This forms polygonal networks of surficial fractures – called ‘thermal-contraction polygons’ (Washburn, 1956). Polygons exhibit different morphologies with time (Black, 1954): initially showing no relief (‘flat-centred polygons’, FCPs), their margins uplift with the growth of ice or sand wedges (‘low-centred polygons, LCPs); subsequently to wedge degradation, polygon margins then collapse into the wedge casts (‘high-centred polygons, HCPs). On Mars, polygons of similar dimensions (~ 5-25 m in diameter) and morphologies (FCP/LCP/HCP) to those on Earth are commonly observed in the mid-latitudes. They are inferred to form by thermal contraction of ice-cemented ground (Mellon, 1997). Further, polygons in Utopia Planitia (UP) have been identified as ice-wedge polygons (Soare et al., 2021). This indicates a potential role of liquid water in UP during the Amazonian, at a period where the martian climate is thought to be non-conducive to the stability of surface liquid water. Here, we seek to understand whether the characteristics of these ice-wedge polygons could be used to understand the subsurface properties of their substrate. Hence, we investigate the density and type (FCP/LCP/HCP) of polygons for three morphological units in UP, in the area (44-52°N 100-130°E) where polygons were identified as ice-wedge polygons by Soare et al. (2021). In UP, we mapped two morphological units: the “sinuous unit” (elongated, sinuous features) and the “boulder unit” (covered in decametre-scale boulders). We then mapped polygons over the two units using a grid-based technique (Ramsdale et al., 2017). We developed three parameters, that we infer reflect various properties of the ground: ρpol, reflecting the cementation of the substrate by ice; ρwf, reflecting the capacity of the substrate to form wedge ice; ρwp, reflecting capacity of the substrate to preserve ground ice. The boulder unit has no polygons. Therefore, it must be a massive material, non-conducive to ice cementation. Its surface is an extensive field of boulders, and shows blocks shattered in place. It points toward a volcanic origin for the boulder unit. This result is consistent with studies that concluded to the presence of volcanic units in UP (e.g. Tanaka et al., 2005). Our parameters show that the sinuous unit was an initially porous material that became cemented by ice, and underwent wedge formation. Therefore, the sinuous unit was deposited on top of the boulder unit, either as water-rich deposits from a large aqueous flow, which subsequently froze; or by condensation of water vapour from the atmosphere within porous sediment. Those two emplacement modes were suggested to have occurred in UP (e.g. Costard and Kargel, 1995; Séjourné et al., 2012). The sinuous unit was then degraded, exposing the underlying boulder unit. These interpretations show that polygon characteristics can be used to unveil properties of their substrate. In our study zone in UP, it allowed us to link geomorphological units with specific geological processes, that were suggested to have occurred in UP. Therefore, the parameters we developed can be considered as additional tools to study the martian geology at the sub-regional scale

Pingo-like mounds and possible polyphase periglaciation/glaciation at/adjacent to the Moreux impact crater

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Relationship between thermal-contraction polygons and substrate properties on Mars

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