Mars: Life, Subglacial Oceans, Abiogenic Photosynthesis, Seasonal Increases and Replenishment of Atmospheric Oxygen

The discovery and subsequent investigations of atmospheric oxygen on Mars are reviewed. Free oxygen is a biomarker produced by photosynthesizing organisms. Oxygen is reactive and on Mars may be destroyed in 10 years and is continually replenished. Diurnal and spring/summer increases in oxygen have been documented, and these variations parallel biologically induced fluctuations on Earth. Data from the Viking biological experiments also support active biology, though these results have been disputed. Although there is no conclusive proof of current or past life on Mars, organic matter has been detected and specimens resembling green algae / cyanobacteria, lichens, stromatolites, and open apertures and fenestrae for the venting of oxygen produced via photosynthesis have been observed. These life-like specimens include thousands of lichen-mushroom-shaped structures with thin stems, attached to rocks, topped by bulbous caps, and oriented skyward similar to photosynthesizing organisms. If these specimens are living, fossilized or abiogenic is unknown. If biological, they may be producing and replenishing atmospheric oxygen. Abiogenic processes might also contribute to oxygenation via sublimation and seasonal melting of subglacial water-ice deposits coupled with UV splitting of water molecules; a process of abiogenic photosynthesis that could have significantly depleted oceans of water and subsurface ice over the last 4.5 billion years.

Seasonal melting simulation of permafrost rock glaciers and their potential contribution to sediment loads in Alpine catchments

<p>A common issue with large scale erosion modelling is that local processes are often unaccounted for, either because they haven’t been included in the model conceptually, or because they are undetected yet. On the other hand, significant deviations from such a general soil erosion model to the measurements can reveal those local processes. We compared the average yearly sediment amounts of a network of turbidity measurement stations in the catchment of the alpine River Inn to the results of the large scale erosion model RUSLE2015 (Panagos et. al.) for long term yearly erosion amounts and found a significant underestimation of sediment loads in three sub catchments. An important source of sediments in alpine rivers comes from glaciers, which explains the high loads in one of the stations, but two of the three high sediment load sub catchments are too low to have substantial valley glaciers. But another potential source of glacial sediment exists in the form of permafrost soils and in this case a specific permafrost form: rock glaciers. Rock glaciers in particular have been spotted in those two high sediment load catchments, but since they are hard to detect from remote sensing due to the surface being covered with rocks, the existence or the exact spatial extent is often unknown. But with rising temperatures in the Alps, the areas in which permafrost rock glaciers can exist decreases every year and the depth of the seasonal melting layer increases.</p><p>We propose the hypothesis that the high sediment loads in those sub catchments are caused by increasingly deeper melting of permafrost rock glaciers. This process releases fine materials which have been trapped frozen since the glacial period and are now being eroded and transported to the alpine streams. To get an estimation of potential erodible material from rock glacier melting in the respective sub catchments, we developed a model to simulate the heat diffusion from the air into the frozen ground, while accommodating for the change in specific thermal capacity. The model (developed in Python) takes air temperature time series data as input and can be configured for varying ground stratification setups with different thermal diffusivity values depending on the ground properties.</p><p>From the simulated melting depth of an average square meter of rock glacier we extrapolate the mass of melted material to the potential permafrost erosion material available in the River Inn sub catchments. We show that this source of sediments can be significant and needs to be factored in should an erosion model be used to calculate sediment input into the rivers. But, with the estimation of sediment load from permafrost origins narrowed down, improving a large-scale erosion model like the RUSLE2015 for this alpine mountain region by accounting for local processes like this one is possible. </p>

Hydrogeological characterization throughout deep geophysical investigations in the Verrès plain (Aosta Valley, north-western Italian Alps)

Although fresh water availability in the Aosta Valley (north-western Italian Alps) is generally granted by glaciers and snow seasonal melting at high altitudes, hydrogeological conditions are not favorable everywhere. Most part of the territory is typically mountainous, with prevailing metamorphic rocks and, secondarily, glacial deposits. Relevant ground water bodies can be found only in the main bottom valley, where glacial excavation, fluvio-glacial and lacustrine sedimentation had maximum intensity, allowing the deposition of important thickness of porous materials. Nevertheless, the geological knowledge of the subsurface is here still poor. These groundwater bodies are monitored by the Environmental Protection Agency of the Aosta Valley Region (ARPA Valle d’Aosta), according to the Italian law (D.Lgs.30/09). This study deals with geophysical investigations in the Verrès plain aquifer (southern Aosta Valley). The main goal of the study has been the first evaluation of groundwater research in potential deep aquifers. Different geophysical methodologies were applied (ERT, TDEM, HVSR, and Re.Mi.), in order to identify the deep aquifer geometry and the rock basement depth.

Genesis and provenance of a new Middle Pleistocene diamicton unit at Happisburgh, NE Norfolk, UK

Glacigenic deposits at Happisburgh, NE Norfolk, record the earliest known expansion of glaciers into lowland eastern England during the Quaternary. The sequence comprises two regionally extensive till units, the Happisburgh Till and Corton Diamicton members of the Happisburgh Glacigenic Formation, deposited during separate ice advances, and intervening glacilacustrine and outwash deposits laid down during ice-marginal retreat. During 2012, a new diamicton unit was discovered within the intervening sorted sediments and its significance is outlined here. Sedimentological and structural evidence suggests, tentatively, that the diamicton forms a small debris fan generated subaerially by a series of water-saturated hyperconcentrated or debris flows. The precise trigger mechanism for these flow deposits remains unclear, but may relate to seasonal melting of surface or buried ice followed by mass-movement, or to more abrupt geological events including periods of intense rainfall, moraine dam failure or a glacier outburst flood.

Seasonal variation of ice melting on varying layers of debris of Lirung Glacier, Langtang Valley, Nepal

Glaciers in the Himalayan region are often covered by extensive debris cover in ablation areas, hence it is essential to assess the effect of debris on glacier ice melt. Seasonal melting of ice beneath different thicknesses of debris on Lirung Glacier in Langtang Valley, Nepal, was studied during three seasons of 2013–14. The melting rates of ice under 5 cm debris thickness are 3.52, 0.09, and 0.85 cm d−1 during the monsoon, winter and pre-monsoon season, respectively. Maximum melting is observed in dirty ice (0.3 cm debris thickness) and the rate decreases with the increase of debris thickness. The energy balance calculations on dirty ice and at 40 cm debris thickness show that the main energy source of ablation is net radiation. The major finding from this study is that the maximum melting occurs during the monsoon season than rest of the seasons.

Ratios of Mg2+/Na+ in snowpack and an ice core at Austfonna ice cap, Svalbard, as an indicator of seasonal melting

Snowpack and ice-core samples were collected from the dome of Austfonna ice cap, Svalbard, in the spring of both 1998 and 1999. The samples were analyzed for anions, cations, pH, liquid electrical conductivity and oxygen isotopes. Concentrations of chemical components in snowpack with a history of melting were much lower than those in unmelted snowpack. There was a clear difference between Mg2+/Na+ ratios previously in melted snowpack (0.03 ± 0.02) and in unmelted snowpack (0.11 ± 0.02). We propose that the Mg2+/Na+ ratio can be used as an indicator of whether or not firn or bubbly ice in the Austfonna ice core has experienced melt percolation. The Mg2+/Na+ ratio indicates that firn or bubbly ice prior to AD 1920 was much less affected by melt percolation than firn or bubbly ice formed after 1920.