Microbial habitability of the early Mars lacustrine environment sustained by iron redox cycling

Several studies have reported new data on the estimated compositions of chemical components at Gale crater; however, there is still a lack of information regarding potential past support of biomass and detectable biomarkers of ancient life. In this study we evaluate microbial habitability of early Mars constrained by the recently reconstructed water chemistry at Gale. The modeled community is based on Fe-metabolizing bacteria with the ability to utilize solid-phase iron oxides (e.g., magnetite) as an electron source or sink. Our results illustrate the plausibility of a sustained community in Gale Lake and provides suggestions for future modeled and laboratory-based studies to further evaluate the past habitability of Mars, biosignatures and their preservation potential, and hidden metabolic potential.One Sentence SummaryThis work provides an existence proof of habitability on early Mars and demonstrates modeling processes by which the habitability of extraterrestrial environments can be explored quantitatively.

The Characteristics of Kasiro Shale and Its Implication to Oil Shale Identification at The Batang Asai, Sarolangun, Jambi

The necessity of oil and natural gas from fossil energy sources in Indonesia is increasing over time, whereas oil and gas reserves generated from conventional reservoirs are decreasing. To anticipate gas shortages, exploration of unconventional resources is needed. The main focus of the rock formation in this research is the Tertiary Miocene Kasiro Formation. This formation is dominated by Shale and Claystone. Shale characteristic from the megascopic aspect of Tertiary Miocene Kasiro Formation in the research area have fissile structure with soft to hard in hardness scale of shale. Shale characteristic from microscopic aspect based on petrography, SEM (Scanning Electron Magnetic) and XRD (X-Ray Diffraction) show illite as main clay mineral. Other clay minerals such as montmorilonite and kaolinite also can be found as well as some important mineral like quartz, chlorite, biotite, alunite and diaspore. Shale diagenesis rate of the Tertiary Miocene Kasiro Formation is defined based on the presence of some clay mineral like illite, kaolinite and montmorillonite. Based on the result of SEM and XRD analyses, the shale diagenesis in the research area can be classified as early mesodiagenesis. The diagenesis rate also can show that oil maturity in the Kasiro shale can be classified as immature to semi mature. Based on the shale characteristic, the Kasiro shale was deposited in a weak current mechanism and based on the presence of alginite, the shale was deposited within lacustrine environment. The lacustrine environment have a characteristic of low oxygen rate that can be seen with the presence of mollusk fossil such as viviparous that indicating a fresh water and weak current enviroment.

Pleistocene plants from Zarzal Formation, middle valley of the Cauca River Basin, Colombia

We report macro and meso palaeobotanical records from the Zarzal Formation, in the Cauca River Depression, and the Quindío-Risaralda Basin between the Western and the Central Cordilleras of Colombia. The fossils correspond to leaves and seeds obtained from layers of mudstones, diatomites, and tuffaceous sandstones deposited in the inter-Andean valleys of Cauca and La Vieja rivers, separated by the Serranía Santa Bárbara ridge between the Valle del Cauca and Quindío departments. The sediments of the Pleistocene Zarzal Formation were deposited in a fluvial-lacustrine environment, with volcanic influence originated in the Central Cordillera to the east of the depositional area. The study here presented allowed the identification of thirteen morphotypes of leaf impressions grouped in six Angiosperm families: Poaceae?/Cyperaceae? and Araceae of the Monocots group, Melastomataceae, Fabaceae and Lauraceae belonging to the Eudicots group and one family of Lycopsida: Thelypteridaceae. On the other hand, very well-preserved silicified micro-seeds were grouped in eight morphotypes, belonging to the botanical groups Cyperaceae and Asteraceae. The fossils found allowed us to identify two types of plant associations that exhibit paleofloristic richness. In the Cauca River Basin, an autochthonous to parautocthonous plant association could correspond to a sub-Andean gallery forest, whilst in the La Vieja River Basin a parautocthonous plant association indicates a swamped floodplain. Keywords: paleoflora, leaves, seeds, Cauca River, La Vieja River, lacustrine deposit.

Intense subaerial weathering of eolian sediments in Gale crater, Mars

After over 8 years of successful surface operations on Mars, the Curiosity rover has revealed much about the environment in Gale crater. Despite early observations of a lacustrine environment, few of the subsequent deposits exhibit demonstrable lacustrine character. We suggest instead that most of the stratigraphic section explored to date can be best explained as eolian and/or volcaniclastic sediments subaerially chemically weathered by acidic precipitation in a reduced atmosphere. Most of the deposits in Gale crater seemingly did not form in an ancient lake, but the results nonetheless shed considerable light on ancient climate, environmental change, and the astrobiology of Mars. Discoveries by Curiosity provide a critical piece to Mars’ global alteration puzzle.

The Early Pleistocene ectothermic vertebrates of Pietrafitta (Italy) and the last Western European occurrence of Latonia Meyer, 1843

The Early Pleistocene site of Pietrafitta (central Italy) produced a rich vertebrate assemblage from the Late Villafranchian Land Mammal Age (late MN18). Geological and paleobotanical data from Pietrafitta indicate a lacustrine environment, surrounded by a humid deciduous broadleaved forest with a temperate climate. The vertebrate assemblage consists of at least 40 taxa including actinopterygians, amphibians, reptiles, birds, and mammals. Here, we concentrate on the ichthyofaunal and herpetofaunal remains. The ichthyofauna includes Barbus Cuvier and Cloquet, 1816, Scardinius Bonaparte, 1837, aff. Squalius Cuvier, 1817, and Tinca Cuvier, 1817. The two anuran genera are the large-sized alytid frog Latonia Meyer, 1843 and the “green frog” Pelophylax Fitzinger, 1843. Three snake precloacal vertebrae were recognized, one attributed to Colubrines indet., another one to ­Natrix sp. Laurenti, 1768, and the largest and most complete vertebra is referred to the genus Vipera s.l. Laurenti, 1768 (cf. gr. “Oriental vipers”). The chelonian fossils, including some complete carapaces and plastrals, are attributed to the European pond turtle (Emys gr. Orbicularis Linnaeus, 1758) and Hermann’s tortoise (Testudo hermanni Gmelin, 1789).

Thermodynamic Constrains on Smectite and Iron Oxide Formation at Gale Crater, Mars: Insights into Potential Free Energy from Aerobic Fe Oxidation in Lake Water–Groundwater Mixing Zone

The presence of saponite and iron oxides in Sheepbed mudstone of Yellowknife Bay at Gale crater on Mars is considered as evidence of a habitable fluvio-lacustrine environment for chemolithoautotrophy. However, the energetic availability for metabolic reactions is poorly constrained. Herein, we propose the possible mixing of surface water and groundwater that (i) explains the formation of magnetite and hematite detected in Sheepbed mudstone and (ii) may work as a potential habitable zone for aerobic Fe2+-oxidizing microbes. Our thermodynamic modeling of water–rock reactions revealed that the formation of abundant saponite in Sheepbed mudstone may occur under various conditions of water-to-rock mass ratios, temperatures (5–200 °C), and initial fluid compositions. In contrast, the formation of iron oxides in the mudstone can be explained only by the mixing of Fe2+-rich groundwater and more oxidized surface waters, where the Fe2+-rich groundwater can be generated by the low-temperature water–rock reactions with a CO2-bearing initial fluid. The calculated bioavailable energy of aerobic Fe2+ oxidation in the fluid-mixing zone on Mars is similar to that estimated for a fluid-mixing zone on Earth actually inhabited by aerobic Fe2+-oxidizing microbes. The findings will contribute to a better understanding of potential habitability on Mars.

Microscopy Observation of Samosir Formation Paleosoil, Tuktuk Sidaong, North Sumatera, Indonesia.

Samosir is the islands that emerge and standing upon on Toba Caldera after it’s the last eruption at 74.000 years ago. Samosir Island known as the caldera floor that uplifts parallel with Toba’s caldera flooding. In this study, we have observed an outcrop in Tumutuk, Samosir Island that hypothesized as a lacustrine deposit, and we found a paleosoil layer that might give more answers about the geological process in this area at the past time. Based on this outcrop, we described it, followed to measure its stratigraphy section, and took representative samples from the paleosoil layer, then observed the samples under the stereo-microscope as polish rock section, in normal light & negative images. As the result we identify several features of paleosoil & its sedimentary grain that shown this paleosoil layer, two events of the volcanoclastic deposits flown, and exposed two-time, and forming soil, it may form in the shallow swamp in a lacustrine environment, coincide with caldera flooding and caldera floor uplift event.

LACUSTRINE DYNAMICS AND TLATEL-TYPE SETTLEMENTS FROM MIDDLE FORMATIVE TO LATE AZTEC IN THE EASTERN PART OF LAKE TEXCOCO, MEXICO

In the territories of the former lakes in the Basin of Mexico, a tlatel was an insular settlement associated with the exploitation of lacustrine resources. This study examines the stratigraphy and geomorphological context of three tlateles in the eastern part of the former Lake Texcoco and correlates their phases of development with regional paleoclimatic trends from the seventh century b.c. to the sixteenth century. The results of this research indicate that fluvio-lacustrine (i.e., deltaic) sedimentation and freshwater springs in the lake basin were important features for the establishment of tlatel settlements in the highly dynamic and saline lacustrine environment. The formation and abandonment of the studied tlateles correlate with changes in other settlements and developments recorded in other parts of Lake Texcoco. Sites and sediments in the eastern part of Lake Texcoco provide proxy information on the lacustrine changes that accompanied the development of Tenochtitlan and other lacustrine settlements in its western part.