TP17

High-altitude Andean wetlands hold extremophilic communities adapted to live in harsh conditions (i.e. high radiation, low rates of precipitation, high rates of evaporation, high salinity, high arsenic concentration, low oxygen pressure, strong winds, or wide daily range in temperatures). They are ecologically interesting settings for understanding the limits of life upon extreme UV radiation and provide natural scenarios to advance knowledge in the evolution of early life on Earth, which emerged upon intense UV radiation due to the lack of an ozone layer in the primitive Earth’s atmosphere. In addition, the unique environmental conditions of the high-altitude Andean lakes show some analogy to Martian paleolakes of the Noachian period (i.e. about 3.5 billion years ago). Therefore, the study of the Andean microbial ecosystem could provide information about life on other planets and we may learn from the microbial survival strategies in the highest perennial lakes and ponds on Earth what happened in the past.

Here, we investigated the microbial ecology of three high-altitude hypersaline ponds from La Puna region (Argentina) showing an increasing extent of desiccation by analyzing their lipid sedimentary record. The aim was to characterize the microbial community structure and metabolic functioning of three hypersaline ponds through the molecular and isotopic (stable carbon and hydrogen) analysis of lipid compounds in their sediments. This work is the first to describe the molecular and isotopic lipid fingerprints in the sediments of astrobiologically interesting wetlands from the Andean Puna region.

We detected lipid biomarkers of cyanobacteria, sulfate-reducing bacteria, purple sulfur bacteria, and archaea in the three alpine ponds, as well as diatoms in the intermediate salinity system. We observed that the relative abundance of biomarkers related to purple sulfur and sulfate-reducing bacteria decreased with salinity, whereas those associated to cyanobacteria and archaea decreased their relative abundance in the mid-saline pond to increase it again and became both prevailing at the highest salinity. Compound-specific isotopic analysis of sedimentary lipid biomarkers revealed that carbon assimilation in the three high-altitude ponds occurred via a combination of the reductive tricarboxylic acid cycle, the reductive pentose phosphate cycle, and the reductive acetyl-CoA pathway. The use of a number of lipid compound ratios as geochemical/environmental proxies allowed the ecological reconstruction of the three lacustrine systems, where a transition along the salinity gradient illustrated the potential impact of desiccation on the microbial community structure. The molecular and compound-specific isotopic analysis of highly resistant lipid biomarkers represents a powerful tool to record those changes over time, which has great value for interpreting the paleobiology of ancient sediment deposits on Earth and beyond.

How to cite: Sánchez-García, L., Carrizo, D., Vignale, F. A., and Farías, M. E.: Molecular and Isotopic impact of desiccation in high-altitude wetlands analogous to Martian paleolakes, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-690, https://doi.org/10.5194/epsc2022-690, 2022.

Abstract

Wind-dominated landscapes can be found on all Solar System bodies with atmospheres. These landscapes record the point of interaction of the atmosphere with the solid surface in a narrow region that also correlates with where field geologists interact with a planetary body. The Altiplano-Puna of Argentina is a high altitude, hyperarid landscape with young and easily eroded deposits and high wind activity. These factors make the region an exceptional analogue for Mars and other planetary regions where wind erosion is dominant, which includes portions of Titan, Venus and Pluto. Our field studies inform our understanding of how wind affects planetary surfaces.

Figure 1. Yardangs of the Puna, carved into ash, surrounded by gravels. With young cinder cone.

Introduction

Wind erosion of planetary bodies yields a variety of landforms, including yardangs (wind-carved ridges), bedrock ridges, sastrugi (ridges formed in hardened snow), with many of these features covered or surrounded by gravels or sands (Fig. 1, ) [1, 2, 3].

These landforms are also found on Mars [4, 5], Titan [6] and Venus. The regular spacing seen in many of these wind-eroded landforms is postulated to have arisen naturally out of wind-sediment relationships possibly controlled by bedrock hardness [7] and sediment supply [8] more than pre-existing fracturing or river channels, though both of those have also been implicated [9].

Our ongoing field project in the Puna of Argentina involves field operations over 5-7 days using observations and simple instrumentation. Our methods are designed to measure the effects of current and past winds, rock properties, and erosive power of sands and gravels on yardang and bedrock ridge morphologies. We investigate the proposition that the simple action of wind on solid surfaces can lead to the complex, self-organized forms observed where wind is dominant and surfaces are erodible.

The Puna Field Site and Methods

The Puna desert is dominated by young deposits of volcanic ash [10], evaporites and basalt cinder cones. The high elevation means air density is lower about ~1/3 compared to sea level. On Mars, the lower air density leads to large and high dust devils, and similarly large dust devils have been observed during our field campaigns in the Puna [11]. The ash deposits are widespread, and often contain up to km-scale (mega) yardangs. The youngest and softest ignimbrite, called the Campo de Piedra Pomez (CPP) [10], contains abundant medium-sized (meter-scale), mesoyardangs. We visited this region in 2015, 2018 and 2019 (Fig. 1).

Fig. 2. Smoke released near a lone yardang, revealing sideways (secondary) winds.

We examined field relationships such as orientations of yardangs, rock hardness and layering. We observed differences in rock colors related to intrinsic composition as well as weathering over time. We recorded relative matrix/pumice hardnesses and subsequent variations in erosional properties. We measured locations and sizes of wind indicators such as dedos (protrusions protected by harder lithics) and scours. We observed the action of wind on a single yardang over the course of a 7-day field excursion with an array of small instruments including Kestrel anemometers, simple smoke candles and a camera (Fig. 2), and a tuft net [12]. We deployed two DJI Mavic drones across the main CPP field to obtain a 3 cm DEM (Fig. 3), which also reveals parameters such as length, orientation, and spacing.

Key Observations

Winds over the time we observed the lone yardang (Fig. 3) in 2019 were dominantly from a direction oblique to the yardang long axis orientation and previously observed primary winds. This secondary wind may impact yardang size and shape. Preliminary results from study of the drone DEM obtained in 2019 reveal a 1:1 width/spacing relationship, similar to other studies. This is ascribed to the steady operation of wind and erosive agents over time on a relatively uniform substrate. A similar ratio was found using a DEM for a portion of the Medusae Fossae Formation (MFF) on Mars.

A dark orange coating on the leeward sides of the yardangs [13] (Figs. 2 and 3) is not presently being eroded. They are likely older surfaces reflective of the slopes of the wind-eroded surfaces at the onset of yardang emergence.

Fig. 3. Drone view of CPP yardang field (DEM images obtained from higher altitude). Person for scale.

Summary and Conclusions

Field studies in the Puna have revealed that unique landforms emerge when wind is dominant. Regularly spaced features such as yardangs or ridges emerge out of the interaction between wind and bedrock. Sizes and spacings of features likely reflect rock hardness properties. The utility of simple, reconnaissance-style field campaigns is evident in the knowledge gained through our studies of the Puna.

References

[1] Blackwelder (1934), Yardangs. GSA Bulletin 45.

[2] Ward (1979), Yardangs on Mars. JGR 8147-8166.

[3] de Silva et al. (2013) Gravel-mantled megaripples of the Puna, GSA Bulletin 125.

[4] Greeley & Iverson (1985), Threshold speeds on Venus, LPSC.

[5] Kerber et al. (2011), Origin of Medusa Fossae Formation Mars, Icarus 216.

[6] Paillou et al. (2016), Radar scattering of linear dunes and mega-yardangs on Titan, Icarus 270.

[7] de Silva S. et al. (2010), Yardangs in terrestrial ignimbrites, PSS 58.

[8] Pelletier et al. (2018), Yardang development JGR 123.

[9] Dong et al. (2012), Yardangs in the Kumtaugh, Geomorphology 139.

[10] Baez et al. (2020), Puna flow dynamics, Bull. Volc. 82.

[11] Lorenz & Radebaugh (2016), Dust devils in thin air, GRL 43.

[12] Kerber et al., in prog, Puna Yardang Observations.

[13] Aulinas et al., (2015), Rock Varnish in Dusty Regions, ESP 40.

How to cite: Radebaugh, J., Kerber, L., McDougall, D., Sevy, J., Rabinovitch, J., and Lorenz, R.: Landscapes of the Argentine Puna Reveal Conditions and Processes on Wind-Eroded Planetary Surfaces, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-715, https://doi.org/10.5194/epsc2022-715, 2022.

Introduction

Sedimentary deposits developed in High-Altitude Andean Lakes (HAAL) share some extreme and environmental characteristics that made them excellent analogues for planetary geology and astrobiology research. These conditions favor the development of a diverse and abundant microbial biota that influence mineral precipitation (e.g. carbonates) and the develpoment of microbially influenced sedimentary deposits typically know as stromatolites. To recognize and differentiate stromatolites from similar laminated deposits purelly formed by chemical processes is not straightforward, and Archean stromatolites are a good example. This makes HAAL good environmental analogues to study microbe-mineral proceeses, and the associated biosignatures. The recent findings of putative marginal lacustrine and delta deposits in the Jezero crater on Mars surface highlight the potential of these systems from and astrobiology perspective. The origin and characteristics of these martian carbonates is still unknown so the evaluation potential scenarios in comparable environmental conditions may shed some light into this uncertainties.

The Laguna Negra (a high altitude lake in Catamarca Province, Argentina) is an outstaning example of HAAL where an active microbial mat system and associated carbonate deposits is well developed. These are located in the mixing zone between groundwater spring-fed pools and the main lacustrine system. The Laguna Negra is a unique natural laboratory that fulfills the environmental criteria suggested for early Earth (Archean) and Mars (Noachian) where spectrum of biotic and abiotic process can be studied improving our ability to interpret the sedimentary record on our planet and beyond.

Geological setting

The Laguna Negra is a shallow hypersaline lake where the pH of the main lake and the groundwater springs feeding the lake fluctuates between ~6 and ~8 and salinity between ~320 and ~9 ppt respectively. The mixing zone between the main lake and groundwater is oversaturated with respect to calcite and aragonite. The carbonate belt consists of oncoids, stromatolites, and laminar crusts that are spatially localized in different zones and associated to different microbial mats systems and chemical conditions. Particularly interesting are the laminar crusts, developed in a zone where no significant microbial mats has been observed, but where a diversity of morphologies and microtextures has been recorded. Although interpreted as purelly chemically precipitated, unravelling the different processes that controls this morphological varibality is still challenging.

Oncoids, Stromatolites and Laminar crusts

Oncoids represented by concentrically laminated discs, spheres, and flattened domes (cm to dm in diameter) that can coalesce to form more complex structures and are typically associated with well-stratified diatom-rich microbial mats. The external surface surface can be smooth or can show pillar-like to shrub-shaped millimeter scale protrusions and ornamentations, particularly on the side affected by wind and currents. Oncoids are partially buried and can show lateral protrusions at the sediment–water and the air–water interface. Although oncoids are sub-spherical in shape, they can show asymmetric growth (bigger below the sediment–water interface). Complex lamination is also a result of oncoid rotation, particularly by cryoturbation and bioturbation.

Although water mixing, CO₂ degassing, and evaporation are particularly important to trigger carbonate precipitation the influence of microbial mats is visible in the macromorphologies (differential growth within the anoxic zone related to metabolisms that increase alkalinity) and a diverse set of microtextures some of which are interpreted as microbially influenced.

Stromatolites more localized and represented by centimeter to decimeter-scale laminated structures (up to 25 cm) that typically have a planar or laminar to columnar shape. They are observed associated with dark colored microbial mats and usually are encrusting the upper surface of oncoids. The columnar structures are usually centimeter-sized. Internal lamination is irregular, overlapping, crenulated-micritic to micro-peloidal laminae that preserve abundant organic remains. These features are suggestive of microbially influenced texture.

Laminar crusts show a patchy distribution and represented by millimeter to decimeter carbonate crusts encrusting volcanic rocks, peloidal sediments as well as organic remains. Can also develop dome-shaped morphologies showing concentric growth patterns. These concentric structures can be slightly assymetrical, showing preferential growth towards the upper half (as opposed to oncoids). Oriented and elongated structures are common (by wind-driven currents in the lake). Plates and domes can be rotated and/or coalesce to form more complex structures or more extensive platforms along the lakeshore. The surface can be smooth or show dendritic to pustular patterns or protusions as well as travertine-like microterracetes.

Isopachous regular laminane is the most common building block, as stated showing a concentric pattern but it is worth mentioning that the wind-oriented structures, in cross-section, develop more complex micro-textures (shrub-like to dendritic/micro-stromatolite microfabrics) that resemble microbially influenced structures.

Given the absence of microbial mats, and the macro-morphologies and micro-textures described (e.g., lamina regularity and degree of inheritance, lack of organic remains within the lamina), these structures have been interpreted as predominantly chemically precipitated carbonates, triggered by oversaturation related to water mixing, strong CO2 degassing, and evaporation.

Final considerations

Both, physocochemical and microbial processes can contribute to a diverse range of morphologies and carbonate microtextures and it is not easy to urvanel their relative contributions. Oncoids, stromatolites and laminar crusts show some distinctive features that suggest some of the driving controls, but also some overlapping characteristics that may be difficult to discriminate. As an example, although laminar crusts generally show (in cross section) a strong lamina regularity, a more diverse set of microtextures can be produced by the influence of advective-diffusive processes, localized scarbonate precipitation, rotation due waves, and cryo-bioturbation, thus increasing lamina complexity that can be confused with microbially influenced textures. Possible origins of the carbonates recorded at Jezero crater, for example including carbonate crusts developed over the basaltic substrate, pore-vein-filling carbonate cements, reworked carbonate material, or even stromatolite-like structures. Although chemical biosignatures (trace element distribution and isotope fractionation) are central in the tool box of astrobiologists, to recognize the putative biogenicity of these carbonates it is necessary to combine chemical analysis with the information provided by the external macro-micro morphology and the internal macro and micro microfabric, something that may not be possible when dealing with rover or image based analysis on outcrops or with sample returned to Earth, where part of the context may be lost.

How to cite: Gomez, F., Matic, M., Perez Valdenegro, P., Boidi, F., and Mlewski, C.: High-Altitude Andean Lakes as Natural Laboratories for Planetary Geology and Astrobiology Research: The Laguna Negra case (Argentina), Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-822, https://doi.org/10.5194/epsc2022-822, 2022.

Abstract: This work describes a new high-altitude Mars analogue site and the stratification of microbial communities with depth within lake sediments. Understanding how microbial communities at this site change with depth may give insights into the type of metabolism that may have dominated paleolake environments on early Mars and the resulting biosignatures.

Introduction: High-Altitude Andean lakes (HAALs) are poly-extreme environments which mimic many of the physiochemical conditions present on Mars during the Noachian (4.1 – 3.7 Gya) and Hesperian Mars (3.7 – 3.0 Gya)^1,2. This combination of physiochemical conditions has led to HAALs being identified as natural laboratories for studying life under conditions analogous to early Earth and early Mars^1,3. Present-day Mars is a cold, hyper-arid planet with surface conditions incapable of supporting liquid water in most locations. However, orbiter, rover, and lander missions have uncovered extensive hydrated mineral deposits and widespread geomorphological evidence of long-lasting fluvial and lacustrine environments, which dried up in the Hesperian⁴. Following the collapse of the martian magnetosphere, conditions on the surface would have become increasingly inclement. However, lake sediments may have offered refuge against desiccation, intense ultra-violet radiation (UV), large diurnal temperature fluctuations, and reduced atmospheric pressures with biosignatures potentially being preserved following lithificaytion⁵. For this reason, the study of analogue environments and the nascent microbiome is crucial in informing targets for biosignature detection. Despite their relevance to early Hesperian Mars, the lakes of the Argentinian Puna (a plateau between 3000 – 6000 m) remain understudied⁶. Here we present the geochemistry and microbial communities associated with the lake water and sediments from the previously undescribed Laguna de Antofagasta (LDA; Catamarca, Argentina, -26.111148, -67.407338) were analysed. We demonstrated that these communities change with depth, which will aid in identifying relevant metabolisms and biosignatures to inform current and future life-detection missions. 

Methods: Lake water and cores (5 x 30 cm) were collected from five sample points located around the perimeter of LDA in April 2022 (Figure 1). For each microbial core, a sister core was collected for geochemical analyses (pH, temperature, and dissolved oxygen (DO) readings) to avoid contamination of microbial cores. Each core was divided evenly into an upper, middle, and bottom section before being stored under anaerobic conditions. The lake water samples were collected and filtered using 0.22 µm Sterivex filters, and all samples were transported to The Open University, UK at 4˚C. Pore and lake water were analysed using ICP-OES and IC analysis to collect bulk chemical and ionic concentrations. DNA was extracted using the XS buffer method⁷, and 16S rRNA gene sequencing was performed to characterise the microbial communities. In addition, Postgate B media was used during culture-dependent analysis to isolate sulphate-reducing bacteria (SRB).