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.

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).