Multidisciplinary approach of the hyperarid desert of Pampas de La Joya in southern Peru as a new Mars-like soil analog

Abstract

The distribution of living organisms, organic matter, and chemical properties in Mars-like environments on Earth can be used as a model to guide the investigation of possible habitable environments on Mars. This work aims to demonstrate that the place known informally as the “Mar de Cuarzo” (Sea of Quartz) in the Pampas de La Joya desert southern Peru (between 16°S and 17°S latitude), contains soils with characteristics similar to those found on the Martian surface. Using a multidisciplinary approach, we studied the environmental data, geology, organic matter content, oxidant activity, and microbiology of this area. Our data show that (1) Mar de Cuarzo is a hyper arid area with a lower concentration of organic matter than those found in the Mars-like soils from Yungay area (Atacama Desert in Chile), while at the same time having, comparable extreme environmental conditions, and very low levels of microorganisms. (2) The detrital components of the soils come essentially from the Andean volcanic chain and local outcrops of Precambrian gneisses and Cretaceous granitic batholiths. (3) The presence of microclimates, geomorphological features, and the high influence of the “El Niño Southern Oscillation (ENSO)” allowed the formation of exotic and heterogeneous chemical deposits in these soils, including iron oxides, sulfates, and other evaporites. (4) Thermal volatilization in these soils (using methods similar to the Viking and Phoenix instruments) shows high oxidant activity. (5) Labeled release experiment (similar to the Viking instrument) shows high degradation of nutrients added in these soils.

Altogether, the Mar de Cuarzo area in the Pampas de La Joya is an interesting place for astrobiological studies as a new analog to Mars, and for comparative analyses with other hyperarid analogs as Yungay.

Introduction

Mars is of great astrobiological interest as a possible location for past or present extraterrestrial life (Bada et al., 2005). Most of our accumulated knowledge on Mars comes from ground and space-based observations (Poulet et al., 2007), Martian meteorites (McKay et al., 1996, Glavin et al., 1999), and spacecraft landers (Squyres et al., 2004, Squyres et al., 2009). Reaching and landing successfully on the surface of Mars is a challenging task because technical components and experimental procedures on board of the spacecraft must operate efficiently and properly upon landing.

In order to test rover instrumentation before mission launch and improve the chances of success, experimental analyses of terrestrial soils similar to those that will be encountered on Mars have become crucial (Sarrazin et al., 2005). Mars-like environments on Earth provide an important tool to prepare for the search for life on future missions to Mars, and lead to a better understanding of the geological, geochemical, and microbiological process that could have occurred on the Red Planet. However, no current analog is appropriate for all necessary tests. Sites on Mars that has been proposed as targets for the search include the Martian surface soils, the fringes of the Martian polar ice, liquid water aquifers that may exist in the subsurface, and deep in the ice-rich Martian polar permafrost. Each of these Mars environments has corresponding analog sites on Earth (McKay, 2004a). Additionally, there is clear evidence for different soil types in Mars, suggesting a range of formation conditions and alteration mechanisms (Gendrin et al., 2005, Morris et al., 2006). Because of this heterogeneity, it is necessary to identify a soil analog that is suitable for the study required.

The analogs on Earth are geographic and chemically diverse, and they also illustrate preservation mechanisms that could guide the search for fossil and structural remnants of microbial life, which could be extrapolated to Mars (McKay, 2004b).

An analog to Mars extensively studied and of great scientific interest is the Atacama Desert, located in northern Chile and southern Peru, which lies on the west slopes of the central Andes between 15°S and 30°S at elevations between sea level and 3500 m.a.s.l. (Houston and Hartley, 2003). This desert is considered one of the most, if not the most, arid regions on Earth (McKay et al., 2003) and the arid core of the Atacama near Yungay Chile contains Mars-like soils (24°4′9.6″S, 69°51′58.8″W) (Navarro-González et al., 2003). These soils are Mars-like in that they contain very low levels of organic matter (20–40 ppm of organic C), a non-biological oxidant, the virtual absence of microscopic life, and exotic mineralogical composition including iron oxides, all of which are common characteristics expected on Mars (Navarro-González et al., 2006). Additionally, the Atacama is one of the oldest deserts in the world with sustained aridity since the Early Miocene (Dunai et al., 2005) and hyperaridity from the Late Pliocene (Hartley and Chong, 2002). Thus it presents interesting landscapes similar to various regions of Mars. Although there are areas considered hyperarid in more than 3000 km along the desert (Houston and Hartley, 2003), the vast majority of studies have focused on studying the Yungay region from northern Chile as well as some precipitation gradients going south from Yungay to ⩾28°S (Navarro-González et al., 2003, Navarro-González et al., 2006, Ewing et al., 2006).

While studies of these analogs help to understand processes that occur in extreme environments in terms of the geological, chemical, physical, and microbiological fields, they could not be well understood or generalized if there are no other environments with the same or different level of development or evolution over time where these processes can be compared.

Recently, other area named Pampas de La Joya, located in the Atacama region of southern Peru between 15°S and 17°S, has been the focus of astrobiological interest because it exhibits hyperarid soils with the lowest levels to organics – even lower than those presented in Yungay. This fact suggested that this region might also contain Mars-like soils (Valdivia-Silva et al., 2005, Valdivia-Silva, 2009). Peeters et al. (2008) showed that these soils had large differences for the geochemical parameters such as pH, redox, and ion concentrations, and chemical composition even for samples taken only several meters apart. Furthermore, they showed high levels of amino acid destruction under Mars-like conditions, indicating interactions between organics and mineralogy composition in these samples that can produce highly oxidizing conditions. Additionally, other recent study that used thermal volatilization technique in six types of hyperarid soils from the Pampas de La Joya showed high oxidant activity depending of organics content and mineralogy composition (Valdivia-Silva et al., 2009). The nature of oxidant(s) present in the soils from Pampas de La Joya is still unknown. Similar to the organic analyses, microbiological studies have also been focused primarily in the Yungay area, although 1000 km to the north, the Pampas de La Joya also presents similar extreme conditions for life. Indeed, comparing the type of microorganisms present in these soil types versus these found in Yungay could help us to better understanding the processes of bacterial evolution in absence and/or minimal amount of water.

In this paper, we report the presence of Mars-like soils in one of the most important locations within the La Joya desert. Since, this place has an independent geographic evolution from Yungay, should allow a better understanding of the geochemical, geomorphological, and microbiological processes in hyperarid soils elsewhere, including the surface of Mars.