Searching for microbial life remotely: Satellite‐to‐rover habitat mapping in the Atacama Desert, Chile

Abstract

[1] The Atacama Desert, one of the most arid landscapes on Earth, serves as an analog for the dry conditions on Mars and as a test bed in the search for life on other planets. During the Life in the Atacama (LITA) 2004 field experiment, satellite imagery and ground-based rover data were used in concert with a 'follow-the-water' exploration strategy to target regions of biological interest in two (1 coastal, 1 inland) desert study sites. Within these regions, environments were located, studied and mapped with spectroscopic and fluorescence imaging (FI) for habitats and microbial life. Habitats included aqueous sedimentary deposits (e.g., evaporites), igneous materials (e.g., basalt, ash deposits), rock outcrops, drainage channels and basins, and alluvial fans. Positive biological signatures (chlorophyll, DNA, protein) were detected at 81% of the 21 locales surveyed with the FI during the long-range, autonomous traverses totaling 30 km. FI sensitivity in detecting microbial life in extreme deserts explains the high percentage of positives despite the low actual abundance of heterotrophic soil bacteria in coastal (<1-10 4 CFU/g-soil) and interior (<1-10 2 CFU/g-soil) desert soils. Remote habitat, microbial and climate observations agreed well with ground-truth, indicating a drier and less microbially rich interior compared to the relatively wetter and abundant biology of the coastal site where rover sensors detected the presence of fog and abundant surface lichens. LITA project results underscore the importance of an explicit focus by all engineering and science disciplines on microbially relevant scales (mm to nm), and highlight the success of satellite-based and 'follow-the-water' strategies for locating diverse habitats of biological promise and detecting the microbial hotspots within them.Citation: Warren-Rhodes, K., et al. (2007), Searching for microbial life remotely: Satellite-to-rover habitat mapping in the Atacama Desert, Chile,

How Do Modern Extreme Hydrothermal Environments Inform the Identification of Martian Habitability? The Case of the El Tatio Geyser Field

“…Because of the altitude and latitude of these sites, a number of environmental parameters similar to those of ancient Mars are present together and include a low average temperature, high-daily temperature variations, thin atmosphere, high solar irradiance, ice, reduced yearly precipitation, and a volcanic and hydrothermal environment. Because of this unique set of conditions, NASA-funded researchers undertook an extensive study in preparation for the search for life on Mars (e.g., [67,68]). In the Chilean Andes, near the Atacama Desert, is located the geothermal site of El Tatio, the largest geyser field in the southern hemisphere.…”

Life in the Atacama: Searching for life with rovers (science overview)

“…SPI provided the intermediate scale in contextual imaging, between the global satellite imagery and the local‐to‐microscopic scale obtained from the fluorescence imager. This scaling continuum and nested imagery was critical in the evaluation of the presence of oases at metric to micrometric scale [ Warren‐Rhodes et al , 2007a, 2007b]. The SPI imager was also used to detect atmospheric changes, specifically the presence of morning and late afternoon fog events in the Coastal Range (as shown at Site A in Figure 1), which signaled the location of potential water accumulation on the ground and, possibly, the concentration of life.…”

“…The FI was used to identify several possible biosignatures [ Cabrol et al , 2005; Wettergreen et al , 2005a, 2005b; Weinstein et al , 2006, also submitted manuscript, 2007; Warren‐Rhodes et al , 2005, 2007a, 2007b]. Chlorophyll was checked by the addition of water to the targets through direct spray.…”

“…An overview of the scientific and technical results of the field investigation is given in section 6. For detailed results on the geological mapping, mineralogy and biology, see Warren‐Rhodes et al [2007a, 2007b], A. Hock (Life in the Atacama: A scoring system for mapping habitability and the robotic exploration for life, submitted to Journal of Geophysical Research, 2007, hereinafter referred to as Hock et al, submitted manuscript, 2007), J. Piatek et al (Surface and subsurface composition of the Life in the Atacama field sites from rover data and orbital image analysis, submitted to Journal of Geophysical Research, 2007, hereinafter referred to as Piatek et al, submitted manuscript, 2007), and S. Weinstein et al (Application of pulsed‐excitation fluorescence imager for daylight detection of sparse life in tests in the Atacama Desert, submitted to Journal of Geophysical Research , 2007, hereinafter referred to as Weinstein et al, submitted manuscript, 2007). Finally in sections 7 and 8 we discuss and conclude on the main results of the field investigations and how the lessons learned could inform future planetary exploration and serve the exploration of extreme terrestrial environments.…”

Application of pulsed‐excitation fluorescence imager for daylight detection of sparse life in tests in the Atacama Desert

“…The ability to acquire fluorescence data in daylight provided the LITA team a tool to potentially map life over large regions as the rover traveled throughout each day. The results of this aspect of the field study are reported by Warren‐Rhodes et al [2007a, 2007b]. More research is required to perfect the dye probes and probe penetration for optimal use.…”