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[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,

[1] As part of the three-year 'Life in the Atacama' (LITA) project, plant and microbial abundance were mapped within three sites in the Atacama Desert, Chile, using an automated robotic rover. On-board fluorescence imaging of six biological signatures (e.g., chlorophyll, DNA, proteins) was used to assess abundance, based on a percent positive sample rating system and standardized robotic ecological transects. The percent positive rating system scored each sample based on the measured signal strength (0 for no signal to 2 for strong signal) for each biological signature relative to the total rating possible. The 2005 field experiment results show that percent positive ratings varied significantly across Site D (coastal site with fog), with patchy zones of high abundance correlated with orbital and microscale habitat types (heaved surface crust and gravel bars); alluvial fan habitats generally had lower abundance. Non-random multi-scale biological patchiness also characterized interior desert Sites E and F, with relatively high abundance associated with (paleo)aqueous habitats such as playas. Localized variables, including topography, played an important, albeit complex, role in microbial spatial distribution. Site D biosignature trends correlated with culturable soil bacteria, with MPN ranging from 10-1000 CFU/g-soil, and chlorophyll ratings accurately mapped lichen/moss abundance (Site D) and higher plant (Site F) distributions. Climate also affected biological patchiness, with significant correlation shown between abundance and (rover) air relative humidity, while lichen patterns were linked to the presence of fog. Rover biological mapping results across sites parallel longitudinal W-E wet/dry/wet Atacama climate trends. Overall, the study highlights the success of targeting of aqueousassociated habitats identifiable from orbital geology and mineralogy. The LITA experience also suggests the terrestrial study of life and its distribution, particularly the fields of landscape ecology and ecohydrology, hold critical lessons for the search for life on other planets. Their applications to robotic sampling strategies on Mars should be further exploited.Citation: Warren-Rhodes, K., et al. (2007), Robotic ecological mapping: Habitats and the search for life in the Atacama Desert,