Biologic and Resource Analog Investigations in Low Light Environments (BRAILLE)

The proposed project will study what may be the best terrestrial analog in the continental U.S. for a key prospective astrobiological target on rocky planets: lava tube caves. Lava tube caves (LTC) have been identified on the Moon and Mars using satellite imagery (e.g., Haruyama et al., 2009; Cushing et al., 2007). Their restricted connection to the atmosphere are thought to represent opportunities for the retention of water (e.g., Williams et al., 2010), a requirement for living systems. Although considered an extreme environment in some aspects (e.g. limited availability of energy and nutrients for life), lava tubes offer stable physical and geochemical conditions and are sheltered from physical weathering and ultraviolet and cosmic ray bombardment. Caves offer direct access to the deep subsurface of extraterrestrial rocky planets without costly and complex drilling/excavation programs. These features, in turn, could serve to enhance the preservation of recognizable biosignatures from the past (e.g., Boston et al., 2001; Léveillé and Datta, 2009). BRAILLE will provide new knowledge about operating a rover remotely in extreme darkness. Although NASA has no current mission plans to target a planetary cave, the upcoming Resource Prospector mission will visit permanently shadowed craters on the moon. This is a significant new challenge, as NASA has limited experience operating in dark settings. Caves are not a perfect analog to the dark lunar surface, but they are a good analog for the extreme darkness of lunar shadowed regions, which are otherwise difficult to simulate on Earth’s surface, even at night. BRAILLE will address several key science questions: SCI1: What are the abundance, diversity, & function of microbial populations in caves, and how do they vary with the physical conditions within a cave? SCI2: To what extent do living microbial communities create persistent biosignatures? SCI3: How do these biosignatures vary with physical parameters in LTCs? SCI4: Do microbial communities influence rock alteration and/(or) extent of secondary mineralization in these low light environments and what information regarding paleohydrology/paleoclimate/paleomicrobiology are recorded in cave materials? Investigations of the microbiology of deep mine environments, subsurface features analogous to caves, have suggested that biodiversity can be quite limited in these extreme environments (e.g., Lin et al., 2006; Sahl et al., 2008; Chivian et al., 2008). However, studies of cave microbial communities have revealed significant biodiversity (e.g., Northup et al., 2003; Garcia et al., 2009; Snider et al., 2009; Moya et al., 2009). We propose to explore a suite of caves with varying rock and fluid compositions, ages, and environmental conditions (such as light, temperature, pH, relative humidity, presence or absence of standing water, ice) and compare and contrast the manner in which these factors influence the biota and the development (and preservation) of biosignatures. Additionally, field instrument data will be compared with laboratory data to evaluate the accuracy and utility of the field equipment.