Spectroscopic Studies on the Puga Hot Spring Deposits, Ladakh, an Astrobiological Martian Analog Site in India

Hot spring localities on continents may represent the most probable locales for the formation of early life constituents on Earth. Apart from liquid water and carbohydrates, these components also include elements like boron that are crucial for stabilization of the complex organic molecules that constitute life. Many of these life sustaining ingredients are commonly found in the vicinity of terrestrial hot springs. Analogously, similar existing or extinct hot spring localities on other planets may constitute prospective astrobiological sites. In the present study, we have characterized the complete mineralogical assemblage of the Puga hot spring deposit, Ladakh, India, using detailed spectroscopic and X-ray diffraction studies. The spectroscopic characterization was done using both field as well as lab based visible/near-infrared (400-2,500 nm) and lab measured mid-infrared (4,000-400 cm(-1)) hyperspectral data. The identified mineral phases include Na-borates, such as borax and tincalconite, and hydrous sulfates such as jarosite, alunite, copiapite, tamarugite, and gypsum, in conjunction with native sulfur, halite, and opaline silica. Borate minerals have been identified from the valley-fill material along with halite and opaline silica, whereas sulfates occur alongside crystalline sulfur deposits. We have compared mineral assemblages found in Puga with other hot spring/hydrothermal deposits on Earth identified as Martian analog sites, and also with mineral assemblages identified in situ on Mars. We argue that the spectral characterization of hydrated borates in natural association with hydrous sulfates can be used for identification of fossil/paleo hydrothermal settings on Mars that are prospective in the search for extinct/extant extra-terrestrial life.