From Intraterrestrials to Extraterrestrials — Viable Haloarchaea in Ancient Salt Deposits

Abstract

During several periods in the Earth’s history, immense sedimentation of halite and some other minerals from hypersaline seas took place. An estimated 1.3 million cubic kilometers of salt were deposited in the late Permian and early Triassic periods alone (ca. 240 to 280 million years ago; Zharkov 1981). The continental land masses were concentrated around the paleoequator and formed the supercontinent Pangaea (Fig. 5.1). Salt sediments developed in large basins, which were connected to the open oceans by narrow channels. The paleoclimate was warm and arid in a wide belt around the equator, causing large-scale evaporation. About 100 million years ago, fragmentation of Pangaea was beginning; the continents were displaced to the north, and folding of new mountain ranges such as the Alps and Carpathians was underway (Einsele 1992). As a result of these movements driven by plate tectonics, huge salt deposits are found today predominantly in the northern regions of the continents, e.g. in Siberia, northern and central Europe (Zechstein series), south-eastern Europe (Alps and Carpathian mountains), and the midcontinent basin in North America (Zharkov 1981). Growing interest is emerging in the exploration of microbial life in subterranean environments, such as deep sub-seafloor sediments, crustal rocks, sedimentary rocks, and also ancient salt deposits (for a review, see Pedersen 2000). It has been estimated that the total amount of carbon in the “intraterrestrial” prokaryotic mass on Earth may be as large or even exceed that of plants and prokaryotes growing on the surface of the Earth (Pedersen 2000).