Figure 1.9 Iron-oxidizing environment. Heated rainwater from magmatic heat convection produces steam that contacts lava and extracts soluble Fe(II). (1) Fe(II) is solubilized in the steam water and (2) rises with steam through porous lava fissures and cracks and reaches the iron vent openings of SW4, as the Fe(II) contacts air (3) Archaea utilize the Fe(II) in their growth by oxidizing the iron to Fe (III). Air oxidation also takes place and adds Fe(III) to the iron-rich layer formed on the solid rocks within the iron vent. (Image credit: the authors).
Figure 1.10 Salt cave environment. (1) Rainwater recharge of the Hawaiian ground water passes slowly through the porous lava rich ground. Fractured lava is heated by the underlying magma and as (2) rainwater descends through crevices and fissures it extracts soluble salts that are present. At greater depths the descending water boils and provides steam and heat so that (3) salts continue to slowly dissolve, rise with steam and deposit as evaporites on a cooler nearby wall, ceiling or as in this model, a shelf. (Image credit: the authors).
Models of the sulfur and ammonia oxidizing environments are available in a previous study [1.3].
1.7 Conclusions
The worldwide abundance of fumaroles compared to hot springs make this an ideal choice as a habitat for early development of life on Earth. These primitive steam habitats characterized by two extreme physical features, low pH and high temperature, typically flourish with Archaea. The fact that these organisms seem to have persisted from the earliest times argues that they may represent the type of living organism that could have evolved else-where beyond planet Earth. Steam caves/vents, while limited in diversity [1.7], represent and remain a rich and potentially useful and reliable source for isolation of unknown and unexplored life forms.
Acknowledgments
We thank the following National Park Service members for assistance with access to collections; Michael Magnuson, Wildlife Biologist, Lassen Volcanic National Park; Rhonda Loh, Chief of Natural Resources Management and Keola Awong, Cultural Specialist and Native Hawaiian Liaison for facilitating our collections of fumaroles and supporting our research efforts in Hawai’i Volcanoes National Park. Jeff Sutton and Aaron Pietruszka, US Geological Survey, offered guidance on the Geology/Geochemistry of our collection areas. Benno Spingler prepared Figure 1.1; Xzayla Zabiti and Anthony Correy provided ideas and participated in the design and construction of the steam collector. We thank our graduate students, Dean Ellis, Courtney Benson, Kate Wall, and Jenny Cornell, and undergraduates, Christa Anderson and Wendy Gutierrez. The authors acknowledge the assistance of Steve Barlow, and use of equipment at the San Diego State University Electron Microscopy Facility acquired by NSF Instrumentation grant DBI-0959908, SB Barlow. Ingrid Niesman, Director of the SDSU Electron Microscope Laboratory facilitated the SEM work. Generous contributions of Schering-Plough Biopharma assisted this study.
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