Vol. 10, No. 7 July 2000 INSIDE • Penrose Conference Report, p. 10 GSA TODAY • Employment Service, p. 17 • Earth Science Week, p. 29 A Publication of the Geological Society of America Hydrothermal Systems: Doorways to Early Biosphere Evolution Jack D. Farmer, Department of Geology, Arizona State University, P.O. Box 871404, Tempe, AZ 85287, USA,
[email protected]. ABSTRACT Hydrothermal systems may have provided favor- able environments for the Figure 1. prebiotic synthesis of Travertine thermal organic compounds neces- spring system at sary for life and may also Angel Terrace, have been a site for life’s Mammoth Hot origin. They could also have Springs, Yellowstone provided a refuge for ther- National Park, Wyoming. mophilic (heat-loving) microorganisms during late, giant-impact events. Phylo- genetic information encoded in the genomes of extant thermophiles pro- vides important clues about this early period of bio- sphere development that are broadly consistent with geo- logical evidence for Archean environments. Hydrother- mal environments often exhibit high rates of miner- alization, which favors microbial fossilization. Thus, hydrothermal deposits are INTRODUCTION often rich storehouses of paleobiologic information. Hydrothermal systems develop anywhere in the crust where water coexists with a heat source. This is illustrated by studies Hydrothermal systems were important in the differentiation and early evolution of Earth because of the microbial biosedi- they linked the global lithospheric, hydrologic, and atmospheric cycles of the elements (Des Marais, mentology of hot springs in 1996). Over geologic time, volatile chemicals released by hydrothermal systems have contributed Yellowstone National Park significantly to the evolution of the oceans and the atmosphere.