It is well known that New Zealand hosts spectacular hot-springs associated with a live super-volcano. Less well known is that these geothermal systems are rapidly mineralizing, entombing within silica a biota adapted to high temperatures, and thus serving as an extreme environment analog in the continuing search for the earliest signs of life on Earth and potentially other planets, such as Mars. This hypothesis stems from the following observations – the deepest roots of today’s “Tree of Life” constitute heat-loving microbes in hot springs; some Precambrian settings for early life were silica-rich and hydrothermally influenced; and siliceous deposits recently found by Martian rover Spirit are interpreted as hot-spring related.

The problem in trying to peer back into “deep time” on Earth is that the very old rocks which may contain the earliest traces of life also tend to be very “beaten up” by later geological events. It can be difficult to prove both biogenicity and original environmental setting in altered rocks billions of years old. Hence, Kathleen Campbell’s research examines siliceous hot-spring deposits to track the integrity of their fossil preservation through time. This method allows us to follow microbes as they “turn to stone” and to examine their history far back into the geological record, thereby fine-tuning studies on the recognition of early terrestrial life. The research has led to discovery of giant, Yellowstone-style, paleo-geothermal systems in the Late Jurassic (150-million-year-old) of Patagonia, Argentina. It also has confirmed hydrothermal signatures in fossil microbe-rich, 3.33 billion-year-old shallow marine rocks of South Africa.

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