Why are hot springs important in understanding the origin of life?
Charles Darwin proposed that life may have begun in a “warm little pond”. In reality, Darwin’s “warm little pond” may have been a hot spring. Hot springs allow organic compounds to form, react, and concentrate meaning the necessary ingredients for life could be created in hot springs. The discovery of the rock geyserite in 3.5-billion-year-old rocks provided evidence of life in hot springs 3 billion years earlier than originally thought. This paints a much different picture than the idea that life formed around deep-sea hydrothermal vents, held since 1977.
How has ancient life been preserved on Earth?
In hot spring environments, microbes and organic matter can become trapped in silica deposits, preserving the microbial community in-situ. Over time, organic material is replaced with silica from the hot spring, creating a mineral replica of the original organism. This allows us to better understand what organisms inhabited hot springs, how the microbial community was organised, and how the microbes may have evolved.
How does geology and biology interact in a hot spring?
Modern hot springs like Rotorua may seem like an inhospitable environment, but they actually contain a wealth of microbial life. These microbes aid in the growth of silica sinter digitates as microbial communities promote silica precipitation. The shape of the digitates (often called “finger-like” structures, and resemble fingers on a hand or tree branches) is influenced by the interaction of microbes with geology and environmental conditions. We study modern hot springs to better understand ancient hot springs where life on Earth may have formed.
How might ancient life be preserved in hot springs on Mars?
The Spirit Rover imaged opaline silica digitate structures at Home Plate in the Columbia Hills region of Mars. These digitate structures have the same morphology (or shape) as digitates found in the El Tatio hot spring in Chile. The El Tatio digitates were shaped in part by microbes. So have we seen evidence for life on Mars, but just don’t know it yet?
Where can we find evidence of early life on Earth?
The Pilbara region of Western Australia preserves a 3.5-billion-year-old hot spring field, that would have been similar to modern-day Rotorua, New Zealand or Yellowstone, USA. Across the ancient hot spring field are stromatolite fossils – wrinkly layers of microbes and sediments that built up over time. The stromatolite fossils in the Pilbara are the oldest convincing evidence of life on Earth.