February Monthly Meeting

Where: Space Place – Carter Observatory
When: Wednesday 7th February 2018 at 7:30 pm
Topic: Hot springs and the search for life on early Earth and Mars – Professor Kathleen Ann Campbell

Terrestrial hot springs harbour microbes adapted to life at high temperatures, up to 100 ⁰C. These ‘extremophiles’ occur in varied hot-spring habitats, from near-boiling vents and geysers to cooler terraces, pools and geothermally influenced marsh, river, and lake settings. Spring discharges contain relatively high concentrations of dissolved ions (silicon, carbonate, iron) and thus may entomb microbial remains in a built-up solid rock deposit, potentially preserving them for hundreds of millions of years or more. Therefore, they represent an array of microbially dominated ‘extreme environments’, encompassing the upper temperature limit for life on land, with a geological record that previously extended back to the Devonian (400 million years ago). ‘Young’ hot spring deposits (in our studies ranging from 150 million years old to today, including New Zealand) are cited as analogue settings for early life on Earth and possibly Mars, at a time (>3 billion years ago) when both planets had no atmospheric free oxygen, early Solar System debris was bombarding their surfaces, and volcanism/impacts and flowing water may have produced ancient hot springs. Recently our team has pushed back the existence of ancient hot springs on Earth by an additional ~3 billion years, and the occurrence of fossil life on land back ~580 million years, with the discovery of ~3.5 billion year old, fossil-rich hot-spring deposits in the Pilbara, Western Australia. Life was already surprisingly diverse so very long ago, and therefore this finding hints at its much older origin (~4 billion years ago), in an as yet unknown setting. Furthermore, Mars Spirit rover studies at Columbia Hills, Gusev Crater, have uncovered evidence for extra-terrestrial hot springs that are at least 3 billion years old. Similar features forming today on Earth entomb microbial life. The current NASA Mars 2020 mission site selection process is underway and our team has advocated a return to Columbia Hills to sample the finger-like, opaline silica deposits there for future sample return to Earth for detailed assessment for potential biosignatures.

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