Evidence for life discovered in 3.48 billion-year-old hot spring deposits in Australia is presented in a study published in Nature Communications this week. The findings extend the known geological record of inhabited terrestrial hot springs on Earth by around 3 billion years, and represent some of the earliest evidence for life on Earth.

Tara Djokic and colleagues examined 3.48 billion-year-old hot spring deposits from the Pilbara Craton in Western Australia. To establish whether the deposits were marine or terrestrial, the team identified the presence of geyserite, which is a mineral deposit created from hot silica fluids, and is only found in terrestrial hot springs. Within the deposits they discovered stromatolites (layered formations, produced by the activity of microbes) and other microbial bio-signatures, indicating that a diverse variety of life existed in this setting 3.48 billion years ago.

Although it is well established that terrestrial hot springs have the potential to host a diverse range of life, evidence for life in this type of setting has previously only been discovered to have existed around 400 million years ago.