Hot spring deposits 3.48 billion years old with the oldest convincing evidence of life on land. The discovery challenges the assumption that life began in the deep ocean. Darwin's speculation about warm little ponds might have been right, and these rocks could be where our story began.
Darwin's lost world
In the Pilbara Craton of Western Australia, you can find some of the oldest, most stable blocks of the Earth's crust. The rocks here, part of the Dresser Formation, are approximately 3.48 billion years old. They preserve an environment that looks surprisingly familiar: a terrestrial hot spring field. This discovery, made by a team including researchers Tara Djokic and Martin Van Kranendonk, provides strong evidence that life existed on land much earlier than previously thought. Before this find, the oldest evidence for life on land came from 2.7-2.9 billion-year-old soils in South Africa. The Dresser Formation fossils push that record back by about 580 million years.
The significant piece of evidence for this ancient land-based environment is geyserite, a silica mineral that only forms in the near-boiling water of terrestrial hot springs and geysers. Its presence here, dated to 3.48 billion years ago, confirms the area was not a shallow sea as once assumed, but a volcanic caldera dotted with freshwater pools. This find supports Charles Darwin's 19th-century hypothesis that life may have originated in a "warm little pond," rather than the more popular deep-sea hydrothermal vent theory.
The fingerprints of ancient life
Within the layers of geyserite and other rocks, scientists identified a variety of biosignatures. These include stromatolites, which are layered structures built by communities of microbes. While stromatolites of this age have been found before, their association with geyserite confirms they lived in a terrestrial setting. Other discoveries include fossilized micro-stromatolites and textures indicative of microbial mats. Well-preserved bubbles are also present, believed to have been trapped in the sticky substances secreted by microbial communities.
The discovery is important for astrobiology and the search for life on Mars. The Martian crust has an age similar to the Pilbara deposits, and ancient hot spring deposits have been identified on the Red Planet, specifically in the Columbia Hills region explored by the Spirit rover. The fact that life could thrive and be preserved in this type of environment so early in Earth's history is why Martian hot springs are a prime target for missions like the Perseverance rover. The Dresser Formation provides a direct geological analogue, helping scientists know what kinds of rocks and biosignatures to search for.
💡Fun Facts
The Pilbara Craton is one of only two well-preserved pieces of Earth's ancient crust from the Archaean Eon, the other being the Kaapvaal Craton in Southern Africa.
The mineral geyserite, evidence of a terrestrial environment, is the same type of deposit found today at geysers in Yellowstone National Park and Iceland.
The microbes of the Dresser Formation lived before the Great Oxidation Event, in an atmosphere with almost no free oxygen.
The discovery pushed back the record of life in terrestrial hot springs by an incredible 3 billion years.
The area is remote, unfenced, and technically accessible at all times. However, it is located in an extremely harsh and isolated desert environment.
Admission
Free
Accessibility
Access requires a high-clearance 4WD vehicle. There are no paved roads or facilities. The terrain is rugged and rocky. Travel is not recommended during the extreme heat of the summer months (November-March). Independent travel requires significant preparation and experience in remote desert travel.