There has always been a big puzzle about the emergence of life on Earth billions of years ago. A new research has provided a fresh argument in this regard, saying that floating rafts of glassy, porous, and gas-rich pumice could have a significant contribution to the origin of life on Earth.
Researchers from Oxford University and the University of Western Australia have argued that with a remarkable set of properties, volcanic pumice could have provided a suitable habitat for the ancient communities of microorganisms that emerged on Earth prior to some 3.5 billion years ago.
According to the study, published in the September issue of the journal Astrobiology, at the time of eruption, pumice develops the highest surface-area-to-volume ratio of any type of rock. It is the only known rock type that can float like a raft at the air-water interface.
Modern day pumice raft on Santorini beach. Photo: University of Oxford
Researchers believe that after it erupts from a volcano, the pumice floats in rafts and enters the tidal zone. After that it becomes beached for long periods of time close to the shore, thus, providing many opportunities for life to develop.
The pumice is exposed to a variety of conditions, including dehydration, and has a remarkable ability to absorb metals, organics and phosphates as well as hosting organic catalysts, such as such as zeolites and titanium oxides, said Professor Martin Brasier of Oxford University's Department of Earth Sciences. Brasier led the work with David Wacey of the University of Western Australia.
3,500m year-old pumice from the Apex Chert, Australia. Photo: University of Oxford
Other key things that pumice is potentially exposed to during its lifecycle include lightning associated with volcanic eruptions, oily hydrocarbons and metals produced by hydrothermal vents, and ultraviolet light from the Sun as it floats on water.
All these conditions have the potential to host, or even generate, the kind of chemical processes that we think created the first living cells, said Brasier.
According to David Wacey, scientists know that earliest organisms thrived between the holes of beach sand grains about 3,400 million years ago. What we are saying here is that certain kinds of beach might have provided a cradle for life, Wacey added.
Researchers said that their hypothesis that floating and beached rafts of highly vesicular volcanic rock provided a remarkable locus for ancient organisms is testable. Laboratory experiments can be conducted to see whether pumice rocks can soak up pertinent organic species from water and create catalysts and new compounds under simulated thermal cycles and ultraviolet light.
The presence of materials like zeolites and phosphates in and around the volcanic grains in prehistoric deposits makes it likely that pumice could have been contributed to prebiotic organic chemistry, as well as in the ensuing colonization and transport of the earliest life on Earth.