Robyn Williams: And so to another of the big questions; how did life start and where? I'm delighted to hear that wine is involved. PhD student in Canberra, Aditya Chopra:
Aditya Chopra: Life. Where does it come from? Life comes from earlier life. But what about the first life, the origins of life? I am on a search to find out where and when our earliest ancestors emerged. Fossilised stromatolites found in rocks at the Strelley Pool formation in the Pilbara region of Western Australia are some of the oldest evidence for life on Earth. Sections of the 3.5 billion-year-old sedimentary structure resembles stromatolites that are built up over thousands of years by photosynthetic microbes. As photosynthetic organisms are relatively complex, we suspect that simple life forms must have existed for many, many millions of years before the photosynthesisers colonised our planet. Our understanding about how these simpler organisms originated and lived is sketchy, but fossil evidence and genomic studies suggest that terrestrial life emerged from nonlife some time during the Earth's tumultuous first billion years. Unfortunately we do not have a time machine to go back four billion years to find out if life originated in a warm little pond, as Darwin imagined, or in a hot doubling soup. Was it in a lake on land or was it a deep sea hydrothermal vent, such as those found along mid-ocean spreading ridges today?
In my research I'm trying to provenance life, just as we can provenance wines. A few years back there were so many counterfeit wines in the international market—you know, the ones that claim to be from one region but are really from another—that scientists were asked if they could help trace where a wine truly came from. So scientists developed a technique to correlate the abundances of elements and their isotopes in the wine to the abundances of elements and their isotopes in the soils of likely winegrowing regions. The technique can be so accurate that it is sometimes possible to even identify the precise vineyard where the grapes that went into making the wine were grown.
My supervisor Charley Lineweaver and I thought perhaps the same technique could be applied to provenance life. Find the chemical composition of life, compare it to the chemicals present at sites where life might have originated, and voila, we might be able to match life forms to particular sites.
So far in my PhD research we have used data reported in earlier studies that analyse the composition of species from across the tree of life. Our early results suggest that the idea to provenance life using its elemental composition has merit. As the research progresses we shall try to determine the composition of the most primitive life forms present on Earth today, and these would serve as a good proxies for the composition of the earliest life forms.
Our method would be essentially to take a spoonful of the bugs, mix them in concentrated acid and then boil them for 24 hours. If they don't dissolve completely we could put them into a pressure cooker to dissolve any stubborn bits. The resulting solution would be injected through a plasma hotter than the surface of the Sun into a mass spectrometer that counts the number of atoms of each of the different elements. Within a few seconds we would have an elemental fingerprint of the life form.
For decades, scientists have analysed environments around the world and reported the present-day composition of when fluids discharged at different times of hydrothermal vents, the composition of warm volcanic lakes and the composition of tidal pools. These studies provide us with our best estimate for the composition of environments which may have been the cradle of Earth's life around four billion years ago.
One day I hope we will be able to compare the abundances of elements in life to the abundances in early Earth environments. Our research could guide us to the site where our ancestors' tale began. If we can better understand the environment where life originated on Earth, we will be in a better position to assess how common the emergence of life is in the universe. Perhaps our findings will enable us to discover new exotic life forms on Earth, or lead us to the even more exciting prospect of finding life on another planet.
Robyn Williams: Adi Chopra, using ideas of terroir from the wine industry to look for the origins of life, doing his PhD at the ANU in Canberra.