Two PhD projects to work on the earliest life on Earth and the setting for the Origin of Life

Where: Australian Centre for Astrobiology, University of New South Wales Sydney, Australia

Supervisor: Professor Martin Van Kranendonk

Two PhD projects are available to be filled at the Australian Centre for Astrobiology, under the supervision of ACA director Prof. Martin Van Kranendonk, and internationally recognised expert on the early Earth and on early life. Both projects are funded by an Australian Research Council Discovery Project awarded to Van Kranendonk “A terrestrial hot spring setting for the origin of life? Darwin’s Warm Little Pond revisited”. This Project aims to test the proposal that a terrestrial hot spring field could have been the setting for the origin of life, in preference over the currently favoured site at deep sea vents (see Van Kranendonk et al., 2017: Scientific American, August 2017, p. 28-35). This will be achieved through a world-first, integrated, and multi-disciplinary study of the rocks, fluids, and molecules that together make up ancient to modern hot spring systems, and experiments on prebiotic organic chemistry using early Earth materials. The project is run in collaboration with leading research scientists from The University of Western Australia (A/Prof Marco Fiorentini; metallogeny, hydrothermal fluids, alteration geochemistry), The University of Auckland (Prof. Kathy Campbell; hotspring facies, fluids, architecture, biosignatures), and the University of California at Santa Cruz (Prof. David Deamer; prebiotic organic geochemistry, hot springs; wet-dry cycling, experiments).

A Hot Spring Origin and early adaptive pathway of life, in seven steps: (1) Synthesis of life's primordial building blocks in space during the formation of our Solar System; (2) Accumulation of in-falling organic components and those generated within hot springs on an early volcanic landscape;
(3) Concentrated organic compounds in a hot spring system utilize sunlight, heat, and chemical energy to drive key prebiotic polymerization reactions; (4) Cycling of the products of these reactions in a fluctuating (wet-dry) 'Origin Pool' drives them through three phases: i) organic membranes in the pool dry down to form layered films between which the building blocks bond together to form polymers; ii) on refilling, the films wet and bud off trillions of lipid protocells that encapsulate random polymers and; iii) Darwinian selection tests protocells producing a pool of survivors with encapsulated polymer cargoes that form a moist gel as the pool level drops. Through iterative cycling, protocells interact, compete for resources, and evolve ever more complex functional polymers until a “progenote gel” emerges that is consistently able to grow and adapt; (5) Distribution of robust progenotes occurs by water, or wind, to distant pools, rivers, and lakes, where they evolve an early form of photosynthesis and ultimately develop the complicated evolutionary innovation of cell division to cross over into the first living microbial community; (6) Adaptation of early microbial communities to stressful salt water estuaries prepares them for access to the more extreme marine environment; (7) Tides at the sea coast select for microbial communities able to cement sand grains together forming the layers that build stromatolites so abundant in the fossil record. Life may now Colonize many niches on land and in the sea, setting the stage for free-living cells and, after billions of years, complex multi-cellular organisms.



This project will investigate the nature of the hydrothermal alteration that underlies the ancient hot spring setting represented by the 3.48 billion-year-old Dresser Formation in the North Pole Dome area of the Pilbara Craton, northwestern Australia. This site has recently been discovered to contain deposits from ancient terrestrial hot springs that contain a range of biosignatures (Djokic et al., 2017: Nature Communications 8:15263). The surficial hot springs were fed by a dense swarm of large black chert+/-barite hydrothermal veins that have altered the footwall to classic epithermal mineral assemblages. Significantly, we have also discovered that this area contains all of the most important elements required for prebiotic chemistry, including concentrations of Boron, Zn, Mn, etc.

This project will investigate the 4-dimensional history of the Dresser hydrothermal fluid system and how it was responsible for concentrating the elements required for prebiotic chemistry. Fieldwork will involve mapping the alteration assemblages and collecting samples for geochemical analyses that will enable the generation of element mobilisation maps that show show the transfer and concentration of elements. Analyses will also include O, and Li and B isotopes of fresh and hydrothermally altered basaltic rocks to determine the amount of chemical alteration and/or surficial weathering. The different alteration assemblages will then be used as substrates in organic geochemistry experiments to be conducted in the Deamer lab, aimed at better understanding the influence of mineralogy and real-world Archean materials on generating complexity in hot spring systems and the formation of prebiotic organic molecules. (Supervisors Van Kranendonk and Fiorentini).




The key ingredients for life in an ancient hot spring. Incoming meteorites deliver simple organic molecules as well as a range of chalcophile and highly siderophile elements (e.g., Au, PGEs) to the surface. Coevally, volcanoes add sulfur as well as other volatile species to the atmosphere. Circulating hydrothermal fluids scavenge and concentrate metals (e.g., Fe, Zn), metalloids (e.g., B), as well as non-metal elements (e.g., P) through intense alteration of the underlying host rocks. Different springs concentrate different elements under differing geochemical conditions, creating “innovation pools”, which share information through wind, splashing of geysers, and the subterranean fracture network. A/W, R/A, and W/R refer to Air/Water, Rock/Air and Water/Rock reactive interfaces.



This project will focus on the active hot springs in the Rotorua district of New Zealand (north Island). Specifically, we are interested in the fluid chemistries, energetics, and biological components of zones of mixing between hot spring pools that have different chemistry, pH, Eh, etc. The aim here is to better understand the potential of mixing zones for promoting increased complexity as applies to the origin of life. This project will involve fieldwork in New Zealand, including mapping of hot spring systems, and sample collection of fluids, substrates, and microbial diversity of different parts of the system, particularly mixing zones. (Supervisors Van Kranendonk and Campbell).



Schematic diagram showing how variation and interaction between hot springs with different chemical properties (different colours) can lead to greater fitness of prebiotic molecules within innovation pools. Inspired by Rachel Whitaker from the University of Illinois.