Our research group uses physical and chemical principles to understand the planets. To study the natural world directly, we rely mostly on solar system solids (i.e. rocks and minerals) as chemical, thermal and chronological archives, as well as test-beds for models of the physical-chemical processes that affect(ed) them. With this knowledge it is timely to extend these explorations to exoplanets and to apply geological concepts towards good theories that make predictions. Generally speaking, our research is field-, laboratory- and modeling-based, and explores the planetary-scale geodynamic conditions that give rise to Earth-like (i.e. rocky) planets. In modeling, we pioneered simulations for the thermal and chemical structure of solid planetary objects using isotopic geochemistry as a strict criterion. In this way, our group has been leading in the active coupling of planet formation theory and dynamics with cosmochemistry, and uses output from galactic chemical evolution models and stellar spectral analysis to provide input parameters for geodynamic simulations.
Two important results:
1. In an RNA-First Process Life on Earth could have began 4.36 billion years ago
Hafnium-tungsten dating of terrestrial rocks indicates that the Earth formed in about 30 Myr after the Sun was born, i.e. about 4530 million years ago. After its formation it was repeatedly struck by stray planetesimals wandering around the inner solar system, in a process that is called 'late accretion.' Yet U-Pb and Sm-Nd dating of terrestrial samples always show a terrestrial intercept age of about 4480 million years ago, which is younger than the oldest ages recorded on the Moon of about 4510 million years ago. We interpret the terrestrial 4480 Ma age as the result of the impact between the young Earth and a lunar-sized object that we call Moneta. It is thanks to Moneta that we have precious metals like gold, silver and platinum to Earth's crust and mantle. It also produced a thick, temporary hydrogen atmosphere that facilitated the creation of molecules necessary for origins of life in an RNA-First hypothesis. Combining the geological aftermath of the Moneta impact with our work on late accretion as well as with experts in pre-biotic chemistry, our group has suggested that life on Earth could have originated around 4360 million years ago.
2. Postulated stages in the origin of life
Prebiotic chemistry produced the building blocks of RNA in the natural environment(s) of the young planet that was formed from the nuclides accumulated in Galactic Chemical Evolution (GCE). After cooling, prebiotic chemistry could commence. The first stage of proto-biological evolution in this scenario begins with RNA molecules that can perform catalytic functions needed to assemble themselves from available building-blocks in their immediate environment. These RNA molecules then evolve as self-replicators that recombine and mutate, and adapt, in the face of selection pressures, to occupy new environmental niches. Subsequently, these RNAs develop an increasingly complex suite of enzymatic activities. The next stage may have been when RNAs incorporated wild proteins synthesized abiotically, ultimately synthesizing their own and began the process of RNA s replicating with other RNAs. Ultimately, DNA appeared as the stable information center with error-correction, but still with mutation and recombination. The crystallization of the genome of life occurred at the time of the universal cenancestor cells (a.k.a. Last Universal Common Ancestors; LUCA); a community of organisms that are rooted in the Bacteria domain.
