Members of the 3CPE engage in research from trying to understand the origin of life on earth, to exploring the habitable environments on Mars, to mapping icy satellites and asteroids in order to understand their chemical interactions, to trying to determine how planetary system forms and evolve and diverge, to building cutting-edge instrument to find new planets beyond the solar system and to trace the chemical pathways from the stars to our world.
In-Situ Studies of Polyextremophiles Under Ultrahigh Pressure
Diamond anvil cells (DACs) can generate static pressures in excess of 300 gigapascals, the pressure within Earth's core, by compressing a medium (such as a liquid) between two cut diamonds, thus providing a transparent ‘window' to examine planetary materials in the created high-pressure chamber using a suite of analytical techniques. Generally used in geophysics and other high-pressure fields of research, we will use a DAC system to analyze the activity of cultured polyextremophile microorganisms (archaea and bacteria) under a range of physicochemical conditions, including high and low temperatures, high pressures, acidity, and nutrient limitation. The design of the DAC gasket available in Jackson's lab allows for four replicate chambers (200 μm diameter) to be spectroscopically examined during incubation without the need for depressurization of microbes or removal from the DAC. Single-cell microbial activity in the DAC will be assessed using redox-sensitive fluorescence tracers, and metabolite production will be tracked via Raman spectrophotometry. While limits to single extreme environmental conditions are known for some microbes, the effects of combined multiple extreme conditions, as are often found in natural habitats, are less constrained. This project will examine and quantify the limits of microbial life by establishing how simultaneous extreme environmental conditions affect cellular viability and activity at the single-cell level over time without the need for decompression or removal from the incubation chamber.
Environmental Controls on the Evolution of Complex Life on Earth
The appearance of eukaryotes roughly 600-800 million years is a singular event in the evolution of Earth's biosphere, and indeed the planet itself. It marks the rapid and virtually complete transition from a planet dominated by single-celled bacterial life, to one dominated by complex, multicellular plants and animals. However, the reasons for this sudden appearance of complex life some 3.7 billion years after the Earth formed are still hotly debated. Potential explanations range from evolutionary innovations that suddenly made complex body forms possible, to environmental determinants in the form of O2 or trace metals, or even population bottlenecks due to mass extinctions during the Snowball glaciations. Uncertainty stems in large part from our limited ability – in the absence of most fossils – to discern which specific organisms were present, where they were living, and what they were doing. Our project will seek to develop new methods for the analysis of carbon isotopes in biomarker compounds specific to eukaryotes. Such data should provide new insights into the metabolism and physiology of ancient organisms, and the environment to which they were responding. This in turn should allow us to test specific ideas about the origins of complex life on Earth.
Io's Sulfur Isotope Cycle: Decoding the History of Tidal Heating
Tides powered by orbital resonances are one of the main drivers of geological activity and heat generation on the Solar System's moons. On Jupiter's moon Io, tidally-driven volcanism dominates the properties of the surface and atmosphere, and this moon has thus long been used as a laboratory for understanding the mechanics of tidal heat generation. However, its high resurfacing rate and young surface, combined with an atmosphere that is dynamically created and lost, leave very few records of its long-term history. The question of how long the galilean satellite orbital resonance has been active and whether the current level of heating is representative or anomalous, including whether Io is currently in thermal equilibrium, remains a fundamental gap in our understanding of Io's thermal history. Isotopic abundances, which can preserve records of processes that occurred over Gyr timescales, present a promising unexplored avenue into filling this gap. Telescope and spacecraft instruments are capable of measuring sulfur isotopologues, but interpretation will rely on an understanding of the isotopic fractionation processes at work on Io. We are developing a box model to characterize and quantify such fractionation in Io's interior and surface environment, including performing some specific petrological and geochemical laboratory experiments to measure fractionation factors that have not been quantified to date under the relevant conditions. The resultant model can be applied to measurements of isotope abundances at Io by telescopes in the near-term and (hopefully) by spacecraft within the next 10-20 years. This work will additionally help us unravel processes occurring in the subsurface of our own planet Earth, such as how and where arc volcanoes acquire their heavy sulphur isotope signal and how to interpret gas measurements collected from volcano monitoring data.
A Novel Isotopic Tracer for Impact Events
The Cretaceous-Paleocene (K/Pg, also known as K/T) boundary saw one of the largest ecological upheavals in Earth's history. The rocks from this time show marked enrichments in iridium (Ir), an element that is typically depleted on the Earth's surface but relatively abundant in some meteorites. This sparked a then largely controversial hypothesis that a large asteroid hit the Earth during this time. While its role in the subsequent mass extinction remains debatable, multiple lines of evidence have since confirmed that a giant impact event did occur around 66 million years ago. In this study, we are going to leverage novel isotopic tracers in K/Pg Boundary samples to identify the type of impactor that hit the Earth during this transition. Impactor contribution preserved in the rock record will be identified as isotopic deviations from a terrestrial/standard composition and have the potential to enable identification of where in the Early Solar System the K/Pg impactor was formed. More importantly, this study will serve as a first step in developing a powerful new tracer for detecting impact events in the sedimentary record.
Formation of Giant Planet Satellites
Four hundred years ago, the astronomer Galileo Galilei announced his discovery of four moons orbiting around the planet Jupiter, each seen as a distinct white dot through his telescope. However, it is only in the span of the last four decades that astronomers have been able to study the Jovian moons in detail to reveal that the four—Io, Europa, Ganymede, and Callisto—are fascinating worlds of their own. The exact story of how these satellites formed, however, remains imperfectly understood. In particular, identifying the specific physical mechanism responsible for the conversion of icy dust into the building blocks of satellites presents a considerable challenge to the theory of satellite formation. To address this problem, we are employing large-scale numerical simulations of resonant drag instabilities — a process through which dust clouds can grow, and eventually coalesce into solid satellitesimals within a differentially rotating gaseous disk. As continued exploration of icy moons within the solar system ventures forward, these calculations will shed light on the origins of these remarkable worlds.