The overarching long-term goal of my research is to investigate and to quantify the potential effects of meteorite impact events on the Earth, Moon and Mars. My research is built around four hypotheses, which is that impact events: (a) can negatively affect pre-existing life; (b) produce substrates suitable for prebiotic chemistry; (c) generate new, unique habitats for life; and (d) generate mineral and hydrocarbon deposits of economic potential.
In order to address these hypotheses, my research focuses on understanding four key processes involved in the formation of meteorite impact structures:
(1) Shock melting and metamorphism
In a series of articles beginning with my PhD work, my research has shown that carbonates and evaporites undergo melting during impact events. Prior to this, it was widely accepted that sedimentary rocks do not melt; rather it was thought that such lithologies decompose, releasing harmful gases such as CO2 and SO2. This has fundamental implications for understanding the destructive environmental effects of impact events, such as the Chicxulub impact 66 million years ago and its possible link to the K-Pg mass extinction. My approach has been to conduct detailed fieldwork followed up with detailed microanalytical studies of samples from impact craters in Canada and around the world. This has provided a framework for others to follow in recognizing evidence for the shock melting of carbonates during impact.
(2) Impact ejecta emplacement
The generation of ejecta deposits is one of the most characteristic, but poorly understood, aspects of the impact cratering process. Building on my earlier work done during my PhD, in 2011 I published a paper that proposed a new multi-stage model for impact ejecta emplacement on the terrestrial planets. A 2018 paper builds upon this work through the study of ejecta deposits at Mistastin Lake impact structure. At Barringer Crater, in addition to detailing carbonate melts (see above), we documented the first occurrence of impact melt and projectile-bearing ejecta. Because so few craters on Earth preserve ejecta deposits, investigation of this topic requires studies of craters on other planetary bodies. Both Mars and the Moon have been the focus for the past 5 years with significant progress in understanding impact ejecta emplacement having been made.
(3) Impact crater collapse
The formation of an impact crater can be divided into three main stages (1) contact and compression, (2) excavation, and (3) modification. My research seeks to better understand how complex craters form through a combination of field studies of craters on Earth and remote sensing studies of craters on the Moon and Mars. One of my early contributions in this area was the detailed mapping of the Haughton impact structure, which provided important insights into how mid-size complex impact craters form. In more recent and ongoing work, I am part of a large international team studying the Chicxulub impact crater and insights into peak-ring formation.
(4) Impact-generated hydrothermal alteration
A big focus for my research is on the growing recognition that impact events are not just agents of destruction but that they also have certain beneficial effects, particularly the generation of hydrothermal systems within an impact crater immediately following its formation. Through detailed mineralogical and geochemical studies of alteration phases at the Haughton, Ries and other impact structures, my research has led to the development of a conceptual model for the origin and evolution of hydrothermal activity within impact craters and how these systems could have acted as potential habitats for life on Early Earth and potentially other planets, such as Mars (see paper here).
Key to all of my research is studying the products of meteorite impact events and investigating the influence that target lithology has on the various aspects of the impact cratering process.