Geochemist Barbara Sherwood Lollar has earned global renown for her contributions to environmental preservation and to our understanding of life underground. A Canada Research Chair and professor in earth sciences at the University of Toronto, she pioneered the use of stable isotopes to pinpoint sources of contamination in our groundwater resources, a breakthrough that is helping practitioners remediate polluted areas. While conducting field research in South Africa and Canada, she discovered and analyzed environments conducive to life deep within the Earth’s crust, a finding that has implications for the search for life on other planets.