Oil sands are a mixture of “bitumen” (a very viscous, heavily biodegraded crude oil), unconsolidated sand, and water bound together by the bitumen and confining stresses. Economic incentives to produce reserves from the western Canada oil sands have driven geological and geochemical mapping to assess fluid quality controls and improve our understanding of the fundamental principles of the biodegradation of oils. While much of this activity has been for practical application, researchers have also had the opportunity to make fundamental advances in our understanding of subsurface biogeochemical processes and the boundaries of life in Earth's crust. Indeed, the huge size and shallow location of oil sands, coupled with the many thousands of wells drilled, mean that on a per cell basis, oil sands represent a most accessible portion of the deep biosphere. Perhaps the most exciting future for the oil sand resource is on the biological front rather than as an energy resource.