The transition to a low-carbon economy depends on several critical materials, among which is cobalt. This metal is a main component in batteries, and therefore, demand for cobalt is expected to increase in the coming years. This paper explores future scenarios for the cobalt system, in light of its role in the low-carbon transition. The future of cobalt is characterized by deep uncertainty: it involves uncertainty on how the system is structured, on the values of variables influencing the system, and on the desirability of outcomes of interest. Therefore, this research uses Exploratory system dynamics modelling and analysis as the method, since it allows to explore an ensemble of models, each with different values for the input variables. The results show that cobalt is likely to remain a critical material for the electric vehicle transition, although the demand for the metal could vary greatly, depending on the size of future batteries and how fast the average oregrade of cobalt will decline. The demand scenarios in turn influence the development of industrial and artisanal mining, and recycling in the cobalt system. Depending on the collection rate of batteries and other cobalt-containing goods at the end of their life, recycled cobalt could account for a significant part of the demand. The by-product nature of cobalt makes future industrial mining dependent on developments in the nickel and copper markets. If the demand for cobalt increases sufficiently and its price levels go up, cobalt could become a co-product for nickel and copper. With regards to scarcity and sustainability of the cobalt system, this research examines the influence of the assumptions of the two opposing paradigms in the literature on these two concepts: the Fixed stock paradigm and the Opportunity cost paradigm. While the Fixed stock paradigm warns for eminent physical scarcity, the Opportunity cost paradigm places its trust in the regulating capabilities of the price of metals, the signal for economic scarcity. This paper argues that the continued discussion on the paradigms, divert the attention from the externalities of mining. Cobalt resources are not likely to soon be depleted, but externalities of mining could continue to increase. More cooperation between scientists of both paradigms could help to increase understanding of metal systems, and to produce better advice on policies for decision makers to cope with the externalities. Increased research into understanding how externalities of mining could be mitigated is therefore recommended.