Scenario analysis has become a prominent approach for sustainability research and problem solving, bridging scientific and societal efforts toward sustainable transitions. Yet, sustainability science -- calling for strong bridges between science and society to link knowledge to action -- requires going beyond future studies. Based on analytical and anticipatory knowledge, sustainability science reaches out to a rigorous inclusion of normative knowledge through scientific and participatory assessments (which future can be considered sustainable and why), as well as for action-oriented knowledge through strategic development (how to achieve a sustainable future given political, financial, and other constraints). This concept converges with the notion of transformative research -- a research creating radically innovative insights and effectively contributing to solutions for the severe sustainability problems facing our society. This symposium departs from a comparison of current participatory scenario studies and explores how participatory research, at the interface between science and society, can incorporate normative and action-oriented knowledge while complying with scientific standards and societal requirements such as saliency, credibility, and legitimacy. The international orientation of the symposium sheds light on potential synergies between approaches from the United States and Europe, while identifying viable ways for transatlantic collaborations in sustainability science.