Participatory science, ranging from citizen to community science, refers to ways that everyday people collaborate with scientists in meaningful ways. There are thousands of participatory projects, each of which can engage thousands, tens of thousands, or even millions of people. Projects occur across varied disciplines such as astronomy, biochemistry, conservation, engineering, and environmental sciences. Research suggests that people engaged in participatory sciences can develop skills, adopt new behaviors and attitudes, increase civic engagement, and more. Some learning outcomes may lead young people into STEM careers, and for adults, lead to everyday science learning. Studies of youth engagement in participatory sciences focus on out of school time experiences. Yet, much remains abstract and aspirational with participatory sciences for adults, which occurs during outside-of-work or leisure time. This Literature Review and Synthesis project is the next step needed to move towards understanding the participatory sciences as sites of adult lifelong learning and leisure. The disciplines, number of projects, and amount of people engaged creates high variation in project structures and outcomes and requires strengthening theoretical foundations of adult science learning in leisure contexts in order to gain new insights. Ultimately, the investigators will move the field forward, in research and practice, with stronger understanding of adult engagement in participatory sciences as