In a European project – CoReflect – researchers in seven countries are developing, implementing and evaluating teaching sequences using a web-based platform (STOCHASMOS). The interactive web-based inquiry materials support collaborative and reflective work. The project methodology is based on the idea of design-based research, which seeks to bridge the often disconnected worlds of academia and educational practices. Hence, the teachers are engaged throughout the project. The learning environments will be iteratively tested and refined, first as pilot projects, then during local implementations, and finally during implementations and synthesis work at the European level. All learning environments are focusing “socio-scientific” issues.  In this article we report from the pilot of the Swedish learning environment with an Astrobiology context. The socio-scientific driving questions were “Should we look for, and try to contact, extraterrestrial life?”, and “Should we transform Mars into a planet where humans can live in the future?” The students are in their last year of compulsory school (16 years old), and worked together in triads. We report from the groups’ decisions and arguments used. A majority of the groups express reluctance towards both the search of extraterrestrial life and the terraforming of Mars.