Inquiry-based science education has become one of the most effective methodologies to learn science; however, proposals in preschool are scarce. Different factors are responsible for this situation, such as the low self-confidence of teachers to teach science and the belief that young children are unable to develop certain reasoning skills. This study reports the implementation of an inquiry-based science project in a preschool setting, in the context of a preservice teacher’s school placement. The project aimed to promote the development of basic and integrated scientific skills, enhance acquisition of conceptual knowledge and make the students enjoy while learning science. The intervention is described thoroughly and illustrated with examples from the real implementation of the theoretical IBSE sequence. At the beginning of the proposal, the students received a hypothetical letter from the astronaut Pedro Duque, in which they were asked for help to plan his trip to living on Mars, a cold planet, with only frozen and saltwater. After some introductory POE (predict, observe, and explain) experiences on the perception of temperature and activities with fresh and saline water, the students performed a piece of research: growing lettuce in four different conditions, combining two variables: temperature and the salinity of water. As the project developed, the students progressively gave better descriptions and justifications, and also showed great interest in performing more “research experiments”. For the preservice teacher, the project provided an excellent opportunity to implement academic knowledge in school practice.