Science moves forward as old hypotheses are tested with new data, resulting in abandonment or revision of old hypotheses. Students commonly fail to have a clear understanding of this, however, and are prone to viewing published work as fact, rather than as the best explanation at the time for a given set of data. Furthermore, students, once presented with a hypothesis to explain a set of data, find it difficult to abandon that hypothesis even in the face of new data that clearly invalidate the old hypothesis. Providing practice in re-evaluating old hypotheses with new data is one way to help students on the path to learning how to set up a new mental frame about a problem and ultimately develop their own new questions and hypotheses. The episodic nature of planetary data acquisition is ideal for creating a flurry of hypotheses that can then be revisited when the next planetary mission delivers a new batch of data. The unavoidable limitations of earlier data combined with the significant leap in data type and quality from one mission to the next make it easier for students to be more comfortable with critical examination of older hypotheses.

Recent Mars Express, MER, Odyssey, and MGS results provide data to test hypotheses published prior to the late 1990s. For example, high resolution MOC and MOLA data allow re-examination of the question of extent of integration of drainage networks in Noachian terrain, a problem that could be incorporated into a geomorphology course. Students can use data from Mars Express and the MER rovers to evaluate earlier hypotheses about the nature and origin of light-colored layered rocks on Mars, something that could be appropriate either for a sedimentary geology course or a petrology course. Students can use MOC and MOLA data in a marine science or geomorphology course to test hypotheses about shorelines in the Northern Lowlands on Mars. Students in a petrology course could use MER results to test conclusions drawn about the compositions of rocks at the Pathfinder/Sojourner site and to revisit the question of what the composition of Surface Type II rocks are on Mars.