The region is believed to harbor one of the most promising locations for the search for past and present life on the red planet. Light- and dark-toned deposits are found in and around the outflow channel Mawrth Vallis. The light-toned materials are the most widespread outcrops of phyllosilicates found on Mars and at places form a up to 200 m thick deposit. A dark cap rock unit overlies the clays, presumably of volcanic origin. Investigations with the spectrometer OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) also onboard Mars Express led to a better understanding of the clay minerals, that are iron-/magnesium-rich and aluminum-rich. In addition, sulfate-bearing deposits have been identified on the channel floor of Mawrth Vallis.Besides the mineralogy, the stratification of the light-toned rocks observable over a large area offers a particular opportunity to study depositional environments and also the climate history of Mars. The phyllosilicates on Mars could indicate surface alteration by aqueous activity and hint to a habitable environment in the Martian past. Liquid water once flowed through Mawrth Vallis, and existed on the surface presumably until 3.6 billion years ago. Maybe even traces of microbes were preserved in the rocks, protected from radiation and erosion by the overlying cap rock. Hence, astrobiologists have a great interest in this region of Mars.