Supersonic retropropulsion (SRP) represents the most likely means to slow down during the descent phase of the next era of Martian missions, i.e. human Mars exploration class missions. A general overview of the Entry-Descent-Landing phase (EDL) is provided, referring to past missions in order to derive their limits and understand the importance of SRP for overcoming them. The preliminary results of NASA studies for the parametrization and conceptual design of a propulsion system implementing SRP during a descent Mars phase are also presented. Among all the fields of interest concerning the application of SRP, the aerodynamic one has been studied since the 60s, representing an important topic of research and development.