Fan-shaped sedimentary deposits located at the mouths of Martian valleys have been interpreted as indicators of wet conditions during Mars history. However, the processes, time and amount of water needed to carve the valleys and form the fans are still debated. I will present the results of a recent detailed morphometric and mass balance analysis of valleys and fan-shaped deposits, which provides new insights into past depositional environments. These results suggest that most fans might have been formed in subaerial settings with significant contributions of alternative processes besides fluvial transport and deposition, thus without necessarily requiring the occurrence of extended epochs of clement climatic conditions during a significant part of Mars history.