Jezero crater has been selected as the landing site for the Mars 2020 Perseverance rover, because it contains apaleolake with two fan-deltas, inlet and outlet valleys. Using the data from the High Resolution Stereo Camera(HRSC) and the High Resolution Imaging Science Experiment (HiRISE), we conducted a quantitative geomorphological study of the inlet valleys of the Jezero paleolake. Results show that the strongest erosion is related to a network of deep valleys that cut into the highland bedrock well upstream of the Jezero crater and likely formed before the formation of the regional olivine-rich unit. In contrast, the lower sections of valleys display poorbedrock erosion and a lack of tributaries but are characterized by the presence of pristine landforms interpreted asfluvial bars from preserved channels, the discharge rates of which have been estimated at 10^3–10^4 m^3s^-1. The valleys’ lower sections postdate the olivine-rich unit, are linked directly to the fan-deltas, and are thus formed inan energetic, late stage of activity. Although a Late Noachian age for the fan-deltas’ formation is not excludedbased on crosscutting relationships and crater counts, this indicates evidence of a Hesperian age with significantimplications for exobiology.