Challenges in crater chronology on Mars as reflected in Jezero crater

The age of a planetary surface may be inferred from the size-frequency distribution of impact craters covering it. On Mars, the accuracy of this crater chronology technique may be compromised by past or present aeolian, fluvial, and pluvial erosion and sedimentation. Here, we review how these processes influence the crater age of the surface, employing as a case study the floor of Jezero crater, the landing site of the Mars 2020 Perseverance rover mission. We count craters and derive the retention ages of three prominent geologic units on the floor of Jezero, discussing some of the challenges faced during crater counting analysis. Our estimate for the retention age of the dark-toned floor unit is slightly younger compared to previous studies and is sensitive to statistical outliers. These factors should be taken into account when calibrating the crater age of the surface of the unit with its measured radiometric age.