Mapping and Characterizing the Northern Fan Deposits in Jezero Crater, Mars.

The northern inlet channel to Jezero crater (Sava Vallis) terminates in a fan‐shaped depositional feature, part of which blends into the separate well‐known western fan delta that is the field site for the Mars 2020 mission's Perseverance rover. Jezero's northern fan potentially represents either a second fan delta within the crater or a distal portion of the western fan. To constrain the fluvial and sedimentological history of Jezero and place the rover's in situ observations in proper geologic context, we photogeologically map the northern fan deposits at a larger mapping scale than previous studies, using ground‐based imaging from the Perseverance rover for context. Fifteen map units are identified using HiRISE‐based interpretations of geologic characteristics and inferred processes as well as crosscutting relative age relationships. Mapped units are also defined based on orbital data from CRISM and THEMIS to assess their compositional signatures. We interpret the northern fan deposits as older than the uppermost blocky unit in the western fan delta, suggesting that they were deposited contemporaneously with or prior to the deposition of the western fan, and under similar climate conditions. The eastern portion of the northern fan deposits shows evidence of fluvial deposition from Sava Vallis, while part of its western side could represent a distal part of the western fan delta. We synthesize our interpretations to present scenarios for the deposition of the northern and western fans, which can help constrain the history of both watersheds and place it into context within the broader Isidis basin region. Plain Language Summary: The Mars 2020 Perseverance rover has primarily focused on using its scientific instruments to study the delta along Jezero crater's western margin. But there are fan‐shaped features that appear to originate from both the crater's western and northern channels ‐ Neretva Vallis and Sava Vallis, respectively. In this project, we compile orbital images, spectroscopy data sets, and images taken by the rover's Mastcam‐Z instrument to investigate whether the northern fan originated from the northern channel or is an outlying part of the western delta. Based on these observations and the geologic map created using them, we show that the northern fan deposits are older than the uppermost unit mapped in the western delta. We also demonstrate how the western portion of the northern fan deposits could be an outer part of the western delta, while the eastern portion may preserve material from Sava Vallis. We show that some units across the northern and western fans are the same or similar, making this work useful as the rover's mission continues. Finally, we present scenarios that could lead to what we see in Jezero today, helping us to understand the potential history of this area and the relationship between the northern and western watersheds. Key Points: Deposition of Jezero crater's northern fan predates that of its western fan blocky material—the western delta's uppermost surficial unitThe northern fan shows evidence of deposition from Sava Vallis, but part of its western region could be a distal part of the western deltaThe stratigraphic and depositional hypotheses presented provide context for the Mars 2020 mission and help constrain the history of both watersheds [ABSTRACT FROM AUTHOR]