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We present an inventory of alluvial fans and deltas within martian impact craters based on a systematic global survey of Context Camera images. Our database includes 314 fan‐hosting craters, with a total of 890 alluvial fans and 114 deltas. Alluvial fans and deltas are more widespread than previously reported (∼40°N to 54°S) and are strongly banded with respect to latitude. Most craters with alluvial fans occur at higher elevations (10°S–30°S) and along the dichotomy boundary (0°–10°N). Deltas occur at lower elevations (0°–40°N) where access to groundwater may have enabled the formation of lakes, and to a lesser extent in the highlands (0°–30°S). Alluvial fans in southern mid‐latitude craters preferentially formed along the northern and southern walls, which may reflect climatic control through solar insolation. The widespread distribution within the observed latitude bands and the similar Hesperian to Amazonian age of alluvial fan‐hosting craters is consistent with late‐stage synoptic precipitation. Plain Language Summary: Martian alluvial fans and deltas are intriguing features because they provide evidence for surface water and a climate that was very different than the present‐day conditions. This study presents a planet‐wide catalog of craters that host alluvial fans and interpreted deltas to understand where and when they formed. We systematically searched images from the Context Camera because this data set has the necessary resolution and coverage to identify and classify the landforms of interest. Our inventory of 314 craters with 890 alluvial fans and 114 deltas shows that these landforms are more numerous and widespread than previously reported. The similar age and distribution of craters with alluvial fans in the southern mid‐latitudes is consistent with a late occurring, widespread (rather than local) source of water. Craters with deltas are preferentially located at lower elevations where interactions with groundwater may have enabled the formation and persistence of lakes. Key Points: Craters with alluvial fans and scarp‐fronted fans (putative deltas) are more numerous than previously reportedThe widespread distribution of craters with alluvial fans in observed latitude bands is consistent with late synoptic precipitationFormation of alluvial fans in southern mid‐latitude craters on northern and southern walls may be influenced by solar insolation patterns [ABSTRACT FROM AUTHOR]

A series of previously unstudied alluvial fans are actively forming along the Hilina Pali escarpment on the south flank of Kīlauea volcano on the Island of Hawaii. These fans are characterized by their steep slopes, coarse grain sizes, and lobate surface morphology. Fans are fed by bedrock channels that drain from the Ka'ū Desert, but sediment is mostly sourced from deeply eroded alcoves carved into the Hilina Pali. Examination of recent deposits indicates that the fans are dominantly constructed from gravel and larger sized sediment. Flow discharges calculated using field measurements of channel geometries and the Manning equation indicate that events inducing sediment transport are of high magnitude and occur during high intensity precipitation events, including Kona storms. The fans along the Hilina Pali appear to be a rare example of fans formed predominately from sieve lobe deposition owing to the area's high slopes, high discharge, coarse bedload, and limited supply of fine-grained sediment. Given such conditions, sieve lobe deposition can form large lobes consisting of boulder-sized material, which may have implications for the identification of depositional processes when interpreting the stratigraphic record. [ABSTRACT FROM AUTHOR]