Wilson, Sharon A., Morgan, Alexander M., Howard, Alan D., and Grant, John A. 2021. "The Global Distribution of Craters With Alluvial Fans and Deltas on Mars." Geophysical Research Letters, 48, (4). https://doi.org/10.1029/2020GL091653.
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 (similar to 40 degrees N to 54 degrees S) and are strongly banded with respect to latitude. Most craters with alluvial fans occur at higher elevations (10 degrees S-30 degrees S) and along the dichotomy boundary (0 degrees-10 degrees N). Deltas occur at lower elevations (0 degrees-40 degrees N) where access to groundwater may have enabled the formation of lakes, and to a lesser extent in the highlands (0 degrees-30 degrees 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.
