Valleys in pit craters on Mars: Characteristics, distribution, and formation mechanisms

New observations of central pit craters on Mars reveal that some craters contain prominent interior valley networks that drain into their central pit. In this study, we catalog the distribution of pit craters with associated valleys, and characterize in detail five diverse, well-preserved examples. In some instances, sedimentary deposits we interpret as either alluvial fans or deltas are found in the central pits, and evidence suggests that at least some of these pits once contained lakes. Fluvial activity within the five pit craters we detail, appears to have occurred relatively late in Mars history, during the Hesperian or Amazonian periods. For this reason, further understanding the formation mechanisms of these valleys has important implications for the history of water on Mars.