The image on the left is a portion of a High Resolution Imaging Science Experiment image showing a bright streak in a gully on the side of a crater in the Centauri Montes region of Mars. The two colored images were generated by the researchers' numerical computer model. The middle image shows how a deposit left by a pure liquid water flood would appear in the gully. The right-hand streak shows the deposit that would be left by a dry debris flow. Only the model for the dry debris flow generated the same fingering as seen in the HiRISE image.