This image contrasts gullies and recurring warm-season slope
flows appearing in the same crater, in the middle southern
latitudes of Mars. It was taken Nov. 27, 2007, by the High
Resolution Imaging Science Experiment (HiRISE) camera on NASA's
Mars Reconnaissance Orbiter. Gullies are on the pole-facing
slope, which is on the northern side of this crater. Recurrent
warm-season flows are on the equator-facing wall. Gullies are
typically much larger than the warm-season flows. As seen in
this crater, gullies have a typical range of features including
alcoves, channels and aprons. The flow features are narrow (one-
half to five yards or meters wide), relatively dark markings on
steep (25 to 40 degree) slopes at a few other southern
hemisphere locations. Repeat imaging by HiRISE shows the
features appear and incrementally grow during warm seasons and
fade in cold seasons. Sequences of observations recording the
seasonal changes in these flows might be evidence of salty
liquid water active on Mars today. Other imager