A special issue of Science magazine focuses on reports by Arizona planetary geologists Alfred McEwen (University of Arizona Lunar and Planetary Lab), WL Jaeger (USGS Astrogeology Team in Flagstaff) and their colleagues, in which it's concluded that "evidence for liquid water [on Mars] is rare and difficult to discern."The collection of articles in the Sept 21 issue on the Mars Reconnaissance Orbiter report that fields of boulders up to about 2 meters in diameter occur in areas previously thought to be riverbeds and ocean floors. Some landforms thought to have been formed by flowing water are now seen as evidence of flowing lava.
Sounding more like Arizona every day.
Dr. Alfred McEwen discusses the findings in a related podcast interview at http://podcasts.aaas.org/science_podcast/SciencePodcast_070921.mp3.