New images taken by the HiRISE camera on NASA’s Mars Reconnaissance Orbiter (MRO) show hills and plateaus with alternating layers of dark and light colored rocks in Candor Chasma, one of several canyons that make up Valles Marineris, a sprawling Martian rift valley that is longer than the contiguous United States and up to seven times deeper than the Grand Canyon. Cutting like a vertical scar across these light and dark bands in Candor Chasma are a series of linear cracks surrounded by „halos“ of light-colored bedrock. In the February 16 issue of the journal „Science“, University of Arizona researchers Chris Okubo and Alfred McEwen argue that the halos are proof that some form of fluid – either water, liquid carbon dioxide, or a combination of the two – once flowed through the bedrock. Similar processes are known to occur on Earth. Veins of gold and silver in rock, for example, are formed when water rich in the dissolved forms of these elements flows through cracks and finally deposit the metals as bright streaks in the rock.
Images showing the haloes along fractures are available on the Web at: