NASA rover finds ancient crystal features on Mars
NASA's nuclear-powered Curiosity Mars rover has discovered dark, stick-shaped features that are thought to have formed over ancient crystals. The features, about the size of rice grains, are another sign that liquid water once flowed on the Red Planet, said project scientist Ashwin Vasavada. The $2.5-billion mission's rover landed on Mars in 2012 and has travelled 18 km since then.