Vanishing Act . ... Phoenix Mission Team , NASA , JPL-Caltech , U. Arizona , Texas A University Explanation: Compare these two close-up pictures taken on sol 20 (left) and sol 24 of a trench dug in the Martian surface by NASA's Phoenix Lander . ... Light-colored, dice-sized chunks, visible in the lower left shadow region of the trench in the sol 20 image have vanished by sol 24 -- a strong indication that the chunks were ice uncovered by digging the shallow trench. ... NASA Official: Jay Norris. ...