Angular Sand on Martian Hills . ... Credit Copyright: Mars Exploration Rover Mission , JPL , NASA Explanation: Why isn't this sand round? The robotic Spirit rover currently rolling across Mars has found notably angular sand in the Columbia Hills on Mars. ... The finding indicates that angular hill sand has tumbled less and likely traveled a shorter distance than the corresponding round plain sand. ... NASA Web Site Statements, Warnings, and Disclaimers . NASA Official: Jay Norris. ...