Mars exploration craft heat shield. Image from NASA's Mars exploration rover Opportunity of the flank piece of its craft's broken heat shield. The heat shield protected Opportunity on its descent to Mars. The rover spent 36 Martian days investigating the effects of the descent on the heat shield and sending images and data to engineers so they could evaluate the shield's performance. Opportunity and its sister rover Spirit were launched in the summer of 2003. Opportunity landed on Mars on 24 January 2004. Its mission is to analyse soil and rocks and search for water. Image taken on Opportunity's 330th Martian day, 28 December 2004.