ISLAMABAD-Final assembly and testing of NASA’s Perseverance rover continues at Kennedy Space Center in Florida as the July launch window approaches. In some of the last steps required prior to stacking the spacecraft components in the configuration they’ll be in atop the Atlas V rocket, the rover’s wheels and parachute have been installed. Perseverance received its six flight wheels on March 30, 2020. While the rover took a test drive last December, it was on “flight spares” that wouldn’t be making the trip to Mars. Designed for the kind of off-roading Perseverance will perform on the Red Planet, the wheels are re-engineered versions of the ones NASA’s Curiosity has been using on its traverses of Mount Sharp. Machined out of a block of flight-grade aluminum and equipped with titanium spokes, each wheel is slightly larger in diameter and narrower than Curiosity’s, with skins that are almost a millimeter thicker. They also feature new treads, or grousers: In place of Curiosity’s 24 chevron-pattern treads are 48 gently curved ones. Extensive testing in the Mars Yard at NASA’s Jet Propulsion Laboratory, which built the rover and manages operations, has shown these treads better withstand the pressure from sharp rocks and grip just as well or better than Curiosity’s when driving on sand.