The Curiosity rover, which launched in November, is about to make a maneuver vital to its successful landing. Later today, the spacecraft carrying the rover will perform a series of engine burns intended to redirect it towards the landing point at Gale Crater. It's necessary because the rocket's initial trajectory was actually set to miss Mars in order to prevent the upper stage from potentially contaminating the planet with microbes from Earth — unlike Curiosity, the rocket wasn't cleaned completely before launch. Since the Curiosity's ultimate mission is to discover whether the crater supports or ever could have supported microbial life, any unintended travelers could fatally affect the project. After the redirect, the craft will continue until August, when the rover will hopefully be deployed and begin its study of Mars.