NASA's $2.5 billion Mars rover Curiosity has successfully entered the Red Planet's atmosphere. Curiosity has also sent back its first signals to mission control. The Mars rover is on a two-year mission seeking evidence that the Red Planet once hosted ingredients for life, according to NASA. The $2.5 billion Curiosity project, formally called the Mars Science Laboratory, is Nasa's first astrobiology mission since the 1970s-era Viking probes.