In 1976 Nasa 's Viking 1 sent back an image of Mars with blue skies . It was the first time that we had seen anything like it, and so people were excited about what they could learn from this new view. Some conspiracy theorists have questioned Nasa 's calibration methods . Nasa admits it is n't an exact science and often uses different versions .
In 1976 Nasa 's Viking 1 sent back an image of Mars with blue skies . Nasa claimed image had yet to be calibrated with right colour balance . Some conspiracy theorists have questioned Nasa 's calibration methods . Nasa admits it is n't an exact science and often uses different versions .