The Grand Canyon has been getting mentioned in a number of recent articles about Mars this month, as Arizona and Mars have something in common: a very big ditch. The first images sent back from the European Space Agency’s Mars Express orbiter showed a deep, nearly unending gorge that is referred to by many as the “Martian Grand Canyon.” Called Valles Marineris, it often gets comparison to Arizona’s top attraction in order to put into perspective the sheer scale of features on Mars.