Washington (AFP) - NASA's MAVEN spacecraft began orbiting Mars on Sunday, on a mission to study how the Red Planet's climate changed over time from warm and wet to cold and dry."Based on observed navigation data, congratulations. MAVEN is now in orbit," said Dave Folta of NASA's Goddard Space Flight Center.The unmanned orbiter has traveled more than 10 months and 442 million miles (711 million kilometers) to reach Mars for a first-of-its kind study of the planet's upper atmosphere.The data from the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft aims to help scientists understand what happened to the water on Mars and the carbon dioxide in its atmosphere several billion years ago.How Mars lost its atmosphere is one of science's biggest mysteries.