NASA has launched its unmanned MAVEN spacecraft toward Mars to study the Red Planet’s atmosphere for clues as to why Earth’s neighbour lost its warmth and water over time.

The white Atlas V 401 rocket carrying the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter blasted off on schedule yesterday.

“Everything is looking good,” said NASA mission control.

The flawless liftoff of the $US671 million ($A717.34 million) spacecraft kicked off the 10-month journey to the Red Planet.

Arrival at Mars is scheduled for September 2014, with the science mission of the solar-wing panelled orbiter set to begin two months later.

The probe is different from past NASA missions because it focuses not on the dry surface but on the mysteries of the never-before-studied upper atmosphere.

Much of MAVEN’s year-long mission will be spent circling the planet 6,000 kilometres above the surface.

However, it will execute five deep dips to a distance of just 125 kilometres above the Martian landscape to get readings of the atmosphere at various levels.

Researchers have described the mission as a search for a missing piece to the puzzle of what happened to Mars’ atmosphere, perhaps billions of years ago, to transform Earth’s neighbour from a water-bearing planet that might have been favourable for life to a dry, barren desert.

“MAVEN is the first spacecraft devoted to exploring and understanding the Martian upper atmosphere,” the US space agency said.

“The spacecraft will investigate how the loss of Mars’ atmosphere to space determined the history of water on the surface.”

NASA has sent a series of rovers to explore the surface of the Red Planet, including its latest, Curiosity, which arrived last year.

The deep space orbiter launched earlier this month by India seeks to find traces of methane from Mars and may arrive two days later than the US spacecraft.

The science goals of the two do not overlap much. The Indian probe will be searching for methane which could prove the existence of some ancient life form, while the US probe seeks answers about the planet’s climate change.

MAVEN’s findings are expected to help pave the way for a future visit by humans to the Red Planet, perhaps as early as 2030, NASA has said.