A US robotic spacecraft entered into orbit around the planet Mars early on Monday morning UTC, at the start of a scheduled one-year mission to probe the factors behind the planet's gradual loss of an atmosphere over millions of years.

The success of the delicate navigational operation was greeted with cheers and applause by the NASA flight control teams supervising the procedure.

"Wow, what a night! You get one shot with Mars orbit insertion and MAVEN nailed it tonight," project manager David Mitchell said, using the acronym given to the spacecraft, which is short for Mars Atmosphere and Volatile Evolution.

After a six-week test phase, MAVEN is to begin investigating the reasons why Mars, the planet most like Earth in the solar system, lost the thicker atmosphere and surface water that researchers believe it once possessed. The answers it finds could shed light on whether the planet was formerly able to support life, albeit possibly only of a microbial nature.

Its findings could also aid in working out how to allow humans to survive on the planet in the future - perhaps as early as 2030.

Mars now has an extremely thin atmosphere.

Long journey

During its mission, the probe will orbit the Red Planet at a distance ranging from 150 kilometers (93 miles) to 6,000 kilometers (3728 miles) from the surface, also undertaking five "deep dips" to an altitude of just 129 kilometers (78 miles) to take atmospheric readings at various levels.

The spacecraft travelled for ten months, covering 711 million kilometers to reach the planet. It becomes the fourth manmade satellite in orbit around Mars, along with two other NASA missions and a European Space Agency mission. NASA also has two rovers, Opportunity and Curiosity, that are currently exploring Mars' surface.

An unmanned Indian spacecraft, the Mars Orbiter Mission (MOM), is set to enter into orbit around Mars on Wednesday, in what is India's first mission to the planet.

tj/ksb (Reuters, dpa, AFP)