Nasa spacecraft first to orbit Mercury

The craft, known as MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging), began the orbit around 9:00 pm (0200 GMT) on a mission to circle the planet for one earth year in an unprecedented study of the tiny, hot planet.

The spacecraft began its journey more than six years ago, travelling through the inner solar system and embarking on flybys of the earth, Venus and Mercury.

Nasa said that “by achieving orbit, this marks the first time that a spacecraft has accomplished this engineering and scientific milestone at our solar system’s innermost planet.”

For the next several weeks, engineers will be focused on ensuring the spacecraft’s systems are all working well in Mercury’s harsh thermal environment.

Starting on March 23, the instruments will be turned on and checked out, and on April 4, the mission’s primary science phase will begin.

MESSENGER was 46 million kilometres from the Sun and 155 million kilometres from the earth when it headed into Mercury’s orbit, Nasa said.

The first Nasa craft to study Mercury since the Mariner mission more than three decades ago, MESSENGER has already been able to return a partial map of the planet’s crater-filled surface after a handful of flybys.

The craft is carrying seven science instruments, including a Mercury Dual Imaging System, the Mercury Atmospheric and Surface Composition Spectrometer and the Energetic Particle and Plasma Spectrometer.

“MESSENGER began its journey in August 2004 and has since travelled about 7.9 billion kilometres through  a range of extreme conditions,” Nasa said.