NASA spacecraft is first to orbit Mercury.

A NASA spacecraft began orbiting Mercury, becoming the first to fly around the solar system's most innermost planet, the space agency said. The craft, known as MESSENGER began the orbit around 2.00 AM 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 Earth, Venus and Mercury. 

An enhanced image of Mercury from the Messenger probe.

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. MESSENGER was 46 million kilometres from the Sun and 155 million kilometres from Earth when it headed into Mercury's orbit, NASA said. The MESSENGER has already been able to return a partial map of the planet's crater filled surface after a handful of flybys.