The 2004 launch of NASA's Messenger probe marked the start of the first mission to the innermost planet in the Solar System since Mariner 10's three flybys in 1974. Messenger is looking at the side of Mercury that Mariner 10 couldn't photograph and is studying the planet's magnetic field and dense core, which is believed to make up at least 60% of its mass.
Having completed a series of flybys, in 2011 it will enter a year-long orbit of the planet.
A key mission goal is to explain why Mercury is the only inner planet besides the Earth to have a global magnetic field.
Photo: Messenger prior to launch (NASA)
After 30 years, there is another mission to Mercury.
BBC News's Christine McGourty reports on Messenger's mission.
In a 14 January 2008 BBC News report, science correspondent Christine McGourty reports on Messenger's mission at Mercury as the spacecraft prepares for its first flyby of the innermost planet in the Solar System. She speaks with Alison Boyle from London's Science Museum.
Sir Patrick Moore talks to Dr David Rothery about Messenger's Mercury images.
The Messenger probe is looking at the side of Mercury that Mariner 10 couldn't photograph and is studying the planet's magnetic field and dense core. Having now completed a series of flybys, in 2011 it will enter a yearlong orbit of the planet.
MESSENGER (an acronym of MErcury Surface, Space ENvironment, GEochemistry, and Ranging) (also the name of the Roman god it is named after) is a robotic NASA spacecraft orbiting the planet Mercury, the first spacecraft ever to do so. The 485-kilogram (1,070 lb) spacecraft was launched aboard a Delta II rocket in August 2004 to study Mercury's chemical composition, geology, and magnetic field. It became the second mission after 1975's Mariner 10 (launched by NASA on November 3, 1973) to reach Mercury successfully when it made a flyby in January 2008, followed by a second flyby in October 2008, and a third flyby in September 2009.
The instruments carried by MESSENGER were tested on a complex series of flybys – the spacecraft flew by Earth once, Venus twice, and Mercury itself three times, allowing it to decelerate relative to Mercury using minimal fuel. MESSENGER successfully entered Mercury's orbit on March 18, 2011, and reactivated its science instruments on March 24, returning the first photo from Mercury orbit on March 29. MESSENGER's formal data collection mission began on April 4, 2011. On March 17, 2012, having collected close to 100,000 images, MESSENGER ended its one-year primary mission and entered an extended mission scheduled to last until March 2013.
During its stay in Mercury orbit, MESSENGER's instruments have yielded significant data, including a characterization of Mercury's magnetic field and the discovery of water ice at the planet's north pole.