A NASA space probe to Mercury, launched in 2004 August. It used two Venus flybys, in 2006 October and 2007 June, to adjust its trajectory. It flew past Mercury three times, in 2008 January and October and 2009 September, before going into near-polar orbit around the planet in 2011 March. The probe studies Mercury's surface composition, geologic history, interior, magnetic field, and tenuous atmosphere, as well as searching for water ice at the poles. Its instruments are the Mercury Dual Imaging System (MDIS), Gamma-Ray and Neutron Spectrometer (GRNS), X-ray Spectrometer (XRS), Mercury Laser Altimeter (MLA), Atmospheric and Surface Composition Spectrometer (ASCS), Energetic Particle and Plasma Spectrometer (EPPS), and a magnetometer.
http://messenger.jhuapl.edu/ Official mission website.
http://www.nasa.gov/mission_pages/messenger/main/ Mission page at NASA.
Subjects: Astronomy and Astrophysics.