Knowra MESSENGER MESSENGER NASA’s robotic spacecraft that orbited Mercury from 2011 to 2015, mapping the planet and measuring its surface, interior, exosphere, and magnetic field.
Mercury orbit insertion : The maneuver that places a spacecraft into orbit around Mercury. MESSENGER entered Mercury orbit on March 18, 2011, after six planetary flybys.
Hollows on Mercury : Irregular, often bright, shallow depressions found in clusters on Mercury’s surface. MESSENGER images revealed these distinctive landforms, which may form as volatile materials escape.
Discovery Program : NASA’s series of competitively selected, relatively low-cost planetary science missions. MESSENGER was selected as the seventh mission in this program.
Mercury's internal structure : The layered interior of Mercury, including its large metallic core, rocky mantle, and crust. MESSENGER gravity and composition data constrained models of the planet’s unusually large core.
Gravity assist : A spacecraft navigation technique that uses a planet’s gravity to change speed or direction. Repeated gravity assists reduced the fuel needed to reach Mercury.
Mercury's water ice : Water ice preserved in permanently shadowed regions near Mercury’s poles. MESSENGER data strengthened evidence for polar deposits hidden from direct sunlight.
Mariner 10 : NASA’s 1973–1975 mission that made the first close-up observations of Mercury. Its three flybys provided the main spacecraft observations of Mercury before MESSENGER.
Mercury's volcanic plains : Broad expanses of volcanic deposits that cover substantial areas of Mercury’s surface. MESSENGER mapped their distribution and established extensive volcanism in the planet’s history.
MESSENGER Dual Imaging System : MESSENGER’s camera system, comprising a wide-angle camera and a narrow-angle camera. Its images mapped Mercury and documented surface features at multiple scales.
Mercury's magnetic field : A global magnetic field generated within Mercury and unusually weak compared with Earth’s. MESSENGER measured its structure and found a strong northward offset of the magnetic equator.
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