Mercury imaged by MESSENGER
Credit: NASA, CIE, APL
Mercury has been visited only once prior to the MESSENGER spacecraft, which is now on its way toward orbiting the inner-most planet. Between 1974 and 1975, Mariner 10 mapped about 45% of the surface of Mercury. It was launched on November 3, 1973 and flew past Venus for observations and a gravity assist to guide it toward Mercury.
Observations of Mariner 10’s three flybys of Mercury showed it to be the densest planet among four rocky inner Solar System planets (Mercury, Venus, Earth, and Mars). Mercury has the oldest surface, it has the largest daily variations in surface temperature, and it is the least explored. Understanding the evolution of the Solar System requires understanding the extreme characteristics of Mercury.
The mission is designed to research six key questions:
The Magnetometer (MAG) will measure the magnetic field’s precise strength and how it varies with position and altitude, and ultimately help determine the source of Mercury’s magnetic field.
The Mercury Laser Altimeter (MLA) will use an infrared laser transmitter and a receiver to map Mercury’s landforms and other surface characteristics. The data will also be used to track the planet’s slight, forced libration, which will tell researchers about the state of Mercury’s core.
The Energetic Particle and Plasma Spectrometer (EPPS) will measure the mix and characteristics of charged particles in and around Mercury’s magnetosphere using an Energetic Particle Spectrometer (EPS) and a Fast Imaging Plasma Spectrometer (FIPS).
Radio Science (RS). The Deep Space Network (DSN) will precisely measure MESSENGER’s speed and distance from Earth. Scientists and engineers will observe changes in MESSENGER’s movements at Mercury in order to measure the planet’s gravity field, and to support the laser altimeter investigation to determine the size and condition of Mercury’s core.
The spacecraft launched on August 3, 2004, aboard a Boeing Delta II rocket from Cape Canaveral Air Force Station, Florida.
MESSENGER will travel more than six and a half years before it begins to orbit Mercury in March 2011. This journey includes a flyby of Earth (in August 2005), two flybys of Venus (October 2006 and June 2007) and three flybys of Mercury (January 2008, October 2008 and September 2009).