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An artist's impression of what MESSENGER may look like when it goes into orbit around Mercury in 2011. The white structure on the left side of the spacecraft is the crucial sunshade. Image courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

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MESSENGER Mission to Mercury

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging)
is the name of a spacecraft that will study Mercury; the planet closest to
the Sun. MESSENGER is scheduled for launch from Cape Canaveral Air Force Station
in Florida in early August 2004. After flying by Mercury three times, the spacecraft
will go into orbit around the planet in March 2011. MESSENGER will study Mercury
from orbit for about one year.

Only one other spacecraft has ever visited Mercury! Mariner
10 flew past this
hot planet three times in 1974 and 1975. Because Mariner 10's flybys were all
on the same side of Mercury, it was able to map slightly less than half of
the planet's surface. One of the main goals of the MESSENGER mission is to
complete the job of mapping the entire surface of Mercury by capturing high
resolution images of the planet's surface.

MESSENGER will investigate some of Mercury's other mysteries. Mercury is the
densest planet and has a large core relative to the planet's overall size.
The spacecraft will measure the planet's gravity and its magnetic field, which
will help us learn more about its interior
structure. MESSENGER will also explore
the composition of the materials on Mercury's surface, which will help us understand
the formation
and history of this small planet. Strange as it may seem, some
scientists think there may be ice on Mercury, hiding from the intense heat
of the nearby Sun in the forever shaded bottoms of large craters near the planet's
poles. MESSENGER's instruments will tell us whether water ice is really to
be found in this most unlikely location.

MESSENGER will follow a roundabout route on its trip to Mercury. In order
to save fuel (and to keep the cost of the mission low), the spacecraft will
fly past Earth in August 2005 and past Venus twice, in October
2006 and June 2007. Each planetary flyby will help steer MESSENGER's trajectory
towards Mercury as the gravity of the planets alters the spacecraft's course.
Finally, MESSENGER will fly past Mercury three times (January 2008, October
2008 and September 2009) before settling into orbit around the planet in 2011.

The Sun is about eleven times brighter, and hotter, in the neighborhood of
Mercury than it is near Earth. MESSENGER's flight systems and instruments had
to be carefully designed and tested to ensure that they could survive the incredible
heat. The spacecraft also carries a sunshade to shelter it from the intense
sunlight, much as beachgoers use umbrellas to mitigate the heat on a summer
afternoon.

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