[meteorite-list] MESSENGER To Make Historic Flyby of Mercury

[Ron Baalke]

Jan. 10, 2008

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov

Paulette Campbell
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240-228-6792
paulette.campbell at jhuapl.edu

RELEASE: 08-003

NASA SPACECRAFT TO MAKE HISTORIC FLYBY OF MERCURY

LAUREL, Md. - On Monday, Jan. 14, a pioneering NASA spacecraft will be 
the first to visit Mercury in almost 33 years when it soars over the 
planet to explore and snap close-up images of never-before-seen 
terrain. These findings could open new theories and answer old 
questions in the study of the solar system. 

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging 
spacecraft, called MESSENGER, is the first mission sent to orbit the 
planet closest to our sun. Before that orbit begins in 2011, the 
probe will make three flights past the small planet, skimming as 
close as 124 miles above Mercury's cratered, rocky surface. 
MESSENGER's cameras and other sophisticated, high-technology 
instruments will collect more than 1,200 images and make other 
observations during this approach, encounter and departure. It will 
make the first up-close measurements since Mariner 10 spacecraft's 
third and final flyby on March 16, 1975. When Mariner 10 flew by 
Mercury in the mid-1970s, it surveyed only one hemisphere. 

"This is raw scientific exploration and the suspense is building by 
the day," said Alan Stern, associate administrator for NASA's Science 
Mission Directorate, Washington. "What will MESSENGER see? Monday 
will tell the tale."

This encounter will provide a critical gravity assist needed to keep 
the spacecraft on track for its March 2011 orbit insertion, beginning 
an unprecedented yearlong study of Mercury. The flyby also will 
gather essential data for mission planning. 

"During this flyby we will begin to image the hemisphere that has 
never been seen by a spacecraft and Mercury at resolutions better 
than those acquired by Mariner 10," said Sean C. Solomon, MESSENGER 
principal investigator, Carnegie Institution of Washington. "Images 
will be in a number of different color filters so that we can start 
to get an idea of the composition of the surface."

One site of great interest is the Caloris basin, an impact crater 
about 800 miles in diameter, which is one of the largest impact 
basins in the solar system.

"Caloris is huge, about a quarter of the diameter of Mercury, with 
rings of mountains within it that are up to two miles high," said 
Louise Prockter, the instrument scientist for the Mercury Dual 
Imaging System at the Johns Hopkins University Applied Physics 
Laboratory in Laurel. "Mariner 10 saw a little less than half of the 
basin. During this first flyby, we will image the other side." 

MESSENGER's instruments will provide the first spacecraft measurements 
of the mineralogical and chemical composition of Mercury's surface. 
It also will study the global magnetic field and improve our 
knowledge of the gravity field from the Mariner 10 flyby. The 
long-wavelength components of the gravity field provide key 
information about the planet's internal structure, particularly the 
size of Mercury's core. 

The flyby will provide an opportunity to examine Mercury's environment 
in unique ways, not possible once the spacecraft begins orbiting the 
planet. The flyby also will map Mercury's tenuous atmosphere with 
ultraviolet observations and document the energetic particle and 
plasma of Mercury's magnetosphere. In addition, the flyby trajectory 
will enable unique particle and plasma measurements of the magnetic 
tail that sweeps behind Mercury. 

Launched Aug. 3, 2004, MESSENGER is slightly more than halfway through 
its 4.9-billion mile journey. It already has flown past Earth once 
and Venus twice. The spacecraft will use the pull of Mercury's 
gravity during this month's pass and others in October 2008 and 
September 2009 to guide it progressively closer to the planet's 
orbit. Insertion will be accomplished with a fourth Mercury encounter 
in 2011.

The MESSENGER project is the seventh in NASA's Discovery Program of 
low-cost, scientifically focused space missions. The Applied Physics 
Laboratory designed, built and operates the spacecraft and manages 
the mission for NASA.

For more information about MESSENGER, visit:

http://www.nasa.gov/messenger

	
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