WASHINGTON -- A NASA spacecraft will conduct the second of three
flybys of Mercury on Oct. 6 to photograph most of its remaining
unseen surface and collect science data.
The MErcury Surface, Space ENvironment, GEochemistry, and Ranging, or
MESSENGER, spacecraft will pass 125 miles above the planet's cratered
surface, taking more than 1200 pictures. The flyby also will provide
a critical gravity assist needed for the probe to become, in March
2011, the first spacecraft to orbit Mercury.
"The results from MESSENGER's first flyby of Mercury resolved debates
that are more than 30 years old, " said Sean C. Solomon, the mission's
principal investigator from the Carnegie Institution of Washington.
"This second encounter will uncover even more information about the
planet."
During the spacecraft's first flyby on Jan. 14, its cameras returned
images of approximately 20 percent of Mercury's surface never before
seen by space probes. Images showed that volcanic eruptions produced
many of Mercury's plains, its magnetic field appears to be actively
generated in a molten iron core, and the planet has contracted more
than previously thought.
"This second flyby will show us a completely new area of Mercury's
surface, opposite from the side of the planet we saw during the
first, " said Louise M. Prockter, instrument scientist for the
spacecraft's Mercury Dual Imaging System at the Johns Hopkins
University Applied Physics Laboratory, or APL, in Laurel, Md.
The second flyby is expected to yield more surprises about the unique
physical processes governing Mercury's atmosphere, as well as
additional information about the charged particles located in and
around Mercury's dynamic magnetic field. An altimeter on the
spacecraft will measure the planet's topography, allowing scientists,
for the first time, to correlate high-resolution topography
measurements with high-resolution images.
A major goal of the orbital phase of the mission is to determine the
composition of Mercury's surface. Instruments designed to make those
measurements will get another peek at Mercury during this flyby.
"We will be able to do the first test of differences in the chemical
compositions between the two hemispheres viewed in the two flybys, "
said Ralph McNutt, the mission's project scientist at APL.
"Instruments also will provide information about portions of
Mercury's surface in unprecedented detail."
The spacecraft is more than halfway through a 4.9-billion-mile journey
to enter orbit around Mercury that includes more than 15 trips around
the sun. In addition to flying by Mercury, the spacecraft flew past
Earth in August 2005 and past Venus in October 2006 and June 2007.
The project is the seventh in NASA's Discovery Program of low-cost,
scientifically focused space missions. The spacecraft was designed
and built by APL. The mission also is managed and operated by APL for
NASA's Science Mission Directorate in Washington.
For more information about the mission, visit: www.nasa.gov/messenger
US $22.75
