MESSENGER Reveals Mercury as Never Seen Before

http://messenger.jhuapl.edu/news_room/details.php?id=111

MESSENGER Mission News
October 7, 2008

MESSENGER Reveals Mercury as Never Seen Before

When Mariner 10 flew past Mercury three times in 1974 and 1975, the
probe imaged less than half the planet. In January, during MESSENGER's
first flyby, its cameras returned images of about 20 percent of the
planet's surface missed by Mariner 10. Yesterday, at 4:40 am EDT,
MESSENGER successfully completed its second flyby of Mercury, and its
cameras captured more than 1,200 high-resolution and color images of
the
planet - unveiling another 30 percent of Mercury's surface that had
never before been seen by spacecraft.

"The MESSENGER team is extremely pleased by the superb performance of
the spacecraft and the payload," said MESSENGER Principal Investigator
Sean Solomon of the Carnegie Institution of Washington. "We are now on
the correct trajectory for eventual insertion into orbit around
Mercury,
and all of our instruments returned data as planned from the side of
the
planet opposite to the one we viewed during our first flyby. When
these
data have been digested and compared, we will have a global
perspective
of Mercury for the first time."

Today, at about 1:50 a.m. EDT, MESENGER turned to Earth and began
transmitting data gathered during its second Mercury encounter. This
spectacular image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
gallery_id=2&image_id=214>
- one of the first to be returned - was snapped by the Wide Angle
Camera
(WAC), part of the Mercury Dual Imaging System (MDIS) instrument,
about
90 minutes after MESSENGER's closest approach to Mercury, when the
spacecraft was at a distance of about 27,000 kilometers (about 17,000
miles).

The bright crater just south of the center of the image is Kuiper,
identified on images from the Mariner 10 mission in the 1970s. For
most
of the terrain east of Kuiper, toward the edge of the planet, the
departing images are the first spacecraft views of that portion of
Mercury's surface. A striking characteristic of this newly imaged area
is the large pattern of rays that extend from the northern region of
Mercury to regions south of Kuiper.

This WAC image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
page=1&gallery_id=2&image_id=215>
is one in a sequence of 55: a five-frame mosaic with each frame in the
mosaic acquired in all 11 of the WAC filters. This portion of
Mercury's
surface was previously imaged under different lighting conditions by
Mariner 10, but this new MESSENGER image mosaic is the
highest-resolution color imaging ever acquired of any portion of
Mercury's surface.

Additionally, some of the images in this mosaic overlap with flyby
data
acquired by the Mercury Atmospheric and Surface Composition
Spectrometer
and Mercury Laser Altimeter instruments, resulting in the first time
that these three instruments have gathered data of the same area of
Mercury. The combination of these three datasets will enable
unprecedented studies of this region of Mercury's surface.

This image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
page=1&gallery_id=2&image_id=216>,
acquired about 89 minutes before the craft's closest approach to
Mercury, resembles the optical navigation images taken leading up to
the
flyby. The resolution of this image is somewhat better than that
obtained by the final optical navigation image set
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
page=&gallery_id=2&image_id=213>,
and the surface visible is newly imaged terrain that was not
previously
seen by either Mariner 10 or during MESSENGER's first flyby.

However, the added resolution is not the main scientific advancement
that will be provided by this image. This WAC image is one of 11
viewed
through different narrow-band color filters, the set of which will
enable detailed color studies of this newly imaged area. In addition,
the Narrow Angle Camera (NAC) acquired a high-resolution mosaic of
most
of this thin crescent view of Mercury at a resolution better than 0.5
kilometers/pixel (0.3 miles/pixel) that will enable the MESSENGER team
to explore this newly imaged region of Mercury's surface in more
detail.

About 58 minutes before MESSENGER's closest approach to Mercury, the
NAC
captured this close-up image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?
page=1&gallery_id=2&image_id=217>
of a portion of Mercury's surface imaged by spacecraft for the first
time. It is one of 44 in a high-resolution NAC mosaic taken of the
approaching crescent-shaped Mercury, as seen at lower resolution in
the
optical navigation images and the approach WAC color image set.

As the MESSENGER team is busy examining this newly obtained view, data
from the flyby continue to stream down to Earth, including higher
resolution close-up images of this previously unseen terrain.
Collectively, these images and measurements made by other MESSENGER
instruments will soon provide a broad range of information for
understanding the formation and geologic history of the innermost
planet.

------------------------------------------------------------------------

Additional information and features from this encounter will be
available online at http://messenger.jhuapl.edu/mer_flyby2.html, so
check back frequently. Following the flyby, be sure to check back to
see
the latest released images and science results!

------------------------------------------------------------------------

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and
Ranging) is a NASA-sponsored scientific investigation of the planet
Mercury and the first space mission designed to orbit the planet
closest
to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and
after flybys of Earth, Venus, and Mercury will start a yearlong study
of
its target planet in March 2011. Dr. Sean C. Solomon, of the Carnegie
Institution of Washington, leads the mission as principal
investigator.
The Johns Hopkins University Applied Physics Laboratory built and
operates the MESSENGER spacecraft and manages this Discovery -class
mission for NASA.

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