MESSENGER Settles Old Debates, Makes New Discoveries at
Mercury
Scientists have argued about the origins of Mercury's
smooth plains and the source of its
magnetic field for more than 30 years. Now, analyses of
data from the January flyby of the planet by
the MESSENGER spacecraft have shown that volcanoes were
involved in plains formation and suggest
that its magnetic field is actively produced in the
planet's core and is not a frozen relic. Scientists
additionally took their first look at the chemical
composition of the planet's surface material. The tiny
craft probed the composition of Mercury's thin atmosphere,
sampled charged particles (ions) near the
planet and demonstrated new links between both sets of
observations and materials on Mercury's
surface. The results are reported in a series of 11 papers
published in a special section of the July 4
issue of Science magazine.
"When you look at the planet in the sky, it looks like
a simple point of light," remarked
MESSENGER project scientist Ralph McNutt, of APL. "But when
you experience Mercury close-up
through all of MESSENGER's 'senses'�seeing it at different
wavelengths, feeling its magnetic
properties and touching its surface features and energetic
particles�you perceive a complex system
and not just a ball of rock and metal. We are all surprised
by how active that planet is and at the
dynamic interrelationships among its core, surface,
exosphere and magnetosphere."
"It's remarkable that this rich lode of data came from
two days of imaging, just 30 minutes of
sampling the planet's magnetosphere and exosphere, and less
than 10 minutes carrying out altimetry
and collecting other data near the time of its closest
approach 125 miles to the surface," said
principal investigator Sean Solomon, of the Carnegie
Institution of Washington. "MESSENGER's first
flyby was a huge success, both in keeping us on target for
the rest of our journey and in advancing our
progress toward answering the science questions that have
motivated this mission."
MESSENGER is a NASA-sponsored scientific investigation
of Mercury and the first space
mission designed to orbit the planet closest to the sun.
The Johns Hopkins Applied
Physics Laboratory
built and operates the MESSENGER spacecraft and manages the
mission for NASA. The spacecraft
launched on Aug. 3, 2004, and in March 2011, after flybys
of Earth, Venus and Mercury, will start a
yearlong study of its target planet.
To read about the flyby's discoveries, go to:
messenger.jhuapl.edu/mer_flyby1.html.
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