[meteorite-list] MESSENGER Revealing More Details About Planet Mercury

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 29 Sep 2011 12:29:48 -0700 (PDT)
Message-ID: <201109291929.p8TJTmnX014343_at_zagami.jpl.nasa.gov>

Sept. 29, 2011

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: 11-330

NASA SPACECRAFT REVEALING MORE DETAILS ABOUT PLANET MERCURY

WASHINGTON -- NASA's MESSENGER spacecraft, the first to achieve orbit
around Mercury, is providing scientists new information about the
planet. The data show widespread flood volcanism similar to Earth,
clearer views of Mercury's surface, the first measurements of its
elemental composition, and details about charged particles near the
planet.

MESSENGER, or the MErcury Surface, Space ENvironment, GEochemistry,
and Ranging spacecraft, conducted 15 laps through the inner solar
system for more than six years before achieving the historic orbit
insertion March 18. The new results are reported in seven papers
published in Science magazine.

"MESSENGER's instruments are capturing data that can be obtained only
from orbit," says principal investigator Sean Solomon, of the
Carnegie Institution of Washington. "Mercury has many more surprises
in store for us as our mission progresses."

Scientists for decades had puzzled over whether Mercury had volcanic
deposits on its surface. New data show a huge expanse of volcanic
plains surrounding the planet's north polar region. These continuous
smooth plains cover more than six percent of the planet's total
surface. The deposits appear typical of flood lavas, or huge volumes
of solidified molten rock similar to those found in the northwest
United States.

"If you imagine standing at the base of the Washington Monument, the
top of the lavas would be something like 12 Washington Monuments
above you," said James Head of Brown University, the lead author of
one of the papers.

Scientists also have discovered vents or openings measuring up to 16
miles (25 kilometers) across that appear to be the source of some of
the large volume of very hot lava that has rushed across Mercury's
surface carving valleys and creating teardrop-shaped ridges in the
underlying terrain.

New images reveal landforms on Mercury suggesting a previously
unrecognized geological process. Images of bright areas appear to be
small, shallow, irregularly shaped depressions. The science team
adopted the term "hollows" for these features to distinguish them
from other types of pits seen on Mercury. Hollows have been found
over a wide range of latitudes and longitudes, suggesting that they
are fairly common across Mercury.

"Analysis of the images and estimates of the rate at which the hollows
may be growing led to the conclusion that they could be actively
forming today," says David Blewett of the Johns Hopkins University
Applied Physics Laboratory (APL) in Laurel, Md., lead author of one
of the reports.

Scientists also now have observations of the chemical composition of
Mercury's surface. The information is being used to test models of
Mercury's formation and further study the relationship between the
planet's tenuous atmosphere and surface makeup. Chemical measurements
reveal a higher abundance of potassium than previously predicted.

"These measurements indicate Mercury has a chemical composition more
similar to those of Venus, Earth, and Mars than expected," says APL's
Patrick Peplowski, lead author of one of the papers.

MESSENGER also has collected the first global observations of plasma
ions-- mostly sodium -- in Mercury's magnetosphere, the volume of
space near the planet dominated by Mercury's magnetic field. These
results reveal that Mercury's weak magnetosphere provides the planet
very little protection from the gusty solar wind, resulting is a very
hostile surface environment with extremes in space weather.

"We were able to observe the formation process of these ions, and it's
comparable to the manner by which auroras are generated in the
Earth's atmosphere near polar regions," said Thomas Zurbuchen of the
University of Michigan and lead author of one of the reports.

MESSENGER was designed and built by APL. The lab manages and operates
the mission for NASA's Science Mission Directorate (SMD) in
Washington. The mission is part of NASA's Discovery Program, managed
for SMD by the agency's Marshall Space Flight Center in Huntsville,
Ala.

For more information about the mission visit:

http://www.nasa.gov/messenger
        
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Received on Thu 29 Sep 2011 03:29:48 PM PDT