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SPACE
THE MYSTERY OF MERCURY
(July 4) - A NASA spacecraft's first flyby of
Mercury has yielded a wealth of information about the inner-most planet, some of
which confirms volcanism occurred there, settling a longstanding debate.
Information about such planetary mysteries as Mercury's magnetic field and
geological history also has flooded in.
"We're really pleased," said Sean C.
Solomon of the Carnegie Institution of Washington, principal investigator for
the MESSENGER probe. "[The data] gives us a lot to chew on."
MESSENGER (short for MErcury Surface, Space ENvironment, GEochemistry, and
Ranging) made its debut flyby of Mercury on Jan. 14, passing about 124 miles
(200 kilometers) over the planet's surface. The spacecraft's instruments took a
closer look at the areas seen by the Mariner 10 mission in 1974 and 1975, which
imaged about 45 percent of the planet's surface, as well as an additional 21
percent of the surface never before seen by a spacecraft.
In a collection of 11 papers detailed in the July
4 issue of the journal Science, mission scientists presented the preliminary
findings of the initial flyby.
Volcanism or impact melt?
Volcanism has long been thought to be a major force in shaping the rocky,
terrestrial planets. Volcanoes still ravage Earth. On Mars, subdued volcanism
may still be alive. Venus is riddled with old volcanoes.
Images of Mercury from the Mariner 10 mission showed areas of smooth plains
covering parts of the planet's surface. Scientists speculated that these could
be volcanic deposits, similar to the basaltic maria (seas) on the Moon. But
unlike the maria, these plains were lighter, not darker, than the surrounding
landscape, and Apollo 16 astronauts had just discovered that similarly light
plains on the Moon were actually impact breccia, or rock that was smashed apart
and then re-welded together again.
This false color picture of Mercury was created by combining many images taken by the probe Mariner 10 when it first flew past Mercury in March, 1974. Mercury's surface looks somewhat like the Moon, with smooth lava plains (called maria on the Moon) and cratered highlands. However, the contrast between the plains and highlands is less dramatic on Mercury: the plains are not as dark as on the Moon and have more craters.
http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level2/mercury.html
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One week ago, the MESSENGER spacecraft transmitted to Earth the first high-resolution image of Mercury by a spacecraft in over 30 years, since the three Mercury flybys of Mariner 10 in 1974 and 1975. MESSENGER's Wide Angle Camera (WAC), part of the Mercury Dual Imaging System (MDIS), is equipped with 11 narrow-band color filters, in contrast to the two visible-light filters and one ultraviolet filter that were on Mariner 10's vidicon camera. By combining images taken through different filters in the visible and infrared, the MESSENGER data allow Mercury to be seen in a variety of high-resolution color views not previously possible. MESSENGER's eyes can see far beyond the color range of the human eye, and the colors seen in the accompanying image are somewhat different from what a human would see.
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mercury
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http://www.spacetoday.org/SolSys/Mercury/MercuryBackground.html
http://www.aerospaceguide.net/planet/planetmercury.html
http://en.wikipedia.org/wiki/Mercury_(planet)
http://www.nineplanets.org/mercury.html
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