[meteorite-list] Vulcanoid Search Continues as MESSENGER Reaches Orbital Perihelion

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 18 Aug 2010 12:03:14 -0700 (PDT)
Message-ID: <201008181903.o7IJ3Ec9002730_at_zagami.jpl.nasa.gov>

http://messenger.jhuapl.edu/news_room/details.php?id=151

MESSENGER Mission News
August 17, 2010

Vulcanoid Search Continues as MESSENGER Reaches Orbital Perihelion

Today MESSENGER will pass within 0.308 astronomical units (AU) of the
Sun (one AU is Earth's distance from the Sun, approximately 150 million
kilometers or 93 million miles), providing MESSENGER scientists with
another opportunity to search for vulcanoids. Named after the
hypothetical planet Vulcan, whose existence was disproven in 1915,
vulcanoids are asteroids that orbit the Sun inside the orbit of the
planet Mercury.

No vulcanoids have yet been discovered, and it is not known if any
exist. But should they be found, these small, rocky asteroids may yield
insights into the formation and early evolution of the solar system.
They might contain material left over from the earliest period of planet
formation and help determine the conditions under which the terrestrial
planets, particularly Mercury, formed. Vulcanoids would also represent
an additional population of impactors that contributed to the cratering
history of Mercury much more than that of any other body. Impacts by
vulcanoids would make the planet's surface appear older, relative to the
surfaces of the Moon and other inner planets, than it actually is.

If they do exist, the vulcanoids would be difficult to spot. First, they
would be very small - less than 60 kilometers (37 miles) in diameter (a
limit set by Earth-based observations) - and their reflected light would
generally be drowned out by the bright glare of the nearby Sun. Because
of their proximity to the Sun, searches for vulcanoids from the ground
can be carried out only during twilight or or dawn or during solar
eclipses.

The mission's imaging team is taking advantage of the probe's proximity
to the region of space inside Mercury's orbit during this perihelion to
continue their search for vulcanoids. The latest search started on
August 14 and continues through today.

"Our searches for vulcanoids may not turn up any objects," says
MESSENGER principal investigator Sean Solomon, of the Carnegie
Institution of Washington, "but a discovery of even one vulcanoid would
change our thinking about the evolution of Mercury. The solar system
still has many surprises in store for us, so it makes sense for us to be
ready for the unexpected."

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Earth and Moon from 114 Million Miles

This image
<http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?gallery_id=2&image_id=388>
was acquired on May 6, 2010, as part of MESSENGER's campaign to search
for vulcanoids. In the lower left portion, the Earth can be seen, as
well as the much smaller Moon to Earth's right. When MESSENGER took this
image, a distance of 183 million kilometers (114 million miles)
separated the spacecraft and Earth. To provide context for this
distance, the average separation between the Earth and the Sun is about
150 million kilometers (93 million miles).

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Engineer Helps MESSENGER Maintain Balance Between Staying Cool and
Staying Powered

Kim Ord worked on the International Space Station at the NASA Johnson
Space Center in Houston, Texas, for ten years. When Houston's heat
became unbearable, she moved to Maryland to work on MESSENGER at the
Johns Hopkins University Applied Physics Laboratory (APL) in Laurel. Ord
is the power and thermal mission operations analyst for MESSENGER's
mission operations team. To learn more about how she helps MESSENGER
preserve the delicate balance between maintaining safe temperatures and
generating sufficient power, read her profile here:
http://messenger.jhuapl.edu/who_we_are/member_focus.html.

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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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Received on Wed 18 Aug 2010 03:03:14 PM PDT