[meteorite-list] Observations Reveal Curiosities On The Surface Of Asteroid Ceres

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:47:04 2004
Message-ID: <200111011807.KAA12790_at_zagami.jpl.nasa.gov>

http://www.swri.org/9what/releases/ceres.htm

Southwest Research Institute (SwRI) News

Observations reveal curiosities on the surface of asteroid Ceres

San Antonio, Texas -- For immediate release

Boulder, Colorado -- October 19, 2001 -- An international team
led by scientists at the Southwest Research Institute (SwRI) has
discovered some curious properties of the largest asteroid,
Ceres. The astronomers observed Ceres with the Hubble Space
Telescope (HST) at ultraviolet wavelengths using a resolution
higher than previously attained. The resulting images are the
first to resolve detail on the surface of Ceres and show features
as small as 50 kilometers across.

Led by Principal Investigator Dr. Alan Stern of SwRI, the team
detected a dark spot on the surface of Ceres, which it nicknamed
"Piazzi" in honor of the discoverer of Ceres. "Although we can't
determine the nature of the spot with these data, whether it is
an area of different coloration or possibly a crater from an
impact by another asteroid, it is pretty big," says Dr. Joel
Parker, also of SwRI, who led the team in the analysis of the
images. "The Piazzi feature has a diameter of about 250
kilometers, which is more than a quarter the size of Ceres. If it
resulted from an impact, the object that hit Ceres would have
been about 25 kilometers across. It must have really shaken
things up."

The high-resolution images allowed the team to refine
measurements of Ceres. Although Ceres is the largest known
asteroid -- estimated to contain more than one-third of the total
mass of all other asteroids combined -- researchers still dispute
its size, even after 200 years of observations. The new HST
measurements indicate that the asteroid is slightly flattened,
with a diameter ranging from 930 to 970 kilometers. Spinning
objects can have a flattened or "squashed" shape depending on how
big they are, how fast they spin, and what kind of material they
are made of. However, the amount of flattening seen on Ceres is
more than expected and may indicate that the inner structure is
not as homogeneous as previously assumed.

"These results are very tantalizing," says Stern. "What we need
to be definitive are observations with better resolution and
frequent enough to follow Ceres through a nine-hour rotation
period to track surface features. This 'movie' would allow us to
finally map the surface of Ceres and figure out what the Piazzi
feature is." The team has already proposed such an experiment
with a new instrument to be installed on HST next year.

The analysis of the Ceres images will be published in the January
2002 issue of The Astronomical Journal. Authors include
researchers from SwRI, the Massachusetts Institute of Technology,
Cornell University, the University of Arizona, and the
Observatoire Midi-Pyrénées in France.

In addition to being the largest asteroid, Ceres was also the
first asteroid to be discovered. In the latter part of the 18th
century, astronomers noted a regular spacing in the planets of
the solar system, but with a gap between Mars and Jupiter where
they expected to find a planet. On January 1, 1801, the Sicilian
astronomer Giuseppe Piazzi at the Palermo Observatory discovered
a moving object in the region. Researchers at the time assumed
that this object, Ceres, was the missing planet. However, early
observations indicated that Ceres was too small to be a planet,
and as more such objects were discovered in the region, they
became known as "asteroids" or "minor planets." Ceres orbits the
sun once every 4.6 years at a distance of 41 million kilometers,
and it spins on its axis once every nine hours.

EDITORS: The Ceres images are available for viewing and download
at www.swri.org/press/ceres.htm.

SwRI is an independent, nonprofit, applied research and
development organization based in San Antonio, Texas, with more
than 2,700 employees and an annual research volume of more than
$315 million.

For more information about exhaust emission measurements, contact
Maria Martinez, (210) 522-3305, Communications Department, or Dr.
Joel Parker, (303) 546-0265, Southwest Research Institute, P.O.
Drawer 28510, San Antonio, Texas, 78228-0510, Fax (210) 522-3547.
Received on Thu 01 Nov 2001 01:07:58 PM PST