[Prev][Next][Index][Thread]

(meteorobs) (Exciting!) Excerpts from "CCNet 103/2001 - 28 September 2001"




An exciting issue! Just as our knowledge about and ability to research
the nature of comets and asteroids expands (thanks, very signficantly,
to the efforts of amateurs), our awareness of their profound importance
in the ontogeny of planetary systems (and ultimately of us) also grows.

Clear skies,
Lew Gramer


------- Forwarded Message

From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet 103/2001 - 28 September 2001
Date: Fri, 28 Sep 2001 10:03:29 +0100

CCNet 103/2001 - 28 September 2001
==================================

"On 12 February this year, the Near-Earth Asteroid Rendezvous
Shoemaker mission landed on the asteroid Eros, completing a journey of
more than 3 billion kilometres. It discovered a complex miniature
world, researchers now reveal. [...] There are thousands of large
boulders on Eros, which is only 33 kilometres long and 13 kilometres across.
The positions 	of the boulders indicate that most of them were scoured out
of a crater 7.6 kilometres wide, formed by the impact of a body several
hundred metres across. The rubble shows that debris from impacts could
still fall back to the surface, despite the asteroid's gravity 	being about
1,000 times weaker than that of the Earth. "This erases about 20 years of
thought that small asteroids should be devoid of any loose material," says
Erik Asphaug of the University of California at Santa Cruz."
JOHN WHITFIELD, Nature, 27 September 2001


[...]

(3) DEEP SPACE 1 CAPTURES BEST-EVER VIEW OF COMET'S CORE
    Ron Baalke <baalke@jpl.nasadot gov>

(4) BORRELLY HAS SCIENTISTS RETHINKING COMET THEORY
    Los Angeles Times, 26 September 2001

(5) MAPPING OF ASTEROID EROS FINDS LARGE ROCKS ON SURFACE WERE
    EJECTED FROM SINGLE CRATER
    Andrew Yee <ayee@nova.astro.utorontodot ca>

[...]
 
(7) ROCK GARDEN ON EROS
    Nature Science Update, 27 September 2001

(8) EXPERTS PUZZLE OVER STRANGE STRUCTURE OF EARTH'S (sic) ASTEROID
    The Independent, 27 September 2001

[...]

(10) SOLAR SYSTEM FORMATION SURPRISES
     Cosmicverse, September 20, 2001 

[...]

================

(3) DEEP SPACE 1 CAPTURES BEST-EVER VIEW OF COMET'S CORE

>From Ron Baalke <baalke@jpl.nasadot gov>

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasadot gov

Contact: JPL/Martha J. Heil      (818) 354-0850                  
         NASA/Dolores Beasley (202) 358-1753

FOR IMMEDIATE RELEASE                     September 25, 2001

NASA SPACERAFT CAPTURES BEST-EVER VIEW OF COMET'S CORE 

In a risky flyby, NASA's ailing Deep Space 1 spacecraft successfully
navigated past a comet, giving researchers the best look ever inside the
glowing core of icy dust and gas.

The space probe's close encounter with comet Borrelly provided the
best-resolution pictures of the comet to date. The already-successful Deep
Space 1, without protection from the little-known comet environment, whizzed
by just 2,200 kilometers (1,400 miles) from the rocky, icy nucleus of the
10-kilometer-long (more than 6-mile-long) comet. 

Exceeding the team's expectations of how this elderly spacecraft would
perform, the intrepid spacefarer sent back black-and-white photos of the
inner core of the comet.  It also measured the types of gases and infrared
waves around the comet, and how the gases interacted with the solar wind.

"Deep Space 1 plunged into the heart of comet Borrelly and has lived to tell
every detail of its spine-tingling adventure!" said Dr. Marc Rayman, the
project manager of Deep Space 1 at the Jet Propulsion Laboratory (JPL),
Pasadena, Calif. "The images are even better than the impressive images of
comet Halley taken by Europe's Giotto spacecraft in 1986."

Rayman added, "After years of nursing this aged and wounded bird along -- a
spacecraft not structured to explore comets, a probe that exceeded its
objectives more than two years ago -- to see it perform its remarkably
complex and risky assignment so well was nothing short of incredible."

"It's mind-boggling and stupendous," said Dr. Laurence Soderblom, the leader
of Deep Space 1's imaging team, and a geologist with the U.S. Geological
Survey, Flagstaff, Ariz. "These pictures have told us that comet nuclei are
far more complex than we ever imagined. They have rugged terrain, smooth
rolling plains, deep fractures and very, very dark material."

Scientists also realized that Borrelly was different than they expected as
Deep Space 1 flew through the coma, the cloud of dust and gas surrounding
the nucleus. They had expected 
that the solar wind would flow symmetrically around the cloud, with the
nucleus in the center. 

Instead, they found that though the solar wind was flowing symmetrically
around the cloud, the nucleus was off to one side shooting out a great jet
of material forming the cloud that makes the comet visible from Earth. "The
formation of the coma is not the simple process we once thought it was,"
said Dr. David Young of the University of Michigan, Ann Arbor, leader of the
team that made the measurements. "Most of the charged particles are formed
to one side, which is not what we expected." 

Deep Space 1 completed its primary mission testing ion propulsion and 11
other advanced, high-risk technologies in September 1999. NASA extended the
mission, taking advantage of the ion propulsion and other systems to
undertake this chancy but exciting encounter with the comet.

Deep Space 1, launched in October 1998 as part of NASA's  New Millennium
Program, is managed by JPL for NASA's Office of Space Science in Washington.
The California Institute of  Technology manages JPL for NASA.

More information can be found on the Deep Space 1 Internet home page at:
http://nmp.jpl.nasadot gov/ds1/ .

=========

(4) BORRELLY HAS SCIENTISTS RETHINKING COMET THEORY
 
>From Los Angeles Times, 26 September 2001
http://www.latimes.com/news/printedition/asection/la-000077137sep26.story?co
ll=la%2Dnews%2Da%5Fsection
       
By USHA LEE McFARLING, TIMES SCIENCE WRITER

The first clear and close-up photos ever taken of a comet have scientists
rewriting much of what they thought they knew about the common and often
dazzling objects that transit our solar system.

"It's mind-boggling and stupendous," said Laurence Soderblum, who led the
team that captured images of the comet Borrelly about 137 million miles from
Earth using NASA's Deep Space 1 spacecraft. Comets, he said, "are far more
complex than we ever imagined."

Comets have long been thought of as relatively homogeneous objects that
generate uniform clouds of dust and gas. The new images contradict those
beliefs. Borrelly's 5-mile-long rocky core is far from uniform. It's an
object of rugged terrain that includes two mountainous peaks, smooth rolling
plains and deep fractures. The core, or nucleus, of the comet is shaped
something like an upside-down bowling pin. "It's a very strange geometry,"
Soderblum said.

Moreover, it is known that comets disrupt the energized particles that come
from the sun and flow through space. But preliminary measurements from Deep
Space 1 show that Borrelly disrupted this "solar wind" in a completely
unexpected manner. The nucleus of the comet did not do the disrupting; the
solar wind was disrupted by charged particles that came from the comet, but
were only on one side of it.

"It's as if a shock wave is not in front of a jet fighter, but a mile off to
the side," said David Young, a space physicist at the University of
Michigan. "It's in the wrong place. Period."

Fascination with comets dates back to ancient times, when people treated the
occasional visitations of mysterious "hairy stars" as omens. Scientists
regard the icy clumps of rock and dust as pristine, frozen remnants of the
material that made up the early solar system. Some researchers theorize that
comets may have been responsible for carrying to Earth the water and organic
materials necessary for life.

Comets "tell us where we came from and where we might be going," Robert M.
Nelson, the project scientist for Deep Space 1, said at a news conference
Tuesday at NASA's Jet Propulsion Laboratory in Pasadena.

Another puzzle from Borrelly is that the nucleus is much darker in some
places than others. The entire object is covered with soot--but some of the
soot is "dark, dark, dark, dark," Soderblum said. Scientists are not sure
why the areas look so different. The darker areas appear to be on top of the
peaks and "are not just shadows," Soderblum added.

The photos lend credence to the idea that comets are less like "dirty
snowballs" than "snowy dirt balls."

"This object is blacker than a charcoal briquette on the surface," said
Donald Yeomans, an expert on comets at JPL who was not directly involved
with the mission.

The inside of the comet is likely to be mainly ice, he said, comparing the
comet to a baked Alaska dessert--a frozen core surrounded by a crust of
different material.

In addition, there is not just one jet of gas coming from the comet, but
jets spewing in several directions. The largest jet is not uniform, but
appears to be made up of at least three columns. And the jets spout from
distinct parts of the comet, most notably the smooth plains, which appear to
be eroding as material spews off.

"This is not a ho-hum picture," Young said. "We've got some explaining to
do."

Scientists said Tuesday they were just beginning to analyze the photos and
voluminous amounts of data gathered by the spacecraft. "All these ideas are
still floating around in our heads," said Daniel Boice, a member of the
science team from the Southwest Research Institute in San Antonio.

The spacecraft that snapped the images, Deep Space 1, was not built to
conduct any science and has far outlived its expected life span. It was
launched in 1998 to spend a year testing exotic new technologies, including
an engine propelled solely by ions and an artificial intelligence
navigational system. But it has been nursed along and rescued once from
complete failure by a band of JPL engineers led by Marc Rayman. Nearly
emptied of gas, it made it to the comet on fumes.

"If this was a car, the fuel light would be on," said Todd Barber, a JPL
propulsion engineer.

Although he is still analyzing information coming from the spacecraft,
Rayman said it appeared to survive the risky 36,900-mile trip through
dangerous cometary debris unscathed. "The only thing unusual about the
spacecraft," he said, "is it has a big grin on it now."

Images of the comet can be viewed at http://www.jpl.nasadot gov 

Copyright 2001 Los Angeles Times 

===============

(5) MAPPING OF ASTEROID EROS FINDS LARGE ROCKS ON SURFACE WERE
    EJECTED FROM SINGLE CRATER

>From Andrew Yee <ayee@nova.astro.utorontodot ca>

News Service
Cornell University

Contact: David Brand
Office: 607-255-3651
E-Mail: deb27@cornelldot edu

EMBARGOED FOR RELEASE: WEDNESDAY, SEPT. 26, 2 P.M. EST

First detailed mapping of asteroid 433 Eros finds most large rocks on
surface were ejected from single crater

ITHACA, N.Y. -- The first detailed global mapping of an asteroid has found
that most of the larger rocks strewn across the body were ejected from a
single crater in a meteorite collision perhaps a billion years ago. 

"One big impact spread all this debris," says Peter Thomas, senior
researcher in Cornell University's Department of Astronomy. "This
observation is helping us start answering questions about how things work on
the surface of an asteroid."

Thomas' report on the crater -- which has the proposed name of Shoemaker --
as a major source of ejected rocks on asteroid 433 Eros appears in the
latest issue (Sept. 27) of the journal Nature . Thomas' fellow authors are
Joseph Veverka, professor of astronomy at Cornell; Mark Robinson of
Northwestern University and Scott Murchie of Johns Hopkins University. The
paper is one
of three detailing the first findings from the controlled landing of the
spacecraft NEAR-Shoemaker on the surface of Eros on Feb. 12, 2001.

Before the landing, the spacecraft had orbited Eros for a year, taking
thousands of high-resolution images of the 21-mile-long asteroid. From the
global map of the surface that was assembled, Thomas and his colleagues were
able to count 6,760 rocks larger than about 16 yards across (15 meters)
strewn over the asteroid's 434 square miles (1,125 square kilometers). They
found that nearly half (44 percent) of these rocks were inside the Shoemaker
crater, positioned near one end of the potato-shaped asteroid. And most of
the rocks of this size along the asteroid's equator appear to have been
ejected from Shoemaker, Thomas says.

"We know they came from Shoemaker because the mapping of the geography of
the pattern [of the rocks] on the surface closely matches the predicted
paths from the one impact event that made Shoemaker," he says. Eros is
estimated to be about 4 billion years old, probably the remnant of a larger
asteroid broken up by a collision with another asteroid. Perhaps a billion
years ago, Eros itself was struck by an object -- a meteorite or small comet
- -- creating a crater nearly 5 miles (7.6 kilometers) wide and shattering
into rocks of all sizes. Some of these rocks "went straight up and straight
down," says Thomas. Most of the remainder traveled as far as two-thirds of
the way around the rotating asteroid in either direction (the asteroid
rotates once every 5 1/4 hours), finally coming to rest on the surface. The
mystery posed by the Eros maps for the researchers is why the same thing
didn't happen with two other large craters on Eros: Himeros, on
the body's convex side, and Psyche, on the concave side. Either the rocks
have been buried, have been eroded or weren't made in the first place, says
Thomas.

One of the big surprises from the maps, Robinson reports in his Nature
paper, is that Eros' surface appears to have a global cover of "loose
fragmental debris." The surface appears to be blanketed with a fine
material, some of which has created flat deposits, particularly in
depressions, such as craters. These fine deposits, Robinson's paper reports,
appear to have
been "sorted" from the upper portion of the asteroid's regolith, or soil.

These so-called "ponded" deposits were visible in the final images
transmitted by the spacecraft before it hit the asteroid's surface. Indeed,
in his paper Veverka reports, "A strong argument is that the last image
shows that the spacecraft landed on or within a few meters of a pond, a
landform known to occur predominantly on the floors of craters."

How has this sorting occurred? Robinson's paper postulates an electrostatic
effect, similar to that indicated on the moon's surface by the Surveyor
spacecraft. Particles can build up photoelectric charges with long exposure
to the sun, and this charge might separate out finer particles, says Thomas.
But he concedes, "This requires a lot of assumptions, and does not explain
all the mechanisms."

The big question for researchers is: Do these observations of the surface
mechanics of Eros indicate that similar processes are under way on other
astronomical bodies? In his paper, Veverka notes it is difficult to make
comparisons because no other such distant body has been so closely mapped.
There are high-resolution views of the asteroids Gaspra and Ida and of
Phobos, a satellite of Mars. Phobos, he writes, does show groupings of rocks
in the vicinity of the crater Stickney that are comparable to those on Eros.
"Nothing comparable to the flat 'pond' deposits has been noted on Gaspra,
Ida or Phobos, even though Phobos coverage is certainly adequate to show
such features if they were present," he writes. In making his assessment of
rock distribution on Eros, Thomas counted about 30,000 rocks. He was able to
do this by using software created by Cornell analyst Jonathan Joseph. The
software allows a researcher to mark a rock in an image, then calculate from
a shape model where the rock is and its size and then to record this
information in a data file.

Thomas's report in Nature is titled "Shoemaker Crater: A major source of
ejecta on asteroid 433 Eros." Veverka's report, which has several
co-authors, is titled "The landing of the NEAR-Shoemaker spacecraft on
asteroid 433 Eros." (Veverka was the principal investigator on the
multispectral imager, or camera, and the NEAR infrared spectrometer, two of
the five instruments on board the spacecraft.) Robinson's report,
co-authored by Thomas, Veverka, Murchie and Brian Carcich of Cornell, is
titled "Morphology, Distribution and Origin of Ponded Deposits on Eros." The
research was supported by NASA.

Related World Wide Web sites:

The following sites provide additional information on this news release.
Some might not be part of the Cornell University community, and Cornell has
no control over their content or availability.

* Near Earth Asteroid Rendezvous Mission
   http://near.jhuapldot edu/

IMAGE CAPTION:
<http://www.news.cornelldot edu/releases/Sept01/Eros.Naturedot deb.html>
Images of 433 Eros taken from the orbiting NEAR-Shoemaker spacecraft: (a),
scale bar, lower right, measures 2 kilometers (1.2 miles), crater Shoemaker
as viewed from the south; (b), scale bar 1 kilometer, crater Psyche; (c),
scale bar 200 meters, interior of crater Shoemaker; (d), scale bar 100
meters, large rock inside Psyche; (e), scale bar 50 meters, and (f), scale
bar 100 meters, large rocks ejected from crater Shoemaker that were
deposited in older craters; (g), scale bar 10 meters, and (h), scale bar 20
meters, the range of shapes of large rocks on Eros -- from angular to
falling apart. NEAR imaging team

=============

(7) ROCK GARDEN ON EROS

>From Nature Science Update, 27 September 2001
http://www.nature.com/nsu/010927/010927-10.html

The surface of the second largest near-Earth asteroid is surprisingly
cluttered.

27 September 2001 
JOHN WHITFIELD

On 12 February this year, the Near-Earth Asteroid Rendezvous Shoemaker
mission landed on the asteroid Eros, completing a journey of more than 3
billion kilometres. It discovered a complex miniature world, researchers now
reveal (1-3).

Far from being a barren lump of rock, the potato-shaped Eros has a dusty
boulder-strewn landscape. "It's like a building site," says astronomer Alan
Fitzsimmons of Queen's University, in Belfast, Northern Ireland.

"We were pleasantly surprised," says Joseph Veverka of Cornell University,
in Ithaca, New York, who led the mission to map Eros. "There was a tendency
to believe that asteroids were very simple."

There are thousands of large boulders on Eros, which is only 33 kilometres
long and 13 kilometres across. The positions of the boulders indicate that
most of them were scoured out of a crater 7.6 kilometres wide, formed by the
impact of a body several hundred metres across.

The rubble shows that debris from impacts could still fall back to the
surface, despite the asteroid's gravity being about 1,000 times weaker than
that of the Earth. "This erases about 20 years of thought that small
asteroids should be devoid of any loose material," says Erik Asphaug of the
University of California at Santa Cruz.

Eros's ability to hang on to its rocks shows that planet formation could be
easier than some theories have suggested, says Asphaug. "Even small bodies
can, under the right circumstances, begin to grow instead of being eroded
away by collisions."

Asteroids may one day be an important source of minerals. The scene on Eros
should cheer would-be asteroid miners, comments Fitzsimmons. "You don't need
to mine an asteroid - it's already been mined by an impact. You can just go
there and pick up what's lying about."

The joint US-Japanese MUSES-C mission aims to collect rock samples from the
similar near-Earth asteroid 1989ML in 2005 and return them to Earth for
analysis.

Dust bowls

More mysterious are the 'ponds' of bluish dust on Eros. The probe landed in
one of these, revealing its contents to be like dry cement. The lowest-lying
regions of Eros hold hundreds of ponds tens of metres wide and a few metres
deep. "Something sorted out the finest stuff and moved it downhill," says
Veverka.

Most of the ponds are in well-lit areas of the asteroid. The researchers
speculate that sunlight may have charged small particles, causing them to
repel each other, rise above the surface of the asteroid and then settle,
running downhill to collect in hollows.

Other features of Eros defy explanation. The boulders, for example, show
signs of erosion, and yet there is no atmosphere or water that might have
caused this. "There are a whole series of things that we haven't seen
before," says Veverka. "That's the wonder of exploration."
  
References
Veverka, J. et al. The landing of the NEAR-Shoemaker spacecraft on asteroid
433 Eros. Nature, 413, 390 - 393, (2001). 
Thomas, P. C., Veverka, J., Robinson, M. S. & Murchie, S. Shoemaker crater
as the source of most ejecta blocks on the asteroid 433 Eros. Nature, 413,
394 - 396, (2001). 
Robinson, M. S., Thomas, P. C., Veverka, J., Murchie, S. & Carcich, B.The
nature of ponded deposits on Eros. Nature, 413, 396 - 400, (2001). 
 
) Nature News Service / Macmillan Magazines Ltd 2001 
 
===========

(10) SOLAR SYSTEM FORMATION SURPRISES

>From Cosmicverse, September 20, 2001 
http://www.cosmiverse.com/space09200102.html

Scientists watching the southern hemisphere star Beta Pictoris have gained
new insights into the formation of solar systems, some of them explaining
previous mysteries. Using the American-French-Canadian satellite telescope
FUSE, they were surprised to learn that orbiting bands of matter contained
no molecular hydrogen despite the presence of carbon monoxide. 

Since the universe is largely hydrogen, and carbon monoxide rarely shows up
in space without H2 nearby, the research team concluded that the carbon must
be coming from the passage of millions of comets. As the comets approach the
star, they emit carbon monoxide, which in frozen form constitutes a large
part of their composition (but not hydrogen, which cannot be trapped this
way). 

This explanation accounts not only for the unexpected CO readings, but also
substantiates the theory that the early life of a solar system includes a
few hundred million years of violence as asteroids disappear in collisions
with each other, tiny planets crash into big ones, and comets evaporate by
the millions. Only then does the orbiting of planets in their course begin. 

Beta Pictoris may well be in the throes of just such an active phase of
planetary system construction. Further indication that something's going on
around Beta has been provided by the same group, using FUSE to detect the
presence of oxygen five times ionized. The latter is typical of very hot
environments such as the corona of a mature star, but Beta is too young to
have a corona, at least according to orthodox standards. Observing all the
activity around Beta may yield insights into the early days of our sun and
its evolving system. 

Source: French Advances in Science and Technology 

Copyright 2001, Cosmiverse 


-------------------------------------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet) 
--------------------------------------------------------------------
The CCNet is a scholarly electronic network. To subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.acdot uk>.
Information circulated on this network is for scholarly and educational use
only. The attached information may not be copied or reproduced for
any other purposes without prior permission of the copyright holders. The
fully indexed archive of the CCNet, from February 1997 on, can be found at
    http://abob.libs.ugadot edu/bobk/cccmenu.html

DISCLAIMER: The opinions, beliefs and viewpoints expressed in the articles
and texts and in other CCNet contributions do not  necessarily reflect the
opinions, beliefs and viewpoints of the moderator of this network.

------- End of Forwarded Message



To stop getting email from the 'meteorobs' list, use the Web form at:
http://www.meteorobs.org/subscribe.html