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CCNet 53/2002 - 23 April 2002
-----------------------------


Charles Rousseaux (Washington Times/CCNet, 22 April 2002) wrote:
"Where were the people carrying the "Down With Asteroids" signs during this
past weekends protests against everything in Washington? ..." Actually, I'd
prefer they stay up there, where they belong.
--John Michael Williams, 23 April 2002


"This is a magic age in the exploration of asteroids. Radar lets us
refine orbits and make detailed images of what are essentially individual
worlds. There's no preferred shape or size. We just never know what we're
going to see out there."
--Steve Ostro, The Orange County Register, 22 April 2002


"I feel more worried now than I did when I started this work," said
[Eleanor] Helin, who began studying asteroids in 1969. "We've long known
that something can hit us. But we're not prepared to deal with it."
--The Orange County Register, 22 April 2002


(1) KEEPING ASTEROIDS' DISTANCE
    The Orange County Register, 22 April 2002

(2) LAB'S INTERACTION WITH ASTEROIDS MAY HIT HOME
    The Orange County Register, 22 April 2002

(3) COMET BORELLLY: DRY AND HOT
    Sky & Telescope, 22 April 2002

(4) SHOOTING FOR THE MOON
    San Francisco Chronicle, 22 April 2002

(5) THE STRANGE CASE OF THE IRON SUN
    Discover Magazine, March 2002

(6) EVIDENCE FOR YOUNG PLANETS FOUND IN DUSTY ORBITS AROUND NEARBY STAR
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(7) RE: THE STRANGE CASE OF THE IRON SUN
    Oliver K. Manuel <om@umr.edu>

(8) HAWAII, RESPONSE #2
    Robert D Brown  <pelorus@nebi.com> 

(9) COMET ENCOUNTERS REVISITED
    Roy Tucker <tucker@noao.edu>

(10) NNEOIC ISSUE ODD RELEASE
     Jonathan Tate <fr77@dial.pipex.com>

(12) AND FINALLY: "DOWN WITH ASTEROIDS"? NO WAY, LET THEM STAY UP THERE!
     John Michael Williams <jwill@AstraGate.net>


===========
(1) KEEPING ASTEROIDS' DISTANCE

>From The Orange County Register, 22 April 2002
http://www.ocregister.com/news/huntasteroids00422cci.shtml

JPL uses radar to track the celestial objects that could one day threaten
Earth.

BY GARY ROBBINS
The Orange County Register

An odd little asteroid will reveal hints about the origins of the solar
system today simply by reflecting radar signals back to an antenna in the
Mojave Desert.

It's no small trick. But scientists can use the return signals to create
pictures of asteroids. In this case, they're looking at 1999 GU3, a piece of
celestial detritus that dates to when the planets formed.

The size, shape and condition of "GU3" will give scientists clues about how
some primordial material coalesced into planets, why some didn't, and how
such worlds as Mars and Earth have evolved in the ether of space.

GU3's message is going to be read by scientists at the Jet Propulsion
Laboratory in Pasadena. JPL has become the world leader in using radar
antennas to create detailed images of asteroids, especially those worrisome
ones known as "Earth-crossers," objects that intersect our orbit. There may
be 300,000 of them the size of Anaheim's Edison Field.

Scientists are able to determine the size, shape, speed, orbit and rotation
of asteroids by how fast radar signals reflect off various parts of the
object to antennas in California or Puerto Rico. The strength of the signal
also plays a role.

JPL's findings are showing asteroids to be stranger than many of the
disaster movies made about them.

"Ten years ago most scientists thought of asteroids as whirling rocks," said
Don Yeomans, a senior scientist at JPL. "Now we know they're exotic. Some
have water. Some don't. Some are almost all metal. Others are just rock. One
is shaped like a dog bone. Another looks like a banana."

JPL and its collaborators also recently announced that it's fairly common
for asteroids to have moons. That was just a theory a few years ago. GU3
doesn't have a companion. But it takes nine days for the rock to rotate
once, making it an oddball. Most asteroids rotate in a matter of hours.

Fear and curiosity are responsible for many of the latest insights.

In 1998, the U.S. House of Representatives instructed the National
Aeronautics and Space Administration to find, follow and characterize (sic)
90 percent of all (sic) near-Earth asteroids (NEAs) within 10 years. NEAs
are generally defined as asteroids a half-mile or wider (sic) that
periodically pass within 30 million miles of Earth.

The reason for the census: to find out if any asteroids could hit Earth and
produce a catastrophe.

The idea is to give humans enough time to find a way to destroy or deflect
potentially damaging objects. JPL is a major player in the project because
it's a NASA center with a masterful record of interacting with objects in
space.

The project gained urgency in January when an asteroid almost as long as the
Huntington Beach Pier came within 518,000 miles of Earth. It had been
discovered only a month earlier by a team led by JPL's Eleanor Helin.

No one knows exactly know many NEAs exist. NASA has officially catalogued
558 asteroids that are at least a half-mile wide. But scientists say that
number probably represents only half the NEAs.

Researchers use optical telescopes to find the NEAs. And they're getting
better at locating them due to improved technology. But many of the most
interesting research has involved radar antennas.

JPL used radar to make an unprecedented long-term prediction: there's a 1 in
300 chance that asteroid 1950 DA - which is about 4,000 feet in diameter --
will hit Earth on March 16, 2880.

To watch for somewhat shorter-term threats, JPL inaugurated Sentry on March
12. It's an automated computer program that evaluates whether any known NEA
has a chance of hitting Earth within the next 100 years.

"This is a magic age in the exploration of asteroids," says Steve Ostro, a
JPL astronomer collaborating with colleague Lance Benner in studying GU3.

"Radar lets us refine orbits and make detailed images of what are
essentially individual worlds. There's no preferred shape or size. We just
never know what we're going to see out there."

That means that Ostro could be in for a surprise today. Arecibo Observatory
in Puerto Rico used its radar antenna to bounce signals off GU3. More
signals are being sent today by the Goldstone Solar System Radar near
Barstow.

The key to success is pinpoint accuracy. Today's signal from Goldstone must
hit a roughly 1,300-foot-wide asteroid that's more than 7.5 million miles
from Earth, traveling about 36,000 mph.

GU3 is one of only 179 asteroids studied with radar.

"Everything about an asteroid - its spin, how much it heats up, what it's
made of - can affect its path and whether it hits Earth," said Jon Giorgini
, another JPL researcher. "We need to know more about the physical
properties of asteroids."

JPL's Helin agrees.

"I feel more worried now than I did when I started this work," said Helin,
who began studying asteroids in 1969. "We've long known that something can
hit us. But we're not prepared to deal with it."
 
Copyright 2002, The Orange County Register

============
(2) LAB'S INTERACTION WITH ASTEROIDS MAY HIT HOME

>From The Orange County Register, 22 April 2002
http://www.ocregister.com/news/asteroidsell00422cci4.shtml

By GARY ROBBINS
The Orange County Register

Like a cop nabbing heavy-footed motorists, astronomers will use radar today
to clock an asteroid that's streaking through the cosmos about 7.5 million
miles from Earth.

The "astro-cops" at Pasadena's Jet Propulsion Laboratory are tracking and
profiling a 1,300-foot-wide rock called 1999 GU3. By the time they're done
bouncing radar signals off it, researchers will be able to create a
composite image of the asteroid, which would create a 5-mile-wide crater if
it hit Earth.

A collision isn't imminent. But the National Aeronautics and Space
Administration is trying to locate, track and characterize hundreds of
near-Earth asteroids, objects a half-mile wide or larger that come within 30
million miles of our planet. The project is meant to identify potential
threats and give the government time to respond.

JPL is deeply involved because it's a NASA center that can use optical
telescopes to find the asteroids and radar antennas to track many of them.
 
Copyright 2002, The Orange County Register
 
============
(3) COMET BORELLLY: DRY AND HOT

>From Sky & Telescope, 22 April 2002
http://skyandtelescope.com/news/current/article_579_1.asp

By J. Kelly Beatty

April 22, 2002 | Scientific intuition tells us that a comet's nucleus should
be a frozen mountain of ice and dust. But that's not what Deep Space 1
discovered when it flew past Comet 19P/Borrelly last year. A recently
released analysis of spacecraft spectra finds that Borrelly's "icy heart"
exhibits no trace of water ice or any water-bearing minerals. Moreover, the
nucleus is actually quite hot - ranging from 300° to 345° Kelvin (80° to
160° F).

What this means, according to Laurence Soderblom (U.S. Geological Survey),
who led the analysis team, is that virtually all of the comet's surface has
become inactive. As further evidence, Soderblom notes that gas and dust
appear to be escaping only from localized jets totaling less than 10 percent
of the surface seen by the spacecraft. Ground-based observations also show
Borrelly to be a weak producer of gas and dust, typically releasing less
than a ton of water per second. Because this comet has been trapped in a
7-year-long orbit around the Sun for at least two centuries, scientists
believe it has exhausted most of the volatile consituents needed to create
an impressive coma and tail.

Deep Space 1's spectra weren't entirely featureless: the comet's inky black
nucleus exhibits an unexplained absorption at 3.29 microns. Soderblom
guesses that this might be the signature of polyoxymethylene (a chained
polymer of formaldehyde, H2CO, previously detected in Comet Halley) or some
other organic compound. The team's full analysis appears in the online
version of Science for April 4th; a summary was presented two weeks earlier
at the Lunar and Planetary Science Conference.

Mission scientists are thrilled to have any spectra at all to work with.
Just as it passed 2,170 kilometers from the comet last September 22nd, Deep
Space 1 scored a direct hit with its camera-spectrometer, recording 45 scans
across the 8-km-long nucleus. And because only a handful of tightly
collimated jets were spewing into space, the spacecraft had a clear
sightline through the inner coma. The resulting images record features on
the nucleus as small as 48 meters - far more detailed than the views of
Comet Halley returned by the Giotto and Vega spacecraft in 1986.

Copyright 2002 Sky Publishing Corp.

=============
(4) SHOOTING FOR THE MOON

>From San Francisco Chronicle, 22 April 2002
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2002/04/22/MN108065.DTL

Lunar surface may hold evidence that asteroids crashed into Earth

Keay Davidson, Chronicle Science Writer  
 
Clues to Earth's earliest days and first microbial inhabitants may survive
in an unexpected place: the moon.

Scientists have long debated what happened on the primordial Earth almost 4
billion years ago. Did primitive microbes wriggle within volcano-heated
pools of water? Did falling asteroids vaporize oceans and gouge craters the
size of small states?

Such questions are terribly hard to answer. The clues have been largely
erased by erosion -- by rain, wind, tides, plate tectonics, and other
natural forces.

But some clues might still exist a quarter of a million miles away, on the
frigid, airless surface of the moon. Long ignored by mainstream scientists,
the idea has begun to attract some serious attention, including the first
serious proposals to go looking for hard evidence.

New calculations by a youthful team of researchers at the University of
Washington and Iowa State suggest a strong probability that asteroid impacts
could have splashed substantial amounts of terrestrial rock toward the moon,
like mud sprayed by a car racing down a dirt road.

Clouds of what the researchers call "terran meteorites" might have sprinkled
across the lunar surface. There, in a much less erosive environment than
exists on Earth -- no wind ever blew and no water ever flowed on the moon --
the rocky relics of Earth's primeval days may endure, awaiting discovery by
future astronauts or remotely controlled robotic vehicles.

Hence the three researchers dub the moon "Earth's attic": a deep-freeze
repository for relics of the terrestrial dawn.

The researchers have outlined a plan to test the hypothesis as part of some
future lunar-prospecting mission. Details were presented for the first time
at a recent astrobiology science conference held at NASA's Ames Research
Center in Mountain View.

After a large impact, the terrestrial rocks "could just fly off Earth and
get scooped up by the moon, or go into orbit around the Sun and then later
on land on the moon," explained John C. Armstrong of the Center for
Astrobiology and Early Evolution at the University of Washington at Seattle.


Perhaps 20 tons of terrestrial rock could be buried over a typical lunar
area of about 40 square miles, according to calculations by Armstrong and
Llyd E. Wells, also at the Seattle center, and Guillermo Gonzalez, assistant
professor in the physics and astronomy department at Iowa State University
in Ames, Iowa.

Armstrong is a graduate student in astronomy who expects to receive his
doctorate at year's end. Wells is a biologist and graduate student in
oceanography.

The surface of the moon is not completely free of erosion: It is pelted by a
steady rain of "micrometeorites" and cosmic rays. The most intact terran
rocks are likely to survive within a few feet of the lunar surface, shielded
by the overlying rock.

Armstrong said the three men got the idea while "stuck in traffic" near the
Ames center in early 2000. Armstrong says they began batting around ideas
for space exploration, "and Guillermo said, 'Say, have you ever thought
about what would happen if an asteroid could blast stuff off the Earth and
onto the moon?' "

A similar question was asked in the 1960s by a famous chemist, Harold C.
Urey, a top adviser to the U.S. space program. His idea drew little
attention, though. One reason: It was hard to imagine how material could be
violently transferred from one world to another without being destroyed in
the process. (To escape Earth gravity, an object must be accelerated to a
speed of 7 miles per second or 25,000 miles per hour.)

In recent years, though, scientists have grown accustomed to finding
fragments of the moon and Mars on Earth, especially in Antarctica. There,
they pluck lunar and Martian meteorites out of the polar ice like kids
plucking raisins from raisin pudding.

They know the Mars rocks come from that planet because they contain small
pockets of gas whose isotopic contents match those recorded in the Martian
atmosphere by the twin Viking robots, which landed on Mars in 1976. Mars
meteorites are clear evidence that chunks of one planet can survive a voyage
to another.

The most controversial Martian meteorite is known as ALH84001 (ALH stands
for the Allan Hills region of Antarctica, where it was found). A few
scientists suspect it contains fossils of Martian microbes.

"The moon is strategically located within the inner solar system as a
collector of debris," Armstrong said. 'It has, potentially, collected
material from all the terrestrial planets," including Earth, Mars and Venus.


"The Earth meteorites on the moon could provide a geological record of early
Earth not available anywhere else in the solar system. . . . While there
isn't a whole lot of Earth stuff up there, some of the Earth material may
contain geochemical and biological information such as isotopic signatures,
organic carbon, biologically derived molecules and minerals, and maybe even
microbial fossils."

Skepticism is expressed by NASA-Ames scientist Dale Cruikshank, a leading
figure in the search for organic molecules in space.

"Earth materials probably exist on the moon," he acknowledged, but cautioned
that they are probably "hugely diluted in the vast and thick dusty layers
that mantle every square inch of our neighbor in space."

Also, any Earth rocks that reached the moon about 4 billion years ago should
have been altered by lunar volcanic activity or changed "chemically and
mechanically beyond recognition" by other natural means, he said in an
e-mail to The Chronicle.

In response, Armstrong agreed that terrestrial materials might be diluted to
a scarcity of one to 10 parts per million. Still, even such scarce particles
are "not insignificant" and could be identified and studied with advanced
scientific methods.

He pointed out that in recent years, scientists have learned a great deal
about the evolution of the solar system by studying interstellar dust
particles (IDPs), which are literally dust grains that drop to Earth from
space. As for lunar vulcanism, Armstrong says it might help, not harm, their
proposal because lava "could actually help protect the material from the
Earth" from lunar erosive processes such as micrometeorites.

If robots or astronauts return to the moon, how could they distinguish
terrestrial meteorites from native lunar rocks? Armstrong's team is now
investigating that question, using small samples of lunar rocks from NASA's
Johnson Space Center in Houston.

One way, they suspect, is by analyzing the rocks' reaction to ultraviolet
light. Ultraviolet light could expose carbonates typically formed in the
presence of liquid water, which has long been abundant on Earth.

Also, future explorers might keep their eyes peeled for rocks with burned or
"ablated" surfaces. Ablation is a clue that they experienced high friction
while shooting through the atmosphere of another planet.

One of the most exciting questions facing space scientists is: Did the inner
solar system experience a horrendous "late heavy bombardment" of asteroids
3.8 billion to 4.1 billion years ago? Scientists have debated this question
for years.

Terrestrial rocks on the moon might "shed a lot of light on the question of
whether there really was a (late) heavy bombardment" at that time, Armstrong
said.

If the late heavy bombardment really happened, might it have wiped out any
early life? Possibly so, some scientists say.

However, Wells speculates that terrestrial life might have survived the
bombardment via an unusual route: brief sojourns in space.

To be specific, asteroid impacts might have hurled rocks with microbes into
space. After thousands of years in the deep-freeze of orbit, the rocks might
have fallen back to Earth and "re-seeded" the planet with life, Wells says.

If he's right, then Earth's first "astronauts" were not Yuri Gagarin and
Alan Shepard but, rather, microbes. Knowing that, maybe you'll show a little
more respect for the greenish mold on your shower wall: It looks humble, but
its ancestors might have boldly gone where no microbe went before.

E-mail Keay Davidson at kdavidson@sfchronicle.com.

©2002 San Francisco Chronicle   

=================
(5) THE STRANGE CASE OF THE IRON SUN

>From Discover Magazine, March 2002
http://www.discover.com/mar_02/feat_iron.html

An iconoclastic theory of the solar system's origin shows how science tests
its truisms.

By Solana Pyne

In the late 1960s, chemist Oliver Manuel made a small but staggering
discovery about meteorites. He noticed that the abundances of certain
elements in meteorites were distinctly different from those in the Earth and
much of the solar system. This observation spurred research showing that our
solar system probably formed from material generated in many different
stars. For Manuel, it also spawned a radical theory about the origins of our
solar system, which he has doggedly pursued for forty years. Nearly all
astronomers agree that the Sun and the rest of the planets formed from an
amorphous cloud of gas and dust 4.6 billion years ago. But Manuel argues,
based on his compositional data, that the solar system was created by a
dramatic stellar explosion--a supernova--and that the iron-encased remnant
of the progenitor star still sits at the center of the Sun.

Manuel fits a popular stereotype, the lone dissenter promoting a new idea
that flies in the face of the scientific establishment. In the real world,
some of these theories eventually have been proven right but vastly more
have been proven wrong. Manuel is under no illusions about the popularity of
his idea. "Ninety-nine percent of the field will tell you it's junk
science," he says. The evidence weighs in heavily against him. If he's
right, however, we need to completely rethink how planetary systems form.
Even if he's wrong, some scientists say, at least he has made people think.

Astrophysicists don't deny the validity of Manuel's original meteorite data.
"It was a good observation," says cosmochemist Frank Podosek of Washington
University. "This was something we hadn't observed before. It was a fruitful
thing to notice, but he picked it up and ran with it very much farther than
the basis could justify."

To support his theory, Manuel pieced together bits of information from
history, astronomy, biology and physics. He founded his theory on isotopes,
variants of an element that have different atomic weights but the same basic
chemical properties. On Earth, isotopes have consistent, well-known relative
abundances. Manuel cited unusual mixes of isotopes in meteorites and
possibly in the atmosphere of Jupiter as evidence that those objects formed
from the outer layers of a supernova, where such strange isotope ratios
would be the norm. The inner planets, made from rocky debris, formed from
heavy elements in the inner part of the supernova, he says, where more
familiar isotope concentrations prevailed. And the Sun, which Manuel argues
is iron-rich, formed around a neutron star, the collapsed remnant of the
exploded star. "This is not a news flash," he says. "This is my conclusion
from 42 years of measuring the abundance of isotopes."

Manuel's insistence both infuriates and amuses others in the field.
Scientists who know him talk about him in a tone that is both weary and
indulgent, as they would describe an eccentric relative. "I happen to like
Oliver," says Donald Burnett, professor of geochemistry at the California
Institute of Technology. "I don't agree with anything he says, but I find
him a colorful character."

There is one widely accepted element in Manuel's scenario. In the universe,
many elements heavier than iron are thought to have been forged in
supernovae. But the evidence increasingly seems to rule out Manuel's
supernova-genesis theory. At the start of the 20th century, many scientists
believed the Sun was made mostly of iron. Manuel cites the historical
support for an iron-rich Sun as evidence for his theory. "A high iron
content for the Sun is not revolutionary but is actually quite compatible
with the history of solar research," he says. But in 1925, astronomer
Cecelia Payne analyzed the light of our star and proposed that the Sun was
most likely a burning ball of hydrogen. By the late thirties, the case was
nearly settled. The surface of the Sun has been proven to be mostly
hydrogen, and many subsequent studies have led to extremely detailed models
of the hydrogen fusion reactions that power our star.

"We can make an explicit model of the Sun, putting its mass and brightness
into the computer, along with the laws of physics and that then produces
right amount of Sunshine and brightness," says Sallie Baliunas, an
astrophysicist at the Harvard-Smithsonian Center for Astrophysics. These
models also explain the various stages of stellar evolution that astronomers
can observe. And the principles of hydrogen fusion are well established,
both in the laboratory and in the detonations of hydrogen bombs. According
to theory and experiment, light hydrogen atoms in the Sun fuse together to
form helium atoms, releasing bursts of energy in the process. All of the
evidence points to our Sun being made primarily of hydrogen.

Manuel argues that the surface is made up mostly of hydrogen only because
elements in the Sun separate according to mass. Hydrogen, the lightest
element, floats to the surface, while heavier elements huddle below. But his
theory creates another problem: If the Sun isn't made of hydrogen, how does
it generate its energy? Fusing a heavy and stable element like iron consumes
more energy than it releases. In his theory, Manuel relies the neutron star
at the center to make up for energy lost when hydrogen is taken out of the
picture. The neutrons that make up the star have higher energy than free
neutrons, he says, so a neutron escaping from the star releases energy. The
free neutron then decays into a proton as it migrates toward the surface,
again releasing energy. The proton, which is a hydrogen atom minus an
electron, fuses to form helium and releases even more energy. He supposes
that some of the decayed neutrons stick around as protons and account for
the abundance of hydrogen on the surface of the Sun and in the solar wind.
Manuel's colleagues are skeptical about this elaborate and unproven
explanation.

Many scientists also find it improbable that our solar system could have
formed quickly from the debris of a supernova. They have only found one
system in which planets formed around a neutron star, and it looks nothing
like our solar system. On the other hand, astronomers have spotted
innumerable stars forming out of clouds of gas and dust and find strong
indications that planets are forming around these protostars.

Finally, there is persuasive evidence that our solar system contains the
remains of many different supernovae. Ironically, Manuel's own discovery
contributed to this understanding. Chemists have traced the strange isotopic
concentrations Manuel first observed to individual grains within meteorites.
The proportions of each isotope vary from grain to grain. If the solar
system formed from a single supernova, all the grains should have roughly
the same abundances of isotopes. Since they don't, most scientists view the
isotopes in a particular grain as a clue to its origin, and, hence, as
evidence that meteorites, and most other bodies in the solar system, are
made of heterogeneous material derived from many stars. That makes Manuel's
theory look less likely than ever. "Fifteen years ago, I would have kept a
question mark in my mind," said cosmochemist Roy Lewis, of the Fermi
Institute at the University of Chicago. "I would have said well he's almost
certainly wrong but by golly if he turns out to be right, won't that be
interesting."

Although most scientists don't believe Manuel's theory, they all acknowledge
that outlandish hypotheses have been proven correct in the past. It seems
especially unlikely in Manuel's case, however. In addition to citing the
contradictory evidence, many scientists also dismiss the iron-Sun theory on
the grounds of simplicity. Most observations of our solar system can be
explained by fairly common processes, so why evoke rare and complicated
explanations?

Still, some scientists see fringe theorists like Manuel as an asset, as they
make people reassess long-held theories. "Manuel is a little off the wall,"
Lewis says. "But science is filled with people a little off the wall. Our
great strength is to allow them to express their views." Manuel's views got
an airing again at the January meeting of the American Astronomical Society
meeting in Washington, DC, where once again they received little notice.

Meanwhile, Manuel continues to argue his theory with an air of implacable
certainty, believing that solar physics is on the verge of a revolution. He
talks as though scientists need only to come to their senses and reassess
the data. "I'm not trying to refute the professional careers of the
scientists whose shoulders I'm standing on," Manuel says. "My work depends
on their evidence. It's just a different interpretation."

----------------------------------------------------------------------------
----
RELATED WEB SITES:
See Oliver Manuel's site at http://www.umr.edu/~om/ Learn more about how the
planets of our solar system formed at http://explorezone.com/
space/planets.htm Find out about the elements formed in a supernova at
http://imagine.gsfc.nasa.gov/ docs/ask_astro/ answers/010125a.html Learn
about our Sun at http://www.seds.org/nineplanets/ nineplanets/sol.html

© Copyright 2002 The Walt Disney Company. Back to Homepage.

==================
(6) EVIDENCE FOR YOUNG PLANETS FOUND IN DUSTY ORBITS AROUND NEARBY STAR

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

W.M. Keck Observatory
Kamuela, Hawaii

Media Contact:
Laura K. Kraft, (808) 885-7887, lkraft@keck.hawaii.edu

April 11, 2002

EVIDENCE FOR YOUNG PLANETS FOUND IN DUSTY ORBITS AROUND NEARBY STAR

TUCSON, Arizona -- Two independent teams of astronomers are presenting the
discovery of new features in an edge-on disk around the nearby star Beta
Pictoris at the Gillett Symposium on "Debris Disks and the Formation of
Planets" in Tucson, Arizona.

Infrared images from the W. M. Keck Observatory reveal an important clue in
the configuration of dust confined to a solar-system sized region close to
the star: the dust orbits in a plane that is offset by approximately 14
degrees from that of the outer disk. Moreover, the offset is in the opposite
direction from that of a larger scale warp detected previously by Hubble
Space Telescope. This double warp is believed to be due to the presence of
one or more unseen planets and constitutes one of the strongest pieces of
evidence yet which links observations of circumstellar disks to the actual
formation of planets.

At the Keck II telescope at Mauna Kea, Hawaii, Prof. David Koerner and
graduate student Zahed Wahhaj of the University of Pennsylvania led a team
of astronomers from NASA's Jet Propulsion Laboratory (JPL), Franklin and
Marshall College, and Caltech in observations of Beta Pic with MIRLIN, a
mid-infrared camera from JPL (http://cougar.jpl.nasa.gov/mirlin.html).
Alycia Weinberger, now at the Carnegie Institution of Washington, and Eric
Becklin and Ben Zuckerman from UCLA carried out observations with the Long
Wavelength Spectrometer at Keck I (LWS)
(http://www2.keck.hawaii.edu:3636/realpublic/inst/lws/lws.html). Both
telescopes have 10-meter (400-inch) apertures. Both MIRLIN and LWS work at
wavelengths between 8 and 20 microns.

Prof. Koerner reported, "We've seen disk features before that could be due
to planets -- inner holes, narrow rings, and variations in azimuthal
brightness. To date, however, most of these were discovered far outside the
region where planets reside in our own solar system, and plausible
non-planetary explanations have been found for some of them. In contrast,
the distorted disk plane in Keck images occurs at Jovian-planet distances
from the star (from 5 to 30 Astronomical
Units or AU; 1 AU is the average distance between the Earth and the Sun).
Moreover, no obvious explanation exists for its origin other than the
gravitational influence of planets. The different inclinations of dust grain
orbits around Beta Pic bear a resemblance to those of planetary orbits in
our own solar system. Pluto's orbit is inclined by 17 degrees compared to
Earth's, and Mercury's differs by 7 degrees, for example. The new Keck
images may be interpreted as circumstantial evidence for a similarly
organized planetary system."

Dr. Weinberger added, "The images show the power of large ground-based
telescopes, like Keck, to reveal disk details in the hot inner portions of
disks." In addition to imaging, Weinberger and colleagues obtained spectra
at different locations along the disk using the same Keck instrument (LWS).
Spectroscopy spreads the disk radiation into component wavelengths, much the
same way that a prism divides up visible light. The result enables astronomers to study
composition as well as geometry. Weinberger's group found that, at the position of the
newly discovered warp, the disk is composed of small silicate particles that
are hotter than expected. Weinberger says, "It may be that as a planet warps
the disk, it also causes more collisions of rocks in its neighborhood." The
very small grains produced in collisions would tend to be hotter, at the
same distance from the star, than larger dust grains. Outside the warp, in
the outer part of the disk, the disk light appears to come either from
larger grains or from dust that is composed of something other than
silicates.

To ensure that the observed offset was not the product of optical distortion
in either the atmosphere or telescope, Zahed Wahhaj carried out computer
modeling of the Keck image using a disk model and images of a nearby star
that were taken at the same time. His analysis provides an estimate of the
uncertainty in the measured value of the offset. "We generated millions of
different computer models of disks and used them to simulate images of Beta
Pic as observed with the Keck telescope. Computational comparisons of the models
with the images showed that the inner disk is offset from the outer disk by
an angle somewhere between 10 and 18 degrees. This is in good agreement with
a value between 11 and 15 degrees, as determined by the other team."

Beta Pictoris is a young star about 20 million years old that is located 63
light years away in the constellation Pictor (the painter's easel). The star
is located too far south to be visible from the continental United States,
but it can be seen in winter from Hawaii where it rises just 20 degrees
above the horizon. In 1983, astronomers discovered dust radiation, first
from Vega, and later from Beta Pictoris using the Infrared Astronomical
Satellite (IRAS).

The Gillett Symposium commemorates Fred Gillett's role in the discovery of
the first IRAS disk detection around Vega and is being held in his memory
one year after his death. Subsequent telescope observations of Beta Pic
yielded the first image of a protoplanetary disk. Like all
observations carried out at visible wavelengths, it required a coronagraph
to block out the glare from the central star. As a consequence, the region
of the disk corresponding to our solar system was not discernible for study.
The human eye is insensitive to the infrared light collected in the new Keck
observations of Beta Pic. The contrast between star and disk radiation is
more favorable, however, so the Jovian planet region was discernible for the
first time.

The W. M. Keck Observatory provides astronomers from associated institutions
access to two 10-meter telescopes, the world's largest. Each telescope
features a revolutionary primary mirror composed of 36 hexagonal segments
that work in concert as a single piece of reflective glass to provide
unprecedented power and precision. Each telescope stands eight stories tall
and weighs 300 tons, yet operates with nanometer precision. The observatory
is operated by the California
Association for Research in Astronomy, a partnership of the California
Institute of Technology, the University of California, and the National
Aeronautics and Space Administration (NASA), which joined the partnership in
October 1996. For more information, visit the W. M. Keck Observatory Web
site at www.keckobservatory.org or send e-mail to: www@keck.hawaii.edu .

IMAGE CAPTIONS:

[Image 1: http://www.hep.upenn.edu/~davidk/bigpress2.gif (731KB)] Dust
around the young nearby star, Beta Pictoris. This image was made with the
Keck II 10-meter (400 inch) telescopes using an infrared camera operating at
18 microns. The inner contours are misaligned with respect to the outer
disk, and provide evidence of a newly discovered warp in the disk (labeled
as "A"). For comparison, an image of reflected light from Beta Pic is shown,
as it appears in observations
taken with the Space Telescope Imaging Spectrometer (STIS) on board the
Hubble Space Telesope (HST). The HST/STIS image is exaggerated in vertical
scale to show a warp which occure further out and in the opposite direction
from that seen in the Keck infrared image. This morphology can be reproduced
as an inner disk with radius 5 to 30 AU and an orbital inclination that is
offset 14 +/- 4 degrees from the large outer disk, and in the opposite sense
of the HST/STIS warp. "B" refers to lobes equidistant from the star that are
consistent with a 40-AU-radius ring or bright inner edge of the outer disk.
"C" is a peak that could be associated with a ring further out that is not
azimuthally symmetric (i.e., its counterpart on the other side of the star
is not very prominent).

[Image 2: http://www.hep.upenn.edu/~davidk/bigmod80.gif (94KB)
Image 3: http://www.hep.upenn.edu/~davidk/bigmod89.gif (21KB)] Examples of
computer representation of the infrared emission from Beta Pic, before the
images were blurred for comparison to Keck results. Viewing angles are 10
degrees above the disk plane (upper [Image 2]) and along the line of sight
from Earth to Beta Pic (lower [Image 3]).
 
============================
* LETTERS TO THE MODERATOR *
============================

(7) RE: THE STRANGE CASE OF THE IRON SUN

>From Oliver K. Manuel <om@umr.edu>

There is an article on Discovery Magazine's web site you may find
interesting <http://www.discover.com/mar_02/feat_iron.html>.  Sallie
Baliunas of Harvard University, Frank Podosek of Washington University, Roy
Lewis of the University of Chicago and the Genesis
Project Principal Investigator - Don Burnett of Cal Tech - comment on the
possibility of an iron-rich Sun.

They do NOT address observations that are unexplained by the standard model:

1. Meteorites trapped two types of xenon, Xe-X (highly enriched in r- and
p-products) and "normal" xenon [Nature  240, 99-101 (1972)]. Xe-X was a
major primordial xenon component at the birth of the solar system. The
(excess Xe-136)/(excess-124) ratio is constant in meteorites.

2. Xe-X is closely linked with primordial helium and neon in diverse
meteorites but the noble gas component with "normal" xenon is devoid of
helium and neon [Science  195, 208-210 (1977); Icarus 41, 312-315 (1980);
Meteoritics 15, 117-138 (1980)].

3. Normal xenon is found in troilite (FeS) of meteorites [Nature 299,
807-810 (1982); Geochem. J. 30, 17-30 (1996)], as well as in the rocky
planets abounding with Fe and S - - Earth and Mars.

4. Xe-X is found in diamond inclusions of meteorites with abundant
primordial helium and neon, trapped in a carbon matrix with normal C-13/C-12
isotope ratio [Nature 326, 160-162 (1987)].

5. The Galileo mission found evidence of Xe-X in the helium-rich atmosphere
of Jupiter [J. Radioanal. Nucl. Chem. 238, 119-121 (1998)].

6. The Galileo mission found hydrogen and helium that could not be
transformed into the anomalous hydrogen and helium isotope ratios of the
solar wind by deuterium burning [Proceedings ACS Symposium, "Origin of
Elements in the Solar System: Implications of Post-1957 Observations"
(Kluwer Plenum Publishers, New York, NY, 2001) pp. 529-543].

7. Primordial helium and neon were plentiful where the outer planets formed,
but light elements were absent where formed rocky planets formed.  This
primordial heterogeneity caused the paucity of light elements in inner
planets [Comments Astrophysics 18, 335-345 (1997)].

8. The Apollo missions found mass fractionated "normal" xenon implanted in
lunar samples by the solar wind, with light mass isotopes enriched by 3.5%
per amu [Science 174, 1334-1336 (1971);
Proc. Lunar Sci. Conf. 2, 1821-1856 (1972)].

9. When photospheric abundance is corrected for the fractionation seen
across the nine isotopes of xenon, Fe and S are found to be abundant
elements in the bulk Sun.  Thus, the link of Fe and S with "normal" xenon
extends to the Sun [Meteoritics 18, 209-222 (1983)].

10. The prevalence of solar wind implanted Li-6 and Be-10 in lunar soils is
too high to be representative of the composition of the entire Sun [Nature
402, 270-273 (1999); Science 294, 352-354 (2001)].
  
11. Combined Pu-244/Xe-136 and U/Pb age dating indicates formation of the
solar system began about 5 billion years ago, soon after a supernova
explosion [Radiochimica Acta 77, 15-20 (1997)].

12. Decay products of short-lived nuclides and isotopic anomalies from
nucleosynthesis are found in massive iron meteorites [Meteoritics & Planet.
Sci., 33, A99 (1998); Nature 415, 881-883
(2002)], as well as in the tiny meteorite inclusions called "interstellar
grains".

13. The abundance of one He-burning product, O-16, is characteristic of at
least six different types of meteorites and planets [Earth Planet. Sci.
Lett. 30, 10-18 (1976)].

Papers cited are from the University of Chicago, Physikalisches
Institut-Bern, the University of Arkansas, CRPG-CNRS at Nancy, the
University of California Berkeley, the University of Tokyo, Harvard
University, and the University of Missouri-Rolla.

With kind regards,

Oliver K. Manuel
Professor of Nuclear Chemistry
University of Missouri
Rolla, MO  65401  USA
Phone: 573-341-4420 or -4344
Fax: 573-341-6033
E-mail: om@umr.edu
http://www.umr.edu/~om/

==============
(8) HAWAII, RESPONSE #2
 
>From Robert D Brown  <pelorus@nebi.com> 

Dear Benny:

I respond a second time to the criticisms provided by Hermann Bouchard to my
thesis "Hawaii: Tombstone of the Dinosaurs" the abstract for which was
originally reproduced in CCNet on April 9.  In his most recent post H.
Bouchard cites extensively from Tarduno et al as if he is presenting
information new to this correspondence.  Bouchard states: "Recent data on
geochemistry (in which I [Bouchard] am not an expert) can be found in the
Leg 197 preliminary report"
(http://www-odp.tamu.edu/publications/prelim/197_prel/prel2.html).

The only "recent data" of geochemical relevance contained in the Tarduno et
al report is an exact reproduction of the data published independently by
Randall Keller in his Nature paper "Isotopic evidence for Late Cretaceous
plume-ridge interaction at the Hawaiian hotspot"
(http://ridge.oce.orst.edu/rkeller/KellerNature2000.html). Randall Keller
was the on board petrologist for the Tarduno work. Tarduno's secondary
citation/reproduction of Keller's earlier publication does not constitute
additional evidence: it is the same data reproduced in a second location. 

Keller et al performed a detailed geochemical analysis of the Detroit
seamount and found that there was no evidence of any type that it resembled
any other Hawaiian hotspot-associated seamount or volcano. Indeed, they
found Detroit to be indistinguishable from common MORB, a finding they noted
to be "unprecedented in the known volcanism from the Hawaiian hotspot".  In
an attempt to reconcile this finding with their "belief/assumption" that
Detroit seamount is a valid member of the HEC, they cited a number of
references relating to other hotspots where plume materials were/are found
to be modified by virtue of their respective proximities to other
mid-oceanic ridges. They then cite Mammerickx  and Sharman's 1988 paper
indicating that the Hawaiian hotspot was located near a MOR ~80Ma. The
relevant Mammerickx  and Sharman seafloor data relating to ancient Pacific
basin MOR can be found online at
http://www.ig.utexas.edu/research/projects/plates/pdfs/iso_chart.pdf in
Figure 11 of that publication (an isochron chart dated at 84.0 Ma). As I
noted in my last response to H. Bouchard, the mantle coordinates for the
Hawaiian hotspot was more than a thousand kilometers distant from this
spreading ridge at that time, eliminating by virtue of sheer distance any
correlation to the other hotspots they cite to buttress their case. This is,
in my opinion, is an example of shoe-horning of data which otherwise simply
does not "fit" the facts.

The important facts are these: 1) Detroit's geochemical profile does not
match those of Hawaiian hotspot seamounts; it matches MORB as found all over
the world.  2) Detroit and Meiji both have geomorphologies (long axes)
running in an east-west direction that correlate with the east-west
direction of the seafloor fracture ("MOR") upon which they rest. 3) The
Hawaiian hotspot was not "near" any known MOR circa 80-84 Ma.  4) The oldest
seamount of the HEC is Suiko, which has an isotopically dated age of 64.7
Ma, correlating nicely with the 65.1 Ma date of the KT extinction event.
Finally (5), there is ZERO evidence that the Hawaiian hotspot is responsible
for volcanism beneath the Eurasian plate.

Resolution of these interpretive differences will require detailed
examination and isotopic characterizations of the seamounts residing between
Suiko and Detroit, data which does not presently exist. It is my expectation
that all such seamounts will date at ages less than 65.1 Ma.
 
Cheers,
Robert D. Brown 
 
=============
(9) COMET ENCOUNTERS REVISITED

>From Roy Tucker <tucker@noao.edu>

Hi Bob,

There are several important points to note when discussing the old cometary
dust issue. If one refers to the original Hoyle/Wickramasingh paper, they
note that an encounter of the earth with a "giant comet" may be expected to
occur only about once in 100 million years, certainly much more
rarely than the millennial time scales that some had speculated. Also, to
make the encounter described in my simple model as severe as possible, I
stipulated that the ENTIRE MASS OF THE COMET was converted to dust and
uniformly distributed within a spherical volume of space with a radius equal
to the orbit of the moon around the earth. My model also had the earth
making a central passage through this spherical cloud to make the encounter
last as long as possible.

Your computation of the energy produced by such a modeled encounter is
correct, the kinetic energy of the dust impacting the atmosphere would equal
about 50% the energy arriving from the sun. The worst possible case would be
if the energy was deposited upon the daytime side in summer under clear
skies. This would be a very warm day, indeed!

HOWEVER, my model of this encounter with a comet is very unrealistic. My
intent was to try to determine an absolute maximum upper limit to dust
deposition for comparison with what has been observed from volcanic events.
In reality, One would not expect to have an entire comet dispersed into a
spherical cloud of dust just before encountering the earth. A real comet
will have only a tiny amount of its mass in the form of a dusty coma at any
one time, and this dust will be very non-uniformly distributed. A more
realistic "worst-possible-case" encounter would have the comet's nucleus
passing just outside the earth's atmosphere on the sunward side. In this
particular case, tidal forces would disrupt the nucleus and a tremendous
burst of dust could be dumped into the atmosphere but the event would last
only seconds or minutes at the most. Such a close approach with a "great
comet" would be extremely rare and may indeed not have occurred during the
history of the solar system. An actual impact or more remote approach would
be more likely.

During the discussions precipitated by my original posting, it became
apparent that the greatest environmental consequence of a non-impact
encounter with a real cometary coma would be due to the introduction into
the upper atmosphere of fine dust with sizes on the order of microns and the
resultant reduction in atmospheric transparency. Even in the highly rarified
upper atmosphere, settling times may be on the order of months or years,
neglecting electrostatic effects in the atmosphere. However, the dust
density to be found in cometary comae and what fraction of this dust is of
micron size is still not well determined. It is certain to be far below my
model.

I enjoy your postings on CCNET and I thank you for the opportunity to
further discuss the cometary dust model.

Best regards,
  - Roy

===================
(10) NNEOIC ISSUE ODD RELEASE

>From Jonathan Tate <fr77@dial.pipex.com>

Benny,

Hail the first bulletin from the NNEOIC! I am sure that Steve "Otto" will be
impressed. It is also strange to hear that 1950 DA is the first NEO with a
non-zero impact probability, and that Torino has changed its spelling. Is
this £300K's worth?

Jay

-------
http://www.nearearthobjects.co.uk/
Hazardous Asteroid Found
04/04/02

New radar observations of Near Earth Asteroid 1950 DA made last year when it
passed within 20 lunar distances of the Earth suggest it may collide with
the Earth. In a paper published today in the journal Science, Dr Steve Otto
and colleages from the NASA Jet Propulsion Laboratory have announced the
results of calculations of the orbit of the asteroid that suggest it has a 1
in 300 chance of colliding with the Earth in the year 2880.

The asteroid is nearly 1.1 km in diameter and if it does collide with the
Earth will produced a crater 22 km in diameter and generate a blast of
radius 300 km. If the collision occur in an ocean it will generate a tsunami
(tidal wave) that could be as high as 250 m at a coastline 1000 km away.

Asteroid 1950 DA is the first Near Earth Object that has a non-zero chance
of colliding with the Earth and is rated 2 on the Torrino Impact Hazard
Scale. It will be carefully monitored in the future. If necessary the path
of the asteroid could be changed to overt an impact.

=============
(12) AND FINALLY: "DOWN WITH ASTEROIDS"? NO WAY, LET THEM STAY UP THERE!

>From John Michael Williams <jwill@AstraGate.net>

Hi Benny.
 
Charles Rousseaux (Washington Times/CCNet, 22 April 2002) wrote:
 
> "Where were the people carrying the "Down With Asteroids" signs
> during this past weekends protests against everything
> in Washington? ..."

Actually, I'd prefer they stay up there, where they belong.
--
                         John
                     jwill@AstraGate.net
                     John Michael Williams

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