PLEASE NOTE:
*
CCNet 84/2001 - 3 July 2001
---------------------------
"Pluto has suffered another demotion with scientists
discovering a
very bright, icy body possibly even larger than the tiny
ice-planet's moon
Charon and orbiting the Sun in the same celestial
neighborhood."
--Space.com, 2 July 2001
"Dr David Jewitt of the University of Hawaii who has
discovered many
KBO's, including the first one ever seen, told BBC News Online:
"We're
inching up to Pluto. It is just a matter of time until we see
Pluto
2, Pluto 3 and so on." Robert Millis agrees: "Until the
Kuiper Belt has
been thoroughly explored, we cannot pretend to know the extent or
the
content of the Solar System."
--BBC News Online, 3 July 2001
"Some years ago, Opik and I published a paper on meteorite
ejection.
We argued that the escape velocity would require an acceleration,
and
force, exceeding the crushing strength of rocks -- similar
to your
argument. Since then I have been persuaded by the evidence put
forth by
Heinrich Waenke and others that certain meteorites did originate
from the
surface of Mars. The obvious explanation is a slow ejection
mechanism rather than an impulsive one, perhaps driven by gas
erupting from Mars."
--S. Fred Singer, 1 July 2001
"... Also virtually impossible would be a gas-entrainment
mechanism
that might increase the time of acceleration because of gradual
expansion following the initial impact. First, there isn't much
gas on
Mars, and pressure hardly increases sound speed at all. Extreme
compression would push many gasses past their triple point and in
effect
liquify them; this is especially true of the carbon dioxide
making up
about 95% of the Martian atmosphere. If we assume optimistically
that the gas was of Earth air composition, its speed of sound at
300
K would be about 330 m/s. The speed of sound in an ideal gas
varies about as
the square root of temperature (v oc sqrt(k*T/m). To accelerate a
rock
to 5 km/s, remembering that the temperature of a gas drops
proportional
to its expansion rate, we would need the gas in a
tightly-fitting,
gun-barrel-like cylinder expanding at something like 20 times its
speed
of sound at 300 K; this would require a temperature of some
400*300 =
120,000 K. The temperature of the Sun's photosphere being only
some 5,500
K, this would seem highly unlikely in a mere asteroid
impact..."
--John Michael Williams, 2 July 2001
(1) KUIPER BELT OBJECT FOUND POSSIBLY AS LARGE AS PLUTO'S MOON
CERRO TOLOLO INTER-AMERICAN OBSERVATORY, 2
June 2001
(2) PLUTO SUFFERS ANOTHER DEMOTION: BIG MOON-SIZED OBJECT FOUND
BEYOND
NEPTUNE
Space.com, 2 June 2001
(3) INCHING UP TO PLUTO AS ANOTHER LARGE KUIPER BELT OBJECT IS
FOUND
BBC News Online, 3 July 2001
(4) DUST DEVILS RESHAPE MARS
Space.com, 2 June 2001
(5) COMETS II: SPACE SCIENCE SERIES ANNOUNCEMENT
Richard P. Binzel <rpb@MIT.EDU>
(6) EJECTION OF MARTIAN ROCKS
S. Fred Singer <singer@sepp.org>
(7) EJECTION OF MARTIAN ROCKS I
John Michael Williams <jwill@AstraGate.net>
(8) THE UNLIKELY PHYSICS OF THE SUPPOSED METEORITES FROM MARS
http://publish.aps.org/eprint/gateway/eplist/aps1999jun25_002
(9) EJECTION OF MARTIAN ROCKS II
John Michael Williams <jwill@AstraGate.net>
(10) TANNER ON TR/J EXTINCTIONS
Hermann Burchard <burchar@mail.math.okstate.edu>
=========
(1) KUIPER BELT OBJECT FOUND POSSIBLY AS LARGE AS PLUTO'S MOON
From CERRO TOLOLO INTER-AMERICAN OBSERVATORY, 2 June 2001
http://www.ctio.noao.edu/news/kuiperobj.html
July 2, 2001
RELEASE: NOAO 01-10
Astronomers from Lowell Observatory, the Massachusetts Institute
of
Technology, and the Large Binocular Telescope Observatory have
discovered an
icy planetary body orbiting the Sun beyond Neptune in the Kuiper
Belt
roughly equal in size to Pluto's moon Charon.
"This object is intrinsically the brightest Kuiper Belt
Object found so
far," says Lowell Observatory Director Robert Millis, leader
of the survey
team. "The exact diameter of 2001 KX76 depends on
assumptions that
astronomers make about how its brightness relates to its size.
Traditional
assumptions make it the biggest by a significant amount, while
others make
it larger by at least 5 percent."
Assuming a reflectivity (or albedo) of 4 percent, 2001 KX76 would
have a
diameter of approximately 1,270 kilometers (788 miles), bigger
than Ceres,
the largest known asteroid. For comparison, Pluto's moon Charon
has an
estimated diameter of 1,200 kilometers (744 miles).
Earlier this year, a Kuiper Belt Object (KBO) called 20000 Varuna
was
announced with an estimated diameter of 900 kilometers, based on
a
calculated reflectivity of 7 percent. Applying this albedo to
2001 KX76
gives it a diameter of roughly 960 kilometers (595 miles).
2001 KX76 was discovered in the course of the Deep Ecliptic
Survey, a
NASA-funded search for KBOs being conducted by the Lowell-MIT-LBT
team using
the National Science Foundation's telescopes at Kitt Peak
National
Observatory near Tucson, AZ, and Cerro Tololo Inter-American
Observatory in
Chile. The team spotted 2001 KX76 in deep digital images of the
southern sky
taken with the 4-meter Blanco Telescope at Cerro Tololo on May 22
by James
L. Elliot of MIT and Lawrence H. Wasserman of Lowell Observatory.
2001 KX76 is currently at a distance of just over 6.4 billion
kilometers (4
billion miles) from the Sun. Its orbit is inclined by
approximately 20
degrees with respect to the orbital plane of the major planets,
but the
detailed shape of its orbit remains uncertain. Available evidence
suggests
that the newly discovered KBO may be in an orbital resonance with
Neptune,
orbiting the Sun three times for each time that Neptune completes
four
orbits.
The brightness and colors of 2001 KX76 have been measured by
Elliot, Susan
Kern, and David Osip, all of MIT, with the Raymond and Beverly
Sackler
Magellan Instant Camera (MagIC) on the 6.5-meter Magellan
Telescope at Las
Campanas Observatory in Chile. The object has a distinctly
reddish color
typical of many primitive bodies in the outer Solar System.
"2001 KX76 is so exciting because it demonstrates that
significant bodies
remain to be discovered in the Kuiper Belt," Millis
explains. "We have every
reason to believe that objects ranging up to planets as large or
larger than
Pluto are out there waiting to be found. Until the Kuiper Belt
has been
thoroughly explored, we cannot pretend to know the extent or the
content of
the Solar System."
The existence of the Kuiper Belt was postulated by J. A.
Fernandez and by M.
Duncan, T. Quinn, and S. Tremaine in the 1980s to explain the
origin of
short-period comets. These comets move around the Sun in the same
direction
as the planets, and are found in orbits that are tipped only
modestly with
respect to the ecliptic plane. These researchers showed that
short-period
comets could not have originated from the more distant spherical
Oort Comet
Cloud as originally believed. They predicted that a second, more
flattened
reservoir of "proto-comets" must lie beyond the orbit
of Neptune.
The first Kuiper Belt Object was found in 1992 by David Jewitt
and Jane Luu
of the University of Hawaii. Since then, astronomers have found
over 400
KBOs, but tens of thousands likely remain to be discovered. These
objects
are believed to be remnants from the formation of the Solar
System, and
consequently are among the most primitive and least-evolved
objects
available for study by planetary astronomers.
About one-quarter of the known KBOs have been found by the Deep
Ecliptic
Survey Team. Other members of the team are Marc Buie of Lowell
and Mark
Wagner of the Large Binocular Telescope Observatory on Mount
Graham, AZ. The
Deep Ecliptic Survey was recently awarded formal survey status at
the
National Optical Astronomy Observatory (NOAO), assuring that this
reconnaissance of the outer Solar System will continue for the
next three
years.
Much more precise measurement of KBO diameters will be possible
with NASA's
upcoming Space Infrared Telescope Facility (SIRTF) mission, due
for launch
in 2002.
Kitt Peak and Cerro Tololo Inter-American Observatory are part of
NOAO,
which is operated by the Association of Universities for Research
in
Astronomy (AURA), Inc., under a cooperative agreement with the
National
Science Foundation.
The survey team's research is supported by the NASA Planetary
Astronomy
Program through grants to Lowell Observatory, Flagstaff, AZ, and
MIT in
Cambridge, MA.
========
(2) PLUTO SUFFERS ANOTHER DEMOTION: BIG MOON-SIZED OBJECT FOUND
BEYOND
NEPTUNE
From Space.com, 2 June 2001
http://www.space.com/scienceastronomy/solarsystem/big_kuiper_object_010702.html
By SPACE.com Staff
Pluto has suffered another demotion with scientists discovering a
very
bright, icy body possibly even larger than the tiny ice-planet's
moon Charon
and orbiting the Sun in the same celestial neighborhood.
The object, called 2001 KX76, orbits beyond Neptune in the Kuiper
Belt of
early solar system ice-and-rock smidgeons.
"This object is intrinsically the brightest Kuiper Belt
Object found so
far," says Lowell Observatory Director Robert Millis, leader
of the survey
team. And brightness is how astronomers calculate size.
Under one assumption about the object's reflectivity (albedo),
2001 KX76 is
probably 788 miles (1,270 kilometers), making it 44 miles larger
across than
Charon and even bigger than Ceres, the largest known asteroid.
"2001 KX76 is so exciting because it demonstrates that
significant bodies
remain to be discovered in the Kuiper Belt," Millis said.
"We have every reason to believe that objects ranging up to
planets as large
or larger than Pluto are out there waiting to be found. Until the
Kuiper
Belt has been thoroughly explored, we cannot pretend to know the
extent or
the content of the Solar System."
Varuna verity
The truth is that 2001 KX76 could be a bit smaller than Charon.
It all
depends on how reflective such objects are.
For instance, earlier this year, a Kuiper Belt Object (KBO)
called 20000
Varuna was announced with an estimated diameter of 558 miles (900
kilometers), based on a calculated reflectivity of 7 percent.
Applying this albedo to 2001 KX76 gives it a diameter of only 595
miles (960
kilometers).
Reddish and resonant
2001 KX76 was discovered in the course of the Deep Ecliptic
Survey, a
NASA-funded search for KBOs.
The team spotted 2001 KX76 in deep digital images of the southern
sky taken
with the 4-meter Blanco Telescope at Cerro Tololo on May 22 by
James L.
Elliot of the Massachusetts Institute of Technology (MIT) and
Lawrence H.
Wasserman of Lowell Observatory.
2001 KX76 currently is just over 4 billion miles (6.4 billion
kilometers)
from the Sun. Its orbit is inclined by approximately 20 degrees
with respect
to the orbital plane of the major planets, but the detailed shape
of its
orbit remains uncertain.
Available evidence suggests that the newly discovered KBO may be
in an
orbital resonance with Neptune, orbiting the Sun three times for
each time
that Neptune completes four orbits.
The object has a distinctly reddish color typical of many
primitive bodies
in the outer Solar System.
KBOs
The existence of the Kuiper Belt was postulated by J. A.
Fernandez and by M.
Duncan, T. Quinn, and S. Tremaine in the 1980s to explain the
origin of
short-period comets.
These comets move around the Sun in the same direction as the
planets and
are found in orbits that are tipped only modestly with respect to
the
ecliptic plane.
These researchers showed that short-period comets could not have
originated
from the more distant spherical Oort Comet Cloud as originally
believed.
They predicted that a second, more flattened reservoir of
"proto-comets"
must lie beyond the orbit of Neptune.
The first Kuiper Belt Object was found in 1992 by David Jewitt
and Jane Luu
of the University of Hawaii. Since then, astronomers have found
over 400
KBOs, but tens of thousands likely remain to be discovered.
These objects are believed to be remnants from the formation of
the Solar
System, and consequently are among the most primitive and
least-evolved
objects available for study by planetary astronomers.
The Deep Ecliptic Survey
About one-quarter of the known KBOs have been found by the Deep
Ecliptic
Survey Team.
Much more precise measurement of KBO diameters will be possible
with NASA's
upcoming Space Infrared Telescope Facility (SIRTF) mission, due
for launch
in 2002.
The survey team's research is supported by the NASA Planetary
Astronomy
Program through grants to Lowell Observatory and MIT. The team
includes
astronomers from Lowell Observatory, MIT and the Large Binocular
Telescope
Observatory.
Copyright 2001, Space.com
========
(3) INCHING UP TO PLUTO ANOTHER LARGE KUIPER BELT OBJECT IS FOUND
From the BBC News Online, 3 July 2001
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1419000/1419508.stm
By BBC News Online science editor Dr David Whitehouse
Astronomers have found one of the largest objects ever detected
orbiting the
Sun.
It was seen in a deep space survey looking for bodies circling
the Sun out
near Pluto, the most distant planet. Only planets are larger than
the new
object, dubbed 2001 KX76.
The icy, reddish world is over a thousand kilometres in size and
astronomers
say there may be even larger ones, bigger than planet Pluto
itself, awaiting
discovery.
"What we have seen may be only the tip of the iceberg,"
co-discoverer Dr
Lawrence Wasserman told BBC News Online.
When we spotted it we just wrote 'wow' on the image, we knew
right away it
was a big one
Lawrence Wasserman Lowell Observatory
The world, for it is big enough to be called a world, has a
typical reddish
hue and is probably covered in ice. It orbits the Sun beyond
Neptune in the
so-called Kuiper Belt - a region that extends far beyond the
known planets.
Since 1992, over 400 Kuiper Belt Objects (KBOs) have been
detected. Their
discovery has revolutionised our view of the distant reaches of
our solar
system.
It is the sheer size of 2001 KX76 that is exciting astronomers.
"When we spotted it we just wrote 'wow' on the image, we
knew right away it
was a big one," Lawrence Wasserman, of the Lowell
Observatory in Arizona,
told BBC News Online.
"This object is intrinsically the brightest Kuiper Belt
Object found so
far," says Lowell Observatory Director Robert Millis.
"The exact diameter of 2001 KX76 depends on assumptions that
astronomers
make about how its brightness relates to its size. Traditional
assumptions
make it the biggest by a significant amount, while others make it
larger by
at least 5%," he added.
2001 KX76 could be as large as 1270 km (788 miles), bigger than
Ceres, the
largest known asteroid - an object that orbits the Sun between
Mars and
Jupiter.
It is even larger than Pluto's moon Charon which has an estimated
diameter
of 1200 km (744 miles).
Uncertain orbit
2001 KX76 was discovered in the course of the Deep Ecliptic
Survey, a
Nasa-funded search for KBOs.
It was seen on 22 May in deep digital images of the southern sky
taken with
the 4-metre Blanco Telescope at Cerro Tololo in Chile.
Astronomers estimate that 2001 KX76 is currently at a distance of
just over
6.4 billion km (4 billion miles) from the Sun. Its orbit is
inclined by
approximately 20 degrees with respect to the major planets, but
the detailed
shape of its orbit remains uncertain.
Available evidence suggests that the newly discovered KBO may be
in an
orbital dance with Neptune, orbiting the Sun three times for each
time that
Neptune completes four orbits.
"2001 KX76 is so exciting because it demonstrates that
significant bodies
remain to be discovered in the Kuiper Belt," Robert Millis
explains.
Lawrence Wasserman agrees: "We have every reason to believe
that objects
ranging up to planets as large or larger than Pluto are out there
waiting to
be found."
Dr David Jewitt of the University of Hawaii who has discovered
many KBO's,
including the first one ever seen, told BBC News Online:
"We're inching up
to Pluto. It is just a matter of time until we see Pluto 2, Pluto
3 and so
on."
Robert Millis agrees: "Until the Kuiper Belt has been
thoroughly explored,
we cannot pretend to know the extent or the content of the Solar
System."
The researchers hope that other astronomers who have access to
large
telescopes over the next few weeks will be able to turn them on
2001 KX76 in
the hope of gathering enough light to get a spectrum of the
object.
Copyright 2001, BBC
========
(4) DUST DEVILS RESHAPE MARS
From Space.com, 2 June 2001
http://www.space.com/scienceastronomy/solarsystem/dust_edgett_010702-1.html
By Jet Propulsion Laboratory
NASA's Mars Global Surveyor spacecraft recently caught sight of a
dust devil
dancing across the Martian surface. While it isn't the first of
the
tornado-like weather systems to be imaged, it is yet another
reminder that
Mars is an ever-changing planet.
Dr. Ken Edgett, a staff scientist at Malin Space Science Systems
in San
Diego, Calif., regularly tracks the dust devils and studies
surface
features. As the operator for the Surveyor's orbiter camera, he
is one of
the first to see fascinating images of the red planet. Dr. Edgett
recently
discussed the importance of dust devils and how they are
transforming the
look of Mars.
Q: First of all, what is a dust devil?
On Mars, Hurricane Andrew would stick in the memory as a gentle
breeze. And
the oppressive heat and biting sandstorms of the Mojave? Hang on
to your
cosmic hats, because the wildest, wackiest and worst weather
known does not
occur on Earth. Click here to find out which planets have the
scariest
forecasts.
A: A dust devil is something that happens both on Earth and on
Mars and
looks somewhat like a mini-tornado. As with tornadoes, dust
devils are
spinning columns of air. Such a column is called a vortex--you
might see the
same effect when you let water run down a bathtub drain. Unlike
tornadoes,
dust devils aren't usually associated with storms. You typically
see them on
dry, sunny summer days when there is anywhere from a little to no
breeze.
You might say they look something like that Tasmanian Devil
cartoon
character - he spins 'round and 'round like a tornado when he
moves.
A dust devil is actually a visual apparition of a wind vortex. If
there
isn't any dust on the ground, a vortex might still form but no
one would see
it. An example of a vortex without dust might be the scene in the
film
American Beauty where the plastic shopping bag is caught on
videotape,
spinning, spiraling, and dancing in the air. Dust devil vortices
form when
the air is fairly calm and the ground is heated by sunlight-this
heats the
air immediately above ground. Hot air rises up the outside of the
spinning
column, while cooler air descends through its middle. If a vortex
passes
over a dusty surface, it will pick up the dust and become a
visible feature
-- a dust devil.
Q: Are Martian dust devils different than devils on Earth?
A: The Martian surface is so much more dusty than Earth because
here we have
rain to wash away most of the dust that settles out of the sky,
but on Mars
it doesn't rain. What's neat about the Martian dust devils is
that they
create "art". All that extra dust on the ground means
that the dust devils
leave tracks behind them where they have either picked up dust or
disturbed
the dust lying about on the surface. Most of the time these
tracks are
darker than the surroundings, but sometimes they are lighter---it
just
depends upon whether the surface under the thin coating of dust
is brighter
or darker than the dust itself. In some places on Mars, you can
get hundreds
of crisscrossing dust devil tracks, they make a pattern that some
say
resembles Jackson Pollack paintings, others say resembles
something their
2-year old might do with crayons.
Q: How do you detect dust devils in the Global Surveyor data?
A: NASA's Mars Global Surveyor spacecraft has the Mars orbiter
camera,
that's actually three-cameras-in-one.
The two wide-angle cameras are used every day to take a global
portrait of
Mars; we use these to document changes in weather and frost
patterns. The
high-resolution camera, on the other hand, is used to see things
up close.
Its main purpose is to examine the geology and
geomorphology---the shape of
the landforms. Every once in a while, however, one of these
cameras captures
a dust devil in action. The high-resolution camera has a very
narrow field
of view---we can only see areas about 3 kilometers (1.9 miles)
across, so no
one really expected we'd ever see a dust devil with this camera.
But we
have.
More amazing to us, sometimes the dust devils are so big that you
can see
them with the wide-angle cameras meaning that they are wide
enough to cover
a couple football fields and stand several kilometers high.
Q: Did you know dust devils existed before Global Surveyor?
A: Vortices, though no one knows if they had dust in them or not,
were
detected by the meteorology experiments on the two Viking landers
in the
late 1970s. Similar detections occurred during the 1997 Mars
Pathfinder
mission. Some of these went right over the lander without causing
damage. In
the mid-1980s, researchers at Cornell University realized that
some of the
Viking pictures taken from orbit showed dust devils---from orbit
what you
see is usually a round, fuzzy-looking cloud that is casting a
very long,
columnar shadow. Researchers at the University of Nevada in Reno
have
suggested that a few of Mars Pathfinder's images also detected
dust
devils---these appear as actual columns of dust moving across the
distant
landscape.
When Mars Global Surveyor arrived in late 1997, we started seeing
in our
high-resolution pictures, thin narrow tracks running across the
surface in
some places, especially in the dust-covered areas. We suspected
these were
caused by dust devils, but we had no proof. Later on we were able
to
photograph some of these tracks a second time, and lo and behold,
they had
changed! In some cases there were more tracks, in others the
original tracks
had completely disappeared and were replaced by new ones, like
some giant
Martian Etch-a-sketch. "There can't be that many dust devils
on Mars, can
there?" we wondered. But indeed it's true that in some areas
out in the
deserts of Arizona and Nevada, people have recorded hundreds of
dust devils
over periods of only a few weeks. So you can have lots of dust
devils, it
happens on Earth.
In December of 1999, we got our first really good image that
actually caught
a dust devil in the act of creating one of these dark streaks. We
were
thrilled! After that, we've now seen dozens of cases where dust
devils are
creating streaks--usually dark streaks, but in early April 2001
we got one
in Amazonis Planitia that was making a very faint bright streak.
Q: Speaking about that dust devil image in Amazonis Planitia,
what was it
like when you first saw that image?
A: I was tickled. It is always neat to see these dust devils in
Global
Surveyor images. We don't get them every day, so when we spot
them they
always create a buzz among the camera operations staff --
"come see what I
found!" This particular dust devil from April was exciting
because it isn't
a round, fuzzy cloud. It's a twisted thing that casts a dark,
bent shadow.
Because the camera is looking straight down, the shadow is what
gives the
best impression of the shape of the thing. Bent dust devils like
this aren't
unusual, but neat nonetheless. The bending is caused by
differences in the
wind at different levels in the lower Martian atmosphere at the
time the
dust devil was moving across the landscape.
Q: If that same dust devil appeared on Earth would it do any
damage?
A: This particular dust devil probably wouldn't cause any real
damage,
though in the April image it was clearly picking up dust and
creating a
faint, bright streak. If you went and stood in the way and the
dust devil
came over you, you'd certainly feel it, though. I once drove my
car into a
dust devil down along I-8 near Yuma, Arizona, and it definitely
jiggled the
car around. Do not try this at home! I should say, however, that
there are
documented cases on Earth where dust devils, as opposed to
tornadoes, have
caused some damage, including buildings, but usually this is not
the case.
Some stronger dust devils can have winds comparable to small
tornadoes.
Q: Why do you study dust devils?
A: Dust devils are one of the mechanisms by which dust is moved
around and
redistributed on Mars. They are part of a process that is active
today,
meaning that Mars is not a "dead" planet but has things
that are happening
right now. Dust devils may contribute some of that dust that
gives the sky
its pinkish color. Dust devils also appear to play a role in
cleaning off
dark surfaces. For hundreds of years, people saw in telescopes
that Mars'
surface markings would change over the course of a year. In
spring, areas
would get darker and then get lighter in autumn. Once upon a
time, it was
thought that the "wave of darkening" was caused by
springtime growth of
vegetation. We now know that blowing dust is what causes these
changes, and
with Mars Global Surveyor's high-resolution images, it now
appears that some
areas darken because dust devils come along in the spring and
summer months
to clean dust off that accumulated in autumn and winter or, at
least, that's
what I think we're seeing with this camera.
Q: Do you have a favorite dust devil image?
A: Yes, it was taken October 14, 1999, in the western Daedalia
Planum
region. I just happen to like this one because it is very
dramatic, though
it is not creating a streak on the surface--they don't all make
streaks.
When it first came in, I was really moved by the experience of
seeing an
event that had taken place on Mars just a few hours earlier.
Q: What is it about dust devils that surprise you?
A: The fact that we can catch them in action! We see such a
limited amount
of the surface with the high-resolution camera, to date we've
photographed
less than 2 percent of the surface, yet we have seen dozens of
dust devils
and thousands of streaks that we think are produced by them. This
must mean
that dust devils are very common all over Mars. It surprises me
that we even
see their streaks at the top of the giant volcano, Olympus Mons,
where the
atmosphere is so thin---about 10 times thinner than at the Mars
Pathfinder
site--that you are almost in a vacuum. When you get lucky and
catch a dust
devil in one of these images, you get an eerie chill down your
spine. These
are dynamic things and you just happened to catch one at the time
the
spacecraft flew overhead. Dust devils give me a chill when I see
them out in
nature on Earth--they often seem to have a mind of their own.
They might
come toward you, then go away from you, as if teasing you. To see
these on
Mars gives me that same sense of being tantalized and teased. The
dust devil
you capture today is something that will not be there tomorrow.
Copyright 2001, Space.com
============
(5) COMETS II: SPACE SCIENCE SERIES ANNOUNCEMENT
From Richard P. Binzel <rpb@MIT.EDU>
Dear Colleague,
The Space Science Series is pleased to announce plans for a new
upcoming
volume: COMETS II
edited by Michel Festou, Uwe Keller, Harold Weaver and planned
for
publication by the University of Arizona Press in 2003.
The process of forming the Scientific Organizing Committee (SOC)
for the
book COMETS II is now underway and persons interested in devoting
substantial effort as a member of the book SOC are invited to
contact the
lead editor:
Michel Festou (festou@ast.obs-mip.fr).
A second announcement will be made soon to solicit community-wide
ideas and
volunteers for chapters for COMETS II.
The principal scientific meeting bringing together authors for
COMETS II
will be the Asteroids Comets Meteors (ACM2002) conference
to be held in
Berlin from July 29 to August 2, 2002. Participation in the book
does not
require participation or attendance at the ACM2002
conference. Information
on the conference is available at the web site:
http://earn.dlr.de/ACM2002
Chapters for COMETS II will be due promptly after the ACM2002
meeting.
A more immediate opportunity for authors and participants of the
COMETS II
book to meet and plan their work is the "5 Years After Hale
Bopp" conference
to be held in Tenerife January 21-25, 2002. Information on this
conference
is available at the web
site: http://r2d2.stcloudstate.edu/
Broad and active participation by the international planetary
science
community in making COMETS II a success is essential and most
certainly
welcomed and encouraged!
Sincerely,
Richard P. Binzel,
General Editor
Space Science Series
============================
* LETTERS TO THE MODERATOR *
============================
(6) EJECTION OF MARTIAN ROCKS
From S. Fred Singer <singer@sepp.org>
Re: CCNet 79/2001 - 18 June 2001
Some years ago, Opik and I published a paper on meteorite
ejection. We
argued that the escape velocity would require an acceleration,
and force,
exceeding the crushing strength of rocks -- similar to your
argument.
Since then I have been persuaded by the evidence put forth by
Heinrich
Waenke and others that certain meteorites did originate from the
surface of
Mars. The obvious explanation is a slow ejection mechanism rather
than an
impulsive one, perhaps driven by gas erupting from Mars.
I have not seen any calculations along these lines.
Best,
Fred
S. Fred Singer, President
Science & Environmental Policy Project
http://www.sepp.org
===========
(7) EJECTION OF MARTIAN ROCKS I
From John Michael Williams <jwill@AstraGate.net>
Hello Fred.
You should read my paper at
http://publish.aps.org/eprint/gateway/eplist/aps1999jun25_002
Gas ejection would be highly unlikely, as discussed in the
"cartoon" text at
the end of the paper. The speed of sound in gas by definition
equals the
speed of expansion of that gas into vacuum. Any gas, even
hydrogen, at less
than astrophysical temperatures, would therefore be able to push
something
entrained with it to at most something like 2 or 3 km/s.
I agree that gas would allow entrained material to be accelerated
intact . .
. exactly because the speed of sound in any gas is below that of
almost any
rock.
The problem is not obviously crushing strength, but rather rate
of
propagation of energy. Young's modulus and other
parameters would be
shared in quantizing sound speed as well as crushing strength,
but the two
ideas actually are independent.
John
jwill@AstraGate.net
John Michael Williams
------------
(8) THE UNLIKELY PHYSICS OF THE SUPPOSED METEORITES FROM MARS
http://publish.aps.org/eprint/gateway/eplist/aps1999jun25_002
By: John Michael Williams (jwill@AstraGate.net)
Several rocks recovered from Antarctica and a few other Earth
locations have
been identified as meteorites supposed to have been ejected from
the planet
Mars in the geologically recent past. Much previous discussion of
these
rocks has been directed at the possible mechanism of ejection,
but little
has been written about the basic physics of the effects of such
ejection on
rock. We show here that no kind of rock known on Earth likely
could have
been ejected at or above the Martian escape speed by an impact,
no matter
what the mechanism. (28 pages)
=========
(9) EJECTION OF MARTIAN ROCKS II
From John Michael Williams <jwill@AstraGate.net>
Hello Fred.
Concerning the possibility of gentle, gaseous acceleration of an
impact
ejectum, here's an extract of some of the revised ms I have been
preparing (I have yet to
complete some of the basic speed-of-sound derivations):
"... Also virtually impossible would be a gas-entrainment
mechanism
that might increase the time of acceleration because of gradual
expansion following the initial impact.
First, there isn't much gas on Mars, and pressure hardly
increases
sound speed at all. Extreme compression would push
many gasses past
their triple point and in effect liquify them; this is especially
true of the carbon dioxide making up about 95% of the Martian
atmosphere.
If we assume optimistically that the gas was of Earth air
composition, its speed of sound at 300 K would be about 330 m/s.
The
speed of sound in an ideal gas varies about as the square root of
temperature (v oc sqrt(k*T/m) ). To accelerate a rock to 5 km/s,
remembering
that the temperature of a gas drops proportional to its expansion
rate, we
would need the gas in a tightly-fitting, gun-barrel-like cylinder
expanding
at something like 20 times its speed of sound at 300 K; this
would require
a temperature of some 400*300 = 120,000 K. The temperature of the
Sun's
photosphere being only some 5,500 K, this would seem highly
unlikely in
a mere asteroid impact..."
==============
(10) TANNER ON TR/J EXTINCTIONS
From Hermann Burchard <burchar@mail.math.okstate.edu>
Dear Benny,
at the GSL/GSA conference in Edinburgh last week, as communicated
to CCNet
June 29 by Andrew Yee, some remarkable empirical observations
were reported
by Larry Tanner giving proof that CAMP basalt eruptions did not
release
sufficient amounts of CO2 to have caused the Tr/J extinctions:
Ann Cairns, Director-Communications
GSA Release No. 01-27
Mass Extinction At The Triassic-Jurassic Boundary: Where's The
Smoking Gun? ....
"The mass extinction that marks the end of the Triassic is
one of
the five largest extinction events of the Phanerozoic
Eon.." ...
Tanner will address possible explanations for this event.
... "Then
there's asteroid impact -- however, no impact structure can be
tied directly to the Triassic-Jurassic boundary. .." ... no
evidence
for any change in the CO2 composition of the atmosphere.
In this connection, very precise dates near 200 Ma were obtained
for the
Tr/J boundary recently:
* Queen Charlotte Islands, British Columbia, Tr/J
radiolarian plancton
extinction strata, the age of 199.6 Ma was
given by Peter Ward et al.
* Brazilian CAMP basalts, 199.0±2.4 Ma mean 40Ar/39Ar age
was given
by Angelo De Min, Paul Renne, et al.
But, Larry Tanner's statement that "no impact structure can
be tied directly
to the Triassic-Jurassic boundary" may not be strictly
correct. He is
referring (see the abstract) to the Manicougan crater in Quebec
being dated
at 214 Ma, which is too early, etc.
However, his statement ignores that structures other than craters
have been
tagged by geologists for impact causation, see list below.
Here, we suggest
specific Tr/J-related instances of such structures, which are
possibly
caused by cosmogenic impact at the 200 Ma epoch:
* Azores mantle hotspot / plume located near the center of
the CAMP
* CAMP basalts in Europe, Africa, N & S America dated
to 200 Ma
* North Atlantic Rift / Mid Ocean Ridge began with CAMP
eruptions
* SSE of Azores hotspot track Atlantis, Cruiser, Great
Meteor seamounts
There are plenty possible and prominent impact structures
available here.
One may accept these as being impact structures or not, depending
on one's
preference of current geological theory. And who knows, a crater
may yet be
found, buried under CAMP basalts on four continents.
Regards,
Hermann
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