PLEASE NOTE:
*
CCNet 73/2001 - 31 May 2001
----------------------------
"Chemicals trapped in ancient glacial or polar ice can move
substantial distances within the ice, according to new evidence
from
University of Washington researchers. That means past analyses of
historic climate changes, gleaned from ice core samples, might
not be
entirely accurate."
--Sandra Hines, University of Washington, 30 May 2001
"What fascinated me personally about [Deep Impact] is, as
the design
went through, it became clear how little we truly know about
comet
interiors."
--Tom Morgan, program scientist for Deep Impact, 30 May 2001
(1) NEAR-EARTH ASTEROID IS TWO CHUNKS IN ONE
Ron Baalke <baalke@jpl.nasa.gov>
(2) COMET P/2001 J1 (NEAT) = COMET BIELA?
Ron Baalke <baalke@ZAGAMI.JPL.NASA.GOV>
(3) COMET P/2001 J1 (NEAT)
INTERNATIONAL ASTRONOMICAL UNION
Circular No. 7635
(4) COMET P/2001 J1 (NEAT) AND 3D/BIELA
Brian G. Marsden <brian@cfaps5.harvard.edu>
(5) NO ACTIVITY FROM COMET SCHWASSMANN-WACHMANN 3 IN 2001
Rainer Arlt <rarlt@aip.de>
(6) SCIENTIST NOW HAS DATE WITH A COMET
The Baltimore Sun, 30 May 2001
(7) ANCIENT CLIMATE RECORDS MAY BE FATALLY FLAWED
Andrew Yee <ayee@nova.astro.utoronto.ca>
(8) TROPICAL CLACIERS FORMED WHILE EARTH WAS GIANT SNOWBALL
Andrew Yee <ayee@nova.astro.utoronto.ca>
(9) TNO (20000) VARUNA
Javier Andres Licandro Goldaracena <jlicandr@ll.iac.es>
(10) THE ORIGIN OF ACUSTIC BOMB-DETECTION SYSTEMS & UFO
MYTHOLOGY
Rolf Sinclair <rolf@santafe.edu>
(11) IMPACT SEQUENCE IN THE GEOLOGICAL RECORD
Duncan A. Lunan <astra@dlunan.freeserve.co.uk>
===========
(1) NEAR-EARTH ASTEROID IS TWO CHUNKS IN ONE
From Ron Baalke <baalke@jpl.nasa.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.nasa.gov
Contact: Martha J. Heil (818)
354-0850
FOR IMMEDIATE
RELEASE
May 30, 2001
NEAR-EARTH ASTEROID IS TWO CHUNKS IN ONE
The clearest radar pictures of a near-Earth double asteroid
system were
taken by astronomers last week using NASA's Goldstone radar
telescope,
revealing clues to the system's current structure but raising
questions
about its origin and future.
A team of astronomers studied images that show the trail of the
smaller
component orbiting a larger object, made with the Goldstone
radar, a
70-meter (230-foot) antenna in California's Mojave Desert. The
asteroid,
1999 KW4, came within five million kilometers of Earth (over 3
million
miles) on Friday, May 25.
"This system, 1999 KW4, is the third binary near-Earth
asteroid pair
revealed by radar, but this is the first time we've been able to
image the
system over a complete orbit of one component around the
other," said Dr.
Steven Ostro of NASA's Jet Propulsion Laboratory, Pasadena,
Calif., leader
of the team that made the discovery. "Goldstone was able to
track the
asteroid for up to eight hours daily for a week. Then we
made close-up
images of each component using the Arecibo telescope in Puerto
Rico, which
is not as fully steerable but is much more powerful."
The images can be seen at http://echo.jpl.nasa.gov/~ostro/kw4_press.tif
.
The radar team also included Dr. Lance Benner and Jon Giorgini of
JPL, Dr.
Jean-Luc Margot of the California Institute of Technology,
Pasadena, and Dr.
Michael Nolan of Arecibo Observatory, Arecibo, Puerto Rico.
"The asteroid pair 1999 KW4 is classified a Potentially
Hazardous Asteroid
because eventually its path through space could intersect
Earth. However,
the radar measurements, which are accurate to 15 meters (about 49
feet),
indicate there is no significant chance of 1999 KW4 colliding
with Earth for
at least a thousand years," said Giorgini. He said the
larger component is
spheroidal and roughly 1.2 kilometers (three-quarters of a mile)
in average
diameter, while the smaller component is asymmetrical and roughly
one-third
as large.
"1999 KW4 is one of fewer than two dozen known asteroids
whose orbits cross
the orbits of Mercury, Venus and Earth," said Benner.
"However, the only
known solar system bodies that get closer to the Sun and have a
more steeply
inclined orbit than 1999 KW4 are comets, so perhaps this object
is an
extinct comet nucleus."
"Our first look at the images suggests an orbital period of
roughly 16
hours," said Margot. Later, detailed analysis of all
the radar data will
determine very precisely the period, which is the time it takes
the smaller
object to orbit the larger one. Using the laws of celestial
mechanics, the
team will measure the objects' masses and densities, which will
tell what
they are made of and how porous they are. For single asteroids,
that kind of
information can only be obtained by sending a spacecraft close to
the body,
and so most asteroids' densities, compositions and meteorite
associations
are not well known. "Yet this kind of information is
the key to
understanding relationships between meteorites, near-Earth
asteroids,
main-belt asteroids and comets," said Margot.
"This might be the first discovery of an ex-comet's
density," said Dr. Don
Yeomans, head of NASA's Near Earth Object program office at JPL.
Three known
objects are officially designated both an asteroid and a comet.
"The existence of binary near-Earth asteroids raises
perplexing questions
about their origins," said Nolan. "Nobody
understands exactly how binary
asteroid systems formed, or even how stable the current binary
systems are,
that is, how they might evolve, with the two components either
separating
completely or collapsing onto one another to form a contact
binary. The
theoreticians really have their work cut out for them now."
Nolan said that
the near-Earth binary systems might have formed during certain
kinds of
collisions. Or, if they came from loosely bound, unconsolidated
piles of
rubble instead of solid rocks, binary asteroids might have formed
during
close passages by Earth when gravity pulls them apart.
The first binary asteroid was found in August 1993 when NASA's
Galileo
spacecraft took pictures of asteroid Ida and revealed its tiny
moon Dactyl.
Current statistics suggest that at least several percent of the
near-Earth
asteroids are binaries. Ostro said that the existence of binary
asteroids on
potentially hazardous orbits means that we have to start figuring
out how to
maneuver spacecraft close to such objects.
"Robotic spacecraft, and eventually people, are destined to
go to such
objects someday, either for defense against one of them, to
exploit mineral
resources, to satisfy our curiosity about what they're like
close-up or
simply for the adventure of exploring a diminutive double
world," Ostro
said.
JPL is a division of the California Institute of Technology
in Pasadena.
==========
(2) COMET P/2001 J1 (NEAT) = COMET BIELA?
From Ron Baalke <baalke@ZAGAMI.JPL.NASA.GOV>
[as posted on the HASTRO mailing list [ HASTRO-L@WVNVM.WVNET.EDU
]
IAU Circular 7635 reports on the similarity of newly discovered
Comet P/2001
J1 (NEAT)'s orbit with Comet Biela. Comet Biela was first
observed in 1772,
and was identified in 1826 by Wilhelm von Biela to have a short
periodic
orbit, only the third periodic comet known at the time (after
Halley and
Encke). In 1846, Comet Biela surprisingly split up into two
fragments. I
believe this was the first time a comet was observed to break up.
The two
fragments were observed for some months after the breakup. In
1852, only one
of the fragments was still visible. Comet Biela hasn't been seen
since 1852.
In 1872, a large meteor storm was linked to the orbit of Comet
Biela. Large
meteor showers in 1885 and 1899 were also attributed to the
comet.
Now, it appears that Comet P/2001 J1 (NEAT) may possibly be one
of the
fragments of Comet Biela that has been missing for nearly 150
years.
Ron Baalke
============
(3) COMET P/2001 J1 (NEAT)
From INTERNATIONAL ASTRONOMICAL UNION Circular No. 7635
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA
02138,
U.S.A.
IAUSUBS@CFA.HARVARD.EDU
or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU
(science)
URL http://cfa-www.harvard.edu/iau/cbat.html
ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)
SUPERNOVAE
B. E. Schaefer, University of Texas at
Austin, on behalf of
the QUEST collaboration (cf. IAUC 7387), reports on the discovery
of eleven apparent supernovae discovered with the QUEST 16-CCD
array camera on the Centro de Investigaciones de Astronomia 1-m
Schmidt telescope at Llano del Hato, Venezuela. The total
area
searched was 264 deg^2 between Mar. 25 and Apr. 1 to R = 20.8,
with
each clear night receiving independent drift scans through B, V,
and R filters. Nightly scans continued until Apr. 4, so
that the
eleven objects all have well-sampled 3-color light curves over
roughly three weeks. Each supernova was found by
subtraction of
QUEST reference images, and each new object has been confirmed
via
six or more independent images taken on three or more nights with
subtractions from three independent reference images.
SN 2001
UT R.A. (2000.0)
Decl. R
Offset
2001bu Mar. 25 10 45 22.19 - 1 28
44.5 19.4 0" E, 0" N
2001bv Mar. 25 13 58 09.11 - 1 51
40.9 19.9 0" E, 2" S
2001bw Mar. 25 14 01 05.50 - 1 08
26.0 19.8 4" E, 4" N
2001bx Mar. 25 14 54 05.62 - 1 42
04.1 20.0 1" W, 3" N
2001by Mar. 25 15 25 52.96 - 2 10
28.7 20.3 0" E, 0" N
2001bz Mar. 25 15 30 13.76 - 0 09
26.0 20.7 2" W, 0" N
2001ca Mar. 25 15 35 41.15 - 0 16
21.6 19.4 0" E, 0" N
2001cb Mar. 25 15 38 44.08 - 0 22
56.6 20.5 0" E, 0" N
2001cc Mar. 25 15 44 13.61 - 1 53
15.5 20.0 0" E, 1" S
2001cd Mar. 25 15 46 38.83 - 0 23
09.2 19.9 1" W, 1" N
2001ce Mar. 25 16 39 28.49 - 1 27
17.9 17.9 0" E, 0" N
COMET P/2001 J1 (NEAT)
As hinted on IAUC 7625, this is a
short-period comet, and
observations by C. W. Hergenrother, T. B. Spahr, and M. Nelson
with
the 1.8-m f/1 VATT Lennon telescope on May 27 make it clear that
the orbital period is $P$ about 7.5-7.9 years. Spahr has
also
identified the comet with a very faint object (not described as
cometary) discovered by A. E. Gleason with the Spacewatch
telescope
on 2000 Oct. 7 and placed on The NEO Confirmation Page but
removed
on Oct. 20 for lack of follow-up. The additional astrometry
and
orbital elements ($P$ = 7.64 yr) are given on MPEC
2001-K43. S.
Nakano has noted some rough similarity to the orbit of comet
3D/Biela.
(C) Copyright 2001
CBAT
2001 May
29
(7635)
Daniel W. E. Green
============
(4) COMET P/2001 J1 (NEAT) AND 3D/BIELA
From Brian G. Marsden <brian@cfaps5.harvard.edu>
Dear Benny,
While I cannot exclude with 100-percent certainty the possibility
that the
new comet P/2001 J1 (NEAT) is the long-lost 3D/Biela, I really
don't think
it is. Contrary to what Ron Baalke writes, the two components of
3D/Biela
observed in 1846 were also observed--farther apart--in 1852 (and
his
identification history should include mention of the fact that
Bessel, Gauss
and others thought the 1772 and 1805 comets to be identical long
before
Biela found the comet in 1826; the problem was that it was not
clear how
many times the comet had been around the sun between 1772 and
1805).
What, indeed, happened to 3D/Biela after 1852? Did it break
up completely?
Some 30 years ago I looked into the possibility of finding that
comet again
and published a number of different orbits based on different
possibilities
for the action of the nongravitational forces on the comet after
1852. For
an epoch around 1971 these orbits all had perihelion distances
under 0.83 AU
and inclinations to the ecliptic under 8.1 degrees.
Coming now to the recent comet, although unusually large
inconsistencies
among the observations made it particularly difficult to
establish the
orbit, and given that the comet's position in the sky makes it
difficult to
observe, I note that some careful observations on May 27 by Carl
Hergenrother and Tim Spahr with the Vatican Advanced Technology
Telescope in
Arizona isolated the revolution period to 7.5-7.9 years. Tim then
realized that the object
had in fact been reported as unusual--though not of cometary
appearance--by
Arianna Gleason at Spacewatch on October 7 last year. The object
was then
listed on The NEO Confirmation Page for almost two weeks,
although it was
obviously too faint for essentially all of the likely follow-up
observers,
and Spacewatch itself evidently just missed the comet's position
when it
recorded the region again on October 19. The October 7
linkage is clearly
correct, and this pins down the current period as 7.64 years.
Running this orbit back gives a moderately close approach to
Jupiter (0.8
AU) in 1972, before which the P/2001 J1 perihelion distance was
0.96 AU and
the inclination 11 degrees. While there was tolerably good
agreement in
orbital eccentricity, argument of perihelion and nodal longitude,
it is
difficult to reconcile the perihelion distance and inclination
with the
3D/Biela values. To get these elements to agree would
require the
nongravitational forces to act in some special way, together with
the
gravitational effects of occasional approaches to Jupiter.
Whether or not the comets are identical, why was the current
comet not
observed earlier in the twentieth century? After all, the
perihelion
distance of under 1 AU does allow moderately close approaches to
the
earth--with a minimum orbital distance of perhaps 0.15 AU and an
actual
minimum distance of perhaps 0.5 AU in 1955. Actually, it is quite
clear that
at many passages through perihelion the small elongation from the
sun would
completely preclude observations, and by the time the object had
moved
around to opposition it would be as faint as when Spacewatch
fortuitously
observed it last October. Even under the more favorable
circumstances of the
1955 perihelion passage, the best one could hope for at a
90-degree
elongation from the sun would be magnitude 15, and more typically
(as this
year), one would have to contend with a maximum elongation of
70-80 degrees
and magnitude 16 if one were lucky. We _were_ lucky that NEAT was
observing
this year so far from opposition, and there would have been no
observing
program with the capability of making the discovery at the
previous
comparable elongation in 1985. Unless the comet is now
anomalously faint,
that it escaped prior detection is fully reasonable--a situation
not a bit
like that of 3D/Biela on several occasions in the late eighteenth
and early
nineteenth centuries.
Regards
Brian
===========
(5) NO ACTIVITY FROM COMET SCHWASSMANN-WACHMANN 3 IN 2001
From Rainer Arlt <rarlt@aip.de>
-------------------------------------
I M O S h o w e r C i r c u l a r
-------------------------------------
NO ACTIVITY FROM COMET SCHWASSMANN-WACHMANN 3 IN 2001
Dust trails produced by Comet Schwassmann-Wachmann 3 near its
perihelion
passages may get close to the Earth and produce meteor activity.
Computations of the evolution of such dust trails by H. Luthen
(Germany)
showed an approach to the 1941 trail for May 30, 2001, 10h
UT (solar
longitude 69.04 deg). The encounter was not very close, and
chances to see
a meteor outburst were slim.
Several observers reported their results from visual and video
monitoring in
the nights of May 24 to May 30. Apart from very few possible
shower members,
no meteor activity from Schwassmann-Wachmann 3 was
observed. Unfortunately,
no report was received for the time after May 30, 12h UT.
The following observers sent in their observations directly to
the Visual
Commission or communicated their results via the mailing list
'meteorobs@jovian.com'.
We are very grateful for their quick contributions.
ARLRA Rainer Arlt (Germany)
BETFE Felix Bettonvil (the Netherlands, VIDEO)
DECGO Goedele Decononck (Belgium)
HOLDA David Holman (USA)
JENPE Peter Jenniskens (USA)
JOHCA Carl Johannink (the Netherlands)
KOOMI Mike Koop (USA)
LANMA Marco Langbroek (the Netherlands)
LUNRO Robert Lunsford (USA)
MOLSI Sirko Molau (Germany, VIDEO)
RENJU Jurgen Rendtel (Germany)
STORO Rosta Stork (Czech Republic, VIDEO)
TRIJO Josep M. Trigo-Rodriguez (Spain)
TUKAR Arnold Tukkers (the Netherlands)
VERCI Cis Verbeeck (Belgium)
---------------------------------------------------
May Observer Time (UT) N
ZHR hR
2001
SW3 (app./true)
---------------------------------------------------
24 JOHCA 2154-2216
0 - 68/65
25 LANMA 2145-2245
1 1.5 68/64
25 TUKAR 2145-2245
0 - 68/64
25 JOHCA 2145-2305
1 1.2 67/63
25 TUKAR 2245-2345
0 - 63/59
25 LANMA 2246-0000
0 - 62/58
25 JOHCA 2305-0005
0 - 61/56
25 TUKAR 2345-0045
1 2.8 57/51
26 LANMA 0000-0112
0 - 54/48
26 JOHCA 0005-0105
0 - 54/48
26 TUKAR 0045-0115
0 - 52/45
29 STORO 2100-0130
1 (video obs.)
29 MOLSI 2103-0215
0 (video obs.)
29 BETFE 2200-0230
0 (video obs.)
29 DECGO 2250-0020
0 - 60/55
29 VERCI 2258-0020
0 - 60/55
29 RENJU 2300-0036
0 - 55/49
30 ARLRA 0017-0100
0 - 49/41
30 TRIJO 0203-0305
0 - 39/30
30 LUNRO 0830-0933
0 - 54/44
30 LUNRO 0933-1035
0 - 40/31
30 HOLDA
casual 0 -
30 JENPE
casual 0 -
30 KOOMI
casual 0 -
30 LUNRO 1035-1138
0 - 30/18
---------------------------------------------------
Solar longitudes refer to equinox J2000.0. The geocentric radiant
position
was assumed at alpha=212, delta=+28, the population index used
was r=3.0.
The radiant elevation is given as apparent and geocentric (true)
values
which differ strongly for a low-velocity shower such as the
SW3-ids with an
entry velocity of V_inf = 17 km/s.
It must thus be noted that shower association might be erroneous
as the
radiant does NOT APPEAR at alpha=212, delta=+28 as given
theoretically, due
to zenithal attraction. The above values of hR (app./true)
indicate
differences of up to 10 degrees.
Rainer Arlt,
2001 May 31
==========
(6) SCIENTIST NOW HAS DATE WITH A COMET
From The Baltimore Sun, 30 May 2001
http://www.sunspot.net/news/printedition/bal-md.comet30may30.story?coll=bal%2Dpe%2Dmaryland
By Frank D. Roylance
Sun Staff
A University of Maryland, College Park scientist has won NASA's
approval to
lead a $279 million space mission that any 10-year-old boy would
understand
and applaud.
Astronomer Michael A'Hearn will lead a team that's planning to
find out
what's inside comet Tempel 1 by smashing into it with a 771-pound
copper
"hammer" -- the biggest they could loft into space.
"It's a guy thing," said College Park astronomer Lucy
McFadden,
co-investigator on the project being led by A'Hearn. "It's
going to be a
blast, that's for sure."
The mission to put the hammer into orbit is scheduled for launch
in January
2004. Impact -- scheduled for July 4, 2005 -- is expected to blow
a
seven-story-deep hole in the comet.
As debris from the comet's interior is ejected, sensors on board
the main
spacecraft -- 300 miles above the comet -- will analyze the
chemistry of the
debris and the crater walls, and radio the results back to Earth.
Scientists will also get video images of the impact and make them
available
for display on the Internet and broadcast television.
The event will also be studied from ground-based observatories.
It might
produce a sudden brightening of the comet visible to amateur
astronomers
with small telescopes.
The 3-mile-wide comet will not be destroyed or knocked from its
orbit,
McFadden said.
"It's like if you throw a pebble at a moving car," she
said. "You're not
going to knock the car off course, unless you frighten the
driver."
Even so, the mission had to pass scrutiny from the National
Aeronautics and
Space Administration for violations of the space agency's
"planetary
protection" rules. The conclusion, McFadden said, was that
the impact would
destroy nothing unique.
"There are millions of comets," she said.
The $279 million mission, called Deep Impact, is one of two space
science
missions selected in 1998 for final design review under NASA's
Discovery
series of "better, faster, cheaper" space science
missons.
Still awaiting NASA's final approval is Messenger, a Discovery
mission to
map and photograph the surface of the planet Mercury. The
spacecraft would
be built and managed by the Johns Hopkins University Applied
Physics Lab in
Laurel.
"What fascinated me personally about [Deep Impact] is, as
the design went
through, it became clear how little we truly know about comet
interiors,"
said Tom Morgan, program scientist for Deep Impact at NASA
headquarters. He
was a member of the group that reviewed the proposal and last
week cleared
the team to start building the spacecraft.
Comets, he said, "are important constituents of the outer
solar system and
keys to understanding the origins of all solar systems."
Comets are composed of dust and frozen gases that scientists
believe are
little changed since the formation of the solar system 4.5
billion years
ago.
The precise composition, and relative proportions of that dust
and gas, hold
clues to the materials and physical conditions present in the
frigid outer
regions of the solar system where comets formed.
But astronomers aren't certain that what they see in their
telescopes -- the
relatively large halo, or "coma" of gas and dust that
has escaped from the
comet's tiny nucleus -- is "pristine."
Some suspect that the material in the coma comes from surface
ices that have
been changed chemically and physically from their primordial
composition by
repeated passages around the sun.
If they want to draw reliable conclusions about the composition
of the early
solar system, they need a look beneath the surface, at the
interior.
"Our idea was to disturb the top surface and expose the
pristine material,"
said Alan Delamere, an engineer at Ball Aerospace, the Colorado
contractor
where Deep Impact will be built.
He and Michael Belton, of the National Optical Observatory in
Tucson,
originated the idea of a comet impact mission.
Images of Halley's comet taken in 1987 showed its surface to be
quite black,
suggesting it was covered by dust instead of its primordial ices,
Delamere
said.
"Ever since that point, I was really disturbed about what
the surface
properties were of the comet, and how little we really knew about
the
mechanism that made it as black as it is."
Deep Impact also could shed light on how fragile comets are.
Although
several recent comets have been seen to break apart, little is
known about
the forces needed to trigger the breakups.
Comet Tempel 1 was discovered in 1867, and it orbits the sun once
every 5.5
years. It was chosen because it has had plenty of time for its
surface
materials to have been changed by the sun.
After its launch, Deep Impact will orbit the sun for a year, then
cruise out
to Tempel 1's orbit for its rendezvous. On July 3, 2005 -- the
day before
impact -- it will release its copper cannonball.
That object will navigate on its own to the comet's surface. It
carries no
explosives, but its mass and speed relative to the comet --
22,300 mph --
will deliver energy equivalent to 4.5 tons of TNT.
Pictures and spectroscopic data on the blast will be gathered by
instruments
on board the main spacecraft, which will fly past the comet at a
safe
distance of more than 300 miles.
"We don't want to get any closer," McFadden said. Small
dust particles could
fog Deep Impact's camera lenses. Bigger debris could destroy the
spacecraft.
Copyright © 2001, The Baltimore Sun
=============
(7) ANCIENT CLIMATE RECORDS MAY BE FATALLY FLAWED
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Office of News and Information
University of Washington
Seattle, Washington
FROM:
Sandra Hines, 206-543-2580, shines@u.washington.edu
Vince Stricherz, 206-543-2580, vinces@u.washington.edu
FOR IMMEDIATE RELEASE: May 30, 2001
Migrating impurities in ancient ice can skew climate research
findings
Chemicals trapped in ancient glacial or polar ice can move
substantial
distances within the ice, according to new evidence from
University of
Washington researchers. That means past analyses of historic
climate
changes, gleaned from ice core samples, might not be entirely
accurate.
"The ice cores themselves are wonderful records of climate.
Nobody is
questioning that," said Alan Rempel, a post-doctoral
research scientist in
the UW Applied Physics Laboratory.
In fact, the research shows that the fingerprint of chemical
variations
within ice cores is much sharper than had previously been
expected. But it
also shows that substances that are climate signatures -- from
sea salt to
sulfuric acid -- travel through the frozen mass along microscopic
channels
of liquid water between individual ice crystals, away from the
ice on which
they were deposited. The movement becomes more pronounced over
time, as the
flow of ice carries the substances deeper within the ice sheet,
where it is
warmer and there is more liquid water between ice crystals. By
contrast,
oxygen isotopes that can indicate past temperatures are carried
mostly
within the ice.
The possible movement of chemical signatures away from the ice on
which they
were deposited means scientists must re-examine questions such as
whether
warm summers coincided with high levels of sea salt in the air,
Rempel said.
But that is only true for ancient ice, since little movement is
shown in ice
less than 100,000 years old.
The findings by Rempel; John Wettlaufer, a senior physicist at
APL; Edwin
Waddington, a UW professor of Earth and space sciences; and APL
visiting
scientist Grae Worster from the University of Cambridge in
England are
published in the May 31 issue of the journal Nature.
Ice sheets (large polar glaciers) are built by thousands of years
of
accumulated snowfall, to depths of thousands of meters. Each
season's
snowfall forms a distinctive layer that can be analyzed
chemically after
being extracted in a core sample.
Certain impurities serve as markers that can tell scientists what
was going
on climatically at various times. Those substances are found
principally in
unfrozen liquid that accumulates at the boundaries of individual
crystals
within the ice sheets.
The new research shows those substances migrate deeper into the
ice sheet,
where it is warmer, faster than the ice on which they were
deposited, said
Wettlaufer, an ice physics expert. The displacement is larger at
greater
depths. The result is that substances found 3 kilometers (1.9
miles) deep
could be 50 centimeters (20 inches) or more away from the ice on
which they
were deposited many thousands of years ago, a distance that
accounts for
about 100 years of snowfall.
"The point of the paper is to suggest that the ice core
community go back
and redo the chemistry," said Wettlaufer. "That's a lot
of work, and we're
hoping to be involved in that."
The Nature article notes that the best high-resolution climate
records over
the past few hundred thousand years have come from ice cores
taken from
Greenland and Antarctica. A core from interglacial ice in central
Greenland
suggests that a sudden cooling took place in the Eemian period
115,000 to
125,000 years ago. However, the new study shows that impurities
used as
climate markers may have moved as much as 20 inches, a distance
large enough
to offset the resolution at which the core was examined and alter
the
interpretation of the ice-core record.
The Vostok core from Antarctica, which goes back some 450,000
years,
contains even greater displacement because of the greater depth,
but it has
not been examined at even the close spatial resolutions of the
Greenland
core, Wettlaufer said.
Rempel said the researchers hope to devise models that can help
scientists
account for the relative movement of different impurities when
making their
ice core measurements.
But in the meantime, said Wettlaufer, scientists doing that
climate work
have to take into account how much their measurements might be
skewed, and
adjust their findings accordingly.
"That would be what we most would want to influence -- the
way people make
their observations," he said. "Since they are doing all
that work, they
can't afford to neglect these important physical processes in
their
interpretation."
###
For more information, contact:
Rempel at (206) 543-1274 or awrempel@apl.washington.edu
Wettlaufer at (206) 543-1300, (206) 543-7224 or wett@apl.washington.edu
Waddington at (206) 543-4585, (206) 543-8020 or edw@geophys.washington.edu
Worster at (206) 685-8334 or gworster@apl.washington.edu
IMAGE CAPTION:
[http://www.washington.edu/newsroom/news/2001archive/05-01archive/k053001.ht
ml] Four microscopic liquid channels, each about 100 microns
across (roughly
1/250th of an inch), come together at the corner where four ice
grains meet.
Because impurities are concentrated in the channels, they stay
liquid even
though the temperature is below freezing -- for the same reason
that ice
melts on the sidewalk when you throw salt on it. (Note 200 micron
scale in
bottom left corner.) Photo credit: Heidi Mader, University of
Bristol
============
(8) TROPICAL CLACIERS FORMED WHILE EARTH WAS GIANT SNOWBALL
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Pennsylvania State University
University Park, Pennsylvania
Contacts:
A'ndrea Elyse Messer, (814) 865-9481, aem1@psu.edu
Vicki Fong, (814) 865-9481, vfong@psu.edu
May 29, 2001
Tropical Glaciers Formed While Earth Was Giant Snowball
Boston, Mass. -- Glacial deposits that formed on tropical land
areas during
snowball Earth episodes around 600 million years ago, lead to
questions
about how the glaciers that left the deposits were created.
Now, Penn State
geoscientists believe that these glaciers could only have formed
after the
Earth's oceans were entirely covered by thick sea ice.
"There is strong geologic evidence of tropical glaciation at
sea level
during those times," Dr. David Pollard, research associate,
Penn State
College of Earth and Mineral Sciences' Environmental Institute,
told
attendees at the spring meeting of the American Geophysical Union
today (May
29) in Boston. "We wanted to determine how low-level
tropical glaciers could
have formed."
Ice can accumulate in the tropics only if temperatures are below
freezing or
around freezing with large amounts of snowfall. Tropical glaciers
exist
today only on high mountain peaks such as the Andes and Mt.
Kilimanjaro, and
do not reach anywhere near sea level.
Pollard and James K. Kasting, professor of geosciences, first
looked at the
possibility that tropical ice sheets formed before the oceans
completely
froze into a snowball Earth, when equatorial oceans were still
ice-free and
could supply enough moisture for substantial snowfall.
During the lead-up to a snowball Earth episode, the Earth
gradually cools
because the amount of carbon dioxide in the Earth's atmosphere
decreases.
Relatively fast weathering of silicate rocks on large tropical
landmasses
causes this decrease that locks up carbon. As the earth
cools, the oceans
begin freezing. The high reflectivity of the snow and ice
that covers the
northern and southern oceans, reflects, rather than absorbs, the
sun's heat
and further cools the planet. This cooling takes place
slowly until the
oceans are frozen to about 30 degrees latitude, or from the North
Pole down
to New Orleans, La. and from the South Pole up to the tip of
South Africa.
"This is the coldest that the Earth can get before all the
entire ocean
surface freezes," says Pollard. "Beyond this,
there is no stable point at
say 20 or 10-degrees latitude: instead, the ice-reflectivity
feedback
becomes unstable and the system collapses rapidly to a snowball
Earth with
all oceans ice covered."
The researchers adjusted a global climate model, GENESIS, to the
coldest
point just before the collapse and used climate outputs of
temperature and
precipitation to drive a dynamic ice-sheet model. They used
paleomagnetic
reconstructions of land mass distributions for 750 and 540
million years
ago, but, because the locations of major mountain chains are
unknown that
long ago, they put mountains analogous to the Andes, all around
the edges of
tropical land masses in their ice-sheet model.
"Ice sheets did form on the tops of these mountains,"
says Pollard.
"However, the ice sheets never flowed down to sea level,
where we find
glacial deposits. Tropical temperatures were still too warm and
melted the
ice before it could flow down from the mountains."
The researchers conclude that it is unlikely that tropical sea
level glacial
deposits formed before the collapse into snowball Earth. However,
having
them form after the oceans freeze also seemed problematic because
once the
oceans are frozen, the rates of precipitation decrease
drastically, to only
a few millimeters per year.
"However, in further simulations with the global climate
model for full
snowball conditions, snowfall did exceed evaporation of snow and
ice in some
land areas, allowing a slow build up of tropical ice sheets that
would
eventually flow to the sea," says Pollard. "It
would have taken several
thousand years to form big ice sheets this way, but since it
takes several
million years to reverse snowball Earth, there would have been
plenty of
time for the ice to form."
Also, snowfall rates would have been gradually increasing during
that time
as carbon dioxide built up. Researchers have estimated that it
required a
buildup of carbon dioxide by volcanic outgassing to 300 times
today's levels
to bring Earth out of snowball Earth, which accounts for the
millions of
years necessary to reverse the process.
Some scientists question whether life could have survived a full
snowball-Earth episode, and therefore suggest that the Earth
never passed
beyond the critical point with sea ice down to about 30 degrees
latitude.
However, the Penn State results imply that full snowball Earth
must have
occurred in order to produce the observed tropical glacial
deposits at sea
level. Others have suggested that oceanic life could have
survived full
snowball episodes below gaps in the ice around volcanic island,
or in
tropical oceans where sunlight may have limited sea ice thickness
to only a
few meters.
**aem**
EDITORS: Dr. Pollard is at (814) 865-2022 or at pollard@essc.psu.edu. Dr.
Kasting may be reached at (814) 865-3207 or at kasting@essc.psu.edu by
email.
============================
* LETTERS TO THE MODERATOR *
============================
(9) TNO (20000) VARUNA
From Javier Andres Licandro Goldaracena <jlicandr@ll.iac.es>
Dear Benny
Regarding to the diameter and albedo determination of TNO (20000)
Varuna,
also known as 2000 WR106, by Jewitt et al., let me comment that
we have
recently obtained near-infrared (0.9 - 2.4
mic) spectra of this TNO and of 2000 EB173, using the Near
Infrared Camera
Spectrograph attached to the 3.56m Telescopio Nazionale Galileo.
The paper
has been accepted for publication in Astronomy and Astrophysics
Letter, and
is also avaliable in the astro-ph/0105434. One of the most
remarcable
results is that we detected water ice in the surface of (20000)
Varuna.
-------------------
NICS-TNG infrared spectroscopy of trans-neptunian objects 2000
EB173 and
2000 WR106.
Licandro, J. (1), Oliva, E. (1,2), and
Di Martino, M. (3)
(1) Centro Galileo Galilei & Telescopio Nazionale Galileo
(2) Osservatorio di Arcetri
(3) Osservatorio Astronomico di Torino
Abstract
We report complete near-infrared (0.9-2.4 $\mu$m) spectral
observations of
trans-neptunian objects (TNOs) 2000 EB173 and 2000 WR106
collected using the
new Near Infrared Camera Spectrometer (NICS) attached to the
3.56m
Telescopio Nazionale Galileo (TNG). Both spectra are very red and
with a
quite strong and broad drop extending throughout the K band.
However, while
2000 EB173 does not show any evidence of narrow absorption
features, the
spectrum of 2000 WR106 has quite deep water ice absorption at 1.5
and 2.0
$\mu$m. Moreover, the latter object is significantly less red
than the
former indicating, therefore, that the surface of 2000 WR106 is
"cleaner"
(i.e. less processed by particle irradiation) than that of 2000
EB173.
Javier Licandro
=================
(10) THE ORIGIN OF BOMB-DETECTION SYSTEMS & UFO MYTHOLOGY
From Rolf Sinclair <rolf@santafe.edu>
RE: LISTENING FOR NUKES: A METEOR DETECTION PROJECT
Space.com, 24 May 2001
MILITARY WARNING SYSTEM ALSO TRACKS BOMB-SIZE
METEORS
The New York Times, 29 May 2001
Hi Benny -
You may be interested to know that the first version of this
acoustic
bomb-detection array was a secret project that flew a series of
balloons
carrying microphones to "listen" for possible nuclear
weapon tests. On July
3, 1947, one of these balloons crashed near Roswell, New Mexico,
and the
attempts to keep the project secret while recovering the pieces
turned
Roswell into the center of the Flying Saucer mythology. [See US
Air Force
"Roswell Report: Fact vs. Fiction in the New Mexico
Desert", or a shorter
version in Bob Park's "Voodoo Science".]
Rolf
===========
(11) IMPACT SEQUENCE IN THE GEOLOGICAL RECORD
From Duncan A. Lunan <astra@dlunan.freeserve.co.uk>
RE: IMPACT SEQUENCE IN THE GEOLOGICAL RECORD
From Hermann Burchard <burchar@mail.math.okstate.edu>
Dear Benny,
In New Scientist, vol. 73 p.320, there was an article titled 'The
World Is a
Bit Cracked' - a news item as I remember. I don't have a note of
the date
but it would have been in the 1970's or very early 80's. It
stated that in
orbital survey photographs a system of parallel crustal fractures
running
north-south had been located in both western Africa and eastern
South
America. The implication was that the Earth's rotation rate had
been altered
before the continents separated, either by the flyby of a massive
object or
more probably by an impact. However it put the age of
the fractures c. 600
million years b.p., so I don't know if it's relevant here.
Best wishes,
Duncan Lunan
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COSMIC IMPACTS AND TSUNAMI: THE UNDERRATED HAZARD
By By Edward A. Byrant, School of Geosciences, University of
Wollongong,
Australia
http://abob.libs.uga.edu/bobk/ccc/ce053101.html
The following text is an extract from Edward A. Bryant's new book
TSUNAMI:
THE UNDERRATED HAZARD, to be published by Cambridge University
Press
(publication c. July 2001).
0 521 77244 3 Hardback £55.00/$74.95
0 521 77599 4 Paperback £19.95/$27.95
For more details and how to order, please visit the CUP website
at
http://uk.cambridge.org/earthsciences/catalogue/052177599X/
Description
In the past decade over ten major tsunami events have impacted on
the
world's coastlines, causing devastation and loss of life.
Evidence for past
great tsunami, or 'mega-tsunami', has also recently been
discovered along
apparently aseismic and protected coastlines. With a large
proportion of the
world's population living on the coastline, the threat from
tsunami can not
be ignored. This book comprehensively describes the nature and
process of
tsunami, outlines field evidence for detecting the presence of
past events,
and describes particular events linked to earthquakes, volcanoes,
submarine
landslides and meteorite impacts. While technical aspects are
covered, much
of the text can be read by anyone with a high school education.
The book
will appeal to students and researchers in geomorphology, earth
and
environmental science, and emergency planning, and will also be
attractive
for the general public interested in natural hazards and new
developments in
science.
Chapter Contents plus excerpt see:
http://abob.libs.uga.edu/bobk/ccc/ce053101.html