PLEASE NOTE:
*
CCNet DIGEST, 1 March 1999
--------------------------
QUOTE OF THE DAY
"...As you know, in one way or
another, the United Nations is
seen as the right place to find answers
to all of these
questions. I was even asked whether the
United Nations had a
programme to locate asteroids which
might be on a trajectory to
crash into Earth. The answer is no. But
international cooperation
at the United Nations does extend into
outer space, on issues
such as space exploration, damage caused
by objects launched into
outer space and the peaceful uses of
outer space in general."
UN Secretary General Kofi Annan, 18 May
1998
(1) DEVIOUS REPORTING
Tom Gehrels <tgehrels@LPL.Arizona.EDU>
(2) CORRECTION OF NEO REPORT IN PHONIX NEW TIMES
Andy Nimmo <andy.nimmo@net.ntl.com>
(3) UN FUNDING & KOFI ANNAN'S COMMENTS ON SPACEGUARD
Michael Paine <mpaine@tpgi.com.au>
(4) MYSTERY OBJECT & ASTEROID 1991 VG
Gonzalo Tancredi <gonzalo@fisica.edu.uy>
(5) A CHIP FROM THE MOON?
Rob McNaught <RMN@AAOCBN3.AAO.GOV.AU>
(6) ASTEROID 4179 TOUTATIS: ZERO IMPACT PROBABILITY FOR THE NEXT
600
YEARS
S.J. Ostro et al., CALTECH, JET PROP LAB
(7) THE EVOLUTION OF LONG-PERIOD COMETS
P. Wiegert & S. Tremaine, YORK
UNIVERSITY,CANADA
(8) WORKSHOP ON ET MATERIAL FROM COLD & HOT DESERTS
Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
(9) ONCE IN A BLUE MOON
NASA Science News <expressnews@sslab.msfc.nasa.gov>
=============
(1) DEVIOUS REPORTING
From Tom Gehrels <tgehrels@LPL.Arizona.EDU>
The article in Phoenix New Times by Tony Ortega has a devious
distortion of an interview. Our LINEAR colleagues have been
reporting on their detectors for the U. S. Air Force for more
than a
decade, freely and in detail. I told Ortega this, and I told him
all
of the following. Whenever I heard a presentation by Grant Stokes
and
his colleagues at a conference, I made it a point to encourage
them
to prove their detectors by finding asteroids near the
Earth. They
are doing that now, and I think it is great. Their advance and
great
success have helped us to obtain better detectors for Spacewatch
too.
Tom Gehrels
===================
(2) CORRECTION OF NEO REPORT IN PHONIX NEW TIMES
From Andy Nimmo <andy.nimmo@net.ntl.com>
While I find everything from CCN fascinating, I must admit I
found
"THE RACE IN NEO DETECTION IS GEARING UP" even more so
than usual,
with the amazing info on LINEAR.
However, I trust Victor Noto has pointed out to the Phoenix New
Times, and will inform those who read the article on his website,
that Luis Alvarez was the Nobel Prize winning physicist and
Walter,
the geologist, his son, and not the other way round as stated in
the
article. Perhaps the fact that Luis' middle name was also
'Walter'
confused them.
Andy Nimmo
===================
(3) UN FUNDING & KOFI ANNAN'S COMMENTS ON SPACEGUARD
From Michael Paine <mpaine@tpgi.com.au>
I have been perusing the UN web site looking for opportunities to
get support for Spaceguard (an idea raised on CCNet). I came
across
the following when searching for "asteroid":
Press Release SG/SM/6564 18 May 1998 (Secretary General Kofi
Annan)
"...As you know, in one way or another, the United Nations
is seen
as the right place to find answers to all of these questions. I
was
even asked whether the United Nations had a programme to locate
asteroids which might be on a trajectory to crash into Earth. The
answer is no. But international cooperation at the United Nations
does extend into outer space, on issues such as space
exploration,
damage caused by objects launched into outer space and the
peaceful
uses of outer space in general."
Daily Press Briefing - 6 - 24 July 1998
"...The note contained a HYPOTHETICAL [my highlight]
illustration of
how time limits would work, the spokesman said. In that
illustration,
the General Assembly decided to establish a programme to detect
near-earth asteroids. The note provided a five-year scenario on
how
that would be dealt with. It was an interesting example
illustrating
how the Secretary-General's proposal would work."
Oh well!
Michael Paine mailto:mpaine@tpgi.com.au
======================
(4) MYSTERY OBJECT & ASTEROID 1991 VG
From Gonzalo Tancredi <gonzalo@fisica.edu.uy>
I would like to make attention to my article "An asteroid in
a earth
like orbit" where I study the dynamics of 1991 VG. The
hypothesis of
an origin in the Moon is considered as the most plausible one.
The article appears in: Cel. Mech. & Dyn. Astron. 69, 119-132
(1998)
A preprint can be downladed from
http://www.fisica.edu.uy/PAGES/gonzalo/listpub.html
Gonzalo Tancredi
Dpto.
Astronomia
Tel : (598-2) 525 86 24/25/26 int. 319
Facultad
Ciencias
Fax : (598 2) 525 05 80
Igua
4225
Email : gonzalo@fisica.edu.uy
11400 Montevideo - URUGUAY
http://www.fisica.edu.uy/PAGES/gonzalo.html
=============
(5) A CHIP FROM THE MOON?
From Rob McNaught <RMN@AAOCBN3.AAO.GOV.AU>
Another source of Earth-like orbits could be objects that grazed
the
Earth's atmosphere and barely escaped. The ablation period
would be
only a few minutes, much shorter than the likely rotation
periods, so
such a history should result in a body with one face covered in
fusion
crust. Perhaps such a process with Jupiter could produce
Trojans?
With regard to the possibility of formation of Jupiter Trojans in
a
similar process in Jupiter's atmosphere, it might be unlikely or
even
impossible to have the body remain intact in such an interaction.
Cheers, Rob
=============
(6) ASTEROID 4179 TOUTATIS: ZERO IMPACT PROBABILITY FOR THE NEXT
600
YEARS
S.J. Ostro*), R.S. Hudson, K.D. Rosema, J.D. Giorgini, R.F.
Jurgens, D.K. Yeomans, P.W. Chodas, R. Winkler, R. Rose, D.
Choate,
R.A. Cormier, D. Kelley, R. Littlefair, L.A.M. Benner, M.L.
Thomas,
M.A. Slade: Asteroid 4179 Toutatis: 1996 radar observations.
ICARUS,
1999, Vol.137, No.1, pp.122-139
*) CALTECH,JET PROP LAB,4800 OAK GROVE DR,PASADENA,CA,91109
We report initial results of daily delay/Doppler observations of
Toutatis with the Goldstone 8510-MHz (3.5-cm) radar during Nov.
25-Dec. 3, 1996. Using the physical model of Toutatis derived
from
1992 radar observations (Hudson and Ostro 1995, Science 270,
84-86) to
analyze the new data, we obtain refined estimates of the
asteroid's
orbit, spin state, and surface properties. The asteroid's
centimeter-to-decameter surface characteristics are strikingly
uniform. The disc-integrated circular polarization (SC/OC) ratio
mu(c)
averages 0.29 +/- 0.01 and is independent of rotational
orientation at
the several percent level. Dual-polarization images reveal a
slight
drop in mu(c) at echo leading edges, which we interpret as the
signature of a smooth surface component. The OC radar albedo
averages
0.24 +/- 0.03; it depends on rotational orientation, as expected
from
the asteroid's angular scattering behavior (limb-darkening
slightly
more than Lambertian). The OC albedo of a sphere with Toutatis'
radar
properties would be 0.21, or three times the lunar value. The
radar
properties and available nonradar constraints are consistent with
Toutatis' surface having a smooth component that is at least 1/3
covered by rocks at least as large as the wavelength. if this
S-class
asteroid is mineralogically similar to stony-iron meteorites,
then the
smooth surface component probably is regolith whose porosity
resembles
that of lunar soil. if the mineralogy is ordinary chondritic,
then the
smooth surface component is probably solid with not much more
than a
centimeter of overlying regolith. We report delay-Doppler
astrometry
referenced to the asteroid's center of mass (COM) for each day of
our
experiment. An orbit solution that incorporates those
measurements as
well as the radar astrometry reported by Ostro et al. (1995,
Science
270, 80-83) and 588 optical astrometric observations from 1988
through
March 1997 has weighted rms residuals of 0.98 arcs, 0.10 Hz (1.8
mm
s(-1) in radial velocity), and 0.49 mu s in time delay (73 m in
range). Integration of that orbit into the past and future shows
that
Toutatis' pattern of close approaches to Venus, Earth, and Mars
is
highly asymmetric about the current epoch. The probability of the
orbit intersecting Earth is zero for at least the next six
centuries.
Toutatis will make its closest planetary approach since at least
1353
and until at least 2562 on Sep. 29, 2004, when the closest
COM-to-COM
separation of Earth and Toutatis will be 1,549,834 +/- 10 km (4.0
lunar distances). We use refined spin-state parameters and the
1995
shape model to generate ''movies'' that predict the asteroid's
rotational motion during its 2004 close approach, in geocentric
and
inertial frames. (C) 1999 Academic Press.
============
(7) THE EVOLUTION OF LONG-PERIOD COMETS
P. Wiegert*) & S. Tremaine: The evolution of long-period
comets.
ICARUS, 1999, Vol.137, No.1, pp.84-121
*) YORK UNIVERSITY,DEPT PHYS & ASTRON,N YORK,ON M3J
1P3,CANADA
We study the evolution of long-period comets by numerical
integration
of their orbits, a more realistic dynamical approach than the
Monte
Carlo and analytic methods previously used to study this problem.
We
follow the comets from their origin in the Oort cloud until their
final escape or destruction, in a model solar system consisting
of the
Sun, the four giant planets and the Galactic tide, We also
examine the
effects of nongravitational forces as well as the gravitational
forces
from a hypothetical solar companion or circumsolar disk. We
confirm
the conclusion of Oort and other investigators that the observed
distribution of long-period comet orbits does not match the
expected
steady-state distribution unless there is fading or some similar
physical process that depletes the population of older comets. We
investigate several simple fading laws, Ne can match the observed
orbit distribution if the fraction of comets remaining observable
after m apparitions is proportional to m(-0.6+/-0.1) (close to
the
fading law originally proposed by Whipple 1962); or if
approximately
95% of comets live for only a few (similar to 6) returns and the
remainder last indefinitely, Our results also yield statistics
such as
the expected perihelion distribution, distribution of aphelion
directions, frequency of encounters with the giant planets and
the
rate of production of Halley-type comets. (C) 1999 Academic
Press.
=============
(8) WORKSHOP ON ET MATERIAL FROM COLD & HOT DESERTS
From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
Workshop on Extraterrestrial Materials from Cold and Hot Deserts
Pilanesberg, South Africa
July 6 - 8, 1999
http://www.mpch-mainz.mpg.de/~kosmo/workshop/circular.htm
Where, When, and What
The Workshop on Extraterrestrial Materials from Hot and Cold
Deserts
will take place in the Kwa-Maritane Resort in the Pilanesberg
Game
Reserve, about 130 km northwest of Johannesburg from July 6 to 8,
1999 prior to the Meteoritical Society Meeting in Johannesburg.
It is planned to leave Johannesburg by bus on July 6th (about
noon)
and return on July 8th in the evening. This schedule will allow
those attending to participate in the Vredefort excursion prior
to
the MetSoc `99 meeting.
This Workshop aims at bringing together persons working with
meteorites or micrometeorites found in the Arctic, the Antarctic,
and in hot deserts. Talks and posters (if the number of submitted
presentations is more than about 30) on the following topics are
welcome:
- new meteorite searches and their results
- unique or rare types of meteorites
- weathering effects of meteorites and implications
- differences between desert meteorites and modern falls
- cosmogenic nuclides and age distributions
- comparisons between micrometeorites and IDPs collected in the
stratosphere
- collections, handling, consortia
Call for Abstracts
Similar to previous Workshops on this topic we plan to publish
extended abstracts (up to 5 pages) in the form of a LPI Technical
Report. Please submit your abstract to Ludolf Schultz before May
15,
1999 as a hard copy and a Word file. After the meeting the
abstract
can be revised and the final version will then be due on Sept.
15,
1999.
FULL DETAILS at
http://www.mpch-mainz.mpg.de/~kosmo/workshop/circular.htm
==============
(9) ONCE IN A BLUE MOON
From NASA Science News <expressnews@sslab.msfc.nasa.gov>
NASA Space Science News for Feb. 26, 1999
Once in a Blue Moon: As February winds down with no full moon at
all, sky watchers are looking forward to two full moons in March
and
the second Blue Moon of 1999.
FULL STORY at
http://science.nasa.gov/newhome/headlines/ast26feb99_1.htm
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