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(meteorobs) Excerpts from "CCNet DIGEST, 10 June 1999"
------- Forwarded Message
From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: CCNet DIGEST, 10 June 1999
Date: Thu, 10 Jun 1999 11:32:56 -0400 (EDT)
CCNet DIGEST, 10 June 1999
--------------------------
[...]
(4) ASTEROID, COMET AND METEOR CONFERENCE SET FOR JULY
UniSci, 8 June 1999
(5) ROTATION & LIGHTCURVE OF ASTEROID 4179 TOUTATIS
A. Kryszczynska et al., ADAM MICKIEWICZ UNIVERSITY POZNAN
[...]
(8) 1620 GEOGRAPHOS & 433 EROS: SHAPED BY PLANETARY TIDES?
W.F. Bottke et al., CORNELL UNIVERSITY
(9) COMPOSITIONAL SURFACE VARIETY AMONG THE CENTAURS
M.A. Barucci et al., PARIS OBSERVATORY
(10) DYNAMICAL EVOLUTION OF ATENS & APOLLO ASTEROIDS
R. Dvorak and E. Pilat Lohinger, UNIVERSITY OF VIENNA
(11) DIAMETER DISTRIBUTION OF EARTH-CROSSING ASTEROIDS
A. Poveda et al., UNIV NACL AUTONOMA MEXICO
(12) ORGANIC MATERIAL FROM SPACE
Michael Paine <mpaine@tpgi.com.au>=20
[...]
------------------------------------------
(4) ASTEROID, COMET AND METEOR CONFERENCE SET FOR JULY
>From UniSci, 8 June 1999
http://unisci.com/stories/19992/0608995.htm
The seventh International Conference on Asteroids, Comets and Meteors=20
(ACM) will be held at Cornell University July 26-30. The conference is=20
sponsored by NASA, the Applied Physics Laboratory of Johns Hopkins=20
University, the Jet Propulsion Laboratory (JPL) and Cornell.
A broad range of scientific sessions will present the latest=20
developments in all aspects of studies on asteroids, comets and=20
meteors, including observations, theories of origin and evolution,=20
discoveries and astrometry.
Scientific sessions
The 450 abstracts submitted have been organized into 28 different=20
sessions, for approximately 18 hours of plenary talks and 18 hours of=20
parallel sessions. In the past, the organization of the ACM scientific=20
program has tended to split sessions along the asteroid, comet, meteor=20
subcategories, resulting in a conference of three parallel topics with=20
few opportunities for cross-disciplinary discussion.=20
This year, an effort was made to organize the plenary sessions to be=20
cross-disciplinary. Session titles will be broad, including such=20
subjects as "Composition," "Spins and Sizes," "Collisional Processes"=20
and "Transitional Objects."
Sessions will include speakers from each of the asteroid, comet, and=20
meteor categories. In addition, poster sessions will draw participation =
from all categories of ACM subjects.
The ACM '99 conference's invited speakers are at the forefront of their =
fields and will be reporting on recent research in their areas of=20
expertise. They were chosen because the recent advances in these areas=20
are particularly exciting and newsworthy.
Invited speakers and their topics will include:
* Steven J. Ostro, JPL: Dramatic new asteroid results from the Arecibo=20
Observatory.
* M.A. Barucci, Observatoire de Paris: Observations of objects at the=20
edge of the solar system.
* Donald Brownlee, University of Washington: Stardust space mission.
* S.J. Bus, Massachusetts Institute of Technology: Findings on=20
structure of asteroid families.
* W.J. Merline, Southwest Research Institute: Discovery of a satellite=20
of asteroid Eugenia.
* Eberhard Gruen, Max Planck Institute: Confirmation of galactic dust=20
near Earth.
(Editor's Note: For a complete list of abstracts, visit the ACM=20
website.)
History of the ACM
The first ACM conference was held in 1983 in Uppsala, Sweden. Follow-up =
meetings were held in Uppsala in 1985 and 1989; in Flagstaff, Ariz., in =
1991; in Belgirate, Italy, in 1993; and in Versailles, France, in 1996. =
The number of participants has grown steadily, from 76 in 1983 to about =
500 in 1996. Attendees are drawn from all over Europe, from Australia,=20
New Zealand, North and South America, India, Central Asia and Japan.
The spirit of the ACM conference has been to welcome scientists and=20
enthusiasts of asteroid, comet and meteor studies of all ages and from=20
all nations to a gathering where ideas can be openly shared and=20
discussed. ACM '99 at Cornell will continue this tradition.=20
------------------------------------------
(5) ROTATION & LIGHTCURVE OF ASTEROID 4179 TOUTATIS
A. Kryszczynska*), T. Kwiatkowski, S. Breiter, T. Michalowski: Relation =
between rotation and lightcurve of 4179 Toutatis. ASTRONOMY AND=20
ASTROPHYSICS, 1999, Vol.345, No.2, pp.643-645
*) ADAM MICKIEWICZ UNIVERSITY POZNAN,ASTRON OBSERV,SLONECZNA=20
36,PL-60286 POZNAN,POLAND
This paper presents results of modelling light variations of a freely=20
precessing asteroid, assuming its ellipsoidal shape and a geometric=20
light scattering law. The method is based on numerical integration of=20
Euler equations, combined with the explicit expression of an asteroid's =
brightness as a function of Euler angles. Modelling is applied to=20
simulate the lightcurve of 4179 Toutatis according to its triaxial=20
ellipsoid shape and spin state given by Hudson & Ostro (1995). A good=20
agreement is obtained between the frequencies of the simulated and=20
observed lightcurves, The results explain some apparent discrepancies=20
between the periods obtained from photometric and radar observations.
Copyright 1999, Institute for Scientific Information Inc.
------------------------------------------
(8) 1620 GEOGRAPHOS & 433 EROS: SHAPED BY PLANETARY TIDES?
W.F. Bottke*), D.C. Richardson, P. Michel, S.G. Love: 1620 Geographos=20
and 433 Eros: Shaped by planetary tides? ASTRONOMICAL JOURNAL, 1999,=20
Vol.117, No.4, pp.1921-1928
*) CORNELL UNIVERSITY,CTR RADIOPHYS & SPACE RES,ITHACA,NY,14853
Until recently, most asteroids were thought to be solid bodies whose=20
shapes were determined largely by collisions with other asteroids.=20
Recent work by Burns and others has shown that many asteroids may be=20
little more than rubble piles, held together by self-gravity; this=20
means that their shapes may be strongly distorted by tides during close =
encounters with planets. Here we report on numerical simulations of=20
encounters between an ellipsoid-shaped rubble-pile asteroid and Earth.=20
After an encounter, many of the simulated asteroids develop the same=20
rotation rate and distinctive shape as 1620 Geographos (i.e., highly=20
elongated with a single convex side, tapered ends, and small=20
protuberances swept back against the rotation direction). Since our=20
numerical studies show that these events occur with some frequency, we=20
suggest that Geographos may be a tidally distorted object. In addition, =
our work shows that 433 Eros, which will be visited by the NEAR=20
spacecraft in 1999, is much like Geographos, suggesting that it too may =
have been molded by tides in the past. Copyright 1999, Institute for=20
Scientific Information Inc.
------------------------------------------
(9) COMPOSITIONAL SURFACE VARIETY AMONG THE CENTAURS
M.A. Barucci*), M. Lazzarin, G.P. Tozzi: Compositional surface variety=20
among the Centaurs. ASTRONOMICAL JOURNAL, 1999, Vol.117, No.4,=20
pp.1929-1932
*) PARIS OBSERVATORY,PL JULES HUSSIEU 5,F-92195 MEUDON,FRANCE
The Centaurs are a particular family of objects with orbits whose=20
semimajor axes fall between those of Jupiter and Neptune. They are=20
likely the transition objects between the Kuiper belt population and=20
short-period comets. To investigate the nature of these particular=20
objects, we have performed optical spectroscopic observations of five=20
Centaurs. The results show a great diversity among the reflectances of=20
the five Centaurs. The colors do not seem to be related to the=20
perihelion distance of the objects. We looked for weak cometary=20
emission features, in particular the CN-band emission at 3880 Angstrom, =
but no CN emission feature has been detected within 3 sigma in any of=20
the investigated spectra. Copyright 1999, Institute for Scientific=20
Information Inc.
------------------------------------------
(10) DYNAMICAL EVOLUTION OF ATENS & APOLLO ASTEROIDS
R. Dvorak and E. Pilat Lohinger: On the dynamical evolution of the=20
Atens and the Apollos. PLANETARY AND SPACE SCIENCE, 1999, Vol.47, No.5, =
pp.665-677
UNIVERSITY OF VIENNA,INST ASTRON,TURKENSCHANZSTR 17,A-1180=20
VIENNA,AUSTRIA
In this investigation we compare the dynamical evolution of the two=20
groups of Earth crossing asteroids namely the Atens which move-grosso=20
mode-inside the orbit of the Earth and the Apollos which move outside=20
the Earth's orbit. The main goal of this study was to compute the=20
encounters of these asteroids with the Earth, respectively the=20
collision probabilities. We also briefly analyzed their qualitative
behavior over one million years and computed the mixing of the two=20
groups. The approach to achieve these results was a purely numerical=20
one: we used extensive numerical integrations in the framework of a=20
dynamical model of the planetary system (consisting of the Sun and the=20
planets Venus through Saturn). Other interesting features of the=20
dynamics of Apollos and Atens are confirmed in our study-e.g. the=20
temporary capture into the 1:1 mean motion resonance with the Earth.=20
Close encounters with the inner planets (primarily with the Earth and=20
with Venus) are the major events which change the orbit of such an=20
asteroid, but the Kozai resonances and the secular resonances have to=20
be taken into account to understand the dynamical evolution over longer =
time intervals. The results of collision probabilities with the Earth=20
are in good agreement with statistically derived results by other=20
authors: approximately 20 (50 for smaller objects) collisions for each=20
Aten and 10 collisions for each Apollo per 1 billion years. (C) 1999=20
Elsevier Science Ltd. All rights=20
reserved.
------------------------------------------
(11) DIAMETER DISTRIBUTION OF EARTH-CROSSING ASTEROIDS
A. Poveda*), M.A. Herrera, J.L. Garcia, K. Curioca: The diameter=20
distribution of Earth-crossing asteroids. PLANETARY AND SPACE SCIENCE,=20
1999, Vol.47, No.5, pp.679-685
*) UNIV NACL AUTONOMA MEXICO,INST ASTRON,CIUDAD UNIV,MEXICO CITY=20
04510,DF,MEXICO
A cumulative distribution function N(d) of diameters of ECAs is derived =
by fitting an exponential function to the observed distribution of=20
absolute magnitudes for the brightest objects (H less than or equal to=20
15.5), where there is evidence of completeness. This luminosity=20
function can be transformed (with appropriate albedos and densities) to =
the frequency distribution of diameters, masses and energies. The=20
distribution of masses thus found is consistent with the self-similar=20
theoretical distribution of masses subject to a steady-state regime of=20
collisions found by Dohnanyi, and by Williams and Wetherill. The=20
frequency of collisions with the earth of asteroids of a given diameter =
or energy is calculated. (C) 1999 Elsevier Science Ltd. All rights=20
reserved.
------------------------------------------
(12) ORGANIC MATERIAL FROM SPACE
>From Michael Paine <mpaine@tpgi.com.au>=20
Dear Benny,
The July issue of Scientific American has a feature article about=20
comets delivering (non-biological) organic material to the surface of=20
planets. See http://www.sciam.com/1999/0799issue/0799bernstein.html
This topic is also covered in a recent posting at the PSRD site:
"Martian Organic Matter in ALH84001?" See=20
http://www.soest.hawaiidot edu/PSRdiscoveries/June99/organicsBecker.html
=20
As Victor Noto's website proclaims "... the Big Rock giveth and taketh
away" :)
=20
Michael Paine
----------------------------------------
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