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(meteorobs) Exccerpts from "CCNet 98/2000 - 29 September 2000"
------- Forwarded Message
From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet, 29 September 2000
Date: Fri, 29 Sep 2000 11:57:20 +0100
CCNet 98/2000 - 29 September 2000
---------------------------------
[...]
(3) ROYAL ASTRONOMICAL SOCIETY MEETING ON ASTEROIDS AND METEORITES
Duncan Steel <D.I.Steel@salford.acdot uk>
[...]
(6) TEMPORAL VARIATION OF THE ZODIACAL DUST CLOUD:
BILL NAPIER ON COMETARY DUST LOADING & CLIMATE CHANGE
[...]
(9) PHYSICAL PROPERTIES OF THE NUCLEUS OF COMET 2P/ENCKE
Y.R. Fernandez et al., ICARUS 147: (1) 145-160 SEP 2000
[...]
========================================================================
(3) ROYAL ASTRONOMICAL SOCIETY MEETING ON ASTEROIDS AND METEORITES
>From Duncan Steel <D.I.Steel@salford.acdot uk>
"Asteroids and Meteorites", London, Friday 13th October
Organisers: Dr Sarah Dunkin (UCL/RAL) skd@star.ucl.acdot uk, Dr Manuel Grande
(RAL) m.grande@rl.acdot uk and Dr Sara Russell (NHM) sarr@nhm.acdot uk
Summary: The vast majority of meteorites are thought to be samples of
asteroids. Meteorites show variations in elemental and isotopic abundances
that are believed to reflect differences in the heliocentric distances of
their parent bodies. However, definite links between meteorite classes and
specific asteroids are rarely achieved. Asteroid research will benefit
greatly
from the NEAR-Shoemaker mission, which will spend one year in orbit around
Eros,
and is already returning much detailed information.
Programme
Morning Session Chair: Manuel Grande
10:30-10.35 Introduction (M. Grande)
10:35-10:55 Diversity of Meteorite Parent Bodies (M. Grady)
10:55-11:15 The Asteroid-Meteoroid Connection (D. Steel)
11:15-11:35 Early Asteroids (D. Hughes)
11:35-11:55 The chronology of asteroid formation and evolution (J.Whitby)
11:55-12:10 Bridging the chondrite-achondrite discontinuity (R. Ash)
12:10-12:30 Cosmochemical Instrumentation for an asteroid mission(I.Wright)
12:30-12:50 Impact Hazard Assessment (M. Bailey)
Lunch 12:50- 14:00
Afternoon Session Chair: Sara Russell
14:00-14:20 NEO observations (A. Fitzsimmons)
14:20-14:35 Co-orbital Asteroids (T Christou)
14:35-14:50 Asteroid geology: Carbonaceous chondrite parent bodies
(P.Bland)
14:50-15:30 Results from NEAR-Shoemaker (P. Clarke)
General Session: Orbital Dynamics of Asteroids(C. Murray)
The Government NEO report (H. Atkinson)
For further details see:
http://www.ras.orgdot uk/meetings/00-2001.htm
All 'G/BGA/MIST' Discussion Meetings are normally held in the Lecture
Theatre of the Geological Society (GS) at Burlington House.
This is a 'G' (Geophysics/Planetary Science)
========================================================================
(6) TEMPORAL VARIATION OF THE ZODIACAL DUST CLOUD:
BILL NAPIER ON COMETARY DUST LOADING & CLIMATE CHANGE
Bill Napier, Armagh Observatory, <wmn@star.arm.acdot uk>
Abstract:
A Markov chain model has been constructed to investigate fluctuations
in the mass of the zodiacal cloud. The cloud is specified by a
three-dimensional grid, each element of which contains the numbers of
dust particles as a function of semi-major axis, eccentricity and
mass. The evolutionary pathways of dust particles due to radiation
pressure are described by fixed transition probabilities connecting
the grid elements. Other elements are absorbing states representing
infall to the Sun or ejection to infinity: particles entering these
states are removed from the system. Particles are injected through the
breakup of comets entering short-period, high-eccentricity orbits at
random times, and are subject to the Poynting-Robertson effect and
removal through collisional disintegration and radiation pressure. The
main conclusions are that the cometary component of the zodiacal cloud
is highly variable, and that in the wake of giant comet entry into a
short-period, near-Earth orbit, the dust influx to the Earth's
atmosphere may acquire a climatically significant optical depth.
Accepted for publication in the Monthly Notices of the Royal Astronomical
Society
========================================================================
(9) PHYSICAL PROPERTIES OF THE NUCLEUS OF COMET 2P/ENCKE
Y.R. Fernandez, C.M. Lisse, H.U. Kaufl, S.B. Peschke, H.A. Weaver, M.F.
A'Hearn, P.P. Lamy, T.A. Livengood, T. Kostiuk: Physical properties of the
nucleus of Comet 2P/Encke
ICARUS 147: (1) 145-160 SEP 2000
We report a new study of the nucleus of Comet 2P/Encke, which the CONTOUR
spacecraft is scheduled to encounter in November 2003. During the comet's
close approach to Earth in July 1997, we measured the mid-infrared thermal
and optical scattered continua with data from the TIMMI instrument (imaging)
at the ESO 3.6-m telescope (wavelength lambda from 8 to 12 mu m), the
ISOPHOT instrument (photometry) aboard ISO (3.6 mu m less than or equal to
lambda less than or equal to 100 mu m), and the STIS instrument (imaging)
aboard HST (5500 Angstrom less than or equal to lambda less than or equal to
11000 Angstrom). The optical images show the nucleus with very little coma
contamination, and the ISO photometry allowed us to separate the comatic and
nuclear contributions to the ESO images. We used the Standard Thermal Model
for slow rotators to calculate an effective nuclear radius of 2.4 km +/- 0.3
km. The comet's mid-IR light curve implies a nuclear rotation period of 15.2
h +/- 0.3 h, although some subharmonics of this also satisfy the data. If we
assume that the nucleus is a triaxial ellipsoid in principal short axis
rotation with the axis direction in 1985 as derived by Sekanina (1988,
Astron. J. 95, 911), then by combining our data with light curves from the
1980s we find that the nucleus' angular momentum vector migrates, making a
would-be circle in less than 81 years, and that one axial ratio is at least
2.6. The nucleus' optical linear phase coefficient is 0.06 mag/degree,
making it one of the most phase-darkened objects known. The surface is also
rougher than that of most asteroids, The visual geometric albedo is 0.05 +/-
0.02, within the range found for other cometary nuclei. (C) 2000 Academic
Press.
Addresses:
Fernandez YR, Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
Univ Maryland, Dept Astron, College Pk, MD 20742 USA.
Univ Hawaii Manoa, Astron Inst, Honolulu, HI 96822 USA.
Space Telescope Sci Inst, Baltimore, MD 21218 USA.
European So Observ, D-85748 Garching, Germany.
European Space Agcy, Satellite Tracking Stn, E-28080 Madrid, Spain.
Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA.
CNRS, Astron Spatiale Lab, F-13376 Marseille 12, France.
NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA.
Copyright ) 2000 Institute for Scientific Information
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