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(meteorobs) Excerpts from "CCNet, 25 May 2000"


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From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: CCNet, 25 May 2000
Date: Thu, 25 May 2000 13:45:45 -0400 (EDT)

CCNet, 62/2000 - 25 May 2000
----------------------------

[...]

(4) IDENTIFICATION OF MOLECULAR-CLOUD MATERIAL IN=20
    INTERPLANETARY DUST
    S. Messenger, WASHINGTON UNIVERSITY

(5) ON THE TRANSPORT OF BODIES WITHIN AND FROM THE ASTEROID BELT
    F. Franklin & M. Lecar, HARVARD SMITHSONIAN CTR ASTROPHYS

[...]

========================================================================

(4) IDENTIFICATION OF MOLECULAR-CLOUD MATERIAL IN=20
     INTERPLANETARY DUST

S. Messenger: Identification of molecular-cloud material in=20
interplanetary dust particles. NATURE, 2000, Vol.404, No.6781,=20
pp.968-971

*) WASHINGTON UNIVERSITY,DEPT PHYS,MCDONNELL CTR SPACE SCI,ST=20
   LOUIS,MO,63130

Interplanetary dust particles (IDPs) collected in the Earth's=20
stratosphere and meteorites are fragments of comets and asteroids.=20
These are 'primitive' meteorites in part because they have preserved=20
materials which predate the formation of the Solar System. The most=20
primitive (least altered) meteorites contain a few parts per million of =

micrometre-sized dust which formed in the atmospheres of giant=20
stars(1). Some meteorites(2) have elevated D/H and N-15/N-14 ratios=20
that are attributed to surviving interstellar organic molecules which=20
have probably been strongly diluted and altered by parent-body=20
processes(2). Most IDPs are chemically, mineralogically, and texturally =

primitive in comparison to meteorites(3,4). Here I show that H and N=20
isotopic anomalies among fragile 'cluster' IDPs are far larger, more=20
common, and less equilibrated than those previously observed in other=20
IDPs or meteorites. In some cases, the D/H ratios that we measure reach =

the values of interstellar molecules, suggesting that molecular-cloud=20
material has survived intact. These observations indicate that cluster=20
IDPs are the most primitive class of Solar System materials currently=20
available for laboratory analysis. Copyright 2000, Institute for=20
Scientific Information Inc.

========================================================================

(5) ON THE TRANSPORT OF BODIES WITHIN AND FROM THE ASTEROID BELT

F. Franklin*) & M. Lecar: On the transport of bodies within and from=20
the asteroid belt. METEORITICS & PLANETARY SCIENCE, 2000, Vol.35, No.2, =

pp.331-340

*) HARVARD SMITHSONIAN CTR ASTROPHYS,60 GARDEN ST,CAMBRIDGE,MA,02138

This paper explores two processes, sweeping secular resonance (Ward,=20
1981) and gas drag (Lecar and Franklin, 1997), at work during the=20
dispersal of the solar nebula. We have two aims not previously=20
considered for the two mechanisms: (1) to explain the likely depletion, =
by a factor of 1000 or so, of the rocky material in the inner belt (2.0 =
< a < 3.2 AU); (2) to introduce a means for providing-or contributing=20
to-the dispersion in semimajor axis of the various asteroidal taxonomic =
classes. We suggest that large asteroids with birthplaces separated by=20
an astronomical unit or more can be finally deposited, owing to drag,=20
at the same semimajor axis. For example, we find that bodies with radii =
up to 100 km can be transferred by gas drag from the outer belt (a >=20
3.3 AU) well into the inner one, and that an object already in the=20
inner belt as large or even larger than Vesta (r =3D 250 km)-thought to =
be the parent body of many meteorites-can be inwardly displaced by as=20
much as an astronomical unit if the nebula dispersal times lie close to =
10(5) years. For such times, a large fraction of the inner belt's=20
primordial mass can be ejected, with most of it passing into the inner=20
solar system. Copyright 2000, Institute for Scientific Information Inc.

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