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(meteorobs) Excerpts from "CCNet, 11/2000 - 26 January 2000"
[
QUERY on item #10 below: my understanding has always been specifically that
carbonaceous chondrites are NOT associated with cometary debris streams... I'd
understood that all of those recovered to date were found to be most likely
associated with class C asteroids - either based on orbital elements inferred
from their entry trajectory, compositional studies, or both. Is this false?
Lew Gramer
]
------- Forwarded Message
From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
Sender: HUMBPEIS@livjm.acdot uk
To: cambridge-conference@livjm.acdot uk
Subject: CCNet, 26 January 2000
Date: Wed, 26 Jan 2000 10:38:38 -0500 (EST)
CCNet, 11/2000 - 26 January 2000
--------------------------------
(1) ICEBALLS NOT RESTRICTED TO SPAIN
Jeremy Tatum <UNIVERSE@uvvm.UVicdot ca>=20
[...]
(4) NEAR SPACECRAFT PASSES FINAL TEST
http://near.jhuapldot edu/news/flash/00jan24_1.html
(5) UPDATE ON ROSETTA MISSION TO COMET WIRTANEN
ESA News <sciweb@estec.esadot nl>
[...]
(9) AMINO ACIDS & EXTRATERRESTRIAL ORGANICS
Iain Gilmour <I.Gilmour@open.acdot uk>=20
(10) THE STRUCTURE OF COMETS AND ORIGIN OF DNA/RNA
Andrew Glikson <geospectral@spirit.com.au>=20
[...]
=============================================
(1) ICEBALLS NOT RESTRICTED TO SPAIN
>From Jeremy Tatum <UNIVERSE@uvvm.UVicdot ca>=20
At about the same time as the Spanish iceball reports, a truck in=20
Victoria, British Columbia, Canada, was struck by an apparent=20
iceball coming from on high. On later investigation, there was=20
found to be a residue described as "a sticky goo mixed with=20
shredded newspaper".
Jeremy Tatum
MODERATOR'S NOTE: Jeremy, could you please provide some additional
sources or references for your rather interesting note.
=============================================
(4) NEAR SPACECRAFT PASSES FINAL TEST
>From http://near.jhuapldot edu/news/flash/00jan24_1.html
NEAR Aces Final Flight Test=20
January 24, 2000
The NEAR spacecraft passed its final flight test last week, flawlessly=20
rehearsing the 30-hour rendezvous sequence that will precede its orbit=20
of asteroid Eros.
The sequence includes a low-phase flyby on Feb. 13, during which NEAR=20
will fly directly between Eros and the sun. The pass affords a unique=20
opportunity to map the minerals on Eros' northern half under optimal=20
lighting; a similar operation in October will cover the asteroid's=20
southern hemisphere.
NEAR remains on course for its Feb. 14 rendezvous with Eros, which is=20
now about 15,250 miles (24,400 kilometers) away from the spacecraft.=20
The NEAR team continues searching for small moons or space debris
around Eros, though none appear in the approach images NEAR has taken=20
over the past two weeks. The latest pictures from NEAR -- as well as a=20
second movie of the asteroid's rotation -- will appear on the NEAR Web=20
site this week.
=============================================
(5) UPDATE ON ROSETTA MISSION TO COMET WIRTANEN
>From ESA News <sciweb@estec.esadot nl>
Exactly three years to go before launch! That was the challenge=20
facing approximately 80 scientists and mission managers from ESA=20
member countries and the United States as they gathered this week at=20
the European Space Research and Technology Centre (ESTEC) in The=20
Netherlands for a progress report on the Rosetta mission to Comet=20
Wirtanen.=20
More at:
http://sci.esa.int/newsitem.cfm?TypeID=3D1&ContentID=3D8931&Storytype=3D=11
=============================================
LETTERS TO THE MODERATOR...
(9) AMINO ACIDS & EXTRATERRESTRIAL ORGANICS
>From Iain Gilmour <I.Gilmour@open.acdot uk>=20
Dear Benny:
There is a misconception about amino acids as indicators of=20
extraterrestrial organics. The occurrence of isovaline in particular=20
is not exactly rare, though its precise biological function is poorly=20
understood.
Isovaline occurs naturally as major constituents of cytotoxic peptides=20
produced by soil fungi such as Trichoderma viride and Trichodema=20
reesii (Bruckner and Pryzbylaki, 1984). The last time I visited Stevns=20
Klint I would not have described the outcrops there as exactly=20
soil-free!
Bruckner, H., and Pryzbylski, M. (1984) J. Chromatog 296, 263-275.
Iain Gilmour
Planetary Sciences Research Institute
The Open University, UK
=============================================
(10) THE STRUCTURE OF COMETS AND ORIGIN OF DNA/RNA
>From Andrew Glikson <geospectral@spirit.com.au>=20
Dear Benny,
=20
In their letter of 25.1.00 Hoyle and Wickmasinghe suggest "the=20
biological molecules would be vastly amplified within cometary=20
interiors", whereas in a communication to me of the same date=20
Wickmansinghe writes: "The amino acid content of carbonaceous=20
chondrites, synthesised abiotically, is largely irrelevant to=20
panspermia. It is the volatile component of cometary outflows=20
that carry biological particles and biological molecules in our=20
model.".=20
=20
It is generally assumed, although to date not directly observed, that
comets form loose aggregates including silicate blocks (possibly
including carbonaceous chondrites), ice and vapour. In terms of Hoyle
and Wickmansinghe's model, whereas the silicate blocks contain =
abiologic
amino acids, the ice and vapour contain biologic amino acids (and
possibly also viruses). Such proposed dichotomy in the composition of
comets overlooks the dynamic interchange of volatiles between silicates
(ie. the carbon in carbonaceous chondrites), ice and vapour, for =
example
during near-sun grazing. Such interchange would hardly allow spatial
separation of biologic and abiologic amino acids in vapour, ice and
solids.
=20
So far as "vastly amplified" molecules within cometary interiors is
concerned, apart from an occupation of the interior of comets by
abiologic amino acids contained in silicates, the authors will be aware
that (1) the chance of amino acids combining at random into a protein
molcule - the basic molecule of life - is 1 in 10^130 - a process =
likely
to require favourable conditions (temperatures under 150 degrees
celsius) as may exist on some planets, and (2) viruses, which contain
either DNA or RNA (but never both) can not multiply on their own except
as parasites within living organisms.
A clarification would be appreciated whether the authors accept=20
the validity of Ockham's razor principle, namely that no more=20
variables need be invoked in a scientific hypothesis than required=20
by the evidence?
Andrew Glikson
26.1.00
----------------------------------------
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