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(meteorobs) Excerpts from "CCNet 62/2001 - 2 May 2001"
------- Forwarded Message
From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet, 2 May 2001
Date: Wed, 2 May 2001 09:59:48 +0100
CCNet 62/2001 - 2 May 2001
---------------------------
(1) DO ASTEROID CONTAIN SEEDS OF LIFE?
Environmental News Network, 27 April 2001
(2) POSSIBLE KEY STEP IN THE ORIGIN OF LIFE IDENTIFIED
UniSci, 1 May 2001
[...]
(7) WHAT MEDIEVAL WITNESSES SAW WAS PERHAPS A BIG LUNAR IMPACT AFTER ALL
Duncan A. Lunan <astra@dlunan.freeserve.codot uk>
[...]
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(1) DO ASTEROID CONTAIN SEEDS OF LIFE?
>From Environmental News Network, 27 April 2001
http://www.enn.com/news/enn-stories/2001/04/04272001/asteroids_43245.asp
A theory about asteroids is gaining more and more credibility among
astronomers, who allow that life on Earth might have been brought here from
another planet.
During a recent conference at the National Aeronautics and Space
Administration's Johnson Space Flight Center in Houston, Texas, astronomers
revealed that asteroids, previously thought to be only remnants of unformed
planets, may actually be ejected from other planets, spreading life as they
travel.
Last year, the theory was offered by a team of scientists from Caltech,
Vanderbildt and McGill universities that a meteorite believed to have come
from Mars could contain fossilized remains of Martian bacteria.
Some astronomers are suggesting that a meteorite such as this - one that
took 16 million years to get to Earth - could have contained microbes from
which all life on Earth evolved.
Jay Melosh, professor of planetary science at the University of Arizona in
Tucson, said: "Over the course of solar system history, perhaps a dozen or
so rocks ejected from the surface of one of the terrestrial planets may fall
onto the surface of a terrestrial planet in another solar system."
Melosh added that Earth "should have received a few such interstellar
wanderers over the course of solar system history."
The planetary scientist said he has no concrete evidence that life
hitchhiked to Earth on an asteroid, but the scenario is possible. "There's
no proof that this happened, but my research suggests that it's plausible,"
Melosh said. "Life could have been exchanged from Earth to Mars and Mars to
Earth if conditions on Mars were ever hospitable. If Mars was once warmer
and wetter, then there's a chance there has been that kind of exchange."
Millions of years ago, the Earth was bombarded by large meteorites whose
impact likely blasted chunks of the planet out into space. Some of that
material could have made it to Mars and to other places in the solar system.
Scientists say Earth was bombarbed by large meteorites millions of years
ago.
Last fall, a group of scientists claimed that they had collected an alien
bacterium 10 miles above the surface of Earth. A report in the Nov. 14, 2000
special edition of Earth, Moon and Planets, a journal published in the
Netherlands, lends credibility to the theory.
"Findings to date indicate that the chemical precursors to life, found in
comet dust, may well have survived a plunge into early Earth's atmosphere,"
said astronomer Peter Jenniskens of the Ames Research Center and the Search
for Extraterrestrial Life Institute.
The idea that the seeds of life fell from space has been a theory of
astronomers Fred Hoyle and Indian astronomer Chandra Wickramasinghe since
the 1970s. They called these seeds from space "panspermia."
In an interview in November with Space.com, a space information news
service, Wickramasinghe said, "I think the results reported by NASA are
clear proof that bacterial particles could survive, hence vindicating
panspermia."
At the NASA conference, researchers noted that the earliest records of life
coincide with the period when impacts to the Earth from space debris first
began to subside some 3.5 billion years ago, before bombardment began again.
Paul Renne, a geologist at the University of California at Berkeley, said:
"Maybe, as others have speculated before, life began on Earth many times,
but the comets only stopped wiping it out about three or four billion years
ago."
Copyright 2001, Environmental News Network
All Rights Reserved
======================================================================
(2) POSSIBLE KEY STEP IN THE ORIGIN OF LIFE IDENTIFIED
>From UniSci, 1 May 2001
http://unisci.com/stories/20012/0501011.htm
For a transition to occur from the pre-biological world of 4 billion years
ago to the world we know today, amino acids--the building blocks of proteins
in all living systems--had to link into chainlike molecules.
Now Robert Hazen and Timothy Filley of the Geophysical Laboratory of the
Carnegie Institution of Washington, and Glenn Goodfriend of George
Washington University have discovered what may be a key step in this process
- -- a step that has baffled researchers for more than a half a century.
Their work, supported by NASA's Astrobiology Institute and the Carnegie
Institution, is reported in today's issue of the Proceedings of the National
Academy of Sciences.
The molecular structure of all but one amino acid is an asymmetrical
arrangement grouped around carbon. This arrangement means that there are two
mirror-image forms of each amino acid; these forms are designated
left-handed (L) and right-handed (D).
All of the chemistry of living systems is distinguished by its selective use
of these (L) and (D), or chiral, molecules. Non-biological processes, on the
other hand, do not usually distinguish between L and D variants.
For a transition to occur between the chemical and biological eras, some
natural process had to separate and concentrate the left- and right-handed
amino acids. This step, called chiral selection, is crucial to forming
chainlike molecules of pure L amino acids.
Hazen and his collaborators performed a simple experiment. They immersed a
fist-sized crystal of the common mineral calcite, which forms limestone and
the hard parts of many sea animals, in a dilute solution of the amino acid
aspartic acid and found that the left-and right-handed molecules adsorbed
preferentially onto different faces of the calcite crystal.
Most minerals are centric, that is, their structures are not handed.
However, some minerals display pairs of crystal surfaces that have a mirror
relationship to each other. Calcite is one such mineral. It is common today,
and was prevalent during the Archaean Era some 4 billion years ago when life
first emerged.
This study suggests a plausible process by which the mixed D- and L-amino
acids in the very dilute "primordial soup" could be both concentrated and
selected on a readily-available mineral surface.
Hazen remarks, "Since the pioneering work of Stanley Miller in the 1950s,
prebiotic synthesis of amino acids has been shown to be relatively easy. The
real challenges now lie in selecting and concentrating L-amino acids, and
then linking those molecules into chainlike proteins.
"Our experiments demonstrate that crystal faces of calcite easily select and
concentrate the amino acids. Experiments now underway will see if the
calcite also promotes the formation of amino acid chains."
The Carnegie Institution of Washington has been a pioneering force in basic
scientific research since 1902. It is a private, nonprofit organization with
five research departments in the U.S.: Terrestrial Magnetism, Plant Biology,
Observatories, Embryology, and the Geophysical Laboratory.
Carnegie is a member of and receives research funding for this study and
other efforts through the NASA Astrobiology Institute (NAI), a research
consortium involving academic, non-profit and NASA centers. The NAI, whose
central administrative office is located at NASA's Ames Research Center in
Mountain View, CA, is led by Dr. Baruch Blumberg (Nobel '76). The institute
also has international affiliate and associate members. Astrobiology is the
study of the origin, evolution, distribution, and future of life in the
universe.
Related website:
The Carnegie Institution of Washington
[Contact: Robert Hazen, Tina McDowell]
01-May-2001
Copyright ) 1995-2001 UniSci. All rights reserved.
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* LETTERS TO THE MODERATOR *
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(7) WHAT MEDIEVAL WITNESSES SAW WAS PERHAPS A BIG LUNAR IMPACT AFTER ALL
>From Duncan A. Lunan <astra@dlunan.freeserve.codot uk>
RE: WHAT MEDIEVAL WITNESSES SAW WAS NOT BIG LUNAR IMPACT, GRAD
STUDENT SAYS
From Ron Baalke <baalke@ZAGAMI.JPL.NASAdot gov>
"The idea that what humans witnessed and chronicled in 1178 A.D. was
a major meteor impact that created the 22-kilometer (14-mile) lunar crater
called Giordano Bruno is myth, a University of Arizona graduate
student has discovered... Such an impact would have resulted in a
blinding, blizzard-like, week-long meteor storm on Earth - yet there are no
such accounts in any known historical record, including the European,
Chinese, Arabic, Japanese and Korean astronomical archives, Withers
said. [...] Yet no vigilant 12th century sky watcher reported such a
storm."
Dear Benny,
On the contrary, there is at least one 1178 record and several possible
ones. These are extracts from the discussion of it in my latest book, which
is now on offer to Random House:
"Ralph of Coggeshall's chronicle doesn't mention either the lunar
event or the eclipse of 1178, but he describes the finding of St.
Alban's relics that year. To it another hand has added the words 'et
lapides pluebant - and stones rained down'.(29)
"About 1% of the ejecta, hurled up from the lunar surface, would
exceed the Moon's escape velocity.(3) The 'sparks' which were seen
flying off into space must have been big, and there are two asteroids in
orbits which could have originated in lunar impacts. The one designated
1991 VG is about ten metres across, though it has some odd features which
I'll come back to in Chapter 21; 1999 CG9 is even larger, between 220
and 380 metres in
diameter.(30)
"But some would have less than the combined escape velocity for the
Earth and Moon.(3) Because they were from the Moon's trailing
hemisphere, some of those could fall on Earth as secondary impacts.
Since the Moon was near the Ecliptic, in June, its declination
(terrestrial latitude, projected on to the sky) would be 23 - 24o North.
Debris from Giordano Bruno crater, at 37o.7 Lunar North, could fall in
England (and in France?) but it depends on the angles of impact and
of the secondaries' ejection from the lunar surface. Around 1200, there
were big meteorite falls in Nebraska (31) and perhaps in New Zealand. (32)
They might have been secondary impacts, or pieces of comet which missed the
Moon altogether: Nebraska is 10o south of southern England, and New
Zealand close to the Antipodes."
In addition::
"Laser retroreflectors, taken to the Moon by Apollo astronauts and
Soviet Lunokhods, show that the Moon's orbital position is still
oscillating from one or more big impact(s) within the last thousand
years, producing a libration of the Moon in its orbit by 15 metres.(18)
Such effects were predicted in the 19th century but not found, proving that
the Moon had not been struck by any impacting body with more than one
100,000th of the Earth's mass.(19) Now we know how low comet masses
are, that has proved quite true, although the size of the crater
indicates that the energy released was around 100,000 megatons."
If the event reported by Gervase of Canterbury wasn't the impact that
generated the Moon's extra libration, it would have to have happened at some
other time, and there should have been falls of secondaries on Earth then
too. I'm not aware of a better candidate event than the 1178 one - does
anyone out there have candidate ones?
Nor, of course, does Withers explain why the monks said it happened twelve
times or more in rapid succession, and why they described what sounds like a
dust veil spreading round the Moon - buoyed up by a temporary atmosphere?
References are:
3. Derral Mulholland & Odile Calame, 'Lunar Crater Giordano Bruno',
Science 199, 875-877 (24th Feb. 1978).
18. Derral Mulholland, 'How High the Moon: a Decade of Laser Ranging',
Sky & Telescope, 60, 4, 274-279 (Oct. 1980).
19. Frangois Arago, "Popular Astronomy", Longman, Brown, Green, Longman
& Roberts, 1858; Mike Baillie, "Exodus to Arthur, Catastrophic Encounters
with Comets", revised edition, Batsford, 2000.
29. J. Stephenson, ed., Ralph of Coggeshall, "Chronicon Anglicanum",
Rolls Series No.66, Longman & Co., London, 1875.
30. Robert Uhlig, 'Chunk of Moon Rock Seen Orbiting the Sun', The Daily
Telegraph, 25th February 1999.
31. (Anon), 'Nebraska Crater Only a Pup', Astronomy Now, 8, 2, 13 (Feb.
1994).
32. Duncan Steel & Peter Snow, 'The Tapanui Region of New Zealand: Site
of a 'Tunguska' Around 800 Years Ago?', in A. Harris & E. Bowell, eds.,
"Asteroids, Comets, Meteors 1991", Lunar & Planetary Institute,
Houston, Texas, 1992.
As the book is already under consideration by publishers, any comments would
be appreciated!
Best wishes,
Duncan Lunan.
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