PLEASE NOTE:
*
CCNet DIGEST, 22 April 1999
---------------------------
QUOTE OF THE DAY
"The people who carved this moon
map were the first scientists,"
says Dr Stooke. "They knew a great
deal about the motion of the
moon. They were not primitive at
all." (BBC Online News, 22 April)
(1) COMMENTS ON POTENTIALLY HAZARDOUS ASTEROID 1999 AN10
BY PAUL CHODAS (NASA, NEO PROGRAM OFFICE)
(2) ASTEROID RESEARCHER DISCOVERS PREHISTORIC MOON MAP
BBC ONLINE NETWORK, 22 April
(3) ICE-RINKS IN HELL: WAS THE ICE ON MERCURY DEPOSITED BY GIANT
IMPACTS?
Andrew Yee <ayee@nova.astro.utoronto.ca>
(4) LEONID ARTICLE
Rob McNaught <rmn@aaocbn.aao.gov.au>
(5) TWO WORLDS - ONE SUN
Andrew Yee <ayee@nova.astro.utoronto.ca>
(6) APRIL'S LYRID METEOR SHOWERS
NASA Science News <expressnews@sslab.msfc.nasa.gov>
============
(1) COMMENTS ON POTENTIALLY HAZARDOUS ASTEROID 1999 AN10
BY PAUL CHODAS (NASA, NEO PROGRAM OFFICE)
[as posted by Ron Baalke <baalke@ssd.jpl.nasa.gov>
Comments on Potentially Hazardous Asteroid 1999 AN10
Asteroid 1999 AN10 made the news recently because, according to a
group
of researchers in Italy, there is a remote possibility that it
could
collide with the Earth in the year 2039. Writing in a
scientific paper
submitted for publication, researchers Andrea Milani, Steven R.
Chesley
and Giovanni B. Valsecchi say that the chance of a collision in
2039 is
exceedingly small, only about one in a billion, but they add that
the
asteroid's orbit will remain threateningly close to the Earth's
orbit
for many centuries to come.
Although the threat posed by 1999 AN10 must certainly be
taken
seriously, the probability of impact for this object is so
miniscule
that the authors of the paper felt no great urgency to inform the
press
of the new calculations, and the other NEO scientists reviewing
the
paper agreed with this policy. To put it into perspective,
consider
that the probability of 1999 AN10 impacting in 2039 is tens of
thousands of times *less* than the probability of an undiscovered
asteroid of equivalent size hitting the Earth during the same
40-year
period. Furthermore, in just a few months, 1999 AN10 will
be observed
again, as it moves back into the nighttime sky, and the new data
will,
in all likelihood, completely eliminate the possibility of impact
in
2039. Researchers should then be able to start examining the
possibility of impacts after 2039.
As it turned out, the Milani et al. paper was publicized not by
the
authors, but by a third party who found it accidentally on one of
the
author's web pages; the authors were not even consulted before
their
results were publicized. An internet debate ensued on such
issues as
why the results had not been made public, and whether or not the
paper
had been peer-reviewed to ensure accuracy. The reasons for not
making
the results public have already been described: basically, there
was no
great urgency to publicize a one-in-a-billion-chance impact 40
years
from now, when even that remote a possibility will likely
disappear in
a few months.
On the issue of peer review, Milani and his colleagues followed a
commendable course. The authors distributed their paper to
qualified
experts more than a week before placing the paper on their web
page,
seeking confirmation of their results. Our group at JPL
examined the
paper and saw no major flaws. We have also confirmed the
existence of
the impact scenario for 2039, and we confirm that the probability
of
impact in 2039 is about one in a billion.
Paul W. Chodas
Research Scientist
NEO Program Office
April 21, 1999
=================
(2) ASTEROID RESEARCHER DISCOVERS PREHISTORIC MOON MAP
From the BBC ONLINE NETWORK, 22 April
http://news.bbc.co.uk/hi/english/sci/tech/newsid_325000/325290.stm
PREHISTORIC MOON MAP UNEARTHED
By BBC News Online Science Editor Dr David Whitehouse
A map of the Moon 10 times older than anything known before has
been
found carved into stone at one of Ireland's most ancient and
mysterious
Neolithic sites.
It has been identified by Dr Philip Stooke of the University of
Western
Ontario in Canada. He spends most of his time preparing maps of
asteroids based on spacecraft observations, but he has also
prepared
detailed maps of the Moon.
What puzzled him greatly was that there was no recorded map of
the moon
older than about 500 years. "I simply could not believe
this," he told
BBC News Online. "I felt there just had to be an older map
somewhere."
Prehistoric tombs
So he began looking in old manuscripts and history books as well
as the
records of excavations of the Neolithic sites of the British
Isles.
Then he found one. It took the eye of an expert to see it for
what it
was. It was carved into a rock in one of Ireland's most
remarkable
prehistoric tombs at Knowth, County Meath.
"I was amazed when I saw it. Place the markings over a
picture of the
full Moon and you will see that they line up. It is without doubt
a map
of the Moon, the most ancient one ever found," said Dr
Stooke.
"It's all there in the carving. You can see the overall
pattern of the
lunar features from features such as Mare Humorun through to Mare
Crisium."
Before this discovery, the oldest map of the Moon was by Leonardo
da
Vinci, drawn about 1505. The Knowth map is 10 times older.
Knowth is already a major focus of research into understanding
prehistoric man. Now it will become one of the most important
scientific sites in the world.
"The people who carved this moon map were the first
scientists," says
Dr Stooke. "They knew a great deal about the motion of the
moon. They
were not primitive at all."
The passage tomb at Knowth is estimated to be about 5,000 years
old. It
was obviously built by men who had a sophisticated understanding
of the
motions of the Sun, Moon and stars.
It is known that many stone circles and ancient tombs are aligned
with
the Sun but less attention has been paid to possible lunar
alignments.
This is despite the fact that at certain times the Moon can rise
or set
at any location on the horizon that the Sun can.
Series of arcs
Investigations at Knowth almost 20 years ago showed that at
certain
times moonlight could shine down the eastern passage of the tomb.
Remarkably, the moonlight would also fall on the Neolithic lunar
map.
During excavations, the stone in question was named Orthostat 47.
Its
right-hand section contains a series of arcs.
The circular limb of the moon is not included in the carving. Dr
Stooke
believes that it may have been drawn on the rock with chalk or
with
coloured paint.
Copyright 1999, BBC
============
(3) ICE-RINKS IN HELL: WAS THE ICE ON MERCURY DEPOSITED BY GIANT
IMPACTS?
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Please note that this article is copyrighted.
[http://helix.nature.com/nsu/990422/990422-10.html]
Ice-rinks in Hell
By HENRY GEE
The temperature on Mercury, the closest of the planets to the
Sun, can
get as high as 700 K (427 °C): yet there are persistent reports
of ice
at its poles. But where did this ice come from? This difficult
question
is tackled by Julianne I. Moses of the Lunar and Planetary
Institute,
Houston, Texas and colleagues in a report in the journal Icarus.
Their
conclusion is that the water on Mercury was probably delivered by
the
impact of water-rich asteroids or comets: however, their study,
which
used model simulations, was hampered by our ignorance both of
Mercury
and the population of 'Sun-grazing' asteroids and comets. It
could be
that the only way to solve the problem definitively is to travel
to
Mercury and see.
The prize could be worth the trip. Mercury could have a thousand
times
as much ice in its polar regions than our Moon, whose deposits of
ice
were revealed by the recent Lunar Prospector mission. Ice on the
Moon
is likely to be well-mixed with dust, but the ice on Mercury is
probably much cleaner -- true ice-rinks in Hell. Despite the
presence
of sunshine bright enough to melt the most obdurate ice-cream
cone in
seconds, there are places on Mercury in permanent shadow, where
temperatures could plummet below the temperatures of around 110 K
(minus 163 °C) required to ensure the stability of ice for the
duration
of the history of the Solar System.
The planet itself is an unlikely source of water. Mercury is very
dense, proportionately richer in metals such as iron than in the
silicate rocks that could be a source of water. It is possible
that the
original rocky crust of Mercury was removed by impacts in the
violent
early history of the Solar System -- impacts which could have
expunged
Mercury's original inventory of water and other 'volatiles'.
Another source could be the constant rain of 'interplanetary dust
particles' (IDPs) that showers the planets (including the Earth)
from
space. Over time, IDPs could have delivered sizeable amounts of
water
to Mercury, but the resulting ice would have been far dirtier
than
indicated by the bright spots of clear, reflective ice implied by
radar
observations.
The most likely prospects are impacts by asteroids and comets.
Comets
contain more ice than asteroids: the impact of a single, large
comet
could deposit enough water on Mercury to account for the
observations.
But cometary impacts are so energetic that most of the impactor
would
be jetted back into space, and the gravity of small Mercury would
not
be powerful enough to capture the débris.
This leaves the asteroids, and a subset of comets whose orbits
are
dominated by the gravitational field of the giant planet Jupiter.
Sadly, we do not know enough about Sun-grazing asteroids and
comets to
make good estimates of the rate at which such things would have
struck
Mercury. The situation is complicated even further by the
possibility
that some extinct and icy remnants of comets travel incognito,
disguised as asteroids -- it is often impossible to tell the
difference
between the two. Whatever the source of the ice on Mercury,
though,
Moses and colleagues claim that there is plenty of it.
© Macmillan Magazines Ltd 1999 - NATURE NEWS SERVICE
================
(4) LEONID ARTICLE
From Rob McNaught <rmn@aaocbn.aao.gov.au>
Hi Benny,
Thanks for mentioning the Leonid article, but there seems to have
been
a mixup somewhere. Your comment suggests that it is the whole
article
that is presented. It is however just an abstract. The original
article
is published in
The Astronomer, 1999 March, Vol 35, pp279-283
David Asher and I have an updated analysis of the time of Leonid
maxima
and a model of the dust trail density, to be published in the
next
issue of the IMO journal (WGN). This is all based on
David's upcoming
paper in MNRAS on the Leonid dust trails.
Cheers, Rob
Robert H. McNaught
rmn@aaocbn.aao.gov.au
=============
(5) TWO WORLDS - ONE SUN
From Andrew Yee <ayee@nova.astro.utoronto.ca>
News Service
Cornell University
Contact: David Brand
Office: (607) 255-3651 E-Mail: deb27@cornell.edu
Martian sundial designed for 2001 space mission is unveiled by
Bill Nye
"The Science Guy"
ITHACA, N.Y. -- For the first time in history, humanity will send
a
sundial to another planet. Inscribed with the motto "Two
Worlds, One
Sun," the sundial will travel to Mars aboard NASA's Mars
Surveyor 2001
lander.
Pictures of the sundial, taken by the lander's panoramic camera
after
its arrival at Mars in January 2002, will reveal the passage of
the
hours and seasons as the sun moves across the Martian sky. And
the
sundial's central black, gray, and white rings and corner color
tiles
will act as a calibration target -- a kind of test pattern -- to
adjust
the brightness and tint of pictures taken by the camera.
In the process, the sundial could become one of the most
photographed
objects ever sent to another world.
The sundial design team included Jon Lomberg, an artist and
creative
consultant to the Mauna Kea Center for Astronomy Education,
Hawaii;
Tyler Nordgren, an artist and astronomer at the U.S. Naval
Observatory
in Flagstaff, Ariz.; sundial expert Woodruff Sullivan, professor
of
astronomy at the University of Washington; Louis Friedman,
executive
director of the Planetary Society; Cornell University astronomers
Steven Squyres and Jim Bell; and Bill Nye, the television writer
and
host of the public television children's science program,
"Bill Nye The
Science Guy."
"Our ancestors made astonishing discoveries about the nature
of the
heavens and our place in it by closely watching the motion of
shadows,"
said Nye, unveiling the sundial design at a press conference at
Cornell
today (April 21). "Now, at the dawn of the next century, we
can make
observations of new shadows, this time on another planet."
Appropriately for a science instrument involving Nye, the sundial
design evolved through suggestions and drawings from children
across
the United States, solicited by Sheri Klug, director of Arizona
State
University's Mars Education and Outreach Program.
The sundial will be 3 inches (about 8 centimeters ) square, and
will
weigh just over 2 ounces (60 grams). Made of aluminum to minimize
its
weight, the anodized metal surfaces will be black and gold. The
photometric surfaces, which will be used to calibrate the Mars
lander's
color panoramic camera, called the Pancam, are made of a special
silicone rubber compound. Photo-etching and engraving will be
used to
apply the lettering and the drawings to the face and side panels
of the
sundial.
The central black, gray and white calibration rings are arranged
to
represent the orbits of Mars and Earth, and red and blue dots
show the
positions of the planets at the time of the landing in 2002.
Portions
of the central shadow post are gold to represent the sun.
The sundial carries a message for future Martian explorers who
may seek
it out, or who may find it by good fortune. The four gold side
panels
around the sundial's base are engraved with the words:
"People launched this spacecraft from Earth in our year
2001. It
arrived on Mars in 2002. We built its instruments to study the
Martian
environment and to look for signs of life. We used this post and
these
patterns to adjust our cameras and as a sundial to reckon the
passage
of time. The drawings and words represent the people of Earth. We
sent
this craft in peace to learn about Mars' past and about our
future. To
those who visit here, we wish a safe journey and the joy of
discovery."
The Pancam is is one of four instruments being developed for the
Mars
2001 lander under the leadership of Squyres, a Cornell professor
of
astronomy, assisted by 20 researchers around the world, including
Bell,
an assistant professor of astronomy, and a team of about 20
Cornell
undergraduates and staff. Together these instruments form the
Athena
Precursor Experiment, or APEX, which will be a prelude to the
Athena
Mars rover and sample return mission in 2003.
To help design the sundial, Arizona State's Klug sought the ideas
of
schoolchildren. Announcements were made at a meeting of the
National
Science Teachers Association in Seattle in 1998, and via several
international electronic mailing lists. Over 160 design concepts
were
submitted from children across the country.
One idea suggested by children was that the sundial bear writing
in
many languages, representing the diverse cultures of Earth. The
face of
the sundial is engraved with the word "Mars" in Arabic,
Bengali,
Braille, Chinese, Danish, English, French, German, Greek,
Hawaiian,
Hebrew, Hindi, Inuktituk, Italian, Japanese, Korean, Lingala,
Malay-Indonesian, Portuguese, Russian, Spanish and Thai. Together
these
languages are used by more than three quarters of Earth's
population.
Also included are ancient Sumerian and Mayan. Mars figured
prominently
in both the Sumerian and Mayan cultures.
Several children also suggested that stick-figure drawings be
included,
representing the people of Earth. Artist Lomberg combined stick
figures
drawn by children with other space-related motifs to create the
series
of drawings that appear on the sundial's side panels. The aim of
these
pictures is to capture the optimistic spirit of the text message,
combining a childlike sense of wonder with a vision of the human
future
in space.
Once the spacecraft lands on Mars and the exact orientation of
the
sundial can be determined, viewers will be able to tell local
Martian
time from sundial images and a computer-generated overlay posted
on the
World Wide Web. Mirrored segments along the outer ring of the
sundial
will also reveal the color of the sky above the lander. Over the
course
of a day, viewers on Earth will thus see the passage of time on
Mars
recorded in the sweep of the shadow of the sundial's central post
and
the changing colors of the Martian sky. The shadow will also
reveal the
changing Martian seasons over the full duration of the mission.
=============
(6) APRIL'S LYRID METEOR SHOWERS
From NASA Science News <expressnews@sslab.msfc.nasa.gov>
NASA Space Science News for April 21, 1999
April's Lyrid Meteor Shower: The oldest known meteor shower peaks
this
week on Thursday morning, breaking a 3 month lull in meteor
activity.
FULL STORY at http://science.nasa.gov/newhome/headlines/ast21apr99_1.htm
----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
The CCNet is a scholarly electronic network. To
subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information circulated on this network is for scholarly and
educational use only. The attached information may not be copied
or
reproduced for any other purposes without prior permission of the
copyright holders. The fully indexed archive of the CCNet, from
February 1997 on, can be found at http://abob.libs.uga.edu/bobk/cccmenu.html