PLEASE NOTE:
*
CCNet DIGEST, 6 May 1998
------------------------
(1) PLANETARY SOCIETY TO AWARD SECOND ROUND OF ASTEROID-DISCOVERY
GRANTS
The Planatary Society
planetary.org/articlearchive/headlines/1998/headln-050598.html
(2) UNIVERIST OF ARIZONA CATALINA SKY SURVEY SPEED UP THEIR
SEARCHES
Andrew Yee <ayee@nova.astro.utoronto.ca>
(3) METEORITE DELIVERY VIA YARKOVSKY ORBITAL DRIFT
Paolo Farinella <paolof@keplero.dm.unipi.it>
(4) WHY WE STILL DON'T KNOW WHERE HOMO SAPIENS EVOLVED
S.L. Smith and F.B. Harrold, University of
Texas
(5) THE CCNet ARCHIVE
Benny J Peiser <b.j.peiser@livjm.ac.uk>
=========================
(1) PLANETARY SOCIETY TO AWARD SECOND ROUND OF ASTEROID-DISCOVERY
GRANTS: GENE SHOEMAKER NEAR-EARTH OBJECT
GRANTS ENCOURAGE DETECTION
OF POTENTIALLY DANGEROUS COMETS AND ASTEROIDS
From The Planatary Society
http://planetary.org/articlearchive/headlines/1998/headln-050598.html
The Planetary Society is seeking applications for the second
round of
selections for the Gene Shoemaker Near-Earth Object Grants. The
purpose
of the grant program is to increase the rate of discovery and
follow-up
studies of asteroids and comets in Earth's vicinity by enabling
amateur
observers, observers in developing countries, and professional
astronomers who, with seed funding, could greatly increase their
programs' contributions to this critical research.
The deadline for receipt of applications for the second round of
selections is June 30, 1998. Previous awardees will not be
considered
for the present selection and applicants for the first round
wishing
consideration in the second selection are requested to submit
new,
updated applications. Application forms are available on this web
site
<http://planetary.org/articlearchive/headlines/1998/headln-050598.html>
The Society's NEO Grant Program is coordinated by Daniel D.
Durda, an
asteroid researcher at the University of Arizona's Lunar and
Planetary
Laboratory. An international advisory group, including noted
near-Earth
object scientists Richard Binzel of the Massachusetts Institute
of
Technology, Clark Chapman of the Southwest Research Institute,
Andrea
Carusi of the Spaceguard Foundation, and Brian Marsden of the
Smithsonian Astrophysical Observatory, will advise the Planetary
Society on the selection of awards for the grants.
FACING THE THREAT OF COMETS AND ASTEROIDS
Popular awareness of the threat of comet and asteroid impacts has
increased dramatically in recent months with the report of a
close
approach past Earth of the asteroid 1997 XF11 in October 2028 and
the
summer release of the movies Deep Impact and Armageddon.
Earth lives in a swarm of near-Earth objects of different sizes
and
orbits. Scientists have only recently begun to understand the
significant contribution NEOs have made to the evolution of Earth
--
and of life on Earth -- just as impacts from comets and asteroids
have
contributed to the evolution of all planets throughout the solar
system.
Less than 200 NEOs have been discovered thus far. Scientists
estimate
that there are several thousand such NEOs larger than one
kilometer and
150,000 to perhaps 100 million larger than 100 meters in size.
While various astronomical groups and NASA advisory committees
have
strongly recommended discovery of these objects be accelerated,
government support for NEO search and follow-up programs remains
modest.
"At the current rate of discovery, it would take decades to
find a
majority of even the large NEOS," says Planetary Society
Executive
Director Louis Friedman.
The Planetary Society hopes that its NEO Grant Program will help
map
the potential hazards of the future, allowing humanity to better
understand the threat of cosmic collisions.
The Society is cooperating with the Spaceguard Foundation, a
European-based international organization, to help fund and
promote
discovery of near-Earth objects.
PREVIOUS GRANT RECIPIENTS
The first four Gene Shoemaker Near-Earth Object Grants were
awarded at
the Celebration of Life service honoring Shoemaker at the US
Geological
Survey Flagstaff Field Center on October 11, 1997. The grants,
totaling
more than $35,000, were awarded to Gordan Garradd of Australia,
Kirill
Zamarashkin of Russia, Walter Wild of the United States, and Bill
Holliday of the United States for upgrades to their programs to
search
for NEOs.
The Society funds for the NEO Grant Program come from its 100,000
members worldwide, whose voluntary dues and donations permit
targeted
support to research and development programs.
====================
(2) UNIVERSITY OF ARIZONA CATALINA SKY SURVEY SPEED UP THEIR
SEARCHES
From Andrew Yee <ayee@nova.astro.utoronto.ca>
University of Arizona News Services
Lori Stiles
UA News Services
520-621-1877
lstiles@u.arizona.edu
Contact(s):
Stephen M. Larson
520-621-4973
slarson@lpl.arizona.edu
May 4, 1998
UA Catalina Sky Survey to make speedy searches for faint
near-earth
asteroids and comets
Astronomers at The University of Arizona in Tucson who in 1992
started
a unique near-Earth asteroid survey in the Santa Catalina
Mountains
north of Tucson are about to begin faster searches for fainter
objects
in large areas of sky where other such surveys seldom look.
Six years ago, Timothy Spahr and Carl Hergenrother, then UA
undergraduate students, with faculty sponsor Stephen M. Larson of
the
UA Lunar and Planetary Laboratory, launched the Bigelow Sky
Survey at
the university's 16-inch Schmidt telescope near Mount Bigelow,
Ariz. It
has been a part time photographic survey, inspired by and
patterned
after the systematic photographic search conducted at the Palomar
Observatory Schmidt telescope in southern California by the late
Eugene
Shoemaker of the U.S.Geological Survey and his wife, Carolyn..
With the photographic system, observers took two images, 30
minutes
apart, of the exact same region of the sky, then compared the
images
under a stereo microscope. Moving objects appeared to
"float" above the
flat star background. It took 60 minutes to thoroughly scan a
pair of
films, Larson said.
Program observers Spahr and Hergenrother made the Bigelow
survey's most
famous discovery, a near-Earth asteroid 200 meters in diameter,
or
roughly four times the size of the impactor that produced Meteor
Crater, Ariz., that missed Earth by about 280,000 miles on May
19,
1996.
Several months ago, Larson's group started a major NASA-funded
upgrade
of the system and renamed the project the Catalina Sky Survey.
Ultimately, Larson said, "With current and anticipated
improvements, we
will be able to detect an object in one-fortieth the exposure
time
needed for photographic observations, or we will be able to
detect
objects 14 times fainter while covering the same area as film
with our
new system. And this does not include improvements using software
to
replace eyeball scanning."
The Catalina Sky Survey is unusual in that program observers hunt
for
Earth- orbit crossing asteroids and comets above the plane of the
ecliptic, or the plane in which the planets revolve.
Other surveys, including the productive and pioneering UA
Spacewatch,
directed by planetary sciences Professor Tom Gehrels, hunt for
near-Earth asteroids along the ecliptic. Most Earth-crossing
asteroids
can be found when their slightly inclined orbits cross the
ecliptic
plane twice each orbit so long as they are near enough or bright
enough
and are observed for a long enough time. Sometimes, they are
close
enough to the Earth that perspective causes them to appear
outside of
the ecliptic.
"Away from the ecliptic plane, we don't see as many of these
objects
because there are fewer of them," Larson said. "But
while we don't find
as many objects, a higher percentage of those we do find have
interesting orbits. We aren't able to detect objects as faint and
small
as the larger (36-inch) Spacewatch telescope, but we will cover
much
more area for the brighter and potentially more dangerous
asteroids."
Larson now is collecting data to test software that operates an
electronic camera on the newly computer-controlled UA Catalina
Schmidt
telescope. The heart of the camera is a very large, very
sensitive
4,096 by 4,096-pixel charge-coupled device (CCD). It is the same
type
of chip used in Eleanor Helin's Near-Earth Asteroid Tracking
program,
sponsored jointly by NASA, the NASA Jet Propulsion Lab and the
U.S. Air
Force. The device can record light 50 times fainter than can be
captured by the most sensitive photographic film.
The Catalina telescope now electronically images a 3x3-degree
field of
view, or a square patch of sky equivalent to six lunar diameters
on a
side. It is capable of finding objects as faint as 20th
magnitude,
which is approaching the sky background level generated by
scattered
city light and auroral airglow that brightens Earth's upper
atmosphere.
The astronomers take from three to five electronic images of the
exact
same sky region about 30 minutes apart. When they perfect the
performance of the telescope, they will be able to precisely
align the
multiple electronic images so that stars and galaxies appear as
single
stationary sources of light and moving objects are seen to move
across
the screen.
Other proposed improvements to the Catalina Sky Survey include
increasing the telescope's light gathering power with a larger
entrance
corrector plate, and to increase computer capacity. Each
electronic
image is 32 megabytes and requires near real-time processing to
extract
moving objects."We now have this fairly fast computer, but
it has to
cope with 16 million pixels per image," Larson said.
John Brownlee, a recent graduate of the UA geosciences program,
is
programming the computer to coordinate the telescope and CCD
control
with data reduction and object detection. Automation of
repetitive
tasks and sequence flexibility to compensate for cloudy weather
will be
major goals.
Spahr recently finished his dissertation, which included data
from the
Bigelow Sky Survey, and has been awarded his doctorate from the
University of Florida. Graduate school has kept him away from
Tucson
during most of the upgrade, but he soon will rejoin the survey
effort
he initiated. This time, he will have state-of-the-art survey
tools.
The Catalina Schmidt telescope is available to the sky survey
team most
of the time, so only the bright moon limits observing time,
Larson
added. "With enough money to hire people, which is the big
operational
expense, we could observe 21 nights a month."
Ideally, the several near-Earth asteroid surveys could cover the
sky
two-to- three times a month, he said. "The Catalina Sky
Survey team
anticipates making significant contributions to the NASA
near-Earth
asteroid inventory effort."
==========================
(3) METEORITE DELIVERY VIA YARKOVSKY ORBITAL DRIFT
From Paolo Farinella <paolof@keplero.dm.unipi.it>
Paolo Farinella, David Vokrouhlicky and William K. Hartmann:
Meteorite
delivery via Yarkovsky orbital drift. ICARUS 132, 378-387, April
1998
ABSTRACT. We provide a unified discussion of the Yarkovsky effect
in
both the original, 'diurnal' variant and also for the `seasonal'
variant which has been recently shown by Rubincam (1995) to be
important for meteorite-sized, regolith-free asteroid fragments.
After
computing the rate of the corresponding semimajor axis drift as a
function of size and spin rate, and comparing the relevant
timescales
with those for collisional disruption and spin reorientation, we
discuss some issues in meteorite science which are put in a new
light
by the relevance of the Yarkovsky effect. In particular, this
mechanism
provides a good explanation for the fact that meteorite cosmic
ray
exposure ages (in particular for irons) are much longer than the
dynamical lifetimes of objects delivered to the Earth-crossing
region
through resonances. Thanks to the Yarkovsky effect, small
asteroid
fragments in the belt undergo a slow drift in semimajor axis
(with a
random-walk component related to their rotational state) and
therefore
have enough mobility to reach the resonances after comparatively
long
times spent in nonresonant main-belt orbits. Metal-rich fragments
have
slower Yarkovsky drift rates than stones, but their much longer
collisional lifetimes may explain why iron meteorites appear to
sample
a larger number of asteroid parent bodies compared to ordinary
chondrites.
=======================
(4) WE STILL DON'T KNOW WHERE HOMO SAPIENS EVOLVED (let alone
how,
.... never mind why)
S.L. Smith and F.B. Harrold: A paradigm's worth of difference?
Understanding the impasse over modern human origins. YEARBOOK OF
PHYSICAL ANTHROPOLOGY, 1997, Vol.40, pp.113-138
UNIVERSITY OF TEXAS, DEPARTMENT OF SOCIOLOGY & ANTHROPOLOGY,
ARLINGTON,
TX, 76019
The modern human origins debate within paleoanthropology has
become
polarized between two dominant models, Recent African Origin
(RAO) and
Multiregional Evolution (MRE). The debate has persisted and shows
no
sign of resolution despite the incorporation of new data and
dates
during the past decade. We examine the reasons for this
stalemate,
focusing on the presentation of these models by their principal
advocates, Christopher Stringer and Milford Wolpoff. In
particular, we
consider whether the RAO-MRE dispute is a paradigm crisis. The
modern
human origins debate can be placed in the broader context of
unresolved
controversies within evolutionary biology (e.g., punctuated
equilibrium
vs. gradualism, use of cladistics, and species definitions).
While the
two sides hold conflicting views, we argue that such differences
do not
constitute a paradigm clash. Since both share a commitment to
Darwinian
evolutionary theory, the debate cannot be characterized as a
paradigm
clash at the level of, e.g., Ptolemaic vs. Copernican astronomy.
Furthermore, we submit that a debate having historical roots
reaching
back into the previous century should not be portrayed as a
conflict
between competing paradigms in the Kuhnian sense. Preferences
toward
discontinuity or continuity wax and wane, persisting in a variety
of
scientific disciplines. We do not predict the quick demise of
either
MRE or RAO but are optimistic that careful evaluation of the
characters
and data on which claims about modern human origins are based
will lead
us toward a resolution of the current impasse. (C) 1997
Wiley-Liss,
Inc.
=====================
(5) THE CCNet ARCHIVE
From Benny J Peiser <b.j.peiser@livjm.ac.uk>
If you are a new list member on the CCNet or you wish to check
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http://abob.libs.uga.edu/bobk/cccmenu.html
Bob Kobres has set up this electronic archive and posts the
communication on the CCNet on the menu on a daily basis.
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