PLEASE NOTE:
*
CCNet 47/2002 - 9 April 2002
----------------------------
"Recent events such as the Australian debate over the need
to
monitor the Southern skies for asteroids - plus the budgetary
reductions suffered in the USA - lead me to propose a long-term
target
that the involved parties may find easier to relate to, whether
they be
astronomers, politicians, or NASA technocrats: WE WILL BEFORE THE
END OF
THIS CENTURY TRACK THE ORBITS OF 200 MILLION ASTEROIDS LARGER
THAN
100m"
--Jens Kieffer-Olsen, 9 April
"These various considerations identify the Cameroon impact
as: (1)
the most probable cause for the Permian extinction; and, (2) as
the
primary reason that Pangaea fragmented into the modern
continental
plates. Finally, certain physical properties and attributes of
the
Cameroon impactor can be discerned from the above scenario when
additional
geochemical findings are included in the analysis. This
characterization
has significant implications re the design and goals of impactor
detection programs, Earth protection schemes, and life- survival
systems
contemplated for the immediate and distant future."
--R.D. Brown, Pelorus Research Laboratory
(1) SMOKING GUN FOR PERMIAN MASS EXTINCTION DISCOVERED?
R.D. Brown, Pelorus Research Laboratory
(2) STRANGE LIGHTS IN THE SKY BAFFLE BAVARIANS
CNN, 8 April 2002
(3) FIREBALLS 6-7 APRIL 2002
Marco Langbroek <marco.langbroek@wanadoo.nl>
(4) NO METEORITE FALL IN BAVARIA
Daniel Fischer <dfischer@astro.uni-bonn.de>
(5) NASA 'ASTEROID-CASTING' OUT OF THIS WORLD
San Fransisco Chronicle, 8 April 2002
(6) COMMENT ON: "KOMATIITES AS PRODUCTS OF IMPACT
VOLCANISM?"
Andrew Glikson <geospec@webone.com.au>
(7) DARK OBJECTS TRANSITING THE SUN
Duncan Steel <D.I.Steel@salford.ac.uk>
(8) CCNet: THINK BIG!
Jens Kieffer-Olsen <dstdba@post4.tele.dk>
(9) AND FINALLY: THE LATEST PLANETARY DEFENSE TECHNOLOGY
Michael Gerrard <Michael_Gerrard@aporter.com>
============
(1) SMOKING GUN FOR PERMIAN MASS EXTINCTION DISCOVERED?
>From R.D. Brown <Pelorus@nebi.com>
AGU 2002 Spring Meeting
http://www.ngdc.noaa.gov/mgg/image/relief_slides2.html
1330h
T22A-08
An Impact Centered Near Cameroon at the Time of the Permian
Extinction
Caused the Fragmentation of Pangaea
* Brown, R D, Pelorus@nebi.com
Pelorus Research Laboratory, 105 South 18th Street, Ord, NE 68862
United
States
Several lines of evidence indicate that an asteroid impact was
responsible
for the Permian extinction, an event temporally followed by the
fragmentation of Pangaea. Until now, however, no suitably large
impact site
has been identified. Taken together, the following geological
structures
constitute 225 degrees of arc curvature of a circle centered on a
point
located off the coast of modern Cameroon: (1) the west coast of
Africa;
extending into (2) the north coast of Africa; and, continuing as
(3) the
Great African Rift throughout its extent. The degree of
circularity for this
geological structure exceeds that employed to identify impact
structures on
the Moon and other solid bodies in heliocentric orbits. By this
measure
alone, one can recognize that a massive impact is the only
physical process
that could have produced the circular fracture geometry that is
observed.
The timing of this impact can be discerned when it is noted that
two
radially oriented transpression ridge faults caused the SA plate
to separate
from the (newly formed) African coastline, and that the
Appalachian
mountains of NA once formed an arc of curvature concentric with
the NW coast
of the modern African plate. Together, these features demonstrate
that the
"Cameroon impact" occurred prior to the fragmentation
of Pangaea and that
Pangaea fractured along fault lines generated by this same
impact. Once one
accepts that Earth's structural geology retains a record of very
large
ancient impacts, the same impact model reveals a previously
unrecognized
power source for plate tectonic motions. If one assumes that the
Cameroon
impactor penetrated all the way through the Pangaean landform of
the Permian
era, it can be seen that NA, SA, and Africa subsequently slid
"downhill" and
away from the upper mantle bulge so produced. As a consequence,
it appears
that gravitational accretion is the larger process that has
powered these
plate tectonic motions into the modern era. These various
considerations
identify the Cameroon impact as: (1) the most probable cause for
the Permian
extinction; and, (2) as the primary reason that Pangaea
fragmented into the
modern continental plates. Finally, certain physical properties
and
attributes of the Cameroon impactor can be discerned from the
above scenario
when additional geochemical findings are included in the
analysis. This
characterization has significant implications re the design and
goals of
impactor detection programs, Earth protection schemes, and
life-survival
systems contemplated for the immediate and distant future.
======
(2) STRANGE LIGHTS IN THE SKY BAFFLE BAVARIANS
>From CNN, 8 April 2002
http://www.cnn.com/2002/TECH/space/04/08/germany.lights.reut/index.html
MUNICH, Germany (Reuters) -- Strange lights in the sky baffled
Bavarians as
hundreds of panicked callers jammed police telephone lines
seeking an
explanation for the phenomenon.
Reports of an unsettling late-night natural light show came late
Saturday
from all over the southern German state as well as the
neighbouring region
of Baden-Wuerttemberg.
Pilots flying into Munich airport radioed the control tower with
reports of
unusual lights in the sky.
The German police said NASA scientists initially thought the
light was
caused by space junk -- floating debris in the Earth's atmosphere
-- but
later said they were still unsure.
The German army reported no unusual movements on its radar.
Scientists said the lights may have the result of a meteor
breaking through
the Earth's atmosphere.
"There are no signs of impact or damage. We can't say what
it was," a police
spokesman said.
Copyright 2002 Reuters.
============
(3) FIREBALLS 6-7 APRIL 2002
>From Marco Langbroek <marco.langbroek@wanadoo.nl>
Dear all,
Now it starts to look like there might have been THREE large
fireballs over
west Europe on the night of 6-7 April. The Bayern event was
reportedly at
~20:30 UTC, the Dutch/Belgian North Sea event at 0:28 UTC and the
Scottish
event at ~3:45 UTC. That is, if there is no mistake in the time
given for
either the Dutch/Belgian or Scottish reports and these are not
one and the
same object.
Note the seeming regularity of approx. 4 hours inbetween each
appearance.
One could perhaps think of fragments of some fragmenting
satellite or rocket
booster re-entering for an extended period along its orbit (this
is just my
suggestion), although Alan Pickup's Decay Watch page does not
give a clear
candidate.
-----------
Dear Benny,
A quick update on the 'fireball mania' over Europe on the night
of 6-7
April.
Dieter Heinlein sent me one of the all-sky photographs of the
s-German
fireball at 20:20 UTC. Looks more like a meteoric fireball then
an
arteficial satellite decay. Indeed, that is the opinion of Dr.
Pavel Spurny
at Ondrejov. Dieter communicated that the 'meteorite' that was
found near
Munchen, is not a meteorite. It is a piece of bitumen. And
indeed, I have
seen a good picture of it: no, no meteorite...
So it seems that there were 3 fireballs that night over Europe of
which at
least 1 was a true, non-artificial fireball. What a night!
- Marco Langbroek (Dutch Meteor Society)
============
(4) NO METEORITE FALL IN BAVARIA
>From Daniel Fischer <dfischer@astro.uni-bonn.de>
Just quickly FYI - the "meteorite" recovered after the
German bolide was
none:
http://meteoros.de/news/news20.htm
Regards,
Daniel
===========
(5) NASA 'ASTEROID-CASTING' OUT OF THIS WORLD
>From San Fransisco Chronicle, 8 April 2002
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2002/04/08/MN48467.DTL
Keay Davidson, Chronicle Science Writer
"Tomorrow's skies will bring scattered showers to Northern
California,
followed by the impact of an asteroid the size of a city block .
. ."
No, that's not the real weather forecast. But it could be, some
time in the
(hopefully distant) future.
The prototype of what one might call "asteroid-casting"
is now online. It's
a NASA Web site -- neo.jpl.nasa.gov/risks/ -- that's tailor-made
for those
space fans, doomsday buffs and otherwise anxious souls who want
to plan
their busy lives around coming apocalypses.
Dubbed Sentry, it's billed as "an automatic near-Earth
asteroid monitoring
system." Launched by NASA's Near-Earth Object Program Office
at Jet
Propulsion Laboratory in Pasadena, the site lists 37 asteroids
whose orbits
may bring them unnervingly close to Earth in the foreseeable
future.
Like weather forecasts of "20 percent chance of rain,"
the site ranks
asteroids threats by their statistical probability of occurring.
Hurtling across the solar system at many miles per second, even a
medium-
sized asteroid could cause immense devastation across a wide
region, akin to
a small nuclear war. Many scientists blame the extinction of the
dinosaurs
65 million years ago on a much larger asteroid that hit Earth,
triggering a
devastating climate change and other eco-horrors.
Fortunately, all 38 asteroids listed on on the site Thursday pose
a "very
low probability" of hitting Earth, program manager Donald K.
Yeomans says.
"Objects normally appear on the Risks Page because their
orbits can bring
them close to the Earth's orbit, and the limited number of
available
observations do not yet allow their trajectories to be
well-enough defined,"
Yeomans said.
For example, Thursday's list was topped by an asteroid drably
named "2002
CU11." That asteroid has a threat rating of "1" on
a 10-point scale known as
the Torino scale, after a 1999 asteroids conference held in
Turin, Italy.
The number "1" means that 2002 CU11 "merits
careful monitoring," says the
site.
It's the only "1" on the chart. The rest are rated
"0," which means they
"are virtually certain to miss Earth or are so small that
any impact would
almost certainly dissipate in the atmosphere," the site
explains.
Still, even the "0s" will be monitored from time to
time in coming years,
just in case. The online list is subject to change as new
observational data
pour in from astronomers around the world.
Copyright 2002, San Francisco Chronicle
============================
* LETTERS TO THE MODERATOR *
============================
(6) COMMENT ON: "KOMATIITES AS PRODUCTS OF IMPACT
VOLCANISM?"
>From Andrew Glikson <geospec@webone.com.au>
Dear Benny,
I refer to Adrian Jones' item on "komatiites as products of
impact
volcanism?" (CCNet 8 April, 2002).
D.H. Green's (1972, 1975, 1981) advanced a compelling model of
komatiite and
tholeiitic basalt petrogenesis through adiabatic mantle melting
triggered by
asteroid impacts, based on experimental petrological studies. In
principle,
large impacts impinging on thin (5-10 km) geothermally active
(15-25 degrees
C/km) oceanic crust would inevitably involve crustal rebound and
near-instantaneous intersection of the experimental pyrolite
solidus,
ensuing in catastrophic partial melting (~30-50%) of mantle
peridotite, with
high magma ascent rates circumventing fractional crystallization.
This would
result in production of high-Mg (~8-15% MgO) to peridotitic
(~20-30% MgO)
komatiite lavas and hypabyssal intrusions.
The great abundance of high-Mg basalts and peridotitic komatiites
in
Archaean greenstone belts - far in excess of post-2.6 Ga
komatiites - has
been variably attributed to higher Archaean geotherms or/and to
Green's
impact rebound model. However, attempts of identifying
connections between
impact events and komatiite volcanism in Archaean greenstone
belts (Glikson,
1976, 1995, 1996, 1999, 2001) have not to date recovered positive
evidence
in this regard, as follows:
High-Mg and peridotitic komatiites commonly overlie significantly
older
supracrustal sequences, and in some instances (Zimbabwe, Pilbara)
overlap
older granitoid nuclei, which do not display evidence of impact
deformation
and shock metamorphism.
Archaean impact fallout units, which include impact vapour
condensation
spherules and debris flow deposits (Lowe and Byerly, 1986; Lowe
et al.,
1992; Byerly and Lowe, 1994) are not overlain by komatiite lavas.
In the
case of the Barberton c.3.24 Ga multiple spherule layers, this
impact
cluster appears to have been associated with the development of
major rift
structures filled with felsic volcanics and turbidites in both
the Kaapvaal
and the Pilbara cratons. Large late Archaean to earliest
Proterozoic impact
fallout units in the Hamersley Basin and the Transvaal (Simonson
and
Hassler, 1997) are not known to be associated with basaltic or
komatiite
volcanic activity.
There can be little doubt in the applicability of Green's model
(1972, 1975,
1981) in Archaean and younger oceanic crustal domains, for which
much of the
geological record has been destroyed through subduction,
downfaulting,
metamorphism and anatexis. Further efforts need to be made to
attempt to
correlate large oceanic impact events with the Precambrian field
evidence.
References: Byerly, G. R. and Lowe, D. R. (1994) Spinels from
Archaean
impact spherules. Geochimica et Cosmochimica Acta 58, 3469-3486;
Green, D.H.
(1972) Archaean greenstone belts may include terrestrial
equivalents of
lunar maria? Earth Planetary Science Letters 15, 263-270; Green,
D.H. (1975)
Genesis of Archaean peridotitic magmas and constraints on
Archaean
geothermal gradients and tectonics. Geology 3:15-18; Green, D. H.
(1981)
Petrogenesis of Archaean ultramafic magmas and implications for
Archaean
tectonics, in Kroner, A., ed., Precambrian plate tectonics:
Amsterdam,
Elsevier, p. 469-489; Glikson, A.Y. (1976) Earliest Precambrian
mafic/ultramafic volcanic rocks: ancient oceanic crust or relic
terrestrial
maria? Geology, 4, 202-205; Glikson, A.Y. (1995) Asteroid/comet
mega-impacts
may have triggered major episodes of crustal evolution. Eos,
February, 1995,
49-55; Glikson, A.Y. (1996) Mega-impacts and mantle melting
episodes: tests
of possible correlations. Australian Geological Survey
Organisation Journal,
16/4, 587-608; Glikson, A.Y. (1999) Oceanic mega-impacts and
crustal
evolution. Geology 27, 387-341; Glikson, A.Y. (2001) The
astronomical
connection of terrestrial evolution: crustal effects of post-3.8
Ga
mega-impact clusters and evidence for major 3.2±0.1 Ga
bombardment of the
Earth-Moon system Journal of Geodynamics, Vol. 32 (1-2): 205-229;
Lowe,
D.R., Byerly, G.R. (1986) Early Archaean silicate spherules of
probable
impact origin, South Africa and Western Australia. Geology 14,
83-86; Lowe,
D.R., Byerly, G.R., Asaro, F. and Kyte, F.T. (1989) Geological
and
geochemical record of 3400 Million years old terrestrial
meteorite impacts.
Science 245, 959-962; Simonson, B.M., Hassler, S.W. (1997)
Revised
correlations in the early Precambrian Hamersley Basin based on a
horizon of
resedimented impact spherules. Aust. J. of Earth Sci., 44, 37-48.
Andrew Glikson
Research School of Earth Science,
Australian National University,
Canberra, ACT 0200
andrew.glikson@anu.edu.au
ph 61 2 6125 4076
RSES/Petrology&Geochemistry/Glikson website:
http://rses.anu.edu.au/pep/staffandstudents/glikson
RSES 2001 Annual Report:
http://rses.anu.au/admin/annrep/2001/ar2001.html
Gondwanaland Flower website:
http://www.webone.com.au/~geospec/Page1.htm
Extraterrestrial impacts & meteorite websites:
http://seds.lpl.arizona.edu/nineplanets/nineplanets/earth.html
http://seds.lpl.arizona.edu/nineplanets/nineplanets/meteorites.html
http://www.lpl.arizona.edu/SIC/impact_cratering/intro/IntroImpact.html
http://gdcinfo.agg.nrcan.gc.ca/crater/index_e.html
http://www.planetary.org/html/neo/Objects-Impacts/impacts.html
http://planetaryweb.ucl.ac.uk/crater.htm
http://www4.tpg.com.au/users/tps-seti/crater.html
===========
(7) DARK OBJECTS TRANSITING THE SUN
>From Duncan Steel <D.I.Steel@salford.ac.uk>
Dear Benny,
In CCNet 45/2002 (8 April 2002), Juan Zapata-Arauco gave a very
interesting
account of some historical observations of dark spots rapidly
crossing the
face of the Sun, and elaborated on the idea that these
might be NEOs
passing relatively close by the Earth. If nothing else this
proves the
universality of the common phrase that "there is nothing new
under the Sun"
- except that here it is "nothing new crossing over the
Sun"!
Such events have been seen often by diligent solar observers who
literally
use their eyes; I once asked Tom Cragg, a long-time night
assistant at the
Anglo-Australian Telescope, whether he ever saw such things
(Tom would pull
out his small solar telescope every clear lunchtime to monitor
sunspots),
and he told me that he'd seen several over the years. Mark
Bailey, a
contributor to CCNet, has seen one, as did an Astronomer Royal
eighty-odd
years ago. See the publications to which I refer below. Thus
these are
clearly real, and not a product of the imagination. Reports are
fairly
consistent in terms of durations of transit and
behaviour/appearance. Juan
is entirely correct to bring them up.
Back in 1988 I had a paper in the magazine The Observatory in
which I
alluded to such dark spots as perhaps being NEOs passing near the
Earth; and
in 1992 I presented a paper at the National Australian Convention
of Amateur
Astronomers in which I advocated that keen amateurs might mount a
programme
to monitor the Sun to search for such events. I append the
relevant text
from my paper (having cut out the introductory background
material for
brevity; the reader might derive a wry smile from the Abstract,
given recent
'developments' in Australia).
I must close by saying that I do not believe that these are
actually solid
asteroids flying close by the Earth, for reasons related to the
size/flux/frequency problems which Juan described. My own belief
is that the
dark spots are perhaps short-lived clouds of dust produced by the
disruption
of small fluffy bodies (de-volatilised comet fragments) with
masses of order
1-10 tonnes as they encounter the magnetosphere (and so become
charged, the
electrostatic repulsion then causing the constituent tiny grains
to
disperse). There are other forms of evidence for the existence of
such
clouds or swarms of dust only close by the Earth (but in
certainly in
space), for example the correlated dust impacts on the Helios
satellite (see
the chapter by Hugo Fechtig, pp.370-382, in the book Comets, ed.
L.
Wilkening, University of Arizona Press, 1982; so far as I am
aware no
alternative explanation for the dust swarms has been
forthcoming).
Kind regards,
Duncan Steel
============================================================================
==
Proceedings of the XVth National Australian Convention of Amateur
Astronomers,
(ed. J. Grida), A1-A7, Adelaide, South Australia, April 1992.
THE SEARCH FOR EARTH-THREATENING ASTEROIDS: WHAT WE ARE DOING,
AND WHAT YOU
COULD DO TOO
Duncan Steel
Abstract: As our knowledge of the population of macroscopic
objects crossing
the terrestrial orbit has increased over the past couple of
decades it has
become clear that our planetary home is subject to large impacts,
with
potentially catastrophic consequences for our species, with a
disturbing frequency. This paradigm shift, whereby astronomers no
longer
look at the pock-marked surface of the Moon and fondly believe
that for some
reason the Earth escapes such cratering, has also led to an
alteration in
the view of many geologists, many of them now recognising that
impacts by
asteroids and comets play an important role in shaping the
surface of this
planet as well as those of the other planets and their satellites
elsewhere
in the solar system. There is now a movement in particular in the
United
States to develop a program to detect essentially all near-Earth
objects
(NEOs: asteroids and comets which may impact our planet), and
Australia is
certain to play a major part in that program, both because of its
geographical location and also the expertise built up over the
past few
years in searching for such objects: of four substantial search
programs
world-wide, three are in the USA and only AANEAS (the
Anglo-Australian
Near-Earth Asteroid Survey) operates from the southern
hemisphere. Many
other countries are also involved, but Australia is well-prepared
to take
the number two position. The discovery of a NEO on a collision
course with
the Earth would make a response essential, and plans for the
interception
and deflection of such an object are also being drawn up. One of
the
problems, however, is that the planned searches (concentrating on
the region
near opposition but stretching sixty degrees north and south of
the
ecliptic) may find almost all asteroids and short-period comets
larger than
0.5-1.0 km across with many years warning before an impact, and
long-period
comets with about a year's warning, but remain very insensitive
to asteroids
in Aten-type orbits (orbits with periods less than one year, so
that the
asteroid spends most of the time within the Earth's orbit and
thus
unobservable by conventional optical techniques, but with
aphelion outside
of 1 AU). It is proposed here that one way of searching for such
potential
impactors, and determining whether there is a substantial
population, is to
watch the Sun and look for them as they cross the solar disk on
straight-line paths taking typically 5-60 seconds to move from
limb-to-limb.
Such events will occur rarely, but automatic observing seems an
easily-achieved target for amateurs equipped with quite simple
apparatus. It
is recommended that consideration be given to setting up an
Australian
Sun-Transiting Object Network (ASTON), with the intention of
ASTON-ishing
the astronomical world.
(Clip introductory sections I-IV)
V. SHORT-LIVED PHENOMENA IN ASTRONOMY
Our knowledge of celestial optical phenomena of short duration
(say, less
than tens of seconds) is very sparse. Recently some searches for
optical
flares and flashes have been carried out (Schaefer, 1985; Content
et al.,
1989), but we still remain comparatively ignorant: we have become
used to
integrating for long periods, with photographic plates and
electronic
devices, with short duration events passing unnoticed unless a
specific
search is made for them (e.g. pulsar flashing). An example would
be
observations of a region in Perseus from where an apparent
optical flasher
associated with a gamma-ray burster had been reported; later
observations
turned out to be negative (Schaefer et al., 1987a,b). There are
also many
observations of transient lunar phenomena which have never been
adequately
explained, and recently a flash on Venus was reported (Kolovos et
al.,
1991). Two problems in this respect are confusion with glints
from
satellites, and head-on meteors. I reference these events here
not
necessarily to provide support for the interpretations offered by
the
observers, but rather to point out that we know little of
short-duration
celestial optical events.
Back in 1970 Professor Sir Hermann Bondi, best known to many
astronomers as
a co-worker of Sir Fred Hoyle on problems of nucleosynthesis and
cosmology
back in the 1950s, presented a talk entitled "The Astronomy
of the Future."
Therein he emphasised our ignorance of short-lived
phenomena:
"I would just like to add a little plea here for one field
of ground-based
optical astronomy, where, again, our knowledge is not even
skin-deep yet...
This is a subject which I would like to call short time-constant
astronomy.
We have all been much impressed by the integrating properties,
first of the
human eye and then of the photographic emulsion [DS: and of
course
electronic detectors since this was written], that there
has been a
concentration ... on
exploring further by increasing integration times. But of course
this has
almost completely excluded observations of transient effects... I
do not
know exactly what I am looking for: it may be that one might
discover
that there are brick ends flying about space and obscuring stars
every now and then for very brief moments... " (Bondi, 1970)
What I would like to suggest here is that there are indeed rocks
(if not
"brick ends") which are obscuring a part of a star
every so often: the rocks
are asteroids, and the star is our Sun. I would also be remiss
not to point
out that Bailey (1976) suggested looking for chance stellar
occultations as a way of detecting comets beyond the planetary
region and
thus otherwise unobservable.
VI. SUN-TRANSITING DARK OBJECTS
Over the years there have been many reports of dark objects
crossing the
face of either the Sun or the Moon which are not explicable in
terms of
terrestrial phenomena (such as birds, aeroplanes, seeds, dust,
hail,
satellites, insects, etc.). For example, see Anonymous (1870);
Anonymous
(1927); Hopman (1898); Steavenson (1920); Corliss (1979). Corliss
(1986)
lists 76 documented events from 1758 to 1983. In 1984 an
astronomy class at
the University of Manchester observed a similar event, a dark
object
crossing the face of the Sun on a straight line path and taking
an estimated
15-25 seconds to do so (O'Sullivan et al., 1985; Olsson-Steel,
1988).
If all terrestrial explanations are excluded, still many
sightings remain
which are apparently astronomical in origin. These fall into
three groups
with respect to time. Some objects move very rapidly across the
Sun or Moon,
taking less than a second to do so, and are therefore most likely
very close to us (just above the atmosphere: boulder-sized
objects like 1991
BA, or Earth-orbiting satellites?). Some take much longer - hours
in some
cases - and may therefore be intra-terrestrial planets like the
imagined
object 'Vulcan' of the nineteenth century. [After John Couch
Adams and
Urbain Le Verrier had both successfully predicted the existence
of Neptune
from the inequalities of the motion of Uranus, Le Verrier
suggested an
intra-Hermian planet - Vulcan - which he thought would explain
the anomalous
precession of Mercury. We now know that this precession is a
General
Relativistic effect; but Le Verrier lived well before Einstein.
In the
present century the fictitious Vulcan has been of more interest
to fans of
Star Trek; but note that there is a real minor planet named
(2309) Mr
Spock]. However, there are many transits which take from about 5
to 60
seconds, and therefore apparently they are dark objects
relatively close to
the Earth; within, say, the distance of the Moon. Typical angular
sizes of
these objects are 10 to 60 arcseconds, or sizes of 500 m to 3 km
if at a
range of ~10,000 km. Whilst our knowledge of the numbers of such
objects is
very hazy, it is believed that there are ~10^9 asteroids larger
than 10 m in
Earth-crossing orbits, and that one comes closer than the lunar
distance at
least once a day, on average. This would not, however, explain
the frequency
with which these transits seem to occur.
If these dark spots are, indeed, NEOs being observed in transit
then they
are of great interest with respect to our knowledge of the
population of
such objects. Since no information is required on their albedo,
their size
can be determined if they are resolved and their distance is
known, whereas
our knowledge of the sizes of NEOs observed from reflected
sunlight is quite
poor. The dynamical aspects of their passage by the Earth are
quite
interesting. Kepler's Law of Areas would say that, since they are
at
essentially the same distance from the Sun as is the Earth at
that time,
their tangential velocities will be the same. This means that if
they are
coplanar then the only relative motion would be radial; for an
NEO with
orbital inclination i the tangential velocities (of NEO and
Earth) will
differ by only a factor (1 - cos i), which is very small for
low-i objects.
The NEO motion perpendicular to the ecliptic will be small since
sin i is
small, this meaning that at such times the apparent angular
motion of a NEO
transiting the Sun will be mainly due to the rotation of the
observer about
the Earth's spin axis.
Observations of such a transit from two different latitudes would
therefore
render its position in space with some accuracy (from
triangulation), and
timings of its immersion and emersion from the solar disk would
allow its
orbit to be determined with reasonable accuracy. From the
distance would
come its size, and if it were passing outwards from the Sun past
the Earth
then optical follow-up using reflected sunlight might be possible
in the
following days. In this way the problem of the Aten asteroids
might be
solved.
VII. AN AUSTRALIAN SUN-TRANSITING OBJECT NETWORK
Clearly, then, verifiable and measurable observations of dark
objects
crossing the face of the Sun (or, indeed, the Moon) would have
considerable
scientific value, and may also contribute to helping to save the
human race
from extinction: is there an Aten asteroid on a collision course
with us? To
me, this is an area in which amateur astronomers could make a
very real
contribution, and therefore I would like to propose the
establishment of an
Australian Sun-Transiting Object Network (ASTON); if our friends
across the
Tasman would also like to get involved then the first word could
be altered
to 'Australasian.' From the outset let me make clear that I am
not
intending to organise such an effort myself: my only contribution
will be
this paper, plus maybe some help with analysing the results.
Quite simple equipment would be needed. Each observing site,
which can be
your own backyard (so long as it's not under an airport approach
path, or
inundated with birdlife), would need a simple heliostat to
project an image
of the Sun continuously onto a screen, a calibrated clock hung
next to the
screen, white paper below the clock to show the date clearly, and
a video
camera to film the lot. Simply set up and film - preferably at
low speed
unless you can regularly change the videotape - then play back at
high speed
in the evening after the Sun has disappeared for the day. Most of
the time
the film will be pretty boring (the screenwriter doesn't change
the
story very much) but every so often a dark object will be seen
crossing in a
straight line. Of course it will then be necessary to exclude all
terrestrial possibilities - and satellites too - but if there are
many such
sites spaced by hundreds of kilometres then correlated sightings
will prove
that the object is thousands of kilometres away. Multiple sites
with
latitude spacing would also allow triangulation to get the range
of the
object, and its three-dimensional motion and thus its
heliocentric orbit.
Obviously operating as many sites as possible for as much of the
time as
possible would be the best bet.
However, it must be said that most days absolutely nothing of
interest with
regard to asteroids will be discovered, and the observer will
have to
console him/herself with watching sunspots moving slowly across
the solar
disk. But this is often the way in science: that a null result is
a useful
result. The frequency of transits - the number of transits per
day, week,
year, who knows? - will be a very useful result since it will
allow the
population of such asteroids to be determined, so long as the
observers keep
scrupulous records of the observing conditions, minimum
detectable size, and
so on. Some simple experiments with viewing imitation black spots
of
differing size crossing a big, round, yellow sheet of paper
should allow the
latter parameter to be determined.
So, I commend ASTON to you for your consideration. It may not be
the sort of
astronomy that you are used to, but just think: no more staying
up late at
night. It is something that would provide some very useful
results, and is
well within the realms of possibility for a group of enthusiastic
amateurs.
REFERENCES
Anonymous (1870). Mon. Not. Roy. Astron. Soc., 30, 135-138.
Anonymous (1927). Nature, 120, 201.
Bailey, M.E. (1976). Nature, 259, 290-291.
Bondi, H. (1970). Q. Jl. Roy. Astron. Soc., 11, 443-450.
Content, R., Borra, E.F., Drinkwater, M.J., Poirier, S., Poisson,
E.,
Beauchemin, M., Boily, E., Gauthier, A. and Tremblay, L.M.
(1989). Astron.
J., 97, 917-922.
Corliss, W.R. (1979). Mysterious Universe: A Handbook of
Astronomical
Anomalies, Sourcebook Project, Glen Arm, Maryland.
Corliss, W.R. (1986). The Sun and Solar System Debris, Sourcebook
Project,
Glen Arm, Maryland.
Hopman, F. (1898). J. Brit. Astron. Assoc., 8, 127-131.
Kovolos, G., Varvoglis, H. and Pylarinou, L. (1991). Earth, Moon
& Planets,
54, 103-117.
Olsson-Steel, D. (1988). The Observatory, 108, 183-185.
O'Sullivan, T., Jordan, C. and Bailey, M. (1985). Sky & Tel.,
70, 196.
Schaefer, B.E. (1985). Astron. J., 90, 1363-1369.
Schaefer, B.E., Barber, M., Brooks, J.J., DeForrest, A., Maley,
P.D.,
McLeod, N.W. III, McNiel, R., Noymer, A.J., Presnell, A.K.,
Schwartz, R. and
Whitney, S. (1987a). Astrophys. J., 320, 398-404.
Schaefer, B.E., Pedersen, H., Gouiffes, C., Poulsen, J.M. and
Pizzichini, G.
(1987b). Astron. Astrophys., 174, 338-343.
Steavenson, W.H. (1920). J. Brit. Astron. Assoc., 31, 107-108.
========
(8) CCNet: THINK BIG!
>From Jens Kieffer-Olsen <dstdba@post4.tele.dk>
CCNet 44/2002 - 5 April 2002
> Asteroids in our Solar System may be more numerous than
> previously thought,according to the first systematic search
for
> these objects performed in the infrared, with ESA`s Infrared
Space
> Observatory, ISO. The ISO Deep Asteroid Search indicates
that there
> are between 1.1 million and 1.9 million `space rocks` larger
than
> 1 kilometre in diameter in the so-called `main asteroid
belt`, about
> twice as many as previously believed.
Dear Benny Peiser,
Recent events such as the Australian debate over the need to
monitor the
Southern skies for asteroids - plus the budgetary reductions
suffered in the
USA - lead me to propose a long-term target that the involved
parties may
find it easier to relate to, whether they be astronomers,
politicians, or
NASA technocrats:
WE WILL BEFORE THE END OF THIS CENTURY TRACK THE ORBITS OF 200
MILLION
ASTEROIDS LARGER THAN 100m
This target is a requirement if the exploration of Mars is to
become a
reality in the 22nd century. An asteroid detection scheme for
Mars is a
prerequisite, if astronauts are to dwell there safely for one
year, a
duration often proposed for the inaugural flight.
A permanent settlement on Mars would require an asteroid
deflection
capability similar to that defending Earth. And with a much
higher
frequency of being put to use.
Considering the large number of asteroids crossing the orbit of
Mars it
seems natural to not limit our target, except to asteroids in
orbits
entirely outside that of Jupiter.
As a consequence of agreeing internationally to meeting this bold
and noble
target the importance, status, and prestige of asteroid studies
would be
lifted, and university students could commit their scientific
future towards
this line of research with confidence.
Yours sincerely
Jens Kieffer-Olsen, M.Sc.(Elec.Eng.)
Slagelse, Denmark
=======
(9) AND FINALLY: THE LATEST PLANETARY DEFENSE TECHNOLOGY
>From Michael Gerrard <Michael_Gerrard@aporter.com>
The latest in planetary defense technology.
http://www2.uclick.com/client/nyt/bd/
Michael Gerrard
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