PLEASE NOTE:


*

CCNet DIGEST, 19 May 1998
-------------------------

(1) BRIGHT FIREBALL, SE QUEENSLAND
    Robert H. McNaught <RMN@aaocbn2.aao.gov.au>

(2) ACCRETION RATE OF COSMIC DEBRIS MEASURED AT THE SOUTH POLE
    S. Taylor et al., COLD REG RES & ENGN LAB

(3) SOUTH AFRICA'S BUSHVELD COMPLEX: NO EVIDENCE FOR IMPACT ORIGIN
    P.C. Buchanan & W.U. Reimold, UNIVERSITY OF WITWATERSRAND

(4) THE TOMS CANYON STRUCTURE: A POSSIBLE LATE EOCENE IMPACT CRATER
    C.W. Poag & L.J. Poppe, US GEOLOGICAL SURVEY

(5) SUICIDE AFTER NATURAL DISASTERS
    E.G. Krug et al., CTR DISEASE CONTROL & PREVENTION

(6) WHO CAN HELP RUSSIAN STUDENTS TO MAKE AN IMPACT
    Valery A. Loobnin" <loobnin@spb.runnet.ru>

===================
(1) BRIGHT FIREBALL, SE QUEENSLAND

From Robert H. McNaught <RMN@aaocbn2.aao.gov.au>

Steve Hutcheons of Brisbane has informed me of a brilliant daylight
fireball seen by thousands from SE Queensland. Even within 30 degrees
of the Sun, the fireball was obvious and one observer from indoors
first noted its presence by its reflection off a table. The media are
taking a strong interest and are trying to uncover security camera
recordings.

Initial information

1998 May 18  21:21 UT +/- 1 min
Mag: -18? apparent
Duration: ~5 secs
Position:  Due East of Brisbane, out to sea perhaps 200km
            (~lat 27.5S,~lng 155.0E)
Dirn of travel: probably NE

Rob McNaught
Eastern Australian Fireball Network
(rmn@aaocbn.aao.gov.au)

==========================
(2) ACCRETION RATE OF COSMIC DEBRIS MEASURED AT THE SOUTH POLE

S. Taylor*), J.H. Lever, R.P. Harvey: Accretion rate of cosmic
spherules measured at the South Pole. NATURE, 1998, Vol.392, No.6679,
pp.899-903

*) COLD REG RES & ENGN LAB, 72 LYME RD, HANOVER, NH, 03755

Micrometeorites are terrestrially collected, extraterrestrial particles
smaller than about 1 mm, which account for most of the mass being
accreted to the Earth. Compared with meteorites, micrometeorites more
completely represent the Earth-crossing meteoroid complex and should
include fragments of asteroids, comets, Mars and our Moon, as well as
pre-solar and interstellar grains. Previous measurements of the flux of
micrometeoroids that survive to the Earth's surface have large
uncertainties owing to the destruction of particles by weathering,
inefficiencies in magnetic collection or separation techniques, low
particle counts, poor age constraint or highly variable concentrating
processes, Here we describe an attempt to circumvent these problems
through the collection of thousands of well preserved and dated
micrometeorites from the bottom of the South Pole water well, which
supplies drinking water for the Scott-Amundsen station. Using this
collection, we have determined precise estimates of the flu and mass
distribution for 50-700-mu m cosmic spherules (melted micrometeorites).
Allowing for the expected abundance of unmelted micrometeorites(1)4 in
the samples, our results indicate that about 90% of the incoming mass
of submillimetre particles evaporates during atmospheric entry. Our
data indicate the loss of glass-rich and small stony spherules from
deep-sea deposits, and they provide constraints for models describing
the survival probability of micrometeoroids. Copyright 1998, Institute
for Scientific Information Inc.

===========================
(3) SOUTH AFRICA'S BUSHVELD COMPLEX: NO EVIDENCE FOR IMPACT ORIGIN

P.C. Buchanan & W.U. Reimold: Studies of the Rooiberg Group, Bushveld
Complex, South Africa: No evidence for an impact origin. EARTH AND
PLANETARY SCIENCE LETTERS, 1998, Vol.155, No.3-4, pp.149-165

UNIVERSITY OF WITWATERSRAND, DEPARTMENT OF GEOLOGY, PRIVATE BAG 3,
ZA-2050 WITWATERSRAND, JOHANNESBURG, SOUTH AFRICA

It has been suggested that the Bushveld Complex of South Africa could
be the result of multiple large meteorite or comet impacts. According
to this hypothesis, part of the lower Rooiberg Group, which forms the
roof of the Complex, represents a sheet of impact melt breccia and
other impact breccias. The present study is an attempt to test the
viability of the impact hypothesis for the Bushveld Complex by
interpreting newly acquired field, geochemical, petrographic, and
textural data for Rooiberg Group and associated rocks. Extensive field
work throughout the Rooiberg Group and, particularly, at the contact
between this unit and the underlying Pretoria Group metasediments has
failed to identify any material that could be interpreted as
impact-related. The Rooiberg Group is predominantly composed of
individual volcanic flows and pyroclastic units representing several
geochemically distinct magma types. These volcanic units are
interbedded with thin, laterally extensive, sedimentary units, a few of
which are sedimentary breccias. The presence of needles of quartz that
map represent paramorphs after tridymite in some Rooiberg Group units
has been used as evidence to support the contention that these rocks
represent superheated impact melt. However, quartz paramorphs after
tridymite have been recognized in terrestrial volcanic provinces (e.g.,
the North Shore Volcanic Group in northeastern Minnesota). Structural
data, including dips of Rooiberg Group strata, suggest that the lobate
shape of the Complex, which resembles several closely-spaced ring
features, is the result of post-Rooiberg Group deformation.
Microdeformation features in quartz from Bushveld-related rocks
do not satisfy the criteria of shock metamorphic planar deformation
features (PDFs) which would be characteristic of impact-induced shock
pressures between similar to 10 and similar to 30 GPa. These data,
especially the absence of macroscopic and microscopic evidence of shock
deformation in pre-Bushveld rocks, are inconsistent with formation of
the Bushveld Complex by impact. (C) 1998 Elsevier Science B.V.

======================
(4) THE TOMS CANYON STRUCTURE: A POSSIBLE LATE EOCENE IMPACT CRATER

C.W. Poag & L.J. Poppe: The Toms Canyon structure, New Jersey outer
continental shelf: A possible late Eocene impact crater. MARINE
GEOLOGY, 1998, Vol.145, No.1-2, pp.23-60

US GEOLOGICAL SURVEY, 384 WOODS HOLE RD, WOODS HOLE, MA, 02543

The Toms Canyon structure (similar to 20-22 km wide) is located on the
New Jersey outer continental shelf beneath 80-100 m of water, and is
buried by similar to 1 km of upper Eocene to Holocene sedimentary
strata. The structure displays several characteristics typical of
terrestrial impact craters (flat floor; upraised faulted rim;
brecciated sedimentary fill), but several other characteristics are
atypical (an unusually thin ejecta blanket; lack of an inner basin,
peak ring, or central peak; being nearly completely filled with
breccia). Seismostratigraphic and biostratigraphic analyses show that
the structure formed during planktonic foraminiferal biochron P15 of
the early to middle late Eocene. The fill unit is stratigraphically
correlative with impact ejecta cored nearby at Deep Sea Drilling
Project (DSDP) Site 612 and at Ocean Drilling Program (ODP) Sites 903
and 904 (22-35 km southeast of the Toms Canyon structure). The Toms
Canyon fill unit also correlates with the Exmore breccia, which fills
the much larger Chesapeake Bay impact crater (90-km diameter; 335 km to
the southwest). On the basis of our analyses, we postulate that the
Toms Canyon structure is an impact crater, formed when a cluster of
relatively small meteorites approached the target site bearing similar
to N 50 degrees E, and struck the sea floor obliquely. (C) 1998
Elsevier Science B.V.

======================
(5) SUICIDE AFTER NATURAL DISASTERS

E.G. Krug*), M.J. Kresnow, J.P. Peddicord, L.L. Dahlberg, K.E. Powell,
A.E. Crosby, J.L. Annest: Suicide after natural disasters. NEW ENGLAND
JOURNAL OF MEDICINE, 1998, Vol.338, No.6, pp.373-378

*) CTR DISEASE CONTROL & PREVENTION, EPIDEM INTELLIGENCE SERVICE, NATL
   CTR INJURY PREVENT & CONTROL, ATLANTA, GA, 30341

Background: Among the victims of floods, earthquakes, and hurricanes,
there is an increased prevalence of post-traumatic stress disorder and
depression, which are risk factors for suicidal thinking. We conducted
this study to determine whether natural disasters affect suicide rates.
Methods: From a list of all the events declared by the U.S.
government to be federal disasters between 1982 and 1989, we selected
the 377 counties that had each been affected by a single natural
disaster during that period, We collected data on suicides during the
36 months before and the 48 months after the disaster and aligned the
data around the month of the disaster. Pooled rates were calculated
according to the type of disaster. Comparisons were made between the
suicide rates before and those after disasters in the affected counties
and in the entire United States.
Results: Suicide rates increased in the four years after floods by 13.8
percent, from 12.1 to 13.8 per 100,000 (P<0.001); in the two years
after hurricanes by 31.0 percent, from 12.0 to 15.7 per 100,000
(P<0.001); and in the first year after earthquakes by 62.9 percent,
from 19.2 to 31.3 per 100,000 (P<0.001). The four-year increase of 19.7
percent after earthquakes was not statistically significant. Rates
computed in a similar manner for the entire United States were stable.
The increases in suicide rates were found for both sexes and for all
age groups. The suicide rates did not change significantly after
tornadoes or severe storms.
Conclusions: Our study shows that suicide rates increase after severe
earthquakes, floods, and hurricanes and confirms the need for mental
health support after severe disasters. (C) 1998, Massachusetts Medical
Society.

========================
(6) WHO CAN HELP RUSSIAN STUDENTS TO MAKE AN IMPACT

From Valery A. Loobnin" <loobnin@spb.runnet.ru>

Hi!

We are Russian students and going to create a computer program
modeling falling meteors into Earth's atmosphere. But we know just a
little bit about that phenomenon.

We have some questions: - how does meteor's form and temerature
                          (and color) change during meteor's falling.
                          We'd like to know formulaes discribing
                          that process.
                        - Maybe some chemical reaction is driving,
                          (which chemical reactions?)
                        - we'd see maybe some photos or movies of that
                          process.
                        - some good ideas are good too
                        - ANY MATH FORMULAS (FOR MODELING)

Bye! Best wishes!

P.S. sorry our english is bad, we know ...

P.S.S. if you know people who know anything about subject tell
       their e-mail (if it's possible). We need any info a lot...

Our e-mails: belyakov@spb.runnet.ru
             loobnin@spb.runnet.ru

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