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Sendhil Revuluri (s-revuluri@uchicago.edu)
University of Chicago

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PHYSICS NEWS UPDATE
A digest of physics news items prepared by Phillip F. Schewe, AIP
Public Information
Number 106   December 14, 1992

THE DEVELOPMENT OF THE ANTARCTIC OZONE HOLE
has been more directly linked to manmade chlorofluorocarbons
(CFCs).  At the American Geophysical Union meeting in San
Francisco last week, Joe Waters of JPL, Aidan Roche of
Lockheed, and other scientists using the Upper Atmosphere
Research Satellite (UARS) reported that the seasonal destruction
of stratospheric ozone in September is preceded in the summer by
a buildup of ozone-killing chlorine compounds deriving from
CFCs.  The UARS team released the first images of this buildup,
showing a considerable gathering of chlorine monoxide in June in
extreme southern latitudes.  Ralph Cicerone of UC Irvine (714-
725-2157) said that the amount of chlorine measured corresponded
to the levels one would expect from the known release of
manmade pollutants.

AN ASTEROID IMPACT MAY HAVE CAUSED THE MASS
EXTINCTION that occurred at the boundary between the
Permian and Triassic periods 250 million years ago, said Michael
Rampino (212-998-8995) of NYU at the AGU meeting.  He
asserted that he has found evidence---in the form of gravity
anomalies and certain rock deposits---for such an impact in the
South Atlantic, in an area where, many scientists believe, South
America, Africa, and other land masses fit together in the
primordial supercontinent called Gondwanaland.  Rampino claims
that the gradual breakup of Gondwanaland into present-day
continents may have been initiated by the catastrophic impact. 
Another scientist at the meeting, Verne Oberbeck of NASA/Ames
(415-604-5496) also believes an impact may have sundered
Gondwanaland and that, in general, impacts should be given more
credit for shaping earlier Earth geology.  In particular, he believes
that the small rock sediments called tillites, usually thought to
result from the grinding and plowing action of glaciers, may in part
be debris from impacts.  Consequently, Oberbeck suggested, there
might have been fewer glacial periods than is usually believed. 
Rampino went so far as to say that all tillites are of impact origin. 
Unlike the theory that describes the KT (Cretaceous-Tertiary)
catastrophe 65 million years ago (when the dinosaurs became
extinct) in terms of an asteroid impact, the notion that the PT
catastrophe was caused by an impact or that tillites result from
impacts is anything but a majority opinion; indeed, many scientists
at the meeting were skeptical about Rampino's and Oberbeck's
ideas.  Thomas Crowley of the Applied Research Corp. (409-846-
1403), a paleo-climatologist, said that his reaction to the proposed
impact origin of tillites was one of "considerable disbelief,
bordering on incredulity."  For one thing, he said, tillite deposits
are too extensive over time and physical extent to have been
caused by an impact.

THE GALILEO SPACECRAFT GOT A GRAVITY BOOST
from the Earth on its Dec. 8 close encounter.  On its way by,
Galileo offloaded more images from last year's flyby of the
asteroid Gaspra.  Meanwhile, Galileo took many photos of Earth
and, on its flight over the Moon, the first color pictures of the
north lunar regions.  Galileo is now traveling toward Jupiter
(arrival date: Dec. 1995) at more than 8 km/sec, allowing it to
cover the Earth-Moon distance in 12 hours (it took the astronauts
3 days).  At the AGU meeting, Torrance Johnson of JPL said that
Galileo would be taking the first photos showing both the Earth
and Moon in one frame.