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From: Eugen Leitl <eugen@leitl.org>
To: "Jon O." <jono@networkcommand.com>
Cc: <bitbitch@magnesium.net>, <garym@canada.com>, <fork@spamassassin.taint.org>
Subject: Re: Asteroids anyone ?
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Date: Fri, 26 Jul 2002 11:29:11 +0200 (CEST)

On Thu, 25 Jul 2002, Jon O. wrote:

 
> Has anyone considered the fact that these occurrances appear to
> be increasing. I'm aware that maybe more publicity surrounding

No, it's just we've started looking. After we've actually started looking 
for deep infrasound (pressure waves) with a network of stations designed 
to enforced the nuke test ban treaty we've discovered that pretty big 
impacts are the norm. Current infrasound stations can detect 
bolides/meteoroids in ~10 T TNT scale, but some 10 kT events are 
relatively frequent. A number of people died in the Tunguska event (1908, 
10-15 MT), despite it hitting in the middle of nowhere.

http://216.239.39.100/search?q=cache:637JrhGDB5gC:www.lpi.usra.edu/meetings/5thMars99/pdf/6081.pdf+bolide+impact+kT+wave&hl=en&ie=UTF-8

In the Earth atmosphere a large number of bright light flashes of energies
in light impulse of about 0.1- 1 kt TNT and higher have been registered by
USA DoD satellites equipped with photoelectric detectors [9-11]. Intense
light impulses are created by impacts of meteoroids disrupted in the
atmosphere (mainly at altitudes of about 30-45 km). Several techniques for
the assessment of meteor- oid's characteristics from the light curves and
heights of peak intensities have been developed [3,12]. Using these
techniques the preatmospheric kinetic energy for Fifth International
Conference on Mars INITIATION OF SANDSTORMS: I.V.Nemtchinov, O.P.Popova,
V.A.Rybakov, V.V.Shuvalov a number of events was determined. The biggest
event is the 1 February 1994 with ini- tial energy as high as 30-40 kt TNT
(or initial mass of about 400 t). The bright flash with light energy of
about 4.5 kt TNT was caused by this meteoroid which deeply penetrated into
the atmosphere (at an angle of 45 degrees and velocity of 24 km/s) and
disintegrated above at altitudes of about 34 km and 21 km [9,12]. Another
famous impact event, the Sikhote-Alin meteor shower (12 February 1947
event), may be compared with the 1 February 1994 event. Initial masses of
these meteoroids are probably the same, as well as the angle of trajectory
inclination, but the initial velocity of the Sikhote-Alin is almost twice
smaller. That caused fragmentation of 1 February 1994 meteoroid at higher
altitudes and probably large fragments constitute a smaller part of the
pre- breakdown mass in contrast to the Sikhote-Alin event. In a rarefied
atmosphere of Mars analogous im- pactors will penetrate into deeper layers
of the atmos- phere.They will disintegrate lower 15 km or even reach the
planet surface, partially in disrupted form. Only the first disruption
would occur if a meteoroid similar to that caused the 1 February 1994 will
enter into the Martian atmosphere. And this body would reach the Mars
surface as a tense swarm of fragments. The meteoroid similar to that
caused the Sikhote-Alin event would hit the surface in a form of large
frag- ments due to its low velocity. They will create crater with the size
similar to that of the undisrupted meteoroid.


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