[meteorite-list] Crater excavation question

From: Frank Prochaska <fprochas_at_meteoritecentral.com>
Date: Thu Apr 22 09:41:09 2004
Message-ID: <NDBBICFKNKHAAEEJLDALEECJCHAA.fprochas_at_premier1.net>

Hello!

Actually, an adiabatic change doesn't by definition preclude a change in
temperature; it by definition precludes a transfer of heat energy from the
system to it's surroundings. These are often sudden, or nearly instanteous
changes, as heat takes time to flow between systems (hence the whole hot
meteorite/cold meteorite thread). An isothermal change by definition
precludes the change in temperature. In an adiabatic change (compression or
decompression) the temperature certainly can change as pressures change, but
not because the energy of the system is changing (ie. heat flowing)due to
interaction with the surroundings of the system (the rest of the moon). The
statement in the book just says that the total energy of the system
(impactor and target/kinetic and potential) doesn't change, but the form of
the energy does and there is an associated change in temperature.


Frank Prochaska



-----Original Message-----
From: meteorite-list-admin_at_meteoritecentral.com
[mailto:meteorite-list-admin_at_meteoritecentral.com]On Behalf Of Sam
Kimpton
Sent: Sunday, February 11, 2001 5:23 AM
To: meteorite-list_at_meteoritecentral.com
Subject: [meteorite-list] Crater excavation question


I was looking over the "Lunar Sourcebook" by Heiken et al. an noticed
something strange in the explanation of the cratering process on page
65.

Section 4.1.2. discusses the generation of compressional and
co-commitant
decompressional shock waves in both the target and projectile. Energy is

released along the free surfaces of both. This is standard theory and I
am
happy with it. What bothers me is the following statement: "Specific
Energies
of the highly compressed target and projectiles are increased upon
adiabatic
decompression after passage of the shock wave. This increase apears as
waste heat."

An adiabatic change by definition precludes a change in temperature.
How is
it possible to have energy liberation in the form of wast heat after an
"adiabatic"
reduction of pressure as stated here?

I post this in the off chance that some clever soul on this list can
elucidate on
this question.

Thanks.

Sam Kimpton



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Received on Sat 10 Feb 2001 05:26:23 PM PST