Shock waves

56 Pages·2009·62.72 MB·English

by  Nils Hoff

Ringvorlesung, WS09/10
Wechselwirkung mit dem Weltraum:
Impaktprozesse und Impaktgeologie
K. Wünnemann, T. Kenkmann, W.U. Reimold
Museum für Naturkunde
Leibniz Institut an der Humboldt-Universität Berlin
Arbeitsgruppe: Impakt- und Meteoritenforschung
Kontakt: [email protected], Tel. [phone]
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Outline:
1.Importance of impact processes
2.Methods to study impact processes
3.Impact craters in the solar system
3.1. Frequency of impact craters
3.2. Crater morphology
4.Formation of an impact crater - 3 stages
4.1. Shock waves - Contact & compression stage
micro/meso-scale modifications in rocks and minerals
4.2. Excavation stage
4.3. Modification stage
4.4. Oblique impacts
5.Atmospheric effects
6.Consequences of impacts
on planetary evolution and life
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Literature:
Monographien:
• Melosh, H.J. (1989): Impact cratering. A geologic process. Oxford University
Press, New York
• French, B. M. (1998): Traces of catastrophe. A handbook of shock-metamorphic
effects in terrestrial meteorite impact structures. LPI-Contribution No. 954
(Download at: http://cass.jsc.nasa.gov/publications/books/CB-954/
CB-954.intro.html)
• Roddy, D.J., Pepin, R. O. Merill, R. B. (1977) Impact and explosion cratering.
Planetary and terrestrial implications. 1301 p., Pergamon
Review Papers:
• Melosh, H.J., and Ivanov, B.A., 1999, Impact crater collapse: Annual Review of
Earth and Planetary Sciences, v. 27, p. 385-415.
• Stöffler D. and Langenhorst F. (1994) Shock metamorphism of quartz in nature
and experiment: I. Basic observation and theory. Meteoritics 29, 155-181.
• Collins G.S., Melosh H.J., Marcus R.A.(2005) Earth Impacts Effects Program:
A Web-based computer program for calculating the regional environmental
consequences of a meteoroid impact on Earth. Meteoritics and Planetary
Science 40, 817-840 (http://www.lpl.arizona.edu/impacteffects/).
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1. The Importance of Impact Processes:
Why study Impact Craters?
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1. The Importance of Impact Processes:
Mars Mercury
Impact Craters are everywhere
Impacts fundamental geological
process in the solar system
Moon
Ida-243
1. The Importance of Impact Processes:
Earth‘s Known Impact Structures
~176
still incomplete
Earth retains the poorest record of impact craters amongst terrestrial planets
Plate tectonics - Erosion – Sedimentation - Life,
Why?
Oceans are relatively young and hard to explore
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1. The Importance of Impact Processes:
Evolution of life
- transfer / origin of life
- mass extinctions on Earth
→
“Leben: Katastrophen und Leben“, W.U. Reimold
Origin of the Moon - Planetary Collisions
Properties / Age of planetary surfaces
→
“Oberflächen: Planetare Einschlagschronologien...“, G. Neukum
Future hazard
Ore / hydrocarbon deposits
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2. Methods
How to study impacts?
• Remote Sensing
• Geophysical Exploration
• Structural Geology
• Mineralogy
(Geochemie, Petrologie)
• Engineering
(Laboratory Experiments)
• Numerical Modelling
• ...
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3. Impact craters in the solar system : Frequency
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Jovian moon Io Callisto Back side of the Moon
Frequency of impact craters on planetary surfaces depends on how
geologically „active“ a planet is
Few craters → young surface Many craters → old surface
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3. Impact craters in the solar system : Crater morphology
Crater morphometry and morphology varies on
different planetary surfaces as a function of size
depends on gravity and material properties

(e.g. strength, density, ...)
Simple-Complex transition
) Moon
m
k ) M a r s
( m

r
ete (k G a n y m e d e
m

a h
iD pt Simple Complex
r e
e
t D
a
r
C r
e
t
a
r
C
Gravity (cm/s2)
Crater Diameter (km)
Pike, 1977
Garvin et al., 2003
Schenk, 1991,2002
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