Transcript Making impact craters from numbers

Making impact craters
from numbers
Natalia Artemieva
[email protected]
Tucson-2007
Content
How to produce billions of numbers quickly?
How to deal with these billions?
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Crater shape
Seismic images
Petrology and shock metamorphism
Geophysics: gravity and magnetic anomalies
Ejecta and material exchange between
planets
Impact craters on the Earth and
on other planets
How to generate numbers?
Navie-Stocks equations: conservation of
mass, momentum and energy:
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Density(3)+Energy(3)+Concentration (2)
+Velocity(3)+Stresses(6)+…..= 11-17….
Discretization of space:
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300300300 = 27106
Discretization of time – millions of steps
In total – up to a billion of numbers on each
time step
How to make them visible?
Look at them
yourself for years…
Ask a kind person to
extract something
useful…
Use post-processing
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ø - low density
 - high density
Density distribution
and crater shape
Bosumtwi crater
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10-km-diameter, 1Myr
Well-preserved and
drilled recently
Numerical shape is
similar to a real one, but
not identical
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Central uplift
Rim height
Too deep
Problems with material
density after the impact
(dilatancy)
1
DENSITY
A
D
0
-1
-2
1
1
E
B
0
0
-1
-1
-2
1
-2
1
F
C
0
0
-1
-1
-2
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
-2
6 -6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
Bake the crater…
Change density according to
damage, temperature, and
lithostatic pressure
Define gravity anomaly
Paint the crater…
Displacement of target material
Maximum shock compression
Correlation with seismic data
and minerals in drill cores
Measure its temperature
Amount of melt and
melt distribution
Post-impact
hydrothermal activity
Density +
Temperature +
Mineralogy =
Magnetic signatures
Ejecta – what is outside the bowl?
Velocity above escape
and solid – meteorites
from Mars and Moon
High velocity (below
escape) – secondary
craters, tektites, distal
ejecta
Low velocity – proximal
ejecta, ejecta blankets.
Ejecta – meteorites from other planets
Velocity above escape
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Moon: 2.4 km/s, no atmosphere
Mars: 5 km/s, thin atmosphere
Earth: 11 km/s, thick
atmosphere
Solid (P< 50 GPa)
Correlation with observations:
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Pre-impact depth
Maximum compression and
maximum temperature
Pre-atmospheric size
1
30
13
79
ALTITUDE, KM
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2
9
0
1.8
-1
144
57
54
148
-2
0
1
2
3
DISTANCE FROM IMPACT POINT, KM
4
Life transfer?
Impact and ejection:
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High pressure and high
temperature
Flight in space
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Vacuum
Low temperature
Cosmic rays
Atmospheric entry
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Heating and ablation
Do we need more numbers?
More cells is better, but computational
time increases dramatically: T ~ h-4.
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Parallel processes
Adaptive mesh
More stable computational scheme
Still unresolved problems:
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Micro-effects versus macro-events
Chemical reactions
Recent publications:
Artemieva N.A. and Ivanov B.A. (2004) Launch of martian meteorites in oblique impacts. Icarus, 171, 84101.
Artemieva, N., T. Karp, and B. Milkereit (2004), Investigating the Lake Bosumtwi impact structure: Insight
from numerical modeling, Geochem. Geophys. Geosyst., 5, Q11016, doi:10.1029/2004GC000733.
Fritz J., Artemieva N., Greshake A. (2005) Ejection of Martian meteorites: petrological data and numerical
modeling. Meteoritics & Planetary Science 40, Nr 9/10, 1393–1411.
McEwen A.S., B. S. Preblich, E. P. Turtle, N. Artemieva, M. P. Golombek, M. Hurst, R. L. Kirk, D. M. Burr, P.
R. Christensen (2005) The Rayed Crater Zunil and Interpretations of Small Impact Craters on Mars. Icarus,
176, 351-381.
Artemieva, N., L. Hood, and B. A. Ivanov (2005), Impact demagnetisation of the Martian crust: Primaries
versus secondaries, Geophys. Res. Lett., 32 (18), L22204, doi:10.1029/2005GL024385.
Artemieva N., Lunine J. (2005) Impact Cratering on Titan II: Global Melt, Ejecta, and Atmosphere Accretion.
Icarus 175: 522-533.
E. Pierazzo, N.A. Artemieva, and B.A. Ivanov (2005) Starting Conditions for Hydrothermal Systems
Underneath Martian Craters: Hydrocode Modeling. GSA Special Paper, 384, 443-457.
H. A. Ugalde, N. Artemieva, B. Milkereit (2005) Magnetization on impact structures – constraints from
numerical modeling and petrophysics. GSA Special Paper, 384, 25-42.
Artemieva N. (2007) Possible reasons of shock melt deficiency in the Bosumtwi drill cores. M&PS 42, issues
4/5, 883-894.
Stöffler, D. and 9 co-authors (2007) Experimental evidence for the potential impact ejection of viable
microorganisms from Mars and Mars-like planets. Icarus 186, 585-588.
Fritz J., Tagle R., Artemieva N. (2007) Lunar Helium-3 in marine sediments: Implications for a late Eocene
asteroid shower. Icarus 189, 591-594.