Making impact craters from numbers Natalia Artemieva Tucson-2007

Content How to produce billions of numbers quickly? How to deal with these billions? 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: Density(3)+Energy(3)+Concentration (2) +Velocity(3)+Stresses(6)+…..= 11-17…. Discretization of space: 300  300  300 = 27  10 6 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 ø - low density  - high density

Density distribution and crater shape Bosumtwi crater 10-km-diameter, 1Myr Well-preserved and drilled recently Numerical shape is similar to a real one, but not identical Central uplift Rim height Too deep Problems with material density after the impact (dilatancy)

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 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: Pre-impact depth Maximum compression and maximum temperature Pre-atmospheric size

Life transfer? Impact and ejection: High pressure and high temperature Flight in space Vacuum Low temperature Cosmic rays Atmospheric entry Heating and ablation

Do we need more numbers? More cells is better, but computational time increases dramatically: T ~ h -4. Parallel processes Adaptive mesh More stable computational scheme Still unresolved problems: 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, Artemieva, N., T. Karp, and B. Milkereit (2004), Investigating the Lake Bosumtwi impact structure: Insight from numerical modeling, Geochem. Geophys. Geosyst., 5, Q11016, doi: /2004GC 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, 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: /2005GL Artemieva N., Lunine J. (2005) Impact Cratering on Titan II: Global Melt, Ejecta, and Atmosphere Accretion. Icarus 175: E. Pierazzo, N.A. Artemieva, and B.A. Ivanov (2005) Starting Conditions for Hydrothermal Systems Underneath Martian Craters: Hydrocode Modeling. GSA Special Paper, 384, H. A. Ugalde, N. Artemieva, B. Milkereit (2005) Magnetization on impact structures – constraints from numerical modeling and petrophysics. GSA Special Paper, 384, Artemieva N. (2007) Possible reasons of shock melt deficiency in the Bosumtwi drill cores. M&PS 42, issues 4/5, 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, Fritz J., Tagle R., Artemieva N. (2007) Lunar Helium-3 in marine sediments: Implications for a late Eocene asteroid shower. Icarus 189,