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English presentation odoardi Presentation Transcript

  • 1. Laboratory experiments for studying Collisional Disruption in the Solar System Based on a Donald R. Davis’ article English presentation Daniel Odoardi Monday, the 6th of December Master EFTIS IUFM de Nice - UNSA
  • 2. Table of contents
    • Why to study collisional disruptions ?
    • Types of collisional outcomes
    • Fragmentation modes
    • Experimental laws
    • Extrapolation to the Solar System
  • 3. Why to study collisional disruptions ?
    • Moon formation caused by a collision between a Mars-size body and the Earth
    • Extinction of the dinosaur (impact in the yucatan 65 million years ago)
    • More than 2000 collisions with a body of a mass greater than 1 kilogram per day
    • Anticipate the consequences of a collision between an asteroid and the Earth
    • Understand the Solar System formation
    • Study of the chondrites : the elementary bricks of the Solar System
    • Collisions between small bodies is the origin of planet formation
  • 4. Type of collisional outcomes A question of velocity
    • Slow velocity impact
        • Accretion
        • Inelastic rebound
    • High velocity impact
        • Cratering
        • Fragmentation
  • 5. Fragmentation modes Question of velocity and target material
    • Rock
        • Low velocity
        • High velocity
    • Ice
        • Low velocity
        • High vleocity
    • Iron
        • High velocity
  • 6. Some definitions
    • Fragmentation degree : f d = M b /M o
        • M b : Mass of the biggest fragment
        • M o : Mass of the original body
        • If f d < 0.5  Fragmentation
        • If f d > 0.5  Cratering
    • Specific energy : Q = E tot / mass
        • It is a kinetic energy
  • 7. The experimental laws
    • 1st experimental law : f d = K . Q -a
      • Where K and a are empirically determined
    • 2nd experimental law : N(>m) = (M b /m) b
    • N(>m) = number of fragments with a mass greather than m and b = 1/(1+f d )
    • Actually, to use two power law gives better results
    • 3rd experimental law : V(m) = V o .(m/M o ) -r
    • V o = V o (Q) and r ~ (1-b).4/9
  • 8. Extrapolation to the Solar System
    • Scale difficulties :
      • Asteroïds are 10 6 at 10 8 bigger than bodies studied in laboratories
      • Specific energy Q* needed to have fragmentation depends of the size of the body
    • Solutions :
      • Power law for take into account the mecanical effects  dominant for small bodies
      • Power law for take into account the gravitationnal effects  dominant for big bodies
  • 9. Conclusions
    • Study of collisional disruptions
      • Predict the consequences of an impact with the Earth
      • Understand the Solar System formation
    • Different types of collisional outcomes
    • Different types of fragmentation modes
    • Tree experimental laws
    • Power laws for extrapolation to the Solar System
  • 10. Thanks for your attention