Laboratory experiments for studying Collisional
Disruption in the Solar SystemBased on a Donald R. Davis’ article
English presentation
Daniel Odoardi Monday, the 6th of December
Master EFTIS IUFM de Nice - UNSA
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Table of contents
• Why to study collisional disruptions ?• Types of collisional outcomes• Fragmentation modes• Experimental laws• Extrapolation to the Solar System
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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
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Type of collisional outcomesA question of velocity
• Slow velocity impact Accretion
Inelastic rebound
• High velocity impact Cratering
Fragmentation
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Fragmentation modesQuestion of velocity and target
material• Rock
Low velocity
High velocity
• Ice Low velocity
High vleocity
• Iron High velocity
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Some definitions
• Fragmentation degree : fd = Mb/Mo
Mb : Mass of the biggest fragment
Mo : Mass of the original body
If fd < 0.5 Fragmentation
If fd > 0.5 Cratering
• Specific energy : Q = Etot / massIt is a kinetic energy
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The experimental laws
• 1st experimental law : fd = K . Q-a
Where K and a are empirically determined
• 2nd experimental law : N(>m) = (Mb/m)b
N(>m) = number of fragments with a mass greather than m and b = 1/(1+fd)
Actually, to use two power law gives better results• 3rd experimental law : V(m) = Vo.(m/Mo)-r
Vo = Vo(Q) and r ~ (1-b).4/9
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Extrapolation to the Solar System
• Scale difficulties : Asteroïds are 106 at 108 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
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Conclusions
• Study of collisional disruptions Predict the consequences of an impact with
the EarthUnderstand 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
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Thanks for your attention
