Oblique Impact: A Process for Obtaining Meteorite Samples from Other Planets

Cratering flow calculations for a series of oblique to normal (10° to 90°) impacts of silicate projectiles onto a silicate halfspace were carried out to determine whether or not the gas produced upon shock-vaporizing both projectile and target material would form a downstream jet that could entrain...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 1986-10, Vol.234 (4774), p.346-349
Main Authors: O'Keefe, John D., Ahrens, Thomas J.
Format: Article
Language:English
Subjects:
Ejecta
Escape velocity
Flow distribution
Flow velocity
Gravity
Lunar And Planetary Exploration
Mars
Mars (Planet)
Meteorites
Meteoritic hypothesis
Meteors & meteorites
Natural history
Planets
Plumes
Silicates
SNC meteorites
Speed
Vapors
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Summary:Cratering flow calculations for a series of oblique to normal (10° to 90°) impacts of silicate projectiles onto a silicate halfspace were carried out to determine whether or not the gas produced upon shock-vaporizing both projectile and target material would form a downstream jet that could entrain and propel SNC meteorites from the Martian surface. The difficult constraints that the impact origin hypothesis for SNC meteorites has to satisfy are that these meteorites are lightly to moderately shocked and yet have been accelerated to speeds in excess of the Martian escape velocity (more than 5 kilometers per second). Two-dimensional finite difference calculations were performed that show that at highly probable impact velocities (7.5 kilometers per second), vapor plume jets are produced at oblique impact angles of 25° to 60° and have speeds as great as 20 kilometers per second. These plumes flow nearly parallel to the planetary surface. It is shown that upon impact of projectiles having radii of 0.1 to 1 kilometer, the resulting vapor jets have densities of 0.1 to 1 gram per cubic centimeter. These jets can entrain Martian surface rocks and accelerate them to velocities greater than 5 kilometers per second. This mechanism may launch SNC meteorites to earth.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.234.4774.346