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Comet-Tail Ejecta Streaks : A Cratering Landform Unique to Titan?

Wednesday, March 3, 2004
Ralph
Lorenz (Lunar & Planetary Lab., University of Arizona)

Ralph Lorenz

The impact fireball in energetic cratering events can 'blow out' of the atmosphere, launching fine ejecta on ballistic suborbital trajectories that lead to worldwide microtektite deposits. The same process on Venus gives distinctive radar-dark parabolic ejecta features where ejecta deposited on the top of the atmosphere in a circle around the source crater and is winnowed by zonal winds. On Saturn's moon Titan, shortly to be explored by the NASA-ESA Cassini-Huygens mission, the peculiar atmospheric structure may prevent this from happening - the large vertical extent of the atmosphere and the low impact velocities in the outer solar system may mean the fireball begins to blow out along the wake direction, but traverses the long distances slowly enough that the wake tunnel gets closed off, trapping the ejecta in a linear cloud in the lower atmosphere. As on Venus, the ejecta is winnowed, but the line source may lead to two streaks like a dual comet tail, or a pair of Nike 'swooshes', a radar-dark one of fin

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