At 05:47 PM 4/9/2012, Warren Smith wrote:

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Melosh also suggests that the upward-expanding fireball would actually help propel the object upwards. I suspect that this effect may be similar to those Soviet-era "supersonic" torpedoes that had small rocket motors facing _forwards_ which pushed the water ahead of the torpedo out of the way.

--??huh? That kind of idea definitely sounds bogus at supersonic speeds.

What do you think that sharp pointy object is on the front of supersonic aircraft? It is intended to create a shock wave which bypasses much of the rest of the aircraft. Melosh also shows a brief picture of a computer simulation of such a high-speed ejection through the atmosphere. I know that computer simulations are only as good as the physics that goes into them, but I'm willing to give the researcher who did this the benefit of the doubt for the moment.

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I don't know whether anyone has directly addressed the issue of Venus.

--you had said any planet to any other was possible. I dispute that. Sounds like you now also dispute it.

You are correct; my language was a bit vague: I said exchange among planets, and from the surface of _a_ planet to other planets. Ejecta from the Moon and from Mars now seems incontrovertible; clearly ejecta from the Earth is somewhat controversial among funsters. Perhaps I should contact this professor and ask him directly.

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I get the impression that this has been a relatively active area of research over the past 10 years, so there may be later results than this 2009 video. Re bacteria surviving: Melosh discusses one of the instruments dropped onto the Moon before one of the Apollo missions brought it back. This instrument had _not_ been sterilized prior to being placed onto the Moon, and was kept sealed when brought back from the Moon. When this instrument was cultured, it showed the presence of live microbes.