Would the impact result in sufficient gas expelled from the vaporization of the meteorite to carry sound waves a distance of a kilometre from the impact? Would the blast wave be sufficient to injure an unprotected astronaut?


It depends largely on the speed at impact, which could vary widely. If it's in a similar orbit to the Earth/moon system around the sun, catching up with the Earth/moon around the sun and the moon around the Earth, that would be pretty bad a kilometer away. The ejecta could certainly turn an astronaut into an astronaught.

On the other hand, if the meteorite were coming in from a different direction, say it was orbiting the sun in a similar orbit to the Earth/moon but in the opposite direction, the speed at impact could be as high as 135,000 miles per hour, or 37.5 miles per second. It would be a spectacular show, launching fragments of the moon into orbit around the Earth and likely beyond. Not a lot, but some. Your astronaut 1 kilometer away could never survive.

  • $\begingroup$ lol, I completely underestimated the effect of an impactor of that size. So would there be an audible sound a kilometre or two away by the vaporized blast fragments carrying the sound waves? $\endgroup$
    – Steve d'Apollonia
    Feb 18 '14 at 16:38
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    $\begingroup$ I'm not sure you'd call a blast wave composed of vaporized rock a "sound wave", first, because it isn't a pressure wave traveling through a gas so much as a super-heated gas traveling through a vacuum, and second, because the scale of the event would be so much greater than anything we would traditionally call "sound". $\endgroup$
    – Marc
    Feb 18 '14 at 17:04
  • $\begingroup$ Need calculations, and extra assumptions: density, regolith properties, angle of incidence, concrete velocity. -1 for the time being, please revise. $\endgroup$ Feb 19 '14 at 4:54
  • $\begingroup$ A useful source is: Melosh, H.J., 1989. Impact Cratering. Oxford University Press, Oxford, UK. By the same author: 2011, Planetary Surface Processes. $\endgroup$ Feb 19 '14 at 5:03
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    $\begingroup$ Methinks the composition of the meteor may be relevant too ... $\endgroup$
    – Everyone
    Feb 22 '14 at 19:18

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