# What would an astronaut on the moon experience if a 1 meter diameter meteorite struck the surface one km away?

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.

• 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?
– Steve d'Apollonia
Feb 18 '14 at 16:38
• 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".
– Marc
Feb 18 '14 at 17:04
• Need calculations, and extra assumptions: density, regolith properties, angle of incidence, concrete velocity. -1 for the time being, please revise. Feb 19 '14 at 4:54
• A useful source is: Melosh, H.J., 1989. Impact Cratering. Oxford University Press, Oxford, UK. By the same author: 2011, Planetary Surface Processes. Feb 19 '14 at 5:03
• Methinks the composition of the meteor may be relevant too ... Feb 22 '14 at 19:18