May 18, 2013
Imbrium Flasher
video from NASA
Meteors streak across Earth's skies - remember February's monster fireball - mostly being consumed by the atmosphere and only infrequently reaching the surface as a meteorite or a crater-forming projectile. But on the Moon the lack of an atmosphere means incoming meteoroids are undetected until they smash onto the lunar surface, creating a momentary flash. And because there is no appreciable lunar atmosphere, meteoroids aren't slowed down, and thus hit at orbital velocities. That was 25 km/s for a 30-40 cm sized asteroid fragment that created a bright impact flash imaged by NASA on March 17, 2013. This flash was 4th magnitude, much brighter than any previous detection by NASA's Meteoroid Environment Office in Huntsville, Alabama. Since the projectile velocity was only about half that of really high speed impacts, the extreme brightness was probably due to its larger than average size. Comparing the image in the video with a Full Moon image suggests that the impact point was in southern Mare Imbrium near the crater Pytheas. The MEO team derived accurate coordinates and already provided them to the LRO Camera team. It will be interesting to see if the roughly 20 m wide crater is fresher appearing than many other similar sized pits that may be hundreds of thousands of years old.
Chuck Wood
Related Links
MEO
21st Century Atlas chart FM1.
Yesterday's LPOD: Steps To the Pole
Tomorrow's LPOD: Layers of Speculation
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