> Cousin Ricky <ric### [at] yahoocom> wrote:
>> On 2021-09-15 6:22 PM (-4), Samuel B. wrote:
>>>
>>> "A" points to three features I suspect might have been produced by asteroids
>>> scraping the surface. Notice how they seem to have occurred on the sides or
>>> upper portions of a (really large) sloping hill? To me that indicates they were
>>> perhaps caused by asteroids hitting the moon at glancing angles... But I can
>>> definitely see how they could have been caused by collapsed lava tubes.
>>
>> I'm guessing rills; if not that, collapsed lava tubes.  It's not
>> intuitive, but as far as I know, impact craters are always circular,
>> regardless of impact angle.  If anything, a glancing impact might create
>> a series of craters, rather than a linear gouge.
> 
> Hmm, interesting. Is it due to the high speeds at which the asteroids are
> travelling, I wonder? Like, they're travelling so fast that any impact becomes an
> explosion?
> 
> Sam
> 



They ARE travelling so fast that the impact cause an explosion.
Supersonic projectiles, velocity in the 1 to 2 km/s range, tend to cause 
circular impact craters within a broad range of incident angles. For the 
asteroids, that's about 8 to 27 Km/s.

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