What would happen if a 75 mile wide asteroid or comet struck our Moon and cracked it into two or more pieces?

Question

What would happen if a 75 mile wide asteroid or comet struck our Moon and cracked it into two or more pieces?

Answer 1

Well...

*One h**l of a light show

*Earth could be bombarded by debris

*Earth's tides could be affected having serious side effects to marine life

just to name a few

Answer 2

Life as we know it on Earth would cease to exist.  Just how that would happen depends on the aftermath of the collision...where the Moon pieces go and stay, for example, will determine what gravitational forces they will exert on our planet.  But one thing is certain, there would be no well-regulated and predictable lunar tides.  That alone could mess up life that depends on ocean and lake tides for their well being.  The food chain might very well be broken.

In addition, the 23.5 degree stable tilt of Earth's axis would likely change as well...again depending on the location of the Moon pieces.  As our four seasons stem from that stable tilt, they would likely be altered as well.  Not only might the tilt angle change, but the tilt could become unstable...giving Earth a wobble like a top about to fall over.  

And that, you must recognize, would not be good for life on Earth.  There would be extreme and deadly climatic and weather changes as the planet wobbled around in its solar orbit.  These changes would far exceed the extreme weather vacillations we are now seeing due to global warming.

The rapid changes in forces due to the wobbling would engender breakdowns in Earth's structures.  Earthquakes, for example, might become extreme and plentiful.  Underlying magma might be released through fissures caused by the astable Earth.  

And glaciers hanging on by a thread due to global warming would be let loose to plunge into the oceans...at once cooling the oceans and desalinating them with fresh water.  That alone could threaten life on Earth by breaking food chains, flooding coast lines, and drastically changing weather patterns and climate.

No, if the Moon cracked into two or more pieces, that could not bode well for mankind or any of Earth's species.  This is one reason NASA just recently began a program to build up our understanding of asteroids and comets...in hopes of being able to come up with better detection and protection from such collisions on the Moon and on the Earth.