What might happen if an object struck and replaced Luna

[highjustice]

I am hoping this might be the right place for this type of question, if not I apologize. I am doing research for a fictional piece and wanted to ask a question on the possible changes in Earth in regards to a meteor impact into our moon.

I am attempting to posit an event where an object strikes the moon in such a way that it causes the destruction of the moon, and the replacement by the new object.

The characteristics of this new object is that it would a crystalline core with a metallic element making up the majority of the object and a surface of rock. A fairly dense object, and the size can be relative to the physics required to make the results I'm looking for theoretically possible. As long as I can reach "theoretically possible", that is all I need.


The end result I'm looking for, and perhaps this is the wrong way to go about it but the other option is restructuring the cataclysmic event in question, is an unrecognizable Earth that consists of different landmass configuration, warmer climate, intense storms over the oceans at the equator, but little change to humans in an evolutionary sense, which may effect the hypothetical amount of time it takes for the Earth to recover to a livable surface state. Most importantly a livable planet with a stable, new moon in place of the old one. Preferably at a lower orbit but leaving human life in a recognizable and largely familiar form as possible.

The amount of time between the event and the present day of the book is irrelevant except in relation to the other pieces (such as humans being much the same in form as today, the amount of time it takes for the change in landmasses, etc). While I understand normal tectonic movement would take millions upon millions of years, I'm hoping that theoretically given any number of factors from such an event that it is possible to have a completely different configuration of landmasses. (change in ocean levels, massive earthquakes, or even chunks of the moon taking up space in the oceans would all be fine)

As if that wasn't convoluted enough I am furthermore looking for a 2nd event that consists of a chunk of this new moon breaking off due to an eruption on the moon and striking the planet, causing enough damage to level mountains (at about 5,000 mi from impact, and they are already nearly falling into the ocean as is, beyond that effects are irrelevant) but hopefully for near full recovery after a couple thousand years max.

This is my first trial run of asking these insane questions, and I know they may sound completely stupid as I have very little background in physics to back up my imagination, which is technically why I'm here. I hate to just arbitrarily say "such and such" happens if it is so outside anything even theoretically possible as to be ridiculous.

If anyone can provide any insight, even if it is to just help me get to a point where I can ask the right questions in the right manner or get me closer to a theoretical positive, I appreciate it.

Oh and I had a hard time even deciding the best place to ask this type of question. It may take multiple scientific professions to start to come up with a full picture of what is theoretically possible, but I figured physics is the best start.

Regards

 

[Drakkith]

How about this. A large object with a significant fraction of the Moons mass strikes it from a direction against the Moons orbital motion, thereby slowing it down and causing it to fall to a lower orbit. This process rains material down on the Earth and changes the landscape of the moon significantly. The impacts from moon debris cause a global temperature drop due to dust in the atmosphere, causing an ice age that reduces global ocean levels. Over a few thousand years the landscape changes significantly due to the advancing and receding ice, along with natural forces. Humanity survives this barely, and is rebuilding.

I think an impact large enough to level a mountain from 5,000 miles away is a BIT too large. Instead you could have the pieces land on certain areas and level that local area.

Also, I don't know what the tidal effects would be like if the Moon fell to a lower orbit, but I assume this would have some kind of effect. Perhaps more volcanoes erupt on Earth?