Qfyilyi

Could a ~150 mile (240 kilometers) crater form from a small object impact?

So the object impacting the site of the crater is a human shape and not able to be destroyed. The location of the impact is in an ocean which is on average 1000 feet (304 meters) deep with the ocean floor made of mostly granite. The atmosphere is also similar to earths. The gravity is half that of earth.

I used Down2Earth's impact calculator to try and find out what it would take to get what you want.

The only parameter I could get even close to what you want was the target site: the bed of a 300m deep water body, on an Earth-like planet. I used the densest projectile and the smallest available size? a 100m wide piece of iron. The angle with the widest crater is that of a head-on crash.

This is what we get:

If instead of Iron we used uranium, or even osmium (the densest element), we would get approximately thrice the energy on the impact. The crater would still be one or two orders of magnitude smaller than what you want. But that's with the 100m wide impactor.

As you can see, for even an osmium man-sized projectile to give you the juice you need, it will need to impact at a considerable fraction of the speed of light. It will open a hole in whatever tectonic plate it hits, besides melting most of the crust around the impact, triggering a new Hadean era. If the planet has an atmosphere, it will evaporate into space. Gasified rocks will form a new, venusian atmosphere that may last a billion years. The debris from the impact will form a new Moon; the planet will have its mass reduced due to losing that debris to form the Moon, so the planet will have a smaller gravity after the impact. Also, its orbit will probably change excentricity around the sun.

If the solar system is already depleted of icy bodies (i.e.: comets) going around the orbit of that planet, it will never get enough water to develop life again. Otherwise give it a billion years for the crust to cool off and the atmosphere to renew itself, and maybe some microbial life will appear. Billions of years later, any intelligent life will never be able to tell that the impact happened.

The Chicxulub impactor is roughly 6.8-50.3 miles in diameter and in this event it released $5.8 cdot 10^{25} J$ of energy.

To figure out how fast a body would have to travel to impart that energy the equation is $E=(1/2)mv^2$.

Assuming average mans body ~80kg (ASSUMING) we get a velocity of $~1.2 cdot 10^{12} m/s$ which is about 4000 times the speed of light.

To scale that out to 150 mile wide crater would be far beyond anything even worth mentioning. Now if this god being were super massively dense, maybe the math would work out.