Earth & Moon Collision, what would it look like? (Curious)

[snooziums]

Hiya

I am curious, what would a collision between the Earth and the Moon look like? Now I realize that the chance of this ever happening is very, very remote, however it is possiable. Maybe something will impact the far side of the Moon, altering it course closer to the Earth.

What would the collision look like? With the Earth having a soft molten core, would the surface of it "shatter" upon the impact? Whhat about the Moon with its cold core?

And what about just before the impact? Would there be severe tides as the Moon approches, likme several hundred foot tides? Would there be a massive gravity difference right before the collision, like near-zero gravity between the Earth and Moon, so that things went flying, or heavy gravity on the other side of the Earth from the collision.

Would the gravity be so strong that the Earth's plates would start breaking up even before the actual impact?

And what would the end result be? Would the two them form a new planet? Would the Moon become the core of this new planet? Would most of the debris fall back to the new world, or would it form new moons, or would it be lost to space forever? Or, would everything fall apart and there be nothing but asteroids of both the Earth and Moon after the collision?

And if they did form a new planet, how long would it take for this new planet to "cool down"?

Would humanity survive such an event? Would live even survive such an event, perhaps frozen in space for a little while until it falls back to the new world after it cools down a bit?

And finally (just for fun), in the extremely more rare event that it did happen within your lifetime, what would your reaction be?

 

[Bob Klase]

And finally (just for fun), in the extremely more rare event that it did happen within your lifetime, what would your reaction be?

Ohhh, I think I'd just die.

Currenty theory is that a small (6-12 miles wide) astroid wiped out most life on earth. Consider that the moon is about 200 times larger than a 12 mile meteor or astroid, I doubt that any life would survive.

 

[aggle-rithm]

The collision that formed the moon involved a smaller Earth and a second body larger than the moon. It melted the entire planet and threw enough material into orbit that the moon formed shortly afterwards.

I think a collision with the moon would be similar, except that the Earth would end up larger still and the moon would be smaller. The magnetic field of the Earth would be unchanged, but it would probably lose a lot of its water and gasses to space. The process of geological change would start over, but I'm not sure life could ever start up again.

BTW, the moon would NOT form a new core because it is made up of the lighter material from the collision of the two planets. The Earth's present core, it is believed, was formed mainly from iron in the rogue planet that collided with it.

 

[Just thinking]

It may depend on the velocity of the approaching moon. A very rapid approach would likely leave nothing but debris thrown out into space, whereas a slow enough approach would rip the moon apart due to tidal forces and result in rings around the Earth. Mind you, this second scenario would still have tremendous effects on Earth too --- it may or may not survive.

 

[Molinaro]

According to the meteor impact effects calculator found here, and under the following assumptions:

Diameter of moon: 3500 KM
Density of moon: 3000 kg/m^3
Impact velocity: 20 km/s
Impact angle: 45 degrees
Hitting the ocean where it is 2 km deep.

And assuming you are watching from 5000 km away from the point of impact you can expect the following:

- The Earth is not strongly disturbed by the impact and loses negligible mass.
- 7.70 percent of the Earth is melted
- The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
- The impact does not shift the Earth's orbit noticeably.

- The crater opened in the water has a diameter of 10500 km

For the crater formed in the seafloor:
- Transient Crater Diameter: 6440 km
- Transient Crater Depth: 2280 km

- Final Crater Diameter: 20200 km
- Final Crater Depth: 5.85 km

- The final crater is replaced by a large, circular melt province.
- The volume of the target melted or vaporized is 8.47e+10 km^3
- Melt volume = 2.43 times the crater volume
- At this size, the crater forms in its own melt pool.

Thermal Radiation:
- Time for maximum radiation: 2,380 seconds after impact
- Your position is inside the fireball.
- The fireball appears 2080 times larger than the sun
- Thermal Exposure: 2.44 x 10^14 Joules/m2
- Duration of Irradiation: 618000 seconds
- Radiant flux (relative to the sun): 395,000

Seismic effects:

- The major seismic shaking will arrive at approximately 1000 seconds.
- Richter Scale Magnitude: 15.0


Don't forget to duck and cover!

 

[alfaniner]

In other words, "Big bada-boom!"

 

[snooziums]

- The Earth is not strongly disturbed by the impact and loses negligible mass.
- 7.70 percent of the Earth is melted
- The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
- The impact does not shift the Earth's orbit noticeably.

Hmm... at that rate, what the heck would affect the Earth in that matter? Anything larger would destroy the Earth, so I guess that the chance of something knocking the Earth out of its orbit or rotation & axis tilt, but not destroying the Earth is just about zero.

- Richter Scale Magnitude: 15.0

Since the richter scale is a log scale, meaning that as the number digits go up and scale increases exponentially, it is hard to even visualize a 15.0 earthquake. Something that strong would tear the ground to shreds and send everything in the ground, including the ground itself, flying.

I wonder if my insurance covers Earth/Moon collisions? And if it does not, maybe I should start selling such insurance.

"Yes, get your Earth/Moon collision insurance! If such an impact occurs, we will have you covered!" (Disclaimer: If all humanity is obliterated, this polity may be void. Not valid on any other planet except the Earth. Insurance holder must be on the Earth when event happens).

 

[Hamradioguy]

For a slightly less destructive take on similar scenarios read "The Big Eye" by Erlich (Planet on collision course with Earth), and "Lucifer's Hammer" by Niven and Pournelle (Comet on collision course with Earth). The first is a bit dated being written in 1949 but it has some good stuff on the 200 inch Palomar telescope and the author imagines a 120 story building in lower NYC with a big TV antenna on the top. The second is survivalist oriented with a host of quirky characters. I'd take the events in either over a moon impact.

 

[rjh01]

In a collision between Earth and a large body (like what wiped out the dinosaurs) then second most dangerous area to be in would be on the far side of the planet. All the energy would go around the earth and meet there.

 

[Cecil]

http://th.nao.ac.jp/~kokubo/moon/kit/movie.html

Here's a simulation of the original formation of the moon, based on the impact theory. It's a big download but worth it.

 

[orpheus]

Another enjoyable book based on an Earth/Moon collision: "The Hopkins Manuscript" by R.C. Sherriff. Out of print now, I think, but easily available online. Very dated (1940), and very much a social commentary - but great fun to read. One of the first sci-fi books I ever read as a child.

 

[wollery]

The collision that formed the moon involved a smaller Earth and a second body larger than the moon. It melted the entire planet and threw enough material into orbit that the moon formed shortly afterwards.

I think a collision with the moon would be similar, except that the Earth would end up larger still and the moon would be smaller. The magnetic field of the Earth would be unchanged, but it would probably lose a lot of its water and gasses to space. The process of geological change would start over, but I'm not sure life could ever start up again.

BTW, the moon would NOT form a new core because it is made up of the lighter material from the collision of the two planets. The Earth's present core, it is believed, was formed mainly from iron in the rogue planet that collided with it.

Probably.

 

[exarch]

I'd say this is a good place to start. More particularly, this video ...

 

[exarch]

- Richter Scale Magnitude: 15.0

Nuff said ...

 

[Zep]

BANG!

 

[Molinaro]

Hmm... at that rate, what the heck would affect the Earth in that matter? Anything larger would destroy the Earth, so I guess that the chance of something knocking the Earth out of its orbit or rotation & axis tilt, but not destroying the Earth is just about zero.

When I first played around with that site I was keyed on that very question! Just what would it take to alter the orbit or rotation.

It took many, many attempts to get an answer. First, it had to be a 90 degree hit and it had to be so big that >40% of the earth was melted by the collision.

Caveat: I don't think that page is intended to be used to simulate planetary/moon collisions.

But it is fun to play around with it anyway!