What would happen if a large asteroid a third of the size of the moon hit the moon?

Answer 1

The asteroid would be 1,147 km in diameter. Impact velocity about 13.4 km/sec (..about 30,000 mph). If the moon wasn't completely fractured, the resulting crater would be 1,300 miles across and 3 miles deep. The energy expended on impact would be about 5^13 megatons. Certainly such an impact event on the moon would eject huge amounts of debris into space, much of which would rain down on Earth with disastrous results on our civilization.

Answer 2

This is needless scaremongering as there are NO asteroids a third the size of the moon. The mass of the entire asteroid belt (of which there are some known 350,000 members) amounts to only 4% of the mass of the moon,

Ceres alone accounts for a third of that total mass and it is in a stable orbit 2.8 AU from the Sun so it is not even a Mars-crosser, let alone a Near Earth Object.

So it is not going to happen and idle speculation has little purpose. Can I suggest that you restrict your worrying to named asteroids and comets with known possible impact dates and the estimated probability of those happening? and forget hypothetical "what would happen if?" fears and anxieties.

THEY ARE ON THE CASE

NASA and the European Space Agency and other partners have a joint programme called Spacewatch which keeps an eye on any celestial object that may perhaps impact in the next 100 years and so please be reassured: as soon as there is news of any such threat to life on earth. the astronomical community worldwide leaps into action to observe and re-calculate the orbit of the body in question,

For a period of 3 days at Christmas 2004 the asteroid Apophis, newly discovered that summer, was causing concern about a possible 2029 impact, However within 3 days hundreds of observations had been undertaken by observatories around the world, even though it was Christmas, and it had proved possible to revise downwards the estimate of the probability of impact to a much smaller one than was first thought to be the case.

Despite all the panic at the time, careful study of the orbit has revealed the current situation to be as follows:

No chance of collision in 2029, As of October 19, 2006 the impact probability for April 13, 2036 is estimated at 1 in 45,000. An additional impact date in 2037 has been identified, however the impact probability for that encounter is 1 in 12.3 million.

Not worth losing any sleep over.

Answer 3

Curious that it is believed that the Moon actually resulted from a collision between a Mar's sized planet and Earth, spraying debris into orbit around the Earth which coalesced into our Moon. The Moon was originally MUCH closer to Earth and is slowly moving further away.

At 1/4 the size of Earth, our moon is exceptionally large as a satellite. Because of this, the Earth "wobbles" very little on its axis, allowing us to have steady seasons and making life, as we know it, possible on Earth.

Our Moon is one of those exceptional accidents, along with our size and distance from the Sun which make many believe that a "Creator" had some hand in all of it.

If the moon were destroyed or knocked out of Erath's orbit by such a large impact, besides the devastating meteor shower on Earth, our seasons would most likely be thrown totally out of kilter and our axis would wobble wildly, much as Mar's axis does.

Short version, we, the human race, would most likely be toast.

Answer 4

Well, the moon would disintregrate and the result would be that a meteor shower on Earth that would have the Presdient send teams of "astronauts" (Bruce Willis, Will Smith, Ben Affleck, and Steve Buscemi, cuz well.. he's into everything) to save the world singlehandedly at Christmastime, all in about 2 and half hours and 5 buckets of popcorn later.

Answer 5

There would be conservation of momentum and much of the kinetic energy would be transformed into thermal energy.

If it was going a few nm/second very little would happen. If it was going significantly near the speed of light, much would happen.

A question to ask is "happen where?". Earth? A billion light years from earth? On the moon?

Answer 6

It could break the Moon into pieces. That is one big asteroid you are talking about there!

Answer 7

It would put on quite a show and could pose a threat to the earth depending on the geometry of the hit. Glancing blow vs. head on and do any significant pieces get kicked toward the earth.

Answer 8

1) It isn't going to happen. There aren't any masses that large traveling in orbits that have any chance of intersecting ours.

2) If it did happen, we would temporarily have another sun in the sky, but we wouldn't be around to appreciate it, because the debris and radiation would kill us all.

Do you stay up nights worrying about things like this?

Answer 9

Good bye Moon!
And if the impact would send any big fraction towards the Earth... good bye Earth!

Answer 10

it could very well bite off a chunk of the earth, and send it into outer space. half of our population will be surviving on this chunk of planet that used to be the earth and the rest of the population will stay on this planet.