Space Rocks

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Space Rocks

Postby Triangle_Man » Mon Nov 28, 2011 6:28 am UTC

I am currently in the middle of writing/editing a longer story, but I am running into some confusion with a certain plot point.

In short, I am curious to know about what would happen if a 5-metre meteorite where to collide with the planet earth. While I wouldn't necessary need to know this for the story I am writing given some of it's more fantastic elements (An alien creature hitching a ride on the space rock? Triangle Man, you so crazy!), I figure that it would be nice to know if I'm going to destroy my fictional world before I even start the story.

So in conclusion, I can't do science, I need to do science, please help.
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Re: Space Rocks

Postby Izawwlgood » Mon Nov 28, 2011 6:34 am UTC

5-meters? My guess is much of it would burn up by the time it hit, and when it did hit, it wouldn't be terribly bad. Like, on the order of maybe destroying a couple houses? World destruction, not even close.

Here, for some context:
http://www.youtube.com/watch?v=wG_ijnffzcs
45m meteor made a crater the size, roughly, of a city block.

Maybe I'm wrong though, I'm not terribly well read on this stuff.
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Re: Space Rocks

Postby Triangle_Man » Mon Nov 28, 2011 6:52 am UTC

I was thinking more along the lines of it being that large by the time it had hit the planet.

But yeah, I'd imagine that no matter where it landed, it would still cause a lot of damage.
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Re: Space Rocks

Postby yurell » Mon Nov 28, 2011 8:20 am UTC

This could be a really useful website for you. It's a calculator to figure out the effects of an asteroid impact, where you define the size, density, speed and angle of impact of the asteroid, as well as what it's crashing into. It also tells you what the effects are at a chosen distance.
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Re: Space Rocks

Postby HopDavid » Tue Nov 29, 2011 5:29 pm UTC

Triangle_Man wrote:I am currently in the middle of writing/editing a longer story, but I am running into some confusion with a certain plot point.

In short, I am curious to know about what would happen if a 5-metre meteorite where to collide with the planet earth. While I wouldn't necessary need to know this for the story I am writing given some of it's more fantastic elements (An alien creature hitching a ride on the space rock? Triangle Man, you so crazy!), I figure that it would be nice to know if I'm going to destroy my fictional world before I even start the story.

So in conclusion, I can't do science, I need to do science, please help.


5 meters in diameter? It'd burn up harmlessly in the upper atmosphere.

Arizona's Meteor Craters as well as the Tunguska event are thought to have come from objects 50 meters in diameter (before they entered the atmosphere)

I believe Chicxulub (aka dinosaur killer) was 6 kilometers.
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Re: Space Rocks

Postby eSOANEM » Tue Nov 29, 2011 6:27 pm UTC

Izawwlgood wrote:5-meters? My guess is much of it would burn up by the time it hit, and when it did hit, it wouldn't be terribly bad. Like, on the order of maybe destroying a couple houses? World destruction, not even close.

Here, for some context:
http://www.youtube.com/watch?v=wG_ijnffzcs
45m meteor made a crater the size, roughly, of a city block.

Maybe I'm wrong though, I'm not terribly well read on this stuff.


5 metres is going to do nothing. It will burn up well before it hits the earth.

Looking at a ridiculous over-estimate of the damage it could do based on the 45m ~ a city block sized crater:

Let us assume crater radius is proportional to the energy of the meteor (seems fairly reasonable, might be area instead of radius though) which is proportional to the volume of the meteor (will give an overestimate as a smaller meteor will be slowed more in the atmosphere).

Let us now assume that the proportion of the meteor burnt off in re-entry is constant across all meteors is constant (this is clearly absurd, it's far more likely to be that the amount burnt off is approximately constant (provided some meteor survives, otherwise it just all goes)). This means That, given a city block 200m across, a crater that size would have a radius ~100m. A 5m rock has 729 times less volume than a 45m rock so, given our assumptions, would produce a crater about 14cm in radius so a foot in diameter.

That's still a noticeable crater and would put a considerable dent in your car however, bear in mind that these assumptions are bound to given enormous over-estimates so any actual crater will be orders of magnitude smaller (and, in all probability won't appear at all).
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Re: Space Rocks

Postby Triangle_Man » Tue Nov 29, 2011 11:12 pm UTC

Thanks for the website, Yurell! I'm running some simulations to figure this out.

Also, I guess I'll have to thank you guys for helping me out with this. My goal here is to basically have a projectile that will serve as a delivery system for the Alien mentioned earlier on (Although that is sort of cheesy...) without destroying the planet. Your explanations have demonstrated that my original guess on the matter isn't going to cut it in this place.

In any case, any more insight on the issue would be appreciated and.

Again, thank you.
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Re: Space Rocks

Postby Erl Kaarik » Wed Dec 21, 2011 1:22 am UTC

Hi there.

As far as i know, a 5-10 meter meteorite (on impact) would create a crater similar to this:

Image

This is the Kaali Crater in Estonia. You can check it out on wikipedia.
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Re: Space Rocks

Postby Turtlewing » Tue Jan 03, 2012 5:11 pm UTC

It's worth noting that the answers and the linked simulator are assuming a natural meteoroid. If the alien is delivered in something designed to safely deliver an alien it will be very different.

For one thing, a heat-shielded drop capsule will suffer less loss of mass as it goes through the atmosphere, and something designed to lithobrake http://en.wikipedia.org/wiki/Lithobraking or to absorb the shock of impact by crumbling (to avoid killing the occupant) will do less damage to the impact sight as well.

You might even have a capsule at the heart of a comet-like body, where it appears to be a comet until the ice melts on entry and a retro-thruster deploys changing it's trajectory and slowing the impact to something the capsule can protect the occupant from by crumbling, which would result in damage comparable to a plane crash or less, if the occupant is human-like.

For a super human you could have the capsule impact with enough force to leave whatever crater is convenient to the story.

You'd also get a nice meteor shower as the comet fragments burn up, and since the capsule crumbled on impact it's not likely to be that distinguishable from a meteorite made from whatever alloy/composite the aliens used in its construction.
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Re: Space Rocks

Postby gmalivuk » Tue Jan 03, 2012 10:24 pm UTC

I find this site to be a more streamlined calculator than the Purdue one.

Also, it seems that a crater's volume is most closely proportional to the energy of the impactor than either its diameter or its area. Which make sense, as a crater is formed when a certain total amount of material is moved from its original location, and this amount is proportional to the energy required to move it.
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