# Asteroid Passes Within 7500 Miles Of Us? **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [June 27, 2011, 11:08pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072 "2011-06-27T23:08:07Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Cat\_Whisperer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cat_whisperer/32/4839_2.png) [@Cat\_Whisperer](https://boards.straightdope.com/u/Cat_Whisperer)\ **Post date:** [June 28, 2011, 5:42am UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/21 "2011-06-28T05:42:24Z")
> [@YogSosoth](#): > > What kind of damage were we looking at if it should hit? This is timely - I just finished reading [Lucifer’s Hammer](http://www.amazon.com/Lucifers-Hammer-Larry-Niven/dp/0449208133), a story about a comet hitting the earth and all the fallout. According to the book, it isn’t good. 🙂 ---
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [June 28, 2011, 6:08am UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/22 "2011-06-28T06:08:03Z")
> [@colonial](#): > > I think anyone who thinks this is paranoid. That’s all you can manage? A pseudo-psychological jab at me?:rolleyes:😃 No “and here’s why:…”. Just a hit and run diagnosis? So here’s what you get back, **colonial** : Well, I _know_ I’m being paranoid, but am I being paranoid _enough_???😉 :rolleyes: ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [June 28, 2011, 4:14pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/23 "2011-06-28T16:14:10Z")
> [@Cat\_Whisperer](#): > > This is timely - I just finished reading [Lucifer’s Hammer](http://www.amazon.com/Lucifers-Hammer-Larry-Niven/dp/0449208133), a story about a comet hitting the earth and all the fallout. According to the book, it isn’t good. 🙂 What would a good comet strike look like? Scientists say that the comet headed towards Earth is, as immanuel Velikovski always claimed, made of spun hydrocarbons. The giant mass of cotton candy is expected to strike the American Midwest. Carnivals and Clowns are standing by. ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [June 28, 2011, 5:50pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/24 "2011-06-28T17:50:05Z")
Damn, and I could have been out there in my little triangular space ship shooting it to little pieces! ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [June 28, 2011, 6:04pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/25 "2011-06-28T18:04:20Z")
According to that article there was never any chance of it hitting us, and even if it had it would have burned up in the atmosphere. Not much of a bullet! ---
**Author:** ![Gray\_Ghost](https://avatars.discourse-cdn.com/v4/letter/g/c0e974/32.png) [@Gray\_Ghost](https://boards.straightdope.com/u/Gray_Ghost)\ **Post date:** [June 28, 2011, 7:38pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/26 "2011-06-28T19:38:27Z")
I will, yet again, mention this [online impact calculator](http://impact.ese.ic.ac.uk/ImpactEffects/) for simulating the effects of a meteor impact. From what I had read and you all have linked, the upper and lower bounds for the object’s composition and velocity were 5-20 m in diameter, and anywhere from 3000-8000 kg/m^3 in density. [2011 MD’s impact velocity](http://neo.jpl.nasa.gov/risk/2011md.html), according to NASA’s Near Earth Object Program, would be 11.24 km/sec., which is rather slow as these things go. Plugging those quantities into the above calculator, and assuming a worst-case scenario of a 90 degree impact angle, iron composition and 20 m in diameter, I get an impact energy of 505 kilotons. It does break up in the atmosphere, but enough is left of the impactor for the fragments to have about 220 kt of impact energy. That forms a crater about 1/3 of a mile across and a few hundred feet deep. You wouldn’t want to be within a mile or 2 of the impact, but 10 miles away would be fine, per the model showing no resulting fireball from the impactor. Again, this is the worst case. Make the asteroid less dense, and the entry angle more acute, and more of it breaks up in the atmosphere for a big light show and less cratering of the ground. Of course, this asteroid’s closet point of approach put it somewhere over the Southern Ocean, where even a straight in impact would have likely hit water, and a 220 kt water impact doesn’t seem to have enough energy to make a far-reaching tsunami. Bad for the fish nearby and it’d certainly light up the sky for miles around, but that would be it. But, if we wait enough, eventually we will come across a large rock with our name on it. ---
**Author:** ![TruCelt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/trucelt/32/523_2.png) [@TruCelt](https://boards.straightdope.com/u/TruCelt)\ **Post date:** [June 28, 2011, 7:48pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/27 "2011-06-28T19:48:14Z")
If an asteroid that size/composition hit the moon though, I’m thinking it would end life as we know it, and without the merciful swiftness of an Earth impact for those affected. How close to the moon did it come? ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [June 28, 2011, 7:54pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/28 "2011-06-28T19:54:24Z")
Why exactly would a bus size piece of rock hitting the moon kill us? ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [June 28, 2011, 7:55pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/29 "2011-06-28T19:55:48Z")
> [@Gray\_Ghost](#): > > It does break up in the atmosphere, but enough is left of the impactor for the fragments to have about 220 kt of impact energy. That forms a crater about 1/3 of a mile across and a few hundred feet deep. You wouldn’t want to be within a mile or 2 of the impact, but 10 miles away would be fine, per the model showing no resulting fireball from the impactor. So how much of a bullet would it have been? ---
**Author:** ![TruCelt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/trucelt/32/523_2.png) [@TruCelt](https://boards.straightdope.com/u/TruCelt)\ **Post date:** [June 28, 2011, 9:00pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/30 "2011-06-28T21:00:19Z")
Keep in mind that the moon has no atmosphere to reduce the impact. Not kill necessarily. Just knock it out of whack, change the tides, which would pretty much change everything else. Might even be for the better in the long run, but any change at all would be choas for decades. . . Does anyone know how much impact energy would be reuired to alter the moon’s orbit? ---
**Author:** ![brewha](https://avatars.discourse-cdn.com/v4/letter/b/91b2a8/32.png) [@brewha](https://boards.straightdope.com/u/brewha)\ **Post date:** [June 28, 2011, 9:10pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/31 "2011-06-28T21:10:12Z")
> [@TruCelt](#): > > Does anyone know how much impact energy would be reuired to alter the moon’s orbit? According to that article there was never any chance of it hitting the moon, and even if it had it wouldn’t have burned up in the atmosphere. Not much of a bullet! ---
**Author:** ![Cat\_Whisperer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cat_whisperer/32/4839_2.png) [@Cat\_Whisperer](https://boards.straightdope.com/u/Cat_Whisperer)\ **Post date:** [June 28, 2011, 9:13pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/32 "2011-06-28T21:13:53Z")
> [@CalMeacham](#): > > What would a good comet strike look like?\ Getting just a small piece or two of the head, I suppose. ---
**Author:** ![bup](https://avatars.discourse-cdn.com/v4/letter/b/6bbea6/32.png) [@bup](https://boards.straightdope.com/u/bup)\ **Post date:** [June 28, 2011, 9:19pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/33 "2011-06-28T21:19:54Z")
> [@TruCelt](#): > > Keep in mind that the moon has no atmosphere to reduce the impact. > > Not kill necessarily. Just knock it out of whack, change the tides, which would pretty much change everything else. Might even be for the better in the long run, but any change at all would be choas for decades. . . Using small binoculars (about 1xmagnification), I can see pretty big craters on the moon that indicate we’ve already survived some big impacts. I don’t think anyone’s ever blamed them for mass extinctions. > [@](#): > > Does anyone know how much impact energy would be reuired to alter the moon’s orbit? It depends how big a change you want. ---
**Author:** ![Alka\_Seltzer](https://avatars.discourse-cdn.com/v4/letter/a/c89c15/32.png) [@Alka\_Seltzer](https://boards.straightdope.com/u/Alka_Seltzer)\ **Post date:** [June 28, 2011, 9:29pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/34 "2011-06-28T21:29:08Z")
> [@TruCelt](#): > > Keep in mind that the moon has no atmosphere to reduce the impact. > > Not kill necessarily. Just knock it out of whack, change the tides, which would pretty much change everything else. Might even be for the better in the long run, but any change at all would be choas for decades. . . No, a rock that size would just leave a fair size crater, it wouldn’t measurably alter the moon’s orbit. Asteroids that size hit the Earth and Moon every century or so. I don’t know if you mis-read it, it was 20 meters across, not 20 miles. ---
**Author:** ![Winston\_Bongo](https://avatars.discourse-cdn.com/v4/letter/w/a9adbd/32.png) [@Winston\_Bongo](https://boards.straightdope.com/u/Winston_Bongo)\ **Post date:** [June 28, 2011, 9:48pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/35 "2011-06-28T21:48:43Z")
If it had hit the earth, is there any chance it would have landed in the Mariana Trench? ---
**Author:** ![Diceman](https://avatars.discourse-cdn.com/v4/letter/d/22d042/32.png) [@Diceman](https://boards.straightdope.com/u/Diceman)\ **Post date:** [June 29, 2011, 11:58am UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/36 "2011-06-29T11:58:41Z")
If it did, it would only stay for about 20 minutes. ---
**Author:** ![Who\_me\_1](https://avatars.discourse-cdn.com/v4/letter/w/958977/32.png) [@Who\_me\_1](https://boards.straightdope.com/u/Who_me_1)\ **Post date:** [June 29, 2011, 1:56pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/37 "2011-06-29T13:56:54Z")
According to that article there was never any chance of it hitting us, and even if it had it would have burned up in the atmosphere. Not much of a bullet! ---
**Author:** ![Cat\_Whisperer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cat_whisperer/32/4839_2.png) [@Cat\_Whisperer](https://boards.straightdope.com/u/Cat_Whisperer)\ **Post date:** [June 29, 2011, 2:55pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/38 "2011-06-29T14:55:19Z")
I note that their lists were very sloppily done. Not much for the bullets. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [June 29, 2011, 3:08pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/39 "2011-06-29T15:08:22Z")
> [@brewha](#): > > According to that article there was never any chance of it hitting the moon, and even if it had it wouldn’t have burned up in the atmosphere. Not much of a bullet! The Moon has no atmosphere. Or is that what you meant? ---
**Author:** ![Greg\_Charles](https://avatars.discourse-cdn.com/v4/letter/g/839c29/32.png) [@Greg\_Charles](https://boards.straightdope.com/u/Greg_Charles)\ **Post date:** [June 29, 2011, 4:00pm UTC](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072/40 "2011-06-29T16:00:49Z")
> [@bup](#): > > Using small binoculars (about 1xmagnification), I can see pretty big craters on the moon that indicate we’ve already survived some big impacts. Small 1x power binoculars … your eyes? [Previous page](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072.md?page=1) [Next page](https://boards.straightdope.com/t/asteroid-passes-within-7500-miles-of-us/587072.md?page=3)