Unknown 7m Asteroid Almost Impacted Earth 289
xp65 writes "A previously undiscovered asteroid came within 14,000 km of Earth — just over one Earth diameter, 1/30 the lunar distance — on Friday, and astronomers noticed it only 15 hours before closest approach. On Nov. 6 at around 16:30 EST, a 7-meter asteroid, now called 2009 VA, came only about 2 Earth radii from
impacting our planet. This is the third-closest known non-impacting Earth approach on record for a cataloged asteroid. The asteroid was discovered by the Catalina Sky Survey and was quickly identified by the Minor Planet Center in Cambridge MA as an object that would soon pass very close to the Earth. JPL's Near-Earth Object Program Office also computed an orbit solution for this object, and determined that it was not headed for an
impact." The article notes, "On average, objects the size of 2009 VA pass this close about twice per year and impact Earth about once every 5 years."
Hardly noticeable if it impacted (Score:5, Informative)
Re:How Much Damage? (Score:5, Informative)
It would most likely bursts into a cloud of fragments at an altitude of 8980 meters. Minor local damage might occur if a larger fragment happens to hit a house.
http://www.lpl.arizona.edu/impacteffects/cgi-bin/crater.cgi?dist=0.001&diam=7&pdens=&pdens_select=8000&vel=17&theta=45&tdens=2500&tdens_select=0 [arizona.edu]
Comment removed (Score:4, Informative)
Re:How Much Damage? (Score:5, Informative)
Re:How Much Damage? (Score:5, Informative)
Re:OH NOES!!! (Score:3, Informative)
We track 90% of the near-earth objects that have a possibility of causing global catastrophe. While there's certainly room for improvement, we've actually been doing quite a lot of looking.
To give a sense of scale, global-catastrophic asteroids are 1 km in diameter; this one was 7 m.
Re:Hardly noticeable if it impacted (Score:3, Informative)
I was about to say - missing a 7 meter asteroid passing at that distance is roughly akin to missing a pea in the middle of the highway you're currently doing 60MPH down. In rush hour traffic.
Re:How Much Damage? (Score:3, Informative)
As a nitpick, that's actually 40 kiloton equivalent (0.40 x 10^-1 megatons = 0.04 megatons = 40 kilotons). You don't get a 400 kiloton airburst until you go up to 15m diameter [arizona.edu]
Re:How Much Damage? (Score:3, Informative)
40 Kiloton, 40. Not 400.
Re:LHC (Score:1, Informative)
Are you kidding? That thing can't even stand up to a bird with a bagel.
It was a baguette, you insensitive clod!
Re:"Impact" Earth? (Score:5, Informative)
Hmmm... well, I realize that checking a dictionary first would've been a lot of work, but here's what m-w has to say about it [merriam-webster.com]. Note that the first entry is for the verb "impact".
Re:How Much Damage? (Score:4, Informative)
What about tsunamis?
Well, other posters have established (well, speculated) that the impact energy would be significantly less than the Hiroshima bomb... there's a link elsewhere in this thread which discusses that a meteorite with a diameter of 10m on impact (meaning significantly larger than 10m when it entered the atmosphere) would have about the explosive force of the Hiroshima bomb.... The number that people are throwing around seems to be around 30-35% of the impact energy, if it hit the ground with a diameter of 7m. I'm going to have to rely on other peoples' calculations, but it does seem to be supported by others.
Let's assume 33%, because the math's easy. The Hiroshima bomb exploded with a peak force of about 18kt, according to Wikipedia. 1/3 of that is 6kt. This is an important number... by any account, it's a big explosion. The largest conventional explosive currently in use in the world is the US-built Massive Ordnance Penetrator (MOP) with a blast yield of 13.6 tonnes... we're talking 400 times more explosive force. If it hit a city with that kind of force, it would do extensive damage.
But let's put this in perspective, and actually answer your question: On May 5, 1954, the US Navy set off Castle Yankee, part of the Operation Castle set of nuclear weapons tests, on the surface of the ocean off Bikini Atoll in Micronesia. The yield of this bomb was 13.5mt, more than 2000x more powerful than this meteorite could possibly be, even assuming that it did not shed any mass at all during entry. Castle Yankee did not cause a tsunami. The likelihood of such a meteorite causing a tsunami is slim to nil.
Re:How Much Damage? (Score:5, Informative)
According to this (I didn't verify any facts) - http://wiki.answers.com/Q/How_much_of_the_Earths_surface_is_inhabited_by_humans [answers.com]
About 1% of the surface is inhabited. So, an impact should directly affect people about once every 500 years. Maybe it's the next time?
Re:How Much Damage? Not much! (Score:4, Informative)
Self-gooooooooaaaaaaal! (Score:3, Informative)
(If the link breaks, the book is Merriam-Webster's dictionary of English usage)
The link is not broken, and here are two snippets that jumped right out at me:
"But since part of the criticism seems to be based on the erroneous notion that that the verb is derived from the noun based on functional shift, we must first pursue a little "
and
"But impact was a verb in English before it was a noun."
and
"This is not a case of a verb derived from an earlier noun."
In summary:
While impact as a verb has been around for a long time, it was not until the '80's that it began to be used in business and political contexts as a buzzword substitute for 'affect'.
To the extent that the link supports that view (m-w says you can avoid impact(v) if you like, but does not suggest it's in any way incorrect, and has numerous examples from the 70s), it's talking about the figurative uses of the verb. Whereas the usage in question here is the literal use of the verb, and is 100% irrefutably correct usage since 1601.
So if that usage "sounds wrong", I think the advice of Meriam-Webster's Dictionary of English Usage is to get over yourself and your incorrect notions.
Re:How Much Damage? (Score:5, Informative)
Asteroid Impact Calculator [arizona.edu]. Handy thing to have bookmarked, in the event that the astronomers see the next one from far enough off.
It's impossible to be sure what the density and angle of incidence would have been in this case, as this sort of data isn't usually published. It's also impossible to be sure of composition, as that depends on where the asteroid was from. Thus, any results you DO get from the calculator are either meaningless (too much garbage in) or extreme values only.
Having said that, such calculators are fun when they find truly massive craters. The crater under the antarctic ice, for example, is so large that the Earth was unlikely to have ever been hit by something that big in the past 4 billion years. Antarctica is very modern, in comparison.
Re:OH NOES!!! (Score:3, Informative)
Apophis is likely to be 100,000 times brighter
(300 / 7)^2 = about 1,800, which is not very close to 100,000
Re:OH NOES!!! (Score:3, Informative)
As a comparison for the non-astronomers:
In college, we had a pretty sweet 0.8m diameter scope. The limiting resolution of that was about 12 magnitude. Magnitude goes up as powers of ten. So 16th magnitude would be 10^4 times dimmer than what we could see with that scope. Even a 1m scope would have issues with that. You'd need fantastic conditions and very, very good mechanics to be able to take exposures long enough to reliably capture 16 magnitude.
Take into account that we can only reliably detect asteroids based on lateral movement against the constant stars in the background, and you have situations like this where the asteroid is nearly undetectable. Keep in mind that the only light is from the sun, and the asteroid is likely as reflective as pavement. Then that reflected light radiates out spherically, and the intensity fades out as one over the square of the distance between the asteroid and the telescope.
There are plenty of asteroids we'll never be able to reliably detect and track. As long as we do so with the ones over 20m, we should be ok. We'll definitely see most of those in time to wring our hands and turn to prayer, for lack of any better way to deal with them.
Re:OH NOES!!! (Score:2, Informative)
Perhaps a better question is: if we can detect the one that's about to hit us, are we likely to be able to do anything about it?
no