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Unknown 7m Asteroid Almost Impacted Earth
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."
Seven meters just isn't all that big. According to the Earth Impact Effects Program using typical data: No crater is formed, although large fragments may strike the surface. The air blast at this location would not be noticed.
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
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You can use this site to get an estimate.
And I forgot to consider that this was an object of 10 meters or so when it impacted Earth and was thus likely far bigger before entering the atmosphere. An object that was 10 meters before entering the atmosphere would, depending on composition and angle of descent, likely burn away completely before reaching ground. But there might be a midair explosion or fireball sufficient to ignite highly flammable structures.
Nonaggression works!
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. Note that the first entry is for the verb "impact".
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.
According to this (I didn't verify any facts) - http://wiki.answers.com/Q/How_much_of_the_Earths_surface_is_inhabited_by_humans
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?
None. We were hit by one about 10 meters across on October 8th but no one wants to put the story out for some reason. http://neo.jpl.nasa.gov/news/news165.html
It all starts at 0
Asteroid Impact Calculator. 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.
It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)