I wonder if they have a set size an asteroid has to be before they consider it "potential" to cause damage if there was a collision with earth but then I guess we don't always know the composition of them.... any one know much on that?
sirchick: Any asteroid bigger than about 10 meters across can cause major regional damage.
At ~10 meters an asteroid can destroy a city.
At ~30 meters, it can destroy a small country (equivalent to a 15 megaton nuke or so).
At ~100 meters, it can cause low to moderate planet-wide damage.
At ~1000 meters, it can cause severe planet wide damage.
At ~5000 meters, mass extinction occurs.
At ~50000 meters, not much but bacteria survive.
At ~500000 meters the entire crust of the planet and upper mantel liquifies, extinguishing all life.
...the Tunguska event object, which is currently believed to be only 100m diameter.
gopher65 - you have to specify your density/velocity assumptions to make your table valid.
The amount of energy in a strike is mass X velocity squared. The mass of an asteroid of a specific size is determined by its density, which can vary all over the map. Even more important is its velocity, which is essentially determined by its orbit. A slow moving quite massive object could do considerably less damage than a much smaller, more dense, fast moving object. The impact velocities are incredibly variable. A hyperbolic orbit moving in the opposite direction of the earths orbit could impact as fast as 20K kilo/sec. A co-orbital object could hit us at a few hundred kilo/sec or even slower.
So unless you are talking absolute worse case, iron-nickel asteroids traveling at 20,000 kilo/sec, your table is misleading.
angle, and target material
gopher65 - you have to specify your density/velocity assumptions to make your table valid.
sirchick
Dec 21, 2012They track hundreds if not thousands. But if we cannot see them yet and they are coming to earth they must be alot smaller or even further away.....if we can see the 140m asteroid... and obviously (to some extent) the smaller they are the less we have to worry.
Naturally that ain't 100% correct, they don't even have to hit the earth surface to cause destruction on earth.
I wonder if they have a set size an asteroid has to be before they consider it "potential" to cause damage if there was a collision with earth but then I guess we don't always know the composition of them.... any one know much on that?