Thread: asteroid impact

Ok, I know that blowing up an asteroid on a collision course with the earth will not change the energy of the asteroid. But can someone explain why having one big impact is better than hundreds of little ones. The smaller fragments of the incoming asteroid would increase the surface area impacting the atmosphere and hence burn up more and hit the ground less. Wouldn't they?

Originally Posted by coxmic

Ok, I know that blowing up an asteroid on a collision course with the earth will not change the energy of the asteroid. But can someone explain why having one big impact is better than hundreds of little ones. The smaller fragments of the incoming asteroid would increase the surface area impacting the atmosphere and hence burn up more and hit the ground less. Wouldn't they?

I think you would try to alter the path just a little bit. If the asteroid was 100% going to hit the earth and we had enough warning could we push the asteroid's path over just a little bit so that it is no longer on course with the earth?

Mine is not the end all of this subject. there are variables. Some of the potential impactors are not solids... It has been observed and confirmed that some are a rubble pile. Loosely held together and easy to dismantle. Just as one of Mars's moons is doomed to fall inwards to be broken into a ring of debris. Not much risk. Its a small mass object. The mention of energy is important. A broken mass of many components is as dangerous as one. The damage and heat transfer directly into a awful mess. The safest option is to gently guide the potential impactor away...gentle and with little energy required. To make it miss is the best option.

if a large object is broken into smaller pieces, then each of those small pieces will have a lower terminal velocity than the larger object would have had, due to their lower mass to air resistance ratio thing, so will do less damage upon impact.

there is an idea that a ship could be sent to an approaching asteroid, containing lots of robot diggers that could just dig, and throw out material from the asteroid, until it was gone.

If you can get only thousands of small peices, that will reduce total damage, even if the the original impact would have been in a thinly populated location. The rub is a few large peices are likely to be among the many small peices. A single large piece could kill a million people. Even robot diggers might not succeed in breaking up some of the tough large peices.
The suggestions of the other posters has the downside that you may change a near miss to a hit. What is best is a hard call. Neil

Thousands of small peices will reduce total damage, even if the the original impact would have been in a thinly populated location. Many small piece means, some, perhaps many of them will miss Earth. The rub is a few large peices are likely to be among the many small peices. A single large piece could kill a million people. Even robot diggers might not succeed in breaking up some of the tough large peices. Neil

Yes Neil i agree... So the idea of deflecting away at such a distance as to eliminate all risk. Science is on the cusp of being able to do that. The only problem is political motivation... Its all about the money.

When we see a planet killer headed our way, then what to do would be hard. We need to think this thru. Miss is better than hit, many pieces MAY be less totally destructive that one unimpeded strike. How big? Where? About all I know is a land strike would be more confined than a sea strike (think one continent, not several, in initial destruction). So the need will be urgent and reaction critical. But the odds as to when it hits are extremely low per lifetime, so current preperations need be in the form of insurance and contingency planning and watching nearby objects orbits.

One large impact will have a higher terminal velocity, and be more likely to spread ejecta over a much wider area. Whether one large impact, two half-massed ones, or five smaller ones, it won't make much difference if they're co-located, as the shock waves will combine and the end results will be much the same.

However, let's take this to the extreme, and instead of five masses, let's break it up into 1,000,000 masses spread evenly over one side of the Earth. By way of example, let's take the Chicxulub crater event in Yucatan. The impactor's estimated size is 6 miles in diameter, which gives us a volume of nearly 50 trillion cubic feet. If we divide that by 1,000,000, we have a volume of 50 million cubic feet per each of 1,000,000 pieces, and each of those pieces would have a radius of 158 feet, for a diameter of 317 feet - about the same size as the Barringer Crater in Arizona (also known as Meteor Crater).

Now the diameter of the Barringer Crater is .737 miles, while the diameter of the Chicxulub crater is 110 miles in diameter.

Personally, think a million Barringer Crater events would decimate the Earth!

But let's take that another step, and assume we could break it up into a billion pieces. At this point, the diameter of each would be just one-third of a foot, and would reach terminal velocity in the atmosphere, and spread out over half the surface of the Earth, one would impact every 835 square feet, for a square roughly 30 feet on a side.

Put simply, the Earth would still be scorched for approximately 10 to 15 seconds by a grapefruit-sized source every 30 feet.

We'd survive.

The question is: How in the world do we split a 6-mile asteroid into a billion pieces?

Hi Mugaliuns: Your arithmetic is very convincing for large impactors. We should not attempt to blow them up. Blowing up small impactors, however might reduce the distruction. How about a 60 meter asteroid? radius 30 meters. Volume 4/3 times 3.14 times 30 times 30 times 30 = 4.19 times 27,000 = 113,000 cubic meters. 113 peices of equal size of 1000 cubic meters = cubes 10 meters on an edge. These would mostly burn up in the atmosphere about 10 seconds apart over a period of 1130 seconds. assuming the peices diverged between being blown up and impacting. Diverged also means some of them, perhaps most of them will miss Earth. Equal size peices is however very improbable, so the largest piece might hit a large city and kill a million people, while odds are only a few hundred people would die from the original 30 meter radius impactor. Worse the 30 meter impactor might have missed Earth, since our path prediction was likely plus or minus 10,000 kilometers at the time we blew it up. Neil