Would breaking up an asteroid before it hit Earth reduce the damage if all of its mass still hit?

[nematode]

I have found there is a common assumption that a big asteroid hitting would be worse (like the dinosaur one) than the same mass and speed of much smaller ones hitting and mostly burning up/exploding in the atmosphere before reaching the ground.  In terms of heating up the atmosphere to an unlivable temperature, are they any different?  I would think a given mass moving at a given speed would impart the same kinetic energy to Earth and its atmosphere regardless of whether it was a big one or an equivalent mass of small ones hitting at once.  If the small ones would do less damage I am curious why, since the total kinetic energy should be the same.

In other words would there be any advantage of a meteor defense system if it broke up a large asteroid but all of the pieces would still hit Earth at the same speed as the initial asteroid?  I realize if you broke it up further out some of the pieces would miss Earth and that would be a benefit, but that is not my scenario.

Thanks.

[swansont]

You wouldn’t have all the energy deposited in the same place. Dispersing it would likely reduce the overall damage. Energy deposited in the both the atmosphere and ground over a wider area, less energy at the primary impact point.

[nematode]

What made me think of it was an article I read awhile ago that stated the dinosaur asteroid heated the entire atmosphere to over 400 degrees F, basically killing everything instantly that was not underground/in the mud or under water at the time.  It is of course quite possible that article was wrong.  I think it was trying to explain why large but submerged predators like crocodilians would survive such an event.  Another aspect was their cold blooded metabolism, which allowed them to survive a long period of following global cooling due to ash in the air, and lack of food, despite being large predators. Their metabolism could practically stop, like frogs hibernating in winter, and they would be none the worse for wear.  (What they ate when they woke up, I have no idea.)

I agree local impact would be worse for a large body, I am thinking more of overall planetary impact of an extinction level event.  Could it be avoided by breaking up the asteroid before it hit?  I am puzzled as to why dispersing it would reduce the overall damage.

[iNow]

There's not one correct answer here other than, "it depends."

What is the size of the starting asteroid? Where would it have impacted? What are the sizes and velocities of the broken up pieces? Where do they impact? 

Details matter here on questions like this, and the answer to your question is maybe, maybe not. 

[swansont]

 

4 minutes ago, nematode said:

  I am puzzled as to why dispersing it would reduce the overall damage.

Consider that a hurricane contains a lot more energy than a nuclear bomb and while hurricanes cause serious damage, they do not flatten cities. It’s dispersed in both area and time. 

Small bits of a broken-up asteroid will burn up in the atmosphere and never impact the earth. 

[nematode]

24 minutes ago, swansont said:

 

Consider that a hurricane contains a lot more energy than a nuclear bomb

That's very interesting, I did not know that.

[nematode]

24 minutes ago, swansont said:

 

Consider that a hurricane contains a lot more energy than a nuclear bomb

That's very interesting, I did not know that.

[studiot]

1 hour ago, nematode said:

What made me think of it was an article I read awhile ago that stated the dinosaur asteroid heated the entire atmosphere to over 400 degrees F

 

The back of my envelope says

 

Mass of atmousphere  5 x 10¹⁸ kg

475 J / ^oF/kg

Temp rise from 100F to 400F   (temps averaged a little higher in the Cretaceous)

 

Total energy required =

 

5x 10¹⁸ x 300 x 475  =  7 x 10²³ Joules.

Edited August 28 by studiot

[J.C.MacSwell]

The square cube law applies here. Smaller objects of the same substance will have proportionately more frontal and surface area for their volume and mass, so will generally dissipate their kinetic energy relatively faster in the atmosphere prior to colliding with the Earth.

[studiot]

Some further figures

 

The estimated mass of the Chixelub metoeroid is between 10¹⁵ and 10¹⁷ kg  say 10¹⁶

 

The estimated speed of this sized asteroid is 2 x10⁴ m/s

 

Thus its kinetic energy is  (10¹⁶ x2 x2 x10⁸) / 2J   =2 x10²⁴ Joules

 

So the meteroid had enough energy to heat the atmousphere up to these levels.

 

 

[nematode]

Quote

The square cube law applies here. Smaller objects of the same substance will have proportionately more frontal and surface area for their volume and mass, so will generally dissipate their kinetic energy relatively faster in the atmosphere prior to colliding with the Earth.

Wouldn't that heat up the atmosphere more/faster than a big rock landing in, say, the ocean?

I would think the energy to heat water to boiling would be much greater because of the energy density of water compared to air.  If all the energy was dissipated in the air, I would expect more total heating of the air than if the rock landed in the water and converted a lot of it to steam/converted underlying rock to magma.

Edited August 28 by nematode
Added quote since post appeared out of order

[swansont]

25 minutes ago, nematode said:

Wouldn't that heat up the atmosphere more/faster than a big rock landing in, say, the ocean?

I would think the energy to heat water to boiling would be much greater because of the energy density of water compared to air.  If all the energy was dissipated in the air, I would expect more total heating of the air than if the rock landed in the water and converted a lot of it to steam/converted underlying rock to magma.

The energy is the same, but it does take more energy to heat up water. An ocean impact can produce a tsunami.

The atmosphere is pretty big, so that heating (as I’ve said) will be spread out in space and time.

[studiot]

The Chicxelub meteorite  impacted into the proto Caribbean, which was larger then.

It penetrated up tp 19 km into the crust, driving molten rock down into the mantle.

Today it has a 3 ring structure, the outer ring being 195 km across.

So the majority of its energy was extended driving deep into the earth and melting the rock to suevite (A breccia formed by shock metamorphism whose angular fragments are set in a glassy matrix).

 

Edited August 28 by studiot

[Ken Fabian]

My understanding is that for a very large object it won't help to break it into smaller ones - it sound like nothing is going to make it better. A lot of the more distant damage from Chicxulub came from atmospheric heating - hot enough to spontaneously start forest fires on the other side of the world. That was from hot ejecta thrown out to space and falling back as well as radiating downwards; I think if broken apart to small enough to not throw ejecta it would cover the world in impacts and the heat would still transfer to atmosphere.

https://www.lpi.usra.edu/science/kring/Chicxulub/

Edited August 29 by Ken Fabian

[swansont]

1 hour ago, Ken Fabian said:

My understanding is that for a very large object it won't help to break it into smaller ones - it sound like nothing is going to make it better.

It’s a matter of degree. It can be better but not avoid a bad outcome. Heating the atmosphere to 199 C instead of 200 C is better, 999 km^2 of impact crater is better than 1000. 

But the question asked was if you reduce damage.

As to whether there’s any advantage of a defense system, it’s going to be “it depends” as iNow said. Above a certain size, you aren’t going to avoid a cataclysm.

[studiot]

12 hours ago, Ken Fabian said:

My understanding is that for a very large object it won't help to break it into smaller ones - it sound like nothing is going to make it better. A lot of the more distant damage from Chicxulub came from atmospheric heating - hot enough to spontaneously start forest fires on the other side of the world. That was from hot ejecta thrown out to space and falling back as well as radiating downwards; I think if broken apart to small enough to not throw ejecta it would cover the world in impacts and the heat would still transfer to atmosphere.

https://www.lpi.usra.edu/science/kring/Chicxulub/

If the meteorite had broken up into fragments we would have expected to find evidence of multiple smaller impact sites.
There is no evidence of this.
Just one large nearly perfectly round crater.

 

Folks often concentrate on the sexy impact period of such a disaster.

The truth is that the impact itself lasted a very short time, as did the temporary heating of the atmousphere and other immediate effects.

The impact itself was sufficiently large as to melt the limestone sediment rock to a glassy material and spray large quantities of glass beads into the air.

As a marine disturbance it also spawned a series of tsunamis.

In the days following the impact the heavier material fell back to earth and has been found over a wide area of the US, Mexico and beyond.

The finer particles remained in the sir for much longer, weeks, months ever years.

The resulting winter caused freezing temperatures, rather than elevated ones.

Evidence for this has been found in studies of the stems and leaves of plants preserved at the moment of impact. They have had ice crystals growing inwards and bursting the cell walls.

 

[Sensei]

People are missing one important factor: when the asteroid disintegration will occur.

The Earth, moving at ~30 km/s around the Sun, and a diameter of ~12742 km, moves away by its entire diameter in just ~ 7 minutes.

In order for all the parts of a disintegrated asteroid to hit the Earth, the disintegration would have to occur in less than just a minutes before the final impact. Which is highly unlikely, if humanity makes any attempt.

Most of the Earth's surface is ocean. Most asteroids and meteors that hit the Earth's surface end up in the sea. The impact of a large object in the ocean creates a high tsunami, and the energy is dissipated over a very large area, and coastal areas are most at risk.

 

[Ken Fabian]

 

 

16 hours ago, studiot said:

If the meteorite had broken up into fragments we would have expected to find evidence of multiple smaller impact sites.
There is no evidence of this.
Just one large nearly perfectly round crater.

 

Folks often concentrate on the sexy impact period of such a disaster.

The truth is that the impact itself lasted a very short time, as did the temporary heating of the atmousphere and other immediate effects.

The impact itself was sufficiently large as to melt the limestone sediment rock to a glassy material and spray large quantities of glass beads into the air.

As a marine disturbance it also spawned a series of tsunamis.

In the days following the impact the heavier material fell back to earth and has been found over a wide area of the US, Mexico and beyond.

The finer particles remained in the sir for much longer, weeks, months ever years.

The resulting winter caused freezing temperatures, rather than elevated ones.

Evidence for this has been found in studies of the stems and leaves of plants preserved at the moment of impact. They have had ice crystals growing inwards and bursting the cell walls.

 

I wasn't claiming it arrived broken up, just suggesting it wouldn't have saved the planet from extreme effects if it had. Less material overall without the ejecta but the material would be arriving with equivalent - enormous -  energy.

Extreme heating enough to start fires around the world first was short lived - a few days at most - but catastrophic by itself. It was followed by extreme global cooling in "nuclear winter" style for a few years, followed by a millennia or more of global warming from the raised CO2 from carbonate rich rock being vaporized plus all that combustion.

From the link - their attempt at modeling the wildfires, or at least, of the downwelling heat extreme enough to start wildfires - not fires in oceans of course but presumably any islands. I would expect that even outside those areas there would be extreme heat -

Quote

This is a movie that shows the spread of wildfires that were generated by the Chicxulub impact event 65 million years ago when large numbers of plants and animals, including dinosaurs, were extinguished.  The fires were generated after debris ejected from the crater was lofted far above the Earth’s atmosphere and then rained back down through the atmosphere.  Like countless trillions of meteors, the debris heated the atmosphere and surface temperatures so high that vegetation on the ground was ignited.  Impact debris racing through the atmosphere was concentrated above the impact site (now Mexico) and the opposite side of the Earth (now the Indian Ocean).  The Earth rotated beneath the returning plume of impact ejecta, so that the first migrated to the west.  Most of the fires were ignited in the first day after the impact, although material continued to fall back into the atmosphere for another 3 days.  This movie is an outcome of a study by David A. Kring and Daniel D. Durda, 2002, Trajectories and distribution of material ejected from the Chicxulub impact crater:  Implications for postimpact wildfires, Journal of Geophysical Research 107, 22p.

 

[studiot]

17 hours ago, Ken Fabian said:

 

 

I wasn't claiming it arrived broken up, just suggesting it wouldn't have saved the planet from extreme effects if it had. Less material overall without the ejecta but the material would be arriving with equivalent - enormous -  energy.

Extreme heating enough to start fires around the world first was short lived - a few days at most - but catastrophic by itself. It was followed by extreme global cooling in "nuclear winter" style for a few years, followed by a millennia or more of global warming from the raised CO2 from carbonate rich rock being vaporized plus all that combustion.

From the link - their attempt at modeling the wildfires, or at least, of the downwelling heat extreme enough to start wildfires - not fires in oceans of course but presumably any islands. I would expect that even outside those areas there would be extreme heat -

 

Can you explain woldfires over the Ocean ?

 

@Sensei  makes a very good point.  +1

 

20 hours ago, Sensei said:

Most of the Earth's surface is ocean. Most asteroids and meteors that hit the Earth's surface end up in the sea.

 

One problem a breakup hypoyhesis must answer is this.

The meteoriod had been travelling for up to billions of years, so all the part had plenty of time to achieve the same velocity, even if lightly attached.

So all the parts will have had momenta and energy proportionate to their masses, and even if only touching wouldhave continued together since there is no friction is space.

So a breakup mechanism is required.

The only reasonable one I can think of would be impact by another object, which as Sensei points out, would have had to occur fairly close to the impact with Earth as the meteroid was travelling at circa 20km/second.
Otherwise much of the material would have been scattered clear of Earth by the side impact.
Clearly it would have to have been a side impact.

[Ken Fabian]

1 hour ago, studiot said:

Can you explain woldfires over the Ocean ?

It looks to me like the modeling shows where the high ejecta would have gone, where the downwelling heat from that would go. I think it is a case of poor wording of that as mapping of wildfires produced rather than more correctly where there would be heat capable of spontaneously starting wildfires. Essentially it is mapping  the cause of what @nematode mentioned -

On 8/29/2024 at 2:09 AM, nematode said:

an article I read awhile ago that stated the dinosaur asteroid heated the entire atmosphere to over 400 degrees F

- which the modeling shows was not evenly distributed. Whether that temperature is a global average or whether everywhere got at least that hot but other parts were a lot hotter (which seems likely) isn't clear.

1 hour ago, studiot said:

So a breakup mechanism is required.

I don't think anyone is saying it did break up, just asking if it would be "better" if it were broken up deliberately, as a meteor defense option.

[Sensei]

12 hours ago, studiot said:

One problem a breakup hypoyhesis must answer is this.

The meteoriod had been travelling for up to billions of years, so all the part had plenty of time to achieve the same velocity, even if lightly attached.

So all the parts will have had momenta and energy proportionate to their masses, and even if only touching wouldhave continued together since there is no friction is space.

So a breakup mechanism is required.

The only reasonable one I can think of would be impact by another object, which as Sensei points out, would have had to occur fairly close to the impact with Earth as the meteroid was travelling at circa 20km/second.
Otherwise much of the material would have been scattered clear of Earth by the side impact.
Clearly it would have to have been a side impact.

The velocity of Halley's comet relative to Earth is one of the highest in the Solar System ~ 70.56 km/s.

https://en.wikipedia.org/wiki/Halley's_Comet

 

Twice a year the Earth passes through the remains of Halley's comet. In early May and late October.

 

  

56 minutes ago, Sensei said:

So a breakup mechanism is required.

Comets are heated and evaporate as they fly past the Sun, which slightly alters their orbit and breaks them into smaller pieces.

Edited September 1 by Sensei

[studiot]

3 hours ago, Sensei said:

The velocity of Halley's comet relative to Earth is one of the highest in the Solar System ~ 70.56 km/s.

https://en.wikipedia.org/wiki/Halley's_Comet

 

Twice a year the Earth passes through the remains of Halley's comet. In early May and late October.

 

  

Comets are heated and evaporate as they fly past the Sun, which slightly alters their orbit and breaks them into smaller pieces.

True but irrelevent.

Halley's is an ice comet.

The irridium signature in the debris of Chicxelub points to a rocky/metallic asteriod.

 

Quote

The main difference between asteroids and comets is their composition, as in, what they are made of. Asteroids are made up of metals and rocky material, while comets are made up of ice, dust and rocky material. Both asteroids and comets were formed early in the history of the solar system about 4.5 billion years ago. Asteroids formed much closer to the Sun, where it was too warm for ices to remain solid. Comets formed farther from the Sun where ices would not melt. Comets which approach the Sun lose material with each orbit because some of their ice melts and vaporizes to form a tail.

 

https://coolcosmos.ipac.caltech.edu/ask/181-What-is-the-difference-between-an-asteroid-and-a-comet-

 

[Sensei]

48 minutes ago, studiot said:

True but irrelevent.

Halley's is an ice comet.

The irridium signature in the debris of Chicxelub points to a rocky/metallic asteriod.

You came up with Chicxelub, not the OP. OP asked about breaking asteroid. I just extended it to any space object and pointed out that comets can have much higher velocity.

 

A metallic asteroid with mass m₁ and velocity relative to Earth v₁ = 20 km/s has kinetic energy:

[math]\frac{1}{2} m_1 v_1^2[/math]

An ice comet with mass m₂ = m₁ / 8.6 (the difference between the density of iron and the density of ice) = 0.116 m₁, and v₂ = 70.56 km/s has kinetic energy:

[math]\frac{1}{2} m_2 v_2^2[/math]

The overall difference between them:

[math]\frac{\frac{1}{2} m_2 v_2^2}{\frac{1}{2} m_1 v_1^2}=\frac{0.915}{7.874} (\frac{70.56}{20})^2=1.45[/math]

(if they are the same size/volume)

Edited September 1 by Sensei

[studiot]

32 minutes ago, Sensei said:

You came up with Chicxelub, not the OP. OP asked about breaking asteroid. I just extended it to any space object and pointed out that comets can have much higher velocity.

Ok perhaps fair enough  but

On 8/28/2024 at 4:19 PM, nematode said:

I have found there is a common assumption that a big asteroid hitting would be worse (like the dinosaur one) ...........