Can an Asteroid or Comet Impact Earth?

by blackspanielgallery

In the event of a large asteroid hitting the Earth, or a comet hitting the Earth, could it be a major problem? What would happen in an impact from a large asteroid or comet?

Is there a possibility of an asteroid hitting the Earth? Or, of a comet hitting the Earth? There are many books and movies claiming such an event would be catastrophic to the point of being an extinction event. Are these books and movies unrealistic, or could it really happen? And if a large asteroid or comet did hit the Earth, would we, the human race, survive?

Doomsday books and movies are designed to make money. But, such events have happened, and we can learn what might happen by analyzing the geological record.

What Are Asteroids?

Can an Asteroid Hit the Earth?

Asteroids occupy, in general, a belt in our solar system located between Mars and Jupiter.  They are space rocks ranging in size from very minute to hundreds of miles across.   As long as they stay in orbit beyond Mars the Earth is safe.  But, they act gravitationally on each other, and are pulled by the planets.  So, whether pulled out of a stable orbit by a planet, or deflected into a path that might impact the Earth by collisions with each other, asteroids can stray into a collision course with the Earth.


DVDs in Asteroid Impact

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Final Target: Planet Earth

What Are Comets?

Can a Comet Hit the Earth?

A comet is a chunk of ice and rock that is believed to be from the Kuiper Belt. The Kuiper Belt is a region occupied by such objects past the planet Neptune, the planet farthest from the sun.  Some comets, after gravitational interaction and collisions, head in through the solar system in long, elliptical orbits about the sun, or even crash into the sun.  When they get close enough the sun causes gas to be released, and the light and particles from the sun push that gas into a tail.  The tail always points away from the sun, and may have water vapor as a major component.  The path of a comet traveling on such a long orbit can be nudged gravitationally into a collision path with the Earth depending on which planets or other objects it interacts with.


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Deep Impact

How Can an Impact Cause Damage?

Does It Matter if the Impact Is from a Comet or an Asteroid?

First, not every impact is serious.  It depends on the energy released as to how much damage is done.  Size is a consideration, small objects impact the Earth every day, and in great numbers.  Some are so small that they vaporize high in the atmosphere from heat generated by friction.  An object the size of a grain of sand might make a streak of light across the sky, but never reach the ground.


Larger objects can and do reach the ground.  In the air they are called meteors.  On the ground they are called meteorites.  Some meteorites are rocky, others have a high metallic content.


Very large objects, a mile or so across, or even more, bring in lots of energy.  Remember that they came from way out in space, and have been accelerating not only by the gravity of the Earth, but also by the gravity of the sun and possibly some of the other planets.   Think about dropping a ball.  As it falls it accelerates, so the farther it falls the faster it is going when it strikes the ground.  Having come so far, these objects are travelling at high speeds when they reach the ground.  Their energy is calculated as half the product of their mass and the square of their speed.  Energy is conserved, so all of that energy goes somewhere.  Much of it goes into heat.


If the object is solid rock it may reach the ground intact.  If the object has gas, or something that can vaporize into gas, like water, an explosion above the ground can occur.  In either case a crater can form.


A massive explosion, whether it is airborne or on the ground, carves out a crater, throwing debris into the air.  The energy raises the temperature of the atmosphere, and if the object is large enough this rise in temperature can be worldwide, causing forests to incinerate.  Plant and animal life is lost if an impacting object has enough energy, including humans.  Then, the debris that is thrown high in the atmosphere screens out the sun for years, dropping the Earth into cold.  This impacts the initial survivors.  There will be few plants and animals that will survive such an event.  The food chain would be interrupted.


A large enough impact can bore down to the mantle, especially if it occurs where the Earth’s crust is thin.  This would expose molten magma, and release toxic gases.

A Shaken Earth

The Result of Seismic Activity after a Meteor Impact

The impact, whether or not it causes the mantle to be exposed, would cause seismic waves as from an unbelievable earthquake.  These waves could also cause tsunamis depending on where the impact happens to be, and how great it happens to be. 


As seismic waves move out they drop in intensity, much like ripples in water from a rock having been thrown into a pond does.  The energy spreads out.  But, unlike the ripples in a pond, when the waves get half way around the Earth they start to come back together.  Think about a sphere.  If you draw circles starting at the top, they are larger until you get half way around, then smaller as you near the bottom.  When the seismic waves converge opposite the point of impact they can rip open the Earth if intense enough, and allow new mountains to suddenly be pushed upwards.  If this happens at sea a tsunami can form.  

Simulation of an Asteroid Impact

What Could Happen

Do Large Meteor Impacts always Do These Things?

Is Size Important?

Normally we do not see this happen, but a large enough object could cause any or all of the above.  Some large objects have impacted the Earth in the past.  So, the doomsday books and movies are literary license being taken with a real basis.  An extinction event is unlikely in the near future, but possible.


Are Any Large Comets or Asteroids Coming Our Way?

Are We Sure?

Well, collectively objects large enough to do major damage are tracked after being found.  They are collectively called Near Earth Objects, or NEOs.  No one is in a panic regarding any impending impact at the present.


The problem is there is an uncertainty.  Those looking for NEOs look in the most likely places, along and just above and below the plane that includes the asteroid belt and the Kuiper belt.  The problem is farther out there is the Ort Cloud, and it also has large objects, but they are not confined to the same plane as the others.  So, a rare impact from an Ort Cloud object can occur with little warning.  There are too few people and resources to watch the entire sky for NEOs.


Feel safe, but with caution.  The most likely part of the sky shows no danger in the near future, but there is always a chance something will slip through unnoticed.

Near Earth Objects

Spotting NEOs

Can We Save the Earth?

Can We Stop an Impact on Earth from Happening?

There are things that are being proposed, including letting sunlight push large sails that would be attached to an errant NEO so the object would deflect enough to miss the Earth.  Other ideas like pushing NEOs with motors, or directional explosions are also up for consideration.  The earlier we detect an NEO, the more options we have of saving the planet, and our options would have a better chance of working.  So, even if one is found, doomsday is not a necessity.  

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Updated: 08/03/2017, blackspanielgallery
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blackspanielgallery on 07/11/2017

I am pleased this helps explain things.

Veronica on 07/11/2017

I find it particularly interesting that asteroids come from between Mars and Jupiter and comets from Kuiper belt . Entirely new to me.
FACTS ! I love them.

Veronica on 07/11/2017


That is FANTASTIC, Carrington, Cheshire is about 4 miles from Frank's house. Carrington would mean herding enclosure in old English place names so it is not uncommon.

Knights came into being round about 11th C onwards.

blackspanielgallery on 07/11/2017

Right now Mike Brown of Cal Tech is predicting a new planet sized object in the Kuiper Belt that may be large like Neptune and Uranus. There is strong evidence of this. But, the object cannot be claimed unless confirmed. They are aggressively looking.

The other possibility is the highly speculative that we are part of a binary system, with the companion star being a brown dwarf on an elongated orbit, si it periodically disturbs the Kuiper Belt. I believe this one is over an even shorter period. It could be so dim we have not yet spotted it.

Ten, Sedna is a planet size Ort Cloud object that is currently in the Kuiper Belt, or at least that close. So, we can only speculate about these things. But things do upset the balance out there.

DerdriuMarriner on 07/11/2017

blackspanielgallery, What do you think of Emeritus Professor John Whitmire's research suggesting that mass extinctions every 26 million to 27 million years -- over the past 500 million years -- may result from Kuiper Belt objects dislodged by the 20,000-year orbit of Planet X? That would mean a next mass extinction 14 million or 15 million years from now.

blackspanielgallery on 07/11/2017

My ancestors were located in Carrington, Cheshire, Manchester. In particular in Smythe - Carrington castle, and at least one had records showing occupation of knight. Nothing at all on the wives. I suspect it was near Ireland, for I have found three spellings of Carrington, one starting with Ker, .

frankbeswick on 07/11/2017

Manchester at that date! Then you have gone really far back. The earliest records for Beswick, which is a Manchester surname, took me back to 1320, though we were already well established by then? What did you discover?

blackspanielgallery on 07/11/2017

Frank, you usually ell me things I did not know. I have learned much from you. Oh, an interesting thing that happened last night is that my ancestry search brought me to your area. It ended up in the late 1000s.

frankbeswick on 07/11/2017

Thanks, BSG. You have told me facts that I did not know. I always appreciate that.

blackspanielgallery on 07/11/2017

Veronica, thanks. I added this because there is a new television series heavily being advertised, I thought there might be too many people just confused after seeing a doomsday scenario program, and we need to be clear.

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