Is The Earth Safe From Rocky Demons Above?

Have you ever looked up into the sky and wondered what was going to drop onto your head? When you look up what do you see? Well if I was to do it now I would see a load of black clouds as I live in the rainy UK  which tends to give me a false sense of security.

The only things that most people think about are planes. But what else is up there? NEOs are up there wandering around in their orbits. NEOs are near Earth objects which consist of meteoroids, asteroids and comets.

NEO Hitting Earth

Meteoroids are rocky bodies about 50 meters across or smaller whose impact with Earth is likely to deliver meteorite samples to the surface, but produce no impact crater. The smallest meteoroids, about the size of grains of sand, produce nothing more than a flash across the sky as they give a lovely display and burn up. if you have never done it, go outside (at night) and look up for an hour. You will see a meteroid flashing across the sky which is well worth getting cold and missing the latest soap.

Asteroids, or minor planets, are rocky bodies larger than 50 meters across. The largest of these known within near-Earth space is 1036 Ganymed, which has an estimated diameter of 41 kilometers (about 25 miles). The second largest is 433 Eros. This 23-kilometer (14-mile) asteroid was the target for the Near-Earth Asteroid Rendezvous (NEAR) mission in 2000.

Whether an object is a comet or an asteroid is found out by looking through a telescope. If a newly discovered object appears fuzzy, then it is a comet. Comets are rock and ice, the ice forming in the outer part of the solar system. When the comets orbit passes close to the sun the ice melts and solar winds push a mixture of gas and dust away causing a tail.

When new observations of a NEO are made, they are submitted to the Minor Planet Centre (MPC) in Massachusetts in the USA. The MPC acts as a clearing house for all new observations. These approved observations are then distributed to the scientific community.

There are two independent centres that use these observations to calculate the risk of any future impacts. One is based in the USA the other in Italy.

In the USA this work is carried out by the Jet Propulsion Laboratory’s Sentry System. Sentry is a highly automated collision monitoring system that continually scans the most current asteroid catalogue for possibilities of future impact with Earth over the next 100 years.

In Italy, the work is carried out by NEODyS, which is based on a continually and (almost) automatically maintained database of near-Earth asteroid orbits. Use the links above to view the output of both systems.

Barringer Impact Crater On Earth

Today, there are around 160 impact craters that have been recognized around the world. If you look further afield,  like the moon for instance, then the impact craters are obvious. The advantage we have over the moon is our atmosphere which tends to burn up any object that comes hurtling towards us. But that is it! The problem comes when the atmosphere isn’t enough to turn the NEO into dust and one hits the ground (without going through any people hopefully).

There is a chance of someone getting hit on their own, but more interestingly and importantly is one hitting the Earth that will cause our civilisation to become extinct. Most of us know that this happened to the dinosaurs and it is believed that a NEO caused it. The devastation caused by a NEO depends on the speed as well as other factors such as whether it is a glancing blow or not but the following is a rough idea of when to take cover and when to kiss it goodbye!

NEOs 50 to 100m in diameter will cause a blast of about 10 to 100 megatons. This will cause local devastation and possible global economic disruption  causing a crater of about 1 km diameter.

Wolfe Creek Australia

The next step is NEOs of a diameter between 100 to 500 meters. These have got a blast of about 100 to 10,000 megatons and create craters up to 5 km wide. This would cause destruction of an area the size of a town or a small state. If it landed in the sea a small tsunami could be produced.

Now we are getting on to the big boys, NEOs of diameters from 0.5 km to 2 km with a massive blast of 10,000 to 500,000 megatons. This will cause a nice pretty, picturesque crater of 20 km wide and some nasty Tsunamis will be produced. A small country would exist no more and the global climate would definitely be high up on the agenda of governments around the world.

If you are interested in the exact results of the hits then this nuclear weapon effects computer (slide rule) may help to give you a better picture.

Or, if you like a video, then the following 10 megaton explosion puts things in perspective.

There are even bigger NEOs out there. With diameters from 2 km to 10 km there really isn’t any point talking about them. But if

Largest Crater Of 100 Km in Manicouagan, Canada

you’re interested it will produce a crater of 20 to 100km and it would basically wipe us out as global events beyond our control uccur. At the moment we can’t defend ourselves against this extinction event, even though we have the technology, but, unfortunately if not the will as the funding for a project is not being provided. If you want to watch what may happen try this interesting film, Asteroid ( Asteroid: The Sky is Falling )

As more and more NEOs are found the odds of being hit by one and the odds of an extinction event have been reduced to about one in 200,000.  This may sound like it will never happen but as more and more NEOs are discovered the odds get worse and one could even be hurtling towards us right now and we know nothing about it.

The point is that it’s only a matter of time until one hits us, it could be right now or it could be in a thousand years but one will hit..

A Near Earth Object called DD45 buzzed the Earth very closely on the second of March 2009. It passed within 70,000 kilometers of the Earth and was just one fifth of the distance from the Earth to the moon, and only twice the distance at which geostationary telecommunications satellites orbit. That is close! It was between 21 and 47 m in diameter and could have wiped out a city. It was only discovered three days before passing its closest point to the earth.

Enterprise Helps? Perhaps Not Just Yet.

The horrible thing is that we just can’t do anything about them at the moment but there are a lot of ideas that we can actually carry out right now but the cash isn’t available. One idea is to launch a nuclear weapon at the NEO.  This, on first look, sounds like a good idea. But it would break the NEO into lots of fragments that could probably do even more damage to the earth. If you fancy watching what Hollywood thinks will happen to a NEO try Armageddon

Another idea which is probably the best, is to intercept the NEO and gently push it so that it will eventually miss Earth. This could take pushing over years. The only problem with this is that we have to see the NEO quite a distance out. There are so many out there that at the moment it is almost impossible to catalogue them all and work out their trajectories. It wouldn’t take too much money to produce a good early warning system and way to divert the NEO. Compared to everything else to do with space this would be a good cheap insurance policy.

A spacecraft that would hover near an asteroid is an idea  and  fire its engines to hold its position. Using the gravitational pull between them the NEO would be slowly towed. It’s a very small force, but you can hover there for a very long time and the combined effect of a small force over a very long time can be enough to deflect the NEO.

One other  idea, which is pretty novel, is to paint the sun side of a NEO with white paint. Because one side is dark and one side is light this would cause a slight change in trajectory and if done far enough away may prevent the impact that we don’t want. if you’re painting on the

Gravity Tractor

NEO then you might as well paint something. How about a Coke ad, a very white one!

We all feel comfortable in our daily lives ignoring the risks (it’s a human thing) but the survival instinct must kick in and we should take hold of our own destiny and this is one of the ways that we can do it. Let’s get something prepared and ready waiting for that big bad NEO that could be a couple of years away waiting to put a big bad hole into our lovely earth.

If you want to read a buuk about this subject try Asteroid: Earth Destroyer or New Frontier?

Some excellent sites are the B612 foundation whose goal is to alter the orbit of an asteroid by 2015.  The Armagh Observatory has a lot of information on NEOs.

Some other related information-

Lincoln Near-Earth Asteroid Research (LINEAR)

Near-Earth Asteroid Tracking (NEAT)

Spacewatch

Lowell Observatory Near-Earth Object Search (LONEOS)

Catalina Sky Survey

Japanese Spaceguard Association (JSGA)

Asiago DLR Asteroid Survey (ADAS)

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