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It was this information which sent ripples through the scientific community, waking up many scientist to the reality that a cataclysmic collision could accur. Even though it was later discovered that the asteroid XF11 actually posed little threat, it made many people become aware that the Earth is just a sitting duck in the shooting gallery of space.
About four and half billion years ago, our solar system was one big huge cloud of gas and rocks, which was slowly moving together under the influence of gravity. As the material compressed together in the centre, the surrounding gas and rocks started to form into other separate lumps. It was from these that our solar system was formed, with the central mass forming the sun and the separate lumps forming the planets that would encircle the sun. However, there was some material left over, which formed the comets and asteroids that threaten and amaze us today.
Asteroids can be put into two separate classes, the 'big' asteroids and the 'small' meteorites. Meteorites are very common and cause little worry among scientist, about 50 000 collide with the earth every year, most burning up in the atmosphere. However, it is the big asteroids that cause the most devastation and which worry most scientists. There is band of asteroids named the asteroid belt which contains many huge asteroids, some being miles in diameter. This belt is about 300 million miles from the sun and acts as the boundary between the inner solar system and the outer solar system. Occasionally, an asteroid from another origin will cross through this belt and 'knock' some of the larger asteroids onto another orbit, possibly being knocked into a collision course with Earth.
Comets however are very different to asteroids in both appearance and makeup. Asteroids are usually made of solid rock which reflects a very small amount of light, but comets tend to contain a lot of water (ice) which refracts the suns rays making the comet appear to glow. This is why many comets where discovered in pre-telescope history, the fact that they 'glow' makes them very easy to see with the naked eye. Comets are very famous for their tails, which some times hang hundreds of miles behind to comet glowing in the suns rays. The tails are a direct result of the solar wind, which 'blows' the small particles and rocks of the comet into the shape of tail. One strange effect of the solar wind is that the tail always points away from the sun (following the direction of the solar wind), which often means a comet that is moving away from the sun will have its tail in front, the comet will be moving backwards.
This is the ultimate dooms day worry, because if an asteroid no more than 1 mile wide actually hit us, it would mean the end of about 30% of the population. If an asteroid like XF11 did hit the planet, it would be the equivalent to 2 million Hiroshima bombs, or 320'000 megatons of dynamite! This much energy would create a crater 20 miles in diameter, and would throw so much dust and material into the air that the sun would be blocked out for weeks. However, this isn't all that it would do, it would also vaporise any living creature within a hundred miles radius of the collision site, and also throw molten rocks hundreds of miles away from the point of impact.
At the present day our solar system contains millions of asteroids, most of which have not been discovered yet. Some of these asteroids are no more than a few feet in diameter and are almost impossible to spot, however, some asteroids measure up to 281 miles wide. In 1884, an astronomer named J. Palisa discovered an asteroid that measured an incredible 37 miles long and 14 miles wide. This amazing asteroid named Ida was the 243rd to be discovered and is also one of the largest in our solar system. Using a telescopic spectrometer, scientists were able to determine that the asteroid was that of a class S asteroid, which means that the asteroid contains large amounts of iron. However, this asteroid posses little threat to us as it still remains within the asteroid belt, it is far from being on any potential cataclysmic orbit.
It is believed that Ida was part of a larger asteroid that was destroyed in a collision with another asteroid. This giant asteroid was believed to be an enormous 300 miles wide, that's bigger than Ireland.
Even though Ida has almost no chance of colliding with us, we cannot assume that another asteroid of equal magnitude couldn't. Approximately 65 million years ago, an asteroid with a diameter of about 10 miles crashed into the Mexican Ocean, destroying 95% of life on Earth. This included almost all the dinosaurs and many forms of plant life, all of which can only be found in fossilised rocks. If an asteroid the size of Ida did hit our planet, virtually all life would be destroyed. If the impact was in the sea (which is the most likely place) it would create a 2 mile high tidal wave that would hit almost every coast line in the world, a crater the size of Scotland on the sea bed and would throw up enough dust to block out the sun for years. The initial explosion would create a sub-sonic shock wave that would be felt all over the world, an atmospheric shock wave that would travel around the world twice and enough heat to vaporise over a hundred cubic miles of sea water instantly. If the asteroid didn't kill you, the dark, cold, lonely and starving world would.
Although Ida may be incredibly big, our solar system contains an even bigger monster. This amazing asteroid is 278 miles wide, and is called Ceres. It was discovered by an astronomer named G. Piazza and was the first to be ever discovered. However, it still remains within the asteroid belt and orbits the sun at a distance of 251 million miles. Unfortunately it is not alone, there are two other giants that also exist in the asteroid belt, their names being Pallas and Vesta. Pallas measures at 158 miles in diameter and was the 2nd asteroid to be found. The astronomer who found this was also responsible for discovering the 4th asteroid, Vesta, which is 159 miles in diameter.
Order of Discovery |
Name | Radius (miles) |
Distance (millions of miles) |
Albedo | Discoverer | Date |
---|---|---|---|---|---|---|
1 | Ceres | 281 | 254.7 | 0.10 | G. Piazzi | 1801 |
511 | Davida | 103 | 292.6 | 0.05 | R. Dugan | 1903 |
15 | Eunomia | 84 | 243.4 | 0.19 | De Gasparis | 1851 |
52 | Europa | 96 | 285.1 | 0.06 | Goldschmidt | 1858 |
951 | Gaspra | 10x6 | 126.2 | 0.20 | Neujmin | 1916 |
10 | Hygiea | 132 | 289.4 | 0.08 | De Gasparis | 1849 |
243 | Ida | 37x14 | 166.2 | unknown | J. Palisa | 1884 |
704 | Interamnia | 103 | 281.9 | 0.06 | V. Cerulli | 1910 |
2 | Pallas | 161 | 255.1 | 0.14 | H. Olbers | 1802 |
16 | Psyche | 81 | 269 | 0.10 | De Gasparis | 1852 |
87 | Sylvia | 84 | 320.9 | 0.04 | N. Pogson | 1866 |
4 | Vesta | 162 | 217.5 | 0.38 | H. Olbers | 1807 |
Millions of years ago, the Earth was under constant bombardment with asteroids and comets, some of which were over a mile wide. As time passed the number of collisions became smaller but the size of the asteroids as stayed pretty much the same. If you look at the moon, you can see hundreds of craters, some of which stretch over a 100 miles wide. With this in view it is easy to believe that the Moon took far more hits than the Earth, but the reality is very different. As the time as passed, the old craters of the planet have been destroyed by the weather, the rock cycle and volcanic activity. Only 120 asteroid impact sites are now visible, most of which can only be seen from Ariel photographs or by the study of the rock formations around suspected impact sites.
The above picture shows a known impact site in Arizona,
America. This crater was created when meteor no bigger than 100m
wide hit the Earth 49000 years ago. The crater was determined as
an impact site when a scientist discovered fragments of meteor in
the centre, the meteor was then later named Canyon Diablo. The
crater may only be 0.73 miles wide but it would of killed any
living thing within a 10 mile radius.
At the end the cretaceous period 65 million years ago, an
asteroid with diameter of about 10 miles impacted on the Earth in
the Gulf of Mexico. This asteroid created one of the biggest
explosions on the Earth since the creation of the planet, and is
also believed to be responsible for wiping out the dinosaurs. At
first, scientist thought that the dinosaurs died to a famine or
some a new disease, but not so long ago, the idea that an
asteroid could of destroyed them became the most favourite and
most believable. It was the discovery of this crater at the
bottom of the Ocean that added to the theory of an asteroid
collision.
This 103 mile wide crater is situated in a unique geographical site, the sulphur rich region allowed the asteroid to kick up billions of tons of sulphur and there fore blocking out the sun for months. As a result of this, the planet then fell into a deep freeze as no light could penetrate the dark layer, causing most of the life on Earth to become extinct.
This is the question that no body is sure that we can answer just yet. At the moment NASA scientist are trying to create a method in which we can stop any space objects hitting us. The favoured idea is that we could detonate a nuclear explosive near the asteroid, deflecting it away from our planet, this would be a lot safer than actually trying to destroy the asteroid. If a nuclear device was planted on the asteroid, it would only shatter the asteroid and make the situation far worse. The second favoured idea is that a jet propulsion system could be placed on the asteroid and used to slowly turn the asteroid onto another orbit.
Asteroids are probably the most deadlest force the solar system can produce, one strike could put man back in the dark ages and would kill almost the entire population of the planet. It is for this reason that I believe that scientists should be allowed to perform more research into a defence system for the planet. At the moment, we only know about a fraction of asteroids which are out there, the asteroid that destroys our planet could only be a year away and we don't even no it exists.
Research into past collision's shows that a large asteroid hits the Earth every 3000 years or so, the last big collision was about 3000 years ago...
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These pages were designed and written by Rob Reather and DJ
Dave.
24th November 1999