Could an Asteroid Hit Earth?

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Subject: Could an Asteroid Hit Earth? Thu Jun 29 2006, 10:39

Here's another essay - enjoy it! hehe.

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We know the precise orbits for over 40,000 asteroids, and several hundred thousand others have been catalogued. Most of those are in the main belt, where some millions of asteroids larger than 1 km in size are thought to circuit the Sun. Using large telescopes astronomers have found almost a thousand minor planets beyond Neptune [and some argue that Pluto is simply the largest of these]. It is anticipated that there are billions of smaller asteroids in this region, but they are mostly too faint to be detected using current telescopes.

Most asteroids are in stable orbits around the Sun, and have stayed in much the same place since they were formed 4.5 billion years ago, when the Sun and the planets were formed. However, Jupiter's gravitational field can sometimes pull bodies out of orbit, and send them off on wayward trajectories through the Solar System. Asteroids in the main belt can also collide with each other, and this is thought to be the biggest reason why asteroids come into the inner Solar System, posing a potential hazard to life on Earth.

Trojans are a type of very stable asteroid. There are two groups of Trojan asteroids, both sharing Jupiter’s orbit. They take the same length of time to orbit the Sun, but half remain 60 degrees in front of the giant planet and half 60 degrees behind. They are safe, and astronomers believe they have been there since the Solar System began. Recently several asteroids have been discovered in the same relationship with Mars. If Earth Trojans exist then they would be very valuable, because they would be the easiest objects to visit in space, but so far none have been found despite several intense searches.

There are also many asteroids known in the region inhabited by the gas giant planets Jupiter, Saturn, Uranus and Neptune. These are called Centaurs. Such asteroids are unstable, and have orbits that are changed markedly every time they come too close to one of those big planets. Some of the smaller moons of these planets are thought to be asteroids captured from Sun-centered to planet-centered paths.

Predicting the path of an asteroid is not an easy task. Even with the best equipment available today, we can’t measure the position or direction of an asteroid exactly. So when we try and work out its future path, there is always a degree of uncertainty. However, the more measurements that we are able to get, the smaller this uncertainty becomes.

Whenever we discover a new NEO or Near Earth Object, we can only make a very rough estimate of its future path. This is why the news sometimes reports that there is a risk of an asteroid hitting Earth. Of an asteroid’s many possible paths, some could result in collisions with our planet. However, as we collect more data, we are usually able to eliminate the chances of the body hitting Earth in the near future.

There are many asteroids and Near Earth Objects of which we have no knowledge. Based on the recent evidence, we can estimate that the chances of an asteroid doing catastrophic damage in the next century are approximately one in 5000. But unless we make an effort to keep track of as many Near Earth Objects as we can, we can never be sure exactly when the next impact will be.

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These are much shorter compared to my other ones lol either way I'm insane.

Sources for this essay beyond my knowledge and reasoning can be found here: http://www.ucolick.org/~mountain/AAA/impact/

Subject: Re: Could an Asteroid Hit Earth? Mon Jul 03 2006, 09:48

Playing off my love for all things space - cunning - a very fascinating read - 50 points.

» Asteroid Continuation Essay
» If you were the last person on earth.....
» Are You Earth, Fire, or Air?
» Asteriods and the Earth
» New Earth Discovered?