Possible Impacts of NEOs with Earth - Research Paper Example

Possible Impacts of NEOs with Earth Near-Earth objects (NEOs) are asteroids, comets and larger meteoroids “whose orbit intersects Earth’s orbit and which may therefore pose a collision danger.”1 These objects, depending on their size, have the ability of causing varying levels of damage to the Earth. If an object is one kilometer or larger in size, an impact with the Earth would cause cataclysmic destruction to the impact site and the surrounding areas, as well as bringing about critical global ramifications. As of April 05, 2010, there are 6,935 NEOs that have been discovered, 804 of which are one kilometer in distance or more. 1,107 of these NEOs have been classified as Potentially Hazardous Asteroids, or PHAs2, which are the objects that astronomers are most concerned about. However, according to astronomers and space scientists, there are over hundreds of thousands of NEOs that have simply gone unaccounted for. Due to the amount of NEOs that have been discovered, and those that have yet to be discovered, many people - civilians and astronomers alike - have wondered what the chances are of a NEO colliding with Earth and the kind of destruction that would be involved when one would collide with the planet. When deciding the potential danger a NEO can ensue, the Torino Impact Hazard Scale, or simply the Torino scale, is consulted, which measures and categorizes the impact hazards that are associated with near-Earth objects. The Torino scale ranges from zero to ten, with zero being that there is no likelihood of a collision, though it also applies to smaller objects that burn up within the Earth’s atmosphere, and ten meaning that a collision is most certainly going to happen, “threatening the future of civilization as we know it.”3 The Torino scale is also split up into five colored zones: white, meaning no hazard, which consists of the zero level; green, normal, which consists of level one; yellow, meriting attention by astronomers, which consists of levels two, three and four; orange, threatening, consisting of levels five, six and seven; and red, certain collisions, which consists of levels eight through ten. Each color and number reveals certain levels of danger and damage in regard to each NEO that is discovered. The Torino scale allows astronomers to understand and keep an eye on certain NEOs that they believe could collide with the Earth, as well as brushing aside the ones that stand no chance of a collision. A meteorite hitting Earth’s atmosphere is a very common occurrence, though these are usually small enough to burn up within the atmosphere. Many of them that do make it past the atmosphere are tiny, often pebble-sized, by the time that they land on Earth’s surface. There are thousands that do not even make it to pebble-sized, but end up as bits of dust. This in itself shows that a NEO impacting the Earth is very plausible, as it happens often with smaller, almost unnoticeable objects. It has been estimated that approximately 37,000-78,000 tons of mass of material fall to Earth on a yearly basis.4 There is sufficient proof that larger NEOs have collided with the Earth in past centuries, such as the asteroid that presumedly wiped out the dinosaurs billions of years ago. Another larger NEO that has collided with the Earth is the meteorite that formed Meteorite Crater in Arizona over 50,000 years ago. The meteorite was 150 feet wide, and the crater it created is one mile across, 2.4 miles in circumference and 550 feet deep.5 There has long since been proof that larger NEOs are capable of colliding with the Earth; however, many of these instances have occurred during times when a majority of Earth was not inhabited, so it is difficult to understand the kind of devastation and destruction that can result from a large NEO colliding with Earth. Although there are thousands of identified NEOs, as well as possible hundreds of thousands of NEOs that have yet to be identified, astronomers have yet to identify any of these as immediate threats. All the same, there is no possible way to actually detect a threat of a NEO making impact with Earth until it is close enough for astronomers to understand and track the path that it is on. Sometimes, this could take as long as the NEO making numerous cycles before astronomers can predict where it is going to travel next, and how much closer to the Earth it will be. There have been many predictions about NEOs hitting the Earth, many of which were made prematurely. In September of 2000, an asteroid was discovered that was anticipated to hit Earth in the year 2030. As of November 2000, this possibility was debunked, with another scientist claiming that there was a one in five hundred chance of the asteroid colliding with Earth.6 While that conclusion stands as such now, it could easily change within the next few cycles that the NEO makes. Despite the fact that it is next to impossible to quickly predict the path of a NEO and to decide on whether or not it will collide with Earth, it is still possible to figure out vague ideas as to which objects pose the biggest threat to us, as well as a potential collision date, which can be changed in the future and with further observations. An example of this would be the Apophis asteroid, which, at 390 meters in size, will “come within the orbit of satellites that provide the Earth with communications in 2029. There is no chance it will impact the Earth in 2029, however there is a slim possibility of an Earth impact by this object in 2036.”7 The slim possibility of this NEO colliding with Earth in 2036 can either be proven or debunked the more that it, and its past and present paths, are studied. Given the size of this particular asteroid, it has been classified as a PHA. The closer an object is to Earth, the easier it is to study it and decide on where it is going and if damage will be what it brings with it. Predicting the NEOs that could collide with Earth are often hit-and-miss, in an almost literal sense. An NEO that is passing the Earth now may not be a threat, but when it comes back around on its next cycle, it could easily put the Earth at risk for a collision. This is the purpose behind looking for these NEOs and figuring out the kind of destruction they can cause, whether or not they are on a set course for Earth. By following the paths of these NEOs, and by conducting research on past collisions that the Earth has seen, astronomers are able to make themselves aware of other possible collisions and the damage that could entail. Earth’s chances of being hit are rather small, however, given the fact that, in comparison to the solar system as a whole, Earth is rather insignificant. The larger asteroids that are capable of doing global damage hit the Earth very rarely, approximately once every one hundred thousand years. Other NEOs, such as comets, are even more rare and will collide with the Earth roughly once every five hundred thousand years.8 Earth’s saving grace is that there is more space in the solar system than solid bodies; indeed, when the Voyager went through the asteroid belt, it was able to do so without damaging collisions with the asteroids, as there was more space than there was asteroids. While astronomers cannot predict precisely when a NEO is going to collide with Earth, or if one even will during our lifetime, it is still widely known that since the Earth has experienced collisions by larger NEOs, and quite a variety of smaller ones, that it is entirely possible for there to be another impact by a NEO. Astronomers relentlessly look for and study the paths of known NEOs, as well as unknown ones that are waiting to be identified. By using the Torino scale, astronomers can figure out the chance of impact by a specific NEO and the damage that could be caused if a NEO would collide with the Earth. Endnotes 1 http://www.armageddononline.org/near_earth_object.php 2 http://neo.jpl.nasa.gov/faq/ 3 http://neo.jpl.nasa.gov/torino_scale.html 4 http://curious.astro.cornell.edu/question.php?number=470 5 http://www.meteorcrater.com/ 6 http://www.spaceref.com/news/viewnews.html?id=244 7 http://www.killerasteroidproject.org/apophis.htm 8 http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question11.html Read More