Impact Events - Extra Credit for Science

This post is the extra credit report I wrote for science on Impact Events. Enjoy!

0.0001pt;"> Earth has a long history of impact events. A common theory amongst historians and astronomers alike is that all of the major extinctions before man may have been caused by an impact event. The most common criticism of this theory is that the asteroid would have to be huge to avoid being burned in the atmosphere, which is true, and that it would have to be even bigger to cast up enough dust and debris to cause mass extinction. Yet, the chances of an asteroid hitting land are only 29.2%, comparably to a 70.8% of hitting water. Not to mention hitting water would be far more catastrophic than hitting land, as the impact would undoubtedly causing megatsunamis, worldwide earthquakes if it hit between the plates, and possibly volcanic eruptions if it landed closely to a volcano or the chain reaction of events caused an eruption.

We do know that had the dinosaurs never ceased to exist, then mammals never would have become the dominant life on Earth, just as every mass extinction inevitably leads to another type of life becoming dominant. So do we love asteroids or hate them? They gave us the chance to rise above the rest, but they may someday kill us in the same way as our predecessors.

Yet, the extinction of the dinosaurs was not the last time that an asteroid of such magnitude struck Earth. Thousands of years ago, ancient astronomers observed the skies, and hypothesized the imminent collision of Earth and a giant meteorite. As can be observed today, such an impact did occur, and has since become the stories of legends. This impact was the Burckle Crater, located just off the coast of Madagascar in the Indian Ocean, estimated to be eighteen miles in diameter, most likely impacting about five-thousand years ago, most likely on the morning of May 10, 2807 BC.

The Burckle Crater has become of many legends. Historians say that the legend of Noah and his ark may be based off of the megatsunamis created by the impact, as may have many great flood legends. The impact also ushered in the First Dynasty of Kish in China, “After the flood had swept over, and the kingship had descended from heaven, the kingship was in Kish.”, as Chinese legend tells it.

There have not been many major impacts since that have been dated or proven, though there are theories. Perhaps one of the most significant were the extreme weather events of 535-536. Civilizations around the world have recorded the weather events; “During this year a most dread portent took place. For the sun gave forth its light without brightness… and it seemed exceedingly like the sun in eclipse, for the beams it shed were not clear.”, in 536 by Byzantine historian Procopius; “A failure of bread from the years 536–539 AD” as recorded by the Gaelic Irish Annals. Temperatures were low around the world, even in the Middle East, which experienced a dry, dense fog. Even China got snow; in August. It can also be noted that 536 is the death of King Arthur in the Celtic legends, leading the Celts to believe the temperature was to forewarn of King Arthur’s death. The most likely scenario, however, is an impact event or the eruption of the supervolcano, Tambora.

In 1972, there was almost a catastrophic impact, called the ‘Great Daylight Fireball’, which entered the atmosphere in daylight over Utah at 14:30 local time, and continued throughout the day north, leaving the atmosphere in Alberta Canada. This meteoroid was filmed by countless people throughout the day. Surprisingly small, a mere three to twelve meters in diameter, the meteoroid’s impact would have caused anywhere between 0.4 to two kilotons of energy upon impact.

Near-Earth-Objects (NEOs) are graded on the Torino scale, which is a method of categorizing impact hazard of NEOs. The scale is 0-10, and color coded. The scale is as is below:

NO HAZARD (white)
0.	The likelihood of a collision is zero, or is so low as to be effectively zero. Also applies to small objects such as meteors and bodies that burn up in the atmosphere as well as infrequent meteorite falls that rarely cause damage.
NORMAL (green)
1.	A routine discovery in which a pass near the Earth is predicted that poses no unusual level of danger. Current calculations show the chance of collision is extremely unlikely with no cause for public attention or public concern. New telescopic observations very likely will lead to re-assignment to Level 0.
MERITING ATTENTION BY ASTRONOMERS (yellow)
2.	A discovery, which may become routine with expanded searches, of an object making a somewhat close but not highly unusual pass near the Earth. While meriting attention by astronomers, there is no cause for public attention or public concern as an actual collision is very unlikely. New telescopic observations very likely will lead to re-assignment to Level 0.
3.	A close encounter, meriting attention by astronomers. Current calculations give a 1% or greater chance of collision capable of localized destruction. Most likely, new telescopic observations will lead to re-assignment to Level 0. Attention by public and by public officials is merited if the encounter is less than a decade away.
4.	A close encounter, meriting attention by astronomers. Current calculations give a 1% or greater chance of collision capable of regional devastation. Most likely, new telescopic observations will lead to re-assignment to Level 0. Attention by public and by public officials is merited if the encounter is less than a decade away.
THREATENING (orange)
5.	A close encounter posing a serious, but still uncertain threat of regional devastation. Critical attention by astronomers is needed to determine conclusively whether a collision will occur. If the encounter is less than a decade away, governmental contingency planning may be warranted.
6.	A close encounter by a large object posing a serious but still uncertain threat of a global catastrophe. Critical attention by astronomers is needed to determine conclusively whether a collision will occur. If the encounter is less than three decades away, governmental contingency planning may be warranted.
7.	A very close encounter by a large object, which if occurring this century, poses an unprecedented but still uncertain threat of a global catastrophe. For such a threat in this century, international contingency planning is warranted, especially to determine urgently and conclusively whether a collision will occur.
CERTAIN COLLISIONS (red)
8.	A collision is certain, capable of causing localized destruction for an impact over land or possibly a tsunami if close offshore. Such events occur on average between once per 50 years and once per several 1,000 years.
9.	A collision is certain, capable of causing unprecedented regional devastation for a land impact or the threat of a major tsunami for an ocean impact. Such events occur on average between once per 10,000 years and once per 100,000 years.
10.	A collision is certain, capable of causing global climatic catastrophe that may threaten the future of civilization as we know it, whether impacting land or ocean. Such events occur on average once per 100,000 years, or less often.

The majority of NEOs are rated 0, with less than ten rated a 1, and none currently rated higher. There have been very few NEOs rated higher than a 1, the first of which was 99942 Apophis. Discovered by Roy A. Tucker, David J. Tholen, and Fabrizio Bernardi on June 19, 2004. Initial observations showed a 2.7%, or 1 in 37, chance of impact in 2029, which led to Apophis being a rated a 1. It was then discovered that chances of 2029 were almost nothing, which normally would have Apophis degraded to a 0. However, Apophis’s close encounter will lead it close to the gravitational keyhole.

A gravitational keyhole is minute section of space, minute in terms of space’s vast continuity, that if an NEO were to pass through, then impact is certain the next time the NEO passes Earth. This is due to the gravitational field of Earth.

In 2029, the keyhole will be about two-thousand feet wide. Apophis in comparison, is about one-thousand three-hundred feet wide. Estimates have been made for this situation, the first of which put the chances of Apophis passing through the gravitational keyhole at 1 in 17. Later estimates put it at 1 in 27. Either way, Apophis’s rating was raised to 4, the current record. If Apophis passes through the keyhole, impact is certain on Friday, April 13, 2036 just off the coast of California. To prevent this, NASA would send a probe to Apophis if it got to close to nudge it off its course slightly, at thirty-one inches a day maximum for three years, which would set it off course by about a mile, more than enough to miss the keyhole. However, Apophis still presents a threat, thus the Planetary Society awarded $50,000 in prize money to students and companies for designs for space probes that would place a tracking device on or near the asteroid. 37 entries were received from 20 countries across 6 continents.

Currently, Apophis is rated 0, being degraded on August 5, 2006, with the reasoning that with a 1 in 45,000 chance of passing through the gravitational keyhole, there’s no need to worry. However, last year, a German thirteen-year-old name Nico Marquardt revealed his statistics of a 1 in 450 chance, stating that NASA had forgotten to calculate in what would happen if Apophis impacted with one or more of the satellites in orbit around Earth. The statement was then confirmed by the ESA and NASA, but in a press conference, NASA denied having any contact with Marquardt, and have not changed their statistics.

While rated a 0, Apophis is still the most studied NEO, what with the fact that it passes Earth every seven years, occasionally less, and comes closer to Earth every following set. Last year was the most recent pass of Apophis, and the next will be 2013. However, the 2029 and 2036 passings are the most studied and scrutinized.

If Apophis stuck Earth, it would make a long journey across the continents, entering the atmosphere in Kazakhstan, go north into Russia, then head south across Central America, and back north to the most western tip of Africa, impacting somewhere along the path, most likely in the Atlantic. Apophis would be traveling so fast it would be violet-hot, going roughly the equivalent of Mach 11. If you see Apophis, the mere sight would burn you. The impact impact be catastrophic, because it would be near or on the coast, causing tsunamis, the debris of the impact will fly up in the air, and come down across the United States and China, fog up the skies, cause major earthquakes, and possibly activate volcanoes and eruptions. The tsunamis would drastically increase water level, so only those on high ground would live, if they weren’t being rained upon by the flaming pieces of Apophis or suffering from an earthquake. The few survivors would more than likely be knocked unconscious, and would awake to see a pitch black world, due to the debris floating in the air. This scenario is ‘Snowball Earth’.
An interesting fact about asteroid impacts is that if the deflection scenario failed, then the people of Earth would know exactly when they would die, to the very last second. One day you would wake up and know that you were going to die that day. Something very interesting about this is one little question: how would society change in the eve of certain destruction? Would we all come together, not as nations, but as a species? Or would the world become a world of pure and utter chaos? Naturally, you will have some of the groups you’ve always had in times of turmoil, such as the ones who look for survival, the ones who accept what they can’t change, the ones who pray, the ones who don’t believe the tales are true, and so forth. Yet, one must hope that it is the first scenario that becomes of man.