On Friday the 13th, of April 2029 an asteroid approximately 330 meters in diameter will transverse the Earth’s orbit, coming nearer to the Earth than any other known asteroid in recorded history. Apophis was discovered in 2004 and after six months of optical and radar observations it was concluded that this asteroid will pass within 35700 km of the Earth, which is an altitude less than that of our satellites in geocentric orbit. Apophis will once again return on 2036, and astronomers say that if the asteroid’s center of mass passes through a small gravitational keyhole in the Earth’s atmosphere in 2029, Apophis’2 2036 orbit could be redirected into the Earth. Astronomers currently rank this asteroid has having little chance of impact, and is 0 on the Torino Scale.

The Torino scale is a scale from 0 to 10 that indicates the threat level of Near Earth Objects (NEO). A zero indicates that there is either no threat of impact, or that the object is too small to penetrate the atmosphere. A ten indicates that the object is likely to impact catastrophically. A NEO is assigned an integer value on the 0 to 10 scale based on impact probability and its kinetic energy. On December 23, 2004, Apophis had been given 1 in 233 chance of impact and a 2 on the Torino scale (Apophis is the first asteroid to have a value larger than 1 on the Torino scale). Later that day the odds of impact were increased to 1 in 64 with a 4 on the Torino scale. By 2006 the chance of impact has been reduced to 1 in 45,000 with a zero on the Torino scale.

In April 2008, a thirteen year old from Germany calculated the chances of collision to be 1 in 450 by factoring changes in the Asteroid’s orbit due to collisions with one or more geosynchronous satellites. To eliminate rumors that NASA and the ESA confirmed these calculations, NASA released a statement saying that the angle of approach relative to Earths equator, and the relatively small size of the satellites leave little or no chance of a satellite-asteroid collision.

Even though NASA has placed a low probability of impact, the threat is real enough that NASA plans on somehow deflecting the asteroid away from the tiny keyhole to prevent a future impact scenario. Some of these plans include nuking the asteroid, painting one half of it white, or by tugging it away using the gravitational pull of a probe. Nuking the asteroid has basically been ruled out because that may just result in showering us with several asteroid segments instead of one large one. Painting half of the asteroid white would result in the painted half of the asteroid reflecting more photons and thus pushing the asteroid in the desired direction, but this solution is impractical. Even if a good plan is developed it will do little good without precise and accurate details and calculations of the asteroid.

In 2008 the Planetary Society developed a $50,000 competition for the best mission designed to track the asteroid, and perform trajectory calculations for a year with an unmanned probe. The goal of the competition is to help Earth’s governments decide whether or not the probe should be deflected. The Planetary Society received 37 entries from 20 countries. The winning entry was designed by an Atlanta based company called Spaceworks Engineering. This plan called ‘foresight’ is planned to launch in 2012, after 5 months of travel it will rendezvous with Apophis, orbit it for one month while taking measurements with a multi-spectral imager. Once the orbiting phase is complete, the probe will follow Apophis around the sun for 10 months while it takes careful measurements of the asteroids orbit.

On Friday the 13th, in April of 2029, Apophis will be observable with the naked eye as it passes over the Earth at a distance of approximately 1/10 that of the moon. If you happen to be watching as the large asteroid come closer to the Earth than any other large asteroid in human history, remember one thing: even though calculus is perfect, the people who use it are not.

Throughout the Earth’s history there have been several mass extinctions. Perhaps the most famous and controversial is the extinction event which killed off the dinosaurs and 70% of all other living creatures on the Earth. This mass extinction occurred about 65 million years ago, and marks the end of the cretaceous period, and is often referred to as the K-T extinction event.

It is referred to as the K-T extinction event because of a layer of sediment found around the world which marks the boundary between the cretaceous and tertiary periods. Below this layer, there are several non-avian dinosaur fossils, and above it there are no such fossils. Besides dinosaurs, several species of plants and invertebrates also disappear from this top layer of soil. The few lucky survivors of the extinction event include several mammalian and bird clades.

The leading hypothesis for this mass extinction event is called the Alvarez hypothesis, named after a team of father and son scientists, Luis and Walter Alvarez, who first suggested it in 1980. The Alvarez team found concentrations of iridium hundreds of times higher than normal in the rocks around the K-T boundary. Iridium is a high density element, which is rarely found in the Earth’s crust; because of its high-density and iron-loving characteristics, iridium is believed to be found at its highest concentrations in the Earth’s core. Because Iridium is an iron-loving element, the Alvarez team speculated that the high concentrations of iridium found around the K-T boundary, was due to a large asteroid impact.

Using the concentrations of iridium found around the K-T boundary, the Alvarez team was able to determine that these concentrations were normal in a type of asteroid known as chondrites. They were also able to calculate that the size of the asteroid would have been about 10 kilometers in diameter. The energy released during such an impact would be equivalent to 100 trillion tons of TNT—twice as powerful as the largest nuclear bomb ever tested.

An impact of this magnitude would likely have produced a dense cloud of dust, which would have engulfed the entire planet. This dust would have blocked off sunlight, which would cause a change in the climate, and temporarily prevented photosynthesis. The lack of photosynthesis could account for the extinction of several species of plant life. The loss of plant life, coupled with a cooling climate, would reverberate through the food chain, causing the extinction of many types of animals, including the dinosaurs.

The scar of such an impact is located in the Yucatan Peninsula, and is called the Chicxulub Crater. This crater was created by an asteroid impact approximately 10km in diameter, and isotope analysis dates this crater to the end of the cretaceous—about 65 million years ago. To some, this is enough to confirm Alvarez hypothesis; but Gerta Keller, a professor of geosciences at Princeton University, believes otherwise.

Professor Keller agrees that the extinction was due to a changing climate, but she disagrees with what may have caused such a change. Her research implies that the mass extinction occurred 300,000 years before the Chicxulub impact. Her team estimates the age of the impact based on spherules found in Texas and New Mexico. A layer of spherules was formed when rock was vaporized by the impact, shot into the stratosphere, and then rained down over North and Central America. This layer was used to determine that the impact happened precisely 300,000 years before the mass extinction occurred.

The layers of sediment above and below the spherules layer show exactly how life was affected by the impact. Keller’s studies show that not a single species found in the layer beneath the spherules layer disappeared from the layer above. She believes that the mass extinction that occurred 300,000 years after the Chicxulub impact was caused by a series of volcanic eruptions in the Deccan Traps.

These volcanic eruptions were periodic, and lasted from 10 to 100 years, producing a volume of lava, in cubic miles, greater than the Rockies and Sierras combined. From each eruption, toxic gas was spewed into the atmosphere and oozing lava spread 650 miles across India, forming the longest lava flows on Earth. The sulfur dioxide injected into the atmosphere would have turned to aerosols, causing global cooling, while acidizing the ocean through acid rain. The marine record shows that 50% of ocean life was killed off by the first eruptions, and the mass extinction was complete by the end of the eruption frenzy.

Everybody asks the question, “What killed the dinosaurs?” Perhaps the better question is, “why didn’t they return?” Keller states that the dinosaurs were steadily dying off before the chicxulub impact; her solution is that the volcanoes were slowly killing everything. Why then didn’t the dinosaurs, or something similar make a comeback after the volcanoes quit, and the Earth regained equilibrium? Did the volcanoes permanently alter the composition of the atmosphere? Did the Chicxulub impact hit the Earth hard enough to change its axial tilt? Was there a reduction in solar flux reaching the Earth due to an aging sun? One thing seems certain: after the demise of the Dinosaurs, there was not enough energy reaching the Earth to sustain such massive life forms. One might speculate that the conditions which led to the demise of these magnificent creatures, also created an environment suitable for the evolution of intelligent life, and eventually present day man.

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