Prophets and soothsayers have been predicting the end of the world for thousands of years, with possible extinction-level events cited as super-volcanoes or earthquakes, giant solar flares, pollution, plague and pestilence, and the favourite of the 20th century, nuclear war. There is no doubt that planet Earth is currently under-going what Confucius would describe as 'interesting times', with all of these proposed threats simmering away ominously in the background as we continue our ordinary lives. One of the other threats which could end Life as we know it, and one which has been credited with extinguishing the dinosaurs millions of years ago, is if the Earth was to be struck by a sizeable asteroid, and it is this scenario which could occur in the not-too-distant future.
Earth is being pelted with space debris on a fairly regular basis and the effects are generally minimal, so an incoming asteroid would need to be reasonably sizeable to create an aftermath resulting in the annihilation of most forms of life in our world. Worryingly, however, Ukrainian scientists recently determined that just such a substantial chunk of space rock was on a collision course with our precariously-placed planet, and was due to make impact in 19 years on August 26th, 2032. The discovery was confirmed by two Russian observatories and also by Italian, British and Spanish astronomers.
The scientists who discovered the asteroid, christened 2013 TV135, established that it measured about 1,345 feet in diameter, and was approaching Earth at a potentially dangerous trajectory. They calculated the odds of an impact as 1 in 63,000, and suggested that if a collision did occur, it would be comparable to the detonation of 2,500 megatons of TNT, the Russian news agency, RIA Novosti, reported.
The Russians are no strangers to asteroid impacts, having suffered two hits this century; the most recent and significant event occurring on Feb. 15 in Chelyabinsk, when a 17–meter meteor struck without warning with a blast equal to 440 kilotons. Consequently the Russians took the latest news very seriously: Russian Vice Premier Dmitry Rogozin, who is in charge of Russian space research, wrote a disturbing post on Twitter after the news was announced: "A 400-meter asteroid is threatening to blow up the Earth. Here is a super target for the national cosmonautics.”
So should we start building our underground shelters and stockpiling the tinned beans before 2032?
Well, in the case of 2013 TV135, NASA says the odds are against it colliding with Earth. US scientists have been evaluating the data provided by their Ukrainian counter-parts, and have determined that the odds of the asteroid colliding with Earth are actually very small.
Unfortunately, a huge global sigh of relief may be premature. Back in 2011, researchers predicted that the asteroid known as 99942 Apophis could hit the Earth in April of 2036, and there is still a slim chance of this happening. Apophis was originally discovered in 2004, and is smaller than 2013 TV135, measuring a comparatively petite 210-330 meters in diameter, but is thought to be more likely to collide with Earth than its big brother and could still pack quite a punch. Its trajectory is predicted to bring it very close to us in 2029 when it will pass within approximately19,400 miles (31,300 kilometers) of our planet, but in 2036, in a “1-in-800-year event,” an even closer approach is expected with a 1 in 45,000 chance of a collision. The impact would rely on a very precise orbit of Earth and for Apophis to enter a “gravity keyhole,” which would alter its trajectory sufficiently to put Earth in its path. The estimated date of impact is thought to be April 13, 2036.
How much can scientists tell us about potential threats from space?
In order to predict and possibly deflect any inbound space-missiles, or "Near-Earth Objects", as they are known, NASA formed a department known as the Near Earth Observation and Asteroid Initiative Program, or '"Spaceguard". Research from the project indicates that, in general, it is not the larger asteroids that cause concern, as these are easily identified, but instead it is the smaller objects travelling towards us from the direction of the sun which could strike us without warning.
Igor Korotchenko, a Russian senior defense expert, had this to say about this and other impending impacts; "For at least the next 50 years, humans will be incapable of protecting Earth against meteors and asteroids. We, humankind, can intercept missiles and planes manufactured by man, but our radars and missiles are helpless against asteroids, as they travel at faster speeds of dozens of miles per second, they have different trajectories and they can be much, much bigger than strategic missiles we are dealing with today". Korotchenko, who is editor in chief of the National Defense journal, added: "How can you intercept or even avert anything coming vertically down at us from outer space?"
What can be done to avert potential asteroid impacts?
NASA is not the only organisation looking at how to deal with incoming space debris: Frank Schäfer of the Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut, EMI in Freiburg, Germany is looking at what asteroids are made of and how this affects a deflection impact. He suggests that one way of dealing with these threats is to deflect them with a space probe deliberately set on a collision course. The space probe need only be the size of a washing machine to send a massive asteroid off on a different trajectory, as apparently it is the velocity and the timing behind the probe rather than its size which makes the vital difference.
“In actual fact, the impact of a space probe would change the speed of the asteroid by just a few centimeters per second but that’s enough to deflect its course to a significant degree over a longer period" says Schäfer. "So if we want to stop an asteroid on collision course with the Earth from hitting us, we’ll need to fire at it many years ahead of time."
H. Jay Melosh, co-author of the 2010 National Research Council report "Defending Planet Earth, suggests that deflection should not be necessary, saying: "The best investment in asteroid defense is not in weapons to deflect them, but in telescopes and surveys to find them. At this point we've found more than 90 percent of the large, civilization-ending asteroids that cross the Earth's orbit and none are threatening us, which lets us breathe a little easier for the next 1,000 years or so; but there are limits to this search."
Melosh, professor of earth, atmospheric and planetary sciences and physics at Purdue University went on to say: "We need to invest in telescopes that can find asteroids on Earth's sunward side, our current blindspot, and in programs to find and track the smaller asteroids, which are less devastating but far more likely to strike us."
What global effects could be expected if a large asteroid did collide with Earth?
The last really large impact occurred in Tunguska, Siberia on June 30th, 1908, though it is thought that in this case, the comet or meteorite may have exploded above the earth as no crater was ever discovered. It was thought that the blast flattened trees and killed livestock for many kilometers around the blast site, which covered over a thousand square miles of rural Siberia.
If this event had occurred over London, it would have destroyed everything within the M25 motorway.
The more recent 440 kiloton impact in Russia caused some damage and injuries to hundreds of people, mainly from shattered window glass.
At the other end of the scale, the meteor implicated in extinction of the dinosaurs 65 million years ago was probably caused by an object some 10-15km wide, so one can determine that asteroids such as Apophis would fall somewhere in between, possibly not extinction-level events extinguishing all life on the planet, but certainly causing massive regional devastation covering thousands of miles.
Is there really any cause for concern?
NASA gave the following statement regarding Apophis: “The impact odds as they stand now are less than one in a million, which makes us comfortable saying we can effectively rule out an Earth impact in 2036. Our interest in asteroid Apophis will essentially be for its scientific interest for the foreseeable future.”
Apophis will be close enough to be visible to the naked eye as it passes Earth in 2029, however, which will give us an indication of just how close it will be.
It is encouraging that scientists are able to make predictions regarding potential impacts, though if it was determined that our planet was definitely in the path of a massive meteorite with little chance of deflecting it, one wonders if ignorance would be preferable than the panic which would undoubtedly ensue. In truth, we are constantly at risk from space debris which sometimes comes alarmingly close without us even being aware of it: in February, asteroid 2012 DA14 was just 17,200 miles away, much closer than the projected course of Apophis.
If you don't consider that 'ignorance is bliss' and would rather know if an asteroid is hurtling towards us, then make sure you visit Unknown Country, where we try to keep you informed of all the most important news affecting our planet.
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