An asteroid the size of the one that wiped out the dinosaurs is a rare occurrence, but it happened once and it is very likely that it will happen again. Scientists estimate it to about once in a million years. But we do not know exactly when; it could be tomorrow, in a year, or perhaps within this decade. Therefore the big extinction level asteroids can be considered the biggest threat for humanity. The smaller asteroids are however much more frequent and still capable of causing enormous damages and killing millions of people, as well as billions of animals.
In 2013 such an asteroid, around 19m in diameter, exploded over the city of Chelyabinsk, damaging hundreds of thousands of homes and wounding 1500 people – and that it did no further damage was very lucky indeed; the next one could be much worse, and could practically speaking come tomorrow:
To quote the National Space Society: “If we don’t do something, sooner or later Earth will be hit by an asteroid large enough to kill all or most of us. That includes the plants and animals, not just people. Maybe this will not happen for millions of years. Maybe in 15 minutes. We don’t know.”
What is an even greater threat to individuals and national societies, is the numerous smaller NEO’s (Near Earth Objects), since we have only detected an estimated one percent of them . There are currently over a million asteroids in our Solar System that are larger than the object that struck Tunguska back in 1908. What impacted the Russian tundra back then was just about 40 meters in size, but the impact was 1000 times more powerful than the nuclear bomb dropped on Hiroshima and capable of completely destroying a small country .
Let’s not forget about the larger ones though: “There are about 1,000 asteroids a kilometer or more in diameter that cross Earth’s orbit (the path Earth takes around the Sun). About a third of these will eventually hit Earth” . It is sadly not unreasonable to estimate that an asteroid that size could kill more than a billion people if it landed in one of the most populated places on earth.
with a diameter of approx. 10km, strikes the U.S.: A possible global extinction event.
In March 2013, approx. 9760 Near Earth Objects (NEOs = asteroids and comets) had been identified and a total of 1380 of these were classified as potentially hazardous asteroids. And that is only the small fraction that we know where are, with millions still waiting to be tracked – preferably before they strike Earth.
By September 2014 these numbers had increased to 12000 NEOs of which 1600 potentially threaten Earth, with millions still undetected and more than 22000 of these bigger than 100m . At EADP we find these statistics extremely alarming.
Currently there is neither an agency nor governmental body who are working on a deflection plan or a planetary defense mission for anything that will hit Earth within 10 years. Thus, when the next asteroid is coming our way we at EADP plan to have an emergency asteroid deflection program ready, to ensure humanity is safe from this hazard.
(the dots representing 100, 10,000 and 1,000,000 GigaJoules correspond to
impact energies of about 300 tons, 18,000 tons and one million tons of TNT
explosives respectively, with Chelyabinsk being a 0.5 million tons TNT event)
 NSS – Planetary Defense
 Sentinel Mission – Asteroids 101
 Sentinel Mission – The threat
 NASA – Bolide Events 1994-2013
 Physics Today – How many asteroids are out there, exactly?