WILL EARTH BE HIT BY AN ASTEROID OF SUBSTANTIAL SIZE.

I am generally fond of Astronomy. When I was going through some videos on youtube I found this video which I had shared above and it made me feel disturbed. Then I thought that I should investigate a little more about the probability of earth taking such a hit.

The latest meteor impact occurred at Kali in Estonia around 700 BC. Multiple craters were formed at the site of impact by the meteor with an estimated velocity of 15 km/s and a mass of around 50 MT. The main crater formed by the impact is 100 meters across with a depth of 22 meters.

Asteroids with a diameter of over 50 meters strike the earth every 1000 years-------- One such strike took place in 1908 at Tunguska in Siberia. This is the largest impact event over land in Earth's recent history. Luckily the impact occurred in a forest and trees in the surrounding area with a diameter of 8 KM got affected. The general agreement among scientists is that this meteor is a few tens of meters across.

Asteroids with an average diameter of 1KM strike the earth every 500,000 years.

Bigger collisions with asteroids 5 KM in diameter occur once every 10 million years-------- The smallest of these impacts would generate 20,000 times as much energy as the greatest bomb ever produced by us and leave a crater 95 km across. One such strike is supposed to have wiped out the Dinosaur population from the earth 6.5 million years ago.

The largest meteor impact crater on the earth is the Barringer crater in the Arizona desert formed 50,000 years ago. This is 1200 meters across and 170 meters deep. This is believed to have been caused by a meteor weighing 150,000 MT at the time of striking the earth and an impact speed of 13 KM/hr.

There are only 3 asteroids with diameters of 500 KM and over that can cause the devastation that is shown in the video. They are 1) Ceres-Dia 952 KM, 2) 2Pallas- 544 KM, 3) 4Vesta-529 KM. Luckily for us none of them have any chance of colliding with the earth. Of the asteroids Vesta is the only one that attains brightness that is is visible to the naked eye.

The TORINO SCALE is a scale for measuring the possibility of an asteroid or a comet hitting the earth. This is valuated between 0 and 10.

On this scale a collision is certain if the object reaches 8 on the scale. None of the objects evaluated by astronomers till date managed to cross 1 till the Asteroid Aphophis did so in 2004. In fact at one time Aphophis was upgraded to 4 which means a 1% chance of a collision capable of regional devastation. With later observations however, it has been downgraded to 0.

Subsequently another asteroid 2004 VD 17 reached a level of 2, but subsequent observations made the scientist downgrade it to 0. All the asteroids discovered earlier have been downgraded to 0. Incidentally, a 0 level indicates almost nil chances of impact.

Presently there are only 3 asteroids with a risk level of 1. Level 1 means a collision is highly unlikely.

The asteroid 2007 VK184 discovered in 2007 has a probability of 1 in 3030 to hit the earth. It has a diameter of 130 meters and travels at a speed of 16KM/Hr.

The asteroids 2011 AG5 and 2011 BM45 discovered in Feb 2011 are rated 1.

Considering the above data it is highly unlikely in the near future that earth would be hit a by an asteroid of substantial size to cause lasting damage.