'If a small object of less than 100 gm can make a deep crater and release this kind of energy, it could only be a meteorite.'
As the debate on whether what fell inside the campus of an engineering college at Nattampalli and on the paddy fields of the Bethaveppampattu village, both in Tamil Nadu, were meteorites or not goes on, Shobha Warrier/Rediff.com spoke to former ISRO (Indian Space Research Organisation) chairman G Madhavan Nair to find out what may have happened.
The villagers of Bethaveppampattu say they heard a ear-piercing noise on January 26 and saw mud splashed all over followed by smoke. On February 6 a suspected meteorite fell on the Bharathidasan Engineering College campus with a deafening sound. Could this be meteorites?
From what I have read about the description of what happened in both places, 99 per cent it could only be a meteorite.
If a small object of less than 100 grams can make a deep crater and also release this kind of energy while travelling through the atmosphere, it could only be a meteorite. The probabilities are quite high.
There are a bunch of objects, which vary from a few centimetres to a few kilometres across in orbit, beyond Mars. These objects are going round the sun. Sometimes, these meteorites collide and this can change their course towards earth.
If it is a piece from a satellite, the size will be very even.
From both places, they could get only small objects as small as a few grams. Can such a small object create a deep crater and create so much sound?
When an object re-enters the earth's orbit, it has the velocity of around a few kilometres per second and it can go up to 10 km per second.
With that velocity, even a small ball with hardly 10 mm in diameter can create a big hole on the ground.
The kinetic energy involved is very high. To some extent, the energy will be taken away by the atmospheric friction and heat and that is what is manifesting as craters.
The deafening sound you hear is because of the break in the sound barrier. Two or three years ago in Russia, a meteorite did not re-enter the orbit but skimmed through the atmosphere. The shock waves it created shattered almost all the windows in a township and injured many people.
At the engineering college they say after they heard the sound, many windows shattered, also the windshields of buses parked nearby.
It could be a meteorite rain and the shock waves created might have caused the damage to nearby objects.
The village and college are just 20 or 25 kms apart. In 2008, a 105 kg meteorite object was found in a place near Krishnagiri, which is around 50 km away.
Why do such incidents occur in this particular area again and again? Is it just a coincidence?
One has to make a study to analyse this. But again, it's just a statistical phenomenon. It is not necessary that a part should break away and come to this region.
That itself happens out of a collision process in the orbit and the deflection that is taking place. But it can have infinite variation in terms of direction and velocity. There is no definiteness about it.
Probably, that area may be open and people can observe it. If it falls in the middle of a forest, it may create a wild fire and people may not notice it.
Why can't meteorites be located before they fall to earth?
Our tracking systems are not capable of identifying very small objects. In all probability, very fine objects hit the earth's surface.
Most of the time these small subjects burn up in the atmosphere itself, but they cannot be tracked when it falls down as they are too small.
If they are big, we can track them and identify when and where it might fall.
