Ashburn, Virginia, USA
- Harish Jharia
I always wondered why aircrafts flying in the sky leave white trails behind them in the sky and what exactly is there in the white stripes that keep the trails stay intact for quite some time. I, as a common man, always believed that the aircraft engines might be releasing huge quantity of smoke as exhaust gases that eventually form extended trails behind them. Nevertheless, I was never convinced with this theory because I knew well that smoke cannot form any defined shape; what to think of formation of a pair of straight parallel stripes out of a dark colored thinly composed polluted mixture of gases like smoke.
Qantas Boeing 747-400
I went through many books and internet sites; but, could not find any straightforward answer for this question. There were many difficult scientific terminologies like trails, contrails, chemtrail etc and chemical analytical reports of exhaust gases emanating from the exhaust ports. I could not understand all this explanations that also contained different weather conditions of temperature, humidity and clouds at different altitudes that also went right above my head. I simply thought as to how all these were connected with the white trail we see forming behind the planes in the sky. I, as a common man, wanted a convincing answer in layman’s simple language so that my doubts were cleared.
The layman’s answer that I evolved:
One fine morning in January winters I observed that the exhaust gases emanating from my car were looking like water vapor as we find escaping from the nozzle of tea cattle. It immediately struck in my mind that there was a catalytic converter installed at the exhaust port of my car that was converting Carbon Mono Oxide into water vapor. That means the white exhaust was nothing but water vapor that turned white after condensation in the chilling temperature of about 7 degrees Celsius outdoors. I imagined that if the temperature were at subzero level, the water vapor would have turned into ice particles.
I think that a similar phenomenon might be working with the exhaust gases emanating from the aircrafts flying at high altitudes of 11000 meters and at subzero temperatures of as low as minus 70 degrees Celsius. Aircrafts like Qantas Boeing 747-400 release huge volumes of exhaust gases while flying at high altitudes like 35000 feet and at minus 70 degrees Celsius. The exhaust gases are inclusive of carbon monoxide that is converted into water vapor by catalytic convertors. This water vapor turns into fine particles of ice when exposed to minus 70 degree temperature. Being in solid state the ice particles create a defined formation of straight white stripes of trails behind the aircraft.