Washington, July 16 : An international group of researchers have suggested that the Tunguska catastrophe in 1908 evidently led to high levels of acid rain, which strengthens the theory that a meteorite had exploded over the Russian region.
This theory is based on the results of analyses of peat profiles taken from the disaster region.
In peat samples corresponded to 1908 permafrost boundary, the researchers found significantly higher levels of the heavy nitrogen and carbon isotopes 15N and 13C.
The highest accumulation levels were measured in the areas at the epicentre of the explosion and along the trajectory of the cosmic body, which caused 200,000 tons of nitrogen to rain down on the region.
Increased concentrations of iridium and nitrogen in the relevant peat layers support the theory that the isotope effects discovered are a consequence of the Tunguska catastrophe and are partly of cosmic origin.
"Extremely high temperatures occurred as the meteorite entered the atmosphere, during which the oxygen in the atmosphere reacted with nitrogen causing a build up of nitrogen oxides," Natalia Kolesnikova, one of the authors of a study by Lomonosov Moscow State University, told the Russian news agency RIA Novosti.
The Tunguska event is regarded as one of the biggest natural disasters of modern times. On 30th June 1908, one or more explosions took place in the area close to the Tunguska River north of Lake Baikal.
The explosion(s) flattened around 80 million trees over an area of more than 2000 square kilometres.
The strength of the explosion is estimated to have been equivalent to between five and 30 megatons of TNT. That is more than a thousand times as powerful as the Hiroshima bomb.
There are a number of different theories about what caused the catastrophe.
However, the majority of scientists assume that it was caused by a cosmic event, such as the impact of a meteorite, asteroid or comet.
According to Dr Tatjana Bottger of the Helmholtz-Centre for Environmental Research, "The levels of accumulation of the heavy carbon isotope 13C measured right on the 1908 permafrost boundary in several peat profiles from the disaster area cannot be explained by any terrestrial process."
"This suggests that the Tunguska catastrophe had a cosmic explanation and that we have found evidence of this material," he added.