The Chicxulub crater situated near the Thcatan penninsula in Mexico was produced by the meteoritic impact of an asteroid estimated to be about 12 km in diameter (Nature, 1997,390,472). This event occured 65 million years ago and may have been the cause of the mass extinctions of animal and plant species that occured at about the same time. The impact is conjectured to have thrown up dust and sulphur compounds into the stratosphere which would have cut down the amount of solar radiation reaching the ground for several years.