Witnesses reported seeing a fireball over southern Ontario slightly after 4.15 pm local time on Sunday 4 May 2014. The incident was also captures on a number of cameras, and Peter Brown of the Meteor Physics Group at Western University has suggested that it was probably caused by a 50-100 cm asteroid exploding in the upper atmosphere due to friction. Such an object would cause an explosion equivalent to several tons of TNT detonating, though this would happen about 45-50 km above the ground, presenting little threat to populations on the surface of the planet.
Fireball over southern Ontario on Sunday 4 May 2014. Sam Singh/The Canadian Press.
Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. It is possible, though unlikely, that this object will have produced meteorites that reached the surface (an object visible in the sky is a meteor, a rock that falls from the sky and can be physically held and examined is a meteorite), though most meteorites come from larger objects that penetrate further into the atmosphere before exploding, and therefore have a better chance of producing fragments that reach the surface.
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