Question: Has there been anything which has come near to the Earths orbit that could be a Threat to us?

Columbus Flight Directors answered on 14 Oct 2015:

Simon: Hi Frozen Comet! The two most likely phenomena that would fit into the category of your question would be:

– A Solar Storm
– An asteroid or comet

Solar Storms occur all the time but especially high in frequency & energy every 11 years of the Solar Cycle. If a large Solar Storm event was to release high energy particles towards Earth so that they entered into our atmosphere this could lead to substantial damage to electronic/electrical equipment on Earth and in space. Luckily this has not happened significantly in the last 100years!

Asteroids and Comets pass through Earth’s orbit regularly. In fact many of the meteor showers you maybe aware of, like “Perseids in August” are the remenants of Cometary material in eccentric orbits around the Earth.

Luckily the Earths orbital track is so big that it is very rare that an Asteroid or Comet of significant size would actually be passing close to the Earth at this time.

However there are exceptions:

You may have heard of the Tunguska explosion of 1908 in Siberia where something exploded a few kms above the surface and flattened millions of trees. It was probably a small asteroid about 60 meters across. If this object had exploded over London it would have caused significant damage and probably large loss of life but since it was in Siberia (a remote area of Eastern Russia) no known fatalities were recorded.

65Million years ago, a large asteroid hit the earth in the Gulf of Mexico. The resulting explosion was so huge that it would have significantly changed Earths climate for hundreds of years. The event also known as the K/T event is coincident with a mass extinction event on Earth where more than 50% of all living animals at that time were wiped out including all of the dinosaurs!