Comets have raised the alarm and have as well installed fear into humans since their first fighting. They're referred to as hairy stars which carry with them a look and shape resembling fiery swords which to a lot of people were considered and seen as bearers of bad omen or omens of dooms. Discoveries, however, have made it known that though comets may have taken life away through cataclysmic impacts, they're probably as well responsible for the improvement of life by supplying Earth with vital molecules.
Snow
Rocks
Dusts
Water
1909
1908
1905
1915
Siberia
California
China
Budapest
2011
2012
2013
2010
50km
200km
100km
150km
Over 7000
1491
2573
985
Over 7,200
Less than 5000
Less than 7,500
5000
1850
1925
1490
1467
Chelyabinsk meteor
Tunguska explosion
Comet Shoemaker-Levy 9
Chicxulub impact
1992
1959
1983
1891