Wednesday, June 03, 2009
It also looks like there have been more cometary ice meteors which, like Tunguska, exploded as airbursts & thus left little record but may have had severe weather effects at the time. This listing is via Wikipedia but I have done them in date order:
50,000 BC Barringer Crater Arizona 2.5 megatons, relatively well preserved because it is in desert
8,900 BC Clovis event Airburst over North America which is hypothesised to have killed off most of the big game at the time (personally I think mankind could have done that die off without help but the charcoal layer evidence of such an airburst is good).
8,000 BC Rio Cuarto craters Argentina 25 megatons
Holocene impact events have been proposed by the dendrochronologist Mike Baillie as a possible cause of several brief (typically 5-10 year) climatic downturns recorded in ancient tree ring patterns. In his book 'Exodus to Arthur: Catastrophic encounters with comets,' he highlights four such events
4,000- 2,000BC Henbury crater Northern Australia, also desert.
2,800 - 3,000 Burkle Crater Indian Ocean at a depth of 12,000 feet. 62.5 megatons. "This time period saw: a) the Indus Valley Civilization and the end of its Early Harappan Ravi Phase at ca. 2800 BC; b) the end of the pre-dynastic "antediluvian" rulers of the Sumerian civilization and the start of the First Dynasty of Kish after 2900 BC. ("After the flood had swept over, and the kingship had descended from heaven, the kingship was in Kish."); c) the pre-Xia dynasty rule of the Three Sovereigns and Five Emperors of China starting ca. 2850 BC (with the first two figures, Fuxi and Nuwa, as husband and wife credited with being the ancestors of humankind after"
1490 In China's Shanxi Province, 10,000 people were said to have been killed in 1490 by a hail of "falling stones" that some astronomers surmise may have been triggered by the breakup of a large asteroid
1863 or 1891? Wabar craters Empty Quarter desert of Saudi Arabia. Discovered by Kim Philby's father.
1908 Tunguska Siberian airburst 10-15 megatons fortunately in a particularly remote part of Siberia!.
1972 Great Daylight Fireball Crossing from Utah to Alberta. This was an Earth grazer entering the atmosphere on such a shallow trajectory that it is less than the Earth's curve & thus exits again. When you consider that the atmosphere is about 100 miles thick & the Earths radius is 4,000 you can see how unusual this is. Had it hit it would have been 1.3-6 kilotons.
1979 Vela Incident Putting this in though it almost certainly didn't happen. "U.S. nuclear detonation detection satellite (Vela 6911) in late September 1979 was possibly not a nuclear test, according to a number of studies posted today by the National Security Archive - The signal appeared to come from a 3,000 mile area that included the South Atlantic, Indian Ocean, tip of Africa, and part of Antarctica. A presidential panel concluded in May 1980 that the signal was more likely an artifact of a meteoroid hitting the satellite and sunlight reflecting off particles ejected as a result of the collision." This had been assumed to be evidence of a South African atomic test & did ratchet up fears of nuclear proliferation. Had it been real it would presumably have ratcheted them up a lot more. Indeed H. Beam Piper's future history contained a northern hemisphere nuclear armageddon triggered off by a megaton explosion in New York State which was later proven to be a meteor.
2000 A fireball exploded over the city of Whitehorse in the Canadian Yukon at an altitude of about 26 kilometers, lighting up the night like day. The meteor that produced the fireball was estimated to be about 4.6 meters in diameter and with a weight of 180 tonnes.
The late Eugene Shoemaker of the U.S. Geological Survey came up with an estimate of the rate of Earth impacts, and suggested that an event about the size of the nuclear weapon that destroyed Hiroshima occurs about once a year. Such events would seem to be spectacularly obvious, but they generally go unnoticed for a number of reasons: the majority of the Earth's surface is covered by water; a good portion of the land surface is uninhabited; and the explosions generally occur at relatively high altitude, resulting in a huge flash and thunderclap but no real damage.
Anti-matter meteor to be precise.
It is a shame that Piper killed himself - his fiction is some of the best SF I've read and I want more of it.
Mind you if such exist & I believe they do, & if such contact was possible it would bring up the Fermi question cubed.