 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
| . |  |
. |
Astronomers Unravel A Mystery From The Dark Ages
Cardiff - Feb 11, 2004 Scientists at Cardiff University, UK, believe they have discovered the cause of crop failures and summer frosts some 1,500 years ago � a comet colliding with Earth. The team has been studying evidence from tree rings, which suggests that the Earth underwent a series of very cold summers around 536-540 AD, indicating an effect rather like a nuclear winter. The scientists in the School of Physics and Astronomy believe this was caused by a comet hitting the earth and exploding in the upper atmosphere. The debris from this giant explosion was such that it enveloped the earth in soot and ash, blocking out the sunlight and causing the very cold weather. This effect is known as a plume and is similar to that which was seen when comet Shoemaker-Levy-9 hit Jupiter in 1995. Historical references from this period - known as the Dark Ages � are sparse, but what records there are, tell of crop failures and summer frosts. The work was carried out by two Cardiff undergraduate students, Emma Rigby and Mel Symonds, as part of their student project work under the supervision of Dr Derek Ward-Thompson. Their findings are reported in the February issue of Astronomy and Geophysics, the in-house magazine of the Royal Astronomical Society. The surprising result of the new work is just how small a comet is needed to cause such dramatic effects. The scientists calculate that a comet not much more than half a kilometre across could cause a global nuclear winter effect. This is significantly smaller than was previously thought. Dr. Ward-Thompson said: "One of the exciting aspects of this work is that we have re-classified the size of comet that represents a global threat. This work shows that even a comet of only half a kilometre in size could have global consequences. "Previously nothing less than a kilometre across was counted as a global threat. If such an event happened again today, then once again a large fraction of the earth's population could face starvation." The comet impact caused crop failures and wide-spread starvation among the sixth century population. The timing coincides with the Justinian Plague, widely believed to be the first appearance of the Black Death in Europe. It is possible that the plague was so rampant and took hold so quickly because the population was already weakened by starvation. Related Links School of Physics and Astronomy SpaceDaily Search SpaceDaily Subscribe To SpaceDaily Express
Discovery Of A Double Impact Crater In Libya
Floirac - Dec 18, 2003Impact cratering is now recognized as a major geological process on Earth. In particular, giant impacts had a fundamental influence on the geological and biological evolution of our planet with possible climatic effects. There are more than 160 confirmed impact craters on Earth, among which 17 are located in Africa, but it is estimated that only 10% of impact craters larger than 10km and younger than 100Ma are known. |
|
|
| The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement |
