|
. | . |
|
by Staff Writers Paris (AFP) Oct 23, 2014
Some 458 million years ago, Earth was whacked in a double asteroid strike, leaving craters visible in Sweden today, space scientists reported on Thursday. The event, they said, can be traced to "one of the largest cosmic catastrophes" in the history of the Solar System -- a mighty collision in the asteroid belt around 12 million years earlier. That smashup caused a 200-kilometre- (120-mile-) asteroid to break up, scattering large chunks of rock, some of which later crossed Earth's orbit. Two of these pieces slammed into shallow seas that covered modern-day Scandinavia, according to the study. With uplift of the Earth's crust, the signature of that event lies in central Sweden -- the 7.5-km Lockne crater, located around 20 kms south of the city of Oestersund, and a 700-metre (yard) crater at nearby Malingen. The study, published in the journal Scientific Reports, backs long-standing suspicions that these craters, just 16 kms apart, were caused by a "doublet", an extremely rare double whammy caused by asteroids travelling in pairs. The team, led by Jens Ormoe of the Centre for Astrobiology in Madrid, Spain, carried out drilling into the craters, looking for traces of sediment altered by impact shock. They also mapped the halo of ejecta -- a ring of debris hurled up by the smash, which landed up to tens of kilometres away from the inner crater. The Lockne impact was created by an object about 600 metres long, while the Malingen impactor was about 150 m long, the experts said. They were so-called "rubble pile" asteroids, or fragments travelling in a cluster. "Doublets" are a debated area of astrophysics. Modelling of asteroids that come close to Earth suggest that about 16 percent of these objects travel in pairs. But of the 188 known craters on Earth, only 10 -- in Canada, Russia, Germany, Finland and Brazil -- are considered to be serious candidates as doublets. The twin impact 458 million years ago would be part of a "shower" of meteors that pummelled Earth after the big breakup in the main asteroid belt. Some experts theorise that this had dramatic consequences for Earth's climate and ecosystems, encouraging an explosion in species called Great Ordovician Biodiversification Event.
Related Links Asteroid and Comet Impact Danger To Earth - News and Science
|
|
The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights 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 Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service. |