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Invisible comet could hit earth, scientists claim 28/10/2004
Research by a Cardiff University astronomy scientist suggests that a comet colliding with earth is more likely than was previously believed.
Professor Chandra Wickramasinghe, Honorary Professor Bill Napier and research student Janaki Wickramasinghe of Cardiff University centre for Astrobiology believe that some comets are not visible using current astronomical scanning equipment.
They argue that if this is the case, international programmes designed to detect near-earth asteroids, and ways to reduce the worst effects of them colliding with Earth may need to be urgently reviewed.
Professor Wickramasinghe said, "It's possible that we are missing many of these Earth-threatening objects and we need to think again about mitigating strategies - some of which assume decades or centuries of warning before impact."
The team has found that the surfaces of inactive comets, if composed of loose, fluffy organic material like cometary meteoroids, develop such small reflectivities - they appear invisible. The near-earth objects may therefore be dominated by a population of fast, kilometres-wide bodies, too dark to be seen with current surveys.
A new NASA mission will scan the entire sky with an infrared telescope - like a powerful set of night vision goggles to search for cool, or failed, stars, called brown dwarfs, and also dark comets and cometary fragments, of the type proposed by Professor Wickramasinghe and his team, that pose a previously unrecognised threat to our planet.
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