Si parla invece di tempeste di detriti spaziali e polvere in arrivo dallo spazio
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The Sun's shifting magnetic field is set to focus a decade-long storm of galactic dust grains towards the inner Solar System, including Earth.
The effect this will have on our planet - if any - is unknown. But some researchers have speculated that sustained periods of cosmic dust bombardment might be related to ice ages and even mass extinctions.
During the last decade, the magnetic field of the Sun acted like a shield, deflecting the electrically charged galactic dust away from the Solar System. However, the Sun's regular cycle of activity peaked in 2001.
As expected, its magnetic field then flipped over, so that south became north and vice-versa. In this configuration, rather than deflecting the galactic dust, the magnetic field should actually channel the dust inwards.
This pattern may have been repeated during previous solar cycles but it is only now that astronomers are beginning to have the data they need to prove it.
Cosmic debris
The data come from the galactic dust grains impacts detected by DUST, an experiment on the ESA/NASA mission Ulysses, which was launched in 1990. The measurements, collected by ESA scientist Markus Landgraf and colleagues at the Max-Planck-Institute in Heidelberg, show that three times more galactic dust is now entering the Solar System than during the 1990s.
The effects of space dust on the Earth are currently unknown, but hotly debated. Every year, about 40,000 tonnes of cosmic debris fall onto the Earth, much of it creating meteors.
Some researchers have suggested recently that high dust inputs into the Earth's atmosphere, sustained for centuries or longer, could be responsible for ice ages and mass extinctions. Langraf is cautious about such claims but told New Scientist: "Everything in interplanetary space eventually affects the planets, but exactly how is very speculative."
High-altitude aircraft
He hopes Ulysses can provide some concrete data. "We get about two dust detections a week. We need to observe from now until 2006 in order to have enough data to see evidence of focusing," he says.
This data could then be correlated with the results from high-altitude aircraft experiments that routinely catch the space dust falling onto Earth. Historical comparisons might also be possible if deep polar ice cores are analysed for galactic dust.
At present, the Ulysses mission is only funded until September 2004. However, an extended mission is currently being considered.
Stuart Clark
www.newscientist.com/news/news.jsp?id=ns99994021
[Modificato da Tiziano A. 08/08/2003 0.42]
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Upper management forced me to release a beta version.
-- God