Cosmic Rain

http://www.astrobio.net/pressrelease/2044/cosmic-rain

For the last 30,000 years, our planet has been hit by a constant rain of cosmic dust particles. Two scientists from the Lamont-Doherty Earth Observatory (LDEO) at Columbia University in New York and the Alfred-Wegener-Institut (AWI) for Polar and Marine Research in Bremerhaven, Germany, have reached this conclusion after investigating the amount of the helium isotope 3He in cosmic dust particles preserved in an Antarctic ice core over the last 30,000 years. They have shown that this rare helium isotope in cosmic dust exceeds that of terrestrial dust in ice by a factor of 5,000. Moreover, measurements of the amount of 4He a helium isotope much more common on Earth in the Antarctic ice strongly suggest a change of origins in terrestrial dust between the last Ice Age and the interglacial warm period we currently live in.

In the journal Science, the scientists from New York and Bremerhaven for the first time presented chronologically resolved measurements of the 3He and 4He flux of interplanetary and terrestrial dust particles preserved in the snow of the Antarctic. According to current estimates, about 40,000 tons of extraterrestrial matter hit the Earth every year.