The earth is being bombarded by space dust – but where does it come from?

The story is at www.physorg.com/print218218067.html and no doubt at the NASA web site too. NASA are saying that every day 100 tons of meteoroids – frangments of dust and gravel and sometimes small rocks enters the atmosphere of the earth – but it is unclear from what source. It is generally assumed the passage of comets leave behind trails of debris after they round the Sun. So many comets have journeyed through the solar system in the last few thousand years that there is an enormous amount of dust out there – and no one knows how long such dust may remain in near space over the course of thousands of years, or longer. NASA has decided to employ SMART cameras to find out what is hitting the earth's atmosphere – so this is an ongoing story which might produce some interesting information.