They have discovered patterns to the meteor displays which suggest that Tempel Tuttle's debris cloud is in fact a tangled mass of ancient filaments of dust - each one thrown off the comet during a different passage past the Sun. Last year, the Earth crashed through a filament thrown off Tempel Tuttle in 1333. Since its creation six centuries ago, all the fine debris has been blown away by the solar wind - leaving only the big bits which caused the spectacular show of fireballs in our skies. This year Asher reckons we will be passing through a filament of dust thrown off in 1899. This one should have more fine material as it is a lot younger and fresher than the filament we passed through last year.
More fine material means a potentially higher number of meteors.
According to Asher we went through this same filament of debris in 1966 when 40 shooting stars a second lit up the skies over Arizona. He and Rob McNaught estimate 20 meteors a minute at the height of this year's storm. Because of the poor track record of predicting the Leonids in the past, satellite operators are not taking advance evasive actions this year. Instead, they will be waiting on the night to see if a potentially dangerous storm breaks, and space agencies around the globe will be keeping watch for them. Ringside seat Nasa and the US Air Force have once again mounted a mission to fly under the breaking storm this week, guaranteeing a ringside seat for the spectacle.