Dr.Bruce Lieberman, a paieontologist at the University of Kansas, originated the idea that a gammma-ray burst specifically could have caused the great Ordovician extinction, 200 million years before the dinosaurs. An ice age is thought to have caused this extinction. But a gammma-ray burst could have caused a fast die-out early on and also could have triggered the significant
drop in surface temperature on Earth.
" One unknown variable is the rate of local gammma-ray bursts"said Thomas. "The bursts we detect today originated far away billions of years ago, before the Earth formed. Among the billions
of stars in our Galaxy, there's a good chance that a massive one relatively nearby exploded and
sent gammma-rays our way. " The Swift mission, launched in November 2004, will help determine
recent burst rates. Other team members are Dr. Claude laird of the University of Kansas, and
Drs. Richard Stolarski, John Cannizzo, and Neil Gehrels of NASA Goddard.