This is about the time that fossil records indicate that many marine molluscs went extinct. Donald Clayton, an astronomer at Clemson University, says the story appears consistent: "The amount of 60Fe found in deposits is about what you might expect from a supernova going off about 100 light-years away." Clayton says 60Fe would be blasted towards Earth when high energy neutrons from the supernova core smack into iron atoms in its outer shell.