WASHINGTON, D.C. — Designed to scan the heavens thousands to billions of light-years beyond the solar system, the Fermi Gamma-ray Space Telescope has now recorded some more down-to-Earth signals. During its first 14 months of operation, the flying observatory has detected 17 gamma-ray flashes associated with terrestrial lightning storms.

The flashes occurred just before, during and immediately after lightning strikes, as tracked by the World Wide Lightning Location Network.

During two recent lightning storms, Fermi recorded gamma-ray emissions of a particular energy that could only have been produced by the decay of energetic positrons, the antimatter equivalent of electrons. The observations are the first of their kind for lightning storms. Michael Briggs of the University of Alabama in Huntsville announced the puzzling findings November 5 at the 2009 Fermi Symposium.

It’s a surprise to have found the signature of positrons during a lightning storm, Briggs said.

During lightning storms previously observed by spacecraft, energetic electrons moving toward the craf