J. H. Adams

High above the Antarctic ice sheet, a balloon with a detector floated for twenty days. It caught tiny particles that had been traveling toward us for millions of years from distant stellar explosions. Now scientists have sorted through the catch and reported how much energy the protons and nuclei of different elements carried.

In the stream of charged particles flying toward us from the depths of the Galaxy, iron turned out to be the odd one out. The ATIC-2 instrument, lifted on a balloon over Antarctica, compared how the fraction of nuclei from sulfur to chromium relative to iron changes with energy.