In Antarctica, balloon lands after 23-day search for particles from outer space

After years of work building an exquisitely sensitive instrument, University of Chicago scientists stood and watched as it flew up and out of sight into the fiercely blue Antarctic sky. Launched on Dec. 20, it would travel for the next 23 days on a NASA balloon along the very highest reaches of the atmosphere, scanning the continent of Antarctica from its 120,000-foot vantage point for minuscule visitors from outer space known as neutrinos.