A new version of aerogel, the particle-collecting substance on NASA’s Stardust spacecraft, has been recognized by Guinness World Records as the solid with the lowest density. Dr. Steven Jones of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., a materials scientist who created the aerogel used by Stardust, also created a lighter version that weighs only 3 milligrams per cubic centimeter (.00011 pounds per cubic inch.) The team received the official certificate yesterday. NASA used aerogel for thermal insulation on the Mars Pathfinder mission. It will also be used on the 2003 Mars Exploration Rover, and may aid a proposed fundamental-physics testing mission and the Mars Scout Program.