Image shows a comet particle collected by the Stardust spacecraft. The particle is made up of the silicate mineral forsterite, also known as peridot in its gem form. It is surrounded by a thin rim of melted aerogel, the substance used to collect the comet dust samples. The particle is about 2 micrometers across. Stardust was a robotic space probe launched by NASA on February 7, 1999. Its primary mission was to collect dust samples from the coma of comet Wild 2, as well as samples of cosmic dust, and return these to Earth for analysis. It was the first sample return mission of its kind. En route to comet Wild 2, the craft also flew by and studied the asteroid 5535 Annefrank. The primary mission was successfully completed on January 15, 2006, when the sample return capsule returned to Earth. A mission extension codenamed NExT culminated in February 2011 with Stardust intercepting comet Tempel 1, a small Solar System body previously visited by Deep Impact in 2005. Stardust ceased operations in March 2011.