Spacecraft Missions to Comets.

Comets have intrigued mankind over centuries. The use of improved astronomical equipment revealed an ever-increasing number of features. It took, however, until the advent of in situ measurements by the means of space research until the complexity of cometary physics and chemistry was recognized. Three comets have been visited by spacecrafts up to now, one mission is in progress (Deep Impact to Tempel-1, in July 2005) and one is planned (Rosetta to Churyumov-Gerasimenko, in 2013), 2 missions failed (CRAF was cancelled in 1992, CONTOUR exploded shortly after launch in 2002). While optical methods give a more global picture of the comet, the analysis of individual dust particles has resulted in the identification of some organic molecules, which may have played an important, steering role in the origin of life processes on the Earth. [ABSTRACT FROM AUTHOR]