Diacetylene

Diacetylene (also known as butadiyne), with the formula C4H2, is a highly unsaturated hydrocarbon that contains one single bond and two triple bonds. It is the first in the series of polyynes.

Occurrence in Nature
Diacetylene has been identified in the atmosphere of Titan and in the protoplanetary nebula CRL 618 by its characteristic vibrational modes. The molecule is mostly likely to have formed in Titan's atmosphere by a reaction between acetylene and the ethynyl radical C2H, which is produced when acetylene undergoes photolysis. This radical can in turn attack the triple bond in acetylene and react efficiently even at cold temperatures.