  In order to examine how the terrestrial life emerged, a number of laboratory
experiments have been conducted since the 1950s. Methane has been one of the
key molecules in these studies. In earlier studies, strongly reducing gas
mixtures containing methane and ammonia were mainly used to simulate possible
reactions in primitive Earth atmosphere, and amino acids and other organic
compounds were detected. Since the primitive Earth atmosphere was estimated to
be less reducing, contribution of extraterrestrial organics to the origin of
life is considered quite important. Extraterrestrial organic chemistry has been
experimentally and theoretically studied intensively, including laboratory
experiments simulating interstellar molecular reactions. Endogenous and
exogenous organics should have been supplied to the primitive ocean. Now
submarine hydrothermal systems are considered one of the plausible sites of
generation of life. Experiments simulating submarine hydrothermal systems where
methane played an important role are now intensively being conducted. We have
recognized the importance of such studies on possible reactions in other solar
system bodies to understand the origins of life. Titan and other icy bodies,
where methane plays significant roles, are especially good targets to be
studied. In the case of Titan, not only methane-containing atmospheres but also
liquidospheres composed of methane and other hydrocarbons have been used in
simulation experiments. This paper summarizes experiments simulating various
terrestrial and extraterrestrial environments, and possible roles of methane in
chemical evolution are discussed.
