The article titled “Methane Clathrates in the Solar System” by Mousis and coworkers in this issue of Astrobiology will be the first in a series of articles that focus on methane. More such works will appear in upcoming issues. These review articles on methane are the result of work carried out by the International Space Science Institute (ISSI) Team 193 under the working title “The Methane Balance: Formation and Destruction Processes on Planets, Their Satellites, and in the Interstellar Medium.” The team consisted of about ten specialists in the complementary fields of astronomy, chemistry, microbiology, geology, planetary science, and physics, and their intent was to address a multitude of questions related to the formation and destruction of methane. Additional experts were brought in to complete the reviews. Issues considered had to do with the formation of methane in the interstellar medium and its role in star-forming regions and protoplanetary disks, the origin and cycles of methane on Titan and other icy moons, and the implications of the existence of methane in the atmosphere of Mars and exoplanets. The team has looked into the mechanisms for the formation of complex biomolecules in methane-dominated atmospheres and aquatic environments, such as the ocean floors of Earth and some satellites of the outer gaseous planets. The members also endeavored to elucidate to what extent microorganisms can survive on methane solely and which terminal electron acceptors would be available for them under different environmental conditions. The overall ambition has been to create novel, cross-discipline research projects for the future.
—Stockholm, February 2015
