In that research, the team sent sparks through a mixture of methane, ammonia, carbon dioxide, and hydrogen sulfide.
people living along Namibia's desert coast have long been familiar with the rotten egg smell that periodically emanates from the Atlantic ocean whenever hydrogen sulfide erupts from the ocean.
Of course, looking for hydrogen sulfide-eating microbes that ooze elemental sulfur means that we'll be looking for similar biological processes we observe on Earth.