Some believe it originated in a random manner, possibly in a chemical “soup” enriched by early atmospheric gases such as methane and carbon dioxide, with energy supplied by lightning or solar ultraviolet light. Others suggest the raw materials, or life itself, were delivered by comets and meteorites – a theory known as “panspermia.” Yet another possibility is that the first life forms lived deep beneath Earth’s surface, where the temperature was far above 100°C, with sulfur in the rocks as their source of nutrition. Warm environments around deep sea volcanic vents, known as black smokers, are another alternative. According to the passage,