In contrast to the classical PERSON@1 experiments , which depend on external sources of energy -LRB- such as simulated lightning or UV irradiation -RRB- , `` Wächtershäuser systems '' come with a built-in source of energy , sulfides of iron and other minerals -LRB- e.g. pyrite -RRB- .

In contrast to the classical PERSON@1 experiments , which depend on other sources of energy -LRB- such as lightning or UV irradiation -RRB- , `` Wächtershäuser systems '' come with a built-in source of energy , sulfides of iron and other minerals -LRB- e.g. pyrite -RRB- .
