The hydrogen, which is escaping into space from a hydrothermal vent on the moon's seafloor, could be a sign of methanogenesis, a form of anaerobic respiration in which microbes produce methane.
The bacteria are anaerobic – they do not breathe oxygen – so are well suited to live in the bowel.
To cope, the body switches from aerobic to anaerobic metabolism.
Charlotte Morton, chief executive of eco-friendly organisation Anaerobic Digestion and Bioresources Association, said: 'The bus also clearly shows that human poo and our wasted food are valuable resources.
