The recent ground-breaking Rosetta mission, where a probe called Philae landed on a comet 500 million miles from Earth, demonstrates the human drive to discover more about comets. Comets are often referred to as ''dusty snowballs'', as they consist of an ice and rock centre (its nucleus) surrounded by a cloud of gas and dust (the coma). Considered leftovers from the formation of our Solar System, the majority of comets inhabit the 'Ooort Cloud', beyond the orbit of Pluto. Occasionally one soars through the Solar System, leaving bright tails in its wake, providing a celestial show to Earth. As a result of this movement, many theories hypothesis that comets may have led to life on Earth.