The making of life on Earth
Comets played a part in making our world a living planet
1 Giant molecular cloud
An interstellar gas cloud collapses under its own gravity to form a group of new stars, one of which is the Sun.
2 Protoplanetary disc
A dusty disc of material forms around the new star. Gravity slowly pulls this material together – a process that will eventually form the planets.
3 Comets form
Far from the Sun, beyond a point known as the ‘ice line’, smaller, icy objects – comets – coalesce.
4 Ultraviolet radiation
UV light from the young Sun could have helped form ribose on some comets, although it has yet to be confirmed with a comet sample.
5 Comet impacts
With much debris flying around the Solar System, the comets get hit hard. The force of the impact creates amino acids.
6 The Earth is bombarded
Over time our planet is peppered with asteroid and comet impacts. The asteroids topped up our water and the comets delivered amino acids.
7 The spark of life
Somewhere deep in the ocean, probably around volcanic vents in the ocean floor, some unknown process turns these molecules into life.