The first life on Earth is thought to have formed around 4 billion years ago, but where did the organic building blocks required for this to happen come from?

One explanation is that organic molecules appeared early in the Earth's evolution, eventually combining into more complex forms, kickstarting the evolution of life as we know it. However, another possibility is that these molecules originated in space, possibly even from within our solar system.

Now, a new study lends credibility to the latter possibility, showing that the building blocks of life can form in a cold, space-like environment, full of radiation.

Researchers from the University of Sherbrooke in Canada simulated conditions in space by blasting thin layers of ice – made from methane and oxygen – in a vacuum with so-called electron radiation.

When radiation comes into contact with interstellar ices in space, chemical reactions occur and new molecules are formed – some of which are the precursor molecules to life as we know it. Various types of ice exist on objects in the solar system, such as comets, asteroids and moons, and it also forms around dust grains in vast interstellar clouds.

In their experiments, the team found that when the ice sheets were subjected to the electron radiation, various different organic molecules were formed, including ethanol, acetic acid, formaldehyde, propylene and ethane.

The team's findings demonstrate that it is possible for life's key ingredients to have been produced in space on the icy surfaces of objects which subsequently collided with our planet.

The results are published in the Journal of Chemical Physics.

Another recent study, conducted by researchers from the University of Edinburgh, suggested that organic molecules could potentially have been brought to Earth on fast-moving streams of interplanetary dust which continually bombard the atmosphere.