Aliens could have started life on Earth? - Study

New research, due to appear in the Astrophysical Journal Letters, shows life may have spread through space like an infectious virus.

Alien life forms may have swept from planet to planet creating the seeds of new species wherever they found a habitable environment through organic 'seeds' of life being transported by asteroids or comets or more unlikely, via an advanced space-faring race visiting new worlds.

Experts believe our civilization was started by the organic 'seeds'.

Lead scientist Dr Henry Lin said: "In our theory clusters of life form, grow, and overlap like bubbles in a pot of boiling water."

The model assumes that life emerging on one living planet spreads outward in all directions.

Co-author Dr Avi Loeb, also from the CfA, said: "Life could spread from host star to host star in a pattern similar to the outbreak of an epidemic.

"In a sense, the Milky Way galaxy would become infected with pockets of life."

Such an epidemic-like pattern should be possible to identify from Earth.

For example, if the Earth happened to be on the edge of a "bubble" of life, all the nearby life-hosting worlds would be in one half of the sky.

Since stars move relative to one another, close neighbours are likely to drift apart over time scales of millions of years.

Stellar drift would have the effect of smearing out the life cluster "bubbles".