The Harvard-Smithsonian Center for Astrophysics is currently debating a theory called panspermia, suggesting life spreads across the galaxy like an epidemic.
Similarly to a virus in an outbreak, life could have originated in a far-away distant world and it was slowly but steadily transmitted to other corners of the universe. Therefore, this controverial theory implies that Earth was ’seeded’ either by a comet carrying organic elements or by an advanced civilization travelling through space.
The hypothesis may seem arguable, but astrophysicists point out that if inhabited planets are eventually discovered, their distribution could be almost irrefutable proof of panspermia.
Harvard scientists Abraham Loeb and Henry Lin have fashioned a model of how life could be transmitted to other worlds. According to this pattern, populated alien worlds might be organized in clusters throughout the galaxy, occupying roughly spherical regions divided by void. If there was life on one particular planet, it would be spread outwards in every direction and eventually establish itself on a planet orbiting a star nearby. For instance, if an asteroid were to hit a planet rich in life, pieces of crust would be projected into space. If these samples contained organic matter, they could seed it in a brand-new environment and eventually populate it.
Another related theory is `directed panspermia`, which suggests a highly advanced civilization could intentionally colonize other worlds by bringing capsules containing its offspring. `Necropanspermia` is also a popular hypothesis claiming cryogenic dead matter could be used just as effectively, removing thus the requirement that alien life should survive the journey.
Whichever the route of transmission , life-sustaining planets would appear in the galaxy, just like oases are found in the desert and inhabited worlds would `form, grow and overlap like bubbles in a pot of boiling water’, explains lead study author Henry Lin. If Earth were on the outer edge of such a bubble then we could encounter alien life on systems`behind` us.
This is a crucial theory in the search for extraterrestrial life, because it explains how its building blocks disperse from a host world to another world in a viral pattern, like an epidemic `infecting` the galaxy.
As researcher Lin suggests, `”If there’s a virus, you have a good idea that one of your neighbors will have a virus too. The Earth is seeding life, or vice versa, there’s a good chance immediate neighbors will also have signs of life.’
At the moment, this engaging thesis is in its early ages, but we do have evidence that it is possible for chunks of crust to split from a planet and reach another one. For instance, a meteorite was found on Earth which shares the same isotopic signature encountered by robots on Mars; this shows the rock actually originated on the Red Planet and was propelled to Earth following an asteroid impact. Similarly, there is a possibility that chunks of Earth ended up on the orbits of Jupiter and Saturn, affecting their moons.
Image Source: Wikipedia