This is my theory about life landing on Earth from outer space. Pretend for a few moments that we on Earth have resolved all our differences and have learned to live as one people. Quite a stretch I know, but pretend for a few minutes.
The people of Earth want to travel to other planets and perhaps galaxies, but they are so far away, and our technology is still lacking. The closest planets we want to move to are generations away. We haven’t developed the ability to create and launch multi generations space vehicles yet.
Yet is the key word. We may be able to in the future, but we can not do this yet. We can give ourselves a jump on making new planets habitable. We can do this by launching rockets carrying micro sized pellets of material for planet scape. Let’s make our planet closer. Lets think about getting to Mars and setting up a viable colony of people there. Mars is something we can do in the foreseeable future.
We are getting better at creating designer microbes and designer bacteria. How about we identify or create a microbe here on Earth that can eat some substance on Mars we do not care about or need once we get there.
Let’s create, modify or otherwise produce this microbe to create a waste product we do want. The microbial waste product could be one of the basic components of atmosphere for example. We create some custom microbes and launch them on a rocket ship to Mars.
As our discoveries, technology and knowledge grows so does our microbe creation. We can create ever more meaningful microbes that create as a by product something we need on Mars once we get there.
Eventually we are in the process of terraforming Mars. Making it closer to something we can inhabit easier. Since we have developed and improved on our microbes and bacteria, there is no sense letting them go to waste.
We package them up and send them off to a further planet we want to someday inhabit. We keep picking out planets further and further away from Earth, but not prohibitively far away from the previous planet we plan on inhabiting some day.
At some point in the process our rockets will be hit by asteroids, or other debris, and our microbes will be dispersed in ever new directions, destined to land on other unknown planets.
Is it possible this has been happening for thousands of years? Projectiles from other civilizations sending out pods of microbes and bacteria with the intent of terraforming planets to their needs for future habitation at some distant point in time?
Some of the pods have been damaged and their contents disbursed landing on barren surfaces starting the process of terraforming? Landing on Earth, most of them benign, but a few not so friendly causing disease and pestilence we had not seen previously?
There does not have to be mal-intent in the actions of sending out projectiles and pods with bacteria and microbes. There just has to be a want to terraform a hostile planet into a planet where future inhabitation may be easier thanks to the efforts of those who lived hundreds or maybe even thousands of generations earlier.
These packages of life terra-forming life may have happened so far in the past the civilizations that sent them do not even know they arrived here on earth.
Alien planet hopping intentions may be lost in time. Only their efforts reamin, lost life forms wandering the galaxies until some planet like mass blocks their path. Some arriving life forms survive and thrive, others perish in a hostile environment. In the end result, it may even have been ourselves who sent life forms into space eons ago.