Life as we know it might have started on a brown dwarf star. Picture a star that has cooled down. The star has gone through a burning down. It is now combining heavy gases with light gas like hydrogen and oxygen. The result is huge thunderstorms and lots of water. Possibly oceans many miles deep, covering a molten core in such a way that a crust has formed. The heat of the star keeps things above freezing. The atmosphere is very thick. I suggest nitrogen is in abundance. I suggest the steam is forming a cloud barrier keeping a lot of that warmth in.
Life is a random process. It first occurs as something simple. Then it knots itself into more and more complicated forms. Finally you have a system developing. I suggest plants of various types parallel evolve with animal forms. More than likely the huge gravity is offset by the pressure of the atmosphere. Water animals would be most likely to develop first. After a billion or more years, random chance forms the first forms of life. It would have to be a form of multiple chances. Eventually this evolves into more and more complicated forms. This would form microscopic life where huge gravitational pulls would have little effect as the forms that are so small. Most of this would be in the form of pond scum. Picture huge mountains formed as volcanos erupt on the surface. The surface is still unstable. Small islands of land form in the upper atmosphere. The heavier metals and rocks come up from the core. And that is how it begins. Land life follows on both plants and animals.
Now picture this brown dwarf star is a maverick formed between the larger star systems. In a billion years it has already made several passes around the galactic core. Only the stars are moving at a different speeds and angle of inclination from the galactic center. In passing, the maverick is attracted to a young sun many times its own size. Around that sun is the debris of another brown dwarf that has gotten too close and broken up to form planets. The planets are rotating clockwise around the equator of the star if you are looking down from the north pole of the star. The new brown dwarf comes in at about a 30-40 degree angle from the South side of the star. It comes in counter clockwise like a bullet. It grazes several of the outer planets. In the process, life is seeded on all the planets it comes into contact with. Most of the life is frozen instantly and dies. Somewhere, somehow some of the life actually survives the impact of two bodies seeding new life on various bodies. Parts of the ocean are attracted to the grazed planets and because it is so small, it survives the impact. Planets are thrown into entirely new orbits as the the huge brown dwarf relative to the smaller planets rearranges things. Others are dragged completely out of the solar system and finally cut loose millions of miles out. At least two planets blow up and become asteroid belts.
The brown dwarf has its own planets around it. At least one has a direct collision with a young planet with a large molten core. This planet is at least the size of Neptune. Another one turns on its side as it is grazed by one of the planets.This explosion might have been where the Earth and Moon came from. If so the two bodies had to have come in close contact with the Brown Dwarf and received an overabundance of life and water. If this is so, then there might be fossil evidence of life on our own Moon several layers deep under the surface.
The evidence for this conjecture is there is a lot more water than should be possible in the entire Solar System. Planets, Moons, asteroids, we find water almost everywhere. Even our own Moon has water on it. There is circumstantial evidence of oceans on Mars. Where did all that water come from. If I am correct, a natural water body would have to have went through the system sometime in our past. The life was already evolved on the home brown dwarf. It had evolved for a lot heavier gravity than we have here.
The real mind blower will be if and when we discover life elsewhere in our Solar System. If it follows the same pattern of DNA and genetics as our own life, then it might have had a common origin somewhere in the past. If I am right then Earth had a much denser atmosphere as little as a million or so years ago. Because much of that atmosphere came from somewhere else.
If I am right, then it is possible that Venus is the result of one of these passes of the Brown Dwarf and probably closer to our historical time than anyone realizes.It could mean the upper atmosphere of that little hot pistol of a planet so similar to our own is full of steam from an ocean that never got cold enough to form. Somewhere down the road, that steam might get cold enough to start a thousand year rain storm on the planet itself. It is also possible the upper atmosphere contains life forms evolved to the specific nasty environment of Venus. It would have to be floating life forms that stay in the temperate zone of the upper atmosphere their entire lives. I don’t know if there are mountains that tall on Venus for them to land and breed. They would have to have evolved a system of breathing much different than our own.
If I am currect, a lot of planets have been seeded in our past. Mars might still have underground life on it. If so it has evolved to the conditions present on the planet.
If I am right, they all have a similar genetic origin.