Rethinking the origins of life on this world and other worlds

Many a science fiction novel is based on the assumption that life has evolved on other worlds around other stars. We still don't know if such life exists. We don't even know how life began on this planet.

The most popular theory is that lightning and ultraviolet radiation from the sun cooked chemicals in the early Earth atmosphere to generate amino acids which eventually organized themselves into replicating organisms. It's a nice theory, but at least one scientist things that life might have actually arisen in the depths of the ocean around hydrothermal vents.

If proven true, that theory would certainly add weight to the thought that life might exist in the dark oceans of Jupiter's moon Europa.

Another hope for life within our own solar system is on Jupiter's moon Titan. The discovery of lakes of liquid methane have prompted one suggestion that future robot probes explore the world by boat.

Too late for boat travel is Mars, but there is growing evidence that it was once a watery world. If the life arose in the ocean depths theory holds water (no pun intended), then maybe we should be looking for evidendence of life on Mars in the areas where the former ocean bottoms lie.

Other oceans in this solar system that certainly won't harbour for life, but would be incredibly cool is the oceans that lie beneath the clouds of Uranus and Nepute. Some scientists think they have ocean of diamonds.

And then there's Jupiter. Is it possible that having a protector like that gas giant is a necessary prequisite for the origin of life on a planet like Earth? Some theorize that it's massive gravity acts as a sort of vacuum cleaner for big chunks of rock that might hit smaller worlds and exterminate any life that is evolving there.