I like to imagine life on Earth began as it's depicted in Star Trek: The Next Generation--compounds in a puddle of goo colliding to form the first proteins, as Patrick Stewart stands around looking vaguely confused. A new theory about the beginnings of life on Earth, as reported by Phys.org, is actually pretty similar--minus Patrick Stewart.
""When the Earth formed some 4.5 billion years ago, it was a sterile planet inhospitable to living organisms," says paleontologist Sankar Chatterjee. "It was a seething cauldron of erupting volcanoes, raining meteors and hot, noxious gasses. One billion years later, it was a placid, watery planet teeming with microbial life – the ancestors to all living things."
Chatterjee thinks he's figured out the sequence of events that took Earth from sterile dead zone to oceanic paradise. Meteorites were the key. Chatterjee divides the history of life's beginnings into four stages: cosmic, geological, chemical and biological. In the cosmic stage, 3.8 - 4.1 billion years ago, meteorites pounded the Earth--we can still see the damage they inflicted in craters on the moon and other planets. When giant meteorites cracked through the planet's crust, they loosed geothermal vents. They also left behind the building blocks of life, and in Greenland, Australia, and South Africa, environmental conditions were perfect for life to form.
"Because of Earth's perfect proximity to the sun, the comets that crashed here melted into water and filled these basins with water and more ingredients," writes Phys.org. "This gave rise to the geological stage. As these basins filled, geothermal venting heated the water and created convection, causing the water to move constantly and create a thick primordial soup."
At this point, the scene was very much like it was depicted in The Next Generation's finale. Convective currents from geothermal vents incubated organic molecules. The first RNA and proteins formed in the craters left behind by meteor strikes. This was the chemical stage. Chatterjee also believes that an older hypothesis about the primordial soup, from professor David Deamer, was correct--fatty lipid materials brought with the meteor strike at some point encapsulated the RNA and proteins, binding them together.
After that, it still took millions of years for cells to begin to form and replicate. And that, says Chatterjee, is life. Pretty simple stuff, huh?