First rain

Our solar system formed about 4.5 billion years ago from a dense cloud of interstellar gas and dust. For hundreds of millions of years, Earth was a burning furnace. The surface eventually cooled down and gases and water slowly trickled out from the mantle and erupted into the atmosphere as steam. One night — one of the short nights of that time which only lasted five hours — the first raindrop fell. Then came the flood. It probably rained for millions of years.

Earth has shifted many times since then. There is not a fragment left from the oldest mountains, not a stone from the shores of the first shallow seas. The young solar system must have been a dangerous place for space travelers. Stone and gravel rumbled around in space like bullets over a battlefield.

The sun did not shine as bright as today. If anyone still had their ways past, there was no place to land: Earth was burning, it had probably melted all the way up to the surface. A burning furnace hidden by clouds and smoke.

Earth’s oldest atmosphere evaporated into space, but later while Earth’s surface began to cool down, new gases and water slowly trickled out of the interior to create a thick layer of steam which in due time would become a sea of water.

As time passed, water would be pushed back into the bowels of Earth as aqueous sediments plunged deep and while continents floated apart or drifted together. But water seeped out of Earth’s crust as hydrogen and oxygen bound up in molten rock combined into acid water. Volcanic eruptions are largely water vapor and gases.

During every billion years, the water molecules in our oceans have at least once been down into the bowels of Earth and turned back to the surface again. At the same time new gases and fluids have seeped up from deeper layers. To this day, perhaps only a third of all volatile substances have reached the surface of Earth.

Space gravel rained down, volcanoes spat out lava, it spewed up carbon dioxide, sulfur dioxide, water chloride and water vapor. The space traveler saw four small planets orbiting near the sun. The innermost planet was doomed from the beginning, it would remain a desert world since it orbited too close to the solar flare.

But on the other three planets, there may once be life. They glow like clear white, shining stars in the space darkness. Clouds reflected the sunlight, almost like snow.

Earth eventually cooled off. One night the first raindrop fell. Then came the flood. It probably rained for millions of years. A violent erosion started as acidic water rushed over the mountains. Storms swept through the air and thunderstorms ravaged. Valleys and caves filled with water. It rained as it could only rain on newborn worlds.

But one day the sun was shining down through a crack in the clouds, a deadly ultraviolet light over a desolate world. One morning the first sunrise came, in a clear sky over glittering water surfaces.

Somewhere on the planet small creatures hovered in the water, beyond reach of the ultraviolet radiation, seedless cells that could let nutrients seep in and which could feed and multiply. It was hot everywhere, carbon dioxide preserved the heat from the sun although it was weak. And all of this may have happened on Venus and Mars as well.

Did life arise in the oceans or did it come from space? We have no idea. But it could have been there ever since the planet cooled off. If so, simple organic molecules may have begun to form and eventually tie up to form RNA, a molecular candidate long attributed as essential for the origin of life.

There were no mountains or large continents four billions of years ago. Today the continents make up around one third of Earth’s surface, at that time it was probably less than 5%. Heat evaporated from the depth of the planet where the radioactive decay was much faster than today. The land masses grew slowly and drifted together into continents.

Mountain ranges are pushed up toward the skies while ocean sea beds are pushed down into the core where it melts and becomes part of the bloodstream that will continue for billions of years. Our planet, once built out of stone, ice and gas, came alive.

Then....,