Marc Wolfe, age 11, of Columbus, Nebraska, for his question:
Was there water here when the earth began?
Naturally nobody was there at the time to give us an on spot report. But scientists have figured out at least part of the story from existing evidence. If their theories are correct, every spot on earth was much too hot for all living things. Apparently the world was so hot that no water could exist on its seething surface. Most authorities agree that things had to cool down before the rains could fall and fill the oceans.
Scientists have ways to date the ages of the earth's rocks and methods to trace their adventures through the ages. These crustal minerals provide masses of evidence, from which it is possible to trace geological events way back to the dawn of the earth's early history. The oldest known rocks indicate that the infant planet was ormed sometime between four, billion and five millian years. ago. Most experts suspect that it condensed and solidified from whirling gases.
However, the newborn earth did not resemble the luxurious world we know today. It was seething hot and completely lifeless. Apparently, at first even the surface was a brew of boiling lava and molten materials. The young planet was shrouded in a pea soup atmosphere of dense gases. Some scientists suspect that the infant earth took shape before the sun ignited. If this is so, the surface was lit by molten minerals, but no sunshine pierced through the midnight clouds.
The evidence suggests that the earth changed rather quickly. In a few million years, the seething surface formed a solid crust. Water and a vast variety of other molecules formed in and below the crust. And an enormous amount of moisture was suspended in the atmosphere. At some unknown time, the heavy clouds shed the first showers. But the newly formed surface was still hot and the falling raindrops immediately frizzled into steam.
No one knows how long the rain fell and returned to the steamy atmosphere. But the surface rocks gradually grew cooler. As last the rain could land without boiling back into the air. The evidence suggests that this was a period of drenching deluges. The rain ran down the barren, rocky slopes and gathered in puddles. Through the years the gushing water cut channels and emptied into huge hollow basins in the earth's crust. After several million years, the super rainy season subsided. The skies cleared and the big crustal basins held the earth's first oceans.
Suppose we shrink the age of the earth to a year. On this time scale, the crust solidified in February. This was soon followed by the awesome rainy season in early March, the earth's first water arrived to stay. By the end of the month the deluging downpours had dumped enough fresh water to fill the first seas. These seas remained, though their shapes have changed and their waters have grown salty through the ages.