By David Martin –
We must’ve been thirsty when we opened our internet tubes for cleaning this week, because all we could think about was water, including the frozen variety. Ice covers about 10% of the Earth’s surface and if all ice melted (not including that in your sweet tea), water coverage over Earth would bump up from 71% to approximately 75% — and that would mean a 230-foot rise in sea level, submerging Florida and the Eastern Shore and making Washington, D.C., a coastal city. By contrast, the National Oceanic and Atmospheric Administration estimates that when we reach 2050, sea level will have risen 1 foot along the East Coast of the U.S.
Some scientists believe, however, that once upon a time, a few billion years ago, Earth was like the movie “Waterworld,” covered with water, no visible land. Where did all that H2O go? Some water vapor is lost to space on a continual basis but not enough to account for waterworld-Earth draining down until land poked out over 29% of the planet’s surface.
The water basically soaked into the Earth’s mantle. Those billions of years ago, Earth was, in scientific terms, hot-hot, and since hot rock can’t hold much water, almost all of the planet’s water stayed on the surface. As Earth cooled, water drained into the mantle. Most of this water is locked into rock at a molecule level, which we should be happy about because if it came to the surface (again), we would all have to live on boats.
When talking about how watery the Earth is, we can lose sight of the fact that only a few drops of that water, relatively, is available for human use. According to an article published by the United States Geological Survey, 96.4% of Earth’s surface water is in oceans, 1.74% is in ice and permanent snow, and only 0.76% is fresh groundwater with another 0.007% in freshwater lakes.
How did all this water — fresh, salty, frozen, liquid, on the surface, below the surface — get on Earth? Now you’re going to start an argument. Or, as scientists would say, we have competing theories.
One theory suggests that water-rich meteorites crashing to Earth over billions of years during our planet’s early life supplied the water we have today. Never allowing a nit to go unpicked, competing scientists point out that the water we have in our oceans contains less deuterium than the water in meteorites. Deuterium, also known as heavy hydrogen, is one of the two stable isotopes of hydrogen. So maybe meteorites aren’t Earth’s Culligan service.
Another theory contends that all the elements needed for Earth’s water were created or present when a rogue planet (not its official name) collided with early Earth and knocked out a chunk that eventually formed our moon.
Then there’s the solar wind theory, speculating that the hydrogen in solar wind combines with the oxygen atoms in the dust from asteroids to create H2O that then streams to Earth. The water created by solar wind apparently has a deuterium level that more closely matches the water in our oceans.
You can also find water, in addition to in asteroids and meteorites, in your brain, which is 73% water … which might explain why so much of our thinking is mushy.