Even as we delight in watching water dance across the riffles in a river, we fear floodwaters sweeping all before them. We treasure a summer afternoon at a lake or seashore, splashing, boating, fishing or swimming but our need for clean water goes far beyond fear or pleasure.
Despite all the water around us, we seldom consciously think about how often we need clean water. We use water to wash our food, our possessions and ourselves. We cook our food in water; constantly drink water in various forms and dispose of our waste with water. We rely on water in our basic manufacturing processes; conduct commerce on water and harvest food directly from it. We play in, on and under water. The life process of our bodies would be impossible without water. Water is necessary to our lives on a lifetime, daily, hourly, instantaneous basis and we cannot substitute any other known substance for water.
For all the importance of water to all species, we do not know where it came from nor how there came to be so much of it, to the point where oceans covers 70 percent of Earth’s surface. The source of water on Earth is one of those questions that seem to have no answer. Well, actually it currently has several answers, none of which has identified conclusively the source of water on Earth.
There are three theories about how Earth acquired water. One contends that the Earth formed with water attached to the dust particles that accreted to form the Earth. Other claims are that the planet came by water through asteroid and comet collisions. The third, and least documented, suggests early plants created water as a byproduct of photosynthesis. All of the theories involved what may have happened during the earliest eras of the Earth.
The accretion theory holds that the dust particles that formed the earth contain grains of the mineral olivine, a mineral common on Earth. The solar system temperature 4.7 billion years ago when Earth formed was roughly 7500 degrees Fahrenheit. The Earth should have been baked dry but olivine holds onto the oxygen in water molecules at temperatures over 1,100 o F.
As the theory goes, Earth accreted more and more of these particles in its formation and water came along with them. Then, as Earth began to cool, the minerals solidified and crystallized in the mantle leaving most of the water behind in the fluid magma. Eventually, over the eons, the trapped water became so concentrated that it bubbled out of the molten magma producing a steamy atmosphere that condensed and fell as rain on the surface. Some even claim that there are oceans of water still trapped in the molten magma in the inner Earth.
The most commonly accepted theory has the Earth receiving its water from interstellar bodies through collisions with comets and asteroids. If they were the source, then something had to hurl the interstellar bodies toward the Earth and the suspected thrower is the huge planet Jupiter. Jupiter is thought to have gone rogue, leaving its circular orbit and taking on an elliptical orbit in the early eons of the solar system due to gravitational effects of the equally massive Saturn. Jupiter cut across the solar system and then went shooting far our beyond our solar system. Once in the gigantic elliptical orbit its massive gravitational strength could have pulled icy outer solar system asteroids and comets from the asteroid belt into elliptical orbits aimed inward toward the sun and on their travels, some would bash into the Earth and bring their water with them.
Although speculations in this vein always include comets and asteroids together, there are now some questions about the comet part of the theory. Scientists have found that water found on and in comets does not match the chemical makeup of the water in our oceans. Asteroids hold water that is a better chemical match. These supposed collisions happened so early in Earth’s existence that there are no impact craters to prove any of it.
The most speculative theory offers that when plants first began photosynthesis the reactions were different than in plants today because our atmosphere then lacked oxygen and was made up of carbon dioxide heavily mixed with hydrogen sulfide. These chemical compounds, when run through photosynthesis, make water a much larger byproduct of photosynthesis. Now in our oxygen rich atmosphere the reaction has changed and the addition of new water to the earth from plants is negligible.
So out of this shroud of mystery came a substance found everywhere on and around the Earth with properties that are vital for all life, as we know it. Regardless of the ultimate source of water, there is a finite amount with only a miniscule 2% overall being fresh water and we do not expect to see any more water come our way. So what we have is what we get. Good reason to take care of all of it.
David L. Deen is Upper Valley River Steward for the Connecticut River Watershed Council. CRWC is celebrating over 60 years as a protector of the Connecticut River.