Chapter Three

Cosmology

3.1  Dr Servettaz devoted a large part of his book to describing the science of the lake, what he called ‘The intimate life of the lake’. Even before launching his description of the biological processes taking place in the lake, Dr Servettaz devotes a whole chapter to the amazing substance without which there would be no life on earth, nor likely anywhere in the universe.  Water.  (A recent search for life elsewhere in the universe – the Kepler mission – selects potentially habitable planets based on whether there is water present.)

3.2 Dr Servettaz summarizes the incredible versatility of this substance that informs every aspect of our daily lives including: we are made of water, if we don't drink it we die, it circulates nutrition in our bodies and enables us to excrete, it controls our temperature through sweat, we express emotion through our tears, we keep clean by washing ourselves, our things and our homes, it dissolve any number of substances to be able to use them, we use it to put out fires, in rivers and oceans it transports our ships, when it rains it enables crops to grow. All life depends on water – from the beginning of time to today and each day.

3.3  But where did it all come from? This is a puzzle even to Cosmologists today. How did a firey ball of rock newly formed from colliding space debris those 4.5 billion years ago, end up with just enough of this wonderful substance eventually needing to support a population of 9 billion people? How come there was sufficient to form oceans covering two thirds of the worlds surface, and not just a couple of small ponds? And how come there was not  too much water so that it covered the entire earth surface,  so preventing life on land, and  homo sapiens from ever evolving? That was a bit of luck. And how did the first water stick to the earth’s firey surface, rather than be boiled off into outer space or decomposed into it hydrogen and oxygen.  Was it there to start with and managed to survive the late heavy meteorite bombardment around 4 billion years ago?  Of did the meteorites turn up a few hundred million years belatedly for Earth's birthday party bringing with them the liquid present without which the party would have little to celebrate? Dr Servettaz was amazed by the miracle of water, and no wonder.

3.4 The Smithsonian Institute shares Dr Servettaz’s wonder of water even today, and this is where cosmology takes over our story. “We don’t know the first thing about it—literally the first. Where does water, a giver and taker of life on planet Earth, come from?

3.5 Here’s the part we think we understand.   Just shy of a trillionth of a trillionth of a second after the Big Bang, the energy that sparked the outward swelling of space transmuted into a hot, uniform bath of particles. During the next three minutes, these primordial constituents bumped and jostled, combined and recombined, yielding the first atomic nuclei. One of the triumphs of modern cosmology is its mathematical description of these processes, which gives accurate predictions for the cosmic abundances of the simplest nuclei—a lot of hydrogen, less helium and trace amounts of lithium.

3.6 Producing copious hydrogen is a propitious start en route to water, but what about the other essential ingredient, oxygen?

3.7 That’s where stars, already plentiful about a billion years after the Big Bang, enter the picture. Deep within their blisteringly hot interiors, stars are nuclear furnaces that fuse the Big Bang’s simple nuclei into more complex elements, including carbon, nitrogen and, yes, oxygen. Later in their lives, when stars go super­nova, the explosions spew these elements into space. Oxygen and hydrogen commingle to make H2O.

3.4 So are we done? Not quite. In fact, this is where things get a little murky. Water molecules were surely part of the dusty swirl that coalesced into the Sun and its planets beginning about nine billion years after the Big Bang. But Earth’s early history, including epochs with high ambient temperatures and no enveloping atmosphere, implies that any initial surface water would have evaporated and drifted back into space. So it is generally thought that water we encounter today , must have been delivered long after Earth formed - by late meteoric arrivals.

3.5 But this is where National Geographic weigh in just a couple of years ago. “The water that makes Earth a majestic blue marble was here from the time of our planet's birth, according to a new study of ancient meteorites, scientists reported Thursday.

3.6 Where do the oceans come from? The study, headed by Adam Sarafian of the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts, found that our seas may have arrived much earlier on our planet than previously thought. The study pushes back the clock on the origin of Earth's water by hundreds of millions of years, to around 4.6 billion years ago, when all the worlds of the inner solar system were still forming.  "Scientists had suspected that our planet formed dry, with high-energy impacts creating a molten surface on the infant Earth, and that water came much later, thanks to collisions with wet comets and asteroids. Some people have argued that any water molecules that were present as the planets were forming would have evaporated or been blown off into space," said study co-author Horst Marschall, a geologist at WHOI. For that reason, he said, scientists thought that "surface water as it exists on our planet today must have come much, much later—hundreds of millions of years later."

3.7  But no one was certain. To pin down the exact time of the arrival of Earth's water, the study team turned to analyzing meteorites thought to have formed at different times in the history of the solar system.

3.8 First, they looked at carbonaceous chondrite meteorites that have been dated as the oldest ones known. They formed around the same time as the sun, before the first planets. Next they examined meteorites that are thought to have originated from the large asteroid Vesta, which formed in the same region as Earth, some 14 million years after the solar system's birth. "These primitive meteorites resemble the bulk solar system composition," said Sune Nielsen of the WHOI, a study co-author. "They have quite a lot of water in them, and have been thought of before as candidates for the origin of Earth's water."

3.9 The team's measurements show that meteorites from Vesta have the same chemistry as the carbonaceous chondrites and rocks found on Earth. This means that carbonaceous chondrites are the most likely common source of water. "The study shows that Earth's water most likely accreted at the same time as the rock," said Marschall. "The planet formed as a wet planet with water on the surface."

3.10 While the authors are not ruling out that some of the water that covers 70 percent of Earth today may have arrived later, their findings suggest that there was enough already here for life to have begun earlier than thought. Knowing that water came early to the inner solar system also means that the other inner planets could have been wet early and evolved life before they became the harsh environments they are today," explained Nielsen.

3.11 And what was the world like in those earliest 500 million years, named Hadean, after Hades the Greek god of the underworld, for the hellish conditions that pertained then. The planet spun madly on its axis – a day being les than 6 hours long. The moon, just recently gauged out of the earth, was far closer causing huge tides across the oceans which then covered most of the planet. The atmosphere was all smog and dust with little oxygen. The crust was riddled with cracks, magma welled and coiled, and volcanoes made Hades’ underworld a constant presence pockmarking the ocean’s surface.

3.12 It was a world out of equibrium – the very anthithesis of today’s Lake Annecy.

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