Abundance of Water — Where Did It All Come From? — Dare to Know

The abundance of water is still a mystery to science. Find out why researchers believe that water may have formed with the Earth from its beginning.

I can remember sitting in my Grade 4 class with Mrs. Martin holding up a standard-issue schoolteacher’s globe. She was pointing out that two-thirds of the Earth’s surface is water.

This has many ramifications, including how challenging it was for the early explorers to discover all of the continents. It also means that many dangerous things like space junk and meteorites end up unnoticed somewhere at the sea’s bottom.

Only About 1% of the Water on Earth Is Drinkable

I’m privileged to live among the Great Lakes in Canada, which has always left me with the impression of abundant freshwater. That’s not true globally. For all the massive volume of seawater on Earth, only about 1% of the water on Earth is drinkable.

Just as the Earth is mostly water, so are we. Our bodies reflect the abundance of water on our planet, being roughly two-thirds H20 as well. In a matter of days, we will die without water. All the cells and organs in our bodies need water to function.

Water lubricates our bodily functions. It makes up saliva and the fluids surrounding the joints. The water in our sweat keeps our body temperature under control. Our bodies also use water to promote healthy digestion.

The Fish Is the Last Thing to Discover Water

Einstein once said that the fish is the last thing to discover water. He was right. We tend to take the abundance of water for granted.

Yet, once scientists began to realize how abundant and vital water is, they’ve wondered what caused its plenitude on our world. The fact that it’s so scarce on all the other planets in our Solar System, especially the rocky interior planet, added to the puzzle.

The conventional wisdom has been that water came from comets. Over a very long time, the thinking has been, icy comets collided with the Earth. They’re thought to have left bodies of water behind on our planet’s surface.

Hard to Imagine Comets Accounting for Abundance of Water

That idea has always been controversial, though, because comets are relatively small. It’s hard to imagine that there could be enough comets crashing into the Earth to account for the abundance of water we see in our vast oceans.

A new article in the journal Science seems to offer a more plausible explanation. A research team from the Centre de Recherches Pétrographiques et Géochimiques in France examined meteorites. They were looking for evidence that water may have been part of the Earth’s makeup from the very beginning.

The team concentrated on a rare type of meteorite called enstatite chondrites. Only about one in fifty meteorites falls under this category.

Meteorite Material Similar to the Primordial Earth

They were essential to this study because they’re made of very similar material to that of the primordial Earth. Everything in the Solar System formed almost at once 4.5 billion years ago out of a disc of debris swirling around the newborn Sun.

That means that these meteorites hold clues to what the Earth was made of when it first formed. The team, led by research specialist Laurette Piani, collected thirteen of the most pristine samples of these rare meteorites for study.

They looked at the water concentration in these meteorites. They found that this meteorite type contains less water than other meteorite categories, but they expected that.

Meteorites Contain Less Water than Other Types

The consensus has been that enstatite chondrites contained little or no water because they formed in the inner solar system, close to the Sun. This led previous scientists to dismiss them and the materials they consist of as potential sources of water for our planet.

Despite this, the team discovered that the samples contain more than enough water to account for the abundance of water residing in the Earth’s rivers, lakes and oceans. Since these meteorites most closely resemble the raw materials from which the Earth formed, this means that Earth’s water supply could have developed along with the planet itself.

As Piani put it, “It’s a very big quantity of water in the initial material, and this was never really considered before.” The team also approached the question from another angle.

“It’s a Very Big Quantity of Water in the Initial Material”

There’s a massive amount of water in the Earth’s interior. In fact, there’s enough water inside our planet to make up several oceans on its surface.

We know the ratio of hydrogen to heavy hydrogen-the isotope scientists call deuterium-in that internal water. So the scientists measured the hydrogen/deuterium ratio in their meteorite samples to see how it compared.

The ratio they came up with for the meteorites was very close to the proportions maintained by the Earth’s internal water supply. The researchers also compared the composition of the various isotopes of nitrogen inside the Earth to the meteorites. They also were consistent with one another.

Water Arose in the Earth’s Raw Materials

These findings confirm the idea that water arose in the original material from which the Earth formed rather than deposited here later on. That doesn’t mean that comets and other types of meteorites couldn’t have also contributed to our water supply.

On the other hand, the new theory provides a much more elegant explanation for the abundance of water we’re blessed with. Rather than resorting to comet collisions or strange variations in the planets’ orbits, the simplest explanation that covers all the facts is that it was here all along.

Every culture tells stories about how the Earth began. For example, the indigenous people in my part of the world, the Anishnabe, recount a tale of Muskrat diving to the bottom of the sea and bringing back a tiny handful of soil.

Abundance of Water Central to the Story of Life

Placing the soil on Turtle’s back caused the life to spread all over Turtle Island, the indigenous name for North America. As in all of these types of stories, the abundance of water plays a central role in life’s origins.

Our modern point of view tends to rob us of these ancient stories. So we need a new, science-based origin story that we can tell each other and from which we can draw renewed inspiration.

Water will have to take centre stage in that new story as well. That makes it vital to understand how and why our planet came to be endowed with massive quantities of life-giving liquid water.

Massive Quantities of Life-Giving Water

The next step for the researchers is to measure the volume of water inside our planet more accurately. This will give scientists a more exact quantity for future models of water formation on the early Earth.

We always have more to learn if we dare to know.
Learn more
Water, Water, Every Where — And Now Scientists Know Where It Came From
The origins of water
Earth’s water may have been inherited from material similar to enstatite chondrite meteorites
Astrobiology: 3 Questions We Need to Answer
Life Began Earlier Than Thought
Exoplanet Water Common Yet Rare

Originally published at https://daretoknow.ca on October 9, 2020.