There is a lot of information about the planet that we take for granted. Land has always been a feature of the earth. Every ocean has unique features that distinguish it from other planets<\/a>. The consensus among scientists is that life began in the oceans and evolved in such a way that it was able to later emerge onto land.<\/p>\n
Our planet has continuously been changing ever since it first formed about five billion years ago. The planet that we know and love today, with an atmospheric composition that is ideally suitable to support life and an abundance of plants and animals, is not what the earth has always looked like.<\/p>\n
The earth has gone through periods of massive bombardment<\/a> from asteroids as well as ice ages that caused the entire planet to become a frozen snowball. It has seen numerous mass extinctions and the re-flourishing of life, as well as changing atmospheric conditions, from what would be toxic to us to what is perfect for us to breathe.<\/p>\n
The Hadean period refers to the first 500 million years of the planet’s history. During this time, the earth was so hot that it was mainly a giant ball of molten rock. Scientists named this period the Hadean after the ancient Greek god of the underworld, Hades<\/a>.<\/p>\n
Asteroids are always running amok throughout our solar system, but most of them are kept out of the earth’s past because Jupiter’s massive gravity attracts them. But before the solar system was fully formed, earth and the other rocky inner planets sustained intense asteroid impacts because Jupiter and the other gas giants were not yet able to move the asteroids away.<\/p>\n
The Hadean period consisted of something known as heavy bombardment<\/a>. The sheer quantity of asteroids that hit the earth probably contributed to the planet being so hot during this time.<\/p>\n
There is some evidence to suggest that there was liquid water on earth during the Hadean period, meaning that life may have actually begun during this time. As the solar system came together so that it looked like what we recognize today, the intense asteroid bombardment ended, and the earth began to cool.<\/p>\n
Towards the end of the Hadean period<\/a>, the liquid water on the earth began to form into oceans. The earliest life forms also began to develop; in fact, evidence suggests that the very first life appeared during the Hadean period.<\/p>\n
Many scientists believe that life on earth began because of chemical processes that occurred in the planet’s primitive oceans. Elements bonded together into the molecules that we know as amino acids, which form the basis for both DNA and proteins.<\/p>\n
Over time, the amino acids evolved into DNA and its cousin, RNA<\/a>, both of which can self-replicate. From there, single-celled organisms evolved and, over time, developed increasingly complicated features. These new features helped them adapt to their environment, as well as grow and reproduce so that they evolved into the life forms we know today.<\/p>\n
The evolution of life on earth did not happen in a straight line. There have been many mass extinctions in which 90% or more of all life forms died out<\/a>. We know about these mass extinctions because of fossils that show life forms that are not in existence today and that share few similarities with other species that are currently in reality.<\/p>\n
Somehow on planet earth, conditions always seem to stabilize enough for life to re-emerge. Some species<\/a> have survived mass extinctions (though we would all be grateful if cockroaches would finally die out) and come back to dominate the planet.<\/p>\n
Despite the great strides that scientists have made in understanding the development and evolution of life on earth, there are still tremendous gaps in their knowledge. One notable example is that many scientists believe life began during the Hadean period. However, so few rocks survive from that part of the earth’s history that there is little to study about those conditions and how life formed.<\/p>\n
Then there are questions about how life made the tremendous leap to homo sapiens<\/a> – us. There is a lot of disagreement about how biological evolution led to the rise of humans.<\/p>\n
Furthermore, there is much disagreement as to whether or not biological evolution is how life began in the first place, or at least how the chemical composition of the earth’s oceans contributed to the development of life. Some scientists have been putting forth different theories<\/a> as to the origins and development of life.<\/p>\n
We certainly do not have all the answers, but the important thing is that scientists continue researching and studying to try to understand the origins and development of life better. They have been refining Charles Darwin’s theory of evolution for over 150 years and adding different bits and pieces that Darwin could have never imagined.<\/p>\n
They are also trying to understand how the chemical and geological conditions on earth supported the development of life. Studying life on earth involves many different fields<\/a> of study outside of biology – chemistry, geology, physics, and many, many other branches of science.<\/p>\n
Benjamin Johnson and Boswell Wing<\/a> are two scientists that went to Australia to conduct some research on the conditions of the early earth. Wing had been leading a research team and told Johnson about a significant bit of exposed ocean crust in the southern part of Australia.<\/p>\n
Johnson embarked on a flight to Perth, and then a 17-hour car ride to a remote location in southern Australia marked inconspicuously by scrubby vegetation and seemingly endless rolling hills. Amidst that landscape is a massive rocky outcrop that was part of the ocean’s crust over three billion years ago<\/a>.<\/p>\n
When water goes through coffee grounds to make your morning brew, it leaves behind traces that can be all but unnoticeable. If the water has a high saline content, the coffee may have a less bitter taste; if the water is alkaline, then the coffee may have a less acidic taste. The minerals in the water will also filter through the coffee grounds and end up in your morning brew.<\/p>\n
A similar scenario is at work in studying this bit of primeval ocean crust<\/a>. The research team set out to find what the water that filtered through that crust was like by examining the “flavors” that are left behind.<\/p>\n
There are no samples of ancient ocean water lying around, but there are ancient rocks that used to be on the ocean floor. The research team collected rock samples from the outcrop of exposed ocean crust to analyze them.<\/p>\n
Specifically, they looked for the oxygen isotopes Oxygen-16 and Oxygen-18. An isotope<\/a> is an atom that has the same number of protons as other atoms of that particular element but a different number of neutrons. The researchers used a methodology that would compare the isotopic content of the primeval ocean to the ocean that we have today.<\/p>\n
Many other research teams have also worked at the same site in Australia and left behind a library of sorts of data and analysis. Johnson and Wing’s team had a lot to work with when they collected and analyzed their data, and they were able to draw conclusions based on a multiplicity of studies that had already been conducted.<\/p>\n
What they found is that the primeval oceans had more Oxygen-18 than the ocean does today<\/a>. Not a lot, but enough for the researchers to question why. By comparing their data and analyses with other studies, they reached some conclusions that may rewrite at least part of the story of the development of life on earth.<\/p>\n
The team posited that the excess Oxygen-18 was sucked up by the heavy clay soils present on the earth’s continents. So why was there more Oxygen-18 in the early oceans than there is today? Because the continents, at that point in time, did not exist.<\/p>\n
From the evidence that they collected, combined with analyses from other studies conducted in the same area, the researchers concluded that the early earth was, in fact, a water world<\/a>. There was little dry land – pretty much the entire planet was covered in oceans.<\/p>\n
That the early earth may have been submerged almost entirely underwater does not mean that there was not any dry land. There may have been “micro-continent<\/a>s,” small landmasses that emerged from the ocean. They may have looked like isolated islands without any plants or animals on them.<\/p>\n
One question that has puzzled scientists for generations is trying to understand just where the water for our oceans came from<\/a> in the first place. Did it form on its own from the hydrogen and oxygen that existed in the earth’s early atmosphere? Did it maybe arrive on asteroids during the substantial bombardment period?<\/p>\n
There are so many questions that we just do not have the answers to. And that is perfectly fine, good even. The best research creates new problems for scientists to ponder so that they can continue their work to understand how our world and the universe work.<\/p>\n
If the early earth was a water world, then a lot of the ideas about where the water came from may be challenged. There is probably an explanation out there that scientists have not yet considered, but that will be conclusive in explaining the origins of water. Moreover, if the research is of good quality, it will generate more questions for scientists to answer.<\/p>\n
Life is essentially a complex of molecules that have developed the ability to replicate themselves<\/a> and, in so doing, reproduce more of their kind. For life to develop, a particular combination of chemicals and atmospheric conditions has to be present.<\/p>\n
If you take a glass of water, you can dissolve some different things into it, and they will combine. Imagine putting a sprinkle of salt and a sprinkle of sugar into a glass of warm water – when you take a sip, you will taste both sugar and salt together, not separately.<\/p>\n
Water is a medium that allows things to combine, and scientists believe that different chemical elements combined in the earth’s early oceans to produce life<\/a>. These oceans were a soupy mix of all of the details necessary for life to form, and they evolved with increasingly complex features that became better and better adapted to survive in their environment.<\/p>\n
Many scientists believe that after life first developed in the ocean, it evolved to a sufficient degree that some species were able to crawl out onto land. They were amphibious, meaning that they were able to survive in both land and water, as they had mechanisms for breathing in both environments.<\/p>\n
These animals evolved so that they developed lungs to breathe air and legs to walk. On and on down the line, we get giant reptiles, such as dinosaurs, as well as mammals, which ultimately evolved into humans. Sure, there are many questions about how evolution occurred<\/a>. But the consensus in the scientific community is that life developed in the oceans and then came out onto land.<\/p>\n
The prevailing idea has been that life had to form in the oceans because water provides the means for chemicals to dissolve and combine into molecules. These molecules could connect with other molecules until DNA formed, along with cells.<\/p>\n
However, if the whole world was an ocean<\/a>, then maybe life evolved in the water simply because that was the only environment present! Perhaps there are actually other ways that life could begin, which actually do not require water, or at least not as much of it as scientists have long believed.<\/p>\n
Perhaps life actually could develop and evolve on land, given the right conditions. We don’t know for sure yet, but maybe the prominence of oceans on the early earth is the primary reason why life began underwater<\/a> than on land. Nevertheless, if life could have possibly evolved on land, then a whole new field could develop out of trying to understand the different potentialities in which life could form.<\/p>\n
Many scientists have dismissed the idea that life could possibly exist on any of the gas giants, such as Jupiter and Saturn<\/a> because life needs liquid water to form. But what if life, at least microbial life forms, actually could develop in a gaseous environment? We don’t know.<\/p>\n
The presence of land on earth has always been pretty much a given. The other inner planets – Mercury, Venus, and Mars<\/a> – are all rocky balls of land. While there is some evidence of ancient canals flowing on Mars, there hasn’t been much of a question about whether that area has always been present on earth.<\/p>\n
If continents have not always just been here, as scientists have long assumed, then where did they come from? The answer is simple: more research is necessary to find out. Hopefully, there will be many different teams of scientists that come together to try to understand the origins of continents.<\/a><\/p>\n
In a paper that Johnson and Wing wrote on their findings, they conceded that there might have been microcontinents<\/a> present throughout earth’s history, even when the planet was a water world. But there were not enough landmasses that held heavy clay soil to absorb the Oxygen-18 isotopes from the primeval ocean.<\/p>\n
Today, there are seven continents: Africa, Antarctica, Asia, Australia, Europe, North America, and South America. These continents have many islands surrounding them, the largest of which is Greenland<\/a> in the North Atlantic. Many of those islands are probably much bigger than the mini-continents that may have existed in the earth’s distant past.<\/p>\n
A lot of what we understand about the continents comes from the theory of plate tectonics. Plate tectonics asserts that the earth’s crust is composed of dozens of plates that shift around over the flowing magma of the planet’s mantle layer.<\/p>\n
Because of that shifting, the continents are moving further and further away from each other and shifting every ocean as we know it. For example, South America and Africa<\/a> were once joined together but became separated from each other and have been moving in opposite directions ever since. Plate tectonics explains a lot. However, it does not reveal the presence of a water world or what the implications are for the development of the continents.<\/p>\n
That is the question. Plate tectonics looks at how all of the continents seem to fit together like a planet-sized jigsaw puzzle and theorize that they were once all part of one giant supercontinent. Scientists refer to this supercontinent as Pangea<\/a>. Pangea broke up hundreds of millions of years ago, and this breakup eventually led to the continents as we see them today.<\/p>\n
What the Johnson and Wing study ultimately exposes is that there is a lot of information that we just do not know. The researchers are helping to raise many questions that more scientists are going to have to try to answer. But scientists are curious people by nature, so there will undoubtedly be some that rise to the occasion.<\/p>\n
Every generation has paradigm-shifting scientists that redefine our understanding of our place in the universe. Galileo pointed his telescope to the heavens. Isaac Newton had the theory of gravity. Albert Einstein had general and special relativity. Albert Wegener<\/a> came up with plate tectonics. Who knows? Maybe history will remember Johnson and Wing as the scientists who transformed our understanding of our planet’s early history.<\/p>\n
As long as scientists remain curious and keep asking questions about the things that they don’t know or understand, they will continue making discoveries that transform our understanding of our planet and our place in the universe. Based on how they respond to the Johnson and Wing<\/a> study, we may soon know a lot more.<\/p>\n