When did the Earth have oceans and continents?
I had to throw this in here because some very exciting data has been found to indicate that the Earth had oceans and continents only two hundred million years after its formation four and a half billion years ago. This is not the model that has been previously proposed. Scientists have found evidence for the fact that water existed in space in asteroids over four and a half billion years ago at the time that the solar system formed. They have found meteorites that contain salt with occluded water that is at least that old. They have also found rocks in Canada that show that the Earth had oceans early on and the only way this could have happened is that asteroids with water hit the Earth soon after its formation. This refutes the idea that the Earth was a ball of molten lava well into the bombardment period. Evidently, it cooled much quicker than previously thought and oceans and continents existed much earlier than thought.
We now know that the moon was formed when a planet about the size of Mars collided with the new Earth right after it had formed. Analyzing moon rocks brought back by the Apollo astronauts has proved this. These moon rocks contained almost no iron but mostly silicates, which means that the moon is composed of the Earth’s crust knocked off when the planet hit the Earth with a glancing blow.
The water-in-asteroid theory of Earth’s ocean formation is contrary to the theory that the water came from comet collisions with Earth during and after the late bombardment period 4.1 to 3.8 billion years ago when asteroids and comets crashed into the Earth like rain. What’s really exciting about the asteroid idea is that evidence has been found that ancient asteroids contained amino acids, the building blocks of life, suggesting the theory that life came from outer space, possibly from Mars, and didn’t originate here on Earth as previously thought.
The other interesting thing about the new ocean formation theory is that it means that there are probably millions of asteroids out there with appreciable water in them. Could they also contain life? NASA has several missions that will investigate asteroids and determine if they have water. I hope I get to see the results of these missions.
We also now know that oxygen was introduced into the Earth’s atmosphere around three and a half billion years ago. This was accomplished by cyanobacteria colonies that formed trillions of tons of oxygen and made it possible for the evolution of all animal and plant life, including us.
Oxygen was poison to the first life forms on Earth and they soon died off, paving the way for the kind of life we are. The earliest life utilized sulfur rather than oxygen as an energy source. The big question is: how did the cyanobacteria evolve? That’s a good question and since it happened so long ago, it’s difficult to determine how it began.
The original Earth atmosphere consisted of nitrogen and carbon dioxide. Oxygen formed 2.4 billion years ago but didn’t get to the levels we see until about six hundred million years ago, and at one time it was around thirty percent instead of the present twenty one percent. Obviously, volcanic eruptions and the proliferation of plant life affected the oxygen concentration.
I think that all of this new data is important but it illustrates that we still don’t understand all of the ways that the Earth formed and how life got started here. I have to admit that all of this is just too exciting to me. I love this stuff!
Thanks for reading.