When you look at a picture of the earth from space it appears to have a lot of water. The blue of the water, combined with the white fluffy clouds and the land masses make it look like a blue and white marble, suspended in space. But in reality, water only makes up about 1% of the total earth and 70% of the surface. Scientists have wondered why there isn’t more water on earth.
As planetary scientists study the formation of planets and planetary systems, they have discovered that the amount of water that is contained on a planet has to do with what is called the ‘snow line’. The snow line is the location in a planetary system where the temperature is cold enough to allow frozen water, or ice to develop. In our own solar system, this snow line is right in the middle of the asteroid belt, in between the orbit of Jupiter and Mars. This area contains thousands and thousands of asteroids that have water of all types. This is an important thing to note, because not all water is the same.
It is believed that the closer a planet is to the snow line, the more chance it has to develop water. When scientists studied the orbit of the earth, they discovered that our planet earth was never really inside the snow line, but stayed just outside of it. This made our planet warmer, but also didn’t give it the chance to retain more water.
When we study the types of asteroids that exist in the asteroid belt, scientists have found a specific type that contains the same type of water that we have on earth. As chunks of the asteroids broke away and headed towards the earth, the smaller items, called meteorites hit the planet. There is one particular type of meteorite that contains the same kind of water that is found on earth. This type of meteorite is called carbonaceous carbonites. While comets and other asteroids have hit the planet, only the carbonaceous carbonites match our earth water.
When you combine the fact of earth’s closer location to the sun, causes it to be warmer and therefore burn off or evaporate liquid water, with the fewer carbonaceous carbonite meteorites that hit the earth and deposited their water contents on the earth, it explains why earth is not completely covered by water.
If the earth’s orbit had been just a bit farther away from the sun this would have made the earth cooler and closer for the carbonaceous carbonites to hit the earth, deposit the water and not allow the water to escape. We should be very happy that the earth is in what is called the ‘Goldilocks Zone”. This is where the temperatures are not too hot and not too cold; they are just right. This means they are just right for all of us to live because the warmer temperatures give us and all of the life on earth the chance to have land to live on.