Some 13 billion years ago, the chemical elements that make life possible began forming in the Universe. Carbon, hydrogen, oxygen, nitrogen and the other 25 elements that are the building blocks of life have their origins in stardust.
The interior of stars was the crucible for element synthesis. When our Sun and its planets formed, about 4.5 billion years ago, they incorporated the remnants of an ancient star that had exploded and died.
Our planet, Earth, formed predominantly from the rocky elements of this exploded star. Jupiter and the other larger planets further away from the Sun retained more of the gaseous materials.
Because our planet was molten at the time, the heavier elements from the ancient star were found in liquid form. The forces of gravity concentrated dense material at our planet’s center and less dense material near its surface.
The differentiation driven by gravity explains why nickel and iron compose most of the planet’s core, located some 1,800 miles below our feet. It is also explains why lighter gases, such as nitrogen, carbon dioxide, and water vapor accumulated in our atmosphere.
Eventually, as the Earth cooled, liquid oceans formed from water condensed from the primitive atmosphere.
We should be thankful for this process of differentiation. Our bodies are mostly composed of the lighter elements of the periodic table, which are abundant in the atmosphere, and in the oceans and the soils of Earth.
When human activities concentrate elements such as phosphorous and mercury at levels vastly in excess of what’s found naturally on the Earth’s surface—that’s when many of today’s environmental problems occur.
Photo, taken on August 13, 2007, courtesy of Nick Ares via Flickr.