New research by scientists may help solve the question of whether our atmosphere was formed by gases naturally emitted by the Earth's interior -- through events like volcanic eruptions or due to comets colliding into the Earth soon after it formed.

Nitrogen makes up approximately 78 percent of the air we breathe. But scientists have never fully understood how it came to be present in the atmospheres around Earth and other planets. Along with carbon, hydrogen and sulfur -- other elements that are essential for life - nitrogen is a volatile element, meaning that its molecules convert from liquid to gas at a low temperature.

And because of the extremely high temperatures that existed when the planets were formed, the thinking goes, nitrogen and its volatile companions should have been lost during that process. The study, by Edward Young, a professor of Earth, planetary, and space sciences, and Jabrane Labidi, a UCLA postdoctoral fellow, was published in the journal Nature. Their work provides a strong argument for the second scenario.

"If nitrogen was added after the Earth was mostly constructed, then nitrogen deep in the Earth would have to have started in the atmosphere, being dragged down by geological and geochemical processes like weathering of rock," said Young.

Answering questions about how our planet works and about the sources of the elements that support life gives scientists a better understanding of how common the circumstances may be that create habitable planets.