Though our planet supports carbon-based life, it has a mysterious carbon deficit, but the element is thousands of times more abundant in comets in the outer solar system than on the earth, even the sun is rich in carbon. The conventional explanation for the deficit is that in the inner region of the dust disc where earth formed, temperatures soared above 1800 kelvin, enough for carbon to boil away, journal New Scientist reported.

But observations of developing solar systems suggested that at earth's distance from the sun, the temperature would be too cool to vaporise carbon dust. Now a team of astronomers from Sejong University in Seoul and the University of Michigan in Ann Arbor wrote in The Astrophysical Journal Letters that fire sweeping through the inner solar system had "scorched away much of the carbon from earth and the other inner planets".

"Hot oxygen atoms in the dusty disc would have readily combined with carbon, burning it to produce carbon dioxide and other gases," said Jeong-Eun Lee of Sejong University. "Any solid carbon in the inner solar system would have been destroyed within a few years," Lee added.

Supporting the theory is the fact that carbon abundance in the asteroid belt surrounding the inner planets increases with the distance from the sun. The carbon that Earth now contains must have been delivered later by asteroids and comets that formed beyond the reach of the early fire, said Edwin Bergin of the University of Michigan. This may have had a hidden benefit: chemical reactions in the outer solar system could have transformed simple carbon compounds into more complex molecules such as amino acids, which are key ingredients of life, Bergin said.