Solar system 'on fire' burned up Earth's carbon

FIRE sweeping through the inner solar system may have scorched away much of the carbon from Earth and the other inner planets.

Though our planet supports carbon-based life, it has a mysterious carbon deficit. The element is thousands of times more abundant in comets in the outer solar system than on Earth, relative to the amount of silicon each body contains. The sun is similarly rich in carbon. "There really wasn't that much carbon that made it onto Earth compared to what was available," says Edwin Bergin of the University of Michigan in Ann Arbor.

The conventional explanation for the deficit argues that in the inner region of the dust disc where Earth formed, temperatures soared above 1800 kelvin, enough for carbon to boil away. But observations of developing solar systems suggest that at Earth's distance from the sun the temperature would be too cool to vaporise carbon dust.

Now a team of astronomers says that fire is to blame. Hot oxygen atoms in the dusty disc would have readily combined with carbon, burning it to produce carbon dioxide and other gases, say Jeong-Eun Lee of Sejong University in Seoul, South Korea, and colleagues, including Bergin, in a paper to appear in The Astrophysical Journal Letters (arxiv.org/abs/1001.0818). Any solid carbon in the inner solar system would have been destroyed within a few years, they calculate.
Fire would have destroyed any solid carbon in the early inner solar system within a few years

Supporting the theory is the fact that carbon abundance in the asteroid belt surrounding the inner planets increases the farther away you get 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, the researchers say. 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 says.