Scientists Expect Earth Swallowed Another Planet… So Life Exists

By: Yassmine ElSayed

CAIRO, Feb. 6 (SEE) - A recent study expected that the ancient collision that formed the moon may also have brought with it all the ingredients needed for life.

According to a report published by livescience.com, it was over 4.4 billion years ago when a Mars-size body smashed into a primitive Earth, launching our moon into permanent orbit around our planet.

But a new study finds that this event could have had a much larger impact than previously thought. The collision could also have imbued our planet with the carbon, nitrogen and sulfur needed for life to form, scientists wrote in the journal Science Advances.

Back then, Earth was a little like Mars is today. It had a core and it had a mantle, but its noncore portion was very poor in volatile elements such as nitrogen, carbon and sulfur.

Elements in the noncore parts of our planet, called the "bulk silicate Earth," can intermingle with each other, but they never interact with the elements of the core. Though some volatiles existed in the core, they couldn't make their way to the planet’s outer layers. And then a collision happened.

One theory holds that special kinds of meteorites, called carbonaceous chondrites, slammed into Earth and gave the bulk silicate Earth these volatile elements. This idea rests on the fact that the ratios of different versions — or isotopes — of nitrogen, carbon and hydrogen seem to match those found on these meteorites. So, proponents of the theory argue, the meteorites must be the source of these elements.

But there's just one problem: the ratio of carbon to nitrogen is off.

While the meteorites have about 20 parts carbon to one part nitrogen, Earth's noncore material has about 40 parts carbon to each part nitrogen, according to study author Damanveer Grewal, a fourth-year Ph.D. student in the Department of Earth, Environmental and Planetary Sciences at Rice University in Houston, Texas.

After running over 1 billion simulations, they found that the scenario that made the most sense — the one that had the most probable timing and could lead to a correct ratio of carbon to nitrogen — was one that posited a collision and merger of Earth with a Mars-size planet that contained about 25 to 30 percent sulfur in its core.

This theory "is very probable," said Célia Dalou, an experimental petrologist at the Centre de Recherches Pétrographiques et Géochimiques in France, who was not a part of the study. "This work is a very successful result of years of research of various different teams."