University of Bern:

Earth is so far the only known planet on which life exists—with liquid water and a stable atmosphere. However, the conditions were not conducive to life when it formed. The gas-dust cloud from which all the planets in the solar system formed was rich in volatile elements essential for life, such as hydrogen, carbon and sulfur.

However, in the inner solar system—the part closest to the sun, where the four rocky planets Mercury, Venus, Earth and Mars and the asteroid belt are located today—these volatile elements could hardly exist.

Due to the high temperature of the sun, they did not condense and initially remained largely in the gas phase. As these gaseous substances were not incorporated into the solid rocky materials from which the planets were formed, the early precursor of Earth, the so-called proto-Earth, also contained very little of these vital substances.

Only celestial bodies that formed further away from the sun in cooler regions were able to incorporate these components. When and how Earth became a life-friendly planet is still not fully understood.

In a new study, researchers from the Institute of Geological Sciences at the University of Bern have now been able to show for the first time that the chemical composition of the early Earth was complete no later than three million years after the formation of the solar system—and in a way that initially made the emergence of life impossible.

Their results, published in the journal Science Advances, suggest that life on Earth was only made possible by a later event. [Continue reading…]