Earth's life may have begun after a colossal collision with a Mars-sized planet, studies hint

Earth is the only planet known to support life as we know it. While there have been many attempts to discover life in the cosmos, none have yielded positive results yet. Surprisingly, Earth too did not have all the requisites present to support life initially. So how did life originate on our Blue Planet? A recent study tries to find the answer. 

It is believed that Earth did not always support life as it does today. About four billion years ago, our Blue Planet was likely a lifeless world. A new study published in Science Advances suggests that the Mars-sized protoplanet Theia, which is said to have given rise to the Moon, may also have delivered some of the essential elements that later made life on Earth possible.

In the study, scientists believe that the origin of Theia was likely farther away from the Sun than our Blue Planet. The paper also hints that the exoplanet was extremely rich in volatile compounds such as carbon and hydrogen. It is because of this that, when Theia collided with the early Earth, the life-supporting elements got delivered to our planet. 

Pascal Kruttasch, the lead author of the study, told Live Science, “We conclude that the moon-forming impactor Theia originated further out in the solar system [than Earth] and was volatile-rich.”

To test their hypothesis, the researchers used a chemical model to analyze isotopes found in meteorites and rocks from Earth. They focused on the radioactive decay of a manganese isotope that was present in the early solar system. Over millions of years, this isotope decayed into chromium, and allowed the scientists to reconstruct the first 15 million years of Earth's formation.

Their analysis also showed that planets forming close to the Sun were relatively poor in volatile elements. Based on these findings, the researchers concluded that the only way Earth got its supply of the volatile compounds was from the collision with Theia.

Another study, published in the Icarus journal, points out that the collision might not just have deposited volatile compounds. In fact, Theia might have delivered vast amounts of water to the barren, rocky, and lifeless regions of a young Earth. The study also suggests that some of that water supposedly deposited by Theia could still be found locked inside the Earth’s mantle. 

Portugal's Institute of Astrophysics and Space Sciences’ Pedro Machado, who is also the co-author of the study, tried to explain the mantle water. Machado said, “Water is less dense than the materials typically found in the Earth's mantle, and it was supposed to have come to the crust or oceans.” This might be because, as per the study, the majority of the water was delivered to the Earth’s mantle by Theia. But as per Machado, “there hasn't been time for this water to reach the surface.”