Earth already had its own water before it crashed with a Mars-like planet. Oxygen concentration found in lunar and Earth rocks pointed scientists to this new theory.
It is widely believed that the Earth's moon was formed after a giant celestial object called Theia collided with proto-Earth, or the young Earth, some 4.5 billion years ago. Although Theia did not survive the high-energy head-on collision, it led to the formation of our moon. What was left from Theia was meshed into Earth and the moon.
A new study published in the journal Science Advances supports this collision theory of Moon-forming impact. The impact is said to be so high-energy that it resulted to the almost complete mixing of materials between proto-Earth and Theia.
Water On Earth Before Theia
However, the study suggests that water could have been present on the surface of the Earth even before the impact that formed the moon.
The research also revealed that no more than 5 to 30 percent of the Earth's water was contributed from the late veneer process or the accretion of water and other elements on Earth from comets, meteorites, and other passing objects.
The very similar oxygen isotopes observed in lunar rocks brought back by Apollo missions and different rocks gathered from the ocean's seabed showed that Earth is much more common to the Moon.
Water Survived The Collision
In their analysis of the oxygen isotopic concentration of lunar and Earth rocks, the scientists uncovered only 3 to 4 parts per million difference between the samples.
However, no substantial difference was noted in the lunar rocks and olivine from basalt rocks. Olivine is a rock-forming mineral found in the Earth's subsurface.
With the very similar isotopic characteristics of the Earth and Moon, the study suggests that water on Earth could have survived the giant collision between a proto-Earth and Theia.
According to the study, the likely source of water on Earth are carbonaceous chondrites, a type of stony meteorites. These stony meteorites have a very distinct oxygen isotope composition, and if the said elements arrived later than the collision, it would mean that the Earth and Moon would exhibit more different oxygen isotope characteristics.
"Consequently, our data indicate that the bulk of Earth's water was accreted before the giant impact and not later, as often proposed," the team wrote stated.
This study can be crucial in the quest for water in Mars. If water is that extremely resilient to survive such catastrophic impact of two celestial bodies colliding, then life-bearing substances can also be found somewhere out there.
"Exoplanets with water on their surfaces may be much more common than we previously thought. And where there's water, there could also be life!" says Richard Greenwood, professor of Planetary and Space Sciences at the School of Physical Sciences Open University in Milton Keynes, United Kingdom.
