New Oxygen Isotope Study Says Water Was Present on Earth Before Impact That Formed the Moon
The Earth was wet before the moon was created.
That's the theory put forth as a result of new findings from a study of oxygen isotopes on both Earth and the moon. If true, it could not only dramatically change our understanding of the way our own planet formed—it could affect the way we look for life-hosting worlds outside of our own solar system.
The prevailing theory as to the creation of the moon is that, at some point in its early infancy, the Earth was struck by a large rock, potentially as large as the entire planet Mars. This caused a chunk of still hot and malleable Earth rock to break off, spinning around until it fell into a comfortable orbit around the planet.
This is a dramatically different origin to most moons in the solar system, but, then, considering its size relative to the Earth, the moon is already considered exceptional. Moons are normally a lot smaller than their planets, and the moon is far too large to have formed out of leftover debris from the creation of the Earth.
It had been previously believed that the water that's found on Earth didn't originate on the planet—it could have been brought here instead by comets and asteroids, arriving in the form of ice, long after the moon had formed.
According to this new study, published in Science Advances, this probably isn't the case. Water residue on the moon matches perfectly with water on Earth, which means that the Earth was already covered in water when the moon split from our planet.
This certainly does go some way to explaining the potentially large pools of water that exist in craters on the moon, but it brings into question an assumed fundamental law of the development of life.
We previously assumed that a large meteor or asteroid striking a planet would be enough to prevent life from being able to form on the planet's surface—surely, with the force of an asteroid big enough to form the moon, the Earth couldn't have stayed fertile after such an impact. Logically, the Earth therefore only became fertile after the moon was already in the sky.
If the moon contains water that came from Earth, though, it suggests that the collision that created our planet's biggest satellite wasn't enough to damage the Earth's environment and prevent life from forming. After all, our own existence is proof that the Earth remains capable of supporting life.
This makes things more complicated for mankind's ongoing search for aliens.
Currently, in order to sort through the countless planets in the galaxy, scientists have been filtering out undesirable planets in order to build up a directory of worlds that are potentially habitable. One condition that makes a planet uninhabitable, we'd thought, is being struck by a huge asteroid (for more information on this phenomenon, ask the dinosaurs).
If the Earth survived its early collision event without losing its water supply and atmosphere, this means that exoplanets across the galaxy that have endured similar events might also be habitable.
In other words, proving that the Earth was wet before the creation of the moon suggests that we should be paying more attention to a whole host of planets that we've been previously ignoring.
The chances of finding alien life just dramatically improved.