A recent study suggests that the earth already had a lot of water before the collision with the protoplanet Theia.
Its unusual size and especially its earth-like chemical composition have always been a mystery. The origin of the moon — the earth’s only natural satellite — has always fascinated astronomers. Where does it come from? Why is it the way it is? The currently widely accepted hypothesis is that the moon was created in a huge cosmic collision, in which a nearly mars-sized object hit the young earth.
A recent study conducted by a group of international researchers confirms that hypothesis but with one catch. The protoplanet called Theia did directly hit Earth and completely destroyed it. However, how our home planet looked before this cataclysmic event, according to the researchers, is not the currently accepted theory. The team led by Richard Greenwood of the English Open University in Milton Keynes suspects that the majority of existing water already existed before the collision. This theory, however, does not quite fit with the current accepted theory that terrestrial water has been brought down to earth by asteroids and comets over time.
The study, which has now been published in the journal Science Advances, is based on studies of rocks brought to Earth by astronauts during the Apollo missions and volcanic rocks from the Earth’s ocean floor. Greenwood and his colleagues specifically studied oxygen isotopes that were remarkably similar to rocks from the Moon from Earth.
The proven parallels support the thesis of the collision of a celestial body with the earth, but they contradict the idea that later comets have brought water to our planet. Had it been so, then the oxygen isotopes of the two celestial bodies would have revealed greater differences. According to the researchers, this can only mean one thing: the water that exists on earth today must have existed before the impact of Theia on the young earth.
The thesis that water could survive such an impact has, according to the scientists, also consequences for the search for life beyond our solar system: Exoplanets, which have emerged from a collision of several celestial bodies, could have produced life in their habitable zone.