The Origin of Earth’s Water

Saturday, May 25, 2019

Illustration of a comet, ice grains and Earth’s oceans. SOFIA found clues in Comet Wirtanen’s ice grains that suggest water in comets and Earth’s oceans may share a common origin. (Credit: NASA/SOFIA/L. Cook/L. Proudfit)

Earth is known as the only planet on the solar system to sustain life. Aside from this, it is also identified to have large amount of water and its axis being stabilized by the moon. Researchers from the University of Münster (Germany) was able to show for the first time, the role of moon on bringing water on the planet. Studies found that the formation of moon 4.4 billion years ago caused to bring water on Earth.

The moon was formed when Earth was hit by a body with the same size as Mars, also called Theia. At first, it was thought that Theia comes from the inner solar system near Earth but later on it turns out that it was originated from the outer solar system and carried large quantities of water, according to Phys.

It might be impossible and shocking to know that Earth has water since it came from dry inner solar system. So how can this be possible? The solar system was formed 4.5 billion years ago and based on previous studies, it is structured where dry and wet materials are separated. The dry material which is called non-carbonaceous meteorites come from inner solar system while the wet material which is rich in water called carbonaceous meteorites come from outer solar system. Even though studies have showed that the carbonaceous meteorites are responsible for water on Earth though it still a mystery on how and when it happened.

"We have used molybdenum isotopes to answer this question. The molybdenum isotopes allow us to clearly distinguish carbonaceous and non-carbonaceous material, and such from the outer and inner solar system," said Dr. Gerrit Budde, paleontology in Münster University and the lead author of the study.

Researchers also found out that Earth's molybdenum isotopic composition lies between the carbonaceous and non-carbonaceous meteorites. It was observed that some of Earth's molybdenum comes from the outer solar system and plays an important role because of its iron-loving property.

"The molybdenum which is accessible today in the Earth's mantle, therefore, originates from the late stages of Earth's formation, while the molybdenum from earlier phases is entirely in the core," said Dr. Christoph Burkhardt, second author of the study.

Based on the results, it shows that carbonaceous material came late on earth given that it was from the outer solar system. Provided this fact, molybdenum was supplied by Theia whose collision with the planet happened 4.4 billion years ago leading to the moon's formation. Nevertheless, it can be concluded that molybdenum in earth's mantle also came from the outer solar system which only means that Theia also originated from the outer solar system. Scientists believed that the collision provided enough carbonaceous material which supplied great amount of water on Earth.

"Our approach is unique because, for the first time, it allows us to associate the origin of water on Earth with the formation of the Moo. To put it simply, without the Moon there probably would be no life on Earth," explained Thorsten Klein, professor of Paleontology at the University of Münster.