CONTEXT:

• A cosmic body that hit the Earth and led to the formation of the Moon about 4.4 billion years ago may have also delivered large quantities of water to our home planet, scientists have found.
• The Earth is the only terrestrial planet with a large amount of water and a relatively large moon, which stabilises the Earth’s axis.
• Both were essential for Earth to develop life.

BACKGROUND:

• The Earth formed in the ‘dry’ inner solar system, and so it is somewhat surprising that there is water on Earth.
• To understand why this the case, we have to go back in time when the solar system was formed about 4.5 billion years ago.
• From earlier studies, we know that the solar system became structured such that the ‘dry’ materials were separated from the ‘wet’ materials: the so-called ‘carbonaceous’ meteorites, which are relatively rich in water, come from the outer solar system, whereas the drier ‘non-carbonaceous’ meteorites come from the inner solar system.
• While previous studies have shown that carbonaceous materials were likely responsible for delivering the water to Earth, it was unknown when and how this carbonaceous material—and thus the water—came to Earth.