Diamonds as the key to unravel the origin of Earth's water

The origin Earth's water is still an unsolved mystery in Earth Sciences.

Yet, answering this question is paramount in order to validate planetary accretion models and determine the conditions for life-sustainable planets to form.

Comparing Earth's original deuterium-to-hydrogen ratio (D/H) with those of Solar system objects such as meteorites, comets and the solar nebula can constrain on the provenance of water.

However, while D/H is precisely determined for extra-terrestrial objects, the exact value for Earth is not known, due to the fact that Earth's primordial D/H got lost since its formation following surface and mantle geological processes.

In fact, current estimates from mantle-derived lavas are challenged by the ability of these samples to retain pristine values, indicating the need for a pristine reservoir that remained unaffected over geological time to be found.

Diamonds from the Earth's mantle may be key as they contain trace amounts of hydrogen and are inert and robust time capsules able to survive over several billion years.

The overarching goal of this project is to determine Earth's primordial D/H by investigating the hydrogen content and isotopic composition of a unique set of worldwide, natural diamonds dating 3.5 to 0.09 billion years ago using newly-developed, high-precision and high-efficiency isotope ratio mass spectrometry.

The isotopic data will be complemented by atomistic state-of-the-art ab initio simulations to understand the atomic and diffusion behaviour of hydrogen in natural diamonds.

The new results will be fundamental to pinpoint Earth's water origin with long-term implications for understanding planet habitability.

In a time where international space agencies are actively searching for potentially habitable planets and extra-terrestrial life, the new knowledge will be fundamental to understanding the geological and biological evolution of planets in our Solar System and beyond.